Non-thermal electron acceleration from magnetically driven reconnection in a laboratory plasma

Abraham Chien, Lan Gao, Shu Zhang, Hantao Ji, Eric G. Blackman, William Daughton, Adam Stanier, Ari Le, Fan Guo, Russ Follett, Hui Chen, Gennady Fiksel, Gabriel Bleotu, Robert C. Cauble, Sophia N. Chen, Alice Fazzini, Kirk Flippo, Omar French, Dustin H. Froula, Julien FuchsShinsuke Fujioka, Kenneth Hill, Sallee Klein, Carolyn Kuranz, Philip Nilson, Alexander Rasmus, Ryunosuke Takizawa

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Magnetic reconnection rapidly converts magnetic energy into some combination of plasma flow energy, thermal energy and non-thermal energetic particles. Various reconnection acceleration mechanisms have been theoretically proposed and numerically studied in different collisionless and low-β environments, where β refers to the plasma-to-magnetic pressure ratio. These mechanisms include Fermi acceleration, betatron acceleration, parallel electric field acceleration along magnetic fields and direct acceleration by the reconnection electric field. However, none of them have been experimentally confirmed, as the direct observation of non-thermal particle acceleration in laboratory experiments has been difficult due to short Debye lengths for in situ measurements and short mean free paths for ex situ measurements. Here we report the direct measurement of accelerated non-thermal electrons from magnetically driven reconnection at low β in experiments using a laser-powered capacitor coil platform. We use kilojoule lasers to drive parallel currents to reconnect megagauss-level magnetic fields in a quasi-axisymmetric geometry. The angular dependence of the measured electron energy spectrum and the resulting accelerated energies, supported by particle-in-cell simulations, indicate that the mechanism of direct electric field acceleration by the out-of-plane reconnection electric field is at work. Scaled energies using this mechanism show direct relevance to astrophysical observations.

Original languageEnglish (US)
Pages (from-to)254-262
Number of pages9
JournalNature Physics
Volume19
Issue number2
DOIs
StatePublished - Feb 2023

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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