ABSTRACT

This INSPIRE award is partially funded by the Aeronomy and Magnetospheric Physics Programs in the Division of Atmospheric and Geospace Sciences in the Directorate for Geoscience, and the Plasma Physics Program in the Directorate for Mathematical and Physical Sciences.

The investigators will study the feasibility of conducting controlled experiments in space using million-electron-volt (MeV) beams of electrons. Energetic particles are fundamental to the geospace environment. These particles, and their interactions that produce gamma rays, x-rays, and radio emissions, shed light on the fundamental physics of the space environment. In geospace, particles are accelerated by various mechanisms in the magnetosphere, with energies upwards of 10 MeV. Targeted space-based particle injection experiments have enabled scientific investigations of space plasmas since at least the 1950s. However, these controlled experiments were mainly based on relatively low-energy electron beams (<40 keV). Controlled experiments with MeV-class electron beams injected between the magnetosphere and the atmosphere will enable several types of important scientific studies. These include atmospheric-ionospheric-magnetospheric coupling and the response of the atmosphere to long-term geomagnetic forcing; establishing how energetic particles are accelerated, transported, and lost; and understanding the origin and effects of wave-particle interactions. This project has two concurrent objectives: the first is scientific, the other technological. Meeting the scientific objectives will require detailed simulations, modeling, and theoretical calculations of beam-induced instabilities, expansion, and collisions to explore the range of properties of the electron beams. The range of beam properties identified in the science investigation will guide the principal technological objective of this project, which is to define the specifications of the linear accelerators with size, power, and form factors amenable to space deployment and capable of generating the beam characteristics needed to achieve science closure. This study addresses high priority science areas identified by the Heliophysics Decadal Survey and has direct relevance to the science objectives of NASA's Living With a Star, Van Allen Probes mission. The research will also have multiple practical applications. For instance, elucidating how wave-particle interactions cause the radiation belts to lose electrons into the ionosphere will enable technologies for the mitigation of space weather effects. Experiments investigating interactions between relativistic electron beams and the atmosphere will provide a host of diagnostic possibilities for understanding discharges and the modification of chemical reaction paths that will enable technologies to modify nitric oxide (NO) and ozone content in the atmosphere.

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