Conversion and Smoothing of MHD Shocks in Atmospheres with Open and Closed Magnetic Field and Neutral Points

Abstract

Planar acoustically dominated magneto\-hydro\-dynamic waves are initiated at the high-$\beta$ base of a simulated 2D isothermal stratified atmosphere with potential magnetic field exhibiting both open and closed field regions as well as neutral points. They shock on their way upward toward the Alfvén-acoustic equipartition surface $a=c$, where $a$ and $c$ are the Alfvén and sound speeds respectively. Expanding on recent 1.5D findings that such shocks mode-convert to fast shocks and slow smoothed waves on passing through $a=c$, we explore the implications for these more complex magnetic geometries. It is found that the 1.5D behaviour carries over to the more complex case, with the fast shocks strongly attracted to neutral points, which are disrupted producing extensive fine structure. It is also observed that shocks moving in the opposite direction, from $a>c$ to $a<c$, split into fast and slow components too, and that again it is the slow component that is smoothed.

26 pages, 13 figures

References in corpus (8)

• Quasi-periodic pulsations in solar and stellar flares: an overview of recent results
• Nonlinear Fast Magnetoacoustic Wave Propagation in the Neighbourhood of a 2D magnetic X-point: Oscillatory Reconnection
• Fluid description of multi-component solar partially ionized plasma
• MHD wave propagation in the neighbourhood of a two-dimensional null point
• MHD mode coupling in the neighbourhood of a 2D null point
• Wave modes excited by photospheric p-modes and mode conversion in a multi-loop system
• Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere
• The formation and dissipation of current sheets and shocks due to compressive waves in a stratified atmosphere containing a magnetic null

Cited by in corpus (3)

• MHD waves in homogeneous and continuously stratified atmospheres
• Numerical simulations of a two-fluid jet at a magnetic null point in a solar arcade
• Fast Magnetoacoustic Wave Behavior within Gravitationally Stratified, Magnetically Inhomogeneous Media