Search NASA⌕ Search

SEARCH · Search NASA

Results for “charge exchange”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Solar wind/local interstellar medium interaction including charge exchange with neural hydrogen

We present results from a hydrodynamic model of the interaction of the solar wind with the local interstellar medium (LISM), self-consistently taking into account the effects of charge exchange between the plasma component and the interstellar neutrals. The simulation is fully time dependent, and is carried out in two or three dimensions, depending on whether the helio-latitudinal dependence of the solar wind speed and number density (both giving rise to three dimensional effects) are included. As a first approximation it is assumed that the neutral component of the flow can be described by a single, isotropic fluid. Clearly, this is not the actual situation, since charge exchange with the supersonic solar wind plasma in the region of the nose results in a 'second' neutral fluid propagating in the opposite direction as that of the LISM neutrals.

Pauls, H. Louis↗
NASA NTRS1981

Charge exchange in the Venus ionosphere as the source of the hot exospheric hydrogen

A global Monte Carlo model of the exosphere of Venus, simulating the normal exospheric processes, as well as the production of a 'hot' hydrogen component by charge exchange of H(+) with H and O, has been computed. The resulting altitude profiles of atomic hydrogen concentration over both the day and night hemispheres are in reasonable agreement with Mariner 5 and Mariner 10 observations of Lyman-alpha, showing that the ionospheric charge exchange reactions are a significant source of 'hot' hydrogen, possibly the dominant source. However, the uncertainties in the available atomic hydrogen data allow for production of a similar amount of nonthermal H by chemical processes involving H2 as suggested by Kumar and Hunten (1974).

Hodges, R. R., Jr.↗
NASA NTRS1984

O(+) charge exchange in the polar wind

O(+) density and flux profiles are calculated for a steady state polar wind flow of O(+) ions and electrons along geomagnetic field lines in the polar cap. Profiles are computed both with and without allowance for accidentally resonant charge exchange (ARCE) between O(+) and H. It is found that ARCE acts to reduce the limiting O(+) escape flux by less than 30 percent for typical atmospheric conditions and by only a factor of about 3.5 for atmospheres with low exospheric temperatures. Allowing for ARCE, the limiting O(+) escape flux is of the order of 5 x 10 to the 8th to 9th/cu cm/s, depending on the atmospheric conditions. This indicates that, contrary to previous predictions, there is no O(+) charge exchange barrier and it is therefore not necessary to have an acceleration mechanism at low altitudes in order to have an appreciable O(+) escape flux.

Barakat, A. R.↗
NASA NTRS1983

Charge exchange in solar wind-cometary interactions

A simple model of a cometary spherically symmetrical atmosphere and ionosphere is considered. An analytic solution of the governing equations describing the radial distribution of the neutral and ion densities is found. The new solution is compared to the well-known solution of the equations containing only ionization terms. Neglecting recombination causes a significant overestimate of the ion density in the vicinity of the comet. An axisymmetric model of the solar wind-cometary interaction is considered, taking into account the loss of solar wind ions due to charge exchange. The calculations predict that for active comets, solar wind absorption due to charge exchange becomes important at a few thousand kilometers from the nucleus, and a surface separating the shocked solar wind from the cometary ionosphere develops in this region. These calculations are in reasonable agreement with the few observations available for the ionopause location at comets.

Gombosi, T. I.↗
NASA NTRS1988

A comprehensive model of ion diffusion and charge exchange in the cold Io torus

A comprehensive analytic model of radial diffusion in the cold Io torus is developed. The model involves a generalized molecular cloud theory of SO2 and its dissociation fragments SO, O2, S, and O, which are formed at a relatively large rate by solar UV photodissociation of SO2. The key component of the new theory is SO, which can react with S(+) through a near-resonant charge exchange process that is exothermic. This provides a mechanism for the rapid depletion of singly ionized sulfur in the cold torus and can account for the large decrease in the total flux tube content inward of Io's orbit. The model is used to demonstrate quantitatively the effects of radial diffusion in a charge exchange environment that acts as a combined source and sink for ions in various charge states. A detailed quantitative explanation for the O(2+) component of the cold torus is given, and insight is derived into the workings of the so-called plasma 'ribbon'.

Barbosa, D. D.↗
NASA NTRS1981

The effect of the charge exchange source on the velocity and 'temperature' distributions and their anisotropies in the earth's exosphere

The velocity distribution of atomic hydrogen in the earth's exosphere is calculated as a function of altitude and direction taking into account both the classic exobase source and the higher-altitude plasmaspheric charge exchange source. Calculations are performed on the basis of a Monte Carlo technique in which random ballistic trajectories of individual atoms are traced through a three-dimensional grid of audit zones, at which relative concentrations and momentum or energy fluxes are obtained. In the case of the classical exobase source alone, the slope of the velocity distribution is constant only for the upward radial velocity component and increases dramatically with altitude for the incoming radial and transverse velocity components, resulting in a temperature decrease. The charge exchange source, which produces the satellite hydrogen component and the hot ballistic and escape components of the exosphere, is found to enhance the wings of the velocity distributions, however this effect is not sufficient to overcome the temperature decreases at altitudes above one earth radius. The resulting global model of the hydrogen exosphere may be used as a realistic basis for radiative transfer calculations.

Hodges, R. R., Jr.↗
NASA NTRS1980

Modulation of terrestrial ion escape flux composition /by low-altitude acceleration and charge exchange chemistry/

Motivated by recent observations of highly variable hot plasma composition in the magnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e(-), H(+), O(+) ionosphere. It is found that the fraction of the steady state escape flux which is O(+) can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O(+) tends to be rapidly converted by charge exchange to H(+). The acceleration is required both to overcome the gravitational confinement of O(+) and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O(+). Constraints are placed on the acceleration processes, and it is shown that O(+) escape is facilitated by observed ionospheric responses to magnetic activity.

Moore, T. E.↗
DOE OSTI2021

Measurement of Piplus - Argon Absorption and Charge Exchange Interactions Using Protodune-sp

ProtoDUNE-SP is a prototype detector for the upcoming Deep Underground Neutrino Experiment (DUNE). It is a Liquid Argon Time Projection Chamber (LArTPC) with a similar configuration to DUNE's detector, and is designed to provide a test-bed for the future experiment. In addition to serving as a prototype, its 0.3 - 7 GeV/ c charged particle beam line provided the ability to perform physics measurements of pions, protons, kaons, muons, and electrons. Importantly, the LArTPC allowed for the measurement of hadronic interactions on argon nuclei.Pions are often present in the final state of neutrino interactions in the energy range of DUNE's neutrino beam. These particles can undergo various types of interactions with argon nuclei in the detector, and this can interfere with the characterization of neutrino interactions in DUNE's far detector. The rate of these so-called secondary interactionswill be accounted for using Monte Carlo simulation of neutrino interactions. Measurements of secondary interaction rates provide necessary data which can be used to estimate and propagate uncertainties or provide tunes of the secondary interaction model used within DUNE's experimental simulation.This analysis provides a simultaneous measurement of the piplus - Ar absorption and charge exchange cross sections using 1 GeV/ c piplus data taken by ProtoDUNE-SP during its initial run period in Fall 2018. This is one of the first hadronic interaction measurements provided by ProtoDUNE-SP. It is also the first piplus - Ar absorption measurement in 20 years and the first ever piplus - Ar charge exchange measurement.Read

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2012

Solar Wind Charge Exchange During Geomagnetic Storms

On March 31st. 2001, a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 RE. The NASA/GSFC Community Coordinated Modeling Center (CCMe) employed a global magnetohydrodynamic (MHD) model to simulate the solar wind-magnetosphere interaction during the peak of this geomagnetic storm. Robertson et aL then modeled the expected 50ft X-ray emission due to solar wind charge exchange with geocoronal neutrals in the dayside cusp and magnetosheath. The locations of the bow shock, magnetopause and cusps were clearly evident in their simulations. Another geomagnetic storm took place on July 14, 2000 (Bastille Day). We again modeled X-ray emission due to solar wind charge exchange, but this time as observed from a moving spacecraft. This paper discusses the impact of spacecraft location on observed X-ray emission and the degree to which the locations of the bow shock and magnetopause can be detected in images.

Robertson, Ina P.↗
NASA NTRS1985

N(+)-N long-range interaction energies and resonance charge exchange

The aerothermodynamic studies of proposed space missions require atmospheric charge-transfer data. N2(+) eigenstate energies are calculated with use of the complete-active-space self-consistent-field method with an extended Gaussian basis set. The N(+)-N charge-exchange cross section, determined from these energies, agrees with merged-beam measurements. This contradicts the previous theoretical conclusion. A simple physical description of the long-range interaction is presented and should expedite future charge-transfer studies.

Stallcop, J. R.↗