Collaborative Research: Turbulence, Structures, and Diffusive Shock Acceleration

University Of Alabama In Huntsville, Huntsville AL

Investigators

Abstract

This project will further our understanding of the origin and properties of highly energetic particles accelerated at shock waves in outer space. Shock waves in the interplanetary and interstellar medium are known to accelerate charged particles to very high (relativistic) energies. Exactly how this is done remains an important open problem. Energized particles irradiate the Earth, satellites and astronauts orbiting the Earth, and spacecraft exploring the heliosphere and other planets. Highly energetic particles represent a hazard to biological systems and technological systems, including communication, positioning, and observational and research satellites. Thus, determining the origin and subsequent properties of very energetic charged particles can have important technological and biological consequences that impact our daily lives and even the national security of the US. This award will support a collaborative effort between the University of Alabama - Huntsville and the New Mexico Consortium, with support from the Department of Energy, to investigate the effects of complex plasma structures that are typically generated at shock waves on the production of highly energetic particles in interplanetary space. This project will, for the first time, develop quantitative and testable models of particle energization in shock generated turbulence, which is in turn dissipated via reconnection current layers, associated magnetic plasmoids, and particle energization. The coupling of diffusive shock acceleration (DSA) and particle acceleration in the turbulent wake of fast shocks cleaves naturally into two: A) the generation, transmission, and amplification of turbulence and structures at collisionless shock waves, and B) the coupled acceleration of electrons and ions at and in the turbulent wake of collisionless shocks. This project will 1) develop models, validated by simulations that describe the transmission and generation of turbulence through and at collisionless quasi-perpendicular and quasi-parallel shock waves; 2) determine whether collisionless shocks can generate magnetic structures downstream of the shock and will describe the downstream evolution of shock-generated structures through reconnection-related processes; 3) explain the interaction of magnetic structures and current sheets, including the heliospheric current sheet, with incident shock waves; and 4) use numerical models and observations of turbulence, magnetic structures, and current sheets interacting with shocks to develop a theory of particle acceleration in the vicinity of shock waves.