Year: 2026
Type: preprint
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 $σ_e^*$ 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.
Source: arXiv (Cornell University)
Authors: Mancini, Nilay, Comisso, Luca, Sironi, Lorenzo
Institutions: Columbia University, Flatiron Institute
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G1047285063, G2103286527, WoU-MMA: Pinning the Generation of Ultra-High-Energy Cosmic Rays with First Principles Plasma Simulations, Collaborative Research: WoU-MMA: Multimessenger Plasma Physics Center (MPPC), G3677525350, Global kinetic modeling of the intrabinary shock in spider pulsars, G8520910697
OpenAlex ID: W7213898882