Magnetic field generation in a plasma in the presence of an ultrashort laser pulse

The description of the Weibel instability linear stage for a plasma interac ting with an ultrashort laser pulse is given. Pulse durations both smaller and larger than the inverse collision frequency of the thermal electrons ar e considered. In the latter case the pulse duration is smaller than the the rmal electron heating time. The growth rate of the instability is derived a nd the possibility of a considerable quasistationary magnetic field amplifi cation demonstrated. (C) 2001 American Institute of Physics.