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Bame, S. J.

Publications and source records attributed to Bame, S. J..

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

ISEE-1 and ISEE-2 fast plasma experiment and the ISEE-1 solar wind experiment

Identical fast plasma experiment (FPE) systems were placed on the ISEE-1 and ISEE-2 spacecraft. The FPE consists of three high efficiency 90 deg spherical section electrostatic analyzers using large secondary emitters and discrete dynode multipliers to detect analyzed particles. Two of them, viewing in opposite directions, produce complete 2D velocity distribution measurements of both protons and electrons every spacecraft revolution. A third FPE analyzer with a divided emitter measures 3D distributions at a slower rate. ISEE-1 also carries a solar-wind experiment (SWE) to measure solar-wind ions with high resolution. The SWE is composed of two 150 deg spherical section analyzers using the same set of plates. The two acceptance fans are tilted with respect to each other so that 3D characteristics of the ion distributions can be derived.

Bame, S. J.↗
NASA NTRS1978

Long-term variations of selected solar wind properties - IMP 6, 7, and 8 results

Studies of the variability of the solar wind are extended to include the minimum of solar cycle 20; attention is given to the He abundance, the relative He-H velocity difference, the He-H temperature ratio, the solar coronal proton density, speed, rms velocity variation, temperature and number flux, and the kinetic and total energy fluxes. The solar wind data are from observations conducted by the IMP-6, -7 and -8 satellites. A well-developed corotating stream structure appearing in January 1973 and disappearing in mid-1976 receives particular consideration. An increase in proton number and total energy fluxes after September 1972 may be due to areal expansion of both polar coronal holes, and may be associated with compression of the low-speed equatorial disk-shaped region postulated to surround the sun in interplanetary space.

Feldman, W. C.↗
NASA NTRS1978

Solar wind stream interfaces

Results are presented for a superposed epoch analysis of discontinuous solar wind interfaces. The average time-space profiles of stream interfaces are discussed with reference to fluid properties (flow speed, pressure ridge, density, electron and proton temperatures) and kinetic properties (electron core and halo, flow speed fluctuations, electron heat flux, alpha particles). Other aspects of stream interfaces are described, such as the persistence of individual interfaces, shock associations, the sector boundaries of the interplanetary magnetic field, and sudden impulses in the geomagnetic field. Interface position is considered in terms of the observed temperature jump. A conceptual model of high-speed stream evolution is proposed.

Gosling, J. T.↗
NASA NTRS1978

Direct observation of the latitudinal extent of a high-speed stream in the solar wind

The latitudinal boundaries of stationary fast solar wind streams emerging from equatorward extensions of the sun's polar coronal holes are studied. Simultaneous data from the Helios 1 and Imp spacecraft at different heliographic latitudes are compared. The measured latitudinal speed gradient of 30 km/s/deg shows that large angular speed gradients occur at the leading edges of fast streams and also with respect to latitude. The data indicate that longitudinal speed gradients are steeper near 0.3 AU than at 1.0 AU. Generally, regions with large angular speed gradients are observed to separate fast streams from the surrounding slower plasma. This suggests the existence of mechanisms which diminish longitudinal speed gradients as the plasma travels toward 1.0 AU. It also seems that the distribution of solar wind speeds on a near-sun spherical surface has large mesalike high-speed regions. Comparisons of Helios 1 and Imp data with corona observations supports the hypothesis that high-speed solar wind streams emerge from coronal holes.

Schwenn, R.↗
NASA NTRS1977

On the alignment of plasma anisotropies and the magnetic field direction in the solar wind

One year's Imp 6 solar wind plasma and magnetic field data are examined to determine whether anisotropies in particle velocity distributions are aligned with the measured interplanetary magnetic field vector. Alignment of components in the analysis plane was generally found to be excellent whenever plasma parameter magnitudes were larger than determination uncertainties, although some spread exists (typical rms approximately equal to 10 deg). By assuming cylindrical symmetry about the simultaneously measured magnetic field vector during the 1-year interval under study, three-dimensional values of selected solar wind plasma thermal parameters were constructed from the two-dimensional plasma measurements, and the statistical properties of their distributions have been tabulated.

Asbridge, J. R.↗
NASA NTRS1977

Noncompressive density enhancements in the solar wind

When the bulk flow speed is nearly constant or falling, high densities are sometimes observed in the solar wind. These densities do not appear to be generated in interplanetary space. It is noted that the magnetic field is not enhanced within these events, and that the proton and/or electron temperatures are low, varying in opposition to the density. About 1/3 of these density events contains interplanetary magnetic field reversals, some of which are noisy and do not qualify as sector boundaries. It is estimated that the average event contains approximately 10 to the 16th g of material and 2.6 x 10 to the 31st ergs, so that aggregated events, when they are common, make a negligible contribution to the total mass and energy budget of the solar wind at 1 AU. It is suggested that there may be an association between density enhancements and solar coronal mass ejection events.

Gosling, J. T.↗
NASA NTRS1977

An unusual aspect of solar wind speed variations during solar cycle 20

Geomagnetic records from 1868 through 1975 indicate that geomagnetic activity during 1973-1975 was unusually enhanced for that phase of the sunspot cycle (5-7 years after solar maximum). Previous work indicates that long-term variations in geomagnetic activity are closely coupled to long-term variations in the bulk flow speed of the solar wind. Thus, it is inferred that reported averages of the solar-wind speed for the 1973-1975 era are unusually large for that phase of the sunspot cycle.

Gosling, J. T.↗
NASA NTRS1977

Preferred solar wind emitting longitudes on the sun

During the 11 1/2-year period from July 1964 through December 1975, high- and low-speed solar wind flows originated from preferred solar longitudes. The preferred longitude effect was most pronounced from 1970 onward but was also evident in the years preceding 1970. The most pronounced modulation in average solar wind speed with longitude (approximately 20%) was obtained when it was assumed that the synodic rotation period of the sun is 27.025 days. Some deep internal structure in the sun must ultimately be responsible for these long-lived longitudinal effects, which appear to rotate rigidly with the sun.

Gosling, J. T.↗
NASA NTRS1977

Evidence for a structure-free state at high solar wind speeds

The variability of the basic solar wind flow parameters in highand low-speed flows is submitted to a statistical analysis. Particular attention is given to the uniformity of solar wind high-speed flow conditions by comparing them with those of the low-speed so-called quiet solar wind. With the exception of the solar wind bulk velocity, the average fractional variation of each of a selected sample of basic solar wind parameters is found to be substantially larger during low-speed flow conditions than during high-speed flow conditions at 1 AU. As a statistical ensemble of events, the only thing steady and uniform about low-speed conditions is the bulk velocity. In all other respects, high-speed flows form a much more uniform ensemble of solar wind conditions than do the low-speed flows. It is concluded that the use of average high-speed flow parameters for comparison with steady-state spherically symmetric models of the coronal expansion is meaningful.

Bame, S. J.↗
NASA NTRS1977

A search for a general gradient in the solar wind speed at low solar latitudes

Long-term averages of solar-wind-speed data obtained in the ecliptic plane from July 1964 through December 1975 have been examined for a regular variation in flow speed associated with earth's yearly excursion to latitudes of plus or minus 7.25 deg about the solar equator. Regular speed modulations of about 70 km/s peaking at the highest latitudes are discernible from mid-1964 through 1966 and from early 1969 to early 1971. During the remainder of this 11.5-year interval, the modulations in speed seem to be aperiodic. A superposed epoch analysis of all the data fails to reveal a general solar latitude gradient in the solar-wind flow for these 11.5 years. It is concluded that with near-earth observations, a latitude dependence of the flow speed is too small to be detected on a regular basis against a background 'noise' of solar-wind streams, which vary in longitude, latitude, and time.

Bame, S. J.↗
NASA NTRS1976

High-speed solar wind flow parameters at 1 AU

Nineteen high-speed solar-wind streams observed at 1 AU between March 1971 and July 1974 are studied to develop a more realistic set of constraints for theories on such streams. The streams were chosen because their speeds exceeded 650 km/s for at least several consecutive three-hour periods and because their properties met certain other criteria. A comparison of average stream parameters with predictions of existing steady-state models shows that no single model is adequate to explain the observations. In particular, it is found that no existing model consistent with reasonable coronal conditions predicts the particle fluxes, the convected proton bulk-flow-energy fluxes, and the convected proton enthalpy fluxes observed at 1 AU when the flow speed exceeds 650 km/s.

Feldman, W. C.↗
NASA NTRS1976

Evidence for the regulation of solar wind heat flux at 1 AU

Observational evidence favoring the local regulation of solar-wind heat flux at 1 AU is reviewed, and four months of IMP 6 plasma and magnetic-field data are merged and analyzed in order to investigate what might be regulating the heat flux. A statistical analysis of the data shows that the solar-wind Alfven speed is probably regulating the heat flux locally at 1 AU and that the Alfven speed, the velocity difference between the peak of low-energy electrons and the bulk plasma velocity, and the solar-wind velocity component projected along the local spiral angle are statistically well correlated for Alfven speeds not exceeding about 70 km/s. A time-series analysis of the data indicates that only the Alfven speed and the velocity difference between the peak of low-energy electrons and the bulk plasma velocity are well correlated both qualitatively and quantitatively on a microscopic time scale. It is strongly suggested that, at times, the solar-wind heat flux is locally regulated by the magnitude of the Alfven speed at 1 AU. Uncertainties in the results are discussed.

Feldman, W. C.↗
NASA NTRS1976

Solar cycle evolution of high-speed solar wind streams

Large amplitude high-speed solar wind streams and streams with maximum speeds in excess of 700 km/sec are far more common in years of declining and minimum solar activity than near solar maximum. Further, the broadest solar wind streams observed directly with space probes during the years 1962-1974 occurred near solar minimum in 1974. Changes in the frequency and nature of solar wind stream structures at the orbit of earth appear to be directly related to the long-term evolution of regions of low density in the solar corona.

Bame, S. J.↗
NASA NTRS1976

Solar wind stream evolution at large heliocentric distances - Experimental demonstration and the test of a model

A stream propagation model which neglects all dissipation effects except those occurring at shock interfaces, was used to compare Pioneer-10 solar wind speed observations, during the time when Pioneer 10, the earth, and the sun were coaligned, with near-earth Imp-7 observations of the solar wind structure, and with the theoretical predictions of the solar wind structure at Pioneer 10 derived from the Imp-7 measurements, using the model. The comparison provides a graphic illustration of the phenomenon of stream steepening in the solar wind with the attendant formation of forward-reverse shock pairs and the gradual decay of stream amplitudes with increasing heliocentric distance. The comparison also provides a qualitative test of the stream propagation model.

Gosling, J. T.↗
NASA NTRS1976

Electron parameter correlations in high-speed streams and heat flux instabilities

Statistical electron parameter correlations associated with high-speed streams are determined with the aim of identifying one or more locally active solar wind heat flux instabilities. Evidence that points toward local regulation of the heat flux at 1 AU is presented, and the results of a search for special signatures expected from the action of the Alfven, magnetosonic, and whistler flux instabilities are discussed. It is shown that under certain conditions, the whistler mode can be active in regulating the heat flux at 1 AU.

Feldman, W. C.↗
NASA NTRS1976

Correlated observations of several auroral substorms on February 17, 1971

The purpose of this study is to correlate in detail auroral activity with the corresponding disturbances in the magnetotail. The auroral data were recorded by optical instruments aboard an airplane flying over the Arctic Ocean along the Alaska meridian and by the Alaska meridian chain of all-sky cameras. The corresponding magnetotail observations were made by various instruments on Vela 6A and Imp 5; the interplanetary magnetic field was monitored concurrently by Explorer 35. Three successive substorms were observed on February 17, 1971. Each substorm was readily identified by the classical auroral and magnetic signatures which accompanied its onset. The observed variations of plasma and magnetic field in the magnetotail were consistent with the idea that a neutral line formed in the range X sub SM between -12 and -18 R sub E at the onset of each substorm expansive phase and then moved tailward past X sub SM = -18 R sub E some tens of minutes afterward. The Z component of the tail magnetic field decreased rather steadily for a period of 1-2 1/2 hours after each substorm and until the onset of the next expansive phase, reaching a minimum value just before each onset.

Hones, E. W., Jr.↗