Naslov
Coronal Shock Formation in Various Ambient Media

Autori
Žic, Tomislav ; Vršnak, Bojan ; Temmer, Manuela ; Veronig, Astrid

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

Skup
IHY-ISWI Regional Meeting: Heliophysical phenomena and Earth's environment

Mjesto i datum
Šibenik, Hrvatska, 07.09.2009. - 13.09.2009

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

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

Sažetak
We consider expanding cylindrical and spherical structures as drivers of MHD shock waves. It is assumed that the source surface accelerates over a certain time interval to achieve a particular maximum velocity. Such an expansion creates a large amplitude simple wave in the ambient plasma. Due to the nonlinear evolution of the wave front, its profile steepens and after a certain time/distance a discontinuity forms, marking the onset of the shock formation. We investigate how the time/distance needed for the shock formation depends on various input parameters: the acceleration phase duration, maximum expansion velocity (defining also acceleration), Alfvén velocity (defining also Mach number), initial size of the piston. For the matter of simplicity we examine a constant-acceleration of the piston in an environment dependent on radial distance. In particular, constant, 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. The model is an extension of the 1-dimensional model by Vršnak and Lulić [2000] ; the basic difference lies in the fact that in the 3D evolution, a decrease of the wave amplitude with distance must be taken into account. We present basic results, focusing on the timing of the shock formation in the low versus high plasma beta environment.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA