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Author name code: gebbie
ADS astronomy entries on 2022-09-14
author:"Gebbie, Katharine B."
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Title: Helium resonance lines in the flare of 15 June, 1973
Authors: Porter, Jason G.; Gebbie, Katharine B.; November, Laurence J.
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 10<SUP>3</SUP> 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 × 10<SUP>4</SUP> 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 × 10<SUP>4</SUP> 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.
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Title: Solar oscillations and convective flows as probes of structure
in the subphotosphere
Authors: Toomre, Juri; Gebbie, Katharine B.
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.
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Title: The excitation of helium resonance lines in solar flares.
Authors: Porter, J. G.; Gebbie, K. B.; November, L. J.
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.
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Title: The excitation of helium resonance lines in solar flares
Authors: Porter, J. G.; Gebbie, K. B.; November, L. J.
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.
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Title: Frequent Ultraviolet Brightenings in Solar Active Regions
Authors: Porter, J. G.; Toomre, J.; Gebbie, K. B.
1985BAAS...17..629P Altcode:
No abstract at ADS
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Title: Helium Resonance Lines in the Solar Flare of 15 June 1973
Authors: Porter, J. G.; Gebbie, K. B.; November, L. J.
1984BAAS...16Q.891P Altcode:
No abstract at ADS
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Title: Frequent ultraviolet brightenings observed in a solar active
region with solar maximum mission
Authors: Porter, J. G.; Toomre, J.; Gebbie, K. B.
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.
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Title: Solar convection
Authors: Toomre, J.; Gebbie, K. B.
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.
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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.
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.
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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.
1982BAAS...14R.939G Altcode: 1982BAAS...14..939G
No abstract at ADS
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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.
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.
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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.
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.
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Title: The detection of mesogranulation on the sun.
Authors: November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.
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.
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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.
1981BAAS...13..914G Altcode:
No abstract at ADS
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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.
1980BAAS...12..907G Altcode:
No abstract at ADS
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Title: The Lifetime of Solar Mesogranulation
Authors: November, L. J.; Gebbie, K. B.; Hill, F.; Toomre, J.; Simon,
G. W.
1980BAAS...12..895N Altcode:
No abstract at ADS
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Title: Mesogranulation -- An Intermediate Scale of Motion on the Sun
Authors: Toomre, J.; November, L. J.; Gebbie, K. B.; Simon, G. W.
1979BAAS...11..641T Altcode:
No abstract at ADS
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Title: Spectral Diagnostics of a Solar Flare in the Helium Resonance
Lines
Authors: Gebbie, K. B.; November, L. J.; Porter, J. G.
1979BAAS...11..677G Altcode:
No abstract at ADS
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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.
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.
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Title: The Variation with Height of Supergranular Velocity Fields
Authors: Gebbie, K. B.; November, L. J.; Toomre, J.; Simon, G. W.
1978BAAS...10Q.672G Altcode:
No abstract at ADS
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Title: The embedded feature model for the interpretation of
chromospheric contrast profiles.
Authors: Steinitz, R.; Gebbie, K. B.; Bar, V.
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.
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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.
1977BAAS....9..337N Altcode:
No abstract at ADS
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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.
1976BAAS....8..311N Altcode:
No abstract at ADS
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Title: On the Variations in the Spectra of AP Stars
Authors: Steinitz, R.; Gebbie, K. B.
1975BAAS....7..512S Altcode:
No abstract at ADS
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Title: The Formation of the HeI λ584 and HeII λ304 Resonance Lines
in the Solar Transition Region
Authors: Gebbie, K. B.; Steinitz, R.
1975BAAS....7..523G Altcode:
No abstract at ADS
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Title: A General Approach to the Interpretation of Chromospheric
Mottles
Authors: Gebbie, K. B.; Steinitz, R.
1975BAAS....7..353G Altcode:
No abstract at ADS
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Title: What Velocities are Consistent with the Interpretation of
Supergranulation as Penetrative Convection?
Authors: Gebbie, K. B.; Toomre, J.
1975BAAS....7Q.363G Altcode:
No abstract at ADS
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Title: On Spatial Variations in the Intensity of Chromospheric HA
Authors: Gebbie, K. B.; Steinitz, R.
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
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Title: On the formation of chromospheric Halpha .
Authors: Steinitz, R.; Gebbie, K. B.; Bar, V.
1974BAAS....6..264S Altcode:
No abstract at ADS
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Title: Comparison of Hα and CA II H and K Spectroheliograms as a
Diagnostic Probe
Authors: Gebbie, K. B.; Steinitz, R.
1974IAUS...56...55G Altcode:
No abstract at ADS
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Title: On the Visibility of Hα Fibrils
Authors: Steinitz, R.; Gebbie, K. B.
1973BAAS....5T.280S Altcode:
No abstract at ADS
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Title: A Mechanism for the Production of Light and Dark Contrasts
in Radiatively Controlled Lines
Authors: Gebbie, K. B.; Steinitz, R.
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.
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Title: The Temperature Control Bracket
Authors: Gebbie, K. B.; Thomas, R. N.
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.
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Title: The Menzel Symposium on Solar Physics, Atomic Spectra, and
Gaseous Nebulae
Authors: Gebbie, Katharine B.
1971spas.conf.....G Altcode:
No abstract at ADS
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Title: Solar Chromosphere and the General Structure of a Stellar
Atmosphere
Authors: Thomas, Richard N.; Gebbie, Katharine B.
1971spas.conf...84T Altcode:
No abstract at ADS
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Title: The Temperature Control Bracket
Authors: Gebbie, K. B.; Thomas, R. N.
1970BAAS....2S.316G Altcode:
No abstract at ADS
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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.
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- .
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Title: Recent Eclipse Data and the Solar Limb
Authors: Gebbie, K. B.; Weart, S. R.; Thomas, R. N.
1969BAAS....1Q.277G Altcode:
No abstract at ADS
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Title: Non-Lte Diagnostic Stellar Spectroscopy. I. Conceptual and
Analytical Back-Ground
Authors: Gebbie, K. B.; Thomas, R. N.
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
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Title: Non-Lte Diagnostic Stellar Spectroscopy. II. on the Schuster
Mechanism for the Production of Emission Lines
Authors: Gebbie, K. B.; Thomas, R. N.
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
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Title: Some problems of radiation transfer in the atmospheres of
hot stars
Authors: Gebbie, Katharine B.
1968JQSRT...8..265G Altcode:
The central stars of planetary nebulae have effective temperatures
ranging from 3 × 10<SUP>4</SUP> °K to about 2 × 10<SUP>5</SUP>
°K. Such stars may therefore be much hotter than the hottest main
sequence stars which have temperatures of about 4 × 10<SUP>4</SUP>
°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.
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Title: Wolf-rayet stars
Authors: Gebbie, Katharine B.; Thomas, Richard N.
1968wrs..conf.....G Altcode:
No abstract at ADS
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Title: Model atmospheres for central stars of planetary nebulae
Authors: Gebbie, K. B.
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.
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Title: A theoretical study of the atmospheres of hot stars
Authors: Gebbie, Katharine Blodgett
1964PhDT........54G Altcode:
No abstract at ADS
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Title: Model Atmospheres for Central Stars of Planetary Nebulæ
Authors: Gebbie, K. B.; Seaton, M. J.
1963Natur.199..580G Altcode:
THE central stars of planetary nebulæ have effective
temperatures<SUP>1-3</SUP>, T<SUB>s</SUB>, ranging from 3 ×
10<SUP>4</SUP> ° K to about 2.5 × 10<SUP>5</SUP> ° K. Such stars
may therefore be much hotter than the hottest main sequence stars
which have temperatures of about 4 × 10<SUP>4</SUP> ° K. To obtain
a better understanding of the nature of very hot stars, a number of
non-grey model atmospheres have been computed.
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Title: Hβ Photometry of BW Vulpeculae
Authors: McNamara, D. H.; Gebbie, K. B.
1961PASP...73...56M Altcode:
No abstract at ADS
