Theory of Plasma Contactors in Ground-Based Experiments and Low Earth Orbit

Previous theoretical work on plasma contactors as current collectors h_ fallen into two categories: collisionles8double layer theory {describing space charge limited contactor clouds) and collisionalquasineutra] theory. Ground based experiments at low current are well explained by double layer theory, but thistheory does not scale well to power generation by electrodynamic tethers in space, since very high anode potentials are needed to draw =,substantial ambient electron current across the magnetic fieldin the absence of collisions (or effective collisions due to turbulence). Isotropic qua_ineutral modelJ of contactor clouds, extending over a region where the effective collisionfrequency ue exceeds the electron cyclotron frequency _ce, have low anode potentials, but would collect very littleambient electron current, much less than the emitted ion current. A new model is presentedl for an anisotropic contactor cloud oriented Mong the magnetic field,with u_ < coos.The electron motion along the magnetic fieldis nearly coRbionleu, forming double layexs in that direction,while acrou the magnetic fieldthe electrons "Research Scienthlt tCla_ of 19S6 Career Development Associate Professor of Aeronautics and Aatronffiutics, Member _Reeearch Auktant;aleo at the Air Force Geophysics L_bor_tory °Copyright (_)Dxnlel Hastings, 1989. All rights reserved. 150 https://ntrs.nasa.gov/search.jsp?R=19910008408 2020-01-02T22:32:15+00:00Z