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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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Numerical Simulations of Impulsively Generated MHD Waves in a Solar Coronal Loop

Selwa M., Murawski K.

Acta Astronomica

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2004

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Vol. 54, No. 2

211--220

EN

We study by numerical means the MHD oscillations in a solar coronal loop. Obtained numerical results show that impulses, which are launched in the ambient plasma, excite oscillations in mass density profiles that reveal asymmetry in a cross-section of the loop. This asymmetry is a consequence of the fact that while a part of the loop is compressed its other part is rarefied, resulting from transverse loop oscillations. Due to a lack of spatial resolution this feature has not been observed in the earlier numerical studies of impulsively generated waves. The numerical simulations reveal distinctive time-signatures which are collected at a detection point inside the loop. For the chosen set of physical parameters, these signatures reveal a dozen or so seconds oscillations in the mass density. These oscillations are usually more complex further out from the trigger. A sufficiently large slow magnetosonic wave generates shocks which temporal evolution we trace in mass density profiles.

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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.