Broadening of Cyclotron Resonance Conditions in the Relativistic Interaction of an Intense Laser with Overdense Plasmas

摘要

The interaction of dense plasmas with an intense laser under a strongexternal magnetic field has been investigated. When the cyclotron frequency forthe ambient magnetic field is higher than the laser frequency, the laser'selectromagnetic field is converted to the whistler mode that propagates alongthe field line. Because of the nature of the whistler wave, the laser lightpenetrates into dense plasmas with no cutoff density, and produces superthermalelectrons through cyclotron resonance. It is found that the cyclotron resonanceabsorption occurs effectively under the broadened conditions, or a wider rangeof the external field, which is caused by the presence of relativisticelectrons accelerated by the laser field. The upper limit of the ambient fieldfor the resonance increases in proportion to the square root of therelativistic laser intensity. The propagation of a large-amplitude whistlerwave could raise the possibility for plasma heating and particle accelerationdeep inside dense plasmas.