Twist and expansion profiles of coronal loops in an active region responsible for coronal heating and solar wind generation
The generation of outflows from the Sun known as solar winds is coupled with the
heating of the solar corona, and both processes are operated in magnetic structures
formed on the Sun. To study themagnetic configuration responsible for these processes,
we use three-dimensional magnetohydrodynamic simulations to reproduce magnetic
structures via flux emergence and investigate their configurations. We focus on two key
quantities characterizing a magnetic configuration: the force-free parameter α and the flux
expansion rate fex, the former of which represents how much a magnetic field is twisted
while the latter represents how sharply amagnetic field expands.We derive distributions
of these quantities in an emerging flux region. Our result shows that an emerging flux
region consists of an outer part where a magnetic loop takes a large flux expansion rate
but a small value of α at their photospheric footpoints, and an inner part occupied by
those loops where a strong electric current flows. We also investigate the expansion
profile of a magnetic loop comprising an emerging flux region. The profile is given
by an exponential expansion type near the solar surface while it is given by a quadratic
expansion type in an outer atmosphere. These detailedmagnetic configurations obtained
by this study contribute to developing a realistic model for the coronal heating and solar
wind generation.
Reference
Lee, H. H. & Magara, T. 2014, PASJ, 66, 39
