What supplies the energy and momentum of the fast solar wind?
In plain words
The fast solar wind leaves the Sun at about $7.5e7\,\mathrm{cm/s}$, and it is not settled whether waves in the magnetic field or bursts of magnetic reconnection push it to that speed.
Precise statement
Determine whether Alfven-wave turbulence, interchange reconnection at the base of coronal holes, or both supply the energy and momentum flux of the fast wind (speed $\sim 7e7\ \text{to}\ 8e7\,\mathrm{cm}/\mathrm{s}$), including the heating of protons and heavy ions above the electron temperature. Answer: the fraction of the energy flux supplied by each process, consistent with Parker Solar Probe and Solar Orbiter data inside and near the Alfven surface.
What would settle it
Parker Solar Probe and Solar Orbiter measurements of wave energy flux and reconnection signatures inside the Alfven surface, connected to remote-sensed coronal-hole source regions, that close the energy budget.
Status in the literature
Unverified note
2021: Parker Solar Probe first crossed into sub-Alfvenic wind; since December 2024 it reaches 9.86 solar radii from the Sun's center.