Interchange magnetic reconnection within coronal holes powers the solar wind

The Parker Solar Probe (PSP) magnetic field data in the solar wind

close to the sun has revealed that the periodicity of bursts of

switchbacks are linked to the spatial periodicity of the magnetic

field at the surface of the sun. The observations point to reconnection between

open and closed magnetic flux in coronal holes (interchange

reconnection) as the driver of switchbacks. The corresponding periodic

enhancements in plasma pressure, wind speed, alpha abundance and

energetic ions further suggest that interchange reconnection is the

fundamental source of energy that drives these bursts and the resulting fast solar wind. We use

the PSP data along with the basic characteristics of reconnection to

deduce the local properties of interchange reconnection near the solar

surface, including the characteristic strength of the reconnecting

magnetic, the ambient density, the rate of reconnection and associated

rate of energy release. An important conclusion of the analysis is

that coronal interchange reconnection is in the collisionless regime

and that the energy released by interchange reconnection is sufficient

to drive the wind. Analytical estimates are supported by

particle-in-cell simulations of interchange reconnection that

establish that the structure of reconnection exhausts match PSP

velocity measurements. The spectra of energetic protons and alpha particles

from the simulations, which take the form of powerlaws at high energy,

also match the observations by the PSP.