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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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NASA NTRS1981

Configuration of Jupiter's magnetic tail and equatorial current sheet

Recent research reports by Behannon et al. (1981) and Connerney et al. (1981) are summarized. It is noted that the analysis made of the detailed neutral sheet crossings by the minimum variance method shows a consistent result with regard to the orientation of the neutral sheet in the magnetic tail as a two-dimensional surface rocking back and forth about the Jupiter sun-line as the rotation of the planet leads to a precession of the tilted dipole magnetic axis. The occurrence of neutral sheet crossings is found not to be consistent with any of the axially symmetric theoretical models proposed earlier on the basis of the 1974 Pioneer 10 observations. It is noted that a simple nonaxially symmetric model has been developed on the basis of the Voyager results which indicates the strong control upon orientation by the interaction of the solar wind with the Jovian magnetosphere. The model is described as simple because it improves the fit of theory to observation but uses fewer parameters. A quantitative model of the magnetodisc equatorial current sheet has been developed for the inner magnetosphere region which matches well the in-situ magnetic field observations.

Ness, N. F.↗
NASA NTRS1990

Production of electron conics by stochastic acceleration parallel to the magnetic field

Electron conics are enhancements in the electron flux at the edges of the electron loss cone. Such enhancements are a common feature in the electron distribution in the auroral zone. In analogy with ion conics, it has been suggested that electron conics are produced by waves which accelerate electrons perpendicular to the magnetic field. However, using a test particle simulation of the electron distribution it is shown that electron conics can be produced purely by stochastic acceleration of the electrons parallel to a dipole magnetic field. A possible wave mode that can produce parallel acceleration is the Alfven-ion cyclotron mode that has recently been shown to modulate the high energy part of the inverted-V electron distribution.

Temerin, Michael A.↗
NASA NTRS2011

Thermal Ion Transport on the Moon and the Formation of the Lunar Swirls

The bright "swirl" features observed on the lunar surface are generally associated with crustal magnetic anomalies. Prominent explanations that invoke these fields include: magnetic shielding in the form of a mini-magnetosphere, which impedes space weathering by the solar wind; magnetically controlled dust transport; and cometary or asteroidal impacts, that could result in shock magnetization with concomitant formation of the swirls. Here we consider another possibility in which the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. We use a simplified model of the fields, which incorporates a two-dipole magnetic field model for Reiner Gamma, and typical solar wind conditions. We will present preliminarily results suggesting that ions created over significant regions of the lunar surface can be transported under the influence of local and interplanetary electromagnetic fields to narrow areas ncar arcas of high crustal magnetic field strength. The flux of these focused ions may be of sufficient intensity to chemically process (or otherwise bleach) the surface leading to the formation of the high albedo component of the lunar swirls. The theory is appealing since through a lensing effect, it is possible that this flux is sufficient to overcome other space weathering processes which would otherwise tend to erase the features. Also, with relatively low energy ions, and consistent with the observed focusing, the ion gyro radii in the local magnetic fields is small enough to resolve the swirls.

Keller, John W.↗
NASA NTRS1978

Measurements of S II optical emission from the thermal plasma of Jupiter

Photometric spectra of the forbidden S II emission lines at 6716 and 6731 A originating in the Jovian magnetosphere are examined. The summed apparent emission rate in the two sulfur lines is plotted against the central-meridian longitude of Jupiter in System III. It is found that the total sulfur brightness exhibited a distinct minimum when the Jovian magnetic dipole was in the plane defined by the earth-Jupiter vector and the Jovian rotational axis. The observations are shown to be qualitatively consistent with an annular emitting region at the magnetic equator with a thickness of about 1 Jupiter radius and an inner radius of 4 to 5 Jupiter radii. The observations also imply a (logarithmic) characteristic electron density of approximately 3.7 per cu cm and a (logarithmic) average column abundance of about 11.5 per sq cm for singly ionized sulfur.

Brown, R. A.↗
NASA NTRS2010

Plasma IMS Composition Measurements for Europa and the Other Galilean Moons

NASA and ESA are planning the joint Europa Jupiter System Mission (EJSM) to the Jupiter system with specific emphasis to Europa and Ganymede, respectively. The Japanese Space Agency is also planning an orbiter mission to explore Jupiter's magnetosphere and the Galilean satellites. For NASA's Jupiter Europa Orbiter (JEO) we are developing the 3D Ion Mass Spectrometer (IMS) with two main goals which can also be applied to the other Galilean moons, 1) measure the plasma interaction between Europa and Jupiter's magnetosphere and 2) infer the 4 pi surface composition to trace elemental and significant isotopic levels. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa's sub-surface ocean, while the second gives information about transfer of material between the Galilean moons, and between the moon surfaces and subsurface layers putatively including oceans. The measurement of the interactions for all the Galilean moons can be used to trace the in situ ion measurements of pickup ions back to either Europa's or Ganymede's surface from the respectively orbiting spacecraft. The IMS instrument, being developed under NASA's Astrobiology Instrument Development Program, would maximally achieve plasma measurement requirements for JEO and EJSM while moving forward our knowledge of Jupiter system composition and source processes to far higher levels than previously envisaged. The composition of the global surfaces of Europa and Ganymede can be inferred from the measurement of ejected neutrals and pick-up ions using at minimum an in situ payload including MAG and IMS also fully capable of meeting Level 1 mission requirements for ocean detection and survey. Elemental and isotopic analysis of potentially extruded oceanic materials at the moon surfaces would further support the ocean objectives. These measurements should be made from a polar orbiting spacecraft about Europa or Ganymede at height 100 km. The ejecta produced by sputtering of the surfaces of Europa and Ganymede has been shown to be representative of the surface composition. Level 2 science on surface geology and composition can then be further enhanced by addition of the following: 3D Ion Neutral Mass Spectrometer (INNS), 3D plasma electron spectrometer (ELS), and hot plasma energetic particle instrument. The measurement approach is to alternate between times measuring pickup ions and times measuring plasma and magnetic field parameters along the spacecraft trajectory. By measuring the pickup ion energy, arrival direction and mass-per-charge, the ion can be traced back along the ejection trajectory to the approximate area of origin if the 3-D electric field and magnetic field are known. In situ observations of plasma flow velocities and vector magnetic fields can be used to determine the local convective electric field (E = -VXB) along the spacecraft trajectory. By combining this information with models of the magnetospheric interaction with Europa, one can generate 3D maps of the electric and magnetic field and compute the trajectories of the pickup ions back to the surface or exospheric points of origin. In the case of Ganymede there is the additional complexity of its own internal dipole magnetic field, while Io's volcanic activity introduces the complexity of a highly structured denser atmosphere. Callisto with its less globally extended exosphere will have a simpler interaction than for Europa (i.e., more like our moon). We will discuss these differences in light of the above proposed technique. Finally, the INNS observations and neutral exosphere models are needed to estimate production rates of pickup ions. The hot plasma measurements are needed to correct for sputtering rates which can be time dependent and electron plasma observations for electron impact ionization rates. Instrument characteristics, field-of-view requirements, modes of operation and effects of radiation on instrument functionality will be discussed.

Sittler, Edward↗
NASA NTRS1978

Particle acceleration in pulsar magnetospheres

The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.

Baker, K. B.↗
NASA NTRS1965

Time history of the magnetospheric cavity

Laboratory scale model simulation of effect of solar wind on magnetosphere by propelling plasma stream into dipole magnetic field - time history of magnetospheric cavity

TIME FUNCTION↗
NASA NTRS1981

A comparison of characteristic times for satellite absorption of energetic protons trapped in the Jovian and Saturnian magnetic fields

The characteristic times for the absorption of energetic particles trapped in the Jupiter and Saturn magnetospheres by the respective planetary satellites are compared on the basis of Pioneer 10 and 11 data. Characteristic radiation lifetimes with respect to satellite absorption were calculated on the basis of a model of the radial diffusion of particles by the violation of the third adiabatic invariant in the presence of perfectly absorbing satellites, taking into account the tilt and offset of the planetary magnetic dipole moment vectors with respect to the spin axis and the finite gyroradii and bounce periods of the trapped particles. For energetic particles of dipole moments from 1 to 10,000 MeV/G, it is found that the Saturnian times average at least an order of magnitude less than the Jovian times, and the Jovian times increase with increasing trapped particle magnetic mirror latitude. If it is assumed that the rates of radial diffusion are comparable in the two magnetospheres, the results indicate that the Saturnian satellites are more efficient absorbers of inwardly diffusing ions than are the Jovian satellites, due to the near rotational symmetry of the Saturnian magnetic field.

Hood, L. L.↗
NASA NTRS1975

Magnetospheres of earth and Jupiter after Pioneer 10

Possible reasons are discussed for the marked differences observed between the magnetospheres of earth and Jupiter, and a model of Jupiter's magnetosphere is proposed which can explain the observations of the Pioneer 10 mission. It is shown that the corotating plasma in Jupiter's plasmasphere is in the form of a flattened disk due to inertial forces and that Jupiter's magnetosphere is, in part, a rigidly rotating warped skew 'magnetodisk'. According to the proposed model, the inner part of the magnetosphere consists of a warped magnetodisk, the dipole field lines are modified by a ring current, and the equatorial plasma density increases with distance in the region beyond the synchronous orbit radius. Considerable attention is given to the effects resulting from spiraling of the magnetic-field lines, the tilt in the magnetic dipole, and the strong viscous interaction of the solar wind on the dawn side of the magnetosphere.

Prakash, A.↗
NASA NTRS2016

Magnetohydrodynamic Turbulence and the Geodynamo

Recent research results concerning forced, dissipative, rotating magnetohydrodynamic (MHD) turbulence will be discussed. In particular, we present new results from long-time Fourier method (periodic box) simulations in which forcing contains varying amounts of magnetic and kinetic helicity. Numerical results indicate that if MHD turbulence is forced so as to produce a state of relatively constant energy, then the largest-scale components are dominant and quasistationary, and in fact, have an effective dipole moment vector that aligns closely with the rotation axis. The relationship of this work to established results in ideal MHD turbulence, as well as to models of MHD turbulence in a spherical shell will also be presented. These results appear to be very pertinent to understanding the Geodynamo and the origin of its dominant dipole component. Our conclusion is that MHD turbulence, per se, may well contain the origin of the Earth's dipole magnetic field.

Shebalin, John V.↗
NASA NTRS2000

The Axisymmetric Pulsar Magnetosphere

We present the structure of the axisymmetric force-free magnetosphere of an aligned rotating magnetic dipole, in the case in which there exists a sufficiently large charge density (whose origin we do not question) to satisfy the ideal MHD condition, E (raised dot) B = 0, everywhere. The unique distribution of electric current along the open magnetic field lines which is required for the solution to be continuous and smooth is obtained numerically. We expect that our solution will be useful as the starting point for detailed studies of pulsar magnetospheres under more general conditions, namely when either the force-free and/or the ideal MHD condition E (raised dot) B = 0 are not valid in the entire magnetosphere. Based on our solution, we consider that the most likely positions of such an occurrence are the polar cap, the crossings of the zero space charge surface by open field lines, and the return current boundary, but not the light cylinder.

Contopoulos, J.↗
NASA NTRS1995

Solar wind interaction with small bodies. 2: What can Galileo's detection of magnetic rotations tell us about Gaspra and Ida

As the Galileo spacecraft passed the asteroids Gaspra in 1990 and Ida in 1993, the magnetometer recorded changes in the solar wind magnetic field that we associate with the presence of the nearby body. This paper focuses on the types of interactions that can produce perturbations in the solar wind. We have suggested that the interaction at Gaspra is consistent with expectations of flow diversion by a magnetic dipole moment and an associated 'magnetosphere' whose scale size is much larger than the diameter of the solid body. The conditions for the Ida flyby leave more room for ambiguity. The observations could plausibly be related to either interaction with a magnetized body or with a conducting body. We will report on details of the observations that may enable us to distinguish between the different types of interaction and to provide quantitative estimates of the physical properties of the asteroids themselves.

Kivelson, M. G.↗
NASA NTRS1990

Evidence for a diurnally rocking plasma mantle at Neptune

Voyager's post-encounter trajectory at Neptune allows the directions of the magnetic field in the magnetosheath produced by the draping of the typical interplanetary field and by alignment with the magnetotail to be distinguished. Changes of the field from the draped to the magnetotail-aligned direction accompanied by decreases of plasma velocity, density, and temperature, observed at intervals of approximately a Neptunian day, are consistent with the assumption that Voyager repeatedly encountered a plasma mantle region extending well in the magnetosheath and modulated by the rotation of the planet's magnetic dipole. Other interpretations are either implausible or inconsistent with the observations. Previously reported periodic velocity decreases in the magnetosheath of Uranus can be interpreted in the same way. Extended plasma mantles may thus be a general property of planetary magnetospheres interacting with the magnetized solar wind. Analogous effects at earth cannot yet be observed because of lack of suitable spececraft missions, but their existence is suggested by theoretical arguments.

Zhang, Ming↗
NASA NTRS1996

Chain Dynamics in a Dilute Magnetorheological Fluid

The structure, formation, and dynamics of dilute, mono-dispersive ferrofluid emulsions in an external magnetic field have been investigated using dynamic light scattering techniques. In the absence of the magnetic field, the emulsion particles are randomly distributed and behave like hard spheres in Brownian motion. An applied magnetic field induces a magnetic dipole moment in each particle. Dipolar interactions between particles align them into chains where correlation functions show two decay processes. The short-time decay shows the motion of straight chains as a whole where the apparent chain length increases with the applied magnetic field and the particle volume fraction. Good scaling results are obtained showing that the apparent chain length grows with time following a power law with exponent of 0.6 and depends on the applied field, particle volume fraction, and diffusion constant of the particles. The long-time decay in the correlation function shows oscillation when the chains reach a certain length with time and stiffness with threshold field This result shows that chains not only fluctuate, but move in a periodic motion with a frequency of 364 Hz at lambda = 15. It may suggest the existence of phonons. This work is the first step in the understanding of the structure formation, especially chain coarsening mechanism, of magnetorheological (MR) fluids at higher volume fractions.

Liu, Jing↗
NASA NTRS2012

Three-Dimensional Magnetohydrodynamic Modeling of the Solar Wind Including Pickup Protons and Turbulence Transport

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfer from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons.We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 deg - .90 deg and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.

Usmanov, Arcadi V.↗
NASA NTRS1972

Jupiter radiation belt engineering model

On the basis of earth observations of the HF and UHF radio emission generated near Jupiter, the presence of energetic charged particles trapped in the planet's dipole magnetic field has been inferred. For electrons, energies of the order of 10 MeV and peak fluxes of the order of 10 to the 7th power per square centimeter per second can be derived from the data for equatorial regions about two planetary radii from the dipole. Energetic protons and lower-energy electrons and protons are also expected, but the limited data require that their fluxes be based on theory or earth analogy. Because descriptions available in the literature suggest large associated uncertainties, both nominal and limiting models for the charged-particle populations of Jupiter's belts are derived. These new engineering models describe electron and proton fluxes and their distributions in energy and position in forms suitable as space vehicle design criteria.

Divine, N.↗
NASA NTRS2001

Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km/s, with a low power requirement of approx. 1 kW per 100 kg of payload and -1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km/s. solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs. Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

Winglee, R. M.↗