J. N. Yates, N. Achilleos, P. Guio
The importance of the Jovian thermosphere with regard to magnetosphere-ionosphere coupling is often neglected in magnetospheric physics. We present the first study to investigate the response of the Jovian thermosphere to transient variations in solar wind dynamic pressure, using an azimuthally symmetric global circulation model coupled with a simple magnetosphere model. In our simulations, the Jovian magnetosphere encounters a solar wind shock or rarefaction region and is subsequently compressed or expanded. We present the ensuing response of the thermospheric flows, momentum sources, and the coupling currents, to these transient events. Transient compressions cause the reversal of magnetosphere-ionosphere coupling currents and momentum transfer between the thermosphere and magnetosphere. Both compression and expansion events cause order-of-magnitude increases in ion drag force and a factor-of-two increase in the rate of advection of momentum. These result in thermospheric temperature changes > 25 K. For auroral emissions, we find that transient compressions double main oval emission and shift the location of the oval ~0.2 deg poleward whilst transient expansions do not significantly change main oval emission but shift its location ~1 deg equatorward.
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http://arxiv.org/abs/1301.3742
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