Direct evidence of nonstationary collisionless shocks in space plasmas

Andrew P. Dimmock (1) , Christopher T. Russell (2) , Roald Z. Sagdeev (3) , Vladimir Krasnoselskikh (4) , Simon N. Walker (5) , Christopher Carr (6) , Iannis Dandouras (7) , C. Philippe Escoubet (8) , Natalia Ganushkina (9) , Michael Gedalin (10) , Yuri V. Khotyaintsev , Homayon Aryan (5, 11) , Tuija I. Pulkkinen , Michael Balikhin

1 IRF - Swedish Institute of Space Physics [Uppsala / Kiruna]
2 EPSS - Department of Earth, Planetary and Space Sciences [Los Angeles]
3 Maryland Center for Fundamental Physics
4 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
5 ACSE - Department of Automatic Control and Systems Engineering [ Sheffield]
6 Imperial College London
7 IRAP - Institut de recherche en astrophysique et planétologie
8 HE Space Operations BV for ESA/ESTEC
9 FMI - Finnish Meteorological Institute
10 Department of Physics [Beer-Sheva]
11 GSFC - NASA Goddard Space Flight Center

Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial , as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom-particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.

Domaines: Planète et Univers [physics]

Andrew P. Dimmock, Christopher T. Russell, Roald Z. Sagdeev, Vladimir Krasnoselskikh, Simon N. Walker, et al.. Direct evidence of nonstationary collisionless shocks in space plasmas. Science Advances , 2019, 5 (2), eaau9926 8 p. ⟨10.1126/sciadv.aau9926⟩. ⟨insu-02080005⟩