The Corona in the Quiet Sun: A Global Substrate Driven by Velocity Filtration?

Abstract EUV coronal images are usually dominated by emission from magnetic active regions and from flares: the magnetic fields generate prominent spatial structures (“loops”) and striking time-dependent behavior. However, the quiet Sun contains regions, covering significant fractions of the solar surface, where evidence for spatial structure or time-dependence is weak or absent. J. D. Scudder suggested that velocity filtration might explain the presence of hot coronal gas without relying on magnetic fields, and without the “deposition” of energy in the corona. Such a process could lead to a coronal component which is essentially independent of the solar cycle. I suggest that the quiet Sun corona is a candidate for a global substrate created by velocity filtration.