Direct Evidence for Magnetic Reflection of Heavy Ions from High Mach Number Collisionless Shocks

Abstract

Strong shocks in collisionless plasmas, such as supernovae shocks and shocks driven by coronal mass ejections, are known to be a primary source of energetic particles. Due to their different mass per charge ratio, the interaction of heavy ions with the shock layer differs from that of protons, and injection of these ions into acceleration processes is a challenge. Here we show the first direct observational evidence of magnetic reflection of alpha particles from a high Mach number quasi-perpendicular shock using in-situ spacecraft measurements. The intense magnetic amplification at the shock front associated with nonstationarity modulates the trajectory of alpha particles, some of which travel back upstream as they gyrate in the enhanced magnetic field and experience further acceleration in the upstream region. Our results in particular highlight the important role of high magnetic amplification in seeding heavy ions into the energization processes at nonstationary reforming shocks.

References in corpus (5)

• Simulations and Theory of Ion Injection at Non-relativistic Collisionless Shocks
• Simulations of Ion Acceleration at Non-relativistic Shocks. III. Particle Diffusion
• Non-linear diffusive acceleration of heavy nuclei in supernova remnant shocks
• Collisionless shock heating of heavy ions in SN 1987A
• The Dynamics of a High Mach Number Quasi-Perpendicular Shock: MMS Observations

Cited by in corpus (3)

• Competitive X-ray and Optical Cooling in the Collisionless Shocks of WR 140
• Drivers of Magnetic Field Amplification at Oblique Shocks: In-Situ Observations
• Interaction of the Prominence Plasma within the Magnetic Cloud of an ICME with the Earth's Bow Shock