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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 397 records · Page 22
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NASA NTRS1984

Solar Terrestrial Physics: Present and Future

The following topics relating to solar-terrestrial interactions are considered: (1) reconnection of magnetic fields; (2) particle acceleration; (3) solar magnetic flux; (4) magnetohydrodynamic waves and turbulence in the Sun and interplanetary medium; (5) coupling of the solar wind to the magnetosphere; (6) coronal transients; (7) the connection between the magnetosphere and ionosphere; (8) substorms in the magnetosphere; (9) solar flares and the solar terrestrial environment; (10) shock waves in the solar terrestrial environment; (11) plasma transport and convection at high latitudes; and (12) high latitude ionospheric structure.

Butler, D. M.↗
NASA NTRS1983

Plasma electron analysis: Voyager plasma science experiment

The Plasma Science Experiment (PLS) on the Voyager spacecraft provide data on the plasma ions and electrons in the interplanetary medium and the magnetospheres of the giant planets Jupiter and Saturn. A description of the analysis used to obtain electron parameters (density, temperature, etc.) from the plasma science experiment PLS electron measurements which cover the energy range from 10 eV to 5950 eV is presented. The electron sensor (D cup) and its transmission characteristics are described. A derivation of the fundamental analytical expression of the reduced distribution function F(e) is given. The electron distribution function F(e), used in the moment integrations, can be derived from F(e). Positive ions produce a correction current (ion feedthrough) to the measured electron current, which can be important to the measurements of the suprathermal electron component. In the case of Saturn, this correction current, which can either add to or subtract from the measured electron current, is less than 20% of the measured signal at all times. Comments about the corrections introduced by spacecraft charging to the Saturn encounter data, which can be important in regions of high density and shadow when the spacecraft can become negatively charged are introduced.

Sittler, E. C., Jr.↗
NASA NTRS1983

Protons from the decay of solar flare neutrons

Fluxes of energetic protons in interplanetary space are observed which are interpreted as the decay products of neutrons generated in a solar flare on 1982 June 3 at 11:42 UT. Because of the particular geometry of this event the spectrum of neutrons escaping from the sun can be constructed with great accuracy in the kinetic energy range 10-100 MeV. The resulting spectrum places stringent constraints on the free parameters used in previously published calculations of neutron production in solar flares. An estimate is made of the diffusion mean free path of charged particles in the interplanetary medium in a new way.

Evenson, P.↗
NASA NTRS1984

Comparison of the solar cosmic ray events on May 7, 1978, and November 22, 1977

Neutron monitor data from the IMP 7 and 8 satellites are used in the present analysis of the cosmic ray events of Nov. 22, 1977, and May 7, 1978, in order to determine the energy spectra of the solar protons from 50 MeV to 10 GeV, together with pitch angle distributions, intensity-time profiles, and anisotropy-time profiles. The solar proton energy spectra obtained agree with the overlapping energy range when the pitch angle distribution is taken into account, and it is noted that the energy spectra covering three decades of energy and eight of intensity, together with their time variations, were very similar for the two events. The May 1978 event is important for the study of solar particle acceleration and their subsequent injection into the interplanetary medium. Although the solar proton propagation of the November 1977 event was diffusive, the solar particle injection was also time-extended and energy-dependent.

Debrunner, H.↗
NASA NTRS1984

Solar He-3-rich events and non-relativistic electron events: A new association

In 15 months of observation by the ISEE-e spacecraft, it was found that virtually all solar greater than or approximately equal to 1.3 MeV/nucleon He-3-rich events are associated with impulsive 2 to approximately 100 keV electron events, although many electron events were not accompanied by detectable He-3 increases. Both the He-3 and the electrons exhibit nearly scatter-free propagation in the interplanetary medium, and the times of onset and maximum for the He-3 and electron increases are closely related by velocity dispertion. The electron events and their related type III solar radio bursts provide, for the first time, identification of the flares which produce He-3-rich events. He-3 appears to be accelerated at the flash phase of solar flares along with nonrelativistic electrons.

Reames, D. V.↗
NASA NTRS1985

Acceleration of ions and electrons to near-cosmic ray energies in a perpendicular shock: The January 6, 1978 event

Acceleration of energetic ions to approx 200 MeV and electrons to approx 2 MeV were detected by the Low Energy Charged Particle (LECP) instrument on Voyager 2 in association with a quasiperpendicular shock of theta sub Bn - 87.5 deg at 1.9 AU. The measurments, obtained at a time resolution of approx. 1.2 sec, reveal structure of the energetic particle intensity enhancements down to a scale of the order of the particle gyroradius, and suggest that acceleration takes place within a gyrodiameter of the shock. The observations are consistent with the prediction of the shock drift acceleration (SDA) mechanism. The absence of any fluctuations in the magnetic field during the shock passage suggest that turbulence is not essential to the shock acceleration process in the interplanetary medium.

Krimigis, S. M.↗
NASA NTRS1985

Channeled propagation of solar particles

Bartley (1966) and McCracken and Ness (1966) identified bundles of interplanetary magnetic field (IMF) lines that differed in direction from the interplanetary field lines in which they were imbedded. These bundles, called filaments differed in direction by as much as several tens of degrees from the surrounding field. The filaments werre first noticed due to the large and sudden change in flow direction of highly anisotropic solar flare protons in the energy range 1 to 13 MeV. Passage of the filaments over the spacecraft required a few hours, implying a diameter for the filaments of approximately 3 x 10 to the 6th power km at a distance of 1 AU from the Sun. In 1968, Jakipii and Parker used Leighton's hypothesis of random walk of magnetic field lines associated with granules and supergranules (1964) to develop a picture of an interplanetary medium composed of a tangle of field lines frozen into the solar wind, but whose feet were carried about by the random motions at the solar surface. Jakipii and Parker noted that using a correlation length of 15,000 km - about the radius of a supergranule - the magnetic structure would be 3 x 10 to the 6th power km in size of the filaments as determined by Bartley and McCracken and Ness. These workers did not find changes in the solar particle intensity, anisotropy ratio or energy spectrum as the spacecraft entered the filament.

Anderson, K. A.↗
NASA NTRS1985

On reflecting boundary behind the Earth's orbit at propagation of fast particles from solar flares

The flares of solar cosmic rays (SCR) associated with the presence of shocks in interplanetary magnetic field and with their propagation at significant heliocentric distances were always of great interest. Some events and problems concerning the peculiarities of propagation of flare CR in the interplanetary medium are considered. The distinguishing feature of such events is the presence of shock front behind the Earth's orbit having formed either directly in the process of shock generation on the Sun or at large heliocentric distances as a result of the interaction of fast and slow quasistationary recurrent solar wind (SW) streams. Based on the experimental material it is shown that the significant nonlinear disturbances in IMF behind the Earth's orbit can yield the occurrence of the additional SCR flux from shock front region as a result of the interaction of flare flux with shock and a partial reflection from it.

Nishkovskikh, A. S.↗
NASA NTRS1985

Anomalous short-term increases in the galactic cosmic ray intensity: Are they related to the interplanetary magnetic cloud-like structures?

Thirty-one short-term increases (time duration 24 hours and amplitude up to 5%) in the galactic cosmic ray intensity, occurring inside Forbush decreases events, have been identified over the period 1966 - 1977. These increases are highly anisotropic and occur after the compression region following the shock; the interplanetary medium is characterized by intense ( 10 nT) and higly fluctuating magnetic field B, high velocity, low density and temperature (flare ejecta piston?). These B-fluctuations seem to be ordered variations which could be representative of magnetic clouds. Also the large cosmic ray increase occurring on 17-18 September 1979, belongs to this category of events.

Iucci, N.↗
NASA NTRS1985

Galactic cosmic ray currents and magnetic field irregularity degree in high-speed solar wind streams

Currents of galactic cosmic rays (GCR) obtained by global survey method are analyzed. The cases of almost total disappearance of GCR currents are compared with the results of direct measurements of the solar wind parameters. The conclusion is made on a restricted application of the convective-diffusive mechanism of the GCR modulation by the solar wind during the occurrence of stationary and regular magnetic fields in the interplanetary medium.

Kuzmin, A. I.↗
NASA NTRS1984

Communicating across the solar system

The exploration of the solar system by means of spacecraft would not be possible in its present form without the art and science of communications. Particularly exacting requirements arise in connection with the study of the planets and the interplanetary medium beyond the orbit of Jupiter. Developments in technology providing the required communication capability are partly based on the principle of the phase-locked loop as a narrow-band tracking filter. Mission objectives and performance are discussed for Pioneers 10 and 11 and Voyagers 1 and 2 which at present are the only spacecraft beyond the orbit of Jupiter. A description is given of challenges related to communication in the case of the passage of Voyager 2 near Uranus in 1986 and near Neptune in 1989, taking into account the approaches employed to meet these challenges. Attention is given to requirements concerning international cooperation regarding the ground network, the development of interagency and intra-agency arraying, and the improvement of antenna efficiency.

Reid, M. S.↗
NASA NTRS1984

Interplanetary radio storms. II - Emission levels and solar wind speed in the range 0.05-0.8 AU

Storms of interplanetary type III radio bursts (IP storms) are commonly observed in the interplanetary medium by the ISEE-3 radio instrument. This instrument has the capability of accurately determining the arrival direction of the radio emission. At each observing frequency, the storm radio sources are tracked as they cross the line-of-sight to the sun. Using a simple model, the emission levels are determined at a number of radio frequencies for four separate storms. The IP storm radiation is found to occur in regions of enhanced density at levels of 0.05 to 0.8 AU. The density in these enhancements falls off faster than R(-2). The solar wind speed in the storm region is also measured. The analysis is consistent with steady conditions in the storm region during a few days around the III storm burst radio emission at the harmonic of the local plasma frequency.

Bougeret, J.-L.↗
NASA NTRS1985

Solar He-3-rich events and nonrelativistic electron events - A new association

In 15 months of observation by the ISEE-e spacecraft, it was found that virtually all solar greater than or approximately equal to 1.3 MeV/nucleon He-3-rich events are associated with impulsive 2 to approximately 100 keV electron events, although many electron events were not accompanied by detectable He-3 increases. Both the He-3 and the electrons exhibit nearly scatter-free propagation in the interplanetary medium, and the times of onset and maximum for the He-3 and electron increases are closely related by velocity dispersion. The electron events and their related type III solar radio bursts provide, for the first time, identification of the flares which produce the He-3-rich events. He-3 appears to be accelerated at the flash phase of solar flares along with nonrelativistic electrons.

Reames, D. V.↗
NASA NTRS1985

Interplanetary conditions during 3-kHz radio-wave detections in the outer heliosphere

Plasma waves detected by the Voyager 1 and 2 spacecraft beyond about 12 AU that may be associated with the turbulence expected at the heliopause are interpreted in terms of the characteristics of the interplanetary medium at large heliocentric distances. The low-energy charged-particle environment in the outer heliosphere during the observations of the unusual plasma-wave signals is addressed. The particle data suggest that the outer heliosphere was unusually stable and free of transient shock and particle events for the roughly eight months during the wave observations.

Lanzerotti, L. J.↗
NASA NTRS1986

The solar radio corona: Manifestations of energetic electrons

Radio observations are powerful tools which are complementary to the space missions devoted to the physics of the flares, of the corona, or of the interplanetary medium. To undertake this task two multifrequency radioheliographs presently exist: the Nancay instrument (the multifrequency facility will be in operation by the end of 1985) observes the middle corona at decimeter-meter wavelengths, and the Clark Lake radioheliograph, operating at decameter wavelengths, is the only one in the world to have the ability of observing the outer corona above the disk.

Pick, M.↗
NASA NTRS1986

Forbush decreases geomagnetic and atmospheric effects cosmogenic nuclides

An overview and synthesis is given of recent developments that have occurred in the areas of Forbush decreases, geomagnetic and atmospheric effects, and cosmogenic nuclides. Experimental evidence has been found for substantial differences in the effects of the various types of interplanetary perturbations on cosmic rays, and for a dependence of these effects on the three-dimensional configuration of the interplanetary medium. In order to fully understand and to be able to simulate the solar cosmic ray particle access to the polar regions of the earth we need accurate models of the magnetospheric magnetic field. These models must include all major magnetospheric current systems (in particular the field aligned currents), and they should represent magnetically quiet time periods as well as different levels of geomagnetic activity. In the evolution of magnetospheric magnetic field models, cosmic ray and magnetospheric physicists should work closely together since cosmic ray measurements are a powerful additional tool in the study of the perturbed magnetosphere. In the field of cosmogenic nuclides, finally, exciting new results and developments follow in rapid succession. Thanks to new techniques and new isotopes the analysis of cosmic ray history has entered into a new dimension.

Flueckiger, E. O.↗
NASA NTRS1986

The relationship between proton temperature and momentum flux density in the solar wind

The relationship between proton temperature and momentum flux density/unit mass at 1 AU is examined using Helios 1 solar wind data from 1974 to 1980. In high-speed plasma (V greater than 500 km/s) T(p) increases with increasing n(0) V-squared, where n(0) and T(p) are the density and proton temperature at 1 AU and V is the flow speed. In lowspeed plasma (V less than 500 km/s), T(p) does not increase with increasing n(0) V-squared, and perhaps tends to decrease slightly. These basic relationships between T(p) and n(0) V-squared are not significantly affected by stream interactions. A qualitative explanation of these results is offered in the context of a solar wind model that includes deposition of momentum and energy extending well outward into the interplanetary medium.

Lopez, R. E.↗
NASA NTRS1986

Energetic ions upstream of planetary bow shocks: Fermi acceleration or leakage

Spacecraft observations of Jupiter, Saturn, and Earth planetary bow shocks are assessed. For Jupiter, the unique composition of magnetospheric plasma, where oxygen and sulfur ions are major components, and the simultaneous presence of MeV electrons enable identification of the upstream particles as originating from within the magnetosphere. The observations at Saturn are phenomonologically similar, but no unique tracer element exists which can identify the origin. Earth observations show that substantial energetic particle activity occurs within the Earth's plasma sheet when upstream ions and electrons are observed in the interplanetary medium. Observations of the three planets are discussed to compare in-situ acceleration in the foreshock region vs. leakage of already accelerated ions from the parent magnetosphere. It is concluded that the evidence favors magnetospheric leakage.

Krimigis, S. M.↗