Naslov
Formation of Coronal Large-Amplitude Waves and the Chromospheric Response

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

Izvornik
Solar physics (0038-0938) 291 (2016), 1; 88-115

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
coronal mass ejections ; waves ; magnetohydrodynamic ; waves ; shock ; flares ; waves

Sažetak
An in-depth analysis of numerical simulations is performed to obtain a deeper insight into the nature of various phenomena occurring in the solar atmosphere as a consequence of the eruption of unstable coronal structures. Although the simulations take into account only the most basic characteristics of a flux-rope eruption, the simulation analysis reveals important information on various eruption-related effects. It quantifies the relation between the eruption dynamics and the evolution of the large-amplitude coronal magnetohydrodynamic wave and the associated chromospheric downward-propagating perturbation. We show that the downward propagation of the chromospheric Moreton-wave disturbance can be approximated by a constant-amplitude switch-on shock that moves through a medium of rapidly decreasing Alfvén velocity. The presented analysis reveals the nature of secondary effects that are observed as coronal upflows, secondary shocks, various forms of wave-trains, delayed large- amplitude slow disturbances, transient coronal depletions, etc. We also show that the eruption can cause an observable Moreton wave and a secondary coronal front only if it is powerful enough and is preferably characterized by significant lateral expansion. In weaker eruptions, only the coronal and transition-region signatures of primary waves are expected to be observed. In powerful events, the primary wave moves at an Alfvén Mach number significantly larger than 1 and steepens into a shock that is due to the nonlinear evolution of the wavefront. After the eruption-driven phase, the perturbation evolves as a freely propagating simple wave, characterized by a significant deceleration, amplitude decrease, and wave-profile broadening. In weak events the coronal wave does not develop into a shock and propagates at a speed close to the ambient magnetosonic speed.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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