Particle acceleration during magnetic reconnection in a low-beta pair plasma

Abstract

Plasma energization through magnetic reconnection in the magnetically-dominated regime featured by low plasma beta (β = 8πnkT 0 /B 2 1) and/or high magnetizationis important in a series of astrophysical systems such as solar flares, pulsar wind nebula, and relativistic jets from black holes, etc. In this paper, we review the recent progress on kinetic simulations of this process and further discuss plasma dynamics and particle acceleration in a low-β reconnection layer that consists of electron-positron pairs. We also examine the effect of different initial thermal temperatures on the resulting particle energy spectra. While earlier papers have concluded that the spectral index is smaller for higher σ, our simulations show that the spectral index approaches p = 1 for sufficiently low plasma β, even if σ ∼ 1. Since this predicted spectral index in the idealized limit is harder than most observations, it is important to consider effects that can lead to a softer spectrum such as open boundary simulations. We also remark that the effects of 3D reconnection physics and turbulence on reconnection need to be addressed in the future.

The role of three-dimensional transport in driving enhanced electron acceleration during magnetic reconnection

“…This is consistent with studies by Guo et al 26,52,53 , that exhibit no substantial difference in energetic particle production between two and three-dimensional simulations in the relativistic regime.…”

Three‐dimensional outflow jets generated in collisionless magnetic reconnection

“…However, in the electron‐proton plasma, it is found that the amplitude of the B x mode is relatively small and the flux rope structure is mostly determined by the B z mode newly discovered in this study. The present simulation demonstrates that the current‐aligned scale of the flux ropes is controlled by the instability in the electron current layer, but not by the instabilities in the flux ropes themselves [e.g., Guo et al , ]. The flow shear modes are stabilized by the guide field because of the magnetic tension force [ Miura and Pritchett , ; Fujimoto and Sydora , ].…”

FIRSTNuSTAROBSERVATIONS OF MRK 501 WITHIN A RADIO TO TeV MULTI-INSTRUMENT CAMPAIGN

“…Notably, the injected particle populations on MJD 56485.0, 56485.9, and 56486.9 are very hard, with an injection index of q = 1.3. Such a hard injection index is difficult to produce with standard shock acceleration scenarios alone, but is possible through a magnetic reconnection event (e.g., as explained in Romanova & Lovelace 1992;Guo et al 2014;Sironi & Spitkovsky 2014). The increase in energy of the particle population (with an additional hardening to the injection index of q = 1.3) between the SED derived for MJD 56485.0 as compared to MJD 56420 indicates an introduction of additional energetic particles to the emission region, requiring some source of energy input.…”