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Sausage oscillations of coronal plasma structures
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Nakariakov, V. M. (Valery M.), Hornsey, Crystal A. and Melnikov, V. F. (2012) Sausage oscillations of coronal plasma structures. The Astrophysical Journal, Volume761 (Number 2). Article number 134. doi:10.1088/0004-637X/761/2/134
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Official URL: http://dx.doi.org/10.1088/0004-637X/761/2/134
Abstract
The dependence of the period of sausage oscillations of coronal loops on length together with the depth and steepness of the radial profile are determined. We performed a parametric study of linear axisymmetric fast magnetoacoustic (sausage) oscillations of coronal loops modeled as a field-aligned low-β plasma cylinder with a smooth inhomogeneity of the plasma density in the radial direction. The density decreases smoothly in the radial direction. Sausage oscillations are impulsively excited by a perturbation of the radial velocity, localized at the cylinder axis and with a harmonic dependence on the longitudinal coordinate. The initial perturbation results in either a leaky or a trapped sausage oscillation, depending upon whether the longitudinal wavenumber is smaller or greater than a cutoff value, respectively. The period of the sausage oscillations was found to always increase with increasing longitudinal wavelength, with the dependence saturating in the long-wavelength limit. Deeper and steeper radial profiles of the Alfvén speed correspond to more efficient trapping of sausage modes: the cutoff value of the wavelength increases with the steepness and the density (or Alfvén speed) contrast ratio. In the leaky regime, the period is always longer than the period of a trapped mode of a shorter wavelength in the same cylinder. For shallow density profiles and shorter wavelengths, the period increases with wavelength. In the long-wavelength limit, the period becomes independent of the wavelength and increases with the depth and steepness of the radial profile of the Alfvén speed.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Divisions: | Faculty of Science > Physics | ||||
| Journal or Publication Title: | The Astrophysical Journal | ||||
| Publisher: | Institute of Physics Publishing, Inc. | ||||
| ISSN: | 0004-637X | ||||
| Official Date: | 2012 | ||||
| Dates: |
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| Volume: | Volume761 | ||||
| Number: | Number 2 | ||||
| Page Range: | Article number 134 | ||||
| DOI: | 10.1088/0004-637X/761/2/134 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
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