Differential Response of Nitric Oxide Radiative Cooling to Moderate and Intense Geomagnetic Storms: Insights From Superposed Epoch Analysis

Abstract

Geomagnetic storms have been a subject of significant interest due to their potential impact on Earth’s upper atmosphere. Nitric oxide (NO) radiative emission is a key feature that can help in understanding and assessing the storm-time response of the Earth’s upper atmosphere. This study attempts to provide a unified and comprehensive understanding of the storm-time response of NO radiative cooling to geomagnetic storms of different strengths and durations by using the superposed epoch analysis method. The satellite-based observations of NO radiative cooling at 5.3 $\mu$m during thirty geomagnetic storms have been analyzed using the superposed epoch analysis. Based on the response time of nitric oxide infrared radiative flux (NOIRF) to reach its peak value, the storms are categorized into three classes. The findings reveal that the response time of NO to a geomagnetic storm is linked to the duration of its main phase. In the case of a long-duration main-phase geomagnetic storm, the response is faster, and it is typically earlier than that during a storm with a short-duration main phase. To understand the behavior of NO during various geomagnetic storms, the temperature and compositional data from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) simulations are used to calculate the NOIRF. The calculated NOIRF shows a good agreement with temporal variations compared to the Sounding of the Atmosphere using Broadband Emission Radiometry observations. The combined results of superposed epoch analysis and TIEGCM conclude that the duration of the main phase of a geomagnetic storm significantly affects the NO density, temperature, and response time of NOIRF.