Abstract
Recent observations of Jupiter's Great Red Spot indicate that the thermosphere above the storm is hotter than its surroundings by more than 700 K. Possible suggested sources for this heating have thus far included atmospheric gravity waves and lightning-driven acoustic waves. Here, we propose that Joule heating, driven by Great Red Spot vorticity penetrating up into the lower stratosphere and coupling to the thermosphere, may contribute to the large observed temperatures. The strength of Joule heating will depend on the local inclination angle of the magnetic field and thus the observed emissions and inferred temperatures should vary with planetary longitude as the Great Red Spot tracks across the planet.This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H3+, H5+ and beyond’.
Highlights
Jupiter’s Great Red Spot (GRS) is thought to be the longest-lived storm in the Solar System
Other hot spots are present in figure 1; we focus on the GRS in this analysis as it is a repeatedly observed feature confirmed by measurements using two different telescope facilities
Any electric fields and currents generated by GRS winds are at sufficiently low magnetic latitudes that they should close within the local atmosphere or in the magnetically conjugate location of the northern hemisphere
Summary
Jupiter’s Great Red Spot (GRS) is thought to be the longest-lived storm in the Solar System. The net heating on a column of air may only be approximately 200 K, which is not enough alone to explain the observed GRS or general mid-to-low latitude temperature enhancement [21]. There are no direct observations of upward propagating acoustic waves at the outer planets Another source of heating is electrodynamic coupling between Jupiter’s thermosphere and stratosphere [23]. There is a net transfer of kinetic energy from the stratosphere to thermal energy in the thermosphere This mechanism requires that (i) the ionosphere extends into the stratosphere and (ii) the wind flows drive divergent/convergent currents, requiring current closure along the magnetic field and into the thermosphere.
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