An oscillating asymmetry to Io's sodium emission cloud

The spatial distribution of sodium emission north and south of Io was observed to have a time-dependent asymmetry correlated with Io's magnetic latitude. The spatial gradient was greatest when Jupiter's north magnetic pole pointed away from Io; this is a configuration of maximum probability of decametric emission. A hypothesis is invoked for explaining the asymmetry and used to calculate preliminary fluxes of low-energy trapped charged particles in the vicinity.