Journal articles: 'Ionospheric variabilities'

1

Li, Lei, Shu Fang Zhang, Yi Zhuo Wang, and Qing Hu. "Solar Activity Effects on the Variabilities of Long-Term Ionospheric TEC." Advanced Materials Research 850-851 (December 2013): 1331–34. http://dx.doi.org/10.4028/www.scientific.net/amr.850-851.1331.

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To reveal the modulating effects of the solar activity on ionospheric TEC, the long-term characteristics of TEC were analyzed. The analysis was based on the data of the sunspot and data of GPS observation provided by IGS analysis centers from 1999 to 2011. The results showed that the variation of monthly mean TEC was of significant regularity. The regularity was caused mainly modulation action of solar activity. In view of the spatial variation of TEC, the monthly mean TEC can be well described for modeling and prediction on base of relationship between TEC and latitude.

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Tsai, Lung-Chih, Shin-Yi Su, Jun-Xian Lv, Terry Bullett, and Chao-Han Liu. "Multi-Station and Multi-Instrument Observations of F-Region Irregularities in the Taiwan–Philippines Sector." Remote Sensing 14, no. 10 (May 10, 2022): 2293. http://dx.doi.org/10.3390/rs14102293.

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In this study, a multi-station and multi-instrument system, organized and proposed for ionospheric scintillation and equatorial spread-F (ESF) specification and their associated motions in the Taiwan–Philippines sector, is outlined. The issues related to the scintillation and ESF event observed on 26 October 2021, at magnetic quiet conditions are presented and discussed. We first indicate the existence of a plasma bubble in the Taiwan–Philippines sector by using the FormoSat-7/Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (FS7/COSMIC2) GPS/GLONASS radio occultation observations. We verify the latitudinal extent of the tracked plasma bubble using the recorded ionograms from the Vertical Incidence Pulsed Ionospheric Radar located at Hualien, Taiwan. We further discuss the spatial and temporal variabilities of two-dimensional vertical scintillation index VS4 maps based on the simultaneous GPS L1-band signal measurements from 133 ground-based receivers located in Taiwan and the surrounding islands. We also operate two high-sampling, software-defined GPS receivers and characterize the targeted plasma irregularities by carrying out spectrum analyses of the received signal. As a result, the derived plasma irregularities moved eastward and northward. Furthermore, the smaller the irregularity scale, the higher the spectral index and the stronger the scintillation intensity were at lower latitudes on the aimed irregularity feature.

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Medvedeva, Irina, and Konstantin Ratovsky. "Studying atmospheric and ionospheric variabilities from long‐term spectrometric and radio sounding measurements." Journal of Geophysical Research: Space Physics 120, no. 6 (June 2015): 5151–59. http://dx.doi.org/10.1002/2015ja021289.

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Gurubaran, S., D. Narayana Rao, G. Ramkumar, T. K. Ramkumar, G. Dutta, and B. V. Krishna Murthy. "First results from the CAWSES-India Tidal Campaign." Annales Geophysicae 26, no. 8 (August 5, 2008): 2323–31. http://dx.doi.org/10.5194/angeo-26-2323-2008.

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Abstract. The first CAWSES-India Tidal Campaign was conducted by the Indian scientific community during March–April 2006. The objectives of this campaign were: (1) To determine the characteristics of tides in the troposphere and lower stratosphere (0–20 km) and mesosphere and lower thermosphere (MLT) region (80–100 km), (2) to explore and identify what lower atmospheric processes drive middle atmospheric tides in the Indian continental region and (3) to provide information on those short-term variabilities of MLT tides that are likely to have an impact on the ionospheric variabilities and contribute to the upper atmospheric weather. Data sets from experiments conducted at the three low latitude radar sites, namely, Trivandrum (8.5° N, 76.9° E), Tirunelveli (8.7° N, 77.8° E) and Gadanki (13.5° N, 79.2° E) and fortnightly rocket launches from Thumba were made use of in this study. An important observational finding reported in this work is that the radar observations at Tirunelveli/Trivandrum indicate the presence of 15–20 day modulation of diurnal tide activity at MLT heights during the February–March period. A similar variation in the OLR fields in the western Pacific (120–160° longitude region) suggests a possible link between the observed tidal variabilities and the variations in the deep tropical convection through the nonmigrating tides it generates.

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Yue, X., W. Wan, L. Liu, and T. Mao. "Statistical analysis on spatial correlation of ionospheric day-to-day variability by using GPS and Incoherent Scatter Radar observations." Annales Geophysicae 25, no. 8 (August 29, 2007): 1815–25. http://dx.doi.org/10.5194/angeo-25-1815-2007.

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Abstract. In this paper, the spatial correlations of ionospheric day-to-day variability are investigated by statistical analysis on GPS and Incoherent Scatter Radar observations. The meridional correlations show significant (>0.8) correlations in the latitudinal blocks of about 6 degrees size on average. Relative larger correlations of TEC's day-to-day variabilities can be found between magnetic conjugate points, which may be due to the geomagnetic conjugacy of several factors for the ionospheric day-to-day variability. The correlation coefficients between geomagnetic conjugate points have an obvious decrease around the sunrise and sunset time at the upper latitude (60°) and their values are bigger between the winter and summer hemisphere than between the spring and autumn hemisphere. The time delay of sunrise (sunset) between magnetic conjugate points with a high dip latitude is a probable reason. Obvious latitude and local time variations of meridional correlation distance, latitude variations of zonal correlation distance, and altitude and local time variations of vertical correlation distance are detected. Furthermore, there are evident seasonal variations of meridional correlation distance at higher latitudes in the Northern Hemisphere and local time variations of zonal correlation distance at higher latitudes in the Southern Hemisphere. These variations can generally be interpreted by the variations of controlling factors, which may have different spatial scales. The influences of the occurrence of ionospheric storms could not be ignored. Further modeling and data analysis are needed to address this problem. We suggest that our results are useful in the specific modeling/forecasting of ionospheric variability and the constructing of a background covariance matrix in ionospheric data assimilation.

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Jacobson, A. R., R. Holzworth, E. Lay, M. Heavner, and D. A. Smith. "Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: regular variabilities and solar-X-ray responses." Annales Geophysicae 25, no. 10 (November 6, 2007): 2175–84. http://dx.doi.org/10.5194/angeo-25-2175-2007.

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Abstract. We present refinements of a method of ionospheric D-region sounding that makes opportunistic use of powerful (109–1011 W) broadband lightning radio emissions in the low-frequency (LF; 30–300 kHz) band. Such emissions are from "Narrow Bipolar Event" (NBE) lightning, and they are characterized by a narrow (10-μs), simple emission waveform. These pulses can be used to perform time-delay reflectometry (or "sounding") of the D-region underside, at an effective LF radiated power exceeding by orders-of-magnitude that from man-made sounders. We use this opportunistic sounder to retrieve instantaneous LF ionospheric-reflection height whenever a suitable lightning radio pulse from a located NBE is recorded. We show how to correct for three sources of "regular" variability, namely solar zenith angle, radio-propagation range, and radio-propagation azimuth. The residual median magnitude of the noise in reflection height, after applying the regression corrections for the three regular variabilities, is on the order of 1 km. This noise level allows us to retrieve the D-region-reflector-height variation with solar X-ray flux density for intensity levels at and above an M-1 flare. The instantaneous time response is limited by the occurrence rate of NBEs, and the noise level in the height determination is typically in the range ±1 km.

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Sridharan, S., S. Sathishkumar, and S. Gurubaran. "Variabilities of mesospheric tides and equatorial electrojet strength during major stratospheric warming events." Annales Geophysicae 27, no. 11 (November 4, 2009): 4125–30. http://dx.doi.org/10.5194/angeo-27-4125-2009.

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Abstract. The present study demonstrates the relationship between the high latitude northern hemispheric major sudden stratospheric warming (SSW) events and the reversal in the afternoon equatorial electrojet (EEJ), often called the counter-electrojet (CEJ), during the winter months of 1998–1999, 2001–2002, 2003–2004 and 2005–2006. As the EEJ current system is driven by tidal winds, an investigation of tidal variabilities in the MF radar observed zonal winds during the winters of 1998–1999 and 2005–2006 at 88 km over Tirunelveli, a site close to the magnetic equator, shows that there is an enhancement of semi-diurnal tidal amplitude during the days of a major SSW event and a suppression of the same immediately after the event. The significance of the present results lies in demonstrating the latitudinal coupling between the high latitude SSW phenomenon and the equatorial ionospheric current system with clear evidence for major SSW events influencing the day-to-day variability of the CEJ.

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Abdu, Mangalathayil A., Paulo A. B. Nogueira, Angela M. Santos, Jonas R. de Souza, Inez S. Batista, and Jose H. A. Sobral. "Impact of disturbance electric fields in the evening on prereversal vertical drift and spread F developments in the equatorial ionosphere." Annales Geophysicae 36, no. 2 (April 9, 2018): 609–20. http://dx.doi.org/10.5194/angeo-36-609-2018.

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Abstract. Equatorial plasma bubble/spread F irregularity occurrence can present large variability depending upon the intensity of the evening prereversal enhancement in the zonal electric field (PRE), that is, the F region vertical plasma drift, which basically drives the post-sunset irregularity development. Forcing from magnetospheric disturbances is an important source of modification and variability in the PRE vertical drift and of the associated bubble development. Although the roles of magnetospheric disturbance time penetration electric fields in the bubble irregularity development have been studied in the literature, many details regarding the nature of the interaction between the penetration electric fields and the PRE vertical drift still lack our understanding. In this paper we have analyzed data on F layer heights and vertical drifts obtained from digisondes operated in Brazil to investigate the connection between magnetic disturbances occurring during and preceding sunset and the consequent variabilities in the PRE vertical drift and associated equatorial spread F (ESF) development. The impact of the prompt penetration under-shielding eastward electric field and that of the over-shielding, and disturbance dynamo, westward electric field on the evolution of the evening PRE vertical drift and thereby on the ESF development are briefly examined. Keywords. Ionosphere (ionospheric irregularities)

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Pallam Raju, D., R. Sridharan, S. Gurubaran, and R. Raghavarao. "First results from ground-based daytime optical investigation of the development of the equatorial ionization anomaly." Annales Geophysicae 14, no. 2 (February 29, 1996): 238–45. http://dx.doi.org/10.1007/s00585-996-0238-9.

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Abstract. A meridional scanning OI 630.0-nm dayglow photometer was operated from Ahmedabad (17.2°N dip lat.) scanning a region towards the south in the upper atmosphere extending over ~5° in latitude from 10.2°N to 15.2°N dip latitude. From the spatial and temporal variabilities of the dayglow intensity in the scanning region we show for the first time, evidence for the passage of the crest of the equatorial ionization anomaly (EIA) in the daytime by means of a ground-based optical technique. The relationship between the daytime eastward electric field over the dip equator in the same longitude zone as inferred from the equatorial electrojet strength and the evolutionary pattern of EIA is clearly demonstrated. The latter as inferred from the dayglow measurements is shown to be consistent with our present understanding of the electrodynamical processes in the equatorial region. The present results reveal the potential of this ground-based optical technique for the investigation of ionospheric/thermospheric phenomena with unprecedented spatial and temporal resolution.

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10

Jayachandran, B., R. Balachandran Nair, N. Balan, and P. B. Rao. "Short term variabilities of ionospheric electron content (IEC) and peak electron density (NP) during solar cycles 20 and 21 for a low latitude station." Journal of Atmospheric and Terrestrial Physics 57, no. 13 (November 1995): 1599–609. http://dx.doi.org/10.1016/0021-9169(95)00087-i.

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11

Jiang, Y., Z. Sheng, and H. Q. Shi. "Modes of zonal mean temperature variability 20–100 km from the TIMED/SABER observations." Annales Geophysicae 32, no. 3 (March 27, 2014): 285–92. http://dx.doi.org/10.5194/angeo-32-285-2014.

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Abstract. In this study we investigate the spatial variabilities of the zonal mean temperature (20–100 km) from the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite using the empirical orthogonal functions (EOFs). After removing the climatological annual mean, the first three EOFs are able to explain 87.0% of temperature variabilities. The primary EOF represents 74.1% of total anomalies and is dominated by the north–south contrast. Patterns in the second and third EOFs are related to the semiannual oscillations (SAO) and mesospheric temperature inversions (MTI), respectively. The quasi-biennial oscillation (QBO) component is also decomposed into the seventh EOF with contributions of 1.2%. Last, we use the first three modes and annual mean temperature to reconstruct the data. The result shows small differences are in low latitude, which increase with latitude in the middle stratosphere and upper mesosphere.

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12

Koh, Kuang Liang, Zhongjian Liu, and Martin Füllekrug. "Lower Ionosphere Effects on Narrowband Very Low Frequency Transmission Propagation: Fast Variabilities and Frequency Dependence." Radio Science 53, no. 5 (May 2018): 611–23. http://dx.doi.org/10.1002/2017rs006456.

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13

Debnath, Subhajit, and Uma Das. "Short-Term Variability of Non-Migrating Diurnal Tides in the Stratosphere from CMAM30, ERA-Interim, and FORMOSAT-3/COSMIC." Atmosphere 14, no. 2 (January 28, 2023): 265. http://dx.doi.org/10.3390/atmos14020265.

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The variability of non-migrating tides in the stratosphere is investigated using temperature data from Canadian Middle Atmosphere Model (CMAM30), ERA-interim reanalysis and Formosa Satellite-3 and Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) from 2006 to 2010 using a ±10-day window. CMAM30 and ERA results show that the amplitudes of non-migrating tides, DS0 and DW2, are negligible in the mid and high-latitude stratosphere, and the results from satellite datasets are significantly affected by aliasing in this region, in spite of using a smaller window size for analysis (±10 days). Significant short term variability ranging from 30 to 100 days is observed in DS0 and DW2 over the equatorial and tropical latitudes. These tides are seen as two prominent bands around the equator with DS0 maximising during boreal summers and DW2 maximising during boreal winters. These variabilities are compared with the variability in amplitude of the stationary planetary wave with wavenumber one (SPW1) in the high-latitude stratosphere using the continuous wavelet transform (CWT). It is found that during boreal winters, the variability of SPW1 at 10 hPa over 65° N is similar to that of DS0 and DW2 over the equator at 0.0007 hPa. This provides evidence that SPW1 from the high-altitude stratosphere moving upward and equator-ward could be interacting with the migrating diurnal tide and generating the non-migrating tides in the equatorial mesosphere and lower thermosphere (MLT). The variabilities, however, are not comparable during summers, with SPW1 being absent in the Northern Hemisphere. It is thus concluded that non-linear interactions could be a source of non-migrating tidal variability in the equatorial MLT region during boreal winters, but during summers, the tidal variabilities have other sources in the lower atmosphere. The anti-symmetric nature of the vertical global structures indicates that these tides could be the result of global atmospheric oscillations proposed by the classical tidal theory.

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Jee, Geonhwa, Young-Bae Ham, Yoonseung Choi, Eunsol Kim, Changsup Lee, Hyuckjin Kwon, Trond S. Trondsen, Ji Eun Kim, and Jeong-Han Kim. "Observations of the Aurora by Visible All-Sky Camera at Jang Bogo Station, Antarctica." Journal of Astronomy and Space Sciences 38, no. 4 (December 2021): 203–15. http://dx.doi.org/10.5140/jass.2021.38.4.203.

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The auroral observation has been started at Jang Bogo Station (JBS), Antarctica by using a visible All-sky camera (v-ASC) in 2018 to routinely monitor the aurora in association with the simultaneous observations of the ionosphere, thermosphere and magnetosphere at the station. In this article, the auroral observations are introduced with the analysis procedure to recognize the aurora from the v-ASC image data and to compute the auroral occurrences and the initial results on their spatial and temporal distributions are presented. The auroral occurrences are mostly confined to the northern horizon in the evening sector and extend to the zenith from the northwest to cover almost the entire sky disk over JBS at around 08 MLT (magnetic local time; 03 LT) and then retract to the northeast in the morning sector. At near the magnetic local noon, the occurrences are horizontally distributed in the northern sky disk, which shows the auroral occurrences in the cusp region. The results of the auroral occurrences indicate that JBS is located most of the time in the polar cap near the poleward boundary of the auroral oval in the nightside and approaches closer to the oval in the morning sector. At around 08 MLT (03 LT), JBS is located within the auroral oval and then moves away from it, finally being located in the cusp region at the magnetic local noon, which indicates that the location of JBS turns out to be ideal to investigate the variabilities of the poleward boundary of the auroral oval from long-term observations of the auroral occurrences. The future plan for the ground auroral observations near JBS is presented.

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Akhil Raj, Sivan Thankamani, Madineni Venkat Ratnam, Daggumati Narayana Rao, and Boddam Venkata Krishna Murthy. "Long-term trends in stratospheric ozone, temperature, and water vapor over the Indian region." Annales Geophysicae 36, no. 1 (January 29, 2018): 149–65. http://dx.doi.org/10.5194/angeo-36-149-2018.

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Abstract. We have investigated the long-term trends in and variabilities of stratospheric ozone, water vapor and temperature over the Indian monsoon region using the long-term data constructed from multi-satellite (Upper Atmosphere Research Satellite (UARS MLS and HALOE, 1993–2005), Aura Microwave Limb Sounder (MLS, 2004–2015), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER, 2002–2015) on board TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics)) observations covering the period 1993–2015. We have selected two locations, namely, Trivandrum (8.4∘ N, 76.9∘ E) and New Delhi (28∘ N, 77∘ E), covering northern and southern parts of the Indian region. We also used observations from another station, Gadanki (13.5∘ N, 79.2∘ E), for comparison. A decreasing trend in ozone associated with NOx chemistry in the tropical middle stratosphere is found, and the trend turned to positive in the upper stratosphere. Temperature shows a cooling trend in the stratosphere, with a maximum around 37 km over Trivandrum (−1.71 ± 0.49 K decade−1) and New Delhi (−1.15 ± 0.55 K decade−1). The observed cooling trend in the stratosphere over Trivandrum and New Delhi is consistent with Gadanki lidar observations during 1998–2011. The water vapor shows a decreasing trend in the lower stratosphere and an increasing trend in the middle and upper stratosphere. A good correlation between N2O and O3 is found in the middle stratosphere (∼ 10 hPa) and poor correlation in the lower stratosphere. There is not much regional difference in the water vapor and temperature trends. However, upper stratospheric ozone trends over Trivandrum and New Delhi are different. The trend analysis carried out by varying the initial year has shown significant changes in the estimated trend. Keywords. Atmospheric composition and structure (middle atmosphere – composition and chemistry; troposphere – composition and chemistry) – meteorology and atmospheric dynamics (climatology)

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Kim, Joowan, and Seok-Woo Son. "Tropical Cold-Point Tropopause: Climatology, Seasonal Cycle, and Intraseasonal Variability Derived from COSMIC GPS Radio Occultation Measurements." Journal of Climate 25, no. 15 (August 1, 2012): 5343–60. http://dx.doi.org/10.1175/jcli-d-11-00554.1.

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Abstract The finescale structure of the tropical cold-point tropopause (CPT) is examined using high-resolution temperature profiles derived from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) global positioning system (GPS) radio occultation measurements for 4 yr from September 2006 to August 2010. The climatology, seasonal cycle, and intraseasonal variability are analyzed for three CPT properties: temperature (T-CPT), pressure (P-CPT), and sharpness (S-CPT). Their relationships with tropospheric and stratospheric processes are also discussed. The climatological P-CPT is largely homogeneous in the deep tropics, whereas T-CPT and S-CPT exhibit local minima and maxima, respectively, at the equator in the vicinity of deep convection regions. All three CPT properties, however, show coherent seasonal cycle in the tropics; the CPT is colder, higher (lower in pressure), and sharper during boreal winter than during boreal summer. This seasonality is consistent with the seasonal cycle of tropical upwelling, which is largely driven by stratospheric and near-tropopause processes, although the amplitude of the seasonal cycle of T-CPT and S-CPT is modulated by tropospheric circulations. On intraseasonal time scales, P-CPT and T-CPT exhibit homogeneous variability in the deep tropics, whereas S-CPT shows pronounced local variability and seasonality. The wavenumber–frequency spectra reveal that intraseasonal variability of CPT properties is primarily controlled by Kelvin waves, with a nonnegligible contribution by Madden–Julian oscillation convection. The Kelvin waves, which are excited by deep convection but often propagate along the equator freely, explain the homogeneous P-CPT and T-CPT variabilities. On the other hand, the vertically tilted dipole of temperature anomalies, which is associated with convectively coupled equatorial waves, determines the local structure and seasonality of S-CPT variability.

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Jin, Yaqi, Lasse B. N. Clausen, Wojciech J. Miloch, Per Høeg, Wojciech Jarmołowski, Pawel Wielgosz, Jacek Paziewski, et al. "Climatology and Modeling of Ionospheric Irregularities over Greenland Based on Empirical Orthogonal Function Method." Journal of Space Weather and Space Climate, June 1, 2022. http://dx.doi.org/10.1051/swsc/2022022.

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This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using rate of change of TEC index (ROTI). The climatology reveals various variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. By fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt and Dst), a climatological model of ionospheric irregularities is developed. The data-model comparison shows satisfactory results with high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we are able to directly compare the climatic variations of the ROTI activity across six solar cycles.

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Ye, Hailun, Xianghui Xue, Tao Yu, Yang‐Yi Sun, Wen Yi, Chi Long, Weifan Zhang, and Xiankang Dou. "Ionospheric F‐Layer Scintillation Variabilities Over the American Sector During Sudden Stratospheric Warming Events." Space Weather 19, no. 8 (August 2021). http://dx.doi.org/10.1029/2020sw002703.

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Anthony Massoud, Alexander, Fabiano Rodrigues, and Sam Shidler. "A height-dependent climatological model of the Equatorial ionospheric Zonal plasma Drifts (EZDrifts): Description and application to an analysis of the longitudinal variations of the zonal drifts." Journal of Space Weather and Space Climate, March 3, 2023. http://dx.doi.org/10.1051/swsc/2023006.

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We introduce the implementation of a global climatological model of the equatorial ionospheric F-region zonal drifts (EZDrifts) that is made available to the public. The model uses the analytic description of the zonal plasma drifts presented by Haerendel et al. (1992) and is driven by climatological models of the ionosphere and thermosphere under a realistic geomagnetic field configuration. EZDrifts is an expansion of the model of the zonal drifts first presented by Shidler and Rodrigues (2021) which was only valid for the Jicamarca longitude sector and two specific solar flux conditions. EZDrifts now uses vertical equatorial plasma drifts from the Scherliess and Fejer (1999) model which allows it to provide zonal drifts for any day of the year, longitude and solar flux condition. We show that the model can reproduce the main results of the Shidler and Rodrigues (2021) model for the Peruvian sector. We also illustrate an application of EZDrifts by presenting and discussing longitudinal variabilities produced by the model. We show that the model predicts longitudinal variations in the reversal times of the drifts that are in good agreement with observations made by C/NOFS. EZDrifts also predicts longitudinal variations in the magnitude of the drifts that can be identified in the June solstice observations made by C/NOFS. We also point out data-model differences observed during Equinox and December solstice. Finally, we explain that the longitudinal variations in the zonal plasma drifts are caused by longitudinal variations in the latitude of the magnetic equator and, consequently, in the wind dynamo contributing to the resulting drifts. EZDrifts is distributed to the community through a public repository and can be used in applications requiring an estimate of the overall behavior of the equatorial zonal drifts.

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dos Santos Prol, Fabricio, Mainul Hoque, and Arthur Amaral Ferreira. "Plasmasphere and Topside Ionosphere Reconstruction using METOP Satellite Data during Geomagnetic Storms." Journal of Space Weather and Space Climate, December 9, 2020. http://dx.doi.org/10.1051/swsc/2020076.

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As part of the space weather monitoring, the response of the ionosphere and plasmasphere to geomagnetic storms is typically under continuous supervision by operational services. Fortunately, Global Navigation Satellite System (GNSS) receivers on board low Earth orbit satellites provides a unique opportunity for developing image representations that can capture the global distribution of the electron density in the plasmasphere and topside ionosphere. Among the difficulties of plasmaspheric imaging based on GNSS measurements, the development of procedures to invert the Total Electron Content (TEC) into electron density distributions remains as a challenging task. In this study, a new tomographic reconstruction technique is presented to estimate the electron density from TEC data along the METOP (Meteorological Operational) satellites. The proposed method is evaluated during four geomagnetic storms to check the capabilities of the tomography for space weather monitoring. The investigation shows that the developed method can successfully capture and reconstruct well-known enhancement and decrease of electron density variabilities during storms. The comparison with in-situ electron densities has shown an improvement around 11% and a better description of plasma variabilities due to the storms compared to the background. Our study also reveals that the plasmasphere TEC contribution to ground-based TEC may vary 10 to 60% during geomagnetic storms, and the contribution tends to reduce during the storm-recovery phase

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Martinez, Benjamin C., and Xian Lu. "Quantifying day-to-day variability of O/N2 and its correlation with geomagnetic activity using GOLD." Frontiers in Astronomy and Space Sciences 10 (February 20, 2023). http://dx.doi.org/10.3389/fspas.2023.1129279.

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We quantify the short-term (<30 day) variability of column O/N2 measured by GOLD from January 2019 to August 2022 for various geomagnetic activity conditions. We find enhanced variabilities at high latitudes during active (Kp ≥ 3.0) times and weak but statistically significant variabilities at low latitudes. For active times, the largest absolute variability of O/N2 ratio is 0.14 and the largest relative variability is 20.6% at ∼60.0°N in Fall, which are about twice those of quiet times. The variability at higher latitudes can be larger than that of lower latitudes by a factor of 5–8. We further quantify contributions of magnetospheric forcing to O/N2 variability in the Ionosphere-Thermosphere region by correlating O/N2 perturbations with Dst. During geomagnetic active times, positive correlations as large as +0.66 and negative correlations as large as −0.65 are found at high and low latitudes, respectively, indicative of storm-induced O and N2 upwelling at high latitudes and down welling at low latitudes. During quiet times, correlations between O/N2 perturbations and Dst become insignificant at all latitudes, implying a more substantial contribution from below. O/N2 variabilities maximize in Fall and decrease towards Summer, while correlations maximize in Spring/Summer and decrease in Winter/Spring, which may be related to seasonal variations of geomagnetic activity and mean circulation.

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Gramapurohit, Pavan D., and N. V. Rao. "Variabilities and dependencies of suprathermal electron exobase altitudes in the martian ionosphere: Insights from MAVEN measurements." Planetary and Space Science, April 2023, 105699. http://dx.doi.org/10.1016/j.pss.2023.105699.

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Journal articles on the topic 'Ionospheric variabilities'

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