Fast Particle Acceleration in 3D Hybrid Simulations of Quasiperpendicular Shocks

Area of Science:

• Plasma astrophysics
• High-energy astrophysics
• Computational physics

Background:

• The origin of cosmic rays is a fundamental question in astrophysics.
• Particle acceleration at collisionless, nonrelativistic shocks is a proposed mechanism.
• Previous kinetic simulations have not consistently reproduced nonthermal particle tails at quasiperpendicular shocks.

Purpose of the Study:

• To investigate particle acceleration and magnetic field amplification at nonrelativistic, weakly magnetized, quasiperpendicular shocks.
• To determine the conditions conducive to the formation of nonthermal particle tails.

Main Methods:

• Utilized hybrid (kinetic ions-fluid electrons) kinetic simulations.
• Performed simulations in three dimensions (3D) to capture complex shock dynamics.
• Compared 3D results with previous two-dimensional (2D) simulations.

Main Results:

• Protons spontaneously developed a nonthermal tail from the thermal bath in 3D simulations, without pre-existing turbulence.
• Particles were rapidly accelerated via shock drift acceleration.
• A maximum energy was determined by particle escape upstream.

Conclusions:

• Three-dimensional effects are crucial for spontaneous nonthermal tail formation at quasiperpendicular shocks.
• Shock drift acceleration is an effective mechanism for accelerating particles in these environments.
• The findings have implications for understanding particle acceleration in heliospheric shocks, supernova remnants, and radio supernovae.