Magnetic Reconnection Null Points as the Origin of Semi-relativistic Electron Beams in a Solar Jet

摘要: Magnetic reconnection, the central engine that powers explosive phenomena throughout Universe, is also perceived as one of principal mechanisms for accelerating particles to high energies. Although various signatures magnetic reconnection have been frequently reported, observational evidence links particle acceleration directly site has rare, especially space plasma environments currently inaccessible $\textit{in situ}$ measurements. Here we utilize broadband radio dynamic imaging spectroscopy available from Karl G. Jansky Very Large Array observe decimetric type III bursts in a solar jet with angular ($\sim$20$''$), spectral ($\sim$1 %), and temporal resolution (50 milliseconds). These observations allow us derive detailed trajectories semi-relativistic (tens keV) electron beams low corona unprecedentedly precision ($<0''.65$). We found each group beams, which corresponds cluster 1-2-second duration, diverges an extremely compact region ($\sim$600 km$^2$) corona. The beam-diverging sites are located behind erupting spire above closed arcades, coinciding presumed location eruption picture supported by extreme ultraviolet/X-ray data modeling. interpret null point where multitudes flux tubes join reconnect. Our suggest points likely consist level density inhomogeneities possibly down 10-km scales. results, at least present case, strongly favor reconnection-driven scenario.