Parker Solar Probe observations of solar wind energetic proton beams
produced by magnetic reconnection in the near-Sun heliospheric current
sheet
Abstract
We report observations of reconnection exhausts and associated ion and
electron separatrix layers in and around the Heliospheric Current Sheet
(HCS) during PSP Encounters 08 and 07, at 16 Rs and 20
Rs. HCS reconnection accelerated protons to almost twice
the solar wind speed and increased the proton core energy by a factor of
~3, due to the Alfvén speed being comparable to the
solar wind flow speed at these near-Sun distances. During E08,
accelerated protons were found to have leaked out of the exhaust along
separatrix field lines, appearing as field-aligned energetic proton
beams in a broad region outside the HCS. Concurrent dropouts of strahl
electrons, indicating disconnection from the Sun, provide further
evidence for the HCS being the source of the beams. Around the HCS in
E07, there were also proton beams but without electron strahl dropouts,
indicating that their origin was non-local and closer to the Sun.