  Electron bulk heating during magnetic reconnection with symmetric inflow
conditions is examined using kinetic particle-in-cell (PIC) simulations. The
degree of electron heating is well correlated with the inflowing Alfv\'en speed
$c_{Ar}$ based on the reconnecting magnetic field through the relation $\Delta
T_e = 0.033 \,m_i\,c_{Ar}^2$, where $\Delta T_{e}$ is the increase in electron
temperature. For the range of simulations performed, the heating shows almost
no correlation with inflow total temperature $T_{tot} = T_i + T_e$ or plasma
$\beta$. An out-of-plane (guide) magnetic field of similar magnitude to the
reconnecting field does not affect the total heating, but it does quench
perpendicular heating, with almost all heating being in the parallel direction.
These results are qualitatively consistent with a recent statistical survey of
electron heating in the dayside magnetopause, which also found that $\Delta
T_e$ was proportional to the inflowing Alfv\'en speed. The net electron heating
varies very little with distance downstream of the x-line. The simulations show
at most a very weak dependence of electron heating on the ion to electron mass
ratio. In the antiparallel reconnection case, the largely parallel heating is
eventually isotropized downstream due a scattering mechanism such as stochastic
particle motion or instabilities. The study highlights key properties that must
be satisfied by an electron heating mechanism: (1) Preferential heating in the
parallel direction; (2) Heating proportional to $m_i\,c_{Ar}^2$; (3) At most a
weak dependence on electron mass; and (4) An exhaust electron temperature that
varies little with distance from the x-line.
