Fast Sausage Waves in Current-Carrying Coronal Loops
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Fast sausage waves in a model coronal loop that consists of a cylindrical core with axial magnetic field and coaxial annulus with purely azimuthal magnetic field are considered. It is shown that the principal mode of fast sausage waves with arbitrary wavelength, which is the mode having no nodes in the radial direction, can be supported by such a loop. All other modes can propagate in such a loop as trapped modes only if their wavelengths are smaller than the cut-off wavelength. The obtained theoretical results are applied to the interpretation of observed periodic pulsations of microwave emission in flaring loops with periods of a few tens of seconds.
KeywordsCoronal seismology Magnetic fields Oscillations
B.B.M. and O.V.K. acknowledge the support by Kalmyk State University grant 2011-767 and by Ministry of Education and Science of Russian Federation grant 21469-2011. M.S.R. acknowledges the support by the STFC grant and by the Royal Society Leverhulme Trust Senior Research Fellowship.
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