Ionospheric variability over Indian low latitude linked with the 2009 sudden stratospheric warming

Abstract

In this paper, we analyze radar observations of E × B drift and plasma irregularities, ionosonde observations of E and F layer parameters including spread F, and magnetic field observations made from Indian low latitudes linked with the 2009 sudden stratospheric warming (SSW) event. E × B drift variations presented here are the first of their kind from the Indian sector as far as the effect of SSW is concerned. Difference of magnetic fields observed from the equator and low-latitude (ΔH) and E × B drift show linear relation, and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior. Remarkable changing patterns in the critical frequency of F 2 layer (f o F 2 ) and F 3 layer (f o F 3 ) were observed after the occurrence of SSW. Large variations with quasi 16 day periodicity were observed in ΔH, f o F 2 , and f o F 3. Both semidiurnal and quasi 16 day wave modulation observed after the 2009 SSW event are consistent with those reported earlier. We also noted quasi 6 day variations in ΔH and f o F 2 soon after the SSW commencement, not much reported before. During the counterelectrojet events linked with the SSW event, while equatorial E s (E sq ) disappeared as expected, there were no blanketing E s (E sb ), a finding not reported and discussed earlier. E sb was also not formed at the off-equatorial location, indicating the absence of required vertical wind shear, but E region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two. Weak F region irregularities were observed in the postmidnight hours, and case studies suggest the possible role of SSW-related background electric field in the manifestation of postmidnight F region irregularities.

Impact of Sudden Stratospheric Warming of 2009 on the Equatorial and Low‐Latitude Ionosphere of the Indian Longitudes: A Case Study

“…They restricted the analysis to the days around SSW period (i.e., January 2009), and the variability thereafter had not been explored. Similarly, Patra et al () investigated the variation of EEJ during the 2009 SSW event over the Indian region, but their study also could not highlight the occurrence of two intense CEJ events reported in the present study. The strong semidiurnal perturbation observed in the zonal wind, EEJ, and TEC around new and full moon phases unambiguously suggests the amplification of semidiurnal lunar tide during the 2009 SSW event.…”

“…The absence of quasi 16 day periodicity around the NE stations suggests that the ionization over NE stations do not get influenced by the EEJ and the consequent fountain effect. The earlier workers also reported the presence of quasi 16 day wave during the SSW events at the low‐latitude ionosphere of the Indian zone, which are linked with the changes in the equatorial electric fields (Laskar et al, ; Patra et al, ; Sripathi & Bhattacharyya, ). The presence of quasi 16 day wave during the SSW event of 2013 was also observed over midlatitude ionosphere (Chen et al, ).…”

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

“…[] have compared the vertical drifts obtained by using 150 km echoes at Gadanki and C/NOFS ion drift measurements and suggested that 150 km echoes do represent vertical drifts during daytime. In fact they also compared their drifts with EEJ strength on monthly basis and found that they are in good agreement [ Patra et al ., ]. While their drifts are comparable to C/NOFS ion drifts in magnitude, however, SF drift model could not reproduce these drifts when drifts are either lower or higher.…”

Ionospheric variations over Indian low latitudes close to the equator and comparison with IRI-2012

“…Considering that large vertical E × B drift can significantly reduce the F2 layer density and form an additional layer (the F3 layer), we would expect an inverse relationship between vertical E × B drift and f oF2. In order to gain some insight into this phenomenon, we have used H data as proxy of E × B drift (Anderson et al, 2002;Patra et al, 2014) and examined the relationship between H and f oF2. Figure 7 shows scatter plots displaying the relationship between the two in different solar activity conditions.…”