Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aas...18912001r&link_type=abstract
American Astronomical Society, 189th AAS Meeting, late abstracts, #120.01; Bulletin of the American Astronomical, Vol. 29, p. 72
Astronomy and Astrophysics
Astronomy
Scientific paper
The interaction of solar acoustic oscillations with magnetic regions on the Sun strongly depends on the distribution of the random magnetic fluxes in space and their physical parameters. The dynamics of differently magnetized regions (sunspots, plages and quiet Sun), their dispersion properties and their response to the propagation of acoustic waves are completely different. For example, the enhanced absorption of acoustic power by sunspot and plage regions is well established. Several authors who have made similar measurements in quiet regions report that the quiet Sun shows small but systematic acoustic emission. The effects, enhanced absorption in active regions and "emission' of acoustic power in quiet sun, are seen in the same range of wave numbers (0.2<= k <= 0.6 Mm(-1) ). We report here that an excess of emission of acoustic power in quiet regions is expected as a result of "inelastic" scattering of acoustic waves by the random ensembles of widely spaced magnetic flux tubes. The outcome of the effect strongly depends on the magnetic filling factor of medium, phi (the total fraction of observed area occupied by fluxes) and the parameters of acoustic wave. It is most efficient in those regions of quiet Sun where k(2R^2<<) phi , R being the characteristic radius of a magnetic flux tube. In this case, resonant interaction is the most important of several physical processes contribute to the energy exchange between the wave and medium. Due to an effect similar to Landau damping, the energy of the incident acoustic wave is accumulated in the system of magnetic flux tubes and causes the acoustic wave (of frequency omega ) to damp at a rate nu_L =~ phi omega . The energy remains for a long time in the form of flux-tube oscillations. Then, in a time nu_ {rad}(-1) , the resonant flux tubes radiate their energy as a secondary acoustic waves, where the radiative damping rate (or the rate of the emission of secondary waves), nu_ {rad} =~ omega k(2) R(2) . The power of emitted waves expressed in terms of the parameters of the medium allows one to specify the regions of an efficient energy input and corresponding range of wave parameters. This research is supported by NASA contract NAG5-3077 at Stanford University and NASA contract NAS8-39747 at Lockheed Martin.
Ryutova Margarita P.
Tarbell Ted D.
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