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Astron. Astrophys. 358, 1090-1096 (2000)

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Frequency dependence of resonant absorption and over-reflection of magnetosonic waves in nonuniform structures with shear mass flow

Á.T. Csík 1, V.M. ade 2 and M. Goossens 1

1 Center for Plasma-Astrophysics, K.U. Leuven, Celestijnenlaan 200 B, 3001 Heverlee, Belgium
2 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, 9000 Gent, Belgium

Received 28 October 1999 / Accepted 16 March 2000


Processes of resonant absorption and over-reflection of magnetosonic modes may occur in nonuniform plasmas with a shear mass flow along the magnetic field. In this work, we study how these two phenomena depend on the frequency [FORMULA] of waves propagating in a given direction prescribed by polar angles [FORMULA] and [FORMULA] of wave vector [FORMULA]. Plasma is assumed nonuniform within a transitional layer that separates two semi-infinite uniform regions. The considered wave propagates only in one of the two regions and is reflected from the nonuniform transitional layer either totally or partially depending on the efficiency of resonant processes.

The resonant absorption and over-reflection are strongly dependent on wave frequency for both the slow and fast magnetosonic mode as shown in corresponding figures.

Under conditions relevant to the solar atmosphere, we found that typical MHD waves with periods from few seconds up to much larger values of several minutes and more, can be resonantly absorbed and also over-reflected. This important fact has to be taken into account in making models of energy transports in the corona.

Key words: Magnetohydrodynamics (MHD) – methods: numerical – Sun: corona – Sun: oscillations

Send offprint requests to: Á.T. Csík

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© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000