Swing wave-wave interaction: coupling between fast magnetosonic and Alfvén waves.
We suggest a mechanism of energy transformation from fast magnetosonic waves propagating across a magnetic field to Alfvén waves propagating along the field. The mechanism is based on swing wave-wave interaction [T. V. Zaqarashvili, Astrophys. J. Lett. 552, 107 (2001)]. The standing fast magnetosonic waves cause a periodical variation in the Alfvén speed, with the amplitude of an Alfvén wave being governed by Mathieu's equation. Consequently, subharmonics of Alfvén waves with a frequency half that of magnetosonic waves grow exponentially in time. It is suggested that the energy of nonelectromagnetic forces, which are able to support the magnetosonic oscillations, may be transmitted into the energy of purely magnetic oscillations. Possible astrophysical applications of the mechanism are briefly discussed.
Zaqarashvili
T V
TV
School of Mathematics and Statistics, University of St. Andrews, St. Andrews, Fife KY16 9SS, Scotland.
Roberts
B
B