Solar Moss Patterns: MHD Turbulence, Reconnection Heating in Coronal Loops, and Magnetic Connection to the Footpoints

We address the origin of the patchy dark and bright emission structure, known as “moss,” observed by extreme ultraviolet observations of the transition region at the footpoints of hot coronal loops. Here we propose an explanation based on turbulent, patchy heat conduction from the corona into the transition region. MHD simulations demonstrate that magnetic turbulence in coronal loops develops a flux rope structure with current sheets near the flux rope boundaries. Localized heating due to current sheet activity such as magnetic reconnection is followed by heat conduction along turbulent magnetic field lines. Employing a two-component 2D MHD + slab model of magnetic turbulence, we show that field line trajectories tend to remain near the flux rope boundaries, resulting in a patchy, network pattern of selective heating of the plasma in the transition region. This is consistent with the pattern of bright regions in the observed moss morphology. Partially supported by the Junior Science Talent Project of the National Science and Technology Development Agency of Thailand, the Sritrang Thong Project of the Faculty of Science at Mahidol University, the Thailand Research Fund, NASA Grant NNG05GG83G, the NASA Heliophysics Theory program, NASA NNX08AI47G, and the SHINE program, NSF ATM0752135.