Author name code: chapman ADS astronomy entries on 2022-09-14 author:"Chapman, Gary Allen" ------------------------------------------------------------------------ Title: Four Solar Cycle Spectrum Variation of the Sun-as-a-Star Authors: Choudhary, D. P.; Chapman, G. A.; Cadavid, A. C.; Cookson, A. Bibcode: 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. Title: The Effect of Sunspot Umbrae on the Total Solar Irradiance Authors: Chapman, G. A.; Choudhary, D. P.; Cookson, A. M. Bibcode: 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. 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. Bibcode: 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 [Σr] 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 ΣK, 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. 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. Bibcode: 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, R2, 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. Title: A Comparison of Sunspot and Umbral Area from the San Fernando Obervatory and SDO Authors: Chapman, G. A.; Cookson, A.; Choudhary, D. P. Bibcode: 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. Title: Modeling SSI Variations using Ground-Based Images from the San Fernando Observatory Authors: Chapman, G. A.; Choudhary, D. P. Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. Title: Observations of the Solar Faculae at San Fernando Observatory and Solar Dynamics Observatory Authors: Prasad Choudhary, Debi; Cookson, Angie; Chapman, Gary; Yassin, Kemal Bibcode: 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. 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. Bibcode: 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) 1021Mx (1022Mx). 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). Title: An Observed Decline in the Amplitude of Recent Solar-Cycle Peaks Authors: Chapman, G. A.; de Toma, G.; Cookson, A. M. Bibcode: 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. Title: Temporal Stability of Sunspot Umbral Intensities: 1986-2012 Authors: de Toma, G.; Chapman, G. A.; Cookson, A. M.; Preminger, D. Bibcode: 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. Title: Analysis of Sunspot Area over Two Solar Cycles Authors: de Toma, G.; Chapman, G. A.; Preminger, D. G.; Cookson, A. M. Bibcode: 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. 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. Bibcode: 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 R2 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. Title: Comparison of TSI from SORCE TIM with SFO Ground-Based Photometry Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. G. Bibcode: 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, R2, of 0.9495 and a quiet-Sun irradiance S0 = 1360.810 ± 0.004 W m−2. These results provide further support for the hypothesis that the quiet Sun is constant over time. Title: Obituary: Earle B. Mayfield (1923-2007) Authors: Chapman, Gary Bibcode: 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.

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.

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.

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.

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.

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.

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.

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. Title: Activity-brightness Correlations for the Sun and Sun-like Stars Authors: Preminger, D. G.; Chapman, G. A.; Cookson, A. M. Bibcode: 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, Σr and Σb, 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, ΣK, 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 Σr and ΣK. 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. Title: Sunspot temperatures from red and blue photometry Authors: Chapman, G. A.; Cookson, A. M.; Preminger, D. G. Bibcode: 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. Title: Activity-brightness Correlations For The Sun And Sun-like Stars Authors: Preminger, D.; Chapman, G.; Cookson, A. Bibcode: 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.

This work has been supported in part by NASA LWS Grant NNX07AT19G and NSF Grant ATM-0848518. Title: Modeling TSI Variations from SORCE/TIM Authors: Chapman, Gary A.; Cookson, A.; Preminger, D. Bibcode: 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, R2, of 0.94798 and a quiet-Sun irradiance, So = 1360.778 ± 0.004 W/m2. 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. Title: Solar Synoptic Maps from the San Fernando Observatory Authors: Hodgson, John, II; Chapman, G.; Preminger, D.; Cookson, A. Bibcode: 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.

This work has been supported in part by NSF grant ATM-0848518. Title: Facular and Sunspot Areas During Solar Cycles 22 and 23 Authors: Chapman, G. A.; Dobias, J. J.; Arias, T. Bibcode: 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. Title: Recent Ground-Based Photometry Compared with Space-Based TSI Authors: Chapman, G. A.; Cookson, A.; Preminger, D. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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

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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 R2 = 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. Bibcode: 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. Bibcode: 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 (rs=− 0.623 and rs=− 0.714, respectively). Maximum umbral contrast was found to be significantly correlated with umbral area (rs=− 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 (rs=0.024, rs=0.033, and rs=0.064, respectively). During the decay phase, no significant correlation was found between average contrast or maximum contrast and time (rs=− 0.057 and rs=0.009, respectively), with a weak dependence seen between maximum umbral contrast and cycle (rs=0.102). Title: Center-to-Limb Variation of the Irradiance Contributions of Bright Active Regions. Authors: Preminger, D. G.; Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 (r2 = 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 r2 = 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. Bibcode: 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 Bibcode: 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. Bibcode: 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.

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. Bibcode: 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. Bibcode: 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. Bibcode: 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 (r2 = 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. Bibcode: 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 r and Σ K, 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 r = Σ K = 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~m2 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. Bibcode: 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. Bibcode: 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. Bibcode: 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/m2) 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 R2 = 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/m2. 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. Bibcode: 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 -2 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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−1. 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. Bibcode: 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. Bibcode: 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-1. 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. Bibcode: 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.

This work has been partially supported by grants from NASA (NAG5-7191) and NSF (ATM-9912132).

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. Bibcode: 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.

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.

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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 R2 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 R2 of 0.91. These fits are affected by noise in both ground-based and space-based data. This value of R2 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. Bibcode: 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 Σr, Σb, and ΣK, the photometric sums over broadband red, broadband blue, and 1-nm bandpass Ca II K images, respectively. Σr and Σb measure the effects of solar features on the variability in S at two different continuum wavelengths. ΣK measures the variability in spectral lines due to solar features. We find that Σr and Σb have no long-term trend. ΣK, 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 Σr and ΣK 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 ΣK, 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. Bibcode: 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 24h 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. Bibcode: 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. Bibcode: 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/m2 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. Bibcode: 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 eff, is heuristically defined as α eff = Dr/(2 x PSI), where Dr 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 r2 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 r2 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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-2 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. Bibcode: 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. Bibcode: 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. Bibcode: 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/m2 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. r2 = 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. Bibcode: 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.

References

Chapman, G.A., Cookson, A.M. & Dobias, J.J. 1997, Ap.J. 482, 541.

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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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.

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. Bibcode: 1996SoPh..168..259C Altcode: Analysis of facular contrast ΔI/Iqs 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−1 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. Bibcode: 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. Bibcode: 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 (R2) of 0.848. The rms noise in the residuals is approximately 0.221 W m-2 (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 R2 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 R2 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 R2 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 anR2 = 0.9131 and a `solar minimum' irradiance,S0, = 1371.76 ± 0.18 W m−2 for the best fit. Title: Observations of Flows around Sunspot Groups Authors: Chapman, G. A.; Walton, S. R. Bibcode: 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. Bibcode: 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. Bibcode: 1994smf..conf..216C Altcode: No abstract at ADS Title: Photometric Observations of the Sun Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1993SoPh..146...49B Altcode: The thermal contrast α, and the umbra-penumbraAu/Ap, were calculated for 63 sunspots of various sizes and morphologies. Contrary to the assumptions of the PSI model, α andAu/Ap were found to be quite variable. The values of α ranged from 0.1807 to 0.4266;Au/Ap ranged from 0.0089 to 0.4899. The values of α andAu/Ap correlated well (r = 0.6018;p<0.005) and the regression for α andAu/Ap was obtained: α = (0.220 ± 0.016) + (0.340 ± O.06)Au/Ap. The values of α andAu/Ap were then compared with complexity ratings, magnetic field strength, time, and μ. The quantities α andAu/Ap were found to be independent of the complexity, magnetic field strength, and time factors. The correlation between α andAu/Ap lead to the proposed division of α into an umbral thermal contrast αu, and a penumbral thermal contrast αp. These values were calculated from the photometric data: αu = 0.57 ± 0.01 and αp = 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 R2=0.97 (21 data points, 18 degrees of freedom). The zero point S0=1367.27 W m-2 agrees well with the solar irradiance measured by ACRIM/SMM during the 1986 activity minimum: the residual standard deviation was 0.13 W m-2 (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 R2=0.99 (17 degrees of freedom) with S0=1366.68+0.08 W m-2. The index of 10.7-cm microwave flux gave R2=0.98, with S0=1366.43+0.11 W m-2. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990BAAS...22..839L Altcode: No abstract at ADS Title: Book-Review - Solar and Middle Atmosphere Variability Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1989BAAS...21.1179W Altcode: No abstract at ADS Title: A Video Spectra - Spectroheliograph (V S2 HG) on the San Fernando Observatory Authors: Chapman, G.; Walton, S. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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−1-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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1987BAAS...19.1132W Altcode: No abstract at ADS Title: Photometric Facular Contrasts Near the Extreme Solar Limb Authors: Lawrence, J. K.; Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1987BAAS...19..926L Altcode: No abstract at ADS Title: Solar variability due to sunspots and faculae. Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1986BAAS...18Q.933C Altcode: No abstract at ADS Title: High Resolution Photometry of Solar Active Regions Authors: Herzog, A. D.; Chapman, G. A. Bibcode: 1986BAAS...18..900H Altcode: No abstract at ADS Title: Solar Irradiance Variations Derived from Magnetograms Authors: Chapman, G. A.; Boyden, J. E. Bibcode: 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. Bibcode: 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 complex1-3. 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 ~1037 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 studies2-9 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. Bibcode: 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. Bibcode: 1986BAAS...18..853C Altcode: No abstract at ADS Title: Solar Irradiance Variations from Photometry of Active Regions Authors: Chapman, G. A.; Meyer, A. D. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985BAAS...17Q.640C Altcode: No abstract at ADS Title: On the Energy Balance of Solar Active Regions Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984BAAS...16..729C Altcode: No abstract at ADS Title: Ground-based measurements of solar irradiance variations. Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984NASCP2310.....L Altcode: 1984QB531.S576.....; 1984siva.work.....L No abstract at ADS Title: What are Faculae Authors: Chapman, G. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984Natur.308..252C Altcode: The cause of sunspots has long been an important, unsettled problem in solar physics. Biermann1 suggested that the strong magnetic field of a sunspot inhibited convection, allowing the sunspot to cool. Parker2, 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 time3 or that the missing energy is re-radiated fairly quickly at different angles by faculae4, 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. Bibcode: 1984sivo.book.....L Altcode: No abstract at ADS Title: Properties of flares observed in the Mg i b2 line at 5172 Å Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D. Bibcode: 1983SoPh...89..341L Altcode: Observations of emission in the MgI b2 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. Bibcode: 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. Bibcode: 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. Bibcode: 1983BAAS...15..950C Altcode: No abstract at ADS Title: Magnetohydrostatic model of solar faculae Authors: Osherovich, V. A.; Chapman, G. A.; Fla, T. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1982BAAS...14..865C Altcode: No abstract at ADS Title: Observations of Solar Flare Emission in the MgIb2 Line at 5172 A Authors: Lawrence, J. K.; Chapman, G. A.; Herzog, A. D. Bibcode: 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. Bibcode: 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. Bibcode: 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 × 1022 Mx just before onset to about 5.6 × 1022 Mx two hours after onset. For the 3B flare on August 7, the flux was about 6.4 × 1022 Mx three hours before onset and about 5.2 × 1022 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. Bibcode: 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. Bibcode: 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-1; 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981BAAS...13..491C Altcode: No abstract at ADS Title: Variations in the solar constant due to solar active regions Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1979BAAS...11..677M Altcode: No abstract at ADS Title: New models of solar faculae. Authors: Chapman, G. A. Bibcode: 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. Bibcode: 1979BAAS...11..422C Altcode: No abstract at ADS Title: The wavelength dependence of the facular excess brightness. Authors: Chapman, G. A.; McGuire, T. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1977BAAS....9..311S Altcode: No abstract at ADS Title: The Wavelength Dependence of the Facular Excess Brighteness. Authors: Chapman, G. A.; McGuitre, T. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1977IAUS...62..261C Altcode: No abstract at ADS Title: Facular line profiles and facular models. Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1974BAAS....6Q.289J Altcode: No abstract at ADS Title: Relationships Between MMF Trajectories and Sunspot Penumbral Filament Structure Authors: Vrabec, D.; Chapman, Gary A. Bibcode: 1974BAAS....6T.296V Altcode: No abstract at ADS Title: Faculae and the `25-day' Solar Fluctuation Authors: Chapman, Gary A.; Ingersoll, Andrew P. Bibcode: 1973NPhS..246...68C Altcode: 1973Natur.246...68C DICKE1 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. Bibcode: 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 Bibcode: 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. Bibcode: 1973BAAS....5Q.270C Altcode: No abstract at ADS Title: Faculae and the Solar Oblateness: A Summary Authors: Chapman, G. A.; Ingersoll, A. P. Bibcode: 1973NYASA.224..306C Altcode: No abstract at ADS Title: Time-Averaged Spectroheliograms Authors: Chapman, G. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1972BAAS....4S.391S Altcode: No abstract at ADS Title: Magnetic Fields and Helium-D3 Spectroheliograms Authors: Chapman, G. A. Bibcode: 1972SoPh...24..288C Altcode: Spectroheliograms, having a resolution approaching 2″, have been obtained which show He-D3 in absorption against the disk. The He-D3 features are compared with the distribution of magnetic fields and with Hα structures. The brightest regions in Hα usually show the strongest D3 absorption. Most Hα dark filaments show some D3 absorption, but the degree of correlation varies from filament to filament. The correlation between BII and He-D3 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. Bibcode: 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. Bibcode: 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. Bibcode: 1971BAAS....3R.260C Altcode: No abstract at ADS Title: The Energy Spectrum from 5 X 1016 to 1021 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. Bibcode: 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. Bibcode: 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 τ5000 = 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. Bibcode: 1970BAAS....2Q.303C Altcode: No abstract at ADS Title: An Interference Filter for Observing the Photospheric Network Authors: Chapman, Gary A. Bibcode: 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. Bibcode: 1970Astr....7...42G Altcode: No abstract at ADS Title: On the Motions of Gas and Dust in NGC 2068 Authors: Stockton, Alan; Chapman, Gary Bibcode: 1970PASP...82..306S Altcode: No abstract at ADS Title: The Photospheric Network Authors: Chapman, G. A.; Sheeley, N. R., Jr. Bibcode: 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. Bibcode: 1968IAUS...35..161C Altcode: No abstract at ADS Title: Local Weakenings of Fraunhofer Lines on the Solar Disk. Authors: Chapman, Gary Allen Bibcode: 1968PhDT.........6C Altcode: No abstract at ADS