Dynamical Properties of Photospheric Flux Tubes at the Footpoints of Hot and Cool Coronal Loops

Abstract

The dynamical properties of photospheric flux tubes at the footpoints of hot (T > 2 MK) and cool (T = 1-2 MK) coronal loops in active region plages are investigated by analyzing the Stokes profile parameters of Fe I λ6302. We show that the footpoints of both hot and cool loops are located at the periphery of small magnetic concentrations, such as pores and azimuth centers, having a field strength of 1-1.8 kG and a spatial size of 2″-5″. The footpoints of cool loops seem to be associated with more densely packed and higher field strength pores and azimuth centers than those of hot loops. Enhanced Stokes V asymmetries, redshifted zero-crossing velocities, and small magnetic filling factors are found at the footpoints of both types of loops, as compared with outside the footpoints. However, the largest asymmetries and more redshifted zero-crossing velocities are observed at the footpoints of hot loops, where the filling factor is smaller than at the footpoints of cool loops. The differences between the profiles emerging from the footpoints of hot and cool coronal loops suggest that heating of the coronal loops could be related to the dynamical properties of photospheric flux tubes. © 2006. The American Astronomical Society. All rights reserved.