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|Title: ||TEC response during severe geomagnetic storms near the crest of equatorial ionization anomaly|
|Authors: ||Jain, Amit|
Gwal, A K
|Keywords: ||Total electron content|
Prompt penetration electric fields (PPE)
Travelling atmospheric disturbances (TAD)
Disturbance dynamo electric fields (DDE)
|Issue Date: ||Feb-2010|
The responses of
the ionosphere near equatorial anomaly crest as observed at Bhopal (geographic
23.2°N, 77.4°E, and magnetic latitude 14.2°N), India for geomagnetic storms during
15 May 2005 (SSC: 0239 hrs UT,
SymH: -305 nT) and
24 August 2005 (SSC: 0615 hrs
UT, SymH: -179 nT) has been studied using total electron content (TEC). TEC
data is recorded by GPS Ionospheric Scintillation and TEC Monitor (GISTM)
GSV4004A at Bhopal.
The temporal variations of vertical total electron content (VTEC) during these
storms were analysed. Fifteen minute average of VTEC is considered for analysis.
More than +68% and +70% deviation in VTEC was observed for 15 May 2005 and 24 August
2005 storms, respectively, relative to average of five quiet days of the
respective months. Significant deviations in VTEC during the main phase of the
storms were found to be associated with the prompt penetration of electric
fields which originate due to the
under-shielding and over-shielding conditions. Peaks like structure in EIA
region were observed for both the storms. Peaks like structure well
before the fountain effect in EIA region were observed for 15 May 2005.
Latitudinal enhancement of anomaly peak in EIA region was also observed for
both the storms. Suppressed equatorial electrojet strength and consequently
VTEC, observed on 25 August 2005 during recovery phase of the storm, are mainly
due to the thermospheric composition changes and also possibly due to the
delayed disturbance dynamo electric fields in this region. The range error is
also discussed in the present paper.
|ISSN: ||0975-105X (Online); 0367-8393 (Print)|
|Appears in Collections:||IJRSP Vol.39(1) [February 2010]|
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