Related papers: Multi-wavelength Emission from the Fermi Bubble I.…
We study the narrowest spectra expected from gamma-ray bursts. We present an analytical function for the spectrum that is emitted from the photosphere of a radiation-dominated flow that is under acceleration. This is the narrowest possible…
The Fermi bubbles were possibly created by large injections of energy into the Galactic Center (GC), either by an active galactic nucleus (AGN) or by nuclear starburst more than ~10 Myr ago. However, the origin of the diffuse gamma-ray…
The prompt emission of gamma-ray bursts (GRBs) is widely thought to be radiation from accelerated electrons, but an appreciably larger amount of energy could be carried by accelerated protons, particularly if GRBs are the sources of…
Laser-accelerated electron beams have been created at a kHz repetition rate from the {\it reflection} of intense ($\sim10^{18}$ W/cm$^2$), $\sim$40 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research…
Turbulence is often invoked to explain the origin of nonthermal particles in space and astrophysical plasmas. By means of 3D fully kinetic particle-in-cell simulations, we demonstrate that turbulence in low-$\beta$ plasmas ($\beta$ is the…
We derive an upper limit to the energy of nuclei accelerated via the Fermi mechanism in any relativistic shockwave, driven by any astrophysical engine. This bound is accessible to current and upcoming ultra-high energy neutrino experiments.…
We consider the radiative acceleration to relativistic bulk velocities of a cold, optically thin plasma which is exposed to an external source of gamma-rays. The flow is driven by radiative momentum input to the gas, the accelerating force…
Generation of anomalously energetic suprathermal electrons was observed in simulation of a high- voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in…
Particle acceleration at astrophysical shocks may be very efficient if magnetic scattering is self-generated by the same particles. This nonlinear process adds to the nonlinear modification of the shock due to the dynamical reaction of the…
A new concept is proposed for accelerating positrons in a nonlinear plasma wakefield accelerator. By loading the wakefield (back of the plasma bubble) with a short electron bunch, an extended area of excessive plasma electron accumulation…
We undertake an investigation of particle acceleration in the context of non-linear electrodynamics. We deduce the maximum energy that an electron can gain in a non-linear density wave in a magnetised plasma, and we show that an electron…
Fermi bubbles, the recently observed giant (~10 kpc high) gamma-ray emitting lobes on either side of our Galaxy (Su et al. 2010), appear morphologically connected to the Galactic center, and thus offer a chance to test several models of…
A recent analysis of the Fermi Large Area Telescope data provided evidence for a high-intensity emission of high-energy gamma rays with a E^-2 spectrum from two large areas, spanning 50{\deg} above and below the Galactic centre (the "Fermi…
The spectral shape of the prompt emissions of gamma-ray bursts (GRBs) is typically expressed by the Band function: smooth joining of two power-law functions for high-energy and low-energy regions. To reveal the origin of the Band function,…
We derive an analytic model for nonlinear "photon bubble" wave trains driven by buoyancy forces in magnetized, radiation pressure-dominated atmospheres. Continuous, periodic wave solutions exist when radiative diffusion is slow compared to…
The origin of cosmic rays in our Galaxy remains a subject of active debate. While supernova remnant shocks are often invoked as the sites of acceleration, it is now widely accepted that the difficulties of such sources in reaching PeV…
We include a general form for the scattering mean free path in a nonlinear Monte Carlo model of relativistic shock formation and Fermi acceleration. Particle-in-cell (PIC) simulations, as well as analytic work, suggest that relativistic…
In the leptonic scenario for TeV emission from a few well-observed shell-type TeV supernova remnants (STTSNRs), very weak magnetic fields are inferred. If fast-mode waves are produced efficiently in the shock downstream, we show that they…
Gamma-ray emission from large structures is useful for tracing the propagation and distribution of cosmic rays throughout our Galaxy. For example, the search for gamma-ray emission from Giant Molecular Clouds may allow us to probe the flux…
The Fermi Bubbles, which comprise two large and homogeneous regions of spectrally hard gamma-ray emission extending up to $55^{o}$ above and below the Galactic Center, were first noticed in GeV gamma-ray data from the Fermi Telescope in…