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  • 1
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    D region predictions (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Present knowledge of D region phenomena is briefly reviewed and the status of current methods of predicting their effects on radio propagation considered. The ELF, VLF and LF navigational and timing systems depend on the stability of the lower part of the D layer where these waves are reflected, whereas MF and HF waves are absorbed as they penetrate the region, in most cases mainly in the upper part of the layer. Possible methods of improving predictions, warnings, and real time operations are considered with particular stress on those which can be implemented in the near future.
    Keywords: GEOPHYSICS
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 573-598
    Format: text
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  • 2
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    The effects of the geosynchronous energetic particle radiation environment on spacecraft charging phenomena (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The energetic electron environment at the geosynchronous orbit is responsible for a variety of adverse charging effects on spacecraft components. The most serious of these is the degradation and failure of a complementary-metal-oxide-semiconductor (CMOS) electronic components as a result of internal charge-buildup induced by the energetic electrons. Efforts to accurately determine the expected lifetime of these components in this orbit are hampered by the lack of detailed knowledge of the electron spectrum and intensity, particularly of the more penetrating energies greater than 1.5 MeV. This problem is illustrated through the calculation of the dose received by a CMOS device from the energetic electrons and associated bremsstrahlung as a function of aluminum shielding thickness using the NASA AE-6 and the Aerospace measured electron environments. Two computational codes which were found to be in good agreement were used to perform the calculations. For a given shielding thickness the dose received with the two radiation environments differ by as much as a factor of seven with a corresponding variation in lifetime of the CMOS.
    Keywords: GEOPHYSICS
    Type: NASA. Lewis Res. Center Proc. of the Spacecraft Charging Technol. Conf.; p 701-713
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  • 3
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    Effects of the August 1972 solar particle events on stratospheric ozone (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: High-energy proton data obtained by polar-orbiting satellite and several balloon flights are used to derive the spatial extent and ionization profiles of regions irradiated by the intense solar particle events (SPE) of August 1972. Backscattered ultraviolet ozone sensors on the Nimbus 4 satellite identified and tracked the polar ozone cavity created by particle ionization during the intense, ten-hour period of August 4, which persisted and rotated as a semirigid mass in an east-to-west direction during 53 days of continuous tracking. Time-dependent chemistry calculations have been performed to show the cause, magnitude, and temporal features of the ozone reduction. Attempts to verify the predicted temperature changes have been unsuccessful due to limitations in the temperature measurement techniques used.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; Mar. 1
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  • 4
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    Coordinated measurements of slot region electron precipitation by plasmaspheric wave bands (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Simultaneous measurements have been made of slot region precipitating electron spectra, wave frequency distributions and plasma density profiles using the P78-1 low altitude satellite and ISEE 1 spacecraft. Broad bands are often observed in the electron energy spectra with a well-defined low energy cutoff which decreases in energy with increasing L value. This is consistent with calculations for first-order cyclotron resonance with waves at the high frequency cutoff of the band. On the basis of electron spectra and plasma densities observed from upper hybrid resonance frequencies, hiss cutoff frequencies are calculated for an assumed first-order cyclotron resonance interaction and compared with wave spectral density profiles. Plasma wave and electron measurements are generally consistent, supporting the precipitation mechanism hypothesis.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 87; June 1
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  • 5
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    Narrow spectral peaks in electrons precipitating from the slot region (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Narrow L-dependent peaks commonly occur in the energy spectra of electrons precipitating from the inner radiation belt at L approximately equal to 1.5-1.85, and the cause of the peaks has been attributed to cyclotron resonance interactions with waves generated by VLF transmitters. In the slot region, L-dependent peaks have also been reported at L approximately equal to 2-3.5, but these have been predominately wider and consistent with their origin being cyclotron resonance interactions involving naturally occurring hiss. The infrequent occurrence of narrow peaks in electrons precipitating at L greater than or approximately equal to 2 is investigated. From coordinated wave and plasma density measurements it is found that if the narrow peaks are formed by first-order cyclotron resonant interactions occurring close to the magnetic equator between narrow band waves and the trapped electron population, then the equatorial plasma density gradients are unusually steep. This finding is consistent with the evidence previously obtained by other techniques for structured plasma density profiles in that L shell region of space.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Oct. 1
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  • 6
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    Morphological study of energetic electron precipitation events using the satellite bremsstrahlung X ray technique (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The precipitation of energetic electrons into the atmosphere is investigated with simultaneous measurements of bremsstrahlung X-rays, emitted from different local time sectors. The measurements were performed from the low-altitude, polar-orbiting satellite P78-1 with an array of X-ray spectrometers (21-139 keV). Magnetic local-time (MLT) profiles of the intensities and energy spectra were obtained for a broad span of L values. From approximately 0930 to 1400 MLT the average X-ray intensity was found to decrease with increasing magnetic local time, whereas from 2200 to 0200 MLT no clear trend with local time was observed. The data presented are noted to correspond closely with the relative electron precipitation (REP)-type events, though no evidence of a distinct group of REP was found.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 1543-155
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  • 7
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    Precipitation of radiation belt electrons by man-made waves A comparison between theory and measurement (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The temporal and spectral shape and the absolute flux level of particle pulses precipitated by a VLF transmitter are examined from a theoretical point of view. A test-particle model of the gyroresonant wave-particle interaction is applied to the parameters of the observed cases for calculating the precipitation characteristics. The temporal shapes of the precipitation pulses are found to be controlled (1) by the pitch angle dependence of the particle distribution near the edge of the loss cone and (2) by the multiple interaction of the particles with the waves due to significant atmospheric backscatter.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 359-369
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  • 8
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    Detailed analysis of radiation data from the Gemini 4 and Gemini 7 proton-electron spectrometer experiments Final report, 13 Jun. 1967 - 30 Dec. 1968 (1968)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Detailed analysis of radiation data from Gemini 4 and 7 proton-electron spectrometer experiments
    Keywords: GEOPHYSICS
    Type: NASA-CR-92444 , LMSC-682411
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  • 9
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    Narrow spikes in the selective precipitation of relativistic electrons in mid-latitudes (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Relativistic electron precipitation spikes were observed in the quasi-trapped population at midlatitudes by an array of electron detectors aboard the low-altitude polar-orbiting satellite 1972-076B. The fluxes of electrons of energies not less than 4 MeV may undergo pronounced enhancements, while the intensities of electrons in the few hundred keV range may not be significantly affected. Energy spectra and pitch angle distributions were measured over the energy range 160 keV to 2.4 MeV with a combination of three spectrometers. Fluxes of energetic electrons (greater than 4 MeV) were measured with high sensitivity in each of two large plastic scintillator anticoincidence counters surrounding a germanium spectrometer.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Jan. 1
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