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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Ion Heating and Flow Driven by an Instability Found in Plasma Couette Flow

Here, we present the first observation of instability in weakly magnetized, pressure dominated plasma Couette flow firmly in the Hall regime. Strong Hall currents couple to a low frequency electromagnetic mode that is driven by high-β (>1) pressure profiles. Spectroscopic measurements show heating (factor of 3) of the cold, unmagnetized ions via a resonant Landau damping process. A linear theory of this instability is derived that predicts positive growth rates at finite β and shows the stabilizing effect of very large β, in line with observations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

Two-state ion heating at quasi-parallel shocks

This paper documents the alternating occurrence of two different ion states of the ion distributions downstream from several quasi-parallel shocks: a cooler (and denser) core/shoulder type and a hotter (less dense) and more Maxwellian type. Three separate lines of evidence are presented to show that the two states are not related in an evolutionary sense, but that both are produced alternately at the shock: (1) the asymptotic downstream plasma parameters (density, ion temperautre, and flow speed) are intermediate between those characterizing the two different states closer to the shock, suggesting that the asymptotic state is produced by a mixing of the two initial states; (2) examples of apparently interpenetrating distributions are found during transitions from one state to the other; and (3) examples of both types of distributions are found at actual crossings of the shock ramp.

Thomsen, M. F.↗
NASA NTRS2009

Oxygen Ion Heat Rate within Alfvenic Turbulence in the Cusp

The role that the cleft/cusp has in ionosphere-magnetosphere coupling makes it a dynamic and important region. It is directly exposed to the solar wind, making it possible for the entry of electromagnetic energy and precipitating electrons and ions from dayside reconnection and other dayside events. It is also a significant source of ionospheric plasma, contributing largely to the mass loading of the magnetosphere with large fluxes of outflowing ions. Crossing the cusp/cleft near 5100 km, the Polar instruments observe the common correlation of downward Poynting flux, ion energization, soft electron precipitation, broadband extremely low-frequency (BB-ELF) emissions, and density depletions. The dominant power in the BB-ELF emissions is now identified to be from spatially broad, low frequency Alfv nic structures. For a cusp crossing, we determine using the Electric Field Investigation (EFI), that the electric and magnetic field fluctuations are Alfv nic and the electric field gradients satisfy the inequality for stochastic acceleration. With all the Polar 1996 horizontal crossings of the cusp, we determine the O+ heating rate using the Thermal Ion Dynamics Experiment (TIDE) and Plasma Wave Investigation (PWI). We then compare this heating rate to other heating rates assuming the electric field gradient criteria exceeds the limit for stochastic acceleration for the remaining crossings. The comparison suggests that a stochastic acceleration mechanism is operational and the heating is controlled by the transverse spatial scale of the Alfvenic waves.

Coffey, Victoria N.↗
NASA NTRS1992

Anisotropic ion heating and parallel O(+) acceleration in regions of rapid E x B convection

A numerical solution to the 20-moment set of transport equations has been found in order to study subauroral ionospheric outflows during periods of enhanced perpendicular ion drifts. The numerical model solves the time-dependent O(+) density, momentum, and both the parallel and perpendicular energy and heat flow equations in the 200-6000 km altitude range. Assuming perpendicular drifts of 3 km/s relative to the neutral atmosphere, we have found that anisotropic heating of O(+) (a result of ion-neutral collisions) leads to a temperature anisotropy, with perpendicular temperatures exceeding 8000 K and parallel temperatures greater than 5000 K (near 200 km altitude). Above approximately 2000 km, transport processes dominate the effects of collisions and wavelike oscillations in O(+) velocity, temperature and heat flux were noted.

Korosmezey, A.↗
NASA NTRS1991

Convection of ion cyclotron waves to ion-heating regions

Results are presented on calculations of the convection, to lower altitudes, of low-frequency ion cyclotron waves generated in the central plasma sheet. In the calculations, ion cyclotron waves generated in the equatorial plane by a proton temperature anisotropy are considered, and the computed growth rates are used to create a model wave distribution. Spectral densities are then mapped along the magnetic field lines, using phase space methods of Ronnmark and Larsson (1988). It was found that, even in the absence of growth associated with a plasma instability, the electric fields of ion cyclotron emissions from the equatorial region will increase substantially as the waves propagate to higher latitudes. It is shown that ion cyclotron waves propagating down the field lines may contribute to the waves observed together with ion conics.

Ronnmark, Kjell↗
NASA NTRS1996

Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources

In an initial study, the He(+) observations from the Retarding Ion Mass Spectrometer on Dynamics Explorer 1 (RIMS/DE 1) was examined for more than 120 transits of the plasmasphere in the fall of 1981. The He(+) to H(+) ratio was determined as it varied spatially over portions of the DE 1 orbit, and its variation with solar and magnetic activities and with local time, focusing specifically on the inner plasmasphere. These variations were compared along the L = 2 field line with calculations made by the Field Line Interhemispheric Plasma (FLIP) code. In a recently submitted paper, the He(+) to H(+) density ratio was examined for all the available data from 1981 to 1984 from the RIMS on DE 1. There are two basic characteristics of the ratio: one is that the ratio decreases with radial distance in the plasmasphere, and the other is the strong dependence of the density ratio on solar activity. In addition to the He(+)/H(+) ratio research, a phenomenon has been studied in the topside ionosphere which relates to the thermal coupling of the ionosphere to the plasmasphere. There is little or no correlation with magnetic and solar activity here. Another study has been directed toward the relation of plasma properties to the density gradients forming the plasmapause. The study has followed a two-pronged approach. First, the observations have been analyzed to determine what happens to the plasma properties across these boundary layers (density gradients). Second, comparisons were made with FLIP model calculations to determine how well the model is able to treat these conditions. Among the significant lessons learned in these studies are two that bear directly on the direction of future investigations in this area. First, composition cannot be viewed independently of thermal structure. Second, solar and magnetic activity effects are real; but the causal relationship between activity and effects is frequently quite complicated because several different processes appear to be operating in different ways and on different time scales. Under these circumstances, large correlation coefficients should not be expected and are not generally found.

Comfort, Richard H.↗
NASA NTRS1974

Parametric study of ion heating in a burnout device (HIP-1)

Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses.

Sigman, D. R.↗
NASA NTRS1973

Ion heating in thermal plasma flows.

The general effects of thermal plasma flows on the thermal structure of the upper ionosphere and inner magnetosphere are discussed. In the light of presented results, it is shown that thermal ions in the outer regions of the plasmasphere and beyond may be substantially hotter than previously thought.

Banks, P. M.↗
DOE OSTI2021

Ion heating in the PISCES-RF liquid-cooled high-power, steady-state, helicon plasma device

Radio frequency (RF) driven helicon plasma sources are commonly used for their ability to produce high-density argon plasmas ( n > 10 19 m -3 ) at relatively moderate powers (typical RF power < 2 kW). Typical electron temperatures are <10 eV and typical ion temperatures are <0.6 eV. A newly designed helicon antenna assembly (with concentric, double-layered, fully liquid-cooled RF-transparent windows) operates in steady-state at RF powers up to 10 kW. We report on the dependence of argon plasma density, electron temperature and ion temperature on RF power. At 10 kW, ion temperatures >2 eV in argon plasmas are measured with laser induced fluorescence, which is consistent with a simple volume averaged 0D power balance model. 1D Monte Carlo simulations of the neutral density profile for these plasma conditions show strong neutral depletion near the core and predict neutral temperatures well above room temperatures. The plasmas created in this high-power helicon source (when light ions are employed) are ideally suited for fusion divertor plasma-material interaction studies and negative ion production for neutral beams.

Physics↗
NASA NTRS1982

Escape of heated ions upstream of quasi-parallel shocks

A simple theoretical criterion by which quasi-parallel and quasi-perpendicular collisionless shocks may be distinguished is proposed on the basis of an investigation of the free escape of ions from the post-shock plasma into the region upstream of a fast collisionless shock. It was determined that the accessibility of downstream ions to the upstream region depends on upstream magnetic field shock normal angle, in addition to the upstream plasma parameters, with post-shock ions escaping upstream for shock normal angles of less than 45 deg, in agreement with the observed transition between quasi-parallel and quasi-perpendicular shock structure. Upstream ion distribution functions resembling those of observed intermediate ions and beams are also calculated.

Edmiston, J. P.↗