Magnetohydrodynamics wave propagation in the neighbourhood of two dipoles 

James McLaughlin Submitted: 20070830 04:05
Context. This paper is the third in a series of investigations by the authors. Aims. The nature of fast magnetoacoustic and Alfvén waves is investigated in a 2D β=0 plasma in the neighbourhood of two dipoles. Methods. We use both numerical simulations (twostep LaxWendroff scheme) and analytical techniques (WKB approximation). Results. It is found that the propagation of the linear fast wave is dictated by the Alfvén speed profile and that close to the null, the wave is attracted to the neutral point. However, it is also found that in this magnetic configuration some of the wave can escape the refraction effect; this had not been seen in previous investigations by the authors. The wave split occurs near the regions of very high Alfvén speed (found near the loci of the two dipoles). Also, for the setup investigated it was found that 40% of the wave energy accumulates at the null. Ohmic dissipation will then extract the wave energy at this point. The Alfvén wave behaves in a different manner in that part of the wave accumulates along the separatrices and part escapes. Hence, the current density will accumulate at this part of the topology and this is where wave heating will occur. Conclusions. The phenomenon of wave accumulation at a specific place is a feature of both wave types, as is the result that a fraction of the wave can now escape the numerical box when propagating in this magnetic configuration.
Authors: McLaughlin, J. A. and Hood, A. W.
Projects: None

Publication Status: Astronomy and Astrophysics, 452, 603613 (2006)
Last Modified: 20070830 04:05


