Fast magnetoacoustic wave trains of sausage symmetry in cylindrical waveguides of the solar corona 

Sergey Shestov Submitted: 20151028 03:37
Fast magnetoacoustic waves guided along the magnetic field by plasma nonuniformities, in particular coronal loops, fibrils and plumes, are known to be highly dispersive, which leads to the formation of quasiperiodic wave trains excited by a broadband impulsive driver, e.g. a solar flare. We investigated effects of cylindrical geometry on the fast sausage wave train formation. We performed magnetohydrodynamic numerical simulations of fast magnetoacoustic perturbations of a sausage symmetry, propagating from a localised impulsive source along a fieldaligned plasma cylinder with a smooth radial profile of the fast speed. The wave trains are found to have pronounced period modulation, with the longer instant period seen in the beginning of the wave train. The wave trains have also a pronounced amplitude modulation. Wavelet spectra of the wave trains have characteristic tadpole features, with the broadband largeamplitude heads preceding lowamplitude quasimonochromatic tails. The mean period of the wave train is about the transverse fast magnetoacoustic transit time across the cylinder. The mean parallel wavelength is about the diameter of the waveguiding plasma cylinder. Instant periods are longer than the sausage wave cutoff period. The wave train characteristics depend on the fast magnetoacoustic speed in both the internal and external media, and the smoothness of the transverse profile of the equilibrium quantities, and also the spatial size of the initial perturbation. If the initial perturbation is localised at the axis of the cylinder, the wave trains contain higher radial harmonics that have shorter periods.
Authors: S. Shestov, V. M. Nakariakov, S. Kuzin
Projects:

Publication Status: ApJ, 814, 135
Last Modified: 20151202 13:53



Fast magnetoacoustic wave trains of sausage symmetry in cylindrical waveguides of the solar corona 

Sergey Shestov Submitted: 20151028 03:37
Fast magnetoacoustic waves guided along the magnetic field by plasma nonuniformities, in particular coronal loops, fibrils and plumes, are known to be highly dispersive, which leads to the formation of quasiperiodic wave trains excited by a broadband impulsive driver, e.g. a solar flare. We investigated effects of cylindrical geometry on the fast sausage wave train formation. We performed magnetohydrodynamic numerical simulations of fast magnetoacoustic perturbations of a sausage symmetry, propagating from a localised impulsive source along a fieldaligned plasma cylinder with a smooth radial profile of the fast speed. The wave trains are found to have pronounced period modulation, with the longer instant period seen in the beginning of the wave train. The wave trains have also a pronounced amplitude modulation. Wavelet spectra of the wave trains have characteristic tadpole features, with the broadband largeamplitude heads preceding lowamplitude quasimonochromatic tails. The mean period of the wave train is about the transverse fast magnetoacoustic transit time across the cylinder. The mean parallel wavelength is about the diameter of the waveguiding plasma cylinder. Instant periods are longer than the sausage wave cutoff period. The wave train characteristics depend on the fast magnetoacoustic speed in both the internal and external media, and the smoothness of the transverse profile of the equilibrium quantities, and also the spatial size of the initial perturbation. If the initial perturbation is localised at the axis of the cylinder, the wave trains contain higher radial harmonics that have shorter periods.
Authors: S. Shestov, V. M. Nakariakov, S. Kuzin
Projects: None

Publication Status: ApJ (in press)
Last Modified: 20151028 15:24




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