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Dyson, P. L.

Publications and source records attributed to Dyson, P. L..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Neutral atmospheric waves determined from Atmospheric Explorer measurements

A description is presented of the first observations of neutral gravity waves in which a sufficient number of wave parameters are detected to allow a specification of the neutral wave characteristics. In situ measurements of neutral wind, temperature, and composition from Atmospheric Explorer are used to obtain wave amplitudes and phases for N2 temperature and wind, and N2, O, and He densities. These amplitudes and phases along with the Doppler shifted wave frequency provide sufficient information to evaluate the wave frequency and the wave vector.

Hoegy, W. R.↗
NASA NTRS1978

Topside sounder observations of equatorial bubbles

Large scale regions of depleted equatorial ionospheric plasma, called equatorial bubbles, are investigated using topside sounder data. The sounder's unique remote measuring capability enables the magnetic field-aligned nature of the bubbles to be investigated. A search of all available Alouette 2 and ISIS 1 ionograms during nighttime perigee passes near the magnetic equator has revealed a variety of echo signatures associated with bubbles. In addition to a sudden drop in electron density, these signatures usually include in situ spread F and ducted traces. The ducted traces have been used to determine the electron density distribution and to infer changes in ion composition along the magnetic field line within the duct associated with the bubble. In some cases it can be determined that the bubble is asymmetric with respect to the magnetic equator. Even though such features require 3 dimensional models for their explanation, the great field-aligned extent of the bubbles (relative to their cross section) suggests that current theories, which ignore variations along the magnetic field, are still applicable.

Dyson, P. L.↗
NASA NTRS1978

Operational modes for a wave injection facility aboard spacelab and a sub-satellite

Various modes of operation are described for an orbiting wave injection facility planned to measure the properties of waves propagating in space plasma. Such a facility would cover a wide frequency range including MF and HF. Phase shift and Doppler shift measurements will yield more accurate measurements of echo time delay and the angle of arrival. Because Spacelab will involve some sub-satellites, some consideration is given to propagation between two vehicles both at HF and VHF.

Dyson, P. L.↗
NASA NTRS1978

On the relation between phase path, group path and attenuation in a cold absorbing plasma

Consideration is given to a cold absorbing plasma in which the collision frequency is zero. Expressions are developed which relate the attenuation and the group and phase refractive indices. It is found that because the expressions for the group and phase refractive indices and the imaginary part of the refractive index are closely related in form, the attenuation is related to the difference between the group and phase paths. Numerical calculations have derived approximations which significantly increase the range of known approximations of this type.

Bennett, J. A.↗
NASA NTRS1974

In situ measurements of the spectral characteristics of F region ionospheric irregularities

The retarding potential analyzer aboard Ogo 6 has provided high-resolution observations of the ion concentration along the satellite path. Changes in ion concentration as small as 0.03% and at times as small as 0.01% could be measured. Spatial resolution varied from 35 to 380 m. Samples of data have been analyzed to determine the spectral properties of the F region irregularities observed. The most common frequency spectrum observed suggests that the responsible irregularities result from the turbulent dissipation of larger irregularities. At the equator, the larger irregularities are probably produced by convective electric fields. At high latitudes, electric fields may also be involved, but other factors such as precipitating particles may contribute to, or be primarily responsible for, the production of large irregularities. Examples of other types of spectra associated with wavelike irregularities and with 'ground glass' (high-frequency noise) irregularities are also shown.

Dyson, P. L.↗