Self-confinement of low-energy cosmic rays around supernova remnants

Abstract

Supernova remnants have long been considered as a promising candidate for sources of Galactic cosmic rays. However, modelling cosmic-ray transport around these sources is complicated by the fact that the overdensity of cosmic rays close to their acceleration site can lead to self-confinement, that is the generation of turbulence upon which these particles scatter. Such a highly non-linear problem can be addressed by numerically solving the coupled differential equations describing the evolution in space and time of the escaping particles and of the turbulent plasma waves. In this work, we focus essentially on the propagation of cosmic rays from supernova remnants in the warm ionized and warm neutral phases of the interstellar medium and propose an extended framework to take into account also the effect of energy loss relevant for cosmic rays of energy below 10 GeV. Interestingly, the diffusion coefficient of low-energy cosmic rays could be suppressed by up to 2 orders of magnitude for several tens of kiloyears after the escape from the shock. The cosmic-ray spectrum outside the supernova remnant flattens below 1 GeV at a sufficiently late time reminiscient of the spectral behaviour observed by Voyager. We also find the grammage accumulated around the source to be non-negligible, with important implications for precision fitting of the cosmic-ray spectra.

The self-confinement of electrons and positrons from dark matter

“…(2.4) with Γ IND as described in ref. [25]. By considering reasonable plasma densities for dwarf galaxies, we found that damping is not relevant in these systems.…”

“…For resonant interaction between Alfvén waves and CR scattering, the wave number k and the momentum p of the CR are related by via the Larmor radius, r L (p res ) = 1/k res 3.3 × 10 7 (E/GeV) (µG/B 0 ) km. Turbulence in a galaxy with sizeable star formation rate, such as the Milky Way, is usually assumed to be injected in the system as an astrophysical feedback, such as from supernova explosions [22]; on the other hand, recent reanalyses -mostly in connection to spectral features in local CR fluxes -have shown that streaming instabilities of CR themselves may be an additional and relevant source of turbulence in the Galaxy [23][24][25]. Self-generation of magnetic turbulence is also studied as a solution to the observed inhibited diffusion in TeV halos around pulsar wind nebulae [26,27].…”

“…with the numerical factor c k = 0.052. The growth rate of the turbulence through streaming instability is given by [24,25]:…”

Fast and accurate AMS-02 antiproton likelihoods for global dark matter fits

“…Particle-in-cell simulations have demonstrated that this mechanism produces power-law spectra for the accelerated particles [54], which can be modified during their escape from the remnant [55,56]. In addition, a break in the injection spectrum at low energies is required to explain data at about few GeV, which could be connected to self-confinement of particles in supernova remnants [57].…”

Diffuse Emission of Galactic High-energy Neutrinos from a Global Fit of Cosmic Rays

“…Such spectral breaks have been observed in the gamma-ray spectra of supernova remnants (SNRs) by Fermi-LAT (Abdo et al 2009a(Abdo et al , 2009b(Abdo et al , 2010a(Abdo et al , 2010b. One possibility is that the break in the diffusion coefficient is due to self-confinement of GCRs in the near-source environment (Jacobs et al 2022). Such a break has also been introduced into models of GCRs on purely phenomenological grounds in order to achieve a better fit to locally measured spectra when not including reacceleration, as is the case for the model constructed here.…”