Showing papers on "Synchrotron radiation published in 1972"

Close Similarity between Photoelectric Yield and Photoabsorption Spectra in the Soft-X-Ray Range

Abstract: Because of the similarity between photoelectric yield and photoabsorption spectra in the soft x-ray region, "yield spectroscopy" can be used as a successful method for investigating fine structure in the electronic excitation spectra of solids. The continuous spectrum of synchrotron radiation is especially appropriate for such measurements. We reinvestigated the structure of the $4d$ excitations in Pr and the $2p$ excitations of Si using a single crystal.

Detection of X-Ray Polarization of the Crab Nebula

Abstract: Two different types of X-ray polarimeters were used in a sounding rocket to search for X-ray polarization of the Crab Nebula. Polarization was detected at a statistical confidence level of 99.7%. If the X-ray polarization is assumed to be independent of energy, the results of this and a previous experiment lead to a polarization of 15.4 (plus or minus 5.2) percent at a position angle of 156 (plus or minus 10) deg. This result confirms the synchrotron model for X-ray emission from the Crab Nebula.

A Scanning X-Ray Microscope Using Synchrotron Radiation

Abstract: Focused synchrotron radiation collimated by means of a pinhole has been used to construct a scanning x-ray microscope capable of making stereoscopic element-discriminating pictures of relatively thick specimens in an atmospheric environment.

The self absorption of gyro-synchrotron emission in a magnetic dipole field: Microwave impulsive burst and hard X-ray burst

Abstract: The gyro-synchrotron emission from a model source with a non-uniform magnetic field is computed taking into account the self absorption. This model seems adequate not only to interpret the radio spectrum and its time variation of microwave impulsive bursts but also to solve the discrepancy between the numbers of non-thermal electrons emitting radio burst and those emitting hard X-ray burst.

Discovery of Giant Radio Outburst from Cygnus X-3

Abstract: A giant radio outburst was observed from the X-ray source Cygnus X-3 on September 2, 1972. Flux density measurements were obtained at 10,522, 6,630 and 3,240 MHz as well as linear polarization measurements at 10,522 MHz. The evidence suggests a model of synchrotron radiation from an expanding cloud of relativistic particles. A computed upper limit for the source distance of ≤400 kpc implies that the source of the radio emission is galactic.

Gravitational synchrotron radiation in the schwarzschild geometry.

Abstract: The existence of a mechanism for gravitational synchrotron radiation is demonstrated in solutions of the wave equation in the Schwarzschild background, with the source a particle in a highly relativistic circular geodesic. The main features (high-frequency harmonics, narrow angular distribution in latitude) are shown to hold for vector (electromagnetic) and tensor (gravitational) radiations, which are expected to be strongly polarized in the orbit plane. Detailed formulas for the spectrum are given in the scalar case.

Energy straggling and radiation reaction for magnetic bremsstrahlung.

Abstract: Using the method of quantum electrodynamics, the energy distribution of particles and emitted photons is calculated for the case when increases in the average energy of the photon emitted by synchrotron radiation to values appreciable compared to the energy of the particle give rise to particle energy straggling and radiation spectrum broadening. The classical radiative reaction effects which may be tested in this type of experiment are outlined, and a detailed quantum mechanical calculation is presented. The significance of energy straggling in astrophysics is discussed briefly.

Can Synchrotron Gravitational Radiation Exist

Abstract: A complete relativistic analysis for gravitational radiation emitted by a particle in circular orbit around a Schwarzschild black hole is presented in the Regge-Wheeler formalism. For completeness and contrast we also analyze the electromagnetic and scalar radiation emitted by a suitably charged particle. The three radiation spectra are drastically different. We stress some important consequences and astrophysical implications.

Photometric Comparison between Two Calculable Vacuum-Ultraviolet Standard Radiation Sources: Synchrotron Radiation and Plasma-Blackbody Radiation

Abstract: Two important principles exist for the calibration of the vuv spectral radiance of secondary-standard lamps by means of calculable standard radiation sources: (1) use of blackbody radiation emitted by a plasma of known temperature and (2) use of electron-synchrotron radiation. Because both methods are rather difficult, a comparison of the two calibration procedures seems necessary. This study demonstrates that in the long-wavelength vuv at λ = 165 nm, significant errors do not occur in the spectral-radiance calibration with either synchrotron radiation and plasma-blackbody radiation. The maximum deviations of the calibration of secondary-standard lamps applying these two calibration methods are within ±20%. Under optimum experimental conditions, the agreement of the two calibrations is within 8%. Furthermore, this study shows that it is possible to do photometry in the vuv by use of secondary-standard gas discharge lamps in a way comparable to the routine technique with tungsten-strip lamps in the visible.

Unusual Radio Events in Cygnus X-3

Abstract: Observations made at Green Bank confirm the findings of Gregory et al.

Source models with electron diffusion

Abstract: The general solution for the energy distribution of relativistic electrons in which electrons generated within the source diffuse and decay through synchrotron or Compton radiation is given for the case in which the magnetic field and the diffusion coefficient are constant. A very simple spherically symmetric model with an electron point-source at the centre is considered and the equations are explicitly solved. It is shown that notwithstanding its great simplicity this model gives a fair representation of the continuous emission of the Crab nebula from the radio to the X-ray region, with the simple assumption that it is due only to ordinary synchrotron radiation. If the central point source is identified with the pulsar there appears to be an upper limit of about 107 MeV to the energy of the electrons accelerated by the pulsar mechanism.

Model of Cygnus X-1

Abstract: The hard X-rays from Cygnus X-1 are attributed to inverse Compton scattering of ultraviolet photons from the B star known to be one component of the source The other component is assumed to be the source of relativistic electrons This provides a natural explanation of the “anti-eclipse” feature of the X-ray variability The electrons should also produce synchrotron radiation in the infrared The predicted flux density at 100 µm is about 10−23 W m−2 Hz−1

Spectroscopy with a Synchrotron Light Source

Abstract: Relativistic electrons undergoing centripetal acceleration in a synchrotron emit a highly collimated forward cone of continuous radiation. The continuum extends from the extreme ultraviolet to the radiofrequency region for electrons of GeV energies and is very suitable for absorption spectroscopy in the region of the ultraviolet extending from a few tens of agstroms to 2000 A. This paper discusses some properties of synchrotron radiation of interest to spectroscopists and some experimental difficulties associated with ultraviolet spectroscopy. Examples we given of ultraviolet spectra of free atoms and molecules and also of solids obtained recently with synchrotron radiation.

The radiation wave zone

Abstract: The criterion for the formation of a radiation wave zone of a charge moving in an arbitrary way is discussed The appearance of a wave zone is investigated in detail for synchrotron radiation and radiation from a charge moving along a hyperbola Special attention is given to the ultrarelativistic case

Results and Problems in the Investigation of the Synchrotron Instability

Abstract: A brief resume of the results of the linear theory of the synchrotron instability is presented, obtained using the quantum method with the Einstein coefficients and the classical method with the kinetic equation. The full equivalence is shown for the results of quantum and classical treatment of synchrotron instability. The expression for the growth-rate of synchrotron radiation in a system of relativistic electrons with an anisotropic momentum distribution is also found and investigated. Such a distribution might be realised in certain sources of cosmic radio emission (for example in pulsars). Certain problems are noted which have not yet been properly solved in studies of the synchroton instability (the instability of a highly rarified plasma, the quasi linear theory of the synchrotron instability, and so on).

Mechanism for the X-ray Pulsations in Cyg X-1

Abstract: The mechanism proposed involves the occurrence of a flare in a region of high magnetic field on the surface of a star. The flare produces oscillations in the magnetic field structure. The oscillations lead to heating of the plasma in a flux tube which emits thermal radiation. The heating may be caused by magnetic pumping or particles accelerated in periodic bursts by the flare. Synchrotron radiation from high energy particles accounts for the hard X-ray emission.

The circular polarization of sources of synchrotron radiation

Abstract: The degree of circular polarizationpc is calculated for two models of a source of synchrotron radiation: (1) A source with an inhomogeneous magnetic field and isotropic angular distribution of the electrons with respect to the magnetic field; (2) A source with a homogeneous magnetic field and anisotropic angular distribution of the electrons in which the anisotropy of angular distribution substantially increases with the electron energy.

Mechanisms of optical, X-ray andγ-radiation from Crab pulsar

Abstract: The synchrotron mechanism of radiation from the Crab pulsar has been investigated on the assumption that the mechanism acts in a source moving with relativistic velocity round a neutron star. A detailed matching has been made of the theoretical spectra of synchrotron radiation from relativistic electrons with the results of measurements of the radiation flux from the Crab pulsar in the infrared, optical and X-ray ranges. The parameters of the radiating region (intensity of the magnetic field, source dimensions, density and lifetime of radiating electrons) have been found. They are expressed through the δ ratio of the energy density of the magnetic field in the source to that of radiating electrons. The level of Comptonγ-radiation in this region is estimated. Possible values of δ at which the level will correspond to the available results of measurements of theγ-radiation flux from the Crab pulsar are given. An estimate is presented for the surface magnetic field of the neutron star which does not contradict those obtained from considerations of the magnetic flux conservation when compressing the object up to the neutron star dimensions.

Diffusion models for Jupiter's radiation belt

Abstract: Solutions are given for the diffusion of trapped particles in a planetary magnetic field in which the first and second adiabatic invariants are preserved but the third is not, using as boundary conditions a fixed density at the outer boundary (the magnetopause) and a zero density at an inner boundary (the planetary surface). Losses to an orbiting natural satellite are included and an approximate evaluation is made of the effects of the synchrotron radiation on the energy of relativistic electrons. Choosing parameters appropriate to Jupiter, the electrons required to produce the observed synchrotron radiation are explained. If a speculative mechanism in which the diffusion is driven by ionospheric wind is the true explanation of the electrons producing the synchrotron emission it can be concluded that Jupiter's inner magnetosphere is occupied by an energetic proton flux that would be a serious hazard to spacecraft.

Thermal and Non-Thermal Soft X-Ray Bursts

Abstract: X-ray bursts observed for energies lower than 25 keV are usually interpreted as being produced by a thermal plasma with several million degrees of temperature.

Polarization of gravitational synchrotron radiation

Abstract: Development of a method of analysis of gravitational polarization in terms of Stokes parameters similar to those used for the electromagnetic case. Analytical expressions for these parameters are obtained for the gravitational synchrotron radiation corresponding to the Schwarzschild black-hole model. It is shown that interference between odd- and even-parity terms makes a significant contribution to the angular dependence of the polarization.