Electric Field Instrument Using Radiated Electrons (E‐FIRE): An Innovative Approach to the Measurement of Electric Fields in the Earth's Magnetosphere

Abstract

We are proposing a novel compact sensor system for measuring electric fields in space plasmas. The measurement of electric fields from earth orbiting satellites has been a difficult challenge for the large scale DC component of this field. Traditional techniques using double-probe style instruments are troubled by contact potentials to the plasma environment and photoelectric effects due to solar radiation. Newer techniques using low energy electron beams put requirements on costly spacecraft electric cleanliness, in order to avoid beam deflection by spacecraft potentials. E-FIRE uses energetic electrons of approximately one MeV in connection with recently developed ion-implanted solid-state detectors which have good position resolution and energy determination. The electrons are produced by a radioactive source with a line spectrum that tags the particles as being emitted from the satellite. These electrons will return to the spacecraft within a few microseconds having displacements of millimeters to centimeters due to the ambient electric (and in some cases magnetic) field, independent of any electric potentials that may have been produced by solar radiation or the interaction of the spacecraft with the local plasma environment.