Active region mass motions observed in soft X-ray lines

Abstract Significant coronal mass motions are deduced from soft X-ray line broadening observed in solar active regions even during quiescent periods. A large data base of Mg XI resonance line profiles near 9.17 A has been acquired with the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS) for a variety of active region conditions and disk locations. For the X-ray bright areas, the typical profiles have an “excess” line width equal to or greater than the thermal Doppler width for Mg ions at the observed coronal temperatures (3–4 MK). The equivalent “excess” velocities of 40–60 km s −1 are higher than those reported previously for cooler lines in other wavebands. The excess velocities show a correlation with magnetic field strength or gradient, but no obvious dependence on the angular distance from Sun center. These FCS data should provide important clues to the coronal heating process.