  Our understanding of magnetic reconnection (MR) under chromospheric
conditions remains limited. Recent observations have demonstrated the important
role of ion-neutral interactions in the dynamics of the chromosphere.
Furthermore, the comparison between spectral profiles and synthetic
observations of reconnection events suggest that current MHD approaches appear
to be inconsistent with observations. First, collisions and multi-thermal
aspects of the plasma play a role in these regions. Second, hydrogen and helium
ionization effects are relevant to the energy balance of the chromosphere. This
work investigates multi-fluid multi-species (MFMS) effects on MR in conditions
representative of the upper chromosphere using the multi-fluid Ebysus code. We
compare an MFMS approach based on a helium-hydrogen mixture with a two-fluid
MHD model based on hydrogen only. The simulations of MRs are performed in a
Lundquist number regime high enough to develop plasmoids and instabilities. We
study the evolution of the MR and compare the two approaches including the
structure of the current sheet and plasmoids, the decoupling of the particles,
the evolution of the heating mechanisms, and the composition. The presence of
helium species leads to more efficient heating mechanisms than the two-fluid
case. This scenario, which is out of reach of the two-fluid or single-fluid
models, can reach transition region temperatures starting from upper
chromospheric thermodynamic conditions, representative of a quiet Sun scenario.
The different dynamics between helium and hydrogen species could lead to
chemical fractionation and, under certain conditions, enrichment of helium in
the strongest outflows. This could be of significance for recent observations
of helium enrichment in the solar wind in switchbacks and CMEs.
