Gyro-resonant electron acceleration at Jupiter

Abstract

A comprehensive survey of data from the Galileo spacecraft suggests that the principle mechanism of ultra-relativistic electron acceleration in Jupiter’s magnetosphere arises from their gyro-resonant interaction with whistler waves, in contrast with conventional understanding. According to existing theory, electrons are accelerated up to ultra-relativistic energies1 inside Jupiter’s magnetic field by betatron and Fermi processes as a result of radial diffusion towards the planet and conservation of the first two adiabatic invariants2,3,4. Recently, it has been shown that gyro-resonant electron acceleration by whistler-mode waves5,6 is a major, if not dominant7, process for accelerating electrons inside the Earth’s outer radiation zone, and has redefined our concept for producing the Van Allen radiation belts8. Here, we present a survey of data from the Galileo spacecraft at Jupiter, which shows that intense whistler-mode waves are observed outside the orbit of the moon Io and, using Fokker–Planck simulations, are strong enough to accelerate electrons to relativistic energies on timescales comparable to that for electron transport. Gyro-resonant acceleration is most effective between 6 and 12 jovian radii (Rj) and provides the missing step in the production of intense synchrotron radiation from Jupiter1,9.

Cite this article

Horne, R., Thorne, R., Glauert, S. et al. Gyro-resonant electron acceleration at Jupiter. Nature Phys 4, 301–304 (2008). https://doi.org/10.1038/nphys897

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