engleski

A Numerical Simulation of Coronal Waves Interacting with Coronal Holes. I. Basic Features

We have developed a new numerical code that is able to perform 2.5D simulations of a magnetohydrodynamic (MHD) wave propagation in the corona, and its interaction with a low-density region, such as a coronal hole (CH). We show that the impact of the wave on the CH leads to different effects, such as reflection and transmission of the incoming wave, stationary features at the CH boundary, or formation of a density depletion. We present a comprehensive analysis of the morphology and kinematics of primary and secondary waves, i.e., we describe in detail the temporal evolution of density, magnetic field, plasma flow velocity, phase speed, and position of the wave amplitude. Effects like reflection, refraction, and transmission of the wave strongly support the theory that large-scale disturbances in the corona are fast MHD waves and distinguish that theory from the competing pseudo- wave theory. The formation of stationary bright fronts was one of the main reasons for the development of pseudo-waves. Here, we show that stationary bright fronts can be produced by interactions of an MHD wave with a CH. We find secondary waves that are traversing through the CH and we show that one part of these traversing waves leaves the CH again, while another part is being reflected at the CH boundary inside the CH. We observe a density depletion that is moving in the opposite direction of the primary wave propagation. We show that the primary wave pushes the CH boundary to the right, caused by the wave front exerting dynamic pressure on the CH.

magnetohydrodynamics: MHD, Sun: corona, Sun: evolution, waves

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