Search NASA⌕ Search

SEARCH · Search NASA

Results for “ion tails”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Interaction of Titan's atmosphere with Saturn's magnetosphere

The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause.

Hartle, R. E.↗
NASA NTRS1985

Spacecraft-induced plasma energization and its role in flow phenomena

Plasma instabilities induced by orbiting vehicles can cause many important phenomena ranging from electron and ion heating and suprathermal electron tail energization, to enhanced ionization and optical emissions. We outline the basic collective processes leading to plasma energization near plasma sheaths and in regions of neutral gas streaming through plasma, and discuss the role of the induced collective effects in producing the optical emission spectra.

Papadopoulos, K.↗
NASA NTRS1986

Unstable-magnetic-drift waves in a plasma with temperature anisotropy

It is pointed out that under certain conditions, such as a weak electron temperature anisotropy, the magnetic-drift wave instability can become rather important, and the growth rate can be greater than the ion gyrofrequency when the scale length of the density gradient is comparable to, or shorter than, the thermal ion gyroradius. The instability is attributed to wave-electron interactions, and the growth rate is far greater than the case investigated by Krall and Rosenbluth (1963) who attributed the instability to wave-ion interactions. The anticipated vanishing of the instability is observed as epsilon sub n/epsilon sub B approaches zero. The presently observed instability may be used to explain the low-frequency fluctuations evidenced by the Active Particle Tracer Explorer Ion Release Module magnetometer measurements, and may contribute to the acceleration of ions along the plasma cometary tail.

Wu, C. S.↗
NASA NTRS1994

Experimental investigation of possible geomagnetic feedback from energetic (0.1 to 16 keV) terrestrial O(+) ions in the magnetotail current sheet

Data from energetic ion mass spectrometers on the ISEE 1 and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O(+) ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic activity as has been suggested in the literature, by contributing a destabilizing mass increase in the magnetotail current sheet. The ISEE 1 data (0.1-16 keV/e) provide in situ observations of the O(+) concentration in the central plasma sheet, inside of 23 R(sub E), during the rising and maximum phases of solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1-17 keV/e) taken during the subsequent solar minimum all within 9 R(sub E). provide a reference for long-term variations in the magnetosphere O(+) content. Statistical correlations between the ion data and the indices, and between different indices. all point in the same direction: there is probably no feedback specific to the O(+) ions, in spite of the fact that they often contribute most of the ion mass density in the tail current sheet.

Lennartsson, O. W.↗
NASA NTRS1993

Experimental investigation of possible geomagnetic feedback from energetic (0.1 to 16 keV) terrestrial O(+) ions in the magnetotail current sheet

Data from energetic ion mass spectrometers on the International Sun Earth Explorer 1 (ISEE 1) and AMPTE/CCE spacecraft are combined with geomagnetic and solar indices to investigate, in a statistical fashion, whether energized O(+) ions of terrestrial origin constitute a source of feedback which triggers or amplifies geomagnetic magnetotail current sheet. The ISSE 1 data (0.1-16 keV/e) provide in situ observations of the O(+) solar cycle 21, as well as inner magnetosphere data from same period. The CCE data (0.1-17 keV/e), taken during the subsequent solar minimum, all within 9 R(sub E), provide a reference for long-term variations in the magnetosphere O(+) content. Statistical correlations between the ion data and the indices, and between different indices, all point in the same direction: there is probably no feedback specific to the O(+) ions, in spite of the fact that they often contribute most of the ion mass density in the tail current sheet.

Lennartsson, O. W.↗
NASA NTRS1986

Accelerated plasma flows at the near-tail magnetopause

ISEE-1 and -2 fast plasma data of ion and electron distributions at 16 energies and 16 velocities are used to study accelerated particle flow events at the near-tail dusk magnetopause. The flows separated the plasma sheet from the magnetosheath, a situation which normally arises when the local magnetosheath and plasma sheet magnetic fields are close to being antiparallel. The flows were directed tailward at speeds up to twice those in the adjoining magnetosheath and had densities similar to those in the magnetosheath. The attendant ion and electron temperatures were between those in the magnetosheath and in the plasma sheet. The flow region closest to the magnetosheath had the highest velocity and the lowest density, and a lowered-density field line region appeared on the earthward side of the accelerated flow region. The flows had the velocity changes of a tangential stress balance and are taken as the location of field line merging near (and perhaps tailward) of the dawn-dusk terminator. Significantly fewer accelerated flows are seen in the dawn tail magnetopause, an asymmetry attributed to a seasonally dependent warping of the midtail neutral sheet or a superimposition of interplanetary magnetic field lines over the dusk magnetopause.

Gosling, J. T.↗
NASA NTRS1997

Nonguiding Center Motion and Substorm Effects in the Magnetotail

Thick and thin models of the middle magnetotail were developed using a consistent orbit tracing technique. It was found that currents carried near the equator by groups of ions with anisotropic distribution functions are not well approximated by the guiding center expressions. The guiding center equations fail primarily because the calculated pressure tensor is not magnetic field aligned. The pressure tensor becomes field aligned as one moves away from the equator, but here there is a small region in which the guiding center equations remain inadequate because the two perpendicular components of the pressure tensor are unequal. The significance of nonguiding center motion to substorm processes then was examined. One mechanism that may disrupt a thin cross-tail current sheet involves field changes that cause ions to begin following chaotic orbits. The lowest-altitude chaotic region, characterized by an adiabaticity parameter kappa approx. equal to 0.8, is especially important. The average cross-tail particle drift is slow, and we were unable to generate a thin current sheet using such ions. Therefore, any process that tends to create a thin current sheet in a region with kappa approaching 0.8 may cause the cross-tail current to get so low that it becomes insufficient to support the lobes. A different limit may be important in resonant orbit regions of a thin current sheet because particles reach a maximum cross-tail drift velocity. If the number of ions per unit length decreases as the tail is stretched, this part of the plasma sheet also may become unable to carry the cross-tail current needed to support the lobes. Thin sheets are needed for both resonant and chaotic orbit mechanisms because the distribution function must be highly structured. A description of current continuity is included to show how field aligned currents can evolve during the transition from a two-dimensional (2-D) to a 3-D configuration.

Kaufmann, Richard L.↗
NASA NTRS2003

Observations of Counter-Streaming Ion Velocity Distributions in LLBL

We analyze ion velocity distributions observed by Interball-Tail at two LLBL crossings under southward and variable magnetosheath magnetic field. These magnetic conditions lead to highly structured LLBL. D-shape ion velocity distributions were observed within LLBL structures along with other reconnection signatures. Another type of the ion velocity distributions observed within LLBL structures consists of two counter-streaming magnetosheath-type components. We consider two possible scenarios that may lead to development of these counterstreaming ion components: reflection of transmitted magnetosheath ions from the ionosphere and creation of these velocity distributions during formation of the LLBL. We argue that observed counter-streaming component could not be due to ionospheric reflection. The observations of these ion velocity distributions are in favor of the multiple reconnections between magnetosheath and magnetospheric flux tubes.

Vaisberg, O. L.↗
NASA NTRS1992

Ion tearing in a magnetotail configuration with an embedded thin current sheet

The ion tearing instability is investigated in a magnetotail configuration that consists of a diffuse plasma sheet current and an embedded, thin current sheet with a strong current. For historical reasons, the thin embedded current sheet will be called a 'neutral sheet', even though the normal component of the magnetic field, Bn, is nonzero. In particular, we assume that the current within the thin current sheet is due to the acceleration of 'Speiserlike' ion trajectories by a cross-tail electric field Ey. It is found that the strong current within the neutral sheet is essentially unimportant to the growth rate of the tearing instability, and that the growth rate scales as (lambda(0)/Lz) squared, where Lz is the overall half thickness of the plasma sheet and lambda (0) is the ion inertial length. In the absence of the current outside the neutral sheet, current filamentation is stable.

Burkhart, G. R.↗
DOE OSTI2020

Impact of dopant-induced optoelectronic tails on open-circuit voltage in arsenic-doped Cd(Se)Te solar cells

Fluctuations refer to inhomogeneity in the distribution of donors and acceptors at the nanometer scale and occur in many compound solar cell materials such as Cu(In,Ga)Se 2 , Cu 2 ZnSn(S,Se) 4 , and CdSe x Te 1-x . In this work, numerical simulations show that these fluctuations produce not only electrostatic potential variation, but also, local changes in the carrier density and effective bandgap. For a CdSe x Te 1-x absorber doped with arsenic, simulations and cathodoluminescence data within single grains demonstrate how donor and acceptor densities—consistent with capacitance-voltage and secondary-ion mass-spectrometry data—produce tails in photoluminescence, quantum efficiency, and absorption measurements. Using multiple theoretical approaches, we demonstrate that the fluctuations can hinder expected performance gains from increased carrier density, and we describe the significant open-circuit voltage deficit observed in the CdSe x Te 1-x :As solar technology. Our results demonstrate that it is critical to characterize and reduce carrier compensation to realize a higher efficiency.

14 SOLAR ENERGY↗
NASA NTRS1983

Energetic particles in the vicinity of a possible neutral line in the plasma sheet

Combined plasma, magnetic field, and energetic particle data obtained from ISEE-1 in the geomagnetic tail during two successive energetic particle burst events are presented. The behavior of protons with energies of more than about 100 keV is very different from that of the 30-100 keV protons which represent the suprathermal tail of the plasma sheet distribution. The more energetic ions appear on a time scale of several minutes following a northward turning of the tail magnetic field. At about the same time the plasma measurements show a velocity of about 200 km/s in the tailward direction. From these results, it is argued that two successive magnetic neutral lines are created well within the plasma sheet and move close to the satellite position in the earthward direction. The extent of the neutral line is then limited to the dusk side of the tail.

Moebius, E.↗
NASA NTRS1989

A small-scale plasmoid formed during the May 13, 1985, AMPTE magnetotail barium release

Plasmoids are closed magnetic-loop structures with entrained hot plasma which are inferred to occur on large spatial scales in space plasma systems. A model is proposed here to explain the brightening and rapid tailward movement of the barium cloud released by the AMPTE IRM spacecraft on May 13, 1985. The model suggests that a small-scale plasmoid was formed due to a predicted development of heavy-ion-induced tearing in the thinned near-tail plasma sheet. Thus, a plasmoid may actually have been imaged due to the emissions of the entrained plasma ions within the plasma bubble.

Baker, D. N.↗
NASA NTRS2010

Observations of Metallic Species in Mercury's Exosphere

From observations of the metallic species sodium (Na), potassium (K), and magnesium (Mg) in Mercury's exosphere, we derive implications for source and loss processes. All metallic species observed exhibit a distribution and/or line width characteristic of high to extreme temperature - tens of thousands of degrees K. The temperatures of refractory species, including magnesium and calcium, indicate that the source process for the atoms observed in the tail and near-planet exosphere are consistent with ion sputtering and/or impact vaporization of a molecule with subsequent dissociation into the atomic form. The extended Mg tail is consistent with a surface abundance of 5-8% Mg by number, if 30% of impact-vaporized Mg remains as MgO and half of the impact vapor condenses. Globally, ion sputtering is not a major source of Mg, but locally the sputtered source can be larger than the impact vapor source. We conclude that the Na and K in Mercury's exosphere can be derived from a regolith composition similar to that of Luna 16 soil (or Apollo 17 orange glass), in which the abundance by number is 0.0027 (0.0028) for Na and 0.0006 (0.0045) for K.

Killen, Rosemary M.↗
NASA NTRS2000

Investigation of the Transport of Solar Ions Through the Earth's Magnetosphere

The objective of this study has been to infer, by statistical means, the most probable mode of entry of solar wind plasma into Earth's magnetotail, using a particular set of archived data from the Lockheed Plasma Composition Experiment on the International Sun-Earth Explorer One (ISEE-1) satellite, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) in the 1970's and 80's. Despite their considerable age, the Lockheed ISEE-1 data are still, at the time of this report, the only substantial ion composition data in the sub-keV to keV energy range available from the magnetotail beyond 9 R(sub E), because of various technical problems with ion mass spectrometers on later missions, and are therefore a unique source of information about the mixing of solar and terrestrial origin plasmas in the tail, within the ISEE-1 apogee of almost 23 R(sub E). The entire set of archived data used in this study, covering the 4.5 years of operation of the instrument and comprising not only tail measurements but also data from the inner magnetosphere as well as data from outside the magnetopause, is now available to the public via the WorldWideWeb at the address: http://cis.spasci.com/ISEE_ions The fundamental assumption of this and other studies of magnetosphere ion composition is that He++ and O+ ions are virtually certain "tags" of solar and terrestrial origins, respectively. This is an assumption with strong theoretical basis and it is corroborated by observational evidence, including the often substantial differences between the velocity distribution functions of those two species. The H+ ions can have a dual origin, in principle, but the close resemblance in the ISEE-1 data between the dynamics of H+ and He++ ions indicates a predominantly solar origin of the H+ ions in the tail, at least. By the same token, the usually minor He+ ions are probably almost entirely of terrestrial origin, because of their similarity to the O+ ions.

Lennartsson, O. W.↗
DOE OSTI2022

Ion Pairing and Molecular Orientation at Liquid/Liquid Interfaces: Self-Assembly and Function

We report that molecular orientation plays a pivotal role in defining the functionality and chemistry of interfaces, yet accurate measurements probing this important feature are few, due, in part, to technical and analytical limitations in extracting information from molecular monolayers. For example, buried liquid/liquid interfaces, where a complex and poorly understood balance of inter- and intramolecular interactions impart structural constraints that facilitate the formation of supramolecular assemblies capable of new functions, are difficult to probe experimentally. Here, we use vibrational sum-frequency generation spectroscopy, numerical polarization analysis, and atomistic molecular dynamics simulations to probe molecular orientations at buried oil/aqueous interfaces decorated with amphiphilic oligomers. We show that the orientation of self-assembled oligomers changes upon the addition of salts in the aqueous phase. The evolution of these structures can be described by competitive ion effects in the aqueous phase altering the orientations of the tails extending into the oil phase. These specific anionic effects occur via interfacial ion pairing and associated changes in interfacial solvation and hydrogen-bonding networks. These findings provide more quantitative insight into orientational changes encountered during self-assembly and pave the way for the design of functional interfaces for chemical separations, neuromorphic computing applications, and related biomimetic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Acceleration of Oxygen Ions in Dipolarization Events: 1. CPS Distributions

Abstract Using an MHD simulation of near tail reconnection associated with a flow burst and the collapse (dipolarization) of the inner tail in combination with test particle tracing we study the acceleration and flux increases of energetic oxygen ions (O + ). The characteristic orbits, distributions, and acceleration mechanisms are governed by the dimensionless parameter σ = ω ci t n , where ω ci is the ion gyro frequency and t n a characteristic Alfvén time of the MHD simulation. For σ < 1, central plasma sheet (CPS) populations after the passage of the dipolarization front are found to resemble half‐shells in velocity space oriented toward dusk. They originate from within the CPS and are energized typically by a single encounter of the region of enhanced cross‐tail electric field associated with the flow burst. For larger σ values ( σ > 1) the O + distributions resemble more closely those of protons, consisting of two counter‐streaming field‐aligned beams and an, albeit more tenuous and irregular, ring population perpendicular to the magnetic field. The existence of the beams, however, depends on suitable earthward moving source populations in the plasma sheet boundary layer or the adjacent lobes. The acceleration to higher energies is found to indicate a charge dependence, consistent with a dominance of more highly charged ions at energies of a few hundred keV. As in earlier simulations, the simulated fluxes show large anisotropies and nongyrotropic effects, phase bunching, and spatially and temporally localized beams.

Birn, J.↗
NASA NTRS1987

Processes associated with the plasma sheet boundary layer

The plasma sheet boundary is an important region of energy and mass transfer in the magnetotail. It is probably formed by energized ions ejected from the cross-tail current sheet. Processes associated with the boundary layer are important to many areas of magnetospheric physics. These areas include energetic particles, plasma sheet sources, auroral precipitation, field-aligned currents and discrete auroral arcs, and substorm initiation.

Lyons, L. R.↗
NASA NTRS1992

The ionosphere of Titan and its interaction with Saturnian magnetospheric electrons

The interaction of superthermal electrons, including both magnetospheric electrons and photoelectrons, with the upper atmosphere and ionosphere of Titan, is studied using a two stream electron transport code. Ionization rates, electron heating rates, and airglow emission rates are calculated. Results of a one dimensional model of the ionosphere of Titan, which includes both photoionization and ionization by magnetospheric electrons, are presented. Preliminary calculations of ionospheric ion outflow down the wake (or tail) of Titan, for time periods when the wake region is illuminated by the Sun, are made.

Cravens, Thomas E.↗