Connecting shock velocities to electron-injection mechanisms

Area of Science:

• Plasma physics
• Astrophysical shock acceleration
• Computational physics

Background:

• Electrons are accelerated to high energies at supernova remnant shocks.
• Diffusive shock acceleration is a primary mechanism, but requires further electron acceleration.
• Electron surfing acceleration by electrostatic waves is a proposed secondary mechanism.

Purpose of the Study:

• To model and compare electron acceleration via wave-electron interactions using particle-in-cell and Vlasov simulations.
• To investigate the role of saturated electrostatic waves in electron acceleration.
• To determine the influence of simulation methods on wave lifetime and surfing acceleration.

Main Methods:

• Utilizing particle-in-cell (PIC) and Vlasov simulations to model wave-electron interactions.
• Simulating nonlinearly saturated electrostatic waves.
• Analyzing electron acceleration dynamics and wave stability.

Main Results:

• Vlasov simulations demonstrate a considerably longer lifetime for saturated waves compared to PIC simulations.
• This difference is attributed to distinct plasma approximations in the simulation methods.
• Surfing acceleration is excluded in both codes for beam speeds exceeding a critical value due to rapid wave collapse.

Conclusions:

• The extended wave lifetime in Vlasov simulations suggests electron surfing acceleration may play a more crucial role at shocks than previously considered.
• The critical beam speed for the exclusion of surfing acceleration due to wave collapse is estimated.
• Simulation method choice significantly impacts the understanding of wave-particle interactions in astrophysical plasmas.