Hydromagnetic wave propagation in inhomogeneous magnetic fields

Abstract

Apart from the case of torsional waves propagating into a magnetic 'beach' where ion cyclotron resonance is encountered, the study of the propagation of magnetohydrodynamic waves in inhomogeneous magnetic fields has received little attention. This paper presents some such results for both torsional waves propagating into magnetic 'beaches' and compressional waves into magnetic 'cliffs'. The inhomogeneous field used consisted of two uniform fields of different magnitude connected by a transition region the length of which could be changed. Attention was concentrated on looking for a wave reflected from the field discontinuity. For torsional waves no reflected wave was detected either for waves of frequency much less than ion cyclotron frequency or for those which encountered ion cyclotron resonance in the low field region. For compressional waves reflection was observed under some conditions. It was most pronounced when the length of the transition region was not appreciably greater than the wave attenuation length and when the wave was cut-off in the high field region. Values of the reflection coefficient and the phase change at reflection are given.