ALBERT

Description: In this paper, we analyze radar observations of E x 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 x 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 (∆H) and E x 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 ∆H, 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 ∆H and f o F 2 soon after the SSW commencement, not much reported before. During the counter-electrojet 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 post-midnight hours and case studies suggest the possible role of SSW related background electric field in the manifestation of post-midnight F region irregularities.