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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 10
Ann. Geophys., 27, 3853–3860, 2009
https://doi.org/10.5194/angeo-27-3853-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 3853–3860, 2009
https://doi.org/10.5194/angeo-27-3853-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  09 Oct 2009

09 Oct 2009

Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study

G. Manju, T. K. Pant, C. V. Devasia, S. Ravindran, and R. Sridharan G. Manju et al.
  • Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum, 695 022, Kerala, India

Abstract. The electrodynamic effects on the low-mid latitude ionospheric region have been investigated using GPS (global positioning system) data, ionosonde data and ΔH values, during the very large solar flare (X17.2/4B) of 28 October 2003. The results bring out the flare induced unusual behaviour of the equatorial ionosphere on this day just prior to sunset. The important observations are i) Large and prolonged Ne enhancements observed from ionosonde data just after the flare-related peak enhancement in EUV flux. The observed enhancement in Ne is due to the increase in ionization production due to the enhanced EUV flux and the persistence of the enhancement is probably due to the prompt penetration related upliftment of the F layer (just prior to the flare peak phase) to higher altitudes, where recombination rates are lower. ii) A significant enhancement in total electron content (TEC) (~10 TEC units) at regions around the Equatorial Ionization Anomaly (EIA) crest region (Ahmedabad) during the flare in association with the flare related EUV flux enhancement. iii) Similar enhancements seen at stations of Jodhpur and Delhi in the mid latitude sector. iv)The flare related flux enhancements in different longitude sectors in the equatorial electrojet region have been shown to produce positive and negative variations in electrojet strength indicating the presence of current systems having positive and negative polarities in different longitude sectors. Thus the flare effect reveals the longitudinal variation of the counter electrojet events in the Equatorial Electrojet (EEJ) region.

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