An observational and theoretical study of the longitudinal variation in neutral temperature induced by aurora heating in the lower thermosphere

Abstract

[1] In this paper, observations by thermosphere, ionosphere, mesosphere energetics and dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry from 2002 to 2012 and by Envisat/Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) from 2008 to 2009 are used to study the longitudinal structure of temperature in the lower thermosphere. In order to remove the longitudinal structure induced by tides, diurnally averaged SABER temperatures are used. For MIPAS data, we use averaged temperatures between day and night. The satellite observations show that there are strong longitudinal variations in temperature in the high-latitude lower thermosphere that persist over all seasons. The peak of the diurnally averaged temperature in the lower thermosphere always occurs around the auroral zone. A clear asymmetry between the two hemispheres in the longitudinal temperature structure is observed, being more pronounced in the Southern than in the Northern Hemisphere. In both hemispheres, the longitudinal variation is dominated by the first harmonic in longitude. The total radiative cooling observed by SABER has a structure in longitude that is similar to that of temperature. Modeling simulations using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model reproduce similar features of the longitudinal variations of temperature in the lower thermosphere. Comparison of two model runs with and without auroral heating confirms that auroral heating causes the observed longitudinal variations. The multiyear averaged vertical structures of temperature observed by the two satellite instruments indicate that the impact of auroral heating on the thermodynamics of the neutral atmosphere can penetrate down to about 105 km.

Simultaneous retrieval of T(p) and CO2 VMR from two-channel non-LTE limb radiances and application to daytime SABER/TIMED measurements

“…The operationally retrieved parameters (T k , O 3 , and several volume emission rates) are routinely used in dynamical and trend studies e.g. Gao et al (2010), Xu et al (2013), Smith et al (2013), Goldberg et al (2013). The absolute values of the T k profiles are not crucial in these cases; only its precision is important.…”

The geospace response to variable inputs from the lower atmosphere: a review of the progress made by Task Group 4 of CAWSES-II

“…Recently, Xu et al (2013) showed longitudinal variations of the thermospheric temperature from satellite observations with SABER and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and simulations with TIE-GCM. Their simulations clarified that auroral heating would cause the observed longitudinal temperature variations.…”

Influence of geomagnetic activity on mesopause temperature over Yakutia

“…One process is the direct effect on the temperature and dynamics. The geomagnetic storm is followed in the atmosphere by ionization, excitation, Joule heating and dissociation processes (Lastovicka, 1996;Xu et al, 2013). There is some evidence of the upper atmosphere temperature change during EPP.…”

“…There is some evidence of the upper atmosphere temperature change during EPP. Xu et al (2013) investigated the longitudinal temperature structure in the lower thermosphere using the SABER/TIMED and MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding) data obtained from 2008 to 2009. The study of these satellite measurements revealed that the maximum of the diurnally averaged temperature in the lower thermosphere is near the longitude of the magnetic pole in both the Northern Hemisphere and the Southern Hemisphere.…”