Related papers: Multi-wavelength Emission from the Fermi Bubble I.…
The physics of particle acceleration in turbulent plasmas is a topic of broad interest, which is making rapid progress thanks to dedicated, large-scale numerical experiments. The first part of this paper presents an effective theory of…
In this paper we investigate the feasibility of bremsstrahlung radiation from `nonthermal' electrons as a source of hard X-rays from the intracluster medium of clusters of galaxies. With an exact treatment of the Coulomb collisions in a…
In turbulent magnetized plasmas, charged particles can be accelerated to high energies through their interactions with the turbulent motions. As they do so, they draw energy from the turbulence, possibly up to the point where they start…
Recent observations of excess radiation at extreme ultraviolet and hard X-ray energies straddling the well known thermal soft X-ray emission have provided new tools and puzzles for investigation of the acceleration of nonthermal particles…
We simulate, using a particle-in-cell code, the chain of acceleration processes at work during the Compton-based interaction of a dilute electron-ion plasma with an extreme-intensity, incoherent gamma-ray flux with a photon density several…
Particle acceleration is expected to take place at shocks that form during the process of large scale structure formation. Electrons accelerated at such shocks can upscatter a small fraction of the photons in the cosmic microwave background…
Due to its ubiquitous presence, turbulence is often invoked to explain the origin of nonthermal particles in astrophysical sources of high-energy emission. With particle-in-cell simulations, we study decaying turbulence in…
Context: The origin of Galactic cosmic rays is still a mystery, in particular the sources and acceleration mechanism for cosmic rays with energies up to or beyond a PeV. Recently LHAASO has and H.E.S.S have shown that two gamma-ray sources…
Gamma-ray bursts are generally considered to be the result of internal shocks generated in an inhomogeneous relativistic outflow that arises from a fireball. In such shocks, the Fermi acceleration of protons is naturally expected to be at…
We examine Fermi-type acceleration at relativistic shocks, and distinguish between the initial boost of the first shock crossing cycle, where the energy gain per particle can be very large, and the Fermi process proper with repeated shock…
Two enigmatic gamma-ray features in the Galactic central region, known as Fermi Bubbles (FBs), were found from Fermi-LAT data. An energy release (e.g., by tidal disruption events in the Galactic center, GC), generates a cavity with a shock…
Intense electromagnetic pulses interacting with a plasma can create a wake of plasma oscillations. Electrons trapped in such oscillations can be accelerated under certain conditions to very high energies. We study the conditions for the…
In highly conducting astrophysical plasmas, charged particles are generically accelerated through Fermi-type processes involving repeated interactions with moving magnetized scattering centers. The present paper proposes a generalized…
Electron acceleration to non-thermal energies is known to occur in low Mach number (M<5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D)…
Collisionless plasma shock theory, which applies for example to the afterglow of gamma ray bursts, still contains key issues that are poorly understood. In this paper we study charged particle dynamics in a highly relativistic collisionless…
We propose the model of the global structure of the electromagnetic fields in the Fermi bubbles (FBs), which makes possible the proton regular acceleration up to ultra-high energies. The poloidal and the toroidal magnetic fields, as well as…
Radio observations at low frequencies with the Low Frequency Array (LOFAR) start discovering gigantic radio bridges connecting pairs of massive galaxy clusters. These observations probe unexplored mechanisms of in situ particle acceleration…
We study collective processes for an electron beam propagating through a background plasma using simulations and analytical theory. A new regime where the instability of a Langmuir wave packet can grow locally much faster than ion frequency…
The Fermi bubbles (FBs) are large gamma-ray emitting lobes extending up to $55\deg$ in latitude above and below the Galactic center (GC). Although the FBs were discovered 8 years ago, their origin and the nature of the gamma-ray emission…
This proceedings paper reports on the theoretical modelling of particle acceleration in magnetised turbulent plasmas. It briefly reviews some recent findings obtained from fully kinetic numerical simulations of large-amplitude, semi to…