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Abstract: Magnetic reconnection is a universal plasma process that rapidly converts magnetic energy into particle energy and is important in many space, astrophysical, and laboratory contexts. The process is believed to trigger solar flares and coronal mass ejections on the Sun and initiate geomagnetic substorms at Earth. Planetary magnetospheres and the solar wind are ideal natural laboratories where one can study the reconnection process with in-situ spacecraft measurements. In these solar system plasma laboratories, reconnection can be studied across a large range of plasma regimes and scale sizes, to seek a universal understanding of the properties of reconnection that can be applied beyond the solar system. In this talk, I will describe some highlights of Parker Solar Probe (PSP) observations of the occurrence and properties of reconnection in the heliopsheric current sheet (HCS) near the Sun (down to 9.8 solar radii). The HCS is the largest current sheet in the solar system, extending from the Sun to well beyond Jupiter. One of the surprises of the PSP mission so far has been the common detection of magnetic reconnection in the HCS near the Sun, despite the fact that the HCS is much thicker than the kinetic scales required for reconnection onset. Another remarkable finding is the common occurrence of magnetic flux rope merging inside the HCS, together with the detection of super-thermal proton energization up to ~400 keV, ~1000 times greater than the available magnetic energy per particle. These new results, enabled by PSP’s proximity to the Sun, suggest that reconnection is almost always active in the HCS near the Sun, and that reconnection could be a significant source of energetic particles in the near-Sun solar wind.

Hosted by Professor Muni Zhou and Professor Yi-Hsin Liu