Abstract
Insufficiently accurate magnetic-field-line mapping between the aurora and the equatorial magnetosphere prevents us from determining the cause of many types of aurora. An important example is the longstanding question of how the magnetosphere drives low-latitude (growth-phase) auroral arcs: a large number of diverse generator mechanisms have been hypothesized but equatorial magnetospheric measurements cannot be unambiguously connected to arcs in the ionosphere, preventing the community from identifying the correct generator mechanisms. Here a mission concept is described to solve the magnetic-connection problem. From an equatorial instrumented spacecraft, a powerful energetic-electron beam is fired into the atmospheric loss cone resulting in an optical beam spot in the upper atmosphere that can be optically imaged from the ground, putting the magnetic connection of the equatorial spacecraft’s measurements into the context of the aurora. Multiple technical challenges that must be overcome for this mission concept are discussed: these include spacecraft charging, beam dynamics, beam stability, detection of the beam spot in the presence of aurora, and the safety of nearby spacecraft.
Highlights
One of the unsolved problems of magnetospheric physics is the cause of the various types of auroral forms (Lanchester, 2017; Denton, 2019)
For a dipole magnetic field the magnitude of this eastward angular shift is predictable (Mozer, 1966; Borovsky et al, 2020c), but for non-dipolar magnetic fields this shift is not predictable and a space experiment would need to determine the loss-cone shift by repeatedly test firing the electron beam with differing amounts of eastward shift while ground cameras work to detect the beam spot
Direct-current electron guns with 10’s of keV energies and 10’s of kW powers have been flown in space numerous times (Winckler et al, 1975; O’Neil et al, 1978; Rappaport et al, 1993; Prech et al, 1995; McNutt et al, 1995; Prech et al, 2018), while a radio-frequency accelerator has only been flown once (a 1-MeV H− beam) (Pongratz, 2018)
Summary
One of the unsolved problems of magnetospheric physics is the cause of the various types of auroral forms (Lanchester, 2017; Denton, 2019). THE MISSION CONCEPT: AN ELECTRON BEAM ILLUMINATING THE MAGNETIC CONNECTION BETWEEN AN EQUATORIAL MAGNETOSPHERIC SPACECRAFT AND THE ATMOSPHERE/IONOSPHERE
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