Effect of Gravity on the Fast Modes of a Horizontal Coronal Slab |
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Authors: | M P McEwan A J Díaz |
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Institution: | (1) School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, KY16 9SS, Scotland, UK |
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Abstract: | Theoretical studies of the normal modes of a coronal slab often neglect gravity, as in Edwin and Roberts (Solar Phys.
71, 239, 1982). Here we study analytically the effect of gravity acting on a horizontal slab as a first step away from a homogeneous medium.
Because of the inclusion of gravity, the symmetry of a homogeneous slab is lost, so the normal modes cannot be classified
into kink and sausage modes. The presence of gravity also modifies the oscillatory frequencies of the slab, as well as the
lower cutoff frequency, resulting in the possible transition between surface and body modes. For general coronal parameters,
the dimensionless gravity term turns out to be small, so these effects are also small.
A.J. Díaz’s current affiliation: Universitat de les Illes Balears, Palma, E-07122, Spain. |
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Keywords: | Sun: corona Sun: oscillations |
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