Responses of High-Latitude Mesopause Height and Temperature to Geomagnetic Storms

Abstract

The impact of geomagnetic storms on the mesopause structure, especially at high latitudes, has received limited attention. In this study, we analyze data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite to investigate how mesopause height and temperature respond to four intense geomagnetic storms: July 2003 (summer in the Northern Hemisphere, NH), July 2004 (winter in the Southern Hemisphere, SH), November 2004 (winter in the NH), and December 2006 (summer in the SH). Before the winter storms, the mesopause is located at approximately 95–100 km at high latitudes. Following the storms, it decreases by ∼8 km at 70°N and 70°S, and the reduction is less at other latitudes. Additionally, mesopause temperature increases significantly during winter storms, with a maximum rise of ∼17 K observed at 70°N and 70°S. These pronounced changes in mesopause height and temperature are evident only during winter storms and occur approximately 0.5 days after the AE index enhancement, whereas summer storms show no substantial impact. This difference is attributed to the higher altitude of the mesopause in winter, which enhances its sensitivity to geomagnetic activity. The observed temperature increases in the mesopause region are primarily driven by chemical heating from an exothermic reaction ($O+O+M\to O_2+M$), and radiative heating from enhanced ozone absorption of solar energy during storms. Furthermore, the lowering of the mesopause height is caused by downward heat conduction from the heated lower thermosphere.