Evidence of a Polar Cyclone on Uranus From VLA Observations
Abstract We present observations of Uranus in northern spring with the Very Large Array from 0.7 to 5 cm. These observations reveal details in thermal emission from Uranus' north pole at 10s of bars, including a dark collar near 80°N and a bright spot at the polar center. The bright central spo...
| Published in: | Geophysical Research Letters |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2023
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| Subjects: | |
| Online Access: | https://doi.org/10.1029/2023GL102872 https://doaj.org/article/84d181de27a54c49bf8462ed9a4c3f4e |
| Summary: | Abstract We present observations of Uranus in northern spring with the Very Large Array from 0.7 to 5 cm. These observations reveal details in thermal emission from Uranus' north pole at 10s of bars, including a dark collar near 80°N 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 10× depletion of NH3 or H2S vapor between 10 and 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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