We investigate particle acceleration in an MHDscale system of multiple current sheets by performing 2D and 3D MHD simulations combined with a test particle simulation. The system is unstable for the tearingmode instability, and magnetic islands are produced by magnetic reconnection. Due to the interaction of magnetic islands, the system relaxes to a turbulent state. The 2D (3D) case both yield −5/3 (− 11/3 and −7/3) powerlaw spectra for magnetic and velocity fluctuations. Particles are efficiently energized by the generated turbulence, and form a powerlaw tail with an index of −2.2 and −4.2 in the energy distribution function for the 2D and 3D case, respectively. We find more energetic particles outside magnetic islands than inside. We observe superdiffusion in the 2D (∼ t 2.27 ) and 3D (∼ t 1.2 ) case in the energy space of energetic particles.
This content will become publicly available on December 1, 2022
Interaction between Multiple Current Sheets and a Shock Wave: 2D Hybrid Kinetic Simulations
Abstract Particle acceleration behind a shock wave due to interactions between magnetic islands in the heliosphere has attracted attention in recent years. The downstream acceleration may yield a continuous increase of particle flux downstream of the shock wave. Although it is not obvious how the downstream magnetic islands are produced, it has been suggested that current sheets are involved in the generation of magnetic islands due to their interaction with a shock wave. We perform 2D hybrid kinetic simulations to investigate the interaction between multiple current sheets and a shock wave. In the simulation, current sheets are compressed by the shock wave and a tearing instability develops at the compressed current sheets downstream of the shock. As the result of this instability, the electromagnetic fields become turbulent and magnetic islands form well downstream of the shock wave. We find a “postcursor” region in which the downstream flow speed normal to the shock wave in the downstream rest frame is decelerated to ∼ 1 V A immediately behind the shock wave, where V A is the upstream Alfvén speed. The flow speed then gradually decelerates to 0 accompanied by the development of the tearing instability. We also observe an efficient production more »
 Award ID(s):
 1655280
 Publication Date:
 NSFPAR ID:
 10308614
 Journal Name:
 The Astrophysical Journal
 Volume:
 922
 Issue:
 2
 ISSN:
 0004637X
 Sponsoring Org:
 National Science Foundation
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