Author name code: leibacher ADS astronomy entries on 2022-09-14 author:"Leibacher, John W." ------------------------------------------------------------------------ Title: Editorial Appreciation Authors: Arregui, Iñigo; Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2022SoPh..297...11A Altcode: No abstract at ADS Title: A journey of exploration to the polar regions of a star: probing the solar poles and the heliosphere from high helio-latitude Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry; Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier, Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry; Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle, Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.; Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic, Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen, Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli, Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W. Bibcode: 2021ExA...tmp...93H Altcode: 2021arXiv210410876H A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO Domingo et al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2), 3-15 2012), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. In this White Paper, submitted to the European Space Agency in response to the Voyage 2050 call, we describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets' space environment. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2021SoPh..296...14L Altcode: No abstract at ADS Title: A Journey of Exploration to the Polar Regions of a Star: Probing the Solar Poles and the Heliosphere from High Helio-Latitude Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.; Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.; Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi, S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.; Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.; Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli, M.; Sekii, T.; Spadaro, D.; Veronig, A. Bibcode: 2020AGUFMSH0110005F Altcode: A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO, STEREO, Hinode, SDO), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and is, of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. We describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets' space environment. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2020SoPh..295....9L Altcode: No abstract at ADS Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2019SoPh..294....3L Altcode: We are pleased to acknowledge, with sincere thanks, the following colleagues who supported the community by reviewing articles for Solar Physics during 2018. Title: Searching for g modes. I. A new calibration of the GOLF instrument Authors: Appourchaux, T.; Boumier, P.; Leibacher, J. W.; Corbard, T. Bibcode: 2018A&A...617A.108A Altcode: 2018arXiv180700998A Context. The recent claims of g-mode detection have restarted the search for these potentially extremely important modes. These claims can be reassessed in view of the different data sets available from the SoHO instruments and ground-based instruments.
Aims: We produce a new calibration of the GOLF data with a more consistent p-mode amplitude and a more consistent time shift correction compared to the time series used in the past.
Methods: The calibration of 22 yr of GOLF data is done with a simpler approach that uses only the predictive radial velocity of the SoHO spacecraft as a reference. Using p modes, we measure and correct the time shift between ground- and space-based instruments and the GOLF instrument.
Results: The p-mode velocity calibration is now consistent to within a few percent with other instruments. The remaining time shifts are within ±5 s for 99.8% of the time series.

The new calibrated series (FITS) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A108 Title: VizieR Online Data Catalog: Sun velocities from GOLF instrument (Appourchaux+, 2018) Authors: Appourchaux, T.; Boumier, P.; Leibacher, J. W.; Corbard, T. Bibcode: 2018yCat..36170108A Altcode: Three time series as FITS file comprising 34797600 data points of GOLF velocity in m/s sampled at 20 sec (no time provided). The time series starts on April 11, 1996 0:00 UT and ends on April 10, 2018 23:59:40 UT. The time series are provided for the photomultipliers PM1 and PM2, and their arithmetic average.

(2 data files). Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2018SoPh..293...14L Altcode: No abstract at ADS Title: Editorial: Last Print Issue of Solar Physics Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2017SoPh..292..196L Altcode: No abstract at ADS Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2017SoPh..292...19L Altcode: We are pleased to acknowledge, with sincere thanks, the following referees who supported the community by refereeing articles for Solar Physics during 2016. Title: A Distant Mirror: Solar Oscillations Observed on Neptune by the Kepler K2 Mission Authors: Gaulme, P.; Rowe, J. F.; Bedding, T. R.; Benomar, O.; Corsaro, E.; Davies, G. R.; Hale, S. J.; Howe, R.; Garcia, R. A.; Huber, D.; Jiménez, A.; Mathur, S.; Mosser, B.; Appourchaux, T.; Boumier, P.; Jackiewicz, J.; Leibacher, J.; Schmider, F. -X.; Hammel, H. B.; Lissauer, J. J.; Marley, M. S.; Simon, A. A.; Chaplin, W. J.; Elsworth, Y.; Guzik, J. A.; Murphy, N.; Silva Aguirre, V. Bibcode: 2016ApJ...833L..13G Altcode: 2016arXiv161204287G Starting in 2014 December, Kepler K 2 observed Neptune continuously for 49 days at a 1 minute cadence. The goals consisted of studying its atmospheric dynamics, detecting its global acoustic oscillations, and those of the Sun, which we report on here. We present the first indirect detection of solar oscillations in intensity measurements. Beyond the remarkable technical performance, it indicates how Kepler would see a star like the Sun. The result from the global asteroseismic approach, which consists of measuring the oscillation frequency at maximum amplitude ν max and the mean frequency separation between mode overtones Δν, is surprising as the ν max measured from Neptune photometry is larger than the accepted value. Compared to the usual reference ν max,⊙ = 3100 μHz, the asteroseismic scaling relations therefore make the solar mass and radius appear larger by 13.8 ± 5.8% and 4.3 ± 1.9%, respectively. The higher ν max is caused by a combination of the value of ν max,⊙, being larger at the time of observations than the usual reference from SOHO/VIRGO/SPM data (3160 ± 10 μHz), and the noise level of the K 2 time series, being 10 times larger than VIRGO’s. The peak-bagging method provides more consistent results: despite a low signal-to-noise ratio (S/N), we model 10 overtones for degrees ℓ = 0, 1, 2. We compare the K 2 data with simultaneous SOHO/VIRGO/SPM photometry and BiSON velocity measurements. The individual frequencies, widths, and amplitudes mostly match those from VIRGO and BiSON within 1σ, except for the few peaks with the lowest S/N. Title: Editorial: 50 Years of Solar Physics Authors: Charbonneau, Paul; Leibacher, John; Mandrini, Cristina; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2016SoPh..291.3461C Altcode: 2016SoPh..tmp..189C No abstract at ADS Title: Preface to Topical Issue: Recalibration of the Sunspot Number Authors: Clette, F.; Cliver, E. W.; Lefèvre, L.; Svalgaard, L.; Vaquero, J. M.; Leibacher, J. W. Bibcode: 2016SoPh..291.2479C Altcode: 2016SoPh..tmp..184C This topical issue contains articles on the effort to recalibrate the sunspot number (SN) that was initiated by the Sunspot Number Workshops. These workshops led to a revision of the Wolf sunspot number (WSN) and a new construction of the group sunspot number (GSN), both published herein. In addition, this topical issue includes three independently proposed alternative SN time series (two Wolf and one group), as well as articles providing historical context, critical assessments, correlative analyses, and observational data, both historical and modern, pertaining to the sunspot-number time series. The ongoing effort to understand and reconcile the differences between the various new sunspot number series is briefly discussed. Title: Are Resonant Helioseimic Modes Excited by Solar Flares? Authors: Leibacher, John W.; Baudin, Frédéric; Rabello Soares, Maria Cristina Bibcode: 2016SPD....47.0710L Altcode: We critically examine reports that flares have been observed to excite resonant p-modes by:-looking in detail at the results of the ring-diagram analysis in terms of duty cycle and center-to-limb variation of ring-diagram power.-applying the same analysis to the Halloween flare using GONG and MDI data.-assessing the stability in terms of oscillation power of both instruments. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2016SoPh..291..337L Altcode: 2016SoPh..tmp...10L No abstract at ADS Title: Preface: Probing the Sun Inside and Out Authors: Harra, Louise; Baker, Deborah; Howe, Rachel; Leibacher, John; van Driel-Gesztelyi, Lidia Bibcode: 2015SoPh..290.3091H Altcode: 2015SoPh..tmp..167H No abstract at ADS Title: Preface: Radio Heliophysics: Science and Forecasting Authors: Bisi, Mario M.; Americo Gonzalez-Esparza, J.; Jackson, Bernard V.; Tokumaru, Munetoshi; Leibacher, John Bibcode: 2015SoPh..290.2393B Altcode: 2015SoPh..tmp..143B No abstract at ADS Title: Excitation of Resonant Helioseimic Modes by Solar Flares. Authors: Leibacher, John W.; Baudin, Frédéric; Rabello Soares,, Maria Cristina Bibcode: 2015IAUGA..2257140L Altcode: Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by:-applying the same analysis to other locations on the Sun at the time of the Halloween flare-analyzing other events also showing a signature of p-mode excitation-looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power. Title: Excitation of Resonant Helioseimic Modes by Solar Flares Authors: Leibacher, John William; Baudin, Frédéric; Rabello Soares, Maria Cristina Bibcode: 2015TESS....110302L Altcode: Flares are known to excite propagating sound waves in the solar atmosphere, and Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, showed that they excite resonant p-modes as well. We confirm and extend here these results by: applying the same analysis to other locations on the Sun at the time of the Halloween flare, analyzing other events also showing a signature of p-mode excitation, looking in detail at the results of the ring diagrams analysis in terms of noise fitting and the center-to-limb variation of ring-diagram power. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2015SoPh..290..657L Altcode: 2015SoPh..tmp...24L No abstract at ADS Title: Helioseismic Ring-diagram Diagnostics of Solar Fares. Authors: Leibacher, John W.; Baudin, Frédéric Bibcode: 2014AAS...22421817L Altcode: Flares are known to excite waves in the solar atmosphere. Maurya et al. (2009), using a local analysis (ring diagrams) of the 2003 Halloween flare, also showed they excite p-modes. We confirm and extend here these results by:-applying the same analysis to other locations on the Sun at the time of the Halloween flare-analyzing another event also showing a signature of p-mode excitation-looking in details at the results of the ring diagrams analysis in terms of noise fitting.The Halloween flare present an apparent localized excitation of p-modes, similar to what is observed for the other event analyzed. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2014SoPh..289.1455L Altcode: 2014SoPh..tmp....6L No abstract at ADS Title: Solar Origins of Space Weather and Space Climate: Preface Authors: González Hernández, I.; Komm, R.; Pevtsov, A.; Leibacher, J. W. Bibcode: 2014SoPh..289..437G Altcode: No abstract at ADS Title: Fifty Years of Seismology of the Sun and Stars Authors: Jain, K.; Tripathy, S. C.; Hill, F.; Leibacher, J. W.; Pevtsov, A. A. Bibcode: 2013ASPC..478.....J Altcode: No abstract at ADS Title: Preface Authors: Tomczyk, Steven; Zhang, Jie; Bastian, Timothy; Leibacher, John W. Bibcode: 2013SoPh..288..463T Altcode: No abstract at ADS Title: Preface Authors: Mansour, Nagi N.; Kosovichev, Alexander G.; Komm, Rudolf; Longcope, Dana; Leibacher, John W. Bibcode: 2013SoPh..287....1M Altcode: No abstract at ADS Title: Preface Authors: Berghmans, D.; De Groof, A.; Dominique, M.; Hochedez, J. -F.; Leibacher, J. W. Bibcode: 2013SoPh..286....1B Altcode: No abstract at ADS Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2013SoPh..283....1L Altcode: No abstract at ADS Title: Preface Authors: Ireland, J.; Young, C. A.; Leibacher, J. W. Bibcode: 2013SoPh..283....3I Altcode: No abstract at ADS Title: Preface Authors: Fleck, Bernhard; Heber, Bernd; Vourlidas, Angelos; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Leibacher, John Bibcode: 2012SoPh..281....1F Altcode: 2012SoPh..tmp..223F No abstract at ADS Title: Preface Authors: Nakariakov, V. M.; Georgoulis, M. K.; Poedts, S.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Leibacher, J. Bibcode: 2012SoPh..280..295N Altcode: 2012SoPh..tmp..226N No abstract at ADS Title: Extracting Low-Degree Timeseries and Modes from Imaged Helioseismology Authors: Leibacher, John W. Bibcode: 2012AAS...22020502L Altcode: Results from a new approach to obtaining helioseismic mode time series will be presented. Title: Preface Authors: Fan, Yuhong; Fisher, George; Leibacher, John Bibcode: 2012SoPh..277....1F Altcode: 2011SoPh..tmp..423F No abstract at ADS Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2012SoPh..276....1L Altcode: No abstract at ADS Title: The Sun-Earth Connection near Solar Minimum: Placing it into Context Authors: Bisi, Mario M.; Thompson, Barbara J.; Emery, Barbara A.; Gibson, Sarah E.; Leibacher, John; van Driel-Gesztelyi, Lidia Bibcode: 2011SoPh..274....1B Altcode: No abstract at ADS Title: Helioseismic Observations of Solar Convection Zone Dynamics Authors: Hill, Frank; Howe, Rachel; Komm, Rudi; Hernández, Irene González; Kholikov, Shukur; Leibacher, John Bibcode: 2011IAUS..271...15H Altcode: The large-scale dynamics of the solar convection zone have been inferred using both global and local helioseismology applied to data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) on board SOHO. The global analysis has revealed temporal variations of the ``torsional oscillation'' zonal flow as a function of depth, which may be related to the properties of the solar cycle. The horizontal flow field as a function of heliographic position and depth can be derived from ring diagrams, and shows near-surface meridional flows that change over the activity cycle. Time-distance techniques can be used to infer the deep meridional flow, which is important for flux-transport dynamo models. Temporal variations of the vorticity can be used to investigate the production of flare activity. This paper summarizes the state of our knowledge in these areas. Title: Deep Meridional Flow Measurements from GONG: Temporal and Depth Variations Authors: Kholikov, Shukur; Leibacher, J.; Hill, F. Bibcode: 2011SPD....42.1618K Altcode: 2011BAAS..43S.1618K We present measurements of meridional flow using time-distance analysis of GONG data. To push the depth profile of the flow deeper, we average time-difference measurements over 15 years. In order to increase the signal-to-noise ratio, and to reduce contamination from other modes, we utilized both phase velocity and low-m filtering. This approach seems to be capable of extending the meridional-flow measurements down to 0.7 Rsun. Our preliminary results indicate that the precision achieved is very close to that required to measure the reverse flow down to the base of the solar convection zone where it is expected to be situated. Typical uncertainties for most depths within mid-latitudes are less than 0.02 seconds. At high latitudes, due to projection effects, error bars increase up to 0.06 seconds. There is a significant change in the nature of the time differences at the bottom of the convection zone. Title: AIA Observations of Sunspot Waves Authors: Leibacher, John W.; Soubrié, E.; Auchère, F.; Baudin, F. Bibcode: 2011SPD....42.2115L Altcode: 2011BAAS..43S.2115L Waves in the low solar atmosphere above sunspots i) present an interesting phenomenon in their own right, ii) are potentially a probe of magnetic structures (e.g. "plumes") in the sunspot atmosphere and a source of excitation of higher, coronal loop waves, and iii) are coupled to umbral flashes and sub-surface, helioseismic waves in a manner that is not fully understood. We present an analysis of AIA observations of waves in AR 11092, showing their propagation, temporal coherence, and angular symmetry; characterizing them in terms of frequency, amplitude, and propagation speed. Title: Helioseismic Studies With Multi-wavelength Data From HMI And AIA Onboard SDO Authors: Hill, Frank; Jain, K.; Tripathy, S.; Kholikov, S.; Gonzalez Hernandez, I.; Leibacher, J.; Howe, R.; Baudin, F.; Carlsson, M.; Chaplin, W.; Tarbell, T. Bibcode: 2011SPD....42.2111H Altcode: 2011BAAS..43S.2111H The successful launch of the Solar Dynamics Observatory (SDO) in February 2010 opens important, new possibilities for helioseismic exploration of the solar interior and atmosphere using multi-wavelength observations from multiple instruments. In order to better understand the solar interior and atmosphere, as well as the physics of the helioseismic modes and waves themselves, we exploit the potential of the Atmospheric Imaging Assembly (AIA) 1600 and 1700 Angstrom continuum measurements and the contemporaneous Helioseismic and Magnetic Imager (HMI) Fe I 6173.3 Angstrom velocity and intensity observations. Standard techniques of helioseismology e.g Sun-as-a-star, spherical harmonic analysis, ring diagrams, and time- distance analysis are applied to obtain acoustic mode parameters and other characteristics. Here we present our preliminary results, and interpret these in the context of the differences in the heights of formation of the lines. Title: The extreme physical properties of the CoRoT-7b super-Earth Authors: Léger, A.; Grasset, O.; Fegley, B.; Codron, F.; Albarede, A. F.; Barge, P.; Barnes, R.; Cance, P.; Carpy, S.; Catalano, F.; Cavarroc, C.; Demangeon, O.; Ferraz-Mello, S.; Gabor, P.; Grießmeier, J. -M.; Leibacher, J.; Libourel, G.; Maurin, A. -S.; Raymond, S. N.; Rouan, D.; Samuel, B.; Schaefer, L.; Schneider, J.; Schuller, P. A.; Selsis, F.; Sotin, C. Bibcode: 2011Icar..213....1L Altcode: 2011arXiv1102.1629L The search for rocky exoplanets plays an important role in our quest for extra-terrestrial life. Here, we discuss the extreme physical properties possible for the first characterised rocky super-Earth, CoRoT-7b ( R pl = 1.58 ± 0.10 R Earth, M pl = 6.9 ± 1.2 M Earth). It is extremely close to its star ( a = 0.0171 AU = 4.48 R st), with its spin and orbital rotation likely synchronised. The comparison of its location in the ( M pl, R pl) plane with the predictions of planetary models for different compositions points to an Earth-like composition, even if the error bars of the measured quantities and the partial degeneracy of the models prevent a definitive conclusion. The proximity to its star provides an additional constraint on the model. It implies a high extreme-UV flux and particle wind, and the corresponding efficient erosion of the planetary atmosphere especially for volatile species including water. Consequently, we make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. As a consequence, the atmosphere is made of rocky vapours with a very low pressure ( P ⩽ 1.5 Pa), no cloud can be sustained, and no thermalisation of the planet is expected. The dayside is very hot (2474 ± 71 K at the sub-stellar point) while the nightside is very cold (50-75 K). The sub-stellar point is as hot as the tungsten filament of an incandescent bulb, resulting in the melting and distillation of silicate rocks and the formation of a lava ocean. These possible features of CoRoT-7b could be common to many small and hot planets, including the recently discovered Kepler-10b. They define a new class of objects that we propose to name " Lava-ocean planets". Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2011SoPh..269....1L Altcode: 2011SoPh..tmp...21L No abstract at ADS Title: Meridional-Flow Measurements from 15 Years of GONG Spherical-Harmonic Time Series Authors: Kholikov, S.; González Hernández, I.; Hill, F.; Leibacher, J. Bibcode: 2011JPhCS.271a2052K Altcode: We present results of meridional-flow measurements for 1995-2009, using travel-time differences from velocity images reconstructed using GONG spherical harmonic (SH) coefficients after applying phase-velocity and low-m filters. This filtering technique increases the signal-to-noise ratio and thus extends travel-time measurements to relatively high latitudes and deep into the convection zone. Preliminary analyses shows a strong one-year periodicity presumably due to solar pole misalignment and B0-angle artifacts, which makes it difficult to see underlying temporal variations. Removing a simple one-year-period sine wave fit reveals long-term temporal variations of the flow on top of this yearly periodicity. High-latitude measurements are affected more stronger by foreshortening and B0 -angle artifacts. We analyze different B0-angle intervals separately, so in each hemisphere better high-latitude visibility comes six months apart. This approach suggests why at high latitudes travel-time measurements of meridional flow shows a tendency to change sign instead of continuing towards the poles. Title: Angular-degree dependence of p-mode frequencies during solar cycle 23 Authors: Tripathy, S. C.; Jain, K.; Salabert, D.; Garcia, R. A.; Hill, F.; Leibacher, J. W. Bibcode: 2011JPhCS.271a2055T Altcode: We analyze simultaneous helioseismic observations collected by the ground- and space-based instruments during solar cycle 23 by computing oscillation frequencies for low- and intermediate-degree p-modes on a time scale of 36 days. We find that the frequency shifts corresponding to different angular degree, ell, indicate different epochs for the onset of the solar cycle 24. The analysis also indicates the presence of double minima between cycles 23 and 24 for some range of ell values. Title: The Future of IHY Campaigns: Transition to the International Space Weather Initiative Authors: Raulin, Jean-Pierre; Davila, Joseph M.; Bogdan, Thomas; Yumoto, Kiyohumi; Leibacher, John Bibcode: 2010HiA....15..501R Altcode: We will present the relevant activities performed during the International Heliophysical Year (IHY) program during the 5 year period 2004 - 2008. The IHY was a major international effort that involved the deployment of new instrumentation, new observations from the ground and in space, and a strong education component. Under the United Nations Office for Outer Space program called Basic Space Science Initiative (UNBSSI), instrument arrays have been deployed to provide global measurements of heliophysical phenomena. As a result, significant scientific and educational collaborations emerged between the organizing groups and the host country teams. In view of the great successes achieved by the IHY during these years, we propose to continue the highly successful collaboration with the UN program to study the universal processes in the solar system that affect the interplanetary and terrestrial environments, and to continue to coordinate the deployment and operation of new and existing instrumentation arrays aimed at understanding the impacts of Space Weather on Earth and the near-Earth environment. To this end, we propose a new program, the International Space Weather Initiative (ISWI). The ISWI strongly complements the International Living With a Star (ILWS) program, providing more attention nationally, regionally, and internationally for the ILWS program. Based on a three-year program activity, the ISWI would provide the opportunity for scientists around the world to participate in this exciting quest to understand the effect of space disturbances on our Earth environment. Title: Using helioseismology to understand and predict the solar cycle Authors: Hill, Frank; Komm, Rudi; Howe, Rachel; Gonzalez Hernandez, Irene; Kholikov, Shukur; Leibacher, John Bibcode: 2010shin.confE.156H Altcode: Helioseismology is now being used to investigate the subsurface flows that are related to the solar cycle. The relevant flows are the east-west zonal flows (torsional oscillation), and the north-south meridional flows. This poster will summarize the relationship of the timing of the solar cycle with the characteristics of the zonal and meridional flows; as well as what we know about the nature of the deep meridional flows that play a role in the dynamo. Title: What Solar Oscillation Tell Us About the Solar Minimum Authors: Jain, K.; Tripathy, S. C.; Burtseva, O.; H´Ndez, I. G.; Hill, F.; Howe, R.; Kholikov, S.; Komm, R.; Leibacher, J. Bibcode: 2010ASPC..428...57J Altcode: 2010arXiv1002.2411J The availability of continuous helioseismic data for two consecutive solar minima has provided a unique opportunity to study the changes in the solar interior that might have led to this unusual minimum. We present preliminary analysis of intermediate-degree mode frequencies in the 3 mHz band during the current period of minimal solar activity and show that the mode frequencies are significantly lower than those during the previous activity minimum. Our analysis does not show any signature of the beginning of cycle 24 until the end of 2008. In addition, the zonal and meridional flow patterns inferred from inverting frequencies also hint at a delayed onset of a new cycle. The estimates of travel time are higher than the previous minimum confirming a relatively weak solar activity during the current minimum. Title: Meridional Flow Measurements from 15 Years of GONG Spherical Harmonic Time Series Authors: Leibacher, John W.; Kholikov, S.; Hill, F. Bibcode: 2010AAS...21640003L Altcode: 2010BAAS...41..855L We present the results of a meridional flow time-distance analysis based on GONG data. In order to increase the signal-to-noise ratio, and to reduce contamination from other modes, we utilize a low-m filtering technique, which seems capable of extending the meridional flow measurements down to the deep layers of the convection zone (0.7R°). Our preliminary results indicate that the precision achieved is very close to that required to measure the reverse flow down to the base of the solar convection zone where it is expected to be situated. To avoid projection effects at high latitudes, and to extend the analysis to higher latitudes, we analyze extreme B-angle time periods separately. We discuss the significance of temporal variations of meridional flow in the presence of additional flows around active regions. Title: Solar Observation Target Identification Convention for use in Solar Physics Authors: Leibacher, John; Sakurai, Takashi; Schrijver, Carolus J.; van Driel-Gesztelyi, Lidia Bibcode: 2010SoPh..263....1L Altcode: 2010SoPh..263....1.; 2010SoPh..tmp...71. We strongly encourage the use of a standardized target identification to be included in pub- lications on solar events. The primary purpose is to enable the automated identification of publications on the same event, or on other related events, in the on-line literature by search engines such as the Astrophysics Data System (ADS). The convention does not aim to categorize or classify events, but is limited specifically to the identification of regions in space and intervals in time within which events occur. Title: Preface Authors: Ireland, J.; Young, C. A.; Leibacher, J. Bibcode: 2010SoPh..262..233I Altcode: 2010SoPh..tmp...46I; 2010SoPh..tmp...58I No abstract at ADS Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2010SoPh..262....1L Altcode: 2010SoPh..tmp...18L No abstract at ADS Title: Unusual Trends in Solar P-Mode Frequencies During the Current Extended Minimum Authors: Tripathy, S. C.; Jain, K.; Hill, F.; Leibacher, J. W. Bibcode: 2010ApJ...711L..84T Altcode: 2010arXiv1002.1690T We investigate the behavior of the intermediate-degree mode frequencies of the Sun during the current extended minimum phase to explore the time-varying conditions in the solar interior. Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), we find that the changes in resonant mode frequencies during the activity minimum period are significantly greater than the changes in solar activity as measured by different proxies. We detect a seismic minimum in MDI p-mode frequency shifts during 2008 July-August but no such signature is seen in mean shifts computed from GONG frequencies. We also analyze the frequencies of individual oscillation modes from GONG data as a function of latitude and observe a signature of the onset of the solar cycle 24 in early 2009. Thus, the intermediate-degree modes do not confirm the onset of the cycle 24 during late 2007 as reported from the analysis of the low-degree Global Oscillations at Low Frequency frequencies. Further, both the GONG and MDI frequencies show a surprising anti-correlation between frequencies and activity proxies during the current minimum, in contrast to the behavior during the minimum between cycles 22 and 23. Title: Variation of Oscillation Mode Parameters over Solar Cycle 23: An Analysis on Different Time Scales Authors: Tripathy, S. C.; Hill, F.; Jain, K.; Leibacher, J. W. Bibcode: 2009ASPC..416..285T Altcode: 2009arXiv0903.2074T We investigate the variation in the mode parameters obtained from time series of length nine, 36, 72 and 108 days to understand the changes occurring on different time-scales. The regression analysis between frequency shifts and activity proxies indicates that the correlation and slopes are correlated and both increase in going from time series of nine to 108 days. We also observe that the energy of the mode is anti-correlated with solar activity while the rate at which the energy is supplied remains constant over the solar cycle. Title: Solar Physics Publication Ethics Policies Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2009SoPh..260....1L Altcode: No abstract at ADS Title: Helioseismic Spectral Diagnostics - An Update Authors: Leibacher, John W.; Baudin, F.; Belkacem, K.; Dupret, M.; Goupil, M.; Gouttebroze, P.; Samadi, R. Bibcode: 2009SPD....40.0716L Altcode: In order to test models of the excitation of p modes and their behavior in the visible atmosphere, we calculate time sequences of Fraunhofer absorption line profiles of the Ni, Fe, K, Na, and Ca lines used in helioseismology, focusing on Sun-as-a-star observations in this initial work. The atmospheric models, which give rise to the line profiles, are based on the VAL-C, perturbed by realistic p-mode eigenfunctions. The time sequences of line profiles are analyzed as for various instruments, to compare predicted and observed mode amplitudes as a function of temporal frequency Title: Measurement of Low Signal-To-Noise Ratio Solar p-Modes in Spatially Resolved Helioseismic Data Authors: Salabert, D.; Leibacher, J.; Appourchaux, T.; Hill, F. Bibcode: 2009ApJ...696..653S Altcode: 2009arXiv0902.2561S We present an adaptation of the rotation-corrected, m-averaged spectrum technique designed to observe low signal-to-noise ratio (S/N), low-frequency solar p-modes. The frequency shift of each of the 2l + 1 m spectra of a given (n, l) multiplet is chosen that maximizes the likelihood of the m-averaged spectrum. A high S/N can result from combining individual low S/N, individual-m spectra, none of which would yield a strong enough peak to measure. We apply the technique to Global Oscillation Network Group and Michelson Doppler Imager data and show that it allows us to measure modes with lower frequencies than those obtained with classic peak-fitting analysis of the individual-m spectra. We measure their central frequencies, splittings, asymmetries, lifetimes, and amplitudes. The low frequency, low- and intermediate-angular degrees rendered accessible by this new method correspond to modes that are sensitive to the deep solar interior down to the core (l <= 3) and to the radiative interior (4 <= l <= 35). Moreover, the low-frequency modes have deeper upper turning points, and are thus less sensitive to the turbulence and magnetic fields of the outer layers, as well as uncertainties in the nature of the external boundary condition. As a result of their longer lifetimes (narrower linewidths) at the same S/N the determination of the frequencies of lower frequency modes is more accurate, and the resulting inversions should be more precise. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2009SoPh..255....1L Altcode: No abstract at ADS Title: POLAR investigation of the Sun—POLARIS Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.; Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.; Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler, D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy, N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt, R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.; Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.; Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T. Bibcode: 2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between the magnetism and dynamics of the Sun’s polar regions and the solar cycle. Title: solarFLAG hare and hounds: estimation of p-mode frequencies from Sun-as-star helioseismology data Authors: Jiménez-Reyes, S. J.; Chaplin, W. J.; García, R. A.; Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher, S. T.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Régulo, C.; Salabert, D.; Toutain, T.; Verner, G. A.; Wachter, R. Bibcode: 2008MNRAS.389.1780J Altcode: 2008arXiv0807.0989J; 2008MNRAS.tmp..954J; 2008MNRAS.tmp.1026J We report on the results of the latest solarFLAG hare-and-hounds exercise, which was concerned with testing methods for extraction of frequencies of low-degree solar p modes from data collected by Sun-as-a-star observations. We have used the new solarFLAG simulator, which includes the effects of correlated mode excitation and correlations with background noise, to make artificial time-series data that mimic Doppler velocity observations of the Sun-as-a-star. The correlations give rise to asymmetry of mode peaks in the frequency power spectrum. 10 members of the group (the hounds) applied their `peak-bagging' codes to a 3456-d data set, and the estimated mode frequencies were returned to the hare (who was WJC) for comparison. Analysis of the results reveals a systematic bias in the estimated frequencies of modes above ~1.8mHz. The bias is negative, meaning the estimated frequencies systematically underestimate the input frequencies.

We identify two sources that are the dominant contributions to the frequency bias. Both sources involve failure to model accurately subtle aspects of the observed power spectral density in the part (window) of the frequency power spectrum that is being fitted. One source of bias arises from a failure to account for the power spectral density coming from all those modes whose frequencies lie outside the fitting windows. The other source arises from a failure to account for the power spectral density of the weak l = 4 and 5 modes, which are often ignored in Sun-as-a-star analysis. The Sun-as-a-star peak-bagging codes need to allow for both sources, otherwise the frequencies are likely to be biased. Title: AsteroFLAG — from the Sun to the stars Authors: Chaplin, W. J.; Appourchaux, T.; Arentoft, T.; Ballot, J.; Baudin, F.; Bazot, M.; Bedding, T. R.; Christensen-Dalsgaard, J.; Creevey, O. L.; Duez, V.; Elsworth, Y.; Fletcher, S. T.; García, R. A.; Gough, D. O.; Jiménez, A.; Jiménez-Reyes, S. J.; Houdek, G.; Kjeldsen, H.; Lazrek, M.; Leibacher, J. W.; Monteiro, M. J. P. F. G.; Neiner, C.; New, R.; Régulo, C.; Salabert, D.; Samadi, R.; Sekii, T.; Sousa, S. G.; Toutain, T.; Turck-Chièze, S. Bibcode: 2008JPhCS.118a2048C Altcode: We stand on the threshold of a critical expansion of asteroseismology of Sun-like stars, the study of stellar interiors by observation and analysis of their global acoustic modes of oscillation. The Sun-like oscillations give a very rich spectrum allowing the internal structure and dynamics to be probed down into the stellar cores to very high precision. Asteroseismic observations of many stars will allow multiple-point tests of crucial aspects of stellar evolution and dynamo theory. The aims of the asteroFLAG collaboration are to help the community to refine existing, and to develop new, methods for analysis of the asteroseismic data on the Sun-like oscillators. Title: Development of a new analysis technique to measure low radial-order p modes in spatially-resolved helioseismic data Authors: Salabert, David; Leibacher, John W.; Appourchaux, Thierry Bibcode: 2008JPhCS.118a2086S Altcode: 2007arXiv0711.2825S In order to take full advantage of the long time series collected by the GONG and MDI helioseismic projects, we present here an adaptation of the rotation-corrected m-averaged spectrum technique in order to observe low radial-order solar p modes. Modeled profiles of the solar rotation demonstrated the potential advantage of such a technique [1, 2, 3]. Here we develop a new analysis procedure which finds the best estimates of the shift of each m of a given (n, ι) multiplet, commonly expressed as an expansion in a set of orthogonal polynomials, which yield the narrowest mode in the m-averaged spectrum. We apply the technique to the GONG data for modes with 1 <= ι <= 25 and show that it allows us to measure lower-frequency modes than with classic peak-fitting analysis of the individual-m spectra. Title: Preface Authors: Gizon, Laurent; Cally, Paul; Leibacher, John Bibcode: 2008SoPh..251....1G Altcode: 2008SoPh..tmp..148G No abstract at ADS Title: Solar Interior Meridional Flows using Zonal Modes from GONG Authors: Leibacher, J. W.; Kholikov, S. Bibcode: 2008AGUSMSP41A..07L Altcode: We present two different time-distance techniques to measure meridional-flow-induced travel-time differences. We use GONG zonal spherical harmonic coefficients ( m = 0 ) and longitude-averaged time series for the 1995 -- 2007 time period. Both data sets represents isolated waves propagating only in the North -- South direction. We demonstrate that it is possible to obtain travel-time differences with lower turning point about 200 Mm, which correspond to the tachocline region. We do not see any evidence of equatorward flow. Title: Low-Frequency Solar p Modes in GONG and MDI Observations using m-Averaged Spectra Authors: Leibacher, J.; Salabert, D.; Appourchaux, T.; Hill, F. Bibcode: 2008AGUSMSP41A..06L Altcode: The GONG and MDI global helioseismology pipelines provide solar acoustic mode parameters for 108- and 72-day time series respectively by fitting the 2 ℓ + 1 individual-m spectra of a given (n, ℓ/) multiplet either individually (GONG) or simultaneously (MDI). Our knowledge of the variable solar interior through helioseismic observations derives primarily from these two analysis pipelines. We have developed a new method to extract the mode parameters by adjusting the rotation- and structure-induced frequency shift for each m-spectrum to minimize the mode width in the m-averaged spectrum. The m-averaged spectrum appears to be a powerful tool for low signal-to-noise-ratio modes in the low-frequency range where the modes have very long lifetimes. Indeed, in the case of spatially-resolved helioseismic data (MDI, GONG, HMI), for a given multiplet (n, ℓ/), there exist 2 ℓ + 1 individual-m spectra, which can result in an average spectrum with a SNR ≫ 1 even when the individual-m spectra have a SNR < 1. We show here that the m-averaged spectrum technique, applied to the GONG 108-day and MDI 72-day time series, gives us access to a whole new range of predicted, low-SNR modes that had not been successfully fitted by the current MDI and GONG peak-fitting pipelines. We show that the modes that are measured by both techniques are extracted without bias. We apply this technique to 360-, 720-, 1080-, and 1440-day long GONG time series to infer the variability of the mode parameters with solar activity in the low-frequency range below ~ 1500 μHz. Title: Searching for p-modes in MOST Procyon data: another view Authors: Baudin, F.; Appourchaux, T.; Boumier, P.; Kuschnig, R.; Leibacher, J. W.; Matthews, J. M. Bibcode: 2008A&A...478..461B Altcode: 2007arXiv0711.0601B Context: Photometry of Procyon obtained by the MOST satellite in 2004 has been searched for p modes by several groups, with sometimes contradictory interpretations.
Aims: We explore two possible factors that complicate the analysis and may lead to erroneous reports of p modes in these data.
Methods: Two methods are used to illustrate the role of subtle instrumental effects in the photometry: time-frequency analysis, and a search for regularly spaced peaks in a Fourier spectrum based on the echelle diagramme approach.
Results: We find no convincing evidence of a p-mode signal in the MOST Procyon data. We can account for an apparent excess of power close to the p-mode frequency range and signs of structure in an echelle diagramme in terms of instrumental effects.

Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2008SoPh..247....1L Altcode: 2008SoPh..tmp....5L No abstract at ADS Title: Preface: A Topical Issue in Honor of Professor Bernard Roberts Authors: Ballester, J. L.; Erdélyi, R.; Hood, A. W.; Leibacher, J. W.; Nakariakov, V. M. Bibcode: 2007SoPh..246....1B Altcode: No abstract at ADS Title: Joint Discussion 17 Highlights of recent progress in the seismology of the Sun and Sun-like stars Authors: Bedding, Timothy R.; Brun, Allan S.; Christensen-Dalsgaard, Jørgen; Crouch, Ashley; De Cat, Peter; García, Raphael A.; Gizon, Laurent; Hill, Frank; Kjeldsen, Hans; Leibacher, John W.; Maillard, Jean-Pierre; Mathis, S.; Rabello-Soares, M. Cristina; Rozelot, Jean-Pierre; Rempel, Matthias; Roxburgh, Ian W.; Samadi, Réza; Talon, Suzanne; Thompson, Michael J. Bibcode: 2007HiA....14..491B Altcode: The seismology and physics of localized structures beneath the surface of the Sun takes on a special significance with the completion in 2006 of a solar cycle of observations by the ground-based Global Oscillation Network Group (GONG) and by the instruments on board the Solar and Heliospheric Observatory (SOHO). Of course, the spatially unresolved Birmingham Solar Oscillation Network (BiSON) has been observing for even longer. At the same time, the testing of models of stellar structure moves into high gear with the extension of deep probes from the Sun to other solar-like stars and other multi-mode pulsators, with ever-improving observations made from the ground, the success of the MOST satellite, and the recently launched CoRoT satellite. Here we report the current state of the two closely related and rapidly developing fields of helio- and asteroseimology. Title: Solar Oscillation Frequency Changes on Time Scales of Nine Days Authors: Tripathy, S. C.; Hill, F.; Jain, K.; Leibacher, J. W. Bibcode: 2007SoPh..243..105T Altcode: 2006astro.ph..8348T We establish that global solar p-mode frequencies can be measured with sufficient precision on time scales as short as nine days to detect activity-related shifts. Using ten years of GONG data, we report that mode-mass and error-weighted frequency shifts derived from nine days are significantly correlated with the strength of solar activity and are consistent with long-duration measurements from GONG and the SOHO/MDI instrument. The analysis of the year-wise distribution of the frequency shifts with change in activity indices shows that both the linear-regression slopes and the magnitude of the correlation varies from year to year and they are well correlated with each other. The study also indicates that the magnetic indices behave differently in the rising and falling phases of the activity cycle. For the short-duration nine-day observations, we report a higher sensitivity to activity. Title: Rotation Of The Deep Solar Interior From A Solar Cycle Of Gong Data Authors: Leibacher, John W.; Salabert, D.; Appourchaux, T.; Hill, F.; Howe, R. Bibcode: 2007AAS...210.2219L Altcode: 2007BAAS...39..127L We use 3960 days of Global Oscillation Network Group (GONG) data to derive the rotation of the deep solar interior. We obtain the splitting of low signal-to-noise multiplets - at low radial order and low spherical harmonic degree - using the m-averaged spectra - a technique that works well even when none of the individual-m spectra are clean enough to be fit. Central frequencies and rotational splittings are estimated down to l = 1 and 1 mHz. We illustrate here the validity of our method and infer the radial rotation profile down to 0.2 solar radius.

This work utilizes data obtained by the Global Oscillation Network Group (GONG) program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofisica de Canarias, and Cerro Tololo Interamerican Observatory. Title: Recent Advances From The GONG Time-distance Helioseismology Team Authors: Hill, Frank; Kholikov, S.; Burtseva, O.; Leibacher, J. W. Bibcode: 2007AAS...210.2213H Altcode: 2007BAAS...39..126H We present some recent work using the time-distance method of local helioseismology as applied to Global Oscillation Network Group (GONG) data. Four projects will be included:

1) North-south travel time differences for zonal modes (m=0) have been computed for the period 1995-2006. These measurements provide information on the meridional flow, and can be used to study temporal variations over the activity cycle.

2) The autocorrelations of the low-degree (l=0, 1, 2, 3) time series have been computed. These functions have been analyzed to obtain a very precise measurement of the large splitting and solar acoustic radius. A significant temporal variation correlated with the activity level can be clearly seen.

3) The lifetimes of high-degree modes have been estimated with the time-distance method. The results for high and low activity will be discussed.

4) A project to search for active regions prior to their emergence has been initiated. Some approaches to the problem will be outlined.

The National Solar Observatory is operated by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation, for the benefit of the astronomical community. Title: On cross-spectrum capabilities for detecting stellar oscillation modes Authors: Appourchaux, T.; Leibacher, J.; Boumier, P. Bibcode: 2007A&A...463.1211A Altcode: Aims:Long-lived stellar oscillation modes are usually detected using Fourier transforms of time series of stellar radial velocities or brightness. It is commonly thought that one could use the cross spectrum of the two signals, or alternatively use the interleaved series of a single signal, to considerably improve the detection level by reducing the noise level.
Methods: We use a statistical analysis of the cross spectrum to compute its mean value and rms value, and use the associated signal-to-noise ratio for stochastically excited modes.
Results: Here, we demonstrate that the gain in the signal-to-noise ratio can indeed be improved for modes with a shorter lifetime than the observation time, but not those with a longer lifetime than the observation time. Title: Some remarks on the state of helioseismology Authors: Leibacher, J. W. Bibcode: 2007AN....328..368L Altcode: I offer some very brief questions and remarks on the state of helioseismology, specifically: i) What is the relationship between the study of a phenomenon in its own right, its use as a tool, and the broader phenomena to which the tool can be applied? ii) Does the jargon of our local helioseismic techniques serve us well? iii) What is the role of the interactions with the areas of science with which helioseismology interacts most closely? Title: Solar MHD Theory and Observations: A High Spatial Resolution Perspective Authors: Leibacher, John; Stein, Robert F.; Uitenbroek, Han Bibcode: 2006ASPC..354.....L Altcode: No abstract at ADS Title: Temporal variations of travel-time differences from GONG++ Authors: Kholikov, S.; Leibacher, J. Bibcode: 2006ESASP.624E..47K Altcode: 2006soho...18E..47K No abstract at ADS Title: Changes to global mode parameters over a solar cycle Authors: Tripathy, S. C.; Hill, F.; Jain, K.; Leibacher, J. W. Bibcode: 2006ESASP.624E..93T Altcode: 2006soho...18E..93T No abstract at ADS Title: Future missions and activities Authors: Leibacher, J. Bibcode: 2006IAUJD..17E..27L Altcode: This overview will present the outstanding scientific questions and the various observational programs to address them that are underway, in development, and on the drawing boards. Title: MDI and GONG Inferences of the Changing Sun Authors: Burtseva, O.; González Hernández, I.; Hill, F.; Howe, R.; Jain, K.; Kholikov, S.; Komm, R.; Leibacher, J.; Toner, C.; Tripathy, S.; Haber, D.; Hindman, B.; Ladenkov, O.; Chou, D. -Y. Bibcode: 2006ESASP.617E..41B Altcode: 2006soho...17E..41B No abstract at ADS Title: Frequency Shifts on Time Scales of Nine Days Authors: Tripathy, Sushanta C.; Hill, F.; Jain, K.; Leibacher, J. W. Bibcode: 2006SPD....37.0501T Altcode: 2006BAAS...38R.223T Since the p-mode frequency changes are thought to be associated with individual active regions that come and go continuously, one would anticipate that the frequencies alsochange continuously on any time scale. However, due to the finite life time of the mode, the correlation between the frequency and activity may depend on the length of the observing run. To test this hypothesis, we calculate and analyze frequency variations on time scales as short as nine-days. Using 10 years of GONG data, we establish that the global p-mode frequencies can be measured with sufficient precision on this timescale to exhibit temporal variations. We also find that these modes are significantly correlated with the strength of solar activity but the correlation coefficients are smaller as compared to long-term measurements from the GONG and SOHO/MDI. Title: Solar FLAG hare and hounds: on the extraction of rotational p-mode splittings from seismic, Sun-as-a-star data Authors: Chaplin, W. J.; Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher, S. T.; Fossat, E.; García, R. A.; Isaak, G. R.; Jiménez, A.; Jiménez-Reyes, S. J.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Pallé, P.; Régulo, C.; Salabert, D.; Seghouani, N.; Toutain, T.; Wachter, R. Bibcode: 2006MNRAS.369..985C Altcode: 2006MNRAS.tmp..515C; 2006astro.ph..6748C We report on results from the first solar Fitting at Low-Angular degree Group (solar FLAG) hare-and-hounds exercise. The group is concerned with the development of methods for extracting the parameters of low-l solar p-mode data (`peak bagging'), collected by Sun-as-a-star observations. Accurate and precise estimation of the fundamental parameters of the p modes is a vital pre-requisite of all subsequent studies. Nine members of the FLAG (the `hounds') fitted an artificial 3456-d data set. The data set was made by the `hare' (WJC) to simulate full-disc Doppler velocity observations of the Sun. The rotational frequency splittings of the l = 1, 2 and 3 modes were the first parameter estimates chosen for scrutiny. Significant differences were uncovered at l = 2 and 3 between the fitted splittings of the hounds. Evidence is presented that suggests this unwanted bias had its origins in several effects. The most important came from the different way in which the hounds modelled the visibility ratio of the different rotationally split components. Our results suggest that accurate modelling of the ratios is vital to avoid the introduction of significant bias in the estimated splittings. This is of importance not only for studies of the Sun, but also of the solar analogues that will be targets for asteroseismic campaigns.

Solar FLAG URL: http://bison.ph.bham.ac.uk/~wjc/Research/FLAG.html

E-mail: wjc@bison.ph.bham.ac.uk ‡

George Isaak passed away in 2005 June 5, prior to the completion of this work. He is greatly missed by us all. Title: Editorial Appreciation Authors: Engvold, Oddbjørn; Harvey, Jack; Leibacher, John; Sakurai, Takashi; Švestka, Zdeněk; van Driel-Gesztelyi, Lidia; Solar Physics editors Bibcode: 2006SoPh..233....1E Altcode: No abstract at ADS Title: Editorial Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2005SoPh..229....3L Altcode: No abstract at ADS Title: The GONG Farside Project Authors: Leibacher, J. W.; Braun, D.; González Hernández, I.; Goodrich, J.; Kholikov, S.; Lindsey, C.; Malanushenko, A.; Scherrer, P. Bibcode: 2005AGUSMSP11B..14L Altcode: The GONG program is currently providing near-real-time helioseismic images of the farside of the Sun. The continuous stream of low resolution images, obtained from the 6 earth based GONG stations, are merged into a single data series that are the input to the farside pipeline. In order to validate the farside images, it is crucial to compare the results obtained from different instruments. We show comparisons between the farside images provided by the MDI instrument and the GONG ones. New aditions to the pipeline will allow us to create full-hemisphere farside images, examples of the latest are shown in this poster. Our efforts are now concentrated in calibrating the farside signal so it became a reliable solar activity forecasting tool. We are also testing single-skip acoustic power holography at 5-7 mHz as a prospective means of reinforcing the signatures of active regions crossing the the east and west limb and monitoring acoustic emission in the neighborhoods of Sun's the poles. This work utilizes data obtained by the Global Oscillation Network Group (GONG) Program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofisico de Canarias, and Cerro Tololo Interamerican Observatory, as well as the Michaelson Doppler Imager on SoHO, a mission of international cooperation between ESA and NASA. This work has been supported by the NASA Living with a Star - Targeted Research and Technology program. Title: How Well do the Oscillation Frequencies Track the Activity ? Authors: Tripathy, S. C.; Leibacher, J. W. Bibcode: 2005AGUSMSP13A..04T Altcode: Variations of solar oscillation frequencies with the solar cycle at both low and intermediate degrees are now well established. This is manifested by an increase in frequencies of the modes from minimum to maximum of the activity cycle. It is also known that the shifts are strongly correlatd with different activity indices on time scales of 72 and 108 days for MDI and GONG data respectively. However, earlier results from cycle 22 indicated that the frequencies change over shorter periods of weeks to months. It is therefore interesting to analyse mode frequencies and other mode parameters from time series of shorter duration. Here, we present results from an analysis where the frequencies are computed from 36 and 108 days long time series; the time series being shifted by three days over a period of about 5 months. The frequencies calculated from the 36 day long time series are much better correlated with the activity indices. Title: Parker Lecture: Local Helioseismology Authors: Leibacher, J. W. Bibcode: 2005AGUSMSP23C..01L Altcode: This brief introduction to the science of local helioseismolgy - the study of travelling sound waves in addition to the standing waves familiar from global helioseismology - will demonstrate how we can now probe the temporally varying spatial inhomogeneities within the solar interior, and illustrate this with results on meridional flows and torsional oscillations, sunspot and active region structure, supergranulation, images of farside of the Sun, as well as signatures of flares. Title: GONG Travel Time Measurements of Meridional Flows for a Decade Authors: Kholikov, S.; Leibacher, J. Bibcode: 2005AGUSMSP11B..04K Altcode: We present measurements of sub-surface meridional flows derived from the difference in travel time between northward and southward propagating sound waves, and their variations during the period from May 1995 to February 2004. We show that for measurements at depths of 20 Mm or deeper, the original low spatial resolution GONG data can be used to extend our study of temporal variations of meridional flows back to the previous solar minimum. In addition to the usual approach using velocity images, we demonstrate that spherical harmonic (SH) coefficient time series for m = 0 provide an effective means for filtering for waves that are propagating directly northward or southward. Another advantage of using SH coefficient time series more generally is that phase velocity filtering can be done for any l range, without an implicit of plane-wave assumption. Title: Remarkable Low Temperature Emission of the 4 November 2003 Limb Flare Authors: Leibacher, J. W.; Harvey, J. W.; Kopp, G.; Hudson, H.; GONG Team Bibcode: 2004AAS...204.0213L Altcode: 2004BAAS...36..669L Strong (> 1.5 times normal intensity) continuum and photospheric line emission of the 4 November 2003 X28 flare was recorded simultaneously by three widely separated GONG instruments. Emission was seen from on the disk to > 20" above the limb for nearly one hour, likely making this event the longest duration white light flare observed to date. GONG observations are one-minute duration integrations of intensity averaged across a Lyot filter bandpass of about 90 pm FWHM centered on the Ni I line at 676.8 nm with 2.5" instrument pixel size. Spatial resolution is limited by diffraction and seeing to greater than 5". Additional measurements include the Doppler shift and strength of the spectrum line. These latter measurements indicate that continuum and line emission contributed about equally to the observed intensity signal. Light curves and images of the flare show a notable two-kernel disk event starting at about 19:33 UTC followed by a much stronger event that peaked at about 19:44. Rare, white-light prominences were visible above the limb after 19:34. Comparison of total solar irradiance measurements from the TIM instrument on board the SORCE spacecraft with full-disk integrated GONG intensities shows the global five-minute oscillation and the white light flare. The latter is much weaker in the GONG data, suggesting that most of the TIM flare signal arises from other, most likely shorter, wavelengths.

This work utilizes data obtained by the Global Oscillation Network Group (GONG) Program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. SORCE is supported by NASA NAS5-97045 Title: Acoustic Holographic Studies of Solar Active Regions Authors: Malanushenko, A.; Braun, D.; Kholikov, S.; Leibacher, J.; Lindsey, C. Bibcode: 2004IAUS..223..283M Altcode: 2005IAUS..223..283M We present results of a study of the morphology and evolution of active regions using solar acoustic holography. These include acoustic signatures of large far-side active regions and their relationship to near-side activity indices a half rotation before and after the farside image, and the direct comparison of near-side acoustic signatures with the standard activity indicators, not only in their own right but also to calibrate the farside acoustic signature. Title: The physics of solar and solar-like oscillations Authors: Bedding, T. R.; Leibacher, J. W. Bibcode: 2004pssl.book.....B Altcode: No abstract at ADS Title: Natural Interpolation and Consistent Extrapolation of Time Series arising from Dense Multi-Mode Spectra Authors: Leibacher, J. W. Bibcode: 2003SPD....34.0810L Altcode: 2003BAAS...35R.823L The study of the temporal variation of phenomenon is often hampered by the incompleteness of our observations. This is particularly disruptive for highly periodic signals that are interrupted by periodic gaps, which introduce sidelobes that are difficult - if not impossible - to remove by deconvolution techniques if the spectral peaks are dense compared to the sidelobe separation. This is the case for the study of many classes of variable stars, including the Sun, where once per day interuptions are the norm. However, for signals with coherence times longer than the interuptions, there is little ambiguity as to the unobserved behaviour of the signal - that is the frequency, phase, and amplitude of a mode can not change significantly during a time small compared with the mode lifetime - and the missing data can be replaced with high fidelity, by an iterative procedure. The interpolated data is consistent with the observed time series, and can also be used to extrapolate the time series for times comparable with the coherence times of the constituent modes. The method works well for spectra of unknown content, and a priori information, e.g. the approximate frequenices of modes, can be simply incorporated to accelerate convergence. Applications to helio- and astereo-seismic time series will be presented. Title: The LoHCo Project. 1 -- Comparison of Ring-Diagram Local Helioseismology on GONG++, MDI and Mt. Wilson Data Sets Authors: Bogart, R. S.; Schou, J.; Basu, S.; Bolding, J.; Hill, F.; Howe, R.; Komm, R. W.; Leibacher, J. W.; Toner, C. G.; Corbard, T.; Haber, D. A.; Hindman, B. W.; Toomre, J.; Rhodes, E. J.; Rose, P. J.; LoHCo Project Team Bibcode: 2003SPD....34.0804B Altcode: 2003BAAS...35..822B Full deployment of the GONG+ enhanced observing network in October 2001 and implementation of ring-diagram helioseismology in the GONG++ analysis pipeline this year has enabled us to make a detailed intercomparison of results obtained through multiple paths, from observation through each of the analysis steps. Such comparisons can provide a certain degree of validation of the implementations of the analysis procedures, hints of systematic errors, and better characterization of the observations, possibly leading to improved calibrations. The Local Helioseismology Comparison (LoHCo) Project has been established to provide standards for intercomparison of results obtained with different local helioseismic analysis techniques applied to the available observational data sources. We present here a detailed comparison of ring-diagram determinations of localized sub-surface flows and frequency shifts obtained from both MDI and GONG in common observing intervals during Carrington Rotation 1988 (2002/3/30 -- 2002/4/26), using both the MDI and the GONG analysis pipelines. We also present preliminary results of similar analyses of data obtained by the Mt. Wilson MOF during the same times.

This work is partially supported by grants from NASA and NSF. Title: Local Helioseismology and Continuous Magnetograms with GONG+ Authors: Leibacher, J.; GONG Team Bibcode: 2003EAEJA.....8124L Altcode: The upgrade from the GONG classic [256x256 rectangular pixel detectors] to the GONG+ system [ 1024x1034 square pixel detectors, and continuous magnetograms] has been successful, and the data are becoming available. The upgrade from the GONG Classic science products [mode frequencies out to nominally spherical harmonic degree < 180] to the GONG+ science products [local helioseismology data products to support "ring diagrams", "time-distance", and "helioseismic holography", high-l global helioseismology, and continuous magnetograms] is well underway, with the pipeline process integration underway. We present the status of the GONG+ data, processing, and preliminary sub-surface flow maps. NSO is sponsored by the National Science Foundation through a cooperative agreement with the Association of Universities for Research in Astronomy, Inc. Title: Global and Local Helioseismology with GONG+ Authors: Leibacher, John Bibcode: 2003IAUJD..12E..46L Altcode: The upgrade from the GONG classic [256x256 rectangular pixel detectors] to the GONG+ system [ 1024x1034 square pixel detectors and continuous magnetograms] has been successful and the data are becoming available. The upgrade from the GONG Classic science products [mode frequencies out to nominally spherical harmonic degree < 180] to the GONG+ science products [local helioseismology data products to support ""ring diagrams"" ""time-distance"" and ""helioseismic holography"" and high-l global helioseismology] is well underway with the pipeline process integration underway.

We present the status of the GONG Classic and GONG+ data processing as well preliminary sub-surface flow maps.

GONG is an international community based collaboration with the NSO Big Bear Solar Observatory Mauna Loa Observatory Learmonth Solar Observatory Udaipur Solar Observatory Observatorio del Teide and the Cerro Tololo Interamerican Observatory.

NSO is sponsored by the National Science Foundation through a cooperative agreement with the Association of Universities for Research in Astronomy Inc. Title: Interpolation and Extrapolation of Time Series Authors: Leibacher, John Bibcode: 2003IAUJD..12E..45L Altcode: Study of the temporal variation of phenomenon is often hampered by the incompleteness of our observations. This is particularly disruptive for highly periodic signals that are interrupted by periodic gaps which introduce sidelobes that are difficult - if not impossible - to remove by deconvolution techniques if the spectral peaks are dense compared to the sidelobe separation. This is the case for the study of many classes of variable stars including the Sun where once per day interuptions are the norm. For signals with coherence times longer than the interuptions there is little ambiguity as to the unobserved behaviour of the signal - that is the frequency phase and amplitude of a mode cannot change significantly during a time small compared with the mode lifetime - and the missing data can be replaced with high fidelity by an iterative procedure. The interpolated data is consistent with the observed time series and can also be used to extrapolate the time series for times comparable with the coherence times of the constituent modes. The method works well for spectra of unknown content and prior information can be simply incorporated to accelerate convergence. Applications to helio- and astereo-seismic time series will be presented. Title: NOAO Newsletter Authors: Isbell, Doug; Lauer, Tod R.; Bell, Dave; vanderBliek, Nicole; Green, Richard; Hinkle, Ken; Adams, Sally; Leibacher, John; Piano, Priscilla; Hopkins, Stephen Bibcode: 2002STIN...0273025I Altcode: This journal issue is the newsletter of the National Optical Astronomical Observatory for the month of September, 2002. It summarizes recent research, and contains information on the US Gemini Program (USGP), telescope access time and other issues at observatories, operations at Kitt Peak National Observatory (KPNO), the National Solar Observatory (NSO), as well as public affairs and educational outreach. Title: MDI and GONG inferences of the changing solar interior Authors: Barban, C.; Howe, R.; Hill, F.; Komm, R. W.; Leibacher, J.; Toner, C.; Bogart, R.; Braun, D.; Haber, D.; Hindman, B.; Lindsey, C. Bibcode: 2002ESASP.508...55B Altcode: 2002soho...11...55B The Global Oscillation Network Group (GONG) and the Solar Oscillations Investigation (SOI) using the Michelson Doppler Imager (MDI) instrument aboard the SOHO spacecraft provide combined data sets that now cover more than six years and allow us to probe the changing dynamics of the convection zone in unprecedented detail. Here we present the latest combined results from both projects, showing the evolution of the migrating zonal flows close to the surface and also changes close to and below the base of the convection zone, as well as changes in the mode parameters related to surface magnetic activity variation in time and latitude. Title: Natural Interpolation and Consistent Extrapolation of Time Series arising from Dense Multi-Mode Spectra Authors: Leibacher, J. W. Bibcode: 2002AAS...200.0405L Altcode: 2002BAAS...34..644L The study of the temporal variation of phenomenon is often hampered by the incompleteness of our observations. This is particularly disruptive for highly periodic signals that are interrupted by periodic gaps, which introduce sidelobes that are difficult - if not impossible - to remove by deconvolution techniques if the spectral peaks are dense compared to the sidelobe separation. This is the case for the study of many classes of variable stars, including the Sun, where once per day interruptions are the norm. However, for signals with coherence times longer than the interruptions, there is little ambiguity as to the unobserved behavior of the signal - that is the frequency, phase, and amplitude of a signal cannot change significantly during a time small compared with the signal lifetime - and the missing data can be replaced with high fidelity, by an iterative procedure. The interpolated data is consistent with the observed time series, and can also be used to extrapolate the time series for times comparable with the coherence times of the constituent modes. The method works well for spectra of unknown content, and a priori information, e.g. the approximate frequencies of modes, can be simply incorporated to accelerate convergence. The National Solar Observatory is operated under a cooperative agreement between the Association of Universities for Research in Astronomy, Inc. and the National Science Foundation. Title: The GONG+ Network Authors: Leibacher, J. W. Bibcode: 2001AGUSM..SP31A03L Altcode: The Global Oscillation Network Group obtains helioseismic data from a six-station network with an overall duty cycle of ≈ 90% and will continue observing for a full solar cycle. The initial, 2562 rectangular pixel detectors are being replaced with 10242 square pixel ones, to enable high quality, continuous local helioseismology and probing closer to the surface. The GONG+ system will also provide continuous magnetograms, and offers the possibility of observing with a cadence as short as 16 seconds. We will present results from the prototype GONG+ instrument and the status of the deployment of the complete network. The Global Oscillation Network Group (GONG) project is supported by the National Science Foundation and operates in collaboration with the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofísico de Canarias, and Cerro Tololo Interamerican Observatory. Title: Generation of Causal Time Series arising from Spectra of Narrow-Band Asymmetric Peaks. Authors: Leibacher, J. W. Bibcode: 2001AGUSM..SP31A04L Altcode: Synthetic time series with known spectral properties are frequently used in the development of analysis techniques, most commonly by assigning random phases to an amplitude spectrum with the desired properties - an approach with significant limitations. For narrow band peaks of the sort encountered in helioseismology, a simple auto-regressive [AR] description yields a physically realisable signal quite naturally. In fact, a second-order AR model is just a discrete representation of the second-order differential equation giving rise to the modes. It is now widely appreciated that the profiles of helioseismic resonances are significantly asymmetric, and this can be incorporated into the generation of artificial time series quite simply by extending the AR approach to include moving averages [MA] excitation. This ARMA model provides an immediate source of the correlated noise that has been invoked to describe the asymmetries. The NSO is sponsored by the National Science Foundation through a cooperative agreement with the Association of Universities for Research in Astronomy, Inc. Title: The GONG+ Network Authors: Leibacher, J. Bibcode: 2001AAS...198.7101L Altcode: 2001BAAS...33..892L The Global Oscillation Network Group obtains helioseismic data from a six-station network with an overall duty cycle of ≈ 90% and will continue observing for a full solar cycle. The initial, 2562 rectangular pixel detectors are being replaced with 10242 square pixel ones, to enable high quality, continuous local helioseismology and probing closer to the surface. The GONG+ system will also provide continuous magnetograms, and offers the possibility of observing with a cadence as short as 16 seconds. We will present results from the prototype GONG+ instrument and the status of the deployment of the complete network. The Global Oscillation Network Group (GONG) project is supported by the National Science Foundation and operates in collaboration with the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofísico de Canarias, and Cerro Tololo Interamerican Observatory. Title: Natural Interpolation and Consistent Extrapolation of Time Series arising from Dense Multi-Mode Spectra Authors: Leibacher, J. W. Bibcode: 2001AGUSM..SP31A05L Altcode: The study of the temporal variation of phenomenon is often hampered by the incompleteness of our observations. This is particularly disruptive for highly periodic signals that are interrupted by periodic gaps, which introduce sidelobes that are difficult - if not impossible - to remove by deconvolution techniques if the spectral peaks are dense compared to the sidelobe separation. This is the case for the study of many classes of variable stars, including the Sun, where once per day interuptions are the norm. However, for signals with coherence times longer than the interuptions, there is little ambiguity as to the unobserved behaviour of the signal - that is the frequency, phase, and amplitude of a mode cannot change significantly during a time small compared with the mode lifetime - and the missing data can be replaced with high fidelity, by an iterative procedure. The interpolated data is consistent with the observed time series, and can also be used to extrapolate the time series for times comparable with the coherence times of the constituent modes. The method works well for spectra of unknown content, and a priori information, e.g. the approximate frequenices of modes, can be simply incorporated to accelerate convergence. The NSO is sponsored by the National Science Foundation through a cooperative agreement with the Association of Universities for Research in Astronomy, Inc. Title: The GONG+ Network Authors: Leibacher, J. W.; GONG Project Team Bibcode: 2000SPD....31.0116L Altcode: 2000BAAS...32..803L The Global Oscillation Network Group obtains helioseismic data from a six-station network with an overall duty cycle of ≈ 90% and will continue observing for a full solar cycle. The initial, 2562 rectangular pixel detectors are being replaced with 10242 square pixel ones, to enable high quality, continuous local helioseismology and probing closer to the surface. The GONG+ system will also provide continuous magnetograms, and offers the possibility of observing with a cadence as short as 16 seconds. We will present results from the prototype GONG+ instrument demonstrating its capabilities. The Global Oscillation Network Group (GONG) project is supported by the National Science Foundation and operates in collaboration with the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofísico de Canarias, and Cerro Tololo Interamerican Observatory. Title: Oscillations of the upper chromosphere Authors: Gouttebroze, P.; Vial, J. -C.; Bocchialini, K.; Lemaire, P.; Leibacher, J. W. Bibcode: 1999SoPh..184..253G Altcode: Variations of intensity and wavelength in several UV lines have been observed with the SUMER spectroheliometer onboard SOHO, and they have been analysed to obtain oscillation spectra and phase differences between lines of different ions. Lines intensities of neutral or singly ionized atoms (with temperature of formation ≤ 30 000 K) exhibit an increase of oscillatory power between 2.5 and 7 mHz, which may be considered as the signature of p modes. Lines of highly ionized elements (with a temperature of formation ≥ 50 000 K) yield power spectra which are continuously decreasing with frequency. Brightness variations of the continuum at different wavelengths between 1000 and 1400 Å present oscillations in the same frequency range. Thus, p modes seem to be efficiently stopped by the transition region. No clear evidence is found for the existence of a chromospheric oscillation mode. Phase comparisons between lines formed at different altitudes (in particular Si i and Si ii) indicate that these lines oscillate in phase, within the precision of the measurements. Title: The global oscillation network group (GONG) project Authors: Leibacher, John W. Bibcode: 1999AdSpR..24..173L Altcode: The Global Oscillation Network Group (GONG) is an international, community-based project to conduct a detailed study of solar internal structure and dynamics using helioseismology. In order to exploit this technique, GONG has developed a network of six extremely sensitive and stable solar velocity imagers to obtain nearly continuous observations of the Sun's ``five-minute'' oscillations. GONG also provides magnetograms nominally every twenty minutes. The system became operational in October 1995, and will operate for an eleven-year solar cycle. The observation duty cycle has averaged about 90%, and single-site data loss due to instrument down time is less than 2%. Data is processed at pace with the collection rate. Progress is underway to replace the original 256 × 242 rectangular pixel cameras, with 1024 × 1024 square pixels cameras to obtain the optimal scientific return from the instruments from the eleven-year run. There are 175 individual members of the GONG, from 70 different institutions, and 20 nations. Title: The Global Oscillation Network Group (GONG) Project Authors: Leibacher, John W.; GONG Project Team Bibcode: 1998ESASP.418....3L Altcode: 1998soho....6....3L The Global Oscillation Network Group (GONG) is an international, community-based project to conduct a detailed study of solar internal structure and dynamics using helioseismology. The system became operational in October 1995, and should operate for an eleven-year solar cycle. There are currently 163 individual members of the GONG, from 70 different institutions, and 20 nations. We highlight here recent performance, results, and progress towards the replacement of the original 256 x 256 rectangular pixel cameras with 1024 x 1024 square pixels cameras to obtain the optimal scientific return from the instruments from the eleven-year run. Title: GONG Spectra in three observables: What is a p-mode frequency? Authors: Harvey, J.; Hill, F.; Komm, R.; Leibacher, J.; Pohl, B.; GONG Team Bibcode: 1998IAUS..185...49H Altcode: No abstract at ADS Title: The Global Oscillation Network Group (GONG) Authors: Leibacher, J.; GONG Project Team Bibcode: 1997SPD....28.0211L Altcode: 1997BAAS...29..894L The Global Oscillation Network Group (GONG) is an international, community-based helioseismology project conducting a detailed study of the internal structure and dynamics of the Sun. GONG is operating a six-station network of full-disk velocity imagers exploring the range from l = 0 to about l = 200. Full network operation began in October 1995. The observation duty cycle has averaged about 90%, and single-site data loss due to instrument down time is less than 2%. The data management group is processing the network data at pace with the collection rate. The current status, recent modifications to the data processing system, and plans for the future will be presented. Title: Sounding solar and stellar interiors: general introduction. Authors: Leibacher, J. Bibcode: 1997IAUS..181....1L Altcode: This Symposium marks a significant milestone in the development of helioseismology - the beginning of observations from GONG and SoHO. A number of very significant astrophysical processes (e.g. rotational shear induced mixing penetrative convection, diffusion, circulation currents) have become fairly directly accessible to our sounding using helioseismology. Title: The seismic structure of the Sun from GONG Authors: Anderson, E.; Antia, H. M.; Basu, S.; Chaboyer, B.; Chitre, S. M.; Christensen-Dalsgaard, J.; Eff-Darwich, A.; Elliott, J. R.; Giles, P. M.; Gough, D. O.; Guzik, J. A.; Harvey, J. W.; Hill, F.; Leibacher, J. W.; Kosovichev, A. G.; Monteiro, M. J. P. F. G.; Richard, O.; Sekii, T.; Shibahashi, H.; Takata, M.; Thompson, M. J.; Toomre, J.; Vauclair, S.; Vorontsov, S. V. Bibcode: 1997IAUS..181..151A Altcode: No abstract at ADS Title: GONG Observations of Solar Surface Flows Authors: Hathaway, D. H.; Gilman, P. A.; Harvey, J. W.; Hill, F.; Howard, R. F.; Jones, H. P.; Kasher, J. C.; Leibacher, J. W.; Pintar, J. A.; Simon, G. W. Bibcode: 1996Sci...272.1306H Altcode: Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells. Title: Perspectives in Helioseismology Authors: Gough, D. O.; Leibacher, J. W.; Scherrer, P. H.; Toomre, J. Bibcode: 1996Sci...272.1281G Altcode: Helioseismology is probing the interior structure and dynamics of the sun with ever-increasing precision, providing a well-calibrated laboratory in which physical processes can be studied under conditions that are unattainable on Earth. Nearly 10 million resonant modes of oscillation are observable in the solar atmosphere, and their frequencies need to be known with great accuracy in order to gauge the sun's interior. The advent of nearly continuous imaged observations from the complementary ground-based Global Oscillation Network Group (GONG) observatories and the space-based Solar and Heliospheric Observatory instruments augurs a new era of discovery. The flow of early results from GONG resolves some issues and raises a number of theoretical questions whose answers are required for understanding how a seemingly ordinary star actually operates. Title: The Current State of Solar Modeling Authors: Christensen-Dalsgaard, J.; Dappen, W.; Ajukov, S. V.; Anderson, E. R.; Antia, H. M.; Basu, S.; Baturin, V. A.; Berthomieu, G.; Chaboyer, B.; Chitre, S. M.; Cox, A. N.; Demarque, P.; Donatowicz, J.; Dziembowski, W. A.; Gabriel, M.; Gough, D. O.; Guenther, D. B.; Guzik, J. A.; Harvey, J. W.; Hill, F.; Houdek, G.; Iglesias, C. A.; Kosovichev, A. G.; Leibacher, J. W.; Morel, P.; Proffitt, C. R.; Provost, J.; Reiter, J.; Rhodes, E. J., Jr.; Rogers, F. J.; Roxburgh, I. W.; Thompson, M. J.; Ulrich, R. K. Bibcode: 1996Sci...272.1286C Altcode: Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations. Title: The Seismic Structure of the Sun Authors: Gough, D. O.; Kosovichev, A. G.; Toomre, J.; Anderson, E.; Antia, H. M.; Basu, S.; Chaboyer, B.; Chitre, S. M.; Christensen-Dalsgaard, J.; Dziembowski, W. A.; Eff-Darwich, A.; Elliott, J. R.; Giles, P. M.; Goode, P. R.; Guzik, J. A.; Harvey, J. W.; Hill, F.; Leibacher, J. W.; Monteiro, M. J. P. F. G.; Richard, O.; Sekii, T.; Shibahashi, H.; Takata, M.; Thompson, M. J.; Vauclair, S.; Vorontsov, S. V. Bibcode: 1996Sci...272.1296G Altcode: Global Oscillation Network Group data reveal that the internal structure of the sun can be well represented by a calibrated standard model. However, immediately beneath the convection zone and at the edge of the energy-generating core, the sound-speed variation is somewhat smoother in the sun than it is in the model. This could be a consequence of chemical inhomogeneity that is too severe in the model, perhaps owing to inaccurate modeling of gravitational settling or to neglected macroscopic motion that may be present in the sun. Accurate knowledge of the sun's structure enables inferences to be made about the physics that controls the sun; for example, through the opacity, the equation of state, or wave motion. Those inferences can then be used elsewhere in astrophysics. Title: The Global Oscillation Network Group (GONG) Project Authors: Harvey, J. W.; Hill, F.; Hubbard, R. P.; Kennedy, J. R.; Leibacher, J. W.; Pintar, J. A.; Gilman, P. A.; Noyes, R. W.; Title, A. M.; Toomre, J.; Ulrich, R. K.; Bhatnagar, A.; Kennewell, J. A.; Marquette, W.; Patron, J.; Saa, O.; Yasukawa, E. Bibcode: 1996Sci...272.1284H Altcode: Helioseismology requires nearly continuous observations of the oscillations of the solar surface for long periods of time in order to obtain precise measurements of the sun's normal modes of oscillation. The GONG project acquires velocity images from a network of six identical instruments distributed around the world. The GONG network began full operation in October 1995. It has achieved a duty cycle of 89 percent and reduced the magnitude of spectral artifacts by a factor of 280 in power, compared with single-site observations. The instrumental noise is less than the observed solar background. Title: Differential Rotation and Dynamics of the Solar Interior Authors: Thompson, M. J.; Toomre, J.; Anderson, E. R.; Antia, H. M.; Berthomieu, G.; Burtonclay, D.; Chitre, S. M.; Christensen-Dalsgaard, J.; Corbard, T.; De Rosa, M.; Genovese, C. R.; Gough, D. O.; Haber, D. A.; Harvey, J. W.; Hill, F.; Howe, R.; Korzennik, S. G.; Kosovichev, A. G.; Leibacher, J. W.; Pijpers, F. P.; Provost, J.; Rhodes, E. J., Jr.; Schou, J.; Sekii, T.; Stark, P. B.; Wilson, P. R. Bibcode: 1996Sci...272.1300T Altcode: Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes. Title: The Global Oscillation Network Group Project Authors: Leibacher, J. W.; Harvey, J. W.; Hill, F.; Hubbard, R.; Kennedy, J. R.; Pintar, J. A.; Bhatnagar, A.; Kennewell, J. A.; Marquette, W.; Patron, J.; Saa, O.; Yasukawa, E.; GONG Project Team Bibcode: 1996AAS...188.5301L Altcode: 1996BAAS...28..903L The NSF-sponsored Global Oscillation Network Group (GONG) project has developed and is operating a network of six velocity imaging instruments around the world, and a data analysis system that can keep up with the massive data flow, in support of a vigorous community that shares in all aspects of this program to explore the structure and dynamics of the solar interior. Data from the first three stations were obtained starting in March 1995, and the full six-station network became operational in early October 1995. The system noise is below the solar background of incoherent surface motions, and the overall data processing pipeline is maintaining cadence with the data flood. The scientific objectives, design and performance of the network, instrumentation, and data processing, and plans for the future will be presented. The National Optical Astronomy Observatories are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. Title: The Solar Acoustic Spectrum and Eigenmode Parameters Authors: Hill, F.; Stark, P. B.; Stebbins, R. T.; Anderson, E. R.; Antia, H. M.; Brown, T. M.; Duvall, T. L., Jr.; Haber, D. A.; Harvey, J. W.; Hathaway, D. H.; Howe, R.; Hubbard, R. P.; Jones, H. P.; Kennedy, J. R.; Korzennik, S. G.; Kosovichev, A. G.; Leibacher, J. W.; Libbrecht, K. G.; Pintar, J. A.; Rhodes, E. J., Jr.; Schou, J.; Thompson, M. J.; Tomczyk, S.; Toner, C. G.; Toussaint, R.; Williams, W. E. Bibcode: 1996Sci...272.1292H Altcode: The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 x 10-5. For a 3-year data set, the fractional error is expected to be 3 x 10-6. The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure. Title: A First Look from the GONG Helioseismology Network Authors: Leibacher, John W.; GONG Project Team Bibcode: 1995AAS...18711401L Altcode: 1995BAAS...27.1447L Helioseismology studies the internal structure and dynamics of the Sun, utilizing very precise measurements of the frequencies of sound waves that propagate throughout the solar interior and are observed at the surface. These waves interfere constructively and form resonant modes with periods near five minutes and lifetimes ranging from weeks to many months. Their frequencies depend directly on the temperature, composition, and motions of the regions of the Sun through which the sound waves propagate, and we will be able to measure these quantities in four dimensions, with remarkable resolution in each. These measurements should provide important new knowledge of the Sun's central temperature, the depth of its convection zone, the abundance of helium and heavy elements, the manner in which the interior rotates, the nature of the internal magnetic field, and how all of these vary in time. Efforts to accurately and precisely measure the mode frequencies from a single observing site have met with fundamental limitations imposed by the inevitable interruptions arising from the day-night cycle. In order to overcome these limitations, and open a new chapter in our understanding of the Sun and stellar interiors, the NSF-sponsored Global Oscillation Network Group (GONG) project has developed 1) a network of six sites around the world providing velocity images with a duty cycle better than 90%, 2) six identical instruments with a system noise lower than the solar background of incoherent surface motions, 3) a data processing system that can keep up with the massive data flow, and 4) a vigorous community that has shared in all aspects of the development of the project. Data from the first two stations started in February 1995 and the full six-station network became operational in early October 1995. Preliminary results indicate that the duty cycle, daily artifact reduction, and instrument performance goals will be met. Merging of the images from the six-sites is being carried out, and the overall data processing pipeline appears to be capable of maintaining cadence with the data flood. Title: Philippe Delache, 1937 - 13 October 1994. Authors: Barlier, F.; Bonnet, R. M.; Fossat, E.; Leibacher, J.; Frisch, U. Bibcode: 1995JAF....47....2B Altcode: No abstract at ADS Title: Status of the Global Oscillation Network Group (GONG) Project Authors: Leibacher, J. W.; GONG Project Team Bibcode: 1995SPD....26..102L Altcode: 1995BAAS...27..949L No abstract at ADS Title: The Global Oscillation Network Group Project Authors: Leibacher, J.; GONG Project Team Bibcode: 1995ASPC...76..381L Altcode: 1995gong.conf..381L No abstract at ADS Title: The Global Oscillation Network Group Project Authors: Leibacher, J. W.; GONG Project Team Bibcode: 1995ESASP.376a.247L Altcode: 1995heli.conf..247L; 1995soho....1..247L The GONG Project is a community-based activity to develop and operate a six-site, imaging helioseismic observing network, to do the basic data reduction and provide the data and software tools to the community, and to coordinate the scientific analysis of the data. The Project deployed the network in 1995, and the data management and analysis center is operational. GONG data are available to any qualified investigator whose proposal has been accepted, however active membership in a GONG Scientific Team will allow early access to the data and the collaborative scientific analysis that the teams have initiated. Title: The Global Oscillation Network Group Site Survey - Part One Authors: Hill, Frank; Fischer, George; Grier, Jennifer; Leibacher, John W.; Jones, Harrison B.; Jones, Patricia P.; Kupke, Renate; Stebbins, Robin T. Bibcode: 1994SoPh..152..321H Altcode: The Global Oscillation Network Group (GONG) Project is planning to place a set of instruments around the world to observe solar oscillations as continuously as possible for at last three years. The Project has now chosen the sites that will comprise the network. This paper describes the methods of data collection and analysis that were used to make this decision. Title: The Global Oscillation Network Group Site Survey - Part Two Authors: Hill, Frank; Fischer, George; Forgach, Suzanne; Grier, Jennifer; Leibacher, John W.; Jones, Harrison P.; Jones, Patricia B.; Kupke, Renate; Stebbins, Robin T.; Clay, Donald W.; Ingram, Robert E. L.; Libbrecht, Kenneth G.; Zirin, Harold; Ulrichi, Roger K.; Websteri, Lawrence; Hieda, Lester S.; Labonte, Barry J.; Lu, Wayne M. T.; Sousa, Edwin M.; Garcia, Charles J.; Yasukawa, Eric A.; Kennewell, John A.; Cole, David G.; Zhen, Huang; Su-Min, Xiao; Bhatnagar, Arvind; Ambastha, Aashok; Al-Khashlan, Abdulrahman Sa'ad; Abdul-Samad, Muhammad-Saleh; Benkhaldoun, Zouhair; Kadiri, Samir; Sánchez, Francisco; Pallé, Pere L.; Duhalde, Oscar; Solis, Hernan; Saá, Oscar; González, Ricardo Bibcode: 1994SoPh..152..351H Altcode: The Global Oscillation Network Group (GONG) Project will place a network of instruments around the world to observe solar oscillations as continuously as possible for three years. The Project has now chosen the six network sites based on analysis of survey data from fifteen sites around the world. The chosen sites are: Big Bear Solar Observatory, California; Mauna Loa Solar Observatory, Hawaii; Learmonth Solar Observatory, Australia; Udaipur Solar Observatory, India; Observatorio del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile. Title: Internal Rotation of the Sun Authors: Duvall, T. L., Jr.; Dziembowski, W.; Goode, P. R.; Gough, D. O.; Harvey, J. W.; Leibacher, J. W. Bibcode: 1994snft.book..414D Altcode: No abstract at ADS Title: A New Description of the Solar Five-Minute Oscillation Authors: Leibacher, J.; Stein, R. F. Bibcode: 1994snft.book..400L Altcode: No abstract at ADS Title: Status of the Global Oscillation Network Group (GONG) Project Authors: Leibacher, J. W.; GONG Project Team Bibcode: 1993BAAS...25.1193L Altcode: No abstract at ADS Title: The Mechanisms of Solar Variability (MSV) program Authors: Leibacher, John W.; Noyes, Robert W.; Simon, George W.; Neidig, Donald F. Bibcode: 1993STIN...9328585L Altcode: The Mechanisms of Solar Variability (MSV) Program aims toward understanding physical causes of variations in the radiative, magnetic, and particle emissions from the Sun. Solar particle and field variations influence the interplanetary medium and the magnetosphere; UV and X-ray variations affect the Earth's upper atmosphere; and total irradiance variations are a possibly significant perturber of tropospheric climate. Solar magnetic variability provides a close-up arena for studying important but otherwise unobservable astrophysical phenomena as well. The MSV program will advance our understanding of the causes of solar variability through high angular resolution observations of the interaction of solar surface magnetic fields and convective motions, as well as related x-ray, ultraviolet, and visible brightness variations. Through these high resolution studies, MSV will complement national programs aimed at monitoring integrated solar outputs, thus contributing to the better understanding and ultimate predictability of global solar variability. Title: GONG Project Update Authors: Harvey, J.; Hill, F.; Kennedy, J.; Leibacher, J. Bibcode: 1993ASPC...42..397H Altcode: 1993gong.conf..397H No abstract at ADS Title: White-light movies of the solar photosphere from the SOUP instrument on Spacelab 2 (Advances in Space Research 1986) Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.; Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka, K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L. Bibcode: 1993inas.book..100T Altcode: No abstract at ADS Title: Ground-based helioseismology networks Authors: Hill, Frank; Leibacher, John Bibcode: 1991AdSpR..11d.149H Altcode: 1991AdSpR..11..149H The diurnal rising and setting of the Sun severely compromises helioseismology from a single ground-based observatory. This periodic interruption creates sidelobes in power spectra at multiples of 1/day (11.57 μHz) centered around each solar line, contaminating the spectra and hampering mode identification and frequency measurement. So far, three strategies have been used to overcome the difficulty - observing from the Polar regions, observing with a network of stations placed around the Earth, or observing from a fully sunlit orbit in space. This paper reports on the status of the networks that are either currently in operation or being planned. These include the Global Oscillation Network Group (GONG) project, the Birmingham network, the IRIS network of the University of Nice, the SCLERA network of the University of Arizona, and the ESTEC network. The scientific objectives and instrumentation of these networks are briefly described. The relationship between networks and the helioseismology experiments on the SOHO mission are described.

Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation. Title: The Large Earth-Based Solar Telescope (LEST) - Its Scientific Objectives and Status Authors: Linsky, J. L.; Leibacher, J.; Smithson, R.; Dunn, R. B. Bibcode: 1990BAAS...22.1238L Altcode: No abstract at ADS Title: The Large Earth-based Solar Telescope (LEST) Project Authors: Leibacher, J. W. Bibcode: 1989BAAS...21..832L Altcode: No abstract at ADS Title: Still active Authors: Leibacher, John W. Bibcode: 1989Natur.337..110L Altcode: No abstract at ADS Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1989epos.conf..303D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays were also discussed. The team members debate three main topics: 1) whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2) whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3) whether most chromospheric heating is driven by electron beams. These debates illustrated the strengths and weaknesses of our current observations and theories. Title: The GONG site survey. Authors: Hill, F.; Ambastha, A.; Ball, W.; Duhalde, O.; Farris, D.; Fischer, G.; Hieda, L.; Zhen, Huang; Ingram, B.; Jackson, P.; Jones, H.; Jones, W.; Kennewell, J.; Kunkel, W.; Kupke, R.; Labonte, B.; Leibacher, J.; Libbrecht, K.; Lu, W.; Morrison, L.; Odell, C.; Pallé, P.; Saá, O.; Sousa, E.; Stebbins, T.; Xiao, Suming; GONG Site Survey Team Bibcode: 1988ESASP.286..209H Altcode: The Global Oscillation Network Group (GONG) project is planning to place six observing stations around the world to observe the solar oscillations as continuously as possible. This paper describes the procedures that are being used to select the six sites. The latest results of measurements of cloud cover obtained by networks of 6 (out of 10) radiometers show a duty cycle of over 93%, with the first diurnal sidelobe in the window power spectrum suppressed by a factor of 400. The results are in good agreement with the predictions of a computer model of the expected cloud cover at individual sites. Title: The Global Oscillation Network Group (GONG) Authors: Harvey, J. W.; Hill, F.; Kennedy, J. R.; Leibacher, J. W.; Livingston, W. C. Bibcode: 1988AdSpR...8k.117H Altcode: 1988AdSpR...8..117H As a community facility, the National Solar Observatory is establishing a six-site ground-based solar observing network around the world. This Global Oscillation Network Group (GONG) aims at essentially continuous imaged observations of global solar oscillations for a minimum of three years. Resulting data will be used to study the solar interior using helioseismology. The heart of the observing instrument is a thermally compensated, wide-field Fourier Techometer operated automatically by a computer control system. Data from the six GONG stations is expected to total over one gigabyte per day. Pipeline processing of these data will proceed contemporaneously, reducing the raw data to several standard product data sets at sustained throughput rates in excess of 6 megaflops and peak rates that may exceed 50 megaflops. In support of widespread scientific participation, software analysis tools based on the Image Reduction and Analysis Facility (IRAF) and data distribution will be provided. Science teams have been formed and are actively supporting the project. The field instrument will reach the prototype stage in early 1989 and full operation of the network is expected in 1992.

Operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation. Title: Correlation Lifetimes of Quiet and Magnetic Granulation from the SOUP Instrument on Spacelab 2 Authors: Title, A.; Tarbell, T.; Topka, K.; Acton, L.; Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Simon, G.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.; Zirker, J. Bibcode: 1988ApL&C..27..141T Altcode: The time sequences of diffraction limited granulation images obtained by the Solar Optical Universal Polarimeter on Spacelab 2 are presented. The uncorrection autocorrelation limetime in magnetic regions is dominated by the 5-min oscillation. The removal of this oscillation causes the autocorrelation lifetime to increase by more than a factor of 2. The results suggest that a significant fraction of granule lifetimes are terminated by nearby explosions. Horizontal displacements and transverse velocities in the intensity field are measured. Lower limits to the lifetime in the quiet and magnetic sun are set at 440 s and 950 s, respectively. Title: GONG: To See Inside Our Sun Authors: Harvey, John W.; Kennedy, James R.; Leibacher, John W. Bibcode: 1987S&T....74..470H Altcode: A world-wide program called GONG (Global Oscillation Network Group) will permit scientists to study the depths of the sun's interior by means of its naturally occurring oscillations. Oscillation measurements have revealed that the rotation rate slows very slightly with deeper penetration into the sun. Preliminary data suggest that GONG should be able to monitor the sun 96 percent of the time; the observations should be free from contamination by the 24-hr periodicity. Title: Ocean Waves in the Photosphere: Measurements of Oscillations with Wavelengths of 1 - 10 Mm from SOUP White Light Images Authors: Tarbell, T. D.; Shine, R. A.; Ferguson, S. H.; Title, A. M.; Leibacher, J. W. Bibcode: 1987BAAS...19Q.936T Altcode: No abstract at ADS Title: L'Héliosismologie Dévoile l'Intérieur du Soleil Authors: Leibacher, J. W.; Leibacher-Ouvrard, L. Bibcode: 1987Rech...18..274L Altcode: No abstract at ADS Title: Chromospheric explosions Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNeice, P.; McWhirter, R. W. P. Bibcode: 1986epos.conf..4.1D Altcode: 1986epos.confD...1D Three issues relative to chromospheric explosions were debated. (1) Resolved: The blue-shifted components of x-ray spectral lines are signatures of chromospheric evaporation. It was concluded that the plasma rising with the corona is indeed the primary source of thermal plasma observed in the corona during flares. (2) Resolved: The excess line broading of UV and X-ray lines is accounted for by a convective velocity distribution in evaporation. It is concluded that the hypothesis that convective evaporation produces the observed X-ray line widths in flares is no more than a hypothesis. It is not supported by any self-consistent physical theory. (3) Resolved: Most chromospheric heating is driven by electron beams. Although it is possible to cast doubt on many lines of evidence for electron beams in the chromosphere, a balanced view that debaters on both sides of the question might agree to is that electron beams probably heat the low corona and upper chromosphere, but their direct impact on evaporating the chromosphere is energetically unimportant when compared to conduction. This represents a major departure from the thick-target flare models that were popular before the Workshop. Title: Helioseismology Authors: Leibacher, J. W. Bibcode: 1986BAAS...18R.686L Altcode: No abstract at ADS Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1986NASCP2439....4D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays are also discussed. The team members debated three main topics: 1. whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2. whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3. whether most chromospheric heating is driven by electron beams. Title: A Simple Irradiance Monitor for Testing Solar Global Oscillation Network Sites Authors: Fischer, G.; Hill, F.; Jones, W.; Leibacher, J.; McCurnin, W.; Stebbins, R.; Wagner, J. Bibcode: 1986SoPh..103...33F Altcode: We describe a simple irradiance monitor intended for use in assessing the suitability of candidate sites for a worldwide network of small solar telescopes. The network will observe the Sun as continuously as possible in order to provide high quality solar oscillation data with low diurnal sidelobe contamination and high temporal frequency resolution. Title: White-light movies of the solar photosphere from the soup instrument on spacelab 2 Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.; Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka, K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L. Bibcode: 1986AdSpR...6h.253T Altcode: 1986AdSpR...6..253T We present initial results on solar granulation, pores and sunspots from the white-light films obtained by the Solar Optical Universal Polarimeter (SOUP) instrument on Spacelab 2. SOUP contains a 30-cm Cassegrain telescope, an active secondary mirror for image stabilization, and a white-light optical system with 35-mm film and video cameras. Outputs from the fine guidance servo provided engineering data on the performance of the ESA Instrument Pointing System (IPS). Several hours of movies were taken at various disk and limb positions in quiet and active regions. The images are diffraction-limited at 0.5 arc second resolution and are, of course, free of atmospheric seeing and distortion. Properties of the granulation in magnetic and non-magnetic regions are compared and are found to differ significantly in size, rate of intensity variation, and lifetime. In quiet sun on the order of fifty percent of the area has at least one ``exploding granule'' occurring in it during a 25 minute period. Local correlation tracking has detected several types of transverse flows, including systematic outflow from the penumbral boundary of a spot, motion of penumbral filaments, and cellular flow patterns of supergranular and mesogranular size. Feature tracking has shown that in quiet sun the average granule fragment has a velocity of about one kilometer per second. Title: Helioseismology Authors: Leibacher, J. W.; Noyes, R. W.; Toomre, J.; Ulrich, R. K. Bibcode: 1985SciAm.253c..48L Altcode: 1985SciAm.253...48L Oscillations of the sun's surface are due to sound waves resonating in the solar interior. In actual observations, such surface displacements are evidenced in the form of Doppler shifts in the wavelengths of light that are absorbed by the moving gases, and as variations in brightness. The spatial pattern and period of surface oscillation allows investigators to deduce the three-dimensional structure of the resonance, and to infer properties of the solar interior. Reflection and refraction below the solar surface confine sound waves within acoustic cavities. Such trapped waves interfere constructively with themselves as they circle the sun, creating the resonances that are detectable as solar surface oscillations. Title: Helioseismology. Authors: Leibacher, J. W.; Noyes, R. W.; Toomre, J.; Ulrich, R. K. Bibcode: 1985SciAm.253c..34L Altcode: 1985SciAm.253...34L Acoustic waves within the sun are visible as oscillations on the solar surface. Their pattern and period hold clues to structure, composition and dynamics in the sun's interior. Title: Linear models of acoustic waves in sunspot umbrae. Authors: Gurman, J. B.; Leibacher, J. W. Bibcode: 1984ESASP.220..205G Altcode: 1984ESPM....4..205G The authors interpret the 5.5 to 8.5 mHz oscillations observed in umbral chromospheres and transition regions as acoustic waves propagating parallel, or nearly parallel, to the temperature gradient. Title: Linear models of acoustic waves in sunspot umbrae Authors: Gurman, J. B.; Leibacher, J. W. Bibcode: 1984ApJ...283..859G Altcode: The two-dimensional, linear hydrodynamics of quiet solar and umbral model atmospheres in a plane-parallel, adiabatic approximation are investigated. The 5.5-8.5 mHz oscillations observed in umbral chromospheres and transition regions are interpreted as acoustic waves propagating parallel, or nearly parallel, to the temperature gradient. These waves are not totally internally reflected by the steep temperature gradient and, thus, are not trapped. Partial reflections, however, are effective in modulating the transmission as a function of frequency. The resonant transmission mechanism of Zugzda, Locans, and Staude (1983) is found to produce a spectrum of resonances in the transmission of acoustic waves in any atmosphere with a temperature minimum. Since the observed umbral oscillations display power in only a narrow range of frequencies, characteristics of the umbral models, wave propagation, and observations that would tend to suppress the higher frequency resonances are examined. Title: Internal rotation of the Sun Authors: Duvall, T. L., Jr.; Dziembowski, W. A.; Goode, P. R.; Gough, D. O.; Harvey, J. W.; Leibacher, J. W. Bibcode: 1984Natur.310...22D Altcode: The frequency difference between prograde and retrograde sectoral solar oscillations is analysed to determine the rotation rate of the solar interior, assuming no latitudinal dependence. Much of the solar interior rotates slightly less rapidly than the surface, while the innermost part apparently rotates more rapidly. The resulting solar gravitational quadrupole moment is J2 = (1.7+/-0.4) × 10-7 and provides a negligible contribution to current planetary tests of Einstein's theory of general relativity. Title: A Multiwavelength Study of a Double Impulsive Flare Authors: Strong, K. T.; Benz, A. O.; Dennis, B. R.; Leibacher, J. W.; Mewe, R.; Poland, A. I.; Schrijver, J.; Simnett, G.; Smith, J. B., Jr.; Sylwester, J. Bibcode: 1984SoPh...91..325S Altcode: Extensive data from the Solar Maximum Mission (SMM) and ground-based observatories are presented for two flares; the first occurred at 12:48 UT on 31 August, 1980 and the second just 3 min later. They were both compact events located in the same part of the active region. The first flare appeared as a typical X-ray flare: the CaXIX X-ray lines were broadened (≡ 190±40 km s-1) and blue shifted (≡ 60±20 km s-1) during the impulsive phase, and there was a delay of about 30 s between the hard and soft X-ray maxima. The relative brightness of the two flares was different depending on the spectral region being used to observe them, the first being the brighter at microwave and hard X-ray wavelengths but fainter in soft X-rays. The second flare showed no significant mass motions, and the impulsive and gradual phases were almost simultaneous. The physical characteristics of the two flares are derived and compared. The main difference between them was in the pre-flare state of the coronal plasma at the flare site: before the first flare it was relatively cool (3 × 106 K) and tenuous (4 × 109 cm-3), but owing to the residual effects of the first flare the coronal plasma was hotter (5 × 106 K) and more dense (3 × 1011 cm-3) at the onset of the second flare. We are led to believe from these data that the plasma filling the flaring loops absorbed most of the energy released during the impulsive phase of the second flare, so that only a fraction of the energy could reach the chromosphere to produce mass motions and turbulence. Title: Helioseismological Determination of Solar Internal Rotation Authors: Leibacher, J. Bibcode: 1984LIACo..25..298L Altcode: 1984tpss.conf..298L; 1984trss.conf..298L No abstract at ADS Title: Closed coronal structures. V - Gasdynamic models of flaring loops and comparison with SMM observations Authors: Pallavicini, R.; Peres, G.; Serio, S.; Vaiana, G.; Acton, L.; Leibacher, J.; Rosner, R. Bibcode: 1983ApJ...270..270P Altcode: The hydrodynamic response of confined magnetic structures to strong heating perturbations is investigated by means of a time-dependent one-dimensional colde which incorporates the energy, momentum, and mass conservation equations. The entire atmospheric structure from the chromosphere to the corona is taken into account. Models with different energy input, heating time dependence, preflare conditions and heating location have been examined in the numerical simulations.

The result of model calculations are compared with observations of flares obtained with the X-ray Polychromator experiment on the Solar Maximum Mission. These include light curves of spectral lines formed over a wide range of coronal flare temperatures, as well as determinations of Doppler shifts for the high temperature plasma. Several examples are used to illustrate the range of the observational variation.

It is shown that the predictions of the numerical simulations are in good overall agreement with the observed evolution of the flare coronal plasma. The model reproduces correctly the temporal profile of X-ray spectral lines and -- to first order at least -- their relative intensities. The upflow velocities predicted by model calculations are in agreement with the observed blueshifts, supporting the interpretation of the blueshifts as due to evaporation of chromospheric material. The possibility of using the comparison of model predictions with observations to derive information on the processes of energy release and transfer in solar flares is discussed. Title: X-ray line ratios from helium-like ions - Updated theory and SMM flare observations Authors: Wolfson, C. J.; Leibacher, J. W.; Doyle, J. G.; Phillips, K. J. H. Bibcode: 1983ApJ...269..319W Altcode: The potential which the conduction of measurements of the three principal lines emitted from helium-like ions has for the determination of plasma electron density was initially pointed out by Gabriel and Jordan (1969). The diagnostic technique is based on the fact that the ratio, R, of the intensity of a forbidden line to the intensity of an intercombination line decreases as electron density increases due to collisional excitation of levels. In the present investigation a further refinement of this procedure is provided by specifically calculating the effects of cascades from levels with principal quantum numbers up to n=6. Two improved spectrometers recently placed in operation include the SOLEX instrument on the satellite P78-1 and the X-ray Polychromator (XRP) instrument on the NASA Solar Maximum Mission satellite. Measurements obtained with one of the spectrometers making up the XRP are presented, taking into account the emission from Ne IX ions. Title: Inner-shell transitions in Fe XIX-XXII in the X-ray spectra of solar flares and Tokamaks Authors: Phillips, K. J. H.; Lemen, J. R.; Cowan, R. D.; Doschek, G. A.; Leibacher, J. W. Bibcode: 1983ApJ...265.1120P Altcode: Calculated spectra of the ions Fe XIX-XXII for various densities and temperatures are presented, thereby extending the work begun by Doschek, Feldman, and Cowan (1981). The calculations are based on a code (the Cowan code) that computes both the level structure of an ion and intensity factors for the 1s-2p satellite lines. A comparison is made between the calculated spectra and those observed in solar flares by the P78-1 and SMM instruments. The observed intensities of Fe XX lines, which are the most sensitive to density, are found to agree well with those calculated in the low-density limit. The agreement for lines arising from other ions is also very good. It is also seen that the predicted density variations in Fe XX are confirmed by the higher density Princeton Large Torus plasmas. Thus a possible useful density diagnostic is indicated for tokamak and high-density astrophysical plasmas, perhaps including some solar flares. Title: Chromospheric evaporation in a well-observed compact flare Authors: Acton, L. W.; Leibacher, J. W.; Canfield, R. C.; Gunkler, T. A.; Hudson, H. S.; Kiplinger, A. L. Bibcode: 1982ApJ...263..409A Altcode: Hudson and Ohki (1972) pointed out that the increase of the soft X-ray emission measure during flares might be accounted for in two different ways, either by 'coronal condensation', or by what they termed 'chromospheric rarefaction', now more commonly called 'chromospheric evaporation'. They ruled out coronal condensation on the basis of cornal mass content arguments. Moore et al. (1980) found it highly probable that the bulk of the mass of the soft X-ray emitting plasma is supplied during the rise phase by chromospheric evaporation from the feet of the soft X-ray loops. On the other hand, Cheng et al. (1981) argued that chromospheric evaporation is not important as a source of soft X-ray plasma. The present investigation is concerned with an event in which direct chromospheric observations contradict the conclusions reached by Cheng et al. Up to now chromospheric evaporation has always been an inference, without compelling positive evidence. In the current investigation, observations are considered which constitute such evidence. Title: The Transmission and Trapping of Acoustic Waves in the Umbral Chromosphere Authors: Gurman, J. B.; Leibacher, J. W. Bibcode: 1982BAAS...14Q.939G Altcode: No abstract at ADS Title: Solar atmospheric dynamics. II - Nonlinear models of the photospheric and chromospheric oscillations Authors: Leibacher, J.; Gouttebroze, P.; Stein, R. F. Bibcode: 1982ApJ...258..393L Altcode: The one-dimensional, nonlinear dynamics of the solar atmosphere is investigated, and models of the observed photospheric (300 s) and chromospheric (200 s) oscillations are described. These are resonances of acoustic wave cavities formed by the variation of the temperature and ionization between the subphotospheric, hydrogen convection zone and the chromosphere-corona transition region. The dependence of the oscillations upon the excitation and boundary conditions leads to the conclusion that for the observed amplitudes, the modes are independently excited and, as trapped modes, transport little if any mechanical flux. In the upper photosphere and lower chromosphere, where the two modes have comparable energy density, interference between them leads to apparent vertical phase delays which might be interpreted as evidence of an energy flux. Title: Impulsive Phase of Flares in Soft X-Ray Emission Authors: Antonucci, E.; Gabriel, A. H.; Acton, L. W.; Culhane, J. L.; Doyle, J. G.; Leibacher, J. W.; Machado, M. E.; Orwig, L. E.; Rapley, C. G. Bibcode: 1982SoPh...78..107A Altcode: Observations using the Bent Crystal Spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the Hard X-ray Burst Spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Non-thermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km s-1 and upward motions of 300-400 km s-1. Title: Solar flare X-ray spectra from the Solar Maximum Mission Flat Crystal Spectrometer Authors: Phillips, K. J. H.; Fawcett, B. C.; Kent, B. J.; Gabriel, A. H.; Leibacher, J. W.; Wolfson, C. J.; Acton, L. W.; Parkinson, J. H.; Culhane, J. L.; Mason, H. E. Bibcode: 1982ApJ...256..774P Altcode: High-resolution solar X-ray spectra obtained with the Flat Crystal Spectrometer aboard the Solar Maximum Mission from two solar flares and a nonflaring active region are analyzed. The 1-22 A region was observed during the flare on 1980 August 25, while smaller spectral regions were repeatedly covered during the 1980 November 5 flare. Voigt profiles were fitted to spectral lines to derive accurate wavelengths and to resolve blends. During the August 25 flare, 205 lines were found in the range 5.68-18.97 A, identifications being provided for all but 40 (mostly weak) lines. Upper limits to flare densities are derived from various line ratios, the hotter (about 10 to the 7th K) ions giving an electron density of less than 10 to the 12th per cu cm for the August 25 flare. Other observed line ratios (e.g., in Fe XVII and Mg XII) indicate a need for revisions in theoretical calculations. Title: Chromospheric and coronal heating mechanisms. Authors: Leibacher, J.; Stein, R. F. Bibcode: 1982SAOSR.392A..23L Altcode: 1982csss....2...23L Dissipation mechanisms in the chromosphere were examined. The problem of a heat flux from a cool region of the star to a hot region of the star, which violates our second law of thermodynamics is discussed. It is suggested that this is caused by a nonthermal energy flux. While convection transports the thermal flux, a very small percentage is converted into a nonthermal flux. The major part of the outgoing convective energy is turned back into the radiation field which gets decoupled from the star when the star becomes transparent and the radiant energy escapes to space. The small nonthermal flux is transmitted upwards and becomes the dominant energy flux still coupled to the star. The importance of recycling of energy via advection and conduction is emphasized. Title: Transition region oscillations in sunspots. Authors: Gurman, J. B.; Leibacher, J. W.; Shine, R. A.; Woodgate, B. E.; Henze, W. Bibcode: 1982ApJ...253..939G Altcode: Time series observations of the profile of the C IV resonance line 1548.19 A obtained in eight sunspots with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission are discussed. All of the sunspots exhibit significant oscillations in line-of-sight velocity with frequencies in the range from 5.8 mHz to 7.8 mHz (periods of 129-173 s). Significant intensity oscillations are observed at the same periods in four of the time series; the maximum intensity is in phase with maximum blueshift. Difference spectroheliograms ('Dopplergrams') of the two halves of the C IV line, as well as observations in the Si IV resonance line 1402.77 A and the O IV intersystem line 1401.16 A, also reveal velocity oscillations at similar frequencies but only over sunspots. Title: Direct evidence for chromospheric evaporation in a well-observed compact flare Authors: Canfield, R. C.; Gunkler, T. A.; Hudson, H. S.; Acton, L. W.; Leibacher, J. W.; Kiplinger, A. L. Bibcode: 1982AdSpR...2k.145C Altcode: 1982AdSpR...2..145C Observations of the solar flare of May 7, 1980 using several Solar Maximum Mission instruments are presented as an investigation of the phenomenon of chromospheric evaporation. The total amount of plasma at temperatures greater than 2 x 10 to the 6th K were determined from the X-ray data, and the amount of plasma that was evaporated from the chromosphere was determined from the H-alpha data. The H-alpha profiles indicate that for the flare as a whole, at the time of peak soft X-ray emission measure, the number of atoms evaporated from the chromosphere was 7 x 10 to the 37th. The soft X-ray emission measure of 1 x 10 to the 49th/cu cm, coupled with the flare volume estimate of 10 to the 26th cu cm, indicates that there were 3 x 10 to the 37th electrons in the soft X-ray plasma with temperatures greater than 2 x 10 to the 6th K. These results indicate that enough material had been evaporated from the chromosphere to account for the X-ray plasma. Taken together, the H-alpha, soft X-ray, and hard X-ray images indicate that chromospheric evaporation is driven both by flare-accelerated electrons during the impulsive phase and by conduction during the thermal phase. Title: The Sun Authors: Leibacher, J. W. Bibcode: 1982obvf.conf....3L Altcode: No abstract at ADS Title: Oscillations and pulsations. Authors: Leibacher, J. W.; Stein, R. F. Bibcode: 1981NASSP.450..263L Altcode: 1981suas.nasa..263L A theory to describe the observed photospheric 5 minute oscillations, chromospheric 3 minute oscillations, and possible motions of the interior with periods ranging from 40 to 160 minutes is discussed. It is similar to the theory of nonradial stellar oscillations developed to describe the low angluar order modes (one or two wavelengths around a circumference); however, the solar oscillations have thousands of wavelengths around a circumference. The properties of waves in stars, their restoring forces, periods and wavelengths, and their propagation and motions are discussed. Title: Wave generation. Authors: Stein, R. F.; Leibacher, J. W. Bibcode: 1981NASSP.450..289S Altcode: 1981suas.nasa..289S There are three principal kinds of wave generation mechanisms, corresponding to each of the three conservation laws that govern fluid motions: a changing mass flux into a stable atmosphere; convective motion; and energy exchange between a wave and the surrounding atmosphere. These mechanisms are applied to three kinds of waves: acoustic, gravity, and Alfven waves. They are pure cases, distinguished by their different restoring forces pressure for acoustic waves, buoyancy for gravity waves, and magnetic tension for Alfven waves. Title: SMM Observations of Soft X-Ray Line Spectra Authors: Leibacher, J. W.; Phillips, K. J. H.; Wolfson, C. J. Bibcode: 1981BAAS...13..555L Altcode: No abstract at ADS Title: Direct Evidence for Chromospheric Evaporation in a Well-Observed Compact Flare Authors: Canfield, R. C.; Acton, L. W.; Gunkler, T. A.; Hudson, H. S.; Kiplinger, A. L.; Leibacher, J. W. Bibcode: 1981BAAS...13R.819C Altcode: No abstract at ADS Title: The Significance of Multiple Flares Authors: Strong, K. T.; Dennis, B. R.; Leibacher, J. W.; Wolfson, C. J. Bibcode: 1981BAAS...13..820S Altcode: No abstract at ADS Title: Solar maximum mission experiment: Early results from the soft X-ray polychromator experiment Authors: Gabriel, A. H.; Antonucci, E.; Phillips, K. J. H.; Culhane, J. L.; Bentley, R. D.; Parmar, A. N.; Rapley, C. G.; Acton, L. W.; Leibacher, J. W.; Wolfson, C. J.; Strong, K. T.; Jordan, C. Bibcode: 1981AdSpR...1m.267G Altcode: 1981AdSpR...1Q.267G The X-Ray Polychromator experiment has been in operation on the SMM satellite for over three months. It is observing flares and active regions in the wavelength range 1Å to 23Å using a number of different modes. These include polychromatic imaging, high resolution line profiles, high dispersion spectra, and light curves with high time-resolution. Data are described together with some of the preliminary analysis and interpretation. Title: Solar Maximum Mission experiment: early results from the soft X-ray polychromator experiment. Authors: Gabriel, A. H.; Culhane, J. L.; Acton, L. W.; Antonucci, E.; Bentley, R. D.; Jordan, C.; Leibacher, J. W.; Parmar, A. N.; Phillips, K. J. H.; Rapley, C. G.; Wolfson, C. J.; Strong, K. T. Bibcode: 1981hea..conf..267G Altcode: No abstract at ADS Title: UVSP/SMM observations of transition region oscillations in sunspots Authors: Gurman, J. B.; Shine, R. A.; Woodgate, B. E.; Leibacher, J. W.; Henze, W. Bibcode: 1981phss.conf..319G Altcode: Using Ultraviolet Spectrometer and Polarimeter data obtained in emission lines formed at temperatures of 70,000 K to 130,000 K, transition region oscillations in sunspots have been observed. The frequency of these oscillations lies in the range 5.8 mHz to 7.8 mHz. Their regular appearance in line-of-sight velocity and their frequent occurrence in intensity in phase with maximum blue shift leads to the interpretation of the oscillations as upward-propagating acoustic waves. The presence in two of the C IV wavelength 1548.19 time series of a phase-shifted oscillation in the line width may be caused by the presence of unidentified blends in the line wings. The energy flux carried by the umbral acoustic waves is less than 2000 erg/sq cm/s, some seven orders of magnitude smaller than the missing radiative flux of sunspots. Title: Velocities observed with the X-ray Polychromator onboard the Solar Maximum Mission Authors: Leibacher, J. W. Bibcode: 1980BAAS...12R.906L Altcode: No abstract at ADS Title: Large-aperture high-resolution X-ray collimator for the Solar Maximum Mission Authors: Nobles, R. A.; Acton, L. W.; Joki, E. G.; Leibacher, J. W.; Peterson, R. C. Bibcode: 1980ApOpt..19.2957N Altcode: A description is presented of a flight-qualified large-aperture 12 x 12-arcsec angular resolution multigrid X-ray collimator developed for the Solar Maximum Mission (SMM) flat crystal spectrometer. This collimator, designed for the 1.4-22.4-A wavelength range, utilizes an optical bench/metering structure to align and support prealigned grid subassemblies. The optical bench is a lightweight, rigid, and stable aluminum honeycomb structure. The grids are of a compound and bimetallic design, having 63.5-micron square holes on an 88.9-micron spacing in 8-micron thick gold, which is in turn supported by a 76-micron thick Invar grid having 600-micron square holes on a 739-micron spacing. The small apertures in the gold provide the 12-arcsec collimation with the Invar grids providing wide angle off-axis blocking out to an approximately 35 arcmin view angle. The collimator has seven individual channels, four of a 5.1- x 10-cm area and three of a 1.3- x 10-cm area. Laboratory measurements gave an average angular resolution of 12.5 arcsec FWHM with 0.259 transmission for the large-area channels and 12.0 arcsec and 0.200 transmission for the small-area channels. A thermal filter composed of two layers of approximately 1000-A thick aluminum prevents solar heating of the front collimator grids by absorbing longer wavelength radiation while passing most of the X radiation in the band of interest. Title: A Small Impulsive Flare Authors: Acton, L. W.; Leibacher, J. W. Bibcode: 1980BAAS...12..904A Altcode: No abstract at ADS Title: The Spatial Dependence of UV and X-Ray Phenomena Occurring During the Impulsive Phase of a Flare Authors: Frost, K. J.; Dennis, B. R.; Orwig, L. E.; Kiplinger, A. L.; Leibacher, J.; Antonucci, E.; Parmar, A. N.; Woodgate, B.; Shine, R.; Cheng, C. -C. Bibcode: 1980BAAS...12..905F Altcode: No abstract at ADS Title: Solar atmospheric dynamics. I - Formation of optically thick chromospheric lines Authors: Gouttebroze, P.; Leibacher, J. W. Bibcode: 1980ApJ...238.1134G Altcode: Two of the most representative chromospheric lines, Mg II k and Ca II K are used to study the formation of optically thick lines in a time-dependent, one-dimensional model of the solar atmosphere. Time sequences of these line profiles are calculated for two kinds of atmospheric motions: propagation of a pulse through the atmosphere, and free oscillations. The mechanisms of formation (especially the displacement of the emitting layers) are studied for different parts of the profiles. Finally, the deformations of the profiles are analyzed using methods also suitable for observations, and the resulting parameters are compared to physical variables in order to evaluate the diagnostic methods. Title: Dynamics of the High Temperature Flare Authors: Leibacher, J. W. Bibcode: 1980BAAS...12..531L Altcode: No abstract at ADS Title: The soft X-ray polychromator for the Solar Maximum Mission. Authors: Acton, L. W.; Culhane, J. L.; Gabriel, A. H.; Bentley, R. D.; Bowles, J. A.; Firth, J. G.; Finch, M. L.; Gilbreth, C. W.; Guttridge, P.; Hayes, R. W.; Joki, E. G.; Jones, B. B.; Kent, B. J.; Leibacher, J. W.; Nobles, R. A.; Patrick, T. J.; Phillips, K. J. H.; Rapley, C. G.; Sheather, P. H.; Sherman, J. C.; Stark, J. P.; Springer, L. A.; Turner, R. F.; Wolfson, C. J. Bibcode: 1980SoPh...65...53A Altcode: The 1.4-22.4 Å range of the soft X-ray spectrum includes a multitude of emission lines which are important for the diagnosis of plasmas in the 1.5-50 million degree temperature range. In particular, the hydrogen and helium-like ions of all abundant solar elements with Z > 7 have their primary transitions in this region and these are especially useful for solar flare and active region studies. The soft X-ray polychromator (XRP) is a high resolution experiment working in this spectral region. The XRP consists of two instruments with a common control, data handling and power system. The bent crystal spectrometer is designed for high time resolution studies in lines of Fe I-Fe XXVI and Ca XIX. The flat crystal scanning spectrometer provides for 7 channel polychromatic mapping of flares and active regions in the resonance lines of O VIII, Ne IX, Mg XI, Si XIII, S XV, Ca XIX, and Fe XXV with 14″ spatial resolution. In its spectral scanning mode it covers essentially the entire 1.4-22.5 Å region. Title: Small-scale dissipative processes in stellar atmospheres. Authors: Leibacher, J. W.; Stein, R. F. Bibcode: 1980HiA.....5..581L Altcode: The outer atmospheres of stars must be heated by some non-thermal energy flux to produce chromospheres and coronae. Processes are discussed which convert the non-thermal energy flux of organized, macroscopic motions into random, microscopic (thermal) motions. Recent advances in the description of the chromosphere velocity field suggest that the acoustic waves observed there transmit very little energy, and hence are probably incapable of heating the upper chromosphere and corona. The apparent failure of this long held mechanism and the growing appreciation of the importance of strong magnetic fields in the chromosphere and corona have led to hypotheses of heating by the dissipation of currents (both oscillatory and quasi-steady). This follows discoveries in laboratory and ionospheric plasmas and work on solar flares, that instabilities can concentrate currents into thin high current density filaments where they dissipate rapidly. Title: Mechanical energy transport Authors: Stein, R. F.; Leibacher, J. W. Bibcode: 1980LNP...114..225S Altcode: 1980IAUCo..51..225S; 1980sttu.coll..225S The properties, generation, and dissipation mechanisms of acoustic, gravity and Alfven waves are described, whose restoring forces are pressure, buoyancy, and magnetic tension, respectively. For acoustic waves, generation by turbulent convective motions and by the Eddington Valve thermal overstability is discussed, considering the 'five-minute' oscillation; dissipation is possible either by radiation or shocks. Generation of gravity waves by penetrative convective motions and by shear arising from supergranule motions is reviewed, and dissipation due to wave breaking, interaction with the mean horizontal fluid flow, and very severe radiative damping is considered. Attention is given to Alfven wave generation by convective motions and thermal overstability, and to dissipation by mode coupling, wave decay, current dissipation, and particle collisions producing Joule or viscous heating. Title: Some Effects of Strong Acoustic Waves on Strong Spectral Lines Authors: Gouttebroze, P.; Leibacher, J. Bibcode: 1980LNP...114..212G Altcode: 1980IAUCo..51..212G; 1980sttu.coll..212G No abstract at ADS Title: Analysis of time dependent phenomena observed with the LPSP OSO-8 instrument Authors: Leibacher, J. W. Bibcode: 1979lock.reptR....L Altcode: Data obtained by the Laboratoire de Physique Stellaire et Planetaire's ultraviolet spectrometer onboard the OSO-8 spacecraft were analyzed in an effort to dynamically model the solar chromosphere as an aid in enhancing knowledge of the dynamical processes themselves and of spectral line formation in the dynamic chromosphere. Repeated spectral scans of strong, optically thick resonance lines formed in the solar chromosphere were examined for indications of oscillatory velocities and intensities among other indications of velocity which were studied, the blue peak is reasonably well defined, and the position of a parabolic filter fitted by the least squares method was used to define it. Observed chromospheric oscillation periods are discussed as well as the variations in altitude of the emitting region which result primarily from the motion up and down during the oscillation. Title: Analysis of time dependent phenomena observed with the LPSP OSO-8 instrument Authors: Leibacher, J. W. Bibcode: 1979lock.reptQ....L Altcode: The dynamics of the solar photosphere and chromosphere are studied. Observations obtained by the Laboratorie de Physique Stellaire et Planetaire's (LPSP) ultraviolet spectrometer onboard the OSO-8 spacecraft are analyzed, and dynamic models of the chromosphere and the emitted resonance line spectrum are calculated. Some of the unpublished data analysis and theoretical modeling which are being prepared for publication are discussed. A discussion of the state of the theory of velocity fields in the solar atmosphere is also presented. An invited review presented at the OSO-8 Workshop on the topic of oscillatory motions in the quiet sun is included. The results of the OSO-8 data analysis prepared in close collaboration with LPSP scientists are presented. Material for two articles is also presented. Title: A Dynamical Representation of the Solar Chromosphere Authors: Leibacher, J. W.; Gouttebroze, P. Bibcode: 1978BAAS...10..671L Altcode: No abstract at ADS Title: Simultaneous time-resolved observations of the H Lalpha , Mg k 2795 Å, and Ca K solar lines. Authors: Artzner, G.; Leibacher, J.; Vial, J. C.; Lemaire, P.; Gouttebroze, P. Bibcode: 1978ApJ...224L..83A Altcode: No abstract at ADS Title: The LPSP instrument on OSO 8. II. In-flight performance and preliminary results. Authors: Bonnet, R. M.; Lemaire, P.; Vial, J. C.; Artzner, G.; Gouttebroze, P.; Jouchoux, A.; Leibacher, J. W.; Skumanich, A.; Vidal-Madjar, A. Bibcode: 1978ApJ...221.1032B Altcode: The paper describes the in-flight performance for the first 18 months of operation of the LPSP (Laboratoire de Physique Stellaire et Planetaire) instrument incorporated in the OSO 8 launched June 1975. By means of the instrument, an absolute pointing accuracy of nearly one second was achieved in orbit during real-time operations. The instrument uses a Cassegrain telescope and a spectrometer simultaneously observing six wavelengths. In-flight performance is discussed with attention to angular resolution, spectral resolution, dispersion and grating mechanism (spectral scanner) stability, scattered light background and dark current, photometric standardization, and absolute calibration. Real-time operation and problems are considered with reference to pointing system problems, target acquisition, and L-alpha modulation. Preliminary results involving the observational program, quiet sun and chromospheric studies, quiet chromospheric oscillation and transients, sunspots and active regions, prominences, and aeronomy investigations are reported. Title: Soft X-Ray Observations during the Preflare Phase of the Solar Flare Phenomenon. Authors: Wolfson, C. J.; Acton, L. W.; Leibacher, J. W. Bibcode: 1978BAAS...10..456W Altcode: No abstract at ADS Title: Early evolution of an X-ray emitting solar active region. Authors: Wolfson, C. J.; Acton, L. W.; Leibacher, J. W.; Roethig, D. T. Bibcode: 1977SoPh...55..181W Altcode: The birth and early evolution of a solar active region has been investigated using X-ray observations from the Lockheed Mapping X-Ray Heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of Hα plage. At that time, a plasma temperature of 4 × 106 K in a region having a density of the order of 1010 cm−3 is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by plasma with a temperature of the order 3 × 106 K. If we assume that the X-rays result from heating due to dissipation of current systems or magnetic field reconnection, we conclude that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration. Title: Velocity fields in the solar atmosphere - Theory Authors: Leibacher, J. W. Bibcode: 1977MmSAI..48..475L Altcode: An attempt is made to present an equationless description of the hydrodynamic state of the lower solar atmosphere. Areas currently being analyzed in some depth and areas which appear amenable to treatment are pointed out. Title: EUV observations of class-C X-ray flare by the LPSP (Laboratoire de Physique Stellaire et Planétaire du Centre National de la Recherche Scientifique) spectrometer on OSO-8. Authors: Jouchoux, A.; Skumanich, A.; Bonnet, R. M.; Lemaire, P.; Artzner, G.; Leibacher, J.; Vial, J. C.; Vidal-Madjar, A. Bibcode: 1977BAAS....9..432J Altcode: No abstract at ADS Title: The LPSP experiment on OSO-8. I - Instrumentation, description of operations, laboratory calibrations and pre-launch performances Authors: Artzner, G.; Bonnet, R. M.; Vial, J. C.; Jouchoux, A.; Leibacher, J.; Vidal-Madjar, A.; Lemaire, P. Bibcode: 1977SSI.....3..131A Altcode: The characteristics of OSO-8, including its solar-pointed instrument assembly and rasters, are discussed, as well as the accompanying Laboratoire de Physique Stellaire et Planetaire (LPSP) instrumentation, which is designed to study the solar atmosphere with high spatial, spectral, and temporal resolution. The LPSP instrument, which consists of two subassemblies, a Cassegrainian telescope and a spectrometer, is described; main optical characteristics, including spectral lines observed, and means of correcting aberrations and eliminating stray light, are given for the spectrometer. Detectors and their capacities, and various filter wheel configurations available for detection of polarized light and discrimination of low orders of diffraction, are also described. The observation program, which consists of a study of solar prominences, flares, and dynamic and three-dimensional physical structures of the chromosphere, as well as determination of seasonal variations of some gases in earth's atmosphere, is reviewed. A detailed account of pre-launch tests and calibration procedures is also given. Title: Extreme-Ultraviolet Observations of New Cycle Sunspots with the LPSP Spectrometer from OSO-8 Authors: Skumanich, A.; Jouchoux, A.; Artzner, G.; Bonnet, R. M.; Leibacher, J.; Lemaire, P.; Vial, J. C.; Vidal-Madjar, A. Bibcode: 1977BAAS....9..340S Altcode: No abstract at ADS Title: On VI Profiles of Solar Quiet and Active Areas Recorded by OSO-8 LPSP Experiment". Authors: Lemaire, P.; Artzner, G.; Vial, J. C.; Bonnet, R. M.; Gottebroze, P.; Jouchoux, A.; Vidal-Madjar, A.; McWhirter, P.; Leibacher, J.; Skumainich, A. Bibcode: 1977uxsa.coll...46L Altcode: 1977IAUCo..43...46L No abstract at ADS Title: OSO-8 Observations of the EUV Chromospheric Network Authors: Artzner, G.; Bonnet, R. M.; Leibacher, J.; Lemaire, P.; Skumanich, A.; Vial, J. C.; Vidal-Madjar, A. Bibcode: 1976BAAS....8..332A Altcode: No abstract at ADS Title: Solar OVI Profiles as Observed by the French Experiment Aboard OSO-8 Authors: Lemaire, P.; Artzner, G.; Bonnet, R. M.; Vial, F. C.; Skumanich, A.; Leibacher, J.; Vidal-Madjar, A. Bibcode: 1976BAAS....8R.331L Altcode: No abstract at ADS Title: Evolution of sunspot and active region morphology as observed on the resonance lines of Ca+ (K, H), Mg+ (k, h), hydrogen (Lalpha , Lbeta ), and O VI from OSO-8 (LPSP). Authors: Artzner, G.; Skumanich, A.; Bonnet, R. M.; Vidal-Madjar, A.; Leibacher, J.; Lemaire, P.; Vial, J. C. Bibcode: 1976BAAS....8..397A Altcode: No abstract at ADS Title: Periodic temporal phenomena in the solar chromosphere as observed from OSO-8 (LPSP). Authors: Vial, J. C.; Leibacher, J.; Lemaire, P.; Artzner, G.; Bonnet, R. M.; Skumanich, A.; Vidal-Madjar, A. Bibcode: 1976BAAS....8..397V Altcode: No abstract at ADS Title: Spatial variations of solar profiles of Ca+ H and K, Mg+ h and k, and Lyman alpha and beta (H I) resonance lines as observed from OSO-8 (LPSP). Authors: Bonnet, R. M.; Artzner, G.; Leibacher, J.; Lemaire, P.; Skumanich, A.; Vial, J. C.; Vidal-Madjar, A. Bibcode: 1976BAAS....8..397B Altcode: No abstract at ADS Title: Prominence Observations with the OSO-8 French Experiment Authors: Vial, J. C.; Artzner, G.; Bonnet, R. M.; Lemaire, P.; Leibacher, J.; Skumanich, A.; Vidalmadjar, A. Bibcode: 1976BAAS....8..344V Altcode: No abstract at ADS Title: Non linear dynamics of stellar atmospheres Authors: Leibacher, J.; Stein, R. F. Bibcode: 1976pmas.conf...69L Altcode: No abstract at ADS Title: Waves in the solar atmosphere. Authors: Stein, R. F.; Leibacher, J. Bibcode: 1974ARA&A..12..407S Altcode: The wave modes in the solar atmosphere are considered, taking into account the equations of motion, pure modes, two-force modes, and magneto-acoustic-gravity waves. Oscillations in the quiet sun are discussed along with models of the 'five-minute' oscillation, oscillations in regions of strong magnetic field, and nonsinusoidal waves. Questions regarding the generation of waves are explored, giving attention to penetrative convection, the Lighthill mechanism, and aspects of thermal overstability. Problems regarding the heating of the chromosphere and the corona are also examined. Title: A New Description of the Solar Five-Minute Oscillation Authors: Leibacher, J. W.; Stein, R. F. Bibcode: 1971ApL.....7..191L Altcode: 1970ApL.....7..191L No abstract at ADS Title: Solar Atmospheric Oscillations. Authors: Leibacher, John William Bibcode: 1971PhDT.........1L Altcode: No abstract at ADS Title: On the Five-Minute Oscillation of the Solar Atmosphere Authors: Stein, R. F.; Leibacher, J. W. Bibcode: 1969ApL.....3...95S Altcode: No abstract at ADS Title: 1417 Mc/sec observations of M31 Authors: Leibacher, John Bibcode: 1964AJ.....69..374L Altcode: An integrated flux of 68X 10-26 W cp has been measured in a region 8 3?5 centered on M31. The spectral index appears to decrease from -0.3 to -0.6 between 158 and 1417 Mc/sec. Comparison with the distribution of emission at lower frequencies shows no appreciable change in spectral index over the galaxy. Title: 1417 Mc/s Observations of M31 Authors: Leibacher, J. W. Bibcode: 1964Ast....69..374L Altcode: No abstract at ADS Title: 1417 Mc/sec Observations of M31. Authors: Leibacher, John W. Bibcode: 1962AJ.....67Q.580L Altcode: Lilley) .-M31 has been observed with the maser-equipped Harvard radio telescope at 1417 Mc/sec. The low-noise temperature of the radiometer permitted the detection of the halo of M3 1 over a region 3? 5 X 80. The integrated value of the flux density was found to be (68*17) X 10~2e W m-2 cps-1. Comparing this with the 408 Mc/sec flux density of Large, Mathewson, and Haslam (Nature 183, 1250, 1959) gives a spectral index of -0.58 *~0.13. This value should be compared with the spectral index obtained from the flux determinations at 408 and 158 Mc/sec (Hanbury, Brown, and Hazard, Monthly Notices Roy. Astron. Soc. 119, 297, 1959) of 0.38*0.11. Brightness temperature profiles along the major and minor axes at 408 and 1417 Mc/sec have been compared; and the 1417 Mc/sec data have been smoothed and compared with the 38 and 178 Mc/sec data of Baldwin and Costain. Both of these comparisons of the distribution of emission show no significant differences in the distribution of intensity across M3 1, and are thus in agreement with the results of Costain and of Adgie and Smith for the Galaxy. The Harvard Radio Astronomy Proj ect is supported by the National Science Foundation.