Global thermospheric disturbances induced by a solar flare: a modeling study

Huijun Le,Zhipeng Ren,Hui Zhang,Libo Liu,Yiding Chen

doi:10.1186/s40623-014-0166-y

Huijun Le, Zhipeng Ren + Show 3 more

Open Access

https://doi.org/10.1186/s40623-014-0166-y

Copy DOI

Abstract

This study focuses on the global thermosphere disturbances during a solar flare by a theoretical model of thermosphere and ionosphere. The simulated results show significant enhancements in thermospheric density and temperature in dayside hemisphere. The greatest thermospheric response occurs at the subsolar point, which shows the important effect of solar zenith angle. The results show that there are also significant enhancements in nightside hemisphere. The sudden heating due to the solar flare disturbs the global thermosphere circulation, which results in the significant change in horizontal wind. There is a significant convergence process to the antisolar point and thus the strong disturbances in the nightside occur at the antisolar point. The peak enhancements of the neutral density around antisolar point occur at about 4 h after solar flare onset. The simulated results show that thermospheric response to a solar flare mainly depends on the total integrated energy into the thermosphere, not the peak value of EUV flux. The simulated results are basically consistent with the observations derived from the CHAMP satellite, which verified the results of this modeling study.

Highlights

Solar flares produce great enhancements in extreme ultaviolet (EUV) and X-ray radiations, which cause sudden and intense disturbances in the Earth’s upper atmosphere
The neutral density enhancement is larger at the region with smaller solar zenith angle, which shows the significant effect of solar zenith angle on the thermospheric response to a solar flare
The results show that the thermospheric density disturbances mainly focus on the sunlight region at the initial stage (Δt < 1 h); the disturbance region gradually extends to the nightside with time

Summary

Introduction

Solar flares produce great enhancements in extreme ultaviolet (EUV) and X-ray radiations, which cause sudden and intense disturbances in the Earth’s upper atmosphere. Ionospheric effects of solar flares, or sudden ionospheric disturbances (SID), have been studied since 1960s owing to their effects on radio communications and navigation systems. Most previous studies related to solar flares have so far focused on the ionospheric responses (e.g., Afraimovich 2000; Leonovich et al 2002; Liu et al 2004, 2006; Mahajan et al 2010; Tsurutani 2005; Wan et al 2005; Zhang et al 2002; Zhang and Xiao 2005; Le et al 2007, 2011, 2013; Liu et al 2011). It may be due to the much less observation of the thermosphere than that of the ionosphere. The observations of the terrestrial effects of solar flares have recently been extended to the neutral atmosphere.

Methods

Results

Conclusion