scholarly journals Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015

2018 ◽  
Vol 36 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Ilya Edemskiy ◽  
Jan Lastovicka ◽  
Dalia Buresova ◽  
John Bosco Habarulema ◽  
Ivan Nepomnyashchikh
Keyword(s):  
South Africa ◽  
Southern Hemisphere ◽  
Geomagnetic Storms ◽  
Geomagnetic Latitude ◽  
Electron Content ◽  
Solar Activity Minimum ◽  
Total Electron ◽  
Ionospheric Response ◽  
Middle Latitudes ◽  
Local Noon

Abstract. Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC) enhancement (LTE) in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2 h after local noon). The plumes moved with the Sun. They peaked near 13:00 UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63–64° S); it persisted for about 10 h, whereas the northern plume persisted for about 2 h more. Both plumes disappeared over the South Atlantic Ocean. No similar LTE event was observed during the prolonged solar activity minimum period of 2006–2009. In 2012–2016 we detected altogether 26 LTEs and all of them were associated with the southward excursion of Bz. The negative Bz excursion is a necessary but not sufficient condition for the LTE occurrence as during some geomagnetic storms associated with negative Bz excursions the LTE events did not appear.

Localized enhancements of total electron content in Southern Hemisphere

2020 ◽  
Author(s):  
Ilya Edemskiy ◽  
Ilya Edemskiy
Keyword(s):  
Southern Hemisphere ◽  
Total Electron Content ◽  
Magnetic Storms ◽  
Occurrence Rate ◽  
Electron Content ◽  
Quiet Time ◽  
Total Electron ◽  
Middle Latitudes ◽  
Near Space ◽  
Global Ionospheric Maps

<p>Localized enhancements of total electron content (TEC) are usually registered during magnetic storms and are often believed to be connected with storm enhanced density (SED) events. Investigating global ionospheric maps we found that such localized TEC enhancements (LTE) could be observed in Southern Hemisphere during both disturbed and quiet time with no clear dependence on parameters of near space. Analysis of occurrence of LTEs in the regions of Indian and Southern Atlantic Oceans showed that part of them (observed during magnetic storms and localized in subpolar latitudes) can be connected with SEDs. Since another part of subpolar LTEs is detected during relatively quiet conditions its generation mechanism should be different despite they have similar spatial distribution. Most of the enhancements are observed in middle latitudes and is detected during all the investigated years. The occurrence rate of LTEs hardly depends on solar activity and the most probable season for LTE detection is April-September (autumn-winter).</p><p>Here we investigate reasons of generation both midlatitudinal and subpolar LTEs trying to define the mechanisms of their generation in details.</p>

An opposite response of the low-latitude ionosphere at Asian and American sectors during storm recovery phase: drivers from below and above

2020 ◽  
Author(s):  
Chao Xiong ◽  
Hermann Luehr ◽  
Yosuke Yamazaki
Keyword(s):  
Geomagnetic Storms ◽  
Recovery Phase ◽  
The Philippines ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Early Recovery ◽  
Total Electron ◽  
Ionospheric Response ◽  
Swarm Satellites ◽  
Opposite Response

<p>The energy input from the solar wind and magnetosphere is thought to dominate the ionospheric response during geomagnetic storms. However, at the storm recovery phase, the role of forces from lower atmosphere could be as important as that from above. In this study, we focused on the geomagnetic storm happened on 6–11 September 2017. The ground-based total electron content (TEC) data as well as the F region in situ electron density measured by the Swarm satellites reveals that at low and equatorial latitudes the dayside ionosphere shows as prominent positive and negative responses at the Asian and American longitudinal sectors, respectively. The global distribution of thermospheric O/N2 ratio measured by global ultraviolet imager on board the TIMED satellite cannot well explain such longitudinally opposite response of the ionosphere. Comparison between the equatorial electrojet variations from stations at Huancayo in Peru and Davao in the Philippines suggests that the longitudinally opposite ionospheric response should be closely associated with the interplay of E region electrodynamics. By further applying nonmigrating tidal analysis to the ground‐based TEC data, we find that the diurnal tidal components, D0 and DW2, as well as the semidiurnal component SW1, are clearly enhanced over prestorm days and persist into the early recovery phase, indicating the possibility of lower atmospheric forcing contributing to the longitudinally opposite response of the ionosphere on 9–11 September 2017.</p>

scholarly journals Ionospheric response to solar extreme ultraviolet radiation variations: comparison based on CTIPe model simulations and satellite measurements

2021 ◽  
Vol 39 (2) ◽  
pp. 341-355
Author(s):  
Rajesh Vaishnav ◽  
Erik Schmölter ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Extreme Ultraviolet ◽  
Electron Content ◽  
Solar Dynamics Observatory ◽  
International Gnss Service ◽  
Average Delay ◽  
Total Electron ◽  
Ionospheric Response ◽  
Flux Model

Abstract. The ionospheric total electron content (TEC) provided by the International GNSS Service (IGS) and the TEC simulated by the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low-latitude and midlatitude TEC response over 15∘ E shows a better correlation of observed TEC and the solar radio flux index F10.7 in the Southern Hemisphere compared to the Northern Hemisphere. Thus, a significant hemispheric asymmetry is observed. The ionospheric delay estimated using model-simulated TEC is in good agreement with the delay estimated for observed TEC against the flux measured by the Solar Dynamics Observatory (SDO) extreme ultraviolet (EUV) Variability Experiment (EVE). The average delay for the observed (modeled) TEC is 17(16) h. The average delay calculated for observed and modeled TEC is 1 and 2 h longer in the Southern Hemisphere compared to the Northern Hemisphere. Furthermore, the observed TEC is compared with the modeled TEC simulated using the SOLAR2000 and EUVAC flux models within CTIPe over northern and southern hemispheric grid points. The analysis suggests that TEC simulated using the SOLAR2000 flux model overestimates the observed TEC, which is not the case when using the EUVAC flux model.

scholarly journals Extreme Solar Events’ Impact on GPS Positioning Results

2021 ◽  
Vol 13 (18) ◽  
pp. 3624
Author(s):  
Janis Balodis ◽  
Madara Normand ◽  
Inese Varna
Keyword(s):  
Time Series ◽  
Space Weather ◽  
Geomagnetic Storms ◽  
Geomagnetic Latitude ◽  
Satellite System ◽  
Rate Of Change ◽  
Electron Content ◽  
Total Electron ◽  
Cycle Slips ◽  
Global Navigation Satellite

The main objective of the present study is to perform an analysis of the space weather impact on the Latvian CORS (Continuously Operating GNSS (Global Navigation Satellite System) Stations) GPS (Global Positioning System) observations, in situations of geomagnetic storms, sun flares and extreme TEC (Total Electron Content) and ROTI (Rate of change of TEC index) levels, by analyzing the results, i.e., 90-second kinematic post-processing solutions, obtained using Bernese GNSS Software v5.2. To complete this study, the 90-second kinematic time series of all the Latvian CORS for the period from 2007 to 2017 were analyzed, and a correlation between time series outliers (hereinafter referred to as faults) and extreme space weather events was sought. Over 36 million position determination solutions were examined, 0.6% of the solutions appear to be erroneous, 0.13% of the solutions have errors greater than 1 m, 0.05% have errors greater than 10 m, and 0.01% of the solutions show errors greater than 50 meters. The correlation between faulty results, TEC and ROTI levels and Bernese GNSS Software v5.2 detected cycle slips was computed. This also includes an analysis of fault distribution depending on the geomagnetic latitude as well as faults distribution simultaneously occurring in some stations, etc. This work is the statistical analysis of the Latvian CORS security, mainly focusing on geomagnetic extreme events and ionospheric scintillations in the region of Latvia, with a latitude around 57° N.

scholarly journals Ionospheric Response to Solar EUV Radiation Variations: Comparison based on CTIPe Model Simulations and Satellite Measurements

2020 ◽  
Author(s):  
Rajesh Vaishnav ◽  
Erik Schmölter ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Electron Content ◽  
Solar Dynamics Observatory ◽  
International Gnss Service ◽  
Average Delay ◽  
Total Electron ◽  
Ionospheric Response ◽  
Solar Radio Flux ◽  
Flux Model

Abstract. The ionospheric Total Electron Content (TEC) provided by the International GNSS Service (IGS), and the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model simulated TEC have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low and mid-latitudes TEC response over 15° E shows a better correlation of observed TEC and the solar radio flux index F10.7 in the Southern Hemisphere compared to the Northern Hemisphere. Thus, a significant hemispheric asymmetry is observed. The ionospheric delay estimated using model simulated TEC is in good agreement with the delay estimated for observed TEC against Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) measured flux. The average delay for the observed (modeled) TEC is 17(16) h. The average delay calculated for observed and modeled TEC is 1 and 2 h longer in the Southern Hemisphere compared to the Northern Hemisphere. Furthermore, the observed TEC is compared with the modeled TEC simulated using the SOLAR2000 and EUVAC flux models within CTIPe over Northern and Southern Hemispheric grid points. The analysis suggests that TEC simulated using the SOLAR2000 flux model overestimates the observed TEC, which is not the case when using the EUVAC flux model.

scholarly journals The nighttime ionospheric response and occurrence of equatorial plasma irregularities during geomagnetic storms: a case study

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Xin Wan ◽  
Chao Xiong ◽  
Shunzu Gao ◽  
Fuqing Huang ◽  
Yiwen Liu ◽  
...  
Keyword(s):  
Large Scale ◽  
Geomagnetic Storms ◽  
Recovery Phase ◽  
Small Scale ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Response ◽  
Plasma Irregularities ◽  
Night Side ◽  
Ionospheric Plasma Density

AbstractRecent studies revealed that the long-lasting daytime ionospheric enhancements of Total Electron Content (TEC) were sometimes observed in the Asian sector during the recovery phase of geomagnetic storms (e.g., Lei (J Geophys Res Space Phys 123: 3217–3232, 2018), Li (J Geophys Res Space Phys 125: e2020JA028238, 2020). However, they focused only on the dayside ionosphere, and no dedicated studies have been performed to investigate the nighttime ionospheric behavior during such kinds of storm recovery phases. In this study, we focused on two geomagnetic storms that happened on 7–8 September 2017 and 25–26 August 2018, which showed the prominent daytime TEC enhancements in the Asian sector during their recovery phases, to explore the nighttime large-scale ionospheric responses as well as the small-scale Equatorial Plasma Irregularities (EPIs). It is found that during the September 2017 storm recovery phase, the nighttime ionosphere in the American sector is largely depressed, which is similar to the daytime ionospheric response in the same longitude sector; while in the Asian sector, only a small TEC increase is observed at nighttime, which is much weaker than the prominent daytime TEC enhancement in this longitude sector. During the recovery phase of the August 2018 storm, a slight TEC increase is observed on the night side at all longitudes, which is also weaker than the prominent daytime TEC enhancement. For the small-scale EPIs, they are enhanced and extended to higher latitudes during the main phase of both storms. However, during the recovery phases of the first storm, the EPIs are largely enhanced and suppressed in the Asian and American sectors, respectively, while no prominent nighttime EPIs are observed during the second storm recovery phase. The clear north–south asymmetry of equatorial ionization anomaly crests during the second storm should be responsible for the suppression of EPIs during this storm. In addition, our results also suggest that the dusk side ionospheric response could be affected by the daytime ionospheric plasma density/TEC variations during the recovery phase of geomagnetic storms, which further modulates the vertical plasma drift and plasma gradient. As a result, the growth rate of post-sunset EPIs will be enhanced or inhibited.

scholarly journals Temporal and spatial variations in ionospheric electron density profiles over South Africa during strong magnetic storms

2013 ◽  
Vol 13 (2) ◽  
pp. 375-384 ◽  
Author(s):  
Y. B. Yao ◽  
P. Chen ◽  
S. Zhang ◽  
J. J. Chen
Keyword(s):  
South Africa ◽  
Electron Density ◽  
Geomagnetic Storms ◽  
Magnetic Storms ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Ionospheric Electron Density ◽  
Density Profiles ◽  
Total Electron ◽  
Electron Density Profiles

Abstract. Observations from the South African TrigNet global navigation satellite system (GNSS) and vertical total electron content (VTEC) data from the Jason-1 satellite were used to analyze the variations in ionospheric electron density profiles over South Africa before and after the severe geomagnetic storms on 15 May 2005. Computerized ionospheric tomography (CIT) was used to inverse the 3-D structure of ionospheric electron density and its response to the magnetic storms. Inversion results showed that electron density significantly increased at 10:00 UT, 15 May compared with that at the same period on 14 May. Positive ionospheric storms were observed in the inversion region during the magnetic storms. Jason-1 data show that the VTEC observed on descending orbits on 15 May significantly increased, whereas that on ascending orbits only minimally changed. This finding is identical to the CIT result.

scholarly journals Latitudinal Dependence of the Ionospheric Slab Thickness for Estimation of Ionospheric Response to Geomagnetic Storms

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 164
Author(s):  
Maria A. Sergeeva ◽  
Olga A. Maltseva ◽  
Ramon Caraballo ◽  
Juan Americo Gonzalez-Esparza ◽  
Pedro Corona-Romero
Keyword(s):  
Space Weather ◽  
Geomagnetic Storms ◽  
Ionospheric Disturbance ◽  
Slab Thickness ◽  
Electron Content ◽  
General Tendency ◽  
Total Electron ◽  
Ionospheric Response ◽  
Latitudinal Dependence ◽  
Longitudinal Sector

The changes in the ionosphere during geomagnetic disturbances is one of the prominent Space Weather effects on the near-Earth environment. The character of these changes can differ significantly at different regions on the Earth. We studied ionospheric response to five geomagnetic storms of March 2012, using data of Total Electron Content (TEC) and F2-layer critical frequency (foF2) along the meridian of 70° W in the Northern Hemisphere. There are few ionosondes along this longitudinal sector: in Thule, Sondrestrom, Millstone Hill and Puerto Rico. The lacking foF2 values between the ionosondes were determined by using the experimental latitudinal dependences of the equivalent ionospheric slab thickness and TEC values. During geomagnetic storms, the following features were characteristic: (a) two-hours (or longer in one case) delay of the ionospheric response to disturbances, (b) the more prominent mid-latitude trough and (c) the sharper border of the EIA northern crest. During four storms of 7–17 March, the general tendency was the transition from negative disturbances at high latitudes to intense positive disturbances at low latitudes. During the fifth storm, the negative ionospheric disturbance controlled by O/N2 change was masked by the overall prolonged electron density increase during 21–31 March. The multiple correlation analysis revealed the latitudinal dependence of dominant Space Weather parameters’ impacts on foF2.

scholarly journals Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Pin-Hsuan Cheng ◽  
Charles Lin ◽  
Yuichi Otsuka ◽  
Hanli Liu ◽  
Panthalingal Krishanunni Rajesh ◽  
...  
Keyword(s):  
Climate Model ◽  
Geomagnetic Latitude ◽  
Detection Algorithm ◽  
Support Vector ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

AbstractThis study investigates the medium-scale traveling ionospheric disturbances (MSTIDs) statistically at the low-latitude equatorial ionization anomaly (EIA) region in the northern hemisphere. We apply the automatic detection algorithm including the three-dimensional fast Fourier transform (3-D FFT) and support vector machine (SVM) on total electron content (TEC) observations, derived from a network of ground-based global navigation satellite system (GNSS) receivers in Taiwan (14.5° N geomagnetic latitude; 32.5° inclination), to identify MSTID from other waves or irregularity features. The obtained results are analyzed statistically to examine the behavior of low-latitude MSTIDs. Statistical results indicate the following characteristics. First, the southward (equatorward) MSTIDs are observed almost every day during 0800–2100 LT in Spring and Winter. At midnight, southward MSTIDs are more discernible in Summer and majority of them are propagating from Japan to Taiwan. Second, northward (poleward) MSTIDs are more frequently detected during 1200–2100 LT in Spring and Summer with the secondary peak of occurrence between day of year (DOY) 100–140 during 0000–0300 LT. The characteristics of the MSTIDs are interpreted with additional observations from radio occultation (RO) soundings of FORMOSAT-3/COSMIC as well as modeled atmospheric waves from the high-resolution Whole Atmosphere Community Climate Model (WACCM) suggesting that the nighttime MSTIDs in Summer is likely connected to the atmospheric gravity waves (AGWs).

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