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Intriligator, D. S.

Publications and source records attributed to Intriligator, D. S..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Direct observations of higher frequency density fluctuations in the interplanetary plasma

Direct observations from the plasma spectrometers on Pioneer 6 at 1 AU in December, 1965, have been used to obtain the power associated with fluctuations in the number density of solar-wind protons in the frequency range from .001 to .01 Hz. A power-law spectrum is obtained in this frequency range. The extension of the power-law density spectrum based on direct observations to these higher frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations and with the dominance of large-scale turbulence in the solar wind. This result is also consistent with direct observations of the solar-wind proton speed and the interplanetary magnetic field.

Intriligator, D. S.↗
NASA NTRS1975

In situ observations of the scale-size of plasma turbulence in the asteroid belt /1.6-3 astronomical units/

Pioneer 10 observations from the Ames Research Center Plasma Analyzer experiment between 1 and 3 AU in 1972 have been used to estimate the power spectra of the streaming speed of solar wind protons. A power-law spectrum is obtained in the 10,000 to 0.001 Hz frequency range which is similar to that obtained for the solar wind proton number density and streaming speed at 1 AU in 1965 December and 1966 January. The power spectra indicate that significant turbulence on the scale of about 1,000,000 km or more is present throughout this range of heliocentric distances, implying the importance of the role of large-scale turbulence between 1 and 3 AU. The power spectra also present qualitatively information concerning the cosmic-ray diffusion tensor at these extended distances.

Intriligator, D. S.↗
NASA NTRS1975

Pioneer 10 observations of the solar wind and its interaction with Jupiter - Plasma electron results

Typical plasma electron spectra obtained during transversal of the Jovian magnetosheath are discussed. Data from the outer magnetosphere show an enhanced energy tail between approximately 50 eV and 200 eV, indicating heating of the solar wind electrons across the Jovian bow shock. Transversal of the inner magnetosphere produced data implying even higher electron temperatures. Results are consistent with ion observations of a high Mach number bow shock and magnetosheath flow field. They are consistent with a contraction of the Jovian magnetosphere resulting from an increase in the solar wind dynamic pressure similar to, but on a larger scale than that observed in the case of the earth's bow shock.

Intriligator, D. S.↗
NASA NTRS1975

Pioneer 10 observations of the Jovian magnetosphere - Plasma electron results

Examination of electron spectra obtained during inbound transversal of the outer Jovian magnetosphere shows a consistent peak near 4 eV where the thermal component of magnetospheric electrons is observed, corresponding to a temperature of about 50,000 K. The existence of a high beta plasma is inferred on the basis of electron and magnetic field measurements, assuming equilibrium between ions and electrons and pressure balance across the magnetophase. Observations imply the existence of thermal plasma in the outer magnetosphere which may be responsible for large-scale inflation of the outer magnetic field. It is concluded that ambient thermal plasma and photoelectrons in the outer magnetosphere will likely prevent charge buildup in spacecraft, but that it remains a possibility in the inner magnetosphere, where thermal electron measurements are obscured by high background.

Intriligator, D. S.↗
NASA NTRS1975

Measurements of large scale turbulence in the solar system

Direct observations of the solar wind between 1965 and 1972 indicate the existence of significant large scale (L is greater than 10 to the 6th km) turbulence in the solar system at heliocentric distances from 1 to 3 AU. These results are based on power spectra of the solar wind proton data obtained by plasma spectrometers on Pioneer 6 and Pioneer 10. The power spectra indicate that there is a power-law frequency dependence between 10 to the -4 Hz and 10 to the -3 Hz of the power spectra of the solar wind proton number density and streaming speed between 1 and 3 AU. The slopes and the amplitudes of the power spectra provide qualitative information concerning the cosmic ray diffusion tensor between 1965 and 1972 and at heliocentric distances between 1 AU and 3 AU.

Intriligator, D. S.↗
NASA NTRS1975

The solar cycle variation in the solar wind and the modulation of cosmic rays

Evidence for a solar cycle variation in the interplanetary plasma is presented based on direct observations of the solar wind by the Pioneer and Vela spacecraft. These data indicate that between 1965 and 1971 there were more days associated with high speed streams during solar maximum than during solar minimum. These observations provide the first observational explanation for the solar modulation of cosmic rays. At solar maximum the probability is highest that cosmic rays entering the solar system will encounter high speed streams. As a result, there is more modulation of cosmic rays at solar maximum than at other times.

Intriligator, D. S.↗
NASA NTRS1975

The solar wind between 0.7 AU and 5.0 AU

A review is given of Pioneer-9 (1968, 1969) and Pioneer-10 and 11 (1973) observations of the solar wind high-speed stream structure as a function of heliocentric distance. Evidence for spatial and temporal variations in this solar wind structure between 5 and 7 AU is presented as well as evidence for the importance of stream-stream interactions in the solar wind. As the high speed stream structure travels outward in the ecliptic plane from the sun, there is evidence of damping which is consistent with the exchange of momentum between the high speed streams and the low speed streams. These interactions may produce scattering centers which will prevent the observation of a significant galactic cosmic ray gradient. The width of the solar wind speed histograms are determined and radial distances on the order of 10 AU are calculated.

Intriligator, D. S.↗
NASA NTRS1975

Direct observations of the solar wind interaction with Jupiter

Pioneer 10 and Pioneer 11 plasma ion and electron observations in the vicinity of Jupiter are summarized. The data, obtained by the Ames Research Center Plasma Analyzer Experiments during the flybys of Jupiter in 1973 and 1974, indicate that the solar wind interaction with Jupiter (e.g., the formation of the Jovian bow shock, the magnetosheath, etc.) is basically similar to the solar wind interaction with the earth and only differs in terms of the scale size of the interaction. The plasma ion and electron measurements obtained on Pioneer 10 and Pioneer 11 are consistent with the proton measurements and indicate that the large, thick Jovian Magnetosphere which is inflated with a thermal plasma, is responsive to relatively minor changes in the solar wind dynamic pressure. The inferred motion of the Jovian bow shock and the speed at which it moved were strikingly similar during the Pioneer 10 and Pioneer 11 flybys.

Intriligator, D. S.↗
NASA NTRS1974

Initial observations of plasma electrons from the Pioneer 10 flyby of Jupiter

Initial results are presented from the electron measurements made by the Ames Research Center Plasma Analyzer during the inbound passage of Pioneer 10 in the vicinity of Jupiter. The observations indicate that as in the case of the earth's magnetosheath, there is an increase in electron temperature across the Jovian bow shock. During the second extended magnetosheath traversal (approximately 54 to 46.5 Jupiter radii) the electron temperatures were generally higher than those observed during the first magnetosheath traversal (109 to 96 Jupiter radii). These higher electron temperatures are in agreement with the measured higher magnitude of the magnetic field and ion density during this traversal. These observations are consistent with the contraction of the Jovian magnetosphere due to an increase in the solar wind dynamic pressure.

Intriligator, D. S.↗
NASA NTRS1974

Pioneer 10 observations of the solar wind interaction with Jupiter

Detailed analysis of the Pioneer 10 plasma analyzer experiment flight data during the Jupiter flyby in late November and early December 1973 has been performed. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found to have a detached standing bow shock wave of high Alfven Mach number. Like the earth, Jupiter has a prominent magnetopause that deflects the magnetosheath plasma and excludes its direct entry into the Jovian magnetosphere. Unlike that of the earth, the sunward hemisphere of Jupiter's outer magnetosphere is found to be highly inflated with thermal plasma and a high-beta region that is highly responsive to changes in solar wind dynamic pressure.

Wolfe, J. H.↗
NASA NTRS1974

The reliability of the daily quick look solar wind velocities as indicators of interplanetary activity

It is shown that the daily quick look solar wind velocities based on the Ames Research Center solar wind plasma data obtained on the Pioneer spacecraft are surprisingly reliable indicators of interplanetary activity. These velocities can appropriately be used in correlation studies with an average accuracy of plus or minus 5%. This accuracy reflects the 'jitter' in the solar wind velocity during quiescent intervals and across high-speed streams.

Intriligator, D. S.↗
NASA NTRS1974

Pioneer 10 observations of the solar wind interation with Jupiter

Pioneer 10 Plasma Analyzer experiment flight data during the Jupiter flyby are presented. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found to have a detached standing bow shock wave of high Alfven Mach number. Jupiter has a prominent magnetopause which deflects the magnetosheath plasma and excludes its direct entry into the Jovian magnetosphere. The sunward hemisphere of Jupiter's outer magnetosphere is found to be highly inflated with thermal plasma and a high beta region which is highly responsive to changes in solar wind dynamic pressure. Observational arguments are presented which tend to discount a thin disklike magnetosphere but, rather, favor a Jovian magnetosphere, albeit probabily considerably flattened as compared to the earth's magnetosphere, yet still with reasonable thickness. Results concerning the shock jump conditions, the magnetosheath flow field and inferred internal magnetospheric plasma are presented.

Wolfe, J. H.↗
NASA NTRS1974

Evidence of solar-cycle variations in the solar wind

Solar-wind observations are presented from July 1965 through June 1971 that show the first evidence for long-term variations in the solar wind associated with changes in the solar-cycle. The observations indicate that the frequency of high-speed streams in the solar wind and their duration vary over the solar cycle. There are more days associated with high-speed streams during solar maximum than during solar minimum. The yearly average of the solar-wind speed varies over the solar cycle and is highest at solar maximum. These measurements also provide the first direct observational evidence for changes in the solar wind which can account for the solar-cycle modulation of the cosmic-ray intensity.

Intriligator, D. S.↗
NASA NTRS1974

Preliminary Pioneer 10 encounter results from the Ames Research Center plasma analyzer experiment

Preliminary results from the Ames Research Center plasma analyzer experiment for the Pioneer 10 Jupiter encounter indicate that Jupiter has a detached bow shock and magnetopause similar to the case at Earth but much larger in spatial extent. In contrast to Earth, Jupiter's outer magnetosphere appears to be highly inflated by thermal plasma and therefore highly responsive in size to changes in solar wind dynamic pressure.

Wolfe, J. H.↗
NASA NTRS1974

The radial gradient and the role of turbulence in the solar system

Pioneer 10 observations from the Ames Research Center Plasma Analyzer experiment between 1 and 3 AU have been used to estimate the power spectra of the solar wind proton streaming speed. The power spectra indicate that significant turbulence on the scale of 1,000,000 km or more is present throughout this range of heliocentric distances, implying the importance of the role of large scale turbulence between 1 and 3 AU.

Intriligator, D. S.↗
NASA NTRS1974

The power associated with density fluctuations and velocity fluctuations in the solar wind

Direct observations from Pioneer 6 of solar-wind-proton fluctuations have been used to obtain the power spectra associated with solar-wind-proton number density and velocity fluctuations in the frequency range of 0.001 to 0.01 Hz, extending previous analyses by an order of magnitude at the higher frequencies. The slopes of the power spectra associated with the density fluctuations and the velocity fluctuations are similar and are in agreement with the shape of the power spectra found at the lower frequencies. The power spectra indicate that the power-law density spectrum observed at lower frequencies extends to at least 0.01 Hz. This smooth variation in the spectrum at these frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations.

Intriligator, D. S.↗
NASA NTRS1972

Evidence of a diffuse magnetopause boundary.

Observational evidence is presented to show that the magnetosphere-magnetopause boundary was diffuse during the Pioneer 8 magnetopause traversal on Dec. 14 and 15, 1967. This boundary was characterized by proton fluxes of significantly lower intensity than those observed in the magnetosheath. In addition, the angles of flow associated with the fluxes at the boundary were more diverse than those observed in the magnetosheath. Proton energy spectra are presented to indicate the change in the spectral shape at the boundary. The observational evidence is consistent with calculations by Axford and Dryer of a viscous magnetopause boundary layer, which is a function of an anomalous nonclassical kinematic viscosity. The observational evidence presented for the diffuse magnetosphere boundary may also be consistent with Dungey's model reconnection of magnetic field lines and an open magnetosphere.

Intriligator, D. S.↗