Fast Prograde Coronal Flows in Solar Active Regions

Abstract

We report the discovery and characterization of high-speed (>100 km/s) horizontal flows in solar active regions, making use of the Sun-as-a-star spectroscopy in the range 5-105 nm provided by the EVE (Extreme Ultraviolet Variability Experiment) spectrometers on the Solar Dynamics Observatory. These apparent flows are persistent on time scales of days, and are well observed in lines of Mg X, Si XII and Fe XVI for example. They are prograde, as evidenced directly by blueshifts/redshifts peaking at the east/west limb passages of isolated active regions. The high-speed flow behavior does not depend upon active-region latitude or solar cycle, with similar behavior in Cycles 24 and 25.