Pitch angle scattering of an energetic magnetized particle by a circularly polarized electromagnetic wave
The interaction between a circularly polarized wave and an energetic gyrating particle is described using a relativistic pseudo-potential that is a function of the frequency mismatch. Analysis of the pseudo-potential provides a means for interpreting numerical results. The pseudo-potential profile depends on the initial mismatch, the normalized wave amplitude, and the initial angle between the wave magnetic field and the particle perpendicular velocity. For zero initial mismatch, the pseudo-potential consists of only one valley, but for finite mismatch, there can be two valleys separated by a hill. A large pitch angle scattering of the energetic electron can occur in the two-valley situation but fast scattering can also occur in a single valley. Examples relevant to magnetospheric whistler waves show that the energetic electron pitch angle can be deflected 5°towards the loss cone when transiting a 10 ms long coherent wave packet having realistic parameters.
© 2013 AIP Publishing LLC. Received 7 February 2013; accepted 26 March 2013; published online 19 April 2013. The author wishes to thank Dr. B. Tsurutani for raising the issue of whether coherent whistler wave chorus elements can cause significant pitch angle transport and for encouraging this analysis. This work was supported by NSF, DOE, and AFOSR.
Published - PhysPlasmas_20_042117.pdf