scholarly journals Localized Increment and Decrement in the Total Electron Content of the Ionosphere as a Response to the April 20, 2018, Geomagnetic Storm

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Carlos Sotomayor-Beltran
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Longitudinal Section ◽  
Recovery Phase ◽  
Electron Content ◽  
Past Study ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Cycle 24 ◽  
Maximum Increment

A moderate geomagnetic storm occurred on April 20, 2018. Using vertical total electron content (VTEC) maps provided by the Center for Orbit Determination in Europe, ionospheric responses to the geomagnetic storm could be identified in generated two-dimensional differential VTEC maps. During the day of the storm the enhancement of the equatorial ionization anomaly (EIA), product of the super-fountain effect was identified. A localized TEC enhancement (LTE) was also observed to the south of the EIA on April 20, 2018. It was also possible to visualize this LTE in a longitudinal section of the EIA as a third crest. The maximum increment of VTEC for the LTE was 204%. This LTE is quite unique because it happened during the expected solar cycle 24 and 25 minimum, and according to a previous study no LTE observation could be done for the last solar two-cycle minimum. The origin of the observed LTE is suggested to be partly product of the super-fountain effect. Finally, a localized TEC decrement (LTD) was observed towards the end of the day, April 20, 2018. Because this LTD consisted in the disappearance of the northern and southern crests of the EIA and this occurred during the recovery phase of the geomagnetic storm, it can be suggested that the LTD origin is due to the westward disturbance electric field. This mechanism was put forward by a past study that also analyzed the responses to a geomagnetic storm (the 2015 St. Patrick’s day storm), being one of the responses the inhibition of both crests of the EIA.

scholarly journals Climatology of ionosphere over Nepal based on GPS total electron content data from 2008 to 2018

2021 ◽  
Vol 39 (4) ◽  
pp. 743-758
Author(s):  
Drabindra Pandit ◽  
Basudev Ghimire ◽  
Christine Amory-Mazaudier ◽  
Rolland Fleury ◽  
Narayan Prasad Chapagain ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Total Electron Content ◽  
Solar Flux ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Maximum Value ◽  
Spring Equinox ◽  
Cycle 24

Abstract. In this study, we analyse the climatology of ionosphere over Nepal based on GPS-derived vertical total electron content (VTEC) observed from four stations as defined in Table 1: KKN4 (27.80∘ N, 85.27∘ E), GRHI (27.95∘ N, 82.49∘ E), JMSM (28.80∘ N, 83.74∘ E) and DLPA (28.98∘ N, 82.81∘ E) during the years 2008 to 2018. The study illustrates the diurnal, monthly, annual, seasonal and solar cycle variations in VTEC during all times of solar cycle 24. The results clearly reveal the presence of equinoctial asymmetry in TEC, which is more pronounced in maximum phases of solar cycle in the year 2014 at KKN4 station, followed by descending, ascending and minimum phases. Diurnal variations in VTEC showed the short-lived day minimum which occurs between 05:00 to 06:00 LT (local time) at all the stations considered, with diurnal peaks between 12:00 and 15:00 LT. The maximum value of TEC is observed more often during the spring equinox than the autumn equinox, with a few asymmetries. Seasonal variation in TEC is observed to be a manifestation of variations in solar flux, particularly regarding the level of solar flux in consecutive solstices.

Analysis of ionospheric vertical total electron content before the 1 April 2014 Mw 8.2 Chile earthquake

2017 ◽  
Vol 21 (6) ◽  
pp. 1599-1612 ◽  
Author(s):  
Weiping Jiang ◽  
Yifang Ma ◽  
Xiaohui Zhou ◽  
Zhao Li ◽  
Xiangdong An ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Chile Earthquake

scholarly journals EFEK CME HALO PENUH PADA IONOSFER LINTANG RENDAH DARI DATA GPS BAKO DI CIBINONG [EFFECT OF FULL HALO CME ON LOW LATITUDE IONOSPHERE FROM BAKO GPS DATA IN CIBINONG]

2018 ◽  
Vol 15 (1) ◽  
pp. 51
Author(s):  
Fakhrizal Muttaqien ◽  
Buldan Muslim
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Geomagnetic Disturbance ◽  
Main Phase ◽  
Gps Data ◽  
Electron Content ◽  
Ionospheric Storm ◽  
Total Electron ◽  
Dst Index ◽  
Software Analysis

A full halo coronal mass ejections (CMEs) are most energetic solar events that eject huge amount of mass and magnetic fields into heliosphere with 360o angular angle. The full halo CME effect on the ionosphere can be determined from the ionospheric total electron content (TEC) derived from GPS data. GPS data from BAKO station in Cibinong, satellite orbital data (brcd files) and intrumental bias data (DCB files) have been used to obtain TEC using GOPI software. Analysis of  the full halo CME data, Dst index, and TEC during October 2003 and February 2014 showed that the full halo CME could cause ionospheric disturbances called ionospheric storms. Magnitude and time delay of the ionospheric storms  depended on the full halo CME speed. For the high-speed full halo CME, the negative ionospheric storm generally occured during recovery phase of the geomagnetic storm. When the initial phase of geomagnetic disturbance with increasing Dst index more than +30 nT, the ionospheric storm occured during main phase of geomagnetic disturbance although the main phase of geomagnetic disturbance did not reach geomagnetic storm condition. ABSTRAKCoronal mass ejection  (CME) halo penuh merupakan peristiwa matahari  berenergi tinggi, yang menyemburkan massa dan medan magnet ke heliosfer dengan sudut angular sebesar 360º. Efek  CME halo penuh pada ionosfer dapat diketahui dari Total Electron Content (TEC). Data GPS BAKO di Cibinong, data orbit satelit (file brcd) dan data bias instrumental (file DCB) dapat digunakan untuk penentuan TEC menggunakan software GOPI. Analisis data CME halo penuh, indeks Dst, dan TEC selama bulan Oktober 2003 dan Februari 2014 menunjukkan bahwa CME halo penuh dapat menimbulkan gangguan ionosfer yang disebut badai ionosfer. Besar dan selang waktu badai ionosfer setelah terjadinya CME, tergantung pada kelajuan CME halo penuh. Untuk CME halo penuh berkelajuan tinggi, badai ionosfer negatif umumnya terjadi pada fase pemulihan badai geomagnet. Jika fase awal gangguan geomagnet diawali dengan peningkatan indeks Dst melebihi +30 nT, maka badai ionosfer dapat terjadi pada fase utama gangguan geomagnet walau gangguan geomagnet setelah  fase awal tidak mencapai kondisi badai geomagnet. 

scholarly journals Total electron content responses to HILDCAAs and geomagnetic storms over South America

2017 ◽  
Vol 35 (6) ◽  
pp. 1309-1326 ◽  
Author(s):  
Patricia Mara de Siqueira Negreti ◽  
Eurico Rodrigues de Paula ◽  
Claudia Maria Nicoli Candido
Keyword(s):  
Solar Wind ◽  
South America ◽  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Time Variability ◽  
Electron Content ◽  
Quiet Time ◽  
Total Electron

Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of storm-time TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O ∕ N2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from  ∼  25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

scholarly journals Adaptive Modeling of the Global Ionosphere Vertical Total Electron Content

2020 ◽  
Vol 12 (11) ◽  
pp. 1822
Author(s):  
Eren Erdogan ◽  
Michael Schmidt ◽  
Andreas Goss ◽  
Barbara Görres ◽  
Florian Seitz
Keyword(s):  
Total Electron Content ◽  
Temporal Variations ◽  
Model Parameters ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Model Uncertainties ◽  
Data Set ◽  
Total Electron ◽  
B Spline ◽  
Run Time

The Kalman filter (KF) is widely applied in (ultra) rapid and (near) real-time ionosphere modeling to meet the demand on ionosphere products required in many applications extending from navigation and positioning to monitoring space weather events and naturals disasters. The requirement of a prior definition of the stochastic models attached to the measurements and the dynamic models of the KF is a drawback associated with its standard implementation since model uncertainties can exhibit temporal variations or the time span of a given test data set would not be large enough. Adaptive methods can mitigate these problems by tuning the stochastic model parameters during the filter run-time. Accordingly, one of the primary objectives of our study is to apply an adaptive KF based on variance component estimation to compute the global Vertical Total Electron Content (VTEC) of the ionosphere by assimilating different ionospheric GNSS measurements. Secondly, the derived VTEC representation is based on a series expansion in terms of compactly supported B-spline functions. We highlight the morphological similarity of the spatial distributions and the magnitudes between VTEC values and the corresponding estimated B-spline coefficients. This similarity allows for deducing physical interpretations from the coefficients. In this context, an empirical adaptive model to account for the dynamic model uncertainties, representing the temporal variations of VTEC errors, is developed in this work according to the structure of B-spline coefficients. For the validation, the differential slant total electron content (dSTEC) analysis and a comparison with Jason-2/3 altimetry data are performed. Assessments show that the quality of the VTEC products derived by the presented algorithm is in good agreement, or even more accurate, with the products provided by IGS ionosphere analysis centers within the selected periods in 2015 and 2017. Furthermore, we show that the presented approach can be applied to different ionosphere conditions ranging from very high to low solar activity without concerning time-variable model uncertainties, including measurement error and process noise of the KF because the associated covariance matrices are computed in a self-adaptive manner during run-time.

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