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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Results of magnetic surveys of the magnetosphere and adjacent regions.

Review of the gross features of the magnetic fields in the magnetosphere and its vicinity that have been explored in the past several years by extensive spacecraft observations. The magnetopause, the bow shock, the magnetosheath, and the geomagnetic tail are discussed. Results of a recent study of the OGO 1 and 3 satellite data taken in the near tail region, the magnetic field disturbances observed in the magnetosphere, and brief accounts of quantitative models of the magnetosphere are also reviewed. Special attention is given to the storm-time ring current and to polar substorms or magnetic bays.

Sugiura, M.↗
NASA NTRS1972

Storm-associated Pc 5 micropulsation events observed at the synchronous equatorial orbit.

Quasi-sinusoidal magnetic-field (micropulsations) are regularly observed at ATS 1 during geomagnetic storms. The wave events typically occur during the main phase and tend to be confined to the afternoon sector. All observed events have been closely correlated with magnetospheric substorm activity. Power spectral analysis shows that the observed oscillations are composed of harmonically related components. Twenty-six wave events were observed in 1967; the analysis of three typical Pc 5 events is presented here. The observations are compared with the predictions of theory for a hot inhomogeneous plasma. It is suggested that the observed micropulsations can be understood as the occurrence of either an Alfven wave instability, or a drift instability, of the enhanced storm-time ring current.

Barfield, J. N.↗
NASA NTRS1972

Plasma wave observations near the plasmapause with the S3-A satellite

The electric field noise phenomena is described which was observed by the S3-A spacecraft near the plasmapause during the magnetic storm of 16 to 17 December, 1971. The occurrence is noted of a region of intense, low frequency (20 Hz to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrent with the rapid decrease in 24.3 or = E or = 35.1 keV ring current protons mirroring near the equator during this storm and may be responsible for the pitch angle diffusion and loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed.

Anderson, R. R.↗
NASA NTRS1972

Program of solar wind data analysis utilizing data from Pioneer 6, Mariner 5 and explorer 35

A combined data analysis and theoretical program aimed at interpreting and utilizing solar wind data obtained from Pioneer 6, Mariner 5, and Explorer 35 has been completed. A theoretical model of the radial dependence of large scale solar wind inhomogeneities was developed and used to map solar wind variations measured by Explorer 35 to various heliocentric distances and to the orbits of Mercury, Venus, and Mars. The model was also used to determine power spectra velocity, density and temperature variations of 20 R sub s from spectra obtained from the Mariner 5 data at an average heliocentric distance of 180 R sub s. Five stream-stream interaction events in the Pioneer 6 data were analyzed which confirmed the picture of a spiral compression ridge interfacing the two streams and the associated east-west deflections of the solar wind flow. Magnetopause crossings observed in Explorer 35 plasma data were used to develop statics on boundary motions at lunar distance. A study of the geomagnetic disturbance field asymmetry was performed and a model of disturbance field from a partial ring current was developed.

Siscoe, G. L.↗
NASA NTRS1972

Magnetospheric particle populations.

Significant results of magnetospheric charged particle measurements conducted within the past two years are reviewed in an attempt to provide a general description of relationships among particle populations in the magnetosheath, plasma sheet, extraterrestrial ring current region, electron trough, pseudotrapping region, and stable-trapping region. Special attention is given to the characteristics of protons, electrons, alpha particles, and particles with charge greater than three in the stable trapping region.

Vette, J. I.↗
NASA NTRS1973

Interplanetary magnetic field and geomagnetic Dst variations.

The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

Patel, V. L.↗
NASA NTRS1973

Particle entry into the equatorial magnetosphere.

Explorer-45 data are reviewed which concern the behavior and dynamics of protons associated with the storm-time and quiet-time extraterrestrial ring current at the equatorial plane. The quiet-time proton energy spectrum exhibits a peak in the interval between 100 and 200 keV. During storm conditions, the intensities of the higher energy protons decrease while the intensities of protons from 10 to 100 keV are greatly enhanced, making them the dominant contributor to the storm-time particle energy density. It is shown that during magnetic storms, the ratio of the particle energy density to the magnetic field energy density reaches values greater than unity, and that the plasmasphere has a strong influence on the characteristics of particle injection.

Fritz, T. A.↗
NASA NTRS1973

SSS-A spacecraft and experiment description.

The scientific objectives of the Explorer-45 mission are discussed. The primary objective is the study of the ring current responsible for the main phase of magnetic storms. Closely associated with this objective is the determination of the relationship between magnetic storms, substorms, and the acceleration of charged particles in the magnetosphere. Further objectives are the measurement of a wide range of proton, electron and alpha-particle energies, and studies of wave-particle interactions responsible for particle transport and loss in the inner magnetosphere. The orbital parameters, the spacecraft itself, and some of its unique features, such as the data handling system, which is programmable from the ground, are described.

Longanecker, G. W.↗
NASA NTRS1973

Energy spectra and pitch angle distributions of storm-time and substorm injected protons.

Discussion of the energy spectra and pitch angle distributions of ring current protons observed with the solid-state proton detector of Explorer 45 during the main and fast recovery phases of a storm on Dec. 17, 1971. Appearances of characteristic changes in the pitch angle distributions of roughly 100-eV protons are interpreted as pitch angle dispersion of rapidly injected protons during their azimuthal drift at L values above 5.

Konradi, A.↗
NASA NTRS1973

Plasma wave observations near the plasmapause with the S3-A satellite.

Description of the electric field noise phenomena observed by the S3-A spacecraft near the plasmapause during the magnetic storm of Dec. 16, 17, 1971. The most striking and unusual feature of these storm time electric field observations is the occurrence of a region of intense low-frequency (20 to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrently with the rapid decrease in low-energy (E ranging from 20 to 50 keV) ring current protons mirroring near the equator during this storm and may be responsible for the loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed.

Anderson, R. R.↗
NASA NTRS1974

Explorer 45 (S 3-A) observations of the magnetosphere and magnetopause during the 4-5 August 1972, magnetic storm period

The Explorer 45 satellite performed extensive field and particle measurements in the heart of the magnetosphere during the double magnetic storm period of August 4-5, 1972. Both ground level magnetic records and the magnetic field deformations measured along the orbit by the satellite indicated the existence of only a moderate ring current. This was confirmed by the measurements of the total proton energy density less than those observed during the December 1971 and June 1972 magnetic storms. The plasmapause in the noon quadrant was eroded continuously from the onset of the first storm at the beginning of August 4 to an altitude below L = 2.07 at about 18 hours on August 5. During the orbit containing the second sudden commencement a large amount of low frequency electric and magnetic field noise was encountered throughout the entire orbit. A noteworthy observation during this orbit was the contraction of the magnetopause to distances inside the satellite at L = 5.2.

Hoffman, R. A.↗
NASA NTRS1973

ATS-5 observations of energetic proton injection

Energetic particle observations from ATS-5 are presented that directly show asymmetric injection of 30- to 300-keV proton fluxes into the nightside magnetosphere to form the asymmetric ring current. The temporal structure of these substorm-correlated proton bursts is consistent with a westward gradient drift from the nightside acceleration region. The drifting protons tend to be accompanied by nondiamagnetic decreases of the magnetic field at the satellite. Adiabatic decreases of the energetic electron fluxes often occur with these changes in the field strength. Nearly 200 proton-only events have been observed, occurring uniformly between 1500 and 2200 LT and not at all before 1200 LT or after 2300 LT.

Bogott, F. H.↗
NASA NTRS1975

Results of magnetospheric barium ion cloud experiment of 1971

The barium ion cloud experiment involved the release of about 2 kg of barium at an altitude of 31 482 km, a latitude of 6.926 N., and a longitude of 74.395 W. Significant erosion of plasma from the main ion core occurred during the initial phase of the ion cloud expansion. From the motion of the outermost striational filaments, the electric field components were determined to be 0.19 mV/m in the westerly direction and 0.68 mV/m in the inward direction. The differences between these components and those measured from balloons flown in the proximity of the extremity of the field line through the release point implied the existence of potential gradients along the magnetic field lines. The deceleration of the main core was greater than theoretically predicted. This was attributed to the formation of a polarization wake, resulting in an increase of the area of interaction and resistive dissipation at ionospheric levels. The actual orientation of the magnetic field line through the release point differed by about 10.5 deg from that predicted by magnetic field models that did not include the effect of ring current.

Adamson, D.↗
NASA NTRS1975

A review of the Jovian magnetosphere based upon Pioneer 10 and 11

Data derived from the plasma, magnetic field, and energetic particle experiments on the December, 1973 and December, 1974 Jupiter encounters are reviewed. A bow shock was discovered on the solar side of the planet, as predicted. However, a smaller magnetic field and larger fluxes of energetic electrons were found than anticipated. A ring current and current sheet in the Jovian plasmasphere are inferred from magnetic field measurements.

Trainor, J. H.↗
NASA NTRS1975

Interplanetary field and plasma during initial phase of geomagnetic storms

Twenty-three geomagnetic storm events during 1966 to 1970 were studied by using simultaneous interplanetary magnetic field and plasma parameters. Explorer 33 and 35 field and plasma data were analyzed on large-scale (hourly) and small-scale (3 min.) during the time interval coincident with the initial phase of the geomagnetic storms. The solar-ecliptic Bz component turns southward at the end of the initial phase, thus triggering the main phase decrease in Dst geomagnetic field. The By component also shows large fluctuations along with Bz. When there are no clear changes in the Bz component, the By shows abrupt changes at the main phase onset. On the small-scale, behavior of the magnetic field and electric field were studied in detail for the three events; it is found that the field fluctuations in By, Bz and Ey and Ez are present in the initial phase. In the large-scale, the behavior field remains quiet because the small-scale variations are averaged out. It appears that large as well as small time scale fluctuations in the interplanetary field and plasma help to alter the internal electromagnetic state of the magnetosphere so that a ring current could causing a geomagnetic storm decrease.

Patel, V. L.↗
NASA NTRS1974

Midday Pc 1-2 pulsations observed at a subcleft location

A class of unstructured Pc 1-2 pulsation activity, as identified on Bar I (70.2 N) records taken during 1968-1972, is found to be present in midday hours on about half of the days in summer months. The events have some tendency to occur in the later part of the ring current recovery phase, especially at times of moderate AE when the cleft lines are just poleward of Bar I. The source lines of the Pc 1-2 are found to lie essentially outside the plasmapause. In terms of the proton cyclotron resonance instability the most likely source regions of the Bar I Pc 1-2 are the detached plasma regions convecting sunward on the dayside and the portion of the cleft plasma on the last closed field lines.

Heacock, R. R.↗
NASA NTRS1975

Local time variations of particle flux produced by an electrostatic field in the magnetosphere

The local time variations of particle distributions, which can be produced by the sudden enhancement of a cross-tail electric field, are examined by using adiabatic theory. The strong coupling between acceleration, inward motion, and east-west drift is emphasized. The model is used to interpret recent measurements of delay times of newly accelerated electrons at different local times at geostationary orbit. Observations of the asymmetric storm time 'ring current' are interpreted in terms of the model without invoking particle loss.

Kivelson, M. G.↗
NASA NTRS1975

An analytical model of the Jovian magnetosphere

Using Euler potentials, we construct a class of axisymmetric magnetic field models that exhibit the general features of the dayside Jovian field as observed by Pioneers 10 and 11. The particular model used for illustration contains a distended, disk-like field along the equator, a blunt, earth-like magnetosphere boundary, and the possibility of multiple trapping regions along a field line. The self-consistent ring current is calculated, together with representative drift periods for energetic particles.

Barish, F. D.↗