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P: Plasmaphysik

P 28: Sonstiges (Poster)

P 28.4: Poster

Monday, March 9, 1998, 18:00–20:00, P 2

Wave excitation in an axisymmetric sunspot. Influence of stratification and magnetic field gradients — •C.-V. Meister 1), A.V. Runov 2), A. Pregla 1), and V.E. Zakharov 3) — 1) Astrophys. Inst. Potsdam, 2) Inst. of Physics, Univ. St. Petersburg, 3) Kaliningrad State Univ.

Sunspots are solar regions with extremely strong magnetic fields of about 3000 G and relatively low temperature of 3000-5000 K. They have an almost axial symmetry with altitudinal changing diameter from about 300 km to nearly 20000 km. In sunspots magnetoacoustic-gravity waves can occur, especially the solar p-modes, which can be observed in detail. The measurements give the possibility to determine the equation of state of the solar plasma with an accuracy above the Debye-Hückel approximation. Thus, here a review of MHD-waves in sunspots is given concerning altitudes from the photosphere to the chromosphere. A MHD-model for sunspots with (in comparison to former works) finite diameter is developed taking into account also stratification effects. First numerical results are presented for magnetic field profiles in equilibrium state basing on the Schlüter-Temesváry similarity condition for the magnetic flux (1958), on experimental horizontal magnetic inductivity profiles of Beckers and Schröter (1969), and on angular dependencies of the magnetic field componets found already by Hale and Nicholson (1938).