MS thesis abstract - Ferry, Jean-Benoit

Author:	Ferry, Jean-Benoit
Degree:	Masters of Science
SERC #:	11-03
File type:	PDF, 19866 kB
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Electron Collection by an Electrodynamic Bare Tether at High Potential

In tethered satellites, it is very important to be able to estimate the electron current collected by the tether. However, this analysis is very difficult because of the presence of the geomagnetic field. We are developing a Particle-In-Cell model. The model uses a boundary condition based on quasi-neutrality, very similar to the one T. Onishi used in his Ph.D Thesis (2002), in order to solve for the local potential at the points of the computational boundary. This condition imposes ne = ni at the boundary. Moreover the motion of particles is computed analytically in a domain close to the tether - inside the sheath. This calculation is made possible by neglecting the space charge effect, which is very small in comparison with the tether potential, and therefore allowing the Laplace equation to be solved. The goal of this analytical domain is to provide a better accuracy in the region where electrons can reach high velocity. Although a similar approach was used by T. Onishi, the goal of this model is to experiment higher voltages for the tether, with bias ratio of the order of 1000 to 2500. Indeed such voltages are the ones of interest for space tethers. In order to be able to reach these voltages, we first conducted a precise analysis of the quiescent un-magnetized case. This analysis allowed us to successfully compare the model with established probe theory results. Moreover it gives a good foundation to explore the more complicated case of a magnetized flowing plasma.