Effect of a laser pulse onto a target

A spontaneous magnetic field (SMF) which arises upon exposure of a target by laser radiation has been studied both experimentally and theoretically. Special attention has been paid to an early SMF component which arises simultaneously with the laser pulse and exists until arrival of the laser plasma into the measurement point. A mechanism is considered theoretically of the occurence of the early SMF component due to formation of a current system, in which fast photoelectrons under photoionization of the background medium by the plasma radiation serve as the source. On the basis of this theoretical model the SMF is calculated for a wide range of background medium pressures and laser powers. Re= . sults of experiments with an external magnetic field indicate existence of a volume current source for formation of the early SMF component and confirm the suggested model