scholarly journals Plasma re-distribution in the African low-latitude ionosphere during intense geomagnetic storms

2020 ◽  
pp. 228-240
Author(s):  
S. O. Ikubanni ◽  
S. J. Adebiyi ◽  
B. O. Adebesin ◽  
O. S. Bolaji ◽  
B. J. Adekoya ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Early Morning ◽  
Recovery Phase ◽  
Electron Content ◽  
East African ◽  
Ionospheric Effect ◽  
Total Electron ◽  
Weather Events ◽  
Intense Storm ◽  
Low Latitude Ionosphere

Intense geomagnetic storms offer opportunity to understand ionospheric response to space weather events. Using Total Electron Content (TEC) data from stations along the east African sector, the two most intense storms during the 24th solar cycle, with similarly occurrence season and time were studied. We observe that ionospheric effect during the main phase is not a function of the severity of the storm, whereas the more intense storm shows greater influence on the African ionosphere during the recovery phase. Plasma movement within the equatorial ionization anomaly (EIA) was evident particularly during the recovery phase, especially during the 2015 event. For both storms, the nighttime/early morning ionospheric effect is more pronounced than the daytime effects across all stations.    

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 Similarity and differences in morphology and mechanisms of the <i>fo</i>F2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

2017 ◽  
Vol 35 (4) ◽  
pp. 923-938 ◽  
Author(s):  
Maxim V. Klimenko ◽  
Vladimir V. Klimenko ◽  
Irina E. Zakharenkova ◽  
Konstantin G. Ratovsky ◽  
Nina A. Korenkova ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Recovery Phase ◽  
Main Phase ◽  
Formation Mechanisms ◽  
Electron Content ◽  
Time Behavior ◽  
Total Electron ◽  
Simultaneous Formation ◽  
Low Latitudes ◽  
Critical Frequency Fof2

Abstract. This study presents an analysis of the ground-based observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American) during geomagnetic storms that occurred on 26–30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC) and the ionospheric F2 peak critical frequency (foF2) during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800–20 000 km) at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O) ∕ n(N2) enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

scholarly journals Storm induced large scale TIDs observed in GPS derived TEC

2009 ◽  
Vol 27 (4) ◽  
pp. 1605-1612 ◽  
Author(s):  
C. Borries ◽  
N. Jakowski ◽  
V. Wilken
Keyword(s):  
Large Scale ◽  
Geomagnetic Storms ◽  
Phase Speed ◽  
Horizontal Resolution ◽  
Electron Content ◽  
Total Electron ◽  
Weather Events ◽  
High Horizontal Resolution ◽  
Field Lines ◽  
Gnss Measurements

Abstract. This work is a first statistical analysis of large scale traveling ionospheric disturbances (LSTID) in Europe using total electron content (TEC) data derived from GNSS measurements. The GNSS receiver network in Europe is dense enough to map the ionospheric perturbation TEC with high horizontal resolution. The derived perturbation TEC maps are analysed studying the effect of space weather events on the ionosphere over Europe. Equatorward propagating storm induced wave packets have been identified during several geomagnetic storms. Characteristic parameters such as velocity, wavelength and direction were estimated from the perturbation TEC maps. Showing a mean wavelength of 2000 km, a mean period of 59 min and a phase speed of 684 ms−1 in average, the perturbations are allocated to LSTID. The comparison to LSTID observed over Japan shows an equal wavelength but a considerably faster phase speed. This might be attributed to the differences in the distance to the auroral region or inclination/declination of the geomagnetic field lines. The observed correlation between the LSTID amplitudes and the Auroral Electrojet (AE) indicates that most of the wave like perturbations are exited by Joule heating. Particle precipitation effects could not be separated.

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 Investigation of Daytime Total Electron Content Enhancements over the Asian-Australian Sector Observed from the Beidou Geostationary Satellite during 2016–2018

2020 ◽  
Vol 12 (20) ◽  
pp. 3406
Author(s):  
Oluwaseyi Jimoh ◽  
Jiuhou Lei ◽  
Fuqing Huang
Keyword(s):  
Total Electron Content ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Recovery Phase ◽  
Geostationary Satellite ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Station ◽  
Latitudinal Dependence ◽  
Geomagnetic Condition

This study focused on the investigation of daytime positive ionospheric disturbances and the recurrence of total electron content (TEC) enhancements. TEC data derived from the Beidou geostationary satellite over the Asian-Australian sector were used to study the occurrence of TEC enhancements during 2016–2018. The occurrence of TEC enhancements under quiet geomagnetic condition was analyzed. Furthermore, the occurrence of TEC enhancements during different geomagnetic storm phases was considered to address the question that relates to the recurrence of TEC enhancements during the recovery phase of geomagnetic storms. The seasonal variation of TEC enhancements displayed equinoctial and solstitial peaks at the middle and low latitudes respectively. Besides, there was no evident systematic latitudinal dependence in the occurrence of TEC enhancements, albeit at the equatorial station, nearly no TEC enhancement was observed under Kp < 3. Meanwhile, the occurrences during the main phases of the geomagnetic storms were significantly above the TEC enhancement baselines except at HKWS. The prominence of TEC enhancements during the main phase in comparison with the initial and recovery phases could be attributed to the effects of prompt penetration electric fields and equator-ward neutral winds. Moreover, the pattern of TEC enhancements during the storm recovery indicates the effects of chemical composition changes, winds, and the possible modulation from the lower atmospheric forcing.

scholarly journals Multi-Scale Ionospheric Anomalies Monitoring and Spatio-Temporal Analysis during Intense Storm

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 215
Author(s):  
Na Cheng ◽  
Shuli Song ◽  
Wei Li
Keyword(s):  
Magnetic Storm ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Ionospheric Disturbance ◽  
Ionospheric Scintillation ◽  
Small Scale ◽  
Electron Content ◽  
Total Electron ◽  
Multi Scale ◽  
Intense Storm

The ionosphere is a significant component of the geospace environment. Storm-induced ionospheric anomalies severely affect the performance of Global Navigation Satellite System (GNSS) Positioning, Navigation, and Timing (PNT) and human space activities, e.g., the Earth observation, deep space exploration, and space weather monitoring and prediction. In this study, we present and discuss the multi-scale ionospheric anomalies monitoring over China using the GNSS observations from the Crustal Movement Observation Network of China (CMONOC) during the 2015 St. Patrick’s Day storm. Total Electron Content (TEC), Ionospheric Electron Density (IED), and the ionospheric disturbance index are used to monitor the storm-induced ionospheric anomalies. This study finally reveals the occurrence of the large-scale ionospheric storms and small-scale ionospheric scintillation during the storm. The results show that this magnetic storm was accompanied by a positive phase and a negative phase ionospheric storm. At the beginning of the main phase of the magnetic storm, both TEC and IED were significantly enhanced. There was long-duration depletion in the topside ionospheric TEC during the recovery phase of the storm. This study also reveals the response and variations in regional ionosphere scintillation. The Rate of the TEC Index (ROTI) was exploited to investigate the ionospheric scintillation and compared with the temporal dynamics of vertical TEC. The analysis of the ROTI proved these storm-induced TEC depletions, which suppressed the occurrence of the ionospheric scintillation. To improve the spatial resolution for ionospheric anomalies monitoring, the regional Three-Dimensional (3D) ionospheric model is reconstructed by the Computerized Ionospheric Tomography (CIT) technique. The spatial-temporal dynamics of ionospheric anomalies during the severe geomagnetic storm was reflected in detail. The IED varied with latitude and altitude dramatically; the maximum IED decreased, and the area where IEDs were maximum moved southward.

scholarly journals Data Assimilation for Ionospheric Space-Weather Forecasting in the Presence of Model Bias

2021 ◽  
Vol 7 ◽  
Author(s):  
Juan Durazo ◽  
Eric J. Kostelich ◽  
Alex Mahalov
Keyword(s):  
Data Assimilation ◽  
Space Weather ◽  
Bias Correction ◽  
Geomagnetic Storms ◽  
Circulation Model ◽  
Storm Event ◽  
Electron Content ◽  
Systematic Bias ◽  
Total Electron ◽  
Mean Square Errors

The dynamics of many models of physical systems depend on the choices of key parameters. This paper describes the results of some observing system simulation experiments using a first-principles model of the Earth’s ionosphere, the Thermosphere Ionosphere Electrodynamics Global Circulation Model (TIEGCM), which is driven by parameters that describe solar activity, geomagnetic conditions, and the state of the thermosphere. Of particular interest is the response of the ionosphere (and predictions of space weather generally) during geomagnetic storms. Errors in the overall specification of driving parameters for the TIEGCM (and similar dynamical models) may be especially large during geomagnetic storms, because they represent significant perturbations away from more typical interactions of the earth-sun system. Such errors can induce systematic biases in model predictions of the ionospheric state and pose difficulties for data assimilation methods, which attempt to infer the model state vector from a collection of sparse and/or noisy measurements. Typical data assimilation schemes assume that the model produces an unbiased estimate of the truth. This paper tests one potential approach to handle the case where there is some systematic bias in the model outputs. Our focus is on the TIEGCM when it is driven with solar and magnetospheric inputs that are systematically misspecified. We report results from observing system experiments in which synthetic electron density vertical profiles are generated at locations representative of the operational FormoSat-3/COSMIC satellite observing platforms during a moderate (G2, Kp = 6) geomagnetic storm event on September 26–27, 2011. The synthetic data are assimilated into the TIEGCM using the Local Ensemble Transform Kalman Filter with a state-augmentation approach to estimate a small set of bias-correction factors. Two representative processes for the time evolution of the bias in the TIEGCM are tested: one in which the bias is constant and another in which the bias has an exponential growth and decay phase in response to strong geomagnetic forcing. We show that even simple approximations of the TIEGCM bias can reduce root-mean-square errors in 1-h forecasts of total electron content (a key ionospheric variable) by 20–45%, compared to no bias correction. These results suggest that our approach is computationally efficient and can be further refined to improve short-term predictions (∼1-h) of ionospheric dynamics during geomagnetic storms.

scholarly journals New GGOS JWG3 on Improved understanding of space weather events and their monitoring

2020 ◽  
Author(s):  
Alberto Garcia-Rigo ◽  
Benedikt Soja
Keyword(s):  
Electron Density ◽  
Space Weather ◽  
International Association ◽  
Real Data ◽  
Weather Conditions ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Weather Events ◽  
Space Geodetic Techniques

&lt;p&gt;Multiple space geodetic techniques are capable of measuring effects caused by space weather events. In particular, space weather events can cause ionospheric disturbances correlated with variations in the vertical total electron content (VTEC) or the electron density (Ne) of the ionosphere.&lt;/p&gt;&lt;p&gt;In this regard and in the context of the new Focus Area on Geodetic Space Weather Research within IAG&amp;#8217;s GGOS (International Association of Geodesy; Global Geodetic Observing System), the Joint Working Group 3 on Improved understanding of space weather events and their monitoring by satellite missions has been created as part of IAG Commission 4, Sub-Commission 4.3 to run for the next four years.&lt;/p&gt;&lt;p&gt;Within JWG3, we expect investigating different approaches to monitor space weather events using the data from different space geodetic techniques and, in particular, combinations thereof. Simulations will be beneficial to identify the contribution of different techniques and prepare for the analysis of real data. Different strategies for the combination of data will also be investigated, in particular, the weighting of estimates from different techniques in order to increase the performance and reliability of the combined estimates. Furthermore, existing algorithms for the detection and prediction of space weather events will be explored and improved to the extent possible. Furthermore, the geodetic measurement of the ionospheric electron density will be complemented by direct observations from the Sun gathered from existing spacecraft, such as SOHO, ACE, SDO, Parker Solar Probe, among others. The combination and joint evaluation of multiple datasets with the measurements of space geodetic observation techniques (e.g. geodetic VLBI) is still a great challenge. In addition, other indications for solar activity - such as the F10.7 index on solar radio flux, SOLERA as EUV proxy or rate of Global Electron Content (dGEC)-, provide additional opportunities for comparisons and validation.&lt;/p&gt;&lt;p&gt;Through these investigations, we will identify the key parameters useful to improve real-time/prediction of ionospheric/plasmaspheric VTEC, Ne estimates, as well as ionospheric perturbations, in case of extreme solar weather conditions. In general, we will gain a better understanding of space weather events and their effect on Earth&amp;#8217;s atmosphere and near-Earth environment.&lt;/p&gt;

Validating the impact of various ionosphere correction on mid to long baselines and point positioning using GPS dual-frequency receivers

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alaa A. Elghazouly ◽  
Mohamed I. Doma ◽  
Ahmed A. Sedeek
Keyword(s):  
Geomagnetic Storms ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Assessment Procedure ◽  
Vertical Total Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Satellite Systems ◽  
Point Positioning ◽  
The Impact

Abstract Due to the ionosphere delay, which has become the dominant GPS error source, it is crucial to remove the ionospheric effect before estimating point coordinates. Therefore, different agencies started to generate daily Global Ionosphere Maps (GIMs); the Vertical Total Electron Content (VTEC) values represented in GIMs produced by several providers can be used to remove the ionosphere error from observations. In this research, An analysis will be carried with three sources for VTEC maps produced by the Center for Orbit Determination in Europe (CODE), Regional TEC Mapping (RTM), and the International Reference Ionosphere (IRI). The evaluation is focused on the effects of a specific ionosphere GIM correction on the precise point positioning (PPP) solutions. Two networks were considered. The first network consists of seven Global Navigation Satellite Systems (GNSS) receivers from (IGS) global stations. The selected test days are six days, three of them quiet, and three other days are stormy to check the influence of geomagnetic storms on relative kinematic positioning solutions. The second network is a regional network in Egypt. The results show that the calculated coordinates using the three VTEC map sources are far from each other on stormy days rather than on quiet days. Also, the standard deviation values are large on stormy days compared to those on quiet days. Using CODE and RTM IONEX file produces the most precise coordinates after that the values of IRI. The elimination of ionospheric biases over the estimated lengths of many baselines up to 1000 km has resulted in positive findings, which show the feasibility of the suggested assessment procedure.

scholarly journals Modification of the low-latitude ionosphere before the 26 December 2004 Indonesian earthquake

2006 ◽  
Vol 6 (5) ◽  
pp. 817-823 ◽  
Author(s):  
I. E. Zakharenkova ◽  
A. Krankowski ◽  
I. I. Shagimuratov
Keyword(s):  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
Ionospheric Effects ◽  
Earthquake Preparation ◽  
Low Latitude Ionosphere ◽  
Positive Effect ◽  
Possible Cause ◽  
Gps Observations

Abstract. This paper investigates the features of pre-earthquake ionospheric anomalies in the total electron content (TEC) data obtained on the basis of regular GPS observations from the IGS network. For the analysis of the ionospheric effects of the 26 December 2004 Indonesian earthquake, global TEC maps were used. The possible influence of the earthquake preparation processes on the main low-latitude ionosphere peculiarity – the equatorial anomaly – is discussed. Analysis of the TEC maps has shown that modification of the equatorial anomaly occurred a few days before the earthquake. For 2 days prior to the event, a positive effect was observed in the daytime amplification of the equatorial anomaly. Maximal enhancement in the crests reached 20 TECU (50–60%) relative to the non-disturbed state. In previous days, during the evening and night hours (local time), a specific transformation of the TEC distribution had taken place. This modification took the shape of a double-crest structure with a trough near the epicenter, though usually in this time the restored normal latitudinal distribution with a maximum near the magnetic equator is observed. It is assumed that anomalous electric field generated in the earthquake preparation zone could cause a near-natural "fountain-effect" phenomenon and might be a possible cause of the observed ionospheric anomaly.

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