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1
Tinsley, B. A., R. Rohrbaugh, H. Rassoul, Y. Sahai, N. R. Teixeira i D. Slater. "Low-latitude aurorae and storm time current systems". Journal of Geophysical Research 91, A10 (1986): 11257. http://dx.doi.org/10.1029/ja091ia10p11257.
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Saka, O., J. S. Kim i D. J. Knecht. "Ionospheric equivalent current systems of low-latitude Pc3 pulsations". Planetary and Space Science 36, nr 7 (lipiec 1988): 641–53. http://dx.doi.org/10.1016/0032-0633(88)90112-2.
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Grafe, A., P. A. Bespalov, V. Y. Trakhtengerts i A. G. Demekhov. "Afternoon mid-latitude current system and low-latitude geomagnetic field asymmetry during geomagnetic storms". Annales Geophysicae 15, nr 12 (31.12.1997): 1537–47. http://dx.doi.org/10.1007/s00585-997-1537-5.
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Abstract. For four geomagnetic storms of middle intensity the relationship between the low-latitude magnetic field asymmetry using ASY indices and the intensity of the auroral eastward and westward electrojet was considered. It was asked whether there exists a connection between ASY and the eastward electrojet. To answer this question equivalent current systems were estimated in mid-latitudes. It was found that the observations obviously show no correlative relationship between the low-latitude magnetic-field asymmetry and the eastward electrojet, whereas one exists between ASY and the westward electrojet. To explain the generally accepted common three-dimensional current system between the partial ring current and the eastward electrojet, a condensor model of the three-dimensional current system was developed. It could be shown that the short periodic variations of the partial ring current are shielded by the condensor and cannot influence the eastward-electrojet current.
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Liu, Ping, Chun Ming Liu i Lian Guang Liu. "Variation Characteristics of Geoelectric Field in Mid-to-Low Latitude Area during Geomagnetic Storms". Advanced Materials Research 1008-1009 (sierpień 2014): 524–29. http://dx.doi.org/10.4028/www.scientific.net/amr.1008-1009.524.
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Large geoelectric field generated in the ground during severe space weather events are sources of geomagnetically induced currents (GICs), which flow in power systems potentially causing damage to system component or failure of the system. In this paper, based on the H and D components of the recent geomagnetic storm data measured at 10 mid-to-low latitude geomagnetic observatories, we analyzed the variation characteristics of the amplitude of north-south and east-west geoelectric components with geographic latitudes. Furthermore, we discussed the possibilities of GIC problem occurrence in transmission lines in different directions at different latitude in China. The result shows that transmission lines in east-west direction at higher latitude are more susceptible to space weather hazard. And it will contribute to the assessment of geomagnetic hazard to power systems and the control of GIC in the current and future power grids in China.
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Barkhatov, N. A., S. E. Revunov, O. T. Cherney, M. V. Mukhina i Zh V. Smirnova. "Neural networks technique for detecting current systems while main phase of geomagnetic storm". E3S Web of Conferences 220 (2020): 01091. http://dx.doi.org/10.1051/e3sconf/202022001091.
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The study demonstrated the technology for searching nonlinear correlations between the intensity indices of auroral electric jets (AU, AL) and ring current intensity indices (SYM, ASY). The well-known connection of the western electrojet with the asymmetric part of the ring current and the eastern electrodett with the symmetric is confirmed. The technology of artificial neural networks was chosen as the main method. Thus, the relationship of magnetic disturbances in the auroral region and magnetic disturbances at middle and low latitudes in the main phase of a geomagnetic storm is investigated. The characteristic lead times in the development of mid-latitude magnetospheric processes relative to polar are determined. An acceptable neural network recovery of auroral electrojet intensity indices from ring current index data is demonstrated.
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Lovati, Giulia, Paola De Michelis, Giuseppe Consolini i Francesco Berrilli. "Pressure-Gradient Current at High Latitude from Swarm Measurements". Remote Sensing 14, nr 6 (15.03.2022): 1428. http://dx.doi.org/10.3390/rs14061428.
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The pressure-gradient current is among the weaker ionospheric current systems arising from plasma pressure variations. It is also called diamagnetic current because it produces a magnetic field which is oriented oppositely to the ambient magnetic field, causing its reduction. The magnetic reduction can be revealed in measurements made by low-Earth orbiting satellites flying close to ionospheric plasma regions where rapid changes in density occur. Using geomagnetic field, plasma density and electron temperature measurements recorded on board ESA Swarm A satellite from April 2014 to March 2018, we reconstruct the flow patterns of the pressure-gradient current at high-latitude ionosphere in both hemispheres, and investigate their dependence on magnetic local time, geomagnetic activity, season and solar forcing drivers. Although being small in amplitude these currents appear to be a ubiquitous phenomenon at ionospheric high latitudes characterized by well defined flow patterns, which can cause artifacts in the main field models. Our findings can be used to correct magnetic field measurements for diamagnetic current effect, to improve modern magnetic field models, as well as to understand the impact of ionospheric irregularities on ionospheric dynamics at small-scale sizes of a few tens of kilometers.
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Belenkaya, E. S., I. I. Alexeev i C. R. Clauer. "Magnetic field of the transition current system: dawn-dusk asymmetry". Annales Geophysicae 25, nr 8 (29.08.2007): 1899–911. http://dx.doi.org/10.5194/angeo-25-1899-2007.
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Abstract. In this paper we consider the interactions of coronal mass ejections (CMEs) with the Earth's magnetosphere for the specific case in which there is a sharp increase in the dynamic pressure (interplanetary shock) that is associated with a simultaneous northward turning of the interplanetary magnetic field (IMF) from the near horizontal direction. Previously, we have shown that under such circumstances, the so-called transition current systems arise. These temporary high-latitude current systems create a low-latitude asymmetric magnetic field on the ground with a large northward field enhancement on the nightside and little or no field increase near local noon. Here we investigate the dawn-dusk asymmetry of the low-latitude on-ground magnetic field of the transition current system caused by the IMF. Analysis of the Region 1 current circuit for northward IMF shows a change in its shape controlled by different IMF components. Due to this geometrical effect, the maximum and minimum magnetic field disturbances appear to be shifted. The obtained results supplement and define more precisely the locations of the magnetic disturbance extrema retrieved recently by Clauer et al. (2001). The results of this study are compared with the available observations. A good accordance is demonstrated.
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Yang, Lucy, Nyree Zerega, Anastasia Montgomery i Daniel E. Horton. "Potential of breadfruit cultivation to contribute to climate-resilient low latitude food systems". PLOS Climate 1, nr 8 (17.08.2022): e0000062. http://dx.doi.org/10.1371/journal.pclm.0000062.
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The number of people in food crisis around the world is increasing, exacerbated by COVID-19, conflict, and climate change. Major crop yields are projected to decrease in low-latitude regions, making tropical and sub-tropical food systems particularly vulnerable. Increased cultivation of breadfruit (Artocarpus altilis), a neglected and underutilized species (NUS), has the potential to enhance climate resilience and overall sustainability of low-latitude agricultural systems. To better understand breadfruit’s cultivation suitability and geographic range in current and future climates, we use breadfruit presence data collected from previous studies and a global citizen science database, and a selection of bioclimactic variables, to build an ensemble of 6 species distribution models that delineate the current climatically viable breadfruit range. We then assess the climatically viable future breadfruit range (2061–2080) under stabilization and high emission scenarios using an ensemble of 8 global circulation model (GCM) projections. The area of suitable breadfruit range within the global tropics and subtropics is projected to decrease ~4.4% in the stabilization scenario and ~4.5% in the high emission scenario. In Southeast Asia and the Pacific Islands, yield quality and consistency show minimal decreases under the high emission scenario, with increases in total suitable area under both. In contrast, in Latin America and the Caribbean, the current suitable breadfruit range is projected to contract ~10.1–11.5% (stabilization-high emission). Present and future model suitability outputs suggest opportunities to successfully expand breadfruit cultivation over the next decades in sub-Saharan Africa, where food insecurity is coincidentally high. However, in all regions, high emission scenario conditions reduce the overall consistency and quality of breadfruit yields compared to the stabilization scenario. Our results have the potential to inform global food security adaptation planning, highlighting breadfruit as an ideal NUS to incorporate in food security adaptation strategies.
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Clilverd, Mark A., Craig J. Rodger, Sarah Dietrich, Tero Raita, Thomas Ulich, Ellen Clarke, Alan W. P. Thomson i Andrew J. Kavanagh. "High-latitude geomagnetically induced current events observed on very low frequency radio wave receiver systems". Radio Science 45, nr 2 (kwiecień 2010): n/a. http://dx.doi.org/10.1029/2009rs004215.
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Spall, Michael A., i David Nieves. "Wind-Forced Variability of the Remote Meridional Overturning Circulation". Journal of Physical Oceanography 50, nr 2 (luty 2020): 455–69. http://dx.doi.org/10.1175/jpo-d-19-0190.1.
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AbstractThe mechanisms by which time-dependent wind stress anomalies at midlatitudes can force variability in the meridional overturning circulation at low latitudes are explored. It is shown that winds are effective at forcing remote variability in the overturning circulation when forcing periods are near the midlatitude baroclinic Rossby wave basin-crossing time. Remote overturning is required by an imbalance in the midlatitude mass storage and release resulting from the dependence of the Rossby wave phase speed on latitude. A heuristic theory is developed that predicts the strength and frequency dependence of the remote overturning well when compared to a two-layer numerical model. The theory indicates that the variable overturning strength, relative to the anomalous Ekman transport, depends primarily on the ratio of the meridional spatial scale of the anomalous wind stress curl to its latitude. For strongly forced systems, a mean deep western boundary current can also significantly enhance the overturning variability at all latitudes. For sufficiently large thermocline displacements, the deep western boundary current alternates between interior and near-boundary pathways in response to fluctuations in the wind, leading to large anomalies in the volume of North Atlantic Deep Water stored at midlatitudes and in the downstream deep western boundary current transport.
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Kakad, Bharati, i Amar Kakad. "Characteristics of probability distribution functions of low- and high-latitude current systems during Solar Cycle 24". Advances in Space Research 65, nr 6 (marzec 2020): 1559–67. http://dx.doi.org/10.1016/j.asr.2019.12.021.
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Wang, H., H. Lühr, S. Y. Ma i P. Ritter. "Statistical study of the substorm onset: its dependence on solar wind parameters and solar illumination". Annales Geophysicae 23, nr 6 (15.09.2005): 2069–79. http://dx.doi.org/10.5194/angeo-23-2069-2005.
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Abstract. Based on 1829 well-defined substorm onsets in the Northern Hemisphere, observed during a 2-year period by the FUV Imager on board the IMAGE spacecraft, a statistical study is performed. From the combination of solar wind parameter observations by ACE and magnetic field observations by the low altitude satellite CHAMP, the location of auroral breakups in response to solar illumination and solar coupling parameters are studied. Furthermore, the correspondence of the onset location with prominent large-scale field-aligned currents and electrojets are investigated. Solar illumination and the related ionospheric conductivity have significant effects on the most probable substorm onset latitude and local time. In sunlight, substorm onsets tend to occur 1h earlier in local time and 1.5° more poleward than in darkness. The solar wind input, represented by the merging electric field, integrated over 1h prior to the substorm, correlates well with the latitude of the breakup. Most poleward latitudes of the onsets are found to range around 73° magnetic latitude during very quiet times. Field-aligned and Hall currents observed concurrently with the onset are consistent with the signature of a westward travelling surge evolving out of the Harang discontinuity. The observations suggest that the ionospheric conductivity has an influence on the location of the precipitating energetic electron which causes the auroral break-up signature. Keywords. Ionosphere (Auroral ionosphere) – Magnetospheric Physics (Current systems; Magnetosphereionosphere interactions)
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Grafe, A. "Are our ideas about <i>Dst</i> correct?" Annales Geophysicae 17, nr 1 (31.01.1999): 1–10. http://dx.doi.org/10.1007/s00585-999-0001-0.
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Abstract. The idea of two separate storm time ring currents, a symmetric and an asymmetric one has accepted since the 1960s. The existence of a symmetric equatorial ring current was concluded from Dst. However, the asymmetric development of the low-latitude geomagnetic disturbance field during storms lead to the assumption of the real existence of an asymmetric ring current. I think it is time to inquire whether this conception is correct. Thus, I have investigated the development of the low-latitude geomagnetic field during all the magnetic local times under disturbed and quiet conditions. The storm on February 6–9, 1986 and a statistical analysis of many storms has shown that the asymmetry does not vanish during the storm recovery phase. The ratio between the recovery phase asymmetry and the main phase asymmetry is low only for powerful storms. Storms of moderate intensity show the opposite. The global picture of the field evolution of the February storm shows clear differences at different local times. For instance the main phase and recovery phase start time does not coincide with Dst. Also the ring current decay is not the same at different local times. Therefore, Dst gives an incorrect picture of the field development. Moreover, asymmetry does not disappear during international quiet days as the investigation of the low-latitude geomagnetic field shows. Considering all these observations, I think we must revise our ideas about the ring current. In my opinion only one ring current exists and this is an asymmetric one. This asymmetry increases during storms and develops rather fast to more or less symmetric conditions. However, in no case is it justified to conclude from Dst that a symmetric ring current exists.Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; storms and substorms)
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Farah, Ashraf. "Single-Frequency Ionospheric-Delay Correction from BeiDou & GPS Systems for Northern Hemisphere". Artificial Satellites 54, nr 1 (1.03.2019): 1–15. http://dx.doi.org/10.2478/arsa-2019-0002.
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Abstract The range delay caused by the ionosphere layer is the major current source of error for GNSS users with single-frequency receivers. GNSS advice users to correct this type of error using ionospheric models whose coefficients are sent in their navigation messages. GPS-users use the Klobuchar model to correct this type of error. GPS navigation message contains the model’s eight coefficients which vary on the basis of seasonal ionospheric variations and average solar flux. The correction accuracy of Klobuchar model is about 50% (rms) of the ionospheric range delay. Beidou system calculates and broadcast 8 parameters of Klobuchar model based on continuous monitoring stations. BeiDou system updates the ionospheric coefficients every two hours. GPS-Klobuchar model uses completely different coefficients than BeiDou-Klobuchar model. This research demonstrates a comparison study between the Klobuchar model using the GPS broadcast coefficients and the same model using BeiDou-coefficients. The correction accuracy offered by the two models has been judged using the most accurate International GNSS Service-Global Ionospheric Maps (IGS-GIMs) for three different-latitude stations along northern hemisphere, one station in low-latitude region, the second station is in mid-latitude region and the third station is in high-latiude region to reflect models’ behaviour in different geographic regions. The study was applied over three different months of the year 2017 that each of them reflects a different activity state for the ionosphere layer. The study proves that BeiDou model is able to show the ionosphere’s day-to-day fluctuations while GPS model can’t. It can be concluded that GPS model offers better behaviour than BeiDou model in correcting range delay in low-latitude and high-latitude geographic regions under any activity state for the ionosphere. BeiDou model offers better correction accuracy than GPS model in mid-latitude under any activity state for the ionosphere.
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Wu, Wei Li. "Study on Magnetic Materials with Numerical Calculation of Geoelectromagnetic Field in Middle-Low Latitude Region". Advanced Materials Research 738 (sierpień 2013): 303–6. http://dx.doi.org/10.4028/www.scientific.net/amr.738.303.
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This paper expounds mechanism of the interact between the vary ionosphere currents and the Earth as a magnetic materials during magnetic storms which create the geoelectromagnetic fields on the Earths surface. Cauchy Distribution model of ionosphere currents above the middle-low latitude area is built for calculation of the fields. In order to predict and evaluate the levels of GIC flowing in technology systems,Complex Image Method (CIM) is applied to calculate geo-electric-magnetic fields on the Earths surface of the middle-low latitude. To test veracity,we compare calculation of the electromagnetic field by Complex Image Method and data measured practically. The good accuracy of CIM here is obtained. i.e,CIM can perform well in Middle-Low latitude area.
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Schram, JB, HL Sorensen, RD Brodeur, AWE Galloway i KR Sutherland. "Abundance, distribution, and feeding ecology of Pyrosoma atlanticum in the Northern California Current". Marine Ecology Progress Series 651 (1.10.2020): 97–110. http://dx.doi.org/10.3354/meps13465.
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During 2016-2018, unprecedented aggregations of the colonial pelagic tunicate Pyrosoma atlanticum were observed in the Northern California Current (NCC). Pyrosomes are common in tropical and sub-tropical ocean waters, but little is known about their abundance, distribution, and trophic ecology in mid-latitude systems. To assess these factors, pyrosomes were collected during cruises in the NCC in May and August 2017. A generalized additive model (GAM) was used to identify relationships between in situ environmental variables (temperature, salinity, fluorescence) and distribution and abundance patterns of pyrosomes in May 2017. Fatty acid (FA) profiles were then characterized as diet indicators, and bulk stable isotope analysis of carbon and nitrogen was used to examine spatial variations in potential food sources and trophic level. The GAM identified sea surface temperature and surface salinity as significant variables related to pyrosome densities. The most abundant FA in the pyrosomes was docosahexanoic acid (22:6ω3), which serves in pelagic systems as a biomarker for dinoflagellates. Common FA biomarkers for bacteria, carnivory, and dinoflagellates differed by latitude, suggesting that pyrosomes have different diets over a broad latitudinal range. The δ15N values of P. atlanticum indicate that pyrosomes may be feeding at a relatively low trophic level compared to other zooplankton groups in this region. Offshore pyrosomes had lower δ13C values than those collected on the shelf, suggesting incorporation of nearshore carbon in pyrosome tissues. Previously documented rapid reproduction and growth of pyrosomes coupled with efficient feeding behavior for common NCC plankters may support their continued presence in this mid-latitude region.
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Zhao, Xudong, Yufei He, Yingyan Wu i Qi Li. "Equivalent Current Systems of Quiet Ionosphere during the 24th Solar Cycle Derived from the Geomagnetic Records in China". Atmosphere 13, nr 11 (5.11.2022): 1843. http://dx.doi.org/10.3390/atmos13111843.
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External and internal equivalent current systems of solar quiet (Sq) were obtained using the spherical harmonic analysis (SHA) method with a “mirror” technique based on geomagnetic records from 46 stations in China during 2008–2019. It is the first attempt to investigate Sq currents using so many stations in the China region for a long period. On the basis of criterion Kp ≤ 2+, geomagnetic vector data were selected to represent monthly Sq variations. After calculating the equivalent currents for each month and each Lloyd season, Sq variation was analyzed in relation to the solar cycle and season. The intensities of both external and internal Sq currents were found consistent with solar activity for the same month or season, while the positions of the current foci were evidently unaffected by solar activity. The intensities of Sq currents also exhibited primary semiannual (annual) variation in the periods of high (low) solar activity. The latitude of the internal current vortex showed evident seasonal variation in Lloyd seasons with high (low) values in the D (J) season, while the external current vortex exhibited no obvious seasonal variation. The strongest correlation between external and internal foci was found in D season, and the internal current foci usually appeared 20–40 min earlier than the external ones. Owing to the complex mechanisms behind Sq variation, some findings will need further analysis in the future.
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Cravatte, S., Elodie Kestenare, Frédéric Marin, Pierre Dutrieux i Eric Firing. "Subthermocline and Intermediate Zonal Currents in the Tropical Pacific Ocean: Paths and Vertical Structure". Journal of Physical Oceanography 47, nr 9 (wrzesień 2017): 2305–24. http://dx.doi.org/10.1175/jpo-d-17-0043.1.
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AbstractThe mean subthermocline and intermediate zonal circulation in the tropical Pacific is investigated using a compilation of shipboard ADCP measurements and absolute geostrophic velocities constructed from a high-resolution 0–2000-m Argo climatology referenced to a 1000-m velocity field derived from Argo float drifts. This reference field is dominated by basinwide alternating zonal jets with a meridional wavelength of about 3°. In regions where the sampling of SADCP data is sufficient, the consistency between the two independent datasets is striking; using the Argo drift reference is crucial to capture the current structures. Two apparently distinct systems of alternating westward and eastward zonal jets are seen in both datasets equatorward of 10°: a series of low-latitude subthermocline currents (LLSCs) below the thermocline, extending from about 200 to 800 m, including the eastward Tsuchiya jets; and a series of low-latitude intermediate currents (LLICs), extending from about 700 to at least 2000 m. These systems seem to merge poleward of 10°. Both series shoal to lighter densities eastward. The subthermocline currents and their associated potential vorticity structures undergo a major shift near 155°W, suggesting some difference in the dynamic regime between the regions west and east of this longitude. Differing behaviors (the LLSCs tend to angle poleward to the east, whereas the LLICs angle slightly equatorward) suggest that these jets may be dynamically distinct, with different forcing mechanisms.
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Kwon, Young-Oh, Michael A. Alexander, Nicholas A. Bond, Claude Frankignoul, Hisashi Nakamura, Bo Qiu i Lu Anne Thompson. "Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review". Journal of Climate 23, nr 12 (15.06.2010): 3249–81. http://dx.doi.org/10.1175/2010jcli3343.1.
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Abstract Ocean–atmosphere interaction over the Northern Hemisphere western boundary current (WBC) regions (i.e., the Gulf Stream, Kuroshio, Oyashio, and their extensions) is reviewed with an emphasis on their role in basin-scale climate variability. SST anomalies exhibit considerable variance on interannual to decadal time scales in these regions. Low-frequency SST variability is primarily driven by basin-scale wind stress curl variability via the oceanic Rossby wave adjustment of the gyre-scale circulation that modulates the latitude and strength of the WBC-related oceanic fronts. Rectification of the variability by mesoscale eddies, reemergence of the anomalies from the preceding winter, and tropical remote forcing also play important roles in driving and maintaining the low-frequency variability in these regions. In the Gulf Stream region, interaction with the deep western boundary current also likely influences the low-frequency variability. Surface heat fluxes damp the low-frequency SST anomalies over the WBC regions; thus, heat fluxes originate with heat anomalies in the ocean and have the potential to drive the overlying atmospheric circulation. While recent observational studies demonstrate a local atmospheric boundary layer response to WBC changes, the latter’s influence on the large-scale atmospheric circulation is still unclear. Nevertheless, heat and moisture fluxes from the WBCs into the atmosphere influence the mean state of the atmospheric circulation, including anchoring the latitude of the storm tracks to the WBCs. Furthermore, many climate models suggest that the large-scale atmospheric response to SST anomalies driven by ocean dynamics in WBC regions can be important in generating decadal climate variability. As a step toward bridging climate model results and observations, the degree of realism of the WBC in current climate model simulations is assessed. Finally, outstanding issues concerning ocean–atmosphere interaction in WBC regions and its impact on climate variability are discussed.
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Giannattasio, Fabio, Alessio Pignalberi, Paola De Michelis, Igino Coco, Michael Pezzopane, Roberta Tozzi i Giuseppe Consolini. "Parallel Electrical Conductivity at Low and Middle Latitudes in the Topside Ionosphere Derived from CSES-01 Measurements". Remote Sensing 14, nr 20 (11.10.2022): 5079. http://dx.doi.org/10.3390/rs14205079.
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The study of electrical currents in the topside ionosphere is of great importance, as it may allow a better understanding of the processes involved in the Sun–Earth interaction and magnetosphere–ionosphere–thermosphere coupling, two crucial aspects debated by the Space Weather scientific community. In this context, investigating the electrical conductivity parallel to the geomagnetic field in the topside ionosphere is of primary importance because: (1) it provides information on the capability of the ionosphere to conduct currents; (2) it relates current density and electric field through Ohm’s law; (3) it can help to quantify the dissipation of currents; (4) it is generally modeled and not locally measured by in situ missions. In this work, we used in situ measurements of electron density and temperature recorded between 2019 and 2021 by the China Seismo-Electromagnetic Satellite (CSES-01) flying with an orbital inclination of 97.4∘ and at an altitude of about 500 km to compute the parallel electrical conductivity in the topside ionosphere at low and middle latitudes at the two fixed local times (LT) characterizing the CSES-01 mission: around 02 and 14 LT. The results, which are discussed in light of previous literature, highlight the dependence of conductivity on latitude and longitude and are compared with those obtained using values both measured by the Swarm B satellite (flying at a similar altitude) and modeled by the International Reference Ionosphere in the same time period. In particular, we found a diurnal variation in parallel electrical conductivity, with a slight hemispheric asymmetry. Daytime features are compatible with Sq and equatorial electrojet current systems, containing “anomalous” low values of conductivity in correspondence with the South Atlantic region that could be physical in nature.
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Zawawi, Anis Adiba, Nur Fadilah Ab Aziz, Mohd Zainal Abidin Ab Kadir, Halimatun Hashim i Zmnako Mohammed. "Evaluation of Geomagnetic Induced Current on 275 kV Power Transformer for a Reliable and Sustainable Power System Operation in Malaysia". Sustainability 12, nr 21 (6.11.2020): 9225. http://dx.doi.org/10.3390/su12219225.
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Geomagnetic induced current (GIC) occurs as a direct consequence of abnormal space weather which starts from the sun and may flow into a power system network through neutral grounding connections. The flow of GIC through grounded neutral power transformer has been a major concern to researchers since it can potentially affect power system equipment. Most of the previous research was focused on high and mid latitude countries only. However, it has been proven that the GIC is not only limited to high and mid latitudes, but also extends to power systems at lower geographic latitudes. This paper aims to investigate the impacts of GIC on selected 275 kV subpower system networks in Peninsular Malaysia, which is among the low latitude countries. Its impact in terms of magnitude and duration is also assessed together with the use of neutral earthing resistor (NER) as a potential blocking component to reduce the impact of GIC on the Malaysian power system network. Results demonstrated that when GIC exists in the power system, power transformers undergo half-cycle saturation that may lead to a reactive power loss and power system voltage instability. In this case, the power transformer can only withstand a maximum GIC value of 7 A, and beyond this value, if prolonged, may lead to voltage instability. It turned out that GIC magnitude had more impact compared to duration. However, long duration with high magnitude of GIC is the most hazardous to power transformers and could potentially cause major faults in the power system network. As part of mitigation, NER with a value of 315.10 Ω can be used to limit the GIC current flow and thus provide protection to the power system network. Clearly, the issue of GIC undoubtedly affects the reliability, security and sustainability of power system operation, especially networks with highly critical load and capacity and, therefore, thorough studies are required to assess and mitigate this issue.
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Alberti, Tommaso, Davide Faranda, Giuseppe Consolini, Paola De Michelis, Reik V. Donner i Vincenzo Carbone. "Concurrent Effects between Geomagnetic Storms and Magnetospheric Substorms". Universe 8, nr 4 (6.04.2022): 226. http://dx.doi.org/10.3390/universe8040226.
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An accurate understanding of dissimilarities in geomagnetic variability between quiet and disturbed periods has the potential to vastly improve space weather diagnosis. In this work, we exploit some recently developed methods of dynamical system theory to provide new insights and conceptual ideas in space weather science. In particular, we study the co-variation and recurrence statistics of two geomagnetic indices, SYM-H and AL, that measure the intensity of the globally symmetric component of the equatorial electrojet and that of the westward auroral electrojet, respectively. We find that the number of active degrees of freedom, required to describe the phase space dynamics of both indices, depends on the geomagnetic activity level. When the magnetospheric substorm activity, as monitored by the AL index, increases, the active number of degrees of freedom increases at high latitudes above the dimension obtained through classical time delay embedding methods. Conversely, a reduced number of degrees of freedom is observed during geomagnetic storms at low latitude by analysing the SYM-H index. By investigating time-dependent relations between both indices we find that a significant amount of information is shared between high and low latitude current systems originating from coupling mechanisms within the magnetosphere–ionosphere system as the result of a complex interplay between processes and phenomena of internal origin activated by the triggering of external source processes. Our observations support the idea that the near-Earth electromagnetic environment is a complex system far from an equilibrium.
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Nair, Deepukumar M., James Parisi, K. M. Nair, Mark McCombs, Michael Smith, Elizabeth Hughes, Ken Souders i in. "Introducing DuPont™ GreenTape™ 9K5 Low Dielectric Constant, Low Temperature Co-Fired Ceramic (LTCC) Tape System". International Symposium on Microelectronics 2011, nr 1 (1.01.2011): 000544–52. http://dx.doi.org/10.4071/isom-2011-wa3-paper4.
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Low Temperature Co-fired Ceramic (LTCC) material systems have been successfully used in microwave and millimeter wave systems for several years. LTCC has very low dielectric loss, high reliability due to inherent hermeticity; high interconnect density, multilayer processing capability leading to true 3D packaging, and better cost-performance balance. While the medium range dielectric constants (7.00 – 8.00) offered by current tape systems have advantages, it is generally difficult to realize high speed systems and efficient antennas on LTCC, especially at millimeter wave frequencies. The difficulty arises from the reduced signal propagation velocity in high-speed applications, and lower radiation efficiency for antennas, both due to higher dielectric constant. To enable and extend applications of LTCC technology to these subsystems, DuPont has developed a new low dielectric constant LTCC system – DuPont™ GreenTape™ 9K5 - which has a dielectric constant of 5.80 (at 10 GHz) that is compatible with the commercial DuPont™ GreenTape™ 9K7 LTCC System. This is achieved without compromising excellent microwave loss properties of the 9KX GreenTape™ platform. These materials systems enable high-speed, high reliability applications while also realizing efficient antennas on LTCC. This paper presents initial characterization of the new DuPont™ GreenTape™ 9K5 LTCC system consisting of low K dielectric tape, gold and silver conductors to evaluate the effects of chemistry, processing conditions, processing latitude, microstructure, and microwave performance. Test coupons with various transmission and resonating structures are designed, fabricated, and tested for the evaluation of transmission losses and dielectric properties. Stability of the material system over multiple re-fire steps is also examined
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Kappenman, John G. "Storm sudden commencement events and the associated geomagnetically induced current risks to ground-based systems at low-latitude and midlatitude locations". Space Weather 1, nr 3 (grudzień 2003): n/a. http://dx.doi.org/10.1029/2003sw000009.
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Dhondt, Steven, Frank Delano Pot i Karolus O. Kraan. "The importance of organizational level decision latitude for well-being and organizational commitment". Team Performance Management 20, nr 7/8 (7.10.2014): 307–27. http://dx.doi.org/10.1108/tpm-03-2014-0025.
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Purpose – This paper aims to focus on participation in the workplace and examines the relative importance of different dimensions of job control in relation to subjective well-being and organizational commitment. These dimensions are job autonomy (within a given job), functional support (from supervisor and colleagues) and organizational level decision latitude (shop-floor consultancy on process improvements, division of labor, workmates, targets, etc.). Interaction with work intensity is looked at as well. Design/methodology/approach – Measurements and data were taken from the European Working Conditions Survey, 2010. The paper focusses on salaried employees only. The sample was further limited to employees in workplaces consisting of at least 50 workers. There are 2,048 employees in the final sample, from Denmark, Ireland, The Netherlands, Finland, Sweden and the UK. In this paper, the focus is not on differences between countries, and adding more countries would have introduced too many country characteristics as intermediate variables. Findings – In the regression analyses, functional support and organizational level decision latitude showed stronger relations with the outcome variables than job autonomy. There was no relation between work intensity and the outcome variables. Two-way interactions were found for job autonomy and organizational level decision latitude on subjective well-being and for functional support and organizational level decision latitude on organizational commitment. A three-way interaction, of all job control variables combined, was found on organizational commitment, with the presence of all types of job control showing the highest organizational commitment level. No such three-way interaction was found for subjective well-being. There was an indication for a two-way interaction of work intensity and functional support, as well as an indication for a two-way interaction of work intensity and organizational level decision latitude on subjective well-being: high work intensity and low functional support or low organizational level decision latitude seemed to associate with low well-being. No interaction was found for any dimension of job control being high and high work intensity. Research limitations/implications – Although this study has all the limitations of a cross-sectional survey, the results are more or less in accordance with existing theories. This indicates that organizational level decision latitude matters. Differentiation of job control dimensions in research models is recommended, and so is workplace innovation for healthy and productive jobs. Originality/value – Most theoretical models for empirical research are limited to control at task level (e.g. the Job Demand-Control-Support model of Karasek and Theorell. The paper aims at nuancing and extending current job control models by distinguishing three dimensions/levels of job control, referring to sociotechnical systems design theory (De Sitter) and action regulation theory (Hacker) and reciprocity (Akerlof). The policy relevance regards the consequences for work and organization design.
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Milan, S. E., A. Grocott, C. Forsyth, S. M. Imber, P. D. Boakes i B. Hubert. "A superposed epoch analysis of auroral evolution during substorm growth, onset and recovery: open magnetic flux control of substorm intensity". Annales Geophysicae 27, nr 2 (11.02.2009): 659–68. http://dx.doi.org/10.5194/angeo-27-659-2009.
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Abstract. We perform two superposed epoch analyses of the auroral evolution during substorms using the FUV instrument on the Imager for Magnetopause-to-Aurora Global Explorer (IMAGE) spacecraft. The larger of the two studies includes nearly 2000 substorms. We subdivide the substorms by onset latitude, a measure of the open magnetic flux in the magnetosphere, and determine average auroral images before and after substorm onset, for both electron and proton aurora. Our results indicate that substorms are more intense in terms of auroral brightness when the open flux content of the magnetosphere is larger, and that magnetic flux closure is more significant. The increase in auroral brightness at onset is larger for electrons than protons. We also show that there is a dawn-dusk offset in the location of the electron and proton aurora that mirrors the relative locations of the region 1 and region 2 current systems. Superposed epoch analyses of the solar wind, interplanetary magnetic field, and geomagnetic indices for the substorms under study indicate that dayside reconnection is expected to occur at a faster rate prior to low latitude onsets, but also that the ring current is enhanced for these events.
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Farah, Ashraf. "Accuracy Assessment Study of UNB3m Neutral Atmosphere Model for Global Tropospheric Delay Mitigation". Artificial Satellites 50, nr 4 (1.12.2015): 201–15. http://dx.doi.org/10.1515/arsa-2015-0016.
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Abstract Tropospheric delay is the second major source of error after the ionospheric delay for satellite navigation systems. The transmitted signal could face a delay caused by the troposphere of over 2m at zenith and 20m at lower satellite elevation angles of 10 degrees and below. Positioning errors of 10m or greater can result from the inaccurate mitigation of the tropospheric delay. Many techniques are available for tropospheric delay mitigation consisting of surface meteorological models and global empirical models. Surface meteorological models need surface meteorological data to give high accuracy mitigation while the global empirical models need not. Several hybrid neutral atmosphere delay models have been developed by (University of New Brunswick, Canada) UNB researchers over the past decade or so. The most widely applicable current version is UNB3m, which uses the Saastamoinen zenith delays, Niell mapping functions, and a look-up table with annual mean and amplitude for temperature, pressure, and water vapour pressure varying with respect to latitude and height. This paper presents an assessment study of the behaviour of the UNB3m model compared with highly accurate IGS-tropospheric estimation for three different (latitude/height) IGS stations. The study was performed over four nonconsecutive weeks on different seasons over one year (October 2014 to July 2015). It can be concluded that using UNB3m model gives tropospheric delay correction accuracy of 0.050m in average for low latitude regions in all seasons. The model's accuracy is about 0.075m for medium latitude regions, while its highest accuracy is about 0.014m for high latitude regions.
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Joo, Byoung-Soo, Jung-Wook Woo, Jeong-Hun Lee, Injoo Jeong, Jungmin Ha, Se-Hee Lee i Soobae Kim. "Assessment of the Impact of Geomagnetic Disturbances on Korean Electric Power Systems". Energies 11, nr 7 (23.07.2018): 1920. http://dx.doi.org/10.3390/en11071920.
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Geomagnetic disturbances have the potential to impact the operation of electric power systems, and thus the assessment of their impacts is required as the first step for secure power system operations. While the effects of the disturbances have been observed primarily at higher latitudes, geomagnetic problems are also observed at mid and low latitude locations, in particular including neighboring countries to Korea such as China and Japan. This paper deals with the assessment of impact of geomagnetic disturbances on Korean electric power systems. For the assessment, the geoelectric fields induced by the geomagnetic disturbances are calculated using geomagnetic data measured over the past 20 years in order to quantify the strength of geomagnetic events in Korea. Then, the geomagnetic currents on the grid driven by the geoelectric fields are computed. Finally, the increased reactive power absorption in high voltage transformers is analyzed and accordingly the change of system voltage magnitudes is identified to evaluate whether the system maintains the voltage stability. The systematic study concludes that during a strong geomagnetic disturbance, the Korean electric power system satisfies the associated standards in the U.S. and maintains system stability.
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Feldstein, Y. I., L. I. Gromova, J. Woch, I. Sandahl, L. Blomberg, G. Marklund i C. I. Meng. "Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents". Annales Geophysicae 19, nr 5 (31.05.2001): 495–519. http://dx.doi.org/10.5194/angeo-19-495-2001.
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Abstract. Abstract. Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ) of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating particles have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic, with the peak near 90°. The next part is the Auroral Oval (AO), a structured electron regime which closely resembles the poleward portion of the night-side auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are pre-dominantly isotropic. In some cases, this plasma regime may be absent in the pre-noon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL) regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995) and the conceptual model by Alexeev et al. (1996) are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL), which is located in the outer radiation belt region; the zone of structured electrons and isotropic ion precipitation (AO) is mapped to the dawn periphery of the Central Plasma Sheet (CPS); the soft small scale structured precipitation (SSSL) is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL). In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA), are observed. The ion energies decrease with increasing latitude. The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM). In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1) and flow out at the AO or DAZ latitudes (Region 2). In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2). In the SSSL, there is anti-sunward convection; in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By ). It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996), for the nightside sector of the auroral oval to the dawn sector.Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; plasma convection)
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Kakad, Bharati, Amar Kakad, Durbha Sai Ramesh i Gurbax S. Lakhina. "Diminishing activity of recent solar cycles (22–24) and their impact on geospace". Journal of Space Weather and Space Climate 9 (2019): A1. http://dx.doi.org/10.1051/swsc/2018048.
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This study examines the variation of different energies linked with the Sun and the Earth’s magnetosphere-ionosphere systems for solar cycles (SCs) 22–24 for which the gradual decrease in the solar activity is noticed. Firstly, we investigated the variation of solar magnetic energy density (SMED) for SCs 21–24 and its relation to the solar activity. We observed distinct double peak structures in SMED for the past four SCs, 21–24. This feature is consistent with noticeable asymmetry in their two peaks. For SCs 22–24 a significant decrease is observed in the integrated SMED of each SC. This reduction is 37% from SCs 22 to 23 and 51% from SCs 23 to 24, which indicates substantial weakening of Sun’s magnetic field for SC 24. Also, the magnetic, kinetic, and thermal energy densities at the Earth’s bow-shock nose are found to be considerably low for the SC 24. We examined the solar wind Alfven speed, magnetosonic Mach number, solar wind-magnetosphere energy coupling parameter (ε), and the Chapman-Ferraro magnetopause distance (LCF) for the SCs 22–24. The estimated maximum stand-off magnetopause distance is larger for SC 24 (LCF ≤ 10.6 RE) as compared to SC 23 (LCF ≤ 10.2 RE) and SC 22 (LCF ≤ 9.8 RE). The solar wind Alfven speeds during SCs 22 and 23 are in the same range and do not exceed ≈73 km/s whereas, it is below 57 km/s for SC 24. A lower bound of solar wind magnetosonic Mach number for SC 24 is larger (M ≥ 6.9) as compared to SC 22 (M ≥ 5.9) and SC 23 (M ≥ 6). We noticed weakening in the energy coupling parameter for SC 24, which resulted in substantial (15%–38%) decrease in average strength of high latitude ionospheric (AE), low latitude magnetospheric (Dst) and equatorial ionospheric (EEJ) current systems in comparison with SC 23. Subsequently, a reduction of ≈30% is manifested in the high latitude Joule heating for SC 24. Overall this study indicates the significant step down in various energies at Sun, Earth’s bow-shock, and near Earth environment for current SC 24, which will have important implication on our Earth’s atmosphere-ionosphere-magnetosphere system.
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Vankadara, Ram Kumar, Sampad Kumar Panda, Christine Amory-Mazaudier, Rolland Fleury, Venkata Ratnam Devanaboyina, Tarun Kumar Pant, Punyawi Jamjareegulgarn, Mohd Anul Haq, Daniel Okoh i Gopi Krishna Seemala. "Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017". Remote Sensing 14, nr 3 (29.01.2022): 652. http://dx.doi.org/10.3390/rs14030652.
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Scintillation due to ionospheric plasma irregularities remains a challenging task for the space science community as it can severely threaten the dynamic systems relying on space-based navigation services. In the present paper, we probe the ionospheric current and plasma irregularity characteristics from a latitudinal arrangement of magnetometers and Global Navigation Satellite System (GNSS) stations from the equator to the far low latitude location over the Indian longitudes, during the severe space weather events of 6–10 September 2017 that are associated with the strongest and consecutive solar flares in the 24th solar cycle. The night-time influence of partial ring current signatures in ASYH and the daytime influence of the disturbances in the ionospheric E region electric currents (Diono) are highlighted during the event. The total electron content (TEC) from the latitudinal GNSS observables indicate a perturbed equatorial ionization anomaly (EIA) condition on 7 September, due to a sequence of M-class solar flares and associated prompt penetration electric fields (PPEFs), whereas the suppressed EIA on 8 September with an inverted equatorial electrojet (EEJ) suggests the driving disturbance dynamo electric current (Ddyn) corresponding to disturbance dynamo electric fields (DDEFs) penetration in the E region and additional contributions from the plausible storm-time compositional changes (O/N2) in the F-region. The concurrent analysis of the Diono and EEJ strengths help in identifying the pre-reversal effect (PRE) condition to seed the development of equatorial plasma bubbles (EPBs) during the local evening sector on the storm day. The severity of ionospheric irregularities at different latitudes is revealed from the occurrence rate of the rate of change of TEC index (ROTI) variations. Further, the investigations of the hourly maximum absolute error (MAE) and root mean square error (RMSE) of ROTI from the reference quiet days’ levels and the timestamps of ROTI peak magnitudes substantiate the severity, latitudinal time lag in the peak of irregularity, and poleward expansion of EPBs and associated scintillations. The key findings from this study strengthen the understanding of evolution and the drifting characteristics of plasma irregularities over the Indian low latitudes.
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Belehaki, A., I. Tsagouri i H. Mavromichalaki. "Study of the longitudinal expansion velocity of the substorm current wedge". Annales Geophysicae 16, nr 11 (30.11.1998): 1423–33. http://dx.doi.org/10.1007/s00585-998-1423-9.
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Abstract. In this work we examine simultaneous observations from the two geosynchronous satellites GOES-5 and GOES-6 located at 282°E and 265°E respectively, and from middle and low latitude ground observatories located within 250°E and 294°E geographic longitude, during isolated substorms of moderate activity. The spatial distribution of our observation points allows us to make a detailed study of the azimuthal expansion of the substorm current wedge. The data analysis shows evidence that the substorm initiation and development mechanism include the cross-tail current diversion/ disruption, the substorm current wedge formation and the azimuthal expansion of the inner plasma sheet. The triggering mechanism is initially confined in a longitudinally narrow sector, estimated to be less than 15° and located very close to local midnight to the east or to the west. The current disruption region expands both eastward and westward in the magnetotail, so that the location of major field-aligned currents flowing into the ionosphere shifts successively eastward, and the location of the currents flowing out of the ionosphere shifts successively westward. Evidence was found that the perturbation travels toward the west with velocities greater than those expanding the wedge eastward. The drastic decrease of the velocity with the azimuthal distance from the location of the disturbance initiation, i.e., the onset sector, indicates that the energy release is a very localized phenomenon. Finally, the transient D perturbation observed by the geosynchronous satellites suggests that the field-aligned currents forming the wedge have a longitudunally limited extent.Key words. Magnetospheric physics (current systems; magnetosphere-ionosphere interactions)
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Manju, G., T. K. Pant, C. V. Devasia, S. Ravindran i R. Sridharan. "Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study". Annales Geophysicae 27, nr 10 (9.10.2009): 3853–60. http://dx.doi.org/10.5194/angeo-27-3853-2009.
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Abstract. The electrodynamic effects on the low-mid latitude ionospheric region have been investigated using GPS (global positioning system) data, ionosonde data and ΔH values, during the very large solar flare (X17.2/4B) of 28 October 2003. The results bring out the flare induced unusual behaviour of the equatorial ionosphere on this day just prior to sunset. The important observations are i) Large and prolonged Ne enhancements observed from ionosonde data just after the flare-related peak enhancement in EUV flux. The observed enhancement in Ne is due to the increase in ionization production due to the enhanced EUV flux and the persistence of the enhancement is probably due to the prompt penetration related upliftment of the F layer (just prior to the flare peak phase) to higher altitudes, where recombination rates are lower. ii) A significant enhancement in total electron content (TEC) (~10 TEC units) at regions around the Equatorial Ionization Anomaly (EIA) crest region (Ahmedabad) during the flare in association with the flare related EUV flux enhancement. iii) Similar enhancements seen at stations of Jodhpur and Delhi in the mid latitude sector. iv)The flare related flux enhancements in different longitude sectors in the equatorial electrojet region have been shown to produce positive and negative variations in electrojet strength indicating the presence of current systems having positive and negative polarities in different longitude sectors. Thus the flare effect reveals the longitudinal variation of the counter electrojet events in the Equatorial Electrojet (EEJ) region.
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Krauklis, I., A. N. Fazakerley, C. J. Owen, P. J. Carter, M. W. Dunlop, A. J. Coates, S. Szita i in. "Preliminary two-point observations of the mid-altitude cusp by Cluster PEACE and FGM". Annales Geophysicae 19, nr 10/12 (30.09.2001): 1579–87. http://dx.doi.org/10.5194/angeo-19-1579-2001.
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Abstract. On 1 October 2000, Cluster spacecraft Samba (Cluster 3) and Tango (Cluster 4) made an outbound crossing of the northern mid-altitude (4.7 RE) cusp region, moving roughly parallel to the noon meridian. We present preliminary observations from this interval made by the PEACE and FGM instruments. The interplanetary magnetic field at the magnetopause is estimated to have turned south at the time of our observations, based on ACE data as well as a rough estimate of the time taken for the solar wind to travel between ACE and the magnetopause. Cluster 3 encountered the low-latitude boundary layer (LLBL) between 12:20:30 to 12:26:00 UT, and the cusp region between 12:26:00 and 12:32:30 UT. Cluster 4 encountered the LLBL between 12:22:00 to 12:29:00 UT, and the cusp region between 12:29:00 and 12:38:00 UT. During the interval between the two spacecraft passages through these regions, the open/closed field line boundary was observed to move equatorward by 0.33° invariant latitude, while the latitudinal extent of the cusp region increased by 0.5°. Both of these observations are consistent with the ongoing reconnection at the sub-solar magnetopause. The magnetic field data indicate that Cluster encountered four field-aligned longitudinally extended current sheets. The most equatorward of these is consistent with the location of a Region 1 current sheet. Two current sheets were observed in the vicinity of the cusp region, though neither of these were thin current sheets. The fourth current sheet was observed in the mantle region and was largely unaffected by the latitudinal expansion of the cusp region.Key words. Magnetospheric physics (current systems; energetic particles, precipitating; magnetopause, cusp and boundary layers)
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Sandholt, P. E., i C. J. Farrugia. "Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect". Annales Geophysicae 30, nr 5 (9.05.2012): 817–30. http://dx.doi.org/10.5194/angeo-30-817-2012.
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Abstract. The traditional explanation of the polar cap magnetic deflections, referred to as the Svalgaard-Mansurov effect, is in terms of currents associated with ionospheric flow resulting from the release of magnetic tension on newly open magnetic field lines. In this study, we aim at an updated description of the sources of the Svalgaard-Mansurov effect based on recent observations of configurations of plasma flow channels, Birkeland current systems and aurorae in the magnetosphere-ionosphere system. Central to our description is the distinction between two different flow channels (FC 1 and FC 2) corresponding to two consecutive stages in the evolution of open field lines in Dungey cell convection, with FC 1 on newly open, and FC 2 on old open, field lines. Flow channel FC 1 is the result of ionospheric Pedersen current closure of Birkeland currents flowing along newly open field lines. During intervals of nonzero interplanetary magnetic field By component FC 1 is observed on either side of noon and it is accompanied by poleward moving auroral forms (PMAFs/prenoon and PMAFs/postnoon). In such cases the next convection stage, in the form of flow channel FC 2 on the periphery of the polar cap, is particularly important for establishing an IMF By-related convection asymmetry along the dawn-dusk meridian, which is a central element causing the Svalgaard-Mansurov effect. FC 2 flows are excited by the ionospheric Pedersen current closure of the northernmost pair of Birkeland currents in the four-sheet current system, which is coupled to the tail magnetopause and flank low-latitude boundary layer. This study is based on a review of recent statistical and event studies of central parameters relating to the magnetosphere-ionosphere current systems mentioned above. Temporal-spatial structure in the current systems is obtained by ground-satellite conjunction studies. On this point we emphasize the important information derived from the continuous ground monitoring of the dynamical behaviour of aurora and plasma convection during intervals of well-organised solar wind plasma and magnetic field conditions in interplanetary coronal mass ejections (ICMEs) during their Earth passage.
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Schmitter, E. D. "Remote auroral activity detection and modeling using low frequency transmitter signal reception at a midlatitude site". Annales Geophysicae 28, nr 9 (30.09.2010): 1807–11. http://dx.doi.org/10.5194/angeo-28-1807-2010.
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Abstract. The low frequency propagation conditions along the path from Iceland to Germany (52° N 8° E) using the NRK/TFK 37.5 kHz transmitter (63.9° N 22.5° W) prove as an easy to monitor and reliable proxy for north auroral activity. Signal processing using wavelet decomposition allows for quantitative activity level estimations. Calibration is based upon NOAA POES auroral activity data. Using an auroral oval model for the local intensity distribution of solar energetic particle precipitation and a wave propagation model ionospheric D-layer height decreases along the path can be derived. This in turn gives a hint to the low latitude extension and intensity of the auroral electrojet currents that can be responsible for communication and power systems failures.
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Chamberlin, Jessica, Camryn Soehnlein, Jason Evans i Benjamin Tanner. "A 1900 Year Sediment Record Suggests Recent Establishment of Black Mangrove (Avicennia Germinans) Stands within a Salt Marsh in St. Augustine, Florida, USA". Quaternary 5, nr 1 (1.01.2022): 2. http://dx.doi.org/10.3390/quat5010002.
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Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change.
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Hatton, Jade E., Katharine R. Hendry, Jonathan R. Hawkings, Jemma L. Wadham, Sophie Opfergelt, Tyler J. Kohler, Jacob C. Yde, Marek Stibal i Jakub D. Žárský. "Silicon isotopes in Arctic and sub-Arctic glacial meltwaters: the role of subglacial weathering in the silicon cycle". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, nr 2228 (sierpień 2019): 20190098. http://dx.doi.org/10.1098/rspa.2019.0098.
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Glacial environments play an important role in high-latitude marine nutrient cycling, potentially contributing significant fluxes of silicon (Si) to the polar oceans, either as dissolved silicon (DSi) or as dissolvable amorphous silica (ASi). Silicon is a key nutrient in promoting marine primary productivity, contributing to atmospheric CO 2 removal. We present the current understanding of Si cycling in glacial systems, focusing on the Si isotope (δ 30 Si) composition of glacial meltwaters. We combine existing glacial δ 30 Si data with new measurements from 20 sub-Arctic glaciers, showing that glacial meltwaters consistently export isotopically light DSi compared with non-glacial rivers (+0.16‰ versus +1.38‰). Glacial δ 30 Si ASi composition ranges from −0.05‰ to −0.86‰ but exhibits low seasonal variability. Silicon fluxes and δ 30 Si composition from glacial systems are not commonly included in global Si budgets and isotopic mass balance calculations at present. We discuss outstanding questions, including the formation mechanism of ASi and the export of glacial nutrients from fjords. Finally, we provide a contextual framework for the recent advances in our understanding of subglacial Si cycling and highlight critical research avenues for assessing potential future changes in these environments.
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Mitchell, Andrew D., i Theodore Samlidis. "Cloud services and government digital sovereignty in Australia and beyond". International Journal of Law and Information Technology 29, nr 4 (1.12.2021): 364–94. http://dx.doi.org/10.1093/ijlit/eaac003.
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Abstract The Australian government has expressed concerns about various ‘data challenges’ confronting the public sector. Similar concerns are reverberating throughout the globe. Other governments continue to voice and act upon their own apprehensions about the threats posed to public and private society by attenuations to their nations’ ‘digital sovereignty’. This article critically examines the Australian government’s potential justifications, particularly under international trade law, for introducing digital sovereignty policies explicitly targeted at protecting government cyber systems and government data. We explore the risks and vulnerabilities of hosting government data offshore or with foreign cloud providers onshore. We find that Australia has sufficient latitude under its existing trade commitments, and within its current procurement framework, to introduce legitimate and proportionate digital sovereignty measures for the public sector.
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Shiau, L. J., S. C. Clemens, M. T. Chen, M. Yamamoto i Y. Yokoyama. "SST phases in the open-ocean and margins of the tropical Pacific; implication on tropical climate dynamics". Climate of the Past Discussions 10, nr 2 (28.04.2014): 1857–99. http://dx.doi.org/10.5194/cpd-10-1857-2014.
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Abstract. The tropical Pacific exerts a major effect on the global climate system and might have driven large extra-tropical climate change. We present a 320 kyr high resolution UK'37-sea surface temperature (SST) record from core MD052928 (11°17.26' S, 148°51.60' E, water depth 2250 m) located off southeastern Papua New Guinea (PNG), in the western tropical Pacific. The age model of the core is based on AMS 14C dating of planktic foraminifers and correlation of benthic to the LR04 stack. The UK'37-SST ranges from 26.5 to 29 °C, showing glacial–interglacial and millennial variations. We assess the phase of the MD052928 UK'37-SST as part of a synthesis of five other SST records from the tropical Pacific at the precession, obliquity, and eccentricity bands. The SST records can be separated into two groups when considering SST phase relative to changes in orbital forcing, ice volume and greenhouse gases (GHGs). SST maxima at open-ocean sites within primary equatorial current systems occur between obliquity maxima and methane (CH4) maxima but early relative to ice volume minima and CO2 maxima at the obliquity band. In contrast, SST maxima at continental margin sites change are in phase with ice minima and CO2 maxima, likely influenced by the slow response of continental ice sheets and GHGs. At the precession band, the early group located on the Warm Pool area indicates a direct influenced by the local insolation, and with the similar phase progress as the obliquity band. These results indicate that the decreased high-low latitudes insolation gradient and increasing low latitude local insolation resulting in tropical Pacific SST rise. Higher SST would supply more moisture resulting in increased CH4 in the tropical wetlands. This promotes increasing CO2 and deglaciation leading to increase continental and continental margin surface temperatures.
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Mozzoni, D. T., M. Mandea i J. Cain. "Magnetic perturbations seen by CHAMP and evaluated using the TIE-GCM". Annales Geophysicae 25, nr 7 (30.07.2007): 1543–54. http://dx.doi.org/10.5194/angeo-25-1543-2007.
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Abstract. The Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) is a self-consistent, global, atmospheric model that can be used to estimate magnetic perturbations at satellite altitude. These computed perturbations can then be compared with the magnetic vector data provided by low-earth orbiting satellites. In this initial study, the quietest day of each month from 2001–2005 was selected for comparison. CHAMP magnetic vector residuals were computed for these intervals using the CHAOS model to remove core and crustal geomagnetic contributions. Under various input parameters, the TIE-GCM predictions were compared with the CHAMP residuals on an orbit by orbit basis. Initial results demonstrate a reasonable agreement between the TIE-GCM estimates and the CHAMP residuals in non-polar, dayside regions (±50° magnetic latitude) where both are able to resolve the Equatorial Electro-Jet (EEJ) and solar quiet (Sq) current systems. Although no clear component or temporal correlation was discerned, evidence showing the decrease in residual comparisons presents the possibility of using the TIE-GCM to pre-process geomagnetic data for main field modeling purposes.
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Nichols, J. D., i S. W. H. Cowley. "Magnetosphere-ionosphere coupling currents in Jupiter’s middle magnetosphere: dependence on the effective ionospheric Pedersen conductivity and iogenic plasma mass outflow rate". Annales Geophysicae 21, nr 7 (31.07.2003): 1419–41. http://dx.doi.org/10.5194/angeo-21-1419-2003.
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Abstract. The amplitude and spatial distribution of the coupling currents that flow between Jupiter’s ionosphere and middle magnetosphere, which enforce partial corotation on outward-flowing iogenic plasma, depend on the values of the effective Pedersen conductivity of the jovian ionosphere and the mass outflow rate of iogenic plasma. The values of these parameters are, however, very uncertain. Here we determine how the solutions for the plasma angular velocity and current components depend on these parameters over wide ranges. We consider two models of the poloidal magnetospheric magnetic field, namely the planetary dipole alone, and an empirical current sheet field based on Voyager data. Following work by Hill (2001), we obtain a complete normalized analytic solution for the dipole field, which shows in compact form how the plasma angular velocity and current components scale in space and in amplitude with the system parameters in this case. We then obtain an approximate analytic solution in similar form for a current sheet field in which the equatorial field strength varies with radial distance as a power law. A key feature of the model is that the current sheet field lines map to a narrow latitudinal strip in the ionosphere, at ≈ 15° co-latitude. The approximate current sheet solutions are compared with the results of numerical integrations using the full field model, for which a power law applies beyond ≈ 20 RJ, and are found to agree very well within their regime of applicability. A major distinction between the solutions for the dipole field and the current sheet concerns the behaviour of the field-aligned current. In the dipole model the direction of the current reverses at moderate equatorial distances, and the current system wholly closes if the model is extended to infinity in the equatorial plane and to the pole in the ionosphere. In the approximate current sheet model, however, the field-aligned current is unidirectional, flowing consistently from the ionosphere to the current sheet for the sense of the jovian magnetic field. Current closure must then occur at higher latitudes, on field lines outside the region described by the model. The amplitudes of the currents in the two models are found to scale with the system parameters in similar ways, though the scaling is with a somewhat higher power of the conductivity for the current sheet model than for the dipole, and with a somewhat lower power of the plasma mass outflow rate. The absolute values of the currents are also higher for the current sheet model than for the dipole for given parameters, by factors of approx 4 for the field-perpendicular current intensities, ≈ 10 for the total current flowing in the circuit, and ≈ 25 for the field-aligned current densities, factors which do not vary greatly with the system parameters. These results thus confirm that the conclusions drawn previously from a small number of numerical integrations using spot values of the system parameters are generally valid over wide ranges of the parameter values.Key words. Magnetospheric physics (current systems, magnetosphere-ionosphere interactions, planetary magnetospheres)
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Liu, Congliang, Yueqiang Sun, Weihua Bai, Qifei Du, Wei Li, Xi Wang i Peixian Li. "Effect of Multiple GNSS Integration on the Number and Spatiotemporal Coverage of Radio Occultation Events". Atmosphere 13, nr 5 (20.04.2022): 654. http://dx.doi.org/10.3390/atmos13050654.
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The development of global navigation satellite systems (GNSSs) and multi-system compatible radio occultation (RO) techniques provides favorable conditions and opportunities for increasing the number of occultation events and improving their spatiotemporal coverage. The performance of the multiple GNSS RO event number, spatiotemporal coverage, and uniformity need assessments by robust and functional approaches. Firstly, a simulation system of RO events, which took the orbit perturbations into account, was established, and the concepts of global coverage fraction and uniformity of RO events were defined. Secondly, numerical experiments were designed to analyze the GNSS RO performances of a single-receiving satellite and satellite constellations under the condition of using current multiple GNSSs as transmitting satellite systems, in which the Earth was divided into 400 × 400 km2 grids. Finally, the number, timeliness, global coverage fraction, and uniformity of GNSS RO events for a single-receiving satellite and receiving satellite constellations were numerically calculated and analyzed. The results showed that ➀ multiple GNSS integration improved the number of GNSS RO events and their global coverage for a single polar-orbit satellite significantly, e.g., the 24 h multiple GNSS RO event number was about 7.8 times that of the single GNSS system, BeiDou navigation satellite system-3, while the corresponding 24 h global coverage fraction increased nearly 3 times. ➁ In the multiple GNSS integration scenario, the constellation composed of 12 polar-orbit low-Earth-orbit satellites achieved 100% RO event global coverage fraction within 24 h, of which the RO detection capability was comparable to the 100 Spire weather satellites and global positioning system (GPS) RO system. ➂ More GNSS RO events of the polar-orbit constellations were distributed in the middle- and high-latitude zones. Therefore, multiple GNSS integration could increase the RO event number and global coverage significantly to benefit the global climate monitoring and global numerical weather prediction, and the polar-orbit constellations were more favorable to atmospheric detection in middle- and high-latitude regions.
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Pinault, Jean-Louis. "Morlet Cross-Wavelet Analysis of Climatic State Variables Expressed as a Function of Latitude, Longitude, and Time: New Light on Extreme Events". Mathematical and Computational Applications 27, nr 3 (4.06.2022): 50. http://dx.doi.org/10.3390/mca27030050.
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This study aims to advance our knowledge in the genesis of extreme climatic events with the dual aim of improving forecasting methods while clarifying the role played by anthropogenic warming. Wavelet analysis is used to highlight the role of coherent Sea Surface Temperature (SST) anomalies produced from short-period oceanic Rossby waves resonantly forced, with two case studies: a Marine Heatwave (MHW) that occurred in the northwestern Pacific with a strong climatic impact in Japan, and an extreme flood event that occurred in Germany. Ocean–atmosphere interactions are evidenced by decomposing state variables into period bands within the cross-wavelet power spectra, namely SST, Sea Surface Height (SSH), and the zonal and meridional modulated geostrophic currents as well as precipitation height, i.e., the thickness of the layer of water produced during a day, with regard to subtropical cyclones. The bands are chosen according to the different harmonic modes of the oceanic Rossby waves. In each period band, the joint analysis of the amplitude and the phase of the state variables allow the estimation of the regionalized intensity of anomalies versus their time lag in relation to the date of occurrence of the extreme event. Regarding MHWs in the northwestern Pacific, it is shown how a warm SST anomaly associated with the northward component of the wind resulting from the low-pression system induces an SST response to latent and sensible heat transfer where the latitudinal SST gradient is steep. The SST anomaly is then shifted to the north as the phase becomes homogenized. As for subtropical cyclones, extreme events are the culmination of exceptional circumstances, some of which are foreseeable due to their relatively long maturation time. This is particularly the case of ocean–atmosphere interactions leading to the homogenization of the phase of SST anomalies that can potentially contribute to the supply of low-pressure systems. The same goes for the coalescence of distinct low-pressure systems during cyclogenesis. Some avenues are developed with the aim of better understanding how anthropogenic warming can modify certain key mechanisms in the evolution of those dynamic systems leading to extreme events.
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Wu, Linghao, Jiaan Wang, Wentao Jia, Jian Zhang i Jingrui Sun. "Research on subpixel partition correction method for simulating star position in star simulation system". Journal of Instrumentation 18, nr 09 (1.09.2023): P09003. http://dx.doi.org/10.1088/1748-0221/18/09/p09003.
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Abstract The accuracy of star position simulation in star simulation systems is a key factor affecting the accuracy of ground calibration experiments for star sensors. In order to solve the problem that the current simulation star position accuracy is restricted by the size of its constituent elements, In this paper, the mathematical model for simulating the star position correction and the gray distribution of the constituent elements is derived, and the functional representation of the azimuth and longitude correction, elevation and latitude correction of the simulated star position is established. Exploring the distribution law of star position simulation error and establishing a corrected sub interval based on it, achieving sub pixel level star position simulation accuracy. The experimental results show that after using the method proposed in this article, the accuracy of star position simulation has been improved by 1.74 times.
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Schuyler, Travis J., Sean C. C. Bailey i Marcelo I. Guzman. "Monitoring Tropospheric Gases with Small Unmanned Aerial Systems (sUAS) during the Second CLOUDMAP Flight Campaign". Atmosphere 10, nr 8 (27.07.2019): 434. http://dx.doi.org/10.3390/atmos10080434.
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Small unmanned aerial systems (sUAS) are a promising technology for atmospheric monitoring of trace atmospheric gases. While sUAS can be navigated to provide information with higher spatiotemporal resolution than tethered balloons, they can also bridge the gap between the regions of the atmospheric boundary layer (ABL) sampled by ground stations and manned aircraft. Additionally, sUAS can be effectively employed in the petroleum industry, e.g., to constrain leaking regions of hydrocarbons from long gasoducts. Herein, sUAS are demonstrated to be a valuable technology for studying the concentration of important trace tropospheric gases in the ABL. The successful detection and quantification of gases is performed with lightweight sensor packages of low-power consumption that possess limits of detection on the ppm scale or below with reasonably fast response times. The datasets reported include timestamps with position, temperature, relative humidity, pressure, and variable mixing ratio values of ~400 ppm CO2, ~1900 ppb CH4, and ~5.5 ppb NH3. The sensor packages were deployed aboard two different sUAS operating simultaneously during the second CLOUDMAP flight campaign in Oklahoma, held during 26–29 June 2017. A Skywalker X8 fixed wing aircraft was used to fly horizontally at a constant altitude, while vertical profiles were provided by a DJI Phantom 3 (DJI P3) quadcopter flying upward and downward at fixed latitude-longitude coordinates. The results presented have been gathered during 8 experiments consisting of 32 simultaneous flights with both sUAS, which have been authorized by the United States Federal Aviation Authority (FAA) under the current regulations (Part 107). In conclusion, this work serves as proof of concept showing the atmospheric value of information provided by the developed sensor systems aboard sUAS.
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ZERARI, Houssam, Lotfi MESSIKH, Abdellah KOUZOU i Salim OUCHTATI. "Smart Energy Management and Monitoring System for Public Lighting System based on Photovoltaic and Storage Systems". Electrotehnica, Electronica, Automatica 69, nr 1 (15.02.2021): 19–29. http://dx.doi.org/10.46904/eea.21.69.1.1108003.
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The public lighting system was being a vital part all over the world for many years. Indeed, as the number of population and urbanism grow, this system is becoming a primordial part of our life comfort. Therefore, it is used extensively leading to an increased important amount of electrical energy being consumed. This paper proposes an idea of an intelligent energy management system (EMS) for public lightening system consumption based on an autonomous hybrid sources of electrical energy. It is composed of a PV system installed at the top of the lightening system and a battery storage system, where an intelligent energy management system is used to ensure the charging of the battery during the daylight with the option of supporting the PV system production in case of low period irradiation during the day. Whereas, during the night, the battery fully powers the lightening system. In the same for the protection of the battery system and its related lifespan, the proposed (EMS) takes into accounts this issue. Furthermore, this system has the ability of recognizing accurately the basic data on the length of the day, the sunrise time and sunset time automatically based on the location of the used public lightening system which is defined by its longitude and latitude. The proposed EMS is built around a special electronics card including display screen of main information with the insertion of special sensors such as current and voltage sensors, which were built by the authors. The proposed system has been tested in a known location where the obtained results prove the validity of the proposed management system for ensuring the operation of the public lightening system.
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Neudegg, D. A., B. J. Fraser, F. W. Menk, G. B. Burns, R. J. Morris i M. J. Underwood. "Magnetospheric sources of Pc1-2 ULF waves observed in the polar ionospheric waveguide". Antarctic Science 14, nr 1 (marzec 2002): 93–103. http://dx.doi.org/10.1017/s0954102002000627.
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Energy from the outer regions of the magnetosphere may be transferred to the polar ionosphere by plasma waves. A magnetometer array operated during the Antarctic winter observed Ultra-Low-Frequency (ULF) plasma waves in the Pc 1–2 (0.1–10.0 Hz) frequency range, propagating parallel to the surface of the Earth in a waveguide or duct centred at ∼300 km altitude in the ionosphere. These compressional fast mode plasma waves most likely originated in the outer magnetosphere as shear mode plasma waves guided along the geomagnetic field. The region of origin in the magnetosphere for the waves is not certain as several widely spaced volumes map along geomagnetic field lines to a relatively close ensemble in the polar ionosphere. This paper compares the direction of propagation for the waves with signatures of magnetospheric regions geomagnetically projecting onto the ionosphere. Regions such as the polar cusp, low latitude boundary layer and mantle were observed by DMSP spacecraft and a SuperDARN high-frequency radar. The most likely region in the polar ionosphere for the fast mode waves to have originated from is equatorwards of the polar cusp, suggesting the field guided waves originated just inside the magnetopause. A case is made for association of the observed Pc1-2 ULF waves with post-noon, field-aligned-current systems driven by reconnection of the solar Interplanetary Magnetic Field (IMF) and the geomagnetic field near the magnetopause.
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Gorr-Pozzi, Emiliano, Héctor García-Nava, Marco Larrañaga, Melissa G. Jaramillo-Torres i Manuel G. Verduzco-Zapata. "Wave Energy Resource Harnessing Assessment in a Subtropical Coastal Region of the Pacific". Journal of Marine Science and Engineering 9, nr 11 (12.11.2021): 1264. http://dx.doi.org/10.3390/jmse9111264.
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Most wave energy converters (WECs) are designed to operate in high-latitude energetic seas, limiting their performance in regions usually dominated by milder conditions. The present study assesses the performance of complete test-stage WECs in farms that satisfy a decentralized energy scheme (DES) on the coast of Baja California, which is considered one of the most energetic regions along the Mexican Pacific. A high-resolution 11-year nearshore wave hindcast was performed and validated with Acoustic Doppler Current Profilers (ADCPs) data to characterize the wave energy resource in the study area. Two hotspots were identified from the wave power climatology. In these sites, the extractive capacities of seven well-known WEC technologies were determined based on their power matrices. Finally, the power extracted by small WEC farms, with the minimum number of devices required to satisfy a DES, was estimated. The studied region has moderate wave power availability with marked seasonality and low inter-annual variability. Out of all the evaluated devices, WaveDragon extracts the highest wave power; however, Pelamis has the best performance, with maximum monthly mean capacity factors up to 40%. Coupling WEC farms with storage modules or hybrid renewable systems are recommended to satisfy a continuous DES during the less energetic summer months.
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Deng, Licai, Yu Xin, Xiaobin Zhang, Yan Li, Xiaojun Jiang, Guomin Wang, Kun Wang, Jilin Zhou, Zhengzhou Yan i Zhiquan Luo. "SONG China project – participating in the global network". Proceedings of the International Astronomical Union 8, S288 (sierpień 2012): 318–19. http://dx.doi.org/10.1017/s1743921312017115.
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AbstractSONG (Stellar Observations Network Goup) is a low-cost ground based international collaboration aimed at two cutting edge problems in contemporary astrophysics in the time-domain: 1) Direct diagnostics of the internal structure of stars and 2) looking for and studying extra solar planets, possibly in the habitable zone. The general plan is to set up a network of 1m telescopes uniformly distributed in geographic latitude (in both hemispheres). China jointed the collaboration (initiated by Danish astronomers) at the very beginning. In addition to SONG's original plan (http://song.phys.au.dk), the Chinese team proposed a parallel photometry subnet work in the northern hemisphere, namely 50BiN (50cm Binocular Network, previously known as mini-SONG), to enable a large field photometric capability for the network, therefore maximising the potential of the network platform. The network will be able to produce nearly continuous time series observations of a number of selected objects with high resolution spectroscopy (SONG) and accurate photometry (50BiN), and to produce ultra-high accuracy photometry in dense field to look for micro-lensing events caused by planetary systems. This project has great synergy with Chinese Astronomical activities in Antarctica (Dome A), and other similar networks (e.g. LCOGT). The plan and current status of the project are overviewed in this poster.