29 research outputs found
Diffusive Shock Acceleration of Cosmic Rays -- Quasi-thermal and Non-thermal Particle Distributions
A well-known paradigm about the origin of Galactic cosmic rays (CRs) is that
these high-energy particles are accelerated in the process of diffusive shock
acceleration (DSA) at collisionless shocks (at least up to the so-called
"knee"energy of eV). Knowing the details of injection of electrons,
protons and heavier nuclei into the DSA, their initial and the resulting
spectrum, is extremely important in many "practical" applications of the CR
astrophysics, e.g. in modelling of the gamma or synchrotron radio emission of
astrophysical sources. In this contribution I we will give an overview of the
DSA theory and the results of observations and kinetic Particle-In-Cell (PIC)
simulations that support the basic theoretical concepts. PIC simulations of
quasi-parallel collisionless shocks show that thermal and supra-thermal proton
distribution functions at the shock can be represented by a single
quasi-thermal distribution - the -distribution that is commonly
observed in out-of-equilibrium space plasmas. Farther downstream, index
increases and the low-energy spectrum tends to Maxwell distribution.
On the other hand, higher-energy particles continue through the acceleration
process and the non-thermal particle spectrum takes a characteristic power-law
form predicted by the linear DSA theory. In the end, I will show what
modification of the spectra is expected in the non-linear DSA, when CR
back-reaction to the shock is taken into account.Comment: 13 pages, 5 figures, 11th International Conference of the Balkan
Physical Union (BPU11), 28 August - 1 September 2022, Belgrade, Serbi
Radial Dependence of Extinction in Parent Galaxies of Supernovae
The problem of extinction is the most important issue to be dealt with in the
process of obtaining true absolute magnitudes of core-collapse supernovae
(SNe). The plane-parallel model which gives absorption dependent on galaxy
inclination, widely used in the past, was shown not to describe extinction
adequately. We try to apply an alternative model which introduces radial
ependence of extinction. A certain trend of dimmer SNe with decreasing radius
from the center of a galaxy was found, for a chosen sample of stripped-envelope
SNe.Comment: 4 pages, 1 table, 2 figures, 6th SCSLSA Pro