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arXiv · 2305.15521

Evidence of a Polar Cyclone on Uranus from VLA Observations

Alex Akins·Mark Hofstadter·Bryan Butler·A. James Friedson·Edward Molter·Marzia Parisi·Imke de Pater
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Abstract

We present observations of Uranus in northern spring with the VLA from 0.7 cm to 5 cm. These observations reveal details in thermal emission from Uranus' north pole at 10s of bars, including a dark collar near 80N and a bright spot at the polar center. The bright central spot resembles observations of polar emission on Saturn and Neptune at shallower pressures. We constrain the variations in temperature and NH3/H2S abundances which could explain these features. We find that the brightness temperature of the polar spot can be recreated through 5 K temperature gradients and/or 10x depletion of NH3 or H2S vapor between 10-20 bars, both consistent with the presence of a cyclonic polar vortex. The contrast of the polar spot may have increased since 2015, which would suggest seasonal evolution of Uranus' polar circulation at depth.

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Alex Akins, Mark Hofstadter, Bryan Butler, A. James Friedson, Edward Molter, Marzia Parisi, Imke de Pater. 2023-05-24. Evidence of a Polar Cyclone on Uranus from VLA Observations. https://doi.org/10.1029/2023gl102872

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