Particle acceleration at an X-type reconnection site with a parallel magnetic field

The acceleration of charged particles at a two-dimensional magnetic reconne ction site is investigated. The magnetic field has an X-type neutral point, while reconnection is driven by a uniform transverse electric field; the e ffect of including a uniform magnetic field component parallel to the drivi ng electric field and transverse to the plane of the X point is studied. We focus on the adiabatic motion of strongly magnetized particles, a valid as sumption everywhere for sufficiently strong parallel magnetic fields but on e which excludes a region around the neutral point for weaker fields. The r egime of interest is fast driven reconnection, in which the electric drift is strong. The trajectories of particles and their dependence on the magnit ude of the parallel magnetic field component are investigated. Particles ca n be accelerated along the magnetic field lines both because of the couplin g of the perpendicular electric drift with the parallel motion, which occur s in an inhomogeneous magnetic field, and the direct acceleration by the el ectric field. The energy spectra of particles leaving the reconnection site are also calculated.