Author name code: keil ADS astronomy entries on 2022-09-14 =author:"Keil, S.L." OR =author:"Keil, Stephen L." OR =author:"Keil, Stephen" OR =author:"Keil, Steve" ------------------------------------------------------------------------ Title: The Daniel K. Inouye Solar Telescope - Observatory Overview Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode, Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.; McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich; von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn, Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.; Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang; Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian; Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard, Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross, Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit; Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon, Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer, Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.; Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer, Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes, Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag; Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik; Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis; Wampler, Stephen B.; Williams, Timothy R.; White, Charles Bibcode: 2020SoPh..295..172R Altcode: We present an overview of the National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere - the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in "service mode" and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow. Title: The Advanced Technology Solar Telescope Construction Status Report Authors: McMullin, Joseph P.; Rimmele, T. R.; Warner, M.; Berger, T.; Keil, S. L. Bibcode: 2013SPD....4440001M Altcode: The Advanced Technology Solar Telescope (ATST) will provide observing capabilities in the visible through infrared wavelengths with unprecedented resolution and sensitivity. Designed to study solar magnetism that controls the solar wind, flares, CMEs and variability in the Sun's output, the ATST will be capable of detecting and spatially resolving the fundamental astrophysical processes at their intrinsic scales throughout the solar atmosphere. The 4-m class facility is currently under construction in Maui, HI on the Haleakala Observatories site with a scheduled completion of July 2019. Since the start of site construction in December of 2012, significant progress has been made toward the development of the observatory buildings (excavation, foundations, working towards the steel erection). In addition, off-site, the major subsystems of the telescope have been contracted, designs are complete and fabrication is underway. We review the science drivers, design details, technical challenges, and provide a construction status update on the subsystems and their integration. Title: Solar Cycle Variability and Surface Differential Rotation from Ca II K-line Time Series Data Authors: Scargle, Jeffrey D.; Keil, Stephen L.; Worden, Simon P. Bibcode: 2013ApJ...771...33S Altcode: 2013arXiv1303.6303S Analysis of over 36 yr of time series data from the NSO/AFRL/Sac Peak K-line monitoring program elucidates 5 components of the variation of the 7 measured chromospheric parameters: (a) the solar cycle (period ~ 11 yr), (b) quasi-periodic variations (periods ~ 100 days), (c) a broadband stochastic process (wide range of periods), (d) rotational modulation, and (e) random observational errors, independent of (a)-(d). Correlation and power spectrum analyses elucidate periodic and aperiodic variation of these parameters. Time-frequency analysis illuminates periodic and quasi-periodic signals, details of frequency modulation due to differential rotation, and in particular elucidates the rather complex harmonic structure (a) and (b) at timescales in the range ~0.1-10 yr. These results using only full-disk data suggest that similar analyses will be useful for detecting and characterizing differential rotation in stars from stellar light curves such as those being produced by NASA's Kepler observatory. Component (c) consists of variations over a range of timescales, in the manner of a 1/f random process with a power-law slope index that varies in a systematic way. A time-dependent Wilson-Bappu effect appears to be present in the solar cycle variations (a), but not in the more rapid variations of the stochastic process (c). Component (d) characterizes differential rotation of the active regions. Component (e) is of course not characteristic of solar variability, but the fact that the observational errors are quite small greatly facilitates the analysis of the other components. The data analyzed in this paper can be found at the National Solar Observatory Web site http://nsosp.nso.edu/cak_mon/, or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters. Title: Solar Differential Rotation in Calcium II K Line Spectra Supported with Spectroheliogram Analysis Authors: Behm, Tyler; Keil, S. L. Bibcode: 2013SPD....44...05B Altcode: Two recent papers report on measuring differential rotation in data that views the Sun as a star. Unlike using tracers at different latitudes to measure the differential rotation, disk-integrated light averages over many latitudes and can only work if the features both exist at a dominate latitude that changes with the solar cycle and they persist long enough to affect the measured rotation rate. Bertello, Pevtsov, and Pietarila (2012, ApJ 761, pg 11) use disk-integrated Ca II K-line data from the SOLIS/ISS instrument to show that a change in rotation rate is clearly visible at the beginning of the current solar cycle in the disk-integrated K-line. Scargle, Keil, and Worden (2013, ApJ in press, arXiv:1303.6303) use the Sacramento Peak K-line series to look at the last current and previous three cycles with fairly strong evidence that the differential rotation is visible in cycle 22, but much harder to see in cycles 21 and 23. In order to understand the differences in the three cycles we report on solar differential rotation measurements in both the Sacramento Peak disk-integrated, Ca II K spectral time series (1977-2012) and full-disk, Ca II K spectroheliogram time series (1977-2002) observed at the Evans Solar Facility. The former data set is the same as used by Scargle et al (2013) and averages about 2-3 measurements per week. For the disk-integrated spectra, we use two interpolation schemes to fill in missing days (regression and singular value decomposition with proxy data sets) and use two methods (power spectra and autocorrelation) to find the rotation rates. We find a clear signature of solar differential rotation for solar cycle 21 and 22 and a partial signature for cycle 23. We test this result by measuring differential rotation using the Ca II K spectroheliograms using phase analysis between longitudinal bands. We have also explored the image features that lead to changes in the disk-integrated spectrum's signal-to-noise. The data analyzed in this presentation can be found at the National Solar Observatory web site http://nsosp.nso.edu/cak_mon/ , or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters and ftp://diglib.nso.edu/Evans_spectroheliograms/.Abstract (2,250 Maximum Characters): Two recent papers report on measuring differential rotation in data that views the Sun as a star. Unlike using tracers at different latitudes to measure the differential rotation, disk-integrated light averages over many latitudes and can only work if the features both exist at a dominate latitude that changes with the solar cycle and they persist long enough to affect the measured rotation rate. Bertello, Pevtsov, and Pietarila (2012, ApJ 761, pg 11) use disk-integrated Ca II K-line data from the SOLIS/ISS instrument to show that a change in rotation rate is clearly visible at the beginning of the current solar cycle in the disk-integrated K-line. Scargle, Keil, and Worden (2013, ApJ in press, arXiv:1303.6303) use the Sacramento Peak K-line series to look at the last current and previous three cycles with fairly strong evidence that the differential rotation is visible in cycle 22, but much harder to see in cycles 21 and 23. In order to understand the differences in the three cycles we report on solar differential rotation measurements in both the Sacramento Peak disk-integrated, Ca II K spectral time series (1977-2012) and full-disk, Ca II K spectroheliogram time series (1977-2002) observed at the Evans Solar Facility. The former data set is the same as used by Scargle et al (2013) and averages about 2-3 measurements per week. For the disk-integrated spectra, we use two interpolation schemes to fill in missing days (regression and singular value decomposition with proxy data sets) and use two methods (power spectra and autocorrelation) to find the rotation rates. We find a clear signature of solar differential rotation for solar cycle 21 and 22 and a partial signature for cycle 23. We test this result by measuring differential rotation using the Ca II K spectroheliograms using phase analysis between longitudinal bands. We have also explored the image features that lead to changes in the disk-integrated spectrum's signal-to-noise. The data analyzed in this presentation can be found at the National Solar Observatory web site http://nsosp.nso.edu/cak_mon/ , or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters and ftp://diglib.nso.edu/Evans_spectroheliograms/. Title: The Advanced Technology Solar Telescope: Science Drivers and Construction Status Authors: Rimmele, Thomas; Berger, Thomas; McMullin, Joseph; Keil, Stephen; Goode, Phil; Knoelker, Michael; Kuhn, Jeff; Rosner, Robert; Casini, Roberto; Lin, Haosheng; Woeger, Friedrich; von der Luehe, Oskar; Tritschler, Alexandra; Atst Team Bibcode: 2013EGUGA..15.6305R Altcode: The 4-meter Advance Technology Solar Telescope (ATST) currently under construction on the 3000 meter peak of Haleakala on Maui, Hawaii will be the world's most powerful solar telescope and the leading ground-based resource for studying solar magnetism. The solar atmosphere is permeated by a 'magnetic carpet' that constantly reweaves itself to control solar irradiance and its effects on Earth's climate, the solar wind, and space weather phenomena such as flares and coronal mass ejections. Precise measurement of solar magnetic fields requires a large-aperture solar telescope capable of resolving a few tens of kilometers on the solar surface. With its 4 meter aperture, the ATST will for the first time resolve magnetic structure at the intrinsic scales of plasma convection and turbulence. The ATST's ability to perform accurate and precise spectroscopic and polarimetric measurements of magnetic fields in all layers of the solar atmosphere, including accurate mapping of the elusive coronal magnetic fields, will be transformative in advancing our understanding of the magnetic solar atmosphere. The ATST will utilize the Sun as an important astro- and plasma-physics "laboratory" demonstrating key aspects of omnipresent cosmic magnetic fields. The ATST construction effort is led by the US National Solar Observatory. State-of-the-art instrumentation will be constructed by US and international partner institutions. The technical challenges the ATST is facing are numerous and include the design of the off-axis main telescope, the development of a high order adaptive optics system that delivers a corrected beam to the instrument laboratory, effective handling of the solar heat load on optical and structural elements, and minimizing scattered light to enable observations of the faint corona. The ATST project has transitioned from design and development to its construction phase. The project has awarded design and fabrication contracts for major telescope subsystems. Site construction has commenced following the successful conclusion of the site permitting process. Science goals and construction status of telescope and instrument systems will be discussed. Title: The Advanced Technology Solar Telescope: design and early construction Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Keil, Stephen L.; Warner, Mark; Barden, Samuel; Bulau, Scott; Craig, Simon; Goodrich, Bret; Hansen, Eric; Hegwer, Steve; Hubbard, Robert; McBride, William; Shimko, Steve; Wöger, Friedrich; Ditsler, Jennifer Bibcode: 2012SPIE.8444E..07M Altcode: The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coudé rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of major subsystems, and integration, test and commissioning activities will also be discussed. Title: Solar Cycle Fine Structure and Surface Rotation from Ca II K-Line Time Series Data Authors: Scargle, Jeff; Keil, Steve; Worden, Pete Bibcode: 2011sdmi.confE..77S Altcode: Analysis of three and a half decades of data from the NSO/AFRL/Sac Peak K-line monitoring program yields evidence for four components to the variation: (a) the solar cycle, with considerable fine structure and a quasi-periodicity of 122.4 days; (b) a stochastic process, faster than (a) and largely independent of it, (c) a quasi-periodic signal due to rotational modulation, and of course (d) observational errors (shown to be quite small). Correlation and power spectrum analyses elucidate periodic and aperiodic variation of these chromospheric parameters. Time-frequency analysis is especially useful for extracting information about differential rotation, and in particular elucidates the connection between its behavior and fine structure of the solar cycle on approximately one-year time scales. These results further suggest that similar analyses will be useful at detecting and characterizing differential rotation in stars from stellar light-curves such as those being produced by NASA's Kepler observatory. Component (b) consists of variations over a range of timescales, in the manner of a "1/f" random process. A time-dependent Wilson-Bappu effect appears to be present in the solar cycle variations (a), but not in the stochastic process (b). The data can be found at the National Solar Observatory web site http://nsosp.nso.edu/data/cak_mon.html, or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters. Title: Solar Polarization Workshop 6 Authors: Kuhn, J. R.; Harrington, D. M.; Lin, H.; Berdyugina, S. V.; Trujillo-Bueno, J.; Keil, S. L.; Rimmele, T. Bibcode: 2011ASPC..437.....K Altcode: No abstract at ADS Title: ATST: The Largest Polarimeter Authors: Keil, S. L.; Rimmele, T. R.; Wagner, J.; Elmore, D.; ATST Team Bibcode: 2011ASPC..437..319K Altcode: The Advanced Technology Solar Telescope's large collecting area, combined with diffraction limited images delivered by adaptive optics, will give it the ability to measure solar magnetic fields down to scales of a few 20-30 km in the solar photosphere and the ability to measure chromospheric and coronal magnetic fields. Title: Tracked Motions of G-band Bright Points Authors: Telford, Olivia; Keil, S. L. Bibcode: 2011AAS...21715503T Altcode: 2011BAAS...4315503T Abstract

Bright points (BPs) are magnetic elements in the photosphere observable in the CN G-band at 4305 Å. High-speed speckle images were taken with the Dunn Solar Telescope in Sunspot, NM with a 80 frame burst every 32 seconds, achieving a resolution of 0.1422” in the reconstructed images. The BPs were tracked by hand and velocities and curls (vorticity) were derived at each time step. Small-scale motions were also tracked using a FFT local correlation tracking algorithm. The velocities obtained from correlation tracking were generally smaller by factors of 2 to 5 than the hand tracked motion in agreement with previous results, however, the hand-tracked BPs tended to move in the direction of the local correlation tracking velocities. The velocities of the BPs were used to estimate the energy associated with these motions, which was found to vary between 1 to 3*1017 erg cm-1 based on observed velocities between 2 to 7 km s-1. This amount of energy could provide a source of heat for the corona, which has a minimum energy requirement of 106 erg cm-2 s-1. In some cases, BPs were seen to travel at 7 km s-1, and changed their direction of motion after collisions with granules. These supersonic speeds could generate shockwaves, which in turn could transfer energy from the BPs to the magnetic field. BPs often spiral around each other, possibly entangling the associated magnetic field providing a mechanism by which energy could be transported to the corona.

This research was funded by the National Science Foundation as part of its REU program. Title: Advanced Technology Solar Telescope: A status report Authors: Keil, S. L.; Rimmele, T. R.; Wagner, J.; ATST Team Bibcode: 2010AN....331..609K Altcode: Magnetic fields control the inconstant Sun. The key to understanding solar variability and its direct impact on the Earth rests with understanding all aspects of these magnetic fields. The Advanced Technology Solar Telescope (ATST) has been design specifically for magnetic remote sensing. Its collecting area, spatial resolution, scattered light, polarization properties, and wavelength performance all insure ATST will be able to observe magnetic fields at all heights in the solar atmosphere from photosphere to corona. After several years of design efforts, ATST has been approved by the U.S. National Science Foundation to begin construction with a not to exceed cost cap of approximately $298M. Work packages for major telescope components will be released for bid over the next several months. An application for a building permit has been submitted. Title: The Advanced Technology Solar Telescope: Science Goals, Design and Project Status. (Invited) Authors: Rimmele, T.; Keil, S. L.; Wagner, J. Bibcode: 2009AGUFMSH53B..10R Altcode: The 4m Advance Technology Solar Telescope (ATST) on Haleakala will be the most powerful solar telescope and the world’s leading resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Sun’s output. The project is about to enter the construction phase and is expected to be fully commissioned in 2017. A brief overview of the science goals and observational requirements of the ATST will be given followed by a summary of the design status of the telescope and its instrumentation will during which the technical and engineering challenges the ATST project faces will be discussed. ATST will provide high resolution and high sensitivity observations of the dynamic solar magnetic fields throughout the solar atmosphere, including the corona. With its 4 m aperture, ATST will resolve features at 0.”03 (20km on the sun) at visible wavelengths. The science requirement for polarimetric sensitivity (10-5 relative to intensity) and accuracy (5x10-4 relative to intensity) place strong constraints on the polarization analysis and calibration units. A high order adaptive optics system delivers a corrected beam to the initial set of state-of-the-art, facility class instrumentation located in the Coude lab facility. A few examples of the many unique science capabilities of the 4m ATST will be discussed. The initial set of first generation instruments includes: 1: the Visible Broadband Imager will provide images at the highest possible spatial and temporal resolution at a number of specified wavelengths in the range from 390 nm to 860 nm. 2: the Visible Spectro-Polarimeter will provide precision vector field measurements simultaneously at diverse wavelengths in the visible spectrum and thus deliver quantitative diagnostics of the magnetic field vector as a function of height in the solar atmosphere, along with the associated variation of the thermodynamic properties. 3: the Diffraction-Limited Near-Infrared Spectro-Polarimeter will record with high temporal cadence the full polarization state of spectral lines in the near infrared wavelength regime from 900 nm to 2300 nm. 4: the Cryogenic Near Infrared-Spectro-Polarimeter will measure solar magnetic fields over a large field-of-view at infrared wavelengths from 1000 nm to 5000 nm in the solar corona. 5: the Visible Tunable Filter will provide two-dimensional spectroscopy and polarimetry by recording diffraction-limited narrow-bandpass images with high temporal resolution. Title: Advanced Technology Solar Telescope Authors: Keil, Stephen L.; Rimmele, Thomas R.; Wagner, Jeremy Bibcode: 2009EM&P..104...77K Altcode: 2008EM&P..tmp...37K High-resolution studies of the Sun’s magnetic fields are needed for a better understanding of the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields are poorly understood. There is incomplete insight into physical mechanisms responsible for chromospheric and coronal structure and heating, causes of variations in the radiative output of the Sun, and mechanisms that trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe scale fundamental to these processes. The planned 4 m aperture ATST will be a unique scientific tool, with excellent angular resolution, a large wavelength range, and low scattered light. With its integrated adaptive optics, the ATST will achieve a spatial resolution nearly 10 times better than any existing solar telescope. The ATST design and development phase began in 2001 and it is now ready to begin construction in 2009. Title: Generation, Evolution and Destruction of Solar Magnetic Fields Authors: Keil, Stephen; Rimmele, Thomas; DeForest, Craig Bibcode: 2009astro2010S.153K Altcode: No abstract at ADS Title: Ca II H & K Spectra From The National Solar Observatory Authors: Livingston, W. C.; Giampapa, M. S.; Harvey, J. W.; Keil, S. L.; Toussaint, R. M. Bibcode: 2008AGUSMSP53B..04L Altcode: When the Sun is observed as a star (i.e., spatially integrated full disk) the cores of the chronospheric H and K resonance lines of singly ionized calcium show the greatest cycle variability (up to 40% peak-to-peak) accessible from the ground. Synoptic archives are available at monthly intervals from 1974 (Kitt Peak) and for K only at almost a daily cadence from 1984 (Sacramento Peak). We discuss these time series and compare them with, for example, sunspot numbers and magnetic fields. Less frequent are center disk observations in which the activity cycle is found to be absent, implying the quiet basal atmosphere is constant and not, say, heated by cycle magnetic activity. New, near daily, spatially integrated full disk solar data from the SOLIS Integrated Sunlight Spectrometer (ISS)agree well with the older work. We now propose to produce calibrated (Houtgast 1970; Solar Phys 15, 273, high points: 387.5, 395.3, and 402.0 nm), low dispersion full disk spectra that may be directly compared with that from solar-type stars. Title: Alfven Waves in the Solar Corona Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.; Schad, T.; Seeley, D. H.; Edmondson, J. Bibcode: 2007AGUFMSH21A0289T Altcode: We present observations of the coronal intensity, line-of-sight velocity, and linear polarization obtained in the FeXIII 1074.7 nm coronal emission line with the Coronal Multi-channel Polarimeter (CoMP) instrument. Analysis of these observations reveal ubiquitous upward propagating waves with phase speeds of 1-4 Mm/s and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. We can definitively identify these as Alfvén waves. An estimate of the energy carried by the waves that we spatially resolve indicates that they are unable to heat the solar corona, however, unresolved waves may carry sufficient energy. Title: Obituary: Richard B. Dunn, 1927-2005 Authors: Keil, Stephen L.; Dooling, David Bibcode: 2007BAAS...39.1056K Altcode: Dr. Richard B. Dunn, astronomer emeritus at the National Solar Observatory, died of a heart attack on September 29, 2005. He was recognized as one of the foremost experimental solar physicists. His innovative designs for telescopes and instruments led to many important discoveries in solar physics.

Born in Baltimore, Maryland, in 1927 and raised in Minneapolis, Minnesota, Dick's parents were Dr. Halbert L. Dunn and Katherine Brandner. Halbert (MD, Ph.D., F.A.P.H.A.) was an physician who became Chief of the National Office of Vital Statistics, Public Health Service. He published a paper "High Level Wellness for Man and Society" that became the founding paper of the field of wellness health care. After their divorce in 1942, Katherine moved to New York and became a social worker. Dick had two older brothers who died before him, Halbert (born in 1921, who became a civil engineer) and Robert (born in 1924, who became an architect).

Dick earned a BS in mechanical engineering and an MS in astronomy at the University of Minnesota. At the end of World War II he served in the United States Army in Japan. For his master's degree, Dick undertook the design and construction of a Lyot-type birefringent filter for observations of solar prominences. This early work led to his acceptance at Harvard, where Professor Donald Menzel encouraged him to continue his work with the 15-inch Cambridge telescope.

In 1951 he conducted part of his doctoral thesis work at the fledgling Sacramento Peak Observatory in southern New Mexico. The observatory director, Dr. John Evans, was impressed with Dick's outstanding instrumental talents and invited him to join as one of the first scientific staff members. During his first few years at Sac Peak, Dick developed two more birefringent filter systems including one with an integrated coronagraph. With this system, he produced the best prominence and spicule observations ever obtained.

Dick's career was dedicated to obtaining solar observations of the highest possible spatial resolution, having unparalleled quality that would reveal the underlying physics. Only by studying the small magnetic structures near the surface, he thought, could we understand such phenomena as the solar flares that periodically disturb the Earth. Many of his instruments were designed with this aim in mind and he was proven correct in the end.

Preeminent in Dick's achievements is the design concept for the Vacuum Tower Telescope, which was commissioned in 1969. It is a completely novel telescope that incorporates several daring engineering concepts. It was the first tower telescope with an evacuated light path, to eliminate internal seeing. It was one of the first to utilize an alt-azimuth mount, under computer control. Upon his retirement in 1998, the telescope was rededicated in his honor as the Richard B. Dunn Solar Telescope (DST).

In the DST, Dick pioneered the concept of the telescope as an integrated observing system; it was the first to incorporate telescope guidance and control and digital data recording operations in a single computer control system. Dick appreciated the advantages of such computer control a decade before the astronomical community generally accepted these concepts. His innovations led the way to similar advances in astronomy as a whole.

The DST achieved Dick's aim of providing high-resolution solar images and great flexibility in combining analyzing instruments. The DST continued as the preeminent high-resolution solar telescope in the world for the next three decades and remains a powerful and versatile system that allows simultaneous measurements using multiple cameras to record high-resolution imaging of solar features and activity, as well as high-sensitivity spectral, polarimetric and other kinds of data, and now incorporates a very effective adaptive optical system.

Another of Dick's major projects was the design of a U.S. Air Force network of solar telescopes. These five identical systems were deployed around the world to give continuous monitoring of solar activity. He was involved with many other instruments, projects and systems. Notable among these was the design of an early solar space telescope and pioneering work in solar adaptive optics.

Dick made several important discoveries with his novel instruments. His early narrow-band filter observations with the DST showed that solar spicules cover only a small area of the solar surface and reside mainly on the super-granule network. He discovered that photospheric magnetic fields emerge in kilogauss strength from sub-arcsecond "filigree."

Dick gained an international reputation for his design expertise and his willingness to help other astronomers. His advice and direct help were eagerly sought, and freely given. One can hardly visit any solar observatory in the world without hearing,"Yes, that was a Dick Dunn design." He was awarded the Hale Prize by the Solar Physics Division of the American Astronomical Society in 1998, "For his bold and imaginative innovation of instrumentation for solar physics, his discovery of important new phenomena on the Sun, and the impact of his contributions on solar physicists worldwide."

But Dick's life and work at the observatory constitute far more than simply that of a skilled experimenter who carried out new kinds of groundbreaking observations with his special instruments. He was the embodiment of those rare individuals with scientific instrumental skills who generate totally new types of systems, their work marked by extremely clever, creative and innovative ideas. In Dick's case, this profile was coupled with the ability to apply enormous energy, patience, commitment and enthusiasm to any instrumental challenge. Over the years his contributions advanced the careers of a whole generation of solar astronomers.

Dick died in his home in Las Cruces, New Mexico, after a long fight with Parkinson disease. Dick is survived by his wife of 55 years, Alice Dunn. Alice was very involved in music and had a beautiful voice. She did Russian translations, worked with the blind (which got Dick interested in developing the translator and printer mentioned below, and remains highly involved in the music scene in Las Cruces.

Dick was a person of many talents and interests, including music, sculpture and sailing, and for example, worked hard to develop an automated Braille translator and Braille printer. He was fascinated with renaissance musical instruments, acquiring a substantial collection, which he later donated to the El Paso Symphony Orchestra. He achieved much enjoyment from his hurdy-gurdy, happily entertaining anyone within earshot! Dick built several musical banks that would play elaborate tunes when a coin was inserted. The coin then rolled along ramps, striking a note each time it fell to the next level, with the length of the ramps determining the timing between notes. Title: Alfvén Waves in the Solar Corona Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.; Schad, T.; Seeley, D. H.; Edmondson, J. Bibcode: 2007Sci...317.1192T Altcode: Alfvén waves, transverse incompressible magnetic oscillations, have been proposed as a possible mechanism to heat the Sun’s corona to millions of degrees by transporting convective energy from the photosphere into the diffuse corona. We report the detection of Alfvén waves in intensity, line-of-sight velocity, and linear polarization images of the solar corona taken using the FeXIII 1074.7-nanometer coronal emission line with the Coronal Multi-Channel Polarimeter (CoMP) instrument at the National Solar Observatory, New Mexico. Ubiquitous upward propagating waves were seen, with phase speeds of 1 to 4 megameters per second and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. An estimate of the energy carried by the waves that we spatially resolved indicates that they are too weak to heat the solar corona; however, unresolved Alfvén waves may carry sufficient energy. Title: Coronal Seismology: The Search for Propagating Waves in Coronal Loops Authors: Schad, Thomas A.; Seeley, D.; Keil, S. L.; Tomczyk, S. Bibcode: 2007AAS...210.9113S Altcode: 2007BAAS...39Q.206S We report on Doppler observations of the solar corona obtained in the Fe XeXIII 1074.7nm coronal emission line with the HAO Coronal Multi-Channel Polarimeter (CoMP) mounted on the NSO Coronal One Shot coronagraph located in the Hilltop Facility of NSO/Sacramento Peak. The COMP is a tunable filtergraph instrument that records the entire corona from the edge of the occulting disk at approximately 1.03 Rsun out to 1.4 Rsun with a spatial resolution of about 4” x 4”. COMP can be rapidly scanned through the spectral line while recording orthogonal states of linear and circular polarization. The two dimensional spatial resolution allows us to correlate temporal fluctuations observed in one part of the corona with those seen at other locations, in particular along coronal loops. Using cross spectral analysis we find that the observations reveal upward propagating waves that are characterized by Doppler shifts with rms velocities of 0.3 km/s, peak wave power in the 3-5 mHz frequency range, and phase speeds 1-3 Mm/s. The wave trajectories are consistent with the direction of the magnetic field inferred from the linear polarization measurements. We discuss the phase and coherence of these waves as a function of height in the corona and relate our findings to previous observations. The observed waves appear to be Alfvenic in character.

"Thomas Schad was supported through the National Solar Observatory Research Experiences for Undergraduate (REU) site program, which is co-funded by the Department of Defense in partnership with the National Science Foundation REU Program." Daniel Seeley was supported through the National Solar Observatory Research Experience for Teachers (RET) site program, which is funded by the National Science Foundation RET program. Title: High Resolution Optical Spectroscopy, Spectropolarimetry and Spectral Imaging of Filament and Flaring Atmospheres Authors: Keil, S. L.; Balasubramaniam, K. S. Bibcode: 2005AGUFMSH41B1129K Altcode: Narrow-band spectral imaging, and Zeeman Stokes polarimetry of the photosphere and chromosphere helps to understand the nature of twisted magnetic fields and their propagation into the chromosphere. We will discuss high resolution, multi-spectral diagnostics using optical spectroscopy, imaging and spectropolarimetric techniques as applied to filament and flaring atmospheres. We trace the twists in magnetic fields through the trail of evidence it leaves at various levels of the atmosphere, as it propagates upward of the photosphere. The diagnostic tools used for this purpose include magnetic and velocity fields at the photosphere and lower chromosphere (Hα), and velocities in the upper chromosphere (Ca II~K line). We deduce the structure of magnetic fields, their relationship to the formation of the filament structure, and magnetic channels. Title: Overview and Status Report on the Advanced Technology Solar Telescope Authors: Keil, S. L.; Rimmele, T.; Wagner, J.; ATST Team Bibcode: 2005AGUSMSP34A..01K Altcode: The ATST is a 4-m aperture, off-axis solar telescope with integrated adaptive optics, low-scattered light, infrared, coronagraphic, and polarimetric capabilities. It will resolve the essential, fine-scale magnetic features and their dynamics that dictate the varying release of energy from the Sun's atmosphere. The ATST design is optimized in terms of throughput, scattered light, and instrumental polarization properties to perform precision vector magnetic field measurements down to its diffraction limit (0.03 arcsec at 500 nm) and throughout the solar atmosphere. Its collecting area, which is a factor of 16 greater than today's solar telescopes, will provide the sensitivity to measure both weak fields and rapidly evolving stronger fields. It has a factor of 64 greater collecting area than the largest existing coronagraph, and will provide the sensitivity and coronagraphic capability needed to measure the weak, fine-scale coronal magnetic fields. With adaptive optics and a set of facility class instrumentation the ATST will be the worlds leading resource for studying solar magnetism. ATST will be the successor to the solar telescopes built in the 1960s and 1970s, and is a natural complement to planned space missions. Starting in late 2001, ATST began a design and development phase. To date the D&D phase has produced and refined a science requirements document and a conceptual design that would meet those requirements. A conceptual design review was held in August of 2003. Following the review, a construction proposal, including a complete work breakdown structure and cost, was submitted in early 2004 and was successfully peer reviewed. NSF astronomy is now in the process of submitting ATST to the NSF Major Research Equipment and Facilities Construction program review process. During the D&D phase, a thorough site survey was also conducted resulting in Haleakala as the site best able to fulfill the ATST science requirements. We present a brief overview of the ATST program, how it fits into the broader picture of solar facilities and capabilities, and discuss the current status of the ATST project and plans for constructing and commissioning the ATST. Title: The Solar Mass-Ejection Imager (SMEI) Mission Authors: Jackson, B. V.; Buffington, A.; Hick, P. P.; Altrock, R. C.; Figueroa, S.; Holladay, P. E.; Johnston, J. C.; Kahler, S. W.; Mozer, J. B.; Price, S.; Radick, R. R.; Sagalyn, R.; Sinclair, D.; Simnett, G. M.; Eyles, C. J.; Cooke, M. P.; Tappin, S. J.; Kuchar, T.; Mizuno, D.; Webb, D. F.; Anderson, P. A.; Keil, S. L.; Gold, R. E.; Waltham, N. R. Bibcode: 2004SoPh..225..177J Altcode: We have launched into near-Earth orbit a solar mass-ejection imager (SMEI) that is capable of measuring sunlight Thomson-scattered from heliospheric electrons from elongations to as close as 18 to greater than 90 from the Sun. SMEI is designed to observe time-varying heliospheric brightness of objects such as coronal mass ejections, co-rotating structures and shock waves. The instrument evolved from the heliospheric imaging capability demonstrated by the zodiacal light photometers of the Helios spacecraft. A near-Earth imager can provide up to three days warning of the arrival of a mass ejection from the Sun. In combination with other imaging instruments in deep space, or alone by making some simple assumptions about the outward flow of the solar wind, SMEI can provide a three-dimensional reconstruction of the surrounding heliospheric density structures. Title: Advanced Technology Solar Telescope: conceptual design and status Authors: Keil, Stephen; Oschmann, Jacobus M., Jr.; Rimmele, Thomas R.; Hubbard, Rob; Warner, Mark; Price, Ron; Dalrymple, Nathan; Goodrich, Bret; Hegwer, Steven; Hill, Frank; Wagner, Jeremy Bibcode: 2004SPIE.5489..625K Altcode: The Advance Technology Solar Telescope (ATST) has finished its conceptual design stage, submitted a proposal for construction funding and is working towards a system level preliminary design review later this year. The current concept (including integrated adaptive optics and instrumentation) will be reviewed with concentration on solutions to the unique engineering challenges for a four meter solar telescope that have been previously presented. The overall status will be given with a concentration on near term milestones and impact on final completion targeted in 2012. Title: Advanced Technology Solar Telescope: a progress report Authors: Oschmann, Jim; Dalrymple, Nathan; Warner, Mark; Price, Ron; Hill, Frank; Hubbard, Rob; Rimmele, Thomas R.; Keller, Christoph U.; Keil, Stephen Bibcode: 2004SPIE.5171..160O Altcode: The 4m ATST will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and other astronomical objects. The design and development phase for the Advance Technology Solar Telescope (ATST) is progressing. The conceptual design review (CoDR) for the ATST is scheduled for August 2003. We present a brief description of the science requirements of ATST, and remind the reader of some of the technical challenges of building a 4-m solar telescope. We will discuss some of the design strategies that will allow us to achieve the required performance specifications, present conceptual designs for the ATST, and summarize the results of trades we have made on our path to the CoDR. The thermal impacts to local, self-induced seeing with respect to some of our system level trades that have been completed will be discussed. Title: Science Goals and Development of the Advanced Technology Solar Telescope Authors: Keil, S. L.; Rimmele, T. R.; Oschmann, J.; Hubbard, R.; Warner, M.; Price, R.; Dalrymple, N.; Atst Team Bibcode: 2004IAUS..223..581K Altcode: 2005IAUS..223..581K The Advanced Technology Solar Telescope (ATST) will perform high-resolution studies of the Sun's magnetic fields needed to understand their role in the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields remain poorly understood. There is incomplete insight as to what physical mechanisms are responsible for heating the corona, what causes variations in the radiative output of the Sun, and what mechanisms trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe scales fundamental to these processes. Title: Synergy of Research and EPO Programs at NSO Authors: Balasubramaniam, K. S.; Keil, S. L.; Penn, M. J.; Dooling, D.; Piano, P.; Diehl, J.; Hunter, R. Bibcode: 2003AGUFMED51C1215B Altcode: The National Solar Observatory with its facilities at Sunspot, NM and Tucson, AZ runs an extensive education and public outreach effort. Much of these efforts are coupled research and education efforts aimed across a spectrum that spans through school teachers, school students, undergraduate and graduate researchers, and the public. In this paper, we will describe the benefits and challenges the NSO program faces, and future prospects of these programs. Title: Design and development of the Advanced Technology Solar Telescope (ATST) Authors: Keil, Stephen L.; Rimmele, Thomas; Keller, Christoph U.; Hill, Frank; Radick, Richard R.; Oschmann, Jacobus M.; Warner, Mark; Dalrymple, Nathan E.; Briggs, John; Hegwer, Steven L.; Ren, Dauxing Bibcode: 2003SPIE.4853..240K Altcode: High-resolution studies of the Sun's magnetic fields are needed for a better understanding of solar magnetic fields and the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields are still poorly understood. There is still incomplete insight as to what physical mechanisms are responsible for heating the corona, what causes variations in the radiative output of the Sun, and what mechanisms trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe scales fundamental to these processes. The 4m aperture Advanced Technology Solar Telescope (ATST) will be a unique scientific tool, with excellent angular resolution, a large wavelength range, and low scattered light. With its integrated adaptive optics, the ATST will achieve a spatial resolution nearly 10 times better than any existing solar telescope. Building a large aperture telescope for viewing the sun presents many challenges, some of the more difficult being: · Heat control and rejection · Contamination and scattered light control · Control of telescope and instrument polarization · Site selection This talk will present a short summary of the scientific questions driving the ATST design, the design challenges faced by the ATST, and the current status of the developing design and siting considerations Title: Technical challenges of the Advanced Technology Solar Telescope Authors: Rimmele, Thomas R.; Keil, Stephen L.; Keller, Christoph U.; Hill, Frank; Briggs, John; Dalrymple, Nathan E.; Goodrich, Bret D.; Hegwer, Steven L.; Hubbard, Rob; Oschmann, Jacobus M.; Radick, Richard R.; Ren, Deqing; Wagner, Jeremy; Wampler, Stephen; Warner, Mark Bibcode: 2003SPIE.4837...94R Altcode: The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and possibly other astronomical objects, such as solar system planets. We briefly summarize the science drivers and observational requirements of ATST. The main focus of this paper is on the many technical challenges involved in designing a large aperture solar telescope. The ATST project has entered the design and development phase. Development of a 4-m solar telescope presents many technical challenges. Most existing high-resolution solar telescopes are designed as vacuum telescopes to avoid internal seeing caused by the solar heat load. The large aperture drives the ATST to an open-air design, similar to night-time telescope designs, and makes thermal control of optics and telescope structure a paramount consideration. A heat stop must reject most of the energy (13 kW) at prime focus without introducing internal seeing. To achieve diffraction-limited observations at visible and infrared wavelengths, ATST will have a high order (order 1000 DoF) adaptive optics system using solar granulation as the wavefront sensing target. Coronal observations require occulting in prime focus, a Lyot stop and contamination control of the primary. An initial set of instruments will be designed as integral part of the telescope. First telescope design and instrument concepts will be presented. Title: Innovative Telescopes and Instrumentation for Solar Astrophysics Authors: Keil, Stephen L.; Avakyan, Sergey V. Bibcode: 2003SPIE.4853.....K Altcode: No abstract at ADS Title: Science Objectives and Technical Challenges of the Advanced Technology Solar Telescope (Invited review) Authors: Rimmele, T.; Keil, S. L.; Keller, C.; Hill, F.; Penn, M.; Goodrich, B.; Hegwer, S.; Hubbard, R.; Oschmann, J.; Warner, M.; Dalrymple, N.; Radick, R.; Atst Team Bibcode: 2003ASPC..286....3R Altcode: 2003ctmf.conf....3R No abstract at ADS Title: The Advanced Technology Solar Telescope Authors: Keller, C. U.; Rimmele, T. R.; Hill, F.; Keil, S. L.; Oschmann, J. M.; ATST Team Bibcode: 2002AN....323..294K Altcode: The Advanced Technology Solar Telescope is the largest solar optical facility currently under development. The National Solar Observatory and its partners have just started the design and development phase with first light being planned for late this decade. The 4-m telescope will provide an angular resolution down to 0.025 arcsec, a large photon flux for precise magnetic and velocity field measurements, and access to a broad set of diagnostics from 0.3 to 28 mu m. We summarize the currently envisioned scientific capabilities of the telescope and its suite of instruments along with a glimpse at some of the early concepts. Title: The Advanced Technology Solar Telescope Authors: Rimmele, T. R.; Keil, S. L.; Keller, C. U.; Hill, F.; Oschmann, J. M.; Warner, M.; Dalrymple, N. E.; ATST Team Bibcode: 2002AAS...200.3408R Altcode: 2002BAAS...34..691R The 4m aperture Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope in the world and a unique scientific tool to study the Sun and other astronomical objects, such as planets. The ATST will replace major existing national solar facilities at the end of this decade. The ATST project has entered the design and development phase. We present an overview of the ATST science drivers and discuss preliminary design concepts and technical challenges. The ATST science goals lead to the following general requirements for the ATST facility: - Diffraction limited angular resolution in the visible and infrared to study fundamental astrophysical processes with unprecedented resolution enabling verification of model predictions. - A high photon flux for accurate measurements of physical parameters throughout the solar atmosphere, such as magnetic strength and direction, temperature and velocity. - Access to a new diagnostics at relatively unexplored infrared wavelength. - Low scattered light to enable coronal observations. - Low instrumental polarization for accurate measurements of magnetic fields. Development of a 4m solar telescope presents many technical challenges. The large aperture drives the ATST to an open-air design and makes thermal control of optics and telescope structure a paramount consideration. To achieve diffraction-limited observations at visible and infrared wavelength ATST will have a high order solar adaptive optics system. Coronal observations require, occulting in prime focus, a Lyot stop and contamination control of the primary. An initial set of instruments will be designed as integral part of the telescope. Preliminary telescope and instrument concepts will be discussed. Title: Calcium II K Spectroheliograms and Disk integrated Spectra Authors: Raffauf, E.; Eydenberg, M.; Keil, S. L. Bibcode: 2001AGUSM..SP21A01R Altcode: We compare spatially resolved Calcium II K spectroheliograms and disk integrated Ca II K spectra. Both data sets are obtained at the Evans Solar Facility at the National Solar Observatory Sacramento Peak on a daily basis. An understanding of the relationship between the spatially resolved and disk integrated data can aid in interpreting spatially unresolved solar and stellar observations, solar irradiance studies in which the Ca II K line serves as a ground-based proxy for solar UV and EUV lines, and differential rotation studies of stars. We present correlations between plage parameters (area and intensity) calculated from the spectroheliograms and various spectral line parameters computed from the disk integrated spectra. We also present a preliminary comparison of rotation curves obtained from the spatially resolved data with rotation rates seen in the disk integrated data. Title: The Advanced Technology Solar Telescope -- Science Goals and Instrument Description. Authors: Rimmele, T. R.; Keil, S. L.; Keller, C. U.; Hill, F. Bibcode: 2001AGUSM..SH31D08R Altcode: High-resolution studies of the Sun's magnetic fields are needed for a better understanding of solar magnetic fields and the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields are still poorly understood. There is still incomplete insight as to what physical mechanisms are responsible for heating the corona, what causes variations in the radiative output of the Sun, and what mechanisms trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe physical scales fundamental to these processes. The 4m aperture ATST will be a unique scientific tool, with excellent angular resolution, a large wavelength range, and low scattered light. With its integrated adaptive optics, the ATST will achieve a spatial resolution nearly 10 times better than any existing solar telescope. The ATST will provide:

Unprecedented angular resolution of 0.03 arcsec in the visible and 0.08 arcsec at 1.6 microns to enable us to clearly resolve and study the fundamental astrophysical processes on their intrinsic scales and to verify model predictions. A high photon flux for accurate and precise measurements of physical parameters, such as magnetic field strength and direction, temperature and velocity, on the short time scales involved. Access to a broad set of diagnostics, from visible to thermal infrared wavelengths. Low scattered light observations and coronagraphic capabilities in the infrared, allowing measurements of coronal magnetic fields. The ATST has been highly ranked by the latest Decadal Survey of Astronomy and Astrophysics and the NAS/NRC study of ground-based solar astronomy. A large part of the solar community will participate in the design and development of the ATST. A strawman telescope design, design challenges and instrument concepts will be discussed. Examples of recent high resolution observations with adaptive optics, that demonstrate the potential of this new technology will be shown. Title: The Advanced Technology Solar Telescope Authors: Keil, S. L.; Rimmele, T. R.; Keller, C. U.; Atst Team Bibcode: 2001ASPC..236..597K Altcode: 2001aspt.conf..597K No abstract at ADS Title: The Advanced Solar Telescope Authors: Keil, S. L.; Rimmele, T. R.; Keller, C.; Hill, F. Bibcode: 2000AAS...197.1710K Altcode: 2000BAAS...32.1433K The planned Advanced Technology Solar Telescope (ATST) will be a 4-m aperture general-purpose solar telescope with integrated adaptive optics and versatile post focus instrumentation. The ATST will achieve an angular resolution of 0.03 arcsec (20 km on the solar surface) in the visible, which is almost an order of magnitude better than what is achieved with current solar telescopes. This will make it possible to resolve the fundamental astrophysical hydrodynamic and magnetohydrodynamic processes and structures in the solar atmosphere such as the building blocks of solar magnetic fields that are believed to be responsible for solar irradiance variations and the heating of the outer solar atmosphere. The ATST will cover the wavelength range from 0.35 to 35 ?m and minimize scattered light. The initial set of post focus instruments will exploit the unique capabilities of the ATST to study magnetic fields at the highest spatial resolution in the visible and near-infrared parts of the spectrum. The ATST was highly recommended by the recent Decadal Study. A proposal for a four-year Design and Development phase has just been submitted to the NSF. Construction is expected to start in FY2005. The National Solar Observatory is operated by the Associated Universities for Research in Astronomy and is funded by the National Science Foundation under a cooperative agreement. Title: Comparison of Disk-Integrated Ca II K-line Spectra and K-line Spectroheliograms Authors: Catanzariti, S. P.; Keil, S. L. Bibcode: 2000SPD....3102119C Altcode: We compare changes in disk-integrated Ca-II K-line spectra with changes observed in full-disk K-line spectroheliograms. Disk-integrated K-line spectra have been obtained on a synoptic basis by the National Solar Observatory (NSO) at both its Kitt Peak and Sacramento Peak sites for the past two solar cycles. NSO also records Ca II K-line spectroheliograms on a daily basis at Sacramento Peak. The disk-integrated observations have been used as a proxy for changes in solar UV and EUV lines that can only be measured from space, as a predictor of satellite drag, to compare the Sun to other active and variable stars and to measure solar differential rotation on the Sun when viewed as a star. The goal of the comparison with the spectroheliograms is to understand and calibrate the causes of change in the disk-integrated spectra. For the past nine months, we have obtained the disk-integrated spectra and spectroheliograms simultaneously, using the Evans Facility to help eliminate sky transparency changes as a source of noise. We have also investigated several methods of normalizing the spectroheliograms before extracting plage area and brightness changes. Correlation between changes in the disk-integrated intensity and changes in the so-called emission index (an integral of the intensity over a one-angstrom band centered on the K-line) with changes in plage area and plage brightness integrated over the solar disk will be presented. Funding for this project was provided by the National Science Foundation and the Air Force Office of Scientific Research. Title: Comparison of disk-integrated Ca II K-line spectra and K-line spectroheliograms. Authors: Catanzariti, S. P.; Keil, S. L. Bibcode: 2000BAAS...32Q.832C Altcode: No abstract at ADS Title: Velocities in Solar Pores Authors: Keil, S. L.; Balasubramaniam, K. S.; Smaldone, L. A.; Reger, B. Bibcode: 1999ApJ...510..422K Altcode: We use high spatial and spectral resolution filtergrams to examine the three-dimensional morphology and velocity fields associated with solar pores in a region of newly emerged magnetic flux. The observed amplitude of the horizontal surface velocities decreases near the pores. Most of the pores exhibit a downflow in the surrounding region. Time-averaged line-of-sight velocities in and near the pores increased with the strength of the associated magnetic field. The LOS velocities are such that the maximum downflow is not centered about the continuum intensity and sometimes traces an annulus ringlike structure around the pore. From a time sequence of continuum images, it appears that some pores shed flux at the photospheric level. ``Cork movies'' of the surface velocities show that the ``corks'' are advected toward weak downflows near the pore locations and that the loci of the advected corks trace boundaries that resemble mesogranular and supergranular flows. We analyze the vertical velocity structure in pores and show that the downflow decreases exponentially with height, with a scale height that is a factor of 2 smaller than the photospheric scale height for granules. The line-of-sight flow associated with the pores appears to expand with height. Our observations are compared with previous measurements of flows in and around pores that were based on both spectrograms and filtergrams. Finally, we provide a phenomenological description for pores. Title: H alpha Synoptic Observations of Flare-Filament Eruption Complex 1997 April 6 - 7 Authors: Balasubramaniam, K. S.; Milano, L.; Keil, S. L. Bibcode: 1998ASPC..140..189B Altcode: 1998ssp..conf..189B No abstract at ADS Title: NSO/AFRL/Sac Peak K-line Monitoring Program Authors: Keil, Stephen L.; Henry, Timothy W.; Fleck, Bernhard Bibcode: 1998ASPC..140..301K Altcode: 1998ssp..conf..301K No abstract at ADS Title: Variability of the Solar Call K Line over the 22 Year Hale Cycle Authors: White, O. R.; Livingston, W. C.; Keil, S. L.; Henry, Timothy W. Bibcode: 1998ASPC..140..293W Altcode: 1998ssp..conf..293W No abstract at ADS Title: Stokes Profile Asymmetries in Solar Active Regions Authors: Balasubramaniam, K. S.; Keil, S. L.; Tomczyk, S. Bibcode: 1997ApJ...482.1065B Altcode: Asymmetries in Stokes polarization spectral line profiles can be attributed to the existence of gradients in the velocity (and magnetic field) over the line-forming region. Models that solve the Stokes radiative transfer equations have incorporated both line-of-sight gradients and gradients perpendicular to the line of sight over the resolution element to produce the observed asymmetries. There have been only a few systematic studies of how these Stokes profile asymmetries vary across spatial structures and as a function of the amplitude of the velocity and magnetic fields, and very little statistical information is available. We present observational results from high spectral and spatial resolution Stokes V profile measurements made in an active region located near disk center and present correlations between the amplitude of the Stokes V asymmetry, the magnetic field strength, and line shifts and line asymmetries observed in the Stokes I profile. In regions where the field strength exceeds a few hundred gauss, we find a good correlation between the amplitude of the measured asymmetry in Stokes V and the observed shifts of the Stokes I profile. We also find a correlation between the asymmetry of the Stokes I profile and the amplitude of the Stokes V profile asymmetry. Title: Design for the Solar Mass Ejection Imager (SMEI) Authors: Keil, S. L.; Altrock, R. C.; Kahler, S. W.; Jackson, B. V.; Buffington, A.; Hick, P. L.; Simnett, G.; Eyles, C.; Webb, D. F.; Anderson, P. Bibcode: 1997SPD....28.0227K Altcode: 1997BAAS...29..897K The Solar Mass Ejection Imager (SMEI) experiment is designed to detect and measure transient plasma features in the heliosphere, including coronal mass ejections (CMEs), shock waves, and structures such as streamers which corotate with the Sun. SMEI will provide measurements of the propagation of solar plasma clouds and high-speed streams which can be used to forecast their arrival at Earth from one to three days in advance. Data from SMEI will be used to develop models and techniques that will, for the first time, allow us to predict the onset and magnitude of geomagnetic storms that disrupt space operations and affect communications and surveillance activities. We will present the current design and observational plans for SMEI. SMEI is currently under construction with instrument completion expected in 1999. We plan to launch SMEI near the next solar maximum and will make the data available to the scientific and space weather forecast communities. Title: Near Infrared Vector Magnetograph Development Authors: Gullixson, Craig; Balasubramaniam, K. S.; Keil, Stephen Bibcode: 1997SPD....28.0226G Altcode: 1997BAAS...29..897G We have developed a two etalon, narrow-band, tunable infrared filter system and are using it to make solar vector magnetograms in the Fe I lines at 1.5648 microns. We present results on the spectral and polarization resolution of the filter system and show maps of the magnetic field in both quiet regions of the solar atmosphere and in a region with a growing sunspot. We will discuss the magnetic sensitivity of the instrument. This system is a prototype instrument for a operational vector magnetograph that will monitor the evolution of solar magnetic fields preceding solar activity. Title: Solar Mass Ejection Imager (SMEI) Authors: Keil, Stephen L.; Altrock, Richard C.; Kahler, Stephen; Jackson, Bernard V.; Buffington, Andrew; Hick, Paul; Simnett, George M.; Eyles, Christopher J.; Webb, David; Anderson, Peter Bibcode: 1996SPIE.2804...78K Altcode: The Solar Mass Ejection Imager (SMEI) experiment is designed to detect and measure transient plasma features in the heliosphere, including coronal mass ejections, shock waves, and structures such as streamers which corotate with the Sun. SMEI will provide measurements of the propagation of solar plasma clouds and high-speed streams which can be used to forecast their arrival at Earth from one to three days in advance. The white light photometers on the HELIOS spacecraft demonstrated that visible sunlight scattered from the free electrons of solar ejecta can be sensed in interplanetary space with an electronic camera baffled to remove stray background light. SMEI promises a hundred-fold improvement over the HELIOS data, making possible quantitative studies of mass ejections. SMEI measurements will help predict the rate of energy transfer into the Earth's magnetospheric system. By combining SMEI data with solar, interplanetary and terrestrial data from other space and ground-based instruments, it will be possible to establish quantitative relationships between solar drivers and terrestrial effects. SMEI consists of three cameras, each imaging a 60 degree(s) X 3 degree(s) field of view for a total image size of 180 degree(s) X 3 degree(s). As the satellite orbits the earth, repeated images are used to build up a view of the entire heliosphere. Title: Flare Genesis Experiment Authors: Murphy, Graham A.; Rust, David M.; Strohbehn, Kim; Eaton, Harry A.; Keil, Stephen L.; Keller, Christoph U.; Wiborg, P. H. Bibcode: 1996SPIE.2804..141M Altcode: In January 1996, the Flare Genesis Experiment was carried for 19 days by a 29.4 M cu. ft helium-filled balloon in the stratosphere above Antarctica, during which over 14000 images of the Sun were recorded. Long-duration ballooning provides a relatively inexpensive means to observe the Sun under near-space conditions and to develop instrumentation and techniques that will be used on future solar space missions. The purpose of the flight was to improve understanding of the mechanisms involved in many different types of solar activity, particularly flares and solar filament eruptions. Achieving this goal demanded the development of a platform for an 80-cm F/1.5 optical telescope that would be stable to 10 arcseconds. In addition, we developed an image motion compensation system capable of holding the Sun's image to better than the system's 0.2 arcsecond diffraction limit. Other key elements on board included a lithium-niobate Fabry-Perot etalon filter to provide a tunable 0.016-nm bandpass over a wide wavelength range, a fast 1534 X 1024-pixel Kodak CCD camera, and 180 GBytes of on-board storage. There was also a system for sending commands and receiving telemetry and a high-speed downlink for sending images during periods when the payload was in line of sight of the ground station. On- board computers provided a command and control system capable of near-autonomous operation. During most of the flight, contact with the payload was sporadic, so operation was primarily under autonomous control. Title: The Flare Genesis Experiment Authors: Rust, D. M.; Murphy, G. A.; Strohbehn, K.; Keil, S. L.; Keller, C. U. Bibcode: 1996AAS...188.6705R Altcode: 1996BAAS...28Q.934R The goal of the Flare Genesis Experiment is to make solar observations at the highest practicable resolution in order to improve understanding of the mechanisms involved in many different types of solar activity, particularly flares and solar filament eruptions. Achieving this goal demanded the development of a balloon-borne platform for an 80-cm F/1.5 optical telescope that could maintain 10 arcsec pointing stability. The first flight of the Flare Genesis Experiment took place in January 1996. In the stratosphere, 37 km above Antarctica, for more than 19 days, the Flare Genesis telescope pointed at the Sun with the planned stability. While the primary science objective, to measure the vector magnetic fields using two liquid crystal polarization modulators, was not achieved on this flight, 18,000 continuum images were obtained. They demonstrate that the major engineering challenges for such a flight were overcome. In addition, we developed an image motion compensation system capable of limiting the motion of the Sun's image on the focal plane to less than the system's 0.2 arcsec diffraction limit. Other key elements on board included a lithium-niobate Fabry-Perot etalon filter to provide a tunable 0.016-nm bandpass over a wide wavelength range, a 1538 x 1024- pixel CCD camera and 100 GBytes of on-board storage. We will describe the payload design and how the instruments performed. We will discuss how the constraints of long duration Antarctic ballooning guided the final design and impacted the results. Two more flights are planned before the next solar maximum. Such long-duration balloon flights provide a relatively inexpensive means to observe the Sun at the highest resolution and to develop instrumentation and techniques for future space missions. Title: Velocities in Solar Pores Authors: Balasubramaniam, K. S.; Keil, S. L.; Smaldone, L. A. Bibcode: 1996AAS...188.0203B Altcode: 1996BAAS...28..820B We investigate the three dimensional structure of solar pores and their surroundings using high spatial and spectral resolution data. We present evidence that surface velocities decrease around pores with a corresponding increase in the line-of-sight (LOS) velocities. LOS velocities in pores increase with the strength of the magnetic field. Surface velocities show convergence toward a weak downflow which appear to trace boundaries resembling meso-granular and super granular flows. The observed magnetic fields in the pores appear near these boundaries. We analyze the vertical velocity structure in pores and show that they generally have downflows decreasing exponentially with height, with a scale height of about 90 km. Evidence is also presented for the expanding nature of flux tubes. Finally we describe a phenomenological model for pores. This work was supported by AFOSR Task 2311G3. LAS was partially supported by the Progetto Nazionale Astrofisica e Fisica Cosmica of MURST and Scambi Internazionali of the Universita degli Studi di Napoli Frederico II. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc. Title: Design Considerations for a Near Infrared Imaging Vector Magnetograph Authors: Gullixson, C. A.; Keil, S. L.; Balasubramaniam, K. S. Bibcode: 1996AAS...188.5603G Altcode: 1996BAAS...28R.911G We present a preliminary design for an imaging vector magnetograph at 15648 Angstroms. This instrument is intended as a potential source of vector magnetic field measurments for the USAF and NOAA solar activity prediction programs. It will consist of a blocking filter, two Fabry-Perot Etalons in tandem, a near-IR (10000 -- 17000 Angstroms) camera and associated polarization optics. Initial test results of the optical characteristics of this instrument and its expected performance characteristics will be described. We are exploring designs for operational vector magnetographs in the near-IR as a way to simplify vector magnetic field measurements while improving their accuracy. This work was supported by AFOSR Task 2311G3. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc. Title: Solar drivers of the interplanetary and terrestrial disturbances Authors: Balasubramaniam, K. S.; Keil, Stephen L.; Smartt, Raymond N. Bibcode: 1996ASPC...95.....B Altcode: 1996sdit.conf.....B No abstract at ADS Title: The Solar Mass Ejection Imager (SMEI): Development and Use in Space Weather Forecasting Authors: Keil, S. L.; Altrock, R. C.; Kahler, S. W.; Jackson, B. V.; Buffington, A.; Hick, P. L.; Simnett, G.; Eyles, C.; Webb, D. F.; Anderson, P. Bibcode: 1996ASPC...95..158K Altcode: 1996sdit.conf..158K No abstract at ADS Title: A search for large-scale photospheric flows as drivers of mass ejections Authors: Balasubramaniam, K. S.; Keil, S. L. Bibcode: 1996ASPC...95..189B Altcode: 1996sdit.conf..189B No abstract at ADS Title: Restored Solar Velocity Measurements Obtained from the May 10, 1994 Annular Solar Eclipse Authors: Keil, S. L.; Balasubramaniam, K. S.; Ljungberg, S. K.; Smaldone, L. A.; Rimmele, T. R. Bibcode: 1995SPD....26..202K Altcode: 1995BAAS...27..951K No abstract at ADS Title: Stokes Profile Asymmetries in Active Regions Authors: Balasubramaniam, K. S.; Keil, S. L.; Tomczyk, S.; Bernasconi, P. Bibcode: 1995SPD....26..205B Altcode: 1995BAAS...27..951B No abstract at ADS Title: Solar and Stellar Chromospheric Contrast - Part One Authors: Donahue, Robert A.; Restaino, Sergio R.; Keil, Stephen L. Bibcode: 1994SoPh..149..257D Altcode: We present an analysis of disk-integrated spectra of the CaII K line (3933.68 å). The selection of parameters in the line profile, and the correlations between them, follow the work of Smith (1960), but represent an innovative aspect in the fact that our data are spatially integrated. Therefore, the subsequent identification of correlations between line-profile parameters in disk-integrated solar spectra may be useful in identifying similar correlations in high-resolution spectra of solar-like stars. Title: Active Region Development: Results from the JHU/APL Vector Magnetograph Authors: Rust, D. M.; Murphy, G.; Balasubramaniam, K. S.; Gullixson, C. A.; Henry, T.; Coulter, R. L.; Keil, S. L. Bibcode: 1994ASPC...68..263R Altcode: 1994sare.conf..263R No abstract at ADS Title: Dynamics of Small Flux Tubes Authors: Reger, Bernard; Keil, Stephen L.; Smaldone, Luigi A.; Cauzzi, Gianna; Balasubramaniam, K. S. Bibcode: 1994ASPC...68..157R Altcode: 1994sare.conf..157R No abstract at ADS Title: Simultaneous Filter and Spectrograph Observations of Active Regions with the Advanced Stokes Polarimeter Authors: Tomczyk, S.; Balasubramaniam, K. S.; Keil, Stephen L. Bibcode: 1994ASPC...68..262T Altcode: 1994sare.conf..262T No abstract at ADS Title: Observations of Active Region Dynamics: Preflare Flows and Field Observations Authors: Keil, Stephen L.; Balasubramaniam, K. S.; Bernasconi, Pietro; Smaldone, Luigi A.; Cauzzi, Gianna Bibcode: 1994ASPC...68..265K Altcode: 1994sare.conf..265K No abstract at ADS Title: Change in the radiative output of the Sun in 1992 and its effect in the thermosphere Authors: White, O. R.; Rottman, G. J.; Woods, T. N.; Knapp, B. G.; Keil, S. L.; Livingston, W. C.; Tapping, K. F.; Donnelly, R. F.; Puga, L. C. Bibcode: 1994JGR....99..369W Altcode: Ground and space measurements of the solar spectral irradiance at radio, visible, UV, and X ray wavelengths show a large decline in the first 6 months of 1992. This sustained drop in the solar output is important in understanding the connection between the emergent magnetic flux on the Sun and the radiative output as well as in understanding the effects of such change in the upper atmosphere of the earth. We present preliminary estimates of the observed changes as the means to spur inquiry into this solar event in the declining phase of solar cycle 22. Typical decreases are 15% in Lyman alpha and 40% in 10.7-cm radio flux. Mass spectrometer and incoherent scatter model calculations at 600 km in the thermosphere indicate a 30% decrease in the temperature and a 3X decrease in the density of the thermosphere near the altitude where both the Upper Atmosphere Research Satellite (UARS) and Hubble Space Telescope (HST) are flying. Decrease of the orbital period of the UARS shows the expected effect of decreasing density at flight altitude. Work in progress indicates that the output change results from the decline in solar magnetic flux to a lower level of activity in the southern hemisphere of the Sun. Title: On the calibration of line-of-sight magnetograms Authors: Cauzzi, G.; Smaldone, L. A.; Balasubramaniam, K. S.; Keil, S. L. Bibcode: 1993SoPh..146..207C Altcode: Inference of magnetic fields from very high spatial, spectral, and temporal resolution polarized images is critical in understanding the physical processes that form and evolve fine scale structures in the solar atmosphere. Studying high spectral resolution data also helps in understanding the limits of lower resolution spectral data. We compare three different methods for calibrating the line-of-sight component of the magnetic field. Each method is tested for varying degrees of spectral resolution on both synthetic line profiles computed for known magnetic fields and real data. The methods evaluated are: (a) the differences in the center of gravity of the right and left circular components for different spectral resolution, (b) conversion of circular polarization, at particular wavelengths, to magnetic fields using model-dependent numerical solutions to the equations of polarized radiative transfer, and (c) the derivative method using the weak field approximation. Each method is applied to very high spatial and spectral resolution circular polarization images of an active region, acquired in the FeI 5250 å Zeeman-sensitive spectral line. The images were obtained using the 20 må pass-band tunable filter at NSO/Sacramento Peak Observatory Vacuum Tower Telescope. We find that the center-of-gravity separation offers the best way of inferring the longitudinal magnetic field. Title: C Class Flares: Dynamics at Multiple Heights in the Solar Atmosphere Authors: Balasubramaniam, K. S.; Keil, S. L. Bibcode: 1993BAAS...25R1214B Altcode: No abstract at ADS Title: Calibrations of the JHU/APL-NSO-USAF Vector Magnetograph Authors: Balasubramaniam, K. S.; Keil, S. L. Bibcode: 1993BAAS...25.1205B Altcode: No abstract at ADS Title: The Sun in a Non-Cycling State Authors: White, O. R.; Skumanich, A.; Lean, J.; Livingston, W. C.; Keil, S. L. Bibcode: 1992PASP..104.1139W Altcode: Using the Baliunas and Jastrow (1990) study of cyclic variability in solar-type stars, we transform existing solar data to the stellar HK irradiance scale and examine the state of the solar chromosphere when a solar-type star shows little cyclic variability and surface magnestis m. To reduce the chromospheric emission to levels for G-type stars showing no chromospheric activity cycles, no only must the sun be free of plages and network; the brightness of the quiet chromosphere in the K line must be reduced to levels seen only in 15% of the quiet Sun area today. In contrast, the present day level of K emission from the sun places it in the class of most active solar-type stars, far removed from a non-cycling state. (SECTION: Stars) Title: Solar Ca II K Measurements and Activity Cycles in Solar-Type Stars Authors: White, O. R.; Livingston, W. C.; Keil, S. L. Bibcode: 1992sers.conf..160W Altcode: No abstract at ADS Title: High-Frequency Acoustic Waves and Effects of Magnetic Fields on Wave Propagation in the Solar Photosphere Authors: Reardon, K. W.; Keil, S. L. Bibcode: 1991BAAS...23.1389R Altcode: No abstract at ADS Title: Narrow Bandpass Filter Solar Observations Authors: Smaldone, L. A.; Cauzzi, G.; Keil, S. L. Bibcode: 1991BAAS...23.1057S Altcode: No abstract at ADS Title: On the Fractal Dimension of Granulation Authors: Newbury, J.; Keil, S. L. Bibcode: 1991BAAS...23Q1048N Altcode: No abstract at ADS Title: Structure and oscillations in quiescent filaments from observations in He i λ10830 å Authors: Yi, Zhang; Engvold, Oddbjorn; Keil, Stephen L. Bibcode: 1991SoPh..132...63Y Altcode: 1991SoPh..132...63Z Observations of two quiescent filaments show oscillatory variations in Doppler shift and central intensity of the He I λ10830 Å line. Title: A Search for Polarization in Ellerman Bombs Authors: Rust, D. M.; Keil, S. L. Bibcode: 1991BAAS...23R1029R Altcode: No abstract at ADS Title: Variations of the Solar Calcium K-line 1976-1989 Authors: Keil, S. L.; Fleck, B. Bibcode: 1989BAAS...21.1185K Altcode: No abstract at ADS Title: Line asymmetries and vertical velocities observed with a narrow-band filter Authors: Keil, S. L.; Bonaccini, D.; Tamblyn, P.; November, L. J. Bibcode: 1989hsrs.conf..272K Altcode: No abstract at ADS Title: Observations of High Frequency Waves in the Solar Atmosphere Authors: Keil, S. L.; Mossman, A. Bibcode: 1989ASIC..263..333K Altcode: 1989ssg..conf..333K No abstract at ADS Title: Observation and Interpretation of Photospheric Line Asymmetry Changes near Active Regions Authors: Keil, S. L.; Roudier, Th.; Cambell, E.; Koo, B. C.; Marmolino, C. Bibcode: 1989ASIC..263..273K Altcode: 1989ssg..conf..273K No abstract at ADS Title: U.S. Observing Facilities Authors: Keil, Stephen L. Bibcode: 1988Sci...240.1263K Altcode: No abstract at ADS Title: Observational Results in Solar Astronomy with the Improved Lockheed Active Mirror System Authors: Smithson, R. C.; Acton, D. S.; Peri, M. L.; Sharbaugh, R. J.; Dunn, R. B.; van der Lühe, O.; Keil, S. L. Bibcode: 1988BAAS...20R.710S Altcode: No abstract at ADS Title: The Effects of Magnetic Structures in the Solar Photosphere on Energy Transport Mechanisms Authors: Keil, S. L. Bibcode: 1987BAAS...19..940K Altcode: No abstract at ADS Title: Vertical motions in quiescent prominences observed in the He I λ10830 Å line. Authors: Engvold, Oddbjorn; Keil, Stephen L. Bibcode: 1986NASCP2442..169E Altcode: 1986copp.nasa..169E The observations contain two-dimensional spectral scans of a total of 17 different prominences on the solar disk from the period 3 to 9 May 1981, using the main spectrograph of the solar vacuum telescope at Sacramento Peak. The following conclusions may be drawn from the data: (1) Blue shifts are much more common than red shifts. In many cases more than 90 per cent of the projected prominence area is associated with blue shifts. (2) The darkest prominence regions show the largest blue shift (v less than 3 km s-1). (3) Red shifts are most commonly seen at prominence edges. (4) The general pattern of prominence velocity persists for several hours. On the scale of about 10 arcsec and less, changes are detectable in the course of 2 to 5 minutes. The observed predominance of the blue shifts is largely in agreement with earlier results from H alpha (cf. Martres et al. 1981). It cannot, however, be concluded definitely that the observed shift really represents a net flow of matter. The situation could possibly be analogous to that of the solar transition region where lines such as C IV lambda 1548 angstroms seem to indicate a net inflow, which can hardly be true, at velocities greater than 4 km s(-1) in the quiet Sun (Athay et al. 1983; Gurman and Athay 1983). If the typical structure element of the prominence is sub-resolution, i.e., 2 to 3 arcsec or worse, as in the present case, an apparent net shift could result if the ascending and the decending elements have different temperature and/or pressure. Different lines could then indicate different flow velocities and even opposite directions. Title: Diagnostics for Propagating Waves in the Solar Photosphere Authors: Keil, Stephen L.; Marmolino, Ciro Bibcode: 1986ApJ...310..912K Altcode: The effects of pure acoustic waves of different frequencies on a number of Fe I lines formed in the photosphere are investigated. A dynamical model of the waves which considers velocity, temperature, and pressure fluctuations as functions of time is used to compute the line profiles. The extent to which the waves cause the lines to fluctuate, the time-averaged properties of the line profiles, and the measurability of vertical phase differences are all determined as functions of the frequency of the propagating wave. It is concluded that there is no intrinsic radiative limit, for frequencies of current observational interest, on ability to measure phase differences. The asymmetry induced by the propagation of acoustic waves in the photosphere is found to depend on the frequency of the waves. Acoustic waves contribute only marginally to line broadening. Title: A Stabilized Spectral Time Sequence of High-Frequency Propagating Waves in the Solar Atmosphere Authors: Keil, S. L. Bibcode: 1986BAAS...18..934K Altcode: No abstract at ADS Title: Initial Solar Observations at Sacramento Peak Using the Lockheed Active Optics System Authors: Smithson, R. C.; Sharbaugh, R. J.; Ramsey, H. E.; Acton, D. S.; Pari, M.; Keil, S. L.; Radick, R. R.; Simon, G. W.; von der Luehe, O.; Zirker, J. B. Bibcode: 1986BAAS...18..933S Altcode: No abstract at ADS Title: Some Effects of Propagating Wave Packets on Solar Spectral Lines Authors: Keil, S. L.; Koo, B. C. Bibcode: 1986BAAS...18Q.702K Altcode: No abstract at ADS Title: Solar Activity Measurement Experiment (SAMEX) Authors: Keil, Stephen L.; Neidig, Donald F. Bibcode: 1986aiaa.meetQ....K Altcode: SAMEX is the first step in providing the Air Force with a Solar Activity Forecasting and Monitoring System in Space (SAFMSS). SAMEX will provide the test bed for a high spatial resolution soft X-ray/EUV imager (20-150 A) and a high resolution vector magnetograph. The proposed payload will be flown as part of the Space Test Program and subsequently used to form the kernel of a Solar Activity Monitoring Satellite (SAMSAT) that has been proposed by the Air Weather Service. Title: How Should Observers Prepare for the SOT / Solar Optical Telescope / Hydrodymanic Experiments Authors: Keil, S. L. Bibcode: 1985tphr.conf...30K Altcode: No abstract at ADS Title: Steady flows in active regions observed with the HeI 10830 Å line Authors: Lites, B. W.; Keil, S. L.; Scharmer, G. B.; Wyller, A. A. Bibcode: 1985SoPh...97...35L Altcode: We show that the He I 10830 A line gives reliable Doppler shift measurements in the upper chromosphere above active regions. Persistent flow patterns in active regions observed near the solar limb show features previously noted in Dopplergrams using the CIV transition region ultraviolet emission line. Unlike the CIV measurements, however, the He I absorption shows a strong correlation with the line-of-sight velocity images in certain regions of some active regions. Title: A search for long-lived velocity fields at the solar poles Authors: Durney, B. R.; Lytle, D. M.; Cram, L. E.; Guenther, D. B.; Keil, S. L. Bibcode: 1985ApJ...292..752D Altcode: A search has been made in the polar regions of the sun for large-scale (50-200 Mm) velocity fields with lifetimes of the order of the solar rotation period (approximately equal to or greater than 30 days). The observations show that any such large-scale, long-lived velocity patterns in the polar regions must have an amplitude less than 5 m/s. Marginally significant detections (at the 2-3 sigma level) were made of two kinds of structures with amplitudes of order 3 m/s. One has a rotation period approximately 38 days (close to the polar rotation period at the sun's surface), and a scale approximately 150 Mm; the other has a period approximately 24 days and a scale approximately 100 Mm. Tentatively, the first structure is interpreted as being of supergranular origin. The second structure is interpreted as the overshooting of the dominant convective mode of the lower solar convection zone - the giant granulation. Title: Effects of Magnetic Fields on the Asymmetry of Photospheric Line Profiles Authors: Keil, S. L. Bibcode: 1985BAAS...17..642K Altcode: No abstract at ADS Title: Stellar Convection. (Book Reviews: The Solar Granulation) Authors: Keil, Stephen L. Bibcode: 1985Sci...227..512B Altcode: No abstract at ADS Title: Stellar Convection. (Book Reviews: The Solar Granulation) Authors: Keil, Stephen L. Bibcode: 1985Sci...227..512K Altcode: No abstract at ADS Title: Steady flows in active regions observed with the He I 10830 Å line. Authors: Lites, B. W.; Keil, S. L.; Scharmer, G. B.; Wyller, A. A. Bibcode: 1985cdm..proc..287L Altcode: No abstract at ADS Title: How should observers prepare for the SOT hydrodynamic experiments. Authors: Keil, S. L. Bibcode: 1985MPARp.212...30K Altcode: The author concentrates on the need to improve observations. He discusses some of the things observers should be doing and some of the problems they must consider to prepare for SOT (Solar Optical Telescope). The author also discusses a few ongoing programs as examples of the type of work that needs to be continued to prepare observationally for SOT. Title: Time-resolved spectral observations of spicule velocities at several heights Authors: Sirajul Hasan, S.; Keil, S. L. Bibcode: 1984ApJ...283L..75S Altcode: 1984ApJ...283L..75H The vacuum telescope of the National Solar Observatory, Sacramento Peak was used to obtain H-alpha spectral observations of spicules. A set of spectra corresponding to five slit positions above the solar limb were recorded every 8 s in order to study the temporal variation of spicules at several heights with high space and time resolution. The short time interval (less than 2 s) between exposures at each height is a new feature of these observations. A typical flow event in a spicule was found to last 10-15 minutes. During this period the velocity did not reverse sign. The temporal behavior of the velocity at different heights in a spicule appeared to show a high correlation, with a time lag less than 7 s, implying signal propagation speeds greater than 300 km/s. Finally, no significant variation of spicule velocity with height in the chromosphere was noticed. Title: On the rotation rate of polar features in the sun Authors: Durney, B. R.; Lytle, D. M.; Keil, S. L. Bibcode: 1984ApJ...281..455D Altcode: The authors evaluate the rotation rate of solar features in the vicinity of the poles with the help of a correlation procedure. The average rotation rates for both poles are systematically smaller than those predicted by Howard and Harvey's formula, but not in serious disagreement with their results. Title: Observations of High Frequency Waves Using a CCD Array Authors: Melroy, P. A.; Keil, S. L. Bibcode: 1984ssdp.conf...19M Altcode: The authors have measured phase shifts between line displacement fluctuations at various intensity levels in Fe I 5576 and 6302 for frequencies up to 40 mHz. Waves with frequencies between 4.2 mHz and 10 mHz are propagating upwards with propagation velocities near the sound speed. The amplitude of the fluctuations corresponds to approximately 100 m/sec. Although the authors measure power in the fluctuations above 10 mHz, the phase shifts drop to zero for higher frequencies. The authors find some evidence for periodic ripples in the high frequency tail of temporal power spectra of the line displacements as reported earlier by Deubner (1976), but these could result from atmospheric and instrumental effects. Title: Line Asymmetries of Partially Resolved Granular Profiles Authors: Keil, S. L. Bibcode: 1984ssdp.conf..148K Altcode: A time series of high-spatial resolution spectrograms made in the solar photospheric line Fe I 5576 is used to extract line profiles formed in bright granular regions and dark intergranular lanes. The author forms various mean profiles to generate representative granular and intergranular profiles. The asymmetry of these mean profiles is compared with asymmetries predicted from models of the granulation flow. The observations are compatible with penetrating convective elements having velocity scale heights of approximately 100 km in the photosphere. Title: Variations in the solar calcium K line 1976-1982 Authors: Keil, S. L.; Worden, S. P. Bibcode: 1984ApJ...276..766K Altcode: Chromospheric variability between 1976 and 1982 as evidenced in Ca II K line observations obtained at Sacramento Peak Observatory is reported. The data on solar variability are compared to similar data collected at Kitt Peak by White and Livingston (1981). The measurement of solar rotation as reflected in the K index was attempted. Partial success was achieved in this second objective, based on limited results in early 1977 and early 1981-1982. While there is good long term (about 6 months) correlation between the K line and the number of plages and sunspots during the rising phase of solar activity, the short term correlation (about 1 week) is poor. Title: Small-scale dynamical processes in quiet stellar atmospheres. Proceedings of a workshop, held at Sunspot, New Mexico, USA, 25 - 29 July 1983. Authors: Keil, S. L. Bibcode: 1984ssdp.conf.....K Altcode: High-resolution observations of small-scale solar dynamics are discussed, taking into account the phase relations of high degree p-modes, power spectra of short-period oscillations, observations of high frequency waves using CCD array, dynamic signatures of quiet sun magnetic fields, and small-scale dynamical processes in the solar chromosphere. Other topics explored are related to projected improvements to high-resolution measurements, interpretation of high-resolution measurements, modelling of small-scale dynamical processes, convection and wave generation, interaction between solar convection and magnetism, low-resolution observations bearing on small-scale dynamical processes in the sun, the interpretation of low resolution observations, the accuracy of models obtained from low-resolution observations, and observations and interpretations of small-scale dynamical processes in stellar atmospheres. Attention is given to the observation of stellar granulation, and Zeeman broadening in solar type stars. Title: Detection of Propagating Waves in the Solar Photosphere Authors: Keil, S. L.; Marmolino, C. Bibcode: 1983BAAS...15Q.971K Altcode: No abstract at ADS Title: The characteristic size and brightness of facular points in the quietphotosphere. Authors: Muller, R.; Keil, S. L. Bibcode: 1983SoPh...87..243M Altcode: 1983SoPh...87..243K Using two very high resolution, white-light plates of the solar granulation, we measure a characteristic size and intensity for facular points. The plates were obtained with the 50 cm refractor at Pic-du-Midi Observatory using a 60 Å bandpass filter center at 5750 Å. After adjustment for atmospheric and instrumental smearing, we find a characteristic size of 0.22 arc sec and a characteristic intensity of 1.3 to 1.5 times the mean continuum intensity. Title: Observations of Polar Velocity Fields Authors: Durney, B. R.; Lytle, D. M.; Cram, L. E.; Guenther, D. B.; Keil, S. L. Bibcode: 1983BAAS...15..716D Altcode: No abstract at ADS Title: High Frequency Waves in the Photosphere Authors: Keil, S. L.; Melroy, P. A. Bibcode: 1983BAAS...15R.705K Altcode: No abstract at ADS Title: Solar Rotation and Variability Observed in the Ca II K Line Authors: Keil, S. L.; Worden, S. P. Bibcode: 1982BAAS...14..623K Altcode: No abstract at ADS Title: A Search for Granular Induced Wave Modes Authors: Keil, S. L. Bibcode: 1981BAAS...13R.911K Altcode: No abstract at ADS Title: Photospheric Line Asymmetry and Granular Velocity Models Authors: Keil, S. L.; Yackovich, F. H. Bibcode: 1981SoPh...69..213K Altcode: We analyze spectral line profiles obtained from regions of the solar surface exhibiting either an upflow or a downflow on a spatial and temporal scale corresponding to the white-light granulation. The differences between their line bisectors are measured to quantify changes in the asymmetry of the profile resulting from granular motion. The observed bisector differences are compared with differences predicted using conflicting granular models. Models, in which the motion of large, long-lived granules decreases rapidly with increasing height in the photosphere, are compatible with the observed line profile asymmetries. Title: Dynamical models of convective penetration and high-spatial resolution observations. Authors: Keil, S. L. Bibcode: 1980BAAS...12..747K Altcode: No abstract at ADS Title: The structure of solar granulation. I - Observations of the spatial and temporal behavior of vertical motions. II - Models of vertical motion Authors: Keil, S. L. Bibcode: 1980ApJ...237.1024K Altcode: The height dependence of the granular contribution to observed photospheric line shifts were deduced using a temporal sequence of spectroscopic measurements each covering a large horizontal distance on the solar disk. The deduced height variations represent the most accurate determination to date because individual granules can be isolated in both time and space simultaneously in several spectral lines. The previous attempts to deduce the height dependence, based on spectrograms having only one spatial resolution which led to conflicting pictures of the granular velocities are discussed; it is shown that a purely spatial separation of oscillatory and granular motions such as used by Mattig and Schlebbe and Durrant et al. (1979) is inadequate for determining granular velocities. Granules are predominant source of line shifts in the photosphere; much of the line-shift fluctuation power at small spatial scales in the stronger lines, which some authors incorrectly attributed to granules, results from high-frequency oscillations. Title: The Structure of Solar Granulation - Part Two - Models of Vertical Motion Authors: Keil, S. L. Bibcode: 1980ApJ...237.1035K Altcode: Several models proposed for the height dependence of the vertical motion associated with granules are used to compute photo spheric line shifts. These predicted line shifts are compared with recent observations of line shifts resulting from granular motion in a number of lines whose heights of formation span the photosphere and low chromosphere. An empirical model of the granular flow giving agreement between predicted and observed line shifts is deduced. At a height 100 km above τ5000 Å = 1 the amplitude of the granular flow is approximately 2 km s-1, and an appropriate scale height for the granular flow at this altitude is ∼80 km. Title: The interpretation of solar line shift observations Authors: Keil, S. L. Bibcode: 1980A&A....82..144K Altcode: The accuracy of height-dependent photospheric velocity fields inferred from observed line shifts by the use of velocity weighting (response) functions is evaluated. Several Fe I profiles for lines near 5150 A are synthesized by using an atmospheric model which includes horizontal fluctuations in temperature and velocity as well as a vertical differential velocity field. For assumed geometries of the granular and oscillatory motions, root-mean-square velocity fluctuations are synthesized and compared with predictions based on the velocity weighting functions. It is found that the line synthesis analysis required larger amplitude granular velocity fluctuations deep in the photosphere and a more rapid fall off with height than those obtained by analyzing the same data with velocity weighting functions. Simple models for the height dependence of the velocity field are used to determine when the assumptions upon which the use of velocity weighting functions are based are no longer valid. Title: Sources of noise in solar limb definitions Authors: Keil, S. L.; Worden, S. P. Bibcode: 1980LNP...125..219K Altcode: 1980nnsp.work..219K A test series of spectroheliograms has been used to evaluate the hypothesis that the rotation and evolution of solar surface structure can function as a source of noise in solar limb definition measurements. The study confirms the hypothesis, and results demonstrate the amount of variation in solar limb position which is attributable to evolutionary changes in solar surface structure. Title: Some effects of acoustic waves on spectral-line profiles. Authors: Cram, L. E.; Keil, S. L.; Ulmschneider, P. Bibcode: 1979ApJ...234..768C Altcode: The paper discusses the formation of spectral lines in the presence of short-period, nonlinear, radiatively damped acoustic waves propagating through a model of the solar atmosphere. The temperature and pressure perturbations associated with the wave strongly influence the line profile. Although their wavelength is less than the depth of the velocity response function of photospheric spectral lines, the acoustic waves produce large (greater than 100 m/s), short-period line shifts. Acoustic waves of sufficient amplitude to account for chromospheric heating do not significantly increase the equivalent widths of photospheric lines and therefore are probably not responsible for photospheric microturbulence. Title: Line Asymmetries Due to Granular Motion Authors: Keil, S. L. Bibcode: 1979BAAS...11..711K Altcode: No abstract at ADS Title: Some Comments on the Interpretation of Photospheric Line Shifts Authors: Keil, S. L. Bibcode: 1979BAAS...11..407K Altcode: No abstract at ADS Title: Sources of Noise in Solar Limb Definitions. Authors: Worden, S. P.; Keil, S. L. Bibcode: 1979BAAS...11..399W Altcode: No abstract at ADS Title: The Height Variation of Velocity and Temperature Fluctuations in the Solar Photosphere Authors: Keil, S. L.; Canfield, R. C. Bibcode: 1978A&A....70..169K Altcode: Summary. The Vacuum Tower Telescope of Sacramento Peak Observatory is used to observe intensity and velocity fluctuations in several Fe I lines as functions of heliocentric angle. We derive the vertical and horizontal components of the velocity fluctuations, using the technique developed by Canfield (1976) to separate granular and oscillatory velocities. We also find a set of height dependent temperature perturbations which are capable of reproducing the observed intensity fluctuations. The horizontal component of the granular velocity is found to be between one and two km 1 greater than the vertical component (depending on height in the atmosphere). A temperature perturbation (constant with height) of 175 1 25 K in the upper layers of the atmosphere [Tsooo 0.1] is sufficient to reproduce the intensity fluctuations in the strong lines. In deeper layers the temperature perturbations must increase rapidly with depth to reproduce the observed intensity fluctuations in the continuum and weak lines. Key words: solar atmosphere - solar velocity fluctuations - solar temperature structure Title: Dynamical Processes in the Solar Atmosphere: Observational and theoretical results concerning the nature of "turbulence" Authors: Keil, S. L.; Cram, L. E. Bibcode: 1978BAAS...10..638K Altcode: No abstract at ADS Title: The Height Dependence of Solar Velocity Fluctuations. Authors: Keil, S. L. Bibcode: 1978BAAS...10..415K Altcode: No abstract at ADS Title: A new measurement of the center-to-limb variation of the rms granular contrast. Authors: Keil, S. L. Bibcode: 1977SoPh...53..359K Altcode: The center-to-limb variation of the root-mean-square granular contrast at 5520 Å is deduced from a set of high-spatial-resolution filtergrams obtained with the Sacramento Peak Observatory Vacuum Tower Telescope. The rms contrast is observed to decrease monotonically between μ = 1.0 and 0.6, and then increase slightly at μ = 0.4. This result is compared with the results of Edmonds (1962) and with the results of Pravdjuk et al. (1974). Title: Intensity, velocity and temperature fluctuations in the upper solar atmosphere. Authors: Altrock, R. C.; Keil, S. L. Bibcode: 1977A&A....57..159A Altcode: High-spatial-resolution photographic spectra of the Mg I 4571-A line at 10 solar disk positions from center to limb are reduced to yield intensity and velocity (line-shift) fluctuations along the spectrograph slit for a height of about 300 km above the continuum level. The data obtained are used to compute rms intensity and velocity fluctuations corrected for instrument smearing. Comparison of the results with those of Cannon and Wilson (1971) reveals a flatter distribution of the rms intensity fluctuation as a function of heliocentric angle and a 60% larger fluctuation at the disk center. It is inferred that the correlation between velocity and intensity fluctuations exhibits a large-scale random structure. The intensity-fluctuation data are analyzed by calculating the emergent intensity from a three-dimensional atmosphere having a sinusoidal checkerboard pattern of temperature with a height-dependent amplitude, taking into account fluctuations in electron pressure. The range of solutions for temperature fluctuations is found to indicate that there are causes other than oscillations for the temperature fluctuations in the upper photosphere. Title: Photospheric Inhomogeneities: Continuum Fluctuations Authors: Keil, S. L. Bibcode: 1976BAAS....8..324K Altcode: No abstract at ADS Title: Models of Solar Granular Structure and the Interpretation of Photospheric Observations. Authors: Keil, S. L. Bibcode: 1974PhDT.........3K Altcode: Research data show that standard methods of deriving solar atmospheric models do not necessarily yield good average models. Data are given on: (1) standard one-dimensional calculations and observations which show these calculations can be misleading, (2) problems of radiation transfer in a two-dimensional two component atmosphere, and calculations of limitations on possible structure and magnitude of horizontal temperature fluctuation using the observed root mean square brightness distribution as a boundary condition, (3) computation of possible effects of weak solar magnetic fields on the granulation pattern, and (4) the examination of possible physical interpretations of granular models obtained. Title: Solar Granulation, Limb Flux, and Oblateness Authors: Kandel, Robert S.; Keil, Stephen L. Bibcode: 1973SoPh...33....3K Altcode: The radiation field, emergent from an inhomogeneous atmosphere, may differ significantly from that calculated using a mean model for such an atmosphere. In the solar case, horizontal anisotropy of the granulation pattern leads to azimuthal dependence of the emergent intensity, and this appears as a latitude-dependent limb flux which may mimic oblateness. We examine this latitude-dependence for several two and three-dimensional models of the inhomogeneous solar atmosphere, with varying degrees of anisotropy in the granulation pattern. Elongation along an east-west axis of about 7% would yield a signal somewhat imperfectly mimicking an excess oblateness of 4 × 10−5. Using the Babcock-Leighton model of the general solar magnetic field we show that some stretching of granules, of this order of magnitude, should be expected. However, it may vary with the solar activity cycle, and in any case the result is very sensitive to the parameters adopted. Even if study of granulation observations should exclude elongations as high as 7%, smaller essentially undetectable elongations may exist. We find that 1 % elongation can account for 25-50 % of a signal corresponding to excess oblateness 4 × 10−5. We conclude that anisotropy of the granulation pattern may influence oblateness determinations; when this is considered together with other effects, much of the claimed oblateness may be eliminated. Title: Granulation Patterns and Solar Oblateness. Authors: Kandel, R. S.; Keil, S. L. Bibcode: 1971BAAS....3R.376K Altcode: No abstract at ADS