{
  "id": "1502.01799",
  "version": "v1",
  "published": "2015-02-06T05:27:20.000Z",
  "updated": "2015-02-06T05:27:20.000Z",
  "title": "Cosmic Ray Transport with Magnetic Focusing and the \"Telegraph\" model",
  "authors": [
    "Mikhail Malkov",
    "Roald Sagdeev"
  ],
  "comment": "14 pages, no figures",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Cosmic rays (CR), constrained by scattering on magnetic irregularities, are believed to propagate diffusively. But a well-known defect of diffusive approximation, whereby not all the particles propagate at realistic speeds, causes attempts to justify an alternative approach based on the \"telegraph\" equation. However, its derivations often lack rigor and transparency leading to incorrect results. The classic Chapman-Enskog method is applied to the pitch-angle averaged spatial CR transport. We show that the convective term arises only from the magnetic focusing effect and no telegraph (second order time derivative) term emerges in any order of the proper asymptotic expansion with systematically eliminated short time scales. However, this term may formally be converted from the fourth order hyper-diffusive term in the Chapman-Enskog expansion. But, within the method's validity range, it may only be important for a short relaxation period associated with either strong pitch-angle anisotropy or spatial inhomogeneity of the initial CR distribution. However, in neither of these two cases a treatment based on merely the isotropic CR component is sufficient, regardless of the correction type (telegraph or hyper-diffusive). Moreover, in a long-time asymptotic regime these corrections are generally insignificant, as the angular anisotropy decays rapidly.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-02-06T05:27:20.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cosmic ray transport",
      "magnetic focusing",
      "eliminated short time scales",
      "pitch-angle averaged spatial cr transport"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/808/2/157"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1343293
    }
  }
}