Enernization of Alpha Particles in the Solar Wind Magnetic Reconnection

The acceleration and heating of solar wind particles by energy dissipation in the magnetic reconnection is an important problem in space physics. Although alpha particles are the second most abundant element in the solar wind, their dynamical behavior in the magnetic reconnection of the solar wind is not well understood. Using the high energy (1500~3000 eV) part of the SWA/PAS instrument on board the Solar Orbiter, we study the kinetic behavior of alpha particles in a magnetic-reconnetion exhaust region within a heliospheric current sheet. In this event, protons and alpha particles have similar bulk velocities. Alpha particles are accelerated and form a jet in the exhaust region. The counter-stream distribution of alpha particles is observed inside the exhuast region, which changes the direction from parallel to perpendicular to the magnetic field direction when the magnetic field is reversed. In addition, a pair of the slow shock/rotational discontinuity is observed in the exhuast region. The exhaust region is heated and bounded by the slow shocks , while the accelerated plasma jet is bounded by the rotational discontinuities.