Auroral Electron Acceleration

Here we describe the results in our recent paper in Nature Communications 12:3103 (2021),
Laboratory measurements of the physics of auroral electron acceleration by Alfven waves

The paper has also been featured as an Editor's Highlight for Nature Communications in the research area of “Astronomy and Planetary Science.”

Training the Next Generation of Scientists

Over the years, a number of young scientists have been trained through efforts to devise, construct, test, and refine the critical specialized instrumentation and techniques needed to achieve the ultimate goal of this project—to measure the acceleration of electrons by Alfven waves under conditions corresponding to Earth's auroral magnetosphere. All of these former graduate students and postdoctoral researchers have gone on to permanent career positions in academia or the research community. Thus, this project has significantly advanced one of the National Science Foundation's strategic objectives—to foster the integration of research and education, with the goal to recruit, train, and prepare a diverse STEM workforce to advance the frontiers of science and participate in the U.S. technology-based economy. Here we briefly list these students, highlighting their contribution to this project and their current positions:
  1. As a postdoctoral researcher for Professor Craig Kletzing, Scott Bounds worked on early designs for Alfven wave antennas for the LAPD experiments, and helped to design, develop, and test the Arbitrary Spatial Waveform (ASW) antenna for launching Alfven waves with careful control of the waveform in the plane perpendicular to the LAPD's axial magnetic field, enabling the wavevector content of these Alfven waves to be determined. This enabled the creation of kinetic or inertial Alfven waves that have a parallel component of the electric field capable of accelerating electrons. Scott Bounds currently holds the position of Associate Research Scientist at the University of Iowa and is involved in building spacecraft hardware and analyzing data collected by rockets and satellites, in particular working on development and construction of the new NASA Small Explorer mission TRACERS.
  2. As a graduate student for Professor Craig Kletzing, Derek Thuecks worked on testing the Arbitrary Spatial Waveform (ASW) antenna for launching Alfven waves in the LAPD in the kinetic Alfven wave and inertial Alfven wave regimes. Furthermore, he worked on the design, construction, and original testing of the Whistler Wave Absorption Diagnostic. Derek Thuecks currently holds the position of Associate Professor of Physics at Washington College in Chestertown, Maryland.
  3. As a graduate student for Professor Gregory Howes, Kevin Nielson used the Astrophysical Gyrokinetics code, AstroGK, to simulate numerically LAPD experiments using the ASW antenna to launch Alfven waves in the kinetic Alfven wave and inertial Alfven wave regimes. Furthermore, he used AstroGK simulations to understand Alfven wave collisions—nonlinear interactions between counterpropagating Alfven waves—which serve as a fundamental block of astrophysical plasma turbulence. The properties of these Alfven wave collisions were first verified by our collaboration using a combination of mathematical modeling, AstroGK numerical simulations, and LAPD experiments. Kevin Nielson is currently a Senior Research Scientist at the Georgia Tech Research Institute. Dr. Nielson's expertise is in applied modeling, simulation, and concept development of electro-optical systems. He principally supports developmental Department of Defense projects in remote sensing and aircraft survivability systems.
  4. As a postdoctoral researcher working with our LAPD collaboration, Jan Drake helped to design, construct, test, and characterize the Elsasser probes used to measure the perpendicular components of the electric and magnetic fields at the same position in the LAPD experiments. She used these probes to conduct the Alfven wave collision experiments on the LAPD that confirmed the nonlinear transfer of energy caused by the interaction between two counterpropagating Alfven waves, confirming that the physics of these Alfven wave collisions served as a fundamental block of astrophysical plasma turbulence. Jan Drake currently holds the position of Associate Professor of Physics at Valdosta State University in Georgia.
  5. As a graduate student for Professor Fred Skiff, supported by an NSF Graduate Research Fellowship, Jim Schroeder ran initial tests of the Whistler Wave Absorption Diagnostic for inertial Alfven waves launched by the ASW antenna and verified that the measured fluctuations in the electron velocity distribution agreed with theoretical predictions, a critical milestone on the way to this final experiment. Later, as a postdoctoral researcher for Professor Gregory Howes, Jim designed, constructed, and tested the high-power sigma antenna, making it possible to launch much larger amplitude Alfven waves so that it was possible to measure the energization rate of the accelerated electrons by applying the field-particle correlation method to the combination of the Elsasser probe measurements and the Whistler Wave Absorption Diagnostic measurements. Jim Schroeder currently holds the position of Assistant Professor of Physics at Wheaton College in Illinois.
  6. As a postdoctoral researcher for Professor Troy Carter at UCLA, supported first by a Department of Energy Fusion Energy Sciences Postdoctoral Fellowship and later by a NASA Jack Eddy Postdoctoral Fellowship, Seth Dorfman helped to perform the auroral electron acceleration experiments on the LAPD. Seth Dorfman is currently a Research Scientist for the Space Science Institute and is based in Los Angeles, California. His current research focuses on the use of laboratory experiments and satellite observations to explore the fundamental plasma physics of our Sun-Earth system, including unstable waves generated by ion and electron beams as well as the interactions between and instabilities arising from large amplitude Alfvén waves.