On the Jitter Radiation

Abstract

In a small scale turbulent medium, when the nonrelativistic Larmor radius R L = mc 2 /eB exceeds the correlation length λ of the magnetic field, the magnetic bremsstrahlung of charged relativistic particles unavoidably proceeds in the so-called jitter radiation regime. The cooling timescale of parent particles is identical to the synchrotron cooling time, thus this radiation regime can be produced with very high efficiency in different astrophysical sources characterized by high turbulence. The jitter radiation has distinct spectral features shifted, compared to synchrotron radiation, towards high energies. This makes the jitter mechanism an attractive broad-band gamma-ray production channel which in highly magnetized and turbulent environments can compete or even dominate over other high energy radiation mechanisms. In this paper we present a novel study on spectral properties of the jitter radiation performed within the framework of perturbation theory. The derived general expression for the spectral power of radiation is presented in a compact and convenient for numerical calculations form.

Polarization Radiation with Turbulent Magnetic Fields from X-Ray Binaries

“…This unique feature of jitter radiation implies direct, model-independent information about the properties of turbulence spectrum. However, synchrotron emission can provide information on energy spectral shapes of emitting relativistic electrons, which is associated with different acceleration mechanisms (see also Kelner et al 2013, for more discussions). With decreasing the angle ϕ, intensities of both jitter and synchrotron radiation increase, which are anti-correlated with their linear polarization degrees.…”

“…For the same mean magnetic field, an electron energy loss due to synchrotron or jitter emission is the same in the large-and small-scale turbulent magnetic fields. However, in the realistic microquasar jet environment, the ratio of the jitter radiation intensity to synchrotron emission one (due to electron population) can be expressed as (Kelner et al 2013), where p ′ is the power-law spectral index of emitting electrons. Therefore, the presence of the large-scale magnetic fields would increase the total radiation fluxes and the corresponding polarization degree.…”

“…In the simulation of synthetical data cube of MHD turbulence, it is usually regarded as a Gauss type distribution with narrow dispersion (e.g., Zhang et al 2016). In some case, a power-law form with wide dispersion is also used (e.g., Kelner et al 2013;Prosekin et al 2016). Besides, in the environment mixing large-and small-scale turbulent magnetic fields, their relative strengths are still needed to further study theoretically.…”

“…Here, B is the strength of the magnetic field as a function of the height of the jet, and other parameters have a conventional meaning. On the contrary, λ ≪ R L , the emission is referred to as diffusive synchrotron radiation (Toptygin & Fleishman 1987), or jitter radiation (Medvedev 2000;Kelner et al 2013). Below, we first study the evolution of relativistic electrons in jets, which has an isotropic distribution along the jets.…”

“…We consider that random, turbulent magnetic fields appear in the jet of black hole X-ray binaries (see Laing 1980;Kelner et al 2013;Prosekin et al 2016 for theoretical basics). These magnetic fields mixed by large-and small-scale random structures are confined to a certain plane (slab), i.e., the limiting case of a three-dimensional geometry of the total compression, which results in the polarized synchrotron and jitter emissions.…”