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Numerical simulations of impulsively excited fast magnetosonic waves in two parallel slabs

Ogrodowczyk R., Murawski K.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2006

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Vol. 10, No 3

227-238

EN

We present numerical results of a temporal evolution of impulsively excited magnetosonic waves in a solar coronal loop that is approximated by a set of two straight plasma slabs of mass density enhancement. Numerical simulations reveal that shapes of wavelet spectra of time signatures of these waves depend on a distance between the strands and on a position of the initial pulse. We find that with a distance growing between these strands short period waves contribute more while long period waves contribute less to the wavelet spectra. We demonstrate that a presence of the second parallel strand affects considerably wave propagation in comparison to one strand alone. We find out that the initial pulse triggers a packet of propagating waves among witch sausage and kink modes are present simultaneously.

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Propagational Aspects of Sunquake Waves

Mędrek M., Murawski K., Nakariakov V.

Acta Astronomica

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2000

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Vol. 50, No. 3

405--416

EN

We present the results of numerical simulations of impulsively generated seismic waves excited by a spatially localized impulse source which is connected with a nearby solar flare. The solar atmosphere is modeled as a two layer medium with constant temperature over the photosphere and linearly growing temperature below the photosphere. Effects of magnetic fields are neglected. Only two dimensional effects are considered. The source is localized slightly below the photosphere. The numerical results show that the initial pulse of enhanced pressure, which can be connected with the thermal energy release by interaction of flare-generated particles with the sub-photospheric medium in the flare-loop footpoint, generates an acoustic (seismic) wave. Interaction of the wave with the solar surface produces perturbations registered as sunquakes. Typical observationally registered features of the sunquakes, such as characteristic wave signatures and acceleration of the wave with the distance from the epicenter, are well reproduced with the model developed. It is found that the seismic waves are essentially dispersive and non-linear. The proposed model provides us with a theoretical basis for sunquake seismology of the solar interior.

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Influence of a Stochastic Flow on Acoustic Waves

Murawski K.

Acta Astronomica

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2000

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Vol. 50, No. 2

269--277

EN

An influence of a random flow on frequencies and amplitudes of the acoustic oscillations is examined on the basis of numerical simulations for the linear hydrodynamic equations.The case of the random flow that is parallel to the direction of a wave propagation is discussed for various parameters of the random field. The numerical results reveal that the sound waves can be both amplified and damped by the random flow as well as their frequencies can be higher and lower than frequencies of the coherent acoustic waves. These effects are more pronounced for stronger random flow. Spectral properties of the sound waves depend on a flow pattern.