Cosmic Blender: How Electrons Outrun Protons express
Near black holes and neutron stars, plasma churns like water in a boiling kettle. But this 'kettle' has no walls — only magnetic fields that twist and tear. At the tears, thin sheets form where magnetic field lines reconnect, giving particles a kick like a surfer catching a wave.
Until now, such simulations treated electrons and protons as having the same mass — simpler, but far from reality. This new work is the first to account for the real masses: a proton is 1836 times heavier than an electron. They also added positrons, the antimatter counterparts of electrons, which are born in the hot plasma. It turns out that acceleration doesn't happen just anywhere; it occurs in thin current sheets where the electric field aligns with the particle's velocity. It's like having a tailwind blowing exactly at a runner's back.
This means that in the plasma jets from black holes, the jets, electrons shine brighter than previously thought. Telescopes see this glow, and now it can be linked more precisely to what happens right at the event horizon.
Original abstract
as written by the authors arXiv:2604.06749
While collisionless plasmas are ubiquitously present near astrophysical compact objects, the impact that their composition has on the high-energy emission is presently unknown. We present the first investigation of particle-acceleration mechanisms in kinetic, special-relativistic turbulence, modeling electrons, positrons, and protons with realistic mass ratios. Under global charge neutrality, we introduce a positron fraction and cover regimes ranging from an electron-proton plasma over to pair-dominated plasmas. Using a novel generalized Ohm's law for multispecies relativistic plasmas, we analyze particle acceleration due to electric fields in reconnection events that self-consistently emerge from turbulence. We demonstrate, for the first time, that energization occurs at reconnection current sheets driven by the divergence of the relativistic pressure tensor, which locally aligns with the particle velocity and leads to an efficient energy transfer. The imbalance between electrons and positrons systematically favors electron acceleration, highlighting the necessity of realistic multispecies modeling to capture the nonthermal contributions in accretion flows and relativistic jets from black holes.
In the plasma near a black hole, an electron accelerates faster than a proton because it is 1836 times lighter, like a cyclist versus a truck on the same hill.