MHD turbulence in "dc" magnetic fields
Abstract
It is long known that a uniform magnetic field in a periodic MHD turbulence code will result in anisotropy in the wavenumber spectrum: high-k components develop more readily perpendicular to B than parallel to it. But electromagnetic conceptual contradictions result from introducing a uniform dc field into a periodic code if the periodic situation is to represent a realizable geometry [1]. "Local anisotropy" has recently been defined and demonstrated to result from purely local mean B fields, avoiding these contradictions [2]. There are also reasons that a uniform dc magnetic field might suppress the inverse magnetic helicity cascade, an important dynamo mechanism. If so, it would be of interest to see if effects of local mean B-fields could be identified in inverse helicity cascades as well. One reason this is important is that it is true that the only detailed, quantitative verifications of MHD turbulence effects we have still come from computer solutions of the MHD equations, which have severe and often unacknowledged limitations in the situations to which they are being applied--situations in which far-reaching inferences are being drawn. [1] D.C. Montgomery et al, Phys. Plasmas 6, 2727 (1999). [2] L.J. Milano et al, Phys. Plasmas 8, 2673 (2001).
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2001
- Bibcode:
- 2001APS..DPPFM1001M