XXXII conference on plasma physics and CF, February 14 – 18, 2005, Zvenigorod
DECAY INSTABILITY OF A LASER WAVE DURING THE TRANSVERSAL
PROPAGATION IN A MAGNETIZED PLASMA
V.B. Krasovitskii,
*
V.G. Dorofeenko,
**
V.A. Turikov
Institute of Applied Mathematics, Moscow, Russia, e-mail: krasovit@mail.ru
*
Institute of Advanced Studies, Vienna, Austria, e-mail: dorofeen@ihs.ac.at
** Russian University of Peoples’ Friendship, Moscow, Russia, e-mail: vturikov@sci.pfu.edu.ru
The presence of a magnetic field may significantly affect the propagation of laser pulses in plasma [1-3]. The effective energy transformation mechanism of the laser wave propagating across the external magnetic field to the plasma electrostatic oscillations was found in paper [4]. Unlike to the two-plasmon decay in isotropic plasma the magnetic field in this case couples transversal and propagating along the initial wave vector k
0
. The growth rate of this instability is proportional to the magnetic field value.
In this report the analysis of the parametric excitation of plasma oscillations is performed taking into account the pump wave dispersion. It is shown that the hydrodynamic growth rate decreases in comparison with the case of the constant laser pulse [4]. The unstable frequency
 pert
 
0
/ 2 is shifted into the region below the plasma frequency. The parametric instability exists in the interval
 p
/ 2
  pert
  p
which follows from the wave numbers matching k pert
 k
0
/ 2 . The considerable decrease of the excited waves group velocity takes place when the frequency approaches the right boundary of this interval. It leads to the effective transformation of their energy to the energy of plasma electrons.
The numerical simulation of the laser pulse interaction with plasma during the propagation across the external magnetic field was performed using the one-dimensional relativistic electromagnetic code. The simulation results are in a good agreement with the linear theory of the parametric excitation of plasma oscillations. On the nonlinear stage of the instability, when the kinetic effects become dominant, up to 85

of the initial pulse energy may be transformed into the particle kinetic energy. The numerical experiments show that the external magnetic field leads to energy increase for the ions accelerated by the charge separation field in the plasma boundary region.
This work was supported by the Department of Mathematical Sciences of Russian Academy of
Sciences under Basic Program № 3 and by the Russian Ministry of Education under Research
Program “Universities of Russia”.
References
[1].
Grebogi C. and Liu C.S. J.Plasma Phys. 1980, 23 , 147.
[2].
Shukla P.K. Phys. Plasmas. 1999, 4, 1363.
[3].
Laham N.M., Al-Khateeb A.M., Al Nasser A.S. and Odeh I.M. Phys. Plasmas. 2000, 7 , 3993.
[4].
Krasovitskii V.B., Dorofeenko V.G., Sotnikov V.I., Bauer B.S. Phys. Plasmas. 2004, 11 , 724.