Velocity-space compression from Fermi acceleration with Lorentz scattering

Journal Article · 24 January 2022 · Physical Review. E

DOI: https://doi.org/10.1103/physreve.105.015207 · OSTI ID:1980199

Waybright, J. C. ^[1]; Mlodik, M. E. ^[2]; Fisch, N. J.  ^[2]

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1. Princeton Univ., NJ (United States); OSTI
2. Princeton Univ., NJ (United States)

The Fermi acceleration model describes how cosmic ray particles accelerate to great speeds by interacting with moving magnetic fields. In this work, we identify a variation of the model where light ions interact with a moving wall while undergoing pitch angle scattering through Coulomb collisions due to the presence of a heavier ionic species. The collisions introduce a stochastic component which adds complexity to the particle acceleration profile and sets it apart from collisionless Fermi acceleration models. The unusual effect captured by this simplified variation of Fermi acceleration is the nonconservation of phase space, with the possibility for a distribution of particles initially monotonically decreasing in energy to exhibit an energy peak upon compression. A peaked energy distribution might have interesting applications, such as to optimize fusion reactivity or to characterize astrophysical phenomena that exhibit nonthermal features.

• Research Organization: Princeton Univ., NJ (United States)
• Sponsoring Organization: USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
• Grant/Contract Number: SC0021248
• OSTI ID: 1980199
• Journal Information: Physical Review. E, Journal Name: Physical Review. E Journal Issue: 1 Vol. 105; ISSN 2470-0045
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English