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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Measurement of the Li/B abundance ratio above 650 MeV/nucleon

A balloon-borne cosmic-ray telescope containing 4 Cerenkov counters and a neon flash tube hodoscope was flown from Sioux City, Iowa in September 1974. The data have been reanalyzed, using information of flashed tubes to reject events due to proton and He interactions. The new event selection has reduced charge overlap between He and Li to an insignificant level, so that abundance ratios involving Li can now be measured with the instrument. Precise correction factors for events lost by inefficiency of the hodoscope have been derived from flight data; they lead to improved accuracy in measurements of light elements.

Byrnak, B.↗
NASA NTRS1979

Persistent emission from X-ray burst sources and the nature of galactic bulge X-ray sources

Intrinsic persistent emission from galactic bulge X-ray sources and the ratio of the average persistent X-ray luminosity to the time-averaged burst luminosity associated with Type I burst sources are discussed in the light of the thermonuclear flash model of X-ray burst emission. Values of the ratio between average persistent luminosity and time-averaged burst luminosity for a large collection of SAS 3 sources are presented to confirm the predictions of the burst model of thermonuclear flashes in freshly accreted matter on a neutron star. The model also predicts a critical value of the persistent accretion rate, below which bursts can occur. It is suggested that the galactic bulge X-ray sources represent neutron stars undergoing accretion, with burst sources accounting for a subset in which the accretion rate is below the critical value.

Van Paradijs, J.↗
NASA NTRS1979

First results on Jovian lightning

Longitudes and latitudes of 20 Jovian lightning flashes are plotted on the basis of observations of the dark side of Jupiter by an unidentified spacecraft. It is suggested that the mechanisms of lightning generation on Jupiter and earth may be similar, that convective electrification is the most plausible mechanism, and that observations of lightning may be used as a tracer of upwelling in the Jovian circulation. The observation of lightning flashes at high latitudes is shown to be consistent with the concept of convective cloud systems generated by internal heating.

Cook, A. F., II↗
NASA NTRS1980

Rate constant for the reaction of hydroxyl radical with formaldehyde over the temperature range 228-362 K

Absolute rate constants for the reaction OH ? H2CO measured over the temperature range 228-362 K using the flash photolysis-resonance fluorescence technique are given. The results are independent of variations in H2CO concentration, total pressure Ar concentration, and flash intensity (i.e., initial OH concentration). The rate constant is found to be invariant with temperature in this range, the best representation being k sub 1 = (1.05 ? or - 0.11) x 10 to the 11th power cu cm molecule(-1) s(-1) where the error is two standard deviations. This result is compared with previous absolute and relative determinations of k sub 1. The reaction is also discussed from a theoretical point of view.

Stief, L. J.↗
NASA NTRS1980

Rate statistics for radio noise from lightning

Radio frequency noise from lightning was measured at several frequencies in the HF - VHF range at the Kennedy Space Center, Florida. The data were examined to determine flashing rate statistics during periods of strong activity from nearby storms. It was found that the time between flashes is modeled reasonably well by a random variable with a lognormal distribution.

Levine, D. M.↗
NASA NTRS1979

Photochemistry of bromoacetylene - Formation of HBr and quenching of excited Br/4 2P 0 1/2/

The photolysis of bromacetylene is examined by means of vacuum ultraviolet flash photolysis-kinetic spectroscopy, with attention given to the production of Br atoms in the 2P 0 3/2 and 2P 0 1/2 states, the production of HBr, and UV absorption attributable to the ethynyl radical. Although Br(2P 0 1/2) and Br(2P 0 3/2) were both directly observed at the shortest delay time after the flash, strongly indicating the presence of the ethynyl radical, transient absorption by C2H was not detected in the range 125 to 180 nm. Quenching rate constants for the decay of the 2P 0 1/2 state of Br, which is observed to form concurrently with the ground state, are derived for quenching by He, CH2Br, CF4, and D2 from the pseudo-first-order decay rates. HBr was observed as a secondary photolysis product, and a model of its formation by the exothermic reaction of ground-state atoms with C2HBR, coupled with the secondary production of Br atoms, is found to agree well with the experiment.

Laufer, A. H.↗
NASA NTRS1979

Pressure and temperature dependence kinetics study of the NO + BrO yielding NO2 + Br reaction - Implications for stratospheric bromine photochemistry

The reactivity of NO with BrO radicals over a wide range of pressure (100-700 torr) and temperature (224-398 K) is investigated using the flash photolysis-ultraviolet absorption technique. The flash photolysis system consists of a high-pressure xenon arc light source, a reaction cell/gas filter/flash lamp combination, and a 216.5 half-meter monochromator/polychromator/spectrography for wavelength selectivity. The details of the reaction and its corresponding Arrhenius expression are identified. The results are compared with previous measurements, and atmospheric implications of the reaction are discussed. The NO + BrO yielding NO2 + Br reaction is shown to be important in controlling the concentration ratios of BrO/Br and BrO/HBr in the stratosphere, but this reaction does not affect the catalytic efficiency of BrOx in ozone destruction.

Watson, R. T.↗
NASA NTRS1980

Three flares with blue continuum, one with a D3 preflare shell

Three flares with short-lived flashes observed with a 65 A wide filter centered on 3835 A are discussed. Observations at other wavelengths indicated it is a 'blue continuum'; the flashes occur in pairs at the ends of flux loops and result from the precipitation of energetic particles. A shell of D3 absorption was observed in one of the flares, considered to be a compressed sheet of dense, hot material that limits the flare until it breaks out as a surge. It is concluded that the blue continuum may be the same as that seen in flare stars.

Zirin, H.↗
NASA NTRS1980

Rate constant for the reaction of hydroxyl radical with formaldehyde over the temperature range 228-362 K

Absolute rate constants for the reaction OH + H2CO have been measured over the temperature range 228-362 K using the flash photolysis-resonance fluorescence technique. The results were independent of variations in forbidden H2CO, total pressure of forbidden Ar and flash intensity (i.e., initial forbidden OH). The rate constant was found to be invariant with temperature in this range, the best representation being k1 = (1.05 + or - 0.11) x 10 to the -11th cu cm/molecule sec where the error is two standard deviations. This result is compared with previous absolute and relative determinations of k1. The reaction is also discussed from a theoretical point of view.

Stief, L. J.↗
NASA NTRS1981

Turbulence in deep radio occultations

The effects of turbulence in the focal region of spherical or weakly oblate refracting bodies on the evolute flashes associated with the crossing of the evolute of the planetary limb by an occulted spacecraft are investigated. The approximate theory of focal evolutes in oblate refractivity fields developed by Eshleman et al. (1979) is combined with a generalized weak scattering scintillation theory that includes the effect of focusing around a curved limb to obtain expressions for the scintillation index and power spectrum. Results are then applied to the radio observations of the crossing of the focal evolute of Jupiter by Voyager 1, in which no flash was detected, and to the effects of the solar coronal plasma on the gravitational lens of the sun.

Haugstad, B. S.↗
NASA NTRS1980

The spectrum of radiation from lightning

A theory is presented for the spectrum of radiation from lightning applicable in the range LF to VHF. This is done by adopting the hypothesis that all events in the flash (e.g., return strokes, K-changes, etc.) can be modelled in terms of a current pulse propagating along a tortuous channel. Using a Fraunhofer approximation for radiation in the far field, a formula for the electric field radiated from an arbitrary event is obtained, and then this result is summed over all events to obtain an expression for the spectrum of the composite flash. The result predicts a spectral decrease as the inverse of frequency (1/v) in agreement with data.

Le Vine, D. M.↗
NASA NTRS1982

Lightning to the ionosphere

It is pointed out that most lightning discharges take place within clouds or between clouds and the ground. There are a few reports, however, of a much rarer form of lightning that has been observed to come out of the top of the thunderstorm cloud and extend vertically for some distance into the clear air above it. A description is presented of the observations of such an incident made by a NASA pilot. The incident occurred when the pilot was flying a T-38 jet aircraft at an altitude of about 40,000 feet over Amarillo in Texas. The pilot found himself behind an extremely fast-moving very large cold front. A large number of lightning flashes could be seen. While most of the lightning flashes were typical, approximately every 50th or 100th discharge would go from the top of a cloud vertically upwards through the clear air towards the ionosphere. Explanations for these observations are discussed.

Vaughan, O. H., Jr.↗
NASA NTRS1982

Lightning attachment patterns and flight conditions for storm hazards, 1980

As part of the NASA Langley Research Center Storm Hazards Program, 69 thunderstorm pentrations were made in 1980 with an F-106B airplane in order to record direct strike lightning data and the associated flight conditions. Ground based weather radar measurements in conjunction with these penetrations were made by NOAA National Severe Storms Laboratory in Oklahoma and by NASA Wallops Flight Center in Virginia. In 1980, the airplane received 10 direct lightning strikes; in addition, lightning transient data were recorded from 6 nearby flashes. Following each flight, the airplane was thoroughly inspected for evidence of lightning attachment, and the individual lightning attachment points were plotted on isometric projections of the airplane to identify swept flash patterns. This report presents pilot descriptions of the direct strikes to the airplane, shows the strike attachment patterns that were found, and discusses the implications of the patterns with respect to aircraft protection design. The flight conditions are also included. Finally, the lightning strike scenarios for three U.S. Air Force F-106A airplanes which were struck during routine operations are given in the appendix to this paper.

Fisher, B. D.↗
NASA NTRS1981

A combined visible and IR technique for the estimation of rainfall amounts from GOES data

The use of visible and infrared techniques for estimating precipitation for flash flood, hydrological, and agricultural applications is discussed. Satellite derived rainfall estimates supplement other data or are the only data available. The Scofield/Oliver convective rainfall technique is used for analyzing a half hour period of heavy rainfall during a Chicago flash flood event. The results of a real time hydrological application of the Scofield/Oliver technique for the Hurricane Allen event are also presented. Visible and IR techniques for agricultural applications are also discussed.

Austin, G. L.↗
NASA NTRS1982

Lightning and surface rainfall during Florida thunderstorms

Lightning and surface rainfall data are presented which were obtained during summer air mass thunderstorms at the NASA Kennedy Space Center. Attention is given to a computer algorithm which employed abrupt changes in the thundercloud electric fields to detect and count flashes. Statistics are given for the occurrence of lightning in 79 storms during the summer seasons of 1976-1980, as well as 28 lightning storms from the summers of 1977 and 1978. The relationship between lightning and rainfall is examined in the case of two thunderstorms whose locations allow a direct comparison of measurements. It is found that when meteorological conditions favor the production of lightning, there is an almost direct proportionality between the total rain volume and the total number of flashes.

Piepgrass, M. V.↗
NASA NTRS1982

Comparison of Venusian lightning observations

Spacecraft observations of Venusian lightning are reviewed to determine the energy dissipation rate. Optical sensors provide data on the total energy dissipated per flash, so long as the contributions of atomic oxygen and ionized carbon are accounted for. Radio probes yield information on the total lightning occurrences. Venera 9-12 radio surveys are reviewed, and event rates of 20-30/sec for Venera 11 are mentioned. Venera 9 observed a sole, 70 sec event period on the Venusian nightside. Comparisons are made between the recorded electromagnetic energy levels and terrestrial lightning data. The nightside occurrence rate is calculated to be 0.08 strokes/sq km per year, while the dayside exhibits 85 flashes/sq km per sec. Energy dissipation rates ranging from 0.0012-0.25 W/sq m are calculated for various flash durations. It is suggested that the lightning occurs in the clouds as part of an organized meteorological system.

Borucki, W. J.↗
NASA NTRS1984

Interpretation of STS-3/plasma diagnostics package results in terms of large space structure plasma interactions

The Plasma Diagnostics Package, which was flown aboard STS-3 recorded various chemical releases from the Orbiter. Changes in the plasma environment were observed to occur during Flash Evaporator System (FES) releases, water dumps and maneuvering thruster operations. During flash evaporator operations, broadband Orbiter-generated electro-static noise is enhanced and plasma density irregularity (delta n/N) is observed to increase by as much as 4 times and is strongly peaked below 6 Hz. In the case of water dumps, background electrostatic noise is enhanced or suppressed depending on frequency and Delta N/N is also seen to increase by as much as 4 times. Various changes in the plasma environment are effected by primary and vernier thruster operations. In addition, thruster activity stimulates electrostatic noise with a spectrum which is most intense at frequencies below 10 kHz.

Kurth, W. S.↗
NASA NTRS1983

Effects of chemical releases by the STS-3 Orbiter on the ionosphere

The Plasma Diagnostics Package, flown aboard STS-3 as part of the first Shuttle payload (OSS-1), recorded the effects of various chemical releases from the Orbiter. Changes in the plasma environment was observed during flash evaporator system releases, water dumps and maneuvering thruster operations. During flash evaporator operations, broadband Orbiter-generated electrostatic noise was enhanced and plasma density irregularities were observed to increase by 3 to 30 times with a spectrum which rose steeply and peaked below 6 Hz. In the case of water dumps, background electrostatic noise was enhanced at frequencies below about 3 kHz and suppressed at frequencies above 2 kHz. Thruster activity also stimulated electrostatic noise with a spectrum which peaked at approximately 0.5 kHz. In addition, ions with energies up to 1 keV were seen during some thruster events.

Pickett, J. S.↗