Authors: Steven R. Cranmer (CU Boulder)

Coronal heating and solar wind acceleration are not “problems” because of an absence of proposed explanations, but because there have been too many proposed explanations. This session is meant to help theorists and observers continue the process of testing, validating, and ultimately winnowing down the list of physical processes that may be responsible for accelerating the solar wind. In this scene-setting talk I will attempt to review the current state of the debate, mainly from the theoretical side, about solar wind origins. The major battle-lines are often drawn between physical processes that involve energy propagating up from the base along open field lines (i.e., in the form of waves or turbulent eddies, which ultimately dissipate) versus those that involve magnetic reconnection between regions of closed and open topology. However, it is likely that the real Sun employs both types of plasma energization, such that our job is then to determine their relative strengths in the different source regions. Of necessity, this talk will be peppered by my own biased opinions about which processes I believe are more important than others, and I will do my best to label those opinions clearly. I should note that I gave a similar talk as this one at the 2019 SHINE Workshop, in Session 13 (“How does plasma origin and/or magnetic topology affect solar wind acceleration?”), and it will be interesting to update it based on the last seven years of advances and discoveries.