Numerical Simulation of Propagation and Transformation of the MHD Waves in Sunspots

Details Numerical Simulation of Propagation and Transformation of the MHD Waves in Sunspots Numerical Simulation of Propagation and Transformation of the MHD Waves in Sunspots

May 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21621106p&link_type=abstract

American Astronomical Society, AAS Meeting #216, #211.06; Bulletin of the American Astronomical Society, Vol. 41, p.867

Computer Science

Sound

Scientific paper

Direct numerical simulation of propagation of MHD waves in stratified medium in regions with non-uniform magnetic field is very important for understanding of scattering and transformation of waves by sunspots. We present numerical simulations of wave propagation through the sunspot in 3D. We compare results propagation in two different magnitostatic models of sunspots refferred to as "deep" and "shallow" models. The "deep" model has convex shape of magnetic field lines near the photosphere and non-zero horizorntal perturbations of the sound speed up to the bottom of the model. The "shallow" model has concave shape of the magnetic field lines near the photosphere and horizontally uniform sound speed below 2 Mm. Waves reduce their amplitude when they reach the center of the sunspot and estore the amplitude when pass the center. For the "deep" model this effect is bigger than for the "shallow" model. The wave amplitude depends on the distance of the source from the sunspot center. For the "shallow" model and source distance of 9 Mm from the sunspot center the wave amplitude at some moment (when the wavefront passes the sunspot center) becomes bigger inside the sunspot than outside. For the source distance of 12 Mm the wave amplitude remains smaller inside the sunspot than outside for all moments of time.
Using filtering technique we separated magnetoacoustic and magnetogravity waves. Simulations show that the sunspot changes the shape of the wave front and amplitude of the f-modes significantly stronger than the p-modes. It is shown, that inside the sunspot magnetoacoustic and magnetogravity waves are not spatially separated unlike the case of the horizontally uniform background model. We compared simulation results with the wave signals (Green's functions) extracted from the SOHO/MDI data for AR9787.

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