Abstract


  THE INTERACTION BETWEEN A MAGNETIC SHOCKTUBE AND AN ALFVENIC TWIST

  T. Williams, Aberystwyth University, tsw9@aber.ac.uk
  Y. Taroyan , Aberystwyth University, Department of Physics, IMPACS, United Kingdom , yot@aber.ac.uk
  V. Fedun, The University of Sheffield, United Kingdom, v.fedun@sheffield.ac.uk

In this study the evolution of a small Alfven twist within a horizontal chromospheric shocktube is modelled using 1.5-D MHD. A supersonic yet sub-Alfvenic plasma flow allows the Alfven twist to become trapped between the photosphere and stationary shock, where it continually amplifies from a small, linear perturbation into a non-linear pulse. The amplification process occurs due to an instability which allows the Alfvén twist to extract kinetic energy from the plasma flow and convert it into magnetic twists with torsional velocities of 10-15 km/s. This amplification and entrapment of the Alfvén twists leads to fast and slow propagating shocks, which disturb the pressure balance of the stationary shock, which destabilises and eventually propagates indefinitely and produces a globally twisted flux tube where $B_{\theta} \approx B_z$. The result of this study have been published in The Astrophysical Journal, 817, 2016 : http://stacks.iop.org/0004-637X/817/92.