relativistic electrons
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Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 32
Author(s):  
Andrei Bykov ◽  
Vadim Romansky ◽  
Sergei Osipov

Recent discovery of fast blue optical transients (FBOTs)—a new class of energetic transient sources—can shed light on the long-standing problem of supernova—long gamma-ray burst connections. A distinctive feature of such objects is the presence of modestly relativistic outflows which place them in between the non-relativistic and relativistic supernovae-related events. Here we present the results of kinetic particle-in-cell and Monte Carlo simulations of particle acceleration and magnetic field amplification by shocks with the velocities in the interval between 0.1 and 0.7 c. These simulations are needed for the interpretation of the observed broad band radiation of FBOTs. Their fast, mildly to moderately relativistic outflows may efficiently accelerate relativistic particles. With particle-in-cell simulations we demonstrate that synchrotron radiation of accelerated relativistic electrons in the shock downstream may fit the observed radio fluxes. At longer timescales, well beyond those reachable within a particle-in-cell approach, our nonlinear Monte Carlo model predicts that protons and nuclei can be accelerated to petaelectronvolt (PeV) energies. Therefore, such fast and energetic transient sources can contribute to galactic populations of high energy cosmic rays.


Author(s):  
Li Xiao ◽  
Ming Zhu ◽  
Xiaohui Sun ◽  
Peng Jiang ◽  
Chun Sun

Abstract The relativistic electrons rotate in the enhanced magnetic field of the supernova remnants and emit the synchrotron radio emission.We aim to use the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to obtain a sensitive continuum map of the SNR VRO 42.05.01 (G166.0+4.3) at 1240 MHz. The 500 MHz bandwidth is divided into low and high-frequency bands centered at 1085 and 1383 MHz to investigate the spectral index variations within the remnant, together with the Effelsberg 2695 MHz data. We obtained an integrated flux density of 6.2±0.4 Jy at 1240 MHz for VRO 42.05.01, consistent with previous results. The spectral index found from TT-plot between 1240 and 2695 MHz agrees with previous values from 408 MHz up to 5 GHz. The three-band spectral index distribution shows a clear flatter value of α ∼ −0.33 in the shell region and steeper index of α = −0.36 − −0.54 in the wing region. The flatter spectral index in the shell region could be attributed to a second-order Fermi process in the turbulent medium in the vicinity of the shock and/or a higher compression ratio of shock and a high post-shock density than that in elsewhere.


Author(s):  
Xiabing Li ◽  
Longfei Gan ◽  
Jing Wang ◽  
Jinlong Jiao ◽  
Shan Jin ◽  
...  

Abstract A semiclassical method is developed to study the spin evolution of a relativistic electron in an fully relativistic laser pulse. Different from the previous classical method which is based on the direct generalization of nonrelativistic spin precession equation, we perform first-principle calculations on the mean values of various spin operators with respect to a relativistic electron wavepacket. It is demonstrated, via theoretical derivation and numerical simulation, that although the Foldy-Wouthuysen operator merits the single-particle interpretation, its mean value obviously deviates from the result of the classical method, which sheds light on not only the understanding of relativistic spin itself but also broad related applications. To achieve a direct observation of such effect, a feasible experimental setup utilizing the asymmetric field of a single-cycle laser is proposed. In such geometry, the deviation is evidenced in the total change of spin which can be easily measured after the interaction.


2021 ◽  
pp. 160-164
Author(s):  
A.S. Mazmanishvili ◽  
N.V. Moskalets ◽  
A.A. Shcherbakov

The paper deals with the efficiency of the capture of a photon flux of the synchrotron radiation (SR) σ- and π-components by the optical window in the SR quantum extraction channel of the NESTOR generator. It also anal-yses the dependence between the capture quality and different radiation wavelengths. Consideration has been giv-en to the beam size effect on the shape and dimensions of the angular distribution of the photon flux. A model has been constructed to describe the optical imaging in the registration plane. Expressions are given for estimating the efficiency of the capture of SR quanta into the optical window of the extraction channel. The factors that exert influence on the efficiency of capturing through the window are analyzed. Examples of numerical calculations are provided for formation of the final SR spectral density of the 225 MeV relativistic electrons at the output of the optical channel. The dimensions of the optical window have been determined, which ensure the reliable registration of the total flux of SR quanta for the chosen spectral range of SR quanta wavelengths.


2021 ◽  
Vol 16 (12) ◽  
pp. P12042
Author(s):  
A.A. Savchenko ◽  
W. Wagner

Abstract We present a new C++ module for simulation of channeling radiation to be implemented in Geant4 as a discrete physical process. The module allows simulation of channeling radiation from relativistic electrons and positrons with energies above 100 MeV for various types of single crystals. In this paper, we simulate planar channeling radiation applying the classical approach in the dipole approximation as a first attempt not yet considering other contributory processes. Simulation results are proved to be in a rather good agreement with experimental data.


2021 ◽  
Vol 923 (1) ◽  
pp. 61
Author(s):  
C.-I. Björnsson

Abstract The synchrotron spectrum of radio knot C in the protostellar object DG Tau has a low-frequency turnover. This is used to show that its magnetic field strength is likely to be at least 10 mG, which is roughly two orders of magnitude larger than previously estimated. The earlier, lower value is due to an overestimate of the emission volume together with an omission of the dependence of the minimum magnetic field on the synchrotron spectral index. Since the source is partially resolved, this implies a low volume-filling factor for the synchrotron emission. It is argued that the high pressure needed to account for the observations is due to shocks. In addition, cooling of the thermal gas is probably necessary in order to further enhance the magnetic field strength as well as the density of relativistic electrons. It is suggested that the observed spectral index implies that the energy of the radio-emitting electrons is below that needed to take part in first-order Fermi acceleration. Hence, the radio emission gives insights to the properties of its pre-acceleration phase. Attention is also drawn to the similarities between the properties of radio knot C and the shock-induced radio emission in supernovae.


2021 ◽  
Vol 104 (9) ◽  
Author(s):  
Michał Drągowski ◽  
Jacek Ciborowski ◽  
Marek Adamus ◽  
Joachim Enders ◽  
Yuliya Fritzsche ◽  
...  

2021 ◽  
Vol 922 (2) ◽  
pp. 130
Author(s):  
Yi Zhang (张艺) ◽  
Ruo-Yu Liu ◽  
S. Z. Chen ◽  
Xiang-Yu Wang

Abstract Recently, gamma-ray halos of a few degree extension have been detected around two middle-aged pulsars, namely, Geminga and PSR B0656+14, by the High Altitude Water Cherenkov observatory (HAWC). The gamma-ray radiation arises from relativistic electrons that escape the pulsar wind nebula and diffuse in the surrounding medium. The diffusion coefficient is found to be significantly lower than the average value in the Galactic disk. If so, given a typical transverse velocity of 300–500 km s−1 for a pulsar, its displacement could be important in shaping the morphology of its gamma-ray halos. Motivated by this, we study the morphology of pulsar halos considering the proper motion of pulsar. We define three evolutionary phases of the pulsar halo to categorize its morphological features. The morphology of pulsar halos below 10 TeV is double peaked or single peaked with an extended tail, which depends on the electron injection history. Above 10 TeV, the morphology of pulsar halos is nearly spherical, due to the short cooling timescale (<50 kyr) for tens of teraelectronvolt electrons. We also quantitatively evaluate the separation between the pulsar and the center of the gamma-ray halo, as well as the influence of different assumptions on the pulsar characteristics and the injected electrons. Our results suggest that the separation between the center of the gamma-ray halo above 10 TeV and the associated pulsar is usually too small to be observable by HAWC or the Large High Altitude Air Shower Observatory. Hence, our results provide a useful approach to constrain the origin of extended sources at very high energies.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
In Hyung Baek ◽  
Hyun Woo Kim ◽  
Hyeon Sang Bark ◽  
Kyu-Ha Jang ◽  
Sunjeong Park ◽  
...  

AbstractThe deflection of charged particles is an intuitive way to visualize an electromagnetic oscillation of coherent light. Here, we present a real-time ultrafast oscilloscope for time-frozen visualization of a terahertz (THz) optical wave by probing light-driven motion of relativistic electrons. We found the unique condition of subwavelength metal slit waveguide for preserving the distortion-free optical waveform during its propagation. Momentary stamping of the wave, transversely travelling inside a metal slit, on an ultrashort wide electron bunch enables the single-shot recording of an ultrafast optical waveform. As a proof-of-concept experiment, we successfully demonstrated to capture the entire field oscillation of a THz pulse with a sampling rate of 75.7 TS/s. Owing to the use of transversely-wide and longitudinally-short electron bunch and transversely travelling wave, the proposed “single-shot oscilloscope” will open up new avenue for developing the real-time petahertz (PHz) metrology.


2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Jun Miyawaki ◽  
Susumu Yamamoto ◽  
Yasuyuki Hirata ◽  
Masafumi Horio ◽  
Yoshihisa Harada ◽  
...  

AbstractAn X-ray is the well-known probe to examine structure of materials, including our own bodies. The X-ray beam, especially at the wavelength of nanometers, has also become significant to directly investigate electronic states of a sample. Such an X-ray is called a soft X-ray and polarization dependence of the light-matter interaction further unveils the microscopic properties, such as orbitals or spins of electrons. Generation of high brilliant beams of the polarized X-ray has linked to development of our experimental science, and it has been made by radiation from relativistic electrons at the synchrotron radiation facilities over the world. Recently, we constructed a new polarization-controlled X-ray source, the segmented cross undulator, at SPring-8, the largest synchrotron radiation facility in the world. The operation is based on interference of X-ray beams, which is sharply contrast to the conventional method of regulating electron trajectory by the mechanical control of magnets. The paradigm shift opened the measurement innovations and allowed us to design new experimental approaches to capture signals that have been hidden in materials. The present review describes the novel X-ray source with the principle of operation and the technical details of optimization. Examples of the frontier spectroscopies that use unique optical properties of the source are introduced, followed by the future prospects for next generation synchrotron radiation facilities.


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