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Research output: Contribution to Journal/Magazine › Letter › peer-review
Research output: Contribution to Journal/Magazine › Letter › peer-review
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TY - JOUR
T1 - Saturn’s Weather-Driven Aurorae Modulate Oscillations in the Magnetic Field and Radio Emissions
AU - Chowdhury, M.N.
AU - Stallard, T.S.
AU - Baines, K. H.
AU - Provan, G.
AU - Melin, Henrik
AU - Hunt, G. J.
AU - Moore, Luke
AU - O'Donoghue, James
AU - Thomas, Emma M.
AU - Wang, Ruoyan
AU - Miller, Steve
AU - Badman, Sarah
PY - 2022/2/16
Y1 - 2022/2/16
N2 - The Cassini spacecraft revealed that Saturn's magnetic field displayed oscillations at a period originally thought to match the planetary rotation rate but later found not to. One of many proposed theories predicts that a polar twin-cell neutral weather system drives this variation, producing observable differences in flows within Saturn's ionosphere. Here, using spectral observations of auroral urn:x-wiley:00948276:media:grl63524:grl63524-math-0001 emission lines taken by the Keck Observatory's Near Infrared Echelle Spectrograph (Keck-NIRSPEC) in 2017, we derive ion line-of-sight velocity maps after grouping spectra into rotational quadrants matching phases of the planetary magnetic field. We measure 0.5 km s−1 wind systems in the ionosphere consistent with predicted neutral twin-vortex flow patterns. These findings demonstrate that neutral winds in Saturn's polar regions cause the rotational period, as determined via the magnetic field, to exhibit differences and time variabilities relative to the planet's true period of rotation in a process never before seen within planetary atmospheres.
AB - The Cassini spacecraft revealed that Saturn's magnetic field displayed oscillations at a period originally thought to match the planetary rotation rate but later found not to. One of many proposed theories predicts that a polar twin-cell neutral weather system drives this variation, producing observable differences in flows within Saturn's ionosphere. Here, using spectral observations of auroral urn:x-wiley:00948276:media:grl63524:grl63524-math-0001 emission lines taken by the Keck Observatory's Near Infrared Echelle Spectrograph (Keck-NIRSPEC) in 2017, we derive ion line-of-sight velocity maps after grouping spectra into rotational quadrants matching phases of the planetary magnetic field. We measure 0.5 km s−1 wind systems in the ionosphere consistent with predicted neutral twin-vortex flow patterns. These findings demonstrate that neutral winds in Saturn's polar regions cause the rotational period, as determined via the magnetic field, to exhibit differences and time variabilities relative to the planet's true period of rotation in a process never before seen within planetary atmospheres.
KW - Saturn
KW - infrared aurorae
KW - planetary period oscillations
KW - H3+
KW - infrared spectroscopy
KW - ground-based astronomy
U2 - 10.1029/2021gl096492
DO - 10.1029/2021gl096492
M3 - Letter
VL - 49
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 3
M1 - e2021GL096492
ER -