Response of low latitude ionosphere to the geomagnetic storm of May 30

Abstract

Response of low latitude ionosphere to the geomagnetic storm of May 30, 2005 in the Indian longitude sector has been investigated by using the GPS data recorded at three stations namely, Udaipur, Hyderabad and Bengaluru. The event is noteworthy due to the fact that the Z component of interplanetary magnetic field (IMF Bz) remained southward for about 10 hours, coincident with the local day time for the Indian longitude sector, along with significantly higher values of AE and ASY-H indices. However, we neither found any evidence for the presence of long lasting storm time electric fields nor could we infer episodes of eastward-westward penetration of electric fields under steady southward IMF Bz and unsteady ring current conditions. On the storm day, the maximum enhancement in the total electron content has been found to be about 60%. The ionosonde observations also showed increased critical frequency (foF 2 ) and the height (h P F 2 ) of the F layer. The foF 2 was enhanced by ∼60% which is consistent with the enhancement in total electron content. The slow rise and long duration enhancement of h P F 2 and foF 2 have been attributed to the upwelling by the meridional neutral winds, caused by continuous energy inputs at higher latitudes. The poleward expansion of the equatorial ionization anomaly has also been observed on May 30. On May 31, the following day of the storm, significantly suppressed anomaly with near absence of its northern crest in the Indian longitude sector, revealed the effect of storm induced disturbance dynamo electric fields.

Ionospheric response to the geomagnetic storm of 15 May 2005 over midlatitudes in the day and night sectors simultaneously

“…Storm time ionospheric changes due to the PP fields have been studied and reported by many earlier workers [ Sastri et al ., ; Basu et al ., ; Maruyama et al ., ; Dashora et al ., ; Bagiya et al ., ; Sharma et al ., ; Galav et al ., , and references therein] of which the recent studies are based on the GPS TEC observations along with other data sets. During the sunlit hours since the PP fields caused by the under shielding condition and ambient electric field remain in the same direction, it results in large E × B vertical plasma drifts.…”