Recent Observations of Plasma and Alfvenic Wave Energy Injection at the Base of the Fast Solar Wind

TL;DR

Recent observations reveal that episodic plasma heating and Alfvenic wave energy injection at the base of the fast solar wind, driven by chromospheric spicules and propagating disturbances, likely accelerate and heat the solar wind.

Contribution

This paper synthesizes recent observational data to propose a combined heating and acceleration mechanism for the fast solar wind involving spicules and Alfvenic waves.

Findings

Chromospheric spicules reach speeds of ~100 km/s.

Coronal emissions indicate rapid heating to ~1 MK.

Alfvenic motions carry sufficient energy to accelerate solar wind.

Abstract

We take stock of recent observations that identify the episodic plasma heating and injection of Alfvenic energy at the base of fast solar wind (in coronal holes). The plasma heating is associated with the occurrence of chromospheric spicules that leave the lower solar atmosphere at speeds of order 100km/s, the hotter coronal counterpart of the spicule emits radiation characteristic of root heating that rapidly reaches temperatures of the order of 1MK. Furthermore, the same spicules and their coronal counterparts ("Propagating Coronal Disturbances"; PCD) exhibit large amplitude, high speed, Alfvenic (transverse) motion of sufficient energy content to accelerate the material to high speeds. We propose that these (disjointed) heating and accelerating components form a one-two punch to supply, and then accelerate, the fast solar wind. We consider some compositional constraints on this concept, extend the premise to the slow solar wind, and identify future avenues of exploration.