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Results for “INNER RADIATION BELT”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

High energy proton model for the inner radiation belt.

Reconsideration of inner radiation belt processes and proton theories. The ability of trapped particles to diffuse across magnetic shells is shown radically to alter the view of magnetospheric processes and to call for such a reconsideration. Inner belt calculations incorporating radial diffusion processes are performed in a manner parametrizing the radial diffusion coefficient. The latter is then varied so as to obtain agreement with experiment. The diffusion coefficient thus obtained is compared with coefficients derived by other means.

Walt, M.↗
NASA NTRS1971

Source and loss processes of protons of the inner radiation belt.

The adequacy of the known source and loss processes to populate the inner radiation belt with protons is examined by calculating the equilibrium trapped-proton distribution, which would result from decay of albedo neutrons, energy-loss collisions, and radial diffusion by changes in the third adiabatic invariant. The strength of the neutron source and the rates of atmospheric energy loss are obtained from available theoretical and experimental data, and the radial-diffusion coefficient is adjusted to give agreement between theory and experiment for equatorially trapped protons with first invariants between 200 and 3000 MeV gauss. The flux intensities, energy spectrums, and radial distributions obtained by the theory are in good agreement with observations, and the radial diffusion coefficient required is consistent with dif*usion coefficients derived by a variety of other methods.-

Farley, T. A.↗
NASA NTRS1988

Electrostatic waves stimulated by coherent VLF signals propagating in and near the inner radiation belt

The excitation of electrostatic waves by whistler-mode VLF signals propagating along magnetic-field lines in and near the earth's inner radiation belt is examined on the basis of ISEE-1 observations obtained during July-December 1983. The data are presented in extensive graphs and characterized in detail. The effect is seen in about 60 percent of the ISEE-1 orbits penetrating the belt and for signals originating in both hemispheres, with an electrostatic-wave effective bandwidth roughly proportional to the local magnetic-field strength. These results are interpreted in terms of a theoretical model in which scattering of the VLF waves off magnetic-field-aligned plasma density irregularities is followed by particle pitch-angle scattering and precipitation in the radiation belt; the latter effect could then produce new irregularities via a feedback mechanism.

Bell, T. F.↗
NASA NTRS1995

Using Jupiter's Synchrotron Radiation as a Probe into Jupiter's Inner Radiation Belts

The Jovian decimetric emission is caused by the combined emission of synchrotron radiation originating from the relativistic electrons trapped in Jupiter's 'Van Allen radiation belts' and thermal emission from the planet's atmosphere. Synchrotron radiation characteristics and variations (which provides insight into the physical properties of Jupiter's inner radiation belts) will be amplified and discussed.

jupiter synchrotron radiation jovian inner radiati↗
NASA NTRS1994

Solar cyclic behavior of trapped energetic electrons in Earth's inner radiation belt

Magnetic electron spectrometer data from six satellites (OV3-3, OV1-14, OGO 5, S3-2, S3-3, and CRRES) have been used to study long-term (1966-1991) behavior of trapped energetic electrons in the inner radiation belt. Comparison of the observed energy spectra at L equal to or greater than 1.35 for different phases of the solar cycle reveals a clear trend toward enhanced fluxes during periods of solar maximum for energies below a few hundred keV; we suggest that this is caused by an increase in the rate of inward radial diffusion from a source at higher L. In contrast, for L less than 1.30, where atmospheric collisions become increasingly important, the electron flux is reduced during solar maximum; we attribute this to the expected increase in upper atmospheric densities. The electron flux above 1 MeV exhibits a systematic decay beyond 1979 to values well below the current NASA AE-8 model. This indicates that the natural background of high-energy electrons has previously been overestimated due to the long lasting presence of electrons produced by nuclear detonations in the upper atmosphere in the late 1950s and early 1960s.

Abel, Bob↗
NASA NTRS1982

On the energy dependence of the radial diffusion coefficient and spectra of inner radiation belt particles - Analytic solutions and comparison with numerical results

A theoretical method by which the energy dependence of the radial diffusion coefficient may be deduced from spectral observations of the particle population at the inner edge of the earth's radiation belts is presented. This region has previously been analyzed with numerical techniques; in this report an analytical treatment that illustrates characteristic limiting cases in the L shell range where the time scale of Coulomb losses is substantially shorter than that of radial diffusion (L approximately 1-2) is given. It is demonstrated both analytically and numerically that the particle spectra there are shaped by the energy dependence of the radial diffusion coefficient regardless of the spectral shapes of the particle populations diffusing inward from the outer radiation zone, so that from observed spectra the energy dependence of the diffusion coefficient can be determined. To insure realistic simulations, inner zone data obtained from experiments on the DIAL, AZUR, and ESRO 2 spacecraft have been used as boundary conditions. Excellent agreement between analytic and numerical results is reported.

Westphalen, H.↗
NASA NTRS2004

Inner Radiation Belt Representation of the Energetic Electron Environment: Model and Data Synthesis Using the Salammbo Radiation Belt Transport Code and Los Alamos Geosynchronous and GPS Energetic Particle Data

The highly energetic electron environment in the inner magnetosphere (GEO inward) has received a lot of research attention in resent years, as the dynamics of relativistic electron acceleration and transport are not yet fully understood. These electrons can cause deep dielectric charging in any space hardware in the MEO to GEO region. We use a new and novel approach to obtain a global representation of the inner magnetospheric energetic electron environment, which can reproduce the absolute environment (flux) for any spacecraft orbit in that region to within a factor of 2 for the energy range of 100 KeV to 5 MeV electrons, for any levels of magnetospheric activity. We combine the extensive set of inner magnetospheric energetic electron observations available at Los Alamos with the physics based Salammbo transport code, using the data assimilation technique of "nudging". This in effect input in-situ data into the code and allows the diffusion mechanisms in the code to interpolate the data into regions and times of no data availability. We present here details of the methods used, both in the data assimilation process and in the necessary inter-calibration of the input data used. We will present sample runs of the model/data code and compare the results to test spacecraft data not used in the data assimilation process.

Friedel, R. H. W.↗
NASA NTRS1976

Evidence that pitch angle scattering is an important loss mechanism for energetic electrons in the inner radiation belt of Jupiter

Analysis of data from the Pioneer 10 flyby discloses that pitch angle scattering plays an important part in determining the distribution of energetic electrons in the inner magnetosphere of Jupiter. Angular distributions measured by a Cerenkov detector reveal that redistribution takes place in pitch angle. Additionally, the radial profile of phase space density along the equator demands simultaneous particle losses. The loss rates are too high to be accounted for by synchrotron radiation loss, but are reasonably attributed to pitch angle scattering into the planetary loss cone.

Fillius, W.↗