A study of O+(2D -2P) 732.0 nm dayglow emission under geomagnetic storm conditions

Abstract

The effect of geomagnetic storms on O⁺(²D -²P) 732.0 nm dayglow emission is studied using recently updated photochemical model of Thirupathaiah et al.¹. Three geomagnetic storms which occurred on 23-27 August 2005, 13-17 April 2006 and 1-5 February 2008 are chosen in the present study. A negative correlation is found between the volume emission rate (VER) and the Dst index for all the three geomagnetic storms. The present study shows that the relative variation of VER with respect to the initial value of VER (before the onset of a geomagnetic storm) during the main phase increases above 260 km. It is also found that the altitude of the peak emission rate does not show any appreciable variation with the activity of geomagnetic storm. A positive correlation is found between the zenith intensity and the atomic oxygen number density. The atomic oxygen number density obtained from NRLMSISE-00 model is compared with the measurements of Earle et al.² during a geomagnetic storm. This comparison shows that the atomic oxygen number density as provided by NRLMSISE-00 model is significantly lower than the measured value. Consequently, the atomic oxygen number density is treated as a variable parameter in the photochemical model and its effect on the VER of 732.0 nm dayglow emission is further studied. The zenith intensity is found to increase about 70% even in the case of weakest storm when the atomic oxygen number density is doubled.