Details

Autor(en) / Beteiligte

• Webb, G. M.
• Xu, Y.
• Biermann, P. L.
• Al-Nussirat, S.
• Mostafavi, P.
• Li, G.
• Barghouty, A. F.
• Zank, G. P.

Titel

Acceleration and Spectral Redistribution of Cosmic Rays in Radio-jet Shear Flows

Ist Teil von

• The Astrophysical journal, 2023-12, Vol.958 (2), p.169

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2023

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract A steady-state, semi-analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity obtained by Webb et al. is generalized to take into account more general cosmic-ray boundary spectra. This involves solving a mixed Dirichlet–Von Neumann boundary value problem at the edge of the jet. The energetic particle distribution function f 0 ( r , p ) at cylindrical radius r from the jet axis (assumed to lie along the z -axis) is given by convolving the particle momentum spectrum f 0 ( ∞ , p ′ ) with the Green’s function G ( r , p ; p ′ ) , which describes the monoenergetic spectrum solution in which f 0 → δ ( p − p ′ ) as r → ∞ . Previous work by Webb et al. studied only the Green’s function solution for G ( r , p ; p ′ ) . In this paper, we explore for the first time, solutions for more general and realistic forms for f 0 ( ∞ , p ′ ) . The flow velocity u = u ( r ) e z is along the axis of the jet (the z -axis). u is independent of z , and u ( r ) is a monotonic decreasing function of r . The scattering time τ ( r , p ) = τ 0 ( p / p 0 ) α in the shear flow region 0 < r < r 2 , and τ ( r , p ) = τ 0 ( p / p 0 ) α ( r / r 2 ) s , where s > 0 in the region r > r 2 is outside the jet. Other original aspects of the analysis are (i) the use of cosmic ray flow lines in ( r , p ) space to clarify the particle spatial transport and momentum changes and (ii) the determination of the probability distribution ψ p ( r , p ; p ′ ) that particles observed at ( r , p ) originated from r → ∞ with momentum p ′ . The acceleration of ultrahigh-energy cosmic rays in active galactic nuclei jet sources is discussed. Leaky box models for electron acceleration are described.