F2region response to geomagnetic disturbances across Indian latitudes: O(1S) dayglow emission

The morphology of ionospheric storms has been investigated across equatorial and low latitudes of Indian region. The deviation in F-2 region characteristic parameters (f(o)F(2) and hF) along with modeled green line dayglow emission intensities is examined at equatorial station Thiruvananthapuram (8.5 degrees N, 76.8 degrees E, 0.63 degrees S geomagnetic latitude) and low-latitude station Delhi (28.6 degrees N, 77.2 degrees E,19.2 degrees N geomagnetic latitude) during five geomagnetic storm events. Both positive and negative phases have been noticed in this study. The positive storm phase over equatorial station is found to be more frequent, while the drop in ionization in most of the cases was observed at low-latitude station. It is concluded that the reaction as seen at different ionospheric stations may be quite different during the same storm depending on both the geographic and geomagnetic coordinates of the station, storm intensity, and the storm onset time. Modulation in the F-2 layer critical frequency at low and equatorial stations during geomagnetic disturbance of 20-23 November 2003 was caused by the storm-induced changes in O/N-2. It is also found that International Reference Ionosphere 2012 model predicts the F-2 layer characteristic (f(o)F(2) and hF) parameters at both the low and equatorial stations during disturbed days quite reasonably. A simulative approach in GLOW model developed by Solomon is further used to estimate the changes in the volume emission rate of green line dayglow emission under quiet and strong geomagnetic conditions. It is found that the O(S-1) dayglow thermospheric emission peak responds to varying geomagnetic conditions.