This scientific article presents experimental evidence of how Alfvén waves, powerful electromagnetic waves commonly associated with auroras, accelerate electrons. The researchers created a laboratory simulation mimicking the auroral zone and measured the interaction between the waves and electrons. Their measurements show that the electrons are accelerated by the waves through a process called Landau resonance, which allows electrons to gain energy as they interact with the wave. This finding directly confirms a long-standing theoretical hypothesis about auroral electron acceleration, offering significant insight into the physics behind the beautiful, luminous auroral displays.

Basic Plasma Science Facility: https://plasma.physics.ucla.edu

Article being discussed: Schroeder, J. W. R., Howes, G. G., Kletzing, C. A., Skiff, F., Carter, T.A., Vincena, S., and Dorfman, S., Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves, Nature Communications 12, 3103, pp 1-9, (2021); https://doi.org/10.1038/s41467-021-23377-5

The Basic Plasma Science Facility is a Collaborative Research Facility that is primarily funded by the US Department of Energy Fusion Energy Sciences program, with additional funding from the National Science Foundation.

This research investigates the electrical resistivity of a plasma during the collision of magnetic flux ropes, which are common structures in astrophysical plasmas. The researchers performed laboratory experiments using the Large Plasma Device (LaPD) at UCLA, measuring the magnetic field, plasma potential, plasma flow, temperature, and density at various spatial locations. They found that the traditional Ohm's Law (describing resistivity) could not be used to calculate the resistivity due to non-local effects. Instead, they used the Kubo conductivity formula, which is derived from the fluctuation-dissipation theorem, to determine the global resistivity. The results indicate that the resistivity is enhanced in regions where the magnetic field lines reconnect and the current density is large, suggesting that the process is related to the scattering of electrons by waves or turbulence in the plasma.

Basic Plasma Science Facility: https://plasma.physics.ucla.edu

Article being discussed: W. Gekelman, T. DeHaas, P. Pribyl, S. Vincena, B. Van Compernolle, R. Sydora, and S. K. P. Tripathi, "Nonlocal Ohm's Law, Plasma Resistivity, and Reconnection During Collisions of Magnetic Flux Ropes," ApJ 853 33, (2018); https://doi.org/10.3847/1538-4357/aa9fec

The Basic Plasma Science Facility is a Collaborative Research Facility that is primarily funded by the US Department of Energy Fusion Energy Sciences program, with additional funding from the National Science Foundation.

Our hosts discuss a paper that reports on an experiment using the Large Plasma Device (LAPD) to study the effects of magnetic reconnection on ions. The experiment used two kink-unstable flux ropes, which are current-carrying columns of plasma that collide and cause magnetic reconnection. Magnetic reconnection is a process that converts stored magnetic energy into particle energy. The experiment observed a field-aligned ion beam with energies up to 15 eV that was correlated with the collision of the ropes and was not heated. The study was supported by 3D gyrokinetic particle simulations which demonstrated that the ion acceleration was caused by a combination of inductive and space charge electric fields, resulting in a non-local acceleration of ions. The authors claim that this is the first experimental observation of a field-aligned ion beam produced by magnetic reconnection.

Basic Plasma Science Facility: https://plasma.physics.ucla.edu

Article being discussed: S. W. Tang, W. Gekelman, and R. D. Sydora, "Experimental observation of a field-aligned ion beam produced by magnetic reconnection of two flux ropes," Phys. Plasmas 30, 082104 (2023); https://doi.org/10.1063/5.0138350

The Basic Plasma Science Facility is a Collaborative Research Facility that is primarily funded by the US Department of Energy Fusion Energy Sciences program, with additional funding from the National Science Foundation.