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At least 1,459 records · Page 81
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NASA NTRS1982

Hot wind from Gamma/2/ Velorum observed in the ultraviolet carbon lines

The close binary system Gamma(2) Vel, consisting of a WC8 and an O9 I star, has been observed in the ultraviolet at various phases. Preliminary analysis of selected data shows that the temperature of the stellar wind from this binary increases outward. This suggests that an additional source of energy other than radiation pressure may exist for the wind. The mass flow occurs in all directions from the binary. However, there is evidence of an increase in the mass flow through the third Lagrangian point, although from the extant data it is not possible to decide whether or not a similar increase in the mass outflow occurs through the second Lagrangian point. There is also evidence of mass surge, which probably is independent of orbital phase.

Kondo, Y.↗
NASA NTRS1982

A new look at the ionosphere of Jupiter in light of the UVS occultation results

Neutral model atmospheres derived from the Voyager UV Spectrometer's solar and stellar occultation data are used to calculate Jupiter ionospheric electron density profiles, demonstrating the inadequacy of such methods. It is also shown that electron densities calculated by means of standard parameters are larger than those measured by both Pioneer and Voyager. McElroy's (1973) suggestion as to the importance of H2 vibrational excitation is investigated, and it is found that no single vibrational temperature is appropriate for the entire thermosphere. The long recombination time constants involved in the plasma's movement, due to either meridional winds or electric fields, through large vertical distances, is shown to account for the observed electron density profiles. It is suggested that the outflow, and possibly the inflow, of plasma may play a role in the definition of electron density profiles.

Mcconnell, J. C.↗
NASA NTRS1982

Axisymmetric inviscid swirling flows produced by bellmouth and centerbody

The effect of large deformation in the flow between the bellmouth and centerbody is considered analytically for application to studies of vortex breakdown in a pipe. Basic equations are defined for axisymmetric inviscid swirling flows at the inflow and outflow sections. Axial and circumferential velocity component profiles are presented, and comparisons are made with trials involving vane angles of 42 deg and Re of 2300. Axial components of the prediction matched well in the inner half of the pipe radius and not well with the outer, while circumferential predictions were good only at the axis. A lack of viscosity was concluded to result in the inaccuracies near the wall.

Nakamura, Y.↗
NASA NTRS1982

Line profiles of T Tauri stars - Clues to the nature of the mass flow

A set of high resolution observations of the H-alpha Na D, He I 5876 A, and H-gamma lines in several T Tauri stars is presented. Repeated observations of some of these objects yield some indication of the importance of time-dependent effects. The line profiles should be useful for detailed radiative transfer modeling. A cursory survey of the profiles suggests that 'turbulent' velocities in some cases may not be negligible in comparison with the bulk flow speeds and that many emission lines, such as Na D, may be formed in a narrow layer near the stellar photosphere. It is suggested that the effects of geometrical occulation of narrow line-emitting regions in general outflow can account for some of the peculiarities of the line profiles. However, some aspects of the line profiles, such as the large-scale, highly variable redshifted Na D absorption in RW Aur, clearly require more complicated motions.

Hartmann, L.↗
NASA NTRS1982

The channels of Mars

Early observations of Mars conducted by means of telescopes are considered. Secchi introduced the Italian word 'canale' ('channel') in 1869 to describe apparent lines on the planet's surface. Between 1877 and 1888 Schiaparelli mapped a profusion of 'canali'. Schiaparelli's work led to famous controversies about Mars. This book attempts to investigate the puzzle posed by the Martian channels, taking into account also the results of the studies conducted with the aid of the two orbiting Viking spacecraft which have produced a total number of nearly 60,000 pictures. The channel types are discussed along with questions regarding the distribution, the ages, and the proposed origins of the channels. Attention is given to the geomorphology of Mars, the patterns and networks of Martian valleys, ice and the Martian surface, the outflow channels, catastrophic flood processes, questions of analogy between terrestrial and Martian geographic features, and Martian phenomena associated with water liquid or water ice.

Baker, V. R.↗
NASA NTRS1981

Hot relativistic winds and the Crab Nebula

Efforts to formulate a self-consistent model of pulsar magnetospheres which links the particle source near the pulsar to the outflowing relativistic wind and couples the wind to the surrounding nebula are reviewed. The use of a relativistic MHD wind is recommended to account for global photon emission and the invisibility of the method of plasma transport. Consideration of a magnetic monopole relativistic wind due to an axially symmetric aligned rotator is combined with calculations of the initial velocity of the wind to show that the flow velocity in such a model will never exceed Mach 1. Extending the solution to the case of a hot relativistic wind at supersonic speeds is noted to yield results consistent with observations of the Crab Nebula

Fujimura, F. S.↗
NASA NTRS1981

Mass loss from cool stars

Recently obtained spectroscopic observations indicating mass loss in cool stars are reviewed with analogies to the solar atmosphere. Spectral diagnostics of mass loss are discussed with new theoretical calculations of chromospheric line profiles. A general picture of mass loss from cool stars is developed and related to chromospheric and coronal emissions measured by IUE and the HEAO-2 Observatory. These winds range in characteristics from the hot (10 to the 6th K) and fast wind with low mass loss found in the dwarf stars to the warm (approximately 10 to the 5th K), moderate speed winds present in hybrid luminous supergiants, and the coolest massive winds emerging from the latest type supergiants exhibiting lowest thermal velocities and circumstellar shells. Evidence for stellar surface inhomogeneity and variability of outflow is briefly discussed.

Dupree, A. K.↗
NASA NTRS1981

Mass loss from interacting close binary systems

The three well-defined classes of evolved binary systems that show evidence of present and/or past mass loss are the cataclysmic variables, the Algols, and Wolf-Rayet stars. It is thought that the transformation of supergiant binary systems into the very short-period cataclysmic variables must have been a complex process. The new evidence that has recently been obtained from the far ultraviolet spectra that a certain subclass of the Algols (the Serpentids) are undergoing fairly rapid evolution is discussed. It is thought probable that the remarkable mass outflow observed in them is connected with a strong wind powered by accretion. The origin of the circumbinary clouds or flat disks that probably surround many strongly interacting binaries is not clear. Attention is also given to binary systems with hot white dwarf or subdwarf components, such as the symbiotic objects and the BQ stars; it is noted that in them both components may be prone to an enhanced stellar wind.

Plavec, M. J.↗
NASA NTRS1982

Ultraviolet spectroscopy of the nova-like variable V3885 Sagittarii /= CD -42 deg 14462/

Low-dispersion long and short wavelength IUE spectra of the nova-like system V3885 Sgr were obtained on 1979 August 24 UT. The UV spectrum exhibits strong, high-temperature absorption lines of C III, C IV, He II, N IV, N V, and Si IV which all have relatively large negative velocities of 600-1000 km/s at their line centers. The C IV (1550 A) features shows a P Cygni-type profile with a blueshifted absorption line; the presence of the P Cygni-type feature strongly suggests a significant mass outflow from the system in the form of a hot stellar wind. The observed continuum fluxes are fitted with theoretical accretion disk model fluxes, and a tentative physical interpretation of the observed spectral properties is presented.

Guinan, E. F.↗
NASA NTRS1982

Non-radial flow near the cometary surface

It is shown that, as a consequence of the non-uniform temperature distribution of the cometary nucleus, large lateral pressure gradients are set up, which in turn drive strong lateral flows. However, at small heliocentric distances the onset of turbulence within a thin boundary layer destroys these steady lateral flows and the eventual outflow of gas from within the outer boundary of this layer is expected to be more or less radial. On the other hand, at large heliocentric distances, turbulence is unlikely to set in, and the lateral flows that are set up, may persist. Consequently, it is expected that the gas flow out of the cometary nucleus at these large distances to be highly non-radial.

Marconi, M. L.↗
NASA NTRS1982

The life cycle of thunderstorm gust fronts as viewed with Doppler radar and rawinsonde data

This paper presents the time-dependent analysis of the thunderstorm gust front with the use of Project NIMROD data. RHI cross sections of reflectivity and Doppler velocity are constructed to determine the entire vertical structure. The life cycle of the gust front is divided into four stages: (1) the formative stage; (2) the early mature stage; (3) the late mature stage; and (4) the dissipation stage. A new finding is a horizontal roll detected in the reflectivity pattern resulting from airflow that is deflected upward by the ground, while carrying some of the smaller precipitation ahead of the main echo core of the squall line. This feature is called a 'precipitation roll'. As determined from rawinsonde data, the cold air behind the gust front accounts for the observed surface pressure rise. Calculations confirm that the collision of two fluids produce a nonhydrostatic pressure at the leading edge of the outflow. The equation governing the propagation speed of a density current accurately predicts the movement of the gust front.

Wakimoto, R. M.↗
NASA NTRS1982

First evidence for a Europa plasma torus

The evidence from the Pioneer 10 plasma analyzer that plasma derived from Europa was present in the Jovian magnetosphere in December 1973 is summarized. Plasma detected between 1900 UT and 2100 UT on December 3, 1973, reveals a number of significant phenomena near the expected position of Europa's L shell. Mass addition to the magnetospheric plasma is indicated by a local increase in density apparently superimposed on the density gradient of Iogenic plasma. This increase in plasma density is unlike any phenomenon observed when the spacecraft is near a lunar L shell. The density shows fluctuations that make possible an estimate of the net outflow speed of magnetospheric ions per Jovian rotation. A radial flow speed in 1973 of 0.37 km/s from the Pioneer data is made, together with an estimate of 1 km/s in 1979 from Voyager 2 data, thus indicating a significant change.

Intriligator, D. S.↗
NASA NTRS1982

Hot mantles, moderate photospheres for Wolf-Rayet stars

The amount of continuous energy from Wolf-Rayet stars and the shape of the continuous spectrum from the ultraviolet to the near infrared correspond to effective temperatures in the range 25,000 to 30,000 K. The value of log g is of the order of 4.0 + or - 0.5. Thus the photospheres of Wolf-Rayet stars correspond to those of moderately hot stars. The line spectra of Wolf-Rayet stars, however, indicate that electron temperatures greater than 30,000 K occur in the outer atmospheres or mantles of these stars. Here outflow is important.

Underhill, A. B.↗
NASA NTRS1982

Voluntary sodium intake during effort in hot environments

The factors that influence the amount of salt that a person adds to his food at mealtime, and the part played by the general requirement for salt in the daily diet stemming from the coluntary input of salt are studied. Careful measurements of salt intake and outflow were performed on ten marchers in a high temperature environment who were given individual salt shakers that were weighed before and after each meal. Some marchers were told to add salt to their meals on specific days. No parallelity was found between the voluntary sodium intake and the general sodium intake, the excretion of sodium in the urine or the environmental heat stress. Individual food habit was found to be the most important factor.

Sohar, E.↗
NASA NTRS1982

Detection of interstellar NH sub 3 in the far-warm and dense gas in Orion-KL

The detection of the (J,K) = a(4,3) yields s(3,3) rotation inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region is reported. The line is in emission and has a FWHM or = to 30 km s 0.15. The far IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3) yields s(3,3) line is very optically thick, and since it is seen in emission, radiative excitation of the (4,3) NH3 level by far IR emission from dust within the source can be ruled out. Radiative excitation via the 10 microns of vibrational transitions of NH3 also seems unlikely. Hence, the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Since the far IR line emission is highly trapped, densities of approximately 10 to the 7th power cu cm are high enough to explain the observations. Shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.↗
NASA NTRS1981

Momentum and energy balance in late-type stellar winds

Observations at ultraviolet and X-ray wavelengths indicate that the classical picture of a static stellar atmosphere containing a radiative equilibrium temperature distribution is inapplicable to the majority of late type stars. Mass loss and the presence of atmospheric regions characterized by gas temperatures in excess of the stellar effective temperature appear to be almost ubiquitous throughout the HR diagram. Evidence pertaining to the thermal and dynamical structure of the outer envelopes of cool stars is summarized. These results are compared with the predictions of several theoretical models which were proposed to account for mass loss from latetype stars. Models in which the outflow is thermally radiatively, or wave driven are considered for identification of the physical processes responsible for the observed wind properties. The observed variation of both the wind, thermal and dynamical structure as one proceeds from the supergiant branch toward the main sequence in the cool portion of the HR diagram give consideration to potential mechanisms for heating and cooling the flow from low gravity stars.

Macgregor, K. B.↗
NASA NTRS1981

The 1980 rocket coronagraph measurements of the solar wind acceleration region

Spectroscopic measurements of temperatures, densities and flow velocities in the solar wind acceleration region provide critical empirical constraints on solar stellar wind theory. Preliminary results of an analysis of H I Lyman-alpha and white light measurements made on 16 February 1980 in a polar coronal region are reported. The hydrogen kinetic temperatures in the observed region were found to be nearly constant with T sub HI approximately equals 10 degrees K at heliocentric distances between 1.5 and 4 solar radii. The outflow velocities were found to be subsonic indicating that the critical point in the observed region was located at r approximately greater than 4 solar radii.

Withbroe, G. L.↗
NASA NTRS1983

The inference of tropical cyclone dynamics using GOES VISSR/VAS data

The sequence of events observed during tropical cyclone Emily, was suggested as a possible mechanism for cyclogenesis. Geostationary Operational Environmental Satellite (GOES) East VISSR/VAS sensors were used. The VISSR visible imagery obtained every 15 minutes was used to define the low tropospheric cyclonic vortex and upper tropospheric horizontal convergence. The VAS water vapor (channels 9 and 10) and carbon dioxide (channels 3 and 4) channels were used to infer upper and middle tropospheric subsidence by monitoring the Adiabatic compressional drying and warming, respectively, occurring within this layer. Evidence of an existing lower tropospheric cyclonic vortex was seen. The satellite derived wind vectors (length of vector is proportional to wind velocity, where the strongest winds were approximately 35 knots) are superimposed on the GOES visible image of tropical storm Emily. Vectors and low level clouds depict the center of the cyclonic vortex immediately south of the large convective cell in the center of the image. Upper tropospheric cloud tracers and rawinsonde reports along the Eastern United States suggest that the southwesterly environmental upper atmospheric flow is converging with the outflow from the convective cell north of the vortex.

Rodgers, E. B.↗