Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Magnetosphere”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Observations of effects from magnetospheric cusp movement during a solar proton event

Observations of a magnetospheric cusp motion event during a solar proton event are presented. The observations were made by a series of riometers and balloon-borne radiation detectors and conductivity probes near Sondre Stromfjord, Greenland. During the arrival of solar protons on August 19, 1979, the balloon-borne detectors recorded two rises and declines in nuclear gamma ray intensity accompanied by a marked softening in the photon spectrum. The observations are interpreted as a shift in detector position from the dayside of the magnetosphere to the polar cap resulting from an equatorward displacement or expansion of the polar cusp by 5 deg in 15 min with a southward turning of the IMF. Instruments on ISEE 3 confirm this interpretation, showing a southward turning of the IMF and a solar wind speed increase. Results imply a proton cutoff energy in the range 6-10 MeV at Sondre Strombjord prior to the cusp motion, and reflect the early effects of field line erosion.

Brown, R. R.↗
NASA NTRS1981

Ion-cyclotron turbulence and diagonal double layers in a magnetospheric plasma

A survey of current concepts regarding electrostatic ion-cyclotron turbulence (theory and experiment), and regarding inclined double potential layers in the magnetospheric plasma is presented. Anomalous resistance governed by electrostatic ion-cyclotron turbulence, and one-dimensional and two-dimensional models of double electrostatic layers in the magnetospheric plasma are examined.

Liperovskiy, V. A.↗
NASA NTRS1982

Charged particle motions in the distended magnetospheres of Jupiter and Saturn

Charged particle motion in the guiding center approximation is analyzed for models of the Jovian and Saturnian magnetospheric magnetic fields based on Voyager magnetometer observations. Field lines are traced and exhibit the distention which arises from azimuthally circulating magnetospheric currents. The spatial dependencies of the guiding center bounce period and azimuthal drift rate are investigated for the model fields. Non-dipolar effects in the gradient-curvature drift rate are most important at the equator and affect particles with all mirror latitudes. The effect is a factor of 10-15 for Jupiter with its strong magnetodisc current and 1-2 for Saturn with its more moderate ring current. Limits of adiabaticity, where particle gyroradii become comparable with magnetic scale lengths, are discussed and are shown to occur at quite modest kinetic energies for protons and heavier ions.

Birmingham, T. J.↗
NASA NTRS1981

Characteristics of hot plasma in the Jovian magnetosphere - Results from the Voyager spacecraft

Measurements of the intensities, energy spectra, angular variations, and composition characteristics of the low-energy ion populations (approximately 30 keV to 4 MeV) obtained by both Voyager spacecraft in the outer (more than about 10 Jupiter radii) Jovian magnetosphere are reported and interpreted. Also shown are some of the energetic electron measurements. Using the spectral and angular ion measurements, density and pressure profiles in the magnetosphere are constructed and then compared with results reported by the plasma wave and plasma science investigations (density) and the magnetic field investigation (pressure).

Krimigis, S. M.↗
NASA NTRS1981

Low-energy charged particle observations in the 5-20 Jupiter-radius region of the Jovian magnetosphere

Ion (greater than 0.5 MeV) and electron (greater than 30 keV) measurements made by the low-energy charged particle instrument during the Voyager 1 and 2 traversals of the 5-20 Jupiter-radius region of the Jovian magnetosphere are presented. The spatial morphology of particle intensities, energy spectra, and composition is emphasized. Diffusive radial transport is also discussed. The Jovian magnetosphere seemed to be much more disturbed during the Voyager 2 passage than during that of Voyager 1. Significant inbound-outbound asymmetries of the radial profiles of intensities are observed; an appropriate magnetic field model to provide closure has not been found. Low-energy electrons are not enhanced or depleted in the Io torus region except at the inner edge, about 5.2 Jupiter-radius, where they sharply decrease. This may be due to enhanced electron loss associated with a region of increased plasma density.

Armstrong, T. P.↗
NASA NTRS1981

Jupiter and Io - A binary magnetosphere

A qualitative assessment is presented of Voyager 1 and 2 data analysis and theoretical interpretation, regarding the Io torus and Jovian aurora, dominant magnetospheric components, plasma waves and radio emissions, with emphasis on the difficulty of accounting for either the Jupiter aurora or Io torus EUV emission luminosities in energetic terms. Jupiter's middle atmosphere is also considered, with attention to observations of corotating ions, their ambiguities and their implications. After a discussion of the question of Jupiter's interaction with the solar wind, as manifested by its magnetic tail, terrestrial magnetospherics are invoked in the construction of a tentative unification of observed phenomena which is within the latitude afforded by the current state of data reduction.

Scarf, F. L.↗
NASA NTRS1982

The gravito-electrodynamics of charged dust in planetary magnetospheres

The orbital dynamics of small electrically charged dust grains within the corotating regions of planetary magnetospheres is considered. Equations are derived for the elliptical epicyclic motion of positively and negatively charged particles about the guiding center in an equilibrium circular orbit under the influence of small perturbations. Those orbits that are stable to the perturbations are found to have a ratio of the semiaxes of the epicycle between 1/2 and 1, depending on the specific charge, and a gyration frequency about the guiding center between the Kepler frequency and the grain gyrofrequency in a nonrotating frame. In the magnetospheres of Jupiter and Saturn, where the grains are expected to be negatively charged and move in a prograde sense, the guiding centers are predicted to have speeds intermediate to the Kepler speed and the corotation speed and thus may undergo a 1:1 magneto-gravitational resonance with a neighboring satellite. Results may be used in the interpretation of the waves in the F ring of Saturn in terms of the dust size distribution.

Mendis, D. A.↗
NASA NTRS1982

Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977

The Rice University convection model is applied to the early main phase of the July 29, 1977 magnetic storm through a computer implementation that self-consistently calculates electric fields, currents, and plasma distributions and velocities in the inner magnetosphere/ionosphere system. On the basis of solar wind parameters and AL index as inputs, the model predicts the injection of plasma sheet plasma to form a substantial storm time ring current whose total predicted strength agrees with the observed Dst index. The possibility that the magnetic field may be sufficiently inflated to make 60 deg field lines extend to the outer magnetosphere is examined. In the model, distortion of the plasma sheet inner edge by magnetospheric compression associated with the sudden commencement temporarily disrupts the normal Birkeland current pattern. Normal Birkeland currents and shielding reassert themselves in about an hour.

Wolf, R. A.↗
NASA NTRS1982

Multiple-spacecraft and correlated riometer study of magnetospheric substorm phenomena

Double-spacecraft observations presented suggest that growth phase phenomena are widespread in the outer magnetosphere and can occur simultaneously at nightside locations 4-5 hours apart in local time. Evidence is also adduced from multiple-spacecraft data and comprehensive magnetometer and riometer data against the concept that growth phase features are not generally due to substorm activity at other locations in the auroral or polar regions. A close relationship is noted between putative energy input to the magnetosphere and the sensitive response of the magnetic field and energetic particles at pre- and near-midnight geostationary orbit locations. This relationship is shown explicitly for the cases of three event periods. Data are also presented which suggest that growth phase features at synchronous orbit can be strictly controlled by IMF orientations.

Baker, D. N.↗
NASA NTRS1982

Particle precipitation induced by short-duration VLF waves in the magnetosphere

The present investigation has the objective to study the precipitation of energetic electrons into the ionosphere due to the interaction of these particles with short-duration VLF waves in the magnetosphere. The physics of the interaction is considered, taking into account the wave structure, the energetic particle distribution, wave-particle interaction, and the computation of the precipitated flux versus time. The obtained formulation is applied to various different magnetospheric conditions. Attention is also given to peak flux and total deposited energy. The results of the investigation demonstrate the role of the energetic particle distribution function, the normalized wave frequency, the L value of the path of propagation, the cold plasma density, and the wave intensity. The precipitated energy flux that would be observed at 1000-km altitude is presented as a function of time relative to the injection of the wave pulse at the same point.

Inan, U. S.↗
NASA NTRS1982

Detection of nonthermal continuum radiation in Saturn's magnetosphere

A detailed analysis of high resolution wideband data from the Voyager 1 and 2 plasma wave receivers has revealed the presence of heretofore undiscovered nonthermal continuum radiation trapped within the Saturnian magnetosphere. The discovery of Saturnian trapped continuum radiation fills a disturbing void in the Saturnian radio spectrum. On the basis of observations at both the earth and Jupiter it was expected that continuum radiation should be a pervasive signature of planetary magnetospheres in general. Special processing of the Voyager 1 plasma wave data at Saturn has now confirmed the existence of weak emissions that have a spectrum characteristic of trapped continuum radiation. Similar radiation was also detected by Voyager 2; however, in this case it is not certain that Saturn was the only source. Considerable evidence exists which suggests that Saturn may have been immersed in the Jovian tail during Voyager 2 encounter, so that Jupiter may provide an additional source of the continuum radiation detected by Voyager 2.

Kurth, W. S.↗
NASA NTRS1982

DE-1 observations of VLF transmitter signals and wave-particle interactions in the magnetosphere

A broadband VLF receiver on the DE-1 satellite measures signals injected into the magnetosphere by ground-based transmitters. VLF emissions triggered by these signals indicate that the waves interact strongly with trapped energetic particles in the magnetosphere. The propagation paths from the source to the satellite are deduced on the basis of the group time delay and Doppler shift. Although there are many different paths, emissions are triggered by the later-arriving pulses that have traversed the geomagnetic equator. First satellite-based observations of emission triggering by high-power communications transmitters and their possible implications are discussed.

Inan, U. S.↗
NASA NTRS1982

Two-component proton spectra in the inner Saturnian magnetosphere

Measurements obtained by the Pioneer-11 spacecraft in Saturn's inner magnetosphere revealed the presence of a high energy proton component, primarily confined within the orbits of satellites Enceladus and Mimas. The high energy component was interpreted as due to protons from cosmic ray neutron albedo decay interactions with the Saturnian rings and, secondarily, the planetary atmosphere, but without detailed knowledge of the differential or integral spectrum. The main objective of the present investigation is to examine in some detail the ion spectra in the considered region of the magnetosphere, and to provide some of the basic input necessary in evaluating various models of energetic particle-ring interactions. The conducted measurements clearly show the presence of low energy ions and electrons inside the orbit of Mimas and provide a measure of the evolution of the hot ion spectrum observed inside the orbit of Rhea into a two-component power law spectrum inside the orbits of Enceladus and Mimas.

Krimigis, S. M.↗
NASA NTRS1982

Large sounding rockets as a base for probing the distant magnetosphere

The Echo program's use of large sounding rockets to inject electron beams into the outer trapping region where the earth's plasma sheet interacts with the inner magnetosphere is discussed. The beams pass through the plasma sheet and the trapping region, reflect at the southern hemisphere conjugate point and return to the vicinity of the rocket where they are detected and analyzed for acceleration and diffusion processes which may also be responsible for the radiation belts. The motion of electron beams in the magnetosphere is discussed from the standpoint of single particle motion, and the trajectories of electrons injected with known energy, known angle between the electron velocity vector and the local magnetic field vector, and known position are examined. The interaction between the rocket motion and the electron drift motion is described, and the advantages and drawbacks of beam detection by optical methods and by throwaway detectors are compared. Planned Echo experiments using the Space Shuttle are discussed

Winckler, J. R.↗
NASA NTRS1983

The adiabatic motion of charged dust grains in rotating magnetospheres

Adiabatic equations of motion are derived for the micrometer-sized dust grains detected in the Jovian and Saturn magnetospheres by the Pioneer 10 and 11 spacecraft. The adiabatic theory of charged particle motion is extended to the case of variable grain charge. Attention is focused on the innermost and outermost limits to the grain orbit evolution, with all orbits tending to become circular with time. The parameters such as the center equation of motion, the drift velocity, and the parallel equation of motion are obtained for grains in a rotating magnetosphere. Consideration is given to the effects of periodic grain charge-discharge, which are affected by the ambient plasma properties and the grain plasma velocity. The charge-discharge process at the gyrofrequency is determined to eliminate the invariance of the magnetic moment and cause the grain to exhibit radial movement. The magnetic moment increases or decreases as a function of the gyrophase of the charge variation.

Northrop, T. G.↗
NASA NTRS1983

Heavy ions in the outer Kronian magnetosphere

The possible sources of the cold plasma observed in the outer magnetosphere of Saturn are analyzed. On the basis of the O(+)-H charge exchange species-specific loss mechanism, as well as abundance and rate considerations, it is concluded that the dominant heavy ion populating the equatorial outer magnetosphere is that of atomic nitrogen. Possible sources of hot plasma are also discussed, as are the inhibition of corotation by mass loading and the radial variation of composition. It is found that the observed deviations from corotation and current mass loading estimates indicate either a somewhat higher ionospheric conductance than is implied by the UVS and RSS measurements, or an overestimate of mass loading. It is suggested that the plasma gap observed by Voyager 1 outbound may be associated with a composition change.

Eviatar, A.↗
NASA NTRS1983

Plasma waves in the Jovian magnetosphere

Any waves which are influenced by the presence of a plasma are called plasma waves. In general, plasma waves can be classified as either electromagnetic, which have both electric and magnetic fields, or electrostatic, which have no magnetic field. The recent Voyager encounters provide the basis for the first comprehensive investigation of plasma waves in the magnetosphere of Jupiter. The most striking feature of the Jovian plasma-wave observations is the very close similarity to the plasma-wave phenomena observed in the earth's magnetosphere. In a description of the plasma-wave results obtained with the aid of Voyager, the observed phenomena are discussed in several broad categories. Attention is given to the upstream waves and the bow shock, the trapped continuum radiation, upper hybrid and electron cyclotron waves, whistler-mode waves, and broadband electrostatic noise.

Gurnett, D. A.↗
NASA NTRS1983

Long-lived particulate or gaseous structure in Saturn's outer magnetosphere

Voyager 1 and 2 and Pioneer 11 data on the variations in the number density of low-energy plasma ions in the outer Saturn magnetosphere are discussed. Low and high latitude observations are compared in reference to the position of the spacecraft crossing of the field line. Abrupt decreases in the number density interrupted the tendancy for the number density to increase with spacecraft approach to Saturn. All three spacecraft are concluded to have encountered the same magnetospheric structure in the field line, with absorbers being present in the equatorial plane. The absorbers are suggested to be either gas or debris, which may be detectable visibly or with occultation techniques.

Lazarus, A. J.↗