explanation blue bibcodes open ADS page with paths to full text
Author name code: white-dick
ADS astronomy entries on 2022-09-14
=author:"White, O. R." OR =author:"White, Oran R." OR =author:"White, Oran Richard"
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Title: Weak Emission Lines in the Wings of Solar H and K
Authors: Livingston, W.; Wallace, L.; White, O. R.
2011SoPh..270..485L Altcode: 2011SoPh..tmp..116L
The rare-earth ions cerium II, lanthanum II, dysprosium II, and
additionally zirconium II and iron II, are seen as weak emission
features in the wings of the solar Ca II H and K lines. The strength of
these emission lines increases on the disk toward the limb. We provide
recent high-resolution observations at disk center and at the limb. The
identity of the weak lines is re-worked. We point out the unique role
of eclipse spectra in distinguishing between the photospheric and
chromospheric origins of emission lines. It is then demonstrated from
our full disk (Sun-as-a-Star) and center disk archives, 1974 - 2010,
that no activity cycle related signal is evident (save for the H and
K lines themselves).
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Title: Sun-as-a-Star, Chromospheric Lines, 1974-2009
Authors: Livingston, W.; White, O. R.; Wallace, L.; Harvey, J.
2010MmSAI..81..643L Altcode:
We update the McMath-Pierce spectral line scan archives for Ca II K,
He I 10830 Å, Ca II 8542 Å, and H I 6562 Å, both for full-disk
and center-disk measurements . The Ca K3 intensity feature displays
a peak-to-peak activity cycle modulation of ∼ 37% and He 10830
Å about 100%. SOLIS observations of the Ca K index suggest a cycle
23-24 minimum in late 2008 followed by a 0.7% rise by late 2009. Other
McMath-Pierce indices display no evidence yet of cycle 24. Center-disk
Ca K index measurements (optically averaged over the central 2-arcmin),
show no particular response to cycle activity, i.e. the quiet disk
is constant. A similar null response is found for the center-disk
Wilson-Bappu effect.
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Title: Irradiance observations of solar active longitudes over three
solar cycles.
Authors: Snow, Martin; Woods, Thomas; White, O. R.
2010cosp...38.1096S Altcode: 2010cosp.meet.1096S
Prior observations of solar activity have shown that there are
longitudes on the Sun which produce active regions consistently for
years at a time. Using the Mg II index record, we have determined the
relative activity on the Sun as a function of Carrington longitude
for each rotation since 1978. There is a longitude band of enhanced
activity that persists not just for a few years, but actually persists
over multiple solar cycles. This longitude has an apparent period of
26.4 days as seen from the Earth. At solar maximum, there is strong
activity at all longitudes on the Sun which masks the contribution
from this band, but in the declining phase, activity from this one
longitude band is predominant. Time series data from other wavelengths,
such as He II, confirm this result.
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Title: The Solar Interior-Atmospheric System
Authors: Athay, R. G.; Low, B. C.; White, O. R.
2008ASPC..383..315A Altcode:
This article discusses an unpublished paradigm by Athay that relates
the general properties of the solar photosphere, chromosphere, and
corona to the stream of photons, kinetic energy, and magnetic fields
flowing from the solar interior. Using the Athay paradigm, we discuss
the physics of the solar atmosphere and its coupling to the solar
dynamo to clarify the connection of observed structures and variations
in the three layers to their hydromagnetic interpretation. The details
of the eleven-year cycles of solar activity are quite different, but
each cycle exhibits two invariant features. First, the chromosphere and
corona are always present above the photosphere in its turbulent state
maintained by the radiative flux escaping at the surface as the solar
luminosity. Second, the solar magnetic field is globally reversed early
in each cycle, accompanied by systematic drifts in magnetic activity
shown in the sunspot butterfly diagram of each cycle. We describe a
scenario for the corresponding systematic changes in the upper solar
atmosphere that recover the minimum-activity corona from one cycle
to the next. We discuss in some detail the mechanisms that heat the
atmosphere and process the magnetic flux continually emerging from the
interior, providing a unified view of the interior-atmospheric system.
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Title: Sun-as-a-Star Spectrum Variations 1974-2006
Authors: Livingston, W.; Wallace, L.; White, O. R.; Giampapa, M. S.
2007ApJ...657.1137L Altcode: 2006astro.ph.12554L
We have observed selected Fraunhofer lines, both integrated over
the full disk and for a small circular region near the center of the
solar disk, on 1215 days over the past 30 years. Our full disk results
for the chromosphere show that Ca II K 3933 Å nicely tracks the 11
yr magnetic cycle based on sunspot number, with a peak amplitude in
central intensity of ~37%. The wavelength of the midline core absorption
feature, called K3, referenced to nearby photospheric Fe, displays
an activity cycle variation with an amplitude of 3 mÅ (6 mÅ center
disk). Other chromospheric lines, such as He I 10830 Å, Ca II 8542 Å,
Hα, and the CN 3883 Å bandhead, track Ca II K intensity with lower
relative amplitudes. In the low photosphere, temperature-sensitive C I
5380 Å appears constant in intensity to 0.2%. In the high photosphere,
the cores of strong Fe I lines, Na D1 and D2, and the Mg I b lines,
present a puzzling signal, perhaps indicating a role for the 22 yr Hale
cycle. Solar minimum around 1985 was clearly seen, but the following
minimum in 1996 was missing. Our center disk results show that both
Ca II K and C I 5380 Å intensities are constant, indicating that the
basal quiet atmosphere is unaffected by cycle magnetism within our
observational error. A lower limit to the Ca II K central intensity
atmosphere is 0.040. This possibly represents conditions as they were
during the Maunder minimum. Converted to the Mount Wilson S-index
(H+K index), the Sun center disk is at the lower activity limit for
solar-type stars. An appendix provides instructions for URL access to
both the raw and reduced data.
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Title: Empirical Modeling of TSI: A Critical View
Authors: de Toma, Giuliana; White, Oran R.
2006SoPh..236....1D Altcode:
Solar empirical models based on regression of two variability indices
for radiation from the photosphere and chromosphere fit total solar
irradiance (TSI) observations with accuracy comparable to the precision
reported for the observations themselves. However, the physical meaning
of the fitting coefficients and their stability during different
phases of the solar cycle has not been examined in detail. We test
the stability of the coefficients in regression models of the VIRGO
TSI observations over the nine years from the minimum of Cycle 23 in
1996 through the maximum to 2005. We also show how the coefficients
converge to the ‘`best fit’' using a search in the coefficient
space. Analysis of TSI variability in different phases of this cycle
shows little change in regression models as long as the time periods
used in the regression are long enough to show the slow solar cycle
variation in TSI. We extend our analysis to TSI observations from ERB,
ACRIM2, ACRIM3, DIARAD, and TIM. The regression models from these
time series show large systematic differences in fitting coefficients
for the plage and sunspot indices that we used. These differences
are significantly larger than the estimated uncertainties in the
coefficients and point to the difficulty of combining observations from
different instruments to create an accurate composite TSI record over
several solar cycles. Our results clearly demonstrate the improvement
in precision of TSI measurements from the Nimbus 7 ERB in Cycle 22 to
the latest SORCE TIM data in Cycle 23.
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Title: Quiet Sun unaffected by Activity Cycle
Authors: Livingston, W.; Gray, D.; Wallace, L.; White, O. R.
2005ASPC..346..353L Altcode:
The Sun's 11 year sunspot cycle, and all related phenomena, are driven
by magnetism in the form of hot flux tubes which thread through the
surface from below. Full disk chromospheric Ca K intensity observations
track the activity cycle. But center disk Ca K and photospheric
temperature sensitive lines are invariant to cycle magnetism. Recent
high resolution photographs of the photosphere show that the flux
tubes are confined between the granulation cells and do not interact
with them. The result is a constant basal atmosphere without cyclic
consequences for the Earth.
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Title: The Mg II Index from SORCE
Authors: Snow, Martin; Mcclintock, William E.; Woods, Thomas N.;
White, Oran R.; Harder, Jerald W.; Rottman, Gary
2005SoPh..230..325S Altcode:
The Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) and the
Spectral Irradiance Monitor (SIM) on the Solar Radiation and Climate
Experiment (SORCE) both measure the solar ultraviolet irradiance
surrounding the Mg II doublet at 280 nm on a daily basis. The SIM
instrument's resolution (1.1 nm) is similar to the Solar Backscatter
Ultraviolet instruments used to compute the standard NOAA Mg II index,
while SOLSTICE's resolution is an order of magnitude higher (0.1
nm). This paper describes the technique used to calculate the index
for both instruments and compares the resulting time series for the
first 18 months of the SORCE mission. The spectral resolution and low
noise of the SOLSTICE spectrum produces a Mg II index with a precision
of 0.6%, roughly a factor of 2 better than the low-resolution index
measurement. The full-resolution SOLSTICE index is able to measure
short-timescale changes in the solar radiative output that are lost
in the noise of the low-resolution index.
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Title: The Spectral Irradiance Monitor (SIM): Early Observations
Authors: Rottman, Gary; Harder, Jerald; Fontenla, Juan; Woods, Thomas;
White, Oran R.; Lawrence, George M.
2005SoPh..230..205R Altcode:
This paper presents and interprets observations obtained by the Spectral
Irradiance Monitor (SIM) on the Solar Radiation and Climate Experiment
(SORCE) over a time period of several solar rotations during the
declining phase of solar cycle 23. The time series of visible and
infrared (IR) bands clearly show significant wavelength dependence
of these variations. At some wavelengths the SIM measurements are
qualitatively similar to the Mg II core-to-wing ratio, but in the
visible and IR they show character similar to the Total Solar Irradiance
(TSI) variations. Despite this overall similarity, different amplitudes,
phases, and temporal features are observed at various wavelengths. The
TSI can be explained as a complex sum of the various wavelength
components. The SIM observations are interpreted with the aid of solar
images that exhibit a mixture of solar activity features. Qualitative
analysis shows how the sunspots, faculae, plage, and active network
provide distinct contributions to the spectral irradiance at different
wavelengths, and ultimately, how these features combine to produce the
observed TSI variations. Most of the observed variability appears to
be qualitatively explained by solar surface features related directly
to the magnetic activity.
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Title: Estimation of TSI Variability During the Declining Phase of
Cycle 23
Authors: White, O. R.; de Toma, G.
2005AGUSMSH23B..06W Altcode:
Our previous study gave an empirical model with only two solar activity
indices that reproduced TSI measurements from 1996 to 2003 in Cycle
23 to within 100 ppm rms (de Toma et al., 2004). The indices used in
the model are: a photometric index derived from full-disk images in
the red continuum at 672.3nm taken at San Fernando Solar Observatory
(the Sigma-red index) and a chromospheric index based on irradiance
measurements in the MgII doublet at 280nm (the MgII core/wing
index). Here, we recompute the empirical model using the latest
VIRGO TSI measurements during the rising and maximum phase of Cycle
23 and compute TSI estimates from the maximum of Cycle 23 toward the
next minimum. Comparison between extrapolations of the model and TSI
observations gives insight on the predictive capability of the model.
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Title: Obituary: Charles Latif Hyder, 1930-2004
Authors: White, Oran Richard
2004BAAS...36.1677W Altcode:
My friend and colleague, Charles Hyder, was a true physicist with
a sound intuitive grasp of fundamentals in modern physics and the
underlying mathematics. I admired his knowledge of the history of modern
physics and quantum mechanics when we discussed contemporary problems
in interpreting solar observations. He had the ability to present his
ideas clearly and persuasively to both students and his colleagues. His
insatiable curiosity about life in general led him to consider the
effects of nuclear weapons development on the human race. Appreciation
of the biological effects of radioactive materials produced in the
course of weapons and power reactor development led him to a more public
career beyond traditional research. <P />Charles Hyder was born April
18, 1930 in Albuquerque, New Mexico. He graduated from Albuquerque
High School and served in the Air Force during the Korean War. He
received a BS and MS in physics from the University of New Mexico
(1958, 1960) and a PhD in astrogeophysics at the University of Colorado
(1964). His positions included the Department of Astronomy and Institute
of Geophysics at UCLA (1964-65), Sacramento Peak Solar Observatory
(1965-1970) and the Goddard Space Flight Center (1970-1977). He also
taught at the University of New Mexico (1970-1977) and was active on
the Solar Maximum Mission science team (1970-1977, 1980-1984). He was
married twice with both marriages ending in divorce. He and his first
wife Ann had three children (Paul, Roxanne and Querida) and he and his
second wife Laurie had a son Niels. <P />Charles Hyder's professional
career in solar physics began in 1961 during his graduate studies at
the Department of AstroGeophysics of the University of Colorado and
continued until 1983 when he chose to follow his convictions to expose
the threat of nuclear proliferation. His early research was in the study
of the quantum mechanics of polarized light produced in the presence of
magnetic fields. Application of this work to interpretation of solar
spectra was a basic theme in fifty-one papers published between 1963
and 1983. Charles' interest in solar prominences and flares led him to
study the physics of in-falling plasma in solar active regions and the
production of the so-called "two ribbon" flares associated with active
region prominences. His final work in solar physics was done on the
Solar Maximum Mission (SMM) in collaboration with colleagues at Goddard
Space Flight Center and Marshall Space Flight Center. <P />After 1983,
Charles' devoted his full energy to exposing the threat of nuclear
weapons and reactor by-products in the biosphere. His was a very
public crusade with a seven month fast in Lafayette Park, Washington
D.C. and a vigorous opposition to the Waste Isolation Pilot Plant
(WIPP) at Carlsbad, New Mexico. His analysis emphasized the need to
understand convection of "hot" containers of radioactive waste in the
WIPP salt bed. He concluded that the containers would eventually emerge
at the surface and be a biological threat. His greatest fear was that
dispersal of plutonium in small amounts worldwide was inevitably leading
to biological mutation and destruction of life as we know it. <P />We
all remember his imposing stature and the strength of his arguments in
discussions of life, physics, and the dangers of radioactive materials
dispersed on the Earth. He led an unconventional life where he truly
reveled in learning and earnestly worked to make a difference.
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Title: Short-term changes in solar spectral irradiance - synthesis
calculations
Authors: White, O. R.; Fox, P. A.
2004AGUFMSH53B0311W Altcode:
We present the latest results from the SunRISE spectral synthesis in
specific spectral bands in the UV, visible, and near-IR in response
to short-term (days-months) solar activity in the latter stage of
solar cycle 23 and compare to observations from SORCE/SIM and other
datasets. We will comment on the degree of redundancy in parts of
the solar spectrum and how this could affect what wavelengths and
bandpasses in the spectrum are important for observing programs.
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Title: Solar Cycle 23: An Anomalous Cycle?
Authors: de Toma, Giuliana; White, Oran R.; Chapman, Gary A.; Walton,
Stephen R.; Preminger, Dora G.; Cookson, Angela M.
2004ApJ...609.1140D Altcode:
The latest SOHO VIRGO total solar irradiance (TSI) time series is
analyzed using new solar variability measures obtained from full-disk
solar images made at the San Fernando Observatory and the Mg II 280 nm
index. We discuss the importance of solar cycle 23 as a magnetically
simpler cycle and a variant from recent cycles. Our results show the
continuing improvement in TSI measurements and surrogates containing
information necessary to account for irradiance variability. Use of the
best surrogate for irradiance variability due to photospheric features
(sunspots and faculae) and chromospheric features (plages and bright
network) allows fitting the TSI record to within an rms difference of
130 ppm for the period 1986 to the present. Observations show that the
strength of the TSI cycle did not change significantly despite the
decrease in sunspot activity in cycle 23 relative to cycle 22. This
points to the difficulty of modeling TSI back to times when only
sunspot observations were available.
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Title: Solar Cycle 23: An Anomalous Cycle?
Authors: de Toma, G.; White, O. R.; Chapman, G. A.; Walton, S. R.;
Preminger, D. G.; Cookson, A. M.
2004AAS...204.3714D Altcode: 2004BAAS...36..711D
We discuss the importance of solar cycle 23 as a magnetically
simpler cycle and a variant from recent cycles. We see a significant
decrease in sunspot activity in cycle 23 relative to cycle 22, but
the strength of the total solar irradiance (TSI) cycle did not change
significantly. The latest SOHO/VIRGO TSI time series is analyzed using
new solar variability measures obtained from full-disk solar images made
at the San Fernando Observatory and the MgII 280nm index. The TSI record
for the period 1986 to the present is reproduced within about 130ppm
RMS using only two indices representing photospheric and chromospheric
sources of variability due to magnetic regions. This is in spite of the
difference in magnetic activity between the two cycles. Our results
show the continuing improvement in TSI measurements and surrogates
containing information necessary to account for irradiance variability.
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Title: Diagnostics of Polar Field Reversal in Solar Cycle 23 Using
a Flux Transport Dynamo Model
Authors: Dikpati, Mausumi; de Toma, Giuliana; Gilman, Peter A.; Arge,
Charles N.; White, Oran R.
2004ApJ...601.1136D Altcode:
Motivated by observed anomalous features in cycle 23, as inferred from
records of photospheric magnetic flux, we develop a flux transport
dynamo-based scheme in order to investigate the physical cause of such
anomalies. In this first study we focus on understanding anomalies
occurring in the polar field evolutionary pattern in cycle 23, namely,
why the polar reversal in cycle 23 was slow, why after reversal the
buildup of the polar field was slow, and why the south pole reversed
approximately a year after the north pole did. We construct a calibrated
flux transport dynamo model that operates with dynamo ingredients such
as differential rotation, meridional circulation, and large-scale
poloidal field source derived from observations. A few other dynamo
ingredients, such as diffusivity and quenching pattern, for which
direct observations are not possible, are fixed by using theoretical
guidance. By showing that this calibrated model can reproduce major
longitude-averaged solar cycle features, we initialize the model at
the beginning of cycle 22 and operate by incorporating the observed
variations in meridional circulation and large-scale surface magnetic
field sources to simulate the polar field evolution in cycle 23. We show
that a 10%-20% weakening in photospheric magnetic flux in cycle 23 with
respect to that in cycle 22 is the primary reason for a ~1 yr slowdown
in polar reversal in cycle 23. Weakening in this flux is also the reason
for slow buildup of polar field after reversal, whereas the observed
north-south asymmetry in meridional circulation in the form of a larger
decrease in flow speed in the northern hemisphere than that in the
southern hemisphere during 1996-2002 and the appearance of a reverse,
high-latitude flow cell in the northern hemisphere during 1998-2001
caused the north polar field to reverse before the south polar field.
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Title: The SunRISE solar synthesis model
Authors: Fox, P.; White, O. R.; Fontenla, J. M.
2004cosp...35.2337F Altcode: 2004cosp.meet.2337F
We present a spectral synthesis approach to making quantitative
estimates of UV and EUV spectral variability. We combine the
identification of solar surface structures from the analysis of images
from the PSPT and spectromagnetograms from NSO/KP, with the theory
for emission, absorption, and transfer of radiation in the solar
atmosphere. We will present the latest results from the spectral
synthesis model and compare them to related observations and comment
on their accuracy and applicability to use in terrestrial atmoshpere
studies. NCAR is sponsored by the National Science Foundation. This
work is partly sponsored by the NSF RISE program.
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Title: Solar irradiance variability: progress in measurement and
empirical analysis
Authors: de Toma, G.; White, O. R.; Chapman, G. A.; Walton, S. R.
2004AdSpR..34..237D Altcode:
Here we report the progress in both measurements and analysis of
total solar irradiance (TSI) during the last 24 years. Recent TSI
measurements made by ACRIM III and VIRGO in the last two years agree to
within 0.5 W m <SUP>-2</SUP> and show the same pattern of short-term
variability. A 24-year composite record of TSI measurements gives
estimates of its variation for two solar cycles. Such composites give
the first estimates of secular variation of the solar output. Our
analysis of TSI data from solar minimum to maximum for cycles 22 and
23 gives nearly identical regression equations because of improvement
in VIRGO degradation corrections, thus, resolving the empirical issue
raised by de Toma et al. [Astrophys. J. Lett. 549 (2001) L131]. This
agreement occurs despite a decrease in cycle 23 of sunspot number by
≈33% below solar maximum values for cycles 21 and 22.
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Title: Solar irradiance variability - comparison of models and
observations
Authors: Fox, P. A.; Fontenla, J. M.; White, O. R.
2004AdSpR..34..231F Altcode:
Over the past decade, regular measurement programs for parts of the
solar spectrum have been established. In recent years substantial
progress has also been made on the physical understanding of these
measurements. To refine our understanding and to make quantitative
estimates of this variability requires a study of the entire solar
spectrum. Our approach to this requirement is to combine empirical
image analysis with the theory for emission, absorption, and transfer
of radiation in the solar atmosphere. The goal is the successful
combination of observed solar images with semi-empirical models and
theory for calculation of a mixed line + continuum spectrum emitted from
realistic representations of the observed solar disk. We present the
latest results from the SunRISE spectral synthesis model in specific
spectral bands in the UV, visible, and near-IR, and compare them to
related observations.
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Title: Redundancy and variability across the solar spectrum.
Authors: Fox, P.; White, O. R.
2004cosp...35.2338F Altcode: 2004cosp.meet.2338F
Intensities in the solar spectrum are fundamentally redundant (meaning
that the shape of the spectrum and its variation in magnitude for
different levels of activity and disk position, is similiar over
certain wavelength ranges. There are three reasons for this: 1)
The solar photosphere is close to local thermodynamic equilibrium
(LTE) and not very far from radiative equilibrium; therefore, the
spectral distribution is close to a Planck function. Under conditions
of radiative equilibrium, the entire spectrum will be determined by
a single variable, the effective temperature. 2) Radiation emergent
from a stellar atmosphere does not originate from a single level in the
atmosphere, rather it is the accumulation of radiation from inside the
atmosphere along the line of sight to the observer. The basic function
in this accumulation process is the contribution (or source) function
which has a maximum near unit optical depth and a width (FWHM) spanning
about two density scale heights. 3) The wavelength dependence of the
opacity allows this contribution function to shift up and down in the
atmosphere according to whether the opacity increases or decreases,
respectively. Since the photospheric temperature decreases outward,
such shifts in the region of radiation formation cause changes in
the emergent intensity. If the opacity had no wavelength dependence,
the peak of the contribution function would be at the same optical
depth for all wavelengths and the redundancy in wavelength would
be limited to narrow bands determined solely by the width of the
contribution function. However, under realistic solar conditions,
our synthesis calculations show that radiation at 500 nm is formed at
the same radiation temperature and depth as that at about 1.3 microns
(for example). The object of this study is to determine how a particular
(smaller) wavelength region may represent a wider band or other bands in
the solar spectrum. To exploit the redundancy in the spectrum requires
an understanding of how the relative variability in well defined
wavelength regions responds to changing solar activity and whether
the correspondence depends on the time scale of the solar activity,
e.g. that of active region emergence compared to the solar cycle
itself. We present details of the investigation of these factors. NCAR
is sponsored by the National Science Foundation. This work is partly
supported by the NSF RISE program.
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Title: Physical Synthesis of the Solar Radiance, a Tool for
Understanding Spectral Irradiance
Authors: Fontenla, J. M.; White, O. R.; Evrett, E. H.; Rottman, G.;
Fox, P.; Harder, J.; Davis, S.
2003AGUFMSH12A1157F Altcode:
In this paper we summarize the current status of our physical modeling
of the solar radiation and briefly describe the key improvements
in the methods we use to compute synthetic solar spectrum. We use 7
solar atmosphere models for summarizing the features observed on the
solar disk, and we compute the emitted spectrum at 10 positions on
the disk. These models and disk positions are intended to cover the
significant features of quiet and active Sun that are linked with solar
irradiance variations. The calculation is extremely detailed and each
of the many thousands of spectral lines is fully resolved so that the
spectra can be convolved with any instrument function and compared with
observations at high or low spectral resolution. Our version 1 code
and models provide very good agreement with observations of spectral
irradiance between ∼450 and ∼1000 nm, but is not accurate outside
that range. We describe the basic procedures used in Version 1 and
the differences with the procedures that will be used in Version 2
for improving the synthesis accuracy over a more extended wavelength
range. We expect that version 2 will be a major step in understanding
the solar spectral irradiance and its variations beyond what is
currently available from any solar irradiance models.
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Title: Has the Sun's Total Output at Minimum and Maximum Changed
Over the Last 24 Years ?
Authors: White, O. R.; de Toma, G.
2002AGUFMSH21B..02W Altcode:
During the last twenty-four years, Total Solar Irradiance (TSI) has
been measured by the Nimbus 7/ERB, SMM/ACRIMI, ERBS/ERBE, UARS/ACRIMII,
SOHO/VIRGO, and ACRIMSAT/ACRIMIII instruments. These measurements allow
construction of a composite TSI record covering more than two solar
cycles. This is the first record capable of revealing secular change in
the Sun's total radiative output in the epoch from 1978 to 2002. Other
space and ground-based observations such as the CaII K index, MgII
core/wing index, 10.7 cm radio flux, and indices for sunspot deficit
and facular excess allow verification and modeling of the composite
TSI record. We review the TSI and irradiance measurements with emphasis
on our ability to detect trends in the radiative output at both solar
minimum and maximum over the last 24 years. Progress (or lack thereof)
in reconstructing the TSI record from spectral irradiance and solar
activity indices will be discussed. The accuracy of the current TSI
records does not allow detection of secular change in amplitude of
the 11-yr Schwabe cycle or the base level at time of solar minimum
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Title: Solar Irradiance Observations during Solar Cycles 22 and 23
Authors: White, O. R.; de Toma, G.; Chapman, G. A.; Walton, S. R.;
Preminger, D. G.; Cookson, A. M.; Harvey, K. L.; Livingston, W. C.
2002AAS...200.5707W Altcode: 2002BAAS...34..737W
We present a study of Total Solar Irradiance (TSI) variations during
solar cycles 22 and 23 from 1986 to the present. We will review the
recent measurements of solar magnetism, solar activity, and radiative
variability from both ground-based and space observatories and compare
TSI observations with empirical models of solar irradiance variability
based on facular and sunspot observations. To estimate facular/plage and
sunspot contribution to TSI we use the photometric indices derived from
the SFO full-disk solar images from 1988 to the present in the CaIIK
line at 393.4nm and in the red continuum at 672.3 nm. In these indices,
each solar structure is included with its measured contrast and area. We
also use the MgII core-to-wing index from space observatories as an
alternative index for plages and network. Comparison of the rising
and maximum phases of the two solar cycles, shows that cycle 23 is
magnetically weaker with sunspot and facular area almost a factor of
two lower than in solar cycle 22. However, analysis of multi-wavelength
observations indicate that different wavelengths respond differently
to the decreased magnetic activity during solar cycle 23.
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Title: Comparison of Solar Photometric Data from Two Telescopes
Authors: Chapman, G. A.; Walton, S. R.; deToma, G.; White, O. R.
2001AAS...199.8804C Altcode: 2001BAAS...33.1433C
Sunspot areas from two photometric telescopes have been compared. The
two telescopes are the Precision Solar Photometric Telescope (PSPT)
operated on Mauna Loa by the High Altitude Observatory (HAO)
and the Cartesian Full Disk Telescope 2 (CFDT2) operated at the
San Fernando Observatory (SFO). The PSPT images originally 2048 x
2048 have been binned by two to agreee more closely with those from
CFDT2. The binned PSPT pixels are 2" x 2" and the CFDT2 pixels are
2.5" x 2.5". A preliminary analysis shows that sunspot areas from the
two are highly correlated although only seven image pairs have been
correlated. Comparing the red PSPT spot areas with the red CFDT2 spot
areas gives an r<SUP>2</SUP> of 0.9947 and a scale factor of 0.909 +/-
0.03 where the scale factor implies the red areas are slightly too
small. For CFDT2 blue images versus the red PSPT the r<SUP>2</SUP>
is 0.9895 with a scale factor of 1.06 +/- 0.05 implying that the blue
areas are slightly too large. Results from other wavelengths and from
an expanded data set will be presented and discussed. This research was
partially supported by grants from NSF, NASA and a visiting scientist
grant from HAO.
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Title: Sunspot Bright Rings: Evidence from Case Studies
Authors: Rast, M. P.; Meisner, R. W.; Lites, B. W.; Fox, P. A.; White,
O. R.
2001ApJ...557..864R Altcode:
We present evidence, from both the Precision Solar Photometric Telescope
and the Advanced Stokes Polarimeter, for a ring of enhanced continuum
intensity surrounding large isolated sunspots. We do not attempt to
evaluate the frequency of the phenomenon based on a large sample of
spots but instead concentrate on illustrative best-case examples. The
rings are about 0.5%-1.0% brighter in red and blue continuum (10 K
warmer) than the surrounding photosphere and extend about one sunspot
radius outward from the outer penumbral boundary. Most of the excess
radiation is not directly associated with the strongest regions of Ca II
K emission surrounding the spots or with measurable vertical magnetic
field when such measurements are available. Moreover, the temporal
evolution of the Ca II K and continuum emission in the ring differ,
with the continuum intensity evolving on a shorter timescale. This
suggests a convective origin for the bright ring, although a role
for weaker, more diffuse magnetic fields cannot be ruled out. While
we have inferred that only about 10% of the radiant energy missing
from the sunspot is emitted through the bright ring, even this small
enhancement may be significant to our understanding of subsurface
sunspot structure and energy transport.
---------------------------------------------------------
Title: Variability of a composite chromospheric irradiance index
during the 11-year activity cycle and over longer time periods
Authors: Lean, J. L.; White, O. R.; Livingston, W. C.; Picone, J. M.
2001JGR...10610645L Altcode:
Chromospheric emission lines are the dominant energy input to
the Earth's upper atmosphere, where they create its embedded
ionosphere. Knowledge of the Sun's chromospheric radiation is
therefore essential for understanding variability in this region, which
contributes significantly to space weather. With the goal of obtaining
a suitable surrogate of extreme ultraviolet irradiance variability
for atmospheric studies, we construct a composite chromospheric index
by comparing and cross calibrating available ground- and space-based
indices. Since ground-based flux observations of the chromosphere
exist only since 1974, we construct 11-year activity cycles of the
index since 1950 by using a parameterization of the daily plage
index and the 100-day smoothed 10.7-cm flux, and prior to that by an
analogous parameterization of the daily and 100-day smoothed sunspot
group numbers. Comparisons of solar and stellar chromospheric indices
suggest that long-term changes in the Sun's chromospheric emission
since the Maunder minimum may exceed recent solar cycle amplitudes by
as much as a factor of 2. We simulate this by adding to the 11-year
activity cycles a speculated varying background component derived
from 15-year smoothed sunspot group numbers that increases from 1900
to 1950 and remains approximately level in the decades since then.
---------------------------------------------------------
Title: Differences in the Sun's Radiative Output in Cycles 22 and 23
Authors: de Toma, Giuliana; White, Oran R.; Chapman, Gary A.; Walton,
Stephen R.; Preminger, Dora G.; Cookson, Angela M.; Harvey, Karen L.
2001ApJ...549L.131D Altcode:
Analysis of the current solar cycle 23 shows a greater increase
in total solar irradiance (TSI) for the early phase of this cycle
than expected from measurements of the total magnetic flux and
traditional solar activity indices, which indicate that cycle 23 is
weaker than cycle 22. In contrast, space observations of TSI from the
Solar and Heliospheric Observatory/VIRGO and the Upper Atmospheric
Research Satellite/ACRIMII show an increase in TSI of about 0.8-1.0
W m<SUP>-2</SUP> from solar minimum in 1996 to the end of 1999. This
is comparable to the TSI increase measured by Nimbus 7/ERB from 1986
to 1989 during the previous cycle. Thus, solar radiative output near
the maximum of the 11 yr cycle has been relatively constant despite
a factor of 2 smaller amplitude increase for cycle 23 in sunspot and
facular areas determined from ground-based observations. As a result,
empirical models of TSI based on sunspot deficit and facular/network
excess in cycle 22 underestimate the TSI measurements in 1999. This
suggests either a problem in the observations or a change in the
sources of radiative variability on the Sun.
---------------------------------------------------------
Title: Data From the Precision Solar Photometric Telescope (Pspt)
in Hawaii From March 1998 to March 1999
Authors: White, Oran R.; Fox, Peter A.; Meisner, Randy; Rast, Mark
P.; Yasukawa, Eric; Koon, Darryl; Rice, Crystal; Lin, Haosheng; Kuhn,
Jeff; Coulter, Roy
2000SSRv...94...75W Altcode:
Two Precision Solar Photometric Telescopes (PSPT) designed and built at
the U.S. National Solar Observatory (NSO) are in operation in Rome and
Hawaii. A third PSPT is now in operation the NSO at Sunspot, NM. The
PSPT system records full disk solar images at three wavelengths:
K line at 393.3 nm and two continua at 409 nm and 607 nm throughout
the observing day. We currently study properties of limb darkening,
sunspots, and network in these images with particular emphasis on data
taken in July and September 1998. During this period, the number of
observations per month was high enough to show directional properties
of the radiation field surrounding sunspots. We show examples of our
PSPT images and describe our study of bright rings around sunspots.
---------------------------------------------------------
Title: Solar Variability Observations - Discussion Session 1a
Authors: White, Oran R.; Rottman, Gary J.
2000SSRv...94...93W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Extreme solar cycle variability in strong lines between 200
and 400 NM
Authors: White, Oran R.; Fontenla, John; Fox, Peter A.
2000SSRv...94...67W Altcode:
Our study of solar cycle irradiance variability in the UV between
200 and 400 nm requires a detailed knowledge of the composition of
the solar spectrum in this wavelength range. We compute the synthetic
spectrum from 250 to 300 nm and compare it with ATLAS3 and SOLSTICE
observations. Synthetic solar spectra for solar minimum and maximum
conditions show large variations in broad, strong UV lines. Strong
lines of FeI between 260 nm and 264 nm show increases between 0.4×
and 3×in their max/min ratio. Our “broad lines” database shows 167
lines with similar properties between 200 nm and 400 nm. Our results
raise issues of the importance of such large variability in narrow
bands and the difficulty of detection in measurements with spectral
resolutions of 1 nm.
---------------------------------------------------------
Title: The SOLAR2000 empirical solar irradiance model and forecast
tool
Authors: Tobiska, W. K.; Woods, T.; Eparvier, F.; Viereck, R.; Floyd,
L.; Bouwer, D.; Rottman, G.; White, O. R.
2000JASTP..62.1233T Altcode: 2000JATP...62.1233T
SOLAR2000 is a collaborative project for accurately characterizing
solar irradiance variability across the spectrum. A new image- and
full-disk proxy empirical solar irradiance model, SOLAR2000, is being
developed that is valid in the spectral range of 1-1,000,000 nm for
historical modeling and forecasting throughout the solar system. The
overarching scientific goal behind SOLAR2000 is to understand
how the Sun varies spectrally and through time from X-ray through
infrared wavelengths. This will contribute to answering key scientific
questions and will aid national programmatic goals related to solar
irradiance specification. SOLAR2000 is designed to be a fundamental
energy input into planetary atmosphere models, a comparative model
with numerical//first principles solar models, and a tool to model or
predict the solar radiation component of the space environment. It is
compliant with the developing International Standards Organization
(ISO) solar irradiance standard. SOLAR2000 captures the essence of
historically measured solar irradiances and this expands our knowledge
about the quiet and variable Sun including its historical envelope
of variability. The implementation of the SOLAR2000 is described,
including the development of a new EUV proxy, E10.7, which has the
same units as the commonly used F10.7. SOLAR2000 also provides an
operational forecasting and global specification capability for solar
irradiances and information can be accessed at the website address
of http:///www.spacenvironment.net.
---------------------------------------------------------
Title: Global Solar Variability: Cycle 23 Indicates a Change from
Recent Cycles
Authors: de Toma, G.; White, O. R.; Chapman, G. A.; Walton, S. R.;
Harvey, K. L.
2000SPD....3102115D Altcode: 2000BAAS...32..831D
This paper focuses on the rising phase of solar cycle 23 from the
time of solar minimum in 1996 to the present high activity level. A
number of observations indicate that cycle 23 maximum is now close, and
maybe is already in the maximum phase. They include the distribution
of coronal streamers, the presence of long--lived solar coronal holes
at low latitudes, the latitudinal distribution of sunspot regions,
and the unipolar magnetic fields in the polar regions. Most of the
activity indices, i.e. sunspot number, sunspot area, photospheric
magnetic flux, 10.7 cm radio flux, and UV irradiances, indicate this
cycle as a relatively weak cycle as compared to cycles 21 and 22. In
particular, observations at San Fernando Observatory of sunspot and
facular area are a factor of two or more lower than in solar cycle
22. This is consistent with the lower magnetic flux measured at NSO/KP
and UV irradiance measurements, but not with total solar irradiance
measurements. We analyze ground--based and space observations to give
a comprehensive picture of the evolution of the current cycle and
compare it to the solar cycle 22.
---------------------------------------------------------
Title: Differences in the Sun's Radiative Output in Cycles 22 and 23
Authors: White, O. R.; de Toma, G.; Chapman, G. A.; Walton, S. R.;
Harvey, K. L.; Cookson, A. M.; Preminger, D. G.
2000SPD....31.0127W Altcode: 2000BAAS...32..806W
We study total solar irradiance (TSI) observations during the rising
phase of cycle 22 and 23 for the 5--year periods during 1986--1990
and 1996--2000. The increase in TSI in cycle 23 is greater than
expected from the observations of the photospheric magnetic flux, and
by traditional activity indices, like sunspot number, 10.7 cm radio
flux, MgII and HeI indices, all of which indicate that cycle 23 is
a relatively weak cycle. Space observations of TSI from SOHO/VIRGO
and UARS/ACRIMII show an increase in TSI of about 1 W/m<SUP>2</SUP>
from 1996 to 2000. This is comparable to the increase observed in
TSI during the previous cycle, from 1986 to 1990 as observed from
Nimbus7/ERB. To resolve the discrepancy between the variability in TSI
observed in the two last cycles, we used the San Fernando Observatory
(SFO) photometric data at 393.4 nm and 672.3 nm to evaluate sunspot
and facular contributions to TSI. The SFO image decomposition technique
has been tested against NSO/KP magnetograms decomposition for selected
days, and they are in good agreement. A 3--parameter fit to Nimbus--7
data for the years 1988--1993 based on SFO data and MgII index gives a
correlation coeff. r<SUP>2</SUP> = 0.9. Extrapolation of the fit in time
largely underestimates the current SOHO/VIRGO TSI measurements. This
suggests there is either a problem in the observations or a change in
nature of radiative sources on the Sun.
---------------------------------------------------------
Title: A Picture of Solar Minimum and the Onset of Solar Cycle
23. I. Global Magnetic Field Evolution
Authors: de Toma, Giuliana; White, Oran R.; Harvey, Karen L.
2000ApJ...529.1101D Altcode:
NSO/Kitt Peak synoptic charts of magnetic flux in the period from 1996
to 1998 are analyzed together with time series for the 10.7 cm radio
flux, sunspot number, and Mg II chromospheric index to determine the
origin of the two times of minimum activity in 1996 and to study their
relationships in the ascending phase of solar cycle 23. The solar
activity minima in February-April and September-November of 1996
are found to correspond to periods of low magnetic activity in the
southern and northern solar hemispheres, respectively. The new solar
cycle becomes dominant in early 1997, but it is only in the summer
of 1997 that a significant increase can be detected in the magnetic
fields observations as well as in irradiance data, and by the end
of 1998, the activity level has increased to a value comparable to
the one observed in 1993. <P />Using the magnetic synoptic charts,
we determine the number of persistent longitude bands of active nests
during this rising phase of solar cycle 23. We find an increase in the
number of active nests from zero in 1996 to three by 1998. We speculate
that these persistent bands of flux emergence correspond to a pattern
of low-order modes of instability of the type found in the theoretical
work of Gilman, Fox, and Dikpati on joint instability of latitudinal
differential rotation and toroidal magnetic fields at the base of the
convection zone. We argue that the observed increase in the number
of active nests is consistent with the increase in the longitudinal
wavenumber of magnetic instabilities in a concentrated toroidal field
in the tachocline discussed in 1999 by Gilman and Dikpati.
---------------------------------------------------------
Title: Temporal properties of He I 1083 nm dark points
Authors: MacQueen, R. M.; Hendrickson, M. A.; Woods, J. C.; Lecinski,
A. R.; Elmore, D. F.; White, O. R.
2000SoPh..191...85M Altcode:
The intensity of a sample of large, high-contrast and isolated dark
points has been observed with full-disk images in the light of He i
1083 nm from the Chromospheric Helium line Intensity Photometer (CHIP)
on Mauna Loa, Hawaii. Temporal variations in the intensity encompassing
a broad range of time scales have been recorded. Long-term changes
in the intensity, although highly variable, are characterized by
e-folding times on the order of 5 h. Superposed on these variations
are frequent intensity variations, which occur over time scales
ranging from the typical observing cadence of 3 min, to tens of
minutes. Microflares-involving intensity changes of at least 50%
over periods of minutes are observed frequently. Rapid cadence (
min) observations reveal differences between rise and decay times and
shorter-term variations in the intensity profiles of these microflares.
---------------------------------------------------------
Title: Data from the Precision Solar Photometric Telescope (PSPT)
in Hawaii from March 1998 to March 1999
Authors: White, Oran R.; Fox, Peter A.; Meisner, Randy; Rast, Mark
P.; Yasukawa, Eric; Koon, Darryl; Rice, Crystal; Lin, Haosheng; Kuhn,
Jeff; Coulter, Roy
2000svc..book...75W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: From Solar Minimum to Solar Maximum: Changes in Total and
Spectral Solar Irradiance
Authors: de Toma, G.; White, O. R.
2000ESASP.463...45D Altcode: 2000sctc.proc...45D
No abstract at ADS
---------------------------------------------------------
Title: Extreme Solar Cycle Variability in Strong Lines Between 200
and 400 nm
Authors: White, Oran R.; Fontenla, John; Fox, Peter A.
2000svc..book...67W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Sources of Solar Variability
Authors: White, O. R.
2000ESASP.463...27W Altcode: 2000sctc.proc...27W
No abstract at ADS
---------------------------------------------------------
Title: Solar Variability Observations
Authors: White, Oran R.; Rottman, Gary J.
2000svc..book...93W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Bright rings around sunspots
Authors: Rast, M. P.; Fox, P. A.; Lin, H.; Lites, B. W.; Meisner,
R. W.; White, O. R.
1999Natur.401..678R Altcode:
There are two possible explanations for why sunspots are dark: the
partial suppression by the sunspot magnetic fields of convective energy
transport from the underlying layers, or the removal of energy from
the sunspot by enhanced hydromagnetic wave radiation. Both processes
would reduce the energy emitted radiatively. The first explanation
is currently favoured, and predicts that the blocked energy should
show up as a bright ring around the spot, with the actual brightness
of the ring sensitive to details of solar convective transport and
sunspot structure. Previous searches for these bright rings were
inconclusive because of the presence of bright, vertical magnetic
flux tubes near the spots, and a lack of sufficient precision in the
observations. Here we report high-photometric-precision observations
of bright rings around eight sunspots. The rings are about 10K warmer
than the surrounding photosphere and extend at least one sunspot
radius out from the penumbra. About 10% of the radiative energy
missing from the sunspots is emitted through the bright rings. We
also report observations of a second set of sunspots, for which
simultaneous magnetic field measurements demonstrate that the rings
are not associated with vertical flux tubes.
---------------------------------------------------------
Title: What is solar cycle minimum?
Authors: Harvey, Karen L.; White, Oran R.
1999JGR...10419759H Altcode:
Establishing the time of minimum between cycles 22 and 23 is complicated
because there are two periods of low solar activity during 1996. To
resolve this controversy, we studied the time of minimum in terms of
the historical basis for defining this fiducial point in the solar
cycle using several measures of solar activity, as well as the cycle
membership of active regions observed during the minimum phase between
these two cycles. Our conclusion is that cycle minimum is not defined
solely on the basis of the occurrence of the minimum in the smoothed
sunspot number, but rather by several additional parameters, including
the monthly (or rotationally) averaged sunspot number, the number
of regions (total, new- and old-cycle), and the number of spotless
days. Using these specific measures of solar activity, we recommend
that the minimum between cycles 22 and 23 occurred in September 1996
(1996.7) and not in May 1996 (1996.4).
---------------------------------------------------------
Title: Calculation of Solar Irradiances. I. Synthesis of the Solar
Spectrum
Authors: Fontenla, Juan; White, Oran R.; Fox, Peter A.; Avrett,
Eugene H.; Kurucz, Robert L.
1999ApJ...518..480F Altcode:
Variations in the total radiative output of the Sun as well as
the detailed spectral irradiance are of interest to terrestrial
and solar-stellar atmosphere studies. Recent observations provide
measurements of spectral irradiance variations at wavelengths in the
range 1100-8650 Å with improved accuracy, and correlative studies
give procedures for estimating the spectral irradiance changes from
solar activity records using indicators such as those derived from
Ca II K and Mg II indices. Here we describe our approach to physical
modeling of irradiance variations using seven semiempirical models to
represent sunspots, plage, network, and quiet atmosphere. This paper
gives methods and details, and some preliminary results of our synthesis
of the variations of the entire irradiance spectrum. Our calculation
uses object-oriented programming techniques that are very efficient
and flexible. We compute at high spectral resolution the intensity
as a function of wavelength and position on the disk for each of the
structure types corresponding to our models. These calculations include
three different approximations for the line source function: one suited
for the very strong resonance lines where partial redistribution
(PRD) is important, another for the most important nonresonance
lines, and another approximation for the many narrow lines that are
provided in Kurucz's listings. The image analysis and calculations
of the irradiance variation as a function of time will be described
in a later paper. This work provides an understanding of the sources
of variability arising from solar-activity surface structures. We
compute the Lyα irradiance to within 3% of the observed values. The
difference between our computations and the Neckel & Labs data is 3%
or less in the near-IR wavelengths at 8650 Å, and less than 1% in the
red at 6080 Å. Near 4100 Å we overestimate the irradiance by 9%-19%
because of opacity sources missing in our calculations. We also compute
a solar cycle variability of 49% in the Lyα irradiance, which is very
close to observed values. At wavelengths between 4100 Å and 1.6 μm,
we obtain spectral irradiance variations ranging from -0.06% to 0.46%
in the visible--the higher values correspond to the presence of strong
lines. The variability in the IR between 1.3 and 2.2 μm is ~-0.15%.
---------------------------------------------------------
Title: Evolution of Solar Magnetic Fields in 1996-1998
Authors: de Toma, G.; White, O. R.; Harvey, K. L.; Rottman, G. J.;
Woods, T. N.
1999AAS...194.9202D Altcode: 1999BAAS...31..986D
NSO/Kitt Peak synoptic charts of magnetic flux in the period from 1996
to 1998 are analyzed together with time series for the 10.7 cm radio
flux, sunspot number, and MgII chromospheric index to determine the
origin of two times of minimum activity in 1996 and to study the rising
phase of the current solar cycle 23 in 1997 and 1998. The two minima
between solar cycle 22 and 23 in the Spring and Fall of 1996 are found
to correspond to periods of low magnetic activity in the southern and
northern solar hemispheres, respectively. The new solar cycle becomes
dominant in early 1997, but it is only in the Summer of 1997 that
a significant increase in activity can be detected in the magnetic
fields observations as well as in irradiance data. By the end of 1998,
the activity level has increased to a value that suggests the current
cycle is about half way to solar maximum. The number of persistent
longitude bands of active nests increases from zero in 1996 to three
by 1998. This value seems consistent with numerical simulations which
study the dependence with longitudinal wavenumber, m, of magnetic
instabilities in concentrated toroidal fields at the tachocline.
---------------------------------------------------------
Title: Magnetic and Radiative Variability of Solar Surface
Structures. I. Image Decomposition and Magnetic-Intensity Mapping
Authors: Harvey, Karen L.; White, Oran R.
1999ApJ...515..812H Altcode:
In order to specify quantitatively the contributions to irradiance
variability by specific types of solar surface structure, we analyzed
full-disk magnetograms and Ca II K images from the National Solar
Observatory and Big Bear Solar Observatory for two sets of several
days in early 1992 and mid-1993. These test days were chosen at
maxima and minima of the rotational modulation in the Lyα irradiance
from the Upper Atmosphere Research Satellite Solar-Stellar Irradiance
Comparison Experiment (UARS/SOLSTICE) spectrometer. For the eight days,
we isolated active regions, decaying active regions, the enhanced
network, the network, and the quiet atmosphere based on their magnetic
flux strength and distribution, filling factor, and association with
sunspots. Transfer of these image decompositions to Ca II K images
gives magnetic flux versus intensity (|B| vs. δK) relationships for
four structures with measurable magnetic flux. In the range 30-400 Mx
cm<SUP>-2</SUP>, these log-log curves are linear with a slope of 0.5,
which suggests that the Ca II K residual intensity is proportional
to the half-power of the magnetic flux density. The separation into
quiet and active Sun structures gives a prediction of the variation
of the |B| versus δK relation for the ensemble of our four principal
structures from minimum to maximum in the activity cycle of the Sun
viewed as a star.
---------------------------------------------------------
Title: Interplanetary Lyman α observations from Pioneer Venus over
a solar cycle from 1978 to 1992
Authors: Pryor, Wayne R.; Lasica, Scott J.; Stewart, A. Ian F.; Hall,
Doyle T.; Lineaweaver, Sean; Colwell, William B.; Ajello, Joseph M.;
White, Oran R.; Kent Tobiska, W.
1998JGR...10326833P Altcode:
The Pioneer Venus Orbiter ultraviolet spectrometer (PVOUVS) routinely
obtained interplanetary hydrogen Lyman α data while viewing ecliptic
latitudes near 30°S from 1978 to 1992 (during solar cycles 21 and
22). We describe “hot” models for this interplanetary Lyman α
data that include the solar cycle variation of (1) the solar flux,
as a function of latitude and longitude; (2) the radiation pressure
on hydrogen atoms; (3) the solar wind flux; (4) the solar EUV flux;
and (5) the multiple scattering correction to an optically thin
radiative transfer model. These models make use of solar radiation
flux parameters (solar wind, solar EUV, and solar Lyman α) from
spacecraft and ground-based solar proxy observations. Comparison of
the upwind data and model indicates that the ratio of the solar Lyman
α line center flux (responsible for the interplanetary signal) to the
observed solar Lyman α integrated flux is constant to within ~20%,
with an effective line width near 1.1 Å. Averaging the solar radiation
pressure and hydrogen atom lifetime over 1 year before the observation
reproduces the upwind intensity time variation but not the downwind. A
better fit to the downwind time series is found using the 1 year average
appropriate for the time that the atoms passed closest to the sun. Solar
Lyman α measurements from two satellites are used in our models. Upper
Atmosphere Research Satellite (UARS) solar Lyman α measurements are
systematically higher than Solar Mesosphere Explorer (SME) values and
have a larger solar maximum to solar minimum ratio. UARS-based models
work better than SME-based models in fitting the PVOUVS downwind time
series Lyman α data.
---------------------------------------------------------
Title: TIMED solar EUV experiment
Authors: Woods, Thomas N.; Bailey, Scott M.; Eparvier, Francis G.;
Lawrence, George M.; Lean, Judith; McClintock, William E.; Roble,
Raymond G.; Rottman, Gary J.; Solomon, Stanley C.; Tobiska, W. K.;
Ucker, Gregory J.; White, O. R.
1998SPIE.3442..180W Altcode:
The solar EUV experiment (SEE) selected for the NASA Thermosphere,
Ionosphere, and Mesosphere Energetics and Dynamics mission will measure
the solar vacuum UV (VUV) spectral irradiance from 0.1 to 200 nm. To
cover this wide spectral range two different types of instruments
are used: grating spectrograph for spectra above 25 nm and a set of
silicon soft x-ray (XUV) photodiodes with thin film filters for below
30 nm. Redundant channels of the spectrograph and XUV photodiodes
provide in-flight calibration checks on the time scale of a week, and
annual rocket underflight measurements provide absolute calibration
checks traceable to radiometric standards. Both types of instrument
have been developed and flight proven as part of a NASA solar EUV
irradiance rocket experiment.
---------------------------------------------------------
Title: Initial CHIP He I Observations of Solar Limb Activity
Authors: MacQueen, R. M.; Blankner, J. G.; Elmore, D. F.; Lecinski,
A. R.; White, O. R.
1998SoPh..182...97M Altcode:
A new instrument capable of 3-min time resolution full-disk and limb
observations in the Hei 1083 nm spectral line has been in operation
at the High Altitude Observatory's Mauna Loa Solar Observatory (MLSO)
since April 1996. We discuss instrument capabilities and performance
and present some initial observations of limb activity from the first
year of instrument operation. We compare limb Hei and Hα observations
of quiescent and active prominences, comment on the role of Doppler
shifts in interpreting the Hei observations, and illustrate the use
of disk/limb Hei observations of a CME-associated eruptive filament
in mass-ejection studies.
---------------------------------------------------------
Title: Chromospheric Helium Imaging Photometer (an Instrument for
High Time Cadence 1083-nm Wavelength Solar Observations)
Authors: Elmore, David F.; Card, Gregory L.; Chambellan, Clarke W.;
Hassler, Donald M.; Hull, Howard L.; Lecinski, Alice R.; MacQueen,
Robert M.; Streander, Kim V.; Streete, John L.; White, Oran R.
1998ApOpt..37.4270E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evolution of Chromospheric Structures Derived from Ca II K
Spectroheliograms: Implications for Solar Ultraviolet Irradiance
Variability
Authors: Worden, John R.; White, Oran R.; Woods, Thomas N.
1998ApJ...496..998W Altcode:
Over 1400 National Solar Observatory Ca II K spectroheliograms
are analyzed for solar structure evolution for the years 1980,
1985, 1987, 1988, 1989, and 1992 through 1996 July with about a 50%
time coverage. This time period includes the maximum of solar cycle
21 and almost all phases of solar cycle 22. The spectral bandpass
and spatial resolution of these images are 0.5 Å and about 8.5",
respectively. The plage, enhanced-network, active-network, and quiet-Sun
features are identified on each image with an algorithm that uses
criteria of intensity, size, filling factor, and continuity. This
decomposition leads to time series of the plage and network areas,
and their spatial distribution on the solar disk, which describe the
solar cycle evolution of these structures. Thus, either the resultant
structure masks or structure time series can be used for modeling the
solar irradiance at other wavelengths. We cannot accurately identify
all of the active network on the solar disk in Ca II K because the
active-network intensities are not much greater than those of the
quiet Sun. Therefore, we identify only the brighter active-network
structures. However, the active network we identify on the Ca II K
image can be used as a proxy for active-network evolution over the
solar cycle. Many results that are useful for modeling solar irradiance
variability are also presented. We find that the intensity contrasts
(ratio of structure intensity to quiet Sun intensity) of the plage,
enhanced network, and active network, averaged over the solar disk,
are 1.95, 1.51, and 1.33, respectively. These contrasts remain
essentially constant over the solar cycle. As expected, we find that
the plage and the enhanced-network time series show a strong 27 day
rotational modulation, but we also find that the active network can
have a weak rotational modulation despite its wider longitudinal
dispersion. The plage and enhanced network typically cover about 13%
and 10%, respectively, of the solar disk during solar-maximum time
periods. During solar moderate and minimum activity levels, the total
plage and enhanced-network areas can reach zero, but the active network
can still cover a large portion of the solar disk.
---------------------------------------------------------
Title: Secular Change in the Quiet Sun Component of the Total Solar
Irradiance at Solar Minimum
Authors: White, O. R.; Mende, W.; Hoyt, D. V.
1998saco.conf..107W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Plage and Enhanced Network Indices Derived from CA II K
Spectroheliograms
Authors: Worden, John R.; White, Oran R.; Woods, Thomas N.
1998SoPh..177..255W Altcode:
NSO Sacramento Peak Caii K images are analyzed for the years 1992
through September 1996 with about a 50% coverage. The plage, decayed
plage, enhanced network, and quiet-Sun features are identified on each
image with an algorithm that uses the criteria of intensity, size,
and filling factor. These algorithms can be adapted for analyzing
spectroheliograms from ground-based or space-based observatories. Plage
and enhanced network indices, for these time periods, are shown. We
present intensity contrasts for the plage, decayed plage, and enhanced
network. We also find that these contrasts, which are an average of
the structures intensity relative to the quiet Sun over the whole disk,
remain essentially constant over the solar cycle.
---------------------------------------------------------
Title: Filament Disparition Brusque and CME - September 25-26,
1996 Event
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.;
Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson,
B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka,
Y.; Nitta, N.
1998ASPC..150..366V Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V
No abstract at ADS
---------------------------------------------------------
Title: Spectral Irradiance and Magnetic Structures
Authors: Harvey, Karen L.; White, Oran R.
1998ASPC..140..247H Altcode: 1998ssp..conf..247H
No abstract at ADS
---------------------------------------------------------
Title: Spectrum Line Strength Variability: Sun-As
Authors: Livingston, W. C.; Wallace, L.; White, O. R.
1998saco.conf..109L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variability of the Solar Call K Line over the 22 Year Hale
Cycle
Authors: White, O. R.; Livingston, W. C.; Keil, S. L.; Henry,
Timothy W.
1998ASPC..140..293W Altcode: 1998ssp..conf..293W
No abstract at ADS
---------------------------------------------------------
Title: Plage and Enhanced Network Indices Derived from CA II K
Spectroheliograms
Authors: Worden, John R.; White, Oran R.; Woods, Thomas N.
1998sers.conf..255W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effect of Spectral Resolution on the MG II Index as a Measure
of Solar Variability
Authors: White, Oran R.; de Toma, Giuliana; Rottman, Gary J.; Woods,
Thomas N.; Knapp, Barry G.
1998sers.conf...89W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effect of Spectral Resolution on the MG II Index as a Measure
of Solar Variability
Authors: White, Oran R.; De Toma, Giuliana; Rottman, Gary J.; Woods,
Thomas N.; Knapp, Barry G.
1998SoPh..177...89W Altcode:
The solar Mgii core-to-wing ratio is a useful index of UV variability
throughout the solar cycle because it has been measured since 1978 in
a series of successive satellite missions: Nimbus 7, Solar Mesosphere
Explorer (SME), the NOAA 9-14 series, Upper Atmosphere Research
Satellite (UARS), and ERS-2. Eventual construction of a single time
series from 1978 to the present by combining these measurements
will give a long record of almost daily UV variability to serve as
a surrogate for estimating both UV and EUV solar radiation. Here we
address the effect of spectral resolution on determination of both
long-term and short-term solar variability from this index. We use
UARS/SOLSTICE measurements of the Mgii line from October 1991 to
December 1996 to study the effect of two spectral resolution regimes
characteristic of existing measurements, 0.20 to 0.25 nm and 1.10
to 1.15 nm, on determination of the amplitude of 27-day rotational
modulation and the more gradual change in chromospheric radiation
in the declining phase of solar cycle 22. The two Mgii indices give
solar variations that differ by a scaling factor of ≈ 2× for both
the solar cycle change from 1992 to 1997 and the amplitude of 27-day
modulation over the same period. Both types of measurements appear
to yield solar signal equally well except at solar minimum when the
solar changes become quite small.
---------------------------------------------------------
Title: Mg II core-to-wing index: Comparison of SBUV2 and SOLSTICE
time series
Authors: de Toma, Giuliana; White, Oran R.; Knapp, Barry G.; Rottman,
Gary J.; Woods, Thomas N.
1997JGR...102.2597D Altcode:
The Mg II core-to-wing index is a ratio of the Mg II chromospheric
emission at 280 nm to the photospheric radiation in the line wings
and is used as an indicator of solar activity. Since October 1991,
the Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) has made
daily irradiance measurements in the range 119-420 nm from the Upper
Atmosphere Research Satellite (UARS). A new Mg II index, based on the
SOLSTICE observations at a spectral resolution of 0.24 nm, is presented
and compared to previous measurements. Spectral irradiance measurements
of the Mg II doublet at low spectral resolution (~1nm) have been made by
the Solar Backscatter UltraViolet (SBUV) instrument on Nimbus 7 since
November 1978 and subsequently by the SBUV2 instruments on NOAA 9 and
NOAA 11 satellites. We compare the SOLSTICE data with the Mg II time
series derived from SBUV2 data by the groups at the National Oceanic and
Atmospheric Administration (NOAA) and at the Goddard Space Flight Center
(GSFC). SOLSTICE data are convolved to the lower SBUV2 resolution, and
the NOAA and GSFC algorithms are then applied to this data set. The
SOLSTICE Mg II indices constructed in this manner simulate the SBUV2
indices and can be used to validate the SBUV2 time series and identify
data problems. From our analysis, we conclude that the NOAA Mg II time
series is the most consistent during the period 1978-1994. The new GSFC
Mg II time series has comparable accuracy for the period starting in
1989. We also derive the linear transformation equations required to
put the high- and low-resolution time series onto common scales.
---------------------------------------------------------
Title: Panel achieves consensus prediction of solar cycle 23
Authors: Joselyn, J. A.; Anderson, J. B.; Coffey, H.; Harvey, K.;
Hathaway, D.; Heckman, G.; Hildner, E.; Mende, W.; Schatten, K.;
Thompson, R.; Thomson, A. W. P.; White, O. R.
1997EOSTr..78..205J Altcode:
In September 1996, a panel of experts on solar cycle prediction
techniques met in Boulder, Colorado, to survey forecasts of solar
and geomagnetic activity and to arrive at a consensus on how the
solar cycle will develop. After two weeks of deliberation, the panel
of 12 scientists (from Australia, Germany, the United Kingdom, and
the United States) agreed that a large amplitude solar cycle with
a smoothed sunspot maximum of approximately 160 is probable near the
turn of the century. The amplitude of the predicted cycle is comparable
to that of the previous two solar cycles (see Figure 1).Our ability to
predict solar and geomagnetic activity is crucial to many technologies,
including the operation of low-Earth orbiting satellites, electric power
transmission grids, geophysical exploration, and highfrequency radio
communications and radars. Because the scale height of Earth's upper
atmosphere (and thus the drag on satellites in low Earth orbit) depends
on the levels of short-wavelength solar radiation and geomagnetic
activity, we need to know the profile and magnitude of the next solar
and geomagnetic cycle in order to plan for reboosting the Hubble Space
Telescope and assembling the International Space Station.
---------------------------------------------------------
Title: Ozone variability in the upper stratosphere during the
declining phase of the solar cycle 22
Authors: Chandra, S.; Froidevaux, L.; Waters, J. W.; White, O. R.;
Rottman, G. J.; Prinz, D. K.; Brueckner, G. E.
1996GeoRL..23.2935C Altcode:
Recent studies of the solar cycle variation of ozone have shown
that the response of ozone in the upper stratosphere to solar UV
variation, as inferred from the SBUV (Solar Backscatter Ultraviolet)
type measurements, is about a factor of two greater than estimated from
2-D photochemical models. Because of potential errors in accounting
for the long term instrument drift in the SBUV type of measurements,
the significance of this discrepancy is difficult to quantify. In this
paper, ozone measurements from the Microwave Limb Sounder (MLS) and
the solar irradiance measurements from the Solar Stellar Irradiance
Comparison Experiment (SOLSTICE) and the Solar Ultraviolet Irradiance
Monitor (SUSIM) onboard the Upper Atmosphere Research Satellite (UARS)
are analyzed to estimate the upper stratosphere ozone response to
changes in the solar UV irradiance. During the three year period of UARS
measurements, analyzed here for the declining phase of the solar cycle
22, the solar irradiance in the 200-205 nm range decreased by about 5 %
from a near solar maximum to a near solar minimum level. During the same
period, ozone mixing ratio measured from the MLS instrument decreased
by about 2-4% in the 0.7-3 hPa region. In the upper stratosphere, the
general characateristics of the MLS time series are similar to those
inferred from the NOAA-11 SBUV/2 measurements. The SBUV/2 trends above
1.5 hPa, however, are significantly greater than those derived from the
MLS data. The UARS data suggest that the long term solar UV response of
ozone in the upper stratosphere is underestimated by 2-D photochemical
models as in previous studies based on the SBUV type measurements.
---------------------------------------------------------
Title: Latitude variations in interplanetary Lyman-α data from the
Galileo EUVS modeled with solar He 1083 nm images
Authors: Pryor, W. R.; Barth, C. A.; Hord, C. W.; Stewart, A. I. F.;
Simmons, K. E.; Gebben, J. J.; McClintock, W. E.; Lineaweaver, S.;
Ajello, J. M.; Tobiska, W. K.; Naviaux, K. L.; Edberg, S. J.; White,
O. R.; Sandel, B. R.
1996GeoRL..23.1893P Altcode:
Observations of interplanetary Lyman-α obtained by the Galileo Extreme
Ultraviolet Spectrometer (EUVS) experiment near solar maximum in 1990
show a distinct migration in the upwind brightness maximum from 36±5°N
to 6±5°N ecliptic latitude over a period of several months. Our
earlier models based on solar Lyman-α flux proxies appropriate
for use in the ecliptic plane ( Pryor et al., 1992; Ajello et al.,
1994) capture the solar rotation effects present in the data, but
do not reproduce this latitude migration. We introduce a new type of
model that uses He 1083 nm images to produce a proxy for Lyman-α as
a function of both solar longitude and latitude. This model reproduces
the observed latitude migration of the Lyman-α brightness maximum.
---------------------------------------------------------
Title: Validation of the UARS solar ultraviolet irradiances:
Comparison with the ATLAS 1 and 2 measurements
Authors: Woods, T. N.; Prinz, D. K.; Rottman, G. J.; London, J.; Crane,
P. C.; Cebula, R. P.; Hilsenrath, E.; Brueckner, G. E.; Andrews, M. D.;
White, O. R.; VanHoosier, M. E.; Floyd, L. E.; Herring, L. C.; Knapp,
B. G.; Pankratz, C. K.; Reiser, P. A.
1996JGR...101.9541W Altcode:
The measurements of the solar ultraviolet spectral irradiance
made by the two Upper Atmosphere Research Satellite (UARS) solar
instruments, Solar Ultraviolet Spectral Irradiance Monitor (SUSIM)
and SOLar STellar Irradiance Comparison Experiment (SOLSTICE), are
compared with same-day measurements by two solar instruments on the
shuttle ATmospheric Laboratory for Applications and Science (ATLAS)
missions, ATLAS SUSIM and Shuttle Solar Backscatter Ultra Violet (SSBUV)
experiment. These measurements from the four instruments agree to within
the 2σ uncertainty of any one instrument, which is 5 to 10% for all
wavelengths above 160 nm and for strong emission features below 160
nm. Additionally, the long-term relative accuracy of the two UARS data
sets is better than the original 2% goal, especially at wavelengths
greater than 160 nm. This level of agreement is credited to accurate
preflight calibrations coupled with comprehensive inflight calibrations
to track instrument degradation. Two solar irradiance spectra, 119 to
410 nm, are presented; the first combines observations from UARS SUSIM
and UARS SOLSTICE taken on March 29, 1992, during the ATLAS 1 mission,
and the second combines spectra for April 15, 1993, during the ATLAS
2 mission. The ATLAS 1 mission coincided with the initial decline
from the maximum of solar cycle 22 when solar activity was relatively
high. The ATLAS 2 mission occurred somewhat later during the declining
phase of the solar cycle 22 when solar activity was more moderate.
---------------------------------------------------------
Title: Determination of Contributions to Irradiances from Plages,
Network and the Quiet Solar Atmosphere
Authors: White, O. R.
1996ASPC...95..598W Altcode: 1996sdit.conf..598W
No abstract at ADS
---------------------------------------------------------
Title: Solar Magnetic Fields: The Key to Understanding Solar
Irradiance Variations
Authors: Harvey, Karen L.; White, Oran R.
1996sprc.rept.....H Altcode:
The objective of this research is the development of a scheme
for analyzing the properties of full-disk solar magnetograms to
determine the variability of different types of solar magnetic
structure and its effect on the variation of the radiation emitted
by these structures. This approach has operational applications
since we consider the analysis of daily synoptic measurements of the
line-of-sight magnetic field on the solar hemisphere visible from the
Earth with the view to using the results to estimate the variability
of solar irradiances at the Earth. However, the study is also one of
fundamental importance in solar physics: the relationship of solar
magnetism to the radiative losses in the solar atmosphere.
---------------------------------------------------------
Title: Solar UV irradiance variability during the declining phase
of the solar cycle 22
Authors: Chandra, Sushil; Lean, Judith L.; White, Oran R.; Prinz,
Dianne K.; Rottman, Gary J.; Brueckner, Guenter E.
1995GeoRL..22.2481C Altcode:
The SUSIM (Solar Ultraviolet Spectral Irradiance Monitor) and the
SOLSTICE (Solar Stellar Irradiance Comparison Experiment) instruments
on the UARS (Upper Atmosphere Research Satellite) have been making
continuous measurements of the solar UV flux in the spectral range
115-420 nm since October 1991. This period, characterized as the
declining phase of solar cycle 22, shows a transition from near maximum
to near minimum solar activity levels. During this period, the solar
UV flux at Lyman α decreased by about 45% from a mean solar maximum
value of about 9 mW/m², and the integrated solar flux between 200-205
nm decreased by about 5% from a mean value of about 47 mW/m². Using the
MgII index as a proxy of solar UV irradiance variability, it is shown
that the temporal relationship of the UARS solar Lyman α irradiance
and the MgII index during solar cycle 22 is significantly different
than during solar cycle 21, inferred from the SME (Solar Mesosphere
Explorer) Lyman α measurements. Moreover, during solar cycle 22, the
scale factor for solar Lyman α irradiance (% change for 1% change
in MgII index) is about 1.5 times larger for long term changes than
for changes over the time scale of a solar rotation. Unlike Lyman α,
the scale factor for the UV flux in the 200-205 nm wavelength range,
is close to unity both for the rotational and longer time scales. The
spectral dependence of the two scale factors in the 120-200 nm range is
derived from the SOLSTICE data which may be used with the MgII index
to estimate the UV irradiance variability in this spectral range for
both short and long time scales.
---------------------------------------------------------
Title: The Solar LY alpha Line Profile
Authors: Woods, Thomas N.; Rottman, Gary J.; White, O. R.; Fontenla,
Juan; Avrett, E. H.
1995ApJ...442..898W Altcode:
Solar Ly-alpha irradiance measurements from the SOLar STellar Irradiance
Comparison Experiment (SOLSTICE) on the Upper Atmosphere Research
Satellite (UARS) have been made since 1991 October with a spectral
resolution of 0.1 nm. The uniqueness of the small molecular oxygen cross
section near Ly-alpha permits the Ly-alpha radiation to penetrate much
deeper into the atmosphere than the other emissions near Ly-alpha. We
have taken advantage of this phenomenon by performing solar occultation
experiments near the Ly-alpha to evaluate precisely the instrument
scattered light contribution. After correcting for scattered light,
the broad wings of the solar Ly-alpha line can be extracted out to 5
nm from line center with a typical accuracy of +/-20%. The variability
in the Ly-alpha wings near 2 nm from line center is about one-half
that of the Ly-alpha core emission, defined within 0.1 nm from line
center. These Ly-alpha profile measurements are found to be consistent
with the Skylab radiance measurements and theoretical models of the
Ly-alpha line profiles computed using partial redistribution of photons
in the source function.
---------------------------------------------------------
Title: Calculation of Absolute Solar Irradiances and Their Variation
with Solar Activity
Authors: White, O. R.; Fontenla, J.; Fox, P.; Avrett, E. H.; Harvey, K.
1995SPD....26..308W Altcode: 1995BAAS...27..954W
No abstract at ADS
---------------------------------------------------------
Title: The Contribution of Components of Magnetic Activity to
Variations in Solar Irradiance
Authors: Harvey, Karen L.; White, Oran R.
1994AAS...18512309H Altcode: 1994BAAS...26R1523H
The evolution of magnetic fields on the solar surface is the principal
underlying cause of variations observed in the radiative output of
the Sun. These magnetic fields are manifested in a wide range of
structures from large active regions with sunspots to small-scale
network elements. In this paper, we address the identification and
separation of the different components of solar magnetic surface
activity in digitally-recorded full-disk magnetograms. Such quantitative
identification provides a tool in learning how the magnetic field
distribution on the visible solar hemisphere effects variability of
the solar radiation received at the earth. Full-disk, high-resolution
magnetograms from the National Solar Observatory are the input to a
logic chain that defines several classes of magnetic structures: active
regions (plage, sunspots), decaying active regions (active network),
and weak and quiet network. The analysis technique employs several
criteria based on size of the region, its polarity, its maximum and
mean field strength, the magnetic filling factor, and association with
sunspots to differentiate and categorize these magnetic structures
and to create image masks that isolate these structure classes in
both magnetograms or spectral intensity images, such as Ca II K and
He I 10830 spectroheliograms. The final products are the image masks
defining the detailed geometrical shape on the visible solar hemisphere
plus a table of numerical parameters summarizing the properties of
each individual magnetic region. This physical classification is then
used to investigate the pixel-by-pixel relation between the observed
longitudinal component of the magnetic field in the different magnetic
structures and the strength of emission lines showing chromospheric
variability. We will show our progress in defining how each type of
solar magnetic structure contributes the variability of the Sun's
radiative output at two epochs in Solar Cycle 22, Jan-Feb 1992 and
Jun-Jul 1993. Our analysis addresses variability on solar rotation
time scales as well as the slower change from maximum conditions in
1992 to moderate levels of activity in 1993.
---------------------------------------------------------
Title: Thermosphere-Ionsphere-Mesosphere Energetics and Dynamics
(TIMED) Solar EUV Experiment
Authors: Woods, Thomas N.; Rottman, Gary J.; Roble, Raymond G.; White,
O. R.; Solomon, Stanley C.; Lawrence, George M.; Lean, Judith; Tobiska,
W. K.
1994SPIE.2266..467W Altcode:
The Solar EUV Experiment (SEE) selected for the NASA thermosphere,
ionosphere, and mesosphere energetics and dynamics (TIMED) mission
will measure the solar vacuum ultraviolet (VUV) spectral irradiance
from 0.1 to 200 nm. To cover this wide spectral range two different
types of instruments are used: a grating spectrograph for spectra
above 25 nm and an avalanche photodiode for spectra below 25 nm. As
part of the in-flight calibration plan, silicon XUV photodiodes with
thin film filters are used as stable broadband photometers between 0.1
and 40 nm. In addition, redundant spectrograph and avalanche photodiode
capabilities provide calibration checks on the time scale of a month,
and annual rocket underflight measurements provide absolute calibration
checks traceable to NIST photometric standards. All three types of
instruments have been developed and flight proven as part of a NASA
solar EUV irradiance rocket experiment.
---------------------------------------------------------
Title: The solar Ca II K index and the Mg II core-to-wing ratio
Authors: Donnelly, R. F.; White, O. R.; Livingston, W. C.
1994SoPh..152...69D Altcode: 1994IAUCo.143...69D; 1994svs..coll...69D
The 1 å index of the solar Ca II K line is compared with the
core-to-wing ratio of satellite measurements of the Mg II h and k
lines. The correlation coefficient r = 0.976 for the Nimbus-7 Mg II
ratio during solar cycle 21 andr = 0.99 for the NOAA9 Mg II ratio in
cycle 22. Linear regression analysis for the full dynamic range of both
data sets is used to combine the Nimbus-7 and NOAA9 Mg II data. These
relations permit the ground-based Ca K index to estimate the solar
UV flux.
---------------------------------------------------------
Title: Observations of Hysteresis in Solar Cycle Variations among
Seven Solar Activity Indicators
Authors: Bachmann, Kurt T.; White, Oran R.
1994SoPh..150..347B Altcode:
We show that smoothed time series of 7 indices of solar activity
exhibit significant solar cycle dependent differences in their
relative variations during the past 20 years. In some cases these
observed hysteresis patterns start to repeat over more than one
solar cycle, giving evidence that this is a normal feature of solar
variability. Among the indices we study, we find that the hysteresis
effects are approximately simple phase shifts, and we quantify
these phase shifts in terms of lag times behind the leading index,
the International Sunspot Number. Our measured lag times range from
less than one month to greater than four months and can be much
larger than lag times estimated from short-term variations of these
same activity indices during the emergence and decay of major active
regions. We argue that hysteresis represents a real delay in the onset
and decline of solar activity and is an important clue in the search
for physical processes responsible for changing solar emission at
various wavelengths.
---------------------------------------------------------
Title: Panel discussions on Total solar irradiance variations and
the Maunder minimum
Authors: Pap, J. M.; White, O. R.
1994seit.conf..235P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Change in the radiative output of the Sun in 1992 and its
effect in the thermosphere
Authors: White, O. R.; Rottman, G. J.; Woods, T. N.; Knapp, B. G.;
Keil, S. L.; Livingston, W. C.; Tapping, K. F.; Donnelly, R. F.;
Puga, L. C.
1994JGR....99..369W Altcode:
Ground and space measurements of the solar spectral irradiance at radio,
visible, UV, and X ray wavelengths show a large decline in the first 6
months of 1992. This sustained drop in the solar output is important
in understanding the connection between the emergent magnetic flux
on the Sun and the radiative output as well as in understanding the
effects of such change in the upper atmosphere of the earth. We present
preliminary estimates of the observed changes as the means to spur
inquiry into this solar event in the declining phase of solar cycle
22. Typical decreases are 15% in Lyman alpha and 40% in 10.7-cm radio
flux. Mass spectrometer and incoherent scatter model calculations at
600 km in the thermosphere indicate a 30% decrease in the temperature
and a 3X decrease in the density of the thermosphere near the altitude
where both the Upper Atmosphere Research Satellite (UARS) and Hubble
Space Telescope (HST) are flying. Decrease of the orbital period of
the UARS shows the expected effect of decreasing density at flight
altitude. Work in progress indicates that the output change results
from the decline in solar magnetic flux to a lower level of activity
in the southern hemisphere of the Sun.
---------------------------------------------------------
Title: The solar spectral irradiances from X ray to radio wavelengths
Authors: White, O. R.
1993STIN...9425260W Altcode:
Sources of new measurements of the solar EUV, UV, and visible spectrum
are presented together with discussion of formation of the solar
spectrum as a problem in stellar atmospheres. Agreement between the
data and a modern synthetic spectrum shows that observed radiative
variability is a minor perturbation on a photosphere in radiative
equilibrium and local thermodynamic equilibrium (LTE). Newly observed
solar variability in 1992 defines a magnetic episode on the Sun
closely associated with changes in both spectral irradiances and the
total irradiance. This episode offers the opportunity to track the
relationship between radiation and magnetic flux evolution.
---------------------------------------------------------
Title: The Sun in a Non-Cycling State
Authors: White, O. R.; Skumanich, A.; Lean, J.; Livingston, W. C.;
Keil, S. L.
1992PASP..104.1139W Altcode:
Using the Baliunas and Jastrow (1990) study of cyclic variability in
solar-type stars, we transform existing solar data to the stellar HK
irradiance scale and examine the state of the solar chromosphere when a
solar-type star shows little cyclic variability and surface magnestis
m. To reduce the chromospheric emission to levels for G-type stars
showing no chromospheric activity cycles, no only must the sun be
free of plages and network; the brightness of the quiet chromosphere
in the K line must be reduced to levels seen only in 15% of the quiet
Sun area today. In contrast, the present day level of K emission from
the sun places it in the class of most active solar-type stars, far
removed from a non-cycling state. (SECTION: Stars)
---------------------------------------------------------
Title: Solar Ca II K Measurements and Activity Cycles in Solar-Type
Stars
Authors: White, O. R.; Livingston, W. C.; Keil, S. L.
1992sers.conf..160W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sun-as-a-star spectrum variability.
Authors: Livingston, William; Donnelly, Richard F.; Grigor'ev, Viktor;
Demidov, M. L.; Lean, Judith; Steffen, Matthias; White, Oran R.;
Willson, Richard L.
1991sia..book.1109L Altcode:
The Sun is observed as a star in order to determine luminosity change,
detect minute variability in average granulation and facular signals,
and to use as a standard against which other stars may be compared. In
this regard, topics discussed include: total irradiance variability
as measured from space by the Activity Cavity Radiometer Irradiance
Monitor and Earth Radiation Budget radiometers; Fraunhofer line heights
of formation and examples of their variability in visible wavelengths;
ultraviolet and extreme ultraviolet irradiance variability as observed
from space; the magnetic origin of irradiance change; and the observed
mean magnetic field of the Sun.
---------------------------------------------------------
Title: Comparison of 10.7 cm radio flux with SME solar Lyman
alpha flux
Authors: Barth, Charles A.; Tobiska, W. Kent; Rottman, Gary J.; White,
Oran R.
1990GeoRL..17..571B Altcode:
Measurements of the solar Lyman alpha flux that were made over a
seven-and-one-half-year period between October 11, 1981 and April
13, 1989 have been compared with ground-based measurements of the
solar 10.7 cm radio flux made over the same time period. There is a
long-term correlation between these two measures of solar flux during
the declining part of the solar cycle. During the solar minimum period,
there is only a poor correlation between the two solar fluxes because
the 10.7 cm radio flux reaches a minimum of 65 × 10<SUP>-22</SUP>
W m<SUP>-2</SUP> Hz<SUP>-1</SUP> and does not vary below this value
while the Lyman alpha flux continues to decline and show long-term
and short-term variations. During the early ascending phase of the
new solar cycle, there is again a correlation between the two fluxes,
although the constant of proportionality between the two is different
from the constant during the declining phase of the previous solar
cycle. Somewhat later, during the period November 25, 1988 — April
13, 1989 (last period when observations of Lyman alpha were made)
a medium-term correlation exists and the proportionality of the two
indices is once again similar to what it was during the declining phase
of the previous solar cycle. A study of the correlation of the 10.7 cm
flux with the Lyman alpha for a 999-day period during the declining
phase showed that for the short-term (27-day) variation there is a
correlation between the two fluxes but the proportionality between them
varies from one solar rotation to the next. The conclusion is that the
solar 10.7 cm radio flux is not a useful index for the prediction of
solar Lyman alpha flux for the short-term, 27-day variations.
---------------------------------------------------------
Title: Estimation of the solar Lyman alpha flux from ground based
measurements of the Ca II K line
Authors: White, O. R.; Rottman, G. J.; Livingston, W. C.
1990GeoRL..17..575W Altcode:
Measurements of the solar Lyman alpha and CaII K from October 1981 to
April 1989 show a strong correlation (r=.95) that allows estimation of
the Lyman alpha flux at 1 AU from 1975 to December 1989. Our estimated
Lyman alpha strength of 3.9 × 10<SUP>11</SUP>±.15 × 10<SUP>11</SUP>
photons/s cm<SUP>2</SUP> on 7 December 1989 is at the same maximum
levels seen in Cycle 21. Relative to other UV surrogates (sunspot
number, 10.7 cm radio flux, and HeI 10830 line strength), Lyman alpha
estimates computed from the K line track the SME measurements well
from solar maximum, through solar minimum, and into Cycle 22.
---------------------------------------------------------
Title: Estimation of the solar Lyman alpha flux from ground based
measurements of the CA II K line
Authors: Rottman, G. J.; Livingston, W. C.; White, O. R.
1990GeoRL..17..575R Altcode:
Measurements of the solar Lyman alpha and Ca II K from October 1981
to April 1989 show a strong correlation (r = 0.95) that allows
estimation of the Lyman alpha flux at 1 AU from 1975 to December
1989. The estimated Lyman alpha strength of 3.9 x 10 to the 11th +
or - 0.15 x 10 to the 11th photons/s sq cm on December 7, 1989 is
at the same maximum levels seen in Cycle 21. Relative to other UV
surrogates (sunspot number, 10.7 cm radio flux, and He I 10830 line
strength), Lyman alpha estimates computed from the K line track the
SME measurements well from solar maximum, through solar minimum,
and into Cycle 22.
---------------------------------------------------------
Title: The Solar Observing Program of the HAO/Lowell/AFGL
Solar-Stellar Spectrophotometry Project (S<SUP>3</SUP>)
Authors: Mihalas, D.; Radick, R.; Lockwood, G. W.; Gilliland, R. L.;
Ramsey, L. W.; Fisher, R.; Livingston, W.; White, O. R.
1988BAAS...20Q1008M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrum Line Intensity as a Surrogate for Solar Irradiance
Variations
Authors: Livingston, W. C.; Wallace, L.; White, O. R.
1988Sci...240.1765L Altcode:
Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant
measurements from 1980 to 1986 are compared with ground-based,
irradiance spectrophotometry of selected Fraunhofer lines. Both data
sets were identically sampled and smoothed with an 85-day running mean,
and the ACRIM total solar irradiance (S) values were corrected for
sunspot blocking (S<SUB>c</SUB>). The Strength of the mid-photospheric
manganese 539.4-nanometer line tracks almost perfectly with ACRIM
S<SUB>c</SUB>. Other spectral features formed high in the photosphere
and chromosphere also track well. These comparisons independently
confirm the variability in the ACRIM S<SUB>c</SUB> signal, indicate
that the source of irradiance is faculae, and indicate that ACRIM
S<SUB>c</SUB> follows the 11-year activity cycle.
---------------------------------------------------------
Title: Short term variability between 120 and 300 MM from Solar
Mesosphere Explorer (SME) observations
Authors: Simon, P. C.; Rottman, G. J.; White, O. R.; Knapp, B. G.
1988STIN...8829709S Altcode:
Solar Mesosphere Explorer solar irradiance data was analyzed by
fast Fourier transform (FFT) to isolate the solar flux modulation
related to the 27-day solar rotation. The 27-day rotation period is
confirmed as the dominant variation in time series of solar spectral
irradiance. This feature is most pronounced at shorter wavelengths,
especially Lyman-alpha, decreasing toward longer wevelengths. The FFT
analysis reveals the amplitude of the 27-day variation in the data
at all wavelengths, 120 to 300 nm, at all times between Jan. 1982 and
Dec. 1986.
---------------------------------------------------------
Title: Variability of the Solar UV Flux (120-300 nm) in the Declining
Phase of Solar Cycle 21
Authors: White, O. R.; Rottman, G. J.
1987BAAS...19Q.926W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variability of chromospheric and photospheric lines in solar
cycle 21
Authors: White, O. R.; Livingston, W. C.; Wallace, L.
1987JGR....92..823W Altcode:
A program to measure the variability of solar spectrum lines in
the visible wavelengths began in 1974 at Kitt Peak Observatory and
continues as we approach the minimum between solar cycles 21 and
22. Both photospheric and chromospheric lines are measured on a
monthly basis using an optical system that permits observation of
the irradiance from the full solar disk as well as a smaller region
near the center of the sun's disk. The full disk measurements of the
Ca II K line quantify the increase and subsequent decrease in line
flux with the change in solar activity. However, spectra of quiet
regions at disk center show little if any variation throughout the
cycle. Photospheric lines separate into two classes according to their
variability: low-excitation lines of neutral metals resemble the K
line in the shape of their solar cycle variability curve, but weaker
lines formed deeper in the photosphere show no variation from 1974 to
1986. All of these findings point to solar activity as the source of
the observed spectral variations, but the largest radiometric effects
occur in chromospheric lines, with little or no evidence of variability
in lines found deep in the photosphere.
---------------------------------------------------------
Title: Variability of chromospheric and photospheric lines in solar
cycle 21
Authors: Livingston, W. C.; Wallace, L.; White, O. R.
1987JGR....92..823L Altcode:
The variability of solar spectrum lines in the visible wavelengths
during solar cycle 21 is examined. Full disk measurements of the
photospheric and chromospheric lines are analyzed. The variation in
granular convection at the sun's surface is studied. It is observed for
the chromospheric lines that increases and decreases in line flux for
Ca II K correspond to the solar activity. The data for the photospheric
lines reveal that only low-excitation lines of neutral metals display
short-term variability.
---------------------------------------------------------
Title: Variation of the Calcium K Line Profile Over Solaar Cycle 21.
Authors: White, O. R.; Livingston, W. C.
1985BAAS...17..640W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sun-as-a-star spectrum variability.
Authors: Livingston, W.; Holweger, H.; Wallace, L.; White, O. R.
1985MPARp.212..184L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The sun as a star - Three-component analysis of chromospheric
variability in the calcium K line
Authors: Skumanich, A.; Lean, J. L.; Livingston, W. C.; White, O. R.
1984ApJ...282..776S Altcode:
A three-component model of the solar cycle variability of the Ca II
K emission is developed using extant contrast and fractional area
parameters for (1) cell, (2) network, and (3) plage components that
are resolution-consistent. A fit has been achieved for the quiet-sun
Ca II K emission (at solar minimum) as observed by White and Livingston
(1981) with cell and network features alone using extant limb-darkening
laws. The occurrence of plages during the growth of the solar cycle
was found to be insufficient to account for the cycle increase in
the K emission and required the introduction of additional network in
excess of the quiet-sun value. The implications of, and evidence for,
such an active network are discussed.
---------------------------------------------------------
Title: Modelling solar spectral irradiance variations at ultraviolet
wavelengths.
Authors: Lean, J. L.; Livingston, W. C.; White, O. R.; Skumanich, A.
1984NASCP2310..253L Altcode: 1984siva.work..253L
The authors examine solar ultraviolet irradiance variations with solar
activity by using a three component model of the Ca II K chromospheric
emission. This model, developed from ground based observations of the
location, area and relative intensity of Ca II K plage, in conjunction
with measurements throughout solar cycle 21 of the full disc Ca II
K emission, includes the contributions to the ultraviolet flux from
both plage and active network emission. Evolution and rotation of
the plage regions on the solar disc produce a 27-day modulation of
the UV flux. Over longer time scales, such as the eleven year solar
cycle, changes in the active network are an important source of UV
flux variability.
---------------------------------------------------------
Title: Fraunhofer line variability, 1975-1983
Authors: Livingston, W.; Holweger, H.; White, O. R.
1984stp..conf..427L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A three-component model of the variability of the solar
ultraviolet flux: 145-200 nM
Authors: Lean, J. L.; White, O. R.; Livingston, W. C.; Heath, D. F.;
Donnelly, R. F.; Skumanich, A.
1982JGR....8710307L Altcode:
A three-component model has been developed to examine the variation
with solar activity of the far ultraviolet irradiance between 145 and
200 nm. This model is based on spatially resolved observations of
the Call K chromosphere and includes the contributions to the full
disk flux from both plage and active network emission. The 27-day
modulation of the ultraviolet flux is explained by the evolution and
rotation of the plage regions on the solar disc. Over the longer time
scale of the eleven-year cycle it is essential that changes in the
active network arising from the decay of plage regions also be solar
flux is it possible to simultaneously reproduce the 27-day variability
observed by the solar backscatter ultraviolet experiment on the Nimbus 7
satellite and the changes from the minimum to the maximum of the solar
activity cycle observed by the rocket experiments of the Laboratory
for Atmospheric and Space Physics and by the extreme ultraviolet
spectrometer on the Atmospheric Explorer E satellite. It is shown that
the AE-E experiment measured a smaller solar cycle variability for the
ultraviolet irradiances than is predicted by the model calculations
because of the spatially restricted field of view of this instrument.
---------------------------------------------------------
Title: The vertical propagation of waves in the solar atmosphere. II
Phase delays in the quiet chromosphere and cell-network distinctions
Authors: Lites, B. W.; Chipman, E. G.; White, O. R.
1982ApJ...253..367L Altcode:
The differences in the phase of the velocity oscillations between
a pair of chromospheric Ca II lines was measured using the Vacuum
Tower Telescope at the Sacramento Peak Observatory. The observed phase
differences indicate that the acoustic modes are trapped or envanescent,
rather than propagating, in the chromosphere. Systematic distinctions
are found in the phase delays between quiet network and cell interior
regions for both intensity and velocity oscillations in photospheric and
chromospheric lines. The theory of linear perturbations in an isothermal
atmosphere is invoked to interpret these differences. From this analysis
it is found that one or more of the following explanations is possible:
(1) the radiative damping is more effective in the network than in the
cell interior; (2) the network features exclude oscillations of large
horizontal wavenumber; or (3) the scale height of the chromosphere is
larger in the network than in the cell interior.
---------------------------------------------------------
Title: Photoelectric observations of propagating sunspot oscillations
Authors: Lites, B. W.; White, O. R.; Packman, D.
1982ApJ...253..386L Altcode:
Repeated intensity and velocity images of a large, isolated sunspot in
both the chromospheric Ca II 8542 A and photospheric Fe I 5576 line were
performed. It is shown by means of a movie of the digital data for the
chromospheric line that a relationship exists between the propagating
umbral disturbances and the running penumbral waves. Power spectra of
the oscillations show a sharp peak at a period of about 170 sec in both
the velocity and intensity signals, and the oscillations at any point
in the sunspot are found to be very regular. The phase relationship
between the velocity and the intensity of the chromospheric oscillations
contrasts with that for the quiet sun. The mechanical energy flux
carried by the observed umbral disturbances does not appear to be a
significant contributor to the overall energy budget of the sunspot
or the surrounding active region.
---------------------------------------------------------
Title: Observed variability in the Fraunhofer line spectrum of solar
flux, 1975 - 1980
Authors: Livingston, W.; Holweger, H.; White, O. R.
1981NASCP2191...95L Altcode: 1981vsc..conf...95L
Over the five years double-pass spectrometer observations of the
Sun-as-a-star revealed significant changes in line intensities. The
photospheric component weakened linearly with time 0 to 2.3%. From a
lack of correlation between these line weakenings and solar activity
indicators like sunspots and plage, a global variation of surface
properties is inferred. Model-atmosphere analysis suggests a slight
reduction in the lower-photospheric temperature gradient corresponding
to a 15% increase in the mixing length within the granulation
layer. Chromospheric lines such as Ca II H and K, Ca II 8543 and the CN
band head weaken synchronously with solar activity. Thus, the behavior
of photospheric and chromospheric lines is markedly different, with
the possibility of secular change for the former.
---------------------------------------------------------
Title: Solar luminosity variation. III - Calcium K variation from
solar minimum to maximum in cycle 21
Authors: White, O. R.; Livingston, W. C.
1981ApJ...249..798W Altcode:
Completion of measurements of the full disk Ca II H and K profiles
from minimum to maximum, in the current solar cycle 21, shows that
while the central intensity of the K line increases by 30% on the
average, a peak change of +40% was recorded near the maximum of solar
activity in late 1979. The 1 A K index shows a smaller, corresponding
increase of 18%, and it is suggested that these changes are due to the
occurrence of solar plages on the visible solar hemisphere. Spectral
features formed above the temperature minimum are closely related in
their variability, but not as well related to changes in the strength
of narrow photospheric lines and the K<SUB>1</SUB> wings. It is found
that Ca II variability correlates closely with the plage index, the
Zurich sunspot number, and the Ottawa 10 cm flux measurements.
---------------------------------------------------------
Title: Photoelectric Observations of Propagating Sunspot Oscillations
Authors: Lites, B. W.; White, O. R.; Packman, D.
1980BAAS...12..897L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variation of Ca II K from Minimum to Maximum in Cycle 21
Authors: White, O. R.
1980BAAS...12..898W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Temporal and spatial fluctuations in strengths and widths of
C IV and SI II lines observed with OSO 8
Authors: Athay, R. G.; White, O. R.
1980ApJ...240..306A Altcode:
The spatial and temporal fluctuations in widths and strengths
are examined for three EUV lines: C IV, wavelength 1548 and Si II,
wavelengths 1816.93 and 1817.45 observed with an effective aperture of
2 x 20 arcsec and with time resolution less than 30 s. Three classes
of fluctuations with substantial amplitude are identified: (1) short
term fluctuations with a characteristic fluctuation time near 5 min,
(2) intermediate term fluctuations with a characteristic time of 30
min or longer, and (3) large scale spatial fluctuations associated
with supergranule cell, network, and plage structure.
---------------------------------------------------------
Title: Impulsive EUV bursts observed in C iv with OSO-8
Authors: Athay, R. G.; White, O. R.; Lites, B. W.; Bruner, E. C., Jr.
1980SoPh...66..357A Altcode:
Time sequences of profiles of the λ1548 line of C IV containing 51 EUV
bursts observed in or near active regions are analyzed to determine the
brightness, Doppler shift and line broadening characteristics of the
bursts. The bursts have mean lifetimes of approximately 150s, and mean
increases in brightness at burst maximum of four-fold as observed with a
field of view of 2″ × 20″. Mean burst diameters are estimated to be
3″, or smaller. All but three of the bursts show Doppler shifts with
velocities sometimes exceeding 75 km s<SUP>−1</SUP>; 31 are dominated
by red shifts and 17 are dominated by blue shifts. Approximately
half of the latter group have red-shifted precursors. We interpret
the bursts as prominence material, such as surges and coronal rain,
moving through the field of view of the spectrometer.
---------------------------------------------------------
Title: Temporal and Spatial Fluctuations in Widths of Solar EUV Lines
Authors: Athay, R. G.; White, O. R.
1980LNP...114...53A Altcode: 1980IAUCo..51...53A; 1980sttu.coll...53A
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric oscillations observed with OSO 8. IV. Power
and phase spectra for C IV.
Authors: Athay, R. G.; White, O. R.
1979ApJ...229.1147A Altcode:
OSO 8 time series of profiles of the C IV line at 1548 A and for the
continuum near 1900 A are analyzed to determine the properties of
solar oscillations in the lower transition region and to obtain phase
delays between the temperature-minimum region and the lower transition
region. Power-spectrum and phase-spectrum analyses of 30-min data
segments are performed. It is found that: (1) short-duration periodic
oscillations in the 3-5 mHz band occur in about 20% of the 30-min
segments; (2) these oscillations are of solar origin and have phase
delays with height characteristic of waves propagating vertically
with phase speeds close to the sound speed; (3) maximum intensity
lags maximum redshift by about 120 deg and leads maximum blueshift
by approximately 60 deg; (4) most of the solar fluctuations in the C
IV line are low-amplitude aperiodic events in which the fluctuation
in intensity is correlated with blueshift; and (5) the intensity
fluctuations are proportional to mean intensity (A) in bright solar
features but to the square root of A in quiet solar regions.
---------------------------------------------------------
Title: Chromospheric Oscillations Observed with OSO 8. II. Average
Phase Spectra for SI II.
Authors: White, O. R.; Athay, R. Grant
1979ApJS...39..347W Altcode:
Time series of intensity and Doppler-shift fluctuations in the Si II
emission lines λ1816.93 and λ1817.45 are Fourier analyzed to determine
the frequency variation of phase differences between intensity and
velocity and between these two lines formed 300 km apart in the middle
chromosphere. Average phase spectra show that oscillations between
2 and 9 mHz in the two lines have time delays from 35 to 40s, which
is consistent with the upward propagation of sound waves at 8. 7.5
km s<SUP>-1</SUP>. In this same frequency band near 3 mHz, maximum
brightness leads maximum blueshift by 600. At frequencies above 11 mHz
where the power spectrum is flat, the phase differences are uncertain,
but approximately 65% of the cases indicate upward propagation. At these
higher frequencies, the phase lead between intensity and blue Doppler
shift ranges from 0° to 180° with an average value of 90°. However,
the phase estimates in this upper band are corrupted by both aliasing
and randomness inherent to the measured signals. Phase differences in
the two narrow spectral features seen at 10.5 and 27 mHz in the power
spectra are shown to be consistent with properties expected for aliases
of the wheel rotation rate of the spacecraft wheel section.
---------------------------------------------------------
Title: Chromospheric oscillations observed with OSO 8. I. Basic
measurements and analytical methods.
Authors: White, O. R.; Athay, R. G.
1979ApJS...39..317W Altcode:
Time series of solar EUV line profiles observed with OSO 8 have
fluctuations arising from instrumental, satellite, and solar
sources. The fluctuations are partly noiselike, partly from long-term
drifts, and partly from periodic oscillations. The Sun contributes to
all three types of fluctuations. However, instrumental effects also
contribute to the noiselike fluctuations and long-term drifts, and
the satellite wheel rotation induces spurious oscillations. Analytical
procedures are discussed for applying Fourier transform techniques and
related statistical tests to isolate the different types of fluctuations
and, in particular, to study the solar oscillations. Strong solar
oscillations are identified near 3 mHz, and aliases of the wheel
rotation frequency are identified at 10.5 and 27 mHz.
---------------------------------------------------------
Title: Chromospheric Oscillations Observed with OSO 8. II. Average
Power Spectra for SI II.
Authors: Athay, Grant R.; White, O. R.
1979ApJS...39..333A Altcode:
Several hundred time series of Si II emission-line profiles at λ1816.93
and λ1817.45 have been analyzed to determine the mean power spectrum of
chromospheric oscillations at a height of about 1200 km in the middle
solar chromosphere. Time series of line intensity and Doppler shift
measured on the solar disk have power spectra with very similar shapes,
i.e., a broad power maximum extending from 2.5 to about 9 mHz superposed
on a flat noise spectrum extending to beyond 30 mHz. Comparison of
power spectra for quiet and active regions shows the broad peak near
3 mHz to narrow and shift to lower frequencies as the line strengths
increase in plages and bright network elements. Statistical tests
suggest that all of the power in the 3 mHz peak is of solar origin and
that somewhat less than one-half of the flat noise spectrum arises from
solar fluctuations. It is shown that gravity waves are unimportant in
the middle chromosphere and that sound' waves at frequencies above about
3 mHz should propagate. The total energy flux in solar oscillations
at all frequencies up to 30 mHz is estimated to be 1 × l0<SUP>4</SUP>
ergs cm<SUP>-2</SUP> s<SUP>-1</SUP> for the average Sun, which is too
small to heat the upper chromosphere and corona.
---------------------------------------------------------
Title: Chromospheric and coronal heating by sound waves.
Authors: Athay, R. G.; White, O. R.
1978ApJ...226.1135A Altcode:
An upper limit to the energy flux in sound waves in the chromosphere
is obtained from observational data, and the required heat input to
the chromosphere is examined. The height dependence of both the energy
flux in sound waves and the required heat input is analyzed. It is
found that the heat input has two maxima and that the flux in sound
waves is too low to produce the second maximum. It is concluded
that the low chromosphere may be heated by sound waves but that a
different mechanism heats the upper chromosphere, transition region,
and corona. The possibility is considered that the microturbulence
derived from line broadening is produced by Alfven waves rather than
sound waves.
---------------------------------------------------------
Title: Solar luminosity variation: II. Behavior of calcium H and K
at solar minimum and the onset of cycle 21.
Authors: White, O. R.; Livingston, W.
1978ApJ...226..679W Altcode:
A program for measuring the solar cycle variation of the profiles of Ca
ii H and K, using the McMath double-pass spectrometer, is described. The
observations are made both at disk center and in integrated light ("the
Sun as a star"). During the 2 year epoch covering minimum activity,
from 1974 October to 1976 October, the integrated light equivalent width
of K as bounded by a 1 A band centered on the line (the K-index) showed
no significant variation (cr = 0.22%). Internal error for a single day,
over a 7li5 period, is a = 0.066%. During 1977, apparently in response
to the onset of cycle 21 activity, the K-index increased by 2.7%, while
the central intensity of K3 rose by 5.7%. These changes are traceable
in detail to plages on the disk. Center disk observations of the quiet
regions containing network and supergranulation cells have shown no
change. Subject headings: Ca ii emission - Sun: activity - Sun: plages
---------------------------------------------------------
Title: Solar EUV emission line profiles of Si ii and Si iii and
their center to limb variations
Authors: Nicolas, K. R.; Brueckner, G. E.; Tousey, R.; Tripp, D. A.;
White, O. R.; Athay, R. G.
1977SoPh...55..305N Altcode:
Spectral line profiles of Si II and Si III are presented which were
observed both at solar center and near the quiet solar limb with the
Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute
intensities and line profiles are derived from the photographic data. A
brief discussion is given of their center-to-limb variations and of
the optical thickness of the chromosphere in these lines. Nonthermal
broadening velocities are found for the optically thin lines from
their full width at half maximum intensity (FWHM).
---------------------------------------------------------
Title: Note on the Distribution of Sunspots Between the North and
South Solar Hemispheres and its Variation with the Solar Cycle
Authors: White, Oran R.; Trotter, Dorothy E.
1977ApJS...33..391W Altcode:
Construction of the time history of the variation of sunspot areas for
both solar hemispheres during the period from 1874 to 1971 indicates
that, on the average, the solar magnetic cycle occurs uniformly in
the north and south solar hemispheres. Subject heading: Sun: sunspots
---------------------------------------------------------
Title: Phase Differences Between Intensity and Doppler-Shift and
Between Two EUV Emission Lines of SI II for 300 SEC and 95 SEC
Chromospheric Oscillations.
Authors: White, O. R.; Athay, R. G.
1977uxsa.coll...13W Altcode: 1977IAUCo..43...13W
No abstract at ADS
---------------------------------------------------------
Title: High Resolution Observations of Solar Velocity Fields from
Spacecrafts and Rockets, Using Spectroscopic Methods
Authors: White, O. R.
1977ebhs.coll...75W Altcode: 1977IAUCo..36...75W
No abstract at ADS
---------------------------------------------------------
Title: The solar output and its variation
Authors: White, Oran R.
1977soiv.conf.....W Altcode: 1977soiv.book.....W; 1977QB531.S58......
No abstract at ADS
---------------------------------------------------------
Title: Power Spectrum Analysis of Time Series in Positions and
Intensities of Solar EUV Lines Observed with OSO-8.
Authors: Athay, R. G.; White, O. R.
1977uxsa.coll...12A Altcode: 1977IAUCo..43...12A
No abstract at ADS
---------------------------------------------------------
Title: Discussion following the presentation by F. Deubner
Authors: White, O. R.
1977ebhs.coll...69. Altcode: 1977IAUCo..36...69.
No abstract at ADS
---------------------------------------------------------
Title: Preface
Authors: White, Oran R.; Newkirk, Gordon, Jr.
1977soiv.confD...7W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary results from the Orbiting Solar Observatory 8:
transition-zone dynamics over a sunspot.
Authors: Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman,
G. J.; Shine, R. A.; Athay, R. G.; White, O. R.
1976ApJ...210L..97B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary results from the Orbiting Solar Observatory 8:
velocities in the solar chromosphere observed in the Si II lambda
1816 line.
Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites,
B. W.; Rottman, G. J.; Athay, R. G.; White, O. R.
1976ApJ...210L.103C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary results from the Orbiting Solar Observatory 8:
observations of optically thin lines.
Authors: Shine, R. A.; Roussel-Dupre, D.; Bruner, E. C., Jr.; Chipman,
E. G.; Lites, B. W.; Rottman, G. J.; Athay, R. G.; White, O. R.
1976ApJ...210L.107S Altcode:
The University of Colorado spectrometer aboard OSO 8 has measured
the high temperature C IV resonance lines (at 1548 and 1551 A) and
the Si IV resonance lines (at 1393 and 1402 A) formed in the solar
chromosphere-corona transition region. Preliminary results include
studies of mean profiles, a comparison of cell and network profiles,
and the behavior of the lines at the extreme solar limb.
---------------------------------------------------------
Title: Preliminary results from the Orbiting Solar Observatory 8:
persistent velocity fields in the chromosphere and transition region.
Authors: Lites, B. W.; Bruner, E. C., Jr.; Chipman, E. G.; Shine,
R. A.; Rottman, G. J.; White, O. R.; Athay, R. G.
1976ApJ...210L.111L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: INVITED PAPER - A Summary of New Observations of the
Chromospheric-Coronal Transition Region from OSO-8
Authors: White, O. R.
1976BAAS....8..376W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Periodic Fluctuations in the Solar Transition Zone
Authors: Bruner, E. C., Jr.; Chipman, E. G.; Shine, R. A.; Lites,
B. W.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.; White, O. R.
1976BAAS....8Q.313B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Model Calculations of Chromospheric Lines Observed by OSO-8
Authors: Shine, R. A.; Lites, B. W.; Chipman, E. G.; Rousel-Dupree,
D.; Bruner, E. C., Jr.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.;
White, O. R.
1976BAAS....8..331S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Velocities in the Solar Chromosphere Observed in the CII
λ1336 Line
Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites,
B. W.; Rottman, G. J.; Orrall, F. Q.; White, O. R.; Athay, R. G.
1976BAAS....8..312C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: OSO-8 Observations of Mean Vertical Motions in the Solar
Transition Region
Authors: Roussel-Dupree, D. C.; Shine, R. A.; Chipman, E. G.; Bruner,
E. C., Jr.; Lites, B. W.; Rottman, G. J.; Orrall, F. Q.; Athay, R. G.;
White, O. R.
1976BAAS....8..312R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Short Period Chromospheric Oscillations Observed with OSO-8
Authors: Athay, R. G.; White, O. R.; Bruner, E. C., Jr.; Chipman,
E. G.; Lites, B. W.; Shine, R. A.; Orrall, F. Q.
1976BAAS....8..312A 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.
1976BAAS....8..311N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Repetitive Brightenings in Active Region Transition Zone
Lines as Observed with OSO-8
Authors: Lites, B. W.; Hansen, E. R.; Shine, R. A.; Chipman, E. G.;
Bruner, E. C., Jr.; Orrall, F. Q.; Athay, R. G.; White, O. R.; Rottman,
G. J.
1976BAAS....8Q.331L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar activity (Activité solaire).
Authors: Newkirk, G.; Dunn, R. B.; Mehltretter, P.; MacQueen, R.;
Bonnet, R. M.; White, O. R.; Fokker, A. D.; Zwaan, C.; Bruzek, A.;
Durrant, C.; Grossmann-Doerth, U.; Mehltretter, J. P.; Svestka, Z.;
de Feiter, L. D.; Tandberg-Hanssen, E.; Howard, R.; Stix, M.; Pneuman,
G. W.; Hundhausen, A. J.; Sawyer, C.; Simon, P.
1976IAUTA..16b..13N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Koobi Fora experiment: continuum observations of solar
spicules during the 30 June 1973 eclipse.
Authors: Kopp, R. A.; White, O. R.; Baur, T. G.
1975A&A....44..299K Altcode:
Summary. Limb observations of chromospheric spicules in the continuum
near 4700 A were obtained during the solar eclipse of 30 June 1973,
in an experiment conducted close to the edge of the path of totality
in northern Kenya. The experimental apparatus and observing techniques
which were employed are described and some results of the data analysis
are presented. The observations indicate that spicules may extend
to substantially greater heights in the corona than one infers from
filtergrams and spectra of the stronger spicule emission lines. The
derived continuum intensity distribution within a single chromospheric
emission feature is interpreted as being due to the collective effect
of one or more spicules within the "blur circle" defined by the
quality of the seeing during eclipse. This intensity distribution,
when corrected for the probable number of spicules contributing
to the observed emission at each height, leads to a straightforward
determination of the spicule electron density as a function of height,
since the continuum emission is almost certainly the result of Thomson
scattering of photospheric radiation by free electrons. The inferred
densities at heights less than 10000 km are in reasonable agreement with
previous determinations. Key words: eclipse electron scattering spicules
---------------------------------------------------------
Title: High Resolution Spectroscopy From Orbiting Solar Observatory
VIII: Transition Zone Dynamics Over a Sunspot
Authors: Bruner, E. C., Jr.; Chipman, E. G.; Lites, B. W.; Rottman,
G. J.; Shine, R. A.; Athay, R. G.; White, O. R.
1975BAAS....7..522B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Persistent Velocity Fields in the Middle Chromosphere
Authors: Lites, B. W.; Bruner, E. C., Jr.; Chipman, E. G.; Shine,
R. A.; Rottman, G. J.; White, O. R.; Athay, R. G.
1975BAAS....7..522L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Velocities in the Solar Chromosphere Observed in the Si II
λ1816 Line
Authors: Chipman, E. G.; Bruner, E. C., Jr.; Shine, R. A.; Lites,
B. W.; Rottman, G. J.; White, O. R.; Athay, R. G.
1975BAAS....7..522C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: OSO-8 Observations of Optically Thin Lines
Authors: Shine, R. A.; Rousell-Dupree, D.; Bruner, E. C., Jr.; Chipman,
E. G.; Lites, B. W.; Rottman, G. J.; Athay, R. G.; White, O. R.
1975BAAS....7Q.552S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comments on the Solar Spectrum and the Possible Origins of
Its Variability
Authors: White, O. R.
1975scea.conf..288W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Temporal Variations of the Magnetic Field in Sunspots
Authors: Schultz, R. B.; White, O. R.
1974SoPh...35..309S Altcode:
We obtained simultaneous spectra with a spatial resolution of 1/2″
and a temporal resolution of 15 s in Hα, Ca II-K, CaII 8542 Å, and
three FeI lines of the sunspot group responsible for the large flares
of August, 1972 (McMath No. 11976). A time series taken 1972, August 3
in the FeI 6173 Å Zeeman sensitive line was analyzed for oscillations
of field strength and the angle between the field and the line of sight,
and for changes of the field associated with the Ca II-K umbral flashes
discovered by Beckers and Tallant (1969). The power spectra show no
significant peaks, conflicting with the results of Mogilevskii et
al. (1972) who reported oscillations in the longitudinal component of
the field strength with periods of 56, 90, and 150 s. Changes in the
field were not observed to be correlated with the occurrence of umbral
flashes. These results place restrictions on magnetic modes of energy
transport between the photospheric layers and the chromospheric layers
where the umbral flashes are observed.
---------------------------------------------------------
Title: Detection of Small Scale Structure in Metal Lines at the
Extreme Solar Limb
Authors: Livingston, W. C.; White, O. R.
1974SoPh...39..289L Altcode:
We describe a tangential limb spectrum at 5870 Å which geometrically
probes the high photosphere through the low chromosphere. Velocity
and brightness structures with sizes ranging from 500 to 1500
km are present in the stronger emission lines. Such structure is
consistent between the Fe I and Ba II lines, and emission knots in
these lines coincide with continuum bright streaks. But no correlation
is evident between structure in the He I D<SUB>3</SUB> line, emission
in the Na I D<SUB>2</SUB> line, and emission in the Fe I and Ba II
lines as a group. Two classes of near-horizontal velocity structure
are seen in the height range from 0 to 500 km above the limb: υ
≤ 1 km s<SUP>−1</SUP> for the weaker metals and υ ∼ 7-10 km
s<SUP>−1</SUP> for the Na I line. Differences in line opacity are
suggested as the cause of the low correlation between the fine structure
in the various lines.
---------------------------------------------------------
Title: Inversion of the Solar Limb-darkening Equation in the Presence
of Noise
Authors: Kunasz, C. V.; Jefferies, J. T.; White, O. R.
1973A&A....28...15K Altcode:
Summary. We discuss the formulation and application of the
Phillips-Twomey method for inverting the integral equation of solar
limb darkening in the presence of noise. We show, through numerical
experiments, that the method can be successfully applied to real data
and that it has clear advantages over those standard methods that
rely on the expression of the source function in an analytic form. In
addition, we briefly discuss some potentially interesting methods
of a different kind, which are still under examination. Key words:
solar limb-darkening - Phillips-Twomey inversion - source function
---------------------------------------------------------
Title: Analysis of the 5 min Oscillatory Photospheric Motion. I:
A Problem in Waveform Classification
Authors: White, O. R.; Cha, M. Y.
1973SoPh...31...23W Altcode:
Four Mt. Wilson measurements (T>4 h) of the photospheric motion
at one point on the Sun are shown to have the characteristics
of a narrow-band random process. The motion is shown to have a
characteristic correlation time of 23 min and a mean power spectrum
that is a smooth, single-peaked function centered at 3.4 mHz. In order
to make this classification we use the analytic signal to estimate
the amplitude, phase, and frequency as functions of time. The power
spectrum analysis differs from the common approaches in that it uses
the theoretical expression for the mean spectrum for a sequence of
random pulses. Because of the random nature of the motion, we doubt
the existence of more than one eigenfrequency characteristic of the
photosphere as a whole. Likewise, any description of the observed
motion in terms of simple deterministic functions will be inadequate
for the data used here.
---------------------------------------------------------
Title: Analysis of the 5 min Oscillatory Photospheric Motion. II:
Statistical Analysis of the Oscillation as a Narrow-Band Random
Process
Authors: Cha, M. Y.; White, O. R.
1973SoPh...31...55C Altcode:
A more objective statistical technique is applied directly to the four
time series used in Paper I. The empirical probability density functions
indicate that the measurements are realizations of a narrow-band random
process with Gaussian statistics. This result allows quantitative
statistical use of the mean autocorrelation function. For example,
a characteristic correlation time is 23 min, and the motion becomes
statistically uncorrelated over intervals greater than 40 min. The
mean autocorrelation function is found to be free of secondary maxima
that have been so troublesome in other analyses. The question raised
in this paper is whether our statistical model of the motion as a
Gaussian random process is also applicable to smaller regions on the
order of 1″ to 2″ in size.
---------------------------------------------------------
Title: High Spatial and Temporal Resolution Observations of the
Magnetic Field in a Sunspot.
Authors: Schultz, R. B.; White, O. R.; Beckers, J. M.
1973BAAS....5..339S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Inversion of the Limb Darkening Equation in the Presence
of Noise
Authors: Kunasz, Chela V.; Jefferies, J. T.; White, O. R.
1973BAAS....5S.274K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Spectra of Near-Vertical Structures on the Solar Disk
Authors: White, O. R.
1972SoPh...27...27W Altcode:
Bright emission arches in the spectra of Hα and the Ca II (H and K
lines) are identified as the spectroscopic picture of the chromospheric
network as it appears near the solar limb. Analysis of the geometrical
properties of these spectroscopic arches indicates that the average
network is a diverging sheet with a divergence angle of ∼ 50°. This
sheet extends to 2600 km and 2000 km as an opaque emission feature in
Hα and the Ca II (H and K) lines, respectively.
---------------------------------------------------------
Title: A First Order Analysis of Variations of the Limb Darkening
and the Shapes for Solar Fraunhofer Lilnes
Authors: Athay, R. G.; Lites, B. W.; White, O. R.; Brault, J. W.
1972SoPh...24...18A Altcode:
New center-to-limb measurements in FeI lines show changes in both
the line profiles and the limb darkening curves that appear to be
characteristic of many other solar lines. Here we seek the constraints
placed on the atmospheric model by these effects. We find that in
addition to a depth varying source function we must also allow the
ratio of the continuous absorption coefficient to the total absorption
coefficient to pass through a minimum in the mid-photosphere. Such an
effect is consistent with inward increases of the Doppler width and
damping constant in the upper photosphere and an inward increase of
the ionization for both iron and hydrogen in the low photosphere.
---------------------------------------------------------
Title: Measurements of the limb darkening in the forbidden Mg i line
at 4571.1 Å
Authors: White, O. R.; Altrock, R. C.; Brault, J. W.; Slaughter, C. D.
1972SoPh...23...18W Altcode:
We report high resolution measurements of the center-to-limb variation
of the MgI line at 4571.1 Å. This forbidden line is of interest because
it should be formed in LTE. Comparison of our measurements with the
Harvard-Smithsonian Reference Atmosphere show that the line center
radiation originates in the temperature minimum region from 330 to 550
km above the point where τ<SUB>continuum</SUB> = 1. Observations near
the limb confirm that the temperature minimum is ∼4200K.
---------------------------------------------------------
Title: The Analysis and Restoration of Astronomical Data via the
Fast Fourier Transform
Authors: Brault, J. W.; White, O. R.
1971A&A....13..169B Altcode:
Since the powerful techniques developed in communications theory
have been little used to Fourier analyze astronomical measurements
and correct them for smearing, we discuss the application of
Fourier transforms and the Fast Fourier Transform algorithm to these
problems. Basic sampling theory and the discrete Fourier transform are
presented flsst, and then applied to the analysis of solar time series
and to the correction of line spectra for observational smearing. The
solution of the empirical restoration problem is based on a fflter
technique, which suppresses the noise and corrects for smearing in
an optimum fashion. Key words: restoration - power spectra - Fourier
transform - sampling
---------------------------------------------------------
Title: Photographic isotopes of solar fine structure.
Authors: Gilliam, L. B.; White, O. R.
1970AASPB...2...10G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comments on the Discovery of the Dark Band in the Hα Solar
Chromosphere
Authors: White, O. R.; Bhavilai, R.
1970ApL.....5..137W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comments on the Height of the Corona-Chromosphere Interface
Authors: White, O. R.
1969cctr.conf..289W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Inversion Problem in Stellar Atmospheres
Authors: White, Oran R.
1968mrad.conf..380W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Chromospheric Spectrum at the 1962 Eclipse
Authors: Dunn, R. B.; Evans, J. W.; Jefferies, J. T.; Orrall, F. Q.;
White, O. R.; Zirker, J. B.
1968ApJS...15..275D Altcode:
A joint expedition of the High Altitude Observatory, Sacramento Peak
Observatory, and the National Bureau of Standards obtained slitless
spectrograms of the flash spectrum at the February 5,1962, total eclipse
of the Sun. The spectrograms covered the wavelength range of about
3200 to 9100 A with a height resolution of 100 km. The spectrographic
equipment, the observations, the photometric calibration procedures,
and the methods adopted to reduce the large quantity of data are
described. The results are presented in a set of tables that show the
wavelength and identification (where known) of each of the 3500 lines
recorded. A separate set of tables lists the intensity of each line at
each height. The latter tables are ordered according to the element,
ionization stage, and multiplet number associated with the line.
---------------------------------------------------------
Title: Inversion of the Limb-Darkening Equation Using the Prony
Algorithm
Authors: White, O. R.
1968ApJ...152..217W Altcode:
King's interesting application of the Prony algorithm to the inversion
of the limb-darkening equation is modified and generalized so that
it can be applied rigorously to limb-darkening curves, spectral line
profiles, and multiplet line intensities Since King's formulation
requires physically inaccessible observa- tions, a change of variable
is introduced in the limb-darkening integral to avoid this difficulty
Calcula- tions on noisy data confirm the seff -limiting property of this
inversion method An approximate method for constructing the smooth S(r)
distribution from the slab solution is presente
---------------------------------------------------------
Title: A Measurement of the Solar H and K Profiles
Authors: White, O. R.; Suemoto, Z.
1968SoPh....3..523W Altcode:
A new series of photometric observations of the H and K lines were
obtained at Sacramento Peak Observatory in 1964 and 1965. In both
the observations and the data reduction special attention was given
to obtaining a suitable average over the solar fine structure and
to defining a proper reference continuum. The results are that the
central intensities of H and K are the same and equal to 4.2% of the
continuum. The limb-darkening curves at the line centres are also the
same for both lines.
---------------------------------------------------------
Title: Resolution of the Hα Double-Limb Controversy
Authors: White, O. R.; Simon, G. W.
1968SoPh....3..269W Altcode:
The discussion of the Hα double limb had reached the point where
the question of its existence as a real solar phenomenon could not be
resolved without new observations made with the Lockheed filter and the
Mount Wilson spectroheliograph. A study of the instrumental profiles
had indicated that there was sufficient off-band light to produce
the observed inner limb step in the Mount Wilson instrument, but this
analysis was not completely satisfactory because of limitations inherent
in the measurement of instrument functions with a Hg-198 source. The
instrumental profile work did indicate, however, that the spectral
purity of the instruments in question could be substantially improved
by the use of narrow-band interference filters. An experimental program
was thus launched to determine the effect of such a blocking filter on
the appearance of the Hα limb. The results of these observations with
three Halle filter systems and the Mount Wilson spectroheliograph are
that the inner limb completely disappears at the center of Hα when a
blocking filter is used to reduce unwanted light, which originates at
wavelengths beyond ±0.8 Å. In addition, the contrast and visibility
of the chromospheric fine structure is increased by eliminating the
off-band light. Thus the experiment conclusively demonstrates that
the apparent inner limb is not a solar feature but is due entirely to
instrumental parasitic light.
---------------------------------------------------------
Title: The Analysis of Spectral-Line Profiles. I. a. Generalized
Theory for the Solar Case
Authors: Jefferies, J. T.; White, O. R.
1967ApJ...150.1051J Altcode:
Recent studies of spectral-line formation are shown to provide a basis
for the analysis of profiles of multiplet lines in the "solar case," i
e., when limb-darkening data are available. The theoretical foundation
is more general than that assuming local thermodynamic equilibrium,
which is included as a special case. A detailed analytical procedure
is given along with a discussion of its shortcomings and limitations.
---------------------------------------------------------
Title: On the Height of Formation of H-Alpha in the Solar Chromosphere
Authors: White, O. R.; Wilson, P. R.
1966ApJ...146..250W Altcode:
Several features of Ha limb spectra, including the line emission beyond
the continuum limb, are analyzed to yield information about the height
of formation of Ha in the solar chromosphere. It is concluded that
de Jager's suggested value for the height of unit optical depth at
the line center (5000 km) is too high. For the chromospheric features
in these spectra the height of formation lies in a range from 1500 km
(above a sunspot) to 2700 km. This is consistent with the limb profile
analysis which yields a range from 1600 to 3000 km for a hypothetical
mean chromosphere.
---------------------------------------------------------
Title: The H-Alpha Double Limb: a Scattered-Light Phenomenon
Authors: Simon, G. W.; White, O. R.
1966ApJ...143...38S Altcode:
Two independent methods are used to demonstrate that the inner
limb observed in Ha spectroheliograms by Cragg, Howard, and Zirin
is an instrumental, not a solar, phenomenon. First, we show that
low-scattered-light spectrograms do not display a double limb. Second,
by photometric analysis of the Iount ilson observations, we find that
there is more than sufficient imaged scattered light in the Iount Vilson
spectroheliograph to produce the observed inner limb by the scattering
of light from the continuum into the Ha core. It is also shown that the
concept of an inner limb is inconsistent with both theoretical models
and other observations of the solar chromosphere. A real Ha double limb,
not previously described, is seen at about 1.0 A in the line wing.
---------------------------------------------------------
Title: An Analysis of Solar Balmer Line Profiles
Authors: White, O. R.
1965SAOSR.174..355W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Empirical Temperature Structure of the Solar
Chromosphere
Authors: White, O. R.
1964ApJ...140.1164W Altcode:
A new analysis of the Balmer-line limb-darkening observations gives
maximum excitation-temperature differences of 165 K between Ha and
H . This new analysis allows for gradients in both the excitation
and the Doppler width, and reproduces the observed limb darkening at
wavelengths out to 0,3 A in Ha.
---------------------------------------------------------
Title: A Photoelectric Observation of the Mean Solar Ha-LINE Profile.
Authors: White, O. R.
1964ApJ...139.1340W Altcode:
New, improved photoelectric observations of the mean solar Ha-line
profile confirm the earlier observations reported by White (1962). The
new measurement of the central line intensity at the center of the
solar disk is 0.155 + 0.002 of the reference continuum.
---------------------------------------------------------
Title: A HE(D<SUB>3</SUB>) Emission Shell in the Solar Chromosphere?
Authors: White, Oran R.
1963ApJ...138.1316W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Analysis of Center-To Variations in Hα, Hβ, and Hγ.
Authors: White, Oran Richard
1963ApJ...137.1217W Altcode:
Using a frequency-independent source function, a Gaussian absorption
coefficient, and a second-order polynomial representation of the data, I
derive a temperature mode] of the solar chromosphere from limb-darkening
observations in Ha, H , and H . The analysis shows a kinetic temperature
that decreases from 14000 to 65000 K as the optical depth at the center
of Ha changes from 0.4 to 21.0. In contrast to the decreasing kinetic
temperature, the source-function temperatures for the three lines are
monotonically increasing functions of optical depth. Furthermore, at
a common point in the atmosphere, the excitation temperatures in Ha,
Hp, and H are not the same.
---------------------------------------------------------
Title: Limb-Darkening Observations of HAlpha, HBeta, and HGamma
Authors: White, Oran Richard
1962ApJS....7..333W Altcode:
We report a new set of photoelectric limb-darkening observations
obtained by making continuousmonochromatic scans across the solar
disk. From these new observations we obtain smooth limb-darkening curves
and line profiles that apply to a quiet, average solar atmosphere. We
find the mean central intensities of Ha, Hp, and H to be 0 154 t 0
001 0.130 + 0.001, and 0.142 + 0.001 relative to the continuum at
the center of the disk. These intensities agree well with the values
obtained previously by Minnaert (1927), Thackeray (1935), Redinan
(1937), and David (1961). In addition to the average sun data, the
observations yield line profiles in plages and filaments, as well as
information about the chromospheric coarse structure.
---------------------------------------------------------
Title: The Center-To Variation of Hydrogen-Alpha Hydrogen-Beta and
Hydrogen-Gamma in the Solar Spectrum.
Authors: White, Oran Richard
1962PhDT.........4W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A General Solution of the Statistical Equilibrium Equations.
Authors: White, O. R.
1961ApJ...134...85W Altcode:
It is shown that those solutions of the statistical equilibrium
equations given by Giovanelli and Jefferies (1954) and Athay (1960)
are particular algebraic forms of a general solution given by Rosseland
(1926). It is then shown that the steady-state population of the energy
states of the general n-level atom is a function of the product of
the mean lifetime (which describes the transitions out of the state)
and an algebraic cof actor (which describes the transitions into
the state). We find that these cofactors can be interpreted as the
probability of transition between two states by all non-redundant
transition sequences. These transitions contain the interlocking
transitions which need to be considered in the general solution. The
frequency-independent source function for the jk transition in
the general n-level atom is derived directly; and we that it can be
written in a general form which contains, as special cases, forms very
similar to those used by Thomas (1957), Thomas and Jefferies (1958),
Athay, (1960) Thomas and Athay (1961), Johnson (1960), and Jefferies
(1960). Furthermore, we find that a specification of the linearized,
frequency-independent source function with the cofactors taken as
parameters permits us to write the source function in essentially the
same form for all lines of a given spectral series.
---------------------------------------------------------
Title: Source Function in a Non-Equilibrium Atmosphere.VI. The
Frequency Dependence of the Source Function for Resonance Line.
Authors: Jefferies, J. T.; White, O. R.
1960ApJ...132..767J Altcode:
The frequency dependence of the line source function is investigated
for the case of pure coherent scattering in the reference frame of
the atom. It is shown that the thermal redistribution due to Doppler
effect gives a form of scattering similar to complete redistribution
in the line core and coherency in the wings. Using a modified form for
this redistribution and allowing for some residual non-coherency due
to collisions in the frame of the atom, an algebraic solution of the
transfer equation is obtained, and emergent line profiles are computed,
for an isothermal atmosphere. It is shown that the line shape in the
transition region from line core to wing is strongly influenced by the
proportion of this residual non-coherency. It is finally suggested that,
until the strength of collisional perturbations is better understood
from theoretical or laboratory studies, theoretical work on line
spectra should adopt complete redistribution in scattering.
