The Mechanism of Electron Injection and Acceleration in Transrelativistic Reconnection

David Ball, Lorenzo Sironi, Feryal Özel

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Electron acceleration during magnetic reconnection is thought to play a key role in time-variable high-energy emission from astrophysical systems. By means of particle-in-cell simulations of transrelativistic reconnection, we investigate electron injection and acceleration mechanisms in low-β electron-proton plasmas. We set up a diversity of density and field structures (e.g., X-points and plasmoids) by varying the guide field strength and choosing whether to trigger reconnection or let it spontaneously evolve. We show that the number of X-points and plasmoids controls the efficiency of electron acceleration, with more X-points leading to a higher efficiency. Using on-the-fly acceleration diagnostics, we also show that the nonideal electric fields associated with X-points play a critical role in the first stages of electron acceleration. As a further diagnostic, we include two populations of test particles that selectively experience only certain components of electric fields. We find that the out-of-plane component of the parallel electric field determines the hardness of the high-energy tail of the electron energy distribution. These results further our understanding of electron acceleration in this regime of magnetic reconnection and have implications for realistic models of black hole accretion flows.

Original languageEnglish (US)
Article number57
JournalAstrophysical Journal
Issue number1
StatePublished - Oct 10 2019


  • X-rays: Binaries
  • accretion, accretion disks
  • galaxies: Jets
  • magnetic reconnection
  • radiation mechanisms: Nonthermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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