Response of the equatorial and low‐latitude ionosphere in the Indian sector to the geomagnetic storms of January 2005

Abstract

The equatorial and low‐latitude ionospheric response to three moderate geomagnetic storms (17, 18, and 22 January) during the period from 16 to 23 January 2005 is investigated in the context of development/inhibition of the Equatorial Ionization Anomaly (EIA) and the subsequent occurrence/nonoccurrence of Equatorial Spread F (ESF) irregularities on these days. The study is carried out using the Total Electron Content (TEC) measured with the GPS receivers along the ∼80°E longitude sector and the F‐layer bottom height obtained from the Ionosonde located over the dip equatorial location of Trivandrum (8.5°N, 77°E, dip latitude ∼0.5°N) in India. It is observed that, for the storms on days 17 and 22, the development of the anomaly was inhibited, probably due to the westward disturbance dynamo electric fields. Subsequently, the post sunset enhancement in the vertical drift of the equatorial F region was also inhibited significantly compared to the quiet day pattern and, as anticipated, no ESF was observed on these days. A large vertical drift of the equatorial F region followed by nearly simultaneous onset of weak ESF was observed on day 18. The late development of the EIA on this day could be due to the eastward prompt penetration electric field associated with the southward turning of the interplanetary magnetic field. Also, strong and distinct F3 layer appeared for a short time in the morning, reappeared later in the noon time, and then quickly ascended to the topside ionosphere during the main phase of the storm on day 18.

Long-term morphological and power spectral studies of VHF amplitude scintillations recorded over Waltair (17.7°N, 83.3°E), India

“…Another important observation is that with the increase in solar activity, scintillation activity also enhances, which corroborates with earlier research studies (Subbarao and Murthy 1994;Sreeja et al 2009;Prasad et al 2012). In addition, there is an appreciable change in onset timings between low (2008 and 2009) and high (2012 and 2013) solar activity years.…”

“…There are many reports on the morphology of ionospheric irregularities in the Indian sector, which include the diurnal, solar cycle, season and geomagnetic activity related variations. Most importantly, an inimitable feature of the incidence of ionospheric irregularities in the Indian sector is the solar activity dependent seasonal behavior (Subbarao and Murthy 1994;Sreeja et al 2009;Prasad et al 2012). In an elaborate sense, the occurrence of ionospheric irregularities maximizes in the post-sunset periods and is more probable during the equinox season of higher solar activity epochs, while during the summer solstice of low solar activity periods, the peak occurrence in the incidence of irregularities during the postmidnight period is a general observational finding.…”

Study of Ionospheric TEC from GPS observations and comparisons with IRI and SPIM model predictions in the low latitude anomaly Indian subcontinental region

“…Variations of TEC in response to geomagnetic storms have been studied by many researchers over Indian region (Dashora et al, 2009;Rao et al, 2009;Sharma et al, 2011;Sreeja et al, 2009;Panda and Gedam, 2012). It is noticed from the Fig.…”

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

“…As described by Abdu (1997;see also Buonsanto, 1999) major modifications in the equatorial ionosphere-thermosphere system during magnetospheric disturbances are produced by (a) prompt equatorward penetration of magnetospheric/high latitude electric fields (see also Senior and Blanc, 1984;Spiro et al, 1988), and (b) disturbance dynamo driven by enhanced global thermospheric circulation resulting from energy input at high latitude (see also Blanc and Richmond, 1980). Recently, Kikuchi et al (2008) and Veenadhari et al (2010) have investigated penetration of magnetospheric electric fields to the equator during magnetic disturbances.…”

“…Several investigators (e.g. Orus et al, 2007;Sreeja et al, 2009;Kane, 2009;Matthiä et al, 2009;McKenna-Lawlor et al, 2010) have studied different aspects associated with the geomagnetic storm or geomagnetic disturbed period around the third week of January 2005. Du et al (2008) have investigated the storm on 21-22 January 2005 and called it an "anomalous" geomagnetic storm as the storm main phase occurs during northward interplanetary magnetic fields (IMFs).…”