Abstract
Abstract. Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been suggested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities observed by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its variation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at L-shells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS) model. This profile confines intense chorus waves near the magnetic equator with a peak intensity at ∼5° latitude. Electron fluxes in the BAS model increase by an order of magnitude for energies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron acceleration by cyclotron-resonant interactions at Jupiter contributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.
Highlights
Jupiter has the most intense radiation belts of all the magnetized planets, with electron energies in excess of 50 MeV at L = 1.4 (Bolton et al, 2002; de Pater and Dunn, 2003)
In order to assess the effect of the combined pitch angle and energy diffusion on the electron flux we have used the British Antarctic Survey Radiation Belt (BAS) model which has been adapted for Jupiter
Previous work has suggested that cyclotron-resonant interactions with chorus waves are a significant factor in creating these radiation belts
Summary
Jupiter has the most intense radiation belts of all the magnetized planets, with electron energies in excess of 50 MeV at L = 1.4 (Bolton et al, 2002; de Pater and Dunn, 2003) These belts are believed to be formed by inward radial transport of electrons from a source beyond the orbit of the moon Io (L = 6.6) on the assumption that the first adiabatic invariant remains conserved (Santos-Costa and Bourdarie, 2001; Sicard and Bourdarie, 2004). Strong whistler-mode waves have been observed outside the orbit of Io (Gurnett et al, 1996; Menietti et al, 2008) in association with magnetic flux interchange instabilities (Kivelson et al, 1997; Thorne et al, 1997; Xiao et al, 2003).
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