Synchrotron radiation

About: Synchrotron radiation is a research topic. Over the lifetime, 14639 publications have been published within this topic receiving 244775 citations. The topic is also known as: magnetobremsstrahlung radiation & Synchrotron Radiation.

Klein-Nishina effects in the spectra of non-thermal sources immersed in external radiation fields

Abstract: We provide a systematic numerical and analytical study of Klein-Nishina (KN) effects in the spectrum produced by a steady-state, non-thermal source where rapidly accelerated electrons cool by emitting synchrotron radiation and Compton up-scattering ambient photons produced outside the source. We focus on the case where q, the ratio of the ambient radiation field to source magnetic field energy densities, significantly exceeds unity. We show that the KN reduction in the electron Compton cooling rate causes the steady-state electron spectrum to harden at energies γ? γ KN , where γ KN = 1/4∈ 0 and ∈ 0 = hv 0 /m e c 2 is the characteristic ambient photon energy. This hardening becomes noticeable in the synchrotron radiation from electrons with energies as low as 0.1 γ KN and changes the synchrotron spectral index relative to its Thomson limit value by as much as Aa ∼0.75 for q >> 1. The source synchrotron spectrum thus shows a high-energy 'bump' or excess, even though the electron acceleration spectrum has no such excess. In contrast, the low-energy Compton gamma-ray spectrum shows little distortion because the electron hardening compensates for the KN decline in the scattering rate. For sufficiently high electron energies, however, Compton cooling becomes so inefficient that synchrotron cooling dominates - an effect omitted in most previous studies. The hardening of the electron distribution thus stops, leading to a rapid decline in Compton gamma-ray emission, i.e. a strong spectral break whose location does not depend on the maximum electron energy. This break can limit the importance of Compton gamma-ray pair production on ambient photons and implies that a source's synchrotron luminosity may exceed its Compton luminosity even though q > 1. We discuss the importance of these KN effects in blazars, micro-quasars and pulsar binaries.

A γ-ray burst with a high-energy spectral component inconsistent with the synchrotron shock model

Abstract: Gamma-ray bursts are among the most powerful events in nature. These events release most of their energy as photons with energies in the range from 30 keV to a few MeV, with a smaller fraction of the energy radiated in radio, optical, and soft X-ray afterglows. The data are in general agreement with a relativistic shock model, where the prompt and afterglow emissions correspond to synchrotron radiation from shock-accelerated electrons. Here we report an observation of a high-energy (multi-MeV) spectral component in the burst of 17 October 1994 that is distinct from the previously observed lower-energy gamma-ray component. The flux of the high-energy component decays more slowly and its fluence is greater than the lower-energy component; it is described by a power law of differential photon number index approximately -1 up to about 200 MeV. This observation is difficult to explain with the standard synchrotron shock model, suggesting the presence of new phenomena such as a different non-thermal electron process, or the interaction of relativistic protons with photons at the source.

Femtosecond x-ray pulses of synchrotron radiation.

Abstract: A method capable of producing femtosecond pulses of synchrotron radiation is proposed. It is based on the interaction of femtosecond light pulses with electrons in a storage ring. The application of the method to the generation of ultrashort x-ray pulses at the Advanced Light Source of Lawrence Berkeley National Laboratory has been considered. The same method can also be used for extraction of electrons from a storage ring in ultrashort series of microbunches spaced by the periodicity of light wavelength.