Energy Partition in Relativistic Electron-Positron-Ion Reconnection
Abstract
Relativistic magnetic reconnection, a prime mechanism for particle acceleration, has been extensively studied in electron--ion and pair plasmas, but how the dissipated energy is shared among species in electron--positron--ion plasmas, and in particular how ions are energized within a pair-dominated layer, remains poorly understood. We develop an analytic theory that couples single-particle orbit dynamics to the collective plasma response, and we validate it with particle-in-cell simulations spanning pair-dominated to electron--ion compositions. Particles are directly energized in electric-dominated regions until the reconnected magnetic field deflects them into the outflow; the characteristic escape length is in turn set by the relativistic skin depth of the reconnection-heated mixture, including the ion contribution. Writing σe* for the magnetic energy available per particle in units of mec2 and μ=mi/me, the mean lepton energy scales as σe*, whereas the mean ion energy scales as μ1/3(σe*)2/3 when ions escape non-relativistically from the electric-dominated regions and approaches the lepton energy when their escape is ultrarelativistic. The predicted energy fractions agree with simulations across composition, mass ratio, and magnetization. The ion share of the dissipated energy can fall far below the commonly assumed ion--lepton equipartition, reducing the energy available for hadronic and neutrino emission in reconnection-powered astrophysical sources.
Related
- Guide field effects on particle acceleration in three-dimensional relativistic magnetic reconnection
- Are E>B regions essential for particle injection in relativistic magnetic reconnection?
- The Birth of Plasmoids: Weibel-Driven Secondary Tearing and its Suppression in Relativistic Reconnection
- Rapid Variability of Radiative Signatures from Driven Relativistic Reconnection
- Sparking Dynamic, Relativistic Magnetic Reconnection in a Twisted Flux Tube
BibTeX
@misc{mancini2026energy,
title = {{Energy Partition in Relativistic Electron-Positron-Ion Reconnection}},
author = {Nilay Mancini and Luca Comisso and Lorenzo Sironi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.21118},
eprint = {2609.21118},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.21118},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Energy Partition in Relativistic Electron-Positron-Ion Reconnection
AU - Nilay Mancini
AU - Luca Comisso
AU - Lorenzo Sironi
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.21118
UR - https://arxiv.org/abs/2609.21118
AB - Relativistic magnetic reconnection, a prime mechanism for particle acceleration, has been extensively studied in electron--ion and pair plasmas, but how the dissipated energy is shared among species in electron--positron--ion plasmas, and in particular how ions are energized within a pair-dominated layer, remains poorly understood. We develop an analytic theory that couples single-particle orbit dynamics to the collective plasma response, and we validate it with particle-in-cell simulations spanning pair-dominated to electron--ion compositions. Particles are directly energized in electric-dominated regions until the reconnected magnetic field deflects them into the outflow; the characteristic escape length is in turn set by the relativistic skin depth of the reconnection-heated mixture, including the ion contribution. Writing σ_e^* for the magnetic energy available per particle in units of m_ec^2 and μ=m_i/m_e, the mean lepton energy scales as σ_e^*, whereas the mean ion energy scales as μ^1/3(σ_e^*)^2/3 when ions escape non-relativistically from the electric-dominated regions and approaches the lepton energy when their escape is ultrarelativistic. The predicted energy fractions agree with simulations across composition, mass ratio, and magnetization. The ion share of the dissipated energy can fall far below the commonly assumed ion--lepton equipartition, reducing the energy available for hadronic and neutrino emission in reconnection-powered astrophysical sources.
ER -