Author name code: gebbie ADS astronomy entries on 2022-09-14 author:"Gebbie, Katharine B." ------------------------------------------------------------------------ Title: Helium resonance lines in the flare of 15 June, 1973 Authors: Porter, Jason G.; Gebbie, Katharine B.; November, Laurence J. Bibcode: 1989SoPh..120..309P Altcode: Time sequences of He I and He II resonance line intensities at several sites within the flare of 15 June, 1973 are derived from observations obtained with the Naval Research Laboratory's Slitless Spectroheliograph on Skylab. The data are compared with predictions in six model flare atmospheres based on two values for the heating rate and three for the flux of photoionizing coronal X-rays and EUV. A peak ionizing flux more than 103 times that in the quiet Sun is indicated. For most conditions in flare kernels the He II Lα and Lβ lines are found to be formed by collisional excitation, thereby contributing to the local cooling of the plasma at temperatures above 6 × 104 K. Emission in the higher Lyman lines is generally the result of a mixture of collisional excitation at these temperatures and photoionization and recombination at temperatures near 2.5 × 104 K. We discuss implications for the common practice of deriving stellar coronal fluxes from He II 1640 Å fluxes assuming dominance of the recombination mechanism. Title: Solar oscillations and convective flows as probes of structure in the subphotosphere Authors: Toomre, Juri; Gebbie, Katharine B. Bibcode: 1987jila.rept.....T Altcode: Application of inverse theory to the observation of high-degree five-minute solar oscillations has led to the detection of horizontal flows below the solar surface that are a combination of solar rotation and giant convection cells. The distinctive displacements in the centroids of the ridges evident in the power diagrams of the oscillations from one observing day to the next arise from different patterns of giant cells being rotated into view. Such observation of frequency splittings for the high degree oscillation modes, combined with refinements in the inversion of the data using optimal averaging and spectral expansions, has shown that helioseismology should permit detailed mapping of velocity and thermal structures below the solar surface. Extensive theoretical studies of fully compressible magnetoconvection have shown that flows are indeed able to concentrate magnetic fields into concentrated flux sheets that are substantially evacuated of gas. The magnetic buoyancy instabilities have been extensively studied. Title: The excitation of helium resonance lines in solar flares. Authors: Porter, J. G.; Gebbie, K. B.; November, L. J. Bibcode: 1986lasf.conf...84P Altcode: The authors have calculated helium resonance line intensities for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. They examine the differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining (1) which of these models most nearly represents the density vs. temperature structure and soft X-ray flux in the flaring solar transition region, and (2) the temperature and dominant mechanism of formation of the helium line spectrum during a flare. Title: The excitation of helium resonance lines in solar flares Authors: Porter, J. G.; Gebbie, K. B.; November, L. J. Bibcode: 1985smm..conf.....P Altcode: Helium resonance line intensities are calculated for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. The differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra are examined. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining which of these models most nearly represents the density vs temperature structure and soft X-ray flux in the flaring solar transition region, and the temperature and dominant mechanaism of formation of the helium line spectrum during a flare. Title: Frequent Ultraviolet Brightenings in Solar Active Regions Authors: Porter, J. G.; Toomre, J.; Gebbie, K. B. Bibcode: 1985BAAS...17..629P Altcode: No abstract at ADS Title: Helium Resonance Lines in the Solar Flare of 15 June 1973 Authors: Porter, J. G.; Gebbie, K. B.; November, L. J. Bibcode: 1984BAAS...16Q.891P Altcode: No abstract at ADS Title: Frequent ultraviolet brightenings observed in a solar active region with solar maximum mission Authors: Porter, J. G.; Toomre, J.; Gebbie, K. B. Bibcode: 1984ApJ...283..879P Altcode: Observations of the temporal behavior of ultraviolet emission from bright points within an active region of the sun are reported. Frequent and rapid brightenings in Si IV and O IV line emission are seen. The observations suggest that intermittent heating events of modest amplitude are occurring at many sites within an active region. By selecting the brightest site at any given time within an active region and then sampling its behavior in detail within a 120 s interval, it is found that about two-thirds of the samples show variations of the Si IV line intensity. The brightenings typically last about 40-60 s; intensity increases of about 20-100 percent are frequently observed. The results suggest that heating due to magnetic field reconnection within an active region is proceeding almost stochastically. Events involving only a modest release of energy occur the most frequently. Title: Solar convection Authors: Toomre, J.; Gebbie, K. B. Bibcode: 1984colo.rept.....T Altcode: A thorough study of convective penetration into the solar atmosphere and convective motions in sub-atmospheric layers on the sun was made. Non-linear anelastic and Boussinesq modal equations were developed and solved to describe solar and stellar convection. An explanation was developed for the lack of penetration of large-scale convective motions into the observable solar atmosphere through the discovery of buoyancy braking near the top of a supposedly unstable layer. Observations of motions in the solar atmosphere led to the discovery of a new scale of solar motion, the so-called mesogranulation. A technique was developed to use changes in the solar five-minute oscillations as a probe of internal solar structure. Using this technique, large-scale, subatmospheric convective eddies were discovered. Title: On the Determination of the Lifetime of Vertical Velocity Patterns in Mesogranulation and Supergranulation Authors: Hill, F.; Toomri, J.; November, L. J.; Gebbie, K. B. Bibcode: 1984ssdp.conf..160H Altcode: Observational studies of the vertical velocities of mesogranulation and supergranulation provide conflicting results for the lifetimes of these patterns when analyzed by two different methods. Visual inspection of the velocity images suggests that mesogranulation has a lifetime in excess of 2 hours, while cross-correlation methods imply a lifetime of only about 40 min. For supergranulation, the correlation technique yields a lifetime of 2.7 hours, far short of the 24 hours found by many other studies considering network structures or horizontal velocities. The authors consider the possible reasons for such discrepancies. Title: Relation of Ephemeral Magnetic Regions to the Low Amplitude Branch of Persistent Vertical Velocities Authors: Gebbie, K. B.; Toomre, J.; Haber, D. A.; Hill, F.; Simon, G. W.; November, L. J.; Gurman, J. B.; Shine, R. A. Bibcode: 1982BAAS...14R.939G Altcode: 1982BAAS...14..939G No abstract at ADS Title: Vertical flows of supergranular and mesogranular scale observed on the sun with OSO 8 Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W. Bibcode: 1982ApJ...258..846N Altcode: A program of observations was carried out in order to study the penetration of supergranular flows over a broad range of heights in the solar atmosphere. Steady Doppler velocities are determined from observations of a Si II spectral line using the Ultraviolet Spectrometer on the Orbiting Solar Observatory 8 (OSO 8) satellite and Fe I and Mg I lines with the diode-array instrument on the vacuum telescope at Sacramento Peak Observatory (SPO). The heights of formation of these spectral lines span about 1400 km or nearly 11 density scale heights from the photosphere to the middle chromosphere. Steady vertical flows on spatial scales typical of supergranulation and mesogranulation have been detected in the middle chromosphere with OSO 8. The patterns of intensity and steady velocity of granular scale are reproducible in successive data sets. The patterns appear to evolve slowly over the 9 hr period spanned by six orbits. Title: Steady flows in the solar transition region observed with SMM Authors: Gebbie, K. B.; Hill, F.; November, L. J.; Gurman, J. B.; Shine, R. A.; Woodgate, B. E.; Athay, R. G.; Tandberg-Hanssen, E. A.; Toomre, J.; Simon, G. W. Bibcode: 1981ApJ...251L.115G Altcode: Steady flows in the quiet solar transition region have been observed with the Ultraviolet Spectrometer and Polarimeter experiment on the Solar Maximum Mission (SMM) satellite. The persistent vertical motions seen at disk center have spatial rms amplitudes of 1.4 km/s in the C II line, 3.9 km/s in Si IV, and 4.2 km/s in C IV. The amplitudes of the more horizontal flows seen toward the limb tend to be somewhat higher. Plots of steady vertical velocity versus intensity seen at disk center in Si IV and C IV show two distinct branches. Title: The detection of mesogranulation on the sun. Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W. Bibcode: 1981ApJ...245L.123N Altcode: Time averages of velocity measurements at disk center on the quiet sun reveal the presence of a fairly stationary pattern of cellular flow with a spatial scale of 5-10 Mm. Such mesogranulation has a spatial rms vertical velocity amplitude of about 60 m/s superposed on the larger scale supergranular flows. The lifetimes of mesogranules appear to be at least 2 hr. Title: Height Dependence of Steady Flows Determined from Coordinated SMM and SPO Observations Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon, G. W.; Gurman, J. B.; Shine, R. A.; Woodgate, B. E. Bibcode: 1981BAAS...13..914G Altcode: No abstract at ADS Title: Steady Flows in the Solar Transition Region Observed with the UVSP Experiment on SMM Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon, G. W.; Athay, R. G.; Bruner, E. C.; Rehse, R.; Gurman, J. B.; Shine, R. A.; Woodgate, B. E.; Tandberg-Hanssen, E. A. Bibcode: 1980BAAS...12..907G Altcode: No abstract at ADS Title: The Lifetime of Solar Mesogranulation Authors: November, L. J.; Gebbie, K. B.; Hill, F.; Toomre, J.; Simon, G. W. Bibcode: 1980BAAS...12..895N Altcode: No abstract at ADS Title: Mesogranulation -- An Intermediate Scale of Motion on the Sun Authors: Toomre, J.; November, L. J.; Gebbie, K. B.; Simon, G. W. Bibcode: 1979BAAS...11..641T Altcode: No abstract at ADS Title: Spectral Diagnostics of a Solar Flare in the Helium Resonance Lines Authors: Gebbie, K. B.; November, L. J.; Porter, J. G. Bibcode: 1979BAAS...11..677G Altcode: No abstract at ADS Title: The height variation of supergranular velocity fields determined from simultaneous OSO 8 satellite and ground-based observations. Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W. Bibcode: 1979ApJ...227..600N Altcode: Results are reported for simultaneous satellite and ground-based observations of supergranular velocities in the sun, which were made using a UV spectrometer aboard OSO 8 and a diode-array instrument operating at the exit slit of an echelle spectrograph attached to a vacuum tower telescope. Observations of the steady Doppler velocities seen toward the limb in the middle chromosphere and the photosphere are compared; the observed spectral lines of Si II at 1817 A and Fe I at 5576 A are found to differ in height of formation by about 1400 km. The results show that supergranular motions are able to penetrate at least 11 density scale heights into the middle chromosphere, that the patterns of motion correlate well with the cellular structure seen in the photosphere, and that the motion increases from about 800 m/s in the photosphere to at least 3000 m/s in the middle chromosphere. These observations imply that supergranular velocities should be evident in the transition region and that strong horizontal shear layers in supergranulation should produce turbulence and internal gravity waves. Title: The Variation with Height of Supergranular Velocity Fields Authors: Gebbie, K. B.; November, L. J.; Toomre, J.; Simon, G. W. Bibcode: 1978BAAS...10Q.672G Altcode: No abstract at ADS Title: The embedded feature model for the interpretation of chromospheric contrast profiles. Authors: Steinitz, R.; Gebbie, K. B.; Bar, V. Bibcode: 1977ApJ...213..269S Altcode: Contrast profiles obtained from chromospheric filtergrams and spectra of bright and dark mottles have to date been interpreted almost exclusively in terms of Becker's cloud model. Here we demonstrate the failure of this model to account in a physically consistent way for the observed contrasts. As an alternative, we introduce an embedded-feature model, restricting our discussion in this paper to stationary features. Our model is then characterized by three independent parameters: the density of absorbing atoms, the geometrical depth, and the profile of the absorption coefficient. An analytic approximation to the contrast resulting from such a model reproduces well the observed behavior of all types of contrast profiles. Title: Vertical and Horizontal Components of Supergranulation Velocity Fields Observed with OSO-8 Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W. Bibcode: 1977BAAS....9..337N Altcode: No abstract at ADS Title: Supergranulation Velocity Fields Observed in the Solar Transition Region with OSO-8 Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.; Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Shine, R. A.; Orrall, F. Q.; Athay, R. G.; White, O. R. Bibcode: 1976BAAS....8..311N Altcode: No abstract at ADS Title: On the Variations in the Spectra of AP Stars Authors: Steinitz, R.; Gebbie, K. B. Bibcode: 1975BAAS....7..512S Altcode: No abstract at ADS Title: The Formation of the HeI λ584 and HeII λ304 Resonance Lines in the Solar Transition Region Authors: Gebbie, K. B.; Steinitz, R. Bibcode: 1975BAAS....7..523G Altcode: No abstract at ADS Title: A General Approach to the Interpretation of Chromospheric Mottles Authors: Gebbie, K. B.; Steinitz, R. Bibcode: 1975BAAS....7..353G Altcode: No abstract at ADS Title: What Velocities are Consistent with the Interpretation of Supergranulation as Penetrative Convection? Authors: Gebbie, K. B.; Toomre, J. Bibcode: 1975BAAS....7Q.363G Altcode: No abstract at ADS Title: On Spatial Variations in the Intensity of Chromospheric HA Authors: Gebbie, K. B.; Steinitz, R. Bibcode: 1974ApJ...188..399G Altcode: We investigate the formation of patterns in Ha spectroheliograms and filtergrams. Introducing a source-sink-control diagram, we conclude that the Ha line source function in the quiet solar chromosphere is indirectly controlled by the photospheric radiation fields in the Balmer and Paschen continua. We demonstrate that in producing the observed patterns, horizontal spatial variations in the shape of the absorption profile are extremely effective compared to changes in the source and sink terms. Applying this mechanism, we compute asymptotic values for the contrasts and visibilities in chromospheric Ha. Subject headings: chromosphere, solar - line formation - spectroheliograms Title: On the formation of chromospheric Halpha . Authors: Steinitz, R.; Gebbie, K. B.; Bar, V. Bibcode: 1974BAAS....6..264S Altcode: No abstract at ADS Title: Comparison of Hα and CA II H and K Spectroheliograms as a Diagnostic Probe Authors: Gebbie, K. B.; Steinitz, R. Bibcode: 1974IAUS...56...55G Altcode: No abstract at ADS Title: On the Visibility of Hα Fibrils Authors: Steinitz, R.; Gebbie, K. B. Bibcode: 1973BAAS....5T.280S Altcode: No abstract at ADS Title: A Mechanism for the Production of Light and Dark Contrasts in Radiatively Controlled Lines Authors: Gebbie, K. B.; Steinitz, R. Bibcode: 1973SoPh...29....3G Altcode: It is argued that visible contrasts can arise even in a line that is controlled wholly by an external radiation field. Lateral differences in the local shapes of the line absorption profile are shown to account for such contrasts. Two cases are treated explicitly: (a) a profile locally broadened by mass flow, and (b) a profile locally narrower due to the suppression of turbulent velocities, as might result from the presence of magnetic fields. Title: The Temperature Control Bracket Authors: Gebbie, K. B.; Thomas, R. N. Bibcode: 1971ApJ...168..461G Altcode: The factors determining the temperature distribution in a stellar atmosphere are divided into transfer effects and population effects. As a measure of the latter, we introduce the Temperature Control Bracket [TCB], which, in radiative equilibrium, describes the control of T by the quantity and spectral distribution of the radiation field. Algebraic expressions for the [TCB] are given in terms of the microscopic rate processes for a pure hydrogen atmosphere. A caricatured computation is presented to demonstrate the influence of the various physical effects on the distribution of T5 in radiative equilibrium. Title: The Menzel Symposium on Solar Physics, Atomic Spectra, and Gaseous Nebulae Authors: Gebbie, Katharine B. Bibcode: 1971spas.conf.....G Altcode: No abstract at ADS Title: Solar Chromosphere and the General Structure of a Stellar Atmosphere Authors: Thomas, Richard N.; Gebbie, Katharine B. Bibcode: 1971spas.conf...84T Altcode: No abstract at ADS Title: The Temperature Control Bracket Authors: Gebbie, K. B.; Thomas, R. N. Bibcode: 1970BAAS....2S.316G Altcode: No abstract at ADS Title: On the Dependence of T_{e} upon Quantity Versus Quality of the Radiation Field in a Stellar Atmosphere Authors: Gebbie, K. B.; Thomas, R. N. Bibcode: 1970ApJ...161..229G Altcode: We derive a simple algebraic expression for T (r) that demonstrates as a function of collisions how and where the control of T shifts from the quantity to the quality of the radiation field in a stellar atmosphere. We obtain explicit formulae for the gray case and show that mechanical heating and nongray processes can be treated algebraically as perturbations. We illustrate the size and effect of these processes by applying them to the Sun in the region tO-2> T5> 1O- . Title: Recent Eclipse Data and the Solar Limb Authors: Gebbie, K. B.; Weart, S. R.; Thomas, R. N. Bibcode: 1969BAAS....1Q.277G Altcode: No abstract at ADS Title: Non-Lte Diagnostic Stellar Spectroscopy. I. Conceptual and Analytical Back-Ground Authors: Gebbie, K. B.; Thomas, R. N. Bibcode: 1968ApJ...154..271G Altcode: We outline an approach to the determination of the state of a stellar atmosphere and delineate those regions where thermodynamic equilibrium state parameters can be adopted either because collisional processes dominate or because the radiation field satisfies certain homogeneity conditions. It is regions satisfying these homogeneity conditions that must be used to determine the boundary values for the state parameters of the LTE interior. The observable regions of a star do not in general satisfy these conditions, and for these layers we summarize an alternative approach to specifying the state parameters and the analytical basis for determining their values. This paper then provides the background for the specific applications in succeeding papers Title: Non-Lte Diagnostic Stellar Spectroscopy. II. on the Schuster Mechanism for the Production of Emission Lines Authors: Gebbie, K. B.; Thomas, R. N. Bibcode: 1968ApJ...154..285G Altcode: We investigate the conditions under which the Schuster mechanism can produce emission lines. We consider Schuster's original formulation, together with Mime's modification and a general non-LTE formulation. We conclude that while emission lines may result in particular circumstances, it is unlikely that observations of bright lines can be interpreted by this mechanism Title: Some problems of radiation transfer in the atmospheres of hot stars Authors: Gebbie, Katharine B. Bibcode: 1968JQSRT...8..265G Altcode: The central stars of planetary nebulae have effective temperatures ranging from 3 × 104 °K to about 2 × 105 °K. Such stars may therefore be much hotter than the hottest main sequence stars which have temperatures of about 4 × 104 °K. All such determinations of temperature are based on the assumption that the central stars radiate as black bodies. To find out to what extent this is true, and to study the effects of a variation in surface gravity on the emergent flux, a number of model atmospheres has been computed. By virtue of their very high temperature these models have two important features: (1) The large contribution of electron scattering to the opacity; (2) The large effect of radiation pressure on the hydrostatic equilibrium. The atmospheres are assumed to be in radiative equilibrium, hydrostatic equilibrium and local thermodynamic equilibrium. The temperature distribution and radiation pressure gradient are approximated by that of the grey body, with a Rosseland mean absorption coefficient. Account is taken only of continuous absorption by hydrogen and helium. The results of these calculations show that in hot stars of low density, where electron scattering is the dominant source of opacity, emission features are to be expected, but that with increasing density, these will revert into absorption. Comparisons with recent calculations by Böhm and Deinzer show that in denser stars, continuous absorption by higher ions of carbon, nitrogen, oxygen and neon will significantly reduce the stellar flux beyond the helium II ionization limit. Title: Wolf-rayet stars Authors: Gebbie, Katharine B.; Thomas, Richard N. Bibcode: 1968wrs..conf.....G Altcode: No abstract at ADS Title: Model atmospheres for central stars of planetary nebulae Authors: Gebbie, K. B. Bibcode: 1967MNRAS.135..181G Altcode: The central stars of planetary nebulae have effective temperatures ranging from 3 X I0 0K to about 2 X I0 0K. To get a better understanding of the nature of very hot stars, nine model atmospheres have been computed for stars of effective temperature between I X I0 0K and 2'5 X I0 0K and differing values of surface gravity. All the models have the same chemical composition, the ratio of helium to hydrogen being by numbers of atoms. The temperature distribution and radiation pressure gradient are approximated by that of a grey body, and a Rosseland mean absorption coefficient is used. A new method for deriving the source function of very hot stars is given together with an outline of the present numerical calculations. It is shown that in hot stars of low density, where electron scattering is the dominant source of opacity, emission features are to be expected, but that with increasing density, these will reverse into absorption. Title: A theoretical study of the atmospheres of hot stars Authors: Gebbie, Katharine Blodgett Bibcode: 1964PhDT........54G Altcode: No abstract at ADS Title: Model Atmospheres for Central Stars of Planetary Nebulæ Authors: Gebbie, K. B.; Seaton, M. J. Bibcode: 1963Natur.199..580G Altcode: THE central stars of planetary nebulæ have effective temperatures1-3, Ts, ranging from 3 × 104 ° K to about 2.5 × 105 ° K. Such stars may therefore be much hotter than the hottest main sequence stars which have temperatures of about 4 × 104 ° K. To obtain a better understanding of the nature of very hot stars, a number of non-grey model atmospheres have been computed. Title: Hβ Photometry of BW Vulpeculae Authors: McNamara, D. H.; Gebbie, K. B. Bibcode: 1961PASP...73...56M Altcode: No abstract at ADS