Magnetically induced ionization and rescatterings in intense laser fields

The dynamics of a classical electron in the field of a nucleus and the electrical and magnetical components of a superintense laser field is investigated analytically. Particular emphasis is placed on the motion in the propagation direction of the laser field which is governed in a competitive manner by a laser induced drift away from the nucleus and an attractive Coulomb force towards it. In order to characterize the ionization and recombination/rescattering dynamics we develop an approximate mapping of the space and momentum coordinates in phase space each time the electron crosses the axis of the laser field propagation. For a certain fraction of the initial phase-space coordinates of the electron in the vicinity of the nucleus we find that the drift can be compensated for due to the attraction of the nucleus. A large number of substantial and almost periodic bursts of acceleration by the nucleus is then possible in the direction of propagation of the laser field. We evaluate the corresponding harmonic spectrum and explain the features deviating from those in the laser parameter regime where the magnetic-field component can be neglected.