Wave perturbations in Earth’s thermosphere in conjunction with X1.7 solar flare: Observational perspective

Abstract

Based on satellite observations, the study examines the effect of an X1.7 flare (which occurred on January 27, 2012) on neutral winds and the formation of wave perturbations in Earth’s thermosphere. The Gravity field and steady state Ocean Circulation Explorer (GOCE) observations of the thermospheric zonal wind speed show an increase of 100 m/s in the north polar and 400S to south polar regions on the day side associated with the X1.7 solar flare. This feature is absent for the geomagnetically quiet days in January 2012, when there are no X-class flares. The wave perturbations in thermosphere, derived from the zonal winds are observed to be strongest in the flare day, than in non-flare days, with power index 40. During the flare day, wave perturbation with a wavelength of about 1110 km is dominant and is found preferentially in southern latitudes (above 400S) on the day side. When compared to non-flare days, the TIMED-derived neutral temperature increases by 45 K around the equatorial zone. The measurements also show the substantial temperature gradients over latitude and longitude in the flare situation. This demonstrates the presence of high thermal gradients in the thermosphere caused by the X1.7 solar flare, which causes zonal wind amplification and the launching of strong waves in the thermosphere.