Classical electron-ion scattering in strongly magnetized plasmas: A generalized Coulomb logarithm and a generalized Gaunt factor
Geller, David Keith
Weisheit, Jon C.
Doctor of Philosophy
Magnetic fields are present in many astrophysical and terrestrial plasmas, and enormous literature is available describing the effect of magnetic fields on the plasma environment. The vast majority of this literature, however, addresses either the relatively weak field regime where electron-ion collisions are Coulombic, or the extremely strong field regime where electron trajectories are described by Landau orbitals. This thesis investigates the intermediate regime, where the field is non-quantizing, yet strong enough to modify the Coulombic nature of the underlying collisional processes. First, a detailed examination of electron-ion scattering in strong magnetic fields is given. This leads to the development of some relatively simple analytic expressions describing classical, small-angle scattering of electrons and ions in strong magnetic fields. Numerical evaluation of these expressions shows quantitatively how strong non-quantizing B fields can significantly inhibit electron deflections. Next, the influence of the field on transport phenomena is explored, and a generalized Coulomb logarithm which includes the effects of a magnetic field is formulated and computed for a wide range of plasma parameters. This generalized Coulomb logarithm is used to illustrate how a strong field influences the electron velocity diffusion coefficient, and the (parallel) electrical and thermal resistivity of a plasma. Finally, the influence of the field on radiation processes is explored, and a generalized Gaunt factor for classical bremsstrahlung emission is formulated and computed for a wide range of plasma parameters. The generalized Gaunt factor is used to show how the broadband background radiation of a plasma is modified by strong fields.