Plasma flow in a dipole pulsar magnetosphere
Pelizzari, Michael Alexander
Master of Science
Several people have recently derived a simple equation describing a neutron star magnetosphere dominated by Lorentz forces. With the assumption of complete charge separation, it is shown that strict application of the MHD approximation places severe physical restrictions on the form of the magnetospheric current distribution. Specifically, the volume current must all have the same sign (outward or inward), and to maintain charge balance, the return current is restricted to the thin sheet which separates the corotating zone from the region where the field lines open to infinity. There is also an upper limit on the current density at any point, corresponding to plasma leaving the stellar surface at the speed of light. Numerical solutions of the pulsar equation are presented, and shown to restrict plausible current distributions even further. One physically acceptable solution is discussed in detail. The magnetic neutral sheet formed by the return current is found to be an insignificant source of synchrotron radiation, except for very rapid rotators.