The dawn−dusk asymmetry in mesosphere and lower thermosphere temperature disturbances during geomagnetic storms at high latitude

Abstract

Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, we quantitatively assessed the dawn–dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere (MLT) during the main phase of geomagnetic storms in this study. An analysis of five geomagnetic superstorm events indicated that during the main phase, negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region. Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides. At high latitudes, 38.2% of the observational points on the dawn side exhibited negative temperature disturbances (less than −5 K), whereas on the dusk side, this percentage was only 29.5%. In contrast, at mid-latitudes, these proportions were 34.1% and 36.5%, respectively, showing no significant difference. We also conducted a statistical analysis of temperature disturbances at different altitudes, which revealed an increase in the proportion of warming disturbances with altitude. Conversely, the proportion of cooling disturbances initially rose with altitude, reaching a peak around 105 km, and subsequently decreased. These temperature disturbance differences could be explained by the day–night asymmetry in vertical wind disturbances during storm conditions.

Keywords

• dawn
• dusk asymmetry
• saber (sounding of the atmosphere using broadband emission radiometry)
• geomagnetic storms
• mesosphere and lower thermosphere