A new pulsar atmospheric model. I. Aligned magnetic and rotational axes

A model is proposed for the plasma atmosphere about a rotating magnetized neutron star with aligned magnetic and rotational axes. The model is generated with the aid of a gedanken experiment in which the rotational velocity Ω of the star is adiabatically increased. By this device it is established that the star will acquire a charge sufficient to stop the charge loss to the nebula, but not the local surface emission. The resulting monopole electric field causes plasma to flow across magnetic surfaces at large distances from the star, where it dominates the dipole magnetic field, thereby forming a current loop from the polar caps to polar annuli. This same electric flow region can also establilsh current loops to the nebula, provided electron-positron pairs are produced. The vacuum electric field has a surface where ExB=0, which is a dome over the polar cap. For larger Ω, radiation losses cause beam particles to be trapped around this surface, forming a relatively stationary, possibly turbulent component of the atmosphere. It is shown that this plasma dome is more stable than the force-free atmosphere, and is therefore presumably maintained by a balance between the radiative capture and diffusion of particles back to the star. A small toroidal, nearly force-free region consisting of opposite charges also exists near the equator and is attached to an equatorial disk, maintained by diffusion. The limited atmospheric extent and toroidal drift velocity suggest that all the magnetic surfaces are closed (near-dipolar)