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Correlated variations of UV and radio emissions during an outstanding Jovian auroral eventAn exceptional Jovian aurora was detected in the FUV on December 21, 1990, by means of Vilspa and Goddard Space Flight Center (GFSC) International Ultraviolet Explorer (IUE) observations. This event included intensification by a factor of three between December 20 and 21, leading to the brightest aurora identified in the IUE data analyzed, and, in the north, to a shift of the emission peak towards larger longitudes. The Jovian radio emission simultaneously recorded at decameter wavelengths in Nancay also exhibits significant changes, from a weak and short-duration emission on December 20 to a very intense one, lasting several hours, on December 21. Confirmation of this intense radio event is also found in the observations at the University of Florida on December 21. The emissions are identified as right-handed Io-independent 'A' (or 'non Io-A') components from the northern hemisphere. The radio source region deduced from the Nancay observations lies, for both days, close to the UV peak emission, exhibiting in particular a similar shift of the source region toward larger longitudes from one day to the next. A significant broadening of the radio source was also observed and it is shown that on both days, the extent of the radio source closely followed the longitude range for which the UV brightness exceeds a given threshold. The correlated variations, both in intensity and longitude, strongly suggest that a common cause triggered the variation of the UV and radio emissions during this exceptional event. On one hand, the variation of the UV aurora could possibly be interpreted according to the Prange and Elkhamsi (1991) model of diffuse multicomponent auroral precipitation (electron and ion): it would arise from an increase in the precipitation rate of ions together with an inward shift of their precipitation locus from L approximately equal 10 to L approximately equal 6. On the other hand, the analysis of Ulysses observations in the upstream solar wind suggests that a significant disturbance in the solar wind, involving the generation of an interplanetary shock and the presence of a CME have interacted with the Jovian magnetosphere at about the time of the auroral event. Both arguments suggest that we may have observed for the first time a magnetic storm-type interaction in an outer planet magnetosphere, affecting simultaneously several auroral processes. Conversely, the observed relationship between the level of UV auroral activity and the detection of decameter emission (DAM), if it were a typical feature, might argue in favour of a more direct and permanent association between the auroral processes leading to UV and radio aurorae, possibly related to 'discrete-arc'-like activity and electron precipitation.
Document ID
19950045584
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Prange, R.
(Universite Paris XI Orsay, France)
Zarka, P.
(Observatoire de Paris-Meudon France)
Ballester, G. E.
(Oxford University Oxford, United Kingdom)
Livengood, T. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Denis, L.
(Groupe de Radioastronomie decametrique de Nancay France)
Carr, T.
(University of Florida, Gainesville, FL United States)
Reyes, F.
(University of Florida, Gainesville, FL United States)
Bame, S. J.
(Los Alamos National Laboratory, Los Alamos, NM United States)
Moos, H. W.
(The Johns Hopkins University Baltimore, MD, United States)
Date Acquired
August 16, 2013
Publication Date
October 25, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: E10
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
95A77183
Funding Number(s)
CONTRACT_GRANT: INSU-PNP/80374200
Distribution Limits
Public
Copyright
Other

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