NUMERICAL SIMULATION OF PROPAGATION AND SCATTERING OF THE MHD WAVES IN SUNSPOTS

Details NUMERICAL SIMULATION OF PROPAGATION AND SCATTERING OF THE MHD WAVES IN SUNSPOTS NUMERICAL SIMULATION OF PROPAGATION AND SCATTERING OF THE MHD WAVES IN SUNSPOTS

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsh23b1535p&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SH23B-1535

Astronomy and Astrophysics

Astrophysics

[7522] Solar Physics, Astrophysics, And Astronomy / Helioseismology, [7524] Solar Physics, Astrophysics, And Astronomy / Magnetic Fields, [7529] Solar Physics, Astrophysics, And Astronomy / Photosphere

Scientific paper

We present comparison of numerical simulation results of MHD wave 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 (7.5 Mm). The "shallow" model has concave shape of the magnetic field lines near the photosphere and horizontally uniform sound speed below 2 Mm. Common feature of MHD waves behaviour in these two models is that for weak magnetic field (less than 1kG at the photosphere) waves reduce their amplitude when they reach the center of the sunspot and restore the amplitude when pass the center. For the "deep" model this effect is bigger than for the "shallow" model. The wave amplitude inside sunspots depends on the strength of the magnetic field. For the "shallow" model with photospheric magnetic field of 2.2 kG the wave amplitude inside the sunspot becomes bigger than outside (opposite to the weak magnetic field). 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. Strong Alfven wave is generated at the wave source location in the "deep" model. This wave exists in the "shallow" model as well, but with much smaller amplitude.

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