Showing papers on "Radio wave published in 1970"
TL;DR: An attempt to account quantitatively for the pulse width, polarization and spectrum of the pulses.
Abstract: An attempt to account quantitatively for the pulse width, polarization and spectrum of the pulses.
170 citations
TL;DR: In this article, the authors measured the relative amplitudes of the extraordinary and ordinary waves as a function of the height in the D-region, assuming that the reflection is due to ionization irregularities.
93 citations
TL;DR: Type 3 solar radio bursts observed at low frequencies for half rotation, discussing occurrence, drift rates, propagation time and emission as discussed by the authors. But they did not specify the type of radio bursts they were emitting.
Abstract: Type 3 solar radio bursts observed at low frequencies for half rotation, discussing occurrence, drift rates, propagation time and emission
84 citations
81 citations
77 citations
TL;DR: In this paper, the center-to-limb variations of spectrum and polarization of microwave impulsive bursts were analyzed using a gyro-synchrotron emission from nonthermal electrons trapped in a magnetic dipole field.
Abstract: In order to interpret the observed center to limb variations of spectrum and polarization of microwave impulsive bursts, gyro-synchrotron emission from nonthermal electrons trapped in a magnetic dipole field is computed. The theoretical spectrum and polarization are consistent with observed ones if we put an outer boundary of the radio source at a layer of 100-60 G or (7–9) × 104 km in height. Rather small observed center-limb variations in intensity and polarization are attributed to the distribution of θ, an angle between the magnetic field and the direction of observer, in the radio source emitting the burst, though the intensity and polarization depend strongly on θ especially at small values of θ.
76 citations
TL;DR: In this paper, the authors used radio interferometry to measure the deflection of a radio source as it passed the sun, which is a separable combination of refraction in the coronal electron plasma and the general relativistic effect.
Abstract: We have used radio interferometry to measure the deflection of a radio source as it passed the sun. This deflection is a separable combination of refraction in the coronal electron plasma and the general relativistic effect. The observed deflection was ${1.04}_{\ensuremath{-}0.10}^{+0.15}$ times that predicted by Einstein's theory of general relativity. The observation also yielded a reasonable value for the coronal electron density.
74 citations
TL;DR: In this article, electron density irregularities convected past space probe relationship to radio intensity power spectrum scintillations were found to be correlated with radio intensity and power spectrum scattering.
Abstract: Electron density irregularities convected past space probe relationship to radio intensity power spectrum scintillations
67 citations
TL;DR: A search for irregularities in signals from the pulsar NP 0532 in the Crab Nebula is described, which includes sub-millisecond bursts, marching subpulses, and variations of polarization.
Abstract: ON time-scales of 0.1 to 10 ms radio signals from pulsars exhibit irregularities which include sub-millisecond bursts1,2, marching subpulses3, and variations of polarization4,5. We now describe a search for such irregularities in signals from the pulsar NP 0532 in the Crab Nebula.
66 citations
TL;DR: In this article, radio reflectivity was used to study the F-region ionospheric modifications produced by the installation described by Utlaut [1970] in a companion paper.
Abstract: Several radio techniques are being employed to study the F-region ionospheric modifications produced by the installation described by Utlaut [1970] in a companion paper. One such technique, discussed here, is the measurement of ‘radio reflectivity,’ the relative power of radio echoes obtained from the perturbed ionosphere. Some theoretical aspects of this technique and its potential for measuring ionospheric parameters are treated in a companion paper by Whitehead [1970]. Preliminary measurements using the technique are reported here. These measurements yielded unexpected results whose possible interpretation is tentatively presented.
61 citations
TL;DR: Type 3 solar radio burst storms at low frequencies, suggesting electron packet exciters propagating with little deceleration as discussed by the authors, suggest electron packet exiters propagate with little acceleration.
Abstract: Type 3 solar radio burst storms at low frequencies, suggesting electron packet exciters propagating with little deceleration
TL;DR: In this article, the authors describe detection of significant changes in the electron temperature in the F2 region produced by absorption of radio-frequency energy propagated at or near the local ionospheric plasma frequency.
Abstract: In recent years methods of producing controlled modifications of the ionosphere by use of high-intensity radio-frequency waves have been proposed; some have been tried with inconclusive results. The present paper describes detection of significant (∼30%) changes in the electron temperature in the F2 region produced by absorption of radio-frequency energy propagated at or near the local ionospheric plasma frequency. The radio-frequency source is the 1-Mw cw transmitter and ∼16° beamwidth antenna array described in the accompanying paper by Utlaut [1970]. As shown by the calculations of Meltz and LeLevier [1970], electron temperature increases of ∼35% can be expected within a few tens of seconds after the transmitter, tuned to within 1% of f0F2, is turned on.
TL;DR: In this article, the authors deduced the interstellar electron spectrum from the nonthermal radio background using the complete diffusion-convection energy-loss theory of solar modulation and showed that the spectrum is similar to that observed at earth.
Abstract: We deduce the interstellar electron spectrum from the nonthermal radio background. From 200 MeV to a few GeV the spectral index is 1.8 and there is evidence for residual solar modulation. Above a few GeV, the spectrum is steeper and the intensity is similar to that observed at earth. A consistent modulation for electrons and protons of the same rigidity can be obtained by using the complete diffusion-convection energy-loss theory of solar modulation.
TL;DR: The heating and hydrodynamic expansion of the F layer caused by absorption of an incident radio wave occurs in several phases as discussed by the authors, and the incident wave field is almost unperturbed.
Abstract: The heating and hydrodynamic expansion of the F layer caused by absorption of an incident radio wave occurs in several phases. During the first minute, energy is imparted to the electron gas through ohmic dissipation, the electron temperature is raised, field-aligned pressure gradients are established, and the plasma begins to expand along the magnetic field. Plasma density changes are small, less than 1%, during this initial phase and the incident wave field is almost unperturbed. During the next several minutes, the plasma accelerates and the F-region density is reduced, albeit slowly, while the electron and ion temperatures approach steady state.
TL;DR: In this article, an extension of Fermat's principle, in which the complex phase refractive index is used instead of only the real part, expresses both of these criteria and leads to a corresponding extension of Snell's law or of Haselgrove's equations to calculate the ray path.
Abstract: Standard ray-tracing programs do not calculate satisfactorily the reflection of LF radio waves from the ionosphere because they do not take losses into account. In lossy media, requiring the ray path to have a minimum attenuation in addition to a minimum wave interference gives a more accurate approximation to the full-wave solution. An extension of Fermat's principle, in which the complex phase refractive index is used instead of only the real part, expresses both of these criteria and leads to a corresponding extension of Snell's law or of Haselgrove's equations to calculate the ray path. Although such a path can have complex coordinates, only those with end points in real space are physically significant. An approximation, in which plane waves in the neighborhood of the receiver are assumed, solves the common ray-tracing problem of homing in on the receiver, a problem that is worse for ray tracing in complex space. Applying ray tracing in complex space to a plane wave incident on a plane stratified medium gives a result that agrees exactly with the result obtained by the phase integral method and that agrees satisfactorily with full-wave solutions above 30 kHz for all results shown.
TL;DR: In this paper, it was shown that the observed modulation of some coronal microwave, X-ray and Type III emission into pulses of 10 sec intervals is a consequence of the stimulation of electron cyclotron waves propagated in the whistler mode in dipole-like bipolar regions of dimension ≈ 0.2 R⊙.
Abstract: We show that the observed modulation of some coronal microwave, X-ray and Type III emission into pulses of 10 sec intervals is a consequence of the stimulation of electron cyclotron waves propagated in the whistler mode in dipole-like bipolar regions of dimension ≈ 0.2 R
⊙. Assuming that a power law spectrum of ≥ 10 keV electrons with a slope similar to solar flare protons can be trapped in a bipolar region, we show that whistlers can be generated by pitch angle instability. The resultant ≈ 10 sec bounce motion of whistler wave trains leads to enhanced, modulated emission in microwave and X-ray frequencies by pitch angle scattering of MeV electrons, and to modulated Type III emission by scattering with coherent plasma waves. A direct prediction of the theory is the existence of sympathetic pulsations at two sources a fraction of a solar radius apart. A second test of the theory is that modulated Type III emission should show strong polarization.
TL;DR: In this paper, the authors examined three solar outbursts which show pulsating radio emissions at metric waves (239 MHz) and showed that such phenomena are peculiar phases of type IV radiation, perhaps connected with absorptions in the solar corona.
Abstract: Three solar outbursts which show pulsating radio emissions at metric waves (239 MHz) are examined. The behaviour of the single frequency, high-time resolution records and the spectral diagrams seem to indicate that such phenomena are peculiar phases of type IV radiation, perhaps connected with absorptions in the solar corona. The spectral analysis of the low-frequency modulation of the emissions show a very definite spectral line with a period ranging from 1s.7 to 3s.1.
TL;DR: In this article, the authors discuss spectra, polarization properties and red giant star model with expanding atmosphere for IR radio emission from IR stars, discussing spectra and polarization properties of IR stars.
Abstract: OH radio emission from IR stars, discussing spectra, polarization properties and red giant star model with expanding atmosphere
01 Jan 1970
TL;DR: In this article, a phenomenological theory of discrete emissions has been advanced, based on cyclotron resonance between energetic electrons and narrow band whistler mode waves traveling along the static magnetic field.
Abstract: Very low frequency whistler mode noise from the magnetosphere frequently appears in the form of narrow band tones of variable frequency called discrete VLF emissions. These tones may appear spontaneously or they may be triggered by transmissions from ground based VLF stations (Helliwell, 1965). They can be observed from within the plasmasphere out to the magnetopause and at frequencies from 300 to 30000 Hz. A phenomenological theory of discrete emissions has been advanced, based on cyclotron resonance between energetic electrons and narrow band whistler mode waves traveling along the static magnetic field (Helliwell, 1967). An important feature of this theory is the maintenance of oscillations through feedback between the waves and the electrons over a path that is long compared with the wavelength.
TL;DR: A mechanism is described whereby the optical radiation from stars embedded in dust-filled HII regions may be converted to microwave and longwave radio emissions.
Abstract: A mechanism is described whereby the optical radiation from stars embedded in dust-filled HII regions may be converted to microwave and longwave radio emissions.
01 Jan 1970
TL;DR: In this paper, the position of the radio source 3C279 was interferometrically monitored to determine the deviation of its 9.602-GHz radiation in the solar gravitational field.
Abstract: : During its occultation by the sun in October 1969, the position of the radio source 3C279 was interferometrically monitored to determine the deviation of its 9.602-GHz radiation in the solar gravitational field. Rapid instrumental calibration and negligible coronal diffraction enabled the measurement of a General Relativity deflection of 1.77 plus or minus 0.20 seconds at the limb of the sun. This is in close agreement with Einstein's prediction. (Author)
TL;DR: Preliminary observations have been carried out to look for radio signals associated with gravitational waves, and although inconclusive, the observations suggest the value of pressing on with further experiments.
Abstract: Preliminary observations have been carried out to look for radio signals associated with gravitational waves. Although inconclusive, the observations from five receivers in the British Isles suggest the value of pressing on with further experiments.