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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
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NASA NTRS1973

Ion cyclotron waves observed in the polar cusp.

During the penetration by Ogo 5 of the low-latitude disturbed polar cusp region on Nov. 1, 1968, while a major magnetic storm was in progress, a variety of plasma wave activity was observed. Observations of waves with amplitudes less than 2% of the background magnetic field intensity and having frequencies between approximately 0.67 and 0.87 times the local proton gyrofrequency are described. The polarization of these waves indicates that they are propagating at an appreciable angle to the local geomagnetic field line direction. The source of these waves has not been determined, but currents and gradient drifts are suggested as possible agents.

Fredricks, R. W.↗
NASA NTRS1973

Electrostatic velocity-space instabilities stimulated near the harmonics of the electron cyclotron frequency in the ionosphere

Data are presented on observations made in the ionospheric plasma that provide evidence for the stimulation of Harris type instabilities at nf sub H in a single electron transition. An illustration is also given of the change in shape of the dispersion curve for a given nf sub H as the upper hybrid frequency crosses the nf sub H value. It was concluded that the instability can exist near nf sub H only when the hybrid frequency nf sub H.

Benson, R. F.↗
NASA NTRS1973

Cyclotron resonance wave amplification in the magnetosphere and energetic particle stability

Detailed electron distribution measurements in the outer magnetosphere now available indicate that the energetic electron anisotropy may be very energy dependent, there being positive anisotropies near the magnetic equator for low-energy particles and negative anisotropies in this region for high-energy particles. Previous wave growth calculations assuming the energetic particle anisotropy to be independent of energy are inaccurate at high energies. The net one-hop whistler mode wave amplification is calculated as a function of frequency for a measured electron distribution at L = 7 for a number of assumed equatorial plasma densities. It is found that an increase in cold plasma density results in a change from a net wave damping to significant wave amplification.

Lucas, C.↗