Atmospheric circulation of Venus measured with visible imaging-spectroscopy at the THEMIS observatory. (arXiv:1905.11078v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gaulme_P/0/1/0/all/0/1">Patrick Gaulme</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmider_F/0/1/0/all/0/1">Francois-Xavier Schmider</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Widemann_T/0/1/0/all/0/1">Thomas Widemann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goncalves_I/0/1/0/all/0/1">Ivan Goncalves</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ariste_A/0/1/0/all/0/1">Arturo Lopez Ariste</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gelly_B/0/1/0/all/0/1">Bernard Gelly</a>
Measuring Venus’ atmospheric circulation at different altitudes is important
for understanding its complex dynamics, in particular the mechanisms driving
the super-rotation. Observationally, Doppler imaging spectroscopy is in
principle be the most reliable way to measure wind speeds of planetary
atmospheres because it directly provides the projected speed of atmospheric
particles. However, high-resolution imaging-spectroscopy is challenging,
especially in the visible domain, and most of the knowledge about atmospheric
dynamics has been obtained with cloud-tracking technique. The objective of the
present work is to measure the global properties of Venus’ atmospheric dynamics
at the altitude of the uppermost clouds, which is probed by reflected solar
lines in the visible domain. Our results are based on high-resolution
spectroscopic observations with the long slit spectrometer of the solar
telescope THEMIS. We present the first instantaneous “radial-velocity snapshot”
of any planet of the solar system in the visible domain, i.e., a complete RV
map of the planet obtained by stacking data on less than 10% of its rotation
period. From this, we measure the properties of the zonal and meridional winds,
which we unambiguously detect. We identify a wind circulation pattern that
significantly differs from previous knowledge about Venus. The zonal wind
displays a “hot spot” structure, featuring about 200 m/s at sunrise and 70 m/s
at noon in the equatorial region. Regarding meridional winds, we detect an
equator-to-pole meridional flow peaking at 45 m/s at mid latitudes, i.e., which
is about twice as large as what was reported so far.
Measuring Venus’ atmospheric circulation at different altitudes is important
for understanding its complex dynamics, in particular the mechanisms driving
the super-rotation. Observationally, Doppler imaging spectroscopy is in
principle be the most reliable way to measure wind speeds of planetary
atmospheres because it directly provides the projected speed of atmospheric
particles. However, high-resolution imaging-spectroscopy is challenging,
especially in the visible domain, and most of the knowledge about atmospheric
dynamics has been obtained with cloud-tracking technique. The objective of the
present work is to measure the global properties of Venus’ atmospheric dynamics
at the altitude of the uppermost clouds, which is probed by reflected solar
lines in the visible domain. Our results are based on high-resolution
spectroscopic observations with the long slit spectrometer of the solar
telescope THEMIS. We present the first instantaneous “radial-velocity snapshot”
of any planet of the solar system in the visible domain, i.e., a complete RV
map of the planet obtained by stacking data on less than 10% of its rotation
period. From this, we measure the properties of the zonal and meridional winds,
which we unambiguously detect. We identify a wind circulation pattern that
significantly differs from previous knowledge about Venus. The zonal wind
displays a “hot spot” structure, featuring about 200 m/s at sunrise and 70 m/s
at noon in the equatorial region. Regarding meridional winds, we detect an
equator-to-pole meridional flow peaking at 45 m/s at mid latitudes, i.e., which
is about twice as large as what was reported so far.
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