Standing Alfven waves in the magnetosphere.
Transverse LF oscillations in geomagnetic field observed during January 1967, noting possibility of being second harmonic of magnetospheric standing Alfven waves
Coleman, P. J., Jr.↗
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Intensity correlations in optical nonlinear processes by photon counting techniques
Intensity correlations in optical parametric noise and second harmonic generation measured by two photon delayed coincidence counting
Davidson, F.↗
A statistical analysis of some non-linear optical effects
Statistical analysis of some nonlinear optical effects including scattering light from rotating glass and second harmonic light generated by pseudo-thermal source
O'Neill, E. L.↗
Maximum temperatures for radiation from plasma waves.
Upper limits to radiation temperatures from plasma waves for emissions near the fundamental and second harmonic of the electron plasma frequency are derived in terms of effective temperature for plasma waves. Results are obtained that differ from those of Melrose (1970) by a factor that can exceed 40,000 for some plasmas.
Smith, D. F.↗
Magnetospheric electron density measurements from upper hybrid resonance noise observed by IMP-6
A band of natural radio noise between the local electron plasma frequency and the upper hybrid resonance frequency is observed by the IMP-6 satellite. The band exists over a large range of geocentric radial distances extending from inside the plasmapause boundary to greater than 10 earth radii in the outer magnetosphere. The center frequency of the noise band decreases with increasing radial distance, and changes abruptly at the plasmapause boundary. The broadband electric field strength of this noise is very small, seldom exceeding 10 microvolts/meter, and probably could not be detected without using long electric antennas of IMP-6. It is believed that this noise is produced by incoherent Cerenkov emission from super-thermal electrons. In some cases a second very narrow noise band was observed at a frequency slightly above the second harmonic of the electron gyrofrequency.
Shaw, R. R.↗
Study of self-focusing and self-phase-modulation in the picosecond-time regime.
Study of the propagation of a single picosecond pulse of a mode-locked Nd-glass laser in CS2 nitrobenzene and toluene by observations of the birefringence and spectral changes in self-focused laser light. Multiple second-harmonic probing beams are used for birefringence measurements in a single IR pulse in various portions of the active cell. The orientational Kerr effect is found to be the prime factor of induced birefringence in nitrobenzene and toluene. The results for CS2 are also consistent with this mechanism and show that the duration of an IR pulse in the focal volume is less than that of the incident pulse. The properties of beams which are focused within the cell by an external lens are also investigated.
Reintjes, J.↗
Decay time of type 3 solar bursts
Type 3 solar bursts observed by OGO-5, below 600 kHz, were analyzed. Decay times were measured, and collisional decay times were computed for distances out to 1 AU. By fitting power functions to the computed and observed decay times, and using local plasma hypothesis, it was found that the ratio rho of computed observed values varies with heliocentric radial distance according to a power function rho = 3r to the 0.7th power, assuming fundamental emission, and rho = 2r to the 0.7th power, assuming second harmonic emission.
Alvarez, H.↗
Design, construction and evaluation of a 12.2 GHz, 4.0 kW-CW high efficiency klystron amplifier
An analytical and experimental program is described, for studying design techniques for optimizing the conversion efficiency of klystron amplifiers, and to utilize these techniques in the development and fabrication of an X-band 4 kW cw klystron, for use in satellite-borne television broadcast transmitters. The design is based on a technique for increasing the RF beam current by using the second harmonic space charge forces in the bunched beam. Experimental analysis was also made of a method to enhance circuit efficiency in the klystron cavities. The design incorporates a collector which is demountable from the tube to facilitate multistage depressed collector experiments employing an axisymmetric, electrostatic collector for linear beam microwave tubes.
Vishida, J. M.↗
Experiments with a four-bladed cyclic pitch stirring model rotor, part 3
The experimental work with the 2-bladed 16-inch diameter model rotor has been continued with a 4-bladed 16.5 inch diameter rotor capable of progressing and regressing cyclic pitch excitation (cyclic pitch stirring). Advance ratios of 0, .19 and .38 were tested at rotor speeds corresponding to non-dimensional blade natural frequencies of 1:14 and 1.19. The results are presented in the form of the first 5 Fourier components of the periodic response modulating function which for a periodic system takes the place of the complex response amplitude ratio of a constant system. In addition, the first and second harmonics of the trim response are presented. The test data are compared to analytical data without rotor wake and to the test data obtained earlier with the two-bladed rotor model of half the blade solidity ratio.
Hohenemser, K. H.↗
Satellite observations of type III solar radio bursts at low frequencies
Type III solar radio bursts have been observed from 10 MHz to 10 kHz by satellite experiments above the terrestrial plasmasphere. Solar radio emission in this frequency range results from excitation of the interplanetary plasma by energetic particles propagating outward along open field lines over distances from 5 earth radii to at least 1 AU from the sun. This review summarizes the morphology, characteristics, and analysis of individual as well as storms of bursts. Substantial evidence is available to show that the radio emission is observed at the second harmonic instead of the fundamental of the plasma frequency. This brings the density scale derived by radio observations into better agreement with direct solar wind density measurements at 1 AU and relaxes the requirement for type III propagation along large density-enhanced regions. This density scale with the measured direction of arrival of the radio burst allows the trajectory of the exciter path to be determined from 10 earth radii to 1 AU.
Fainberg, J.↗
Microwave diode amplifiers with low intermodulation distortion
Distortions can be greatly reduced in narrow-band applications by using the second harmonic. The ac behavior of simplified diode amplifier has negative resistance depending on slope of equivalent I-V curve.
Cooper, H. W.↗
The solar elogation distribution of low frequency radio bursts
Over 500 days of low frequency (less than 5 MHz) radio observations from the IMP-6 spacecraft were accumulated to produce a two dimensional map (frequency versus elongation) of solar type III burst occurrences. This map indicates that most solar bursts are emitted at the second harmonic of the plasma frequency rather than the fundamental. The map also shows that the solar wind electron density varies.
Kaiser, M. L.↗
Type II bursts at hectometric and kilometric wavelengths from interplanetary shocks
Data are presented on type II and type III radio bursts observed at hectometric and kilometric wavelengths in the interplanetary medium by IMP-6. Thirty-two discrete frequencies were recorded which ranged from 4.9 MHz down to 30 kHz. Intensity contours are plotted for the data, and it is noted that the type II emission was observed at both the plasma frequency characteristic of its point of origin in the corona and the second harmonic of that frequency. It is suggested that hectometric and kilometric type III bursts are observed at twice the plasma frequency of the source.
Malitson, H. H.↗
Stabilized Nd:YAG laser output
Stabilization system consists of feedback-loop-controlled piezoelectric crystal to one of the reflectors to vary optical path length within laser cavity. Average second harmonic of fundamental 1.06 micrometer laser radiation is detected by integrating detector.
Osmundson, J.↗
Pulse width fluctuations in mode-locked Nd:YAG lasers
The experiment consisted of a flashlamp-pumped Nd:YAG laser rod in the Brewster-Brewster configuration, passively modelocked by a thick flowing dye in contact with the high reflectivity rear mirror. A single pulse was selected by a cylindrical-ring electrode Pockel's cell, and amplified by two Nd:YAG amplifiers. Calibrated photodiodes measured the total pulse energy at the fundamental frequency and the total pulse energy at the second harmonic frequency. The signals were monitored by a digital data acquisition system and displayed on a teletype printer.
Bechtel, J. H.↗
The solar elongation distribution of low-frequency radio bursts
Over 500 days of low-frequency (less than 1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency, rather than the fundamental. The map also shows that the solar wind electron density varies as an inverse power of heliocentric distance, with the exponent somewhat less than 2 to perhaps 3 or higher.
Kaiser, M. L.↗
Acoustic Signatures of a Model Fan in the NASA-Lewis Anechoic Wind Tunnel
One-third octave band and narrowband spectra and continuous directivity patterns radiated from an inlet are presented over ranges of fan operating conditions, tunnel velocity, and angle of attack. Tunnel flow markedly reduced the unsteadiness and level of the blade passage tone, revealed the cutoff design feature of the blade passage tone, and exposed a lobular directivity pattern for the second harmonic tone. The full effects of tunnel flow are shown to be complete above a tunnel velocity of 20 meters/second. The acoustic signatures are also shown to be strongly affected by fan rotational speed, fan blade loading, and inlet angle of attack.
Dietrich, D. A.↗
Waves in active and passive periodic structures - A review
The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scattering from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode converters, couplers, second-harmonic generators, deflectors, modulators, and transducers in the fields of integrated optics and integrated surface acoustics. Work on insect compound eyes, mechanical structures, ocean waves, pulse compressions, temperature waves, and cholesteric liquid crystals, and particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and superlattices. Recent advances in fabrication techniques for very fine gratings are also covered.
Elachi, C.↗