Amplification of spontaneous magnetic fields due to inverse bremsstrahlungabsorption of high frequency radiation

The theory of the linear stage of the Weibel instability growth due to anis otropic heating of electrons undergoing inverse bremsstrahlung absorption o f high frequency electromagnetic radiation is reported. The possibility is shown of a significant amplification of spontaneous magnetic fields for bot h the cases of circularly and linearly polarized high frequency radiation. Numerical calculations and comparisons are reported for a wide range of the process parameters, covering the cases of weak and strong high-frequency r adiation fields. Among others, if the linearly polarized field is strong, t he magnetic field amplification for typical conditions is found to be less significant as compared to the case of strong circularly polarized field. T he reverse result is found for the case of weak linearly and circularly pol arized fields. (C) 2000 American Institute of Physics. [S1070-664X(00)01910 -8].