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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A dynamical model of the ejection of planetary nebulae

In order to study the ejection of planetary nebulae, the present work considers a star evolving up the red giant branch a second time. The star has a carbon oxygen core surrounded by a helium-burning shell source, a helium shell, and a hydrogen-rich shell. The mathematical model consists of a He shell and a hydrogen-rich shell overlying a hard core. It is concluded that the pulsation of long-period variables and the ejection of planetary nebulae are due to the same physical process: namely, radiation momentum and energy transfer to the gas. Furthermore, planetary nebulae ejection appears to be preceded by long-period variability.

Sparks, W. M.↗
NASA NTRS1974

Studies of hydrodynamic events in stellar evolution. III Ejection of planetary nebulae

Investigation of the dynamic behavior of the hydrogen-rich envelope (0.101 solar mass) of an evolved star (1.1 solar mass) as the luminosity rises to 19,000 solar luminosities during the second ascent of the red-giant branch. For luminosities in the range 3100 less than L less than 19,000 solar luminosities the H-rich envelope pulsates like a long-period variable (LPV) with periods of the order of a year. As L reaches 19,000 solar luminosities, the entire H-rich envelope is ejected as a shell with speeds of a few times 10 km sec. The ejection occurs on a time scale of a few LPV pulsation periods. This ejection is shown to be related to the formation of a planetary nebula. The computations are based on an implicit hydrodynamic computer code. Tand rho-dependent opacities and excitation and ionization energies are included. As the H-rich envelope is accelerated off the stellar core, the gap between envelope and core is approximated by a vacuum filled with radiation.

Kutter, G. S.↗
NASA NTRS1975

The sources of material comprising a mass ejection coronal transient

The origin of the material ejected during a white-light coronal transient on August 26 and 27, 1973, is investigated using simultaneous observations of a slowly ascending prominence and the more rapid accompanying coronal transient. Nearly identical simultaneous images of the prominence were obtained over a six-hour period in the H-alpha and He II (304 A) emission lines; contemporaneous Skylab coronograph observations over approximately 1.5 hours showed that the mass-ejection coronal transient rose above the ascending prominence. Based on analysis of these observations, it is concluded that: (1) the bulk of the ejected material originated in the lower corona, despite the lack of an observed depletion there; (2) the material in the transient was at coronal temperature and was visible in polarized radiation due to Thomson scattering of photospheric light by free electrons; and (3) the total event was far larger, more energetic, and longer lasting than would have been inferred from the prominence observations alone.

Hildner, E.↗
NASA NTRS1977

Cold air performance of a 12.766-centimeter-tip-diameter axial-flow cooled turbine. 2: Effect of air ejection on turbine performance

An air cooled version of a single-stage, axial-flow turbine was investigated to determine aerodynamic performance with and without air ejection from the stator and rotor blades surfaces to simulate the effect of cooling air discharge. Air ejection rate was varied from 0 to 10 percent of turbine mass flow for both the stator and the rotor. A primary-to-air ejection temperature ratio of about 1 was maintained.

Haas, J. E.↗
NASA NTRS1977

Coronal mass-ejections-kinematics of the 19 December 1973 event

A detailed description of the observed kinematics of the coronal disturbance of December 19, 1973, is presented along with inferences about the temperatures, densities, magnetic fields, and electric currents within the event. This disturbance consisted of the eruption of a previously quiescent prominence, an associated ejection of coronal material, and the destruction of a large coronal streamer. Observations of the prominence and the corona with a scanning spectroheliometer and a white-light coronagraph aboard Skylab before, during, and after the prominence eruption are discussed, and the temperature and density in the eruptive prominence are traced as the prominence rose to a height of 3 solar radii over 7 hr. The results obtained are shown to reinforce previous arguments that the material comprising the bulk of the mass ejected from the corona in transient events arises from the low corona rather than from the eruptive prominence, which may accompany the coronal mass ejection.

Schmahl, E.↗
NASA NTRS1978

Prompt solar proton events and coronal mass ejections

Data from the HAO white-light coronagraph and the X-ray telescope on Skylab have been used to investigate the coronal manifestations of 18 prompt solar proton events observed on the IMP 7 spacecraft during the Skylab period. Evidence is found that a mass-ejection event is a necessary condition for the occurrence of a prompt proton event. Mass-ejection events can be observed directly in the white-light coronagraph when they occur near the limb and inferred from the presence of a long-decay X-ray event when they occur on the disk. It is suggested that: (1) the occurrence of mass-ejection events facilitates the escape of protons - whether accelerated at low or high altitudes - to the interplanetary medium; and (2) there may exist a proton acceleration region above or around the outward moving ejecta far above the flare site.

Kahler, S. W.↗
NASA NTRS1981

Sputter ejection of matter from Io

Direct collisional interaction of magnetospheric particles, particularly 520-eV S ions, with Io, cause sputter removal of matter. It is estimated that direct sputtering of a full-disk S-containing atmosphere with an exobase at a few hundred km, can provide up to 5 x 10 to the tenth S atoms per sq cm-s. Supplies of S and O required to stabilize the torus are estimated to be from 10 to the 10th to 10 to the 12th per sq cm-s. Sputtering rates are calculated for an atmosphere containing a one percent concentration of Na and K, and are found to be large enough to supply the fluxes required to maintain the Na and K clouds. Sputtering is found to remove heavy molecules from the atmosphere, and the rate of direct sputtering of unprotected surfaces is calculated for ejections of S and Na. Atomic species on the surface are ejected at a rate proportional to the surface abundance; and plume sputtering, avalanche cascading, and ionic saltation which lead to spatial and temporal variations in the number of ejected particles are observed.

Haff, P. K.↗
NASA NTRS1985

Bipolar Ejection of Matter from Hot Stars

A general program on the internal velocities in H II regions was carried out within the past decade by the use of photographic Fabry-Perot interferometry, in the H (alpha) line and lately also in the N IIlambda 6584 line. Among the score of objects studied three H II regions and one planetary nebula possess pronounced symmetry around their ionizing stars. Velocity data combined with morphological properties suggest strongly that the nebulae were formed essentially by matter ejected from the central star and that ejection occurred preferentially from diametrially opposite regions on the star, that is, in a bi-polar fashion. The nebulae are discussed individually and a model for the ejection mechanism is presented.

Pismis, P.↗
NASA NTRS1984

Recurrent mass ejections observed in H-alpha and CIV

Time sequences of recurrent mass ejections have been observed during a coordinated SMY program (Sept. 1, 1980 - Sept. 23, 1980 - Oct. 2, 1980). Comparison of the temporal evolution of H-alpha and CIV brightnesses shows a weak phase lag between H-alpha and CIV maxima, in the case of homologous flares, with CIV brightness maxima preceding H-alpha maxima. The analysis of the variation of the ejection velocities is expected to lead to the determination of an energy balance. Such recurrent ejections could be due to periodic energy storage and periodic reorganization of magnetic field as envisaged to occur for flares, but at lower energy levels.

Schmieder, B.↗
NASA NTRS1985

Coronal mass ejections - 1979-1981

An overview of observations of coronal mass ejections (CMEs) during the interval March 28, 1979 through December 31, 1981 is presented. An introduction is first provided to the instrument used in the observations, the method of identifying CMEs, the concepts of CME structural classes, CME importance categories, and the distribution of mass ejections among these classes and categories. The properties of CMEs are given for all mass ejections regardless of their structural classes or importance categories, and then for each class and category. After a brief discussion of the instrument duty cycle, the occurrence rate is presented for all CMEs and for major CMEs, for fast CMEs only, and finally for equatorial CMEs only. The results are compared to those obtained previously.

Howard, R. A.↗
NASA NTRS1986

Stable Ejection Seat

Drogue chute for ejection seat slows down seat in more stable fashion than conventional parachutes and thus improves chances for survival. Square drogue linked to seat from its corners suppresses tendency of seat to rotate in pitch and yaw. New parachute expected to reduce dynamic forces on ejected person and extend maximum possible ejection altitude by 50 percent. Used at high or low speeds.

Hirsch, R. S.↗
NASA NTRS1986

Wave speeds in the corona and the dynamics of mass ejections

A disturbance or coronal mass ejection being advected by the solar wind will expand at the fastest local characteristic speed - typically approximately the fast-mode speed. To estimate this characteristic wave speed and the velocity field in the ambient corona, it is necessary to know the magnetic field, temperature, and density. Only the density is known from coronal observations. The temperature, magnetic field, and velocity are not yet directly measured in the outer corona and must be estimated from a model. In this study, it is estimated that the magnetic field, solar wind velocity, and characteristic speeds use the MHD model of coronal expansion between 1 and 5 solar radii (R solar radii) with a dipole magnetic field at the base. This model, for a field strength of about 2 gauss at the base, gives flow speeds at low latitudes (near the heliospheric current sheet) of 250 km/s at 5 R solar radii and, 50 km/s at 2 solar radii, and fast-mode speeds to 400 to 500 km/s everywhere between 2 and 5 solar radii. This suggests that the outer edge of a velocity of mass ejection reported by MacQueen and Fisher (1983) and implies that the acceleration mechanism for coronal mass ejections is other than simple entrainment in the solar wind.

Suess, S. T.↗
NASA NTRS1986

Coronal mass ejections and coronal structures

Research on coronal mass ejections (CMF) took a variety of forms, both observational and theoretical. On the observational side there were: case studies of individual events, in which it was attempted to provide the most complete descriptions possible, using correlative observations in diverse wavelengths; statistical studies of the properties CMEs and their associated activity; observations which may tell us about the initiation of mass ejections; interplanetary observations of associated shocks and energetic particles even observations of CMEs traversing interplanetary space; and the beautiful synoptic charts which show to what degree mass ejections affect the background corona and how rapidly (if at all) the corona recovers its pre-disturbance form. These efforts are described in capsule form with an emphasis on presenting pictures, graphs, and tables so that the reader can form a personal appreciation of the work and its results.

Hildner, E.↗
NASA NTRS1986

Disruption of a coronal streamer by an eruptive prominence and coronal mass ejection

The coronal mass ejection of August 18, 1980 is analyzed using images from the coronagraph on the Solar Maximum Mission (SMM) satellite. The event occurred at the site of a large coronal helmet streamer and evolved into the three-part structure of a bright frontal shell, followed by a relatively dark space surrounding a bright filamentary core as seen in many mass ejections of the SMM epoch. The bright core can be identified as material from a prominence whose eruption was observed from the ground. The mass of the frontal shell is equal to that of the coronal helmet streamer, indicating that the shell is the coronal material previously in the helmet streamer, displaced and set into motion by the erupting prominence and surrounding cavity. The mass ejected in the bright core (or prominences) is estimated to be 50 percent larger than the 'coronal' material in the front loop.

Illing, R. M. E.↗
NASA NTRS1987

The velocity field of a coronal mass ejection - The event of September 1, 1980

The velocity field of a mass ejection that was observed by the coronagraph of the SMM satellite over the northwest limb of the sun at about 0600 UT on September 1, 1980 is studied in detail. A descriptive account of the event is given, concentrating on qualitative features of the mass motion and suggesting a possible origin of the unusual two-loop structure. The velocity field is analyzed quantitatively, and the implications of the results for the mass ejection theory are considered. It is concluded that a self-similar description of the velocity field is a gross oversimplification and that although some evidence of wave propagation can be found, the bright features in the mass ejection are plasma structures moving with frozen-in magnetic fields, rather than waves propagating through plasmas and magnetic fields.

Low, B. C.↗
NASA NTRS1987

A linear MHD instability analysis of solar mass ejections with gravitation

The linear MHD instability of a cylindrical plasma is used to investigate the origin of solar mass ejections, and the dispersion relation is solved numerically. The initial plasma-flow velocity is found to have a significant effect on the instability criteria and growth rate, and the instability growth-rate is shown to be larger in cases where plasma flow exists, relative to the static case. Results suggest that the plasma column may break into small pieces. Assuming a thin-tube approximation, gravity is found to have little effect on the instability of quasi-horizontal ejection, but to have considerable effect on the vertical ejection. In considering the gravitational force, an exact analytical solution is found for the vertical case, while asymptotic solutions are given for the horizontal and oblique cases.

Song, M. T.↗
NASA NTRS1987

Activity associated with the solar origin of coronal mass ejections

Solar coronal mass ejections (CMEs) observed in 1980 with the HAO Coronagraph/Polarimeter on the Solar Maximum Mission (SMM) satellite are compared with other forms of solar activity that might be physically related to the ejections. The solar phenomena checked and the method of association used were intentionally patterned after those of Munro et al.'s (1979) analysis of mass ejections observed with the Skylab coronagraph to facilitate comparison of the two epochs. Comparison of the results reveals that the types and degree of CME associations are similar near solar activity minimum and at maximum. For both epochs, most CMEs with associations had associated eruptive prominences, and the proportions of association of all types of activity were similar. A high percentage of association between SMM CMEs and X-ray long duration events is also found, in agreement with Skylab results. It is concluded that most CMEs are the result of the destabilization and eruption of a prominence and its overlying coronal structure, or of a magnetic structure capable of supporting a prominence.

Webb, D. F.↗
NASA NTRS1988

Evidence that magnetic energy shedding in solar filament eruptions is the drive in accompanying flares and coronal mass ejections

The dependence of the magnetic energy on the field expansion and untwisting of the flux tube in which an erupting solar filament is embedded has been determined in order to evaluate the energy decrease in the erupting flux tube. Magnetic energy shedding by the filament-field eruption is found to be the driving mechanism in both filament-eruption flares and coronal mass ejections. Confined filament-eruption flares, filament-eruption flares with sprays and coronal mass ejections, and coronal mass ejections from quiescent filament eruptions are all shown to be similar types of events.

Moore, Ronald L.↗