Auroral processes at the outer planets

The mean electron energy may be significantly different in different auroral zones.
The Io tail CR is remarkably low in comparison with the high-latitude aurora and independent of its brightness (<E> ~ 50 keV or less). This is consistent with a model where the tail corresponds to an upward field aligned current closing the magnetospheric circuit in Jupiter’s ionosphere.
The CR in the main oval is associated with electron energies from ~50 to several 100 keV. It is statistically positively correlated with the intensity. Brightness increase in the main oval is accompanied by hardening of the electron energy spectrum. This result is consistent with acceleration by potential drops accompanying upward field-aligned currents which carry a nearly constant particle number flux. The electron mean energy is also variable in the polar spots but it is not correlated with the main oval brightness nor its own intensity, suggesting different, uncorrelated mechanisms.
Polar brightenings (duration ~ 50-100 sec, rise time ~30 sec) have been observed. They are not necessarily associated with an increase of the mean electron energy. The mean electron energy can even decrease during the intensification.
No correlation is observed between changes in main oval and high latitude (polar cap) features.