Naslov
Formation of Coronal Shocks

Autori
Žic, Tomislav ; Vršnak, Bojan

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, ostalo

Skup
IXth Hvar Astrophysical Colloquium: Solar minimum meeting

Mjesto i datum
Hvar, Hrvatska, 22.09.2008. - 26.09.2008

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Shock waves ; Magnetohydrodynamics (MHD) ; Sun: corona ; Sun: coronal mass ejections (CMEs) ; Sun: flares

Sažetak
Coronal MHD shock wave signatures (type II burst and Moreton wave) appear in close association with the flare impulsive phase and/or the coronal mass ejection (CME) acceleration phase. Flares and CMEs are very powerful dynamic processes, capable of generating plasma motions perpendicular to the magnetic field lines, which is a necessary requirement for the formation of magnetosonic shocks that excite type II bursts. The expansion creates a large-amplitude perturbation in the ambient plasma, which evolves into the shock after a certain time and distance owing to the nonlinear evolution of the wavefront profile. We consider an expanding two- and three-dimensional piston as a driver of an MHD shock wave (in a cylindrical and spherical symmetry, respectively). For the matter of simplicity we examine a constant-acceleration of the piston in an environment dependent on radial distance. In particular, const., 1/r and 1/r2 phase velocities of a low-amplitude waves are analyzed and compared in high beta (≈ sound) and low beta cases. Our main interest is to find shock-formation time and distance under the mentioned conditions.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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