Responses of Mesosphere and Lower Thermosphere Temperature to the Geomagnetic Storm on 7–8 September 2017

Meng Sun,Jianyong Lu,Zheng Li,Jingyuan Li,Chunli Gu,Yufeng Tian,Mengbin Zhu

doi:10.3390/universe8020096

Abstract

The variations of neutral temperature in the mesosphere and lower thermosphere (MLT) region, during the 7–8 September 2017 intense geomagnetic storm, are studied using observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. They are also studied using simulations by the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM). The neutral temperature data cover the altitudes from 80 km to 110 km between 83° N and 52° S latitude, obtained from both SABER observations and model simulations. The SABER observations reveal that temperature increases (the maximum increase is larger than 35 K at ~108 km) and decreases (the maximum decrease is larger than 20 K at ~105 km) during the geomagnetic storm. The storm effects penetrate down to ~80 km. In observations, temperature variations corresponding to the storm show hemispheric asymmetry. That is, the variations of temperature are more prominent in the northern hemisphere than in the southern hemisphere. Conversely, the TIMEGCM outputs agree with the observations in general but overestimate the temperature increases and underestimate the temperature decreases at high and middle latitudes. Meanwhile, the simulations show stronger temperature decreases and weaker temperature increases than observations at low latitudes. After analyzing the temperature variations, we suggest that vertical winds may play an important role in inducing these significant variations of temperature in the MLT region.

Highlights

During geomagnetic storms, strong convective electric fields produce enhanced Joule heating and particle precipitation in the auroral oval
Using the temperature measured from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, after the case study and statistical analysis, Wang et al [15] reported a temperature increase larger than ~20 K at 80◦ N, which occurred in the mesosphere and lower thermosphere (MLT) region during geomagnetic storms
In both SABER observations and Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) simulations, there was a temperature decrease followed by an increase

Summary

Introduction

Strong convective electric fields produce enhanced Joule heating and particle precipitation in the auroral oval. The enhanced Joule heating and auroral particle precipitation change the atmospheric circulation and cause perturbations of neutral temperature and density, winds, composition, and ionospheric electron densities [1,2,3]. These disturbances can be transported to the mesosphere and lower thermosphere (MLT) region and lower latitudes through dynamic and chemical processes [4,5,6,7,8]. Using the temperature measured from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, after the case study and statistical analysis, Wang et al [15] reported a temperature increase larger than ~20 K at 80◦ N, which occurred in the MLT region during geomagnetic storms

Results

Discussion

Conclusion