Relativistic electron beam propagation in the Earth's atmosphere: Modeling results

Abstract

Linear accelerators (linacs), capable of producing 5 MeV energy electron beams at 80 mA currents, are now down to a size that allow them to be flown on sounding rockets or balloons. This opens up new opportunities for atmospheric/ionospheric modification experiments where the mesosphere and thermosphere regions of the atmosphere can be perturbed down to 40 km altitude. In this paper beam propagation and atmospheric perturbation effects are studied by Monte Carlo simulations and by analytical means. It is shown that the earth' magnetic field severely limits the radial expansion of the beam otherwise induced by electron‐neutral collisions. It is also shown that the so‐called “envelope‐equations” from high‐energy laboratory physics adequately describe beam propagation in the upper atmosphere. The plasma density and electric conductivity modifications to the atmosphere are calculated from the Monte Carlo simulations. Inside the beam the conductivity in the 40–50 km altitude region is enhanced more than one order of magnitude by a 10 µs‐duration pulse. Some ideas for future scientific investigations are discussed, including the generation of electrical discharges by beams injected over thunderstorm regions.

Study of Relativistic Electron Beam Propagation in the Atmosphere-Ionosphere-Magnetosphere

“…As an extension to the study by Neubert et al [1996], the beam envelope equations have been used to predict beam propagation characteristics of interest (energy, radius, divergence) as a function of altitude over a variety of injection parameters, including beam energy (1-lOOMeV), divergence (0.01-0.1 radians), and relativistic electron beam study current (0.1 -10 4 A). Effects of beam-generated electric and magnetic fields were included in the analysis.…”

“…ne of day; I = large-scale models of beam propagation in the Earth's atmosphere-ionosphere-magnetosphere [Neubert et al, 1996;Kazanov etal., 1999]. In particular, the following questions have been addressed:…”

“…The complete set of envelope equations are given as [Lawson, 1988;Humphries, 1990;Neubert et a/., 1996]: …”

“…They include: (1) Study of the energetic electron population in the magnetosphere, (2) Modification of the atmospheric electric potential structure, and (3) Modification of chemical reaction paths in the middle atmosphere stimulated by naturally precipitating relativistic electrons. In a later study Neubert et al [1996], also showed that beam confinement by the external axial magnetic field significantly reduces the amount of radial expansion due to small-angle scattering and inelastic collision losses, constraining the beam's radius to be less than its gyroradius at a 90° pitch angle. These initial results provided sufficient encouragement to scientists at the Air Force Research Laboratory (AFRL) to consider that long-range propagation of MeV electrons beams in the Earth's upper atmosphere is theoretically feasible.…”

Diagnostics of an artificial relativistic electron beam interacting with the atmosphere

“…Following on the initial studies of Banks et al [1987Banks et al [ , 1990, Neubert et al [1996] provided the first detailed modeling of a 5 MeV beam interacting with the upper atmosphere between 40 and 60 km altitude using a Monte Carlo simulation approach. They calculated electron density perturbations and conductivity changes, and proposed that the experiment could be used to study the electrification of the upper atmosphere and chemical reaction paths in this altitude range.…”