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 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 Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms

2008 ◽  
Vol 26 (4) ◽  
pp. 893-903 ◽  
Author(s):  
◽  
◽  
◽  
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Activity ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Defense Meteorological Satellite Program ◽  
Low Latitudes ◽  
Global Ionospheric Maps ◽  
Geomagnetic Activities

Abstract. Sometimes the ionospheric total electron content (TEC) is significantly enhanced during low geomagnetic activities before storms. In this article, we investigate the characteristics of those interesting TEC enhancements using regional and global TEC data. We analyzed the low-latitude TEC enhancement events that occurred around longitude 120° E on 10 February 2004, 21 January 2004, and 4 March 2001, respectively. The TEC data are derived from regional Global Positioning System (GPS) observations in the Asia/Australia sector as well as global ionospheric maps (GIMs) produced by Jet Propulsion Laboratory (JPL). Strong enhancements under low geomagnetic activity before the storms are simultaneously presented at low latitudes in the Asia/Australia sector in regional TEC and JPL GIMs. These TEC enhancements are shown to be regional events with longitudinal and latitudinal extent. The regions of TEC enhancements during these events are confined at narrow longitude ranges around longitude 120° E. The latitudinal belts of maxima of enhancements locate around the northern and southern equatorial ionization anomaly (EIA) crests, which are consistent with those low-latitude events presented by Liu et al. (2008). During the 4 March 2001 event, the total plasma density Ni observed by the Defense Meteorological Satellite Program (DMSP) spacecraft F13 at 840 km altitude are of considerably higher values on 4 March than on the previous day in the TEC enhanced regions. Some TEC enhancement events are possibly due to contributions from auroral/magnetospheric origins; while there are also quasi-periodic enhancement events not related to geomagnetic activity and associated probably with planetary wave type oscillations (e.g. the 6 January 1998 event). Further investigation is warrented to identify/separate contributions from possible sources.

Analysis of Plasma Bubble Signatures in Total Electron Content Maps of the Low-Latitude Ionosphere: A Simplified Methodology

2020 ◽  
Vol 41 (4) ◽  
pp. 897-931 ◽  
Author(s):  
César Buchile Abud de Oliveira ◽  
Teddy Modesto Surco Espejo ◽  
Alison Moraes ◽  
Emanoel Costa ◽  
Jonas Sousasantos ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Plasma Bubble ◽  
Low Latitude ◽  
Total Electron ◽  
Low Latitude Ionosphere

scholarly journals Storm Time Total Electron Content Modeling Over African Low-Latitude and Midlatitude Regions

2018 ◽  
Vol 123 (9) ◽  
pp. 7889-7905 ◽  
Author(s):  
Jean Claude Uwamahoro ◽  
John Bosco Habarulema ◽  
Patrice Martin Okouma
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Content Modeling

scholarly journals Influence of the Ionosphere Model on the Solution of a VLBI Geodetic Experiment

1988 ◽  
Vol 129 ◽  
pp. 551-552
Author(s):  
G. Petit ◽  
J. F. Lestrade ◽  
C. Boucher ◽  
F. Biraud ◽  
A. Rius ◽  
...  
Keyword(s):  
South America ◽  
Total Electron Content ◽  
Dual Band ◽  
Single Frequency ◽  
Electron Content ◽  
Critical Aspect ◽  
Total Electron ◽  
Geodetic Vlbi ◽  
Ionosphere Model ◽  
First Time

The GRIG-2 geodetic VLBI experiment was conducted in 1985, linking for the first time South America, Europe and Africa. At the single frequency band of 1.66 GHz which was used, the monitoring of the ionosphere is a critical aspect and several predictions of Total Electron Content (TEC) were used. One of them is derived from dual band Doppler observations of TRANSIT satellites, which were simultaneously conducted. The influence of these models on the solution is presented, with comparisons with other VLBI solutions. Decimetric accuracy has been achieved.

Longitudinal dependence of ionospheric total electron content in the South Atlantic Geomagnetic Anomaly

Nature ◽  
1976 ◽  
Vol 261 (5562) ◽  
pp. 677-679 ◽  
Author(s):  
PIERRE KAUFMANN ◽  
L. RIZZO PIAZZA ◽  
O. MASSAMBANI ◽  
V. N. DINIZ BORGES ◽  
E. H. KOPPE
Keyword(s):  
Total Electron Content ◽  
South Atlantic ◽  
Electron Content ◽  
The South ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Geomagnetic Anomaly

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.

Sign in / Sign up

Export Citation Format

Share Document