THEORY OF RESONANT AND STIMULATED EXCITATION OF MAGNETIC-MOMENT FIELDS IN WAVE-PLASMA INTERACTIONS

Theories of two nonlinear processes of magnetic-moment-field generatio n in wave-plasma interactions are presented here. These processes are (i) resonant excitation of a moment field (REMF) and (ii) stimulated e xcitation of a moment field (SEMF). This field generally evolves from the wave-induced bending of the direction of motion of constituents of a plasma. It is important when it has a large value, and when it grow s to large values with time, because then it effectively controls the wave-induced features of a plasma. Specifically, this growing field gi ves rise to a strong anisotropy of the plasma in the region of the com mon direction of propagation of the involved waves, which leads to enh ancement of synchrotron and bremmsstrahlung losses, and filamentation. The REMF is a static field of resonance when the beat frequency of tw o waves equals the frequency of another wave, all propagating in the s ame direction. The three possible cases of such interaction, involving waves of only high frequencies, with unmagnetized plasmas, for which the REMF formula has been calculated, are (a) two transverse waves and one longitudinal wave, (b) two longitudinal waves and one transverse wave, and (c) three transverse waves. The SEMF is a parametrically sti mulated nonoscillating, exponentially temporally growing field of stim ulated Brillouin scattering from a signal Alfven wave, a pump Alfven w ave, and a signal sound wave. A second simultaneous resonance occurs o nly for weak nonlinearity and finite electrical conductivity, when the signal Alfven wave frequency equals the parametric frequency shift. T his, being a slow process of transfer of plasma kinetic energy to fiel d energy, can be a strong candidate for evolution of the field in plas ma configurations of outer space.