The Role of Coronal Hole and Active Region Boundaries in Solar Wind Formation

TL;DR

This paper reviews how outflows from active region and coronal hole boundaries contribute to solar wind formation, discussing observations, possible mechanisms, and the extent of plasma contribution to the solar wind.

Contribution

It provides a comprehensive review of solar outflows at different regions, analyzing their potential role in solar wind generation and comparing various explanatory models.

Findings

Active region outflows range from 10 to 200 km/s.

Outflows are observed at boundaries of active regions and coronal holes.

The contribution of these outflows to the solar wind remains uncertain.

Abstract

Hinode observations have provided a new view of outflows from the Sun. These have been focussed in particular on flows emanating from the edges of active regions. These flows are long lasting and seem to exist to some extent in every active region. The flows measured have values ranging between tens of km s$^{-1}$ and 200 km s$^{-1}$. Various explanations have been put forward to explain these flows including reconnection, waves, and compression. Outflows have also been observed in coronal holes and this review will discuss those as well as the interaction of coronal holes with active regions. Although outflowing plasma has been observed in all regions of the Sun from quiet Sun to active regions, it is not clear how much of this plasma contributes to the solar wind. I will discuss various attempts to prove that the outflowing plasma forms part of the solar wind.