title: Laser self-focusing in the presence of quasistatic axial direct current.
abstract: We try to understand the presence of a quasistatic magnetic field on the basis of the stability of the laser-plasma system. A general theoretical model of laser self-focusing in the absence of a quasistatic magnetic field (QMF) is extended to discuss self-focusing in the presence of a QMF. Various transverse intensity profiles under different axial collective electronic speeds V(z) are calculated. Numerical results indicate that for suitable laser power and plasma density, the increment in V(z) can lead to a further separation between the photon fluid and the electron fluid and hence a decrement in the energy of the laser-plasma system. This causes it to be possible for the system state without a QMF, or V(z) =0 state, to be not stable relative to some V(z) not equal 0 states.
authors.affiliation: Shanghai Institute of Optics and Fine Mechanics, P.O. Box 800-211, Shanghai 201800, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Lin
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Chen
authors.forename: Ru-Xin
authors.initials: RX
authors.lastname: Li
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Xu