CHANGES IN THE SPATIAL DISTRIBUTION OF JUPITER’S SYNCHROTRON RADIATION IN RESPONSE TO EXTERNAL INFLUENCES DURING THE CASSINI FLYBY OF JUPITER

Abstract:

We examine radio observations of Jupiter to discuss the response of Jupiter’s electron-belt emission to external influences during the Cassini flyby of Jupiter. To demonstrate that Jupiter's synchrotron emission was varying during the last weeks of December 2000 and first weeks of January 2001, we compare the radio measurements from 2-3 January 2001 with VLA observations obtained on 20-21 December 1988, when viewing geometry and array configuration were comparable. Our analysis of interferometric and tomographic maps of brightness distribution indeed shows that the electron-belt emission was differently distributed around the planet in December 1988 and January 2001. The analysis of the 1988 and 2001 VLA data sets with VLA data from May 1997 further confirms that the spatial distribution of the electron belt on 2-3 January 2001 was different from that usually observed. The dynamical behavior of the solar activity at the time of the Cassini flyby of Jupiter strongly suggests that the emission from the electron radiation belt was responding to external influences on a timescale of days to a couple of weeks. We argue that the radiation belt was responding to solar wind structures rather than to solar irradiation, as the correlation with the solar UV/EUV radio flux is ruled out. Here we present our latest results obtained from a multi-source data analysis of the response of Jupiter’s electron-belt emission to solar wind structures that involves the use of spacecraft, solar, and Earth-based measurements.