| Presentation Title: | Interchange magnetic reconnection as the driver of the fast
solar wind |
| Author(s): | J. F. Drake, S. D. Bale, M. Swisdak and the PSP Science Team |
Abstract:
The mechanism that drives the solar wind has been a topic
of extensive scientific debate since the 1960's when the existence of
the solar wind was confirmed with spacecraft observations. In its
recent closest approaches to the sun the Parker Solar Probe (PSP)
spacecraft is revealing wind structure not seen by spacecraft at
1AU. The bursty radial flows and associated local reversals of the
radial magnetic field (switchbacks) exhibit a spatial periodicity that
is linked to that of network magnetic field near the solar surface
(Bale et al, 2021, 2023). The observations point to magnetic reconnection
between open and closed magnetic flux in coronal holes (interchange
reconnection) as the driver of these bursts. The corresponding
enhancements in plasma pressure, wind speed, and energetic ions
further suggest that interchange reconnection is the fundamental
source of energy that drives the 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
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. The bursty nature of
interchange reconnection has implications for the development of the
turbulence, including switchbacks, in the solar wind.