Electron acceleration by wave turbulence in a magnetized plasma

• Published in: Nature physics Vol. 14; no. 5; pp. 475 - 479
• Main Authors: Rigby, A., Cruz, F., Albertazzi, B., Bamford, R., Bell, A. R., Cross, J. E., Fraschetti, F., Graham, P., Hara, Y., Kozlowski, P. M., Kuramitsu, Y., Lamb, D. Q., Lebedev, S., Marques, J. R., Miniati, F., Morita, T., Oliver, M., Reville, B., Sakawa, Y., Sarkar, S., Spindloe, C., Trines, R., Tzeferacos, P., Silva, L. O., Bingham, R., Koenig, M., Gregori, G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2018; Nature Publishing Group; Nature Publishing Group (NPG)
• Subjects: 639/766/1960/1134; 639/766/1960/1135; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Electron acceleration; Energy; Experiments; Fluorine; Injection; Laboratories; Lasers; Letter; Magnetic fields; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Particle physics; Physics; Physics and Astronomy; Plasma; Plasmas (physics); Simulation; Theoretical; Thermal emission; Turbulence; Variation; Velocity; X-rays
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-018-0059-2

Astrophysical shocks are commonly revealed by the non-thermal emission of energetic electrons accelerated in situ 1 – 3 . Strong shocks are expected to accelerate particles to very high energies 4 – 6 ; however, they require a source of particles with velocities fast enough to permit multiple shock crossings. While the resulting diffusive shock acceleration 4 process can account for observations, the kinetic physics regulating the continuous injection of non-thermal particles is not well understood. Indeed, this injection problem is particularly acute for electrons, which rely on high-frequency plasma fluctuations to raise them above the thermal pool 7 , 8 . Here we show, using laboratory laser-produced shock experiments, that, in the presence of a strong magnetic field, significant electron pre-heating is achieved. We demonstrate that the key mechanism in producing these energetic electrons is through the generation of lower-hybrid turbulence via shock-reflected ions. Our experimental results are analogous to many astrophysical systems, including the interaction of a comet with the solar wind 9 , a setting where electron acceleration via lower-hybrid waves is possible. Electrons can be accelerated by astrophysical shocks if they are sufficiently fast to start with. As laboratory laser-produced shock experiments reveal, this can be achieved by lower-hybrid waves generated by a shock-reflected ion instability.