Nonlinear Parker Instability of Isolated Magnetic Flux in a Plasma
Abstract
The nonlinear evolution of the Parker instability in an isolated horizontal magneticflux sheet embedded in a twotemperature layer atmosphere is studied by using a twodimensional MHD code. In the solar case, this twolayer model is regarded as a simplified abstraction of the sun's photosphere/chromosphere and its overlying much hotter (coronal) envelope. The horizontal flux sheet is initially located in the lower temperature atmosphere so as to satisfy magnetostatic equilibrium under a constant gravitational acceleration. Ideal MHD is assumed, and only perturbations with k parallel to the magneticfield lines are investigated. As the instability develops, the gas slides down the expanding loop, and the evacuated loop rises as a result of enhanced magnetic buoyancy. In the nonlinear regime of the instability, both the rise velocity of a magnetic loop and the local Alfven velocity at the top of the loop increase linearly with height and show selfsimilar behavior with height as long as the wavelength of the initial perturbation is much smaller than the horizontal size of the computing domain.
 Publication:

The Astrophysical Journal
 Pub Date:
 March 1989
 DOI:
 10.1086/167212
 Bibcode:
 1989ApJ...338..471S
 Keywords:

 Chromosphere;
 Magnetic Flux;
 Magnetohydrodynamic Stability;
 Solar Atmosphere;
 Gravitational Effects;
 Magnetohydrodynamic Waves;
 Solar Corona;
 Velocity Distribution;
 Solar Physics;
 HYDROMAGNETICS;
 INSTABILITIES;
 PLASMAS;
 SUN: ATMOSPHERE;
 SUN: CHROMOSPHERE