Fast magnetohydrodynamic oscillations in a force-free line-tied coronal arcade

A. J. Diaz, T. Zaqarashvili, B. Roberts

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

Aims. We discuss a simple model of a line-tied coronal arcade with piecewise constant density to explore the effects of curvature on radially polarised fast modes.

Methods. A partial differential equation is derived for the velocity perturbation of the fast modes and it is solved analytically in terms of Bessel functions of half integer order, obtaining a dispersion relation.

Results. The properties of the modes are studied in terms of the parameters. All the modes are leaky under these conditions. Besides the usual kink and sausage modes, new families are described: the vertical, swaying ( longitudinal), and rocking modes arise.

Conclusions. The damping rates are similar to observed rates. For thin arcades the modes are markedly different from those of a straight slab and resemble more the modes of a circular membrane.

Original languageEnglish
Pages (from-to)709-717
Number of pages9
JournalExperimental Astronomy
Volume455
DOIs
Publication statusPublished - Aug 2006

Keywords

  • Sun : oscillations
  • Sun : magnetic fields
  • Sun : corona
  • MAGNETIC-FLUX TUBES
  • FAST MHD OSCILLATIONS
  • LOOP OSCILLATIONS
  • KINK OSCILLATIONS
  • VERTICAL OSCILLATIONS
  • WAVE-PROPAGATION
  • LEAKY
  • MAGNETOSPHERE
  • RESONANCES
  • CURVATURE

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