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.

The ionospheric response to perturbation electric fields during the onset phase of geomagnetic storms

1992 ◽  
Vol 70 (7) ◽  
pp. 575-581 ◽  
Author(s):  
N. Jakowski ◽  
A. Jungstand ◽  
K. Schlegel ◽  
H. Kohl ◽  
K. Rinnert
Keyword(s):  
Total Electron Content ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Slab Thickness ◽  
Electron Content ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Critical Frequency Fof2 ◽  
Eiscat Radar ◽  
Onset Phase

The generation and propagation of ionospheric storms are studied by analyzing EISCAT radar, and vertical-sounding and total-electron-content data obtained under different geophysical conditions. Both, case studies as well as the average storm pattern of percentage deviations of different ionospheric parameters from their corresponding reference values such as total electron content, F2-layer critical frequency foF2, F2-layer height hmF2, and slab thickness τ indicate the action of a perturbation electric field during the first few hours during the onset phase of geomagnetic storms. Considering the onset phase of the storm on July 28–29, 1987 evidence has been found that high-latitude electric fields may penetrate to lower latitudes before the ring current has developed. In most cases this process is accompanied by a positive phase in the upper ionosphere and F2-layer ionization. Different mechanisms are assumed to be responsible for the daytime and nighttime behaviour, respectively. The negative phase propagates equatorward with velocities in the order of 70–350 m s−1 following a strong heating of the thermosphere and ionosphere due to the auroral electrojet.

scholarly journals Storm-time total electron content and its response to penetration electric fields over South America

2011 ◽  
Vol 29 (10) ◽  
pp. 1765-1778 ◽  
Author(s):  
P. M. de Siqueira ◽  
E. R. de Paula ◽  
M. T. A. H. Muella ◽  
L. F. C. Rezende ◽  
M. A. Abdu ◽  
...  
Keyword(s):  
South America ◽  
Total Electron Content ◽  
Electric Fields ◽  
Equatorial Region ◽  
Electron Content ◽  
The South ◽  
Low Latitude ◽  
Total Electron ◽  
Vertical Drift ◽  
Magnetometer Data

Abstract. In this work the response of the ionosphere due to the severe magnetic storm of 7–10 November 2004 is investigated by analyzing GPS Total Electron Content (TEC) maps constructed for the South America sector. In order to verify the disturbed zonal electric fields in South America during the superstorm, ionospheric vertical drift data obtained from modeling results are used in the analysis. The vertical drifts were inferred from ΔH magnetometer data (Jicamarca-Piura) following the methodology presented by Anderson et al. (2004). Also used were vertical drifts measured by the Jicamarca ISR. Data from a digisonde located at São Luís, Brazil (2.33° S, 44.2° W, dip latitude 0.25°) are presented to complement the Jicamarca equatorial data. Penetration electric fields were observed by the comparison between the equatorial vertical drifts and the Interplanetary Electric Field (IEF). The TEC maps obtained from GPS data reflect the ionospheric response over the South America low-latitude and equatorial region. They reveal unexpected plasma distributions and TEC levels during the main phase of the superstorm on 7 November, which is coincident with the local post-sunset hours. At this time an increase in the pre-reversal enhancement was expected to develop the Equatorial Ionization Anomaly (EIA) but we observed the absence of EIA. The results also reveal well known characteristics of the plasma distributions on 8, 9, and 10 November. The emphasized features are the expansion and intensification of EIA due to prompt penetration electric fields on 9 November and the inhibition of EIA during post-sunset hours on 7, 8, and 10 November. One important result is that the TEC maps provided a bi-dimensional view of the ionospheric changes offering a spatial description of the electrodynamics involved, which is an advantage over TEC measured by isolated GPS receivers.

scholarly journals Emergence of a localized total electron content enhancement during the severe geomagnetic storm of 8 September 2017

2019 ◽  
Vol 37 (2) ◽  
pp. 153-161 ◽  
Author(s):  
Carlos Sotomayor-Beltran ◽  
Laberiano Andrade-Arenas
Keyword(s):  
Statistical Method ◽  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Orbit Determination ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
The Pacific

Abstract. In this work, the results of the analysis on total electron content (TEC) data before, during and after the geomagnetic storm of 8 September 2017 are reported. One of the responses to geomagnetic storms due to the southern vertical interplanetary magnetic field (Bz) is the enhancement of the electron density in the ionosphere. Vertical TEC (VTEC) from the Center for Orbit determination in Europe (CODE) along with a statistical method were used to identify positive and/or negative ionospheric storms in response to the geomagnetic storm of 8 September 2017. When analyzing the response to the storm of 8 September 2017 it was indeed possible to observe an enhancement of the equatorial ionization anomaly (EIA); however, what was unexpected was the identification of a local TEC enhancement (LTE) to the south of the EIA (∼40∘ S, right over New Zealand and extending towards the southeastern coast of Australia and also eastward towards the Pacific). This was a very transitory LTE that lasted approximately 4 h, starting at ∼ 02:00 UT on 8 September where its maximum VTEC increase was of 241.2 %. Using the same statistical method, comparable LTEs in a similar category geomagnetic storm, the 2015 St. Patrick's Day storm, were looked for. However, for the aforementioned storm no LTEs were identified. As also indicated in a past recent study for a LTE detected during the 15 August 2015 geomagnetic storm, an association between the LTE and the excursion of Bz seen during the 8 September 2017 storm was observed as well. Furthermore, it is very likely that a direct impact of the super-fountain effect along with traveling ionospheric disturbances may be playing an important role in the production of this LTE. Finally, it is indicated that the 8 September 2017 LTE is the second one to be detected since the year 2016.

Variation on Solar Wind Parameters and Total Electron Content Over Middle‐ to Low‐Latitude Regions During Intense Geomagnetic Storms

Radio Science ◽  
2020 ◽  
Vol 55 (11) ◽  
Author(s):  
Roshan Kumar Mishra ◽  
Binod Adhikari ◽  
Narayan Prasad Chapagain ◽  
Rabin Baral ◽  
Priyanka Kumari Das ◽  
...  
Keyword(s):  
Solar Wind ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Solar Wind Parameters

scholarly journals The Feature of Ionospheric Mid-Latitude Trough during Geomagnetic Storms Derived from GPS Total Electron Content (TEC) Data

2022 ◽  
Vol 14 (2) ◽  
pp. 369
Author(s):  
Na Yang ◽  
Tao Yu ◽  
Huijun Le ◽  
Libo Liu ◽  
Yang-Yi Sun ◽  
...  
Keyword(s):  
North America ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Quiet Time ◽  
Ionospheric Storm ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Storm Effects ◽  
Storm Effect

This study aims to investigate the features of the ionospheric mid-latitude trough over North America by using the MIT total electron content data obtained during three geomagnetic storms that occurred in August 2018, September 2017, and March 2015. The mid-latitude trough position sharply moves equatorward from the quiet-time subauroral latitude to mid-latitude with the decrease in SYM-H during geomagnetic storms. We find that the ionospheric behavior of TEC around the mid-latitude trough position displays three kinds of ionospheric storm effect: negative ionospheric storm effect, unchanged ionospheric behavior, and positive ionospheric storm effect. These ionospheric storm effects around the mid-latitude trough position are not always produced by the mid-latitude trough. The ionospheric storm effects produced by the mid-latitude trough are limited in the narrow mid-latitude trough regions, and are transmitted to other regions with the movement of the mid-latitude trough.

scholarly journals Analysis of Ionospheric Vertical Total Electron Content before the 2014 Mw8.2 Chile Earthquake

2017 ◽  
Author(s):  
Weiping Jiang ◽  
Yifang Ma ◽  
Xiaohui Zhou ◽  
Zhao Li ◽  
Xiangdong An ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Meridional Wind ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Seasonal And Diurnal Variations ◽  
Chile Earthquake

This paper studies ionospheric vertical total electron content (VTEC) variations before the 2014 Mw8.2 Chile earthquake. VTEC derived from 14 GPS (Global Positioning System) stations and GIM (Global Ionospheric Map) were used to analyze ionospheric variations before the earthquake using the sliding interquartile range method, and results showed that significant positive VTEC anomalies occurred on 28 March. To explore possible causes of these anomalies, effects of solar and geomagnetic activities were examined, and VTEC variations during 17 March to 31 March in 2009-2013 were cross-compared. Also, VTEC for a full year before the earthquake was investigated. Results indicated that these anomalies were weakly associated with high solar activities and geomagnetic storms and that these anomalies were not normal seasonal and diurnal variations. An analysis of the spatial distribution of the observed anomalies was also presented, and it demonstrated that anomalies specifically appeared around the epicenter on 28 March. It suggests that observed anomalies may be associated with the subsequent Chile earthquake. Equatorial anomaly variations were analyzed to discuss the possible physical mechanism, and results showed that the equatorial anomaly unusually increased on 28 March, which indicates that anomalous electric fields generated in the earthquake preparation area and the meridional wind are possible causes of the observed ionospheric anomalies.

scholarly journals Ionospheric Total Electron Content responses to HILDCAAs intervals

2019 ◽  
Author(s):  
Regia Pereira Silva ◽  
Clezio Marcos Denardini ◽  
Manilo Soares Marques ◽  
Laysa Cristina Araújo Resende ◽  
Juliano Moro ◽  
...  
Keyword(s):  
Solar Wind ◽  
Total Electron Content ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Long Duration ◽  
Wind Velocities ◽  
Hourly Distribution

Abstract. The High-Intensity Long-Duration and Continuous AE Activities (HILDCAA) intervals are capable of causing a global disturbance in the terrestrial ionosphere. However, the ionospheric storms' behavior due to these geomagnetic activity forms is still not widely understood. In this study, we seek to comprise the HILDCAAs disturbance time effects in the Total Electron Content (TEC) values with respect to the quiet days' pattern analyzing local time and seasonal dependences, and the influences of the solar wind velocity to a sample of ten intervals occurred in 2015 and 2016 years. The main results showed that the hourly distribution of the disturbance TEC may vary substantially between one interval and another. Doing a comparative to geomagnetic storms, while the positive ionospheric storms are more pronounced in the winter, this season presents less geoeffectiveness or almost none to HILDCAA intervals. It was find an equinoctial anomaly, since the equinoxes represent more ionospheric TEC responses during HILDCAA intervals than the solstices. Regarding to the solar wind velocities, although HILDCAA intervals are associated to High Speed Streams, this association does not present a direct relation regards to TEC disturbances in low and equatorial latitudes.

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 Study of Total Electron Content and Electron Density Profile from Satellite Observations During Geomagnetic Storms

2019 ◽  
Vol 5 (1) ◽  
pp. 59-66
Author(s):  
B. B. Rana ◽  
N. P. Chapagain ◽  
B. Adhikari ◽  
D. Pandit ◽  
K. Pudasainee ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electron Density ◽  
Total Electron Content ◽  
Density Profile ◽  
Geomagnetic Storms ◽  
Electron Density Profile ◽  
Wind Pressure ◽  
Electron Content ◽  
Total Electron ◽  
Geomagnetic Indices

Total Electron Content (TEC) and electron density profile are the key parameters in the mitigation of ionospheric effects on radio wave communication system. In this study, the variations of TEC and electron density profile have been analyzed using satellite data from four different latitude-longitude sectors (13°N -17°N, 88°E - 98°E), (30°N - 50°N, 95°W - 120°W), (26°S - 29°S, 163°W - 167°W,) and (45°S - 60°S, 105°W-120°W) during different geomagnetic storms. The interplanetary magnetic field (Bz), solar wind velocity (Vsw), solar wind pressure (Psw) and geomagnetic indices, aurora index -AE, Kp and disturbed stormed time index (Dst) are also analyzed to distinguish their effects on TEC and electron density. The geomagnetic indices and solar wind parameters are correlated with the TEC and electron density. The study showed that the value of TEC and electron density vary significantly with different latitude, longitude, altitude and solar activities. The result also concludes that the electron density profile increases with the altitude, acquired peak value around 250km-300km and decreased beyond the altitude of 300 km.

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