Current-voltage characteristics of an electron-emitting, satellite in the ionosphere

Abstract

The limitation on the current that a sphere at a large positive potential ϕ can draw from a surrounding collisionless plasma in a magnetic field is investigated. The model assumes that for eϕ ≫ kTe the ions are excluded from the region of high potential surrounding the sphere. This region increases in size as ϕ increases, thus presenting an increased cross‐sectional area through which electrons can be collected from the plasma along magnetic field lines. We suggest that there is a critical density at which the electron cloud surrounding the positive body is sufficiently turbulent that the electrons are free to diffuse radially across magnetic field lines and thereby reach the sphere. This model yields a saturation current I ∝ ϕ/lnϕ, which scales directly with the density, thermal velocity, and square of the body size. At high background electron concentrations a space‐charge‐limited flow model that predicts I ∝ ϕ6/7 is more applicable, whereas the more pessimistic limit of I ∝ ϕ1/2, which follows from the conservation of the single particle constants of motion in time invariant electric and magnetic fields, is appropriate when the background electron concentration is low.

Charging and the cross-field discharge during electron accelerator operation on a rocket.

“…However the outgoing ions from the ionizations will be slow compared to electrons and may significantly modify the space charge around the rocket, and act to considerably relax the space charge limit on the current which can be drawn from the ionosphere at a given rocket potential (LINSON, 1969). As a consequence these few slow ions may have an important effect in limiting charging at altitudes where there is still some significant neutral atmosphere.…”

“…It has been suggested by GALEEv et al (1976) and independently by the present authors (CARTWRIGHT et al,1978) that this mechanism might ignite a cross-field discharge (also called Penning discharge, PIG discharge and rotating electrons discharge) and that the resulting current might be enough to keep the rocket neutralized and hold its potential at the modest value necessary to keep the cross-field discharge going. This would reduce the rocket potential well below values predicted by BEARD and JOHNSON (1961), PARKER andMURPHY (1967) andLINSON (1969). Such a discharge has been produced in a laboratory experiment by SASAKI et al (1984).…”

Rotating Electrons Discharge Model for a Spacecraft Emitting a High Power Electron Beam in Space

“…Theoretical models of the spacecraft charging due to the beam injection have been presented by BEARD and JOHNSON (1961), PARKER andMURPHY (1967), andLINSON (1969). Beard and Johnson propose a charging model based on the space-charge-limit current where the magnetic field can be neglected.…”

Recent results from studies of electron beam phenomena in space plasmas

“…In ization of the neutral atmosphere provides little addition, it is probably responsible for much of the additional plasma. While the beam-system interelectrostatic noise observed from the beam-emitting actions mentioned previously have been thought to spacecraft both at low frequencies as observed in the increase the electron current across the magnetic field, SEPAC space shuttle experiment (Neubert et al, and thereby increase the return current through wave-1986 ; Cai et al, 1987) and at high frequencies as induced particle diffusion (Linson, 1969 ;Hastings, 1987), there are practical limits to the efficiency of such processes. Furthermore, while laboratory experiments indicate that such processes occur in this environment, it has not been possible to establish their importance in space experiments.…”