An Observational and Modelling Study of Auroral Upwelling in the Thermosphere
Technical Report,01 Feb 2015,31 Jan 2016
University College London London United Kingdom
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This is a study of the importance of the altitude of energy deposition for causing upwelling of the upper atmosphere. Observations in the auroral regions of Scandinavia, in parallel with a modelling study, are presented. Independent measurements of the thermosphere were made using Fabry-Perot Interferometers, and of the ionosphere over a range of altitudes 100-600km using the EISCAT and KAIRA radars. The CMAT2 simulations augment the Carlson et al. 2012 simulations that successfully replicated the doubling of thermospheric density at the cusp observed by the CHAMP satellite Lhr et al., 2004. The Carlson mechanism was tested qualitatively by investigating whether similar upwelling was observed in the auroral region, and could be supported by model simulations. Both dayside cusp and nightside auroral regions have large electric fields generated by either dayside or nightside magnetic reconnection, respectively. The experiments and model simulations show that the manifestation of heating in the density changes and structure of the upper atmosphere is complex. The location of the heat source, whether due to soft or hard particle precipitation, is one aspect, but the location with respect to the magnetospheric dynamo is also critically important.