scholarly journals Scattering of HF Radio Waves by a Spherical Electron Cloud in the Presence of a Magnetic Field

1971 ◽  
Author(s):  
Milton M. Klein ◽  
Norman W. Rosenberg
Keyword(s):  
Magnetic Field ◽  
Electron Cloud ◽  
Radio Waves

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

scholarly journals Solar Spike Suggests a More Active Sun

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Nola Redd
Keyword(s):  
Magnetic Field ◽  
The Sun ◽  
Radio Waves ◽  
The Magnetic Field

Radio waves are providing a new way to probe the Sun and suggest that the magnetic field of its corona may be stronger than long thought.

scholarly journals Radio Emission Model of a 'Typical' Pulsar

1987 ◽  
Vol 40 (6) ◽  
pp. 755 ◽  
Author(s):  
AZ Kazbegi ◽  
GZ Machabeli ◽  
G Melikidze
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Emission Model ◽  
Radio Waves ◽  
Resonance Case ◽  
Pulsar Magnetosphere ◽  
Pulsar Emission ◽  
Dipole Magnetic Field ◽  
New Type ◽  
The Magnetic Field

The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.

scholarly journals Ha, ha, ha, ha, staying alive, staying alive: A radio pulsar with an 8.5-s period challenges emission models

2000 ◽  
Vol 177 ◽  
pp. 185-188 ◽  
Author(s):  
M. D. Young ◽  
R. N. Manchester ◽  
S. Johnston
Keyword(s):  
Magnetic Field ◽  
Equation Of State ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Pair Creation ◽  
Radio Pulsar ◽  
Radio Waves ◽  
Long Period ◽  
Emission Models ◽  
S Period

AbstractWe report the discovery of the longest known radio pulsar period. PSR J2144–3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s. Under the usual assumptions about the stellar equation of state, this pulsar has an average surface dipolar magnetic field strength of ~ 2.0 × 1012G. According to popular theories of the emission mechanism this pulsar should not be emitting radio waves because its long period and magnetic field strength make pair creation impossible for all reasonable magnetic field configurations. Either assumptions about the equation of state are incorrect, or the emission theories must be revised.

scholarly journals Magnetic Fields in the Spiral Galaxy NGC 6946

1993 ◽  
Vol 157 ◽  
pp. 311-312
Author(s):  
Matthias Ehle ◽  
Rainer Beck
Keyword(s):  
Magnetic Field ◽  
Spiral Galaxy ◽  
High Frequency ◽  
Uniform Magnetic Field ◽  
Large Scale ◽  
Dynamo Model ◽  
Model Parameters ◽  
Radio Waves ◽  
Spiral Pattern ◽  
Ngc 6946

High frequency polarization observations reveal the existence of a large-scale ordered magnetic field in the disk of the spiral galaxy NGC 6946. At lower frequencies the disk is no longer transparent to polarized radio waves due to Faraday depolarization. The spiral pattern of the uniform magnetic field and the distribution of polarized intensities are fairly well simulated by a dynamo model. The model parameters indicate that the dynamo does not only operate in the disk, but also in the halo.

Electron Cloud in Various Kinds of Magnetic Field of BEPCII

2006 ◽  
Vol 23 (2) ◽  
pp. 336-339
Author(s):  
Liu Yu-Dong ◽  
Guo Zhi-Yuan ◽  
Qin Qing ◽  
Wang Jiu-Qing
Keyword(s):  
Magnetic Field ◽  
Electron Cloud

IONOSPHERIC REFLECTION OF VERY LONG RADIO WAVES

1950 ◽  
Vol 28a (6) ◽  
pp. 549-557 ◽  
Author(s):  
J. P. Stanley
Keyword(s):  
Magnetic Field ◽  
Reflection Coefficient ◽  
Wave Reflection ◽  
Simplified Model ◽  
Angle Of Incidence ◽  
Vertical Magnetic Field ◽  
Radio Waves ◽  
Long Wave ◽  
Theoretical Results ◽  
Good Agreement

A simplified model of the long-wave-reflecting region of the ionosphere, first considered in a previous paper, is used to calculate the theoretical variation of sky wave reflection coefficient with angle of incidence and with the angle of dip of the earth's magnetic field. The resulting curves are found to be in good agreement with experiment. They lead to the conclusion that theoretical results based on the assumption of a vertical magnetic field will not lead to errors in vertical incidence sky wave reflection coefficient greater than about 10%, even though the field is inclined at an angle of as much as 23° to the vertical.

scholarly journals The oblique reflexion of very long wireless waves from the ionosphere

1947 ◽  
Vol 189 (1016) ◽  
pp. 130-147 ◽  
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Theoretical Basis ◽  
Plane Waves ◽  
Angle Of Incidence ◽  
Vertical Magnetic Field ◽  
Radio Waves ◽  
Contour Integrals ◽  
General Terms ◽  
Made In

An attempt is made in the paper to provide a satisfactory theoretical basis for a future discussion of the experimental data on the propagation of very long radio waves (18,800 m.) given by Best, Ratcliffe & Wilkes, and Budden, Ratcliffe & Wilkes. The reflexion of very long plane waves incident obliquely on a horizontally stratified ionized medium with a vertical magnetic field is first considered in general terms, and it is shown that the medium can be divided into a transition region and a reflecting region. If the ionization in the reflecting region increases linearly with height it is shown that propagation is governed by the following equations: ∂ 2 L / ∂ζ 2 + (α + ζ) L + β M = 0, ∂ 2 M / ∂ζ 2 + (α - ζ) M + β L = 0, where α and β are constants depending on the angle of incidence. Under the conditions of the experiments β is small, and a solution, in terms of contour integrals, valid in this case is obtained.

scholarly journals Radiation Bursts from a Presupernova Collapsar

2005 ◽  
Vol 192 ◽  
pp. 215-218
Author(s):  
Volodymyr Kryvdyk
Keyword(s):  
Magnetic Field ◽  
Radiation Flux ◽  
Thermal Emission ◽  
Broad Band ◽  
Initial Energy ◽  
Variable Magnetic Field ◽  
Particle Spectrum ◽  
Radio Waves ◽  
Stellar Radius ◽  
Stellar Collapse

SummaryThe radiation from the magnetic presupernova star is calculated. This radiation will generate when the magnetosphere of presupernova star compresses during collapse and its magnetic field increases considerably. The variable magnetic field will accelerate the charged particle, which generate radiation when moving in the magnetic field. The particles dynamics and their non-thermal emission in the magnetospheres of presupernova collapsing star with initial dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere are considered. The radiation flux depend on the distance to the star, its magnetic field, and the particle spectrum in the magnetosphere. This flux can be observed by means of modern instruments in broad band (from radio waves to gamma rays). The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of radiation bursts with duration equal to the stellar collapse time.

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