  Ion resonance instability of toroidal electron plasmas in a tight aspect
ratio axisymmetric toroidal device is reported for ${Ar}^+$ ions of different
initial density values using a high fidelity 3D3V PIC solver. Stability of a
recently discovered quiescent quasi-steady state (QQS) of a toroidal electron
plasma obtained from "seed" solution as a result of entropy extremization at
zero inertia, is addressed to the presence of a small ion population. An ion
fraction ($f$) and corresponding number of secondary electrons are preloaded
into the system after the electron plasma attains a QQS state. Driven by the
ions, the electron plasma exhibits destabilized "center of charge motion" ($m =
1$) along with increased poloidal mode coupling ($m = 1$ to $9$) with dominant
$m = 2$ mode. The growth in wall probe current is algebraic in nature and
increases for $f$ $\geq$ $0.005$, showing saturation at later time. Higher
values of ion temperatures than the electron temperatures indicate a resonant
energy transfer from electron plasma to ions via ion-resonance and concomitant
ion heating. The volume averaged temperature value of the electron plasma rises
with simulation time, attaining a quasi-steady nature near the end of the
simulation time. As can be expected from conservation of adiabatic invariants,
the flux tube averaged electron temperatures along parallel and perpendicular
directions are found to scale as $1/R^2$ and $1/R$ respectively, where $R$ is
the major radial variable, though the plasma is nearly collision-less.
