A possible universal origin of hadronic cosmic rays from ultrarelativistic ejecta of bipolar supernovae

Abstract

Based on the "cannonball model" for gamma-ray bursts of Dar and De Rújula it is proposed that masses of baryonic plasma ("cannonballs"), ejected in bipolar supernova explosions in our Galaxy are the sources of hadronic Galactic cosmic rays (CRs) at all energies. The propagation of the cannonballs in the Galactic disk and halo is studied. Two mechanisms for the acceleration of the observed CRs are proposed. The first is based on ultrarelativistic shocks in the interstellar medium and could accelerate the bulk of CRs up to the "knee" energy of 4 × 10 15 eV. The second operates with second-order Fermi acceleration within the cannonball. If the total initial energy of the ejected plasmoids in a SN explosion is 10 53 ergs or higher this second mechanism may explain the CR spectrum above the knee up to the highest observed energies. It is shown that together with plausible assumptions about CR propagation in the Galactic confinement volume the observed spectral indices of the CR spectrum can be theoretically understood to first order. The model allows a natural understanding of various basic CR observations like the absence of the Greisen-Zatsepin cutoff, the anisotropy of arrival directions as function of energy and the small Galactocentric gradient of the CR density.

Models of the knee in the energy spectrum of cosmic rays

“…Upper right panel: Source and acceleration related models by Erlykin and Wolfendale [22], Plaga [24], as well as Völk and Zirakashvili [23]. Lower left panel: Diffusion models by Kalmykov et al [42], Ogio and Kakimoto [28], as well as Roulet et al [29].…”

“…Völk and Zirakashvili [23] consider reacceleration by spiral shocks in the galactic wind. Plaga [24] proposes cosmic rays being accelerated by cannon balls ejected into the galactic halo.…”

“…Within the framework of the cannonball model, originally proposed by Dar and De Rújula [40] to explain gamma-ray bursts, Plaga [24] discusses a mechanism for the acceleration of cosmicray hadrons. The author investigates if masses of baryonic plasma ("cannonballs"), ejected in bipolar supernova explosions, could be the universal sources of hadronic galactic cosmic rays.…”

A theory of cosmic rays

“…Radio, X-ray and γ-ray observations of supernova remnants (SNRs) provide clear evidence that electrons are accelerated to high energies in these sites. So far, they have not provided unambiguous evidence that SNRs accelerate CR nuclei and are their main source in any energy range [10]. Moreover, SNRs cannot accelerate CRs to energies as large as E[knee] [11], though this point is still debated.…”

“…One prominent example of a discussion of these points is the 1957 review by Philip Morrison [7]. A much later and very incisive example is the commentary by Rainer Plaga in [10]. Yet, having received so much attention in spite of its well-known flaws and limitations, this conventional SNR theory of relatively lowenergy CRs is unlikely to be abandoned.…”