A Study of 732.0 nm Dayglow Emission in Equatorial Region under Geomagnetic Storm Conditions

Abstract:

A comprehensive model is developed to study 732.0 nm dayglow emission under geomagnetic storm conditions. The Solar2000 EUV (extreme ultraviolet) flux model, neutral atmosphere model (NRLMSISE-00), latest transition probabilities and updated reaction rate coefficients are incorporated in the present model. Three geomagnetic storms of varying intensities (strong, moderate and weak) are used in the present study. The volume emission rates of 732.0 nm dayglow emission are calculated for each storm at Tirunelveli (8.7⁰N, 77.8⁰E). A negative correlation is found between the volume emission rate (VER) and the Dst index for all the three geomagnetic storms. The present study also 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. A positive correlation is found between the zenith intensity of 732.0 nm dayglow emission and the atomic oxygen number density. Further, the atomic oxygen number densities obtained from the NRLMSISE-00 model during a geomagnetic storm are compared with the measurements. It is found that the atomic oxygen number densities given by NRLMSISE-00 model are significantly lower than the measured values. Consequently, the atomic oxygen number density in the present model is varied under the limit of measurements to study its effect on 732.0 nm dayglow emission. An increase of more than 50% in the zenith intensity above the normal level (before the onset of the storm) is found when the atomic oxygen number density is doubled in the model.