INTERACTION BETWEEN BIASED SUNLIT ELECTRON COLLECTORS IN AN INFINITE-DEBYE-LENGTH MAGNETOPLASMA - ELECTRON-TEMPERATURE THRESHOLD EFFECT

The interaction between two electrically coupled collectors in an infi nite Debye-length magnetoplasma is studied by the use of a simple semi analytical model of particle collection by spherical probes. Because t he ambient magnetic field confines the orbits of the particles, the pe rturbations due to photoelectron emission or screening of the ambient electron flux are ''guided'' along the magnetic field direction, When one collector is used as a density probe, depending on the size of the other collector with respect to the mean Larmor radius of the photoel ectrons, the model predicts either an electron temperature threshold o r a satellite potential threshold in order that the photoelectron curr ent between the collectors overcomes the ambient electron current to t he probe. This explains the variation of the modulation patterns of bi ased Langmuir probe measurements observed in the vicinity of amoral ar cs.