  We perform direct analysis of mirror mode instabilities from the general
dielectric tensor for several model distributions, in the longwavelength limit.
The growth rate at the instability threshold depends on the derivative of the
distribution for zero parallel energy. The maximum growth rate is always $\sim
k_\parallel v_{T\parallel}$ and the instability is of nonresonant kind. The
instability growth rate and its dependence on the propagation angle depend on
the shape of the ion and electron distribution functions.
