Physics – Plasma Physics
Scientific paper
Apr 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003jgra..108.1162m&link_type=abstract
Journal of Geophysical Research (Space Physics), Volume 108, Issue A4, pp. SSH 10-1, CiteID 1162, DOI 10.1029/2002JA009252
Physics
Plasma Physics
16
Space Plasma Physics: Waves And Instabilities, Solar Physics, Astrophysics, And Astronomy: Magnetic Fields, And Astronomy: Corona, And Astronomy: Flares, And Astronomy: Coronal Mass Ejections
Scientific paper
We present the results of magnetohydrodynamic (MHD) simulations of the nonlinear development of instabilities of magnetically sheared arcades and show how they relate to plasmoid ejections and coronal mass ejections (CMEs). To model the arcade disruptions, we capitalize on a family of analytical solutions for initial states; these describe magnetic arcades in uniform gravity that are characterized by magnetic shear. Two-and-a-half-dimensional (2.5-D) time-dependent simulations were performed with the ZEUS-2D code to show the response of the arcades to small velocity perturbations. The model arcades respond by rising and expanding, and most significantly, we find shearing motions naturally arise in conjunction with the instability. This field line shearing is in response to the Lorentz force, which drives large-amplitude Alfvén waves, which in turn transport magnetic shear from the lower to the upper extremities of the arcades. The self-induced shear Alfvén waves, coupled with magnetic buoyancy, provide a feedback mechanism that drives the arcades to a loss of equilibrium and disruption following a long period of slow rise and expansion. These simulations of arcade disruptions may be relevant with regard to CME initiation for three major reasons. First, the arcade disruptions are the result of undriven magnetic buoyancy instabilities. Second, magnetic field line shearing is an intrinsic aspect of the instability that occurs spontaneously and is driven only by the magnetic tension force. (No imposed shear motions are specified.) Third, the arcade disruption process has been found to repeat without prompting.
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