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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Nitric acid and ammonia emissions from a mid-latitude prescribed wetlands fire

The first simultaneous measurements of gaseous nitric acid and ammonia in the smoke plume of a wetlands biomass burn were obtained. The measurements were made using tungsten oxide-coated diffusion denuder tubes from a helicopter during a prescribed burn on November 9, 1987, at the Merritt Island National Wildlife Refuge, located at the NASA John F. Kennedy Space Center, Florida. The mean NH3 and HNO3 mixing ratios measured in the smoke plume were 19 ppbv and 14 ppbv, respectively, both significantly higher than background mixing ratios. Nitric acid correlated well with carbon dioxide produced by the combustion. The mean CO2-normalized emission ratio for HNO3 was found to be 0.00012. Ammonia, however, dit not correlate well with CO2, suggesting a more complex relationship between combustion and production/release of NH3.

Lebel, P. J.↗
NASA NTRS1988

Effect of mid-altitude ion heating on ion outflow at polar latitudes

The effect of ion heating on polar ion outflow, when either the parallel or perpendicular (or both) ion temperatures at the exobase are elevated above values typical for the ionosphere, was investigated using a modified semikinetic steady-state model of Barakat and Schunk (1983) that allowed for anisotropic ion heating at the exobase and eliminated lower boundary potential jumps. In addition, the relative impact of the ion heating vs electron heating on the oxygen escape fluxes was investigated by examining the flux of O(+) ions for various combinations of electron and ion temperatures. It is demonstrated that the O(+) escape flux can be increased, to levels as high as were obtained by Barakat and Schunk (1983) with the electron temperatures of 10,000 K, by raising, instead, the ion temperatures (but to values considerably less than the 100,000 K observed by Moore et al., 1986).

Li, Peng↗
NASA NTRS1988

Interior characteristics at mid-levels of thunderstorms in the southeastern United States

Data characterizing the vertical wind structure and hydrometeors within cumulonimbus clouds in the southeastern United States were collected by the armored T-28 aircraft during the 1986 Cooperative Huntsville Meteorological Experiment (COHMEX). Data analysis concentrated on the hydrometeor character and development, as well as the general microphysical and kinematic structure of the clouds penetrated. The high reflectivities which sometimes exceeded the usual 55 dBz limit set for the T-28, are not necessarily related to hail in the COHMEX storms. Instead, large numbers of millimeter-size particles were found, while the hail infrequently encountered was generally small. The fact that the larger hydrometeors were usually found in narrow and weak updrafts that appeared to be well mixed suggests that a coalescence mechanism was active in many of the storms. The depth of warm cloud (typically about 3.5 km) present in these storms apparently allows ample time for particles to reach the observed millimeter sizes. The presence of cloud droplets in the largest sizes measured supports this mechanism. Ice processes play a role in the precipitation, but hail was unable to grow very large in these storms probably because the high concentrations of observed growth centers suggest a natural beneficial competition process.

Musil, Dennis J.↗
NASA NTRS1988

Observations of neutral circulation at mid-latitudes during the Equinox Transition Study

Measurements of ion drift velocity made by the Millstone Hill incoherent scatter radar have been used to calculate the meridional neutral wind velocity during the Sept. 17 to 24, 1984 period. Strong daytime southward neutral surges were observed during the magnetically disturbed days of September 19 and 23, in contrast to the small daytime winds obtained as expected during the magnetically quiet days. The surge on September 19 was also seen at Arecibo. In addition, two approaches have been used to calculate the meridional wind component from the radar-derived height of the F-layer electron density peak. Results confirm the wind surge, particularly when the strong electric fields measured during the disturbed days are included in the calculations. The two approaches for the F-layer peak wind calculations are applied to the radar-derived electron density peak height as a function of latitude to study the variation of the southward daytime surges with latitude.

Buonsanto, M. J.↗
NASA NTRS1988

Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone - A case study

Evidence of transverse ion energization at altitudes of several earth radii in the auroral zone was reexamined using several hundred hours of high-sensitivity and high-resolution plasma data obtained by the Dynamics Explorer 1 satellite. The data on particle environment encountered at midaltitudes in the auroral zone disclosed rapid variations in the values of total density, thermal structure, and composition of the plasma in the interval measured; the modes of low-frequency plasma waves also varied rapidly. It was not possible to unambiguously identify in these data particle and wave signature of local transverse ion energization; however, many intervals were found where local transverse ion heating was consistent with the observations.

Peterson, W. K.↗
NASA NTRS1988

In situ northern mid-latitude observations of ClO, O3, and BrO in the wintertime lower stratosphere

In order to test photochemical theories linking chlorofluorocarbon derivatives to O3 depletion at high latitudes in the springtime, several related atmospheric species, including O3, ClO, and BrO were measured in the lower stratosphere. The flight path extended to the center of the polar jet associated with but outside of the Arctic vortex, in which the abundance of O3 was twice its midlatitude value, whereas BrO levels were five parts per trillion (pptv) by volume between 18 and 21 km, and 2.4 pptv below that altitude. The ClO mixing ratio was as much as 65 pptv at 60 N latitude at an altitude of 20 km, and was enhanced over midlatitude values by a factor of three to five at altitudes above 18 km and by as much as a factor of 40 at altitudes below 17 km. Levels of ClO and O3 were highly correlated on all measured distance scales, and both showed an abrupt change in character at 54 N latitude. The ClO abundance north of 54 N was probably caused by low NO2 levels in the flight path.

Brune, W. H.↗
NASA NTRS1988

The effect of mid-latitude electron precipitation on the geoelectric field

A simple model is outlined to describe electron precipitation from the population of charged particles trapped in the earth's magnetic field; almost all of the precipitation is shown to occur in the region of the South Atlantic Anomaly. When the effect of a dawn-to-dusk electric field across the magnetosphere is included in the model, a diurnal modulation of the precipitated electron flux is predicted. Experimental evidence which supports the diurnal modulation model is described.

Sheldon, W. R.↗
NASA NTRS1989

An improved rocket ozonesonde (Rocoz-A). III - Northern mid-latitude ozone measurements from 1983 to 1985

The results of the ozone measurements taken during rocket-busted flights of the rocket ozonesonde Rocoz-A at the NASA Wallops Flight Facility from August 1983 to September 1985 are presented. Nineteen profiles were obtained using Rocoz-A and electrochemical concentration cell ozonesondes, standard U.S. meteorological radiosondes, and Super-Loki datasondes. The results were found to agree with the Krueger and Minzner (1976) midlatitude ozone model for the 1976 U.S. Standard Atmosphere.

Barnes, Robert A.↗
NASA NTRS1988

Plasma waves associated with diffuse auroral electrons at mid-altitudes

Using simultaneous observations from the DE-1 High-Altitude Plasma Instrument and the Plasma Wave Instrument, a study is made of 28 auroral-zone crossings, equally divided among dayside and nightside cases covering a range of Kp values from 1- to 8. In the diffuse auroral region, electrostatic emissions of frequencies up to a few kHz are associated with low-energy field-aligned electron beams. Of 18 cases (11 nightside; 7 dayside) examined at high resolution in the particle data, 15 (9 nightside; 6 dayside) exhibited field-aligned beams with electrostatic waves. In most cases, the beams were upward-directed, but occasionally they traveled both up and down the field line. The electrostatic emissions are interpreted as electron-acoustic waves excited by the field-aligned beams.

Sharber, J. R.↗
NASA NTRS1989

Evidence of the mid-latitude impact of Antarctic ozone depletion

Record low ozone values found over Australia and New Zealand during December 1987 following the record low Antarctic values of October 1987 are analyzed. The sudden decline of ozone amounts in midmonth rule out photochemical effects as a cause and permit the underlying processes to be investigated on a case study basis. Using data from ozone sondes, radiosondes, the Nimbus-7 total ozone mapping spectrometer, and meteorological analyses from the National Meteorological Center, it is argued that these low values resulted from transport of ozone-poor air from higher latitudes. Thus, it seems that the chemical destruction of ozone over Antarctica in early spring is having an impact on lower latitudes.

Atkinson, Roger J.↗
NASA NTRS1990

A mid-latitude balloon-borne observation of total odd nitrogen

A balloon-borne instrument to measure total odd nitrogen NO(y) has been developed. A converter which enables catalytic conversion of NO(y) into nitric oxide on a heated gold surface is combined with a chemiluminescence detector. The conversion efficiency for NO2 was measured to be close to 100 percent at pressures between 60 and 7 mb. The major source of errors in the balloon-borne measurements are the uncertainties in the estimates of the sample flow rate and the zero level of the instrument. The NO(y) concentration was measured at altitudes between 12 and 28 km with a precision of about 25 percent on a balloon experiment conducted at latitude 44 deg N in June 1989. The NO(y) concentration has been measured to be 1.5 + or - 0.4, 3 + or - 0.7, 10 + or - 3, and 14 + or - 4 ppbv at altitudes of 17, 20, 25, and 28 km, respectively.

Kondo, Y.↗
NASA NTRS1990

Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

Fejer, B. G.↗
NASA NTRS1988

Statistical detection of the mid-Pleistocene transition

Statistical methods have been used to show quantitatively that the transition in mean and variance observed in delta O-18 records during the middle of the Pleistocene was abrupt. By applying these methods to all of the available records spanning the entire Pleistocene, it appears that this jump was global and primarily represents an increase in ice mass. At roughly the same time an abrupt decrease in sea surface temperature also occurred, indicative of sudden global cooling. This kind of evidence suggests a possible bifurcation of the climate system that must be accounted for in a complete explanation of the ice ages. Theoretical models including internal dynamics are capable of exhibiting this kind of rapid transition.

Maasch, K. A.↗
NASA NTRS1990

Longitudinal variation of mid-latitude hiss from six long duration balloon flights

The longitudinal variation of midlatitude hiss as measured on six balloons at latitudes of 35-55 deg S, shows a significant minimum at 70-80 deg E, about 1000 km east of the geomagnetic conjugate of the Soviet transmitter UMS (17.1 kHz). It is suggested that the well documented pitch-angle diffusion induced by the UMS signal removes the ability of the trapped electrons to maintain the amplification of the hiss to at least the reflection and reducting losses (about 20 dB) at the ends of the echoing ducted path. The eastward shift of the minimum from the conjugate of UMS is primarily caused by the time taken by the eastward-drifting electrons to recover this ability, though the effect is enhanced by the east-west asymmetry in the propagation of hiss under the ionosphere.

Dowden, R. L.↗
NASA NTRS1991

Lateral variation in upper mantle temperature and composition beneath mid-ocean ridges inferred from shear-wave propagation, geoid, and bathymetry

Resolution of both the extent and mechanism of lateral heterogeneity in the upper mantle constraints the nature and scales of mantle convection. Oceanic regions are of particular interest as they are likely to provide the closest glimpse at the patterns of temperature anomalies and convective flow in the upper mantle because of their young age and simple crustal structure relative to continental regions. Lateral variations were determined in the seismic velocity and attenuation structure of the lithosphere and astenosphere beneath the oceans, and these seismological observations were combined with the data and theory of geoid and bathymetry anomalies in order to test and improve current models for seafloor spreading and mantle convection. Variations were determined in mantle properties on a scale of about 1000 km, comparable to the thickness of the upper mantle. Seismic velocity, geoid, and bathymetry anomalies are all sensitive to variations in upper mantle density, and inversions were formulated to combine quantitatively these different data and to search for a common origin. Variations in mantle density can be either of thermal or compositional origin and are related to mantle convection or differentiation.

Sheehan, Anne Francis↗
NASA NTRS1991

Air mass origins and troposphere-to-stratosphere exchange associated with mid-latitude cyclogenesis and tropopause folding inferred from Be-7 measurements

The 1984 extratropical mission of NASA's Stratosphere-Troposphere Exchange Project (STEP) studied cross-jet transport in regions of cyclogenesis and tropopause folding. Correlations of Be-7, ozone, water vapor, and potential vorticity measured on a NASA U-2 research aircraft flying in high shear regions above the jet core are indicative of mixing between the cyclonic and the anticyclonic sides of the jet and are consistent with the hypothesis that small-scale entrainments of upper tropospheric air into the lower stratosphere during cyclogenesis are important in maintaining the vertical gradients of Be-7, ozone, water vapor and other trace constituents in the lower few kilometers of the midlatitude stratosphere. Correlations between Be-7, and ozone suggest a lower tropical stratospheric origin for the ozone-poor lamina observed above the jet core.

Kritz, Mark A.↗