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Author name code: chapman
ADS astronomy entries on 2022-09-14
author:"Chapman, Gary Allen"
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Title: Four Solar Cycle Spectrum Variation of the Sun-as-a-Star
Authors: Choudhary, D. P.; Chapman, G. A.; Cadavid, A. C.; Cookson, A.
2020AGUFMA227.0008C Altcode:
The chromospheric activity of the Sun is governed by the magnetic
field anchored in the photosphere. The solar cycle 23 was a smaller
cycle compared to the recent cycles, in terms of sunspot number and
total disk integrated magnetic field. Comparison of the chromospheric
lines in past cycles may provide insight of the effect of magnetic
field on solar atmosphere. In this paper, we study the dependence
of chromospheric activity on magnetic field of the Sun-as-a-star
in four solar cycles during 1977-2018. The study is conducted by
merging the data obtained by Dr. W. Livingston and the observations by
Integrated Sunlight Spectrometer (ISS) and Vector Spectromagnetograph
(VSM) of Synoptic Optical Long-term Investigations of the Sun (SOLIS)
instrument. The chromospheric activity is measured as the line depth
and equivalent width (EW) of spectral lines in Hα, He I 10830 nm,
Ca II 854.2 nm, Ca II H and K, and Na D I 589.6 nm obtained with the
ISS. The full disk mean total magnetic flux (FDMTMF) observed with
the VSM is used as the measure of magnetic activity of the Sun. The
equivalent width of Ca II K and He I 10830 nm measured by Livingston
along with the Magnetic Plage Strength Index (MPSI) value and a Mount
Wilson Sunspot Index (MWSI) obtained with 150-Foot Solar Tower in
Mt. Wilson Observatory are used to further study the relationship
between the magnetic field and chromospheric activity.
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Title: The Effect of Sunspot Umbrae on the Total Solar Irradiance
Authors: Chapman, G. A.; Choudhary, D. P.; Cookson, A. M.
2020AGUFMA227.0007C Altcode:
Most studies of the contribution of sunspots on the total solar
irradiance (TSI) are based on the area of sunspots of constant average
darkness. However, the average darkness (contrast) depends on the
relative area of the umbra, the dark "core" of many sunspots. We will
present results from a study of photometric observations, that measure
the actual contrast of sunspots and their effect on TSI. This work is
partially supported by NASA grant 80NSSC18K1328.
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Title: Variability in Irradiance and Photometric Indices During the
Last Two Solar Cycles
Authors: Choudhary, Debi Prasad; Cadavid, Ana Cristina; Cookson,
Angela; Chapman, Gary A.
2020SoPh..295...15C Altcode:
The Total Solar Irradiance (TSI) primarily varies on an 11-year time
scale and is governed by features such as sunspots and associated
decay products such as plage and faculae. These short-lived physical
features can also modulate the solar irradiance at intermediate and
short temporal scales. Here we investigate the periodic variations,
at solar-surface-rotation time scales, of photometric indices
derived from images obtained at the San Fernando Observatory (SFO),
and we compare them to the properties of the contemporaneous TSI
as measured by the Total Irradiance Monitor (TIM) onboard the SOlar
Radiation and Climate Experiment (SORCE) spacecraft. Both the daily
ground- and space-based data, which span from early 2003 to late 2018,
present missing pixels. We use an autoregressive gap-filling method to
construct continuous time series to be analyzed via Fourier and wavelet
spectral techniques. Lomb-Scargle periodograms, which can handle time
series with missing data, are used for comparison. Both the Fourier
spectral power and the periodograms yield compatible results with
statistically significant periodicities in the range 25 - 35 days. All
of the time series have maximum power at 27 days. Significant secondary
periods are found at 29 - 30 days and 34 - 35 days. Wavelet analyses
of the full time series show that the photometric index resulting
from the red-continuum photometric sum [Σ<SUB>r</SUB>] and the
TSI exhibit common high power at surface-solar-rotation scales
during the active part of the solar cycle. The phase relation at
the surface-solar-rotation scales is not definite. During the solar
minimum interval between Solar Cycles (SCs) 23 and 24, variations in
the TSI are found to be related to variations both in the photometric
index Σ<SUB>K</SUB>, calculated from Ca II K-line photometric sums
and in the magnetic flux in the solar activity latitudinal band (as
found in previous work). This suggests that the TSI changes during the
minimum are caused by the reduced line-blanketing effect of diffused
magnetic field.
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Title: Temporal relations between total solar irradiance and
photometric indices during the last two solar cycles.
Authors: Cadavid, A. C.; Choudhary, D. P.; Chapman, G. A.; Cookson, A.
2019AGUFMSH11D3391C Altcode:
Our present understanding, from both empirical and semi-empirical
models, indicates that the variations in the Total Solar Irradiance
(TSI) on time scales of days to the solar cycle are primarily
associated with solar surface magnetic activity, which encompasses
sunspots, faculae, and the network. In previous work, approximately
seven years of TSI measurements from the Total Irradiance Monitor
(TIM) on board the SOlar Radiation and Climate Experiment (SORCE)
spacecraft were compared with photometric indices derived from red and
K-line images obtained on a daily basis at the San Fernando Observatory
(SFO), California State University Northridge (CSUN). The best linear
regression model yielded a coefficient of multiple determination,
R<SUP>2</SUP>, of 0.9495. Expanding on this earlier work and employing
additional analysis techniques not previously used, we consider 16
years of SORCE and SFO data, from early 2003 to late 2018. We use
an autoregressive gap filling method to construct continuous series
which can be analyzed via Fourier and wavelet spectral techniques in
order to investigate the characteristics of the time signals on short
temporal scales. Lomb-Scargle periodograms, which can handle time
series with missing data, are used for comparison. Both the Fourier
spectral power and the periodograms yield compatible results with
significant periodicities on the solar rotation time scales. For both
active and quiet Sun periods, cross-wavelet transforms between the
TSI and the photometric indices signals are used to identify regions
of high common power in the time-frequency maps. The wavelet transform
coherence indicates local periods and times during which the photometric
indices signals and TSI have significant coherence and phase locking,
independent of the power.
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Title: A Comparison of Sunspot and Umbral Area from the San Fernando
Obervatory and SDO
Authors: Chapman, G. A.; Cookson, A.; Choudhary, D. P.
2016AGUFMSH31B2559C Altcode:
Sunspot area is an important and basic datum for determining the level
of solar activity. We report on a study of spot total and umbral areas
determined from images obtained by the San Fernando Observatory (CSUN)
and the Solar Dynamics Observatory spacecraft. This research has been
supported by grants from NASA and NSF.
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Title: Modeling SSI Variations using Ground-Based Images from the
San Fernando Observatory
Authors: Chapman, G. A.; Choudhary, D. P.
2015AGUFMSH32A..05C Altcode:
Full-Disk photometric images are obtained on a daily basis at the San
Fernando Observatory. The images are at wavelengths of 672, 472, and
393 nm. From these images, relative irradiance indices are calculated
and compared with SSI variations at selected wavelengths. We will
present results of modeling spacecraft SSI variations with our indices.
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Title: A Different View of Solar Spectral Irradiance Variations:
Modeling Total Energy over Six-Month Intervals
Authors: Woods, Thomas N.; Snow, Martin; Harder, Jerald; Chapman,
Gary; Cookson, Angela
2015SoPh..290.2649W Altcode: 2015SoPh..tmp..113W
A different approach to studying solar spectral irradiance (SSI)
variations, without the need for long-term (multi-year) instrument
degradation corrections, is examining the total energy of the irradiance
variation during 6-month periods. This duration is selected because
a solar active region typically appears suddenly and then takes 5 to
7 months to decay and disperse back into the quiet-Sun network. The
solar outburst energy, which is defined as the irradiance integrated
over the 6-month period and thus includes the energy from all phases of
active region evolution, could be considered the primary cause for the
irradiance variations. Because solar cycle variation is the consequence
of multiple active region outbursts, understanding the energy spectral
variation may provide a reasonable estimate of the variations for the
11-year solar activity cycle. The moderate-term (6-month) variations
from the Solar Radiation and Climate Experiment (SORCE) instruments can
be decomposed into positive (in-phase with solar cycle) and negative
(out-of-phase) contributions by modeling the variations using the San
Fernando Observatory (SFO) facular excess and sunspot deficit proxies,
respectively. These excess and deficit variations are fit over 6-month
intervals every 2 months over the mission, and these fitted variations
are then integrated over time for the 6-month energy. The dominant
component indicates which wavelengths are in-phase and which are
out-of-phase with solar activity. The results from this study indicate
out-of-phase variations for the 1400 - 1600 nm range, with all other
wavelengths having in-phase variations.
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Title: A Different View of Solar Spectral Irradiance Variations:
Modeling Total Energy of a Solar Outburst Period in 2005 and its
Comparison to Solar Cycle 23 and 24 Measured Variability
Authors: Woods, Thomas N.; Snow, Martin; Harder, Jerald; Chapman,
Gary; Cookson, Angela
2015IAUGA..2224203W Altcode:
A different approach to studying solar spectral irradiance (SSI)
variations, without the need for long-term (multi-year) instrument
degradation corrections, is by examining the total energy of the
irradiance variation during solar outburst periods. A solar active
region typically appears suddenly and then takes about seven months
to decay and disperse back into the quiet Sun network. An outburst
period is defined as a time when one major active region dominates the
irradiance variation. The solar outburst energy, which includes the
energy from all phases of active region evolution, could be considered
the primary cause for irradiance variations. Because solar cycle
variation is the consequence of multiple active region outbursts,
understanding the variation from a single active region outburst can
provide a reasonable estimate of the variations for the 11-year solar
activity cycle. The moderate-term (~6 months) variations from the
Solar Radiation and Climate Experiment (SORCE) instruments during
a solar outburst period in early 2005 are decomposed into positive
(in-phase with solar cycle) and negative (out-of-phase) contributions
by modeling the variations using the San Fernando Observatory (SFO)
facular excess and sunspot deficit proxies, respectively. These fitted
excess and deficit variations are then integrated over time for the
energy during this outburst period, and the dominant component indicates
which wavelengths are in-phase and which are out-of-phase with solar
activity. The results from this study indicate out-of-phase variations
for the 1210-1600 nm range, with all other wavelengths having in-phase
variations.
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Title: Observations of the Solar Faculae at San Fernando Observatory
and Solar Dynamics Observatory
Authors: Prasad Choudhary, Debi; Cookson, Angie; Chapman, Gary;
Yassin, Kemal
2015TESS....120314P Altcode:
In this paper we compare the full disk images of the Sun obtained
in 393.4 nm Ca II K line from Cartesian Full Disk Telescopes (CFDT)
of San Fernando Observatory (SFO) and 1600Å and 1700Å images from
Solar Dynamic Telescope (SDO). The facular excess and facular area
are determined for these two types of images using the data reduction
procedure developed at SFO. We find strong correlation between the
derived quantities from SFO and SDO images. Also, the facular excess and
facular area show a very good correlation with the sunspot numbers. The
sunspot numbers derived from the SDO images from our model agrees well
with tabulated values.
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Title: Small-scale and Global Dynamos and the Area and Flux
Distributions of Active Regions, Sunspot Groups, and Sunspots:
A Multi-database Study
Authors: Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Windmueller,
John C.; Amouzou, Ernest C.; Longcope, Dana W.; Tlatov, Andrey G.;
Nagovitsyn, Yury A.; Pevtsov, Alexei A.; Chapman, Gary A.; Cookson,
Angela M.; Yeates, Anthony R.; Watson, Fraser T.; Balmaceda, Laura A.;
DeLuca, Edward E.; Martens, Petrus C. H.
2015ApJ...800...48M Altcode: 2014arXiv1410.6281M
In this work, we take advantage of 11 different sunspot group,
sunspot, and active region databases to characterize the area
and flux distributions of photospheric magnetic structures. We
find that, when taken separately, different databases are better
fitted by different distributions (as has been reported previously
in the literature). However, we find that all our databases can be
reconciled by the simple application of a proportionality constant,
and that, in reality, different databases are sampling different
parts of a composite distribution. This composite distribution
is made up by linear combination of Weibull and log-normal
distributions—where a pure Weibull (log-normal) characterizes the
distribution of structures with fluxes below (above) 10<SUP>21</SUP>Mx
(10<SUP>22</SUP>Mx). Additionally, we demonstrate that the Weibull
distribution shows the expected linear behavior of a power-law
distribution (when extended to smaller fluxes), making our results
compatible with the results of Parnell et al. We propose that this is
evidence of two separate mechanisms giving rise to visible structures
on the photosphere: one directly connected to the global component of
the dynamo (and the generation of bipolar active regions), and the other
with the small-scale component of the dynamo (and the fragmentation of
magnetic structures due to their interaction with turbulent convection).
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Title: An Observed Decline in the Amplitude of Recent Solar-Cycle
Peaks
Authors: Chapman, G. A.; de Toma, G.; Cookson, A. M.
2014SoPh..289.3961C Altcode: 2014SoPh..tmp...72C
There has been much speculation about the extended minimum between Solar
Cycles 23 and 24. Cycle 24 itself has been unusually weak compared with
recent cycles. We present quantitative evidence for the weakness of
both Cycles 23 and, particularly, 24. The data are objective indices
derived from precision photometric images obtained on a daily basis
at the San Fernando Observatory. These data form the longest running,
homogeneous photometric record known to us. We show sunspot areas from
red images and facular/network areas from Ca II K-line images. Spot
and facular area are a simple and direct measurement of the strength
of solar activity. The data clearly show the decline in the amplitude
of sunspot maxima for Cycles 23 and 24 compared with Cycle 22. The
relative amplitudes of mean spot area for Cycles 22 through 24 are
1.0, 0.74, and 0.37, respectively. There is also an indication that
the facular-to-spot area ratio has increased in Cycle 24.
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Title: Temporal Stability of Sunspot Umbral Intensities: 1986-2012
Authors: de Toma, G.; Chapman, G. A.; Cookson, A. M.; Preminger, D.
2013ApJ...771L..22D Altcode:
We examine the relative intensity of sunspot umbrae during the period
from 1986 to 2012 using photometric images from the San Fernando
Observatory. We confirm the presence of a relationship between the mean
umbral core intensity and the mean sunspot area, as found in previous
studies, and do not find a notable change in this relationship between
cycles 22 and 23. We looked for a possible time variation in the sunspot
umbral contrast during the 27 yr covering cycles 22, 23, and the rise
of cycle 24, and we did not find a significant change. These findings
do not indicate that sunspots have become less dark during cycles 23
and 24.
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Title: Analysis of Sunspot Area over Two Solar Cycles
Authors: de Toma, G.; Chapman, G. A.; Preminger, D. G.; Cookson, A. M.
2013ApJ...770...89D Altcode:
We examine changes in sunspots and faculae and their effect on total
solar irradiance during solar cycles 22 and 23 using photometric images
from the San Fernando Observatory. We find important differences in
the very large spots between the two cycles, both in their number and
time of appearance. In particular, there is a noticeable lack of very
large spots in cycle 23 with areas larger than 700 millionths of a
solar hemisphere which corresponds to a decrease of about 40% relative
to cycle 22. We do not find large differences in the frequencies of
small to medium spots between the two cycles. There is a decrease
in the number of pores and very small spots during the maximum phase
of cycle 23 which is largely compensated by an increase during other
phases of the solar cycle. The decrease of the very large spots, in
spite of the fact that they represent only a few percent of all spots
in a cycle, is primarily responsible for the observed changes in total
sunspot area and total sunspot deficit during cycle 23 maximum. The
cumulative effect of the decrease in the very small spots is an order
of magnitude smaller than the decrease caused by the lack of large
spots. These data demonstrate that the main difference between cycles
22 and 23 was in the frequency of very large spots and not in the very
small spots, as previously concluded. Analysis of the USAF/NOAA and
Debrecen sunspot areas confirms these findings.
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Title: Modeling Total Solar Irradiance with San Fernando Observatory
Ground-Based Photometry: Comparison with ACRIM, PMOD, and RMIB
Composites
Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. G.
2013SoPh..283..295C Altcode:
We model total solar irradiance (TSI) using photometric irradiance
indices from the San Fernando Observatory (SFO), and compare
our model with measurements compiled from different space-based
radiometers. Space-based measurements of TSI have been obtained recently
from ACRIM-3 on board the ACRIMSAT. These data have been combined with
other data sets to create an ACRIM-based composite. From VIRGO on board
the Solar and Heliospheric Observatory (SOHO) spacecraft two different
TSI composites have been developed. The VIRGO irradiance data have
been combined by the Davos group to create a composite often referred
to as PMOD (Physikalisch-Meteorologisches Observatorium Davos). Also
using data from VIRGO, the Royal Meteorological Institute of Belgium
(RMIB) has created a separate composite TSI referred to here as the RMIB
composite. We also report on comparisons with TSI data from the Total
Irradiance Monitor (TIM) experiment on board the Solar Radiation and
Climate Experiment (SORCE) spacecraft. The SFO model correlates well
with all four experiments during the seven-year SORCE interval. For
this interval, the squared correlation coefficient R<SUP>2</SUP>
was 0.949 for SORCE, 0.887 for ACRIM, 0.922 for PMOD, and 0.924
for RMIB. Long-term differences between the PMOD, ACRIM, and RMIB
composites become apparent when we examine a 21.5-year interval. We
demonstrate that ground-based photometry, by accurately removing
TSI variations caused by solar activity, is useful for understanding
the differences that exist between TSI measurements from different
spacecraft experiments.
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Title: Comparison of TSI from SORCE TIM with SFO Ground-Based
Photometry
Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. G.
2012SoPh..276...35C Altcode:
Total solar irradiance (TSI) measurements have been available from
the TIM instrument on the SORCE spacecraft since 2003. We compare
TSI data, both 24-h and 6-h averages, with photometric indices from
red and K-line images obtained on a daily basis at the San Fernando
Observatory (SFO). For 1253 days of data from 2 March 2003 to 5 May
2010 we compare the data in linear multiple regression analyses. The
best results come from using two photometric indices, the red and
K-line photometric sums, and SORCE TSI 6-h averages interpolated to
the SFO time of observation. For this case, we obtain a coefficient
of multiple determination, R<SUP>2</SUP>, of 0.9495 and a quiet-Sun
irradiance S<SUB>0</SUB> = 1360.810 ± 0.004 W m<SUP>−2</SUP>. These
results provide further support for the hypothesis that the quiet Sun
is constant over time.
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Title: Obituary: Earle B. Mayfield (1923-2007)
Authors: Chapman, Gary
2011BAAS...43..018C Altcode:
Earle B. Mayfield passed away peacefully in his sleep 28 May 2007
in Los Osos, near San Luis Obispo. He retired there to grow orchids,
make wine and teach part-time at California Polytechnic University, San
Luis Obispo (Cal Poly SLO). He was born in Oklahoma City in 1923. After
his discharge from the Coast Guard he went to UCLA where he graduated
in physics in 1950. He married Peggy Masterson in 1952 after they met
while they both worked at the China Lake Test Station. He obtained a
Ph.D. in physics in 1959 from the University of Utah. He is survived by
his wife, seven children and 14 grandchildren. <P />In 1960 Mayfield
joined The Aerospace Corporation where he became a strong proponent
of expanding the Corporation's activities in solar research. In
1966, with Mayfield's support, observations of supergranulation
were obtained from Thule, Greenland, that spanned nearly 62 hours
of continuous coverage: the longest continuous solar observations
at that time. <P />He was instrumental in the effort to design and
construct an advanced 24-inch aperture vacuum solar telescope. The
resulting diffraction limited image had an un-vignetted field-of-view
of about 0.8 Re. An auxiliary 11-inch vacuum telescope was available
for full-disk observations. Both telescopes were F/20 with reflecting
surfaces having proprietary overcoated silver. At the Coude focus
was a vacuum spectroheliograph. It was determined that a peninsula
jutting out into the Upper Van Norman Reservoir provided superior
seeing conditions that was the site of an U.S. Air Force Air Weather
Service station. This became the San Fernando Observatory, which was
dedicated in February 1969 just before an ad hoc meeting of the Solar
Physics Division in Pasadena. Mayfield was its first director. <P />In
1971, under Mayfield's direction, Aerospace developed the first digital
video magnetograph supported by a NASA grant. This provided real-time
magnetograms of solar active regions. <P />In 1973, James Underwood
came to Aerospace and the Aerospace solar group became collaborators in
the S-056 X-ray telescope experiment onboard Skylab. The flight films
from the S-056 experiment were developed by the Aerospace solar group's
photographic team. The 24-inch vacuum telescope was used extensively
in support of the S-056 experiment. <P />When stable external funding
failed to materialize, Aerospace closed the observatory in the summer
of 1975 and donated the facility to California State University,
Northridge in 1976 with the help of Paul Richter. <P />Mayfield retired
from the Aerospace Corporation in 1985 and moved to Los Osos. He became
an adjunct professor at Cal Poly SLO and helped with student projects
in the Physics Department. One of his projects involved the design and
construction of a solar spectrograph for studying the Zeeman effect in
sunspots. <P />In the early 1970s, Mayfield and Bob Leighton of Caltech
organized a series of informal meetings that came to be called the
Local Group to advance communication among solar astronomers in Southern
California. Mayfield's leadership in solar physics extended not only to
building new facilities, instruments, and doing cutting-edge science,
he also aided the careers of many students and other solar physicists.
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Title: Activity-brightness Correlations for the Sun and Sun-like Stars
Authors: Preminger, D. G.; Chapman, G. A.; Cookson, A. M.
2011ApJ...739L..45P Altcode: 2011arXiv1107.5564P
We analyze the effect of solar features on the variability of the
solar irradiance in three different spectral ranges. Our study is
based on two solar-cycles' worth of full-disk photometric images
from the San Fernando Observatory, obtained with red, blue, and Ca
II K-line filters. For each image we measure the photometric sum,
Σ, which is the relative contribution of solar features to the
disk-integrated intensity of the image. The photometric sums in the
red and blue continuum, Σ<SUB>r</SUB> and Σ<SUB>b</SUB>, exhibit
similar temporal patterns: they are negatively correlated with solar
activity, with strong short-term variability, and weak solar-cycle
variability. However, the Ca II K-line photometric sum, Σ<SUB>K</SUB>,
is positively correlated with solar activity and has strong variations
on solar-cycle timescales. We show that we can model the variability
of the Sun's bolometric flux as a linear combination of Σ<SUB>r</SUB>
and Σ<SUB>K</SUB>. We infer that, over solar-cycle timescales, the
variability of the Sun's bolometric irradiance is directly correlated
with spectral line variability, but inversely correlated with continuum
variability. Our blue and red continuum filters are quite similar to
the Strömgren b and y filters used to measure stellar photometric
variability. We conclude that active stars whose visible continuum
brightness varies inversely with activity, as measured by the Ca
HK index, are displaying a pattern that is similar to that of the
Sun, i.e., radiative variability in the visible continuum that is
spot-dominated.
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Title: Sunspot temperatures from red and blue photometry
Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. G.
2011IAUS..273..325C Altcode:
Photometric images are used to measure the temperature of sunspots at
different wavelengths. Images at 672.3 nm and 472.3 nm are obtained
at the San Fernando Observatory using the CFDT2 (2.5” x 2.5”
pixels). Images at 607.1 nm and 409.4 nm are obtained by the PSPT
at Mauna Loa Observatory. Monochromatic intensities are converted
to temperatures as in Steinegger et al (1990). The pixel by pixel
temperature for a sunspot is converted into a bolometric contrast for
that sunspot according to Chapman et al (1994). Sunspot temperatures,
i.e., their bolometric contrasts, are calculated from both red (672.3
nm) and blue wavelengths (472.3 nm) and compared.
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Title: Activity-brightness Correlations For The Sun And Sun-like Stars
Authors: Preminger, D.; Chapman, G.; Cookson, A.
2011SPD....42.1812P Altcode: 2011BAAS..43S.1812P
We examine the effects of active regions on the relative brightness of
the solar disk at three different wavelengths. Our study is based on
photometric parameters derived from images taken at the San Fernando
Observatory, and examines daily data for two full solar cycles. We
measure the contrast of solar features on broadband red and blue
images, and on Ca II K-line images, which allows us to compute the net
brightness variations due to solar activity. We show that while the Ca
II K-line variability is directly correlated with the solar activity
cycle, variability in the red and blue continuum is anti-correlated
with solar activity, on solar cycle timescales. Our blue and red
continuum filters are quite similar to the Stromgren b and y filters
used to measure stellar photometric variability. Sun-like stars whose
continuum brightness varies inversely with activity are therefore
revealed to be similar to the Sun. <P />This work has been supported
in part by NASA LWS Grant NNX07AT19G and NSF Grant ATM-0848518.
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Title: Modeling TSI Variations from SORCE/TIM
Authors: Chapman, Gary A.; Cookson, A.; Preminger, D.
2011SPD....42.1814C Altcode: 2011BAAS..43S.1814C
Total Solar Irradiance (TSI) measurements have been available from
the TIM instrument on the SORCE spacecraft since 2003. We compare TSI
data with photometric indices from red and K-line images obtained on
a daily basis at the San Fernando Observatory (SFO). For 1375 days of
data from 2003 March 02 to 2010 May 05 we compare the data in linear
multiple regression analyses. The best results come from using only two
photometric indices, the red and K-line photometric sums, and SORCE TSI
6-hour averages interpolated to the SFO time of observation. For this
case, we obtain a coefficient of multiple correlation, R<SUP>2</SUP>,
of 0.94798 and a quiet-Sun irradiance, S<SUB>o </SUB>= 1360.778 ±
0.004 W/m<SUP>2</SUP>. These results provide tighter contstraints
than before on hypotheses linking TSI variations with assumed changes
in the quiet Sun. This research has been partially supported by NSF
Grant ATM-0848518.
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Title: Solar Synoptic Maps from the San Fernando Observatory
Authors: Hodgson, John, II; Chapman, G.; Preminger, D.; Cookson, A.
2011SPD....42.1722H Altcode: 2011BAAS..43S.1722H
We are developing a set of synoptic image maps compiled from daily
photometric images taken at the San Fernando Observatory. Our initial
maps show the progression of solar features across the central meridian
for approximately one solar rotation. The red continuum maps show the
photometric contrast of solar features in the photosphere while the
Ca II K-line maps show the same in the lower chromosphere. Comparing
these maps with each other, and with those of other solar groups,
will yield information regarding the evolutionary patterns of solar
activity at different heights of the solar atmosphere. This is a first
step toward a comprehensive set of synoptic maps covering the period
from mid-solar cycle 22 in 1988 to the present. <P />This work has
been supported in part by NSF grant ATM-0848518.
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Title: Facular and Sunspot Areas During Solar Cycles 22 and 23
Authors: Chapman, G. A.; Dobias, J. J.; Arias, T.
2011ApJ...728..150C Altcode:
We present an analysis of facular/network and sunspot areas (and their
ratio) covering most of cycle 22 and all of cycle 23. The data are
corrected areas (in microhemispheres) from full-disk solar images
using two photometric telescopes at the San Fernando Observatory,
CFDT1 and CFDT2. Images from CFDT2 have approximately twice the spatial
resolution of CFDT1. Sunspot areas are obtained from red images where
spots are determined as those pixels darker than -8.5%. Facular/network
areas are from Ca II K-line images where facular/network pixels are
brighter than 4.8%. Regressions of facular area versus spot area for
CFDT1 give a slope term of 25. For CFDT2, the slope term is 33. The
average ratio of facular to spot area for cycle 22 is 45 and for cycle
23 the ratio is 42. These values are substantially higher than those
from earlier studies. The increase is due to a combination of higher
spatial resolution and the removal of a correction factor in μ. For
the 0.3 nm K-line images, the spot to facular/network ratio is 138
for six years of cycle 23. A relation is given for the dependence of
facular/network area on contrast. The relationship of facular/network
area to sunspot area is linear for data from both telescopes.
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Title: Recent Ground-Based Photometry Compared with Space-Based TSI
Authors: Chapman, G. A.; Cookson, A.; Preminger, D.
2010AGUFMGC21B0871C Altcode:
Solar activity continues at low levels with occasional modest
increases. We will compare indices from ground-based photometry with
variations in Total Solar Irradiance (TSI) from SORCE/TIM as well as
other space-based instruments. During the solar minimum of 2008-2009
regressions of solar indices with SORCE/TIM gave a quiet sun TSI of
1360.62 +/- 0.04 W/m^2. This work has been partly supported by NSF
grant ATM-0848518.
---------------------------------------------------------
Title: Empirical Modeling of Radiative versus Magnetic Flux for
the Sun-as-a-Star
Authors: Preminger, Dora; Nandy, Dibyendu; Chapman, Gary; Martens,
Petrus C. H.
2010SoPh..264...13P Altcode: 2010arXiv1006.4354P; 2010SoPh..tmp...92P
We study the relationship between full-disk solar radiative flux at
different wavelengths and average solar photospheric magnetic-flux
density, using daily measurements from the Kitt Peak magnetograph
and other instruments extending over one or more solar cycles. We
use two different statistical methods to determine the underlying
nature of these flux - flux relationships. First, we use statistical
correlation and regression analysis and show that the relationships are
not monotonic for total solar irradiance and for continuum radiation
from the photosphere, but are approximately linear for chromospheric
and coronal radiation. Second, we use signal theory to examine the
flux - flux relationships for a temporal component. We find that
a well-defined temporal component exists and accounts for some of
the variance in the data. This temporal component arises because
active regions with high magnetic-field strength evolve, breaking
up into small-scale magnetic elements with low field strength, and
radiative and magnetic fluxes are sensitive to different active-region
components. We generate empirical models that relate radiative flux to
magnetic flux, allowing us to predict spectral-irradiance variations
from observations of disk-averaged magnetic-flux density. In most cases,
the model reconstructions can account for 85 - 90% of the variability
of the radiative flux from the chromosphere and corona. Our results
are important for understanding the relationship between magnetic and
radiative measures of solar and stellar variability.
---------------------------------------------------------
Title: ACS after SM4: On-orbit Verification of the HST Advanced
Camera for Surveys Repair
Authors: Golimowski, David A.; Cheng, E. S.; Loose, M.; Sirianni, M.;
Lupie, O. L.; Smith, L. J.; Arslanian, S.; Boyce, K. R.; Chapman, G.;
Chiaberge, M.; Desjardins, T.; Dye, D.; Ellis, T.; Grogin, N. A.; Lim,
P.; Lucas, R. A.; Maybhate, A.; Mil, K. J.; Mutchler, M.; Ricardo,
R.; Scott, B.; Serrano, B.; Suchkov, A.; Waczynski, A.; Welty, A. D.;
Wheeler, T.; Wilson, E.
2010AAS...21546209G Altcode: 2010BAAS...42..494G
The newly replaced CCD electronics box (CEB-R) of the Hubble
Space Telescope (HST) Advanced Camera for Surveys (ACS) features a
programmable SIDECAR ASIC manufactured by Teledyne. The CEB-R not only
restores the functionality of the ACS Wide Field Camera (WFC), but
it allows optimization of the WFC's imaging performance via on-orbit
adjustment of CCD bias and clock voltages and serial-data transmission
timing. We describe the strategy, preparation, execution, and results
of the ACS Optimization Campaign, an unprecedented on-orbit extension
of ground-based integration and testing that was conducted during the
HST Servicing Mission Observatory Verification period.
---------------------------------------------------------
Title: Solar Irradiance Variations Related to Intensity and Magnetic
Flux of Solar Features
Authors: Pap, Judit M.; Jones, H.; Parker, D.; Chapman, G.; Floyd, L.
2010cosp...38.1783P Altcode: 2010cosp.meet.1783P
Solar total and spectral irradiance have been measured since late
1978. These measurements have demonstrated that solar irradiance changes
from minutes to the 11-year solar cycle. Con-sidering the astrophysical
and climate importance of irradiance variations, considerable efforts
have been put forward to develop irradiance models to explain the origin
of irradiance varia-tions and have information for those time intervals
when measurements don't exist. However, most of the current models are
simple empirical models, using the Photometric Sunspot Index to describe
the darkening effect of sunspots and either the CaK index or the Mg II
h k core-to wing ratio to describe the facular excess flux. While these
models can explain reasonably well the short-term variations, long-term
variations over years to the cycle are not well-accounted. Since the
SOHO era we have combined the MDI intensity images and magnetograms
to ac-count for the effect and the role of active region evolution
to irradiance variations. Similar studies have been done routinely
at the San Fernando Observatory, California State University. More
recently we have used the SPM data from NSO Kitt Peak to deduct various
activity components, and new efforts at UCLA are in progress to develop
a sophisticated method to identify various features. Using observations
by SDO/HMI we will have further insight into active region evolution,
especially during the rising portion of cycle 24, following the long
and deep minimum of cycle 23. In this paper we compare data derived
from various images and compare them to irradiance variations. One of
the main goals is to identify weak magnetic fields and estimate their
contribution to irradiance changes. We will study cycle 23 in detail,
and will discuss how the used methods and techniques can be applied
to HMI on SDO.
---------------------------------------------------------
Title: Comparison of Independent Feature Recognition Method for
Time Series Analysis of Irradiance Variations Based on Statistical
Feature Recognition
Authors: Pap, Judit M.; Bertello, L.; Chapman, G.; Floyd, L. E.;
Jones, H.; Malanushenko, E.; Preminger, D.; Turmon, M.
2009SPD....41.0934P Altcode:
Solar total and UV irradiances have been observed over three decades,
and recently spectral irradiance data are available from the Solar
Irradiance Monitor (SIM) on the SORCE Mission. Results of these
measurements show that irradiance varies on various time scales from
minutes to decades. To better understand the origin of irradiance
changes, we need to use spatially resolved data rather than full
disk indices. For this purpose various automated image processing
and analyses techniques have been developed. Using these image
processing techniques, we separated quiet-sun, network, faculae and
sunspots. On one hand, we compare the area data of these features
derived from various images to validate results and discuss future
efforts needed to coordinate efforts between various groups working
on image analysis. Another goal is to compare the variations of the
identified features with total solar and UV irradiances to establish
to what degree <P />the identified images explain short and long-term
irradiance variations.
---------------------------------------------------------
Title: A portable solar adaptive optics system
Authors: Ren, Deqing; Penn, Matt; Wang, Haimin; Chapman, Gary;
Plymate, Claude
2009SPIE.7438E..0PR Altcode:
We are developing a portable adaptive optics system for solar
telescopes. The adaptive optics has a small physical size and is
optimized for diffraction-limited imaging in the 1.0 ~ 5.0-μm infrared
wavelength range for 1.5-m class solar telescopes. By replacing a
few optical components, it can be used with a solar telescope of any
aperture size that is currently available. The software is developed by
LabVIEW. LabVIEW's block diagram based programming makes it suitable for
rapid development of a prototype system. The portable adaptive optics
will be used with a 1.5-meter solar telescope for high-resolution
magnetic field investigation in the infrared. We discuss the design
philosophy for such a portable, low-cost, and high-performance
system. Estimated performances are also presented.
---------------------------------------------------------
Title: Comparison Of Solar Surface Features Identified By The
Autoclass Pattern Recognition Software From Mount Wilson Observatory
Data To Solar Surface Feature Areas Measured By The San Fernando
Observatory
Authors: Parker, Daryl; Preminger, D.; Ulrich, R.; Bertello, L.;
Cookson, A.; Chapman, G.
2009SPD....40.1607P Altcode:
In previous work, the AutoClass software, a Bayesian pattern recognition
program based on a finite mixture model, developed by Cheeseman and
Stutz (1996), has been used on Mount Wilson Solar Observatory (MWO)
intensity and magnetogram images to identify spatially resolved areas on
the solar surface associated with Total Solar Irradiance (TSI) and to
classify the identified areas in terms of traditional categories-spot,
plage, quiet, etc. Those results, were in turn used to (1) model TSI
variations as measured by satellite and composite TSI observations,
with a correlation of better than 0.96, for the period 1996-2008-most
of Cycle 23, and (2) create solar images as they would be seen by a
hypothetical TSI instrument able to capture resolved images. Here,
we compare the same regions identified by AutoClass which were found
to be associated with TSI, and the indices derived from them, with the
following areas measured by the San Fernando Observatory (SFO): (1)
sunspot area in red continuum; (2) facular area in red continuum; (3)
sunspot area in wide Ca K-line (WK-line); (4) plage area in WK-line;
and (5) plage plus network area in WK-line. The correlations of
the AutoClass-MWO indices with the different SFO area measurements
varies from better than 0.91 to over 0.98, depending on the type
of feature. The comparison of the spatially resolved surface areas
identified by AutoClass in the MWO images to the areas of the different
feature observed at SFO, and the creation of spatially resolved images
depicting those areas, should enable better identification of the
types of surface features associated with TSI measurements and their
evolution over a solar cycle. The comparison should also assist in
validating the automated categorization of solar features found using
the AutoClass automated pattern recognition software.
---------------------------------------------------------
Title: Solar Features Faint but Still Present in 2009
Authors: Cookson, Angela; Preminger, D.; Chapman, G.
2009SPD....40.1104C Altcode:
The San Fernando Observatory (SFO) full-disk photometric image
archive spans twenty years and includes the cycle 22/23 minimum and
the current cycle 23/24 extended minimum. We measure sunspot deficit,
faculae/plage/network excess, and disk-integrated variability on red
continuum (672.3 nm) and Ca II K-line (393.4 nm) images. A combined
plage/network index shows excess remaining above zero as the cycle 23/24
minimum progresses while plage excess alone drops to zero, indicating
an absence of large-scale bright regions but a continuing presence of
diffuse network. We construct feature-based models of TSI variability
and compare our models to the PMOD, ACRIM, and IRMB TSI Composites to
determine whether our data reflect the extremely low TSI levels deduced
from spacecraft measurements during the current extended solar minimum.
---------------------------------------------------------
Title: Solar Cycle 24: Where are you?
Authors: Chapman, Gary A.; Cookson, A.; Preminger, D.
2009SPD....40.1101C Altcode:
Photometric images have been obtained on a daily basis since 1986 at
the San Fernando Observatory. We will compare sunspot and facular areas
from cycle 22 with those of cycle 23. Both spot areas and facular areas
were lower during the maximum of cycle 23 compared to cycle 22. The
distribution in spot areas will be compared. The extended minimum
in spot area following cycle 23 is delaying the beginning of cycle
24. This work has been partially supported by NSF grant ATM-0533511.
---------------------------------------------------------
Title: Radiative Vs. Magnetic Flux For The Sun-as-a-star
Authors: Preminger, D.; Nandi, D.; Chapman, G.; Martens, P.
2009SPD....40.1111P Altcode:
We study the relationship between full-disk solar radiative flux at
different wavelengths and average solar photospheric magnetic flux
density, using daily measurements from the Kitt Peak magnetograph
and other instruments extending over one or more solar cycles. We
use statistical methods to determine the underlying nature of these
flux-flux relationships. For total solar irradiance and for continuum
radiation from the photosphere, the relationships are non-linear, but
for chromospheric and coronal radiation the relationships are linear. We
find that scatter plots of radiative flux vs Kitt Peak magnetic flux
density show significant variance, due in part to the presence of a
temporal component in some of the flux-flux relationships. This temporal
relationship arises because an active region with high magnetic field
strength evolves, breaking up into small-scale components with low
field strength, while the Kitt Peak magnetic field measurements are
somewhat insensitive to very strong and very weak magnetic fields. We
find that average magnetic flux density measured by Kitt Peak can be
used as a proxy for radiative flux, but with limited accuracy.
---------------------------------------------------------
Title: Spectral Irradiance Variations and Magnetic Field Changes
During Solar Cycle 23.
Authors: Pap, J. M.; Bertello, L.; Chapman, G.; Floyd, L. E.; Harder,
J.; Jones, H.; Malanuskenko, O.; Preminger, D.; Turmon, M.
2008AGUFMSH13A1504P Altcode:
Both total irradiance and the Mg core-to-wing ratio was high at the
maximum of weak solar cycle 23. However, photometric observations
from the San Fernando Observatory show that both the number and size
of active regions (spots and faculae) were low at the maximum of
solar cycle 23 which points to the importance of the role of weak
magnetic fields in irradiance variations. The purpose of this paper
is to use new SOLIS spectromagnetograph observations in conjunction
with a newly developed image analysis technique to compare irradiance
time series as function of wavelengths with various surface magnetic
features. One major goal is to compare features derived from the
SOLIS images using the new technique with well-established features
from SFO. Another important goal is to determine the contribution
of active regions/weak fields to irradiance variations at various
wavelengths, using the SOHO/VIRGO and SORCE/SIM data. A third goal
is to determine the extent of irradiance variations not explained by
magnetic structures. To do this, we use a new analysis technique to
evaluate SOLIS spectromagnetograph observations.
---------------------------------------------------------
Title: RHESSI Observations of Facular Limb Darkening at 670 nm
Authors: Zahid, H. J.; Chapman, G.; Fivian, M. D.; Hudson, H.
2008AGUFMSH23A1623Z Altcode:
We use observations from the solar aspect sensor of RHESSI to
characterize the facular limb brightening function. The RHESSI
observations, made with a rotating telescope in space, have great
advantages in the rejection of systematic errors in the very precise
photometry required for such an observation. The facular photometry is
differential relative to a mean background limb-darkening function. The
data base consists of about 1,000 images per day from linear CCDs with
1.73 arc sec square pixels, observing a narrow band at 670 nm. Each
image shows a chord crossing the disk at a different location as the
spacecraft rotates and precesses around its nominal solar pointing,
with amplitude of a few arc sec. We reassemble these line images into
synoptic images with a relatively low time cadence but an almost full
coverage of more than six years. We further mask these images against
SOHO/EIT 284A images in order to select magnetic regions. The resulting
mean limb-darkening function is clearly resolved in radius and has a
maximum at mu = 0.24 and approaches zero at the limb, consistent with
Spruit's "hot wall" model. The contrast is positive at disk center,
and we discuss explanations for this.
---------------------------------------------------------
Title: On the Variability of the Apparent Solar Radius
Authors: Chapman, G. A.; Dobias, J. J.; Walton, S. R.
2008ApJ...681.1698C Altcode:
Full-disk photometric solar images at a wavelength of 672.3 nm have
been obtained daily since 1986 using the CFDT1 (Cartesian Full Disk
Telescope No. 1). An analysis of these images from 1986 through the end
of 2004 December has shown a peak-to-peak variation in the geocentric
north-south solar radius of 0.136 +/- 0.01, approximately in phase
with the solar cycle. The multiple correlation coefficient squared is
R<SUP>2</SUP> = 0.0404 (R = 0.2). While this correlation coefficient
is small, due to the large number of data points (N = 4042), the level
of significance is less than 0.02. The radius had a maximum value near
the times of maximum activity for solar cycles 22 and 23.
---------------------------------------------------------
Title: A Comparison of Feature Classification Methods for Modeling
Solar Irradiance Variation
Authors: Jones, H. P.; Chapman, G. A.; Harvey, K. L.; Pap, J. M.;
Preminger, D. G.; Turmon, M. J.; Walton, S. R.
2008SoPh..248..323J Altcode:
Physical understanding of total and spectral solar irradiance variation
depends upon establishing a connection between the temporal variability
of spatially resolved solar structures and spacecraft observations of
irradiance. One difficulty in comparing models derived from different
data sets is that the many ways for identifying solar features such as
faculae, sunspots, quiet Sun, and various types of "network" are not
necessarily consistent. To learn more about classification differences
and how they affect irradiance models, feature "masks" are compared as
derived from five current methods: multidimensional histogram analysis
of NASA/National Solar Observatory/Kitt Peak spectromagnetograph data,
statistical pattern recognition applied to SOHO/Michelson Doppler
Imager photograms and magnetograms, threshold masks allowing for
influence of spatial surroundings applied to NSO magnetograms, and
"one-trigger" and "three-trigger" algorithms applied to California
State University at Northridge Cartesian Full Disk Telescope intensity
observations. In general all of the methods point to the same areas of
the Sun for labeling sunspots and active-region faculae, and available
time series of area measurements from the methods correlate well with
each other and with solar irradiance. However, some methods include
larger label sets, and there are important differences in detail,
with measurements of sunspot area differing by as much as a factor
of two. The methods differ substantially regarding inclusion of fine
spatial scale in the feature definitions. The implications of these
differences for modeling solar irradiance variation are discussed.
---------------------------------------------------------
Title: The Behavior of Sunspot Contrast during Cycle 23
Authors: Wesolowski, M. J.; Walton, S. R.; Chapman, G. A.
2008SoPh..248..141W Altcode: 2008SoPh..tmp...21W
Results are presented from a study of various sunspot contrast
parameters in broadband red (672.3 nm) Cartesian full-disk digital
images taken at the San Fernando Observatory (SFO) over eight years,
1997 - 2004, of the twenty-third sunspot cycle. A subset of over 2700
red sunspots was analyzed and values of average and maximum sunspot
contrast as well as maximum umbral contrast were compared to various
sunspot parameters. Average and maximum sunspot contrasts were found
to be significantly correlated with sunspot area (r<SUB>s</SUB>=−
0.623 and r<SUB>s</SUB>=− 0.714, respectively). Maximum umbral
contrast was found to be significantly correlated with umbral area
(r<SUB>s</SUB>=− 0.535). These results are in agreement with the
works of numerous other authors. No significant dependence was detected
between average contrast, maximum contrast, or maximum umbral contrast
during the rising phase of the solar cycle (r<SUB>s</SUB>=0.024,
r<SUB>s</SUB>=0.033, and r<SUB>s</SUB>=0.064, respectively). During
the decay phase, no significant correlation was found between average
contrast or maximum contrast and time (r<SUB>s</SUB>=− 0.057 and
r<SUB>s</SUB>=0.009, respectively), with a weak dependence seen between
maximum umbral contrast and cycle (r<SUB>s</SUB>=0.102).
---------------------------------------------------------
Title: Center-to-Limb Variation of the Irradiance Contributions of
Bright Active Regions.
Authors: Preminger, D. G.; Chapman, G. A.
2007AGUFMSH53A1075P Altcode:
We investigate the variable contribution to TSI of a typical bright
active region as it evolves and transits the solar disk. Bright
active regions are manifest as bright faculae on images of the solar
photosphere, but are in fact 3- dimensional structures, stretching up
to coronal heights. Using spacecraft observations of TSI, and ground-
based red and Ca-K line images from the San Fernando Observatory, we
compute the center-to-limb variation of the irradiance contributions
of bright active regions. We evaluate the red continuum irradiance
component that originates in the photosphere and the spectral line
irradiance component that originates in the lower chromosphere. We
also attempt to infer the bolometric contrast of a bright active
region. This work is supported in part by NSF grant ATM-0533511.
---------------------------------------------------------
Title: On The Variability Of The Solar Radius
Authors: Chapman, Gary A.; Dobias, J.
2007AAS...210.2221C Altcode: 2007BAAS...39..127C
We have examined approximately 18 years of full-disk photometric images
of the Sun (1986 through 2004) obtained at the San Fernando Observatory
(SFO) looking for variations in the solar radius. The data are from
the Cartesian Full Disk Telescope number 1 (CFDT1). This telescope
produces images having 512 x 512 pixels with a pixel size of 5.12
arc-sec. We have only used red images obtained at a wavelength of
672.3 nm. Except for infrequent repairs or upgrades, the telescope
is seldom modified. Operating at F/40, the focus of the telescope
is not routinely adjusted. We have corrected for focal changes due
to telescope modifications, differential atmospheric refraction, and
temperature changes. We have compared observed image radii with those
calculated from the ephemeris. The residuals are then fit by least
squares to sinusoids of 10 and 11 year periods to look for a solar
cycle signal. For the 11 year period we find that the apparent solar
radius is greatest at cycle maximum for solar cycles 22 and 23. The
peak-to-peak amplitude is 0.136 +/- 0.010 arc-sec with a multiple
regression coefficient, squared, of 0.0404 which is significant at
better than p = 0.02 level. The cause of the apparent radius change
is under investigation. This work was partially supported by grants
from NASA ( NAG5-12905) and NSF (ATM-0533511). Many CSUN students have
contributed to this work.
---------------------------------------------------------
Title: A Comparison of Sunspot Photometric Indices From Ground-Based
Data and MDI/SOHO
Authors: Chapman, G.; Monaco, R.
2006AGUFMSH41A..05C Altcode:
Comparing ground-based and space-based sunspot photometric indices is
useful in extending the time series for studying variatons in total
solar irradiance (TSI). Photometric sunspot indices from CFDT2 images
obtained at the San Fernando Observatory have been compared with those
from images obtained by MDI/SOHO and the Mauna Loa PSPT. We find
very high correlations between them (R greater than about 0.99 for
most). However, sunspot darkness is overestimated using MDI images
by between 10 to 20 %. A composite sunspot deficit created from red
and blue SFO/CFDT2 images correlates well (R =.99, n=53) with deficits
from PSPT red images. This work has been partially supported by grants
from NASA (NAG5-12905) and the NSF (ATM-0533511).
---------------------------------------------------------
Title: The Growth of Facular Area Surrounding Large, Decaying Sunspots
Authors: Chapman, G. A.; Hoffer, A. S.
2006SoPh..237..321C Altcode: 2006SoPh..tmp...20C
In a previous paper, we investigated the facular area around 31
decaying sunspots of varied size. The growth of facular area as a
function of spot decay was marginally significant (r<SUP>2</SUP> =
0.1255, p = 0.05). Using new data, this paper examines the change in
facular area surrounding large decaying sunspots some of which grew very
rapidly. The data are from full-disk photometric images taken with CFDT2
(2.5″ pixels). For 10 sunspots, we find a statistically significant
increase in facular area as a function of the spot decay rate with a
regression coefficient, squared, of r<SUP>2</SUP> = 0.611 (p < 0.02).
---------------------------------------------------------
Title: A Comparison of Sunspot Photometric Indices from Ground-Based
Data and MDI/SOHO
Authors: Chapman, Gary A.; Monaco, R. J.
2006SPD....37.0711C Altcode: 2006BAAS...38..229C
Comparing ground-based and space-based sunspot photometric indices is
useful in extending the time series for studying variations in total
solar irradiance (TSI). Photometric sunspot indices from CFDT2 images
obtained at the San Fernando Observatory have been compared with those
from images obtained by MDI/SOHO and the Mauna Loa PSPT. We find
very high correlations between them (R greater than about 0.99 for
most). However, sunspot darkness is overestimated using MDI images by
between 10 to 20%. A composite sunspot deficit created from red and
blue SFO/CFDT2 images correlates well (R = 0.99, n=53) with deficits
from PSPT red images. This work has been partly supported by grants
from NASA (NAG5-12905) and the NSF (ATM-0533511).
---------------------------------------------------------
Title: Free-Flight Testing in Support of the Mars Science Laboratory
Aerodynamics Database
Authors: Brown, Jeff; Bogdanoff, David; Chapman, Gary; Loomis, Mark;
Tam, Tim; Yates, Leslie
2006JSpRo..43..293B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Linear Mode Photon Counting LADAR Camera Development for the
Ultra-Sensitive Detector Program
Authors: Jack, M.; Bailey, S.; Edwards, J.; Burkholder, R.; Liu, K.;
Asbrock, J.; Randall, V.; Chapman, G.; Riker, J.
2006amos.confE..93J Altcode:
Advanced LADAR receivers enable high accuracy identification of targets
at ranges beyond standard EOIR sensors. Increased sensitivity of these
receivers will enable reductions in laser power, hence more affordable,
smaller sensors as well as much longer range of detection. Raytheon
has made a recent breakthrough in LADAR architecture by combining very
low noise ~ 30 electron front end amplifiers with moderate gain >60
Avalanche Photodiodes. The combination of these enables detection of
laser pulse returns containing as few as one photon up to 1000s of
photons. Because a lower APD gain is utilized the sensor operation
differs dramatically from traditional "geiger mode APD" LADARs. Linear
mode photon counting LADAR offers advantages including: determination
of intensity as well as time of arrival, nanosecond recovery times
and discrimination between radiation events and signals. In our talk
we will review the basic amplifier and APD component performance, the
front end architecture, the demonstration of single photon detection
using a simple 4 x 4 SCA and the design of a fully integrated photon
counting camera under development in support of the Ultra-Sensitive
Detector (USD) program sponsored by the Air Force Research Laboratory
at Kirtland AFB, NM. <P />Work Supported in Part by AFRL - Contract #
FA8632-05-C-2454 Dr. Jim Riker Program Manager.
---------------------------------------------------------
Title: HST Two-Gyro Mode
Authors: Sembach, K.; Sirianni, M.; Arribas, S.; Bergeron, L. E.;
Biagetti, C.; Biretta, J. A.; Chapman, G.; Cox, C.; Dashevsky, I.;
de Jong, R. S.; Doxsey, R.; Koekemoer, A. M.; Kozhurina-Platais, V.;
Lallo, M.; Lucas, R. A.; Mack, J.; Malhotra, S.; Nelan, E.; Noll, K.;
Pavlovsky, C.; Proffitt, C. R.; Reinhart, M.; Sahu, K.; Schultz, A.;
Vick, A.; Wiklind, T.; Xu, C.; Clapp, B.
2006hstc.conf..375S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparisons between Ground-Based Photometry and Space-Based
Measurements of the Total Solar Irradiance
Authors: Chapman, G.; Cookson, A.; Dobias, J.; Walton, S.
2005AGUSMSH23B..07C Altcode:
We will review the usefulness of ground-based full-disk photometry in
conjunction with space-based measurements of the Total Solar Irradiance
(TSI). It is known that sunspots and faculae cause changes in the
TSI. These features need to be modeled using ground-based photometry
and their effects removed in order to search for possible other causes
of TSI variation. Work to date has shown that approximately 94% of the
variance in TSI can be explained by sunspots and faculae/network. Since
ground-based photometry is carried out daily, it can help identify
anomalies in space-based TSI measurements. Finally, ground-based
photometry can help in tying together TSI measurements from different
spacecraft that have different native irradiance scales. This work
has been partially supported by grants from NASA and NSF.
---------------------------------------------------------
Title: On the Facular Area Surrounding Decaying Sunspots
Authors: Chapman, G. A.; Hoffer, A. S.; Walton, S. R.
2005SoPh..226...37C Altcode:
The change in facular area around decaying sunspots is investigated. The
data are from full-disk photometric images from CFDT1 (5 arc sec
pixels) obtained at the Ca II K-line λ = 393.4 nm. The 31 active
regions are from a list previously used to study the decay rate of
sunspots. We find a weak, marginally significant relation between spot
decay rate and growth of the surrounding facular region (r<SUP>2</SUP>
= 0.1255). We conclude that, for this group of decaying sunspots,
the growth or decay of the surrounding facular region was not clearly
related to the decay rate of an active region's sunspots.
---------------------------------------------------------
Title: Implications of Ground Based Photometric Images for Long Term
Solar Irradiance Variations
Authors: Walton, S. R.; Preminger, D. G.; Chapman, G. A.
2004AGUFMSH53A0303W Altcode:
The San Fernando Observatory (SFO) has produced photometric full
disk solar images at 5 arc second resolution since 1986, and 2.5 arc
second resolution since 1989. We have previously shown that the best
quantities for solar irradiance modeling are the photometric sums Σ ,
defined as the summed residual intensity on these photometric images. In
particular, a linear regression of total solar irradiance S to the time
series of Σ <SUB>r</SUB> and Σ <SUB>K</SUB>, the photometric sums in
broadband red and Ca~II~K filters, respectively, does an excellent job
of reproducing S during cycle 22 (Preminger, Walton, and Chapman 2002,
JGR 107, Issue A11, SSH 6-1). We have also shown (Walton, Preminger and
Chapman 2003, Solar Phys. 213, 301) that variations in the chromospheric
network appear to account for no more than 25% of the change in S over
the solar cycle. In this talk, we extend these results to cycle 23 and
discuss their implication for long term changes in S. In particular,
if Σ <SUB>r</SUB> = Σ <SUB>K</SUB> = 0 can be taken as representing
the complete absence of solar activity, then one would conclude that the
minimum level of S is not much below those currently observed at solar
minimum; quantitatively, about 0.3 W~m<SUP>2</SUP> below that level.
---------------------------------------------------------
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.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: The Spots of October 2003: The Largest Irradiance Dip of
Cycle 23
Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. P.; Walton,
S. R.
2004AAS...204.0214C Altcode: 2004BAAS...36..669C
In October 2003, two large active regions rotated onto the solar
disk. During their transit across the disk, a third region emerged
and rapidly grew. These active regions produced the largest decrease
(over 4 W/m<SUP>2</SUP>) in the total solar irradiance (TSI) for cycle
23. Irradiance variations derived from ground-based photometry have been
compared with the TSI record from the TIM/SORCE experiment. We find that
ground-based irradiance variations due to sunspots and faculae/network
are correlated with the TIM/SORCE TSI with a multiple correlation
coefficient R<SUP>2</SUP> = 0.9754 for an eight-month interval from
1 June 2003 to 31 January 2004. The residuals between the TIM/SORCE
TSI and the ground-based data had a daily rms of approximately 80
ppm. The value of the quiet Sun irradiance was found to be 1361.3 ±
0.1 W/m<SUP>2</SUP>. This work was partially supported by grants from
NASA and NSF.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: Photometry of the full solar disk at the San Fernando
Observatory
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.; Preminger,
D. G.; Walton, S. R.
2004AdSpR..34..262C Altcode:
Daily photometry of the full solar disk began at the San Fernando
Observatory in mid-1985. At present, observations with two
photometric telescopes produce images in the red, blue and CaII
K-line. The smaller telescope obtains images that are 512 ×
512 pixels. The larger one obtains images that are 1024 × 1024
pixels. In addition, the larger telescope produces images with a
narrower K-line and an IR filter. Images are processed to determine
a number of photometric quantities including sunspot deficits and
facular/network excesses. These photometric quantities are highly
correlated with fluctuations in the total solar irradiance (TSI)
from spacecraft experiments.
---------------------------------------------------------
Title: Recent Progress in Modeling Variations in TSI
Authors: Chapman, G.; Cookson, A.; Dobias, J.; Preminger, D.;
Walton, S.
2004cosp...35.3231C Altcode: 2004cosp.meet.3231C
Sunspots and faculae/network are known to be associated with variations
in the Total Solar Irradiance (TSI). A major astrophysical question
is whether there is another component to TSI variations. In order to
answer this question it is necessary to account for the effects of
magnetic activity as accurately as possible. As part of this effort,
daily full-disk photometric images continue to be obtained at the San
Fernando Observatory (SFO). A recent comparison of SFO photometric data
with TSI measurements from the TIM experiment on the SORCE satellite has
been carried out. For an eight-month interval, June 2003 through January
2004, a multiple regression has given an R^2 of 0.9754 (N = 136) and
a quiet Sun irradiance, S_0 of 1361.35 ± 0.11 W/m^2. Corrections for
detector degradation and interpolation to the SFO observation times are
expected to offer slight improvements to these results. The SFO data are
being combined with those from the Precision Solar Photometric Telescope
(PSPT) to create a more complete set of ground-based photometry. This
work has been partly supported by grants from NASA and NSF.
---------------------------------------------------------
Title: Modeling the total solar irradiance: recent progress and
new questions
Authors: Walton, Stephen R.; Preminger, Dora G.; Chapman, Gary A.
2003ESASP.535..265W Altcode: 2003iscs.symp..265W
We report on the recent results from the San Fernando Observatory
(SFO) in our efforts to understand the sources of solar irradiance
variability. The results are based on the SFO's ongoing full disk
photometric images program, which has now accumulated about 1-1/2
solar cycles of data. The results are in three parts: (1) statistics
of solar active regions and their possible variation during the
solar cycle; (2) modeling of the total solar irradiance using the
photometry of both individual features and the entire disk; and (3)
the relative contribution of bright features to increases in total
solar irradiance. Our main conclusions are, respectively: solar active
regions change in ways which affect their use in total irradiance
modeling; the solar cycle change in total irradiance is dominated by
changes in the line blanketing; and that large faculae dominate the
solar cycle in irradiance. Because resolved absolute photometry of
the solar disk has not yet been carried out, all of these results are
based on regression analyses. We discuss what progress we can still
make with such analyses, and close with a prediction of what future
absolute solar photometry may tell us.
---------------------------------------------------------
Title: Imaging Spectropolarimetry of Ti I 2231 nm in a Sunspot
Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.;
Livingston, W.
2003SoPh..215...87P Altcode:
Spectro-polarimetric observations at 2231 nm were made of NOAA 10008
near the west solar limb on 29 June 2002 using the National Solar
Observatory McMath-Pierce Telescope at Kitt Peak and the California
State University Northridge - National Solar Observatory infrared
camera. Scans of spectra in both Stokes I and Stokes V were collected;
the intensity spectra were processed to remove strong telluric
absorption lines, and the Stokes V umbral spectra were corrected for
instrumental polarization. The sunspot temperature is computed using
the continuum contrast and umbral temperatures down to about 3700 K are
observed. A strong Ti i line at 2231.0 nm is used to probe the magnetic
and velocity fields in the spot umbra and penumbra. Measurements of the
Ti i equivalent width versus plasma temperature in the sunspot agree
with model predictions. Zeeman splitting measurements of the Stokes I
and Stokes V profiles show magnetic fields up to 3300 G in the umbra,
and a dependence of the magnetic field on the plasma temperature
similar to that which was seen using Fe i 1565 nm observations of the
same spot two days earlier. The umbral Doppler velocity measurements
are averaged in 16 azimuthal bins, and no radial flows are revealed to
a limit of ± 200 m s<SUP>−1</SUP>. A Stokes V magnetogram shows a
reversal of the line-of-sight magnetic component between the limb and
disk center sides of the penumbra. Because the Ti i line is weak in
the penumbra, individual spectra are averaged in azimuthal bins over
the entire penumbral radial extent. The averaged Stokes V spectra show
a magnetic reversal as a function of sunspot azimuthal angle. The mean
penumbral magnetic field as measured with the Stokes V Zeeman component
splitting is 1400 G. Several weak spectral lines are observed in the
sunspot and the variation of the equivalent width versus temperature
for four lines is examined. If these lines are from molecules, it is
possible that lines at 2230.67, 2230.77, and 2231.70 nm originate from
OH, while the line at 2232.21 nm may originate from CN.
---------------------------------------------------------
Title: The Contribution of Faculae and Network to Long-Term Changes
in the Total Solar Irradiance
Authors: Walton, Stephen R.; Preminger, Dora G.; Chapman, Gary A.
2003ApJ...590.1088W Altcode:
A new database of individual solar features has been compiled from
the full-disk photometric Ca II K images taken at the San Fernando
Observatory (SFO) during solar cycle 22. The distribution of facular
region sizes differs at different phases of the solar cycle; the area
coverage of large active regions is reduced by a factor of about 20
at solar minimum compared to solar maximum, while the smaller regions
cover about half as much area at minimum as at maximum. The irradiance
contribution of large features is about 10 times greater at maximum than
at minimum, while that of small features is about twice as large. We
have used this data set to model the fraction of variation in the
total solar irradiance S that is due to solar features of various
sizes. The data show that large-scale bright solar features, i.e.,
faculae, dominate the ~0.1% change in S between solar maximum and
solar minimum. Using a variety of data sets, we conclude that large
active regions produce about 80% of the total change.
---------------------------------------------------------
Title: Weak Infrared Molecular Lines Reveal Rapid Outflow in Cool
Magnetic Sunspot Penumbral Fibrils
Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.;
Livingston, W.
2003ApJ...590L.119P Altcode:
New imaging spectropolarimetric observations of the Evershed flow
in sunspot penumbrae using weak infrared molecular absorption lines
are presented. A plane-polar coordinate system in the sunspot frame
is defined, allowing averaging of many raw spectra. Molecular lines
show Doppler shifts implying typical horizontal outflow speeds of 6
and up to 9 km s<SUP>-1</SUP>. The Ti I polarimetric spectra show the
same rapid outflow and suggest an average penumbral magnetic field
strength of 1400 G. While these observations show Doppler shifts of
the entire line profile, the velocities are in better agreement with
previous measurements from spectral line asymmetries.
---------------------------------------------------------
Title: A Comparison of Summed Continuum and CaII K-line Images
Authors: Chapman, G. A.; Cookson, A. M.; Walton, S. R.; Smith, C.
2003SPD....34.0707C Altcode: 2003BAAS...35..821C
Full-disk photometric images are obtained with two telescopes on
a daily basis at the following wavelengths: 393 nm (CaII K-line),
472 nm and 672 nm. In order to explore the characteristics of the
fainter facular/network elements, we obtain, on occasion, up to 10
images as closely spaced in time as possible. For the work reported
on here, we have used red continuum images at 672 nm (bandpass 10 nm)
from the CFDT2 telescope (pixel size 2.5" x 2.5"). These images have
been coaligned and summed to reduce noise from non-magnetic intensity
features. The customary image processing tools have been applied (Walton
et al. 1998). The quiet sun rms intensity fluctuation drops from about
0.58 % on a single image to about 0.21 % on the summed image. On the
summed red image, bright facular/network features as faint as about
0.6 % become visible across the solar disk. These features will be
compared with those found on images obtained in the CaII K-line to
determine their reality in terms of K-line faculae. <P />This work
has been partially supported by grants from NASA (NAG5-7191) and NSF
(ATM-9912132). <P />Reference Walton, S.R., Chapman, G.A., Cookson,
A.M., Dobias, J.J. and Preminger, D.G. 1998, Solar Phys. 179, 31-42.
---------------------------------------------------------
Title: Photospheric Line Equivalent Widths in Calcium K Faculae
Authors: Walton, S. R.; Preminger, D. G.; Chapman, G. A.; Cookson,
A. M.
2003SPD....34.0706W Altcode: 2003BAAS...35..821W
We have recently shown (Preminger, Walton, and Chapman 2002) that
the total solar irradiance S can be modeled by a linear combination
of photometric quantities which measure the fractional brightness
change in the continuum and in the Ca II K line. We concluded that
the change in S on solar cycle time scales is caused by variations in
spectral lines, not in the continuum. <P />In order to further test
this conclusion, we have begun comparing our photometric Ca II K images
with line equivalent width maps made in Fe I 6302.5. Bright features
in our K images are well correlated with areas of lower equivalent
width. We are beginning to quantitatively measure this correlation
and will present further results at the meeting. <P />This research
has been supported by NSF grant ATM-9912132.
---------------------------------------------------------
Title: Weak IR Lines Reveal Rapid Outflow in Cool Magnetic Penumbra
Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.;
Livingston, W.
2003SPD....34.1106P Altcode: 2003BAAS...35..827P
New imaging spectropolarimetric observations of the Evershed flow in
sunspot penumbrae using weak infrared molecular absorption lines are
presented. A plane-polar coordinate system in the sunspot frame is
defined, allowing averaging of many raw spectra. Molecular lines show
Doppler shifts implying typical horizontal outflow speeds of 6 to 9
km/sec. The Ti I polarimetric spectra show the same rapid outflow
and suggest an average penumbral magnetic field strength of 1400
Gauss. While these observations show Doppler shifts of the entire
line profile the velocities are in better agreement with previous
measurements from spectral line asymmetries.
---------------------------------------------------------
Title: A Statistical Analysis of the Characteristics of Sunspots
and Faculae
Authors: Walton, Stephen R.; Preminger, Dora G.; Chapman, Gary A.
2003SoPh..213..301W Altcode:
We present results from a study of sunspots and faculae on continuum
and Ca ii K images taken at the San Fernando Observatory (SFO) during
1989-1992; a total of approximately 800 images in each bandpass were
used. About 18 000 red sunspots, 147 000 red faculae, and 800 000 Ca
ii K faculae were identified based on their contrasts. In addition,
we computed the contrasts of pixels on the red images cospatial with Ca
ii K faculae. Sunspot contrasts show a strong dependence on size but no
dependence on heliocentric angle. There are continuous but systematic
differences among facular regions. We find that the contrast of Ca
ii K faculae is relatively insensitive to heliocentric angle, but is
a strong function of facular size, in the sense that larger Ca ii K
faculae are always brighter. The contrast of red faculae is a function
of both heliocentric angle and size: the contrast functions show that
larger regions contain larger flux tubes, contain deeper flux tubes,
and have larger filling factors than small facular regions. Comparisons
of cospatial pixels on red and Ca ii K images show a tight correlation
between the average contrast of a region in the continuum and its size
and heliocentric angle in the Ca ii K images. The average contrast of
all facular regions is positive everywhere on the disk, even though
the largest regions contain flux tubes which appear dark at disk center.
---------------------------------------------------------
Title: Temperature Dependence of Molecular Line Strengths and Fe i
1565 nm Zeeman Splitting in a Sunspot
Authors: Penn, M. J.; Walton, S.; Chapman, G.; Ceja, J.; Plick, W.
2003SoPh..213...55P Altcode:
Spectroscopic observations at 1565 nm were made in the eastern half of
the main umbra of NOAA 9885 on 1 April 2002 using the National Solar
Observatory McMath-Pierce Telescope at Kitt Peak with a tip-tilt
image stabilization system and the California State University
Northridge-National Solar Observatory infrared camera. The line depth
of the OH blend at 1565.1 nm varies with the observed continuum
temperature; the variation fits previous observations except that
the continuum temperature is lower by 600 K. The equivalent width of
the OH absorption line at 1565.2 nm shows a temperature dependence
similar to previously published umbral molecular observations at 640
nm. A simple model of expected OH abundance based upon an ionization
analogy to molecular dissociation is produced and agrees well with the
temperature variation of the line equivalent width. A CN absorption
line at 1564.6 nm shows a very different temperature dependence, likely
due to complicated formation and destruction processes. Nonetheless a
numerical fit of the temperature variation of the CN equivalent width
is presented. Finally a comparison of the Zeeman splitting of the Fe i
1564.8 nm line with the sunspot temperature derived from the continuum
intensity shows an umbra somewhat cooler for a given magnetic field
strength than previous comparisons using this infrared 1564.8 nm line,
but consistent with these previous infrared measurements the umbra is
hotter for a given magnetic field strength than magnetic and temperature
measurements at 630.2 nm would suggest. Differences between the 630.2
nm and 1564.8 nm umbral temperature and magnetic field relations are
explained with the different heights of formation of the lines and
continua at these wavelengths.
---------------------------------------------------------
Title: On the decay rate of sunspots
Authors: Chapman, G. A.; Dobias, J. J.; Preminger, D. G.; Walton, S. R.
2003GeoRL..30.1178C Altcode: 2003GeoRL..30d..27C
We have analyzed the decay of 32 sunspots observed during the years
1988 through 2001 at the San Fernando Observatory (SFO). The data are
from digital images obtained in the red (672 nm) with the Cartesian
Full Disk Telescope No.1 (CFDT1). We find that the rate of decay is
strongly correlated with the total sunspot area and the umbral to
total area ratio. The multiple correlation coefficient is 0.93. Thus,
the unexplained variance from this simple model is (1-0.87). We find
that for the sunspots of this study, the decay rate is not a constant
and that there is no significant correlation between the decay rate
and the square root of the total spot area.
---------------------------------------------------------
Title: Modeling the Variations in TSI Using Precision Ground-Based
Photometric Images
Authors: Chapman, G. A.; Walton, S. R.; Cookson, A. M.; Dobias, J. J.;
Preminger, D. G.
2002AGUFMSH21B..01C Altcode:
Precision photometric full-disk images of the sun have been obtained
at the San Fernando Observatory (SFO) beginning in mid-1985. Images
in several wavelengths are obtained daily but for modeling the Total
Solar Irradiance (TSI) from spacecraft, the red (672 nm) and the
K-line (393 nm) images have been the most useful. Two telescopes are
in regular operation, Cartesian Full Disk Telescope (CFDT) number
1 and 2. They produce images that have 512 x 512 pixels and 1024 x
1024 pixels, respectively. Multiple linear regressions of sunspot
deficits and facular excesses compared with Nimbus-7 and ACRIM-I
values of TSI give values of R<SUP>2</SUP> of from 0.80 to 0.85,
depending on data intervals and the particular spacecraft. More recent
fits to the composite TSI of Fröhlich and Lean for cycle 22 give
values of R<SUP>2</SUP> of 0.91. These fits are affected by noise in
both ground-based and space-based data. This value of R<SUP>2</SUP>
suggests, especially considering the effects of noise, that less than
10% of the TSI variance is unexplained by the effects of sunspots and
faculae/network. We are in the process of determining whether or not
the coefficients from fits to cycle 22 TSI will also provide good fits
to cycle 23 TSI. This research has been partially supported by grants
from NSF (ATM-9912132) and NASA (NAG5-7191 and NAG5-7778).
---------------------------------------------------------
Title: Photometric quantities for solar irradiance modeling
Authors: Preminger, D. G.; Walton, S. R.; Chapman, G. A.
2002JGRA..107.1354P Altcode:
We analyze photometric quantities for the modeling of the total
solar irradiance, S. These quantities are derived from full-disk
solar images taken at the San Fernando Observatory. We introduce a
new quantity, the photometric sum, Σ, which is the sum over an entire
image of each pixel's contribution to the irradiance in that image. Σ
combines both bright and dark features; and because the sum is over
the entire image, it will include low contrast features that cannot
be identified directly. Specifically, we examine Σ<SUB>r</SUB>,
Σ<SUB>b</SUB>, and Σ<SUB>K</SUB>, the photometric sums over
broadband red, broadband blue, and 1-nm bandpass Ca II K images,
respectively. Σ<SUB>r</SUB> and Σ<SUB>b</SUB> measure the effects
of solar features on the variability in S at two different continuum
wavelengths. Σ<SUB>K</SUB> measures the variability in spectral lines
due to solar features. We find that Σ<SUB>r</SUB> and Σ<SUB>b</SUB>
have no long-term trend. Σ<SUB>K</SUB>, however, varies in phase with
the solar cycle. We carry out several multiple linear regressions on
the value of S from cycle 22; the best fit uses Σ<SUB>r</SUB> and
Σ<SUB>K</SUB> and reproduces the observed composite S with a multiple
regression coefficient R = 0.96. We conclude that the long-term change
in S over the solar cycle can be accounted for by the variability in
the spectral lines as measured by Σ<SUB>K</SUB>, assuming no change
in the quiet Sun; the contribution of the continuum to the variations
in S is only on active region timescales.
---------------------------------------------------------
Title: A Study of AR 9144; A Fast-Growing EFR
Authors: Chapman, G. A.
2002SoPh..209..141C Altcode:
This paper is a study of NOAA region 9144, an emerging flux region
(EFR) which grew rapidly beginning 25 August 2000. This region was
visible in SOHO data at 0 UT on 25 August 2000 as a small, isolated
spot. It was recognizable as an active region with multiple spots by
06:00 UT on the 25th and was a fully developed AR by 24<SUP>h</SUP> UT
on the 26th of August. Data are presented from the Michelson Doppler
Imager (MDI) experiment on the Solar and Heliospheric Observatory
satellite (SOHO), from Big Bear Solar Observatory (BBSO) and from
the San Fernando Observatory (SFO). The MDI data are Dopplergrams,
magnetograms, and continuum images. The BBSO data are high-resolution
Hα filtergrams. The SFO data are Dopplergrams, magnetograms and
continuum images from the Video SpectraSpectroHeliograph (VSSHG). MDI
Doppler images show that during the rapid growth of this EFR during
the day of 26 August, the most obvious feature in area and lifetime
is a red-shifted area in the trailing part of the region. SFO Doppler
images show a more complex pattern, but still dominated by red shifts
in the trailing part of the region near the end of the day of 26 August.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: The Contribution of Faculae and Network to Long Term Changes
in the Total Solar Irradiance
Authors: Walton, S. R.; Preminger, D. G.; Chapman, G. A.
2002AAS...200.5709W Altcode: 2002BAAS...34..738W
A new database of individual solar features has been compiled from
the full disk photometric images taken at the San Fernando Observatory
(SFO) since 1989. The distribution of facular region sizes differs at
different phases of the solar cycle; the area coverage of large active
regions is reduced by a factor of about 20 at solar minimum compared
to solar maximum, while the smaller regions cover about half as much
area at minimum as at maximum. We have used this data set to model
the fraction of variation in the total solar irradiance S which is
due to solar features of various sizes. The data show that large-scale
solar features dominate the 0.1% change in S between solar maximum and
solar minimum; the chromospheric network produces about 15% to 25%
of the total change. We have also used new total irradiance models
to evaluate the plausible level of S in the absence of all magnetic
activity on the sun, and conclude that S would be reduced by about
0.3 W/m<SUP>2</SUP> below the level presently observed at activity
minimum. This work was supported by NSF grant ATM-9912132 and NASA
grants NAG5-7191 and NAG5-7778.
---------------------------------------------------------
Title: Further Studies of the Bolometric Contrast of Sunspots
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.; Walton, S. R.
2002AAS...200.3806C Altcode: 2002BAAS...34..699C
Daily images are obtained at the San Fernando Observatory (SFO)
of the full solar disk with two photometric telescopes, CFDT1 and
CFDT2. CFDT1 produces images with 5" x 5" pixels while CFDT2 produces
images with 2.5" x 2.5" pixels. In a previous paper (Chapman et
al. 1994) we reported on the bolometric contrast of sunspots using
red images from CFDT1. The bolometric contrast, α <SUB>eff</SUB>,
is heuristically defined as α <SUB>eff</SUB> = D<SUB>r/(2</SUB> x
PSI), where D<SUB>r</SUB> is the photometric deficit in the red image
and PSI is the usual Photometric Sunspot Index. Here, we will report
on studies of the bolometric contrast from red CFDT2 images. We will
examine the effects of higher spatial resolution and we will look for
differences in the bolometric contrast between cycle 22 and 23. This
research was partially supported by grants from NSF (ATM-9912132) and
NASA (NAG5-7191). Reference: Chapman, G.A., Cookson, A.M. and Dobias,
J.J. 1994, Ap.J. 432, 403.
---------------------------------------------------------
Title: Growth and Decay of Solar Active Regions
Authors: Dobias, J. J.; Chapman, G. A.; Cookson, A. M.; Preminger,
D. G.; Walton, S. R.
2002AAS...200.5710D Altcode: 2002BAAS...34..738D
We report here on a study of growth and decay rates of sunspot and
facular areas of solar active regions. The data used in this project
come from an ongoing program of daily photometric observations of the
sun with the Cartesian Full Disk Telescope No. 1 (CFDT1) at the San
Fernando Observatory (SFO). Sunspot regions are determined from images
taken with a red filter centered at 672.3 nm with a bandpass of 9.7 nm,
while images taken with a Ca II K line filter, centered at 393.4 nm and
with a bandpass of only 1nm, are used to find facular areas. Before
any areas can be found on any observed images, they have to be
calibrated then flattened by removing limb darkening thus producing
contrast images. Sunspot areas are then determined from any pixel with
contrast of -8.5% or less, while any pixel on a K line contrast image
with a contrast of +4.8%/μ or higher, where μ is the cosine of the
heliocentric angle, is considered to be a facular pixel. To identify
the areas as clearly as possible, studied active regions were usually
observed on the sun with relatively low activity; that means that
each region is either alone on the sun's disk or with only very few
other active regions present. Furthermore, to obtain growth and decay
patterns of the areas as reliably as possible, only such active regions
must be chosen for which there is as complete observational coverage as
possible. At the present time studies have been finished for only a few
active regions, but analysis of several others is on going. Obtained
results will be presented at the meeting. This work is supported by
NSF grant ATM-9912132 and NASA grants NAG5-7191 and NAG5-7778.
---------------------------------------------------------
Title: Solar irradiance variability: current questions and the need
for improved accuracy and precision
Authors: de Toma, G.; White, O.; Chapman, G.; Walton, S.
2002cosp...34E1106D Altcode: 2002cosp.meetE1106D
In this paper, we review the recent observations of solar spectral
and total irradiance variability as measured by ground-based and space
observatories during solar cycles 22 and 23. We compare empirical models
of solar irradiance variability based on photometric observations
of faculae and sunspots with total solar irradiance measurements to
demonstrate the capability of empirical models to reproduce solar
radiative variability. We also examine our current understanding
of solar radiative variations over solar cycle and longer time
scales. Finally, we discuss the need for improved absolute accuracy
and precision to understand the solar radiative variability and its
influence on the Earth's climate.
---------------------------------------------------------
Title: Results from a Program of Full Disk Solar Photometry
Authors: Chapman, G.; Cookson, A.; Dobias, J.; Preminger, D.;
Walton, S.
2002cosp...34E.669C Altcode: 2002cosp.meetE.669C
Photometry of the full solar disk has been carried out at the San
Fernando Observatory since 1985. A number of quantities are computed
from images obtained in the red, blue and K-line. Photometric irradiance
deficits due to sunspots and excesses due to faculae and network are
highly correlated with variations in the total solar irradiance (TSI)
from spacecraft. Multiple correlation coefficients as high as 0.95 to
0.97, depending on spacecraft and interval, have been obtained. Recent
work shows that the short-term rotation variation of the TSI is due
to the coming and going of active regions whereas the solar cycle
variations on the scale of the solar cycle are due to changes in line
blanketing associated with faculae and network.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: Obituary: Adrian D. Herzog
Authors: Chapman, Gary; Walton, Stephen
2001BAAS...33.1568C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effect of Magnetic Fields on Solar Irradiance Variations
Authors: Pap, J. M.; Arge, N.; Chapman, G.; Floyd, L. E.; Turmon, M.
2001AGUFMSH11C0731P Altcode:
In this paper we show the relation between solar total and UV irradiance
and magnetic field variations. Comparison of the multi-decade long
irradiance and magnetic field measurements indicates that the shape and
magnitude of irradiance variations are different from that of magnetic
indices. Specifically, while magnetic indices show that solar cycle
23 is weaker than the two previous cycles, the long-term variation of
total solar irradiance within the last three solar cycles is rather
symmetrical, showing that its maximum and minimum levels were about
the same within their measuring uncertainties. Study of UV irradiance
variations also shows that UV irradiance is higher at the maximum of
cycle 23 than magnetic indices, such as sunspot number, the full disk
magnetic flux, and faculae indices. The long-term irradiance data
bases are compared with the Kitt Peak full disk magnetic field and
the Wilcox polar magnetic field measurements as well as photometric
measurements of sunspots and faculae.
---------------------------------------------------------
Title: Solar Feature Identification using Contrasts and Contiguity
Authors: Preminger, Dora G.; Walton, Stephen R.; Chapman, Gary A.
2001SoPh..202...53P Altcode:
We present a new technique for the rapid, automatic identification
of solar features on full-disk photometric images. The technique
permits the detection of features whose contrasts are only slightly
above the noise level. Contrast and contiguity criteria are used
to identify pixels belonging to an individual feature. The criteria
used are simple and objective, and do not require one to guess at the
contrast distribution of the features. Comparison of Ca ii K images
with magnetograms shows excellent agreement between the identified
features and observed magnetic features. In addition, we can now
reliably identify faculae on continuum images. Since this technique can
be rapidly applied to a large set of images, it allows us to compile
a database of the physical and photometric properties of individual
solar features.
---------------------------------------------------------
Title: An Improved Determination of the Area Ratio of Faculae
to Sunspots
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.; Walton, S. R.
2001ApJ...555..462C Altcode:
We report new results on the ratio of facular area to sunspot area from
a program of continuing photometric observations using the Cartesian
Full Disk Telescope No. 1 (CFDT1) at the San Fernando Observatory
(SFO). The facular areas are determined from images obtained with a
1 nm bandpass Ca II K line filter, and sunspot areas are determined
from red images at 672 nm with a 10 nm bandpass filter. On the K line
images faculae were identified by pixels that had a contrast equal to or
greater than 4.8% divided by μ. Previously, we found that the average
facular-to-spot area ratio was 16.7+/-0.5 during the latter part of
solar cycle 22 and that there was a small but statistically significant
rise in the ratio with time. If we take an average from the beginning
of the K line data (mid-1988) until the middle of 1996, excluding days
of zero sunspot area, the average ratio is 16.4+/-0.4. The average ratio
from mid-1996 to the end of 1999 November is 12.6+/-0.5. Including days
of zero sunspot area for these same intervals we find average ratios of
16.8+/-0.5 and 13.2+/-0.6, respectively. We have recently reprocessed
our K line images, which have been photometrically “cleaned.” We
can now reliably identify facular pixels with a contrast criterion of
2.4%, resulting in an increase in the average facular-to-spot ratio
of approximately 3. The average facular and sunspot areas for cycle
23 are significantly lower than for cycle 22.
---------------------------------------------------------
Title: The Decline of Solar Cycles 22 and 23 Compared
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.; Walton, S. R.
2001AGUSM..SP31B07C Altcode:
During the declining phase of solar cycle 22, a dramatic drop by
a factor of two occured in the corrected area of photospheric
faculae as determined by a 1 nm bandwidth K-line filter. This
filter, in the Cartesian Full Disk Telescope no. 1 (CFDT1) at the
San Fernando Observatory, responds primarily to faculae in the upper
photosphere. Although the sunspot area (determined from red photometric
images) also dropped at this time, it seemed to recover over the
succeeding months. In the year 2000 during the peak or declining
phase of cycle 23, the spot area dropped suddenly by a factor of
two or more. However, at this time the facular area seemed to fall
only slightly. Sunspot area and facular area data will be presented
and discussed for these two cycles. This research has been partially
supported by grants from NSF (ATM-9912132) and NASA (NAG5-7191).
---------------------------------------------------------
Title: Thousands of Faculae Can't be Wrong
Authors: Walton, S. R.; Preminger, D. G.; Chapman, G. A.
2001AGUSM..SP21A04W Altcode:
We present results from a study of facular regions on images taken at
the San Fernando Observatory (SFO) CFDT1 telescope; the images are
512 square full disk photometric images taken through two filters:
672.3~nm center, 10~nm bandpass (“red”) and 393.4~nm center, 1~nm
bandpass (“Ca~II~K”). Faculae were identified using an algorithm
which requires three adjacent pixels above a contrast trigger, allowing
reliable identification of very faint features (contrasts of order a
few tenths of a percent). Over 147,000 red faculae were identified, and
about 800,000 Ca~II~K faculae. In addition, we computed the contrasts
of pixels on the red images cospatial with Ca~II~K faculae. Our
observations were interpreted with reference to flux tube models
of solar faculae. There are continuous but systematic differences
among facular regions. We find that the contrast of Ca~II~K faculae
is relatively insensitive to heliocentric angle, but is a strong
function of facular size, in the sense that larger Ca~II~K faculae
are always brighter. The contrast of red faculae is a function of both
heliocentric angle and size. We conclude that larger regions contain
larger flux tubes, contain deeper flux tubes, and have larger filling
factors than small facular regions. Comparisons of cospatial pixels on
red and Ca~II~K images show a tight correlation between the average
contrast of a region in the continuum and its size and heliocentric
angle in the Ca~II~K images. This relation might allow deduction of
the average continuum facular contrast for time periods when only
areas and locations of Ca~II~K faculae are available, and is thus
important for proxies of the solar irradiance. The largest Ca~II~K
faculae are found in the activity belts, but the smaller regions are
more uniformly distributed, so our smaller Ca~II~K regions are actually
bright network. Graphs of dN/dA, the differential size distribution,
of Ca~II~K faculae, show that network is equally prevalant at all
phases of the solar cycle, and thus cannot account for changes in
solar irradiance from maximum to minimum. This work was supported by
NSF grant ATM-9912132 and NASA grant NAG5-7191.
---------------------------------------------------------
Title: Rotation of CaII K-line Faculae in Solar Cycles 22 and 23
Authors: Chapman, G. A.; Lawrence, J. K.; Walton, S. R.
2001AAS...198.7103C Altcode: 2001BAAS...33Q.893C
We have examined the temporal behavior of CaII K-line faculae for
parts of solar cycles 22 and 23. The data are from photometric images
obtained at the San Fernando Observatory (SFO) using the Cartesian Full
Disk Telescope no. 1 (CFDT1). The images are 512 by 512 pixels, each
pixel being 5.12 arc-sec square. The bandpass of the K-line filter
is 1 nm. For the interval mid-1988 to mid-1996 (most of cycle 22)
we find an autocorrelation very much like that published in Chapman,
Cookson and Dobias (1997). At a lag of 150 to 160 days, the 27-day
rotational modulation disappears, reappearing later but at a different
phase. For the second interval, from mid-1996 to the end of 1999,
the autocorrelation shows the 27-day rotational modulation persisting
out to a lag of nearly one year. Lomb periodograms will be shown for
these data for several intervals and the results will be discussed. This
research has been partially supported by NSF Grant ATM-9912132 and NASA
Grant NAG5-7191. Reference: Chapman, G.A., Cookson, A.M. and Dobias,
J.J. 1997, Ap.J. 482, 541.
---------------------------------------------------------
Title: Sunspot Areas Compared by Hemisphere
Authors: Chapman, G. A.; Walton, S. R.
2001AGUSM..SP31B03C Altcode:
Photometric images of the whole solar disk are obtained on a daily
basis at the San Fernando Observatory. Red images obtained at 672 nm
are used to determine total and umbral areas as well as photometric
quantities. New software (Preminger, Walton and Chapman, 2001) permits
a search for features by size and location. We will present results
of separately comparing sunspot areas for the northern and southern
hemisphere for the past two solar cycles using data from the smaller
photometric telescope (CFDT1) which has pixels of approximately 5"
x 5". This research has been partially supported by NSF (ATM-9912132)
and NASA (NAG5-7191). Reference Preminger, D.G., Walton, S.R. and
Chapman, G.A. 2001 submitted to Solar Phys.
---------------------------------------------------------
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: Solar Photosphere: Faculae
Authors: Chapman, G.
2000eaa..bookE2253C Altcode:
Photospheric faculae, often called white-light faculae, are best seen
away from the center of the solar disk beginning at a heliocentric
angle of about 60°. They appear as irregular bright patches whose
contrast increases towards the solar LIMB, and are more extensive when
they accompany sunspot groups. Near the limb they tend to appear as
facular granules. The facular granules consist of aggreg...
---------------------------------------------------------
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: New Measurements of the Ratio of Facular to Sunspot Area
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
2000SPD....31.0126C Altcode: 2000BAAS...32..805C
We report new results on the ratio of facular area to sunspot area from
a program of continuing photometric observations using the Cartesian
Full Disk Telescopes at the San Fernando Observatory (SFO). The facular
areas are determined from images obtained with a 1 nm bandpass K-line
filter and the sunspot areas are determined from red images at 672
nm. On the K-line images faculae were identified by pixels that had a
contrast equal to or greater than 4.8% divided by μ . Previously, we
found the average facular to spot area ratio was 16.7 +/- 0.5 during
the latter part of solar cycle 22 (Chapman, Cookson & Dobias,
1997) and that there was a small but statistically significant rise
in the ratio with time. If we take an average from the beginning of
the K-line data (mid-1988) until the middle of 1996, excluding days of
zero sunspot area, the average ratio is 17.5 +/- 5.1. The average ratio
from mid-1996 to the end of November 1999 is 12.6 +/- 4.8. Including
days of zero sunspot area for these same intervals we find an average
ratio of 21.5 +/- 9.2 and 19.9 +/- 15.3, respectively. We have recently
reprocessed our K-line images which have been photometrically cleaned
(Walton et al. 1998). We can now reliably identify facular pixels with
a contrast criterion of 2.4% resulting in an increase in the average
facular to spot ratio of approximately three. This research has been
partially supported by NSF Grant ATM-9504374 and NASA Grants NAGW-3017
and NAG5-4973. <P />References <P />Chapman, G.A., Cookson, A.M. &
Dobias, J.J. 1997, Ap.J. 482, 541. <P />Walton, S.R., Chapman, G.A.,
Cookson, A.M., Dobias, J.J. and Preminger, D.G. 1998 Solar Phys. 179,
31.
---------------------------------------------------------
Title: An analysis of full-disk observations of facular contrast in
the blue and red
Authors: Ahern, Sean; Chapman, G. A.
2000SoPh..191...71A Altcode:
Full-disk images from the Cartesian Full-Disk Telescope no. 2 (CFDT2)
were used to study the center-to-limb (CLV) variation of facular
contrast in two colors. The CFDT2 images, which have 2.5 arc sec pixels,
were obtained during the summer months of 1993, 1994 and 1995. In order
to minimize the bias in finding faint facular features in continuum
images, we have used coaligned images obtained in the Ca K-line to
identify faculae. Faculae were sorted into 20 annular bins of equal
width. To reduce the effects of seeing, faculae were not identified
closer to the limb than μ=0.2. The facular pixel contrasts were fitted
to various trial functions. The contrast in the blue filter (470.6 nm)
rose from 0.122% at disk center to 12.2% at μ=0.2. The contrast in
the red filter (672.3 nm) rose from 0.13% at disk center to 8.16% at
μ=0.2. We have also analyzed the facular contrasts multiplied by their
μ-value to obtain an estimate of facular flux tube contrasts. These
flux tube contrasts increased roughly linearly from μ=0.95 to 0.25. The
blue flux tube contrast reached a maximum of 2.48% near μ=0.25. The
red flux tube contrast reached a maximum of 1.59% at μ=0.2. These
contrast values are not corrected for the filling factor. The blue
curve leveled off slightly betwen μ=0.25 and 0.2 while the red curve
showed no deviation from its linear trend. These results may provide
some support for the hot wall model of facular flux tubes.
---------------------------------------------------------
Title: A Search For Variations in the Solar Radius
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.; Walton, S. R.
1999AAS...194.9302C Altcode: 1999BAAS...31..988C
We report on an ongoing analysis of the radius of solar images from two
photometric telescopes at the San Fernando Observatory. Data used from
CFDT1 with 5 arc-sec pixels begins in 1986. Data used from CFDT2 with
2.5 arc-sec pixels begins in the summer of 1992. The solar diameter is
determined along the length of the linear diode array in the geocentric
north-south direction by fitting the entire image as described in
Walton, et al. (1998). Previously, we reported a solar radius variation
in phase with the solar cycle using data from CFDT1. A reanalysis
of those data have resulted in a much smaller radius variation than
that reported in Chapman, et al. (1998). We will report on efforts
to compare the radius found from CFDT1 images with that from CFDT2
images. The two instruments have undergone improvements but each at
different times. We will discuss possible radius variations between
the two instruments. This work was supported by NSF grant ATM-9504374
and NASA grant NAG5-4973. References Chapman, G.A., Cookson, S.R.,
Dobias,J.J. and Walton, S.R. 1998, Spring AGU Meeting. Walton, S.R.,
Chapman, G.A., Cookson, A.M., Dobias, J.J. and Preminger, D.G. 1998,
Solar Phys. 179, 31.
---------------------------------------------------------
Title: Doppler Patterns Associated with Emerging Flux Regions
Authors: Chapman, G. A.
1998SoPh..183...15C Altcode:
We have observed several emerging flux regions (EFRs) using the Video
Spectra-Spectro-Heliograph (VSSHG) at the San Fernando Observatory
(SFO). The best studied region, NOAA 7968, was near disk center when
it was observed on 5-8 June 1996. This EFR showed no organized upflow
between the leader and follower spots over the 4-day period covered
by our observations. The main concentrations of magnetic flux in the
region (leader and follower) showed a slow separation as flux emerged,
but little or no upflow was seen. Two other EFRs were observed for
part of a single day each and one region was observed for only one
sequence. For all regions observed, no discrete features were seen
between the leader and follower polarity sunpots that had upflowing
material as the regions grew. In all cases, the downward velocities
were smaller in area than the magnetic parts of the regions. At times
there were several localized areas of greater-amplitude downflows
near sunspots.
---------------------------------------------------------
Title: Processing Photometric Full-Disk Solar Images
Authors: Walton, S. R.; Chapman, G. A.; Cookson, A. M.; Dobias, J. J.;
Preminger, D. G.
1998SoPh..179...31W Altcode:
Daily, photometric, full-disk digital solar images have been taken at
the San Fernando Observatory (SFO) at two resolutions and in several
wavelengths for more than eleven years. We describe the standard data
processing techniques used for these images, including: calibration,
limb fitting, geometric correction, and production of a solar contrast
map by limb-darkening removal. The resulting contrast maps have a
photometric accuracy which is often a few tenths of a percent. We
show that the geometric accuracy of our images, as measured by the
reproducibility of disk and sunspot areas, is very high as well. The
techniques described in this paper should be applicable to any
instrument producing full-disk photometric images.
---------------------------------------------------------
Title: Diachronic Photometric Full-Disk Solar Images
Authors: Chapman, G. A.
1998ASPC..140..237C Altcode: 1998ssp..conf..237C
No abstract at ADS
---------------------------------------------------------
Title: Precision Ground-Based Photometry from Full-Disk Images
Authors: Chapman, G. A.; Walton, S. R.
1998sers.conf..437C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A New Data System for the San Fernando Observatory Video
Spectra-Spectroheliograph
Authors: Walton, S. R.; Chapman, G. A.
1997AAS...191.7410W Altcode: 1997BAAS...29.1325W
The San Fernando Observatory Video Spectra-Spectroheliograph (SFO
VSSHG) has been used for observation of vector magnetic fields on
the Sun for the last several years, and was described in Walton and
Chapman (1996), Solar Phys. 166, 267. The current VSSHG camera is a
commercial video format (512 by 480) CCD camera from which spectra are
recorded on analog 3/4” professional grade videocasettes. Recently,
commercial off-the-shelf hardware has become available which can
equal the high speed and capacity of this system in a pure digital
mode. We are developing a new data system for the VSSHG consisting
of a 1024 square digital CCD camera capable of 15 frames per second,
an Intel Pentium-II based personal computer with fast-wide SCSI hard
disk, and a DLT-7000 digital linear tape drive. This combination of
off-the-shelf hardware, purchased for about \$30,000, should achieve
the data rate of 7.5 megabytes per second (MB/s) required for recording
5 frames per second from the CCD camera to the hard disk in real time,
which is sufficient for the VSSHG. The DLT tape drive can record 35
gigabytes at a rate of 5 MB/s uncompressed, and a small amount of data
compression should allow it to record spectra in real time as well. As
of this writing, only the computer has been received, but preliminary
tests show that its hard disk performs at speeds well over 10 MB/s
with no special optimizations. We will take delivery on the camera
soon, and hope to have the first images with the new camera early
this winter. A detailed description of the data system and on-line
processing algorithms will be presented.
---------------------------------------------------------
Title: Variations in the Solar Radius during Solar Cycle 22
Authors: Chapman, G.; Cookson, A.; Dobias, J.; Walton, S.
1997AAS...19112001C Altcode: 1997BAAS...29.1402C
We have observed an apparent change in the solar radius that is in phase
with the solar cycle during cycle 22. The maximum radius was during
the period corresponding to the maximum of solar cycle 22. The data are
from two full-disk photometric telescopes in daily operation at the San
Fernando Observatory. Each telescope has a linear array of photodiodes
and obtains a complete image of the sun by using the earth's rotation
to scan the array from west to east across a solar image produced by
an achromatic objective lens. Examining the radius for the red images
(673 nm, bandpass 10 nm) we find that the radius exhibits a peak to
peak variation of approximately 0.3 to 0.4 arc-sec. This result is in
approximate agreement with that found by Ulrich and Bertelo (1995)
from Mt. Wilson images obtained in the wing of the Fe-line 525.0
nm. However, our results refer to deeper layers in the photosphere
since the SFO red images are very nearly continuum images. Whether
this variation represents a real change in the solar radius or just
a change in the structure of the atmosphere remains to be seen. This
research has been partially supported by grants from NSF and NASA.
---------------------------------------------------------
Title: Solar Variability and the Relation of Facular to Sunspot
Areas during Solar Cycle 22
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1997ApJ...482..541C Altcode:
The total irradiance of the Sun has been found to vary mostly because
of changes in the areas of dark sunspots and bright faculae. Improved
observations, such as those discussed in this paper, are needed
to understand better the interplay between these two competing
features. In this paper, faculae are determined by observations using
a filter centered at the Ca II K line (393.4 nm) with a bandpass of
0.9 nm. This filter allows the detection of faculae across the entire
solar disk rather than just at the limb, as is the case for white-light
faculae. Sunspots are detected with a filter at 672.3 nm with a bandpass
of 9.7 nm. The mean ratio of facular to sunspot area was found to be
16.7 +/- 0.51 for a 71/2 year period during solar cycle 22 but showed
a significant increase as the solar cycle progressed. This ratio
suggests that the irradiance excess associated with faculae outweighs
the irradiance deficit associated with sunspots by about 50%. The
facular area also exhibited a quadratic dependence on sunspot area,
as suggested by Foukal, but there is no clear evidence of a turnover in
facular area at large sunspot areas. Lagged cross-correlations between
facular and sunspot areas showed a clear rotational modulation extending
to lags of five to six rotations when spots led faculae. Lags in the
opposite direction, however, showed the rotational modulation falling
abruptly after about two rotations.
---------------------------------------------------------
Title: Processing Photometric Full-Disk Solar Images
Authors: Walton, S. R.; Chapman, G. A.; Cookson, A. M.; Dobias, J. J.;
Preminger, D. G.
1997SPD....28.0222W Altcode: 1997BAAS...29..897W
The Cartesian Full Disk Telescopes (CFDTs) at the San Fernando
Observatory (SFO) produce daily full-disk digital solar images using
a linear Reticon diode array scanned by the Earth's rotation. In this
paper, we describe in some detail the data processing techniques used
to extract photometric information from CFDT images. We believe our
experience in this field will be found useful by other workers as more
instruments are built and operated with similar scientific goals to
the CFDT. We describe: 1. our photometric calibration techniques and
accuracy; 2. the method we use to identify the position of the limb;
3. production of a contrast map from the image, including finding a mean
limb darkening curve; 4. identification of solar features. Preprints
of a paper giving all algorithms in detail will be available at the
meeting. This research has been supported by NASA grant NAGW-3017 and
NSF grant ATM-9504374.
---------------------------------------------------------
Title: An Analysis of the Blue and Red Contrasts of Photospheric
Faculae
Authors: Chapman, G. A.; Ahern, Sean
1997SPD....28.1403C Altcode: 1997BAAS...29..918C
Full disk images have been obtained with the Cartesian Full Disk
Telescope 2 (CFDT2) at the San Fernando Observatory, beginning in 1992
July to the present. This system produces digital, photometric images
with 2.5" pixels. Images from this system for 110 days during the summer
months of 1993, 1994 and 1995 have been used in this analysis. The
images used were obtained in the Ca II K-line, in the blue at 470.6 nm,
and in the red at 672.3 nm. The Ca II K-line images were used only to
locate facular pixels, identified as those with a contrast of 4.8% or
higher. The co-aligned K-line images permit the unbiased detection of
low contrast faculae in the blue and red images. In all three filters,
the facular pixel contrasts showed an increase proportional to 1/mu
. Contrasts near disk center in the K-line, blue and red filters
were found to be about 7%, 0.12%, and 0.13%, rising to about 25%, 12%
and 8%, respectively, at mu = 0.2, the limit of analysis. The change
of contrast as a function of mu tend to support the "hot wall" model
for facular emission. We thank the many student observers and staff
who helped obtain the images used here. This work has been partially
supported by NASA grant NAGW-3017 and NSF grant ATM-9504374. Reference
Ahern, Sean, M.S. Thesis, CSU, Northridge (August 1996).
---------------------------------------------------------
Title: Spectral Properties of Solar Convection and Diffusion
Authors: Ruzmaikin, A. A.; Cadavid, A. C.; Chapman, G. A.; Lawrence,
J. K.; Walton, S. R.
1996ApJ...471.1022R Altcode:
We present the results of a study of the scaling properties of
solar photo spheric motions. We use time series of Doppler images
obtained in good seeing conditions with the San Fernando Observatory
28 cm vacuum telescope and vacuum spectroheliograph in video
spectra-spectroheliograph mode. Sixty line-of- sight Doppler images of
an area of the quiet Sun near disk center are investigated. They were
taken at 60 s intervals over a 1 hr time span at ∼2" resolution. <P
/>After filtering to remove 5 minute acoustic oscillations, the
time-spatial spectrum of the velocity is calculated. To study the
turbulence of photospheric flows in the mesogranulation scale range,
we estimate two scaling parameters in the spectrum: the exponent of
the spatial part of the power spectrum and the exponent governing the
scaling of time correlations of each spatial mode. These parameters
characterize the type of diffusion involved and the fractal dimension of
the diffusion front. Our results indicate that the turbulent diffusion
produced by motions in this scale range is not normal diffusion but
superdiffusion.
---------------------------------------------------------
Title: An analysis of 1983 Observations of Facular Contrast with an
Extreme Limb Photometer
Authors: Chapman, G. A.; Ziegler, B.
1996SoPh..168..259C Altcode:
Analysis of facular contrast ΔI/I<SUB>qs</SUB> from Extreme Limb
Photometer (ELP) data of the summer of 1983 yield a mean contrast of
0.91 ± 0.19% and 1.57 ± 0.16% for apertures 1 and 2 located at μ=
0.198 and at μ = 0.111, respectively. The ratio of the mean contrast
in the outer aperture (closer to the limb) to that of the inner one is
1.71 ± 0.40, indicating an increase in the mean facular contrast toward
the limb. This result is in agreement with observations made in 1975,
1979, and 1982. The errors are dominated by the random presence of
solar active regions. The combined results from all seasons follow an
approximately μ<SUP>−1</SUP> curve. Facular excess solar oblateness
signals for 1983 are 33.8 ± 6.6 arc ms and 16.5 ± 2.1 arc ms for ELP
apertures 1 and 2, respectively, in reasonable agreement with the 1983
excess solar oblateness results of Dicke, Kuhn, and Libbrecht (1985).
---------------------------------------------------------
Title: The San Fernando Observatory Video Spectra-Spectroheliograph
Authors: Walton, Stephen R.; Chapman, Gary A.
1996SoPh..166..267W Altcode:
We describe recent work in the development of the San Fernando
Observatory (SFO) Video Spectra-Spectroheliograph (VSSHG), a
spectrum-based instrument for the measurement of the solar Stokes
profiles. Its most important features are: simultaneous measurement
of Stokes I plus one of Stokes Q, U, or V; spatial sampling of
0.5 arc sec; spectral sampling of 8.8 mÅ; and time sampling of
one minute (for one pair of Stokes profile) to three minutes (for
all four profiles). Routine data processing is carried out using a
moments technique; tests of this technique show it to be reasonably
accurate. Sample data are shown and briefly discussed: a longitudinal
magnetogram and Dopplergram of NOAA 5573 observed on 17 August, 1989,
and a vector magnetic field map and Dopplergram of NOAA 6659 observed
on 10 June, 1991.
---------------------------------------------------------
Title: Variations in total solar irradiance during solar cycle 22
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1996JGR...10113541C Altcode:
In this study, we have attempted to model the variations in total
solar irradiance from two spacecraft. Specifically, we have modeled
the Earth Radiation Budget on the Nimbus 7 spacecraft and the active
cavity radiometer irradiance monitor (ACRIM-I) on the Solar Maximum
Mission (SMM) spacecraft using ground-based photometry of sunspots
and faculae from the San Fernando Observatory (SFO). Additionally,
for some cases, solar backscatter ultraviolet/2 data on the Mg II
core-to-wing ratio from the NOAA 9 spacecraft was used. We have found
that most of the solar cycle variation in the total solar irradiance
can be accounted for by sunspots and faculae/network. The unexplained
variation is not greater than approximately 0.0022% (22 ppm) per year
for most of solar cycle 22. Using Nimbus 7 data from March 2, 1985,
to December 13, 1993 (1281 data points), as the dependent variable,
with the SFO photometric sunspot index (PSI) and the NOAA 9 Mg II
core-to-wing ratio for the faculae/network as independent variables
(the best model for this interval), we obtained a multiple correlation
coefficient squared (R<SUP>2</SUP>) of 0.848. The rms noise in the
residuals is approximately 0.221 W m<SUP>-2</SUP> (162 ppm). This rms
noise appears to be dominated by noise in the spacecraft data. For
the same model, but for the time interval from March 2, 1985, to
July 14, 1989, we obtained an R<SUP>2</SUP> of 0.838 for 718 data
points. The same type of model for this same interval, substituting
SMM/ACRIM-I total irradiance for Nimbus 7, gave an R<SUP>2</SUP> of
0.857 for 685 data points. Our best correlation, however, came from a
three-parameter model, fitting Nimbus 7 data to the SFO digital PSI,
the SFO facular index PFIFA, and the NOAA 9 data for the interval
May 30, 1988, to December 13, 1993, giving an R<SUP>2</SUP> of 0.887
(745 data points). These strong correlations suggest that most of the
variation in solar irradiance is associated with known solar magnetic
features. Whether or not these magnetic features can explain all of
the solar irradiance variability will require more stable and accurate
long-term measurements from space and the ground.
---------------------------------------------------------
Title: Downflows in a Large EFR
Authors: Chapman, G. A.; Walton, S. R.
1996AAS...188.7904C Altcode: 1996BAAS...28..955C
We observed an emerging flux region (EFR) on January 3, 1996 with the
Video Spectra-Spectroheliograph (VSSHG) of the San Fernando Observatory
(SFO). The region, BBSO no. 3652, was selected based on a BearAlert
from the Big Bear Solar Observatory. Its position was N11 W11 at
2045 UT. The region grew from 110 microhemispheres (microhem) on the
3rd to 190 microhem on the 4th (W. Marquette, private communication,
1996). The observations, carried out over a 3-1/2 hour period beginning
at 20:07 UT, consist of two-dimensional spectra of the 630.25 nm solar
line analyzed for circular and linear polarization. The spectra are
used to produce maps with 0.5 arc-sec pixels of the vector magnetic
field, line-of-sight velocity and core and continuum intensity. A
complete set of such images were produced every ten minutes during
the observing period. From a preliminary analysis of about one-third
of the data, we find that there is a persistent downflow located near
the central portion of the EFR and very little upflow. Any possible
upflows are either of low amplitude or cover a much smaller area than
the downflow. The net downflow for the entire EFR is approximately
180-190 m/s. The strongest downflow, approximately 900-1000 m/s,
occurs in the area of one of the larger sunspots in the EFR. This
research was supported in part by NSF Grant ATM-9115111.
---------------------------------------------------------
Title: Spectral Properties of the Solar Background Velocity Field
Authors: Cadavid, A. C.; Chapman, G. A.; Lawrence, J. K.; Ruzmaikin,
A. A.; Walton, S. R.
1996AAS...188.3506C Altcode: 1996BAAS...28Q.872C
We study the scaling properties of time series of Doppler images
obtained in good seeing conditions with the San Fernando Observatory
28 cm vacuum telescope and vacuum spectroheliograph in video
spectra-spectroheliograph mode. The images correspond to two areas
of quiet Sun near disk center taken at 60 second intervals from one
hour to six hour spans at ~ 2 arcsec resolution. After removal of 5
min acoustic oscillations the time-spatial spectrum of the velocity is
calculated. To study the turbulence of photospheric flows we estimate
two scaling parameters: the exponent of the spatial part of the power
spectrum and the exponent governing the scaling of time correlations
of each spatial mode. The implied diffusive behavior produced by the
solar convection in the mesogranulation scale range is discussed. This
includes characterization of the type of diffusion involved and the
fractal dimension of the diffusion front.
---------------------------------------------------------
Title: Modelling Variations in Total Solar Irradiance during Cycle 22
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1995AAS...18712201C Altcode: 1995BAAS...27.1453C
We have compared total solar irradiance from Nimbus-7 and ACRIM1 with
ground- based photometry from the San Fernando Observatory (SFO). The
ground-based photometry consisted of photometric sunspot deficits and
a photometric facular index. In some instances, we have included UV
data from NOAA-9. For Nimbus-7 data, from 30 May 1988 to 13 December
1993, using all three sets of data, we find for 745 days of data a
coefficient of multiple correlation, R\^2, of 0.89. The value of the
quiet sun irradiance was 1371.67 +/- 0.21 W/m\^2. For a subset of these
Nimbus-7 data, the rms noise was 0.19 W/m\^2. For ACRIM1 data, for the
period from March 1985 to July 1989 the value of R\^2 was 0.81 for 685
days of data. For this interval, only the photometric sunspot deficit
and NOAA9 UV data were used. The quiet sun irradiance was 1366.96 +/-
0.21 W/m\^2. The Nimbus-7 analysis, from 30 May 1988 to 13 December
1993, covers the rise, peak, and decline for solar cycle 22. The
residuals show no evidence of the rise and decline in irradiance that
can be seen in the Nimbus-7 data. We conclude that, to an uncertainty of
about 200 parts per million of the mean irradiance, sunspots, faculae,
and the network appear to explain all of the long term variation in the
total solar irradiance. This research has been partially supported by
grants from NSF (ATM-9115111) and NASA (NAGW-3017). Most of the SFO
observations have been obtained by students to numerous to list.
---------------------------------------------------------
Title: Observing with HST I: A Proposal's Journey from Submission
to Data Receipt
Authors: Chapman, G.; Whittenberg, K.; Hathaway, W.; Ready, C.
1995AAS...187.3901C Altcode: 1995BAAS...27.1334C
“What happens to my HST proposal after Phase II submission?” is an
oft-heard question as investigators continue to express a desire for
better insight into the process of transforming an accepted proposal to
a product ready for execution onboard the Hubble Space Telescope. Each
proposal must proceed through a variety of processes whose tasks range
from implementation and Long Range Planning, to scheduling, execution
and data receipt. Although the process is continually improving, and
is more efficient than ever before, its flow is unknown to many beyond
the Space Telescope Science Institute. In this paper, we address the
opening question by presenting the life-cycle of an HST proposal from
the initial Call for Proposals to data receipt.
---------------------------------------------------------
Title: Downflows Associated with an Emerging Flux Region
Authors: Chapman, G. A.; Walton, S. R.
1995SPD....26..203C Altcode: 1995BAAS...27..951C
No abstract at ADS
---------------------------------------------------------
Title: Spectra of Solar Magnetic Fields and Diffusion
Authors: Ruzmaikin, A. A.; Cadavid, A. C.; Chapman, G. A.; Lawrence,
J. K.; Walton, S. R.
1995ASPC...76..292R Altcode: 1995gong.conf..292R
No abstract at ADS
---------------------------------------------------------
Title: Correlations Between Full Disk Magnetograms and Solar Contrast
Authors: Walton, S. R.; Chapman, G. A.; Jayasinha, Y.
1994AAS...185.4410W Altcode: 1994BAAS...26.1378W
We have embarked on a pilot project to investigate the photometric
properties of sunspots as a function of cycle phase and the relation
between those properties and the magnetic field. The present study uses
full-disk solar contrast maps from the San Fernando Observatory (SFO)
Cartesian Full Disk Telescope 2 (CFDT2) and full-disk magnetograms
from the National Solar Observatory Spectromagnetograph during the
period 11 August to 23 August 1992; active region NOAA 7260 transited
the disk during this period. The CFDT2 instrument is scanned by the
earth's rotation, so its astrometric quality is very high. We fit an
accurate limb to the CFDT2 intensity map, and used this limb plus the
time difference between the CFDT2 and NSO images to re-interpolate
the CFDT2 image onto the same image scale, orientation, and time of
observation as the NSO images. A contrast map is then produced from the
CFDT2 image. This procedure is entirely automatic and quite accurate,
and is thus potentially suitable for the unattended processing of
much larger amounts of data. From these co-aligned images, we produce
two-dimensional histograms, using CFDT2 images taken in both red
continuum and the core of the K line. These histograms contain quite
a bit of scatter around zero field and zero contrast, which seems to
be real. We do see a difference between small and large spots, in the
sense that smaller sunspots show a slower growth of negative contrast
with increasing flux than large sunspots. In other words, if one chooses
a pixel inside a small and a large sunspot with the same magnetic flux,
the corresponding contrast will be larger in the large spot. There is a
”cutoff” flux of about 1500G above which the sunspot stays at the same
contrast, roughly 20%, as the field strength increases. This research
was supported in part by grants NSF ATM-9115111 and NASA NAGW-3017,
and by the NSF Young Scholars Program. We are grateful to J. Harvey
and H. Jones of NSO for providing the magnetograms.
---------------------------------------------------------
Title: On the Ratio of Facular Area to Sunspot Area
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1994AAS...18512305C Altcode: 1994BAAS...26Q1523C
The ratio of the area of faculae (or network) to the area of sunspots
is an important issue when discussing the energy balance within
solar active regions. It is also of importance for the variability
of solar-type stars. We have studied the ratio of facular to sunspot
area for several years of photometric data from the San Fernando
Observatory. The data are from full disk photometric images obtained
with the CFDT1 (Cartesian Full Disk Telescope, 5" pixels). The
sunspot corrected area is determined from a red image (672.3 nm,
bandpass = 10 nm) and the corrected facular area is from a K-line
image (393 nm, bandpass = 1 nm). The facular and sunspot areas are
from the entire disk without regard to location or association with
active regions. We carried out a regression of the following form:
$ A_F = a + b A_S + c A_S(2) where A_F is the corrected facular area
and A_S is the corrected sunspot area. We find the following: begin
{tabular}{ccccccc} period &a &\sigma_a &b &\sigma_b
&c &\sigma_c 1989 &19,819 &7,047 &6.89 &1.6
&-0.00074 &0.00033 10/1/91 to 12/31/92 &10,274 &5,904
&10.1 &1.48 &-0.0014 &0.00044 end {tabular} The value
of a and \sigma_a are in micro-hemispheres. The negative sign for
the coefficient c$ indicates that increase in facular area does not
keep pace with the increase in spot area for large spots. However,
at no point does the slope go negative. These results are preliminary,
as the latest reduction software has not been used. Results for 1990,
1991 and 1993 should be available by the time of the meeting. We find
that the ratio of facular to sunspot area is approximately 10 but
the detailed fit varies with the solar cycle. There is a significant
quadratic term but much smaller than that found by Foukal (1994). This
research was supported in part by grants NSF ATM-9115111 and NASA
NAGW-3017. Reference Foukal, P. 1994, Science 264, 238.
---------------------------------------------------------
Title: Observations of Changes in the Bolometric Contrast of Sunspots
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1994ApJ...432..403C Altcode:
Rapid changes in the total solar irradiance from space borne sensors are
largely due to the passage of large sunspots across the disk. The effect
of sunspots has often been modeled, using ground-based observations,
by the use of a sunspot index such as the PSI, which assumes that
all sunspots have the same thermal structure, which remains constant
with time. In this paper, we report on photometric observations
of sunspot groups that show significant differences in their mean
bolometric contrast ( up to a factor of 2) and some of which show
cooling or warming during their disk transit. Most of these changes
can be ascribed to the changing ratio of umbral-to-prenumbral area. By
measuring the mean temperature or bolometric contrast, together with
corrected (hemispherical) areas, we can determine the instantaneous
solar luminosity fluctuation and its diurnal change due to individual
sunspot groups. These results show that the use of solar indices based
on estimates of sunspot area and fixed sunspot contrast, such as the
photometric sunspot index, do not remove all of the significant sunspot
effects from satellite measurements of the total solar irradiance.
---------------------------------------------------------
Title: Solar irradiance from Nimbus-7 compared with ground-based
photometry
Authors: Chapman, G. A.; Cookson, A. M.; Hoyt, D. V.
1994SoPh..149..249C Altcode:
We have compared total solar irradiance from Nimbus-7 with ground-based
photometry from the San Fernando Observatory (SFO) for 109 days between
June 1 and December 31, 1988. We have also included in some analyses
NOAA-9 SBUV2 data orF10.7 radio flux. The Nimbus-7 data are from orbital
samples, averaged to the mean time of observation at SFO. Using the same
parameters as in Chapmanet al. (1992), the multiple regression gives
anR<SUP>2</SUP> = 0.9131 and a `solar minimum' irradiance,S<SUB>0</SUB>,
= 1371.76 ± 0.18 W m<SUP>−2</SUP> for the best fit.
---------------------------------------------------------
Title: Observations of Flows around Sunspot Groups
Authors: Chapman, G. A.; Walton, S. R.
1994ASPC...68..283C Altcode: 1994sare.conf..283C
No abstract at ADS
---------------------------------------------------------
Title: A Possible Siphon Flow Associated with Emergence of New Flux
Authors: Walton, Stephen R.; Corbin, Kyeong H.; Chapman, Gary A.
1994ASPC...68...75W Altcode: 1994sare.conf...75W
No abstract at ADS
---------------------------------------------------------
Title: Flows in active regions: penumbral, superpenumbral and Evershed
Authors: Chapman, G. A.; Walton, S. R.
1994smf..conf..216C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Photometric Observations of the Sun
Authors: Chapman, G. A.
1994svsp.coll..117C Altcode: 1994IAUCo.143P.117C
No abstract at ADS
---------------------------------------------------------
Title: Changes in the Bolometric Contrast of Sunspots
Authors: Chapman, G. A.; Cookson, A. M.; Dobias, J. J.
1993AAS...183.2509C Altcode: 1993BAAS...25.1332C
We report on photometric observations of sunspots carried out with the
Cartesian Full Disk Telescope (CFDT) at the San Fernando Observatory
(SFO). The pixel size is 5.1 arc-sec and the wavelength for the data
discussed here is 6723 Angstroms. Fluctuations in total solar irradiance
due to sunspots are often modeled using a constant value of alpha,
which we are calling the bolometric contrast of a sunspot. We have
defined alpha_ {eff} as DEF/(2 times PSI), where DEF is the sunspot's
photometric deficit relative to the quiet photosphere, and PSI is
the digitally determined Photometric Sunspot Index (Willson et al.,
1981). For 40 sunspot groups, we find that alpha_ {eff} = (0.276 +/-
0.051) + (3.22 +/- 0.34) 10(-5) A_s, where A_s is the corrected area
of the sunspot in micro-hemispheres. The coefficient of determination
is r(2) = 0.1936, which is significant at the p = 0.005 level. We also
find that alpha_ {eff} is highly correlated with the ratio of umbral
to total spot area (A_u/A_s). For 86 sunspot-days we find alpha_ {eff}
= (0.219 +/- 0.018) + (0.643 +/- 0.028) (A_u/A_s) with the linear
coefficient of determination r(2) = 0.859. This suggests that an
improved PSI can be constructed from knowledge of a sunspot's umbral
to total area ratio. The use of such an improved PSI or, better still,
actual photometry should reduce the statistical noise in comparisons
with spacecraft measurements of the total solar irradiance. This work
has been partially supported by grants from NSF and NASA.
---------------------------------------------------------
Title: Scattered Light in Solar Images using Hankel Transforms
Authors: Walton, S. R.; Chapman, G. A.; Cookson, A. M.; Preminger, D.
1993AAS...183.5908W Altcode: 1993BAAS...25.1387W
We have been investigating the scattered light properties of the
San Fernando Observatory (SFO) Cartesian Full Disk Telescope
(CFDT). Recently, Toner and Jeffries (1993, Ap. J. 415, 852)
have published a technique for the accurate determination of the
solar limb position, based on the Hankel transform of a radial solar
profile. They show that the Hankel transform of the observed solar limb
profile yields a seeing-independent determination of the solar limb
position and limb darkening profile. In principle, the ratio of the
transform of the observed profile to that of the model, polynomial,
solar limb darkening would then be the modulation transfer function
(MTF) of the atmosphere and telescope. In practice, as with all such
ratios of an observed power spectrum to an analytic one, the noise at
high spatial frequencies makes the division difficult. We have taken
a different approach. Using observed limb profiles from the SFO CFDT,
we do a non-linear least-squares fit of the observed profile to the
convolution of a model limb darkening profile and a model MTF. The model
limb darkening is an expansion in orthonormal Legendre polynomials in mu
rather than simple powers of mu, as orthonormal polynomials have many
desirable numerical features. The model MTF is a sum of short-range
(typically Gaussian) and long-range (typically Lorentzian) parts
(Lawrence, Chapman, Herzog, and Shelton 1985, Ap. J. 292, 297). We
will present results from these model fits and comment on their
robustness. We gratefully acknowledge Eric Hansen of Dartmouth College,
who supplied us with a copy of his Hankel transform code. This work
has been partially supported by NSF grant ATM-9115111 and NASA grants
NAGW-2770 and NAGW-3017.
---------------------------------------------------------
Title: A Study of the Contrast of Sunspots from Photometric Images
Authors: Beck, John G.; Chapman, Gary A.
1993SoPh..146...49B Altcode:
The thermal contrast α, and the
umbra-penumbraA<SUB>u</SUB>/A<SUB>p</SUB>, were calculated for
63 sunspots of various sizes and morphologies. Contrary to the
assumptions of the PSI model, α andA<SUB>u</SUB>/A<SUB>p</SUB>
were found to be quite variable. The values of α ranged from
0.1807 to 0.4266;A<SUB>u</SUB>/A<SUB>p</SUB> ranged from 0.0089
to 0.4899. The values of α andA<SUB>u</SUB>/A<SUB>p</SUB>
correlated well (r = 0.6018;p<0.005) and the regression for α
andA<SUB>u</SUB>/A<SUB>p</SUB> was obtained: α = (0.220 ± 0.016)
+ (0.340 ± O.06)A<SUB>u</SUB>/A<SUB>p</SUB>. The values of α
andA<SUB>u</SUB>/A<SUB>p</SUB> were then compared with complexity
ratings, magnetic field strength, time, and μ. The quantities α
andA<SUB>u</SUB>/A<SUB>p</SUB> were found to be independent of the
complexity, magnetic field strength, and time factors. The correlation
between α andA<SUB>u</SUB>/A<SUB>p</SUB> lead to the proposed division
of α into an umbral thermal contrast α<SUB>u</SUB>, and a penumbral
thermal contrast α<SUB>p</SUB>. These values were calculated from the
photometric data: α<SUB>u</SUB> = 0.57 ± 0.01 and α<SUB>p</SUB> =
0.26 ± 0.006.
---------------------------------------------------------
Title: Association of a Siphon Flow with the Emergence of New Flux
Authors: Corbin, K. H.; Walton, S. R.; Chapman, G. A.
1993BAAS...25.1217C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Magnetograph Comparison Workshop
Authors: Jones, H.; Bogart, R.; Canfield, R.; Chapman, G.; Henney,
C.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet, V.;
Rabin, D.; Ulrich, R.; Walton, S.
1993BAAS...25.1216J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Intercomparison of Seven Magnetographs
Authors: Walton, S. R.; Bogart, R. S.; Chapman, G. A.; Henney, C.;
Jones, H.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet,
V.; Rabin, D.
1993BAAS...25.1205W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Field of Solar Physics - Review and Recommendations for
Groundbased Solar Research
Authors: Chapman, G. A.; Noci, Giancarlo; Rickard, J. J.
1992SoPh..142..415C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of Changes in Sunspot Cooling
Authors: Chapman, G. A.; Cookson, A. C.; Dobias, J. J.
1992AAS...181.9405C Altcode: 1992BAAS...24R1269C
No abstract at ADS
---------------------------------------------------------
Title: Photometric Measurements of Sunspots Deficits and Facular
Excesses
Authors: Chapman, G. A.; Lawrence, J. K.; Hudson, H. S.
1992sers.conf..135C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Precise ground-based solar photometry and variations of
total irradiance
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Walton,
S. R.; Hudson, H. S.; Fisher, B. M.
1992JGR....97.8211C Altcode:
Variations in the total solar irradiance measured by the active cavity
radiometer irradiance monitor (ACRIM) on SMM have been correlated
with measures of magnetic activity on the solar disk. Quantitative
indices of magnetic activity were derived from ground-based, full-disk,
photometric images of the Sun at red (6723 Å) and violet (3934-Å K
line) wavelengths. The red images have been obtained on a daily basis
at the San Fernando Observatory since 1985, and the K line images
since 1988. Sunspot irradiance deficits are calculated directly
from the red images while proxy measures of facular irradiance
excesses are derived from the K line images. The images analyzed
here were made during 21 days between June 20 and July 14, 1988,
a period centered on the disk passage of a large sunspot group. The
best two-parameter multiple correlation coefficient between the
ACRIM data and the photometric data is R<SUP>2</SUP>=0.97 (21 data
points, 18 degrees of freedom). The zero point S<SUB>0</SUB>=1367.27
W m<SUP>-</SUP><SUP>2</SUP> agrees well with the solar irradiance
measured by ACRIM/SMM during the 1986 activity minimum: the residual
standard deviation was 0.13 W m<SUP>-</SUP><SUP>2</SUP> (about 100
ppm). The multiple correlations were extended to include measures
of the irradiance contribution of “network” magnetic fields,
unassociated with active regions. NOAA 9 spacecraft observations of UV
MgII lines at 2800 Å gave R<SUP>2</SUP>=0.99 (17 degrees of freedom)
with S<SUB>0</SUB>=1366.68+0.08 W m<SUP>-2</SUP>. The index of 10.7-cm
microwave flux gave R<SUP>2</SUP>=0.98, with S<SUB>0</SUB>=1366.43+0.11
W m<SUP>-</SUP><SUP>2</SUP>. We can thus model short-term irradiance
changes to within 100 ppm relative precision from ground-based data.
---------------------------------------------------------
Title: Sunspot Deficits Measured With a New, 3-inch Full Disk
Photometric Telescope
Authors: Chapman, G. A.; Walton, S. R.
1992AAS...180.1706C Altcode: 1992BAAS...24..754C
A new photometric telescope has begun operation which is similar
to the old CFDT (Cartesian Full Disk Telescope). The new one has a
3-inch aperture objective and a 1024 element linear diode array. Each
pixel corresponds to 2.5 arc-sec on the sky. As with the old CFDT
(Chapman, et al./ 1989, Ap. J. 343, 547) this telescope uses the
earth's diurnal motion to scan the array and build up a 1024 x 1024
pixel image of the solar disk and nearby sky. Results will be presented
here comparing sunspot areas and deficits as measured with the new
and old CFDT. Analysis of images obtained under conditions of poor
seeing on 24 December 1991 show that the new CFDT gives sunspot areas
and deficits that are 1.36 and 1.16 times greater, respectively, than
those from the old CFDT. This research has been partially supported
by NSF Grant ATM-8817634 and NASA Grant NAG-5-1219.
---------------------------------------------------------
Title: Doppler and Magnetic Studies of the Flare-Producing Area of
NOAA 6659
Authors: Walton, S. R.; Chapman, G. A.; David, R. S.
1992AAS...180.5102W Altcode: 1992BAAS...24..813W
The San Fernando Observatory Video Spectra-Spectroheliograph (VS(2)
HG) produces simultaneous spectra-spectroheliograms in two orthogonal
polarizations; during four successive scans, all four Stokes vectors
are recorded over a spectral region approximately 1.5 Angstroms wide,
with pixels of 8 m Angstroms in the spectral direction and 0.46 seconds
of arc in the spatial direction. Since each individual scan produces a
continuum, line core, and Doppler map, these are both simultaneous and
co-spatial, essentially by definition. The continuum images from each
scan are used to align the separate scans of Stokes Q, U, and V. From
these aligned scans, maps of the vector magnetic field are produced. A
brief description of the VS(2) HG can be found in Lawrence, Chapman,
and Walton (1991), Ap. J. 375, 771; a detailed description of the data
processing procedure is in preparation. We observed active region
NOAA 6659 using the VS(2) HG on 7 June and 10 through 15 June 1991,
a period from two days before to six days after its central meridian
passage. The Doppler maps from the 7th and the 10th show a blueshifted
area just to the west of the northernmost sunspot of the group. This
area was especially prominent on the 10th, and was co-spatial with
the west ribbon as seen in Hα of an M3.2 flare which occurred at
1654 UT. (This region produced a very large flare (X12.0) at 11 June
0229 UT, but as of this writing, we don't have the precise location
of this flare.) The vector maps show a strong tangential component of
the magnetic field in this area. The direction of the tangential field
changes rapidly across the area of the blueshift. The later observations
(12 and 13 June) show what, given the disk position, appears to be an
area of downflow in the same area: i.e., a redshift on the disk center
side and a blueshift on the limbward side. We will show and discuss
further the maps at the meeting. This research has been partially
supported by NASA grant NAGW-2453 and NSF grant ATM-9115111.
---------------------------------------------------------
Title: Ground-Based Photometry and Interpolated Nimbus - 7 Total
Solar Irradiance
Authors: Chapman, G. A.; Hoyt, D. V.
1991BAAS...23.1442C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Weak Magnetic Fields and Solar Irradiance Variations
Authors: Lawrence, J. K.; Chapman, G. A.; Walton, S. R.
1991ApJ...375..771L Altcode:
NOAA active region 5643 was observed from August 17 to 21, 1989. Sets
of video spectra-spectroheliograms including the Fe I line at 6302.5
A were made at least daily with the San Fernando Observatory 28 cm
vacuum telescope and vacuum spectroheliograph. These give simultaneous,
co-registered digital images representing monochromatic continuum
intensity, line core intensity and line-of-sight magnetic field. Three
different criteria are used to define the pixels representing the
quiet sun and the facular portions of the images. These criteria
are the magnetic field strength, the line core intensity, and the
distribution of continuum intensities. Each of these definition schemes
is used to estimate the irradiance change due to facular emission. The
magnetic field and the continuum intensity distribution definitions
give estimates which agree closely. The line core intensity definition
leads to larger estimates of the facular irradiance contribution. Some
model-dependent investigations of the contrasts and sizes of individual
facular elements also are presented.
---------------------------------------------------------
Title: Total Solar Irradiance Variations Compared with Ground-Based
Photometry at the SFO
Authors: Chapman, G. A.; Lawrence, J. K.; Hudson, H. S.
1991BAAS...23.1067C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ground-Based Modelling of Solar Irradiance Variations
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.; Walton,
S. R.; Hudson, H. S.; Fisher, B. M.
1991BAAS...23..960L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Continuum Contrast and Center to Limb Variation of Solar
Magnetic Elements Observed in the Photosphere
Authors: Swearingen, D. J.; Walton, S. R.; Chapman, G. A.; Lawrence,
J. K.
1991BAAS...23..960S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Recent results from the San Fernando Observatory video
spectra-spectroheliograph.
Authors: Chapman, G. A.; Walton, S. R.
1991sopo.work...37C Altcode:
Results are presented from VSSHG observations of an extensive sunspot
group, NOAA 5669, that transited disk center on 4 September 1989. The
data are presently processed to obtain four images: a saturation-free
longitudinal magnetogram, a Dopplergram, a continuum image, and a line
core spectroheliogram. All images are from two-dimensional spectral data
with a spectral window of about 1 Å, centered on the 6302.5 Å line
of neutral iron. The images show the well-known "fringing" of sunspot
fields, the "unsymmetrical" Evershed flow as well as large-scale flow
patterns within the active region.
---------------------------------------------------------
Title: Photometric Observations of the Energetics of Small Solar
Active Regions
Authors: Lawrence, J. K.; Chapman, G. A.
1990ApJ...361..709L Altcode:
The energetics of small solar active regions was investigated using
for the analysis the photometric solar images taken from July 29 to
September 6, 1984 with the San Fernando Observatory's 28-cm vacuum
telescope, vacuum spectroheliograph, and dual 512 element Reticon
linear diode arrays. Ten small newly formed regions were observed,
whose entire sunspot evolution apparently occurred within the observed
disk crossing. Seven of these showed a net energy excess of a few times
10 to the 33th ergs during this time. These results are discussed in
connection with the 0.1 percent decline in solar irradiance observed
by the SMM/ACRIM and Nimbus 7/ERB radiometers between 1980 and 1986.
---------------------------------------------------------
Title: A program of photometric measurements of solar irradiance
fluctuations from ground-based observations.
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Walton, S. R.
1990NASCP3086...16C Altcode: 1990cisv.nasa...16C
Photometric observations of the sun have been carried out at the
San Fernando Observatory since early 1985. Since 1986, observations
have been obtained at two wavelengths in order to separately measure
the contributions of sunspots and bright facular to solar irradiance
variations. The authors believe that the contributions of sunspots can
be measured to an accuracy of about ±30 ppm. The effect of faculae is
much less certain, with uncertainties in the range of ±300 ppm. The
larger uncertainty for faculae reflects both the greater difficulty
in measuring the facular area, due to their lower contrast compared
to sunspots, and the greater uncertainty in their contrast variation
with viewing angle on the solar disk. Recent results from two separate
photometric telescopes will be compared with bolometric observations
from the ACRIM that was on board the Solar Max satellite.
---------------------------------------------------------
Title: Solar Variability Measured by SMM/ACRIM Compared with
Ground-Based Photometry
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Walton,
S. R.; Hudson, H. S.; Fisher, B.
1990BAAS...22..897C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Relation Between Irradiance Excess and Magnetic Field
for the Sun
Authors: Wilson, R. J.; Walton, S. R.; Chapman, G. A.
1990BAAS...22..793W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Continuum Contrast of Photospheric Faculae Compared to their
Magnetic Flux
Authors: Lawrence, J. K.; Chapman, G. A.; Walton, S. R.
1990BAAS...22..839L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Solar and Middle Atmosphere Variability
Authors: Chapman, G. A.
1989Sci...246..246C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary Results from the Video Spectra-Spectro-Heliograph
at the San Fernando Observatory
Authors: Chapman, G. A.; Walton, S. R.
1989BAAS...21.1179C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of Sunspot Areas from the San Fernando Observatory's
Cartesian Full Disk Telescope and Rotating Full Disk Photometer
Authors: Herzog, A. D.; Chapman, G. A.; Gluczsak, M.
1989BAAS...21.1110H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Photometric Observations of Net Energy Excesses in Small
Solar Active Regions
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1989BAAS...21.1179L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of SFO Full-Disk Photometric Images with NSO
Full-Disk Magnetograms
Authors: Walton, S. R.; Wilson, R. J.; Chapman, G. A.
1989BAAS...21.1179W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Video Spectra - Spectroheliograph (V S<SUP>2</SUP> HG)
on the San Fernando Observatory
Authors: Chapman, G.; Walton, S.
1989hsrs.conf..402C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Photometric Measurements of Solar Irradiance Variations Due
to Sunspots
Authors: Chapman, G. A.; Herzog, A. D.; Laico, D. E.; Lawrence, J. K.;
Templer, M. S.
1989ApJ...343..547C Altcode:
A photometric telescope constructed to obtain photometric sunspot areas
and deficits on a daily basis is described. Data from this Cartesian
full disk telescope (CFDT) are analyzed with attention given to the
period between June 4 and June 17, 1985 because of the availability
of overlapping sunspot area and irradiance deficit data from
high-resolution digital spectroheliograms made with the San Fernando
Observatory 28 cm vacuum solar telescope and spectroheliograph. The
CFDT sunspot deficits suggest a substantial irradiance contribution
from faculae and active region plage.
---------------------------------------------------------
Title: Magnetic Fields from Video Spectra-Spectroheliograms: A Test
of the Center of Gravity Method
Authors: Walton, S. R.; Chapman, G. A.
1989BAAS...21..854W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Field Strengths from a Digital Magnetogram compared
with those from Viedo Spectra-Spectroheliograms (VSSHG)
Authors: Chapman, G. A.; Herzog, A. D.; Walton, S. R.
1989BAAS...21..862C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sunspot Deficits for 1985 Determined with a 2. 5cm telescope
and Linear Diode Array
Authors: Davis, G.; Chapman, G. A.
1989BAAS...21Q.842D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
1989epos.conf....1P Altcode:
Contents: 1. Introduction. 2. Magnetohydrodynamic
instability. 3. Preflare magnetic and velocity fields. 4. Coronal
manifestations of preflare activity.
---------------------------------------------------------
Title: Photometric Observations of Facular Contrasts near the
Solar Limb
Authors: Lawrence, J. K.; Chapman, G. A.
1988ApJ...335..996L Altcode:
Digital, photometric images of several active regions near the solar
limb made with 1.5 A effective bandpass at 6264 A are analyzed. From
three to ten images were made per day on several days during 1983, 1984,
and 1987 with the San Fernando Observatory 28 cm vacuum solar telescope
and spectroheliograph and 512 element Reticon linear diode arrays. Pixel
spacing is 0.94 arcsec. Pixels in each image were sorted into quiet sun
and facular intensity distributions by mu value, where mu = cos theta
and theta is the heliocentric angle between the pixel and the direction
of earth. These distributions were converted to overall average values
of facular pixel contrast relative to the quiet sun background by mu
value, and a center-limb variation of contrast per facular element was
derived. If one is careful to distinguish between contrasts per unit
projected area (pixel contrasts) and contrasts per facular element
or individual flux tube, the results are in reasonable agreement with
those of other workers. The center-limb contrast variation resembles a
'hot wall' model of facular emission, with indications of an additional
emitting component which protrudes above the photospheric level.
---------------------------------------------------------
Title: Observations from 1982 OF Facular Limb Darkening and Excess
Solar Oblateness
Authors: Chapman, G. A.; Oseas, J. M.
1988SoPh..116..215C Altcode:
Observations of facular regions on 35 days during 1982 obtained with
the Extreme Limb Photometer are reported. The data were obtained at
a wavelength of 0.53 μm with two apertures, No. 1 covering 36 arc
sec and No. 2 covering 11 arc sec, inwards from the limb. The mean
contrasts for all regions detected are 1.05 ± 0.12% and 1.59 ± 0.16%,
respectively. The mean contrast of the faculae closer to the limb
(aperture 2) is 1.51 ± 0.23 times that from aperture No. 1. This
contrast ratio can be fit to a μ<SUP>−1</SUP>-curve. These results
are consistent with those from 1975 and 1979 observations and may be
consistent with the facular limb-darkening function determined by
Libbrecht and Kuhn (1984, 1985) if our data are normalized by the
area of the solar surface. However, no calibrations or corrections
are required to obtain the mean facular contrast presented here.
---------------------------------------------------------
Title: Full Disk CaII K-line Observations of the Sun with a One-Inch
Telescope (CFDT)
Authors: Chapman, G. A.; Walton, S. R.; Bird, M.; Bulharowski, T.;
Cordero, E.; Gluszczak, M.; Mach, C.; Manes, J.; Parker, D.; Wagner, J.
1988BAAS...20..910C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of NOAO 4835 Using the SFO RFDP
Authors: Walton, S. R.; Chapman, G. A.; Herzog, A. D.; Gluszczak,
M. R.; Arndt, J.; Sherk, J.
1988BAAS...20..680W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Photometric Determination of Facular Contrasts near the Solar
Disk Center
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1988ApJ...324.1184L Altcode:
The authors have analyzed pairs of simultaneous, co-registered, digital,
photometric images of several solar active regions made with 3 Å
effective bandpasses in the Ca II line at 8662 Å and in the nearby
clean continuum at 8642 or 8682 Å. From these data the authors derive a
continuum facular contrast at disk center of 0.74%±0.11%. This contrast
remains roughly constant from disk center to r = 0.45 R_sun; before
increasing. These results lead to an increase of 10% - 20% in earlier
estimates of facular contributions to solar luminosity fluctuations,
which were found to be 70% - 120% of the sunspot contributions.
---------------------------------------------------------
Title: Modelling of total solar irradiance variability from
ground-based observations
Authors: Chapman, G. A.
1988AdSpR...8g..21C Altcode: 1988AdSpR...8...21C
The total solar irradiance, measured in recent years by satellite
detectors /1, 2/, has shown variations both short term and long
term. Attempts to understand these variations in terms of sunspots
and faculae have met with limited success /3-5/. Correlations between
satellite total irradiance measurements and proxy irradiance based
on sunspot and plage or facular areas explain only 50-70% of the
variance. It is important to know if this poor correlation is due
to the irradiance models' noise in the sunspot and plage areas, or
some global solar fluctuation. Comparisons will be presented between
published sunspot areas and digital, ground-based measurements. A new
program of precise, relative photometry at the San Fernando Observatory
will be described and its results will be compared with the ACRIM/SMM
data and with model irradiance fluctuations based on published sunspot
and plage areas. The San Fernando photometric data can produce sunspot
irradiance fluctuation information that is repeatable to within about
10 millionths of the mean irradiance. Individual sunspot areas can be
several standard deviations from published values.
---------------------------------------------------------
Title: Solar and middle atmosphere variability
Authors: Chapman, G. A.
1988AdSpR...8g....C Altcode: 1988AdSpR...8.....C
Papers dealing with space and ground-based observations of solar
variability are presented, covering topics such as the observation of
total irradiance variability from Nimbus satelliites, measurement of the
earth radiation budget satellite extraterrestrial solar constant, models
of total solar irradiance variability, tests for the properties of solar
gravity mode signals in total irradiance observations, the theoretical
interpretation of total solar irradiance variations, and observations of
solar UV, EUV, and X-ray variability. Other topics include the solar UV
Mg II core-to-wing ratio during the rise of solar cycle 22, an absolute
extreme-UV solar spectral irradiance monitor, multiyear variations of
solar oscillations, temporal variations in the acoustic and f-mode
eigenfrequency spectrum of the sun, variability of solar diameter,
variability of spectroscopic temperature of the sun, and solar motion
and the variability of solar activity. Additional subjects include the
variability of global solar properties, variability of solar granulation
and solar mesogranulation, rocket flight observations of the mesoscale
structure in the temperature minimum region, long-term variabiliy of
solar magnetic fields, the use of general systems theory to study
solar activity, asymmetry of the main solar dipole field resulting
in a 12-month wave in geomagnetic activity, the IMF sector boundary
effects in the middle atmosphere, and the influence of corpuscular
radiation on changes in the middle atmosphere and troposphere.
---------------------------------------------------------
Title: Analysis of SFO RFDP Observatons of Active Regions
Authors: Walton, S. R.; Chapman, G. A.; Herzog, A. D.; Gluszczak,
M. R.; Klein, M. L.
1987BAAS...19.1132W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Photometric Facular Contrasts Near the Extreme Solar Limb
Authors: Lawrence, J. K.; Chapman, G. A.
1987BAAS...19R1132L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous Observations of Active Regions
Authors: Herzog, A. D.; Chapman, G. A.; Walton, S. R.; Gluszczak,
M. R.; Klein, M. L.
1987BAAS...19.1118H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sunspot Areas from a Small Photometric Telescope
Authors: Chapman, G. A.; Johnson, L.; Herzog, A. D.
1987BAAS...19..941C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Analysis and Comparison of Sunspot Areas and Irradiance
Deficits
Authors: Laico, D. E.; Chapman, G. A.; Herzog, A. D.
1987BAAS...19..926L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar variability due to sunspots and faculae.
Authors: Chapman, G. A.
1987JGR....92..809C Altcode:
Results of photometry of solar active regions and their effect on the
solar irradiance in the visible part of the spectrum are presented. The
effects of sunspots and faculae are given separately, since the
measurement of sunspot irradiance fluctuations is less uncertain. It
is argued that energy balance may exist between sunspot deficits and
facular excesses. The uncertainty, however, is + or - 15 percent (1
sigma). This possible balance also depends on the correct mathematical
model for the contrast of faculae as a function of position on the solar
disk. Extreme Limb Photometer (ELP) data are presented in such a way
as to show that the model for facular limb darkening is consistent
with the assumptions inherent in the irradiance modeling. The ELP
data support the notion that energy balance between spots and faculae
is possible. It is emphasized that even if there is energy balance,
there will still be variations in the solar irradiance at the earth.
---------------------------------------------------------
Title: Variations of solar irradiance due to magnetic activity.
Authors: Chapman, G. A.
1987ARA&A..25..633C Altcode:
The variability of the solar luminosity (as detected by the SMM Active
Cavity Irradiance Monitor and by the Nimbus-7 Earth Radiation Budget
experiment) and its relation to magnetic activity on the sun are
discussed, reviewing the results of recent investigations. Topics
addressed include the use of indirect (area-type and magnetic)
luminosity measurements, direct photometry of active regions, observing
programs and instrumentation, and theoretical models. Diagrams, graphs,
and photographs are provided.
---------------------------------------------------------
Title: Preflare magnetic and velocity fields
Authors: Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach,
A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.;
Porter, J. G.; Schmeider, B.
1986epos.conf.1.16H Altcode: 1986epos.confA..16H
A characterization is given of the preflare magnetic field, using
theoretical models of force free fields together with observed field
structure to determine the general morphology. Direct observational
evidence for sheared magnetic fields is presented. The role of this
magnetic shear in the flare process is considered within the context
of a MHD model that describes the buildup of magnetic energy, and the
concept of a critical value of shear is explored. The related subject
of electric currents in the preflare state is discussed next, with
emphasis on new insights provided by direct calculations of the vertical
electric current density from vector magnetograph data and on the role
of these currents in producing preflare brightenings. Results from
investigations concerning velocity fields in flaring active regions,
describing observations and analyses of preflare ejecta, sheared
velocities, and vortical motions near flaring sites are given. This
is followed by a critical review of prevalent concepts concerning the
association of flux emergence with flares
---------------------------------------------------------
Title: A Comparison of ACRIM Irradiance and Digital Sunspot Areas
Authors: Chapman, G. A.; Corbin, M.; Johnson, L.; Klein, M.;
Martinez, C.
1986BAAS...18Q.933C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High Resolution Photometry of Solar Active Regions
Authors: Herzog, A. D.; Chapman, G. A.
1986BAAS...18..900H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Irradiance Variations Derived from Magnetograms
Authors: Chapman, G. A.; Boyden, J. E.
1986ApJ...302L..71C Altcode:
Pseudo-irradiance fluctuations have been derived from parameterized
magnetogram signals. These pseudo-irradiance fluctuations are calibrated
by least-squares comparison with ACRIM/SMM data. The resulting Mount
Wilson irradiance can be examined for a complete sunspot cycle. The
results do not appear to be overly sensitive to the mathematical form
of the parameterization.
---------------------------------------------------------
Title: Time-integrated energy budget of a solar activity complex
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.
1986Natur.319..654C Altcode:
The 0.1-0.3% dips in solar irradiance during disk passages of large
sunspot groups suggest the possibility of fluctuations in the solar
luminosity. This raises the question of whether the energy not radiated
by the dark sunspots is stored within the Sun for long periods of
time, or is radiated by faculae during the several-month lifetime of
a solar activity complex<SUP>1-3</SUP>. Here we examine the sunspot
and facular contributions to luminosity fluctuations due to a solar
activity complex over its lifetime from June to November 1982. Both
direct, photometric observations of irradiance fluctuations and modelled
`proxy' fluctuations based on published sunspot and calcium plage areas
are used. We find that the total facular energy excess is between 70 and
120% of the sunspot deficit of ~10<SUP>37</SUP> erg. Thus, at a minimum,
a major portion of the missing sunspot flux is radiated by faculae, and
energy balance or even an excess is possible. This work differs from
earlier studies<SUP>2-9</SUP> in that our data cover a longer period
of time, more photometric data are included, and our analysis considers
the effect of partial occultation of active regions by the solar limb.
---------------------------------------------------------
Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
1986NASCP2439....1P Altcode:
Contents: 1. Introduction: the preflare state - a review of previous
results. 2. Magnetohydrodynamic instability: magnetic reconnection,
nonlinear tearing, nonlinear reconnection experiments, emerging flux and
moving satellite sunspots, main phase reconnection in two-ribbon flares,
magnetic instability responsible for filament eruption in two-ribbon
flares. 3. Preflare magnetic and velocity fields: general morphology of
the preflare magnetic field, magnetic field shear, electric currents in
the preflare active region, characterization of the preflare velocity
field, emerging flux. 4. Coronal manifestations of preflare activity:
defining the preflare regime, specific illustrative events, comparison
of preflare X-rays and ultraviolet, preflare microwave intensity and
polarization changes, non-thermal precursors, precursors of coronal
mass ejections, short-lived and long-lived HXIS sources as possible
precursors.
---------------------------------------------------------
Title: A digital analysis of sunspot areas.
Authors: Chapman, G. A.; Herzog, A. D.; Lin, H.
1986BAAS...18..853C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Irradiance Variations from Photometry of Active Regions
Authors: Chapman, G. A.; Meyer, A. D.
1986SoPh..103...21C Altcode:
The Extreme Limb Photometer (ELP) has been used to measure
the irradiance fluctuation of the Sun due to selected active
regions. Forty-five active regions that were completely scanned at
various disk positions are included in the analysis. The contribution of
these active regions to a global solar irradiance fluctuation has been
correlated with photometric sunspot and facular indices (PSI and PFI)
using published values of sunspot and calcium plage areas. The measured
ELP fluctuations are converted to a global brightness fluctuation,
ΔB/B. The sunspot component of ΔB/B correlates with PSI with r =
0.95. The facular component of ΔB/B correlates with PFI with r -
0.72. The expression for PFI is important to the question of energy
balance between sunspots and faculae and the results presented here
are not incompatible with energy balance between the two phenomena;
that is the energy deficit of sunspots may be balanced by the energy
excess of faculae.
---------------------------------------------------------
Title: A Two-Dimensional Solar Photometer Scanned by The Earth's
Rotation
Authors: Chapman, G. A.; Herzog, A. D.; Templer, S.
1985BAAS...17..896C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Rotating Full Disk Reticon Photometer at the San Fernando
Observatory
Authors: Herzog, A. D.; Chapman, G. A.; Lawrence, J. K.; Templer, S.
1985BAAS...17..833H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The importance of improved facular observations in
understanding solar constant variations
Authors: Schatten, K. H.; Miller, N.; Sofia, S.; Endal, A. S.;
Chapman, G.
1985ApJ...294..689S Altcode:
A new study of solar irradiance modeling has been undertaken to improve
the previous modeling efforts and perhaps to resolve the energy-balance
question. In the present study, the daily sunspot and facular areas
(using plages as a proxy measure of faculae) have been utilized, as
well as a plage intensity index to examine brightness variations. It
is noted that the reported plage areas changed by a factor of 2 near
the end of 1979. Although this can be partially modeled because
a commensurate change in plage brightness occurs, it leads to the
conclusion that facular areas and brightness uncertainties prevent a
definitive answer to the energy-balance question with this technique.
---------------------------------------------------------
Title: Solar luminosity fluctuations during the disk transit of an
active region
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.; Shelton, J. C.
1985ApJ...292..297L Altcode:
Monochromatic, photometric observations, obtained with a 512 element
linear diode array, of the solar irradiance fluctuations caused
by an active region during its entire disk transit in 1982 August
are presented. Different methods of data analysis are described and
interrelated. The maximum sunspot fluctuation, as a fraction of quiet
sun irradiance, is about -800 parts per million (ppm). Faculae have a
maximum irradiance fluctuation of about +200 ppm. By integrating over
the viewing angle during disk transit it was possible to determine
that, for visible wavelengths, the facular luminosity excess is about
50 percent of the sunspot luminosity deficit. These results indicate
that faculae are an important element in active-region energetics. The
effects of stray light and bolometric corrections are also discussed.
---------------------------------------------------------
Title: Preliminary Results from the Extreme Limb Photometer 1982
and 1983 Observing Seasons
Authors: Oseas, J.; Chapman, G. A.
1985BAAS...17..639O Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Possibility of Energy Balance Over the Lifetime of a
Solar Activity Complex
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1985BAAS...17..610L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Irradiance Variations Derived from MT. Wilson Observatory
Daily Magnetograms
Authors: Chapman, G. A.; Boyden, J. E.
1985BAAS...17Q.640C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Energy Balance of Solar Active Regions
Authors: Chapman, G. A.
1985spit.conf..342C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations concerning energy balance in solar magnetic
regions.
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.
1984ESASP.220..241C Altcode: 1984ESPM....4..241C
Variations in the solar irradiance detected by the Solar Maximum
Mission satellite have shown that sunspots alter the flow of heat near
the photosphere. Analysis of these observations suggest (1) that there
is storage of energy in active regions and (2) a significant fraction
(over one-half) of this stored energy is radiated from magnetic elements
(faculae) of the active region.
---------------------------------------------------------
Title: Observations Concerning the Energy Budget of a Solar Activity
Complex
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Shelton, J. C.
1984BAAS...16..991C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary Analysis of Multi-color Reticon Data at the San
Fernando Observatory
Authors: Herzog, A. D.; Mason, S. F.; Chapman, G. A.; Lawrence, J. K.
1984BAAS...16.1001H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar luminosity fluctuations and active region photometry
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Shelton, J. C.
1984ApJ...282L..99C Altcode:
Monochromatic observations, obtained with a 512-element diode array,
of the irradiance fluctuations of the sunspots and faculae of an active
region during its disk transit in August 1982 are presented. Bolometric
and stray light corrections are approximately equal in magnitude but
opposite in sign, so they have not been applied. The maximum sunspot
fluctuation, as a fraction of the quiet-sun irradiance, is -800 parts
per million (ppm). Faculae have a maximum irradiance fluctuation of
about +200 ppm near the limbs. It is found that the facular energy
excess is more than 50 percent of the sunspot energy deficit, which
is -5.8 x 10 to the 35th ergs. These observations show that faculae
are an important element in active region energy balance.
---------------------------------------------------------
Title: Preliminary Observations on the Energy Budget of a Solar
Activity Complex, July-Sept. 1982
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Eskenas,
Kim; Mallory, Carolyn; Shelton, J. C.
1984BAAS...16..729C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ground-based measurements of solar irradiance variations.
Authors: Chapman, G. A.
1984NASCP2310...73C Altcode: 1984siva.work...73C
A brief review is presented of observing and data analysis programs
being carried out at the San Fernando Observatory. A digital analysis
of sunspot area from full disk photographs shows good correlation
with areas published in the Solar Geophysical Data Bulletin with scale
factor near unity. Results are presented from photoelectric photometry
of active regions using the Extreme Limb Photometer. Results are
presented for the August 1982 passage of a large active region. This
active region caused a maximum dip in the quiet sun irradiance of
about 800 parts per million.
---------------------------------------------------------
Title: A Global Irradiance Program
Authors: Hudson, H. S.; Chapman, G. A.; LaBonte, B. J.
1984NASCP2310..313H Altcode: 1984siva.work..311H
Basic requirements for a long-term program of ground-based measurements
of the solar brightness are outlined.
---------------------------------------------------------
Title: Two-dimensional photometry of active regions.
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.; Shelton, J. C.
1984NASCP2310...91L Altcode: 1984siva.work...91L
The authors describe a set of two-dimensional photometric images
of solar active regions (AR's). Preliminary analysis of the data is
described, and estimates are presented of the contribution of an AR to
total solar irradiance variations during its 1982 August 3 - 16 disk
passage. Results indicate an excess contribution near the limb and a
deficit away from the limb.
---------------------------------------------------------
Title: Solar Irradiance Variations on Active Region Time Scales
Authors: Labonte, B. J.; Chapman, G. A.; Hudson, H. S.; Willson, R. C.
1984NASCP2310.....L Altcode: 1984QB531.S576.....; 1984siva.work.....L
No abstract at ADS
---------------------------------------------------------
Title: What are Faculae
Authors: Chapman, G.
1984NASCP2310..149C Altcode: 1984siva.work..149C
No abstract at ADS
---------------------------------------------------------
Title: Center-to-limb variations in the two-dimensional contrast of
photospheric faculae
Authors: Chapman, G. A.; Gingell, T. W.
1984SoPh...91..243C Altcode:
A semi-empirical model of a facular flux tube has been used to determine
its center-to-limb appearance. The model is that of Osherovich et
al. (1983). This model is in MHSE and includes tension forces. Results
are presented in the form of contour maps, cross-sections of the
contrast on axis, and integrated contrast as a function of viewing
angle. Results are generally consistent with those of Caccin and
Severino (1979), but not with observations of Chapman and Klabunde
(1982).
---------------------------------------------------------
Title: A Digital Analysis of Sunspot Areas
Authors: Chapman, G. A.; Groisman, G.
1984SoPh...91...45C Altcode:
Full-disk white light images of the Sun have been digitized, calibrated,
and examined to determine objective sunspot areas for the early
part of the operation of the Solar Maximum Mission satellite. We
find that published sunspot areas determined from synoptic programs
compare favorably with our digital areas. The mean residual between
published areas and our digital areas is approximately 80 millionths
of a hemisphere. The largest residual found is 642 millionths on April
1980 for Hale No. 16752.
---------------------------------------------------------
Title: On the energy balance of solar active regions
Authors: Chapman, G. A.
1984Natur.308..252C Altcode:
The cause of sunspots has long been an important, unsettled problem in
solar physics. Biermann<SUP>1</SUP> suggested that the strong magnetic
field of a sunspot inhibited convection, allowing the sunspot to
cool. Parker<SUP>2</SUP>, on the other hand, proposed that a sunspot
was cooled by the generation of waves that carried away the thermal
energy. The solar `constant' has been measured with a daily uncertainty
of about 10 parts per million (p.p.m.) by the Active Cavity Radiometer
Irradiance Monitor (ACRIM) on board the Solar Maximum Mission (SMM)
satellite launched in February 1980. The ACRIM has shown that the
solar constant changes with solar activity, showing dips of the order
of 0.1-0.3% associated with sunspots. This discovery has provoked
renewed attempts to understand the sunspot phenomenon. Two divergent
views are emerging: that the missing energy is stored in the convection
zone for long periods of time<SUP>3</SUP> or that the missing energy is
re-radiated fairly quickly at different angles by faculae<SUP>4</SUP>,
non-spot magnetic fields that often accompany sunspots. The consequences
are that in the first case an 11-yr modulation is expected in the
solar output whereas in the second case it is not. I point out here
that facular emission may equal the missing energy from sunspots,
over a period of some weeks or months, suggesting that the missing
energy is stored by being converted from kinetic into magnetic energy
after which it decays back into thermal energy in the faculae.
---------------------------------------------------------
Title: Solar irradiance variations on active region time
scales. Proceedingsof a workshop held at the California Institute
of Technology, Pasadena, California, June 20 - 21, 1983.
Authors: Labonte, B. J.; Chapman, G. A.; Hudson, H. S.; Willson,
R. C.; Newkirk, G. A., Jr.; Bruning, D. H.
1984sivo.book.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Properties of flares observed in the Mg i b<SUB>2</SUB>
line at 5172 Å
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1983SoPh...89..341L Altcode:
Observations of emission in the MgI b<SUB>2</SUB> line at 5172 Å are
presented for 13 flares. Also discussed are 3 flares which occurred in
regions under observation but which showed no Mg emission. The Mg flare
kernels resemble white-light flare kernels in their general morphology
and location. Comparison of Mg filtergrams with magnetograms indicates
that the Mg kernels occur at the feet of magnetic arches across neutral
lines. Time-lapse Mg filtergram films indicate photospheric shearing
motions near flare sites for several hours before flare onset.
---------------------------------------------------------
Title: Stray Light Corrections in Two-Dimensional Solar Photometry
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.; Shelton, J. C.
1983BAAS...15..951L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Irradiance Measurement of Big Bear Active Region #511
Authors: Herzog, A. D.; Chapman, G. A.; Lawrence, J. K.; Shelton, J. C.
1983BAAS...15R.973H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observed Energy Balance of Active Region 18511, August 1982
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Shelton, J. C.
1983BAAS...15..950C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetohydrostatic model of solar faculae
Authors: Osherovich, V. A.; Chapman, G. A.; Fla, T.
1983ApJ...268..412O Altcode:
A self-similar magnetohydrostatic model of solar faculae is
presented. The model is based on the Schlueter-Temesvary equation,
originally derived for sunspots. Magnetic tension and twisted magnetic
field are taken into account. The exact magnetohydrostatic solution
obtained from an observationally derived pressure deficit basically
confirms Chapman's semiempirical facular model without tension. The
difference between a facula and a sunspot and the thermodynamic
consequences of a twisted magnetic field are discussed. Pressure and
temperature profiles at different heights are presented.
---------------------------------------------------------
Title: Two-Dimensional Photometry of Active Region BBSO No. 18511
Authors: Chapman, G. A.; Herzog, A. D.; Lawrence, J. K.; Shelton, J. C.
1983BAAS...15R.717C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Active Region Photometry Compared to Plage and Sunspot Areas
Authors: Chapman, G. A.; Meyer, A. D.
1983BAAS...15..719C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Properties of Flares Observed in the MgI b2 Line at 5172 A
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1983BAAS...15..697L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A study of the magnetic evolution of active regions and its
relation to solar flares
Authors: Chapman, G.
1983ucnr.rept.....C Altcode:
Observations of solar magnetic fields and associated activity,
obtained with a Magnesium b-line (5172 A) Etalon Filter, are
described. Particular emphasis is placed on flares visible in the
wings of the Magnesium line; such flare structures are of small size
(4-6 arcsec) and their intensities are strongly correlated with soft
X-ray fluxes.
---------------------------------------------------------
Title: Measurements of the limb darkening of faculae near the
solar limb
Authors: Chapman, G. A.; Klabunde, D. P.
1982ApJ...261..387C Altcode:
Measurements are presented of the contrast at 525 nm of solar
faculae. The measurements were obtained using an extreme limb photometer
(ELP) in 1975 and 1979 at the San Fernando Observatory. The mean
contrast of active regions was determined from the limb inward
to 54 arcsec, averaged over an annulus determined using the slits
of the ELP. It is found that the contrast of faculae increases with
heliocentric angle theta, from mu approximately 0.25 to mu approximately
0.065, where mu is the cosine of theta. The average value of the mean
contrast of facular regions is 2.1%, with a possible upper limit of
approximately 5% at mu approximately 0.1, determined from regions with
the greatest filling factor. When corrected for a filling factor of
10-15%, this mean contrast implies a contrast for individual faculae
of 30-50%.
---------------------------------------------------------
Title: Active Region Photometry and Solar Variability
Authors: Chapman, G. A.; Groisman, G.; Herzog, A. D.; Lawrence, J. K.;
Meyer, A. D.; Shelton, J. C.
1982BAAS...14..865C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of Solar Flare Emission in the MgIb<SUB>2</SUB>
Line at 5172 A
Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D.
1982BAAS...14..898L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of estimated and observed active region intensity
balance.
Authors: Chapman, G. A.; Meyer, A. D.
1982BAAS...14..573C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic flux changes associated with the solar flares of
August 1972
Authors: Mayfield, E. B.; Chapman, G. A.
1981SoPh...70..351M Altcode:
The active region associated with Mt. Wilson sunspot group 18 935
(McMath, 11 976) which had a central meridian passage on August 4 and
5, 1972 produced a number of flares during transit. These included two
importance 3B flares on August 4 and 7 as well as several of importance
1 and 2. Calculations of the total magnetic flux in this region were
made during the period July 31 through August 9 using data from six
observatories. For the 3B flare on August 4, the total flux changed
from about 7.2 × 10<SUP>22</SUP> Mx just before onset to about 5.6 ×
10<SUP>22</SUP> Mx two hours after onset. For the 3B flare on August
7, the flux was about 6.4 × 10<SUP>22</SUP> Mx three hours before
onset and about 5.2 × 10<SUP>22</SUP> Mx three hours after onset. An
importance 2B flare on August 2 had no measurable effect on the flux
nor did any of several 1N or 1B flares which also occurred in this
region during the period. The flux changes measured for the 3B flares
occurred in the umbral and penumbral fields and no significant changes
were observed in facular fields.
---------------------------------------------------------
Title: Continued analysis of OSO-8 and Kitt Peak data on solar faculae
Authors: Chapman, G. A.
1981ucnr.rept.....C Altcode:
An improved semi-empirical model of phosphoric faculae is presented in
tabular form. The limitations of the model as well as other possible
improvements are discussed.
---------------------------------------------------------
Title: Observations of Solar Irradiance Variability
Authors: Willson, R. C.; Gulkis, S.; Janssen, M.; Hudson, H. S.;
Chapman, G. A.
1981Sci...211..700W Altcode:
High-precision measurements of total solar irradiance, made by the
active cavity radiometer irradiance monitor on the Solar Maximum
Mission satellite, show the irradiance to have been variable
throughout the first 153 days of observations. The corrected data
resolve orbit-to-orbit variations with uncertainties as small as
0.001 percent. Irradiance fluctuations are typical of a band-limited
noise spectrum with high-frequency cutoff near 0.15 day<SUP>-1</SUP>;
their amplitudes about the mean value of 1368.31 watts per square
meter approach ± 0.05 percent. Two large decreases in irradiance of
up to 0.2 percent lasting about 1 week are highly correlated with
the development of sunspot groups. The magnitude and time scale of
the irradiance variability suggest that considerable energy storage
occurs within the convection zone in solar active regions.
---------------------------------------------------------
Title: Sunspots and the solar constant.
Authors: Meyer, A. D.; Chapman, G. A.
1981BAAS...13..491M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of the wavelength dependence of the average
contrast of sunspots
Authors: Chapman, G. A.; Meyer, A. D.
1981phss.conf..446C Altcode:
The Extreme Limb Photometer has been used to observe the contrast of
sunspots and faculae in conjunction with the Active Cavity Radiometer
Irradiance Monitor on the SMM spacecraft. Some of these observations
were obtained at five wavelengths from 0.43 to 1.01 micron. The
largest average contrast at 0.52 micron was -17% over an area 38.5
x 51 in covering only the largest spot in Boulder AR no. 2684. It
was found, for five sunspots, far from the limb, that the wavelength
dependence of the contrast, averaged over the entire sunspot, followed
a 1/lambda-law. No evidence was found for localized bright emission
around the sunspots with an upper limit of about 3%, a limit set by
the granular intensity rms variation of 1.3% at 0.52 micron.
---------------------------------------------------------
Title: Active regions from the photosphere to the chromosphere.
Authors: Chapman, G. A.
1981sars.work...43C Altcode:
The structures and physical conditions in that portion of a solar active
region extending from the photosphere to the corona are considered. A
horizontally averaged model of a solar plage is developed which is in
reasonable agreement with observations, and significant discrepancies
existing between quiet sun models and UV and IR spectra are noted which
cast doubt on the reliability of such models. The nature of the flux
tubes comprising the small-scale structure of the active regions is
discussed, and the concept of filling factor is described as a basis
for a flux tube model explaining changes in spectral properties. The
effects of two-dimensional radiative transfer are examined for flux
tubes of various cross-sectional size, and it is found that the neglect
of explicit horizontal radiative interactions is a good approximation
to the two-dimensional treatment. The radiative power loss from active
regions is discussed for homogeneous and flux tube models, and a
significant difference in total heating requirements is found. Finally,
attention is given to the characteristics of the transition zone.
---------------------------------------------------------
Title: Magnetic field evolution observed in conjunction with SMM,
19 - 26 June 1980.
Authors: Chapman, G. A.; Thorman, S. C.; Lawrence, J. K.
1981BAAS...13..491C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variations in the solar constant due to solar active regions
Authors: Chapman, G. A.
1980ApJ...242L..45C Altcode:
Solar activity is expected to affect the solar constant at some
level. Recent observations and data analysis show the amount of
variation to be expected for active regions, faculae, and sunspots
on the apparent solar brightness. It is concluded that the maximum
effect is about 20 times greater for sunspots than for faculae per unit
area. Because facular areas are 25-30 times those for sunspots, the
effect on the solar constant of faculae and sunspots is approximately
equal and opposite, being typically in the neighborhood of 40-100 parts
per million (ppm), but on occasion able to reach over 200 ppm. The
issue of energy balance is not discussed here, for it requires further
data analysis as well as information on the facular and sunspot limb
darkening.
---------------------------------------------------------
Title: The Magnetic Field Flux in Facular Regions
Authors: Mouradian, Z.; Chapman, G.; Dumont, S.; Fang, Ch.; Feng,
Y.; Pecker, J. C.
1980jfss.conf..121M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Contrast of Faculae near the Solar Limb
Authors: Chapman, G. A.; Klabunde, D. P.
1979BAAS...11..658C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Flux Changes Associated with the Solar Flares of
August 1972
Authors: Mayfield, E. B.; Chapman, G. A.
1979BAAS...11..677M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New models of solar faculae.
Authors: Chapman, G. A.
1979ApJ...232..923C Altcode:
A new semiempirical model of photospheric faculae is presented in
tabular form. The magnetic field is estimated from horizontal pressure
equilibrium without tension forces. The geometry of the flux tube is
determined from this estimated magnetic field and an assumed flux of
4.4 x 10 to the 17th gauss sq cm. The model is discussed in relation
to recent observations.
---------------------------------------------------------
Title: Variations in the Solar Brightness due to Active Regions
Authors: Chapman, G. A.
1979BAAS...11..422C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The wavelength dependence of the facular excess brightness.
Authors: Chapman, G. A.; McGuire, T. E.
1977ApJ...217..657C Altcode:
Observations are presented of the wavelength dependence of photospheric
solar faculae obtained during August 1975. Systematic observations
with an extreme limb photometer were carried out in five different
bands. Plots of the limb brightness of a facular region for each of the
five colors are presented in a graph. Another graph shows the wavelength
dependence of the facular excess brightness, normalized to unity for
the green filter used. The wavelength variation to be expected from the
facular contribution to oblateness measurements is listed in a table.
---------------------------------------------------------
Title: Bright X-ray arcs and the emergence of solar magnetic flux.
Authors: Chapman, G. A.; Broussard, R. M.
1977ApJ...216..940C Altcode:
The Skylab S-056 and S-082A experiments and ground-based magnetograms
have been used to study the role of bright X-ray arcs and the emergence
of solar magnetic flux in the McMath region 12476. The S-056 X-ray
images show a system of one or sometimes two bright arcs within a
diffuse emitting region. The arcs seem to directly connect regions of
opposite magnetic polarity in the photosphere. Magnetograms suggest
the possible emergence of a magnetic flux. The width of the main arc
is approximately 6 arcsec when most clearly defined, and the length
is approximately 30-50 arcsec. Although the arc system is observed to
vary in brightness over a period exceeding 24 hours, it remains fixed
in orientation. The temperature of the main arc is approximately 3
x 10 to the 6th K. It is suggested that merging magnetic fields may
provide the primary energy source, perhaps accompanied by resistive
heating from a force-free current.
---------------------------------------------------------
Title: The effects of partial redistribution on facular K line
profiles.
Authors: Heasley, J. N.; Kneer, F.; Chapman, G. A.
1977SoPh...52..309H Altcode:
We present theoretical Ca II K-line profiles and filtergram contrasts
for several recent models of solar faculae. The line profiles vary
greatly between models and between complete and partial frequency
redistribution non-LTE calculations for any given model. The filtergram
contrasts are relatively insensitive to the line formation theory which
greatly simplifies the calculation for comparison with observations. All
of the models considered exhibit K-line contrasts smaller than the
mean value observed by Mehltretter.
---------------------------------------------------------
Title: Observations During the Impulsive Phase of the August 7,
1973, Solar Flare.
Authors: Sheeley, N. R., Jr.; Kane, S. R.; Vorpahl, J. A.; Chapman,
G. A.
1977BAAS....9..311S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Wavelength Dependence of the Facular Excess Brighteness.
Authors: Chapman, G. A.; McGuitre, T. E.
1977BAAS....9..357C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An improved measurement of a spectrogram of a "gap".
Authors: Chapman, G. A.; Sheeley, N. R., Jr.
1977SoPh...51...61C Altcode:
A spectrogram of the 5250 Å region previously obtained during a period
of excellent seeing has been remeasured and calibrated by reference
to the preliminary KPNO photometric atlas. This analysis, using the
logarithm of opacitance instead of an H-D plot, has reduced some of
the effects of scattered light and shows greater facular line contrast.
---------------------------------------------------------
Title: Facular line profiles and facular models
Authors: Chapman, G. A.
1977ApJS...33...35C Altcode:
Profiles for lines near 5250 A have been calculated from facular
models and compared with observed profiles. The observations are from
photographic and photoelectric spectra. The atomic parameters are
determined by comparison of calculated profiles with those observed for
the quiet sun. The effects of finite spatial resolution and a magnetic
field are required to obtain agreement with observed facular line
profiles. The empirical magnetic field deduced by matching observed and
calculated profiles is reasonably consistent with that in the facular
models. The main purpose of this paper is to show that by including the
effects of scattered photospheric light and a strong magnetic field,
reasonable agreement can be achieved between observed and calculated
facular line profiles. Results are also presented for the wing of the
Ca II K line, showing line profiles and effective filtergram contrasts
for several facular models. It is concluded that observations made
with weak Fraunhofer lines are not very useful for discrimination
among facular models, particularly without simultaneous magnetic-field
measurements. The K line may offer a better discriminator. The facular
model presently favored has a magnetic field strength of about 1500
gauss at the surface of the photosphere.
---------------------------------------------------------
Title: Facular models, the K-line, and magnetic fields.
Authors: Chapman, G. A.
1977IAUS...62..261C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Facular line profiles and facular models.
Authors: Chapman, G. A.
1977A&AS...33...35C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Bright X-Ray Arcs and the Emergence of Solar Magnetic Flux
Authors: Chapman, G. A.; Broussard, R. M.
1976BAAS....8Q.317C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary results from the S-056 X-ray telescope experiment
aboard the Skylab-Apollo Telescope Mount
Authors: Underwood, J. H.; Chapman, G. A.; Janssens, T. J.; Landecker,
P. B.; Mayfield, E. B.; McKenzie, D. L.; Vorpahl, J. A.; Walker,
A. B. C., Jr.; Milligan, J. E.; Deloach, A. C.
1976skls.conf..179U Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements of excess brightness from solar faculae and the
implication for solar oblateness.
Authors: Chapman, G. A.
1975NYASA.262..481C Altcode:
Photometric brightness scans were made of the extreme solar limb in an
attempt to show that solar oblateness excess is due to the activity of
faculae. Apparent geometrical oblateness produced by specific facular
regions was observed on 12 of 18 observing days, with the remaining
6 days revealing no oblateness-excess signals.
---------------------------------------------------------
Title: Facular Models and Line Profiles.
Authors: Chapman, G. A.
1975BAAS....7..449C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Temperature Variation with Latitude in the Upper Solar
Photosphere: Relevance to Solar Oblateness Measurements and Facular
Models
Authors: Ingersoll, A. P.; Chapman, G. A.
1975SoPh...42..279I Altcode:
Altrock and Canfield's observations of temperature variation with
latitude in the upper solar photosphere refer to higher levels
(smaller optical depths) than those to which Dicke and Goldenberg's
solar oblateness observations refer. These higher levels account for
only 1% of Dicke and Goldenberg's observed intensity. Thus Altrock and
Canfield's observations are not inconsistent with models which have
been proposed to account for solar oblateness observations by means
of a brightness variation with solar latitude.
---------------------------------------------------------
Title: Solar granulation and oscillations as spatially random
processes.
Authors: Lynch, D. K.; Chapman, G. A.
1975ApJ...197..241L Altcode:
Using Sheeley and Bhatnagar's technique to separate the slowly
varying and oscillatory component of the photospheric velocity field,
we analyze high spatial resolution A6102.7 velocitygrams (subtracted
spectroheliograms). A new way of interpreting the power spectra is
presented. By invoking simple random models of the velocity field,
the shape of the power spectra and autocorrelation functions can be
explained quantitatively, and the results show that there are no
large cells in either field. The oscillations have a mean size of
6'.'9, and the rms velocity amplitude is 0.42 km s '. For the slowly
varying component (granulation at disk center), we find Vrms = 0.24
km s -`. The effects of seeing are discussed. The interpretation of
our results leads to the identification of a restricted region in the
diagnostic diagram in which the oscillations fall. Subject headings:
granules and supergranules, solar - solar atmospheric motions
---------------------------------------------------------
Title: A Photometer for Measuring the Brightness of Features Near
the Extreme Solar Limb
Authors: Chapman, G. A.
1975BAAS....7..351C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Recent Measurements of the Flux Excess from Solar Faculae
and the Implication for the Solar Oblateness
Authors: Chapman, G. A.
1975PhRvL..34..755C Altcode:
Direct observation of the excess brightness from photospheric faculae
are presented. This excess brightness is, at times, large enough to
produce an apparent oblateness that exceeds that reported by Dicke
and Goldenberg. These results support the Chapman-Ingersoll facular
explanation for the excess solar oblateness and support the findings of
Hill et al. by offering a possible source for their excess equatorial
brightness which, they showed, can produce an apparent, nongeometrical
oblateness.
---------------------------------------------------------
Title: Time-Averaged Observations of the Sun with a 3840 Å Filter
Authors: Chapman, Gary A.
1974SoPh...37..151C Altcode:
Observations of the Sun with a 3840 Å interference filter of 12 Å
full-width at half-maximum are compared with broad band filtergrams at
5300 Å and 6103 Å magnetograms. The limit for detecting faculae by
the three techniques is compared. An improvement in detecting faculae
at 3840 Å can be obtained by time-averaged photographs with the
time-averaging done either at the telescope or in the darkroom. The
former method has certain disadvantages. The 3840 Å filter can show
the presence of faculae near the limb much better than white-light
photographs or magnetograms. This feature makes 3840 Å filtergrams
useful in conjunction with solar oblateness studies.
---------------------------------------------------------
Title: On the Nature of the Small-Scale Solar Magnetic Field
Authors: Chapman, G. A.
1974ApJ...191..255C Altcode:
It is proposed that the nonsunspot solar magnetic field has everywhere
the same strength and that this field strength is approximately gauss in
the region of formation of moderate-strength Fraunhofer lines. Several
points are presented in support of these ideas. Subject heading:
magnetic fields, solar
---------------------------------------------------------
Title: Preliminary Results Using a MgI b-Line Filter to Photography
the Photospheric Network
Authors: Chapman, G. A.
1974BAAS....6Q.285C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar X-ray Features and Events
Authors: Janssens, T. J.; Chapman, G. A.; de Loach, A. C.; McKenzie,
D. L.; Milligan, J. E.; Underwood, J. H.
1974BAAS....6Q.289J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relationships Between MMF Trajectories and Sunspot Penumbral
Filament Structure
Authors: Vrabec, D.; Chapman, Gary A.
1974BAAS....6T.296V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Faculae and the `25-day' Solar Fluctuation
Authors: Chapman, Gary A.; Ingersoll, Andrew P.
1973NPhS..246...68C Altcode: 1973Natur.246...68C
DICKE<SUP>1</SUP> has presented evidence for a new solar fluctuation
having a period of 25 d. Here we show that photospheric faculae can
explain this period.
---------------------------------------------------------
Title: Photospheric Faculae and the Solar Oblateness: a Reply to
"faculae and the Solar Oblateness" by R. H. Dicke
Authors: Chapman, Gary A.; Ingersoll, Andrew P.
1973ApJ...183.1005C Altcode:
Dicke has recently contested our statement in an earlier paper that
faculae could account for a large part, if not all, of the solar
oblateness signal measured by Dicke and Goldenberg in 1966. Using the
facular oblateness signal published in our earlier paper and some
hitherto unpublished data from his 1966 observations, he concludes
that faculae account for only a small part (11 percent) of the observed
excess oblateness. His analysis considers data only from a restricted
48-day sample and is based on the assumption that only the observed
oblateness signal is subject to error. Our analysis considers data
from all 64 days on which observations were made, and is based on the
assumption that both the observed oblateness signal and the facular
signal are subject to error. We find that faculae account for at least
one-third to one-half of the observed excess oblateness, depending
on whether 48 days or 64 days are used in the analysis. Moreover,
faculae may account for all of the observed excess oblateness provided
the facular error is sufficiently large. Thus faculae cannot be
excluded as the major source of Dicke and Goldenberg's 1966 oblateness
signal. Subject headings: faculae, solar - rotation, solar - gravitation
---------------------------------------------------------
Title: On the Source of the Slowly Varying Component at Centimeter
and Millimeter Wavelengths
Authors: Shimabukuro, Fred I.; Chapman, Gary A.; Mayfield, Earle B.;
Edelson, Sidney
1973SoPh...30..163S Altcode:
The general features of the slowly varying component at centimeter
and millimeter wavelengths are explained by magneto-ionic thermal
emission. A model of an active region is constructed in which the
electron temperature and density profile is based on recent EUV
measurements, and the current-free magnetic field configuration is
derived from a longitudinal magnetogram and scalar potential theory. In
the model, the contributions of the reflected component of the inward
extraordinary wave is important in determining the characteristic
features of the radio flux and polarization. Emission by the mechanism
of resonance absorption does not appear to be a significant factor in
this model.
---------------------------------------------------------
Title: Recent Observations of the Sun with a 3840 A Filter
Authors: Chapman, G. A.
1973BAAS....5Q.270C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Faculae and the Solar Oblateness: A Summary
Authors: Chapman, G. A.; Ingersoll, A. P.
1973NYASA.224..306C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time-Averaged Spectroheliograms
Authors: Chapman, G. A.
1972SoPh...26..299C Altcode:
The great improvement in signal-to-noise as a result of time-averaging
a sequence of λ 6103-core spectroheliograms is shown. It is
suggested that such a technique should greatly enhance the network
seen on filtergrams made with the 3840 Å violet filter (Chapman,
1970). Finally, the evolution of a sunspot, observed with time-lapse
spectroheliograms is discussed.
---------------------------------------------------------
Title: Photospheric Faculae and the Solar Oblateness
Authors: Chapman, Gary A.; Ingersoll, Andrew P.
1972ApJ...175..819C Altcode:
Photospheric faculae near the equatorial solar limb may provide the
excess brightness which Ingersoll and Spiegel showed would explain
Dicke and Goldenberg's oh lateness measurement. Three lines of evidence
support this statement: (1) the excess emission of faculae may arise in
optically thin regions, as required by the Ingersoll-Spiegel hypothesis;
(2) faculae are sufficiently widespread on the solar surface to account
quantitatively for the observed signal; and (3) temporal fluctuations
in the expected signal due to faculae in 1966 are correlated with
fluctuations in the observed signal at the 1 percent level. (The
probability of the correlation coefficient for uncorrelated data
exceeding the observed vaine is less than 1 percent.) Although this
evidence clearly demonstrates that faculae make a sizable contribution
to the observed oblateness signal, it does not preclude an equally
sizable contribution due to true gravitational oblateness Evidence that
faculae may not be the only source of oblateness signal comes from the
apparent fact that the ratio of fluctuation amplitude to mean signal
amplitude is greater for the facular signal than for the observed
oblateness signal. However, this difference may be due to errors in
reading the photographs from which the facular signal was derived,
or to differences in processing the two sets of data. A better test
of our hypothesis cannot be made until the daily oblateness signals
and their standard deviations are available. In any case, it appears
that further data analysis will be necessary before a reliable value
of the solar oblateness can be inferred.
---------------------------------------------------------
Title: Photospheric Faculae and the Solar Oblateness
Authors: Chapman, G. A.; Ingersoll, A. P.
1972BAAS....4S.379C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Source of the Slowly Varying Component at Centimeter
and Millimeter Wavelengths
Authors: Shimabukuro, F. I.; Chapman, G. A.; Edelson, S.; Mayfield,
E. B.
1972BAAS....4S.391S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Fields and Helium-D<SUB>3</SUB> Spectroheliograms
Authors: Chapman, G. A.
1972SoPh...24..288C Altcode:
Spectroheliograms, having a resolution approaching 2″, have
been obtained which show He-D<SUB>3</SUB> in absorption against the
disk. The He-D<SUB>3</SUB> features are compared with the distribution
of magnetic fields and with Hα structures. The brightest regions
in Hα usually show the strongest D<SUB>3</SUB> absorption. Most Hα
dark filaments show some D<SUB>3</SUB> absorption, but the degree of
correlation varies from filament to filament. The correlation between
B<SUB>II</SUB> and He-D<SUB>3</SUB> absorption is rather poor and the
He features are much more diffuse than the photospheric magnetic field.
---------------------------------------------------------
Title: Nova in Large Magellanic Cloud.
Authors: Gilmore, A. C.; Millington, R. E.; Chapman, G. A.
1972IAUC.2449....1G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Eclipse of Radio Emission on 7 March, 1970 at 10 cm Wavelength
from the Active Region Associated with McMath Plage 10618 (Papers
presented at the Proceedings of the International Symposium on the
1970 Solar Eclipse, held in Seattle, U. S. A. , 18-21 June, 1971.)
Authors: Mayfield, Earle B.; Chapman, Gary A.; Straka, Ronald M.
1971SoPh...21..460M Altcode:
Radio emission of 10 cm from the whole disk was monitored during the
eclipse of 7 March, 1970 by the Aerospace San Fernando Observatory and
AFCRL Sagamore Hill Solar Radio Observatory. For both, the active region
associated with sunspot 17 774, McMath region 10 618, was occulted. At
Sagamore Hill the entire region was occulted. At SFO only the southern
half of the sunspot group and the hydrogen plage southeast of the
group was occulted. This region produced an importance class 1N flare
and 10 cm burst beginning at 1601 UT and was enhanced about 15 flux
units above the mean value of 190 units at onset.
---------------------------------------------------------
Title: Fraunhofer-line weakening in solar faculae.
Authors: Chapman, G. A.
1971BAAS....3R.260C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Energy Spectrum from 5 X 10<SUP>16</SUP> to 10<SUP>21</SUP>
eV.
Authors: Bell, C. J.; Bray, A. D.; Brownlee, R. G.; Chapman, G.; David,
S.; Denehy, B.; Goorevich, L.; Horton, L.; Loy, J.; McCusker, C. B. A.;
Outhred, A.; Peak, L. S.; Ulrichs, J.; Wilson, L.; Winn, M. M.
1971ICRC....3..989B Altcode: 1971ICRC...12..989B
No abstract at ADS
---------------------------------------------------------
Title: On the Physical Conditions in the Photospheric Network:
An Improved Model of Solar Faculae
Authors: Chapman, Gary A.
1970SoPh...14..315C Altcode:
Semi-empirical models of solar faculae, cospatial with strong
photospheric magnetic fields, have been constructed from continuum
observations. The center-to-limb contrast of the various models was
computed taking into account their geometrical shape. The adopted
model whose horizontal size was taken to be 750 km, indicates that, in
field regions, the temperature begins to rise outwards at z ≈ -125 km
(above τ<SUB>5000</SUB> = 1) and that the extrapolated temperature at
z ≈ -400 km is about 1500 K above that of the undisturbed atmosphere;
the electron density is higher by a factor of about 30.
---------------------------------------------------------
Title: A New Model of Photospheric Faculae
Authors: Chapman, G. A.
1970BAAS....2Q.303C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Interference Filter for Observing the Photospheric Network
Authors: Chapman, Gary A.
1970SoPh...13...78C Altcode:
Photographs of the Sun, recently obtained with a violet interference
filter (λ ≃ 3840 Å), show the photospheric network (or photospheric
faculae) with a contrast of typically 20% across the entire solar
disk. Since this network is cospatial with photospheric magnetic
fields, one is able to determine thepositions (not polarity) of these
magnetic fields with fairly modest equipment. Furthermore, numerous
dark structures and a faint dark network can be seen through the
violet filter.
---------------------------------------------------------
Title: Miscellanea.
Authors: Gainsford, M. J.; Hollis, A. J.; Carter, B. A.; Isles, John;
Muirden, James; Ring; Chapman; Winstanley, G.; Henshaw, C.; Voss, E. J.
1970Astr....7...42G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Motions of Gas and Dust in NGC 2068
Authors: Stockton, Alan; Chapman, Gary
1970PASP...82..306S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Photospheric Network
Authors: Chapman, G. A.; Sheeley, N. R., Jr.
1968SoPh....5..442C Altcode:
Spectroheliograms, obtained in certain Fraunhofer lines with the
82-cm solar image at the Kitt Peak National Observatory, show a bright
photospheric network having the following properties: It resembles,
but does not coincide with, the chromospheric network, the structure
of the photospheric network being finer and more delicate than the
relatively coarse structure of the chromospheric network.
---------------------------------------------------------
Title: Correlations Between Brightness Fields and Magnetic Fields
on the Sun
Authors: Chapman, G. A.; Sheeley, N. R., Jr.
1968IAUS...35..161C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Local Weakenings of Fraunhofer Lines on the Solar Disk.
Authors: Chapman, Gary Allen
1968PhDT.........6C Altcode:
No abstract at ADS
