Electron and positron spectra in three-dimensional spatial-dependent propagation model *

Abstract

The spatial-dependent propagation (SDP) model has been demonstrated to account for the spectral hardening of both primary and secondary Cosmic Rays (CRs) nuclei above about 200 GV. In this work, we further apply this model to the latest AMS-02 observations of electrons and positrons. To investigate the effect of different propagation models, both homogeneous diffusion and SDP are compared. In contrast to the homogeneous diffusion, SDP brings about harder spectra of background CRs and thus enhances background electron and positron fluxes above tens of GeV. Thereby, the SDP model could better reproduce both electron and positron energy spectra when introducing a local pulsar. The influence of the background source distribution is also investigated, where both axisymmetric and spiral distributions are compared. We find that considering the spiral distribution leads to a larger contribution of positrons for energies above multi-GeV than the axisymmetric distribution. In the SDP model, when including a spiral distribution of sources, the all-electron spectrum above TeV energies is thus naturally described. In the meantime, the estimated anisotropies in the all-electrons spectrum show that in contrary to the homogeneous diffusion model, the anisotropy under SDP is well below the observational limits set by the Fermi-LAT experiment, even when considering a local source.

Statistically study the optimal local sources for cosmic ray nuclei and electron

“…It was first introduced as a Two Halo model (THM) (Tomassetti 2012) to explain the spectral hardening of both proton and helium above 200 GeV (Adriani et al 2011). Afterwards, it is further applied to secondary and heavier components (Tomassetti 2015;Feng et al 2016;Guo et al 2016;Liu et al 2018;Tian et al 2020;Yuan et al 2020), diffuse gamma-ray distribution (Guo & Yuan 2018) and large-scale anisotropy (Liu et al 2019;Qiao et al 2019). For a comprehensive introduction, one can refer to Guo et al (2016) and Liu et al (2018).…”

“…where r and z are cylindrical coordinate, R is the particle's rigidity, β is the particle's velocity in unit of light speed, D 0 and η are constants. For the parameteriza-tion of F (r, z) and δ(r, z), one can refer to (Tian et al 2020). The total half-thickness of the propagation halo is z h , and the half-thickness of the inner halo is ξz h .…”

Ultrahigh-energy diffuse gamma-ray emission from cosmic-ray interactions with medium surrounding acceleration sources

“…It has been recognized in recent years that the propagation of CRs in the Milky Way should depend on the spatial locations, as inferred by the HAWC observations of extended γ-ray halos around pulsars (Abeysekara et al 2017) and the spatial variations of the CR intensities and spectral indices from Fermi-LAT observations (Yang et al 2016;Acero et al 2016). The spatially-dependent propagation (SDP) model was also proposed to explain the observed hardenings of CRs (Tomassetti 2012(Tomassetti , 2015Feng et al 2016;Guo et al 2016b;Liu et al 2018;Guo & Yuan 2018;Tian et al 2020), and also the large-scale anisotropies with the help of a nearby source (Liu et al 2019;Qiao et al 2019;Yuan et al 2021).…”

The expectation of LHAASO sensitivity on the cosmic-ray electron

“…• WCDA, covering an area of about 78,000 m 2 In order to enlarge the dynamic range, a 1.5-inch PMT is placed aside each large PMT in one of the two smaller ponds.…”

“…As discussed in [1], TeV electrons lost most of their energy on a time scale of 10 5 yr and their propagation distances are therefore confined by several hundred parsecs. Spatial distribution of nearby sources [1] and new cosmic ray propagation models [2] may produce significant deviations in the most energetic part of the observed spectrum compared to the conventional state calculated by the GALPROP interstellar propagation code [3]. Measuring the spectrum of CREs above TeV energy is important to constrain the models of the cosmic ray's propagation and search for the nearby sources.…”