A pole to pole pressure temperature map of Saturn’s thermosphere from Cassini Grand Finale data. (arXiv:2102.09983v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Brown_Z/0/1/0/all/0/1">Zarah Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koskinen_T/0/1/0/all/0/1">Tommi Koskinen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mueller_Wodarg_I/0/1/0/all/0/1">Ingo Mueller-Wodarg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+West_R/0/1/0/all/0/1">Robert West</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jouchoux_A/0/1/0/all/0/1">Alain Jouchoux</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Esposito_L/0/1/0/all/0/1">Larry Esposito</a>
Temperatures of the outer planet thermospheres exceed those predicted by
solar heating alone by several hundred degrees. Enough energy is deposited at
auroral regions to heat the entire thermosphere, but models predict that
equatorward distribution is inhibited by strong Coriolis forces and ion drag. A
better understanding of auroral energy deposition and circulation are critical
to solving this so-called energy crisis. Stellar occultations observed by the
Ultraviolet Imaging Spectrograph instrument during the Cassini Grand Finale
were designed to map the thermosphere from pole to pole. We analyze these
observations, together with earlier observations from 2016 and 2017, to create
a two-dimensional map of densities and temperatures in Saturns thermosphere as
a function of latitude and depth. The observed temperatures at auroral
latitudes are cooler and peak at higher altitudes and lower latitudes than
predicted by models, leading to a shallower meridional pressure gradient. Under
modified geostrophy, we infer slower westward zonal winds that extend to lower
latitudes than predicted, supporting equatorward flow from approximately 70 to
30 degrees latitude in both hemispheres. We also show evidence of atmospheric
waves in the data that can contribute to equatorward redistribution of energy
through zonal drag.
Temperatures of the outer planet thermospheres exceed those predicted by
solar heating alone by several hundred degrees. Enough energy is deposited at
auroral regions to heat the entire thermosphere, but models predict that
equatorward distribution is inhibited by strong Coriolis forces and ion drag. A
better understanding of auroral energy deposition and circulation are critical
to solving this so-called energy crisis. Stellar occultations observed by the
Ultraviolet Imaging Spectrograph instrument during the Cassini Grand Finale
were designed to map the thermosphere from pole to pole. We analyze these
observations, together with earlier observations from 2016 and 2017, to create
a two-dimensional map of densities and temperatures in Saturns thermosphere as
a function of latitude and depth. The observed temperatures at auroral
latitudes are cooler and peak at higher altitudes and lower latitudes than
predicted by models, leading to a shallower meridional pressure gradient. Under
modified geostrophy, we infer slower westward zonal winds that extend to lower
latitudes than predicted, supporting equatorward flow from approximately 70 to
30 degrees latitude in both hemispheres. We also show evidence of atmospheric
waves in the data that can contribute to equatorward redistribution of energy
through zonal drag.
http://arxiv.org/icons/sfx.gif
