Diurnal Response of the Thermospheric radiative cooling to March 16–21, 2015 Geomagnetic Storm

Abstract

It is well known that huge amount of energy is deposited into the high latitude thermosphere region during geomagnetic storm events. The energy deposition increases the thermospheric temperature by hundreds of degree kelvin. The radiative cooling by Nitric Oxide (NO) at 5.3 μm and CO2 at 15 μm emissions, being dominant coolants in the thermosphere, play important roles in regulating the thermospheric temperature during geomagnetic storm period. We utilized the NO 5.3 μm and CO2 15 μm radiative emissions, as observed by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) onboard NASA’s TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite, to investigate the diurnal response of thermospheric cooling to March 16–21, 2015 storm. We also used the atomic oxygen density and temperature from the TIMED-SABER satellite to explore their correlations with the cooling flux. It is observed that the CO2 and NO cooling emissions respond differently to the March 16–21, 2015 storm during day and night. Both the NO (about five times) and CO2 (about 70%) emission show strong enhancement during storm period. A stronger enhancement and a quicker recovery is observed in the NO 5.3 μm emission. Although the CO2 emission shows lesser enhancement than the NO emission, it lasts longer than the later. The CO2 emission takes about 5–6 days to return to its pre-onset value. The response of the NO 5.3 μm emission is short-term and lasts for about 3–4 days before returning to the pre-onset value. The NO and CO2 emission exhibit strong positive correlation with the storm’s intensity both during day and night suggesting that more intense is the storm more energy exits the thermosphere.