Early acceleration of electrons and protons at the nonrelativistic quasiparallel shocks with different obliquity angles

The early acceleration of protons and electrons in the nonrelativistic collisionless shocks with three obliquities are investigated through 1D particle-in-cell simulations. In the simulations, the charged particles possessing a velocity of 0.2c flow towards a reflecting boundary, and the shocks with a sonic Mach number of 13.4 and an Alfven Mach number of 16.5 in the downstream shock frame are generated.In these quasi-parallel shocks with the obliquity angles θ = 15°, 30° and 45°, some of the protons and the electrons can be injected into the acceleration processes, and their downstream spectra in the momentum space show a power law tail at a time of 1.89 × 10^5ω^-1pe, where ωpe is the electron plasma frequency.Moreover, the charged particles reflected at the shock excite magnetic waves upstream of the shock. The shock drift acceleration is more prominent with a larger obliquity angle for the shocks, but the accelerated particles diffuse parallel to the shock propagation direction more easily to participate in the diffusive shock acceleration. In the early acceleration stage, more energetic protons and electrons appear in the downstream of the shock for θ = 15° compared with the other two obliquities. Moreover, in the upstream region, the spectrum of the accelerated electrons is the hardest for θnB = 45° among the three obliquities, whereas the proton spectra for θnB = 15° and 45° are similar as a result of the competition of the effectiveness of the shock drift acceleration and the diffusive shock acceleration.

Numerically investigating the peculiar periphery of a supernova remnant in the medium with a density gradient:the case of RCW 103

The young shell-type supernova remnant RCW 103 has peculiar properties in the X-ray morphology obtained with Chandra.The southeastern shell is brighter in the X-rays,and the curved border of the shell in this region is flatter than the other part.We investigate the formation of the peculiar periphery of the supernova remnant RCW 103 using 3D hydrodynamical simulation.Assuming that the supernova ejecta has been evolved in the medium with a density gradient,the detected shape of the periphery can be generally reproduced.For RCW 103,with the ejecta mass of 3.0 M,the density of the background material of 2.0 cm^(-3),and a gradient of 3.3-4.0 cm^(-3)pc^(-1),the X-ray periphery can be generally reproduced.The simulation turned out that the asymmetry of the SNR RCW 103 is mainly due to the inhomogeneous medium with a density gradient.

Investigating the morphology of the supernova remnant G349.7+00.2 in the medium with a density gradient

G349.7+00.2 is a young Galactic supernova remnant(SNR)with a mushroom morphology in radio and X-rays,and it has been detected across the entire electromagnetic spectrum from radio to high energyγ-rays.Moreover,the remnant is interacting with a molecular cloud based on the observations in the radio and infrared band.The reason for the formation of the periphery and the dynamical evolution of the remnant is investigated using 3D hydrodynamical(HD)simulations.Under the assumption that the supernova ejecta is evolved in the medium with a density gradient,the shell is composed of two hemispheres with different radii,and the smaller hemisphere is in relatively dense media.The resulting periphery of remnant is consistent with detected ones,and it can be concluded that the peculiar periphery of G349.7+00.2 can be reproduced as the remnants interacting with the medium with a density gradient.