Observational Analysis of the Relation between Coronal Loop Heating and Photospheric Magnetic Fields

摘要

The solar corona and the photosphere are linked through magnetic field lines, and heating energy is supposed to be supplied from the footpoints of each coronal loop along magnetic field lines. Thus it is important to examine properties of photospheric magnetic fields at the footpoints of the coronal loops in order to understand heating of the coronal loops. We performed simultaneous observations of photospheric magnetic properties and coronal loop structures using the ground based telescopes and Transition Region And Coronal Explorer (TRACE). Footpoint locations were identified in the TRACE images, and the structure in the photosphere was examined by Advanced Stokes Polarimeter (ASP) or Dutch Open Telescope (DOT). Most of the coronal loops emanating from a sunspot had their footpoints around the boundary between the umbra and the penumbra. Furthermore, bright loops were revealed to have their footpoints at the locations where there was highly interlaced magnetic configuration. We observed fragmentation of an umbra and formation of a light bridge in decaying sunspots, and found possible association between such phenomena in the decaying spots and the coronal loops. These observational results suggest that spatial fluctuation of magnetic fields forms current sheets at the base of the corona, resulting in heating of the coronal loops.