Laboratory evidence for proton energization by collisionless shock surfing

Abstract

Charged particles can be accelerated to high energies by collisionless shock waves in astrophysical environments, such as supernova remnants. By interacting with the magnetized ambient medium, these shocks can transfer energy to particles. Despite increasing efforts in the characterization of these shocks from satellite measurements at the Earth's bow shock and powerful numerical simulations, the underlying acceleration mechanism or a combination thereof is still widely debated. Here, we show that astrophysically relevant super-critical quasi-perpendicular magnetized collisionless shocks can be produced and characterized in the laboratory. We observe characteristics of super-criticality in the shock profile as well as the energization of protons picked up from the ambient gas to hundreds of keV. Kinetic simulations modelling the laboratory experiment identified shock surfing as the proton acceleration mechanism. Our observations not only provide the direct evidence of early stage ion energization by collisionless shocks, but they also highlight the role this particular mechanism plays in energizing ambient ions to feed further stages of acceleration. Furthermore, our results open the door to future laboratory experiments investigating the possible transition to other mechanisms, when increasing the magnetic field strength, or the effect induced shock front ripples could have on acceleration processes.

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Cited by in corpus (9)

• Particle energization in colliding subcritical collisionless shocks investigated in the laboratory
• Characterization of the stability and dynamics of a laser-produced plasma expanding across strong magnetic field
• High-power laser experiment on developing supercritical shock propagating in homogeneously magnetized plasma of ambient gas origin
• Criteria for ion acceleration in laboratory magnetized quasi-perpendicular collisionless shocks: when are 2D simulations enough?
• Observation of Fermi acceleration with cold atoms
• Investigating particle acceleration dynamics in interpenetrating magnetized collisionless super-critical shocks
• Detailed characterization of laboratory magnetized super-critical collisionless shock and of the associated proton energization
• Plasma Flow Generation and Particle Acceleration from Expanding Magnetic Bubbles
• Biermann-battery driven magnetized collisionless shock precursors in laser produced plasmas