Chorus, ECH, and Z mode emissions observed at Jupiter and Saturn and possible electron acceleration

Abstract

In this paper we compare and contrast chorus, electron cyclotron harmonics (ECH), and Z mode emissions observed at Jupiter and Saturn and relate them to recent work on electron acceleration at Earth. Intense chorus emissions are observed near the magnetic equator, the likely source region, but the strongest intensities are on either side of the magnetic equator. Chorus intensities at Jupiter are generally about an order of magnitude larger than at Saturn, and the bandwidth of chorus at Jupiter can reach 7 or 8 kHz (∼0.6 fc), while at Saturn it is typically <2 kHz (∼0.6 fc, also). No higher-latitude information is available at Jupiter; however, high inclination orbits at Saturn by Cassini reveal strong chorus intensities at latitudes extending to over 30. At Jupiter, initial studies reveal the chorus intensities are sufficient to accelerate electrons by a stochastic process; however, the high density levels near the source region of chorus at Saturn indicate a less efficient process except for local regions such as within plasma injection regions. The role of Z mode in electron acceleration and the role of ECH waves in pitch angle scattering at both Jupiter and Saturn require further study. © 2012. American Geophysical Union. All Rights Reserved.