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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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NASA NTRS1979

Shoe-box orbit determination system for SMM preliminary results

The implementation of both sequential and batch methods of estimation on IMP-16 microprocessors was investigated. Simulated data was used from a tracking and data relay satellite whose target satellite was the Solar Maximum Mission. An interesting feature of the hardware was the use of two interconnected IMP-16's. Some preliminary results from the study, as well as the difficulties and advantages in the use of microprocessors, are presented.

Tasaki, K. K.↗
NASA NTRS1978

Low frequency spectra of type III solar radio bursts

Flux density spectra have been determined for 91 simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10 to the -14th W/sq m/Hz. The primary factor controlling the spectral peak frequency of these bursts appears to be a variation in intrinsic power radiated by the source as the exciter moves outward from the sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations.

Weber, R. R.↗
NASA NTRS1979

Hydrogen over helium enhancement in successive solar flare particle events from the same active region

An analysis of all of the identified solar-flare-associated energetic particle events in the 1972-1975 period observed with instruments aboard the IMP 7 and IMP 8 satellites has revealed at least eight occasions when more than one particle-producing flare occurred within the same McMath active plage region during its transit of the visible solar disk. A strong tendency for second flares to produce hydrogen over helium (p/alpha) enhanced energetic particle fluxes when compared with the first flare in the 1.8-10.0 MeV per nucleon range emerged in these multiflare regions. The p/alpha enhancement is apparently transient, and for flares separated by at least about 100 hours the p/alpha ratio tends toward its preflare value. It is suggested that the substrate plasma in an active region may be enriched prior to a flare in elements heavier than hydrogen and the composition may not be significantly altered during subsequent acceleration, escape, and propagation. Thus, the preflare history of the active region must be added to the list of factors influencing observed solar-particle-event composition.

Briggs, P. R.↗
NASA NTRS1979

Electromagnetic and electrostatic emissions at the cusp-magnetosphere interface during substorms

Strongly peaked electrostatic emissions near 10.0 kHz and electromagnetic emissions near 0.56 kHz have been observed by the VLF wave detector on board Imp 6 on crossings from the earth's magnetosphere into the polar cusp during the occurrence of large magnetospheric substorms. The electrostatic emissions were observed to be closely confined to the cusp-magnetosphere interface. The electromagnetic emissions were of somewhat broader spatial extent and were seen on higher-latitude field lines within the cusp. Using these plasma wave observations and additional information provided by plasma, magnetometer and particle measurements made simultaneously on Imp 6, theories are constructed to explain each of the two classes of emission. The electromagnetic waves are modeled as whistlers, and the electrostatic waves as electron-cyclotron harmonics. The resulting growth rates predict power spectra similar to those observed for both emission classes. The electrostatic waves may play a significant role via enhanced diffusion in the relaxation of the sharp substorm time cusp-magnetosphere boundary to a more diffuse quiet time boundary.

Curtis, S. A.↗
NASA NTRS1978

The isotopic composition of galactic cosmic ray lithium, beryllium and boron

The isotopic composition of galactic-cosmic-ray Li, Be, and B has been measured near 100 MeV/nucleon by using the University of Chicago IMP 7 and IMP 8 cosmic-ray telescopes during 1973-1975. The measured abundances allow detailed checks of models of interstellar propagation and solar modulation to be made and conclusions to be drawn concerning the spectral forms at the source and the minimum solar modulation level. For example, comparing these results with local interstellar spectra calculated by using a 'leaky box' model, it is found that if solar modulation is ignored, there is no unique leakage mean free path consistent with all the observations. However, by taking account of a sizable level of residual solar modulation, excellent agreement is obtained between the calculated and measured abundances. Thus, these isotopic abundances confirm the old hypothesis that cosmic-ray Li, Be, and B are produced as secondaries in interstellar space.

Garcia-Munoz, M.↗
NASA NTRS1978

Spectra and composition 2-40 MeV/nucleon of ions Z = 2-28 in solar cosmic ray events

Solid-state detectors on IMP 7 and IMP 8 provide measurements in interplanetary space of ion energy spectra and relative composition from He through Ni in the energy range 2-40 MeV/nucleon. The large solar events of July 3-9, September 11-16, and September 20-26, 1974, are analyzed in detail. Spectra are fit by either power laws in energy or by momentum-dependent exponentials. Spectral slope is independent of ion charge for elements beyond C. Substantial time variations in the He/O and (Fe + Ni)/O ratios are noted. New limits are derived for the abundances of Li, Be, B, F, Na, Al, P, S, Ar, and Ca. Analysis of additional events from 1973 through 1976 suggests a systematic enhancement of the He/O and C/O ratios in low-energy corotating flux increases compared with flare-associated particle fluxes.

Mcguire, R. E.↗
NASA NTRS1978

The quiet-time low energy nucleon spectrum during 1975

The paper reports measurements during quiet time periods in 1975 over the range of Ep from about 0.3 to 5 MeV for protons and E-alpha from about 0.7 to 11 MeV/nuc for helium nuclei. The data are obtained from the JHU/APL experiments on earth-orbiting IMP-7 and IMP-8 spacecraft. Both spacecraft are spinning, and data from the experiment are acquired in both spin-averaged and sectored form. It is shown that the earth's atmosphere continues to be a most important contributor to the proton population in the Ep range of 0.29-0.5 MeV, and that the 1975 intensities are virtually identical to those measured in 1973, suggesting the absence of solar modulation at these low (no more than about 5 MeV/nuc) energies. Lack of solar modulation argues against a galactic origin.

Krimigis, S. M.↗
NASA NTRS1979

Observations pertaining to the dynamics of the plasma sheet

Plasmas on the surface of the plasma sheet at its interface with high-latitude lobes are studied at about 30-40 earth radii (Re) in the tail of the earth's magnetosphere with Lepedea plasma instrumentation on board the earth-orbiting Imp 7 and Imp 8 satellites. Protons at this interface are frequently found to be flowing toward earth with velocities greater than 400 km/s. Proton bulk speeds measured near the plasma sheet surface are typically greater than those at locations deeper within the plasma sheet. Ten of the twenty cases studied exhibit plasma sheet cooling. Typical plasma sheet conditions are observed to prevail deep within the plasma sheet coincident with the earthward streaming at the boundary of the plasma sheet. A three-parameter model is described that explains the velocity distributions measured for the earthward-jetting plasma.

Decoster, R. J.↗
NASA NTRS1979

Technique to determine location of radio sources from measurements taken on spinning spacecraft

The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

Fainberg, J.↗
NASA NTRS1980

Interplanetary monitoring platform engineering history and achievements

In the fall of 1979, last of ten Interplanetary Monitoring Platform Satellite (IMP) missions ended a ten year series of flights dedicated to obtaining new knowledge of the radiation effects in outer space and of solar phenomena during a period of maximum solar flare activity. The technological achievements and scientific accomplishments from the IMP program are described.

Butler, P. M.↗
NASA NTRS1979

Energetic particle activity at 5-min and 10-s time resolution in the magnetotail and its relation to auroral activity

The paper examines several energetic particle bursts associated with substorm events in the magnetotail using data from the Imp 7 and 8 spacecraft experiments. Individual proton and electron bursts observed by the spacecraft do not always coincide nor does magnetotail activity correlate strongly with auroral activity on time scales less than 1 hr. The pitch angle distributions were determined with a time resolution of 10 s by combining magnetic field and particle measurements on Imp 8; during intense particle bursts the 0.3-MeV protons exhibit unidirectional or bidirectional anisotropies along the magnetic field. The data suggest the presence of small localized acceleration regions in the magnetotail observable when magnetically connected to the spacecraft; little evidence is found for a single neutral line extending across the width of the magnetotail.

Carbary, J. F.↗
NASA NTRS1980

The modulation of galactic cosmic rays between 1 and 17 AU

The galactic cosmic-ray intensity was at approximately solar minimum levels from early 1972 to December 1977. Beginning in early 1978 and ending in June, steady decreases in the galactic proton and helium intensities were observed at 1 AU by IMP-7 and 8. No significant decrease was observed at Pioneer 10 at 16 AU until the second half of April; this time sudden transitions to new intensity levels were observed for protons and helium at low and high energies. The new intensity levels were maintained through January 1979, both at 1 AU and at Pioneer 10. Differential energy spectra from IMP-8, Pioneer 11 and Pioneer 10 are presented and their changes discussed.

Von Rosenvinge, T. T.↗
NASA NTRS1980

Streaming energetic electrons in earth's magnetotail - Evidence for substorm-associated magnetic reconnection

This letter reports the results of a systematic study of streaming greater than 200 keV electrons observed in the magnetotail with the Caltech Electron/Isotope Spectrometers aboard IMP-7 and IMP-8. A clear statistical association of streaming events with southward magnetic fields, often of steep inclination, and with substorms as evidenced by the AE index is demonstrated. These results support the interpretation that streaming energetic electrons are indicative of substorm-associated magnetic reconnection in the near-earth plasma sheet.

Bieber, J. W.↗
NASA NTRS1981

The Goddard program of gamma-ray transient astronomy

The Goddard program of gamma-ray burst studies is briefly reviewed. The past results, present status and future expectations are outlined regarding our endeavors using experiments on balloons. IMP-6 and IMP-7, OGO-3, ISEE-1 and ISEE-3, Helios-2, Solar Maximum Mission, the Einstein Observatory, Solar Polar and the Gamma Ray Observatory, and with the interplanetary gamma-ray burst networks, to which some of these spacecraft sensors contribute. Additional emphasis is given to the recent discovery of a new type of gamma-ray transient, detected on 5 March, 1979.

Cline, T. L.↗
NASA NTRS1981

The low-energy galactic cosmic ray carbon, nitrogen, and oxygen isotopic composition

It is found that C, N, and O elemental and isotopic ratios in the galactic cosmic rays measured near the earth with the IMP 7 telescope of the University of Chicago have had the values N/O = 0.25 + or 0.02; C/O = 1.06 + or - 0.03; C-13/C = 0.04-0.10; N-15/N = 0.47 + or - 0.06; and O-18/O less than or equal to 0.03. It is noted that these results are confirmed by IMP 8 measurements. The measurements are extrapolated back to the cosmic ray source using exponential and truncated exponential path length distributions whose parameters have been determined by fitting cosmic ray B/C and sub-Fe/Fe ratios measured previously.

Guzik, T. G.↗
NASA NTRS1981

Earthward transport of energetic protons in the earth's plasma sheet

An analysis is made to assess the transport of energetic protons (0.29-0.50 MeV) at downstream distances of 30-45 earth radii in the earth's plasma sheet surveyed by the IMP 7 and IMP 8 spacecraft. It is found that there is a net earthward transport of these particles, although tailward streaming is observed as frequently as earthward streaming. The averaged flux is 200 per sq cm s in this energy range and the total flux over the plasma sheet region is 4 x 10 to the 22nd per s. It is suggested that this net earthward flux of energetic protons may contribute to the population of the outer radiation belt.

Lui, A. T. Y.↗
NASA NTRS1981

Spatial distribution of energetic particles in the distant magnetotail

The spatial distribution of energetic particles in the distant magnetotail is analyzed by using identical sets of two complementary energetic particle experiments aboard the IMP 7 and 8 spacecraft. It is noted that the combined IMP 7 and 8 data set provides nearly 10 years of satellite observation. The quantitative distributions of energetic electrons in two energy ranges and energetic protons are given in terms of occurrence frequency and the average particle flux intensity over an 80 earth radii x 70 earth radii plane perpendicular to the sun-earth line. A particle distribution in the shape of an O with a crossbar over the solar magnetospheric YZ plane in the antisolar direction is clearly demonstrated at all energies and for both species. It is pointed out that the O part of the distribution corresponds to the magnetosheath region and that the crossbar is the average plasma sheet configuration. A distinct, species dependent, dawn-dusk asymmetry in particle distribution is observed in the plasma sheet and, to a lesser extent, in the magnetosheath.

Meng, C.-I.↗
NASA NTRS1981

Detailed study on acceleration and propagation of energetic protons and electrons in the magnetotail during substorm activity

High time resolution measurements of energetic particles and magnetic field measurements by the IMP 8 satellite in the distant magnetotail are presented for November 26, 1973, when exceptionally intense particle bursts were detected by both the IMP 7 and 8 spacecraft. During the onset of the most intense burst as well as at other times, oppositely directed anisotropies of protons and electrons parallel to the tail field and lasting up to about 60 sec were observed, implying the presence of field-aligned electric fields. The particle and field observations are discussed in the context of proposed mechanisms for the acceleration of particles during various dynamical magnetospheric processes. Satellite instrument readings are presented through the extensive use of graphs.

Kirsch, E.↗