Comptonization by Reconnection Plasmoids in Black Hole Coronae II: Electron-Ion Plasma

Abstract

We perform two-dimensional particle-in-cell simulations of magnetic reconnection in electron-ion plasmas subject to strong Compton cooling and calculate the X-ray spectra produced by this process. The simulations are performed for trans-relativistic reconnection with magnetization $1\le \sigma \le 3$ (defined as the ratio of magnetic tension to plasma rest-mass density), which is expected in the coronae of accretion disks around black holes. We find that magnetic dissipation proceeds with inefficient energy exchange between the heated ions and the Compton-cooled electrons. As a result, most electrons are kept at a low temperature in Compton equilibrium with radiation, and so thermal Comptonization cannot reach photon energies $\sim 100$ keV observed from accreting black holes. Nevertheless, magnetic reconnection efficiently generates $\sim 100$ keV photons because of mildly relativistic bulk motions of the plasmoid chain formed in the reconnection layer. Comptonization by the plasmoid motions dominates the radiative output and controls the peak of the radiation spectrum $E_{\mathrm{pk}}$. We find $E_{\mathrm{pk}}\sim 40$ keV for $\sigma =1$ and $E_{\mathrm{pk}}\sim 100$ keV for $\sigma =3$. In addition to the X-ray peak around 100 keV, the simulations show a non-thermal MeV tail emitted by a non-thermal electron population generated near X-points of the reconnection layer. The results are consistent with the typical hard state of accreting black holes. In particular, we find that the spectrum of Cygnus~X-1 is well explained by electron-ion reconnection with $\sigma \sim 3$.

Accepted for publication in MNRAS: 16 pages, 15 figures, 1 table, 8 appendices. Part-I can be accessed at arXiv:2107.00263

References in corpus (16)

• Instability of current sheets and formation of plasmoid chains
• Relativistic Jets Shine through Shocks or Magnetic Reconnection?
• The corona contracts in a black-hole transient
• Radiation Reaction Effects on Radiation Pressure Acceleration
• Particle acceleration in axisymmetric pulsar current sheets
• A Review of the 0.1 Reconnection Rate Problem
• Electron and proton heating in trans-relativistic magnetic reconnection
• Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-Timing Analysis
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. I. Compression-Driven Instabilities and the Electron Heating Mechanism
• Reconnection in Marginally Collisionless Accretion Disk Coronae
• Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations
• Magnetic reconnection and plasmoid formation in three-dimensional accretion flows around black holes
• The energetics of relativistic magnetic reconnection: ion-electron repartition and particle distribution hardness
• Comptonization by Reconnection Plasmoids in Black Hole Coronae I: Magnetically Dominated Pair Plasma
• Electron and Proton Heating in Transrelativistic Guide Field Reconnection
• Non-ideal fields solve the injection problem in relativistic reconnection

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