Generation of a magnetosonic signal by a pulse of acoustic waves in an anisotropically conducting medium

L. P. Gorbachev - Yu. E. Savchenko

Abstract
We study the generation of a magneto sonic signal by a pulse of acoustic waves in the frequency range ν_ni << ω << ω_i, where ν_ni is the frequency of collisions between neutral particles and ions and wi is the gyrofrequency of the ions. The medium is considered to be a three- component partially ionized gas, consisting of ions, electrons, and neutral particles. The external magnetic field is perpendicular to the direction of propagation of the acoustic waves. The magnetic pressure is much higher than the gasdynamical pressure, and collisions of charged particles with one another are neglected. The distribution of the parameters of the medium is nonuniform in the direction of propagation of the waves and is approximated by a stratification into layers, in each of which the parameters are constant, undergoing discontinuities at the boundaries. A reorganization is effected by a region in which the acoustic wave length is larger than the mean free path of the neutral particles. Joining of the solutions for separate layers is accomplished by a matrix method suitable for realization on a computer. We give an example of the numerical calculation of an induction pulse of the magnetic field generated by an acoustic signal in the Earth's atmosphere.