Universität zu Köln

Hue, V, Greathouse, T. K., Bonfond, B., Saur, J., Gladstone, G. R., Roth, L., Davis, M. W., Gerard, J-C, Grodent, D. C., Kammer, J. A., Szalay, J. R., Versteeg, M. H., Bolton, S. J., Connerney, J. E. P., Levin, S. M., Hinton, P. C. and Bagenal, F. (2019). Juno-UVS Observation of the Io Footprint During Solar Eclipse. J. Geophys. Res-Space Phys., 124 (7). S. 5184 - 5200. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9402

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Abstract

The two main ultraviolet-signatures resulting from the Io-magnetosphere interaction are the local auroras on Io's atmosphere, and the Io footprints on Jupiter. We study here how Io's daily eclipses affect the footprint. Previous observations showed that its atmosphere collapses in eclipse. While remote observers can observe Io's local auroras briefly when Io disappears behind Jupiter, Juno is able to follow the Io footprint in the unlit hemisphere. Theoretical models of the variability of the energy flux fed into the Alfven wings, ultimately powering the footprints, are not sufficiently constrained by observations. For the first time, we use observations of Io's footprint from the Ultraviolet Spectrograph (UVS) on Juno recorded as Io went into eclipse. We benchmark the trend of the footprint brightness using observations by UVS taken over Io's complete orbit and find that the footprint emitted power variation with Jupiter's rotation shows fairly consistent trends with previous observations. Two exploitable data sets provided measurements when Io was simultaneously in eclipse. No statistically significant changes were recorded as Io left and moved into eclipse, respectively, suggesting either that (i) Io's atmospheric densities within and outside eclipse are large enough to produce a saturated plasma interaction, that is, in the saturated state, changes in Io's atmospheric properties to first order do not control the total Alfvenic energy flux, (ii) the atmospheric collapse during the Juno observations was less than previously observed, or (iii) additional processes of the Alfven wings in addition to the Poynting flux generated at Io control the footprint luminosity.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hue, V UNSPECIFIED UNSPECIFIED UNSPECIFIED Greathouse, T. K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bonfond, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Saur, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gladstone, G. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roth, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Davis, M. W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerard, J-C UNSPECIFIED UNSPECIFIED UNSPECIFIED Grodent, D. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kammer, J. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Szalay, J. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Versteeg, M. H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bolton, S. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Connerney, J. E. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Levin, S. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hinton, P. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bagenal, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-135835
DOI:	10.1029/2018JA026431
Journal or Publication Title:	J. Geophys. Res-Space Phys.
Volume:	124
Number:	7
Page Range:	S. 5184 - 5200
Date:	2019
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9402
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language DUSK ELECTRIC-FIELD; WAVE CURRENT SYSTEM; PLASMA INTERACTION; HST/STIS OBSERVATIONS; ATMOSPHERE; ULTRAVIOLET; EMISSION; JUPITER; SO2; SUBLIMATION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13583