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SUMMARY:Non-classical diffusion of the cosmic rays in the Galaxy: Energy s
 pectra of primary nuclei
DTSTART;VALUE=DATE-TIME:20210609T080500Z
DTEND;VALUE=DATE-TIME:20210609T082000Z
DTSTAMP;VALUE=DATE-TIME:20261011T214118Z
UID:indico-contribution-149@indico.nevod.mephi.ru
DESCRIPTION:Speakers: Anatoly Lagutin (Altai State University)\nIn the las
 t decade\, measurements of the cosmic ray (CR) nuclei in the GV–TV rigid
 ity region by new-generation balloon-borne and satellite instruments allow
 ed to establish new features in CR spectra. It was found that both spectra
  of most abundant primary CR nuclei and the secondary cosmic rays at rigid
 ity $R > 100−200$ GV exhibit a hardening with increasing rigidity. Thus 
 they deviate from a single power law.\n\nThese newly discovered features a
 re not easy to explain under standard scenario of cosmic ray origin\, acce
 leration and propagation in the Galaxy. Under the standard theory\, the pr
 imary nuclei are thought to be produced\, up to at least several PV\, by s
 upernova remnant shock waves by diffusive shock acceleration mechanism tha
 t predicts power-law spectra $J \\propto R^{−\\gamma}$ with slope $\\gam
 ma ≈ 2.0 − 2.2$. The subsequent CR transport in the turbulent Galactic
  magnetic fields is modeled as a diffusion process in quasi-homogeneous me
 dium with the diffusion coefficient $D(R) = D_0 (R/1$ GV$)^\\delta$\, with
  $\\delta \\approx  (0.3 − 0.8)$. Under these assumptions\, the spectrum
  of primary nucleus $i$ generated by the global-scale steady state distrib
 ution of sources $S(r\,R)$ is described by a single power law with index $
 \\eta = \\gamma + \\delta$\, which is clearly at odds with the observed ha
 rdening of CR hadrons at GV–TV region.\n\nHowever\, theory and observati
 ons show that the ISM is inhomogeneous (fractal-like) at the scale of hund
 reds of parsecs. Stars formation regions also demonstrate fractal features
  with spatial scales up to about a kpc. Since the particles emitted by Gal
 actic sources en route to the Solar system pass through regions of the Gal
 axy that have different properties\, in such a inhomogeneous ISM\, the nor
 mal diffusion model is certainly not kept valid.\n\nThe non-homogeneous ch
 aracter of matter distribution and associated spatially intermittent magne
 tic field leads to the need to incorporate these ISM features into the cos
 mic ray diffusion model. A possible way to generalize the normal diffusion
  model is to replace the assumption about statistical homogeneity of inhom
 ogeneities distribution by their fractal distribution. Non-classical diffu
 sion  is manifested\, in particular\, by abnormally large free paths of pa
 rticles (so-called “Lévy flights”) and a long stay of particles in in
 homogeneities\, leading to a presence of the so-called “Lévy traps”.\
 n\nIn the current study\, we demonstrate that non-classical diffusion mode
 l of the cosmic rays in the inhomogeneous Galaxy\, developed by the author
 s\, allows to describe the main features of nuclei spectra observed in the
  Solar system. Particularly\, in this model the key feature of the all par
 ticle energy spectrum — the knee at 3$\\cdot10^{15}$ eV — appears natu
 rally without additional assumptions. The observed changes in the slope of
  energy spectra of primary nuclei at rigidity $R > 100−200$ GV caused by
  the transition from the contribution of multiple distant Galactic sources
  to the contribution of mainly local ones.\n\nhttps://indico.nevod.mephi.r
 u/event/6/contributions/149/
LOCATION:Online Zoom
URL:https://indico.nevod.mephi.ru/event/6/contributions/149/
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