Response of the EIA ionosphere to the 7-8 May 2005 geomagnetic storm

•We studied response of low-latitude ionosphere to a moderate geomagnetic storm of 7-8 May 2005 from a near EIA crest region.•A significant enhancement of TEC after sunset and during post-midnight hours is observed in low latitudes during disturbed day.•The ionospheric plasma bubbles and pre-reversal enhancement (PRE) occured after rapid decrease in Sym-H index.•TEC fluctuations with moderate and strong scintillations during post-sunset to post-midnight period respectively. In this paper, response of low latitude ionosphere to a moderate geomagnetic storm of 7–8 May 2005 (SSC: 1920UT on 7 May with Sym-H minimum, ∼−112nT around 1600UT on 8 May) has been investigated using the GPS measurements from a near EIA crest region, Rajkot (Geog. 22.29°N, 70.74°E, Geomag.14°), India. We found a decrease in total electron content (TEC) in 12h after the onset of the storm, an increase during and after 6h of Sym-H deep minimum with a decrease below its usual-day level on the second day during the recovery phase of the storm. On 8 May, an increase of TEC is observed after sunset and during post-midnight hours (maximum up to 170%) with the formation of ionospheric plasma bubbles followed by a nearly simultaneous onset of scintillations at L-band frequencies following the time of rapid decrease in Sym-H index (−30nT/h around 1300UT).