Universität zu Köln

Musacchio, Fabrizio ORCID: 0000-0002-9043-3349, Saur, Joachim ORCID: 0000-0003-1413-1231, Roth, Lorenz ORCID: 0000-0003-0554-4691, Retherford, Kurt D., McGrath, Melissa A., Feldman, Paul D. and Strobel, Darrell F. (2017). Morphology of Ganymede's FUV auroral ovals. J. Geophys. Res-Space Phys., 122 (3). S. 2855 - 2877. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9402

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Abstract

We study the morphology of Ganymede's FUV aurora by analyzing spectral images obtained over the past two decades by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. The observations cover the eastern and western elongation as well as various magnetic latitudes of Ganymede within the Jovian plasma sheet. We find both asymmetries in the spatial distribution of auroral brightness on the observed moon disk and temporal variation correlated to Ganymede's changing magnetic latitude. The total disk brightness is on average 1.42 +/- 0.07 times brighter on the leading side (95.4 +/- 2.1R) than on the trailing side (67.2 +/- 2.9R). The brightness ratio of the sub-Jovian hemisphere to the anti-Jovian hemisphere is 1.81 +/- 0.06 on the leading side and 1.41 +/- 0.14 on the trailing side, respectively. Inside the Jovian current sheet, the brightness of the auroral ovals increases by a factor of 1.45 +/- 0.02 on the leading side and decreases by a factor of 0.80 +/- 0.02 on the trailing side. At the current sheet center, the auroral ovals shift 4.1 degrees +/- 0.7 degrees latitude toward Ganymede's planetographic equator on the leading side and 2.9 degrees +/- 1.5 degrees toward the poles on the trailing side. Both effects, the variation of brightness and the movement of the ovals are correlated to a stronger interaction of Jupiter's magnetospheric plasma with Ganymede's minimagnetosphere inside the current sheet. Finally, we calculate the latitudinal difference of the northern and southern ovals from Ganymede's magnetic equator. The result suggests a farther westward orientation of Ganymede's dipole magnetic moment at approximately 47 degrees + 58 degrees/-43 degrees west longitude compared to previous estimates.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Musacchio, Fabrizio UNSPECIFIED orcid.org/0000-0002-9043-3349 UNSPECIFIED Saur, Joachim UNSPECIFIED orcid.org/0000-0003-1413-1231 UNSPECIFIED Roth, Lorenz UNSPECIFIED orcid.org/0000-0003-0554-4691 UNSPECIFIED Retherford, Kurt D. UNSPECIFIED UNSPECIFIED UNSPECIFIED McGrath, Melissa A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Feldman, Paul D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Strobel, Darrell F. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-237236
DOI:	10.1002/2016JA023220
Journal or Publication Title:	J. Geophys. Res-Space Phys.
Volume:	122
Number:	3
Page Range:	S. 2855 - 2877
Date:	2017
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9402
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language GALILEO ULTRAVIOLET SPECTROMETER; RESISTIVE MHD SIMULATIONS; MAGNETIC-FIELD; IOS INTERACTION; WATER-VAPOR; MAGNETOSPHERE; SATELLITES; SPACECRAFT; MODELS Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/23723