Compressible Dynamic Alignment

  1. J. H. Waite Jr.,
  2. J. L. Burch and
  3. R. L. Moore
  1. R. B. Dahlburg1,
  2. J. M. Picone1 and
  3. J. T. Karpen2

Published Online: 18 MAR 2013

DOI: 10.1029/GM054p0095

Solar System Plasma Physics

Solar System Plasma Physics

How to Cite

Dahlburg, R. B., Picone, J. M. and Karpen, J. T. (1989) Compressible Dynamic Alignment, in Solar System Plasma Physics (eds J. H. Waite, J. L. Burch and R. L. Moore), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM054p0095

Author Information

  1. 1

    Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington, D.C. 20375

  2. 2

    E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, D.C. 20375

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780875900742

Online ISBN: 9781118664315



  • Space plasmas;
  • Sun;
  • Magnetosphere;
  • Astrophysics


Dynamic alignment has been proposed to account for correlations between the magnetic and velocity fields of the solar wind. This dynamic alignment problem is part of a more general class of problems, related to self-organization in compressible magnetohydrodynamic (MHD) turbulence, which is not yet well understood. In previous work we demonstrated that dynamic alignment occurs in two-dimensional compressible turbulent magnetofluids (Dahlburg et al., 1988a). In this paper we discuss numerical simulations which further our understanding of dynamic alignment in compressible MHD. By varying the initial average Mach number, we determine the influence of compressibility on dynamic alignment in the “Orszag-Tang vortex,” a frequently investigated two-dimensional MHD configuration. As the Mach number is raised we observe a time delay in growth of correlation between the magnetic field and the velocity field. As the Mach number approaches zero, the results for the compressible runs converge to the incompressible result. Our results indicate that the details of dynamic alignment depend on the solenoidality of the initial flow profile, as well as the degree to which the initial mechanical pressure resembles the appropriate incompressible mechanical pressure.