SEARCH · Search NASA

Results for “dynamical process”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Development of algorithms for using satellite meteorological data sets to study global transport of stratospheric aerosols and ozone

The utilization of stratospheric aerosol and ozone measurements obtained from the NASA developed SAM II and SAGE satellite instruments were investigated for their global scale transports. The stratospheric aerosols showed that during the stratospheric warming of the winter 1978 to 1979, the distribution of the zonal mean aerosol extinction ratio in the northern high latitude exhibited distinct changes. Dynamic processes might have played an important role in maintenance role in maintenance of this zonal mean distribution. As to the stratospheric ozone, large poleward ozone transports are shown to occur in the altitude region from 24 km to 38 km near 55N during this warming. This altitude region is shown to be a transition region of the phase relationship between ozone and temperature waves from an in-phase one above 38 km. It is shown that the ozone solar heating in the upper stratosphere might lead to enhancement of the damping rate of the planetary waves due to infrared radiation alone in agreement with theoretical analyses and an earlier observational study.

Want, P. H.↗

NASA NTRS1985

Ephemeral regions versus pseudo ephemeral regions

New studies of the quiet Sun reveal that ephemeral active regions constitute minority rather than a majority of all the short lived, small scale bipolar features on the Sun. In contrast to the recognized patterns of growth and decay of ephemeral regions, various examples of the creation of other temporary bipoles nicknamed pseudo ephemeral regions are illustrated. The pseudo ephemeral regions are the consequence of combinations of small scale dynamic processes of the quiet Sun including: (1) fragmentation of network magnetic fields, (2) the separation of opposite polarity halves of ephemeral regions as they grow and evolve, and (3) the coalescence of weak network or intranetwork magnetic fields. New observations offer the possibility of resolving the discrepancies that have arisen in the association of ephemeral regions with X-ray bright points. Many X-ray bright points may be related to those pseudo ephemeral regions which have begun to exhibit magnetic flux loss.

Martin, S. F.↗

NASA NTRS1984

Analysis of stress-strain relationships in silicon ribbon

An analysis of stress-strain relationships in silicon ribbon is presented. A model to present entire process, dynamical Transit Analysis is developed. It is found that knowledge of past-strain history is significant in modeling activities.

Dillon, O. W., Jr.↗

NASA NTRS1985

Late-stage planetesimals: How big?

Numerical simulation of the early stages of planet growth show that a few bodies nearly 1000 km in diameter may have formed within approx. 100,000 yr after solid material grew into km scale planetesimals by gravitational instability. Even after such large bodies formed, the bulk of the mass of the future terrestrial planet zone resided in small bodies. Subsequent evolution is difficult to model because it requires simultaneous consideration of continuum (multitudinous small bodies) and discrete (a few large bodies) evolution. Some relevant issues include definition of accretional feeding zones, evaluation of the range of gravitational influence, viscous transport and diffusion, orbital commensurabilities, role of gas, etc. The first large bodies may have been (1) the embryos of the final planets, which grew by accreting tiny planetesimals, or (2) merely the first of many 1000+ km bodies, which grew independently and later collided to form the planets. Models of late stage accretion that assume all bodies to be initially nearly Moon sized provide insight into relevant collisional and dynamical processes. The chief point in this research is that the correct size distribution during the later stages of planet growth remains unknown.

Greenberg, R.↗

NASA NTRS1984

Supermassive monopole stars

In this paper, the evolution of a superheavy monopole-dominated universe is reexamined; in particular, the evolution of rotation-stabilized monopole-burning 'stars', balancing effects of radiation and annihilation are examined. In contrast to earlier results, it is found that this can lead to complete burning of all poles present in such an object within finite time. If monopoles can be brought within acceptable limits by dynamical processes, an inflationary epoch of the early universe need not be associated with grand unification.

Fry, J. N.↗

NASA NTRS1984

The global distribution and variability of stratospheric constituents measured by LIMS

The purpose of the Nimbus 7 LIMS experiment was to sound the composition and structure of the upper atmosphere and provide data for study of photochemistry, radiation, and dynamics processes. Vertical profiles were measured of temperature and ozone (O3) over the 10-km to 65-km range and water vapor, nitrogen dioxide, and nitric acid over the 10-km to 50-km range. Latitude coverage extended from 64 deg S to 84 deg N. Several general features of the atmosphere have emerged from data analyzes thus far. Nitrogen dioxide exhibits rapid latitudinal variations in winter and shows hemispheric asymmetry with generally higher vertical column amount in the summer hemisphere. HNO3 data show that this gas is highly variable with altitude, latitude, and season. Smallest mixing ratios occur in the tropics, and the largest values occur in the high latitude winter hemisphere. The results show that O3, NO2, and HNO3 are strongly affected during a stratospheric warming.

Russell, J. M., III↗

NASA NTRS1983

Dual Doppler lidar measurements of winds in the JAWS experiment

Differences are noted in the operations of Doppler lidar and radar for the case of a thunderstorm outflow observed during the Joint Airport Weather Studies project field experiments. Calculated wind fields agreed with surface wind observations made routinely by the Portable Automated Mesonet stations. The lidar data are found to complement Doppler radar observations; while the latter is superior for the measurement of wind fields within convective storms, the former is more useful in examinations of dynamical processes in regions outside storm.

Rothermel, J.↗

NASA NTRS1985

The charge-energy-mass spectrometer for 0.3-300 keV/e ions on the AMPTE CCE

The charge-energy-mass (CHEM) spectrometer on the Charge Composition Explorer (CCE) has the function to measure the energy spectra, pitch-angle distributions, and ionization states of ions in the earth's magnetosphere and magnetosheath in the energy range from 0.3 to 300 keV/charge with a time resolution of less than 1 min. The obtained data will provide essential information on outstanding problems related to ion sources and dynamical processes of space plasmas and of suprathermal ions. A description of the CHEM experiment is given, taking into account the principle of operation, the sensor, the electronics, instrument characteristics, specifications, and requirements. Questions of postlaunch performance are also discussed.

Gloeckler, G.↗

NASA NTRS1984

The origin and evolution of planetary rings

Roche (1847) suggested that Saturn's rings may be the fragments of a disrupted satellite rather than the uncoagulated remnant of a circumplanetary disk from which the regular satellites formed. In order to address this unresolved central issue, attention is given to the dynamical processes of viscous spreading, gas drag, particulate coagulation, and the effect of further matter infall from heliocentric orbit onto the planet/disk, all of which act on a gas/solid disk in Keplerian motion. In view of these considerations, it is suggested that rings were created by the disruption of large satellites which were less sensitive to the destructive processes present during the planet's formation. This hypothesis explains the presence of shepherd satellites, such as large collision fragments, which coexist in the same orbital range as the ring particles.

Harris, A. W.↗

NASA NTRS1985

Venus nightside ionospheric troughs - Implications for evidence of lightning and volcanism

The inferred presence of lightning has been a potentially very important result from the in situ exploration of the environment of Venus by the Pioneer Venus Orbiter (PVO). The evidence for lightning has been derived from impulsive low-frequency plasma wave events recorded by the Orbiter electric field detector. The present paper is concerned with an alternative interpretation of the plasma results. It is shown that prominent examples of the plasma waves which have previously been specifically attributed to lightning are associated with distinct nightside ionization troughs. It is suspected that many of the plasma wave disturbances are not due to lightning but rather result from energetic and dynamic processes to be expected in the vicinity of the magnetic field and plasma configurations involved.

Taylor, H. A., Jr.↗

NASA NTRS1985

Use of observational and model-derived fields and regime model output statistics in mesoscale forecasting

Various empirical and statistical weather-forecasting studies which utilize stratification by weather regime are described. Objective classification was used to determine weather regime in some studies. In other cases the weather pattern was determined on the basis of a parameter representing the physical and dynamical processes relevant to the anticipated mesoscale phenomena, such as low level moisture convergence and convective precipitation, or the Froude number and the occurrence of cold-air damming. For mesoscale phenomena already in existence, new forecasting techniques were developed. The use of cloud models in operational forecasting is discussed. Models to calculate the spatial scales of forcings and resultant response for mesoscale systems are presented. The use of these models to represent the climatologically most prevalent systems, and to perform case-by-case simulations is reviewed. Operational implementation of mesoscale data into weather forecasts, using both actual simulation output and method-output statistics is discussed.

Forbes, G. S.↗

NASA NTRS1986

The Sun at high spatial resolution: The physics of small spatial structures in a magnetized medium

An attempt is made to provide a perspective on the problem of spatial structuring on scales smaller than can presently be directly and regularly observed from the ground or with which current space-based instrumentation can be anticipated. There is abundant evidence from both observations and theory that such spatial structuring of the solar outer atmosphere is ubiquitous not only on the observed scales, but also on spatial scales down to (at least) the subarcsecond range. This is not to say that the results to be obtained from observations on these small scales can be anticipated: quite the opposite. What is clear instead is that many of the classic problems of coronal and chromospheric activity - involving the basic dissipative nature of magnetized plasmas - will be seen from a novel perspective at these scales, and that there are reasons for believing that dynamical processes of importance to activity on presently-resolved scales will themselves begin to be resolved on the sub-arcsecond level. Since the Sun is the only astrophysical laboratory for which there is any hope of studying these processes in any detail, this observatioinal opportunity is an exciting prospect for any student of magnetic activity in astrophysics.

Rosner, R. T.↗

NASA NTRS1985

The evolution of Ertel's potential vorticity during stratospheric sudden warmings

In the winter stratosphere of the Northern Hemisphere, the disruption of the westerly vortex and associated warming of polar latitudes is a well known phenomenon. It has become apparent that some important dynamical processes in the stratosphere are highly nonlinear and are best thought of locally rather than in terms of the interaction between the zonal-mean flow and harmonic waves around latitude circles. The importance of nonlinear processes was suggested by McIntyre and Palmer (1983, 1984) who used isentropic maps of Ertel's Potential Vorticity to show that during disturbed episodes material lines may become strongly and irreversibly deformed in certain places. They adopted the term planetary wave breaking to describe this process. Isentropic maps of Q are used to follow the evolution of a Canadian warming in November - December 1981 and a particularly strong warming in January 1982. The advection of Q over large distances on isentropic surfaces was a striking feature of the flow during each event. This could be identified because of our ability to follow the movement of material lines due to the approximate conservation of Q over several days. The advection of Q was a nonlinear process because its changing distribution affected the advecting wind field. The Canadian warming did not lead to a permanent change in the structure of the westerly vortex, as defined by the coarse-grain field of Q, whereas the January event was accompanied by a substantial loss of resolved Q which was never fully recovered.

Fairlie, T. D. A.↗

NASA NTRS1985

Satellite observations of 557.7 NM airglow as a diagnostic technique to study the dynamics of the lower thermosphere

Photometric observations of the airglow limb at 557.7 nm have been made from the ISIS 2 satellite since 1971. From an analysis of 32,000 airglow limb observations obtained during the first two years of operation, the major temporal and spatial characteristics of the night airglow have been identified. Maxima occur in mid-October and mid-April at all latitudes. There is a marked variation with latitude during the equinox periods, with peak intensities near 35 degrees in autumn and near 25 degrees in spring. It is possible to gain considerable insight into the behavior of the lower thermosphere by combining the airglow observations with a simple model of the photochemical and dynamical processes. In this way a pattern of the latitude and temporal variation of atomic oxygen concentration at the peak of the layer as well as the eddy diffusion in this altitude region have been inferred. The concentration of atomic oxygen shows midlatitude peaks near equinox, and minima about one month after solstice. Average values at midlatitudes are about 1.3 times those at the equator. The amplitude of the semiannual component is about 20% of the mean value at 35 degrees as compared to 10% at the equator, and the amplitude of 12-month component is about 12% at 35 deg and 5% at the equator. The semiannual component has a minimum that occurs approximately 3 weeks (plus or minus) after solstice at all latitudes, while the 12-month component peaks in the summer hemisphere at solstice (plus or minus 2 months).

Cogger, L. L.↗

NASA NTRS1985

Measurements of CCl3F, CCl2F2, CCl4, N2O and SF6 in the Northern Hemisphere stratosphere

An overview of the Department of Energy's High Altitude Sampling Program and some recent trace gas measurement results are presented. Analysis of whole air samples, collected in pressurized bottles, provides information on stratospheric inventories and distributions for CCl3F, CCl2F2, CCl4, N2O and SF6 in the Northern Hemisphere. Based on a linear regression analysis of the data the estimated mean Northern Hemisphere stratospheric concentration of each gas increased as follows: CCl3F changed from 54 to 142 p1/1 (4/74-11/83); CCl2F2 changed from 133 to 268 p1/1 (4/76-11/83); SF6 changed from 160 to 480 f1/1 (4/74-11/83); CC1, changed from 58 to 91 p1/1 (4/75-11/83); N2O changed from 246 to 261 n1/1 (4/76-11/83). The calculated mean Northern Hemisphere stratospheric concentrations of N2O, CCl3F, CCl2F2, and CCl4 after 1980 show larger than expected fluctuations with time. Recent volcanic activity may be a partial cause for these fluctuations through induced changes in stratospheric dynamical processes.

Leifer, R.↗

NASA NTRS1985

A special ozone observation at Syowa Station, Antarctica from February 1982 to January 1983

The behavior of stratospheric ozone at high latitudes is especially interesting, since the stratospheric ozone at high latitudes is thought to be transported from low latitudes through dynamical processes. However, only limited information has so far been obtained, because ozone observations at high latitudes are sparse. There are only two ozone observation stations operating in Antarctica: Syowa Station and Amundsen-Scott, where the total ozone has been observed in sunlit months only. To make up for this deficiency, extensive observations were carried out at Syowa Station as part of MAP. Some preliminary results of these observations are described.

Chubachi, S.↗

NASA NTRS1984

The effect of physical parameterizations and initial data on the numerical prediction of the President's Day cyclone

Results are presented from a series of forecast experiments which were conducted to assess the importance of large-scale dynamical processes, diabatic heating, and initial data to the prediction of the President's Day cyclone. The synoptic situation and NMC model forecasts for this case are summarized, and the analysis/forecast system and experiments are described. The GLAS Model forecast from the GLAS analysis at 0000 GMT 18 February is found to have correctly predicted intense coastal cyclogenesis and heavy precipitation. A forecast with surface heat and moisture fluxes eliminated failed to predict any cyclogenesis while a similar forecast with only the surface moisture flux excluded showed weak development. Diabatic heating resulting from oceanic fluxes significantly contributed to the generation of low-level cyclonic vorticity and the intensification and slow rate of movement of an upper level ridge over the western Atlantic.

Atlas, R.↗

NASA NTRS1986

Solar wind proton temperature-velocity relationship

Helios 1 data are analyzed to find an experimental fit for the temperature-velocity relationship at 1 AU. It is shown that the proton temperature-velocity changes at a velocity of approximately 500 km/s. Interplanetary dynamic processes, i.e., stream interactions, are shown to affect the temperature-velocity relationships less than 22 percent; the functional form of these relationships appears to be preserved throughout the solar cycle. It is pointed out that any comprehensive model of the solar wind will have to address the difference in the temperature-velocity relationship between the low- and high-speed wind, since this is a product of the acceleration and subsequent heating process generating the solar wind.

Lopez, R. E.↗