Artificial Aurora Experiment: Experiment and principal results

Abstract

An electron accelerator was flown on an Aerobee 350 rocket from Wallops Island, Virginia, in January 1969. At altitude the accelerator put out a series of electron‐beam pulses up to 1 sec long aimed downward along the magnetic‐field line. Several electron energies up to a maximum of 9.5 kev were used. The beam current was also varied up to a maximum of 490 ma. The highest power pulses were detected on the ground by sensitive optical systems. The vehicle neutralization was accomplished by collecting an ionospheric current equal to the beam current on a large aluminized mylar foil deployed perpendicular to the magnetic field. Attempts were made to measure electromagnetic waves that might be produced by the beam and also to measure with radar the ionization trail resulting from the beam interacting with the atmosphere. The artificial auroral rays produced by the electron beams appeared at the right place and time with about the right shape and intensity. This experiment demonstrates the feasibility of propagating electron beams long distances in space with relatively small alterations resulting from plasma instabilities or beam propagation problems.

On the role of magnetic mirroring in the auroral phenomena

“…By the same token a spatially strongly limited plasma may thus be more stable against this kind of wave growth. In fact, both artificial generation of thin "auro ral" electron beams (Hess et al, 1971) and theoretical investigations (Jones and Kellogg, 1973) do indicate that a thin structure of precipitating electrons is very stable to energy degradation by wave-particle interaction. This finding has an important implication with respect to the present auroral model.…”

“…-27 -The extent of energy degradation of the primary electrons will probably be a function of the spatial structure of the precipitation, as indicated by straightforward calcu lations (of for instance Hess et al, 1971). That is, a widely extended structure is seemingly particularly suscep tible to instabilities in velocity space because it allows unstable traveling waves to grow for extended periods of time.…”

Recent results from studies of electron beam phenomena in space plasmas

“…In this way additional detailed information on beam dynamics and radiation can be obtained. Since the very first space-borne electron beam experiment (Hess et al, 1971), it has been conjectured that pulsed electron beams could be used as virtual antennas for commutation purposes, for instance between space and ground or between two platforms in space. Reams have an advantage over conventional electric dipole antennas or magnetic dipole loop antennas, which is particularly important in the VLF whistler mode frequency range ; because of the large wavelength of VLF waves it takes very long electric dipoles or large loops to efficiently radiate VLF waves.…”

Ignition of the Beam-Plasma-Discharge and its Dependence on Electron Density

“…This discharge state has received considerable attention in recent years as a result of increased interest in mechanisms for vehicle neutralization during spaceborne accelerator experiments (Bernstein, et al, 1980;Cambou, et al, 1978), enhanced beam-plasma ionization processes (Bernstein, et al, 1978), and in general single-particle or collective phenomena initiated by beam injection into neutral gas and charged-particle environments (Hess et al, 1971;Winckler, et al, 1975;Hendrickson and Winckler 1976;Cambou, et al, 1975;Monson and Kellogg 1978a;Szuszczewicz 1979;Jost et al, 1980). As the subject of a continuing series of experiments in a large vacuum chamber facility (Bernstein et al, 1978) it was determined that the BPI) appears at a critical energetic- where VB, B, P and L are the beam energy (voltage), the superimposed magnetic field, the ambient pressure and the beam length (gun aperture-to-collector distance), respectively.…”