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Results for “e + A collisions”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

High-latitude E Region Ionosphere-thermosphere Coupling: A Comparative Study Using in Situ and Incoherent Scatter Radar Observations

We present in situ and ground-based measurements of the ratio k of ion cyclotronangular frequency to ion-neutral momentum transfer collision frequency to investigateionosphere-thermosphere (IT) coupling in the auroral E region. In situ observations were obtained by NASA sounding rocket 36.234, which was launched into the nightsideE region ionosphere at 1229 UT on 19 January 2007 from Poker Flat, AK. The payload carried instrumentation to determine ion drift angle and electric field vectors. Neutral winds were measured by triangulating a chemical tracer released from rocket 41.064 launched two minutes later. k is calculated from the rotation of the ion drift angle relative to the E-cross-B drift direction in a frame co-rotating with the payload. Between the altitudes of 118 km and 130 km k increases exponentially with a scale height of 9.3 +/- 0.7 km, deviating from an exponential above 130 km. k = 1 at an altitude z(sub0) of 119.9 +/- 0.5 km. The ratio was also estimated from Poker Flat Incoherent Scatter Radar (PFISR) measurements using the rotation of ion velocity with altitude. Exponential fits to the PFISR measurements made during the flight of 41.064 yield z(sub0) 115.9 +/- 1.2 km and a scale height of 9.1 +/- 1.0 km. Differences between in situ and ground-based measurements show that the E region atmospheric densities were structured vertically and/or horizontally on scales of 1 km to 10 km. There were no signs of ionospheric structure in ion density or ion temperature below scales of 1 km. The observations demonstrate the accuracy with which the in situ and PFISR data may be used as probes of IT coupling.

Burchill, J. K.↗
NASA NTRS1983

A theoretical study on the mechanism of electronic to vibrational energy transfer in Hg/3P/ + CO

The mechanism of electronic-to-vibrational (E-V) energy transfer in Hg(3P) + CO collisions has been studied theoretically. The configuration interaction (CI) method was employed to calculate potential energy surfaces of the collision system. A simplified theoretical model, based on the reaction coordinate concept and the calculated potential energy characteristics, was used to discuss the mechanism of the singlet-triplet transition and the energy disposal in the collision. The results obtained were that: (a) the quenching process processed via a collision complex mechanism; and that (b) the triplet-singlet transition occurs near the collinear geometry. A model classical trajectory calculation gives a product CO vibrational distribution in good agreement with the experimental result.

Kato, S.↗
NASA NTRS2018

CA Risk Assessment Approaches

Current single-Pc approach work well when subtended by appropriate hypothesis-testing framework. Reframing construct in terms of miss distance distribution would confer certain advantages such as reducing to same import as Pc, but still convey some additional information. Methods to incorporate known uncertainties in covariances and HBR should be pursued that can also be framed in terms of miss distance distribution. We present Plausibilistic II and Possibilistic constructs, to determine their adequacy and viable recommendation.

Conjunction↗
NASA NTRS1985

A Simulation of High Latitude F-Layer Instabilities in the Presence of Magnetosphere-Ionosphere Coupling

A magnetic-field-line-integrated model of plasma interchange instabilities is developed for the high latitude ionosphere including magnetospheric coupling effects. We show that primary magnetosphere-ionosphere coupling effect is to incorporate the inertia of the magnetospheric plasma in the analysis. As a specific example, we present the first simulation of the E x B instability in the inertial regime, i.e., nu sub i omega where nu sub i is the ion-neutral collision frequency and omega is the wave frequency. We find that the inertial E x B instability develops in a fundamentally different manner than in the collisional case ni sub i omega. Our results show that striations produced in the inertial regime are spread and retarded by ion inertial effects, and result in more isotropic irregularities than those seen in the collisional case.

Mitchell, H. G., Jr.↗
NASA NTRS1984

SU(2) x U(1) vacuum and the Centauro events

It is proposed that the fireballs invoked to explain the Centauro events are bubbles of a metastable superdense state of nuclear matter, created in high energy (E is approximately 10 to the 15th power eV) cosmic ray collisions at the top of the atmosphere. If these bubbles are created with a Lorentz factor gamma approximately = 10 at their CM frame, the objections against the origin of these events in cosmic ray interactions are overcome. Assuming further, that the Centauro events are to the explosive decay of these metastable bubbles, a relationship between their lifetime, tau, and the threshold energy for bubble formation, E sub th, is derived. The minimum lifetime consistent with such an interpretation in tau is approximately 10 to the -8th power sec, while the E sub th appears to be insensitive to the value of tau and always close to E sub th is approximately 10 to the 15th power eV. Finally it is speculated that if the available CM energy is thermalized in such collisions, these bubbles might be manifestations of excitations of the SU(2) x U(1) false vacuum. The absence of neutral pions in the Centauro events is then explained by the decay of these excitations.

Kazanas, D.↗
NASA NTRS1994

Energetic electrons in the magnetophere of Saturn

The energy spectra and angular distributions of electrons observed by Pioneer 11 as a function of radial distance in the inner magnetosphere of Saturn are reanalyzed and phase space densities are then calculated. The radial dependence of phase space density requires a distributed loss process. The loss is greatest in the region of the E ring (5.5 less than L less than 8.5) and is attributed to collisions with the ring particles in agreement with earlier work by Van Allen et al. (1980b). Quantitative analysis yields the following properties of the E ring: the particle radii are in the range of 4 x 10(exp -5) to 3.2 x 10(exp -4) cm and the thickness of the ring is approximately 3 R(sub s). Between the inner edge of the E ring (5.5 R(sub s)) and the outer edge of the A ring (2.3 R(sub s)) there are more energetic electrons than can be supplied by radial diffusion from an external source. Detailed calculations show that a cosmic ray albedo neutron decay (CRAND) source in the A and B rings is a plausible source for this excess. The radial diffusion coefficient required to explain the E ring absorption and CRAND source for electrons is 1 x 10(exp -12) greater than D(sub 0) greater than 3 x 10(exp -12) R(sub s)(exp 2)/s, assuming that D(sub LL) = D(sub 0)L(exp 3). As part of the reanalysis program, a method for the deconvolution of pitch angle distributions observed by simple detectors on a rotating spacecraft is developed. This process removes the instrumental response and rotational smear due to finite sampling periods and yields true angular distributions.

Randall, B. A.↗
NASA NTRS1994

Energetic electrons in the magnetosphere of Saturn

The energy spectra and angular distributions of electrons observed by Pioneer 11 as a function of radial distance in the inner magnetosphere of Saturn are reanalyzed and phase space densities are then calculated. The radial dependence of phase space density requires a distributed loss process. The loss is greatest in the region of the E ring (5.5 less than L less than 8.5) and is attributed to collisions with the ring particles in agreement with earlier work by Van Allen et al. (1980). Quantitative analysis yields the following properties of the E ring: the particle radii are in the range of 4 x 10(exp -5) to 3.2 x 10(exp -4) cm and the thickness of the ring is approximately 3 R(sub s). Between the inner edge of the E ring (5.5 R(sub s)) and the outer edge of the A ring (2.3 R(sub s)) there are more energetic electrons than can be supplied by radial diffusion from an external source. Detailed calculations show that a cosmic ray albedo neutron decay (CRAND) source in the A and B rings is a plausible source for this excess. The radial diffusion coefficient required to explain the E ring absorption and CRAND source for electrons is 1 x 10(exp -12) greater than D(sub 0) greater than 3 x 10(exp -12) R(exp 2, sub s)/s, assuming that D(sub LL) = D(sub 0)L(exp 3). As part of the reanalysis program, a method for the deconvolution of pitch angle distributions observed by simple detectors on a rotating spacecraft is developed. This process removes the instrumental response and rotational smear due to finite sampling periods and yields true angular distributions.

Randall, B. A.↗
NASA NTRS1966

The Martian surface.

Martian surface markings, brightness along optical equator, crater erosion, asteroid collision and yellow dust clouds

MARS SURFACE↗