Alfvén wave experiments with liquid rubidium in a pulsed magnetic field

Abstract

Magnetic fields are key ingredients for heating the solar corona to temperatures of several million Kelvin. A particularly important region with respect to this is the so-called magnetic canopy below the corona, where sound and Alfvén waves have roughly the same speed and can, therefore, easily transform into each other. We present the results of an Alfvén-wave experiment with liquid rubidium carried out in a pulsed field of up to 63 T. At the critical point of 54 T, where the speeds of Alfvén waves and sound coincide, a new 4 kHz signal appears in addition to the externally excited 8 kHz torsional wave. This emergence of an Alfvén wave with a doubled period is in agreement with the theoretical predictions of a parametric resonance between the two wave types. We also present preliminary results from numerical simulations of Alfvén and magneto-sonic waves using a compressible MHD code. Figs 4, Refs 14.