Twist and expansion profiles of magnetic loop responsible for coronal heating and solar wind generation
Generation of a plasma outflow from the Sun known as the solar wind is coupled with heating of a solar atmospheric plasma, and both processes are expected to operate in the solar magnetized atmosphere
composed of magnetic loops. To investigate the magnetic field configuration responsible for these processes,
we performed a pair of three-dimensional magnetohydrodynamic simulations for reproducing flux emergence, in which an emerging flux region was produced by a strongly (weakly) twisted flux tube in one (the other) simulation. We focused on two
quantities characterizing the magnetic configuration, force-free α and flux
expansion rate f_ex, the former of which represents how much a magnetic loop is twisted around its axis,
while the latter how sharply the loop expands along its axis. We derived spatial distributions
of these quantities in the two emerging flux regions to find that both
regions have outer part where loops take large values of f_ex
but small values of |α| around their photospheric footpoints, and inner part where loops take large values of |α|, indicating that strong field-aligned current flows along these loops. We also examined expansion
profiles of selected loops to find that they showed an exponential profile near the photosphere while a quadratic
profile well above the photosphere.
Reference
Lee, H. H. & Magara, T. 2014, PASJ, 66, 39
