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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Energetic particle events /greater than or equal to 30 keV/ of Jovian origin observed by Voyager 1 and 2 in interplanetary space

Detailed observations of ion events of Jovian origin as observed by the low energy charge particle (LECP) instrumentation on Voyager 1 and 2 during the inbound and outbound pass for both spacecraft are reported. The general characteristics of these events are examined, and a comparison is made with similar observations at earth. Careful attention is given to the compositional signature of the Jovian ion events. Two of the specific events discussed in detail are selected to display the range of variability and complexity of the Jovian-produced interplanetary ion events. The observations are seen as strongly implying that the Jovian magnetosphere is the source of a significant fraction of the particles.

Zwickl, R. D.↗
NASA NTRS1981

Time and energy dependence of heavy ion abundances in solar flare energetic particle events

Data from a survey of solar flare events undertaken by the UMD/MPI ULET telescope on the IMP-8 satellite during the period 1973-1977 yields examples of time and energy dependence of the abundances and spectra of the He, C, O and Fe heavy ions. Time variations are found in the O/He, O/C and Fe/O ratios which appear to be inconsistent with models based entirely on rigidity-dependent propagation in the interplanetary medium. It is speculated that such other factors as the abundance differences at the flare site on the sun, or features of the acceleration and release mechanisms, may play an important role in the variations discussed.

Mason, G. M.↗
NASA NTRS1981

A supra-thermal energetic particle detector /STEP/ for composition measurements in the range of about 20 keV/nucleon to 1 MeV/nucleon

A novel detector system is described, employing a time-of-flight versus residual energy technique which allows measurement of particle composition (H-Fe), energy spectra and anisotropies in an energy range unaccessible with previously flown sensors. Applications of this method to measurements of the solar wind ion composition are also discussed.

Mason, G. M.↗
NASA NTRS1982

Modulation of energetic particle fluxes by a mixed mode of transverse and compressional waves

Modulation characteristics of particle fluxes in the presence of a mixed mode of compressional and transverse magnetic waves at hydromagnetic frequencies are investigated through kinetic perturbation of the distribution function. The magnetospheric medium where the particles are modulated contains both the magnetic and pressure gradients. The modulation features are found to be strongly dependent on the energy and pitch angle of the particles. Drifting particles can resonate with waves whose phase velocities are close to their drift velocities. When this occurs, the modulation amplitudes become significantly large and large phase shifts will occur. It is pointed out that resonance is important for particles with mid pitch angles (40-70 deg). The phase shift between the particle modulations and the magnetic field oscillations are strongly controlled by the combined effects of transverse and compressional wave components and/or the occurrence of drift resonance. Numerical calculations are performed using the dispersion relation of drift mirror Alfven waves as an example of waves with both compressional and transverse components.

Lin, C. S.↗
NASA NTRS1983

The isotropic condition of energetic particles emitted from a large solar flare

Isotope abundance ratios for 5 to 50 MeV/nuc nuclei from a large solar flare were measured. The measurements were made by the heavy isotope spectrometer telescope (HIST) on the ISEE-3 satellite orbiting the Sun near an Earth-Sun liberation point approximately one million miles sunward of the Earth. Finite values for the isotope abundance ratios C-13/C-12, N-15/N-14, O-18/O-16, Ne-22/Ne-20, Mg-25/Mg-24, and Mg-26/Mg-24, and upper limits for the isotope abundance ratios He-3/He-4, C-14/C-12, O-17/O-16 and Ne-21/Ne-20 were reported. Element abundances and spectra were measured to compare the flare with other reported flares. The flare is a typical large flare with low Fe/O abundance or = to 0.1). For C-13/C-12, N-15/N-14, O-18/O-16, Mg-25/Mg-24 and Mg-26/Mg-24 isotope abundance ratios agree with the solar system abundance ratios. Measurement for Ne-22/Ne-20 agree with the isotopic composition of the meteoritic component neon-A.

Spalding, J.↗
NASA NTRS1983

Understanding the heliosphere and its energetic particles

Classes of cosmic ray variations observed by Helios 1 and 2 spacecraft, Pioneer 10 and 11, and Voyager 1 and 2 spacecraft are reviewed as they correspond to classes of interplanetary flows. Topics covered include: (1) corotating flows, corotating Forbush decreases, and 27-day variations; (2) transients and Forbush decreases; (3) systems of transients and long lasting Forbush decreases; and (4) 11-year variations.

Burlaga, L. F.↗
NASA NTRS1982

Propagation of energetic particles in the solar wind

A summary is given of recent results from the direct determination of the charge states of He, C, O, and Fe. These results are used in discussing compositional variations during individual solar particle events. It is shown that ratio changes by a factor of approximately 10 during the onset phase of solar particle events can be explained not only by rigidity-dependent interplanetary propagation but also by rigidity-dependent diffusive propagation in the corona. Increasing experimental evidence is seen that other processes, such as compositional variations at the source and discontinuities of the interplanetary magnetic field separating two different particle populations, may be important. No common explanation is seen for all the variations, and it is concluded that each must be investigated on its own.

Klecker, B.↗
NASA NTRS1983

Acceleration and confinement of energetic particles in the 1980 June 7 solar flare

Pulsations with large amplitude and duration have been observed during the hard X-ray and microwave radio bursts associated with the 1980 June 7 solar flare. The high time resolution measurements of 20-800 keV X-rays were made with the X-ray spectrometers aboard the ISEE 3 and P78-1 spacecraft. The radio measurements, covering metric to microwave wavelengths, were made at the Nobeyama and Toyokawa observatories in Japan. The temporal evolution of the X-ray and radio spectra and the polarization and spatial structure of the microwave source have been examined. The following interpretation is found to be consistent with the observations: (1) the variations in the electron acceleration/injection spectrum are responsible for the observed variations in the hard X-ray and microwave emissions; (2) the locations of the hard X-ray and microwave sources are probably different, the X-ray source being located at a lower altitude.

Kane, S. R.↗
NASA NTRS1983

Energetic particle microsignatures of Saturn's satellites

During Voyager's 1980 and 1981 encounters with Saturn, the low energy charged particle experiment observed satellite microsignatures in ions and electrons. Each of the five major satellites within Titan's orbit were associated with at least one absorption feature in the high time resolution data. Microsignatures are usually observed in the corotational wake region within about 25 deg in azimuth of a satellite, and do not generally occur at times predicted by a centered, aligned dipole. A better predictive model seems to be that of an aligned, axisymmetric field with significant quadrupole and octupole terms.

Carbary, J. F.↗
NASA NTRS1984

Temporal variations of nucleonic abundances in solar flare energetic particle events. II - Evidence for large-scale shock acceleration

A survey of the roughly 1 MeV per nucleon ion abundance over the range H-Fe measured with 3 hr time resolution during large solar particle events from November 1973 through December 1977, under near solar minimum conditions, is presented. For all the monitored species, a strong decrease in average flux level occurred with increase of the optical flare site distance from the W 60 deg connection point. The 3 hr abundance ratios He/H, O/He, and Fe/He were observed to fluctuate by a factor of about two about their average values for given flare events, and the size of these fluctuations was independent of the distance to the optical flare site. The monitored abundance ratios exhibited no dependence on distance to the optical flare site. The physical mechanism suggested to explain these observations is large-scale shock acceleration from a shock wave originating at the flare site and propagating as far away as 100 deg heliolongitude.

Mason, G. M.↗
NASA NTRS1985

Injection of energetic particles following the gamma-ray flares on June 7, 1980, as observed on Helios 1

On June 7, 1980, two flares with impulsive gamma-ray emission were observed at 0117 Ut and 0312 UT. Measurements of the University of Kiel cosmic-ray experiment on HELIOS-1 are presented. The first approx. 0.5 MeV electrons escaped from the Sun to interplanetary space simultaneously with the hard X-ray burst. For the 0312 UT flare the protons and alpha-particle in the 3 - 20 MeV/nucleon range were injected from the Sun with a delay of approx. 40 min, followed by two subsequent new emissions.

Neustock, H. H.↗
NASA NTRS1985

Shock and statistical acceleration of energetic particles in the interplanetary medium

Definite evidence for particle acceleration in the solar wind came around a decade ago. Two likely sources are known to exist: particles may be accelerated by the turbulence resulting from the superposition of Alfven and Magnetosonic waves (Statistical Acceleration) or they may be accelerated directly at shock fronts formed by the interaction of fast and slow solar wind (CIR's) or by traveling shocks due to sporadic coronal mass ejections. Naurally both mechanisms may be operative. In this work the acceleration problem was tackled numerically using Helios 1 and 2 data to create a realistic representation of the Heliospheric plasma. Two 24 hour samples were used: one where there are only wave like fluctuations of the field (Day 90 Helios 1) and another with a shock present in it (Day 92 of Helios 2) both in 1976 during the STIP 2 interval. Transport coefficients in energy space have been calculated for particles injected in each sample and the effect of the shock studied in detail.

Valdes-Galicia, J. F.↗
NASA NTRS1985

Diffusion in the chromosphere and the composition of the solar corona and energetic particles

Composition observations, in the solar photosphere, and in the upper transition region (TR) and corona imply a change of composition of the solar atmosphere somewhere between the photosphere and the upper TR. Heavy elements with first ionization potential (FIP) 9 eV (high-FIP element) are approx. 4 times less abundant in the TR and corona than in the photosphere, as compared to both hydrogen and heavy elements with lower low-FIP elements. A separation is suggested between neutral and ionized elements in a region where the high-FIP elements are mostly neutral, and the low-FIP elements ionized. This occurs in the chromosphere at altitudes above 600 km and below 2000 km above Photosphere. Whether the diffusion processes can explain the observed change in composition is investigated.

Vauclair, S.↗