Bibcode
Parchevsky, K.; Kosovichev, A. G.; Khomenko, E.; Collados, M.
Bibliographical reference
American Geophysical Union, Fall Meeting 2009, abstract #SH23B-1535
Advertised on:
12
2009
Citations
0
Refereed citations
0
Description
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.