  How thermal equilibrium is determined in a weakly collisional plasma is a
fundamental question in plasma physics. This letter shows that the turbulence
driven by the magnetic curvature and density gradient tends to equilibrate the
temperature between species without collisions in a magnetospheric plasma. The
classical stability analysis in terms of energetic consideration reveals the
interchangeable roles of electrons and ions for destabilization depending on
their temperatures. Nonlinear gyrokinetic simulations confirm that the
higher-temperature destabilizing species gives free energy to heat the other
species to achieve the equal temperature state.
