Diagnostics of an artificial relativistic electron beam interacting with the atmosphere

Abstract

We use a Monte Carlo model to simulate the interaction of a beam of relativistic (0.5–10 MeV) electrons with the upper atmosphere as they are injected downward from a notional high‐altitude (thermospheric/ionospheric) injection platform. The beam parameters, defined by realistic parameters of a compact linear accelerator, are used to create a distribution of thousands of electrons. Each electron is injected downward from 300 km altitude toward the dense atmosphere, where it undergoes elastic and inelastic collisions, leading to secondary ionization, optical emissions, and X‐rays via bremsstrahlung. In this report we describe the model initialization (i.e., development of the electron distribution), essential features of the Monte Carlo model, and secondary outputs, including optical emissions, X‐ray fluxes, secondary ionization, and backscattered energetic electron fluxes. Optical emissions are propagated to the ground through the lower atmosphere, including the effects of atmospheric absorption and scattering, to estimate the brightness of the emission column for a given beam current and energy. Similarly, X‐ray fluxes are propagated to hypothetical detectors on balloons and satellites. Secondary ionization is used to estimate the radar signal returns from various ground‐based radar facilities. Finally, simulated backscattered electron fluxes are measured at the injection location. The simulation results show that each of these diagnostics should be readily detectable by appropriate instruments.

Discovery of 1 Hz Range Modulation of Isolated Proton Aurora at Subauroral Latitudes

“…Based on these observations and estimations of the source regions, MeV and sub‐MeV electrons can cause an electron aurora simultaneously with the IPA. Marshall et al () simulated optical emissions generated by relativistic electron beam using a Monte Carlo model. The dominant emissions are the first and second positive systems of N 2 and the first negative systems of in their simulations.…”

Pitch Angle Dependence of Energetic Electron Precipitation: Energy Deposition, Backscatter, and the Bounce Loss Cone

“…The EPMC model used here is adapted from the Monte Carlo model of Lehtinen et al (). This model has been used for a variety of purposes in recent years, including calculating the atmospheric effects of an artificial beam of relativistic electrons (Marshall et al, ) and studying the effects of bremsstrahlung propagation into the stratosphere (Xu et al, ).…”

Relativistic Particle Beams as a Resource to Solve Outstanding Problems in Space Physics

“…Beam Detectability and Ground-Based Diagnostics Neubert et al (1996), Krause (1998), and Krause et al (1999) demonstrated that relativistic beams injected from the ionosphere into the atmosphere below would produce significant electron-density enhancements, optical emissions, and measureable height-integrated X-ray fluxes. Marshall et al (2014) expanded on the work of Krause (1998) to calculate optical emissions observable from the ground, Xray production and propagation and detectability from satellites and balloons, and backscattered electrons that could be observed from Low Earth Orbit (LEO). That study showed that optical signatures were likely detectable, X-ray fluxes were likely to be far too low from either LEO or balloon altitudes, and ionization could likely be measured form the ground using incoherent scatter radar.…”

“…That study investigated a pulse of electrons with 0.05-1 Joules of total energy. Recent accelerator design efforts are targeting a beam total energy of 100-1,000 J, prompting a revisit to the calculations of Marshall et al (2014).…”