scholarly journals Fast-cooling synchrotron radiation in a decaying magnetic field and γ-ray burst emission mechanism

2014 ◽  
Vol 10 (5) ◽  
pp. 351-356 ◽  
Author(s):  
Z. Lucas Uhm ◽  
Bing Zhang
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Emission Mechanism ◽  
Fast Cooling ◽  
Γ Ray ◽  
Burst Emission

scholarly journals Microvariability of S5 0716+714, a γ-Ray Blazar

1998 ◽  
Vol 188 ◽  
pp. 442-443 ◽  
Author(s):  
R. Nesci ◽  
E. Massaro ◽  
M. Maesano ◽  
F. Montagni ◽  
F. D'Alessio ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
General Scheme ◽  
Plasma Jet ◽  
Line Of Sight ◽  
First Case ◽  
Γ Ray ◽  
Geometrical Effects ◽  
High Level ◽  
Different Time Scales

Like many radio-selected blazars, 0716+714 shows a high level of variability on different time scales, as short as a few days (e.g. Wagner et al 1996, Ghisellini et al. 1997). The mechanism of the emission in the optical band, in the general scheme of a relativistic plasma jet highy collimated toward the observer, is generally believed to be synchrotron radiation from electrons in a strong magnetic field. Our monitoring of S5 0716+714 is aimed to clarify whether the flux variations are chromatic or achromatic. In the first case, one could guess that variations in the spectrum of the injected electrons are responsible for the flux variations; in the second case, geometrical effects like small changes in the angle between the jet and the line of sight could be more likely (Wagner et al. 1993).

scholarly journals Thermalization of synchrotron radiation from field-aligned currents

1988 ◽  
Vol 6 (3) ◽  
pp. 493-501 ◽  
Author(s):  
William Peter ◽  
Anthony L. Peratt
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Energy Density ◽  
Radiation Spectrum ◽  
Axial Magnetic Field ◽  
Three Dimensional ◽  
Synchrotron Emission ◽  
Microwave Background ◽  
Strong Function ◽  
Current Filaments

Three-dimensional plasma simulations of interacting galactic-dimensioned current filaments show bursts of synchroton radiation of energy density 1·2 ×10−13 erg/cm3 which can be compared with the measured cosmic microwave background energy density of 1·5 × 10−13 erg/cm3. However, the synchrotron emission observed in the simulations is not blackbody. In this paper, we analyze the absorption of the synchrotron emission by the current filaments themselves (i.e., self-absorption) in order to investigate the thermalization of the emitted radiation. It is found that a large number of current filaments (>1031) are needed to make the radiation spectrum blackbody up to the observed measured frequency of 100 GHz. The radiation spectrum and the required number of current filaments is a strong function of the axial magnetic field in the filaments.

scholarly journals Analyzing the propagation of EUV waves and their connection with type II radio bursts by combining numerical simulations and multi-instrument observations

2020 ◽  
Vol 644 ◽  
pp. A90
Author(s):  
A. Koukras ◽  
C. Marqué ◽  
C. Downs ◽  
L. Dolla
Keyword(s):  
Magnetic Field ◽  
Wave Front ◽  
Ray Tracing ◽  
Radio Burst ◽  
Radio Bursts ◽  
Type Ii ◽  
Fast Mode ◽  
Type Ii Radio Bursts ◽  
The Magnetic Field ◽  
Burst Emission

Context. EUV (EIT) waves are wavelike disturbances of enhanced extreme ultraviolet (EUV) emission that propagate away from an eruptive active region across the solar disk. Recent years have seen much debate over their nature, with three main interpretations: the fast-mode magneto-hydrodynamic (MHD) wave, the apparent wave (reconfiguration of the magnetic field), and the hybrid wave (combination of the previous two). Aims. By studying the kinematics of EUV waves and their connection with type II radio bursts, we aim to examine the capability of the fast-mode interpretation to explain the observations, and to constrain the source locations of the type II radio burst emission. Methods. We propagate a fast-mode MHD wave numerically using a ray-tracing method and the WKB (Wentzel-Kramers-Brillouin) approximation. The wave is propagated in a static corona output by a global 3D MHD Coronal Model, which provides density, temperature, and Alfvén speed in the undisturbed coronal medium (before the eruption). We then compare the propagation of the computed wave front with the observed wave in EUV images (PROBA2/SWAP, SDO/AIA). Lastly, we use the frequency drift of the type II radio bursts to track the propagating shock wave, compare it with the simulated wave front at the same instant, and identify the wave vectors that best match the plasma density deduced from the radio emission. We apply this methodology for two EUV waves observed during SOL2017-04-03T14:20:00 and SOL2017-09-12T07:25:00. Results. The simulated wave front displays a good qualitative match with the observations for both events. Type II radio burst emission sources are tracked on the wave front all along its propagation. The wave vectors at the ray-path points that are characterized as sources of the type II radio burst emission are quasi-perpendicular to the magnetic field. Conclusions. We show that a simple ray-tracing model of the EUV wave is able to reproduce the observations and to provide insight into the physics of such waves. We provide supporting evidence that they are likely fast-mode MHD waves. We also narrow down the source region of the radio burst emission and show that different parts of the wave front are responsible for the type II radio burst emission at different times of the eruptive event.

Synchrotron Radiation Spectra

1972 ◽  
Vol 2 (3) ◽  
pp. 142-144 ◽  
Author(s):  
L. J. Gleeson ◽  
K. C. Westfold
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Energy Distribution ◽  
Power Law ◽  
Uniform Magnetic Field ◽  
Charged Particles ◽  
Radiation Spectra ◽  
Field Lines

In this paper we give an account of the corrections that must be made to the formula for the emissivity ηf due to a power-law energy distribution of ultrarelativistic charged particles in a uniform magnetic field B0 in directions well away from the field lines when the effects of upper and lower cut-off values E2 and E1 in the energy distribution are not negligible.

Evaluation of an elliptically polarized undulator for the future Taiwan Photon Source

2021 ◽  
Vol 16 (12) ◽  
pp. P12017
Author(s):  
H.-W. Luo ◽  
T.-Y. Chung ◽  
C.-H. Lee ◽  
C.-S. Hwang
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Synchrotron Radiation ◽  
Transverse Field ◽  
Longitudinal Direction ◽  
X Ray ◽  
Elliptically Polarized ◽  
Transverse Position ◽  
Photon Source ◽  
Field Integral

Abstract The resonant photon energy of an adjustable-phase undulator (APU) is varied with the relative motion of the magnet arrays along the longitudinal direction. There exists, however, a transverse field gradient (TFG) of order 100 T/m in an APU of small gap (∼10 mm). Whereas the TFG might affect the electron beam as it contributes to the dynamic field integral and the radiation integrals, the TFG might also degrade the performance of the synchrotron radiation due to the transverse position-dependent magnetic field. The effects of the TFG on the present Taiwan Photon Source (TPS) and future TPS-upgraded are analyzed to investigate the feasibility of an APU that operates in the soft x-ray region.

Circularly Polarized Synchrotron Radiation in Dipolar Magnetic Fields with Application to the Planet Jupiter

1969 ◽  
Vol 1 (6) ◽  
pp. 274-276 ◽  
Author(s):  
L. J. Gleeson ◽  
M. P. C. Legg ◽  
K. C. Westfold
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Magnetic Fields ◽  
Linear Polarization ◽  
Thin Shell ◽  
Total Radiation ◽  
Circularly Polarized ◽  
Preliminary Account ◽  
The Magnetic Field

This paper is a preliminary account of the calculation of the circularly polarized synchrotron radiation received from a distribution of electricallycharged particles confined to a thin shell in the magnetic field of a dipole. Calculations of the total radiation and the degree of linear polarization have previously been carried out, and these calculations are duplicated in part.

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