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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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Siscoe, G. L., W. Lotko i B. U. Ö. Sonnerup. "A high-latitude, low-latitude boundary layer model of the convection current system". Journal of Geophysical Research 96, A3 (1991): 3487. http://dx.doi.org/10.1029/90ja02362.
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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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Yamauchi, Masatoshi, Magnar G. Johnsen, Carl-Fredrik Enell, Anders Tjulin, Anna Willer i Dmitry A. Sormakov. "High-latitude crochet: solar-flare-induced magnetic disturbance independent from low-latitude crochet". Annales Geophysicae 38, nr 6 (3.11.2020): 1159–70. http://dx.doi.org/10.5194/angeo-38-1159-2020.
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Abstract. A solar-flare-induced, high-latitude (peak at 70–75∘ geographic latitude – GGlat) ionospheric current system was studied. Right after the X9.3 flare on 6 September 2017, magnetic stations at 68–77∘ GGlat near local noon detected northward geomagnetic deviations (ΔB) for more than 3 h, with peak amplitudes of >200 nT without any accompanying substorm activities. From its location, this solar flare effect, or crochet, is different from previously studied ones, namely, the subsolar crochet (seen at lower latitudes), auroral crochet (pre-requires auroral electrojet in sunlight), or cusp crochet (seen only in the cusp). The new crochet is much more intense and longer in duration than the subsolar crochet. The long duration matches with the period of high solar X-ray flux (more than M3-class flare level). Unlike the cusp crochet, the interplanetary magnetic field (IMF) BY is not the driver, with the BY values of only 0–1 nT out of a 3 nT total field. The equivalent ionospheric current flows eastward in a limited latitude range but extended at least 8 h in local time (LT), forming a zonal current region equatorward of the polar cap on the geomagnetic closed region. EISCAT radar measurements, which were conducted over the same region as the most intense ΔB, show enhancements of electron density (and hence of ion-neutral density ratio) at these altitudes (∼100 km) at which strong background ion convection (>100 m s−1) pre-existed in the direction of tidal-driven diurnal solar quiet (Sq0) flow. Therefore, this new zonal current can be related to this Sq0-like convection and the electron density enhancement, for example, by descending the E-region height. However, we have not found why the new crochet is found in a limited latitudinal range, and therefore, the mechanism is still unclear compared to the subsolar crochet that is maintained by a transient redistribution of the electron density. The signature is sometimes seen in the auroral electrojet (AE = AU − AL) index. A quick survey for X-class flares during solar cycle 23 and 24 shows clear increases in AU for about half the > X2 flares during non-substorm time, despite the unfavourable latitudinal coverage of the AE stations for detecting this new crochet. Although some of these AU increases could be the auroral crochet signature, the high-latitude crochet can be a rather common feature for X flares. We found a new type of the solar flare effect on the dayside ionospheric current at high latitudes but equatorward of the cusp during quiet periods. The effect is also seen in the AU index for nearly half of the > X2-class solar flares. A case study suggests that the new crochet is related to the Sq0 (tidal-driven part) current.
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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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Liu, Zhiyu, Qiang Lian, Fangtao Zhang, Lei Wang, Mingming Li, Xiaolin Bai, Jianing Wang i Fan Wang. "Weak Thermocline Mixing in the North Pacific Low-Latitude Western Boundary Current System". Geophysical Research Letters 44, nr 20 (28.10.2017): 10,530–10,539. http://dx.doi.org/10.1002/2017gl075210.
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Caley, T., J. H. Kim, B. Malaizé, J. Giraudeau, T. Laepple, N. Caillon, K. Charlier i in. "High-latitude obliquity as a dominant forcing in the Agulhas current system". Climate of the Past 7, nr 4 (26.11.2011): 1285–96. http://dx.doi.org/10.5194/cp-7-1285-2011.
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Abstract. The Agulhas Current transport of heat and salt from the Indian Ocean into the South Atlantic around South Africa (Agulhas leakage), can affect the Atlantic meridional overturning circulation (AMOC) and, thus, influence global climate. However, efforts to elucidate forcing mechanisms connecting the Agulhas leakage with the upstream dynamics of the current have been hampered by a lack of climate records extracted from the area where the Agulhas current originates. We determine 800-kyr sea surface temperature (SST) and salinity (SSS) records from the "precursor" region of the Agulhas current and show that these records contain strong 100-kyr and 41-kyr cycles. This latter obliquity-driven cycle is nearly in phase with changes in the annual mean insolation and air temperature at high southern latitudes. In contrast, our SST and SSS records did not reveal precession-driven cycles, which is surprising given the low-latitude location of the upstream Agulhas current. Together, this indicates that the dynamics of the Agulhas current system is mainly controlled by high latitude obliquity through its influence on the position of the Southern Hemisphere subtropical front (STF) and its associated westerlies. Our study demonstrates that obliquity may drive an important part of the 100 kyr cycles observed in the system rather than precession. Our results also suggest that a stronger Agulhas current, associated with a northward shift of the wind system during glacial periods, leads to reduced leakage, in accordance with the theory. We argue that during terminations, stronger Agulhas leakage of heat and salt was triggered by increased obliquity exerting a positive feedback on the global climate system through modulating long-term AMOC variations.
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Sunoj Valiaparambil Sebastian, John, Xuejun Dong, Calvin Trostle, Hanh Pham, Madhumita V. Joshi, Russell W. Jessup, Mark D. Burow i Tony L. Provin. "Hemp Agronomy: Current Advances, Questions, Challenges, and Opportunities". Agronomy 13, nr 2 (6.02.2023): 475. http://dx.doi.org/10.3390/agronomy13020475.
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Hemp (Cannabis sativa L. ssp. sativa) has a long history of domestication due to its versatile use. Recently, different sectors in the economy are investigating hemp cultivation to increase agronomic production and to limit delta-9-tetrahydrocannabinol (THC). Despite the rapid growth of hemp literature in recent years, it is still uncertain whether the knowledge gained from higher latitude regions is applicable to low latitude and tropical regions where hemp has not been grown traditionally. This review provides a comprehensive and updated survey of hemp agronomy, focusing on environmental and management factors influencing the growth and yield of hemp, methods of cannabinoids detection and quantification, and hemp breeding. This review suggests that some previous claims about hemp as a low input crop may not hold true in low-latitude regions. Additional research strategies, such as the integration of experimentation and modeling efforts, are encouraged to hasten new discoveries. Furthermore, to effectively increase the outputs of value products (cannabinoids, seeds, fiber and biomass, etc.) while limiting the THC level, new collaborations between hemp agronomists and economists may streamline the production process by increasing the efficiency of the total production system of hemp as a multifaceted crop.
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Qiu, Bo, Shuiming Chen, Daniel L. Rudnick i Yuji Kashino. "A New Paradigm for the North Pacific Subthermocline Low-Latitude Western Boundary Current System". Journal of Physical Oceanography 45, nr 9 (wrzesień 2015): 2407–23. http://dx.doi.org/10.1175/jpo-d-15-0035.1.
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AbstractSubthermocline western boundary circulation along the low-latitude North Pacific Ocean (2°–25°N) is investigated by using profiling float and historical CTD/expendable CTD (XCTD) data and by analyzing an eddy-resolving global OGCM output. In contrast to the existing paradigm depicting it as a reversed pattern of the wind-driven circulation above the ventilated thermocline (i.e., depth < 26.8 σθ), the subthermocline western boundary circulation is found to comprise two components governed by distinct dynamical processes. For meridional scales shorter than 400 km, the boundary flows along the Philippine coast exhibit convergent patterns near 7°, 10°, 13°, and 18°N, respectively. These short-scale boundary flows are driven by the subthermocline eastward zonal jets that exist coherently across the interior North Pacific basin and are generated by the triad instability of wind-forced annual baroclinic Rossby waves. For meridional scales longer than 400 km, a time-mean Mindanao Undercurrent (MUC) is observed from 6° to 13°N together with another northward-flowing boundary flow beneath the Kuroshio from 16° to 24°N. Rather than remote eddy forcing from the interior Pacific Ocean, both of these broad-scale subthermocline boundary flows are induced by baroclinic instability of the overlying wind-driven western boundary currents, the Mindanao Current, and Kuroshio.
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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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Krauklis, I., i D. Orr. "The effects of ionospheric 'phase mixing' on a distributed driven shear Alfvén ulf pulsation'". Annales Geophysicae 12, nr 2/3 (31.01.1994): 188–94. http://dx.doi.org/10.5194/angeo-12-188-1994.
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Abstract. A numerical simulation study of the ultra-low frequency (ULF) H-component magnetic field at the Earth's surface arising from a perturbation ionospheric Hall current has been developed. The Hall current system is driven by field-aligned currents (FACs) associated with shear Alfvén field line resonances (FLRs) driven by fast mode global cavity oscillations. The ionospheric phase mixing of the Hall current manifests itself in a number of ways in the ground field, these are: (i) Smoothing the spectral maxima of the ground signal: (ii) Loss in clarity of the harmonic structure of the spectra: (iii) A small increase in the damping rate of the ULF wave at the resonance latitude and (iv) small localised minimum in the spectra at the resonance latitude.
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Liu, Jann-Yenq, Chien-Hung Lin, Panthalingal Krishnanunni Rajesh, Chi-Yen Lin, Fu-Yuan Chang, I.-Te Lee, Tzu-Wei Fang, Dominic Fuller-Rowell i Shih-Ping Chen. "Advances in Ionospheric Space Weather by Using FORMOSAT-7/COSMIC-2 GNSS Radio Occultations". Atmosphere 13, nr 6 (24.05.2022): 858. http://dx.doi.org/10.3390/atmos13060858.
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This paper provides an overview of the contributions of the space-based global navigation satellite system (GNSS) radio occultation (RO) measurements from the FORMOSAT-7/COSMIC2 (F7/C2) mission in advancing our understanding of ionospheric plasma physics in the purview of space weather. The global positioning system (GPS) occultation experiment (GOX) onboard FORMOSAT-3/COSMIC (F3/C), with more than four and half million ionospheric RO soundings during April 2006–May 2020, offered a unique three-dimensional (3D) perspective to examine the global electron density distribution and unravel the underlying physical processes. The current F7/C2 carries TGRS (Tri-GNSS radio occultation system) has tracked more than 4000 RO profiles within ±35° latitudes per day since 25 June 2019. Taking advantage of the larger number of low-latitude soundings, the F7/C2 TGRS observations were used here to examine the 3D electron density structures and electrodynamics of the equatorial ionization anomaly, plasma depletion bays, and four-peaked patterns, as well as the S4 index of GNSS signal scintillations in the equatorial and low-latitude ionosphere, which have been previously investigated by using F3/C measurements. The results demonstrated that the denser low-latitude soundings enable the construction of monthly global electron density maps as well the altitude-latitude profiles with higher spatial and temporal resolution windows, and revealed longitudinal and seasonal characteristics in greater detail. The enhanced F7/C2 RO observations were further applied by the Central Weather Bureau/Space Weather Operation Office (CWB/SWOO) in Taiwan and the National Oceanic and Atmospheric Administration/Space Weather Prediction Center (NOAA/SWPC) in the United States to specify the ionospheric conditions for issuing alerts and warnings for positioning, navigation, and communication customers. A brief description of the two models is also provided.
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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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Talari, Prashanthi, i Sampad Kumar Panda. "Occurrences of counter electrojets and possible ionospheric TEC variations round new Moon and full Moon days across the low latitude Indian region". Journal of Applied Geodesy 13, nr 3 (26.07.2019): 245–55. http://dx.doi.org/10.1515/jag-2019-0014.
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Abstract The present paper investigates the alterations in ionospheric Total Electron Content (TEC) over a low latitude location Bangalore (Geographic latitude {12.9^{\circ }}\hspace{2.38387pt}\text{N} and longitude {77.6^{\circ }}\hspace{2.38387pt}\text{E}; Geomagnetic latitude 4.{5^{\circ }}\hspace{2.38387pt}\text{N}) in India, corresponding to the new Moon and full Moon days which are associated with abnormality in the eastward Equatorial Electrojet (EEJ) currents. It has been well established that even during certain geomagnetic quiet days, the EEJ current direction is reversed, resulting in a westward electrojet current called Counter Electrojet (CEJ) which is more prominent around the new Moon and full Moon days, favored by Sun–Moon–Earth alignments and lunar orbital characteristics. The Global Positioning System (GPS) derived TEC at Bangalore is investigated for full Moon and new Moon and their adjacent days during the period 2008–2015. The presence of CEJ during these days suggests the foremost role of driving EEJ current over the equator in the alterations of spatiotemporal distributions of TEC over the low latitude region. The deviations in quiet time TEC during new Moon and full Moon days are quantified in this study that may give a thrust towards modeling of lunar tidal effects in the flipped ionospheric parameter over the Indian region. The study would also support analysis of future solar eclipse effects on ionosphere those involve additional photoionization production/recombination processes corresponding to the passage of lunar shadow and cooling effects. Moreover, the results underpin modeling and mitigation of ionospheric error in the satellite-based positioning, navigation, and communication applications.
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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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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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Montañez, Isabel Patricia. "Current synthesis of the penultimate icehouse and its imprint on the Upper Devonian through Permian stratigraphic record". Geological Society, London, Special Publications 512, nr 1 (29.09.2021): 213–45. http://dx.doi.org/10.1144/sp512-2021-124.
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AbstractIcehouses are the less common climate state on Earth, and thus it is notable that the longest-lived (c.370 to 260 Ma) and possibly most extensive and intense of icehouse periods spanned the Carboniferous Period. Mid- to high-latitude glaciogenic deposits reveal a dynamic glaciation–deglaciation history with ice waxing and waning from multiple ice centres and possible transcontinental ice sheets during the apex of glaciation. New high-precision U–Pb ages confirm a hypothesized west-to-east progression of glaciation through the icehouse, but reveal that its demise occurred as a series of synchronous and widespread deglaciations. The dynamic glaciation history, along with repeated perturbations to Earth System components, are archived in the low-latitude stratigraphic record, revealing similarities to the Cenozoic icehouse. Further assessing the phasing between climate, oceanographic, and biotic changes during the icehouse requires additional chronostratigraphic constraints. Astrochronology permits the deciphering of time, at high resolution, in the late Paleozoic record as has been demonstrated in deep- and quiet-water deposits. Rigorous testing for astronomical forcing in low-latitude cyclothemic successions, which have a direct link to higher-latitude glaciogenic records through inferred glacioeustasy, however, will require a comprehensive approach that integrates new techniques with further optimization and additional independent age constraints given challenges associated with shallow-marine to terrestrial records.
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Wen, Xixi, i Wansuo Duan. "Errors in Current Velocity in the Low-latitude North Pacific: Results from the Regional Ocean Modeling System". Advances in Atmospheric Sciences 36, nr 4 (31.01.2019): 397–416. http://dx.doi.org/10.1007/s00376-018-8140-4.
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Pyatibrat, E. D. "Justification of the effectiveness of organized summer recreation under different climatic and geographical conditions for normalizing the organism functional state in veterans of extreme activities". Medicо-Biological and Socio-Psychological Problems of Safety in Emergency Situations, nr 4 (10.02.2019): 34–39. http://dx.doi.org/10.25016/2541-7487-2018-0-4-34-39.
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Relevance. Participation in military conflicts, long-term vital threat, irregular working hours, frequent moving to new places of residence impose negative imprints in the form of various functional disorders and even the formation of psychogenic diseases on employees of various law enforcement agencies.Intention. To assess the impact of organized summer holidays under different climatic conditions on the functional state of the veterans of law enforcement agencies previously engaged in activities under extreme conditions.Methodology. 65 retired men soldiers of different law enforcement agencies aged 45 to 54 years were examined before and after organized summer holidays under different climatic conditions. Hemodynamic parameters, mobility of nervous processes and current mental state were assessed.Results and Discussion. After a river cruise in the North-West and mid-latitudes of Russia, decreased tension of the functional circulatory system as well as improved mobility of nervous processes and current mental state were reported. On the contrary, increased tension of the functional circulatory system, decreased mobility of nervous processes, well-being, activity, mood and increased anxiety were reported after holidays at low-latitude resorts.Conclusion. Thus, the functional state of veterans of law enforcement agencies who survived repeated mental trauma and vital threat, was effectively restored after a river cruise in the North-West and mid-latitudes of Russia.
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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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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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Lopez, R. E., V. G. Merkin i J. G. Lyon. "The role of the bow shock in solar wind-magnetosphere coupling". Annales Geophysicae 29, nr 6 (25.06.2011): 1129–35. http://dx.doi.org/10.5194/angeo-29-1129-2011.
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Abstract. In this paper we examine the role of the bow shock in coupling solar wind energy to the magnetosphere using global magnetohydrodynamic simulations of the solar wind-magnetosphere interaction with southward IMF. During typical solar wind conditions, there are two significant dynamo currents in the magnetospheric system, one in the high-latitude mantle region tailward of the cusp and the other in the bow shock. As the magnitude of the (southward) IMF increases and the solar wind becomes a low Mach number flow, there is a significant change in solar wind-magnetosphere coupling. The high-latitude magnetopause dynamo becomes insignificant compared to the bow shock and a large load appears right outside the magnetopause. This leaves the bow shock current as the only substantial dynamo current in the system, and the only place where a significant amount of mechanical energy is extracted from the solar wind. That energy appears primarily as electromagnetic energy, and the Poynting flux generated at the bow shock feeds energy back into the plasma, reaccelerating it to solar wind speeds. Some small fraction of that Poynting flux is directed into the magnetosphere, supplying the energy needed for magnetospheric dynamics. Thus during periods when the solar wind flow has a low Mach number, the main dynamo in the solar wind-magnetosphere system is the bow shock.
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Yang, Fan, Lian Guang Liu, Qi Li i Dong Mei Yang. "Comparison Study of the Geomagnetically Induced Current Level of Power Grid in Different Latitude". Advanced Materials Research 463-464 (luty 2012): 305–9. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.305.
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Geomagnetically induced current (GIC) relates to factors such as magnetic amplitude, geotecture and structure of power grid. On the basis of geotecture, according to the geomagnetic storm data of Dec 2006, employing the plan wave method, this paper finish the calculation of GIC level of 2012 Beijing planning power gird, and compare the result to the measure data of Shanghe substation, in Yanghuai transmission system. The comparison shows that power grid is much more affected by geotecture, direction and length of transmission line, grid topology and electrical parameters in mid-low latitude area
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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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Wang, Tianyu, Yan Du i Minyang Wang. "Overlooked Current Estimation Biases Arising from the Lagrangian Argo Trajectory Derivation Method". Journal of Physical Oceanography 52, nr 1 (styczeń 2022): 3–19. http://dx.doi.org/10.1175/jpo-d-20-0287.1.
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Abstract An Argo simulation system is used to provide synthetic Lagrangian trajectories based on the Estimating the Circulation and Climate of the Ocean Model, phase II (ECCO2). In combination with ambient Eulerian velocity at the reference layer (1000 m) from the model, quantitative metrics of the Lagrangian trajectory–derived velocities are computed. The result indicates that the biases induced by the derivation algorithm are strongly linked with ocean dynamics. In low latitudes, Ekman currents and vertically sheared geostrophic currents influence both the magnitude and the direction of the derivation velocity vectors. The maximal shear-induced biases exist near the equator with the amplitudes reaching up to about 1.2 cm s−1. The angles of the shear biases are pronounced in the low-latitude oceans, ranging from −8° to 8°. Specifically, the study shows an overlooked bias from the float drifting motions that mainly occurs in the western boundary current and Antarctic Circumpolar Current (ACC) regions. In these regions, a recently reported horizontal acceleration measured via Lagrangian floats is significantly associated with the strong eddy–jet interactions. The acceleration could induce an overestimation of Eulerian current velocity magnitudes. For the common Argo floats with a 9-day float parking period, the derivation speed biases induced by velocity acceleration would be as large as 3 cm s−1, approximately 12% of the ambient velocity. It might have implications to map the mean middepth ocean currents from Argo trajectories, as well as to understand the dynamics of eddy–jet interactions in the ocean.
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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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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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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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Rastogi, R. G., D. R. K. Rao, S. Alex, B. M. Pathan i T. S. Sastry. "An intense SFE and SSC event in geomagnetic <i>H</i>, <i>Y</i> and <i>Z</i> fields at the Indian chain of observatories". Annales Geophysicae 15, nr 10 (31.10.1997): 1301–8. http://dx.doi.org/10.1007/s00585-997-1301-x.
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Abstract. Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.
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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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Shaikhislamov, I. F., Yu P. Zakharov, V. G. Posukh, E. L. Boyarintsev, A. V. Melekhov, V. M. Antonov i A. G. Ponomarenko. "Region-1 field aligned currents in experiments on laser-produced plasma interacting with magnetic dipole". Proceedings of the International Astronomical Union 6, S274 (wrzesień 2010): 40–43. http://dx.doi.org/10.1017/s1743921311006545.
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AbstractIn previous experiments by the authors a generation of intense field aligned current (FAC) system on Terrella poles was observed. In the present report a question of these currents origin in a low latitude boundary layer of magnetosphere is investigated. Experimental evidence of such a link was obtained by measurements of magnetic field generated by tangential sheared drag. Results suggest that compressional and Alfven waves are responsible for FAC generation. The study is most relevant to FAC generation in the Earth and Hermean magnetospheres following pressure jumps in Solar Wind.
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Caley, T., J. H. Kim, B. Malaizé, J. Giraudeau, T. Laepple, N. Caillon, K. Charlier i in. "High-latitude obliquity forcing drives the agulhas leakage". Climate of the Past Discussions 7, nr 3 (30.06.2011): 2193–215. http://dx.doi.org/10.5194/cpd-7-2193-2011.
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Abstract. The Agulhas Current (AC) transport of heat and salt from the Indian Ocean into the South Atlantic around South Africa (Agulhas leakage), has a profound role in the decadal variability of the Atlantic meridional overturning circulation (AMOC), which influences global climate. On glacial-interglacial timescales, paleostudies postulate that Agulhas leakage plays a decisive role for AMOC resumption during terminations (glacial-interglacial transitions). However, efforts to elucidate forcing mechanisms connecting Agulhas leakage with glacial-interglacial AMOC variability have been hampered due to a lack of climate records extracted from the area where the AC originates. Here we present 800-kyr sea surface temperature (SST) and salinity (SSS) records from the "precursor" region of the AC. These records contain strong obliquity-driven 41-kyr cycles, nearly in phase with changes in annual mean insolation and air temperature at high southern latitudes. In contrast, precession-driven cycles were negligible in our SST records, which is surprising given the low-latitude location of the Agulhas leakage. Together, this suggests that long-term Agulhas leakage dynamics are associated with a high latitude rather than a tropical climate forcing mechanism, probably by varying the position of the Southern Hemisphere subtropical convergence (STC) and its associated westerlies. We argue that during terminations stronger Agulhas leakage was triggered by increased obliquity exerting a positive feedback on the global climate system through modulating long-term AMOC variations.
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Chen, Zan-ming, Chun-ming Liu, An-qi Li i Yue Yan. "Modeling Calculation and Influencing Factors of Geomagnetically Induced Current in Sanhua Power Grid". Journal of Physics: Conference Series 2564, nr 1 (1.08.2023): 012034. http://dx.doi.org/10.1088/1742-6596/2564/1/012034.
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Abstract The time-varying magnetic field of a magnetic storm induces an electric field in the earth, which generates geomagnetically induced currents (GIC) when it acts on the power grid and has many hazards to the power system. In this paper, we model and calculate the ground-induced electric field and geomagnetically induced currents for 20 magnetic storms from 2008 to 2018, and investigate the effects of two factors, magnetic storm strength, and earth conductivity, on the geomagnetically induced currents, which are important for the prevention and control of GIC in large-scale power grids in low- and mid-latitude regions.
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Shin, V. I., M. S. Vorobyov, P. V. Moskvin, V. N. Devyatkov, V. V. Yakovlev, N. N. Koval, M. S. Torba, R. A. Kartavtsov i S. A. Vorobyov. "Latitude and amplitude modulation of the beam current for controlling its power during a submillisecond pulse". Izvestiya vysshikh uchebnykh zavedenii. Fizika, nr 11 (2022): 176–84. http://dx.doi.org/10.17223/00213411/65/11/176.
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Methods for controlling the power electron beam in a source based on a low-pressure arc discharge with layer stabilization of the emission plasma boundary are described. The control is carried out by the method of amplitude and latitude modulation within the duration of the beam current pulse with a time resolution of 10 μs at a submillisecond pulse duration. Two ways to control the power of the electron beam are implemented: the first one is based on changing the concentration of the emission plasma by modulating the arc discharge current, the second method uses grid control (the mode of operation of the plasma triode) at the constant discharge current. Simplified diagrams of the power supply sources of the discharge and intergrid control voltage, typical oscillograms of the main currents of the discharge system, a graph of a quick-acting power change, and a control characteristic of a plasma triode are presented.
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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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Calabia, Andres, Chukwuma Anoruo, Munawar Shah, Christine Amory-Mazaudier, Yury Yasyukevich, Charles Owolabi i Shuanggen Jin. "Low-Latitude Ionospheric Responses and Coupling to the February 2014 Multiphase Geomagnetic Storm from GNSS, Magnetometers, and Space Weather Data". Atmosphere 13, nr 4 (24.03.2022): 518. http://dx.doi.org/10.3390/atmos13040518.
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The ionospheric response and the associated mechanisms to geomagnetic storms are very complex, particularly during the February 2014 multiphase geomagnetic storm. In this paper, the low-latitude ionosphere responses and their coupling mechanisms, during the February 2014 multiphase geomagnetic storm, are investigated from ground-based magnetometers and global navigation satellite system (GNSS), and space weather data. The residual disturbances between the total electron content (TEC) of the International GNSS Service (IGS) global ionospheric maps (GIMs) and empirical models are used to investigate the storm-time ionospheric responses. Three clear sudden storm commencements (SSCs) on 15, 20, and 23 February are detected, and one high speed solar wind (HSSW) event on 19 February is found with the absence of classical SSC features due to a prevalent magnetospheric convection. The IRI-2012 shows insufficient performance, with no distinction between the events and overestimating approximately 20 TEC units (TECU) with respect to the actual quiet-time TEC. Furthermore, the median average of the IGS GIMs TEC during February 2014 shows enhanced values in the southern hemisphere, whereas the IRI-2012 lacks this asymmetry. Three low-latitude profiles extracted from the IGS GIM data revealed up to 20 TECU enhancements in the differential TEC. From these profiles, longer-lasting TEC enhancements are observed at the dip equator profiles than in the profiles of the equatorial ionospheric anomaly (EIA) crests. Moreover, a gradual increase in the global electron content (GEC) shows approximately 1 GEC unit of differential intensification starting from the HSSW event, while the IGS GIM profiles lack this increasing gradient, probably located at higher latitudes. The prompt penetration electric field (PPEF) and equatorial electrojet (EEJ) indices estimated from magnetometer data show strong variability after all four events, except the EEJ’s Asian sector. The low-latitude ionosphere coupling is mainly driven by the variable PPEF, DDEF (disturbance dynamo electric fields), and Joule heating. The auroral electrojet causing eastward PPEF may control the EIA expansion in the Asian sector through the dynamo mechanism, which is also reflected in the solar-quiet current intensity variability.
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Yeager, Stephen, i Gokhan Danabasoglu. "Sensitivity of Atlantic Meridional Overturning Circulation Variability to Parameterized Nordic Sea Overflows in CCSM4". Journal of Climate 25, nr 6 (14.03.2012): 2077–103. http://dx.doi.org/10.1175/jcli-d-11-00149.1.
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Abstract The inclusion of parameterized Nordic Sea overflows in the ocean component of the Community Climate System Model version 4 (CCSM4) results in a much improved representation of the North Atlantic tracer and velocity distributions compared to a control CCSM4 simulation without this parameterization. As a consequence, the variability of the Atlantic meridional overturning circulation (AMOC) on decadal and longer time scales is generally lower, but the reduction is not uniform in latitude, depth, or frequency–space. While there is dramatically less variance in the overall AMOC maximum (at about 35°N), the reduction in AMOC variance at higher latitudes is more modest. Also, it is somewhat enhanced in the deep ocean and at low latitudes (south of about 30°N). The complexity of overturning response to overflows is related to the fact that, in both simulations, the AMOC spectrum varies substantially with latitude and depth, reflecting a variety of driving mechanisms that are impacted in different ways by the overflows. The usefulness of reducing AMOC to a single index is thus called into question. This study identifies two main improvements in the ocean mean state associated with the overflow parameterization that tend to damp AMOC variability: enhanced stratification in the Labrador Sea due to the injection of dense overflow waters and a deepening of the deep western boundary current. Direct driving of deep AMOC variance by overflow transport variations is found to be a second-order effect.
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Olatunbosun, LG, A. O. Olabode i EA Ariyibi. "Variability of Equatorial Electrojet (EEJ) at EIA regions". Physics & Astronomy International Journal 6, nr 1 (25.01.2022): 1–4. http://dx.doi.org/10.15406/paij.2022.06.00241.
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The EEJ is a worldwide solar-driven wind that results in the solar quiet (Sq) current system in the E region of the earth’s ionosphere. The variability of some features such as EEJ, are very important in understanding the complex nature of the ionosphere, especially the low-latitude ionosphere. The magnetometer data from stations located near the equator and outside the edge of the electrojet strip for Africa and India stations were used to estimate and investigate the variability of EEJ in African and Indian Low-Latitudes. The stations are Addis Ababa, Ethiopia (geographic lat/long: 9.03oN/38.76oE) and at Mbour, Senegal for African region (geographic lat/long 14.392oN/343.042oE) and Hyderabad, India (geographic lat/long: 17.413oN/78.555oE) and Beijing Ming Tombs, China for Indian region (geographic lat/long: 40.3oN/116.2oE). The data in XYZ orientation was used to estimate the EEJ strength. The result shows that EEJ exhibits diurnal and seasonal variations and that its variability is stronger in African station than in Indian station, so also is the occurrence of counter electrojet (CEJ).
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Li, Ningbo, Lianwu Guan, Yanbin Gao, Shitong Du, Menghao Wu, Xingxing Guang i Xiaodan Cong. "Indoor and Outdoor Low-Cost Seamless Integrated Navigation System Based on the Integration of INS/GNSS/LIDAR System". Remote Sensing 12, nr 19 (8.10.2020): 3271. http://dx.doi.org/10.3390/rs12193271.
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Global Navigation Satellite System (GNSS) provides accurate positioning data for vehicular navigation in open outdoor environment. In an indoor environment, Light Detection and Ranging (LIDAR) Simultaneous Localization and Mapping (SLAM) establishes a two-dimensional map and provides positioning data. However, LIDAR can only provide relative positioning data and it cannot directly provide the latitude and longitude of the current position. As a consequence, GNSS/Inertial Navigation System (INS) integrated navigation could be employed in outdoors, while the indoors part makes use of INS/LIDAR integrated navigation and the corresponding switching navigation will make the indoor and outdoor positioning consistent. In addition, when the vehicle enters the garage, the GNSS signal will be blurred for a while and then disappeared. Ambiguous GNSS satellite signals will lead to the continuous distortion or overall drift of the positioning trajectory in the indoor condition. Therefore, an INS/LIDAR seamless integrated navigation algorithm and a switching algorithm based on vehicle navigation system are designed. According to the experimental data, the positioning accuracy of the INS/LIDAR navigation algorithm in the simulated environmental experiment is 50% higher than that of the Dead Reckoning (DR) algorithm. Besides, the switching algorithm developed based on the INS/LIDAR integrated navigation algorithm can achieve 80% success rate in navigation mode switching.
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Hanuise, C., J. C. Cerisier, F. Auchère, K. Bocchialini, S. Bruinsma, N. Cornilleau-Wehrlin, N. Jakowski i in. "From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere". Annales Geophysicae 24, nr 1 (7.03.2006): 129–51. http://dx.doi.org/10.5194/angeo-24-129-2006.
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Abstract. During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME). Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1) the expansion of the auroral oval, and aurorae seen at mid latitudes, (2) the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3) the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4) the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.
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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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Zhang, Rong, i Geoffrey K. Vallis. "Impact of Great Salinity Anomalies on the Low-Frequency Variability of the North Atlantic Climate". Journal of Climate 19, nr 3 (1.02.2006): 470–82. http://dx.doi.org/10.1175/jcli3623.1.
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Abstract In this paper, it is shown that coherent large-scale low-frequency variabilities in the North Atlantic Ocean—that is, the variations of thermohaline circulation, deep western boundary current, northern recirculation gyre, and Gulf Stream path—are associated with high-latitude oceanic Great Salinity Anomaly events. In particular, a dipolar sea surface temperature anomaly (warming off the U.S. east coast and cooling south of Greenland) can be triggered by the Great Salinity Anomaly events several years in advance, thus providing a degree of long-term predictability to the system. Diagnosed phase relationships among an observed proxy for Great Salinity Anomaly events, the Labrador Sea sea surface temperature anomaly, and the North Atlantic Oscillation are also discussed.
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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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Bradshaw, E. G., i M. Lester. "SABRE observations of Pi2 pulsations: case studies". Annales Geophysicae 15, nr 1 (31.01.1997): 40–53. http://dx.doi.org/10.1007/s00585-997-0040-3.
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Abstract. The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.
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Deng, Zhongxin, Rui Wang, Yi Liu, Tong Xu, Zhuangkai Wang, Guanyi Chen, Qiong Tang, Zhengwen Xu i Chen Zhou. "Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance". Remote Sensing 13, nr 5 (3.03.2021): 945. http://dx.doi.org/10.3390/rs13050945.
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In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.
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Cheng, C. C., C. T. Russell, V. Angelopoulos, I. R. Mann, K. H. Glassmeier i W. Baumjohann. "THEMIS observations of double-onset substorms and their association with IMF variations". Annales Geophysicae 29, nr 3 (28.03.2011): 591–611. http://dx.doi.org/10.5194/angeo-29-591-2011.
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Abstract. On 16 July 2008, two pairs of consecutive bursts of Pi2 pulsations were recorded simultaneously across the THEMIS ground-based observatory system. Wavelet transformation reveals that for each high-latitude pair, the dominant frequency of the first burst is higher than that of the second. But at low latitudes, the dominant frequency does not change. It is suggested that both pairs result from fast magnetospheric cavity waves with the second burst also containing shear Alfvén waves. INTERMAGNET magnetograms at auroral latitudes showed magnetic variations affected by two recurrent electrojets for each pair. The ground-based magnetometers and those at geostationary orbit sensed magnetic perturbations consistent with the formation of the substorm current wedge. Four consecutive enhancements of energetic electron and ion fluxes detected by the THEMIS probes in the dayside magnetosphere appeared in the later afternoon and then in the early afternoon. The horizontal magnetic variation vectors had vortex patterns similar to those induced by the upward and downward field-aligned currents during substorm times. The hodogram at mid-L stations had a polarization pattern similar to the one induced by the substorm current wedge for each Pi2 burst. The mapping of ground Pi2 onset timing to the interplanetary magnetic field (IMF) observations shows that they appear under two cycles of north-to-south and then north variation. CLUSTER 4 in the south lobe observed wave-like magnetic fluctuations, probably driven by near-Earth reconnection, similar to those on the ground. These two observations are consistent with the link of double-onset substorms to magnetotail reconnection externally triggered by IMF variations.
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Chew, Kuew Wai, C. K. Leong i Bok Min Goi. "Contour Data Acquisition System for Electric Vehicle Distance Estimation Method". Applied Mechanics and Materials 479-480 (grudzień 2013): 503–7. http://dx.doi.org/10.4028/www.scientific.net/amm.479-480.503.
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The conventional distance estimation system only uses a constant speed and a constant level of road elevation to estimate the driving mileage for a vehicle. This technique leads to a low accuracy. In the current project, a new estimation technique namely; the Contour Positioning System (CPS) for an electric vehicle has been proposed. The CPS has a better estimation on the electric vehicle battery usage because of the consideration of road elevation, regenerative energy etc. In order to perform the CPS calculation, the elevation profile of the selected destination must be known. In this paper, the technique to extract the elevation profile i.e. latitude, longitude and altitude has been performed and evaluated using Google Maps or Google EarthÒ. This method enables the user to obtain the road information and compute the amount of energy needed to reach the said destination.
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Keiling, A., M. Fujimoto, H. Hasegawa, F. Honary, V. Sergeev, V. S. Semenov, H. U. Frey i in. "Association of Pi2 pulsations and pulsed reconnection: ground and Cluster observations in the tail lobe at 16 <i>R<sub>E</sub></i>". Annales Geophysicae 24, nr 12 (21.12.2006): 3433–49. http://dx.doi.org/10.5194/angeo-24-3433-2006.
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Abstract. Simultaneous measurements from the Cluster spacecraft and several ground stations (SAMNET, IMAGE, Kakioka, Hermanus) provide evidence for an association of Pi2 pulsations and pulsed reconnection in the magnetotail. On 8 September 2002, substorm-related Pi2 pulsations were recorded with the same waveform (same frequency) in the tail lobe at 16 RE and time-delayed on the ground (both nightside and dayside) spanning L values from 1.23 to 6.11. The tail lobe Pi2 pulsations were a series of nightside flux transfer event (NFTE) pulses propagating at a speed of 600–800 km/s towards Earth, which for the first time relates these two magnetospheric phenomena. NFTEs have previously been considered as the remote signature of tail reconnection. The first ground onset of the Pi2 pulsations occurred at high- and midlatitude ground stations with a time delay of ~30 s with respect to the tail lobe Pi2, followed by lower latitude ground stations. The largest pulsations were observed at high latitude (ten times larger than at low latitude) near the polar cap boundary. The polarization pattern of the ground Pi2s in the H-D plane was consistent with a periodically driven field-aligned current (FAC) system. In addition, fast mode waves must have also played a role in the inner magnetosphere because of propagation effects among ground stations and because of the simultaneous occurrence of dayside low-latitude Pi2. Auroral brightening occurred in the region of upflowing FAC, and the auroral electrojet expanded poleward together with the auroral bulge both of which are typical substorm signatures. Hence, we conclude that the substorm-related Pi2 pulsations in space at 16 RE and on the ground were remotely driven by pulsed reconnection in the magnetotail, that is, reconnection not only provided the energy but its temporal variations also determined the characteristic Pi2 frequency. Scenarios are discussed that address the connection of pulsed reconnection and the driven current system in the ionosphere. These results show that reconnection can be coupled to the ionosphere through what is phenomenologically known as Pi2 pulsations. As a corollary, it is shown that the time history of events fits within the modified NENL model of substorms.