  To understand the essential physics needed to reproduce magnetic reconnection
events in 2.5-D particle-in-cell (PIC) simulations, we revisit the Geospace
Environmental Modeling (GEM) setup. We set up a 2-D Harris current sheet (that
also specifies the initial conditions) to evolve the reconnection of
antiparallel magnetic fields. In contrast to the GEM setup, we use a much
smaller initial perturbation to trigger the reconnection and evolve it more
self-consistently. From PIC simulation data with high-quality particle
statistics we study a symmetric reconnection site, including separatrix layers,
as well as the inflow and the outflow regions. The velocity distribution
functions (VDFs) of electrons have a fine structure and vary strongly depending
on their location within the reconnection setup. The goal is to start
cataloging multidimensional fine-structured electron velocity distributions
showing different reconnection processes in the Earth's magnetotail under
various conditions. This will enable a direct comparison with observations
from, e.g., the NASA Magnetospheric MultiScale (MMS) mission, to identify
reconnection-related events. We find regions with strong non-gyrotropy also
near the separatrix layer and provide a refined criterion to identify an
electron diffusion region in the magnetotail. The good statistical significance
of this work for relatively small analysis areas reveals the gradual changes
within the fine structure of electron VDFs depending on their sampling site.
