Scaling of Magnetic Dissipation and Particle Acceleration in ABC Fields

Abstract

Using particle-in-cell (PIC) numerical simulations with electron-positron pair plasma, we study how the efficiencies of magnetic dissipation and particle acceleration scale with the initial coherence length ${\lambda }_0$ in relation to the system size $L$ of the two-dimensional (2D) `Arnold-Beltrami-Childress' (ABC) magnetic field configurations. Topological constraints on the distribution of magnetic helicity in 2D systems, identified earlier in relativistic force-free (FF) simulations, that prevent the high-$(L/{\lambda }_0)$ configurations from reaching the Taylor state, limit the magnetic dissipation efficiency to about ${\epsilon }_{\mathrm{diss}}\simeq 60\%$. We find that the peak growth time scale of the electric energy ${\tau }_{\mathrm{E},\mathrm{peak}}$ scales with the characteristic value of initial Alfven velocity ${\beta }_{\mathrm{A},\mathrm{ini}}$ like ${\tau }_{\mathrm{E},\mathrm{peak}}\propto ({\lambda }_0/L){\beta }_{\mathrm{A},\mathrm{ini}}^{-3}$. The particle energy change is decomposed into non-thermal and thermal parts, with non-thermal energy gain dominant only for high initial magnetisation. The most robust description of the non-thermal high-energy part of the particle distribution is that the power-law index is a linear function of the initial magnetic energy fraction.

Published in Journal of Plasma Physics, 17 pages, 7 figures, 1 table

References in corpus (14)

• Fast TeV variability in blazars: jets in a jet
• Formation of Hard Power-laws in the Energetic Particle Spectra Resulting from Relativistic Magnetic Reconnection
• MAGIC discovery of VHE Emission from the FSRQ PKS 1222+21
• Gamma-ray flares from the Crab Nebula
• Discovery of Powerful Gamma-Ray Flares from the Crab Nebula
• Relativistic Jets Shine through Shocks or Magnetic Reconnection?
• Blazar flares powered by plasmoids in relativistic reconnection
• Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet's Tale
• Kinetic turbulence in relativistic plasma: from thermal bath to non-thermal continuum
• Particle acceleration in the driven relativistic reconnection
• Determining the Dominant Acceleration Mechanism during Relativistic Magnetic Reconnection in Large-scale Systems
• Variable gamma-ray emission from the Crab Nebula: short flares and long "waves"
• The energetics of relativistic magnetic reconnection: ion-electron repartition and particle distribution hardness
• Hard Synchrotron Spectra from Magnetically Dominated Plasma Turbulence