On cosmic rays and final equilibrium states for the Parker instability

If the Parker instability develops in a system consisting of a conducting interstellar gas and a magnetic field in a galactic gravitational field, the tension of the field lines will eventually stop their inflation. Even if cosmic rays are present, final equilibrium states of the system are still possible. We suggest that such final states will be similar to those calculated in the absence of cosmic rays (Mouschovias, 1974), except that field lines will be more deformed. A fat radio disk in a quasi-steady state may thus form. Based on our formalism one may predict the synchrotron emission along spiral arms in which the magnetogravitational instability develops.