Volume 412, Number 1, December II 2003
|Page(s)||L7 - L10|
|Published online||25 November 2003|
Letter to the Editor
Global sausage modes of coronal loops
Physics Department, University of Warwick, Coventry, CV4 7AL, UK e-mail: email@example.com
2 Radiophysical Research Institute (NIRFI), Nizhny Novgorod, 603950, Russia e-mail: firstname.lastname@example.org, email@example.com
3 New Jersey Institute of Technology, Newark, NJ 07102, USA
Corresponding author: V. M. Nakariakov, firstname.lastname@example.org
Accepted: 25 October 2003
Sufficiently thick and dense coronal loops can support global sausage magnetoacoustic modes. We demonstrate that the oscillation period of this mode, calculated in the straight cylinder approximation, is determined by the length of the loop, not by its diameter, as it was previously assumed. The existence condition for this mode is the ratio of the loop length to its diameter to be less than about a half of the square root of the density contrast ratio. This mode has a maximum of the magnetic field perturbation at the loop apex and nodes at the footpoints. We demonstrate that the 14-17 s quasi-periodic pulsations, oscillating in phase at a loop apex and at its legs, observed with the Nobeyama Radioheliograph, are interpreted in terms of the global sausage mode.
Key words: magnetohydrodynamics (MHD) / waves / Sun: activity / Sun: corona / Sun: oscillations / Sun: radio pulsations
© ESO, 2003
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