Propagation of fast MHD perturbations in coronal potential arcades.
Abstract
We present an analytical approach, using Fourier transformations, to investigate the phenomenon of wave propagation in a coronal potential magnetic field. The system is initially at rest and later set into motion by a photospheric perturber with specified spatial and temporal properties. The disturbances thus excited at the base of the arcade are transmitted into the corona by the fast mode, which is characterised by motions in the direction normal to the unperturbed magnetic field. Under the assumption of a spatially periodic perturber, the time-dependent partial differential equation that arises is shown to be identical to the Klein-Gordon equation. Therefore, the system is dispersive and modes in the spectrum of the exciter with different frequencies travel upwards at different speeds. Furthermore, normal modes with frequencies below the cut-off frequency become evanescent, being unable to propagate into the corona. The method used results in the need of computing numerically a semi-infinite integral, which turns out to be considerably less computer-time consuming than integrating numerically the fast mode partial differential equation.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1996
- Bibcode:
- 1996A&A...314..636C
- Keywords:
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- SUN: CORONA;
- SUN: MAGNETIC FIELDS;
- MAGNETOHYDRODYNAMICS