Relativistic cyclotron resonance condition as applied to Type II interplanetary radio emission

William M. Farrell (1) , Michael L. Kaiser (1) , Stuart D. Bale (2) , M. D. Desch (1) , R. J. Fitzenreiter (1) , Keith Goetz (3) , Jean-Louis Bougeret (4, 5, 6)

1 Laboratory for Extraterrestrial Physics
2 SSL - Space Sciences Laboratory [Berkeley]
3 School of Physics and Astronomy, University of Minnesota
4 DESPA - Departement de recherche SPAtiale
5 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
6 Physique des plasmas

We demonstrate that energy from energetic electrons upstream of interplanetary (IP) shocks are able to couple directly to the o-mode radio branch via the relativistic cyclotron harmonic resonance interaction, thereby creating the Type II radiation observed from IP shocks. The conditions required for the electron/wave resonance are that the wave frequency, f, lies near the local plasma frequency, f_p, and near (but not exactly at) the cyclotron harmonics, mf_c, where m is the cyclotron harmonic number. We compare the details of this relativistic electron cyclotron harmonic theory with observations in a Type II source region, with good agreement in many areas including the prediction of "Zeeman" splitting of the Type II emission. Based on the character of the high-resolution emission spectrum, we can narrow the Type II source location to the IP shock foot region and place some general conditions on shock topology required for Type II emission.

Domaines: Astrophysique [astro-ph]

William M. Farrell, Michael L. Kaiser, Stuart D. Bale, M. D. Desch, R. J. Fitzenreiter, et al.. Relativistic cyclotron resonance condition as applied to Type II interplanetary radio emission. Journal of Geophysical Research Space Physics, 2004, 109, pp.02106. ⟨10.1029/2003JA009965⟩. ⟨hal-03786457⟩