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The effect of a static magnetic field on the growth of a rippled electromagnetic beam

This paper presents an investigation of the growth of a radially symmetrical ripple, superimposed on a Gaussian electromagnetic beam in a collisionless magnetized plasma. On account of the non-uniform intensity distribution of the main beam, the d.c. component of the ponderomotive force becomes finite and leads to modification of the background density. There is feedback from the main beam to the ripple, which subsequently grows at the cost of the pump wave. The effect of the plasma and pump parameters is studied in detail. An interesting feature is that the ripple always grows, irrespective of the phase relationship of the main beam and the ripple. This is due to strong self-focusing of the main beam for the chosen set of parameters.