Princeton Center for Heliophysics Seminar

There is interest in operating a 1-MeV 1-kWatt electron accelerator on a spacecraft in the tenuous plasma of the Earth’s distant magnetosphere. The desire is to fire the electron beam into the atmospheric loss cone to optically excite the atmosphere at the magnetic footpoint of the accelerator. A NASA-funded engineering mission design was just completed for this mission concept. To bring the concept to reality, several plasma-physics problems had to be overcome. This talk will focus on 6 of those problems. (1) Designing an electron beam with a divergence smaller than the loss cone. (2) Knowing where the loss cone is located when there are finite-gyroradii effects. (3) Overcoming electron-beam-driven spacecraft charging. (4) Checking beam-plasma stability. (5) Examining whether ambient magnetospheric plasma waves will scatter the beam electrons. (6) Detecting the optical beamspot with ground-based imagers. Five out of six of these problems were difficult.