Electric field observations of ionospheric whistlers
Whistler mode wave propagation amplitude, polarization and dispersion in lower ionosphere, discussing electric field experiment with Nike- Tomahawk sounding rocket
Aggson, T. L.↗
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Vibration detection using lasers
Interference displacement patterns produced when light from a laser illuminates diffusely reflecting, vibrating surface are observed and photographed. Standing wave modes on model surface can be interpreted in order to yield amplitude and frequency of vibrations. Flat, white surfaces yield best interference patterns, even over considerable surface curvature.
Massey, G. A.↗
Polarization of proton whistlers
Whistler-mode waves circular polarization measurement by OGO 6 satellite, noting application to hiss, chorus and ion density studies
Smith, R. L.↗
Numerical solution for propagation of coupled longitudinal and transverse waves normal to the applied magnetic field in a three-fluid medium.
The solution was obtained without approximating the dispersion relation. This was made possible by the use of a computer method for carrying out the extremely large number of algebraic manipulations involved. The three-fluid model employed accounts for the interaction of the electron, ion, and neutral species. The solution for the e-folding distance describes the damping characteristics of each wave mode. Each of the e-folding solutions corresponds to one of the phase velocity solutions.
Mcclendon, R. W.↗
Pitch-angle diffusion of radiation belt electrons within the plasmasphere.
Study of the formation of the quiet-time electron slot, which divides the radiation belt electrons into an inner and an outer zone. The pitch-angle diffusion of radiation belt electrons resulting from resonant interactions with the observed plasmaspheric whistler-mode wave band is quantitatively investigated. The effects of wave propagation obliquely to the geomagnetic field direction with the resulting diffusion at all cyclotron-harmonic resonances and the Landau resonance are evaluated along with the effects of interactions occuring at all geomagnetic latitudes. The results obtained account for the long-term stability of the inner radiation zone, the location of its outer edge as a function of electron energy, and the removal of electrons to levels near zero throughout the slot. Computed pitch-angle distributions and precipitation decay rates are in good agreement with slot-region observations.
Lyons, L. R.↗
Amplitude variations of whistler-mode signals caused by their interaction with energetic electrons of the magnetosphere
Whistler mode waves that propagate through the magnetosphere exchange energy with energetic electrons by wave-particle interaction mechanisms. Using linear theory, a detailed investigation is presented of the resulting amplitude variations of the wave as it propagates. Arbitrary wave frequency and direction of propagation are considered. A general class of electron distributions that are nonseparable in particle energy and pitch-angle is proposed. It is found that the proposed distribution model is consistent with available whistler and particle observations. This model yields insignificant amplitude variation over a large frequency band, a feature commonly observed in whistler data. This feature implies a certain equilibrium between waves and particles in the magnetosphere over a wide spread of particle energy, and is relevant to plasma injection experiments and to monitoring the distribution of energetic electrons in the magnetosphere.
Bernard, L. C.↗
Mirroring within the Fokker-Planck formulation of cosmic ray pitch angle scattering in homogeneous magnetic turbulence
The Fokker-Planck coefficient for pitch angle scattering, appropriate for cosmic rays in homogeneous, stationary, magnetic turbulence, is computed from first principles. No assumptions are made concerning any special statistical symmetries the random field may have. This result can be used to compute the parallel diffusion coefficient for high energy cosmic rays moving in strong turbulence, or low energy cosmic rays moving in weak turbulence. Becuase of the generality of the magnetic turbulence which is allowed in this calculation, special interplanetary magnetic field features such as discontinuities, or particular wave modes, can be included rigorously. The reduction of this results to previously available expressions for the pitch angle scattering coefficient in random field models with special symmetries is discussed. The general existance of a Dirac delta function in the pitch angle scattering coefficient is demonstrated. It is proved that this delta function is the Fokker-Planck prediction for pitch angle scattering due to mirroring in the magnetic field.
Goldstein, M. L.↗
Ion effects on ionospheric electron resonance phenomena
Ion effects are often observed on topside-sounder stimulated electron plasma wave phenomena. A commonly observed effect is a spur, appearing after a time delay corresponding to the proton gyro period, attached to the low frequency side of an electron plasma resonance. The spurs are often observed on the resonances at the electron plasma frequency f sub N, the harmonics nf sub H of the electron cyclotron frequency f sub H (n = 2, 3, 4, ...), and occasionally on the upper hybrid frequency. The spurs on the f sub N resonance are usually quite small unless the f sub N resonance overlaps with an nf sub H resonance; very large spurs are observed during such overlap conditions. Proton spurs are only observed on the nf sub H resonances when the electron plasma waves associated with these resonances are susceptible to the Harris instability and when the electromagnetic z wave can be initiated by the sounderpulse. This instability is the result of a sounder stimulated anisotropic electron velocity distribution. The observations suggest that energy is fed into the nf sub H longitudinal plasma wave from the z wave via wave-mode coupling. The magnitude of the nf sub H spurs for large n is much greater than for small n.
Benson, R. F.↗
One-dimensional multimode and multistate oscillator: A concept
Device's voltage amplitude distribution is similar to that of standing waves on transmission line. It can be used for fast, efficient information encoding, decoding, and memory. Device operates in response to brief tone burst setting up standing-wave mode of oscillation which is unique for each possible burst frequency.
Aumann, H. M.↗
Mirroring in the Fokker-Planck coefficient for cosmic-ray pitch-angle scattering in homogeneous magnetic turbulence
The Fokker-Planck coefficient for pitch-angle scattering, appropriate for cosmic rays in homogeneous stationary magnetic turbulence is computed without making any specific assumptions concerning the statistical symmetries of the random field. The Fokker-Planck coefficient obtained can be used to compute the parallel diffusion coefficient for high-energy cosmic rays propagating in the presence of strong turbulence, or for low-energy cosmic rays in the presence of weak turbulence. Because of the generality of magnetic turbulence allowed for in the analysis, special interplanetary magnetic field features, such as discontinuities or particular wave modes, can be included rigorously.
Goldstein, M. L.↗
Ion effects on ionospheric electron resonance phenomena
Ion effects are often observed on topside-sounder-stimulated electron plasma wave phenomena and the present study is concerned with the spur effect relative to electron plasma resonance. A spur appears after a time delay corresponding to the proton gyroperiod and is observed mainly on the resonances at the electron plasma frequency and the harmonics of the electron cyclotron frequency. Proton spurs occur at the harmonic resonances only, when the electron plasma waves associated with these resonances are susceptible to the Harris instability and when the electromagnetic wave can be initiated by the sounder pulse. This instability results from a sounder-stimulated anisotropic electron velocity distribution. The observations suggest that energy is fed into the harmonics of the longitudinal plasma wave from the electromagnetic wave through wave-mode coupling. The observations were made during eight passes of the Alouette-2 satellite.
Benson, R. F.↗
The quiet time structure of energetic /35-560 keV/ radiation belt electrons
Detailed Explorer 45 observations of quiet time pitch angle distributions and equatorial radial profiles of energetic radiation belt electrons are presented. The observed pitch angle distributions in the slot region and the outer regions of the plasmasphere are found to agree with the values expected from resonant interactions with the plasmaspheric whistler mode wave band, and Coulomb collisions are found to be the dominant electron loss mechanism in the inner zone. The overall structure of quiet time radial profiles is shown to agree with the equilibrium structure expected to result from a balance between pitch angle scattering losses and radial diffusion from an outer zone source, and this agreement suggests that the dominant quiet time source and loss mechanisms have been correctly identified. Electron fluxes in the inner plasmasphere are found to remain nearly constant during the quiet periods due to their decoupling from magnetic activity variations in the outer plasmasphere.
Lyons, L. R.↗
A study of sound transmission in curved duct bends by the Galerkin method
A computational procedure based on the Galerkin method is developed to study the sound transmission and reflection characteristics of circularly curved bends of rectangular ducts. This procedure is adaptable to routine computer calculation. An important component of the computer program consists of a QR iterative algorithm which solves the matrix eigenvalue problem generated by the Galerkin method. The present procedure produced very satisfactory convergent results when applied even to cases where the incident wave has high frequency and high wave mode numbers. Some properties of the Galerkin solution are investigated. Its relationship to the classical solution by the method of separation of variables is discussed.
Tam, C. K. W.↗
Some comments on the whistler mode instability at Jupiter
The paper considers the possibility that electrons with energies exceeding 21 MeV at Jupiter interact resonantly with obliquely propagating whistler mode waves. The equatorial pitch angle distributions are deduced from the Pioneer 10 and 11 data points of Van Allen et al. (1975). For the L shell subgroup 7, there is observed a 'hat-shaped' pitch angle distribution which is similar to that found within the earth plasmasphere.
Scarf, F. L.↗
Spacecraft observations of man-made whistler-mode signals near the electron gyrofrequency
The reported investigation extends the range of whistler-mode wave observations to a wave frequency/electron gyrofrequency ratio of about 0.9, where an abrupt cutoff is observed. This cutoff can be explained entirely in terms of accessibility and hence, if there is damping, it must be limited to normalized frequencies above 0.9. In connection with a study of the behavior of the signal intensity, ray tracings were carried out at 80 kHz. The ray-tracing calculations were carried out with the aid of a computer program written by Walter (1969) and modified by Angerami (1970).
Dunckel, N.↗
Induced emission of extraordinary mode radiation in tokamaks
The implications of the formation of a positive slope in the runaway electron tail in tokamak plasmas are investigated in regard to the radiation in the vicinity of the electron plasma frequency. In particular, it is shown that the amplification of extraordinary mode waves may result.
Freund, H. P.↗
Diffuse Jovian aurora influenced by plasma injection from Io
The paper demonstrates that the broad band of whistler-mode waves observed within the high density torus surrounding Io is consistent with electron cyclotron generation. Cyclotron resonant instability of Jovian energetic electrons is enhanced due to the lower resonant electron energy within the equatorial high density plasma torus surrounding the orbit of Io. The higher energy resonant electron scattering and the corresponding energetic electron lifetimes indicate that an efficient local acceleration process is required to replenish the precipitating relativistic electrons. Calculated energy deposition into the Jovian atmosphere should provide a dominant source of middle atmospheric ionization and excite a continuous band of diffuse auroral emission. It is suggested that the diffuse Jovian aurora should be influenced by the variable volcanic activity on Io which is thought to be an important source of plasma, since the cyclotron scattering process is strongly influenced by the ambient equatorial thermal plasma density.
Thorne, R. M.↗
Effects of power line radiation into the magnetosphere
Observations of the effects of VLF power line radiation on whistler-mode waves in the magnetosphere are reviewed. High-altitude OGO-3 spectral data reveal evidence of enhanced chorus activity over populated regions starting at harmonics of the power-line frequencies. Low-altitude Ariel 3 measurements of 3.2 kHz noise intensity also indicate an enhancement of VLF activity over populated areas and their conjugates, however the relative importance of power line radiation, whistlers and spontaneous emissions is not known. The low-altitude polar-orbiting OGO-4 satellite also observed noise spectra at the harmonics of power line frequencies over industrial regions. Ground observations from Eights and Siple, Antarctica indicate that power line radiation effects on magnetospheric ducted paths peak at 3 kHz and near dawn, and exhibit a pronounced decrease on Sundays in the conjugate region, when power consumption is at a minimum. Experiments simulating power line radiation effects have also been performed. It is suggested that power line radiation effects magnetospheric activity by lowering the threshold for wave growth, with the localization of VLF sources acting to localize corresponding particle precipitation without necessarily affecting global average precipitation.
Helliwell, R. A.↗