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Showing papers on "Radio wave published in 1988"


Book
26 Aug 1988
TL;DR: In this article, the authors present a course book on radio propagation for students of physics or electrical engineering or mathematics, with a focus on the ionosphere and magnetosphere and the theory of their effect on radio waves.
Abstract: This book is concerned with the ionosphere and the magnetosphere, and the theory of their effect on radio waves. It includes accounts of some mathematical topics now widely used in this study, particularly W. K. B. approximations, Airy integral functions and integration by steepest descents. The subject is divided into ray theory and full wave theory. Ray theory is useful for high frequencies when the ionosphere is treated as a horizonally stratified medium. The discussion of the magnetosphere, whose structure is more complicated, includes an account of whistlers and ion cyclotron whistlers. The book has been planned both for final year undergraduates and as a reference book for research. It is suitable as a course book on radio propagation for students of physics or electrical engineering or mathematics. Some of the topics are presented from an elementary viewpoint so as to help undergraduates new to the subject. The later parts are more advanced. Because the subject is so large and has seen many important recent advances, some topics have had to be treated briefly, but there is a full bibliography with about 600 references.

273 citations


Journal ArticleDOI
TL;DR: In this article, radio pictures of 47 lightning flashes that struck ground 1430 m above mean sea level (msl) to the north of Johannesburg, over a period of 16 years were obtained using a hyperbolic method, i.e., by taking differences between times at which radio noise from lightning arrived at five widely spaced stations.
Abstract: We present information obtained from VHF radio pictures of 47 lightning flashes that struck ground 1430 m above mean sea level (msl) to the north of Johannesburg, over a period of 16 years. Radio pictures were obtained using a hyperbolic method, i.e., by taking differences between times at which radio noise from lightning arrived at five widely spaced stations. These data were supplemented by recordings of electric field change. We found that stepped leaders and intracloud streamers emitted pulses and progressed at speeds that averaged 1.6×105 ms−1. Stepped leaders ranged in length from 3 to 13 km. BIL (breakdown-intermediate-leader) waveforms of electric field change were caused by stepped leaders whose branched channels followed complicated paths. The electric field changes they recorded in an effective bandwidth of 3.5 kHz could be reproduced faithfully by calculations based on an assumption that the radio sources became charged at the expense of a region near the origin of each leader. Some return strokes radiated trains of noise, called Q noise, whose sources extended at speeds near 108 ms−1. Sources of this Q noise retraced leader channels before extending them at these high speeds. Interstroke processes radiated Q noise whose sources extended at speeds that averaged 8.7×107 ms−1. Most Q sources (98%) were directed vertically, but they pervaded regions that retrogressed at “speeds” that averaged 2.2×104 ms−1 in directions away from the starting points of the flashes. This retrogression was directed horizontally, but the vertical Q streamers caused J changes to have positive or negative slopes according to the relative positions of Q sources and the reversal cone. Sixty percent of our sample of ground flashes were endowed with portions that were cloud flashes or were themselves minor components of cloud flashes. A more detailed summary appears at the end of the paper.

146 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the mode coupling and examined the parameter dependence of the damping rate of the global mode in the box model and derived the complex frequencies of the compressional wave by finding the singularities of the associated Green's function.
Abstract: In the terrestrial magnetosphere, the inhomogeneous magnetic field and plasma density give rise to a continuous spectrum of field line resonant frequencies. Compressional disturbances with characteristic frequencies lying within the range of the spectrum may couple to transverse oscillations of resonant field lines. The coupling is of particular interest for global compressional modes trapped in the magnetic cavity. These modes decay in time through the coupling, even in the absence of dissipation. The importance of the process is that, through the damping of the global modes, large-scale motion can drive localized field line resonances. In this study, we investigate the mode coupling and examine the parameter dependence of the damping rate of the global mode. The problem is discussed as an initial value problem in the box model which retains most of the significant physics yet remains mathematically tractable. To treat the coupling, we use the analogy of Landau damping in a homogeneous plasma. From the Laplace transform approach, we obtain the complex frequencies of the compressional wave by finding the singularities of the associated Green's function. Once the complex frequency has been found numerically, we obtain the corresponding waveforms in the box. Many observed wave properties can then be obtained. The calculations agree well with other simulation work and correspond to results obtained for the reflection of radio waves from the ionosphere and for plasma heating by absorption of radiation.

134 citations


Journal ArticleDOI
TL;DR: In this paper, two models are proposed for the prediction of the excess path length of radio waves from ground-based measurements of pressure, temperature, and humidity, at zenith and at a given apparent elevation angle.
Abstract: Two models are proposed here for the prediction of the excess path length of radio waves from ground-based measurements of pressure, temperature, and humidity, at zenith and at a given apparent elevation angle. They can be applied to the correction of high-accuracy range measurements between ground beacons and orbiting satellites. Both of these models use the same formulation for the hydrostatic component of the excess path, ΔLh, with an accuracy better than 5 mm, as compared to measurements of ΔLh. However, two distinct methods have been developed for the wet component ΔLw of the excess path length. The first is based on a theoretical assumption regarding the relative humidity profile and leads to an appropriate accuracy for locations corresponding to standard conditions (≈ 2 cm) with a very small mean deviation ( 4 cm, offsets as large as 4 cm). The second model is implemented by the use of an extended radiosonde data base covering the whole world and a 1-year period. It leads to an rms deviation from measured data comparable to the first method, but to reduced values of the offset, and thus to an overall improvement of the prediction. One advantage of such a method is that it provides a simple global model of the excess path length, with an accuracy comparable to other sophisticated ones.

90 citations


Journal ArticleDOI
18 Nov 1988-Science
TL;DR: High-power electromagnetic waves beamed into the ionosphere from ground-based transmitters illuminate the night sky with enhanced airglow and comprise a major source of long-term variability in plasma densities during ionospheric heating experiments.
Abstract: High-power electromagnetic waves beamed into the ionosphere from ground-based transmitters illuminate the night sky with enhanced airglow. The recent development of a new intensified, charge coupled-device imager made it possible to record optical emissions during ionospheric heating. Clouds of enhanced airglow are associated with large-scale plasma density cavities that are generated by the heater beam. Trapping and focusing of electromagnetic waves in these cavities produces accelerated electrons that collisionally excite oxygen atoms, which emit light at visible wavelengths. Convection of plasma across magnetic field lines is the primary source for horizontal motion of the cavities and the airglow enhancements. During ionospheric heating experiments, quasi-cyclic formation, convection, dissipation and reappearance of the cavites comprise a major source of long-term variability in plasma densities during ionospheric heating experiments.

85 citations


Journal ArticleDOI
TL;DR: The first observations of density depletions exceeding 50% are reported, extending hundreds of kilometers along the geomagnetic field and exhibits many of the characteristics associated with thermal cavitons.
Abstract: High-power hf electromagnetic waves have been used to generate large electron-density cavities in the night-time F-region ionospheric plasma. Previous modification experiments have described induced density perturbations of only a few percent. Here we report the first observations of density depletions exceeding 50%, extending hundreds of kilometers along the geomagnetic field. These cavities are thermally driven, with electron temperatures in the depletions increased by factors of 3 to 4. The depletion dynamics exhibits many of the characteristics associated with thermal cavitons.

76 citations


Patent
23 Mar 1988
TL;DR: In this paper, a radio/wire switchable facsimile machine includes a switch which switchingly establishes the wire mode or the radio mode, in one embodiment, the switch is manually operated.
Abstract: A facsimile machine including a data processing system for processing data to be transmitted and received data according to a predetermined manner, which system typically comprises a MODEM, a buffer and a CODEC. The facsimile machine includes two or more interface units dedicated for performing a wire communication function for communicating image data in a wire communication mode using a telephone network and a radio communication function for communicating image data in a radio or wireless communication mode using radio waves. The radio/wire switchable facsimile machine includes a switch which switchingly establishes the wire mode or the radio mode. In one embodiment, the switch is manually operated. In a second embodiment the switch automatically establishes either one of the wire and radio modes in accordance with the current status of a predetermined signal, typically an off-hook signal, which indicates whether the handset of a telephone unit is hooked or unhooked or whether the microphone of a radio set is hooked or unhooked.

74 citations


Journal ArticleDOI
TL;DR: In this paper, a comparison between the propagation data and ground-level meteorological measurements indicated a high correlation between the scintillation characteristics and the water vapor contribution to the radio refractive index inferred from local humidity and temperature data.
Abstract: Radio waves with frequencies above 10 GHz at low-elevation-angle paths are significantly affected not only by rain but also by atmospheric irregularities in the troposphere The tropospheric scintillation due to irregularities of the refractive index in the troposphere is investigated using 14/11-GHz low-elevation measurements made during 1983 at Yamaguchi, Japan The diurnal and seasonal variations, frequency dependence derived from a comparison of the 11- and 14-GHz signals, and elevation-angle dependence of the scintillation data are presented A comparison between the propagation data and ground-level meteorological measurements indicated a high correlation between the scintillation characteristics and the water vapor contribution to the radio refractive index inferred from local humidity and temperature data This suggests a method for predicting the severity of scintillation fading using local measurements of meteorological parameters >

60 citations



Journal ArticleDOI
TL;DR: In this paper, the channel transfer characteristics of high-frequency (HF) radio signals propagating through the disturbed ionosphere were measured in a series of experiments conducted in the polar cap, auroral, and equatorial regions.
Abstract: The channel transfer characteristics of high-frequency (HF) radio signals propagating through the disturbed ionosphere were measured in a series of experiments conducted in the polar cap, auroral, and equatorial regions. Transmissions over one-hop F layer paths were observed to be distorted in the range (propagation time) and Doppler domains on the order of hundreds of microseconds and tens of hertz, respectively. A frequency-modulated continuous wave (FMCW) waveform was used for oblique sounding purposes, and a pseudorandom noise phase modulation with a 20-kHz bandwidth was used to measure range and Doppler spreads. The oblique sounding data were used to define a three-layer quasi-parabolic model of the ionospheric electron density profile, which in turn was used in the calculation of the channel scattering function to compare with the observed range and Doppler spreads.

47 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present solutions of the wave equations which show that oscillatory structures will develop when a powerful radio wave beam propagates through the defocusing region of the ionosphere.
Abstract: We present solutions of the wave equations which show that oscillatory structures will develop when a powerful radio wave beam propagates through the defocusing region of the ionosphere.

Journal ArticleDOI
TL;DR: The Very Long Baseline Array (VLBA) as discussed by the authors is a radio telescope that can synthesize a resolution equivalent to that of a large aperture by combining data from smaller radio antennas that are widely separated.
Abstract: The development of radio technology in World War II opened a completely new window on the universe. When astronomers turned radio antennas to the heavens, they began to find a previously unknown universe of solar and planetary radio bursts, quasars, pulsars, radio galaxies, giant molecular clouds and cosmic masers. Not only do the radio waves reveal a new world of astronomical phenomena but also-because they are much longer than light waves-they are not as severely distorted by atmospheric turbulence or small imperfections in the telescope. About 25 years ago radio astronomers became aware that they could synthesize a resolution equivalent to that of a large aperture by combining data from smaller radio antennas that are widely separated. The effective aperture size would be about equal to the largest separation between the antennas. The technique is called synthesis imaging and is based on the principles of interferometry. Radio astronomers in the U.S. are now building a synthesis radio telescope called the Very-Long-Baseline Array, or VLBA. With 10 antennas sited across the country from the Virgin Islands to Hawaii, it will synthesize a radio antenna 8,000 kilometers across, nearly the diameter of the earth. The VLBA'S angular resolution will be less thanmore » a thousandth of an arc-second-about three orders of magnitude better than that of the largest conventional ground-based optical telescopes. Astronomers eagerly await the completion early in the next decade of the VLBA, which is expected, among other things, to give an unprecedentedly clear view into the cores of quasars and galactic nuclei and to reveal details of the processe-thought to be powered by black holes-that drive them.« less

Journal ArticleDOI
TL;DR: In this paper, two different source mechanisms that can cause the spectral broadening of VLF radio signals traversing the ionosphere, a phenomenon first observed by Bell et al. are proposed.
Abstract: Two different source mechanisms that can cause the spectral broadening of VLF radio signals traversing the ionosphere, a phenomenon first observed by Bell et al. (1983), are proposed. The first is a nonlinear scattering of the whistler-mode VLF signals by preexisting ionospheric density fluctuations that render a mode conversion to lower hybrid waves. In the absence of ionospheric irregularities, a second mechanism, that involves a parametric instability, can excite the lower hybrid waves, as was proposed by Lee and Kuo (1984). Since both types of spectra were recorded in experiments, it is concluded that the two suggested source mechanisms contribute additively to the observed spectral broadening of injected VLF waves.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the role of low collisional cooling rates combined with strong thermal conduction along geomagnetic field lines played a key role in elevating F region temperatures and spreading the electron temperature enhancements far outside the region where radio wave energy is deposited.
Abstract: Under current solar minimum conditions at Arecibo, Puerto Rico, large (∼1000–2000 K) enhancements in electron temperature are observed in the winter, nighttime ionosphere when high-power 3-MHz radio waves reflect near the F region peak. Computational modeling has been performed to determine the cause of the unusually large temperature enhancements. The results indicate that low collisional cooling rates combined with strong thermal conduction along geomagnetic field lines play a key role in elevating F region temperatures and spreading the electron temperature enhancements far outside of the region where radio wave energy is deposited. Thus, the dramatically large temperature enhancements are attributable primarily to expected low cooling rates of the electron gas, rather than unexpectedly high heating rates.

Patent
14 Oct 1988
TL;DR: In this paper, a radio-optical interface between a first modulated radio wave (15) and a light wave (18) is presented, where the transmitted light wave is subjected to wavelength modulation.
Abstract: A radio-optical transmission system in particular for space telecommunications, comprising a radio-optical interface between a first modulated radio wave (15) and a light wave (18), wherein the transmitted light wave (18) is subjected to wavelength modulation.

Journal ArticleDOI
TL;DR: In this paper, the ionosphere was modified with powerful, high-frequency radio waves transmitted by the Heating facility near Tromso, Norway, where the enhanced ion and plasma lines were observed, and the SEE amplitude variation on long time scale (seconds to tens of seconds) shows similarity with the long-time scale behavior of the amplitude of the plasma lines observed by EISCAT.
Abstract: The ionosphere was modified with powerful, high-frequency radio waves transmitted by the Heating facility near Tromso, Norway. The modified ionosphere was observed using the Tromso and Kiruna European Incoherent Scatter (EISCAT) UHF system together with a 145-MHz portable CW radar and equipment for reception of stimulated electromagnetic emissions (SEE). Enhanced ion and plasma lines were observed. They persisted throughout heater periods of more than a minute, contrary to earlier observations at Tromso. Spectral features in the plasma lines were repeatedly observed at frequency shifts which are not explained by current theories. The SEE amplitude variation on long time scale (seconds to tens of seconds) shows similarity with the long–time scale behavior of the amplitude of the plasma lines observed by EISCAT. No obvious correlation seems to exist between the SEE and discovered radar spectral features.

Journal ArticleDOI
TL;DR: In this paper, the phase data were modeled assuming the source to be a simple point dipole located in the ionosphere at the point of maximum HF radiation and provided good agreement with experimental phase data only when the HF beam was deflected toward the ELF/VLF receiver.
Abstract: The generation of ELF/VLF radio waves by heating the auroral ionosphere with a powerful HF transmitter, modulated at the ELF/VLF frequency, is now well documented. Recently, results were presented of the phase of the ELF/VLF signals received at a distance of 500 km from such a source as the HF beam was deflected toward and away from the receiver by up to 37° from the vertical. The phase data were modeled assuming the source to be a simple point dipole located in the ionosphere at the point of maximum HF radiation. This simple model provided good agreement with experimental phase data only when the HF beam was deflected toward the ELF/VLF receiver. The model of the ELF/VLF generation mechanism presented here includes contributions from the majority of the HF radiation pattern illuminating the ionosphere and assumes it to be a continuous source of ELF/VLF excitation. Computations based on this new model provide excellent agreement with the experimental phase data at all beam deflection angles. The use of this model to improve the power efficiency of the generation of ELF/VLF radio waves by HF heating facilities by more than a factor of 3 is discussed.

Journal ArticleDOI
TL;DR: In this paper, the properties of radio waves generated by electron beams in space were investigated using data from the wideband wave receiver on the Spacelab 2, which was found to confirm the results of the STS 3/OSS-1 mission.
Abstract: The properties of radio waves generated by electron beams in space were investigated using data from the wideband wave receiver on the Spacelab 2. The VLF observations were found to confirm the results of the STS 3/OSS-1 mission. It was found that a 1-keV electron beam injected from the orbiter produced copious broadband electromagnetic emissions. When the electron beam was square-wave modulated, narrow-band emissions at the pulsing frequency and harmonics of that frequency were produced along with the broadband emissions. The observations indicated that dc 50-mA electron beams and pulsed 50-percent duty-cycle 100-mA beams produce broadband radiation which is comparable in intensity and spectral shape at all points for which the wave field was sampled.

Journal ArticleDOI
TL;DR: In this paper, Liouville's theorem for radiation, of which the generalized etendue is a consequence, implies that the propagation of radio waves from the actual to the apparent source in the solar corona (i.e., the scatter image of the true source) is constant along the ray path, where μ is the refractive index, where d2Ω and d2A are the ranges, respectively, of solid angle and area that define a ray (actually a bundle of rays).
Abstract: Liouville's theorem for radiation, of which the generalized etendue is a consequence, implies μ2 d2Ω d2A = constant along the ray path, where μ is the refractive index and d2Ω and d2A are the ranges, respectively, of solid angle and of area that define a ray (actually a bundle of rays). Implications of this concept on the propagation of radio waves from the actual to the apparent source in the solar corona (i.e., the scatter image of the true source) are discussed. The implications for sources of fundamental plasma radiation include: (1)The observed solid angle ΔΩ (defining the directivity) and apparent area ΔA of the source are compatible with Liouville's theorem only if the apparent source (the scatter image of the true source) corresponds to the envelope of subsources with a small ‘filling factor’ f. (2) The brightness temperature TBof the actual source is greater than that of the apparent source by f-1. (3) For sources of fundamental plasma radiation the factor f is very small (≲ 10-2). (4) A long-standing discrepancy between the observed low value of TB at meter/decameter wavelengths for the quiet Sun and the known coronal temperature may be resolved by noting that the implied coronal temperature is given by TBf and that the factor f must be significantly less than unity.

Proceedings ArticleDOI
T. Maeda1, Tasuku Morooka1
06 Jun 1988
TL;DR: In this article, a modified version of the random field measurement (RFM) is proposed, which is based on the assumption that the cumulative probability of reception should be the same for both the unknown and the reference antennas.
Abstract: The radiation frequency of a small built-in antenna in portable radio equipment could not be measured accurately because of the nearby electric parts and the human body. A description is given of a measurement method taking account of these influences. The authors devise a modified version of the random field measurement (RFM), which is based on the assumption that the cumulative probability of reception should be the same for both the unknown and the reference antennas. This method has an advantage of being able to measure the radiation efficiency including the effects of the human body. Experimental results using the indoor RFM are presented and some inherent problems with this measurement scheme are discussed. An alternate method of using radio wave scatterers surrounding the transmitting antenna is proposed to improve the accuracy of the measurement. >

Journal ArticleDOI
TL;DR: In this paper, results of some recent ionospheric modification experiments undertaken with the Max-Planck Institut fur Aeronomie (Lindau) high power facility at Tromso, Norway, are reviewed.
Abstract: High power radio waves are capable of exciting a variety of parametric plasma instabilities in the ionosphere. Certain instabilities of this type result in the generation of electrostatic plasma waves and plasma density irregularities. These generation processes are often accompanied by strong anomalous absorption of the high power radio waves and this, in turn, gives rise to the large scale modification of the temperature and density of the ionospheric plasma. Results of some recent ionospheric modification experiments undertaken with the Max-Planck Institut fur Aeronomie (Lindau) high power facility at Tromso, Norway, are reviewed. The interpretation of these results in terms of the nonlinear development and saturation of the plasma instabilities involved is also discussed.

Journal ArticleDOI
TL;DR: In this article, it was demonstrated that radio-frequency (rf) waves applied below the ion cyclotron frequency (ω/Ωi≊0.75) can stabilize a mirror plasma against the interchange instability.
Abstract: It is demonstrated that radio‐frequency (rf) waves applied below the ion cyclotron frequency (ω/Ωi≊0.75) can stabilize a mirror plasma against the interchange instability. A set of phased antennas in the Phaedrus‐B tandem mirror central cell [Phys. Rev. Lett. 59, 206 (1987)] is used to select the rf azimuthal mode number (m). When the m=−1 mode is selected, the ponderomotive force from the left‐hand polarized wave fields is sufficient to stabilize the plasma. Measurements of the rf mode number and of the wave polarization indicate strong excitation of m=−1 modes with much of the wave having a left‐hand polarization.

Journal ArticleDOI
TL;DR: The Voyager Planetary Radio Astronomy (PRAD) experiment revealed prominent "arcs" when the radio intensity at 1-40 MHz was displayed in time-frequency coordinates as discussed by the authors, which are consistent with multiple currents flowing along longitudinally separated Jovian magnetic flux tubes, each current radiating conically at angles up to about 90 degrees.
Abstract: The Voyager Planetary Radio Astronomy (PRAD) experiment revealed prominent 'arcs' when the radio intensity at 1-40 MHz was displayed in time-frequency coordinates. These data are consistent with multiple currents flowing along longitudinally separated Jovian magnetic flux tubes, each current radiating conically at angles up to about 90 deg. The spacings between adjacent PRA arcs, and also between adjacent S burst arc segments observed at the Nancay Observatory, were analyzed and found to be so brief, less than 1-3 min, that either these currents and any associated Alfven waves survive for at least a few circulations of Jupiter by Io (a hypothesis independently supported by the observations of arcs at all Io phase angles), or each such Alfven current can radiate at several different cone-angles simultaneously (a hypothesis independently supported by the observation of such behavior in the S burst arcs).


Journal ArticleDOI
TL;DR: In this paper, 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).
Abstract: 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.

Journal ArticleDOI
TL;DR: In this paper, the authors used the high-power, high-frequency (HF) facility at Arecibo, Puerto Rico, has been used to study the excitation of Langmuir waves in mid-latitude sporadic E. Measurements of the temporal evolution of the so-called HF-enhanced plasma line (HFPL) were made using the arecibo 430MHz radar.
Abstract: The high-power, high-frequency (HF) facility at Arecibo, Puerto Rico, has been used to study the excitation of Langmuir waves in mid-latitude sporadic E. Measurements of the temporal evolution of the so-called HF-enhanced plasma line (HFPL) were made using the Arecibo 430-MHz radar. After HF turn-on in the plasma the HFPL exhibits a rapid growth phase followed by a quick overshoot. During periods of strong HFPL excitation the e-folding growth time of the HFPL power is typically ≲ 20 µs, and the total overshoot period is ∼1 ms. On the basis of the current observations, mode conversion of the HF wave into Langmuir waves near HF reflection appears to be a promising mechanism for the production of Langmuir waves in sporadic E. Caviton formation at the critical layer is expected to accompany this process, and there is some evidence that the 430-MHz radar is probing the plasma in a region where density cavities of this nature form. While no specific explanation is offered for the HFPL overshoot, it appears that this phenomenon is fundamental to the Langmuir wave excitation process.

Journal ArticleDOI
TL;DR: In this paper, the well-known decametric radio S-bursts from Jupiter, observed in France and Australia at frequencies from 10 to 26 MHz, have been found to exhibit equally spaced discrete spectral components which can be attributed to the adjacent longitudinal oscillation modes of natural radio lasers.
Abstract: Like the comparable AKR radio emissions from earth's magnetosphere, the well-known decametric radio S-bursts from Jupiter, observed in France and Australia at frequencies from 10 to 26 MHz, have been found to exhibit equally spaced discrete spectral components which can be attributed to the adjacent longitudinal oscillation modes of natural radio lasers. Implying sizes of only a few kilometers for the individual radio lasers producing the S-bursts, the frequency spacing of these modes was roughly constant with frequency and about 30 to 50 kHz. Their corresponding temporal spacings, however, varied inversely proportional to the observing frequency, suggesting that the radio lasers producing the S-bursts were expanding uniformly at a rate of about 4 km/s. Presumably caused by the projected motion of Io with respect to the planet, this expansion of the S-burst radio lasers would account for the downward frequency drifts of the S-bursts without the energetic electron bunches which have heretofore always been assumed necessary to account for such behavior.

Patent
12 Jan 1988
TL;DR: In this article, the reliability of the position and speed of a moving body by processing radio waves received from plural satellites into one-channel sequence data by a CPU, and measuring and comparing variation in offset from the frequency of a reference oscillation with a threshold value was investigated.
Abstract: PURPOSE:To improve the reliability of the position and speed of a moving body by processing radio waves received from plural satellites into one-channel sequence data by a CPU, and measuring and comparing variation in offset from the frequency of a reference oscillation with a threshold value. CONSTITUTION:When a power source is turned on, the radio waves received by an antenna 1 from the plural satellites are amplified 2 and converted to the 1st IF by the reference oscillator 10 and a frequency synthesizer 9. The 1st IF is amplified 4 and converted 5 to the 2nd IF, which is amplified 6 and phase-compared 7 with the output of the frequency synthesizer 9. A dummy noise code is generated 13 wit the output of a CPU8 under the control of a dummy noise code period numeral control oscillator 14 to impose modulation 11 upon the output of a numeric control oscillator 12 for carrier phase synchronization, so that the output is inputted to the 2nd frequency converter 5. A double loop from the CPU8 back to the CPU8 is formed eventually to track a carrier in series to calculate whether the offset of the frequency is large or small. Consequently, the reliability of the position and speed of the moving body is decided.

Journal ArticleDOI
TL;DR: In this article, Doppler shifts in HF radio transmissions through the ionospheric F region following the Coalinga, California earthquake of May 1983 were described as peaks or broad bands of enhanced power in the spectra of the HF transmissions.
Abstract: In a previous report, Doppler shifts in HF radio transmissions through the ionospheric F region following the Coalinga, California earthquake of May 1983 were described. We report here on disturbances which appeared between 400 and 500 s after the earthquake as peaks or broad bands of enhanced power in the spectra of the HF transmissions and not as Doppler shifts. While the time delay (600–800 s) before the occurrence of the Doppler shifts corresponds to the acoustic travel time to the F region, the time delay for the spectral changes indicates a travel time to the ionospheric E region. We believe that the occurrence of the spectral changes represents the presence of temporary E-region propagation modes induced by the passage of the acoustic waves responsible for the Doppler shifts observed at higher altitudes. Because the enhanced spectral power occurs at negative frequency relative to that of the F-region propagation modes, the disturbances could be the result of reflections from electron density gradients induced by upwardly propagating acoustic waves.

01 Jan 1988
TL;DR: The low frequency, non thermal, highly polarized radio emissions coming from the four planets, the Earth, Jupiter, Saturn and Uranus, are thought to be produced by coherent amplification of electromagnetic waves at the electron gyrofrequency, due to the conversion of the energy contained in anisotropic distributions of energetic electrons as discussed by the authors.
Abstract: The low frequency, non thermal, highly polarized radio emissions coming from the four planets, the Earth, Jupiter, Saturn and Uranus, are thought to be produced by coherent amplification of electromagnetic waves at the electron gyrofrequency, due to the conversion of the energy contained in anisotropic distributions of energetic electrons. The proposed mechanisms predict a preferenced emission in the extraordinary, right–hand polarized (R– X) mode with respect to the local magnetic field, as actually confirmed, in most of the cases, by observations.