A fragmented and extended Alfven critical zone in the young solar wind

Motivated by theoretical, numerical, and observational evidence, we explore the possibility that the critical transition between sub-Alfv'enic flow and super-Alfv'enic flow in the solar atmosphere takes place in fragmented and disconnected subvolumes within a general region. We refer to this as Alfv'en critical zone. The initial observations of sub-Alfv'enic periods by Parker Solar Probe do not yet provide sufficient evidence to distinguish this possibility from that of a folded surface that separates simply connected regions. Subsequent orbits may enable Parker Solar Probe to make such a distinction. Here we use a global magnetohydrodynamic model of the solar wind, coupled self-consistently to a turbulence transport model, to generate possible realizations of such an extended and fragmented Alfv'en critical zone. Understanding this transition will inform theories of coronal heating, solar wind origin, solar angular momentum loss, particle acceleration and related physical processes in stellar winds beyond the Sun.