Understanding particle acceleration in astrophysical plasmas

Energetic electrons are ubiquitous in astrophysical plasmas, as they are considered to be behind the surges of emission across the electromagnetic spectrum at wavelengths from radio to gamma rays. These dynamic phenomena include stellar flares, supernova explosions (see the figure) (1), gamma ray bursts, and extragalactic jets. Energetic electrons are also directly observed in situ during terrestrial substorms. Despite these rich observations and substantial progress in theory, numerical simulations, and laboratory experiments over the past few decades, however, the mechanisms by which the electrons obtain their energy still remain elusive. On page 974 of this issue, Matsumoto et al. (2) make progress toward resolving these issues.