Jupiter’s Radio Rotation Period: A 50-year Average
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C. A. Higgins and D. SolusDepartment of Physics & Astronomy Middle Tennessee State Univ., Murfreesboro, TN
F. Reyes and the late T. D. Carr (Emeritus)Department of AstronomyUniversity of Florida, Gainesville, FL
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History of Rotation History of Rotation Period measurementsPeriod measurements Galileo (1610) Schroeter (1787) Surface features Marth (1875, 1885) Jupiter ephemeris, Sys I and Sys II defined Williams (1896) nine zones of latitude Shain (1956) Radio Rotation Period Gallet (1957), Gardener and Shain (1958) Carr et al. (1958) - - - System III (1957) IAU (1962) --- first defined System III (1957) period 1960s and 70s many measurements: DAM and DIM Riddle & Warwick (1976) + 25 scientists agreed to the System III (1965) - - - 9h 55m 29.71s
Duncan (1971) decimetric measurement Carr (1972) decametric measurement Kaiser & Alexander 1972) decametric & power spectrum Berge (1974) decimetric measurement
IAU (1977) System III (1965) Sandel & Dessler (1988) System IV
System IV
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18TL
1
8TR
20TL
2
0TR
22TL
2
2TR
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• 5° bins Jupiter CML• Ephemeris SysIII (1965)
nObservatio
Activity
tt
PO .. Source A
Source B
Source C
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• Peaks are Source A Occurrence Probability• 12-yr Declination Effect (DE)
DE
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Multiple 12-yr dataCML shift < 0Period < SysIII(1965)
CML shift > 0 Period > SysIII(1965)
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• P’ – new rotation period (in decimal hours)• P – old rotation period (9.92492 h = 9h 55m 29.71s)• Δt – time between observation epochs in years (this
example t = 24.017 y or 210533 h)• 360 – number of degrees per rotation• - degrees shift in longitude of the second histogram
with respect to the first that maximizes the correlation coefficient (this example -6.8°)
• Example = -6.8° → 9.92491 h ( = 9h 55m 29.68s)
tPP
360
1'1
0
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Weighted Mean Period 9h 55m 29.689 ± 0.004s
SysIII (1965)NewPeriod
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Weighted Mean Period 9h 55m 29.689 ± 0.004s Max Possible Drift ≈ 4 ms/yr (from Higgins et al., JGR 1997)
SysIII (1965)NewPeriod
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Jupiter’s Internal Rotation PeriodJupiter’s Internal Rotation Period
Rotation Periods 1σ
Rotation Period Measurements
00.10.20.30.40.50.60.70.80.9
1
0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80
Rotation Period (in excess of 9h 55m 29s)
Sys III (1965)
Yu & Russell(2009)
Higgins et al.(1997)
Higgins et al.(MOP 2011)
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ConclusionsConclusions Jupiter’s DAM Rotation Period
Weighted Mean Period 9h 55m 29.689s ± 0.004s Max Possible Drift ~ 4 ms/yr
No conclusive secular variation Radio sources are stable over long term observations
Discussion Differential rotation Other calculations IAU has returned the period back to Sys III (1965) IAU would like a response from the MOP community
Thank you!
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Entered UF at 16; M.S. in 1940 WWII (physicist at Aberdeen, MD) Worked with A-bomb tests at Bikini First PhD in Astrophysics at UF (1958) Co-founder of UFRO, Radio program Univ. of Chile Involved with creation of Arecibo radio telescope Designed and build a 26 MHz array of (640 dipoles) 2 Books and many book chapters (Jupiter, Physics of the Jovian Magnetosphere, Radio Astronomy) Co-investigator of PRA group for Voyager missions Jupiter radio emissions (rotation and S-bursts) ASTEROID #96288 named and dedicated for Tom Advised over 25 PhD and MS theses Pioneer in VLBI > 30 years UF Professor; Retired in 1995 Loved Florida’s natural habitat and itsconservation
Dr. Thomas D. CarrDr. Thomas D. Carr1917 - 20111917 - 2011