English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We derive a consistent set of moments equations for CR-magnetohydrodynamics,assuming a gyrotropic distribution function (DF). Unlike previous efforts wederive a closure, akin to the M1 closure in radiation hydrodynamics (RHD), thatis valid in both the nearly-isotropic-DF and/or strong-scattering regimes, andthe arbitrarily-anisotropic DF or free-streaming regimes, as well as allowingfor anisotropic scattering and transport/magnetic field structure. We presentthe appropriate two-moment closure and equations for various choices of evolvedvariables, including the CR phase space distribution function, number density,total energy, kinetic energy, and their fluxes or higher moments, and theappropriate coupling terms to the gas. We show that this naturally includes andgeneralizes a variety of terms including convection/fluid motion, anisotropicCR pressure, streaming, diffusion, gyro-resonant/streaming losses, andre-acceleration. We discuss how this extends previous treatments of CRtransport including diffusion and moments methods and popular forms of theFokker-Planck equation, as well as how this differs from the analogous M1-RHDequations. We also present two different methods for incorporating a reducedspeed of light (RSOL) to reduce timestep limitations: in both we carefullyaddress where the RSOL (versus true c) must appear for the correct behavior tobe recovered in all interesting limits, and show how current implementations ofCRs with a RSOL neglect some additional terms.

A Consistent Reduced-Speed-of-Light Formulation of Cosmic Ray Transport Valid in Weak and Strong-Scattering Regimes