Theoretical studies of the pulsar magnetosphere
Quantitative models of the plasma magnetosphere surrounding a rotating. magnetized. neutron star (pulsar) are studied in this thesis. Both the aligned model (rotation axis parallel to magnetic axis) and the nonaligned model are considered. An energy analysis is performed on two explicit models of the aligned rotator due to Jackson. The unknown parameters of these models are determined by calculating the minimum total energy states of the models. It is found that the minimum energy analysis favors states with extended. dynamically active magnetospheres with a high degrees of corotation. By calculating total power input to the magnetosphere via collisions in the stellar crust. and the total power radiated due to azimuthal drift motion. it is determined that the minimum energy states are the only states where a power balance can be achieved. Consideration of a local power balance condition and dissipative flows in the magnetosphere shows that neither model is completely self-consistent. but one is considerably better than the other. Properties of both models are discussed. The nonaligned model is studied by considering the motion of single charged particles in the radiation and static fields assumed to exist outside of the inner magnetosphere. By gradually increasing the complexity of the model used. it is shown that trapped orbits exist beyond the light cylinder for the most realistic case. This case involves wave fields plus static electric and magnetic fields. and includes the effect of radial and angular dependence and radiation reaction. Properties of these orbits are used to develop a simple model of a toroidal electron plasma region outside the star plus inner magnetosphere. It is suggested that such a region may emit high frequency. pulsed radiation. As background to the particle orbit calculations. an approximate version of the Lorentz-Dirac equation of motion for a radiating charged particle is given. and exact solutions are presented for two cases of physical interest. Orbits are calculated for a charge in a uniform magnetic field and in a linearly polarized plane wave. Solutions are compared to those obtained from another approximate equation of motion due to Shen.
pulsar magnetospheres, aligned model, non-aligned model, azimulthal drift motion
University of Illinois - Urbana-Champaign
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