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B. H. Mauk, J. Saur (The Johns Hopkins University, Applied Physics Laboratory)
The Cassini Magnetospheric Imaging Instrument (MIMI) has now discovered bi-directional electron beams near the magnetic equator of Saturn's magnetosphere (J. Saur et al., 2005). The beams are narrowly collimated along the local magnetic field vector and occur at positions that map magnetically to the vicinity of Saturn's aurora as measured by the Hubble Space Telescope. Similar electron beams have been observed at both Earth and Jupiter. It is thus becoming likely that the upward (anti-planetary), low altitude acceleration of electron beams, as distinct from the downward acceleration that directly causes bright auroral emissions, is a universal characteristic of auroral phenomena. At Earth the upward acceleration is known to occur in the regions of the downward magnetic field-aligned electric current that constitutes the closure currents of the global auroral electric circuit. Here we examine in greater detail the context and relative characteristics of the electron beams at Saturn, Jupiter, and Earth. We draw conclusions about the general relationship between the upward acceleration and the global auroral electric circuits at all three planets and address the importance of spatial structuring, and perhaps turbulence, in the generation of global auroral displays.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.