Author name code: thompson-michael ADS astronomy entries on 2022-09-14 author:"Thompson, Michael J." ------------------------------------------------------------------------ Title: Self-Reported Demographics of 2014–2021 Principle Investigators Proposing to NASA Planetary Science Research Programs Authors: Thompson, M.; Jensen, H. B.; Papas, L. L.; Taha, N.; New, M. H. Bibcode: 2022LPICo2679.2049T Altcode: The NASA Division of Planetary Science will present demographic data of Principle Investigators proposing to Research Opportunities in Space and Earth Sciences (ROSES) programs for the years 2014–2021. Title: Improving Idea Through Nasa's Planetary Science Division's Proposal Processes Authors: Daou, D.; Moore, L.; Nahm, A. L.; Rinehart, S. A.; Santiago-Materese, D.; Thompson, M.; Vander Kaaden, K. E.; Watkins, R. N.; Zellner, N. Bibcode: 2022LPICo2679.2043D Altcode: NASA, including the Planetary Science Division, is strongly committed to promoting a culture of inclusion, diversity, equity, and accessibility. A multitude of actionable efforts are underway to increase IDEA throughout the proposal process. Title: Possible Mechanism(s) in the Photo-Magnetic Production of Enantiomer Excesses Authors: Cooper, G.; Jackson, W.; Thompson, M.; Rios, A. C.; Yeung, K.; Dateo, C. Bibcode: 2022LPICo2678.2843C Altcode: Did early solar system photo-magnetic forces create enantiomer excesses in organic compounds? Title: Outgassing Experiments on Carbonaceous Chondrites and Their Implications for Titan's Secondary Atmosphere Authors: Duncan, T.; Yu, X.; Thompson, M.; Kim, K.; Telus, M.; Joshi, T.; Lederman, D. Bibcode: 2021LPI....52.2664D Altcode: Outgassed organics / Inside Titan / May resupply / The mysterious methane. Title: Pre-Flight Calibration of the Mars 2020 Rover Mastcam Zoom (Mastcam-Z) Multispectral, Stereoscopic Imager Authors: Hayes, Alexander G.; Corlies, P.; Tate, C.; Barrington, M.; Bell, J. F.; Maki, J. N.; Caplinger, M.; Ravine, M.; Kinch, K. M.; Herkenhoff, K.; Horgan, B.; Johnson, J.; Lemmon, M.; Paar, G.; Rice, M. S.; Jensen, E.; Kubacki, T. M.; Cloutis, E.; Deen, R.; Ehlmann, B. L.; Lakdawalla, E.; Sullivan, R.; Winhold, A.; Parkinson, A.; Bailey, Z.; van Beek, J.; Caballo-Perucha, P.; Cisneros, E.; Dixon, D.; Donaldson, C.; Jensen, O. B.; Kuik, J.; Lapo, K.; Magee, A.; Merusi, M.; Mollerup, J.; Scudder, N.; Seeger, C.; Stanish, E.; Starr, M.; Thompson, M.; Turenne, N.; Winchell, K. Bibcode: 2021SSRv..217...29H Altcode: The NASA Perseverance rover Mast Camera Zoom (Mastcam-Z) system is a pair of zoomable, focusable, multi-spectral, and color charge-coupled device (CCD) cameras mounted on top of a 1.7 m Remote Sensing Mast, along with associated electronics and two calibration targets. The cameras contain identical optical assemblies that can range in focal length from 26 mm (25.5∘×19.1∘FOV ) to 110 mm (6.2∘×4.2∘FOV ) and will acquire data at pixel scales of 148-540 μm at a range of 2 m and 7.4-27 cm at 1 km. The cameras are mounted on the rover's mast with a stereo baseline of 24.3 ±0.1 cm and a toe-in angle of 1.17 ±0.03∘ (per camera). Each camera uses a Kodak KAI-2020 CCD with 1600 ×1200 active pixels and an 8 position filter wheel that contains an IR-cutoff filter for color imaging through the detectors' Bayer-pattern filters, a neutral density (ND) solar filter for imaging the sun, and 6 narrow-band geology filters (16 total filters). An associated Digital Electronics Assembly provides command data interfaces to the rover, 11-to-8 bit companding, and JPEG compression capabilities. Herein, we describe pre-flight calibration of the Mastcam-Z instrument and characterize its radiometric and geometric behavior. Between April 26th and May 9th, 2019, ∼45,000 images were acquired during stand-alone calibration at Malin Space Science Systems (MSSS) in San Diego, CA. Additional data were acquired during Assembly Test and Launch Operations (ATLO) at the Jet Propulsion Laboratory and Kennedy Space Center. Results of the radiometric calibration validate a 5% absolute radiometric accuracy when using camera state parameters investigated during testing. When observing using camera state parameters not interrogated during calibration (e.g., non-canonical zoom positions), we conservatively estimate the absolute uncertainty to be <10 % . Image quality, measured via the amplitude of the Modulation Transfer Function (MTF) at Nyquist sampling (0.35 line pairs per pixel), shows MTFNyquist=0.26 -0.50 across all zoom, focus, and filter positions, exceeding the >0.2 design requirement. We discuss lessons learned from calibration and suggest tactical strategies that will optimize the quality of science data acquired during operation at Mars. While most results matched expectations, some surprises were discovered, such as a strong wavelength and temperature dependence on the radiometric coefficients and a scene-dependent dynamic component to the zero-exposure bias frames. Calibration results and derived accuracies were validated using a Geoboard target consisting of well-characterized geologic samples. Title: Methane: the Ideal Biosignature for the JWST Era? Authors: Thompson, M.; Krissansen-Totton, J.; Fortney, J. Bibcode: 2021BAAS...53c1024T Altcode: The next phase of exoplanet science will focus on characterizing exoplanet atmospheres, including those of low-mass, terrestrial planets. A comprehensive understanding of possible biosignatures that may be detected with the next generation of ground and space telescopes is warranted. While some biosignature gases, such as oxygen and phosphine, have recently been reviewed in depth (Meadows et al. 2018 and Sousa-Silva et al. 2020), these will likely be extremely difficult to detect with JWST. In contrast, while it has not been thoroughly reviewed, methane at Earth-like biogenic fluxes is one of the only biosignatures that may be readily detectable with JWST (Krissansen-Totton et al. 2018a). In fact, an early Earth-like, methane-rich atmosphere would be easier to detect with JWST than modern Earth's oxygen-rich atmosphere (ibid). Here we present our preliminary work on a comprehensive review of methane biosignatures and false positives. Biogenic methane production, or methanogenesis, is a simpler metabolism than oxygenic photosynthesis, that is carried out by anaerobic microbes (i.e., those not requiring oxygen for growth). Methanogens use either CO2 and H2 or acetate as substrates (Schwieterman et al. 2018). This process could be widespread due to the likely ubiquity of the CO2+H2 redox couple in terrestrial planet atmospheres, and the antiquity of methanogenesis on Earth (Wolfe and Fournier 2018). We briefly review the current understanding of the origin and evolution of methanogens, the organisms responsible for methanogenesis, and how this process relates to origins-of-life theories. When CH4 is invoked as a possible biosignature it is often included with a strongly oxidizing companion gas (e.g., CO2 or O2/O3). This is because it is difficult to explain abundant CH4 if a terrestrial planet atmosphere's redox state is more oxidizing so that the thermodynamically stable form of carbon would not be CH4 (Schwieterman et al. 2018). However, even in atmospheres devoid of oxygen, CH4 has a short photochemical lifetime on habitable zone rocky planets, and the large fluxes required to sustain high CH4 abundances are likely much greater than could be supplied by abiotic processes (e.g., magmatic outgassing, serpentinization) (Krissansen-Totton et al. 2018b, Wogan et al. 2020). In addition, many abiotic, geological processes that produce CH4 are expected to also produce abundant CO, which life readily consumes, so the presence of CH4 and CO2 but absence of CO strengthens the case for biogenicity (Krissansen-Totton et al. 2018b). Although CH4+CO2 (minus CO) might coexist in thermodynamic equilibrium on planets without large surface oceans (Woitke et al. 2020), in practice, such atmospheres would be photochemically unstable and, in particular, the CH4 would have a short lifetime (less than ~1 Myrs). In addition to briefly discussing methane on Mars and Titan, we review the presence of methane in Jovian and sub-Neptune planet atmospheres. In many giant planets, methane is the most abundant carbon-bearing gas and can be replenished indefinitely because, although methane is photodissociated in the upper atmosphere, hydrogen is never depleted and carbon and hydrogen can recombine deeper in the atmosphere where temperatures and pressures are high enough for methane production to be thermodynamically favorable and kinetically viable (Moses et al. 2013). On the other hand, terrestrial planets with high mean molecular weight atmospheres do not have deep enough atmospheres to replenish methane without an additional source (abiotic or biotic). In terrestrial atmospheres without a replenishment source, methane is photodissociated and hydrogen is lost to space on short timescales (~10s of thousands of years for ~1 bar atmospheres). For planets in the sub-Neptune regime, we seek to determine how much atmosphere is necessary for a planet to sustain methane via thermodynamic recombination against photodissociation. In summary, for terrestrial planets to have methane-rich atmospheres, the methane must be constantly replenished. We explore to what extent abiotic CH4 replenishment is possible based on prior work on abiotic methane sources including water-rock reactions, volcanic outgassing, and impacts (e.g., Etiope & Lollar 2013, Wogan et al. 2020, Kress & McKay 2003). We review methane false positives on terrestrial planets and determine if they are likely to produce methane fluxes as large as those caused by known biogenic sources. Through this comprehensive review, we will develop a framework for identifying methane biosignatures and discuss detectability prospects with JWST. Title: VizieR Online Data Catalog: PGCCs in lambda Orionis complex. II. Cores at 850um (Yi+, 2018) Authors: Yi, H. -W.; Lee, J. -E.; Liu, T.; Kim, K. -T.; Choi, M.; Eden, D.; Evans, N. J., II; di, Francesco J.; Fuller, G.; Hirano, N.; Juvela, M.; Kang, S. -J.; Kim, G.; Koch, P. M.; Lee, C. W.; Li, Di; Liu, H. -Y. B.; Liu, H. -L.; Liu, S. -Y.; Rawlings, M. G.; Ristorcelli, I.; Sanhueza, P.; Soam, A.; Tatematsu, K.; Thompson, M.; Toth, L. V.; Wang, Ke; White, G. J.; Wu, Y.; Yang, Y. -L. Bibcode: 2021yCat..22360051Y Altcode: As part of the legacy survey, "SCUBA-2 Continuum Observations of Pre-protostellar Evolution" (SCOPE; Liu+ 2018ApJS..234...28L and Eden+ 2019MNRAS.485.2895E ; proposal code: M16AL003), we observed 58 Planck Galactic Cold Clumps (PGCCs) in the "CV Daisy" mapping mode, which is suitable for small and compact sources with sizes of less than 3' at 450 and 850um with the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) at the 15m James Clerk Maxwell Telescope (JCMT).

We also included archival data of 38 PGCCs located in the Orion A and B clouds from the JCMT Science Archive hosted by the Canadian Astronomical Data Centre (CADC).

Table 1 lists information about the 96 PGCCs.

We also included data from the Wide-Field Infrared Survey Explorer (WISE) AllWISE catalog (Wright+ 2010, see II/328).

Finally, we obtained 119 cores within the 40 detected PGCCs in the Orion complex. In the λ Orionis cloud, there are 8 detected PGCCs, from which 15 cores are identified. The Orion A cloud has 74 cores in 23 PGCCs, and the Orion B cloud has 30 cores in 9 PGCCs. The list of cores in each cloud is found in Tables 2-4.

(4 data files). Title: Outgassing Experiments on Carbonaceous Chondrites to Understand the Formation of Titan's Atmosphere Authors: Duncan, T.; Yu, X.; Thompson, M.; Kim, K. Bibcode: 2020AGUFMP071...08D Altcode: Titan is the only known moon in the Solar System with a substantial atmosphere of N 2 and CH 4 , however, its origin and evolution are not well understood. Titan's present amount of atmospheric CH 4 was predicted to be destroyed photochemically on very short timescales compared to the age of the Solar System suggesting a resupply mechanism is necessary [1]. Cassini provided new insight into the origin of Titan's atmosphere by measuring abundances of primordial noble gases and found that instead of being incorporated during formation, Titan's atmosphere is likely linked to its interior [2][3]. Recent theoretical modeling of Titan's atmosphere and interior [4][5] suggests that its atmosphere could have originated in part by outgassing of primordial organics in its interior. Insoluble organic matter (IOM) found in carbonaceous chondrites may serve as an analog for the organic material in Titan's interior and provide experimental constraints on the outgassed component of its atmosphere. Therefore, outgassing experiments on carbonaceous chondrites can help inform how Titan obtained its secondary atmosphere, and in particular reveal a possible source for Titan's atmospheric CH 4 . By heating primitive meteorite samples and measuring the abundances of their released volatiles, we may be able to connect what we see in the lab to species in Titan's atmosphere today. In this study, we use samples of Murchison, a CM carbonaceous chondrite, which contains substantial amounts of insoluble organic matter (IOM).We heated 3 mg of powdered (20-100 µm and <20 µm) Murchison samples from room temperature to 1200° C in a furnace and continuously monitored 10 outgassed volatile species with a Residual Gas Analyzer (RGA). We plan to conduct additional experiments with other primitive meteorites and their extracted IOM to further investigate the link between outgassing of primitive materials and the origin of Titan's atmosphere.

Yung, Y. L., et al. 1984 , Astrophys. J. , 55, 465

Niemann, H. B., et al. 2005, Nature, 438, 779

Niemann, H. B., et al. 2010, J. Geophys. Res. , 115, 65

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Neri, A., et al. 2019, Earth Planet. Sci. Letts , 530, 6 Title: Carbonaceous Chondrite Outgassing Experiments to Constrain the Formation of Titan's Atmosphere Authors: Kim, K.; Thompson, M.; Yu, X.; Duncan, T.; Telus, M.; Joshi, T.; Lederman, D. Bibcode: 2020DPS....5221803K Altcode: The origin of Titan's thick N2 and CH4 dominated atmosphere is an outstanding puzzle in planetary science. Photochemical models predict that Titan's current atmospheric methane would be quickly destroyed by photolysis in ~30 million years [1], suggesting a possible need for a mechanism to replenish the methane [2]. One potential mechanism has been linked to the interior composition and structure of Titan, and to better understand this question of methane persistence in the atmosphere, we turn to Titan's atmospheric formation [3]. Titan's atmosphere may have been produced in part from interior outgassing with evidence coming from the detection of outgassed 40Ar, a radiogenic decay product of 40K, that was detected by the Huygens Gas Chromatograph and Mass Spectrometer [4]. Recent studies suggest that organic material similar to the refractory organics found in comets may be a necessary component of Titan's interior, and outgassing of such material could provide significant amounts of N2 and CH4 to replenish Titan's atmosphere [5][6]. For this study, we analyze carbonaceous (CM) chondrites because they contain insoluble organic matter (IOM), which is similar to cometary refractory organics and may serve as an analog to part of the interior material of Titan. In particular, we studied samples from the Murchison meteorite because it is a pristine CM carbonaceous chondrite fall with a significant IOM component. We performed a suite of stepped heating experiments that will help place experimental constraints on the amounts of outgassed carbon and nitrogen compounds from CM chondrites to help inform the outgassed origin and composition of Titan's atmosphere. We performed these experiments on powdered Murchison samples with two grain size distributions, one including grains between 20-100 microns in diameter and the other with grain diameters <20 microns. We present the results of our stepped heating experiments in which we heated these powdered samples up to 1200 C in a furnace connected to a residual gas analyzer (RGA) that continuously monitored the partial pressures of 10 different outgassed species (e.g., C, CO, CO2, CH4, N, N2). By measuring the abundances of outgassed volatiles, we compare our results to prior experimental work on IOM from carbonaceous chondrites and discuss how these experiments will inform the outgassing origin and composition of Titan's atmosphere.

1: Yung, Y. L., et al. 1984. ApJ., 55. ; 2: Hörst, S. M. 2017. J. Gphys Res., 122. ; 3: Nixon, C., et al, 2018. Pl. Sp. Sci., 155. ; 4: Niemann, H.B., et al. 2005. Nat. 438. ; 5: Miller, K. E., et al. 2019. ApJ., 871. ; 6: Néri, A., et al. 2019. E. Pl. Sci Lts, 530. Title: VizieR Online Data Catalog: Abundances of Gaia DR2 wide binaries (Hawkins+, 2020) Authors: Hawkins, K.; Lucey, M.; Ting, Y. -S.; Ji, A.; Katzberg, D.; Thompson, M.; El-Badry, K.; Teske, J.; Nelson, T.; Carrillo, A. Bibcode: 2020yCat..74921164H Altcode: Stellar parameters and abundances for 50 stars in 25 wide binaries observed with McDonald Observatory in 2019.

(3 data files). Title: VizieR Online Data Catalog: SCUBA-2 Ambitious Sky Survey (Nettke+, 2017) Authors: Nettke, W.; Scott, D.; Gibb, A. G.; Thompson, M.; Chrysostomou, A.; Evans, A.; Hill, T.; Jenness, T.; Joncas, G.; Moore, T.; Serjeant, S.; Urquhart, J.; Vaccari, M.; Weferling, B.; White, G.; Zhu, M. Bibcode: 2020yCat..74680250N Altcode: This beam-sized source catalogue is based on scans of Scuba-2 imagery obtained between 2012 May 15 and 2014 May 12 using the James Clerk Maxwell Telescope. There are three catalogues as well as one PDF file which details a source comparison of samples from each catalogue.

(4 data files). Title: Assessing the Threat of Major Outbreaks of Vector-Borne Diseases Under a Changing Climate Authors: Thompson, R. N.; Thompson, M. J.; Hurrell, J. W.; Sun, L.; Obolski, U. Bibcode: 2020ASSP...57...25T Altcode: Michael J. Thompson served as the Director of the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, where he was also a Senior Scientist. In September 2013, Michael became the Deputy Director and Chief Operating Officer of NCAR, enjoying a very close working relationship with Director Jim Hurrell. During this time, Michael oversaw an organisation conducting research in a range of fields, including his own topics of solar and stellar physics, as well as others such as atmospheric chemistry and climate science. At the same time, his son Robin was completing a PhD in mathematical epidemiology at the University of Cambridge, UK, after which he was awarded an independent Junior Research Fellowship at the University of Oxford. However, the work conducted at NCAR and Robin's research have more overlap than might at first be expected. Here we present results from a collaboration that was set up following Michael's untimely death in October 2018, between climate scientists (Jim Hurrell and Lantao Sun) and mathematical epidemiologists (Robin Thompson and Uri Obolski). Specifically, we propose a framework for studying the effect of climate variability and change on vector-borne disease risk. We introduce a new quantity—the Instantaneous Outbreak Risk (IOR)—which quantifies the risk posed by an invading pathogen accounting for the climatic conditions when that pathogen enters the population. We show how the IOR can be used to assess the threat from vector-borne diseases under a changing climate. Title: The Impact of a Fossil Magnetic Field on Dipolar Mixed-Mode Frequencies in Sub- and Red-Giant Stars Authors: Bugnet, L.; Prat, V.; Mathis, S.; García, R. A.; Mathur, S.; Augustson, K.; Neiner, C.; Thompson, M. J. Bibcode: 2020ASSP...57..251B Altcode: 2020arXiv201208684B The recent discovery of low-amplitude dipolar oscillation mixed modes in massive red giants indicates the presence of a missing physical process inside their cores. Stars more massive than ∼ 1.3 M⊙ are known to develop a convective core during the main-sequence: the dynamo process triggered by this convection could be the origin of a strong magnetic field inside the core of the star, trapped when it becomes stably stratified and for the rest of its evolution. The presence of highly magnetized white dwarfs strengthens the hypothesis of buried fossil magnetic fields inside the core of evolved low-mass stars. If such a fossil field exists, it should affect the mixed modes of red giants as they are sensitive to processes affecting the deepest layers of these stars. The impact of a magnetic field on dipolar oscillations modes was one of Pr. Michael J. Thompson's research topics during the 90s when preparing the helioseismic SoHO space mission. As the detection of gravity modes in the Sun is still controversial, the investigation of the solar oscillation modes did not provide any hint of the existence of a magnetic field in the solar radiative core. Today we have access to the core of evolved stars thanks to the asteroseismic observation of mixed modes from CoRoT, Kepler, K2 and TESS missions. The idea of applying and generalizing the work done for the Sun came from discussions with Pr. Michael Thompson in early 2018 before we lost him. Following the path we drew together, we theoretically investigate the effect of a stable axisymmetric mixed poloidal and toroidal magnetic field, aligned with the rotation axis of the star, on the mixed modes frequencies of a typical evolved low-mass star. This enables us to estimate the magnetic perturbations to the eigenfrequencies of mixed dipolar modes, depending on the magnetic field strength and the evolutionary state of the star. We conclude that strong magnetic fields of ∼ 1MG should perturb the mixed-mode frequency pattern enough for its effects to be detectable inside current asteroseismic data. Title: On the Limits of Seismic Inversions for Radial Differential Rotation of Solar-Type Stars Authors: Santos, Ângela R. G.; Mathur, Savita; García, Rafael A.; Thompson, Michael J. Bibcode: 2020ASSP...57..269S Altcode: Seismic data contains information on stellar internal rotation, which plays an important role on dynamo models. Due to the uncertainties on the observations and stellar models, determining internal rotation of main-sequence solar-type stars has been challenging. Here, we use artificial rotational splittings for two-zone profiles to explore the limitations to constrain internal rotation profiles. Title: Meteorite Outgassing Experiments to Inform Chemical Abundances of Super-Earth Atmospheres Authors: Thompson, M.; Fortney, J. J.; Telus, M.; Lederman, D.; Joshi, T. Bibcode: 2019AGUFM.P23B3487T Altcode: At present, there is no first­ principles understanding of how to connect a terrestrial planet's bulk composition to its atmospheric properties. Since terrestrial exoplanets likely form their atmospheres through degassing (Elkins­-Tanton & Seager 2008), a logical first step to build such a theory for super­Earths is to assay meteorites, the left­over building blocks of planets, by heating them to measure the outgassed volatiles. Our Solar System presents a wide variety of meteorite types, including chondrites which are primitive unaltered rocks believed to be representative of the material that formed the rocky planets. We present the current results of our meteorite outgassing experiments in which we heated a variety of chondritic meteorite samples, at carefully controlled rates to temperatures from 200 to 1200 °C and measured the partial pressures and relative abundances of the outgassed volatile species (e.g., CO2, H2O, CH4, H2, O2, S, Na) as a function of temperature and time. Our experimental set­up consisted of a residual gas analyzer connected to a furnace to heat samples at specified rates. We compare the results of these experiments to Schaefer and Fegley's prior theoretical chemical equilibrium and kinetics calculations which modeled thermal outgassing for a wide variety of chondrites to predict the composition of terrestrial atmospheres formed via outgassing of specific types of meteorites (Schaefer & Fegley 2007, Schaefer & Fegley 2010). In addition to testing and validating Schaefer and Fegley's models, the results from our experiments inform the phase space of chemical abundances used in atmospheric models of super­Earth exoplanets. Title: Overview of the Search for Space Weathering Signals on the Surface of Bennu: One Rock Type, or Two? Authors: Clark, B. E.; Ferrone, S. M.; Kaplan, H. H.; Zou, X. -D.; Trang, D.; DellaGiustina, D. N.; LeCorre, L.; Golish, D. R.; Li, J. -Y.; Ballouz, R. -L.; Hergenrother, C. W.; Rizk, B.; Burke, K. N.; Bennett, C. A.; Keller, L.; Howell, E. S.; Lantz, C.; Barucci, M. A.; Fornasier, S.; Thompson, M.; Michel, P.; Molaro, J.; Jawin, E. R.; Delbo, M.; Simon, A.; Reuter, D.; Pajola, M.; Lauretta, D. S. Bibcode: 2019LPICo2189.2125C Altcode: We provide an overview of the evidence for space weathering on asteroid (101955) Bennu, and summarize relevant findings from several ongoing parallel studies of surface processes and surface properties. Title: Lightcurve Analysis and Rotation Period of 6372 Walker Authors: Hayes-Gehrke, Melissa N.; Berk, Marley; Fatodu, Abisola; Kanani, Bhargin; Kropschot, Quinn; Marks, Julia; Misangyi, Ella; Nguyen, Matthew; Stone, Julie; Suniga, Joshua; Thompson, Michael; Vorsteg, Matthew; Wagman, Timothy; Marchini, Alessandro; Banfi, Massimo; Papini, Riccardo; Salvaggio, Fabio; Brincat, Stephen M.; Galdies, Charles; Winston Grech Bibcode: 2019MPBu...46..388H Altcode: From 2019 March-May, images of minor planet 6372 Walker were captured to investigate its rotation period. Our analysis found a period of 44.25 ±0.01 h. Title: VizieR Online Data Catalog: Radio observations of G074.11+00.11 (Saajasto+, 2019) Authors: Saajasto, M.; Harju, J.; Juvela, M.; Tie, L.; Zhang, Q.; Liu, S. -Y.; Hirano, N.; Wu, Y.; Kim, K. -T.; Tatematsu, K.; Wang, K.; Thompson, M. Bibcode: 2019yCat..36300069S Altcode: This catalogue contains the radio observations of a cold clump G074.11+00.11. The catalogue contains all of the observed molecular lines, however, please note that not all of the observed molecules were detected. The included data has been obtained from several telescopes: Purple Mountain Observatory (PMO), Korean Very Long Baseline Interferometry Network (KVN), the Submillimeter Telescope (SMT), and the Submillimeter Array (SMA). For a more detailed description of the data, velocity resolutions etc. please see the Section 2, Observations of the main paper and the references therein.

(24 data files). Title: Space Weathering of Carbonaceous Asteroids and Meteorites Authors: Loeffler, M. J.; Thompson, M.; Keller, L. P. Bibcode: 2018AGUFM.P21D3381L Altcode: It is well known that solar wind particles and micrometeorite impacts alter the surface regolith of airless bodies, such as the Moon and asteroids. On the scale of the regolith grains, these alterations are manifested through physical and chemical changes of the outer layers, which can be due to a combination of direct irradiation or redeposition of material evaporated during irradiation. Laboratory studies focusing on simulating lunar- and asteroid-type space weathering in iron-bearing minerals have been relatively successful at showing that much of the changes in optical properties (spectral reddening and darkening in the visible-near-infrared region) are driven by the formation of chemically reduced iron produced through either solar wind bombardment or micrometeorite impacts. However, a similar correlation has not yet been made for carbonaceous asteroids and meteorites, as laboratory experiments have shown a variety of trends, suggesting that weathering in these types of minerals may be more complicated. Thus, we have begun a systematic study where we are looking at space weathering in diagnostic minerals found in carbonaceous asteroids and meteorites, focusing on how the optical, structural and chemical properties of these minerals' components are altered by ion and laser irradiation. Here we present some of our most recent results on effects that micrometeorite impacts, simulated with a pulsed laser, has on sulfide minerals, using the our new ultra-high vacuum system at Northern Arizona University. Title: Solar Physics from Unconventional Viewpoints Authors: Gibson, Sarah E.; Vourlidas, Angelos; Hassler, Donald M.; Rachmeler, Laurel A.; Thompson, Michael J.; Newmark, Jeffrey; Velli, Marco; Title, Alan; McIntosh, Scott W. Bibcode: 2018FrASS...5...32G Altcode: 2018arXiv180509452G We explore new opportunities for solar physics that could be realized by future missions providing sustained observations from vantage points away from the Sun-Earth line. These include observations from the far side of the Sun, at high latitudes including over the solar poles, or from near-quadrature angles relative to the Earth (e.g., the Sun-Earth L4 and L5 Lagrangian points). Such observations fill known holes in our scientific understanding of the three-dimensional, time-evolving Sun and heliosphere, and have the potential to open new frontiers through discoveries enabled by novel viewpoints. Title: The Coronal Solar Magnetism Observatory Authors: Thompson, Michael J.; Tomczyk, Steven; Gibson, Sarah E.; McIntosh, Scott W.; Landi, Enrico Bibcode: 2018IAUS..335..359T Altcode: The Coronal Solar Magnetism Observatory (CoSMO) is a proposed new facility led by the High Altitude Observatory and a consortium of partners to measure magnetic field and plasma properties in a large (one degree) field of view extending down to the inner parts of the solar corona. CoSMO is intended as a research facility that will advance the understanding and prediction of space weather. The instrumentation elements of CoSMO are: a white-light coronagraph (KCor), already operational at the Mauna Loa Solar Observatory (MLSO); the Chromosphere and Prominence Magnetometer (ChroMag), due for deployment to MLSO next year; and the CoSMO Large Coronagraph (LC) which has completed Preliminary Design Review. Title: Design of a next generation synoptic solar observing network: solar physics research integrated network group (SPRING) Authors: Gosain, Sanjay; Roth, Markus; Hill, Frank; Pevtsov, Alexei; Martinez Pillet, Valentin; Thompson, Michael J. Bibcode: 2018SPIE10702E..4HG Altcode: Long-term synoptic observations of the Sun in different wavelength regions are essential to understand its secular behavior. Such observations have proven very important for discovery of 11 year solar activity cycle, 22 year magnetic cycle, polar field reversals, Hale's polarity law, Joy's law, that helped Babcock and Leighton to propose famous solar dynamo model. In more recent decades, the societal impact of the secular changes in Sun's output has been felt in terms of solar inputs to terrestrial climate-change and space-weather hazards. Further, it has been realized that to better understand the activity phenomena such as flares and coronal mass ejections (CMEs) one needs synoptic observations in multiple spectral lines to enable tomographic inference of physical parameters. Currently, there are both space and ground based synoptic observatories. However, given the requirements for the long-term stability and reliability of such synoptic datasets, ground-based facilities are more preferable. Also, the ground based observatories are easy to maintain or upgrade while detailed and frequent calibrations are easily possible. The only ground-based facility that currently provides full-disk velocity and magnetic field maps of the Sun around the clock and at good cadence, is the Global Oscillations Network Group (GONG) network of National Solar Observatory (NSO) which is operational since the mid 90s. Due to its aging instrumentation, operating for nearly three decades, and new requirements to obtain multiwavelength observations, a need is felt in the solar community to build a next generation synoptic observatory network. A group of international observatories have come together under the auspices of SOLARNET program, funded by European Union (EU), to carryout a preliminary design study of such a synoptic solar observing facility called "SPRING", which stands for Solar Physics Research Integrated Network Group. In this article we will present concept of SPRING and the optical design concept of its major instruments.ts. Title: Signatures of Solar Cycle 25 in Subsurface Zonal Flows Authors: Howe, R.; Hill, F.; Komm, R.; Chaplin, W. J.; Elsworth, Y.; Davies, G. R.; Schou, J.; Thompson, M. J. Bibcode: 2018ApJ...862L...5H Altcode: 2018arXiv180702398H The pattern of migrating zonal flow bands associated with the solar cycle, known as the torsional oscillation, has been monitored with continuous global helioseismic observations by the Global Oscillations Network Group (GONG), together with those made by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) and its successor, the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), since 1995, giving us nearly two full solar cycles of observations. We report that the flows now show traces of the mid-latitude acceleration that is expected to become the main equatorward-moving branch of the zonal flow pattern for Cycle 25. Based on the current position of this branch, we speculate that the onset of widespread activity for Cycle 25 is unlikely to be earlier than the middle of 2019. Title: Solar Observations Away from the Sun-Earth Line Authors: Gibson, Sarah E.; McIntosh, Scott William; Rachmeler, Laurel; Thompson, Michael J.; Title, Alan M.; Velli, Marco C. M.; Vourlidas, Angelos Bibcode: 2018tess.conf40340G Altcode: Observations from satellite missions have transformed the field of solar physics. High-resolution observations with near-continuous temporal coverage have greatly extended our capability for studying long-term and transient phenomena, and the opening of new regions of the solar spectrum has made detailed investigation of the solar atmosphere possible.

However, to date most solar space-based missions have been restricted to an observational vantage in the vicinity of the Sun-Earth line, either in orbit around the Earth or from the L1 Lagrangian point. As a result, observations from these satellites represent the same geometrical view of the Sun that is accessible from the Earth.

Understanding the deep interior structure of the Sun and the full development of solar activity would really benefit from fully three-dimensional monitoring of the solar atmosphere and heliosphere. On the one hand, simultaneous spacecraft observations from multiple vantage points would allow studies of the deep interior structure of the sun via stereoscopic helioseismology; on the other, distributed observations would allow the understanding of the complete evolution of activity complexes and enhance space weather predictions dramatically.

Presently, observations of the Sun away from Earth are obtained by the STEREO pair of satellites, which have provided an unprecedented global view by orbiting around to the far side of the Sun, and the Ulysses mission, which achieved a high-inclination (80˚) near-polar orbit (but which, however, did not include any solar imaging instruments). The forthcoming Solar Orbiter mission, which will orbit the sun and reach a maximum inclination of 34˚ out of the ecliptic should provide the first detailed mapping of the sun's polar fields. In addition, Solar Probe Plus will explore the outer corona and inner Heliosphere with very rapid solar encounters at a minimum perihelion 9.86 solar radii from the center of the Sun.

We explore some of the new opportunities for solar physics that can be realized by future missions that provide sustained observations from vantage points away from the Sun-Earth line (and in some cases the ecliptic plane): observations from the far side of the Sun, over its poles, or from the L5 Lagrangian point. Title: Flyby and Impact of Chariklo: A New Frontiers Class Centaur Reconnaissance Mission Concept from the 2017 NASA-JPL Planetary Science Summer Seminar Authors: Bouchard, M. C.; Howell, S. M.; Chou, L.; Thompson, M.; Cusson, S.; Marcus, M.; Brodsky Smith, H.; Bhattaru, S.; Balock, J. J.; Brueshaber, S.; Eggl, S.; Jawin, E. R.; Miller, K. E.; Rizzo, M.; Steakley, K.; Thomas, N. H.; Trent, K.; Ugelow, M.; Budney, C. J.; Mitchell, K. L. Bibcode: 2018LPI....49.2087B Altcode: This abstract summarizes a New Frontiers mission concept to the Centaur Chariklo that was created during the 2017 NASA/JPL Planetary Science Summer Seminar. Title: Solar Magnetic Fields Authors: Balogh, André; Cliver, Edward; Petrie, Gordon; Solanki, Sami; Thompson, Michael; von Steiger, Rudolf Bibcode: 2018smf..book.....B Altcode: No abstract at ADS Title: The Life Cycle of Active Region Magnetic Fields Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet, V.; Thompson, M. J. Bibcode: 2018smf..book..317C Altcode: No abstract at ADS Title: The Life Cycle of Active Region Magnetic Fields Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet, V.; Thompson, M. J. Bibcode: 2017SSRv..210..317C Altcode: 2016SSRv..tmp...46C We present a contemporary view of how solar active region magnetic fields are understood to be generated, transported and dispersed. Empirical trends of active region properties that guide model development are discussed. Physical principles considered important for active region evolution are introduced and advances in modeling are reviewed. Title: Prospects and Challenges for Helioseismology Authors: Toomre, J.; Thompson, M. J. Bibcode: 2017hdsi.book....7T Altcode: No abstract at ADS Title: Helioseismology and Dynamics of the Solar Interior Authors: Thompson, M. J.; Brun, A. S.; Culhane, J. L.; Gizon, L.; Roth, M.; Sekii, T. Bibcode: 2017hdsi.book.....T Altcode: No abstract at ADS Title: Preface: Helioseismology and Dynamics of the Solar Interior Authors: Gizon, Laurent; Thompson, Michael J.; Brun, A. Sacha; Culhane, J. Len; Roth, Markus; Sekii, Takashi Bibcode: 2017hdsi.book....1G Altcode: No abstract at ADS Title: Solar Dynamics, Rotation, Convection and Overshoot Authors: Hanasoge, S.; Miesch, M. S.; Roth, M.; Schou, J.; Schüssler, M.; Thompson, M. J. Bibcode: 2017hdsi.book...85H Altcode: No abstract at ADS Title: MeerGAL: the MeerKAT Galactic Plane Survey Authors: Thompson, M.; Goedhart, S.; Goedhart, S.; Benaglia, P.; Beuther, H.; Blomme, R.; Chrysostomou, A. C.; Clark, J. S.; Dickinson, C.; Ellingsen, S.; Fenech, D.; Hindson, L.; Longmore, S. N.; van Langevelde, H. J.; MacLeod, G.; Molinari, S.; Prinja, R.; Purcell, C. R.; Stevens, I.; Umana, G.; Urquhart, J. S.; Vlemmings, W.; Walsh, A. J.; Yang, A. Y.; Zijlstra, A. Bibcode: 2016mks..confE..15T Altcode: 2016PoS...277E..15T No abstract at ADS Title: Solar Dynamics, Rotation, Convection and Overshoot Authors: Hanasoge, S.; Miesch, M. S.; Roth, M.; Schou, J.; Schüssler, M.; Thompson, M. J. Bibcode: 2015SSRv..196...79H Altcode: 2015SSRv..tmp...24H; 2015arXiv150308539H We discuss recent observational, theoretical and modeling progress made in understanding the Sun's internal dynamics, including its rotation, meridional flow, convection and overshoot. Over the past few decades, substantial theoretical and observational effort has gone into appreciating these aspects of solar dynamics. A review of these observations, related helioseismic methodology and inference and computational results in relation to these problems is undertaken here. Title: Prospects and Challenges for Helioseismology Authors: Toomre, J.; Thompson, M. J. Bibcode: 2015SSRv..196....1T Altcode: 2015SSRv..tmp...22T Helioseismology has advanced considerably our knowledge of the interior of the Sun over the past three decades. Our understanding of the Sun's internal structure, its dynamics, rotation, convection and magnetism, have all been advanced. Yet there are challenges, areas where the results from helioseismology are tantalizing but inconclusive, and aspects where the interpretation of the data has still to be put on a firm footing. In this paper we shall focus on a number of those challenges and give our assessment of where progress needs to be made in the next decade. Title: A helioseismic view of the Sun's internal structure and dynamics Authors: Basu, S.; Thompson, M. J. Bibcode: 2015exse.book..170B Altcode: No abstract at ADS Title: Temporal evolution of the solar torsional oscillation and implications for cycle 25 Authors: Hill, Frank; Howe, Rachel; Komm, Rudolf; Schou, Jesper; Thompson, Michael; Larson, Timothy Bibcode: 2015TESS....110502H Altcode: The zonal flow known as the torsional oscillation has been observed on the Sun’s surface since 1980 and in its interior since 1995. It has two branches that migrate during the solar cycle, with one moving towards the equator and the other towards the poles. The rate at which these branches migrate in latitude is tightly correlated with the timing of the solar cycle, as seen during the long minimum between cycles 23 and 24. The poleward branch generally becomes visible 10 to 12 years before the appearance of the magnetic activity associated with the corresponding sunspot cycle as it did for the current cycle 24. However, the poleward flow for cycle 25, which was expected to appear in 2008-2010, was not observed. Subsequent analysis showed that it is a very weak flow, and is masked by an apparent change in the background solar differential rotation rate. We will present the latest observations of the zonal flow as determined from global helioseismology, and will discuss the implications for the strength and timing of cycle 25. Title: SKA tomography of Galactic star-forming regions and spiral arms Authors: Loinard, L.; Thompson, M.; Hoare, M.; van Langevelde, H. J.; Ellingsen, S.; Brunthaler, A.; Forbrich, J.; Rygl, K.; Rodríguez, L. F.; Mioduszewski, A. J.; Torres-López, R. M.; Dzib, S. A.; Ortiz-León, G. N.; Bourke, T.; Green, J. A. Bibcode: 2015aska.confE.166L Altcode: 2015PoS...215E.166L No abstract at ADS Title: The ionised,radical and molecular Milky Way: spectroscopic surveys with the SKA Authors: Thompson, M.; Beuther, H.; Dickinson, C.; MOttram, J.; Klaassen, P.; Ginsburg, A.; Longmore, S.; Remijan, A.; Menten, K. M. Bibcode: 2015aska.confE.126T Altcode: 2014arXiv1412.5554T; 2015PoS...215E.126T The bandwith, sensitivity and sheer survey speed of the SKA offers unique potential for deep spectroscopic surveys of the Milky Way. Within the frequency bands available to the SKA lie many transitions that trace the ionised, radical and molecular components of the interstellar medium and which will revolutionise our understanding of many physical processes. In this chapter we describe the impact on our understanding of the Milky Way that can be achieved by spectroscopic SKA surveys, including "out of the box" early science with radio recombination lines, Phase 1 surveys of the molecular ISM using anomalous formaldehyde absorption, and full SKA surveys of ammonia inversion lines. Title: The impact of SKA on Galactic Radioastronomy: continuum observations Authors: Umana, G.; Trigilio, C.; Cerrigone, L.; Cesaroni, R.; Zijlstra, A. A.; Hoare, M.; Weis, K.; Beasley, A.; Bomans, D.; Hallinan, G.; Molinari, S.; Taylor, R.; Testi, L.; Thompson, M. Bibcode: 2015aska.confE.118U Altcode: 2014arXiv1412.5833U; 2015PoS...215E.118U The SKA will be a state of the art radiotelescope optimized for both large area surveys as well as for deep pointed observations. In this paper we analyze the impact that the SKA will have on Galactic studies, starting from the immense legacy value of the all-sky survey proposed by the continuum SWG but also presenting some areas of Galactic Science that particularly benefit from SKA observations both surveys and pointed. The planned all-sky survey will be characterized by unique spatial resolution, sensitivity and survey speed, providing us with a wide-field atlas of the Galactic continuum emission. Synergies with existing, current and planned radio Galactic Plane surveys will be discussed. SKA will give the opportunity to create a sensitive catalog of discrete Galactic radio sources, most of them representing the interaction of stars at various stages of their evolution with the environment: complete census of all stage of HII regions evolution; complete census of late stages of stellar evolution such as PNe and SNRs; detection of stellar winds, thermal jets, Symbiotic systems, Chemically Peculiar and dMe stars, active binary systems in both flaring and quiescent states. Coherent emission events like Cyclotron Maser in the magnetospheres of different classes of stars can be detected. Pointed, deep observations will allow new insights into the physics of the coronae and plasma processes in active stellar systems and single stars, enabling the detection of flaring activity in larger stellar population for a better comprehension of the mechanism of energy release in the atmospheres of stars with different masses and age. Title: GONG, Helioseismology, and the Sun's internal dynamics Authors: Thompson, Michael Bibcode: 2015TESS....121401T Altcode: GONG has made remarkable contributions to the development of helioseismology and our understanding of the solar interior. Even before GONG produced any data, the teams of community scientists formed under the auspices of the GONG project led to significant advances in helioseismology, for example the development of helioseismic inversion techniques. Once the network became operational and the first observations started coming in, GONG data revealed as never before the Sun's internal dynamics, in particular the solar internal rotation. In this talk I shall review GONG's contribution to helioseismology and the helioseismic results from the project. Title: Very low-luminosity Class I/Flat outflow sources in sigma Orionis: Clues to alternative formation mechanisms for very low-mass stars Authors: Riaz, Basmah; Whelan, E.; Thompson, M.; Vorobyov, E.; Lodieu, N. Bibcode: 2015AAS...22544907R Altcode: We present an optical through sub-millimetre multi-wavelength study of two very low-luminosity Class I/Flat systems, Mayrit 1701117 and Mayrit 1082188, in the sigma Orionis cluster. We performed moderate resolution (R 1000) optical ( 0.4-0.9mu) spectroscopy with the TWIN spectrograph at the Calar Alto 3.5-m telescope. The spectra for both sources show prominent emission in accretion- and outflow-associated lines. The mean accretion rate measured from multiple line diagnostics is 6.4x10^{-10} Msun/yr for Mayrit 1701117, and 2.5x10^{-10} Msun/yr for Mayrit 1082188. The outflow mass loss rates for the two systems are similar and estimated to be 1x10^{-9} Msun/yr. The activity rates are within the range observed for low-mass Class I protostars. We obtained sub-millimetre continuum observations with the Submillimetre Common-User Bolometer Array (SCUBA-2) bolometer at the James Clerk Maxwell Telescope. Both objects are detected at a >5-sigma level in the SCUBA-2 850mu band. The bolometric luminosity of the targets as measured from the observed spectral energy distribution over 0.8-850mu is 0.18+/-0.04 Lsun for Mayrit 1701117, and 0.16+/-0.03 Lsun for Mayrit 1082188, and is in the very low-mass range. The total dust+gas mass derived from sub-millimetre fluxes is 36 M_Jup and 22 M_Jup for Mayrit 1701117 and Mayrit 1082188, respectively. There is the possibility that some of the envelope material might be dissipated by the strong outflows driven by these sources, resulting in a final mass of the system close to or below the sub-stellar limit. Given the membership of these objects in a relatively evolved cluster of 3 Myr of age, we consider an alternate formation mechanism in the context of the `hybrid' model of disk fragmentation, followed by ejection of a gaseous clump. Title: The Sun's Interior Structure and Dynamics, and the Solar Cycle Authors: Broomhall, A. -M.; Chatterjee, P.; Howe, R.; Norton, A. A.; Thompson, M. J. Bibcode: 2015sac..book..191B Altcode: No abstract at ADS Title: Very low-luminosity Class I/flat outflow sources in σ Orionis Authors: Riaz, B.; Thompson, M.; Whelan, E. T.; Lodieu, N. Bibcode: 2015MNRAS.446.2550R Altcode: 2014arXiv1410.3377R We present an optical to submillimetre multiwavelength study of two very low-luminosity Class I/flat systems, Mayrit 1701117 and Mayrit 1082188, in the σ Orionis cluster. We performed moderate-resolution (R ∼ 1000) optical (∼0.4-0.9 μm) spectroscopy with the Cassegrain Twin Spectrograph (TWIN) spectrograph at the Calar Alto 3.5-m telescope. The spectra for both sources show prominent emission in accretion- and outflow-associated lines. The mean accretion rate measured from multiple line diagnostics is 6.4 × 10-10 M⊙ yr-1 for Mayrit 1701117 and 2.5 × 10-10 M⊙ yr-1 for Mayrit 1082188. The outflow mass-loss rates for the two systems are similar and estimated to be ∼1 × 10-9 M⊙ yr-1. The activity rates are within the range observed for low-mass Class I protostars. We obtained submillimetre continuum observations with the Submillimetre Common-User Bolometer Array (SCUBA-2) bolometer at the James Clerk Maxwell Telescope. Both objects are detected at a ≥5σ level in the SCUBA-2 850-μm band. The bolometric luminosity of the targets as measured from the observed spectral energy distribution over ∼0.8-850 μm is 0.18 ± 0.04 L⊙ for Mayrit 1701117 and 0.16 ± 0.03 L⊙ for Mayrit 1082188 and is in the very low mass range. The total dust+gas mass derived from submillimetre fluxes is ∼36 MJup and ∼22 MJup for Mayrit 1701117 and Mayrit 1082188, respectively. There is the possibility that some of the envelope material might be dissipated by the strong outflows driven by these sources, resulting in a final mass of the system close to or below the substellar limit. Title: The Sun's Interior Structure and Dynamics, and the Solar Cycle Authors: Broomhall, A. -M.; Chatterjee, P.; Howe, R.; Norton, A. A.; Thompson, M. J. Bibcode: 2014SSRv..186..191B Altcode: 2014arXiv1411.5941B The Sun's internal structure and dynamics can be studied with helioseismology, which uses the Sun's natural acoustic oscillations to build up a profile of the solar interior. We discuss how solar acoustic oscillations are affected by the Sun's magnetic field. Careful observations of these effects can be inverted to determine the variations in the structure and dynamics of the Sun's interior as the solar cycle progresses. Observed variations in the structure and dynamics can then be used to inform models of the solar dynamo, which are crucial to our understanding of how the Sun's magnetic field is generated and maintained. Title: Deciphering Solar Magnetic Activity. I. On the Relationship between the Sunspot Cycle and the Evolution of Small Magnetic Features Authors: McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Davey, Alisdair R.; Howe, Rachel; Krista, Larisza D.; Malanushenko, Anna V.; Markel, Robert S.; Cirtain, Jonathan W.; Gurman, Joseph B.; Pesnell, William D.; Thompson, Michael J. Bibcode: 2014ApJ...792...12M Altcode: 2014arXiv1403.3071M Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ~22 yr. The principal variation of sunspots, an ~11 yr variation, modulates the amount of the magnetic field that pierces the solar surface and drives significant variations in our star's radiative, particulate, and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11 yr sunspot variation is intrinsically tied to the spatio-temporal overlap of the activity bands belonging to the 22 yr magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints and the magnetic scale on which they appear to form, we show that the landmarks of sunspot cycle 23 can be explained by considering the evolution and interaction of the overlapping activity bands of the longer-scale variability. Title: A New Ground-Based Network for Synoptic Solar Observations: The Solar Physics Research Integrated Network Group (SPRING) Authors: Hill, Frank; Roth, Markus; Thompson, Michael; Gusain, Sanjay Bibcode: 2014AAS...22412354H Altcode: SPRING is a project to develop a geographically distributed network of instrumentation to obtain synoptic solar observations. Building on the demonstrated success of networks to provide nearly-continuous long-term data for helioseismology, SPRING will provide data for a wide range of solar research areas. Scientific objectives include internal solar dynamics and structure; wave transport in the solar atmosphere; the evolution of the magnetic field over the activity cycle; irradiance fluctuations; and space weather origins. Anticipated data products include simultaneous full-disk multi-wavelength Doppler and vector magnetic field images; filtergrams in H-Alpha, CaK, and white light; and PSPT-type irradiance support. The data will be obtained with a duty cycle of around 90% and at a cadence no slower than one minute. The current concept is a multi-instrument platform installed in at least six locations, and which will also provide context information for large-aperture solar telescopes such as EST and the DKIST. There is wide support for the idea within the EU and the US solar research communities. The project is in the early planning stages, and we are open to and looking for participants in the science and instrument definition. Title: Grand Challenges in the Physics of the Sun and Sun-like Stars Authors: Thompson, Michael Bibcode: 2014FrASS...1....1T Altcode: 2014arXiv1406.4228T The study of stellar structure and evolution is one of the main building blocks of astrophysics, and the Sun has an importance both as the star that is most amenable to detailed study and as the star that has by far the biggest impact on the Earth and near-Earth environment through its radiative and particulate outputs. Over the past decades, studies of stars and of the Sun have become somewhat separate. But in recent years, the rapid advances in asteroseismology, as well as the quest to better understand solar and stellar dynamos, have emphasized once again the synergy between studies of the stars and the Sun. In this article I have selected two "grand challenges" both for their crucial importance and because I thnk that these two problems are tractable to significant progress in the next decade. They are (i) understanding how solar and stellar dynamos generate magnetic field, and (ii) improving the predictability of geo-effective space weather. Title: Future mmVLBI Research with ALMA: A European vision Authors: Tilanus, R. P. J.; Krichbaum, T. P.; Zensus, J. A.; Baudry, A.; Bremer, M.; Falcke, H.; Giovannini, G.; Laing, R.; van Langevelde, H. J.; Vlemmings, W.; Abraham, Z.; Afonso, J.; Agudo, I.; Alberdi, A.; Alcolea, J.; Altamirano, D.; Asadi, S.; Assaf, K.; Augusto, P.; Baczko, A-K.; Boeck, M.; Boller, T.; Bondi, M.; Boone, F.; Bourda, G.; Brajsa, R.; Brand, J.; Britzen, S.; Bujarrabal, V.; Cales, S.; Casadio, C.; Casasola, V.; Castangia, P.; Cernicharo, J.; Charlot, P.; Chemin, L.; Clenet, Y.; Colomer, F.; Combes, F.; Cordes, J.; Coriat, M.; Cross, N.; D'Ammando, F.; Dallacasa, D.; Desmurs, J-F.; Eatough, R.; Eckart, A.; Eisenacher, D.; Etoka, S.; Felix, M.; Fender, R.; Ferreira, M.; Freeland, E.; Frey, S.; Fromm, C.; Fuhrmann, L.; Gabanyi, K.; Galvan-Madrid, R.; Giroletti, M.; Goddi, C.; Gomez, J.; Gourgoulhon, E.; Gray, M.; di Gregorio, I.; Greimel, R.; Grosso, N.; Guirado, J.; Hada, K.; Hanslmeier, A.; Henkel, C.; Herpin, F.; Hess, P.; Hodgson, J.; Horns, D.; Humphreys, E.; Hutawarakorn Kramer, B.; Ilyushin, V.; Impellizzeri, V.; Ivanov, V.; Julião, M.; Kadler, M.; Kerins, E.; Klaassen, P.; van 't Klooster, K.; Kording, E.; Kozlov, M.; Kramer, M.; Kreikenbohm, A.; Kurtanidze, O.; Lazio, J.; Leite, A.; Leitzinger, M.; Lepine, J.; Levshakov, S.; Lico, R.; Lindqvist, M.; Liuzzo, E.; Lobanov, A.; Lucas, P.; Mannheim, K.; Marcaide, J.; Markoff, S.; Martí-Vidal, I.; Martins, C.; Masetti, N.; Massardi, M.; Menten, K.; Messias, H.; Migliari, S.; Mignano, A.; Miller-Jones, J.; Minniti, D.; Molaro, P.; Molina, S.; Monteiro, A.; Moscadelli, L.; Mueller, C.; Müller, A.; Muller, S.; Niederhofer, F.; Odert, P.; Olofsson, H.; Orienti, M.; Paladino, R.; Panessa, F.; Paragi, Z.; Paumard, T.; Pedrosa, P.; Pérez-Torres, M.; Perrin, G.; Perucho, M.; Porquet, D.; Prandoni, I.; Ransom, S.; Reimers, D.; Rejkuba, M.; Rezzolla, L.; Richards, A.; Ros, E.; Roy, A.; Rushton, A.; Savolainen, T.; Schulz, R.; Silva, M.; Sivakoff, G.; Soria-Ruiz, R.; Soria, R.; Spaans, M.; Spencer, R.; Stappers, B.; Surcis, G.; Tarchi, A.; Temmer, M.; Thompson, M.; Torrelles, J.; Truestedt, J.; Tudose, V.; Venturi, T.; Verbiest, J.; Vieira, J.; Vielzeuf, P.; Vincent, F.; Wex, N.; Wiik, K.; Wiklind, T.; Wilms, J.; Zackrisson, E.; Zechlin, H. Bibcode: 2014arXiv1406.4650T Altcode: Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constants Title: On the shape of the mass-function of dense clumps in the Hi-GAL fields . II. Using Bayesian inference to study the clump mass function Authors: Olmi, L.; Anglés-Alcázar, D.; Elia, D.; Molinari, S.; Pestalozzi, M.; Pezzuto, S.; Schisano, E.; Testi, L.; Thompson, M. Bibcode: 2014A&A...564A..87O Altcode: 2013arXiv1311.2736O Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin, their evolution, and their detailed physical properties. In particular, the relationship between the mass distribution of these clumps (also known as the "clump mass function", or CMF) and the stellar initial mass function (IMF) is still poorly understood.
Aims: To better understand how the CMF evolve toward the IMF and to discern the "true" shape of the CMF, large samples of bona-fide pre- and proto-stellar clumps are required. Two such datasets obtained from the Herschel infrared GALactic Plane Survey (Hi-GAL) have been described in Paper I. Robust statistical methods are needed to infer the parameters describing the models used to fit the CMF and to compare the competing models themselves.
Methods: In this paper, we apply Bayesian inference to the analysis of the CMF of the two regions discussed in Paper I. First, we determine the posterior probability distribution for each of the fitted parameters. Then, we carry out a quantitative comparison of the models used to fit the CMF.
Results: We have compared several methods of sampling posterior distributions and calculating global likelihoods, and we have also analyzed the impact of the choice of priors and the influence of various constraints on the statistical conclusions for the values of model parameters. We find that both parameter estimation and model comparison depend on the choice of parameter priors.
Conclusions: Our results confirm our earlier conclusion that the CMFs of the two Hi-GAL regions studied here have very similar shapes but different mass scales. Furthermore, the lognormal model appears to better describe the CMF measured in the two Hi-GAL regions studied here. However, this preliminary conclusion is dependent on the choice of parameter priors. Title: Study of KIC 8561221 observed by Kepler: an early red giant showing depressed dipolar modes Authors: García, R. A.; Pérez Hernández, F.; Benomar, O.; Silva Aguirre, V.; Ballot, J.; Davies, G. R.; Doğan, G.; Stello, D.; Christensen-Dalsgaard, J.; Houdek, G.; Lignières, F.; Mathur, S.; Takata, M.; Ceillier, T.; Chaplin, W. J.; Mathis, S.; Mosser, B.; Ouazzani, R. M.; Pinsonneault, M. H.; Reese, D. R.; Régulo, C.; Salabert, D.; Thompson, M. J.; van Saders, J. L.; Neiner, C.; De Ridder, J. Bibcode: 2014A&A...563A..84G Altcode: 2013arXiv1311.6990G Context. The continuous high-precision photometric observations provided by the CoRoT and Kepler space missions have allowed us to understand the structure and dynamics of red giants better using asteroseismic techniques. A small fraction of these stars show dipole modes with unexpectedly low amplitudes. The reduction in amplitude is more pronounced for stars with a higher frequency of maximum power, νmax.
Aims: In this work we want to characterise KIC 8561221 in order to confirm that it is currently the least evolved star among this peculiar subset and to discuss several hypotheses that could help explain the reduction of the dipole mode amplitudes.
Methods: We used Kepler short- and long-cadence data combined with spectroscopic observations to infer the stellar structure and dynamics of KIC 8561221. We then discussed different scenarios that could contribute to reducing the dipole amplitudes, such as a fast-rotating interior or the effect of a magnetic field on the properties of the modes. We also performed a detailed study of the inertia and damping of the modes.
Results: We have been able to characterise 36 oscillations modes, in particular, a few dipole modes above νmax that exhibit nearly normal amplitudes. The frequencies of all the measured modes were used to determine the overall properties and the internal structure of the star. We have inferred a surface rotation period of ~91 days and uncovered a variation in the surface magnetic activity during the last 4 years. The analysis of the convective background did not reveal any difference compared to "normal" red giants. As expected, the internal regions of the star probed by the ℓ = 2 and 3 modes spin 4 to 8 times faster than the surface.
Conclusions: With our grid of standard models we are able to properly fit the observed frequencies. Our model calculation of mode inertia and damping give no explanation for the depressed dipole modes. A fast-rotating core is also ruled out as a possible explanation. Finally, we do not have any observational evidence of a strong deep magnetic field inside the star.

Table 3 and Appendix A are available in electronic form at http://www.aanda.org Title: First Images from the Cript Muon Tomography System Authors: Armitage, J.; Botte, J.; Boudjemline, K.; Erlandson, A.; Robichaud, A.; Bueno, J.; Bryman, D.; Gazit, R.; Hydomako, R.; Liu, Z.; Anghel, V.; Golovko, V. V.; Jewett, C.; Jonkmans, G.; Thompson, M.; Charles, E.; Gallant, G.; Drouin, P. -L.; Waller, D.; Stocki, T. J.; Cousins, T.; Noel, S. Bibcode: 2014IJMPS..2760129A Altcode: The CRIPT Cosmic Ray Imaging and Passive Tomography system began data taking in September 2012. CRIPT is a “proof of principle” muon tomography system originally proposed to inspect cargo in shipping containers and to determine the presence of special nuclear materials. CRIPT uses 4 layers of 2 m x 2 m scintillation counter trackers, each layer measuring two coordinates. Two layers are used to track the incoming muon and two for the outgoing muon allowing the trajectories of the muon to be determined. The target volume is divided into voxels, and a Point of Closest Approach algorithm is used to determine the number of scattering events in each voxel, producing a 3D image. The system has been tested with various targets of depleted uranium, lead bricks, and tungsten rods. Data on the positional resolution has been taken and the intrinsic resolution is unfolded with the help of a simulation using GEANT4. The next steps include incorporation of data from the spectrometer section, which will assist in determining the muon's momentum and improve the determination of the density of the target. Title: Oscillations and Surface Rotation of Red Giant Stars Authors: Hedges, C.; Mathur, S.; Thompson, M. J.; MacGregor, K. B. Bibcode: 2013ASPC..479..197H Altcode: 2013arXiv1308.0644H More than 15000 red giants observed by Kepler for a duration of almost one year became public at the beginning of this year. We analysed a subsample of 416 stars to determine the global properties of acoustic modes (mean large separation and frequency of maximum power). Using the effective temperature from the Kepler Input Catalog, we derived a first estimate of the masses and radii of these stars. Finally, we applied wavelets to look for a signature of surface rotation, which relies on the presence of spots or other surface features crossing the stellar visible disk. Title: The Torsional Oscillation and the Timing of the Solar Cycle: Is it Maximum Yet? Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Larson, T. P.; Schou, J.; Thompson, M. J. Bibcode: 2013ASPC..478..303H Altcode: After the late start to Cycle 24 there are some indications that activity may have peaked as early as late 2011 and that the polar-field reversal has already occurred in the North. We use helioseismic measurements of the migrating zonal flow pattern known as the torsional oscillation to estimate the length of the solar cycle, and find that it has held steady at about 12.3 years since late 2009, which would point to solar maximum in 2013 as expected. Title: The High-latitude Branch of the Solar Torsional Oscillation in the Rising Phase of Cycle 24 Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Larson, T. P.; Rempel, M.; Schou, J.; Thompson, M. J. Bibcode: 2013ApJ...767L..20H Altcode: We use global heliseismic data from the Global Oscillation Network Group, the Michelson Doppler Imager on board the Solar and Heliospheric Observatory, and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, to examine the behavior, during the rising phase of Solar Cycle 24, of the migrating zonal flow pattern known as the torsional oscillation. Although the high-latitude part of the pattern appears to be absent in the new cycle when the flows are derived by subtracting a mean across a full solar cycle, it can be seen if we subtract the mean over a shorter period in the rising phase of each cycle, and these two mean rotation profiles differ significantly at high latitudes. This indicates that the underlying high-latitude rotation has changed; we speculate that this is in response to weaker polar fields, as suggested by a recent model. Title: A New Multi-Wavelength Synoptic Network for Solar Physics and Space Weather Authors: Hill, Frank; Roth, Markus; Thompson, Michael Bibcode: 2013EGUGA..1511892H Altcode: Continuous solar observations are important for many research topics in solar physics, such as magnetic field evolution, flare and CME characteristics, and p-mode oscillation measurements. In addition, space weather operations require constant streams of solar data as input. The deployment of a number of identical instruments around the world in a network has proven to be a very effective strategy for obtaining nearly continuous solar observations. The financial costs of a network are 1-2 orders of magnitude lower than space-based platforms; network instrumentation can be easily accessed for maintenance and upgrades; and telemetry bandwidth is readily available. Currently, there are two solar observing networks with consistent instruments: BiSON and GONG, both designed primarily for helioseismology. In addition, GONG has been augmented with continual magnetic field measurements and H-alpha imagery, with both being used for space weather operational purposes. However, GONG is now 18 years old and getting increasingly more challenging to maintain. There are also at least three scientific motivations for a multi-wavelength network: Recent advances in helioseismology have demonstrated the need for multi-wavelength observations to allow more accurate interpretation of the structure and dynamics below sunspots. Vector magnetometry would greatly benefit from multi-wavelength observations to provide height information and resolve the azimuthal ambiguity. Finally, space weather operations always need a consistent reliable source of continual solar data. This presentation will outline the scientific need for a multi-wavelength network, and discuss some concepts for the design of the instrumentation. A workshop on the topic will be held in Boulder this April. Title: On the shape of the mass-function of dense clumps in the Hi-GAL fields . I. Spectral energy distribution determination and global properties of the mass-functions Authors: Olmi, L.; Anglés-Alcázar, D.; Elia, D.; Molinari, S.; Montier, L.; Pestalozzi, M.; Pezzuto, S.; Polychroni, D.; Ristorcelli, I.; Rodon, J.; Schisano, E.; Smith, M. D.; Testi, L.; Thompson, M. Bibcode: 2013A&A...551A.111O Altcode: 2012arXiv1209.4465O Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin and evolution. In particular, the relationship between the mass distribution of these clumps (also known as the clump mass function or CMF) and the stellar initial mass function (IMF), is still poorly understood.
Aims: To discern the "true" shape of the CMF and to better understand how the CMF may evolve toward the IMF, large samples of bona-fide pre- and proto-stellar clumps are required. The sensitive observations of the Herschel Space Observatory (HSO) are now allowing us to look at large clump populations in various clouds with different physical conditions.
Methods: We analyze two fields in the Galactic plane mapped by HSO during its science demonstration phase (SDP), as part of the more complete and unbiased Herschel infrared GALactic Plane Survey (Hi-GAL). These fields underwent a source-extraction and flux-estimation pipeline, which allowed us to obtain a sample with thousands of clumps. Starless and proto-stellar clumps were separated using both color and positional criteria to find those coincident with MIPS 24 μm sources. We describe the probability density functions of the power-law and lognormal models that were used to fit the CMFs. For the lognormal model we applied several statistical techniques to the data and compared their results.
Results: The CMFs of the two SDP fields show very similar shapes, but very different mass scales. This similarity is confirmed by the values of the best-fit parameters of either the power-law or lognormal model. The power-law model leads to almost identical CMF slopes, whereas the lognormal model shows that the CMFs have similar widths.
Conclusions: The similar CMF shape but different mass scale represents an evidence that the overall process of star formation in the two regions is very different. When comparing with the IMF, we find that the width of the IMF is narrower than the measured widths of the CMF in the two SDP fields. This may suggest that an additional mass selection occurs in later stages of gravitational collapse. Title: Minor Planet Observations [J13 La Palma-Liverpool Telescope] Authors: Foster, P.; Ashcroft, H.; Robinson, D.; Ellender, N.; Hill, S.; Browne, J.; Thompson, M.; Thomas, H.; Mill, C.; Edwards, J.; Martin, S.; Thorpe, C.; Llewellyn-Davies, S.; Hewitt, J.; Kettle, P.; Woodruff, K.; Edwar, J.; Emmett, J.; Culshaw, B. Bibcode: 2013MPC..82706...1B Altcode: No abstract at ADS Title: A Coral Sea Rehearsal for the Eclipse Megamovie Authors: Hudson, H. S.; Davey, A. R.; Ireland, J.; Jones, L.; Mcintosh, S. W.; Paglierani, R.; Pasachoff, J. M.; Peticolas, L. M.; Russell, R. M.; Suarez Sola, F. I.; Sutherland, L.; Thompson, M. J. Bibcode: 2012AGUFMSH11C..06H Altcode: The "Eclipse on the Coral Sea" - 13/14 November 2012 (GMT/Australia) - will have happened already. Our intention is to have used this opportunity as a trial run for the eclipse in 2017, which features 1.5 hours of totality across the whole width of the continental US. Conceived first and foremost as an education and public outreach activity, the plan is to engage the public in solar science and technology by providing a way for them to include images they have taken of the solar eclipse, into a movie representation of coronal evolution in time. This project will assimilate as much eclipse photography as possible from the public. The resulting movie(s) will cover all ranges of expertise, and at the basic smartphone or hand-held digital camera level, we expect to have obtained a huge number of images in the case of good weather conditions. The capability of modern digital technology to handle such a data flow is new. The basic purpose of this and the 2017 Megamovie observations is to explore this capability and its ability to engage people from many different communities in the solar science, astronomy, mathematics, and technology. The movie in 2017, especially, may also have important science impact because of the uniqueness of the corona as seen under eclipse conditions. In this presentation we will describe our smartphone application development (see the "Transit of Venus" app for a role model here). We will also summarize data acquisition via both the app and more traditional web interfaces. Although for the Coral Sea eclipse event we don't expect to have a movie product by the time of the AGU, for the 2017 event we do intend to assemble the heterogenous data into beautiful movies within a short space of time after the eclipse. These movies may have relatively low resolution but would extend to the base of the corona. We encourage participation in the 2012 observations, noting that no total eclipse, prior to 2017, will occur in a region with good infrastructure for extended observations. The National Center for Atmospheric Research is sponsored by the National Science Foundation. The Megamovie project is supported by NSF grant AGS-1247226, and JMP's eclipse work about the eclipses of 2012 is supported by NSF grant AGS-1047726. Title: Fundamental Properties of Stars Using Asteroseismology from Kepler and CoRoT and Interferometry from the CHARA Array Authors: Huber, D.; Ireland, M. J.; Bedding, T. R.; Brandão, I. M.; Piau, L.; Maestro, V.; White, T. R.; Bruntt, H.; Casagrande, L.; Molenda-Żakowicz, J.; Silva Aguirre, V.; Sousa, S. G.; Barclay, T.; Burke, C. J.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Cunha, M. S.; De Ridder, J.; Farrington, C. D.; Frasca, A.; García, R. A.; Gilliland, R. L.; Goldfinger, P. J.; Hekker, S.; Kawaler, S. D.; Kjeldsen, H.; McAlister, H. A.; Metcalfe, T. S.; Miglio, A.; Monteiro, M. J. P. F. G.; Pinsonneault, M. H.; Schaefer, G. H.; Stello, D.; Stumpe, M. C.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.; Thompson, M. J.; Turner, N.; Uytterhoeven, K. Bibcode: 2012ApJ...760...32H Altcode: 2012arXiv1210.0012H We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos parallaxes, asteroseismic densities, bolometric fluxes, and high-resolution spectroscopy, we derive a full set of near-model-independent fundamental properties for the sample. We first use these properties to test asteroseismic scaling relations for the frequency of maximum power (νmax) and the large frequency separation (Δν). We find excellent agreement within the observational uncertainties, and empirically show that simple estimates of asteroseismic radii for main-sequence stars are accurate to <~ 4%. We furthermore find good agreement of our measured effective temperatures with spectroscopic and photometric estimates with mean deviations for stars between T eff = 4600-6200 K of -22 ± 32 K (with a scatter of 97 K) and -58 ± 31 K (with a scatter of 93 K), respectively. Finally, we present a first comparison with evolutionary models, and find differences between observed and theoretical properties for the metal-rich main-sequence star HD 173701. We conclude that the constraints presented in this study will have strong potential for testing stellar model physics, in particular when combined with detailed modeling of individual oscillation frequencies. Title: Measurements of CO Redshifts with Z-Spec for Lensed Submillimeter Galaxies Discovered in the H-ATLAS Survey Authors: Lupu, R. E.; Scott, K. S.; Aguirre, J. E.; Aretxaga, I.; Auld, R.; Barton, E.; Beelen, A.; Bertoldi, F.; Bock, J. J.; Bonfield, D.; Bradford, C. M.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooke, J.; Cooray, A.; Dannerbauer, H.; Dariush, A.; De Zotti, G.; Dunne, L.; Dye, S.; Eales, S.; Frayer, D.; Fritz, J.; Glenn, J.; Hughes, D. H.; Ibar, E.; Ivison, R. J.; Jarvis, M. J.; Kamenetzky, J.; Kim, S.; Lagache, G.; Leeuw, L.; Maddox, S.; Maloney, P. R.; Matsuhara, H.; Murphy, E. J.; Naylor, B. J.; Negrello, M.; Nguyen, H.; Omont, A.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Serjeant, S.; Smith, D.; Temi, P.; Thompson, M.; Valtchanov, I.; Verma, A.; Vieira, J. D.; Zmuidzinas, J. Bibcode: 2012ApJ...757..135L Altcode: 2010arXiv1009.5983L We present new observations from Z-Spec, a broadband 185-305 GHz spectrometer, of five submillimeter bright lensed sources selected from the Herschel-Astrophysical Terahertz Large Area Survey science demonstration phase catalog. We construct a redshift-finding algorithm using combinations of the signal to noise of all the lines falling in the Z-Spec bandpass to determine redshifts with high confidence, even in cases where the signal to noise in individual lines is low. We measure the dust continuum in all sources and secure CO redshifts for four out of five (z ~ 1.5-3). In one source, SDP.17, we tentatively identify two independent redshifts and a water line, confirmed at z = 2.308. Our sources have properties characteristic of dusty starburst galaxies, with magnification-corrected star formation rates of 102 - 3 M ⊙ yr-1. Lower limits for the dust masses (~ a few 108 M ⊙) and spatial extents (~1 kpc equivalent radius) are derived from the continuum spectral energy distributions, corresponding to dust temperatures between 54 and 69 K. In the local thermodynamic equilibrium (LTE) approximation, we derive relatively low CO excitation temperatures (lsim 100 K) and optical depths (τ <~ 1). Performing a non-LTE excitation analysis using RADEX, we find that the CO lines measured by Z-Spec (from J = 4 → 3 to 10 → 9, depending on the galaxy) localize the best solutions to either a high-temperature/low-density region or a low/temperature/high-density region near the LTE solution, with the optical depth varying accordingly. Observations of additional CO lines, CO(1-0) in particular, are needed to constrain the non-LTE models. Title: Fast Rotating Solar-like Stars Using Asteroseismic Datasets Authors: García, R. A.; Ceillier, T.; Campante, T. L.; Davies, G. R.; Mathur, S.; Suárez, J. C.; Ballot, J.; Benomar, O.; Bonanno, A.; Brun, A. S.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Deheuvels, S.; Elsworth, Y.; Handberg, R.; Hekker, S.; Jiménez, A.; Karoff, C.; Kjeldsen, H.; Mathis, S.; Mosser, B.; Pallé, P. L.; Pinsonneault, M.; Régulo, C.; Salabert, D.; Silva Aguirre, V.; Stello, D.; Thompson, M. J.; Verner, G.; PE11 Team of Kepler WG#1 Bibcode: 2012ASPC..462..133G Altcode: 2011arXiv1109.6488G The NASA Kepler mission is providing an unprecedented set of asteroseismic data. In particular, short-cadence light-curves (∼ 60 s samplings), allow us to study solar-like stars covering a wide range of masses, spectral types and evolutionary stages. Oscillations have been observed in around 600 out of 2000 stars observed for one month during the survey phase of the Kepler mission. The measured light curves can present features related to the surface magnetic activity (starspots) and, thus we are able to obtain a good estimate of the surface (differential) rotation. In this work we establish the basis of such research and we show a potential method to find stars with fast surface rotation. Title: Seismic Analysis of Four Solar-like Stars Observed during More Than Eight Months by Kepler Authors: Mathur, S.; Campante, T. L.; Handberg, R.; García, R. A.; Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot, J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker, S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão, I. M.; Creevey, O. L.; Dogan, G.; Bazot, M.; Cunha, M. S.; Elsworth, Y.; Huber, D.; Hale, S. J.; Houdek, G.; Karoff, C.; Lundkvist, M.; Metcalfe, T. S.; Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Stello, D.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Clarke, B. D.; Girouard, F. R.; Hall, J. R.; Quintana, E. V.; Sanderfer, D. T.; Seader, S. E. Bibcode: 2012ASPC..462..180M Altcode: 2011arXiv1110.0135M Having started science operations in May 2009, the Kepler photometer has been able to provide exquisite data for solar-like stars. Five out of the 42 stars observed continuously during the survey phase show evidence of oscillations, even though they are rather faint (magnitudes from 10.5 to 12). In this paper, we present an overview of the results of the seismic analysis of 4 of these stars observed during more than eight months. Title: Solar and stellar activity: diagnostics and indices Authors: Judge, Philip G.; Thompson, Michael J. Bibcode: 2012IAUS..286...15J Altcode: 2012arXiv1201.4625J We summarize the fifty-year concerted effort to place the ``activity'' of the Sun in the context of the stars. As a working definition of solar activity in the context of stars, we adopt those globally-observable variations on time scales below thermal time scales, of ~105 yr for the convection zone. So defined, activity is dominated by magnetic-field evolution, including the 22-year Hale cycle, the typical time it takes for the quasi-periodic reversal in which the global magnetic-field takes place. This is accompanied by sunspot variations with 11 year periods, known since the time of Schwabe, as well as faster variations due to rotation of active regions and flaring. ``Diagnostics and indices'' are terms given to the indirect signatures of varying magnetic-fields, including the photometric (broad-band) variations associated with the sunspot cycle, and variations of the accompanying heated plasma in higher layers of stellar atmospheres seen at special optical wavelengths, and UV and X-ray wavelengths. Our attention is also focussed on the theme of the Symposium by examining evidence for deep and extended minima of stars, and placing the 70-year long solar Maunder Minimum into a stellar context. Title: Latest Results on the Torsional Oscillation and Solar Cycle 25 Authors: Hill, Frank; Howe, R.; Schou, J.; Thompson, M.; Larson, T.; Komm, R. Bibcode: 2012AAS...22012302H Altcode: The Torsional Oscillation in the Sun is a zonal (East-West) flow that is slightly faster than the background differential rotation profile. The location of this flow slowly migrates in latitude over a period of several years. There are two branches of the flow: an equatorward branch that underlies the active regions, and a poleward branch. The timing of the equatorward migration is correlated with the timing of the solar cycle such that the activity for a cycle appears when the center of the flow reaches latitude 25 degrees. In addition, the poleward branch appears about 12 years prior to the activity for a cycle. Thus we should have observed the onset of Cycle 25 in 2008, but did not. This poster will update the observations to 2012, and present a new analysis that shows that the Cycle 25 flow appeared in 2010, but was hidden by a change in the background differential rotation profile. These results suggest that the next minimum will be two years longer than average, and that Cycle 25 will begin in 2022. Title: A Uniform Asteroseismic Analysis of 22 Solar-type Stars Observed by Kepler Authors: Mathur, S.; Metcalfe, T. S.; Woitaszek, M.; Bruntt, H.; Verner, G. A.; Christensen-Dalsgaard, J.; Creevey, O. L.; Doǧan, G.; Basu, S.; Karoff, C.; Stello, D.; Appourchaux, T.; Campante, T. L.; Chaplin, W. J.; García, R. A.; Bedding, T. R.; Benomar, O.; Bonanno, A.; Deheuvels, S.; Elsworth, Y.; Gaulme, P.; Guzik, J. A.; Handberg, R.; Hekker, S.; Herzberg, W.; Monteiro, M. J. P. F. G.; Piau, L.; Quirion, P. -O.; Régulo, C.; Roth, M.; Salabert, D.; Serenelli, A.; Thompson, M. J.; Trampedach, R.; White, T. R.; Ballot, J.; Brandão, I. M.; Molenda-Żakowicz, J.; Kjeldsen, H.; Twicken, J. D.; Uddin, K.; Wohler, B. Bibcode: 2012ApJ...749..152M Altcode: 2012arXiv1202.2844M Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure and evolution for the large sample of solar-type stars in the field. We perform a uniform analysis of 22 of the brightest asteroseismic targets with the highest signal-to-noise ratio observed for 1 month each during the first year of the mission, and we quantify the precision and relative accuracy of asteroseismic determinations of the stellar radius, mass, and age that are possible using various methods. We present the properties of each star in the sample derived from an automated analysis of the individual oscillation frequencies and other observational constraints using the Asteroseismic Modeling Portal (AMP), and we compare them to the results of model-grid-based methods that fit the global oscillation properties. We find that fitting the individual frequencies typically yields asteroseismic radii and masses to ~1% precision, and ages to ~2.5% precision (respectively, 2, 5, and 8 times better than fitting the global oscillation properties). The absolute level of agreement between the results from different approaches is also encouraging, with model-grid-based methods yielding slightly smaller estimates of the radius and mass and slightly older values for the stellar age relative to AMP, which computes a large number of dedicated models for each star. The sample of targets for which this type of analysis is possible will grow as longer data sets are obtained during the remainder of the mission. Title: Estimating stellar mean density through seismic inversions Authors: Reese, D. R.; Marques, J. P.; Goupil, M. J.; Thompson, M. J.; Deheuvels, S. Bibcode: 2012A&A...539A..63R Altcode: 2012arXiv1201.1844R Context. Determining the mass of stars is crucial both for improving stellar evolution theory and for characterising exoplanetary systems. Asteroseismology offers a promising way for estimating the stellar mean density. When combined with accurate radii determinations, such as are expected from Gaia, this yields accurate stellar masses. The main difficulty is finding the best way to extract the mean density of a star from a set of observed frequencies.
Aims: We seek to establish a new method for estimating the stellar mean density, which combines the simplicity of a scaling law while providing the accuracy of an inversion technique.
Methods: We provide a framework in which to construct and evaluate kernel-based linear inversions that directly yield the mean density of a star. We then describe three different inversion techniques (SOLA and two scaling laws) and apply them to the Sun, several test cases and three stars, α Cen B, HD 49933 and HD 49385, two of which are observed by CoRoT.
Results: The SOLA (subtractive optimally localised averages) approach and the scaling law based on the surface correcting technique described by Kjeldsen et al. (2008, ApJ, 683, L175) yield comparable results that can reach an accuracy of 0.5% and are better than scaling the large frequency separation. The reason for this is that the averaging kernels from the two first methods are comparable in quality and are better than what is obtained with the large frequency separation. It is also shown that scaling the large frequency separation is more sensitive to near-surface effects, but is much less affected by an incorrect mode identification. As a result, one can identify pulsation modes by looking for an ℓ and n assignment which provides the best agreement between the results from the large frequency separation and those from one of the two other methods. Non-linear effects are also discussed, as is the effects of mixed modes. In particular, we show that mixed modes bring little improvement to the mean density estimates because of their poorly adapted kernels. Title: Disc frequencies for brown dwarfs in the Upper Scorpius OB association: implications for brown dwarf formation theories Authors: Riaz, B.; Lodieu, N.; Goodwin, S.; Stamatellos, D.; Thompson, M. Bibcode: 2012MNRAS.420.2497R Altcode: 2011arXiv1111.3929R We have investigated the brown dwarf (BD) and stellar disc fractions in the Upper Scorpius (USco) OB association and compared them with several other young regions. We have compiled the most complete sample of all spectroscopically confirmed BDs in USco and have made use of the Wide-field Infrared Survey Explorer (WISE) catalogue to identify the disc candidates. We report on the discovery of 12 new BD discs in USco, with spectral types between M6 and M8.5. The WISE colours for the new discs are similar to the primordial (transition) discs earlier detected in USco. Combining with previous surveys, we find the lowest inner disc fractions (∼20-25 per cent) for a wide range in stellar masses (∼0.01-4.0 M⊙) in the USco association. The low disc fractions for high-mass stars in USco (and the other clusters) are consistent with an evolutionary decline in inner disc frequency with age. However, BD disc fractions are higher than those for the stars in 1-3 Myr clusters, but very low in the ∼5 Myr old USco. Also, primordial BD discs are still visible in the ∼10 Myr old TW Hydrae association, whereas the higher mass stars have all transitioned to the debris stage by this age. The disc frequencies for BDs and low-mass stars do not show any dependence on the stellar density or the BD/star number ratio in a cluster. We also find no convincing evidence that any of the well-known disc dispersal mechanisms for stars are active in BD discs. We suggest that the large differences in the observed BD disc fractions between regions may well be due to different BD formation mechanisms and therefore different initial disc fractions/properties.

We also present a WISE spectral energy distribution classification scheme, based on the Ks and WISE bands of 3.4-12 μm. We have determined certain thresholds in the WISE spectral slope versus spectral type diagrams to distinguish between the red population of Class I/II systems and the Class III sequence. We have found the WISE [3.4] - [12] colour to provide the best distinction between the photospheric and the disc population. Our work includes a comparison of the sensitivities of WISE and Spitzer disc surveys. We estimate that WISE can be incomplete for discs at spectral type later than M8 in distant clusters such as SOri. WISE should be able to recover the M8-M9 discs in the nearby young clusters. Title: Kepler-21b: A 1.6 R Earth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070 Authors: Howell, Steve B.; Rowe, Jason F.; Bryson, Stephen T.; Quinn, Samuel N.; Marcy, Geoffrey W.; Isaacson, Howard; Ciardi, David R.; Chaplin, William J.; Metcalfe, Travis S.; Monteiro, Mario J. P. F. G.; Appourchaux, Thierry; Basu, Sarbani; Creevey, Orlagh L.; Gilliland, Ronald L.; Quirion, Pierre-Olivier; Stello, Denis; Kjeldsen, Hans; Christensen-Dalsgaard, Jörgen; Elsworth, Yvonne; García, Rafael A.; Houdek, Günter; Karoff, Christoffer; Molenda-Żakowicz, Joanna; Thompson, Michael J.; Verner, Graham A.; Torres, Guillermo; Fressin, Francois; Crepp, Justin R.; Adams, Elisabeth; Dupree, Andrea; Sasselov, Dimitar D.; Dressing, Courtney D.; Borucki, William J.; Koch, David G.; Lissauer, Jack J.; Latham, David W.; Buchhave, Lars A.; Gautier, Thomas N., III; Everett, Mark; Horch, Elliott; Batalha, Natalie M.; Dunham, Edward W.; Szkody, Paula; Silva, David R.; Mighell, Ken; Holberg, Jay; Ballot, Jerôme; Bedding, Timothy R.; Bruntt, Hans; Campante, Tiago L.; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel; Mathur, Savita; Mosser, Benoit; Régulo, Clara; White, Timothy R.; Christiansen, Jessie L.; Middour, Christopher K.; Haas, Michael R.; Hall, Jennifer R.; Jenkins, Jon M.; McCaulif, Sean; Fanelli, Michael N.; Kulesa, Craig; McCarthy, Don; Henze, Christopher E. Bibcode: 2012ApJ...746..123H Altcode: 2011arXiv1112.2165H We present Kepler observations of the bright (V = 8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R Earth object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequency-power spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34 ± 0.06 M ⊙ and 1.86 ± 0.04 R ⊙, respectively, as well as yielding an age of 2.84 ± 0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3σ) that the transit event is caused by a 1.64 ± 0.04 R Earth exoplanet in a 2.785755 ± 0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of ~10 M Earth (2σ). HD 179070 is the brightest exoplanet host star yet discovered by Kepler.

Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology, the Mayall telescope at Kitt Peak National Observatory, and the WIYN Observatory which is a joint facility of NOAO, University of Wisconsin-Madison, Indiana University, and Yale University. Title: Solar-cycle variation of oscillation frequencies and surface magnetic field Authors: Tan, S.; Thompson, M. J.; Centeno, R. Bibcode: 2011AGUFMSH13B1933T Altcode: We investigate the relationship between solar oscillation frequencies and surface magnetic fields over the course of the last solar cycle. Using MDI and GONG data, we study the variation in the even frequency-splitting coefficients ak (describing solar asphericity and effects of the magnetic field), and the variation in the coefficients Bk of the latitudinal Lengendre decomposition of the surface magnetic field, during the period 1996 - 2010. We find a strong linear correlation between the a and B coefficients, during both the rising and declining phases of the solar cycle, consistent with results published in 2001 (Antia et al.). We also investigated different ways to handle the magnetic field decomposition at the poles, and find that the linear correlation persists, though with varying intercepts. The variation of slope with coefficient index that we find is non-monotonic, which disagrees with the previous study by Antia et al. (2001). Title: Asteroseismic Diagrams from a Survey of Solar-like Oscillations with Kepler Authors: White, Timothy R.; Bedding, Timothy R.; Stello, Dennis; Appourchaux, Thierry; Ballot, Jérôme; Benomar, Othman; Bonanno, Alfio; Broomhall, Anne-Marie; Campante, Tiago L.; Chaplin, William J.; Christensen-Dalsgaard, Jørgen; Corsaro, Enrico; Doǧan, Gülnur; Elsworth, Yvonne P.; Fletcher, Stephen T.; García, Rafael A.; Gaulme, Patrick; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel; Karoff, Christoffer; Kjeldsen, Hans; Mathur, Savita; Mosser, Benoit; Monteiro, Mario J. P. F. G.; Régulo, Clara; Salabert, David; Silva Aguirre, Victor; Thompson, Michael J.; Verner, Graham; Morris, Robert L.; Sanderfer, Dwight T.; Seader, Shawn E. Bibcode: 2011ApJ...742L...3W Altcode: 2011arXiv1110.1375W Photometric observations made by the NASA Kepler Mission have led to a dramatic increase in the number of main-sequence and subgiant stars with detected solar-like oscillations. We present an ensemble asteroseismic analysis of 76 solar-type stars. Using frequencies determined from the Kepler time-series photometry, we have measured three asteroseismic parameters that characterize the oscillations: the large frequency separation (Δν), the small frequency separation between modes of l = 0 and l = 2 (δν02), and the dimensionless offset (epsilon). These measurements allow us to construct asteroseismic diagrams, namely the so-called Christensen-Dalsgaard diagram of δν02 versus Δν, and the recently re-introduced epsilon diagram. We compare the Kepler results with previously observed solar-type stars and with theoretical models. The positions of stars in these diagrams places constraints on their masses and ages. Additionally, we confirm the observational relationship between epsilon and T eff that allows for the unambiguous determination of radial order and should help resolve the problem of mode identification in F stars. Title: Constructing a One-solar-mass Evolutionary Sequence Using Asteroseismic Data from Kepler Authors: Silva Aguirre, V.; Chaplin, W. J.; Ballot, J.; Basu, S.; Bedding, T. R.; Serenelli, A. M.; Verner, G. A.; Miglio, A.; Monteiro, M. J. P. F. G.; Weiss, A.; Appourchaux, T.; Bonanno, A.; Broomhall, A. M.; Bruntt, H.; Campante, T. L.; Casagrande, L.; Corsaro, E.; Elsworth, Y.; García, R. A.; Gaulme, P.; Handberg, R.; Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Mosser, B.; Salabert, D.; Schönrich, R.; Sousa, S. G.; Stello, D.; White, T. R.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Thompson, M. J.; Caldwell, D. A.; Christiansen, J. L.; Wohler, B. Bibcode: 2011ApJ...740L...2S Altcode: 2011arXiv1108.2031S Asteroseismology of solar-type stars has entered a new era of large surveys with the success of the NASA Kepler mission, which is providing exquisite data on oscillations of stars across the Hertzsprung-Russell diagram. From the time-series photometry, the two seismic parameters that can be most readily extracted are the large frequency separation (Δν) and the frequency of maximum oscillation power (νmax). After the survey phase, these quantities are available for hundreds of solar-type stars. By scaling from solar values, we use these two asteroseismic observables to identify for the first time an evolutionary sequence of 1 M sun field stars, without the need for further information from stellar models. Comparison of our determinations with the few available spectroscopic results shows an excellent level of agreement. We discuss the potential of the method for differential analysis throughout the main-sequence evolution and the possibility of detecting twins of very well-known stars. Title: Herschel-ATLAS: rapid evolution of dust in galaxies over the last 5 billion years Authors: Dunne, L.; Gomez, H. L.; da Cunha, E.; Charlot, S.; Dye, S.; Eales, S.; Maddox, S. J.; Rowlands, K.; Smith, D. J. B.; Auld, R.; Baes, M.; Bonfield, D. G.; Bourne, N.; Buttiglione, S.; Cava, A.; Clements, D. L.; Coppin, K. E. K.; Cooray, A.; Dariush, A.; de Zotti, G.; Driver, S.; Fritz, J.; Geach, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Jarvis, M. J.; Kelvin, L.; Pascale, E.; Pohlen, M.; Popescu, C.; Rigby, E. E.; Robotham, A.; Rodighiero, G.; Sansom, A. E.; Serjeant, S.; Temi, P.; Thompson, M.; Tuffs, R.; van der Werf, P.; Vlahakis, C. Bibcode: 2011MNRAS.417.1510D Altcode: 2010arXiv1012.5186D; 2011MNRAS.tmp.1395D We present the first direct and unbiased measurement of the evolution of the dust mass function of galaxies over the past 5 billion years of cosmic history using data from the Science Demonstration Phase of the Herschel-Astrophysical Terahertz Large Area Survey (Herschel-ATLAS). The sample consists of galaxies selected at 250 ?m which have reliable counterparts from the Sloan Digital Sky Survey (SDSS) at z < 0.5, and contains 1867 sources. Dust masses are calculated using both a single-temperature grey-body model for the spectral energy distribution and also a model with multiple temperature components. The dust temperature for either model shows no trend with redshift. Splitting the sample into bins of redshift reveals a strong evolution in the dust properties of the most massive galaxies. At z= 0.4-0.5, massive galaxies had dust masses about five times larger than in the local Universe. At the same time, the dust-to-stellar mass ratio was about three to four times larger, and the optical depth derived from fitting the UV-sub-mm data with an energy balance model was also higher. This increase in the dust content of massive galaxies at high redshift is difficult to explain using standard dust evolution models and requires a rapid gas consumption time-scale together with either a more top-heavy initial mass function (IMF), efficient mantle growth, less dust destruction or combinations of all three. This evolution in dust mass is likely to be associated with a change in overall interstellar medium mass, and points to an enhanced supply of fuel for star formation at earlier cosmic epochs. Title: OT2_mthomp01_2: Confirming a sample of massive and luminous debris disks identified in the Herschel-ATLAS Authors: Thompson, M. Bibcode: 2011hers.prop.2085T Altcode: Debris disks are the remains of planetary system formation, tracing the existence of planetesimal-sized objects in orbit around main sequence stars. Current and planned surveys of debris disks (including the Herschel Key Projects DEBRIS and DUNES) are deep surveys aimed at characterising the typical population of disks and targeted at samples of a few hundred nearby objects. These deep narrow surveys are relatively insensitive to the rarities in the debris disk population, some of which may be luminous and/or massive disks that have undergone recent disruptive collisional events. We have recently shown that the primarily extragalactic Key Project, the Herschel-ATLAS, can be used as a wide and shallow survey of debris disks by combining its excellent optical coverage and statistical techniques more commonly employed to identify galaxies. The combination of Herschel-ATLAS, DEBRIS and DUNES thus forms a powerful nested tier of surveys that will be sensitive to disks across the spectrum from exosolar analogues to rare disks that cannot be inferred from local populations. In this proposal we seek time to image 23 candidate disks that we have discovered in the Herschel-ATLAS with PACS so that we may confirm them as true debris disks and model their SEDs to extract mass, temperature and fractional luminosity. We will confirm whether these disk candidates are in fact the most luminous disks yet detected. Title: Stellar hydrodynamics caught in the act: Asteroseismology with CoRoT and Kepler Authors: Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 2011IAUS..271...32C Altcode: 2011arXiv1104.5191C Asteroseismic investigations, particularly based on data on stellar oscillations from the CoRoT and Kepler space missions, are providing unique possibilities for investigating the properties of stellar interiors. This constitutes entirely new ways to study the effects of dynamic phenomena on stellar structure and evolution. Important examples are the extent of convection zones and the associated mixing and the direct and indirect effects of stellar rotation. In addition, the stellar oscillations themselves show very interesting dynamic behaviour. Here we discuss examples of the results obtained from such investigations, across the Hertzsprung-Russell diagram. Title: Minor Planet Observations [F65 Haleakala-Faulkes Telescope North] Authors: Fitzsimmons, A.; Roche, P.; Micheli, M.; Guido, E.; Lister, T.; Miller, P.; Tripp, A.; Holmes, R.; Miles, R.; Buzzi, L.; Fogl, S.; Howes, N.; Sostero, G.; Blyth, H.; Foglia, S.; Armstrong, J. D.; Sobaje, C. S.; Boaz, R. Z.; Thompson, M.; Pfluke, A. Bibcode: 2011MPC..75687...1F Altcode: No abstract at ADS Title: Probing Subsurface Flows Around Sunspots with 3-Dimensional Ring Inversions Authors: Featherstone, Nicholas Andrew; Hindman, Bradley W.; Thompson, Michael J.; Toomre, Juri Bibcode: 2011shin.confE...7F Altcode: We examine convective flows around sunspots as inferred through ring-analysis helioseismology of MDI Dopplergrams. These flow measurements were obtained using a novel 3-D inversion procedure termed Adaptively Resolved Ring-Diagram Inversions, or ARRDI, which uses sensitivity kernels based on the Born approximation. The ARRDI algorithm is multi-scale in nature, folding together information from tiles located at different positions on the solar surface and from tiles of different sizes, thus enabling fine control of the horizontal resolution and the probing depth. When we apply ARRDI to sunspots, we measure outflows persisting to depths of at least 7 Mm. In many instances, the surface outflow diminishes within the upper 3 Mm of the convection zone. Beyond 3 Mm, such outflows strengthen and attain peak amplitudes of 200 m/s at depths of 5-7 Mm. We discuss the implications of such a two-component outflow for understanding the magneto-hydrodynamic behavior and evolution of sunspots. Title: Solar-like Oscillations in KIC 11395018 and KIC 11234888 from 8 Months of Kepler Data Authors: Mathur, S.; Handberg, R.; Campante, T. L.; García, R. A.; Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot, J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker, S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão, I. M.; Creevey, O. L.; Doǧan, G.; Elsworth, Y.; Huber, D.; Hale, S. J.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Quintana, E. V.; Sanderfer, D. T.; Seader, S. E. Bibcode: 2011ApJ...733...95M Altcode: 2011arXiv1103.4085M We analyze the photometric short-cadence data obtained with the Kepler mission during the first 8 months of observations of two solar-type stars of spectral types G and F: KIC 11395018 and KIC 11234888, respectively, the latter having a lower signal-to-noise ratio (S/N) compared with the former. We estimate global parameters of the acoustic (p) modes such as the average large and small frequency separations, the frequency of the maximum of the p-mode envelope, and the average line width of the acoustic modes. We were able to identify and to measure 22 p-mode frequencies for the first star and 16 for the second one even though the S/N of these stars are rather low. We also derive some information about the stellar rotation periods from the analyses of the low-frequency parts of the power spectral densities. A model-independent estimation of the mean density, mass, and radius is obtained using the scaling laws. We emphasize the importance of continued observations for the stars with low S/N for an improved characterization of the oscillation modes. Our results offer a preview of what will be possible for many stars with the long data sets obtained during the remainder of the mission. Title: A more realistic representation of overshoot at the base of the solar convective envelope as seen by helioseismology Authors: Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G.; Rempel, M.; Thompson, M. J. Bibcode: 2011MNRAS.414.1158C Altcode: 2011MNRAS.tmp..440C; 2011arXiv1102.0235C The stratification near the base of the Sun's convective envelope is governed by processes of convective overshooting and element diffusion, and the region is widely believed to play a key role in the solar dynamo. The stratification in that region gives rise to a characteristic signal in the frequencies of solar p modes, which has been used to determine the depth of the solar convection zone and to investigate the extent of convective overshoot. Previous helioseismic investigations have shown that the Sun's spherically symmetric stratification in this region is smoother than that in a standard solar model without overshooting, and have ruled out simple models incorporating overshooting, which extend the region of adiabatic stratification and have a more-or-less abrupt transition to subadiabatic stratification at the edge of the overshoot region. In this paper we consider physically motivated models which have a smooth transition in stratification bridging the region from the lower convection zone to the radiative interior beneath. We find that such a model is in better agreement with the helioseismic data than a standard solar model. Title: Preparation of Kepler light curves for asteroseismic analyses Authors: García, R. A.; Hekker, S.; Stello, D.; Gutiérrez-Soto, J.; Handberg, R.; Huber, D.; Karoff, C.; Uytterhoeven, K.; Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Mathur, S.; Ballot, J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Houdek, G.; Jenkins, J. M.; Kjeldsen, H.; McCauliff, S.; Metcalfe, T.; Middour, C. K.; Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.; Smith, J. C.; Thompson, M. J. Bibcode: 2011MNRAS.414L...6G Altcode: 2011arXiv1103.0382G The Kepler mission is providing photometric data of exquisite quality for the asteroseismic study of different classes of pulsating stars. These analyses place particular demands on the pre-processing of the data, over a range of time-scales from minutes to months. Here, we describe processing procedures developed by the Kepler Asteroseismic Science Consortium to prepare light curves that are optimized for the asteroseismic study of solar-like oscillating stars in which outliers, jumps and drifts are corrected. Title: On the effects of rotation on acoustic stellar pulsations: validity domains of perturbative methods and close frequency pairs Authors: Burke, K. D.; Reese, D. R.; Thompson, M. J. Bibcode: 2011MNRAS.414.1119B Altcode: 2011MNRAS.tmp..475B; 2011arXiv1102.0382B Pulsation frequencies of acoustic modes are calculated for realistic rotating stellar models using both a perturbative and a two-dimensional approach. A comparison between the two yields validity domains which are similar to those previously obtained in Reese et al. for polytropic models. One can also construct validity domains based on polynomial fits to the frequencies from the two-dimensional approach, and these also turn out to be similar, thus further confirming the agreement between the perturbative and the two-dimensional approaches at low rotation rates. Furthermore, as was previously shown in Espinosa et al., adjacent frequencies in multiplets come close together, thus forming pairs. This phenomenon, exclusive to two-dimensional calculations, is shown to be an unlikely explanation of the close frequency pairs observed in δ Scuti stars. A systematic search for all close frequency pairs in the calculated spectrum is also carried out. The number of close frequency pairs is shown to agree with what is expected based on a Poisson distribution, but does not match the number or distribution of close pairs in stars such as FG Vir. Furthermore, a lack of close frequency pairs appears at low rotation rates, where frequency multiplets do not overlap. δ Scuti stars currently reported as having close frequency pairs do not fall in this interval. Title: Predicting the Detectability of Oscillations in Solar-type Stars Observed by Kepler Authors: Chaplin, W. J.; Kjeldsen, H.; Bedding, T. R.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Appourchaux, T.; Elsworth, Y.; García, R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Verner, G. A.; Batalha, N.; Borucki, W. J.; Brown, T. M.; Bryson, S. T.; Christiansen, J. L.; Clarke, B. D.; Jenkins, J. M.; Klaus, T. C.; Koch, D.; An, D.; Ballot, J.; Basu, S.; Benomar, O.; Bonanno, A.; Broomhall, A. -M.; Campante, T. L.; Corsaro, E.; Creevey, O. L.; Esch, L.; Gai, N.; Gaulme, P.; Hale, S. J.; Handberg, R.; Hekker, S.; Huber, D.; Mathur, S.; Mosser, B.; New, R.; Pinsonneault, M. H.; Pricopi, D.; Quirion, P. -O.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; Stello, D.; Suran, M. D. Bibcode: 2011ApJ...732...54C Altcode: 2011arXiv1103.0702C Asteroseismology of solar-type stars has an important part to play in the exoplanet program of the NASA Kepler Mission. Precise and accurate inferences on the stellar properties that are made possible by the seismic data allow very tight constraints to be placed on the exoplanetary systems. Here, we outline how to make an estimate of the detectability of solar-like oscillations in any given Kepler target, using rough estimates of the temperature and radius, and the Kepler apparent magnitude. Title: Evidence for the Impact of Stellar Activity on the Detectability of Solar-like Oscillations Observed by Kepler Authors: Chaplin, W. J.; Bedding, T. R.; Bonanno, A.; Broomhall, A. -M.; García, R. A.; Hekker, S.; Huber, D.; Verner, G. A.; Basu, S.; Elsworth, Y.; Houdek, G.; Mathur, S.; Mosser, B.; New, R.; Stevens, I. R.; Appourchaux, T.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Ballot, J.; Benomar, O.; Corsaro, E.; Campante, T. L.; Gaulme, P.; Hale, S. J.; Handberg, R.; Jarvis, E.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; Stello, D.; Mullally, F.; Li, J.; Wohler, W. Bibcode: 2011ApJ...732L...5C Altcode: 2011arXiv1103.5570C We use photometric observations of solar-type stars, made by the NASA Kepler Mission, to conduct a statistical study of the impact of stellar surface activity on the detectability of solar-like oscillations. We find that the number of stars with detected oscillations falls significantly with increasing levels of activity. The results present strong evidence for the impact of magnetic activity on the properties of near-surface convection in the stars, which appears to inhibit the amplitudes of the stochastically excited, intrinsically damped solar-like oscillations. Title: Large-scale Zonal Flows During the Solar Minimum -- Where Is Cycle 25? Authors: Hill, Frank; Howe, R.; Komm, R.; Christensen-Dalsgaard, J.; Larson, T. P.; Schou, J.; Thompson, M. J. Bibcode: 2011SPD....42.1610H Altcode: 2011BAAS..43S.1610H The so-called torsional oscillation is a pattern of migrating zonal flow bands that move from mid-latitudes towards the equator and poles as the magnetic cycle progresses. Helioseismology allows us to probe these flows below the solar surface. The prolonged solar minimum following Cycle 23 was accompanied by a delay of 1.5 to 2 years in the migration of bands of faster rotation towards the equator. During the rising phase of Cycle 24, while the lower-level bands match those seen in the rising phase of Cycle 23, the rotation rate at middle and higher latitudes remains slower than it was at the corresponding phase in earlier cycles, perhaps reflecting the weakness of the polar fields. In addition, there is no evidence of the poleward flow associated with Cycle 25. We will present the latest results based on nearly sixteen years of global helioseismic observations from GONG and MDI, with recent results from HMI, and discuss the implications for the development of Cycle 25. Title: Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission Authors: Chaplin, W. J.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Basu, S.; Miglio, A.; Appourchaux, T.; Bedding, T. R.; Elsworth, Y.; García, R. A.; Gilliland, R. L.; Girardi, L.; Houdek, G.; Karoff, C.; Kawaler, S. D.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Verner, G. A.; Ballot, J.; Bonanno, A.; Brandão, I. M.; Broomhall, A. -M.; Bruntt, H.; Campante, T. L.; Corsaro, E.; Creevey, O. L.; Doğan, G.; Esch, L.; Gai, N.; Gaulme, P.; Hale, S. J.; Handberg, R.; Hekker, S.; Huber, D.; Jiménez, A.; Mathur, S.; Mazumdar, A.; Mosser, B.; New, R.; Pinsonneault, M. H.; Pricopi, D.; Quirion, P. -O.; Régulo, C.; Salabert, D.; Serenelli, A. M.; Silva Aguirre, V.; Sousa, S. G.; Stello, D.; Stevens, I. R.; Suran, M. D.; Uytterhoeven, K.; White, T. R.; Borucki, W. J.; Brown, T. M.; Jenkins, J. M.; Kinemuchi, K.; Van Cleve, J.; Klaus, T. C. Bibcode: 2011Sci...332..213C Altcode: 2011arXiv1109.4723C In addition to its search for extrasolar planets, the NASA Kepler mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solar-type stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar properties (such as mass, radius, and age) and to test theories of stellar evolution. We find that the distribution of observed masses of these stars shows intriguing differences to predictions from models of synthetic stellar populations in the Galaxy. Title: Wave absorption and moat flow in AR9787 Authors: Roth, M.; Thompson, M. J. Bibcode: 2011JPhCS.271a2022R Altcode: We present the results of a study of the wave absorption and the moat flow around the sunspot in AR9787 (the "HELAS sunspot", so-called because it has been the object of in-depth study at a HELAS workshop) using Fourier-Hankel decomposition of the oscillatory wave field. We carry out inversions both for the flow speed and for the sound speed perturbation as a function of depth. The results are compared with results from time-distance helioseismology. Title: Ring-analysis flow measurements of sunspot outflows Authors: Featherstone, Nicholas A.; Hindman, Bradley W.; Thompson, Michael J. Bibcode: 2011JPhCS.271a2002F Altcode: We present a local helioseismological analysis of the convective flows around sunspots. The flow deductions were obtained from MDI Dopplergrams using ring-analysis techniques to measure Doppler shifts induced in solar acoustic oscillations. A novel multi-scale 3-D inversion procedure was used to self-consistently combine all ring-analysis data taken from a mosaic of analysis tiles spanning the solar disk. The inversion is multi-scale because in addition to folding together information from tiles located at different positions on the solar surface, it is capable of incorporating tiles of different sizes, thus, enabling fine control of the horizontal resolution and the probing depth. The inversion is based on sensitivity kernels computed with the Born approximation. Our inversion results indicate that outflow observed at the surface surrounding sunspots persists to unexpectedly deep depths (~ 7 Mm). These outflows appear to have two components, being comprised of a superficial moat flow and a deeper outflow whose strength peaks around 5 Mm. Title: First Global Rotation Inversions of HMI Data Authors: Howe, R.; Larson, T. P.; Schou, J.; Hill, F.; Komm, R.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2011JPhCS.271a2061H Altcode: We present the first 2-dimensional global rotational inversions of medium-degree p-mode data from the Helioseismic and Magnetic Imager, and compare the results with inversions of Michelson Doppler Imager data for the same time period. The inferred rotation profiles show good agreement between the two instruments. Title: Helioseismic Tests With the FLASH Simulation Code Authors: González-Morales, Pedro A.; Jain, Rekha; Thompson, Michael J. Bibcode: 2011JPhCS.271a2013G Altcode: We show our first results from local helioseismic simulations using the numerical code FLASH by testing its suitability for simulating subphotospheric wave motions in helioseismology. In order to check the capability of this code for different sources of waves, we have implemented a non-magnetic plane-parallel atmosphere adding a source term to the energy equation. We confirm the capabilities of FLASH code for investigating the propagation of sound waves into a realistically stratified solar interior. Title: Progress on the Baker Observatory Sub-minute Survey Authors: Reed, Mike; Gilker, J.; Thompson, M.; Hicks, L.; Quint, A.; Metzger, A. Bibcode: 2011AAS...21733408R Altcode: 2011BAAS...4333408R The Baker Observatory Sub-minute Survey is designed to look for phenomena with short-period variability. Typical exposure times are under 15 seconds, surveying a magnitude range of 10-13 in white light. Known short-period phenomena include pulsating subdwarf B stars, white dwarfs, rapidly oscillating Ap stars and Delta Scuti stars. Currently, most sky surveys are interested in observing the entire sky and as such, the temporal cadence is best suited for variations of several hours or longer. Our survey observes single fields for four hour spans on two separate (non-adjacent) nights. During Phase I of our survey, we have selected 40 fields which contain at least one known variable star. It is then a blind study to determine if we can recover the known variable and search for new variables within each field. Observations for Phase I are nearly complete and we are enhancing our procedures and detection algorithms to optimize sensitivity to variations over many time scales. Our data are excellent for detecting variability shorter than two hours, even down to amplitudes of a millimagnitude (depending on S/N). This material is based upon work supported by the National Science Foundation under Grant No. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work was partially funded by the Missouri Space Grant Consortium, funded by NASA and Missouri State University. Title: The torsional oscillation and the new solar cycle Authors: Howe, R.; Hill, F.; Komm, R.; Christensen-Dalsgaard, J.; Larson, T. P.; Schou, J.; Thompson, M. J.; Ulrich, R. Bibcode: 2011JPhCS.271a2074H Altcode: We present updated observations of the pattern of migrating solar zonal flows known as the torsional oscillation, covering 15 years of helioseismic measurements with GONG and MDI and 30 years of surface Doppler observations from Mount Wilson. We compare the behavior of the flows during the extended solar minimum following Cycle 23 with that in earlier minima. We demonstrate that the timing of the migration of the zonal flow belts may be of some use in predicting the start of the new cycle. We also note that the behavior of the high-latitude part of the pattern currently differs from that seen early in the previous cycle, with the high-latitude poleward-migrating branch still not established. Title: Rotation-rate variations at the tachocline: An update Authors: Howe, R.; Komm, R.; Hill, F.; Christensen-Dalsgaard, J.; Larson, T. P.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2011JPhCS.271a2075H Altcode: After 15 years of GONG and MDI observations of the solar interior rotation, we revisit the issue of variations in the rotation rate near the base of the convection zone. The 1.3-year period seen in the first few years of the observations disappeared after 2000 and has still not returned. On the other hand, the agreement between GONG and MDI observations suggests that variations seen in this region have some solar origin, whether a true rotation-rate change or possibly mere stochastic variation; we present a numerical experiment supporting this contention. Title: A new code for Fourier-Legendre analysis of large datasets: First results and a comparison with ring-diagram analysis Authors: Doerr, H. -P.; Roth, M.; Zaatri, A.; Krieger, L.; Thompson, M. J. Bibcode: 2010AN....331..911D Altcode: 2010arXiv1011.4152D Fourier-Legendre decomposition (FLD) of solar Doppler imaging data is a promising method to estimate the sub-surface solar meridional flow. FLD is sensible to low-degree oscillation modes and thus has the potential to probe the deep meridional flow. We present a newly developed code to be used for large scale FLD analysis of helioseismic data as provided by the Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI) instrument, and the upcoming Helioseismic and Magnetic Imager (HMI) instrument. First results obtained with the new code are qualitatively comparable to those obtained from ring-diagram analyis of the same time series. Title: Asteroseismology of solar-type stars with Kepler I: Data analysis Authors: Karoff, C.; Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Garcia, R. A.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Basu, S.; Bedding, T. R.; Campante, T. L.; Eggenberger, P.; Fletcher, S. T.; Gaulme, P.; Handberg, R.; Hekker, S.; Martic, M.; Mathur, S.; Mosser, B.; Regulo, C.; Roxburgh, I. W.; Salabert, D.; Stello, D.; Verner, G. A.; Belkacem, K.; Biazzo, K.; Cunha, M. S.; Gruberbauer, M.; Guzik, J. A.; Kupka, F.; Leroy, B.; Ludwig, H. -G.; Mathis, S.; Noels, A.; Noyes, R. W.; Roca Cortes, T.; Roth, M.; Sato, K. H.; Schmitt, J.; Suran, M. D.; Trampedach, R.; Uytterhoeven, K.; Ventura, R. Bibcode: 2010AN....331..972K Altcode: 2010arXiv1005.0507K We report on the first asteroseismic analysis of solar-type stars observed by Kepler. Observations of three G-type stars, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: About 20 modes of oscillation can clearly be distinguished in each star. We discuss the appearance of the oscillation spectra, including the presence of a possible signature of faculae, and the presence of mixed modes in one of the three stars. Title: Four years of HELAS Authors: Roth, M.; Lühe, O. v. d.; Aerts, C.; Christensen-Dalsgaard, J.; Corbard, T.; Daszyńska-Daszkiewicz, J.; Di Mauro, M. P.; Gizon, L.; Jiménez-Reyes, S.; Monteiro, M. J. P. F. G.; Pallé, P. L.; Thompson, M. J. Bibcode: 2010AN....331.1084R Altcode: The European Coordination Action on HELio- and ASteroseismology (HELAS) has completed its fourth and final year of initial funding by the European Commission. Set up as a network which combines solar and stellar physics communities in the important and vigorously evolving field of seismology, HELAS has been able to coordinate the efforts of European astronomers with remarkable success. Four large international conferences including the HELAS-IV conference on Lanzarote as well as many workshops were organized with a substantial contribution from HELAS. About a dozen workshops, addressing specialized questions in global and local helioseismology and asteroseismology were entirely organized by HELAS. Data analysis tools to prepare the European communities for the upcoming influx of data from new missions have been prepared, tested and demonstrated. Lecture notes and outreach material have been assembled and prepared for general access. As a result, HELAS has an important impact on the scientific output of the astrophysics seismology communities and significantly increased the visibility of European research in this field. This paper summarizes the activities and accomplishments of HELAS. Title: Asteroseismology of solar-type stars with Kepler: II. Stellar modeling Authors: Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Chaplin, W. J.; Basu, S.; Bonanno, A.; Di Mauro, M. P.; Doğan, G.; Eggenberger, P.; Karoff, C.; Stello, D.; WG1, KASC Bibcode: 2010AN....331..977M Altcode: 2010arXiv1006.5695M Observations from the Kepler satellite were recently published for three bright G-type stars, which were monitored during the first 33.5 days of science operations. One of these stars, KIC 11026764, exhibits a characteristic pattern of oscillation frequencies suggesting that the star has evolved significantly. We have derived initial estimates of the properties of KIC 11026764 from the oscillation frequencies observed by Kepler, combined with ground-based spectroscopic data. We present preliminary results from detailed modeling of this star, employing a variety of independent codes and analyses that attempt to match the asteroseismic and spectroscopic constraints simultaneously. Title: A Precise Asteroseismic Age and Radius for the Evolved Sun-like Star KIC 11026764 Authors: Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Molenda-Żakowicz, J.; Appourchaux, T.; Chaplin, W. J.; Doǧan, G.; Eggenberger, P.; Bedding, T. R.; Bruntt, H.; Creevey, O. L.; Quirion, P. -O.; Stello, D.; Bonanno, A.; Silva Aguirre, V.; Basu, S.; Esch, L.; Gai, N.; Di Mauro, M. P.; Kosovichev, A. G.; Kitiashvili, I. N.; Suárez, J. C.; Moya, A.; Piau, L.; García, R. A.; Marques, J. P.; Frasca, A.; Biazzo, K.; Sousa, S. G.; Dreizler, S.; Bazot, M.; Karoff, C.; Frandsen, S.; Wilson, P. A.; Brown, T. M.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Campante, T. L.; Fletcher, S. T.; Handberg, R.; Régulo, C.; Salabert, D.; Schou, J.; Verner, G. A.; Ballot, J.; Broomhall, A. -M.; Elsworth, Y.; Hekker, S.; Huber, D.; Mathur, S.; New, R.; Roxburgh, I. W.; Sato, K. H.; White, T. R.; Borucki, W. J.; Koch, D. G.; Jenkins, J. M. Bibcode: 2010ApJ...723.1583M Altcode: 2010arXiv1010.4329M The primary science goal of the Kepler Mission is to provide a census of exoplanets in the solar neighborhood, including the identification and characterization of habitable Earth-like planets. The asteroseismic capabilities of the mission are being used to determine precise radii and ages for the target stars from their solar-like oscillations. Chaplin et al. published observations of three bright G-type stars, which were monitored during the first 33.5 days of science operations. One of these stars, the subgiant KIC 11026764, exhibits a characteristic pattern of oscillation frequencies suggesting that it has evolved significantly. We have derived asteroseismic estimates of the properties of KIC 11026764 from Kepler photometry combined with ground-based spectroscopic data. We present the results of detailed modeling for this star, employing a variety of independent codes and analyses that attempt to match the asteroseismic and spectroscopic constraints simultaneously. We determine both the radius and the age of KIC 11026764 with a precision near 1%, and an accuracy near 2% for the radius and 15% for the age. Continued observations of this star promise to reveal additional oscillation frequencies that will further improve the determination of its fundamental properties. Title: Modeling the Subsurface Structure of Sunspots Authors: Moradi, H.; Baldner, C.; Birch, A. C.; Braun, D. C.; Cameron, R. H.; Duvall, T. L.; Gizon, L.; Haber, D.; Hanasoge, S. M.; Hindman, B. W.; Jackiewicz, J.; Khomenko, E.; Komm, R.; Rajaguru, P.; Rempel, M.; Roth, M.; Schlichenmaier, R.; Schunker, H.; Spruit, H. C.; Strassmeier, K. G.; Thompson, M. J.; Zharkov, S. Bibcode: 2010SoPh..267....1M Altcode: 2009arXiv0912.4982M; 2010SoPh..tmp..171M While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this article, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out a helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by Gizon et al. (2009a, 2009b). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat. Title: Erratum: Erratum to: Helioseismology of Sunspots: A Case Study of NOAA Region 9787 Authors: Gizon, L.; Schunker, H.; Baldner, C. S.; Basu, S.; Birch, A. C.; Bogart, R. S.; Braun, D. C.; Cameron, R.; Duvall, T. L.; Hanasoge, S. M.; Jackiewicz, J.; Roth, M.; Stahn, T.; Thompson, M. J.; Zharkov, S. Bibcode: 2010SSRv..156..257G Altcode: 2010SSRv..tmp...99G No abstract at ADS Title: VISTA Variables in the Vía Láctea (VVV): Current Status and First Results Authors: Saito, R.; Hempel, M.; Alonso-García, J.; Toledo, I.; Borissova, J.; González, O.; Beamin, J. C.; Minniti, D.; Lucas, P.; Emerson, J.; Ahumada, A.; Aigrain, S.; Alonso, M. V.; Amôres, E.; Angeloni, R.; Arias, J.; Bandyopadhyay, R.; Barbá, R.; Barbuy, B.; Baume, G.; Bedin, L.; Bica, E.; Bronfman, L.; Carraro, G.; Catelan, M.; Clariá, J.; Contreras, C.; Cross, N.; Davis, C.; de Grijs, R.; Dékány, I.; Janet Drew, J. D.; Fariña, C.; Feinstein, C.; Fernández Lajús, E.; Folkes, S.; Gamen, R.; Geisler, D.; Gieren, W.; Goldman, B.; Gosling, A.; Gunthardt, G.; Gurovich, S.; Hambly, N.; Hanson, M.; Hoare, M.; Irwin, M.; Ivanov, V.; Jordán, A.; Kerins, E.; Kinemuchi, K.; Kurtev, R.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Martín, E.; Masetti, N.; Mennickent, R.; Merlo, D.; Messineo, M.; Mirabel, F.; Monaco, L.; Moni Bidin, C.; Morelli, L.; Padilla, N.; Palma, T.; Parisi, M. C.; Parker, Q.; Pavani, D.; Pietrukowicz, P.; Pietrzynski, G.; Pignata, G.; Rejkuba, M.; Rojas, A.; Roman Lopes, A.; Ruiz, M. T.; Sale, S.; Saviane, I.; Schreiber, M.; Schröder, A.; Sharma, S.; Smith, M.; Sodré, L., Jr.; Soto, M.; Stephens, A.; Tamura, M.; Tappert, C.; Thompson, M.; Valenti, E.; Vanzi, L.; Weidmann, W.; Zoccali, M. Bibcode: 2010Msngr.141...24S Altcode: VISTA Variables in the Vía Láctea (VVV) is a public ESO near-IR variability survey aimed at scanning the Milky Way Bulge and an adjacent section of the mid-plane. VVV observations started in October 2009 during ESO science verification. Regular observations for the first year of the survey have been conducted since February 2010 and will cover a total area of 520 square degrees in five passbands and five epochs. Here we address the first results obtained from the VVV Survey as well as the current status of the observations. Title: Herschel ATLAS: The cosmic star formation history of quasar host galaxies Authors: Serjeant, S.; Bertoldi, F.; Blain, A. W.; Clements, D. L.; Cooray, A.; Danese, L.; Dunlop, J.; Dunne, L.; Eales, S.; Falder, J.; Hatziminaoglou, E.; Hughes, D. H.; Ibar, E.; Jarvis, M. J.; Lawrence, A.; Lee, M. G.; Michałowski, M.; Negrello, M.; Omont, A.; Page, M.; Pearson, C.; van der Werf, P. P.; White, G.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D. G.; Burgarella, D.; Buttiglione, S.; Cava, A.; Dariush, A.; de Zotti, G.; Dye, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.; Ivison, R. J.; Lagache, G.; Leeuw, L.; Lopez-Caniego, M.; Maddox, S.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Samui, S.; Sibthorpe, B.; Smith, D. J. B.; Temi, P.; Thompson, M.; Valtchanov, I.; Verma, A. Bibcode: 2010A&A...518L...7S Altcode: 2010arXiv1005.2410S We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 < z < 6 and absolute I-band magnitudes -22 > IAB > -32 We use the science demonstration observations of the first ~16 deg2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at >5σ at 250,350 and 500 μm. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 > IAB > -24 have a comoving star formation rate (derived from 100 μm rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with IAB < -26 have a maximum contribution to the star formation density at z ~ 3. The volume-averaged star formation rate of -22 > IAB > -24 quasars evolves as (1 + z)2.3±0.7 at z < 2, but the evolution at higher luminosities is much faster reaching (1 + z)10±1 at -26 > IAB > -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia with important participation from NASA. Title: Herschel-ATLAS: The dust energy balance in the edge-on spiral galaxy UGC 4754 Authors: Baes, M.; Fritz, J.; Gadotti, D. A.; Smith, D. J. B.; Dunne, L.; da Cunha, E.; Amblard, A.; Auld, R.; Bendo, G. J.; Bonfield, D.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D.; Cooray, A.; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Frayer, D.; Gonzalez-Nuevo, J.; Herranz, D.; Ibar, E.; Ivison, R.; Lagache, G.; Leeuw, L.; Lopez-Caniego, M.; Jarvis, M.; Maddox, S.; Negrello, M.; Michałowski, M.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Samui, S.; Serjeant, S.; Temi, P.; Thompson, M.; van der Werf, P.; Verma, A.; Vlahakis, C. Bibcode: 2010A&A...518L..39B Altcode: 2010arXiv1005.1773B We use Herschel PACS and SPIRE observations of the edge-on spiral galaxy UGC 4754, taken as part of the H-ATLAS SDP observations, to investigate the dust energy balance in this galaxy. We build detailed SKIRT radiative models based on SDSS and UKIDSS maps and use these models to predict the far-infrared emission. We find that our radiative transfer model underestimates the observed FIR emission by a factor of two to three. Similar discrepancies have been found for other edge-on spiral galaxies based on IRAS, ISO, and SCUBA data. Thanks to the good sampling of the SED at FIR wavelengths, we can rule out an underestimation of the FIR emissivity as the cause for this discrepancy. Instead we support highly obscured star formation that contributes little to the optical extinction as a more probable explanation.

Herschel is an ESA space observatory with science instruments provided by European-led principal- investigator consortia and with important participation from NASA. Title: Herschel-ATLAS: Extragalactic number counts from 250 to 500 microns Authors: Clements, D. L.; Rigby, E.; Maddox, S.; Dunne, L.; Mortier, A.; Pearson, C.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D.; Burgarella, D.; Buttiglione, S.; Cava, A.; Cooray, A.; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Frayer, D.; Fritz, J.; Gardner, Jonathan P.; Gonzalez-Nuevo, J.; Herranz, D.; Ibar, E.; Ivison, R.; Jarvis, M. J.; Lagache, G.; Leeuw, L.; Lopez-Caniego, M.; Negrello, M.; Pascale, E.; Pohlen, M.; Rodighiero, G.; Samui, S.; Serjeant, S.; Sibthorpe, B.; Scott, D.; Smith, D. J. B.; Temi, P.; Thompson, M.; Valtchanov, I.; van der Werf, P.; Verma, A. Bibcode: 2010A&A...518L...8C Altcode: 2010arXiv1005.2409C
Aims: The Herschel-ATLAS survey (H-ATLAS) will be the largest area survey to be undertaken by the Herschel Space Observatory. It will cover 550 sq. deg. of extragalactic sky at wavelengths of 100, 160, 250, 350 and 500 μm when completed, reaching flux limits (5σ) from 32 to 145 mJy. We here present galaxy number counts obtained for SPIRE observations of the first ~14 sq. deg. observed at 250, 350 and 500 μm.
Methods: Number counts are a fundamental tool in constraining models of galaxy evolution. We use source catalogs extracted from the H-ATLAS maps as the basis for such an analysis. Correction factors for completeness and flux boosting are derived by applying our extraction method to model catalogs and then applied to the raw observational counts.
Results: We find a steep rise in the number counts at flux levels of 100-200 mJy in all three SPIRE bands, consistent with results from BLAST. The counts are compared to a range of galaxy evolution models. None of the current models is an ideal fit to the data but all ascribe the steep rise to a population of luminous, rapidly evolving dusty galaxies at moderate to high redshift.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Title: Herschel-ATLAS: Blazars in the science demonstration phase field Authors: González-Nuevo, J.; de Zotti, G.; Andreani, P.; Barton, E. J.; Bertoldi, F.; Birkinshaw, M.; Bonavera, L.; Buttiglione, S.; Cooke, J.; Cooray, A.; Danese, G.; Dunne, L.; Eales, S.; Fan, L.; Jarvis, M. J.; Klöckner, H. -R.; Hatziminaoglou, E.; Herranz, D.; Hughes, D. H.; Lapi, A.; Lawrence, A.; Leeuw, L.; Lopez-Caniego, M.; Massardi, M.; Mauch, T.; Michałowski, M. J.; Negrello, M.; Rawlings, S.; Rodighiero, G.; Samui, S.; Serjeant, S.; Vieira, J. D.; White, G.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D. G.; Burgarella, D.; Cava, A.; Clements, D. L.; Dariush, A.; Dye, S.; Frayer, D.; Fritz, J.; Ibar, E.; Ivison, R. J.; Lagache, G.; Maddox, S.; Pascale, E.; Pohlen, M.; Rigby, E.; Sibthorpe, B.; Smith, D. J. B.; Temi, P.; Thompson, M.; Valtchanov, I.; Verma, A. Bibcode: 2010A&A...518L..38G Altcode: 2010arXiv1005.2407G To investigate the poorly constrained sub-mm counts and spectral properties of blazars we searched for these in the Herschel-ATLAS (H-ATLAS) science demonstration phase (SDP) survey catalog. We cross-matched 500 μm sources brighter than 50 mJy with the FIRST radio catalogue. We found two blazars, both previously known. Our study is among the first blind blazar searches at sub-mm wavelengths, i.e., in the spectral regime where little is still known about the blazar SEDs, but where the synchrotron peak of the most luminous blazars is expected to occur. Our early results are consistent with educated extrapolations of lower frequency counts and question indications of substantial spectral curvature downwards and of spectral upturns at mm wavelengths. One of the two blazars is identified with a Fermi/LAT γ-ray source and a WMAP source. The physical parameters of the two blazars are briefly discussed. These observations demonstrate that the H-ATLAS survey will provide key information about the physics of blazars and their contribution to sub-mm counts.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Title: Herschel-ATLAS: The angular correlation function of submillimetre galaxies at high and low redshift Authors: Maddox, S. J.; Dunne, L.; Rigby, E.; Eales, S.; Cooray, A.; Scott, D.; Peacock, J. A.; Negrello, M.; Smith, D. J. B.; Benford, D.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D.; Dariush, A.; de Zotti, G.; Dye, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.; Ibar, E.; Ivison, R.; Jarvis, M. J.; Lagache, G.; Leeuw, L.; Lopez-Caniego, M.; Pascale, E.; Pohlen, M.; Rodighiero, G.; Samui, S.; Serjeant, S.; Temi, P.; Thompson, M.; Verma, A. Bibcode: 2010A&A...518L..11M Altcode: 2010arXiv1005.2406M We present measurements of the angular correlation function of galaxies selected from the first field of the H-ATLAS survey. Careful removal of the background from galactic cirrus is essential, and currently dominates the uncertainty in our measurements. For our 250 μm-selected sample we detect no significant clustering, consistent with the expectation that the 250 μm-selected sources are mostly normal galaxies at z ⪉ 1. For our 350 μm and 500 μm-selected samples we detect relatively strong clustering with correlation amplitudes A of 0.2 and 1.2 at 1', but with relatively large uncertainties. For samples which preferentially select high redshift galaxies at z~2-3 we detect significant strong clustering, leading to an estimate of r0 ~ 7-11 h-1 Mpc. The slope of our clustering measurements is very steep, δ ~ 2. The measurements are consistent with the idea that sub-mm sources consist of a low redshift population of normal galaxies and a high redshift population of highly clustered star-bursting galaxies.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Title: OT1_mthomp01_1: Confirming a sample of luminous debris disk candidates identified in the Herschel ATLAS Authors: Thompson, M. Bibcode: 2010hers.prop.1318T Altcode: Debris disks are the remains of planetary system formation, tracing the existence of planetesimal-sized objects in orbit around main sequence stars. Current and planned surveys of debris disks (including the Herschel Key Projects DEBRIS and DUNES) are deep surveys aimed at characterising the typical population of disks and targeted at samples of a few hundred nearby objects. These deep narrow surveys are relatively insensitive to the rarities in the debris disk population, some of which may be luminous and/or massive disks that have undergone recent disruptive collisional events. We have recently shown that the primarily extragalactic Key Project, the Herschel-ATLAS, can be used as a wide and shallow survey of debris disks by combining its excellent optical coverage and statistical techniques more commonly employed to identify galaxies. The combination of Herschel-ATLAS, DEBRIS and DUNES thus forms a powerful nested tier of surveys that will be sensitive to disks across the spectrum from exosolar analogues to rare disks that cannot be inferred from local populations. In this proposal we seek time to image the three candidate disks that we discovered in the Herschel-ATLAS Science Demonstration Phase with PACS so that we may confirm them as true debris disks and model their SEDs to extract mass, temperature and fractional luminosity. We will confirm whether these disk candidates are in fact the most luminous disks yet detected. Title: Helioseismology over the Solar Cycle Authors: Thompson, M. J. Bibcode: 2010ASPC..428...23T Altcode: 2010arXiv1003.3888T Helioseismology has produced unprecedented measurements of the Sun's internal structure and dynamics over the past 25 years. Much of this work has been based on global helioseismology. Now local helioseismology too is showing its great promise. This review summarizes very briefly the principal global results that may be relevant to an understanding of the origins of solar magnetism. Recent results regarding the variation of frequencies over the solar cycle and the temporal variations of subsurface flows are briefly summarized. Title: Developing Physics-Based Procedures for Local Helioseismic Probing of Sunspots and Magnetic Regions Authors: Birch, Aaron; Braun, D. C.; Crouch, A.; Rempel, M.; Fan, Y.; Centeno, R.; Toomre, J.; Haber, D.; Hindman, B.; Featherstone, N.; Duvall, T., Jr.; Jackiewicz, J.; Thompson, M.; Stein, R.; Gizon, L.; Cameron, R.; Saidi, Y.; Hanasoge, S.; Burston, R.; Schunker, H.; Moradi, H. Bibcode: 2010AAS...21630805B Altcode: We have initiated a project to test and improve the local helioseismic techniques of time-distance and ring-diagram analysis. Our goals are to develop and implement physics-based methods that will (1) enable the reliable determinations of subsurface flow, magnetic field, and thermal structure in regions of strong magnetic fields and (2) be quantitatively tested with realistic solar magnetoconvection simulations in the presence of sunspot-like magnetic fields. We are proceeding through a combination of improvements in local helioseismic measurements, forward modeling of the helioseismic wavefield, kernel computations, inversions, and validation through numerical simulations. As improvements over existing techniques are made they will be applied to the SDO/HMI observations. This work is funded through the the NASA Heliophysics Science Division through the Solar Dynamics Observatory (SDO) Science Center program. Title: The Solar Dynamo Authors: Jones, Chris A.; Thompson, Michael J.; Tobias, Steven M. Bibcode: 2010SSRv..152..591J Altcode: Observations relevant to current models of the solar dynamo are presented, with emphasis on the history of solar magnetic activity and on the location and nature of the solar tachocline. The problems encountered when direct numerical simulation is used to analyse the solar cycle are discussed, and recent progress is reviewed. Mean field dynamo theory is still the basis of most theories of the solar dynamo, so a discussion of its fundamental principles and its underlying assumptions is given. The role of magnetic helicity is discussed. Some of the most popular models based on mean field theory are reviewed briefly. Dynamo models based on severe truncations of the full MHD equations are discussed. Title: The Asteroseismic Potential of Kepler: First Results for Solar-Type Stars Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García, R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki, W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.; Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt, H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan, G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.; Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe, R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic, M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.; Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.; Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi, D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.; Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.; Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss, L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev, A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.; Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes, R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.; Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre, V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.; Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A. Bibcode: 2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: about 20 modes of oscillation may be clearly distinguished in each star. We discuss the appearance of the oscillation spectra, use the frequencies and frequency separations to provide first results on the radii, masses, and ages of the stars, and comment in the light of these results on prospects for inference on other solar-type stars that Kepler will observe. Title: The Smallest Lunar Grains: Analytical TEM Characterization of the Sub-Micron Size Fraction of a Mare Soil Authors: Thompson, M.; Christoffersen, R. Bibcode: 2010LPI....41.2191T Altcode: Analytical TEM observations show the sub-micron size fraction of a mature mare soil is highly enriched in glass grains, including spherules, relative to the larger size fractions, including the sub 10 micron size fraction as a whole. Title: The Solar Dynamo Authors: Jones, Chris A.; Thompson, Michael J.; Tobias, Steven M. Bibcode: 2010plma.book..591J Altcode: No abstract at ADS Title: Baker Observatory Subminute Survey Authors: Gilker, Justin; Reed, M.; Doennig, A.; Quint, A.; Hicks, L.; Thompson, M. Bibcode: 2010AAS...21541805G Altcode: 2010BAAS...42..275G We are conducting a small-scale short-period stellar variability survey using our 16-inch telescope at Baker Observatory. The goal is to search for previously undetected variability types and to increase membership of known pulsation classes. We are currently in the first portion of this survey which is to understand the sensitivity of our observations. Our strategy is to have four hour runs with short integrations and observe each field twice. We have begun collecting data with at least one known type of variable star in each field and are doing a blind study to recover the known variable and seek new variable stars. Our initial strategy for detecting variability is to use Fourier techniques for short-period (1 - 30 minutes) variability, phase-dispersion techniques for mid-period (0.5 to 4 hours) and a brightness comparator between the runs for long-period (4 hours to days) variations.

This research is sponsored by the National Science Foundation grant 0913175 and The Missouri Space Grant Consortium, funded by NASA. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect views of the National Science Foundation. Title: Analysis of Acoustic Wave Propagation in the Subphotosphere with Localized Magnetic Field Concentration Authors: Zharkov, S.; Shelyag, S.; Thompson, M. J. Bibcode: 2009ASPC..416...75Z Altcode: We present the time-distance analysis of numerical simulations of acoustic wave propagation and dispersion in the solar subphotosphere with a localized magnetic field concentration. Title: Iterative Inversion for Solar and Stellar Internal Rotation Authors: Sudnik, M.; Thompson, M. J. Bibcode: 2009ASPC..416..411S Altcode: We investigate the feasibility and efficiency of using an iterative method used in geophysics for solving the inverse problem of inferring from frequency splittings the internal rotation of the Sun or other stars. Title: The internal dynamics and magnetism of the sun -- the perspective from global helioseismology (Invited) Authors: Howe, R.; Hill, F.; Komm, R.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 2009AGUFMSH11B..04H Altcode: Helioseismology allows us to probe the interior dynamics of the Sun. Observations over the past three decades reveal the interior rotation profile, with a near-surface shear layer, differential rotation throughout the convection zone, a strong shear layer -- the tachocline -- at the base of the convection zone, and approximately uniform rotation in the radiative interior. Since the mid 1990's, continuous observations from the Global Oscillations Network Group and the Michelson Doppler Imager have allowed the study of subtle temporal variations in the rotation within the convection zone. The so-called "torsional oscillation" pattern of migrating zonal flows accompanying the surface activity migration during the solar cycle has been shown to penetrate deep within the convection zone. During the current extended solar minimum, the flow bands can be seen to migrate more slowly towards the equator than was seen in the previous minimum. There have also been (still unconfirmed) findings of shorter-term variations in the rotation rate close to the tachocline during the early years of the previous solar cycle. This review will describe the important results and give an update on the most recent observations of the interior dynamics as we await the rise of solar cycle 24. Title: The Herschel ATLAS Key Project Authors: Serjeant, S.; Eales, S.; Dunne, L.; Clements, D.; Cooray, A.; de Zotti, G.; Dye, S.; Ivison, R.; Jarvis, M.; Lagache, G.; Maddox, S.; Negrello, M.; Thompson, M.; Herschel Atlas Consortium Bibcode: 2009ASPC..418..523S Altcode: The Herschel Astrophysical Terahertz Large Area Survey (ATLAS) is the largest Open Time Key Project on the Herschel Space Observatory. This legacy survey will cover 550 deg2, an order of magnitude larger than all other Herschel extragalactic surveys combined, and will provide more extragalactic sources than all other Herschel surveys combined. Herschel ATLAS builds on the ground-breaking AKARI All-Sky Survey and has six primary science themes, described here. More information can be found on the consortium web site, http://h-atlas.astro.cf.ac.uk . Title: Numerical Simulation of Acoustic Wave Propagation in the Solar Sub-Photosphere with Localized Magnetic Field Concentration Authors: Shelyag, S.; Zharkov, S.; Fedun, V.; Erdélyi, R.; Thompson, M. J. Bibcode: 2009ASPC..416..167S Altcode: The results of numerical simulations of acoustic wave propagation and dispersion in the solar sub-photosphere with a localised magnetic field concentration are presented. The initial equilibrium density and pressure stratifications are derived from a standard solar model and adjusted to maintain magnetohydrostatic and convective stability. Acoustic waves are generated by a perturbation located at the height corresponding to the visible surface of the Sun. The time-distance diagram of the vertical velocity perturbation at the level corresponding to the visible solar surface shows that the magnetic field perturbs and scatters acoustic waves and absorbs the acoustic power of the wave packet. Title: The Torsional Oscillation and the Solar Minimum Authors: Howe, R.; Hill, F.; Komm, R.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 2009AGUFM.U34A..03H Altcode: The so-called torsional oscillation is a pattern of zonal flow bands, detected at the solar surface by direct Doppler measurements and within the convection zone by helioseismic measurements such as those carried out by the Global Oscillations Network Group and the Michelson Doppler Imager, that migrates from mid-latitudes towards the equator and poles with each solar cycle. In the current minimum the low-latitude branch of the pattern can be seen to have taken at least a year longer to migrate towards the equator than was the case in the previous minimum. A flow configuration matching that of the previous minimum was reached during 2008, and by early 2009 the fast-rotating belt associated with the new cycle had reached the latitude at which the onset of activity was seen in Cycle 23, but magnetic activity has remained low. We will present the most recent results and consider the implications for the new solar cycle. Title: The Torsional Oscillation and the Solar Cycle: Is it Minimum Yet? Authors: Howe, R.; Komm, R.; Hill, F.; Larson, T.; Schou, J.; Thompson, M. J.; Ulrich, R. K. Bibcode: 2009ASPC..416..269H Altcode: The torsional oscillation pattern of migrating zonal flows is related to the solar activity cycle. In the approach to solar minimum, we compare the current flow profile with that seen at the previous minimum, using Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) data as well as Mount Wilson Doppler observations that reach further back in time. Will the flow pattern at the upcoming minimum match that for the previous one? Title: Mode identification in rapidly rotating stars Authors: Reese, D. R.; Thompson, M. J.; MacGregor, K. B.; Jackson, S.; Skumanich, A.; Metcalfe, T. S. Bibcode: 2009A&A...506..183R Altcode: 2009arXiv0905.4889R Context: Recent calculations of pulsation modes in rapidly rotating polytropic models and models based on the Self-Consistent Field method have shown that the frequency spectrum of low degree pulsation modes can be described by an empirical formula similar to Tassoul's asymptotic formula, provided that the underlying rotation profile is not too differential.
Aims: Given the simplicity of this asymptotic formula, we investigate whether it can provide a means by which to identify pulsation modes in rapidly rotating stars.
Methods: We develop a new mode identification scheme which consists in scanning a multidimensional parameter space for the formula coefficients which yield the best-fitting asymptotic spectra. This mode identification scheme is then tested on artificial spectra based on the asymptotic formula, on random frequencies and on spectra based on full numerical eigenmode calculations for which the mode identification is known beforehand. We also investigate the effects of adding random frequencies to mimic the effects of chaotic modes which are also expected to show up in such stars.
Results: In the absence of chaotic modes, it is possible to accurately find a correct mode identification for most of the observed frequencies provided these frequencies are sufficiently close to their asymptotic values. The addition of random frequencies can very quickly become problematic and hinder correct mode identification. Modifying the mode identification scheme to reject the worst fitting modes can bring some improvement but the results still remain poorer than in the case without chaotic modes. Title: Photospheric high-frequency acoustic power excess in sunspot umbra: signature of magneto-acoustic modes Authors: Zharkov, S.; Shelyag, S.; Fedun, V.; Erdélyi, R.; Thompson, M. J. Bibcode: 2009arXiv0909.5332Z Altcode: We present observational evidence for the presence of MHD waves in the solar photosphere deduced from SOHO/MDI Dopplergram velocity observations. The magneto-acoustic perturbations are observed as acoustic power enhancement in the sunspot umbra at high-frequency bands in the velocity component perpendicular to the magnetic field. We use numerical modelling of wave propagation through localised non-uniform magnetic field concentration along with the same filtering procedure as applied to the observations to identify the observed waves. Guided by the results of the numerical simulations we classify the observed oscillations as magneto-acoustic waves excited by the trapped sub-photospheric acoustic waves. We consider the potential application of the presented method as a diagnostic tool for magnetohelioseismology. Title: A Note on the Torsional Oscillation at Solar Minimum Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Schou, J.; Thompson, M. J. Bibcode: 2009ApJ...701L..87H Altcode: 2009arXiv0907.2965H We examine the evolution of the zonal flow pattern in the upper solar convection zone during the current extended solar minimum, and compare it with that during the previous minimum. The results suggest that a configuration matching that at the previous minimum was reached during 2008, but that the flow band corresponding to the new cycle has been moving more slowly toward the equator than was observed in the previous cycle, resulting in a gradual increase in the apparent length of the cycle during the 2007-2008 period. The current position of the lower-latitude fast-rotating belt corresponds to that seen around the onset of activity in the previous cycle. Title: Acoustic wave propagation in the solar sub-photosphere with localised magnetic field concentration: effect of magnetic tension Authors: Shelyag, S.; Zharkov, S.; Fedun, V.; Erdélyi, R.; Thompson, M. J. Bibcode: 2009A&A...501..735S Altcode: 2009arXiv0901.3680S Aims: We analyse numerically the propagation and dispersion of acoustic waves in the solar-like sub-photosphere with localised non-uniform magnetic field concentrations, mimicking sunspots with various representative magnetic field configurations.
Methods: Numerical simulations of wave propagation through the solar sub-photosphere with a localised magnetic field concentration are carried out using SAC, which solves the MHD equations for gravitationally stratified plasma. The initial equilibrium density and pressure stratifications are derived from a standard solar model. Acoustic waves are generated by a source located at the height corresponding approximately to the visible surface of the Sun. By means of local helioseismology we analyse the response of vertical velocity at the level corresponding to the visible solar surface to changes induced by magnetic field in the interior.
Results: The results of numerical simulations of acoustic wave propagation and dispersion in the solar sub-photosphere with localised magnetic field concentrations of various types are presented. Time-distance diagrams of the vertical velocity perturbation at the level corresponding to the visible solar surface show that the magnetic field perturbs and scatters acoustic waves and absorbs the acoustic power of the wave packet. For the weakly magnetised case, the effect of magnetic field is mainly thermodynamic, since the magnetic field changes the temperature stratification. However, we observe the signature of slow magnetoacoustic mode, propagating downwards, for the strong magnetic field cases. Title: VISTA Milky Way Public Survey Authors: Minniti, D.; Lucas, P.; Ahumada, A. V.; Zoccali, M.; Catelan, M.; Morelli, L.; Tappert, C.; Pignata, G.; Toledo, I.; Ruiz, M. T.; Carraro, G.; Casassus, S.; Bronfman, L.; Barbá, R. H.; Gamen, R.; Gieren, W.; Geisler, D.; Pietrzynski, G.; Mennickent, R. E.; Kurtev, R.; Borissova, J.; Mirabel, F.; Ivanov, V. D.; Saviane, I.; Vanzi, L.; Monaco, L.; Rejkuba, M.; Messineo, M.; Bedin, L.; Stephens, A.; Barbuy, B.; Bica, E.; Clariá, J. J.; CASU (VDFS) Team; WFAU (VDFS) Team; Emerson, J.; Drew, J.; López-Correidora, M.; Martin, E.; Goldman, B.; Gianinni, T.; Eisloeffel, J.; Groot, P.; Fabregat, J.; Hambly, N.; Longmore, A.; Walton, N.; de Grijs, R.; Hoare, M.; Schroeder, A.; Naylor, T.; Barlow, M.; Zijlstra, A.; White, G.; Gosling, A.; McGowan, K.; Adamson, A.; Bandyopadhyay, R.; Thompson, M.; Cropper, M.; Lucey, J.; Kerins, E.; Hodgkin, S.; Pinfield, D. Bibcode: 2009RMxAC..35..263M Altcode: We propose a public IR variability survey, named ``Vista Variables in the Vía Láctea'' (VVV), of the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. This would take 1920 hours, covering ∼ 10^9 point sources within an area of 520 sq deg, including 33 known globular clusters and ∼ 350 open clusters. The final products will be a deep IR atlas in 5 passbands and a catalogue of ∼ 10^6 variable point sources. These will produce a 3-D map of the surveyed region (unlike single-epoch surveys that only give 2-D maps) using well-understood primary distance indicators such as RR Lyrae stars. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, SPITZER, HST, CHANDRA, INTEGRAL, and ALMA for a complete understanding of the variable sources in the inner Milky Way. Several important implications for the history of the Milky Way, for globular cluster evolution, for the population census of the bulge and center, and for pulsation theory would follow from this survey. Title: Helioseismology of Sunspots: A Case Study of NOAA Region 9787 Authors: Gizon, L.; Schunker, H.; Baldner, C. S.; Basu, S.; Birch, A. C.; Bogart, R. S.; Braun, D. C.; Cameron, R.; Duvall, T. L.; Hanasoge, S. M.; Jackiewicz, J.; Roth, M.; Stahn, T.; Thompson, M. J.; Zharkov, S. Bibcode: 2009SSRv..144..249G Altcode: 2008SSRv..tmp..188G; 2010arXiv1002.2369G Various methods of helioseismology are used to study the subsurface properties of the sunspot in NOAA Active Region 9787. This sunspot was chosen because it is axisymmetric, shows little evolution during 20-28 January 2002, and was observed continuously by the MDI/SOHO instrument. AR 9787 is visible on helioseismic maps of the farside of the Sun from 15 January, i.e. days before it crossed the East limb. Oscillations have reduced amplitudes in the sunspot at all frequencies, whereas a region of enhanced acoustic power above 5.5 mHz (above the quiet-Sun acoustic cutoff) is seen outside the sunspot and the plage region. This enhanced acoustic power has been suggested to be caused by the conversion of acoustic waves into magneto-acoustic waves that are refracted back into the interior and re-emerge as acoustic waves in the quiet Sun. Observations show that the sunspot absorbs a significant fraction of the incoming p and f modes around 3 mHz. A numerical simulation of MHD wave propagation through a simple model of AR 9787 confirmed that wave absorption is likely to be due to the partial conversion of incoming waves into magneto-acoustic waves that propagate down the sunspot. Wave travel times and mode frequencies are affected by the sunspot. In most cases, wave packets that propagate through the sunspot have reduced travel times. At short travel distances, however, the sign of the travel-time shifts appears to depend sensitively on how the data are processed and, in particular, on filtering in frequency-wavenumber space. We carry out two linear inversions for wave speed: one using travel-times and phase-speed filters and the other one using mode frequencies from ring analysis. These two inversions give subsurface wave-speed profiles with opposite signs and different amplitudes. The travel-time measurements also imply different subsurface flow patterns in the surface layer depending on the filtering procedure that is used. Current sensitivity kernels are unable to reconcile these measurements, perhaps because they rely on imperfect models of the power spectrum of solar oscillations. We present a linear inversion for flows of ridge-filtered travel times. This inversion shows a horizontal outflow in the upper 4 Mm that is consistent with the moat flow deduced from the surface motion of moving magnetic features. From this study of AR 9787, we conclude that we are currently unable to provide a unified description of the subsurface structure and dynamics of the sunspot. Title: The Solar Dynamo Authors: Weiss, N. O.; Thompson, M. J. Bibcode: 2009SSRv..144...53W Altcode: 2008SSRv..tmp..155W It is generally accepted that the strong toroidal magnetic fields that emerge through the solar surface in sunspots and active regions are formed by the action of differential rotation on a poloidal field, and then stored in or near the tachocline at the base of the Sun’s convection zone. The problem is how to explain the generation of a reversed poloidal field from this toroidal flux—a process that can be parametrised in terms of an α-effect related to some form of turbulent helicity. Here we first outline the principal patterns that have to be explained: the 11-year activity cycle, the 22-year magnetic cycle and the longer term modulation of cyclic activity, associated with grand maxima and minima. Then we summarise what has been learnt from helioseismology about the Sun’s internal structure and rotation that may be relevant to our subject. The ingredients of mean-field dynamo models are differential rotation, meridional circulation, turbulent diffusion, flux pumping and the α-effect: in various combinations they can reproduce the principal features that are observed. To proceed further, it is necessary to rely on large-scale computation and we summarise the current state of play. Title: Introduction to Solar Magnetism: The Early Years Authors: Balogh, A.; Thompson, M. J. Bibcode: 2009SSRv..144....1B Altcode: The year 2008 marked the one hundredth anniversary of the observational discovery by George Ellery Hale of magnetic field in sunspots (Hale in Astrophys. J. 28:315-343, 1908). This observation, the first to suggest a direct link between the best-known variable features on the Sun and magnetism, started a line of research that has widened considerably over the last 100 years and is continuing today. Knowledge about all aspects of the Sun has increased in a remarkable way over the past few decades. Variations in the appearance of the Sun and its corona, as well as deeper sources of quasi-regular and chaotic changes that make up solar variability have been extensively documented by both ground-based and space-based solar observatories. It has been recognized that solar magnetism is the key phenomenon that drives solar variability. The workshop devoted to the origin and dynamics of solar magnetism held in the International Space Science Institute in Bern, Switzerland, from 21 to 25 January 2008 reviewed the status of the field and has led to this volume that brings together the best available knowledge and understanding of solar magnetism 100 years after Hale’s pioneering paper. This introductory paper gives an outline of the history of research into solar variability up to the work of Hale and his colleagues. The achievements of the past decades are discussed extensively in the other contributions to this volume. Title: Introduction to Solar Magnetism: The Early Years Authors: Balogh, A.; Thompson, M. J. Bibcode: 2009odsm.book....1B Altcode: The year 2008 marked the one hundredth anniversary of the observational discovery by George Ellery Hale of magnetic field in sunspots (Hale in Astrophys. J. 28:315-343, 1908). This observation, the first to suggest a direct link between the best-known variable features on the Sun and magnetism, started a line of research that has widened considerably over the last 100 years and is continuing today. Knowledge about all aspects of the Sun has increased in a remarkable way over the past few decades. Variations in the appearance of the Sun and its corona, as well as deeper sources of quasi-regular and chaotic changes that make up solar variability have been extensively documented by both ground-based and space-based solar observatories. It has been recognized that solar magnetism is the key phenomenon that drives solar variability. The workshop devoted to the origin and dynamics of solar magnetism held in the International Space Science Institute in Bern, Switzerland, from 21 to 25 January 2008 reviewed the status of the field and has led to this volume that brings together the best available knowledge and understanding of solar magnetism 100 years after Hale's pioneering paper. This introductory paper gives an outline of the history of research into solar variability up to the work of Hale and his colleagues. The achievements of the past decades are discussed extensively in the other contributions to this volume. Title: The Solar Dynamo Authors: Weiss, N. O.; Thompson, M. J. Bibcode: 2009odsm.book...53W Altcode: It is generally accepted that the strong toroidal magnetic fields that emerge through the solar surface in sunspots and active regions are formed by the action of differential rotation on a poloidal field, and then stored in or near the tachocline at the base of the Sun's convection zone. The problem is how to explain the generation of a reversed poloidal field from this toroidal flux—a process that can be parametrised in terms of an α-effect related to some form of turbulent helicity. Here we first outline the principal patterns that have to be explained: the 11-year activity cycle, the 22-year magnetic cycle and the longer term modulation of cyclic activity, associated with grand maxima and minima. Then we summarise what has been learnt from helioseismology about the Sun's internal structure and rotation that may be relevant to our subject. The ingredients of mean-field dynamo models are differential rotation, meridional circulation, turbulent diffusion, flux pumping and the α-effect: in various combinations they can reproduce the principal features that are observed. To proceed further, it is necessary to rely on large-scale computation and we summarise the current state of play. Title: The Origin and Dynamics of Solar Magnetism Authors: Thompson, M. J.; Balogh, A.; Culhane, J. L.; Nordlund, Å.; Solanki, S. K.; Zahn, J. -P. Bibcode: 2009odsm.book.....T Altcode: No abstract at ADS Title: Helioseismology of Sunspots: A Case Study of NOAA Region 9787 Authors: Gizon, L.; Schunker, H.; Baldner, C. S.; Basu, S.; Birch, A. C.; Bogart, R. S.; Braun, D. C.; Cameron, R.; Duvall, T. L.; Hanasoge, S. M.; Jackiewicz, J.; Roth, M.; Stahn, T.; Thompson, M. J.; Zharkov, S. Bibcode: 2009odsm.book..249G Altcode: Various methods of helioseismology are used to study the subsurface properties of the sunspot in NOAA Active Region 9787. This sunspot was chosen because it is axisymmetric, shows little evolution during 20-28 January 2002, and was observed continuously by the MDI/SOHO instrument. AR 9787 is visible on helioseismic maps of the farside of the Sun from 15 January, i.e. days before it crossed the East limb. Title: Recent Developments in Local Helioseismology Authors: Thompson, M. J.; Zharkov, S. Bibcode: 2008SoPh..251..225T Altcode: 2008SoPh..tmp...42T Local helioseismology is providing new views of subphotospheric flows from supergranulation to global-scale meridional circulation and for studying structures and dynamics in the quiet Sun and active regions. In this short review we focus on recent developments, and in particular on a number of current issues, including the sensitivity of different measures of travel time and testing the forward modelling used in local helioseismology. We discuss observational and theoretical concerns regarding the adequacy of current analyses of waves in sunspots and active regions, and we report on recent progress in the use of numerical simulations to test local helioseismic methods. Title: Time Distance Analysis of the Emerging Active Region NOAA 10790 Authors: Zharkov, S.; Thompson, M. J. Bibcode: 2008SoPh..251..369Z Altcode: 2008arXiv0807.3000Z; 2008SoPh..tmp..140Z We investigate the emergence of Active Region NOAA 10790 by means of time - distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic-flux and thus obtain a provisional estimate of the speed of emergence of around 1 km s−1. Title: Editors' note Authors: Jiménez Reyes, S. J.; Reese, D. R.; Thompson, M. J. Bibcode: 2008AN....329..439J Altcode: No abstract at ADS Title: Views of the Solar Torsional Oscillation Authors: Howe, R.; Komm, R. W.; Hill, F.; Schou, J.; Thompson, M. J. Bibcode: 2008AGUSMSP41A..05H Altcode: The pattern of zonal flows migrating towards the equator over the solar cycle, known as the torsional oscillation, is well established from both helioseismology and surface Doppler measurements. However, the exact appearance of the pattern will vary depending on the form of the overall rotation profile that has been subtracted, even when the data cover a full eleven-year cycle. Here we compare the appearance of the flow pattern when applying several different methods to the MDI and GONG data for Solar Cycle 23. Title: Stellar Astrophysical Fluid Dynamics Authors: Thompson, Michael J.; Christensen-Dalsgaard, Jørgen Bibcode: 2008safd.book.....T Altcode: Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A. Spiegel and Jean-Luc Thiffeault; 27. Formation of planetary systems Douglas N. C. Lin; 28. The solar-cycle global warming as inferred from sky brightness variation Wasaburo Unno and Hiromoto Shibahashi. Title: Meridional flow profile measurements with SOHO/MDI Authors: Mitra-Kraev, U.; Thompson, M. J. Bibcode: 2007AN....328.1009M Altcode: 2007arXiv0711.4968M We present meridional flow measurements of the Sun using a novel helioseismic approach for analyzing SOHO/MDI data in order to push the current limits in radial depth. Analyzing three consecutive months of data during solar minimum, we find that the meridional flow is as expected poleward in the upper convection zone, turns equatorward at a depth of around 40 Mm (∼0.95 R_⊙), and possibly changes direction again in the lower convection zone. This may indicate two meridional circulation cells in each hemisphere, one beneath the other. Title: Varied Mechanisms for Star Formation in Bright-Rimmed Clouds Authors: Morgan, Larry; Urquhart, J.; Thompson, M.; White, G.; Figura, C. Bibcode: 2007AAS...211.8914M Altcode: 2007BAAS...39..880M Bright-rimmed clouds (BRCs) are potential examples of triggered star-formation regions, in which photoionisation driven shocks caused by the expansion of HII regions induce protostellar collapse within the clouds. A sample of optically bright BRCs at the edge of HII regions has been observed at multiple wavelengths in order to investigate the possibility that star-formation is present. Such activity may be related to photoionisation induced shocks caused by the massive stars powering the HII regions.

The sample has been observed at radio, infrared and submillimetre wavelengths, these observations reveal dense cores present within the heads of 44 observed BRCs drawn from a catalogue of IRAS sources embedded within HII regions, supportive of the scenario proposed by radiatively driven implosion (RDI) models. The physical properties of these cores indicate the presence of star formation across the majority of our sample. This star-formation appears to be predominately in the regime of intermediate to high mass and may indicate the formation of clusters. IR observations indicate the association of early star forming sources with the sample.

A fundamental difference appears to exist between different morphological types of BRC. Morphological variations in BRCs have previously been attributed to an evolutionary scenario of RDI. However, the physical properties of cores found within different types of BRC indicate that the strength of the ambient ionisation field is highly correlated with the attributes of certain cores, and not with others. The suggestion is that different morphological types of BRC have followed different evolutionary pathways, this is supported by the mass distributions of cores associated with the different morphologies. Title: Asteroseismology and interferometry Authors: Cunha, M. S.; Aerts, C.; Christensen-Dalsgaard, J.; Baglin, A.; Bigot, L.; Brown, T. M.; Catala, C.; Creevey, O. L.; Domiciano de Souza, A.; Eggenberger, P.; Garcia, P. J. V.; Grundahl, F.; Kervella, P.; Kurtz, D. W.; Mathias, P.; Miglio, A.; Monteiro, M. J. P. F. G.; Perrin, G.; Pijpers, F. P.; Pourbaix, D.; Quirrenbach, A.; Rousselet-Perraut, K.; Teixeira, T. C.; Thévenin, F.; Thompson, M. J. Bibcode: 2007A&ARv..14..217C Altcode: 2007arXiv0709.4613C Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like pulsators, have boosted the impact of this field of research within astrophysics and have led to a significant increase in the size of the research community. In the present paper we start by reviewing the basic observational and theoretical properties of classical and solar-like pulsators and present results from some of the most recent and outstanding studies of these stars. We centre our review on those classes of pulsators for which interferometric studies are expected to provide a significant input. We discuss current limitations to asteroseismic studies, including difficulties in mode identification and in the accurate determination of global parameters of pulsating stars, and, after a brief review of those aspects of interferometry that are most relevant in this context, anticipate how interferometric observations may contribute to overcome these limitations. Moreover, we present results of recent pilot studies of pulsating stars involving both asteroseismic and interferometric constraints and look into the future, summarizing ongoing efforts concerning the development of future instruments and satellite missions which are expected to have an impact in this field of research. 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: Forward modelling of sub-photospheric flows for time-distance helioseismology Authors: Shelyag, S.; Erdélyi, R.; Thompson, M. J. Bibcode: 2007A&A...469.1101S Altcode: 2007astro.ph..3067S Context: The results of forward modelling of acoustic wave propagation in a realistic solar sub-photosphere with two cases of steady horizontal flows are presented and analysed by the means of local helioseismology.
Aims: This paper is devoted to an analysis of the influence of steady flows on the propagation of sound waves through the solar interior.
Methods: The simulations are based on fully compressible ideal hydrodynamical modelling in a Cartesian grid. The initial model is characterised by solar density and pressure stratifications taken from the standard Model S and is adjusted in order to suppress convective instability. Acoustic waves are excited by a non-harmonic source located below the depth corresponding to the visible surface of the Sun. Numerical experiments with coherent horizontal flows of linear and Gaussian dependences of flow speed on depth are carried out. These flow fields may mimic horizontal motions of plasma surrounding a sunspot, differential rotation or meridional circulation. An inversion of the velocity profiles from the simulated travel time differences is carried out. The inversion is based on the ray approximation. The results of inversion are then compared with the original velocity profiles.
Results: The results of forward modelling of acoustic wave propagation in a realistic solar sub-photosphere with two cases of steady horizontal flows are presented. The influence of steady flow on the propagation of sound waves through the solar interior is analysed. A time-distance analysis technique is applied to compute the direct observable signatures of the background bulk motions on travel times and phase shifts. This approach allows direct comparison with observational data. Further, we propose a method of obtaining the travel-time differences for the waves propagating in sub-photospheric solar regions with horizontal flows. The method employs directly the difference between travel-time diagrams of waves propagating with and against the background flow.
Conclusions: The analysis shows that the flow speed profiles obtained from inversion based on the ray approximation differ from the original ones. The difference between the original and observed profiles is caused by the fact that the wave packets propagate along the ray bundle, which has a finite extent, and thus reach deeper regions of the sub-photosphere in comparison with ray theory. Title: Optimized data masks for focussed solar tomography: background and artificial diagnostic experiments Authors: Hughes, S. J.; Pijpers, F. P.; Thompson, M. J. Bibcode: 2007A&A...468..341H Altcode: Context: The use of solar tomography for detecting subsurface features in the Sun is now well established. It customarily proceeds from an analysis of data on the solar surface given weightings in a predetermined geometric (e.g. centre-annulus) configuration.
Aims: We seek to improve these weightings by developing a scheme for choosing optimal combinations of data that maximise the contribution from signal at a desired horizontal and depth location.
Methods: We employ a subtractive optimally localized averaging (SOLA) scheme to pick weights for particular data points and analyse the quality of the results.
Results: We show in this work that particularly by using wave kernels instead of rays for modelling purposes, one can do well at localizing a measurement through our techniques while achieving desirable error-magnification properties. Title: Solar Cycle Changes Over 11 Years of Medium-Degree Helioseismic Observations Authors: Howe, Rachel; Komm, R. W.; Hill, F.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 2007AAS...210.2218H Altcode: 2007BAAS...39..127H The Global Oscillations Network Group (GONG) has now completed, and the Michelson Doppler Imager (MDI) aboard SOHO will soon complete, a full eleven years of continuous observations of the medium-degree solar oscillations. This enables us to follow changes in the acoustic mode parameters and interior dynamics over a full solar cycle. We present results from observations of convection-zone dynamics, in which the torsional oscillation pattern seen at the surface can be followed throughout most of the bulk of the convection zone, and also changes in the frequency, lifetime and amplitude of the modes which can be shown to be closely related in space and time to the migrating pattern of surface activity.

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. SOHO is a mission of international cooperation between ESA and NASA. Title: Time distance study of isolated sunspots Authors: Zharkov, S.; Nicholas, C. J.; Thompson, M. J. Bibcode: 2007AN....328..240Z Altcode: 2008arXiv0802.2524Z We present a comparative seismic study of conditions around and beneath isolated sunspots. Using the European Grid of Solar Observations' Solar Feature Catalogue of sunspots derived from SOHO/MDI continuum and magnetogram data, 1996-2005, we identify a set of isolated sunspots by checking that within a Carrington Rotation there were no other spots detected in the vicinity. We then use level-2 tracked MDI Dopplergrams available from SOHO website to investigate wave-speed perturbations of such sunspots using time-distance helioseismology. Title: A procedure for the inversion of f-mode travel times for solar flows Authors: Jackiewicz, J.; Gizon, L.; Birch, A. C.; Thompson, M. J. Bibcode: 2007AN....328..234J Altcode: 2007astro.ph..2345J We perform a two-dimensional inversion of f-mode travel times to determine near-surface solar flows. The inversion is based on optimally localized averaging of travel times. We use finite-wavelength travel-time sensitivity functions and a realistic model of the data errors. We find that it is possible to obtain a spatial resolution of 2 Mm. The error in the resulting flow estimate ultimately depends on the observation time and the number of travel distances used in the inversion. Title: Outstanding problems in local helioseismology Authors: Gizon, L.; Thompson, M. J. Bibcode: 2007AN....328..204G Altcode: 2010arXiv1002.2347G Time-distance helioseismology and related techniques show great promise for probing the structure and dynamics of the subphotospheric layers of the Sun. Indeed time-distance helioseismology has already been applied to make inferences about structures and flows under sunspots and active regions, to map long-lived convective flow patterns, and so on. Yet certainly there are still many inadequacies in the current approaches and, as the data get better and the questions we seek to address get more subtle, methods that were previously regarded as adequate are no longer acceptable. Here we give a short and partial description of outstanding problems in local helioseismology, using time-distance helioseismology as a guiding example. Title: The Effect of Abnormal Granulation on Acoustic Wave Travel Times and Mode Frequencies Authors: Petrovay, K.; Erdélyi, R.; Thompson, M. J. Bibcode: 2007SoPh..240..197P Altcode: 2007astro.ph..2076P Observations indicate that in plage areas (i.e. in active regions outside sunspots) acoustic waves travel faster than in the quiet Sun, leading to shortened travel times and higher p-mode frequencies. Coupled with the 11-year variation of solar activity, this may also explain the solar cycle variation of oscillation frequencies. While it is clear that the ultimate cause of any difference between the quiet Sun and plage is the presence of magnetic fields of order 100 G in the latter, the mechanism by which the magnetic field exerts its influence has not yet been conclusively identified. One possible such mechanism is suggested by the observation that granular motions in plage areas tend to be slightly "abnormal", dampened compared to the quiet Sun. Title: A Magnetometer For The Solar Orbiter Mission Authors: Carr, C. M.; Horbury, T. S.; Balogh, A.; Baumjohann, W.; Bavassano, B.; Breen, A.; Burgess, D.; Cargill, P. J.; Brooker, N.; Erdõs, G.; Fletcher, L.; Forsyth, R. J.; Giacalone, J.; Glassmeier, K. -H.; Hoeksema, J. T.; Goldstein, M. L.; Lockwood, M.; Magnes, W.; Masimovic, M.; Marsch, G.; Matthaeus, W. H.; Murphy, N.; Nakariakov, V. M.; Pacheco, J. R.; Pincon, J. -L.; Riley, P.; Russell, C. T.; Schwartz, S. J.; Szabo, A.; Thompson, M.; Vainio, R.; Velli, M.; Vennerstrom, S.; Walsh, R.; Wimmer-Schweingruber, R.; Zank, G. Bibcode: 2007ESASP.641E..41C Altcode: The magnetometer is a key instrument to the Solar Orbiter mission. The magnetic field is a fundamental parameter in any plasma: a precise and accurate measurement of the field is essential for understanding almost all aspects of plasma dynamics such as shocks and stream-stream interactions. Many of Solar Orbiter's mission goals are focussed around the links between the Sun and space. A combination of in situ measurements by the magnetometer, remote measurements of solar magnetic fields and global modelling is required to determine this link and hence how the Sun affects interplanetary space. The magnetic field is typically one of the most precisely measured plasma parameters and is therefore the most commonly used measurement for studies of waves, turbulence and other small scale phenomena. It is also related to the coronal magnetic field which cannot be measured directly. Accurate knowledge of the magnetic field is essential for the calculation of fundamental plasma parameters such as the plasma beta, Alfvén speed and gyroperiod. We describe here the objectives and context of magnetic field measurements on Solar Orbiter and an instrument that fulfils those objectives as defined by the scientific requirements for the mission. Title: The Parkes methanol multibeam survey Authors: Cohen, R. J.; Caswell, J. L.; Brooks, K.; Burton, M. G.; Chrysostomou, A.; Cox, J.; Diamond, P. J.; Ellingsen, S.; Fuller, G. A.; Gray, M. D.; Green, J. A.; Hoare, M. G.; Masheder, M. R. W.; McClure-Griffiths, N.; Pestalozzi, M.; Phillips, C.; Thompson, M.; Voronkov, M.; Walsh, A.; Ward-Thompson, D.; Wong-McSweeney, D.; Yates, J. A. Bibcode: 2007IAUS..237..403C Altcode: 2006IAUS..237E..89B A new 7-beam methanol multibeam receiver was successfully commissioned at Parkes in January, and has begun surveying the Milky Way for newly forming stars, that are pinpointed by strong methanol maser emission at 6.7 GHz. The Parkes survey of the Milky Way for methanol masers is two orders of magnitude faster than previous systematic surveys using 30-m class dishes. The first 26 days of observations have yielded 377 methanol sources, of which 150 are new discoveries. Preliminary results will be presented. Title: Observational results and issues concerning the tachocline Authors: Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 2007sota.conf...53C Altcode: No abstract at ADS Title: Temporal variations in solar rotation at the bottom of the convection zone: The current status Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2007AdSpR..40..915H Altcode: We present the most recent results on the short-period variations in the solar rotation rate near the base of the convection zone. The 1.3-year period which was reported in the early years of solar cycle 23 appears not to persist after 2001, but there are hints of fluctuations at a different period during the declining phase of the cycle. Title: T he Solar Dynamo - What Have We Learned From Helioseismology? Authors: Thompson, M. J. Bibcode: 2007ESASP.641E..25T Altcode: 2006ESASP.641E..25T Helioseismology provides a unique tool for probing the solar dynamo by observing the evolution of the solar interior over the solar activity cycle. In particular, helioseismology has now imaged the subphotospheric large-scale flows (solar subsurface weather), differential rotation and meridional circulation. It has also probed the stratifica- tion and flows under active regions and sunspots. Here I briefly review the recent advances from helioseismology in probing aspects of the solar interior relevant to an understanding of the solar dynamo problem, and assess the current state of theoretical modelling of the solar dynamo. Title: The Pulsation Properties of the Double-Mode RR Lyrae Variable V79 in Messier 3 Authors: Clement, C. M.; Thompson, M. Bibcode: 2007JAVSO..35..336C Altcode: The double-mode RR Lyrae variable V79 in M3 was observed on seven nights in April 2006 with a 14-inch Schmidt-Cassegrain telescope. A total of 275 CCD frames were obtained. An analysis of these observations indicates that the first overtone period P1 was 0.3590 day, the fundamental period P0 was 0.4834 day, and the amplitude ratio A1 /A0 was 1.00 ± 0.22. These results imply that the fundamental period increased and that the strength of the fundamental mode oscillations relative to the first-overtone may have increased since 1998 when the star was previously observed. The data also indicate that the periods may fluctuate from cycle to cycle. Title: Forward Modeling of Acoustic Wave Propagation in the Quiet Solar Subphotosphere Authors: Shelyag, S.; Erdélyi, R.; Thompson, M. J. Bibcode: 2006ApJ...651..576S Altcode: The results of numerical simulations of acoustic wave propagation and dispersion in the nonmagnetic solar subphotosphere are presented. Initial equilibrium density and pressure stratifications are taken from a standard solar model but modified to suppress convective instabilities in fully compressible two-dimensional ideal hydrodynamical modeling. Acoustic waves are generated by sources located below the height corresponding to the visible solar surface. The dynamic response of the solar interior to two acoustic source types, namely a harmonic source and one representing downward-propagating photospheric plumes, is studied. A large number of randomly distributed localized cooling sources with random amplitudes is also introduced. The methods used to analyze the simulation data are similar to ones used in observational studies in local helioseismology. Time-distance diagrams of the pressure and vertical velocity perturbations at the level corresponding to the solar surface show the appearance of wave packets propagating with different speeds, which are reflected at different depths beneath the subphotosphere. The (ω, kh) power spectra, derived from the vertical velocity data, show the existence of g-, f-, and p-modes p-mode ridges are identifiable up to high radial orders of n~11 g-modes appear in the simulations, unlike in the real Sun, where they cannot propagate in the convectively unstable solar subphotosphere. Cross-correlation analysis of vertical velocity perturbations shows a good correspondence with the observed time-distance helioseismic data for quiet Sun. Thus, the ability of the implemented approach of forward modeling to investigate propagation of acoustic, internal, and surface gravity waves in a realistic solar interior model is shown. Title: Helioseismology of sub-photospheric flows Authors: Shelyag, S.; Erdélyi, R.; Thompson, M. J. Bibcode: 2006ESASP.624E.123S Altcode: 2006soho...18E.123S No abstract at ADS Title: The DynaMICS perspective Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies, S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.; Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.; Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat, E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.; Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes, I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.; Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.; Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.; Thompson, M.; Vauclair, S.; Zahn, J. P. Bibcode: 2006ESASP.624E..24T Altcode: 2006soho...18E..24T No abstract at ADS Title: The effects of rotation on frequency of stellar oscillations Authors: Burke, K. D.; Thompson, M. J. Bibcode: 2006ESASP.624E.107B Altcode: 2006soho...18E.107B No abstract at ADS Title: European helio- and asteroseismology network HELAS Authors: Roth, M.; Luhe, O. v. d.; Palle, P.; Thompson, M. J.; Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G.; Gizon, L.; Di Mauro, M. P.; Aerts, C.; Daszynska-Daszkiewicz, J.; Corbard, T. Bibcode: 2006ESASP.624E.130R Altcode: 2006soho...18E.130R The Helio- and Asteroseismology Network (HELAS) is a Coordinated Action funded by the FP6-Infrastructure-Programme of the European Commission. Currently, HELAS consists of ten members. The objective of HELAS is to co-ordinate European activities in helio- and asteroseismology. HELAS will transfer knowledge and data analysis techniques, and will prepare the European research community for important missions in the immediate future. Title: Effect of sunspot structure from p-modes scattering Authors: Gordovskyy, M.; Jain, R.; Thompson, M. J. Bibcode: 2006ESASP.624E..14G Altcode: 2006soho...18E..14G No abstract at ADS Title: Meridional flow measurements with statistical waveform analysis Authors: Mitra-Kraev, U.; Thompson, M. J.; Woodard, M. F. Bibcode: 2006ESASP.624E..57M Altcode: 2006soho...18E..57M No abstract at ADS Title: Comparative study of isolated sunspots using time-distance helioseismology Authors: Zharkov, S.; Nicholas, C. J.; Thompson, M. J. Bibcode: 2006ESASP.624E..61Z Altcode: 2006soho...18E..61Z No abstract at ADS Title: Solar Convection Zone Dynamics: How Sensitive Are Inversions to Subtle Dynamo Features? Authors: Howe, R.; Rempel, M.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Larsen, R. M.; Schou, J.; Thompson, M. J. Bibcode: 2006ApJ...649.1155H Altcode: The nearly 10 year span of medium-degree helioseismic data from the Global Oscillation Network Group and the Michelson Doppler Imager has allowed us to study the evolving flows in the solar convection zone over most of solar cycle 23. Using two independent two-dimensional rotation inversion techniques and extensive studies of the resolution using artificial data from different assumed flow profiles, including those generated from sample mean field dynamo models, we attempt to assess the reality of certain features seen in the inferred rotation profiles. Our results suggest that the findings from observations of a substantial depth dependence of the phase of the zonal flow pattern in the low latitudes, and the penetration of the flows deep into the convection zone, are likely to be real rather than artifacts of the inversion process. Title: SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun Authors: Fletcher, Karen; Thompson, Michael Bibcode: 2006ESASP.624E....F Altcode: 2006soho...18E....F No abstract at ADS Title: Time-Distance Measurements of Cross-Correlation Asymmetries around NOAA AR 10486 Authors: Jensen, Jesper M.; Pijpers, Frank P.; Thompson, Michael J. Bibcode: 2006ApJ...648L..75J Altcode: We apply time-distance helioseismology to NOAA AR 10486 in order to examine the effect the presence of magnetic fields has on the resulting cross-correlations. Large-amplitude asymmetries between waves propagating in opposite directions are observed. The asymmetries can be attributed to suppression and absorption of seismic waves by the magnetic field. Unraveling the effects of magnetic field on the waves from the effects of sound-speed perturbations and flows is one of the major challenges facing time-distance helioseismology. Title: Vista Variables in the Via Lactea (VVV) Authors: Ahumada, A. V.; Minniti, D.; Adamson, A.; Bandyopadhyay, R.; Barbá, R.; Barbuy, B.; Barlow, M.; Bedin, L.; Bica, E.; Borissova, J.; Bronfman, L.; Carraro, G.; Casassus, S.; Catelan, M.; Clariá, J.; Cropper, M.; Dalton, N.; de Grijs, R.; Drew, J.; Eisloeffel, J.; Emerson, J.; Fabregat, J.; García, P.; Geisler, D.; Giannini, T.; Gieren, W.; Goldman, B.; Gosling, A.; Groot, P.; Hambly, N.; Hoare, M.; Irwin, M.; Ivanov, V.; Kerber, L.; Kurtev, R.; Longmore, A.; López-Corredoira, M.; Lucas, P.; Lucey, J.; McGowan, K.; Mennickent, R.; Messineo, M.; Mirabel, F.; Monaco, L.; Morelli, L.; Naylor, T.; Pietrzynski, G.; Pignata, G.; Rejkuba, M.; Ruiz, M. T.; Saviane, I.; Schreiber, M.; Schroeder, A.; Stephens, A.; Tappert, C.; Thompson, M.; Vanzi, L.; Walton, N.; White, G.; Zijlstra, A.; Zoccali, M. Bibcode: 2006IAUJD..13E..50A Altcode: We describe a proposal for a public IR variability survey of the entire Milky Way Bulge and a large portion of the Southern Galactic Plane with VISTA at ESO Paranal Observatory. The survey will take about 180 nights, covering 5×10^8 point sources within an area of about 600 sq deg, including 40 known globular clusters and more than one hundred known open clusters. The final products of our VVV survey will be a deep IR atlas of the bulge and inner disk, along with a catalogue of more than a million variable point sources. These will allow to map the 3-D structure of the bulge and inner disk (unlike single epoch surveys that only give 2-D maps) using well understood primary distance indicators such as RR-Lyrae stars, and to obtain important information on the age of the Milky Way stellar populations. The survey will also detect hundreds of star formation regions, and allow to examine the environmental dependence of star formation. The VISTA observations will be combined with data from MACHO, OGLE, EROS, 2MASS, DENIS, VST, SPITZER, HST, CHANDRA, INTEGRAL and ALMA for a complete understanding of the variable sources in the inner Milky Way. Several important implications for the history of the Milky Way, for globular cluster evolution, for the population census of the bulge and center, and for pulsation theory would follow from this survey. Title: Scientific Objectives of the Novel Formation Flying Mission Aspiics Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies, S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.; Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.; Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat, E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.; Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes, I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.; Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.; Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.; Thompson, M.; Vauclair, S.; Zahn, J. P. Bibcode: 2006ESASP.617E.164L Altcode: 2006soho...17E.164L No abstract at ADS Title: On the Choice of Phase-Speed Filters For Helioseismic Travel-Time Measurements Authors: Zharkov, S.; Jensen, J. M.; Thompson, M. J. Bibcode: 2006ESASP.617E..48Z Altcode: 2006soho...17E..48Z No abstract at ADS Title: The EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO): Science Plan and Instrument Overview Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies, S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.; Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.; Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat, E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.; Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes, I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.; Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.; Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.; Thompson, M.; Vauclair, S.; Zahn, J. P. Bibcode: 2006ESASP.617E.165W Altcode: 2006soho...17E.165W No abstract at ADS Title: Sound Wave Travel Times in Plage Areas - The Effect of Abnormal Granulation Authors: Petrovay, K.; Erdélyi, R.; Thompson, M. J. Bibcode: 2006ESASP.617E..73P Altcode: 2006soho...17E..73P No abstract at ADS Title: Helas-European Helio- and Asteroseismology Network Authors: Roth, M.; Lühe, O. v. d.; Pallé, P.; Thompson, M.; Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G; Gizon, L.; Di Mauro, M. P.; Aerts, C.; Daszynska-Daszkiewicz, J.; Corbard, T. Bibcode: 2006ESASP.617E.157R Altcode: 2006soho...17E.157R No abstract at ADS Title: Sensitivity of Time-Distance Helioseismic Measurements to Spatial Variation of Oscillation Amplitudes. I. Observations and a Numerical Model Authors: Rajaguru, S. P.; Birch, A. C.; Duvall, T. L., Jr.; Thompson, M. J.; Zhao, J. Bibcode: 2006ApJ...646..543R Altcode: 2006astro.ph..4048R It is well known that the observed amplitude of solar oscillations is lower in sunspots than in quiet regions of the Sun. We show that this local reduction in oscillation amplitudes, combined with the phase-speed filtering procedure in time-distance helioseismic analyses, could be a source of systematic errors in the range of 5%-40% in the measured travel-time anomalies of acoustic waves around sunspots. Removing these travel-time artifacts is important for correctly inferring the subsurface structure of sunspots. We suggest an empirical correction procedure and illustrate its usage for a small sunspot. This work uses data from SOHO MDI. Title: The Dynamics Project Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies, S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.; Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.; Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat, E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.; Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes, I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.; Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.; Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.; Thompson, M.; Vauclair, S.; Zahn, J. P. Bibcode: 2006ESASP.617E.162T Altcode: 2006soho...17E.162T No abstract at ADS Title: Triggered star formation in bright-rimmed clouds: the Eagle nebula revisited Authors: Miao, J.; White, Glenn J.; Nelson, R.; Thompson, M.; Morgan, L. Bibcode: 2006MNRAS.369..143M Altcode: 2006astro.ph..3230M; 2006MNRAS.tmp..464M A three-dimensional smoothed particle hydrodynamics model has been extended to study the radiation-driven implosion effect of massive stars on the dynamical evolution of surrounding molecular clouds. The new elements in the upgraded code are the inclusion of Lyman continuum in the incident radiation flux and the treatment of hydrogen ionization process; the introduction of ionization heating and recombination cooling effects; and the addition of a proper description of the magnetic and turbulent pressures to the internal pressure of the molecular cloud. This extended code not only provides a realistic model to trace the dynamical evolution of a molecular cloud, but also can be used to model the kinematics of the ionization and shock fronts and the photoevaporating gas surrounding the molecular cloud, which the previous code is unable to handle.

The application of this newly developed model to the structure of the middle Eagle nebula finger suggests that the shock induced by the ionizing radiation at the front side of the head precedes an ionization front moving towards the centre of the core, and that the core at the fingertip is at a transition stage evolving toward a state of induced star formation. The dynamical evolution of the velocity field of the simulated cloud structure is discussed to illustrate the role of the self-gravity and the different cloud morphologies which appear at different stages in the evolutionary process of the cloud. The motion of the ionization front and the evaporating gas are also investigated. The modelled gas evaporation rate is consistent with that of other current models and the density, temperature and chemical profiles are in agreement with the observed values.

The relative lifetimes of different simulated cloud morphologies suggest a possible answer to the question of why more bright-rimmed clouds are observed to possess a flat-core than an elongated-core morphology. Title: Large-Scale Zonal Flows Near the Solar Surface Authors: Howe, R.; Komm, R.; Hill, F.; Ulrich, R.; Haber, D. A.; Hindman, B. W.; Schou, J.; Thompson, M. J. Bibcode: 2006SoPh..235....1H Altcode: Migrating bands of weak, zonal flow, associated with the activity bands in the solar cycle, have been observed at the solar surface for some time. More recently, these flows have been probed deep within the convection zone using global helioseismology and examined in more detail close to the surface with the techniques of local helioseismology. We compare the near-surface results from global and local helioseismology using data from the Michelson Doppler Imager and the Global Oscillation Network Group with surface Doppler velocity measurements from the Mount Wilson 150-foot tower and find that the results are in reasonable agreement, with some explicable differences in detail. All of the data sets show zones of faster rotation approaching the equator from mid-latitudes during the solar cycle, with a variation at any given location that can be approximately, but not completely, described by a single sinusoid and an amplitude that does not drop off steeply below the surface. Title: Magnetohelioseismology Authors: Thompson, Michael J. Bibcode: 2006RSPTA.364..297T Altcode: No abstract at ADS Title: An introduction to astrophysical fluid dynamics Authors: Thompson, Michael J. Bibcode: 2006iafd.book.....T Altcode: No abstract at ADS Title: Jets in the Solar Tachocline as Diagnostics of Global MHD Processes Authors: Christensen-Dalsgaard, J.; Corbard, T.; Dikpati, M.; Gilman, P. A.; Thompson, M. J. Bibcode: 2005ASPC..346..115C Altcode: Multiple theories predict the existence of prograde fluid jets in the solar tachocline. We find helioseismic evidence of a prograde jet near 60° latitude in N and S hemispheres that persists through almost all of the current solar cycle. This evidence favors a hydrodynamic origin for the jet, from global instability of the differential rotation of the tachocline. We see no evidence for jets that migrate toward the equator with the advancing solar cycle, which tends to rule out jets associated with toroidal field bands in the tachocline. Title: Solar Convection-Zone Dynamics, 1995-2004 Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R.; Schou, J.; Thompson, M. J. Bibcode: 2005ApJ...634.1405H Altcode: The nine-year span of medium-degree helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) allows us to study the evolving zonal flows in the solar convection zone over the rising phase, maximum, and early declining phase of solar cycle 23. Using two independent two-dimensional rotation inversion techniques, we investigate the depth profile of the flow pattern known as the torsional oscillation. The observations suggest that the flows penetrate deep within the convection zone-perhaps to its base-even at low latitudes, and that the phase of the pattern is approximately constant along lines of constant rotation rather than lines of constant latitude. Title: Acoustic Wave Propagation in the Solar Subphotosphere Authors: Shelyag, S.; Erdelyi, R.; Thompson, M. J. Bibcode: 2005AGUFMSH53A1237S Altcode: Local time-distance helioseismology aims to get an information about the internal structure of subphotospheric region of the Sun, like flows and sound speed perturbations, by investigation of observed travel times of the oscillatory responses of subphotosphere to a perturbation. We present the results of simulations of acoustic wave propagation and dispersion in the non-magnetic solar subphotosphere. We use methods similar to the observational ones to produce results aiming to reproduce observational data from local helioseismology. The VAC code (G. Toth) is used to carry out the simulations. The code can solve the full system of ideal hydrodynamic equations in two or three dimensions. All the results presented are carried out in 2D. The simulations use realistic solar density and pressure stratifications and are based on fully compressible ideal hydrodynamical model. Acoustic waves are produced by perturbations located near the layer corresponding to the visible surface of the Sun. The simulation domain is 150 Mm wide and 52.6 Mm deep, and has a resolution of 600x4000 grid points; the upper boundary of the domain is near the temperature minimum. The density profile for the initial plane-parallel model is taken from Christensen-Dalsgaard's standard Model S. We suppress convective motions of the fluid in the domain by slight change of adiabatic index γ_1. This approach has an advantage among other approaches because the waves we study, while they propagate through the quiescent medium, can be clearly observed far from the source undisturbed by convective fluid motions. First we study the propagation of acoustic waves produced by a harmonic pressure perturbation, then, in order to follow the criteria of realism we introduce more involved perturbation source, described as a source in the energy equation of the HD system of equations. The source used corresponds to a localized cooling event causing mass inflow and sound waves extinction (M. Rast, 1999). In order to reproduce the helioseismogram of the quiet Sun we introduce a number of randomly distributed sources with random amplitudes and present a comparison of the simulated data with the observations. Title: How Sensitive are Rotation Inversions to Subtle Features of the Dynamo? Authors: Howe, R.; Rempel, M.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Komm, R.; Hill, F. Bibcode: 2005ASPC..346...99H Altcode: Global rotation inversions can probe the pattern of zonal flows well into the convection zone. In this paper, we test the ability of the inversions to constrain the predictions of dynamo models. A flux-transport dynamo model, including a mean-field theory of differential rotation and allowing for feedback of the Lorentz force on differential rotation and meridional flow, was used to produce a 22-year cycle of simulated rotation profiles. These were then subjected to simulated inversions with realistic mode sets and errors, in order to test how well the subtle subsurface features of the input profile could be recovered. The preliminary results are quite encouraging. Title: Preface (Advances in astronomy. From the big bang to the solar system) Authors: Thompson, Michael Bibcode: 2005aabb.bookD..11T Altcode: No abstract at ADS Title: Seismic analysis of the second ionization region of helium in the Sun - I. Sensitivity study and methodology Authors: Monteiro, Mário J. P. F. G.; Thompson, Michael J. Bibcode: 2005MNRAS.361.1187M Altcode: 2005astro.ph..6286M; 2005MNRAS.tmp..632M The region of the second ionization of helium in the Sun is a narrow layer near the surface. Ionization induces a local change in the adiabatic exponent Γ1, which produces a characteristic signature in the frequencies of p modes. By adapting the method developed by Monteiro, Christensen-Dalsgaard & Thompson, we propose a methodology for determining the properties of this region by studying such a signature in the frequencies of oscillation.

Using solar data we illustrate how the signal from the helium ionization zone can be isolated. Using solar models which each use different physics - the theory of convection, equation of state and low-temperature opacities - we establish how the characteristics of the signal depend on the various physical processes contributing to the structure in the ionization layer. We further discuss how the method can be used to measure the solar helium abundance in the envelope and to constrain the physics affecting this region of the Sun.

The potential usefulness of the method we propose is shown. It may complement other inversion methods developed to study the solar structure and to determine the envelope helium abundance. Title: Comparison of GONG and MDI: Sound-Speed Anomalies beneath Two Active Regions Authors: Hughes, S. J.; Rajaguru, S. P.; Thompson, M. J. Bibcode: 2005ApJ...627.1040H Altcode: Travel times of acoustic waves are calculated from Dopplergrams of solar oscillations obtained using the Global Oscillation Network Group (GONG) ground-based network and the Michelson Doppler Imager (MDI) instrument on board the SOHO satellite. These travel times are inverted using a standard ray approximation to ascertain the sound-speed anomalies below two active regions. Some simple methods for ignoring the possibly corrupted measurements from within a sunspot are considered, as are diagnostics for optimizing the inversion. Results are then presented for two different spot regions, and the results of the instruments are compared: both regions behave in similar ways, and the agreement between the two instruments is good. First-skip and second-skip data are found to produce similar results for deeper layers of the model, but the significance of the shallower results from second-skip data is questionable. We conclude that GONG data are appropriate for time-distance analysis. Title: Global, Local and Surface Measurements of Large-Scale Zonal Flows Near the Solar Surface Authors: Howe, R.; Komm, R. W.; Haber, D. A.; Hindman, B. W.; Ulrich, R. K.; Schou, J.; Thompson, M. J.; Hill, F. Bibcode: 2005AGUSMSP32A..03H Altcode: Migrating bands of weak zonal flow, associated with the activity bands in the solar cycle, have been observed at the solar surface for some time. More recently, these flows have been probed deep within the convection zone using global helioseismology, and examined in more detail close to the surface with the techniques of local helioseismology. We compare the results from global and local helioseismology using data from the Michelson Doppler Imager and the GONG network and also Doppler measurements from Mount Wilson, and find that the results are in reasonable agreement, with some explicable differences in detail. This was work was supported by the National Science Foundation and NASA. Title: Helioseismic Ring Analyses of Artificial Data Computed for Two-dimensional Shearing Flows Authors: Hindman, Bradley W.; Gough, Douglas; Thompson, Michael J.; Toomre, Juri Bibcode: 2005ApJ...621..512H Altcode: The local helioseismological technique of ring analysis has been crucial in the discovery of complex large-scale flows in the Sun's near-surface shear layer. However, current implementations of ring-analysis procedures assume that the flow field is horizontally homogeneous over the analysis region. This assumption is certainly incorrect, and in the present paper we assess the significance of this approximation by analyzing artificial data sets computed from models of horizontal shear flows. We consider the simple case of purely horizontal and unidirectional flow that varies solely in the horizontal direction orthogonal to the flow in a piecewise-constant manner. An ensemble of plane waves is incident on the flow, and the scattered wave field produced by the prescribed two-dimensional flow is computed to generate an artificial helioseismic power spectrum. The artificial spectrum is processed in a manner similar to standard ring analysis, and the flow field that is thereby inferred is compared with the known imposed flow. We find that the inferred flow velocity is essentially an average of the true flow velocity over the region of the analysis, weighted by the square of the spatial apodization function used in processing the oscillation signal. Furthermore, the shape of a p-mode line profile is determined by the distribution of speeds across the analysis region. Title: The use of frequency-separation ratios for asteroseismology Authors: Otí Floranes, H.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2005MNRAS.356..671O Altcode: 2005MNRAS.356..671F The systematic patterns of separations between frequencies of modes of different degree and order are a characteristic of p-mode oscillations of stars. The frequency separations depend on the internal structure of the star and so measuring them in the observed oscillation spectra of variable stars gives valuable diagnostics of the interior of a star. Roxburgh & Vorontsov proposed using the ratio of the so-called small frequency separation to the large frequency separation as a diagnostic of the stellar interior, and demonstrated that this ratio was less sensitive than the individual frequency separations themselves to uncertain details of the near-surface structure. Here we derive kernels relating the frequency separation ratio to structure, and show why the ratio is relatively insensitive to the near-surface structure in terms of the very small amplitude of the kernels in the near-surface layers. We also investigate the behaviour of the separation ratio for stars of different masses and ages, and demonstrate the usefulness of the ratio in the so-called asteroseismic Hertzsprung-Russell diagram. Title: Local Modulation of Solar Oscillations by Magnetic Fields Authors: Nicholas, C. J.; Thompson, M. J.; Rajaguru, S. P. Bibcode: 2004SoPh..225..213N Altcode: The amplitudes of solar oscillations measured in Doppler velocity are modulated by the presence of a strong photospheric magnetic field. Here we show that the amount of modulation cannot be predicted solely on the local photospheric magnetic field strength. Qualitatively, magnetic fields of similar strength have similar effects on the oscillations. Quantitatively, however, we find a `neighborhood effect', so that the presence of a nearby sunspot affects oscillations in the area in its vicinity that has normal quiet-Sun magnetic field strength. Thus, different types of magnetic regions alter the oscillatory power to a varying degree, and the p-mode power within regions of similar magnetic field strength is more reduced if there is a sunspot present. The neighborhood effect falls off with distance from the sunspot. We also show that our measurements of the power modulation, in which we look at the effects on oscillations pixel by pixel, can be made consistent with results of amplitude modulation of modes as obtained from ring-diagram analysis of active regions, but only if the neighborhood effect on quiet-Sun regions is taken into account. Title: Comparison of GONG and MDI Sound-Speed Anomalies Beneath Two Active Regions Authors: Hughes, S. J.; Rajaguru, S. P.; Thompson, M. J. Bibcode: 2004ESASP.559..493H Altcode: 2004soho...14..493H No abstract at ADS Title: Detection of Jets and Associated Toroidal Fields in the Solar Tachocline Authors: Christensen-Dalsgaard, J.; Corbard, T.; Dikpati, M.; Gilman, P. A.; Thompson, M. J. Bibcode: 2004ESASP.559..376C Altcode: 2004soho...14..376C No abstract at ADS Title: How Sensitive are Rotation Inversions to Subtle Features of the Dynamo? Authors: Howe, R.; Rempel, M.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Schou, J.; Thompson, M. J. Bibcode: 2004ESASP.559..468H Altcode: 2004soho...14..468H No abstract at ADS Title: The Effect of Strong Magnetic Fields on Acoustic Power in Their Surroundings at the Surface of the Sun Authors: Nicholas, C. J.; Thompson, M. J.; Rajaguru, S. P. Bibcode: 2004ESASP.559..590N Altcode: 2004soho...14..590N No abstract at ADS Title: Optimal Masks for Deep Focussing Authors: Hughes, S. J.; Pijpers, F. P.; Thompson, M. J. Bibcode: 2004ESASP.559..488H Altcode: 2004soho...14..488H No abstract at ADS Title: Subphotospheric Flows Near Active Region NOAA 10486 Authors: Haber, D. A.; Hindman, B. W.; Toomre, J.; Bogart, R. S.; Thompson, M. J. Bibcode: 2004ESASP.559..148H Altcode: 2004soho...14..148H No abstract at ADS Title: The Phase of the Torsional Oscillation Pattern Authors: Howe, R.; Komm, R. W.; Hill, F.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 2004ESASP.559..476H Altcode: 2004soho...14..476H No abstract at ADS Title: Asteroseismology: Asteroseismology of Sun-like stars Authors: Elsworth, Yvonne P.; Thompson, Michael J. Bibcode: 2004A&G....45e..14E Altcode: Seismology has become a powerful tool for analysis of the interior of the Sun; it has great potential for the study of oscillations in solar-like stars. Asteroseimology could provide direct information about detailed properties of stellar interiors, bringing the potential for testing theories of stellar evolution and structure. Current stellar models are simple with few direct observational constraints; consequences such as age estimates are uncertain to a factor of two. A recent attempt at asteroseismology on Procyon, a likely candidate star, found no detectable oscillations. In this paper we discuss the asteroseismology of solar-like stars in the context of studies of the Sun and then indicate possible reasons for the Procyon results. Title: Application of Local-Area Helioseismic Methods as Predictors of Space Weather Authors: Jensen, J. M.; Lundstedt, H.; Thompson, M. J.; Pijpers, F. P.; Rajaguru, S. P. Bibcode: 2004ESASP.559..497J Altcode: 2004soho...14..497J No abstract at ADS Title: Convection-Zone Dynamics from GONG and MDI, 1995-2004 Authors: Howe, R.; Komm, R. W.; Hill, F.; Christensen-Dalsgaard, J.; Haber, D. A.; Schou, J.; Thompson, M. J. Bibcode: 2004ESASP.559..472H Altcode: 2004soho...14..472H No abstract at ADS Title: Solar interior: Helioseismology and the Sun's interior Authors: Thompson, Michael J. Bibcode: 2004A&G....45d..21T Altcode: Helioseismology is the study of the solar interior using observations of waves on the Sun's surface. It has done much to improve our understanding of the interior of the Sun, testing the physical inputs used to model stellar interiors and providing a detailed map of the Sun's structure and internal rotation. This in turn has greatly influenced theories of the solar magnetic dynamo. These interior studies thus make a valuable bridge between solar physics and studies of the structure and evolution of other stars. Recent developments include new local techniques for unprecedented studies of subsurface structures and flows in emerging active regions, under sunspots, and even of active regions on the far side of the Sun. These developments hold the possibility of a real understanding of how the interior links to solar magnetic activity in the corona and heliosphere. Finally, studies such as those of the deep solar interior are on the verge of becoming possible for other stars exhibiting similar multimode oscillations. Title: Subphotospheric Flows Around Active Region NOAA 10486 Authors: Haber, D. A.; Hindman, B. W.; Toomre, J.; Bogart, R. S.; Thompson, M. J.; LoHCo Team Bibcode: 2004AAS...204.0211H Altcode: 2004BAAS...36Q.669H We have used MDI Dynamics Program Doppler data taken between October 18th and November 15th 2003 to study the interaction of solar subsurface flows with NOAA 10486, one of the most dynamic active regions of the past solar cycle. Using the local helioseismic techniques of ring and time-distance analyses, we assess the horizontal flows that surrounded and permeated this region and how they varied with depth in the upper 14 Mm of the convection zone. We examine and identify structures in the flow field that may have been associated with the energetic flares that occurred during the period of observation. This research is in part supported by NASA through grants NAG5-11920, NAG5-10917, and NAG5-12491. Title: Comparison OF Noise Properties Of GONG And MDI Time-Distance Helioseismic Data Authors: Rajaguru, S. P.; Hughes, S. J.; Thompson, M. J. Bibcode: 2004SoPh..220..381R Altcode: The recently upgraded system of the ground-based Global Oscillation Network Group (GONG) network of helioseismic observatories has started to provide higher-resolution solar oscillation measurements suitable for local helioseismic studies. Selecting simultaneously observed regions on the Sun by both GONG and the space-borne Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory (SOHO), we perform a comparative analysis of time-distance measurements focussing on the noise properties. Title: Organized Subsurface Flows near Active Regions Authors: Haber, D. A.; Hindman, B. W.; Toomre, J.; Thompson, M. J. Bibcode: 2004SoPh..220..371H Altcode: Local helioseismic techniques, such as ring analysis and time-distance helioseismology, have already shown that large-scale flows near the surface converge towards major active regions. Ring analysis has further demonstrated that at greater depths some active regions exhibit strong outflows. A critique leveled at the ring-analysis results is that the Regularized Least Squares (RLS) inversion kernels on which they are based have negative sidelobes near the surface. Such sidelobes could result in a surface inflow being misidentified as a diverging outflow at depth. In this paper we show that the Optimally Located Averages (OLA) inversion technique, which produces kernels without significant sidelobes, generates flows markedly similar to the RLS results. Active regions are universally zones of convergence near the surface, while large complexes evince strong outflows deeper down. Title: ENEAS: the European Network of Excellence in AsteroSeismology Authors: Aerts, C.; Baglin, A.; Christensen-Dalsgaard, J.; Goupil, M. J.; Houdek, G.; Kjeldsen, H.; Kollath, Z.; Kurtz, D.; Lebreton, Y.; Maceroni, C.; Noels, A.; Schwarzenberg-Czerny, A.; Škoda, P.; Solano, E.; Thompson, M. J. Bibcode: 2004ESASP.538..247A Altcode: 2004sshp.conf..247A Asteroseismology is one of the major important science topics in astrophysics in the coming decade. Several recent breakthroughs have indeed been made in Europe in this field. The observational data will improve significantly in the near future, as upgraded ground-based instruments are being built and two European asteroseismic space missions are planned for launch between 2005 and 2008. They will provide us for the first time with ultra-high-accuracy, high-temporal resoluton data from space for stars other than the Sun. A successful asteroseismic study involves many different steps, from state-of-the-art raw data treatment to theoretical physical modelling of the oscillation frequencies. Our network is set up to meet the needs of combining and exchanging the different expertises of the participating institutes, of training PhD students and of both training and exchanging post-doctoral researchers. This will guarantee the most fruitful and efficient exploitation of the very substantial investments that are being made in Europe in future observations of stellar oscillations, strengthening Europe's leading position in this research field. Also, it will be a test-bed for the development of efficient procedures for collaboration across the internet, involving a vast range of procedures and skills, as well as extensive common use of a broad variety of data. Furthermore, procedures will be incorporated for the joint training of students, which is an essential part of our project. Title: Application of local-area helioseismic methods as predictors of spaceweather Authors: Jensen, J. M.; Lundstedt, H.; Thompson, M. J.; Pijpers, F. P.; Rajaguru, S. P. Bibcode: 2004cosp...35.2195J Altcode: 2004cosp.meet.2195J Many of the phenomena observed on the Sun are of magnetic origin. The solar wind, Coronal Mass Ejections and flares are all phenomena closely linked to Sun's magnetic field. The technology based society of today can be strongly influences by these phenomena. The high energetic particles emitted in connection with CMEs and flares are able to cause enough damage to satellites to render them useless. It is therefore of great interest to understand the physical processes behind these phenomena. During the last three decades helioseismology has investigated the solar interior by measurements of the global eigenmode frequencies. The global nature of these data makes it impossible to resolve phenomena which are highly localized in the Sun. Within the last decade local-area helioseismic methods have emerged as powerful tools for investigating localized phenomena in the solar convection zone such as flows and magnetic activity. With these methods it has become possible to study structures around and below active regions. Observations have been made of flows and temperature variations surrounding and extending below sunspots thereby enabling the study of dynamical processes below the solar surface in actice regions. These studies can help to understand the processes behind phenomena such as flares and CMEs which can influence the Earth. With local-area helioseismic methods a wealth of new information has or will become available, which hopefully can be used to increase the reliability of space weather predictions. With the data available from the SOHO satellite and the GONG network it is possible to monitor large-scale flows in the Sun in connection with magnetic active regions using local-area helioseismic methods. We propose to use these observed flows as indicators for future space weather. If observations of the magnetic configuration in active regions are supplemented with information of the flow fields surrounding the active region it might be possible to improve on flare prediction. To this end we propose to use physics-based neural network to investigate if the flow fields can be used to predict flares and space weather. The goal is to incorporate these data into the space weather forecast models developed at the Swedish Institute of Space Physics in Lund. A space weather forecast service prototype was developed within the ESA Space Weather Programme Study and an ESA Pilot Project is in progress. The Lund division of the institute also runs the RWC-Sweden of ISES. Here we present preliminary results of this new approach of using helioseismological data. Title: The Significance of Density and Attenuation in the Local Helioseismology Authors: Tong, C. H.; Thompson, M. J.; Warner, M. R.; Pain, C. C. Bibcode: 2003ApJ...596L.263T Altcode: We present results from numerical simulations in order to demonstrate the significance of density and attenuation in helioseismic data modeling and in the interpretation of reconstructed solar models. Attenuation beneath active regions causes significant dispersion as well as temporal shifts of the helioseismic signals. These effects can be considerably more significant than those caused by sound-speed anomalies. On the basis of the differential changes in the waveform of the signals as a function of density, we propose the modeling of density for the estimation of the relative contribution from buoyancy and magnetic fields toward the origin of the fluid flows in the solar interior. Title: Helioseismic Signals and Wave Field Helioseismology Authors: Tong, C. H.; Thompson, M. J.; Warner, M. R.; Pain, C. C. Bibcode: 2003ApJ...593.1242T Altcode: We investigate the effect of sound-speed perturbations on the characteristics of helioseismic signals in order to demonstrate the feasibility and desirability of wave field helioseismology. The oscillatory nature of the signals with varying frequency content allows us to characterize the waveform of the signals by the amplitudes of the peaks and troughs as well as by the time lags between successive peaks and troughs. Sinusoidal sound-speed perturbations with an amplitude of 1% of the local sound speed produce more than +/-10% changes in the amplitudes of the peaks and troughs. The same sound-speed perturbations produce changes in the time lags between successive peaks and troughs of the signals that are comparable with the variations of first-break travel times of the oscillatory wave packet. The vertical and horizontal sound-speed perturbations result in distinct patterns of changes in the shape of the helioseismic signals. These changes in the amplitudes and travel-time lags are differential for the successive peaks and troughs: the magnitude is higher for the later peaks and troughs. We also observe that these variations in the amplitude and travel-time lags are more sensitive to shorter wavelength sound-speed perturbations at relatively small source-receiver offsets. Therefore, our results indicate that the waveform of the signals is variable and sensitive to sound-speed perturbations. These observations can be explained by the more dispersive nature of the low-frequency components in the seismic signals at shallow depths. The relatively high sensitivity of these perturbations in the waveform of the signals to sound speed, density, and vertical density gradient at shallow depths due to dispersion is an important modeling consideration. Title: A Comparison of Solar p-Mode Parameters from MDI and GONG: Mode Frequencies and Structure Inversions Authors: Basu, S.; Christensen-Dalsgaard, J.; Howe, R.; Schou, J.; Thompson, M. J.; Hill, F.; Komm, R. Bibcode: 2003ApJ...591..432B Altcode: Helioseismic analysis of solar global oscillations allows investigation of the internal structure of the Sun. One important test of the reliability of the inferences from helioseismology is that the results from independent sets of contemporaneous data are consistent with one another. Here we compare mode frequencies from the Global Oscillation Network Group and Michelson Doppler Imager on board SOHO and resulting inversion results on the Sun's internal structure. The average relative differences between the data sets are typically less than 1×10-5, substantially smaller than the formal errors in the differences; however, in some cases the frequency differences show a systematic behavior that might nonetheless influence the inversion results. We find that the differences in frequencies are not a result of instrumental effects but are almost entirely related to the data pipeline software. Inversion of the frequencies shows that their differences do not result in any significant effects on the resulting inferences on solar structure. We have also experimented with fitting asymmetric profiles to the oscillation power spectra and find that, compared with the symmetric fits, this causes no significant change in the inversion results. Title: First results from Time-Distance inversions of GONG+ data. Authors: Rajaguru, S. P.; Hughes, S. J.; Thompson, M. J. Bibcode: 2003SPD....34.0801R Altcode: 2003BAAS...35..821R We present first results from time-distance helioseismic analysis of a few active regions using the new merged sequences of data from GONG+ instruments. In particular we focus on issues related to the resolution achievable from GONG+ data and also estimate their noise properties.Results from inversions for sound speed changes beneath active regions will be presented with initial comparisons between first and second bounce time-distance data for acoustic rays passing under a spot. We acknowledge support from the UK Particle Physics and Astronomy Research Council. Title: Stellar Astrophysical Fluid Dynamics Authors: Thompson, Michael J.; Christensen-Dalsgaard, Jørgen Bibcode: 2003safd.book.....T Altcode: Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A. Spiegel and Jean-Luc Thiffeault; 27. Formation of planetary systems Douglas N. C. Lin; 28. The solar-cycle global warming as inferred from sky brightness variation Wasaburo Unno and Hiromoto Shibahashi. Title: Asteroseismology Across the HR Diagram Authors: Thompson, M. J.; Cunha, M. S.; Monteiro, M. J. P. F. G. Bibcode: 2003aahd.conf.....T Altcode: Ground-based observations have detected solar-like oscillations on Sun-like stars, and diagnostics similar to those used in helioseismology are now being used to test and constrain the physics and evolutionary state of these stars. Multi-mode oscillations are being observed in an abundance of other stars, including slowly pulsating B stars (SPB stars), delta-Scuti stars, Ap stars and the pulsating white dwarfs. New classes of pulsators continue to be discovered across the Herzsprung-Russell diagram. Yet the chances still to be faced to make asteroseismology across the HR diagram a reality are formidable. Observation, data analysis and theory all pose hard problems to be overcome. This book, reflecting the goal of the meeting, aims to facilitate a cross-fertilisation of ideas and approaches between fields covering different pulsators and with different areas of expertise. The book successfully covers most known types of pulsators, reflecting a highly productive and far reaching interchange of ideas which we believe is conveyed by the papers and posters published, making it a reference for researchers and postgraduate students working on stellar structure and evolution.

Link: http://www.wkap.nl/prod/b/1-4020-1173-3 Title: Time-distance analysis of GONG+ data Authors: Rajaguru, S. P.; Hughes, S. J.; Thompson, M. J. Bibcode: 2003ESASP.517...75R Altcode: 2003soho...12...75R We show our first time-distance analyses of data from GONG+. We present details of our method of analysing the data and travel-time anomalies measured over an active region when compared to that over a quiet region. The dataset used for studying the active region is from a merged sequence of GONG+ Doppler images. Title: Time-distance helioseismology of subsurface flows Authors: Hughes, Stephen J.; Thompson, Michael J. Bibcode: 2003ESASP.517..307H Altcode: 2003soho...12..307H We revisit the work of Giles (1999) in an attempt to extend the work on large scale flows using the technique of time-distance helioseismology. The basic process and techniques are discussed and some initial results are shown. The behaviour of the meridional and zonal flows is found to be similar to that found by Giles and separately by ring diagram methods (Haber et al. 2002). Title: Transient oscillations near the solar tachocline Authors: Toomre, Juri; Christensen-Dalsgaard, Jorgen; Hill, Frank; Howe, Rachel; Komm, Rudolf W.; Schou, Jesper; Thompson, Michael J. Bibcode: 2003ESASP.517..409T Altcode: 2003soho...12..409T We report on further developments in the 1.3-yr quasi-periodic oscillations reported by Howe et al. (2000). These are small (6 to 8 nHz peak-to-peak) oscillations in the inferred rotation rate near the bottom of the convection zone and in the outer part of the radiative interior. The oscillations are strongest and most coherent at about a fractional radius of 0.72 in the equatorial region. Further monitoring of the oscillations near the equator shows that they continued for a period after the end of the data analyzed by Howe et al., but appear to have now diminished in amplitude. This is reminiscent of the transient behavior of similar (1.3 to 1.4 yr) periodicities in solar-wind and geomagnetic datasets previously reported. We speculate that the near tachocline oscillation is associated with the rising phase of the solar cycle. We discuss tests performed to eliminate various possible explanations of the oscillations due to systematic errors in the data and in their analyses. Title: On variation of the latitudinal structure of the solar convection zone Authors: Antia, H. M.; Chitre, S. M.; Thompson, M. J. Bibcode: 2003A&A...399..329A Altcode: 2002astro.ph.12095A The latitudinal sound-speed structure of the Sun's convection zone gives insight into the physical processes occurring there, specifically the cellular convection and possibly the presence of magnetic fields. Using helioseismic data from the GONG network and MDI instrument on SOHO, we map the latitudinal acoustic structure of the convection zone from 1995 to 2002. The temporally averaged structure confirms previous findings of an excess in sound speed at the 10-4 level at 60 degrees latitude. There also appear to be some variation with time, with the peak in sound-speed asphericity at 60 degrees growing towards the maximum of solar activity according to the MDI data. However, we present some evidence that such variation may be associated with instrumental variation between the epochs before and after SOHO was temporarily lost in 1998. Nonetheless, some genuine temporal variation may be present, and we discuss the possible physical causes of that. Title: Helioseismology present and future Authors: Thompson, Michael J. Bibcode: 2003ESASP.517..209T Altcode: 2003soho...12..209T The subject of helioseismology is in a exciting phase of expansion. In terms of the methods being developed and applied, the new and challenging results coming out from the high-quality data that present observational campaigns, networks and missions are providing, the arrival of GONG+, the prospects for new missions including Solar Dynamics Observatory, and the recent ground-based results and exciting prospects for asteroseismology of other solar-like stars. I pick up on some themes of the conference, and expand on the above developments and activities. Title: Acoustic Wave Propagation in the Sun: Implications for Wave Field and Time-Distance Helioseismology Authors: Tong, C. H.; Thompson, M. J.; Warner, M. R.; Rajaguru, S. P.; Pain, C. C. Bibcode: 2003ApJ...582L.121T Altcode: We present results of the numerical simulation of acoustic wave propagation in the Sun's subphotospheric layers. A finite-difference code is used to calculate the pressure perturbation in the frequency domain. We show that the oscillatory seismic signals are closely associated with the solar density and sound speed structures. Owing to the acoustic cutoff frequency, the reduction in the group velocity relative to the background sound speed varies significantly with frequency, especially at low frequencies. This variation causes acoustic wave dispersion, which results in the nonuniform frequency content in the oscillatory signals in the wave packets. An asymptotic arrival generated by the constructive interference of the high-order bounces is observed in the synthetic seismic traces. The synthetic seismic traces presented in this study can provide the basis for wave field tomography, in which phase and amplitude information (including the nonresonant frequencies) is exploited, to enhance the spatial resolution of the reconstructed solar models. Title: Rotation of the solar interior Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2003dysu.book...55C Altcode: Helioseismology allows us to infer the rotation in the greater part of the solar interior with high precision and resolution. The results show interesting conflicts with earlier theoretical expectations, indicating that the Sun is host to complex dynamical phenomena, so far hardly understood. This has important consequences for our ideas about the evolution of stellar rotation, as well as for models for the generation of the solar magnetic field. An overview of our current knowledge about solar rotation is given, much of it obtained from the SOHO spacecraft, and the broader implications are discussed. Title: Preface (Stellar astrophysical fluid dynamics) Authors: Thompson, Michael J.; Christensen-Dalsgaard, Jørgen Bibcode: 2003safd.bookD...9T Altcode: No abstract at ADS Title: On Asteroseismic Constraints for Modelling the δ Scuti Stars V480 Tau and θ2 Tau A Authors: Di Mauro, M. P.; Pijpers, F.; Christensen-Dalsgaard, J.; Paternò, L.; Teixeira, T.; Thompson, M. J. Bibcode: 2003ASPC..305..161D Altcode: 2003mfob.conf..161D We investigate the structure and evolution of δ Scuti stars and discuss how basic properties as well as global oscillation frequencies are modified by moderate rotation. We present theoretical analyses of V480 Tau, observed during the MUSICOS 1996 campaign (Hao et al. 2001), and of θ2 Tau A, monitored by the WIRE satellite (Poretti et al. 2002). We compare the observed spectra of frequencies with the theoretical oscillation frequencies calculated by including rotational effects. Title: Seismological analysis of the Helium ionization zones in low- and moderate-mass stars Authors: Miglio, A.; Christensen-Dalsgaard, J.; di Mauro, M. P.; Monteiro, M. J. P. F. G.; Thompson, M. J. Bibcode: 2003aahd.conf..537M Altcode: The region of the second ionization of helium in solar-like stars is a narrow subsurface layer whose thermodynamic properties are responsible for the presence of a characteristic signature in the oscillation frequencies of the p modes. Here, with the aim of detecting the acoustic depth of the second helium ionization zone, we consider two methods of analysing the signal generated in the oscillation frequencies by the sharp decrease in the first adiabatic exponent Γ1, which occurs where ionization takes place. The properties of the ionization zone, once determined by seismological means, may be used to put constraints on the structure of the stars, in particular on the envelope helium abundance. Title: Seismic Study of Temporal Variations of Solar Magnetic Field Authors: Antia, H. M.; Chitre, S. M.; Thompson, M. J. Bibcode: 2003IAUJD..12E..30A Altcode: The temporal variations of acoustic frequencies of solar oscillations with the solar activity cycle are studied with a view to understanding the changes in the Sun's internal magnetic field. The data used are even a-coefficients from the GONG and MDI observations of the Sun's p-mode oscillations. These coefficients describe the modification of the frequencies by agents such as magnetic fields or latitudinal thermal perturbations that break the spherical symmetry of the Sun but that - unlike rotational advection and Coriolis forces - do not distinguish eastward- and westward-propagating acoustic waves. It is hoped that such a study will shed light on the mechanism of the solar dynamo. Title: A selective overview Authors: Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 2003safd.book....1C Altcode: Contents: 1. Introduction. 2. On taking mixing-length theory seriously. 3. The solar spoon. 4. Deep roots of solar cycles. 5. Helioseismology: oscillations as a diagnostic of the solar interior. 6. Inverting helioseismic data. 7. On the detection of subphotospheric convective velocities and temperature fluctuations. 8. Prospects for asteroseismic inference. Title: The Internal Rotation of the Sun Authors: Thompson, Michael J.; Christensen-Dalsgaard, Jørgen; Miesch, Mark S.; Toomre, Juri Bibcode: 2003ARA&A..41..599T Altcode: Helioseismology has transformed our knowledge of the Sun's rotation. Earlier studies revealed the Sun's surface rotation, but now a detailed observational picture has been built up of the internal rotation of our nearest star. Unlike the predictions of stellar-evolution models, the radiative interior is found to rotate roughly uniformly. The rotation within the convection zone is also very different from prior expectations, which had been that the rotation rate would depend primarily on the distance from the rotation axis. Layers of rotational shear have been discovered at the base of the convection zone and in the subphotospheric layers. Studies of the time variation of rotation have uncovered zonal-flow bands, extending through a substantial fraction of the convection zone, which migrate over the course of the solar cycle, and there are hints of other temporal variations and of a jet-like structure. At the same time, building on earlier work with mean-field models, researchers have made great progress in supercomputer simulations of the intricate interplay between turbulent convection and rotation in the Sun's interior. Such studies are beginning to transform our understanding of how rotation organizes itself in a stellar interior. Title: A Sub-mm Imaging Survey of Ultracompact HII Regions Authors: Thompson, M.; Hatchell, J.; MacDonald, G.; Millar, T. Bibcode: 2002ASPC..267..429T Altcode: 2001astro.ph.12444T; 2002hsw..work..429T Ultracompact (UC) H II regions are currently the best known tracer of massive YSOs and represent the earliest confirmed stage of massive star formation. In excess of 150 UC HII regions have been detected, mainly by radio surveys. Whilst the environments of UC HII regions are known very well on the small scale (a few arcseconds) they are not well known on scales over 40 arcsec. This is because most UC HII's have, to date, been observed using either interferometers (to gain information on small scales at the expense of large scales) or by single-position large-beam (typically 40 arcsec or worse) spectroscopy. To redress this issue we recently undertook an imaging survey of over 100 UC HII regions using SCUBA on the JCMT, which enables us to rapidly map with high-resolution the dust emission from the clumps in which the UC HII's are embedded. Title: Induced Star Formation Near HII Regions: the Fate of Three Clouds in IC 1848 Authors: Thompson, M.; White, G.; Miao, J.; Fridlund, M.; Huldtgren, M. Bibcode: 2002ASPC..267..431T Altcode: 2002hsw..work..431T From a combination of NVSS archive radio continuum data and JCMT 12CO and 13CO maps we have evaluated the pressure balance between the ionised exterior and molecular interior of three bright-rimmed clouds. We predict that photo-ionisation shocks are currently being driven into two of the clouds whilst the third is likely to be in a pre-shock state. Title: Flux Transport Solar Dynamos with Near-Surface Radial Shear Authors: Dikpati, Mausumi; Corbard, Thierry; Thompson, Michael J.; Gilman, Peter A. Bibcode: 2002ApJ...575L..41D Altcode: Corbard & Thompson analyzed quantitatively the strong radial differential rotation that exists in a thin layer near the solar surface. We investigate the role of this radial shear in driving a flux transport dynamo operating with such a rotation profile. We show that despite being strong, near-surface radial shear effectively contributes only ~1 kG (~30% of the total) to the toroidal fields produced there unless an abnormally high, surface α-effect is included. While 3 kG spot formation from ~1-2 kG toroidal fields by convective collapse cannot be ruled out, the evolutionary pattern of these model fields indicates that the polarities of spots formed from the near-surface toroidal field would violate the observed polarity relationship with polar fields. This supports previous results that large-scale solar dynamos generate intense toroidal fields in the tachocline, from which buoyant magnetic loops rise to the photosphere to produce spots. Polar fields generated in flux transport models are commonly much higher than observed. We show here that by adding enhanced diffusion in the supergranulation layer (originally proposed by Leighton), near-surface toroidal fields undergo large diffusive decay preventing spot formation from them, as well as reducing polar fields closer to the observed values. However, the weaker polar fields lead to the regeneration of a toroidal field of less than ~10 kG at the convection zone base, too weak to produce spots that emerge in low latitudes, unless an additional poloidal field is produced at the tachocline. This is achieved by a tachocline α-effect, previously shown to be necessary for coupling the north and south hemispheres to ensure toroidal and poloidal fields that are antisymmetric about the equator. Title: Solar internal rotation as seen from SOHO MIDI data Authors: Vorontsov, S. V.; Christensen-Dalsgaard, J.; Schou, J.; Strakhov, V. N.; Thompson, M. J. Bibcode: 2002ESASP.508..111V Altcode: 2002soho...11..111V We report results of inverting the rotational splittings of solar p-mode frequencies measured from the MDI data, using an adaptive regularization technique as described by Strakhov & Vorontsov (2001). We analyse the spatial and temporal structure of the variations in the internal rotation, which constitute the 11-yr solar torsional oscillations. We employ all the data collected over half a solar cycle to analyse further the time-independent component of the differential rotation, particularly focusing on the solar tachocline region. We address systematic errors in the rotational splitting measurements, as indicated by the inversion residuals, which appear to restrict the accuracy of the current helioseismic measurements. Title: Effect of subsurface radial differential rotation on flux-transport solar dynamo Authors: Corbard, T.; Dikpati, M.; Gilman, P. A.; Thompson, M. J. Bibcode: 2002ESASP.508...75C Altcode: 2002soho...11...75C A near-surface radial gradient of rotation was recently inferred and quantified from MDI f-modes observations by Corbard & Thompson (2001). We show, from our preliminary simulation of the large-scale solar magnetic field, by using a flux-transport type dynamo, that despite being strong, this gradient plays only a small role compared to the tachocline in shearing the poloidal fields to produce toroidal fields. This happens primarily because the turbulent diffusivity near the surface wins in the competition of generation versus decay of the magnetic fields unless an abnormally high α-effect is considered there. This supports the results of previous flux-transport as well as interface and overshoot layer dynamo models that the major toroidal fields of the Sun are generated in the tachocline. Title: Helioseismic Measurement of Solar Torsional Oscillations Authors: Vorontsov, S. V.; Christensen-Dalsgaard, J.; Schou, J.; Strakhov, V. N.; Thompson, M. J. Bibcode: 2002Sci...296..101V Altcode: Bands of slower and faster rotation, the so-called torsional oscillations, are observed at the Sun's surface to migrate in latitude over the 11-year solar cycle. Here, we report on the temporal variations of the Sun's internal rotation from solar p-mode frequencies obtained over nearly 6 years by the Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory (SOHO) satellite. The entire solar convective envelope appears to be involved in the torsional oscillations, with phase propagating poleward and equatorward from midlatitudes at all depths throughout the convective envelope. Title: A Comparison of Solar p-Mode Parameters from the Michelson Doppler Imager and the Global Oscillation Network Group: Splitting Coefficients and Rotation Inversions Authors: Schou, J.; Howe, R.; Basu, S.; Christensen-Dalsgaard, J.; Corbard, T.; Hill, F.; Komm, R.; Larsen, R. M.; Rabello-Soares, M. C.; Thompson, M. J. Bibcode: 2002ApJ...567.1234S Altcode: Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) onboard SOHO, we compare frequency-splitting data and resulting inversions about the Sun's internal rotation. Helioseismology has been very successful in making detailed and subtle inferences about the solar interior. But there are some significant differences between inversion results obtained from the MDI and GONG projects. It is important for making robust inferences about the solar interior that these differences are located and their causes eliminated. By applying the different analysis pipelines developed by the projects not only to their own data but also to the data from the other project, we conclude that the most significant differences arise not from the observations themselves but from the different frequency estimation analyses used by the projects. We find that the GONG pipeline results in substantially fewer fitted modes in certain regions. The most serious systematic differences in the results, with regard to rotation, appear to be an anomaly in the MDI odd-order splitting coefficients around a frequency of 3.5 mHz and an underestimation of the low-degree rotational splittings in the GONG algorithm. Title: The subsurface radial gradient of solar angular velocity from MDI f-mode observations Authors: Corbard, T.; Thompson, M. J. Bibcode: 2002SoPh..205..211C Altcode: 2001astro.ph.10361C We report quantitative analysis of the radial gradient of solar angular velocity at depths down to about 15 Mm below the solar surface for latitudes up to 75° using the Michelson Doppler Imager (MDI) observations of surface gravity waves (fmodes) from the Solar and Heliospheric Observatory (SOHO). A negative outward gradient of around −400 nHz/R⊙, equivalent to a logarithmic gradient of the rotation frequency with respect to radius which is very close to −1, is found to be remarkably constant between the equator and 30° latitude. Above 30° it decreases in absolute magnitude to a very small value at around 50°. At higher latitudes the gradient may reverse its sign: if so, this reversal takes place in a thin layer extending only 5 Mm beneath the visible surface, as evidenced by the most superficial modes (with degrees l>250). The signature of the torsional oscillations is seen in this layer, but no other significant temporal variations of the gradient and value of the rotation rate there are found. Title: SOLA inversions for the core structure of solar-type stars Authors: Basu, S.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2002ESASP.485..249B Altcode: 2002sshp.conf..249B; 2001astro.ph.10446B The Subtractive Optimally Localized Averages (SOLA) method, developed and extensively used in helioseismology, is applied to artificial data to obtain measures of the sound speed inside a solar-type star. In contrast to inversion methods which fit models to some aspect of the data, methods such as SOLA provide an honest assessment of what can truly be resolved using seismic data, without introducing additional assumptions such as that the space of admissible stellar models is small. The resulting measures obtained from SOLA inversion can subsequently be used to eliminate putative stellar models. Here we present results of experiments to test the reliability of SOLA inferences using solar models and models of solar-type stars. Title: On inverting asteroseismic data Authors: Thompson, M. J.; Christensen-Dalsgaard, J. Bibcode: 2002ESASP.485...95T Altcode: 2002sshp.conf...95T; 2001astro.ph.10447T Some issues of inverting asteroseismic frequency data are discussed, including the use of model calibration and linearized inversion. An illustrative inversion of artificial data for solar-type stars, using least-squares fitting of a small set of basis functions, is presented. A few details of kernel construction are also given. Title: Asteroseismic inference for solar-type stars Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2002ESASP.485..291M Altcode: 2001astro.ph.10445M; 2002sshp.conf..291M The oscillation spectra of solar-type stars may in the not-too-distant future be used to constrain certain properties of the stars. The C-D diagram of large versus small frequency separations is one of the powerful tools available to infer the properties - including perhaps masses and ages - of stars which display a detectable spectrum of oscillation. Also, the border of a convective region in a solar-type star gives rise to a characteristic periodic signal in the star's low-degree p-mode frequencies. Such a signature contains information about the location and nature of the transition between convective and non-convective regions in the star. In this work we address some of the uncertainties associated with the direct use of the C-D diagram to evaluate the mass and age of the star due to the unknown contributions that make the stars different from the evolutionary models used to construct our reference grid. We also explore the possibility of combining an amplitude versus period diagram with the C-D diagram to evaluate the properties of convective borders within solar-type stars. Title: Rotation of the solar interior Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 2001astro.ph.10607C Altcode: Helioseismology has allowed us to infer the rotation in the greater part of the solar interior with high precision and resolution. The results show interesting conflicts with earlier theoretical expectations, indicating that the the Sun is host to complex dynamical phenomena, so far hardly understood. This has important consequences for our ideas about the evolution of stellar rotation, as well as for models for the generation of the solar magnetic field. Here we provide an overview of our current knowledge about solar rotation, much of it obtained from observations from the SOHO spacecraft, and discuss the broader implications. Title: Variations of the solar interior with the cycle: observational aspects. Authors: Corbard, Thierry; Jimenez-Reyes, S. J.; Thompson, M. J.; Tomczyk, S. Bibcode: 2001sf2a.conf..109C Altcode: Helioseismic observations of long duration now open the possibility of studying the variation of the interior of the Sun during its cycle of activity. In particular, the possible dynamic or structure variations of the interface between the convective zone and the radiative interior, or tachocline, is of great interest to constrain solar dynamo models and to understand the phenomena at the origin of the cycle of activity observed at the surface. We have analysed the observations obtained during the 6 last years by the LOWL instrument located at Mauna Loa, Hawaii as well as the observations in integrated disc covering more than one solar cycle (1984-2000) by MARK-I instrument at the Peak del Teide, Tenerife. The results concerning the signature of the solar activity on the pressure modes of low and medium degrees and seeks for possible variations of the dynamic of the tachocline will be presented and replaced in the theoretical context. Title: Comparing Global Solar Rotation Results from MDI and GONG Authors: Howe, R.; Komm, R. W.; Hill, F.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Corbard, T. Bibcode: 2001AGUSM..SP31A14H Altcode: The GONG (Global Oscillations Network Group) project and the Solar Oscillations Investigation (SOI) using the Michelson Doppler Imager (MDI) instrument aboard the SOHO spacecraft have jointly accumulated more than five years of data on medium-degree solar p-modes, including nearly four years of contemporaneous observations. The inferences of interior solar rotation from the two projects are broadly consistent and show similar temporal variations, but there are also significant systematic differences. We report here on the results of an ongoing attempt to cross-compare the results and analysis techniques of the two projects. Three 108-day periods, at low, medium and high solar activity epochs, have been analysed, with both MDI and GONG analysis being applied to each data set, and the results are compared. Title: Variations in Rotation Rate Within the Solar Convection Zone From GONG and MDI 1995-2000 Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2001AGUSM..SP31A15H Altcode: Helioseismic measurements with the Michelson Doppler Imager (MDI) instrument aboard SOHO, and complementary measurements from the Global Oscillation Network Group (GONG) project, are revealing changes deep within the Sun as the solar cycle progresses. We will present the latest results based on recent data from both experiments, including flows in the upper part of the convection zone and variations in the rotation rate near its base. Title: Seismology of solar-type stars Authors: Basu, S.; Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G.; Thompson, M. J. Bibcode: 2001ESASP.464..407B Altcode: 2001soho...10..407B Seismology of solar-type stars other than the Sun becomes a realistic possibly with the upcoming MOST, COROT and MONS missions, and the ESA mission Eddington. We report on the results of experiments with artificial data from models of solar-type stars to assess further what we might learn about the internal structure of such stars. Title: Inversion for the solar internal rotation with an adaptive regularization technique Authors: Vorontsov, S. V.; Christensen-Dalsgaard, J.; Schou, J.; Strakhov, V. N.; Thompson, M. J. Bibcode: 2001ESASP.464..559V Altcode: 2001soho...10..559V We report the first preliminary results of applying the adaptive regularization technique (Strakhov and Vorontsov 2000) to the inversion for the solar internal rotation. The 360d SOHO MDI data set with 18-th degree fit to the rotational splittings is used in the 1.5-D and 2-D inversions, and we used the 72d data sets (Schou 1999) to trace the possible variations with solar activity. Title: Comparing mode frequencies from MDI and GONG Authors: Howe, R.; Hill, F.; Basu, S.; Christensen-Dalsgaard, J.; Komm, R. W.; Munk Larsen, R.; Roth, M.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2001ESASP.464..137H Altcode: 2001soho...10..137H We present results of analyses of MDI and GONG time series covering the same time intervals, and using both the MDI and GONG peakbagging algorithms. We discuss some of the likely causes of differences between the inferred frequencies and frequency splittings. In addition, we consider the effect of these differences on the results of inversions for the solar internal rotation and sound speed. Title: Solar cycle changes in convection zone dynamics from MDI and GONG 1995 - 2000 Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Munk Larsen, R.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2001ESASP.464...19H Altcode: 2001soho...10...19H The combined GONG and MDI medium-degree helioseismic data sets now cover just over 5 years and allow us to probe the changing dynamics of the convection zone in unprecedented detail. Here we present the latest 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. Title: Temporal variations of the Sun's internal structure and dynamics: a theoretical perspective Authors: Thompson, Michael J. Bibcode: 2001ESASP.464...39T Altcode: 2001soho...10...39T As is well known from surface observations of magnetic fields, flow fields and radiation fluxes, the Sun is a highly dynamical object and varies on many timescales, one of the most prominent being the 22-year period of the solar activity cycle. Recently there has been much direct evidence from helioseismology (e.g. the many contributions to this Session) for temporal variations also in the solar interior, on timescales of months and years. In this review talk I consider the theoretical expectations of how the solar interior (structure, magnetic field, velocity field) might change over the solar cycle and on other timescales, how these changes can be expected to influence the measurable properties of the oscillations, and possible theoretical interpretations of some of the recent helioseismic results on temporal variations of the solar interior. Title: Interior Solar-Cycle Changes Detected by Helioseismology Authors: Howe, R.; Hill, F.; Komm, R. W.; Christensen-Dalsgaard, J.; Munk Larsen, R.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2001IAUS..203...40H Altcode: Helioseismic measurements with the MDI instrument aboard SOHO, and complementary measurements from the GONG network, are revealing changes deep within the Sun as the solar cycle progresses. We will present results based on recent data from both experiments, including variations in the rotation rate deep inside the convection zone. Title: On the signature of the solar activity at the base of the convective envelope Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 2001ESASP.464..535M Altcode: 2001soho...10..535M A we approach the solar maximum for the current cycle it is timely to establish what helioseismology can tell us about the internal changes the Sun undergoes as the cycle progresses. In this work we use SOI-MDI data in order to identify changes occurring to the stratification of the Sun at the base of the convective envelope. Both changes with time (averaged over colatitude) and changes over time at different colatitudes are addressed. These are discussed in terms of the changes in the properties of the convection at the base of the envelope in the region where the tachocline is present. Those variations could be attributed to the interaction between convection, rotation and magnetic fields, which must be intrinsically time-dependent phenomena, possibly correlated with the observed changes occurring over the cycle in the envelope up to the surface. Title: The Sun's acoustic asphericity and magnetic fields in the solar convection zone Authors: Antia, H. M.; Chitre, S. M.; Thompson, M. J. Bibcode: 2000A&A...360..335A Altcode: 2000astro.ph..5587A The observed splittings of solar oscillation frequencies can be employed to separate the effects of internal solar rotation and to estimate the contribution from a large-scale magnetic field or any latitude- dependent thermal perturbation inside the Sun. The surface distortion estimated from the rotation rate in the solar interior is found to be in good agreement with the observed oblateness at solar surface. After subtracting out the estimated contribution from rotation, there is some residual signal in the even splitting coefficients, which may be explained by a magnetic field of approximately 20 kG strength located at a depth of 30000 km below the surface or an equivalent aspherical thermal perturbation. An upper limit of 300 kG is derived for a toroidal field near the base of the convection zone. Title: Seismic study of stellar convective regions: the base of the convective envelope in low-mass stars Authors: Monteiro, Mário J. P. F. G.; Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 2000MNRAS.316..165M Altcode: The possibility of observing solar-type oscillations on other stars is of great relevance to investigating the uncertain aspects of the internal structure of stars. One of these aspects is the convective overshoot that takes place at the borders of the envelopes of stars of mass similar to, or lower than, the Sun. It affects the temperature stratification, mixing, rotation and magnetic-field generation. Asteroseismology can provide an observational test for the studies of the structure of such overshoot regions. The seismic study of the transition in the Sun, located at the base of the convection zone, has been successful in determining the characteristics of this layer in the Sun. In this work we consider the extension of the analysis to other solar-type stars (of mass between 0.85 and 1.2Msolar) in order to establish a method for determining the characteristics of their convective envelopes. In particular, we hope to be able to establish seismologically that a star does indeed possess a convective envelope, to measure the size of the convective region and also to constrain the properties of an overshoot layer at the bottom of the envelope. The limitations in terms of observational uncertainties and stellar characteristics, and the detectability of an overshoot layer, are discussed. Title: Helioseismic Search for Magnetic Field in the Solar Interior Authors: Antia, H. M.; Chitre, S. M.; Thompson, M. J. Bibcode: 2000JApA...21..343A Altcode: No abstract at ADS Title: Solar-Cycle Changes in Convection-Zone Dynamics from SOI and GONG Data Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Larsen, R. M.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2000SPD....31.0113H Altcode: 2000BAAS...32..803H The combined GONG and MDI medium-degree helioseismic data sets now cover more than 4.5 years and allow us to probe the changing dynamics of the convection zone in unprecedented detail. Here we present the latest 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. This work utilizes data obtained by the Global Oscillation Network Group (GONG) project, managed by the National Solar Observatory, a Division of the National Optical Astronomy Observatories, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. SOHO is a joint project of ESA and NASA. Title: Seismology of solar-type stars Authors: Thompson, M. J. Bibcode: 2000mons.proc...15T Altcode: I review the asteroseismology of solar-type stars. The emphasis is on the theory of what may be learned and how. I draw on our experience of performing low-degree seismology on the Sun. Title: Deeply Penetrating Banded Zonal Flows in the Solar Convection Zone Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Larsen, R. M.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2000ApJ...533L.163H Altcode: 2000astro.ph..3121H Helioseismic observations have detected small temporal variations of the rotation rate below the solar surface that correspond to the so-called ``torsional oscillations'' known from Doppler measurements of the surface. These appear as bands of slower- and faster-than-average rotation moving equatorward. Here we establish, using complementary helioseismic observations over 4 yr from the GONG network and from the MDI instrument on board SOHO, that the banded flows are not merely a near-surface phenomenon: rather, they extend downward at least 60 Mm (some 8% of the total solar radius) and thus are evident over a significant fraction of the nearly 200 Mm depth of the solar convection zone. Title: Solar shear flows deduced from helioseismic dense-pack samplings of ring diagrams Authors: Haber, D. A.; Hindman, B. W.; Toomre, J.; Bogart, R. S.; Thompson, M. J.; Hill, F. Bibcode: 2000SoPh..192..335H Altcode: We report on large-scale horizontal flows in the solar convection zone and their variability in time and space using a local-helioseismology technique known as ring-diagram analysis. By performing this analysis on a dense mosaic of individual regions on the solar disk, i.e., a `Dense-Pack' sampling, and repeating the analysis periodically on several time scales, we are able to assess the variation of horizontal flows from day-to-day, week-to-week, and year-to-year. We find that although there are changes in the flows on all these time scales, there are also basic patterns that persist. On a daily time scale we observe that the flow is reduced in those areas which are occupied by large active regions. On somewhat longer time-scales we see bands of persistent fast and slow zonal flow that are identifiable as torsional oscillations. As we examine these bands during a series of years, we find that these bands migrate toward the equator as solar activity increases. Similarly, the latitudes at which the meridional flow reaches maximum follow these regions of fast zonal flow as they migrate equatorwards. These Dense-Pack samplings also reveal substantial differences in the zonal and meridional flow patterns in the northern and southern hemispheres. Title: Time Variability of Rotation in Solar Convection Zone From soi-mdi Authors: Toomre, J.; Christensen-Dalsgaard, J.; Howe, R.; Larsen, R. M.; Schou, J.; Thompson, M. J. Bibcode: 2000SoPh..192..437T Altcode: The variation of rotation in the convection zone over a period of two years from mid-1996 is studied using inversions of SOI-MDI data. We confirm the existence of near-surface banded zonal flows migrating towards the equator from higher latitudes, and reveal that these banded flows extend substantially beneath the surface, possibly to depths as great as 70 Mm (10% of the solar radius). Our results also reveal apparently significant temporal variations in the rotation rate at high latitudes and in the vicinity of the tachocline over the period of study. Title: Dynamic Variations at the Base of the Solar Convection Zone Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Larsen, R. M.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 2000Sci...287.2456H Altcode: We have detected changes in the rotation of the sun near the base of its convective envelope, including a prominent variation with a period of 1.3 years at low latitudes. Such helioseismic probing of the deep solar interior has been enabled by nearly continuous observation of its oscillation modes with two complementary experiments. Inversion of the global-mode frequency splittings reveals that the largest temporal changes in the angular velocity Ω are of the order of 6 nanohertz and occur above and below the tachocline that separates the sun's differentially rotating convection zone (outer 30% by radius) from the nearly uniformly rotating deeper radiative interior beneath. Such changes are most pronounced near the equator and at high latitudes and are a substantial fraction of the average 30-nanohertz difference in Ω with radius across the tachocline at the equator. The results indicate variations of rotation close to the presumed site of the solar dynamo, which may generate the 22-year cycles of magnetic activity. Title: Helioseismic detection of temporal variations of solar rotation rate near the base of the convection zone Authors: Howe, R.; Christensen-Dalsgaard, J.; Hill, F.; Komm, R. W.; Larsen, R. M.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 1999AAS...19510702H Altcode: 1999BAAS...31R1530H The differential rotation of the Sun and its ability to generate large-scale magnetic fields through cyclic dynamo action appear to be intimately linked. It is now commonly thought that the global dynamo behavior responsible for the emergence of active regions is derived from strong organized toroidal magnetic fields generated by rotational shear in a thin region (the tachocline) at the base of the convection zone. The magnetic field could well have a feedback effect on the fluid motions in the region. We are thus motivated to use helioseismology to look for changes in rotation profiles near the tachocline as the Sun's magnetic cycle progresses. This approach has become possible using frequency-splitting data for p- and f-mode oscillations derived over four years (from May 1995 to Sept 1999) of full-disk Doppler observations from the ground-based Global Oscillation Network Group (GONG) project and from the Michelson Doppler Imager (MDI) experiment aboard the SOHO spacecraft. Inversions using two different methods of the splittings from these two independent data sets reveal systematic variations of the rotation rate close to the base of the convection zone, with different behavior at low and high latitudes. Notable are variations of order 6 nHz in rotation rates near the equator, to be compared with the radial angular velocity contrast across the tachocline of about 30 nHz. These exhibit several nearly repetitive changes with a period of about 1.2-1.4 years and appear to be real changes in the deep convection zone and tachocline rotation rates that need to be followed as the solar cycle progresses. The GONG project is managed by the National Solar Observatory, a Division of the National Optical Astronomy Observatories, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. SOHO is a joint project of ESA and NASA. Title: Helioseismic Constraints on the Structure of the Solar Tachocline Authors: Charbonneau, P.; Christensen-Dalsgaard, J.; Henning, R.; Larsen, R. M.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1999ApJ...527..445C Altcode: This paper presents a series of helioseismic inversions aimed at determining with the highest possible confidence and accuracy the structure of the rotational shear layer (the tachocline) located beneath the base of the solar convective envelope. We are particularly interested in identifying features of the inversions that are robust properties of the data, in the sense of not being overly influenced by the choice of analysis methods. Toward this aim we carry out two types of two-dimensional linear inversions, namely Regularized Least-Squares (RLS) and Subtractive Optimally Localized Averages (SOLA), the latter formulated in terms of either the rotation rate or its radial gradient. We also perform nonlinear parametric least-squares fits using a genetic algorithm-based forward modeling technique. The sensitivity of each method is thoroughly tested on synthetic data. The three methods are then used on the LOWL 2 yr frequency-splitting data set. The tachocline is found to have an equatorial thickness of w/Rsolar=0.039+/-0.013 and equatorial central radius rc/Rsolar=0.693+/-0.002. All three techniques also indicate that the tachocline is prolate, with a difference in central radius Δrc/Rsolar~=0.024+/-0.004 between latitude 60° and the equator. Assuming uncorrelated and normally distributed errors, a strictly spherical tachocline can be rejected at the 99% confidence level. No statistically significant variation in tachocline thickness with latitude is found. Implications of these results for hydrodynamical and magnetohydrodynamical models of the solar tachocline are discussed. Title: Rotation of the solar interior Authors: Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 1999CSci...77.1460C Altcode: No abstract at ADS Title: Effects of line asymmetries on the determination of solar internal structure Authors: Rabello-Soares, M. C.; Christensen-Dalsgaard, J.; Rosenthal, C. S.; Thompson, M. J. Bibcode: 1999A&A...350..672R Altcode: 1999astro.ph..8250R Despite the strong evidence that the peaks in the spectrum of solar oscillations are asymmetric, most determinations of mode frequencies have been based on fits of symmetric Lorentzian profiles to the Fourier or power spectra of oscillation time strings. The systematic errors resulting from neglecting the line asymmetry could have serious effects on inversions for the solar internal structure and rotation. Here we analyse artificial data based on simple models of the intrinsic line asymmetry, using GONG mode parameters with asymmetries found by one of us (Rosenthal \cite{rosenthal2}). By fitting Lorentzians to the resulting spectra, we estimate the likely properties of the errors introduced in the frequencies. We discuss whether these frequency shifts have a form similar to the near-surface layers uncertainties and are therefore suppressed in the solar structure inversion. We also estimate directly their contribution, if any, in the solar sound-speed and density determinations using the SOLA technique. Title: A note on Saio's estimate of second-order effects of rotation on stellar oscillation frequencies Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1999A&A...350..852C Altcode: In many cases, oscillating stars rotate so rapidly that second-order effects must be taken into account in analyses of the oscillation frequencies. Such investigations have commonly been based on results provided by Saio (1981) for a polytropic model. Here we compare those with frequency changes for more realistic models; we point out that a simple correction to Saio's data allows them to be used in the observationally relevant case of comparing models at fixed luminosity and effective temperature. Title: Rotation of the solar core from BiSON and LOWL frequency observations Authors: Chaplin, W. J.; Christensen-Dalsgaard, J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; Larsen, R. M.; New, R.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1999MNRAS.308..405C Altcode: Determination of the rotation of the solar core requires very accurate data on splittings for the low-degree modes which penetrate to the core, as well as for modes of higher degree to suppress the contributions from the rest of the Sun to the splittings of the low-degree modes. Here we combine low-degree data based on 32 months of observations with the BiSON network and data from the LOWL instrument. The data are analysed with a technique that specifically aims at obtaining an inference of rotation that is localized to the core. Our analysis provides what we believe is the most stringent constraint to date on the rotation of the deep solar interior. Title: Strange baryon production in p-Pb collisions at 158 GeV img1.gif: a comparison with VENUS model Authors: Virgili, T.; WA97 Collaboration; Andersen, E.; Antinori, F.; Armenise, N.; Bakke, H.; Bán, J.; Barberis, D.; Beker, H.; Beusch, W.; Bloodworth, I. J.; Böhm, J.; Caliandro, R.; Campbell, M.; Cantatore, E.; Carrer, N.; Catanesi, M. G.; Chesi, E.; Dameri, M.; Darbo, G.; Diaczek, A.; Di Bari, D.; Di Liberto, S.; Earl, B. C.; Elia, D.; Evans, D.; Fanebust, K.; Fini, R. A.; Fontaine, J. C.; Ftácnik, J.; Ghidini, B.; Grella, G.; Guida, M.; Heijne, E. H. M.; Helstrup, H.; Holme, A. K.; Huss, D.; Jacholkowski, A.; Jones, G. T.; Jovanovic, P.; Jusko, A.; Kachelhoffer, T.; Kinson, J. B.; Kirk, A.; Klempt, W.; Knudsen, B. T. H.; Knudson, K.; Králik, I.; Lenti, V.; Lietava, R.; Loconsole, R. A.; Løvhøiden, G.; Lupták, M.; Mack, V.; Manzari, V.; Martinengo, P.; Mazzoni, M. A.; Meddi, F.; Michalon, A.; Michalon-Mentzer, M. E.; Middelkamp, P.; Morando, M.; Muciaccia, M. T.; Nappi, E.; Navach, F.; Norman, P. I.; Osculati, B.; Pastircák, B.; Pellegrini, F.; Piska, K.; Posa, F.; Quercigh, E.; Ricci, R. A.; Romano, G.; Rosa, G.; Rossi, L.; Rotscheidt, H.; Safarik, K.; Saladino, S.; Salvo, C.; Sándor, L.; Scognetti, T.; Segato, G.; Sené, M.; Sené, R.; Simone, S.; Snoeys, W.; Staroba, P.; Szafran, S.; Thompson, M.; Thorsteinsen, T. F.; Tomasicchio, G.; Torrieri, G. D.; Tveter, T. S.; Urbán, J.; Venables, M.; Villalobos Baillie, O.; Virgili, T.; Volte, A.; Votruba, M. F.; Závada, P. Bibcode: 1999JPhG...25..345V Altcode: img2.gif, img3.gif, and img4.gif yields measured by the WA97 experiment at central rapidity in p-Pb interactions at 158 GeV/c are compared to those predicted by VENUS 4.12. The VENUS model, although in reasonable agreement with the img2.gif and the negative particle data, fails to reproduce the data on multistrange baryons and anti-baryons. Title: Time-Variability of the Inferred Rotation in the Upper Convection Zone Authors: Toomre, J.; Christensen-Dalsgaard, J.; Howe, R.; Larsen, R. M.; Schou, J.; Thompson, M. J. Bibcode: 1999soho....9E..87T Altcode: We present results of inverting for the rotation of the upper convection zone, using frequency splittings derived from successive 72-day time series of SOI-MDI observations. Schou (1999; also Schou et al. 1998) has studied the evolution of the pattern of small-scale zonal flows in the near-surface layers using f-mode splittings and has found that this flow pattern migrates equatorward in a manner similar to that seen in the so-called torsional oscillation observed in surface Doppler measurements. In the present work we look at the time variability of the rotation at greater depth, in the upper convection zone, by inverting both f- and p-mode splittings. The evolution of the flow is less regular than is seen at the surface, but we do observe apparently significant variations in the inferred flow pattern, on latitudinal scales similar to those seen at the surface. In particular, in the subsurface shear layer we see intriguing variations, with the first year's data showing apparent emergence of zonal flows of some 10-15 m/s amplitude at around 20 degrees latitude. Title: Convective Envelopes in Solar-Type Stars: What Can We Learn from their Seismic Study? Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1999ASPC..173..273M Altcode: 1999sstt.conf..273M No abstract at ADS Title: Simulation of Wave Fields to Assess the Sensitivity of Ring-Diagram Analyses to Shearing Flows Authors: Hindman, B. W.; Gough, D. O.; Haber, D. A.; Thompson, M. J.; Toomre, J. Bibcode: 1999soho....9E..64H Altcode: Ring-diagram analyses of acoustic-wave distortion by flows map horizontal motions within the solar convection beneath the localized regions where the observations are taken. To leading order, the flow field responsible for the advection of waves is taken to be horizontally uniform across the region. Current ring-diagram analyses are only carried out to this order, although in reality the flow is likely to vary across the local patch of the Sun. It is crucial for the interpretation of the results of ring-diagram analyses that the effects of shearing flows be assessed. Furthermore, the present analyses ignore any influence on the ring parameters of flows exterior to the region being studied. We present a progress report on the forward calculation of the modification of ring parameters produced by spatially varying flow fields. We examine effects of flow fields both inside and outside the region of observation. Additionally, we assess the influence of the non-uniform flow on the maps of the velocity field obtained by inverting the ring-parameter data. The effect of the inhomogeneous flow can be studied as a scattering problem. We have developed Green functions connecting an underlying inhomogeneous horizontal flow to the scattered wave field that results when an incident plane wave encounters the flow. By considering an ensemble of such incident waves, ring parameters can be inferred from the wave field. One application is to analyze artificial data sets, computed from models that contain horizontal shear flows. The scattered wave field produced by a prescribed 3-D shearing flow is computed, and the original and scattered wave fields are combined to generate an artificial helioseismic data set. The artificial data so produced should then be passed through a ring-diagram analysis and the deduced velocity field compared to the known imposed flow. Another application is to compute 3-D kernels relating the ring parameters to the underlying flow: these will in the future permit 3-D inversions for the flows within the solar convection zone, using mosaics of many ring-diagram samplings. Title: Helioseismic Studies of Differential Rotation in the Solar Envelope by the Solar Oscillations Investigation Using the Michelson Doppler Imager Authors: Schou, J.; Antia, H. M.; Basu, S.; Bogart, R. S.; Bush, R. I.; Chitre, S. M.; Christensen-Dalsgaard, J.; Di Mauro, M. P.; Dziembowski, W. A.; Eff-Darwich, A.; Gough, D. O.; Haber, D. A.; Hoeksema, J. T.; Howe, R.; Korzennik, S. G.; Kosovichev, A. G.; Larsen, R. M.; Pijpers, F. P.; Scherrer, P. H.; Sekii, T.; Tarbell, T. D.; Title, A. M.; Thompson, M. J.; Toomre, J. Bibcode: 1998ApJ...505..390S Altcode: The splitting of the frequencies of the global resonant acoustic modes of the Sun by large-scale flows and rotation permits study of the variation of angular velocity Ω with both radius and latitude within the turbulent convection zone and the deeper radiative interior. The nearly uninterrupted Doppler imaging observations, provided by the Solar Oscillations Investigation (SOI) using the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft positioned at the L1 Lagrangian point in continuous sunlight, yield oscillation power spectra with very high signal-to-noise ratios that allow frequency splittings to be determined with exceptional accuracy. This paper reports on joint helioseismic analyses of solar rotation in the convection zone and in the outer part of the radiative core. Inversions have been obtained for a medium-l mode set (involving modes of angular degree l extending to about 250) obtained from the first 144 day interval of SOI-MDI observations in 1996. Drawing inferences about the solar internal rotation from the splitting data is a subtle process. By applying more than one inversion technique to the data, we get some indication of what are the more robust and less robust features of our inversion solutions. Here we have used seven different inversion methods. To test the reliability and sensitivity of these methods, we have performed a set of controlled experiments utilizing artificial data. This gives us some confidence in the inferences we can draw from the real solar data. The inversions of SOI-MDI data have confirmed that the decrease of Ω with latitude seen at the surface extends with little radial variation through much of the convection zone, at the base of which is an adjustment layer, called the tachocline, leading to nearly uniform rotation deeper in the radiative interior. A prominent rotational shearing layer in which Ω increases just below the surface is discernible at low to mid latitudes. Using the new data, we have also been able to study the solar rotation closer to the poles than has been achieved in previous investigations. The data have revealed that the angular velocity is distinctly lower at high latitudes than the values previously extrapolated from measurements at lower latitudes based on surface Doppler observations and helioseismology. Furthermore, we have found some evidence near latitudes of 75° of a submerged polar jet which is rotating more rapidly than its immediate surroundings. Superposed on the relatively smooth latitudinal variation in Ω are alternating zonal bands of slightly faster and slower rotation, each extending some 10° to 15° in latitude. These relatively weak banded flows have been followed by inversion to a depth of about 5% of the solar radius and appear to coincide with the evolving pattern of ``torsional oscillations'' reported from earlier surface Doppler studies. Title: A strategy for fitting partially blended ridges in GONG solar p-mode spectra Authors: Howe, R.; Thompson, M. J. Bibcode: 1998A&AS..131..539H Altcode: Observations of solar oscillations by the Global Oscillation Network Group (GONG) using a network of telescopes deployed around the Earth eliminate temporal aliases from the oscillation power spectra to a very substantial extent, making the measurement of oscillation mode parameters much cleaner than with single-site observations. However, the problem of spatial aliasing, which arises from the fact that we see only one side of the Sun, still causes some problems. We discuss some of the issues affecting the estimation of medium-l solar acoustic mode parameters from the data obtained by the GONG network, and in particular the contamination by spatial leakage. We determine the areas in the l-nu plane in which such leakage is a problem, and finally we describe a method for improving the mode frequency estimation in such regions, thus extending the range of modes for which useful frequency estimates can be obtained. Title: The Rotation of the Solar Core Inferred by Genetic Forward Modeling Authors: Charbonneau, P.; Tomczyk, S.; Schou, J.; Thompson, M. J. Bibcode: 1998ApJ...496.1015C Altcode: Genetic forward modeling is a genetic algorithm-based modeling technique that can be used to perform helioseismic inversions of the Sun's internal angular velocity profile. The method can easily accommodate constraints such as positivity and monotonicity and readily lends itself to the use of robust statistical goodness-of-fit estimators. After briefly describing the technique, we ascertain its performance by carrying out a series of inversions for artificial splitting data generated from a set of synthetic internal rotation profiles characterized by various small inward increases in angular velocity in the deep solar core (r/R⊙ <= 0.5). These experiments indicate that the technique is accurate down to r/R⊙ ~= 0.2, and retains useful sensitivity down to r/R⊙ ~= 0.1.

We then use genetic forward modeling in conjunction with the LOW degree L (LOWL) 2 year frequency-splitting data set to determine the rotation rate in the deep solar core. We perform a large set of one-dimensional and 1.5-dimensional inversions using regularized least-squares minimization, conventional least-squares minimization with a monotonicity constraint (∂Ω/∂r <= 0), and inversions using robust statistical estimators. These calculations indicate that the solar core rotates very nearly rigidly down to r/R⊙ ~ 0.1. More specifically, on spatial scales >~0.04 R⊙ we can rule out inward increases by more than 50% down to r/R⊙ = 0.2, and by more than a factor of 2 down to r/R⊙ = 0.1. Thorough testing of various possible sources of bias associated with our technique indicates that these results are robust with respect to intrinsic modeling assumptions. Consequences of our results for models of the rotational evolution of the Sun and solar-type stars are discussed. Title: Slow Poles and Shearing Flows from Heliospheric Observations with MDI and GONG Spanning a Year Authors: Schou, J.; Christensen-Dalsgaard, J.; Howe, R.; Larsen, R. M.; Thompson, M. J.; Toomre, J. Bibcode: 1998ESASP.418..845S Altcode: 1998soho....6..845S We invert one year of coeval high-resolution rotational splitting data (up to degree l 250) from GONG and SOI-MDI. The first 4 months of MDI data uncovered several new features in the rotation of the solar convective envelope: surface and subsurface zonal bands corresponding to the so-called torsional oscillations, superimposed on the overall smooth latitudinal surface rotation; a drop in the near-polar surface rotation rate below the rate extrapolated from lower latitudes; and an indication of a prograde jet-like feature at high latitudes at a depth of about 5 percent of the solar radius. Using the 1 year of data from the MDI and GONG instruments, we test the robustness and stationarity of these features. As an aid to testing the robustness of our inferences, we use two independent inversion methods (2-D regularized least squares and SOLA) and apply them to the splitting data obtained from both GONG and MDI. Title: Seismic Constraints on Sound Speed in the Solar Core Authors: Rabello-Soares, M. C.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1998ESASP.418..511R Altcode: 1998soho....6..511R Direct seismic information about the structure of the solar core from measured p-mode frequencies is based on only a modest number of modes of low degree. Hence it is difficult to obtain local measures of, for example, the variation of the sound speed in the core. However, even averages of the central sound-speed difference between the Sun and a model would be of considerable diagnostic value, provided that these averages could be effectively restricted to a sufficiently small region. Chaplin et al. (1998) developed a technique, based on the method of optimally localized averages introduced by Backus & Gilbert, to construct an average of the rotation of the solar core, and this was applied with some success to combined BiSON and LOWL data. Here we investigate a similar procedure for constructing averages of the sound-speed difference between the Sun and a reference model, localized to the core. These provide seismic constraints on core structure that are only minimally sensitive to uncertainties in other regions of the Sun. Title: The Base of the Convection Zone and the Solar Magnetic Cycle: Seismic Detection of Their Connection Authors: Monteiro, Mario J. P. F. G.; Christensen-Dalsgaard, Jorgen; Thompson, Michael J. Bibcode: 1998ESASP.418..495M Altcode: 1998soho....6..495M It is now possible to detect small variations with time of the characteristics of the transition at the bottom of the solar convection zone, as determined from the periodic signal in the frequencies (Christensen-Dalsgaard et.al. 1995, Basu 1997). Such measurements may allow us to establish whether and in what manner the deeper convection zone changes with the solar magnetic cycle. This would be important for understanding the dynamics at the base of the convection zone and the origin of the solar cycle. It will also help in understanding the physics of convective overshoot, its interaction with rotation and magnetic fields, and the effects on the stratification. In this work we investigate the limits on the detectability of small changes in the stratification at the base of the convection zone, and attempt to constrain the amplitude of the changes from currently available seismic data. Title: On the seismic signature of the HeII ionization zone in stellar envelopes Authors: Monteiro, M. J. P. F. G.; Thompson, M. J. Bibcode: 1998IAUS..185..317M Altcode: The method developed for the seismic measurement of convective overshoot (Christensen-Dalsgaard et al 1995, MNRAS 276, 283) can be extended in order to study the layer where the second ionization of helium takes place in a star's envelope. Because this zone is confined to a very thin region the effects on the structure can be treated as the result of a localized perturbation to an otherwise smooth behaviour. Therefore, we may hope to be able to use the characteristic periodic signal in the frequencies of oscillation, arising from such a localized perturbation, to determine important aspects of this region. In this poster we present the theoretical analysis of such a signal showing how its different characteristics are associated with the different physical aspects contributing for the zone of the second ionization of helium. Some of these aspects we consider are the envelope helium abundance and the properties of the equation of state (EOS). In this way we attempt to establish how such a characteristic signal can be used to study seismologically the Sun and other stars. Title: Asteroseismology and Stellar Rotation Authors: Kjeldsen, H.; Arentoft, T.; Bedding, T.; Christensen-Dalsgaard, J.; Frandsen, S.; Thompson, M. J. Bibcode: 1998ESASP.418..385K Altcode: 1998soho....6..385K Δ Scuti stars are observed to rotate with surface velocities of the order 100-200 km/s corresponding to a rotation period of about one day. Rotation removes the frequency degeneracy in the azimuthal order m of the modes and thus allows the possibility of determining the angular velocity inside the star. Rotation also perturbs the internal structure of the star, making the star oblate, as well as changing the internal stratification. Such perturbations will result in a systematic change of all frequencies, if compared with a non-rotating star of similar mass and age. In this way even the radial (l = 0) mode frequencies will be affected by the rotation of the star. We discuss how basic properties as well as frequencies of δ Scuti stars are affected by fast rotation and we investigate the impact of these changes on our interpretation of observed frequencies used in an asteroseismic analysis. We discuss the results in the light of the currently available frequency data for δ Scuti stars in the Praesepe cluster. Title: Looking for Variations with Latitude of the Base of the Solar Convection Zone Authors: Monteiro, M. J. P. F. G.; Thompson, M. J. Bibcode: 1998ESASP.418..819M Altcode: 1998soho....6..819M The Sun's m-averaged frequencies of global oscillations have been used successfully in determining the basic characteristics of the base of the solar convective region (e.g. Christensen-Dalsgaard et.al. 1995, Basu 1997). In particular, it has been possible to constrain its location and more particularly the extent of convective overshoot. With higher quality data now available it is becoming possible to isolate the properties of this region at different latitudes. This is important for the modelling aspects such as mixing and convective overshoot occurring at the base of the convection zone. It can also have interesting interplay with the rotation profile around the region of the tachocline and the generation of magnetic fields. Such properties as deeper penetration of the convection at certain latitudes may be intimately connected with the angular velocity profile there, and the identification of such characteristics in the thermal stratification is therefore important to complement the information from the rotation inversions (Schou et al. 1998). Here we present an analysis of SOI--MDI data to try to detect such latitudinal variations. Title: Space Asteroseismology on Later-type Stars Authors: Roxburgh, Ian W.; Thompson, Michael J. Bibcode: 1998Ap&SS.261...13R Altcode: 1999Ap&SS.261...13R No abstract at ADS Title: Inversion Methods Authors: Thompson, M. J. Bibcode: 1998IAUS..185..125T Altcode: No abstract at ADS Title: What We Have Learned from Helioseismology Authors: Thompson, Michael J. Bibcode: 1998Ap&SS.261...23T Altcode: 1999Ap&SS.261...23T The Sun's global oscillations, which are studied both in spatially unresolved ("Sun-as-a-star") and resolved observations of the solar disk, have enabled helioseismology to probe in detail the solar interior. I review first what is learned from the unresolved measurements, since this gives an idea of what we may in the not too distant future be able to learn about the interiors of other stars undergoing solar-type oscillations. I then look at the main results from resolved observations, which have begun to reveal the structure and dynamics of the interior of a star in exquisite detail. Title: Effects of Line Asymmetries on the Determination of Solar Oscillation Frequencies Authors: Christensen-Dalsgaard, J.; Rabello-Soares, M. C.; Rosenthal, C. S.; Thompson, M. J. Bibcode: 1998ESASP.418..147C Altcode: 1998soho....6..147C Despite the strong evidence that the peaks in the spectrum of solar oscillations are asymmetric, most determinations of mode frequencies have been based on fits of symmetric Lorentzian profiles to the Fourier or power spectra of oscillation time strings. The systematic errors resulting from neglecting the line asymmetry could have serious effects on inversions for the solar internal structure and rotation. Here we analyze artificial data based on simple models of the intrinsic line asymmetry. By fitting Lorentzians to the resulting spectra, we estimate the likely properties of the errors introduced in the frequencies and consider the possible effects on the inversions. Title: Seismic detection of boundaries of stellar convective regions Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1998IAUS..185..315M Altcode: The seismic study of the base of the convection zone in the Sun (eg Christensen-Dalsgaard et al 1995, MNRAS 276, 283) has been successful in determining not only the position of the base of the convective envelope, but also the characteristics of this transition layer. In this poster we consider other types of star possessing convective envelopes or cores and seek to establish the conditions under which we may determine important characteristics of their convective regions. In particular we may hope to establish seismologically that a star does indeed posess a convective envelope or core and to measure the size of that convective region. The method used consists in identifying a signal in the observed frequencies whose characteristics depend on the location of the border of a convective region in the star. The limitations in terms of observational uncertainties and stellar characteristics are presented. Title: Detection of the Lower Boundary of Stellar Convective Envelopes from Seismic Data Authors: Monteiro, Mário J. P. F. G.; Christensen-Dalsgaard, Jørgen; Thompson, Michael J. Bibcode: 1998Ap&SS.261...41M Altcode: 1999Ap&SS.261...41M No abstract at ADS Title: Diagnostic Potential of the Solar f Modes Authors: Chitre, S. M.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1998ESASP.418..141C Altcode: 1998soho....6..141C The frequencies of f modes of intermediate and high degree l of a stellar model in hydrostatic equilibrium are essentially given by ω = square root {g kh}, where to a good first approximation g is the surface gravitational acceleration G M / R2 and kh = square root {l(l+1)}/R, M and R being the mass and radius respectively of the model. More precisely, the frequency is determined not simply by the surface values of these quantities but by a weighted average over the region where the mode has appreciable amplitude. Thus the frequencies of the f modes depend on the density stratification in the near-surface region (Gough 1985, 1993). Given the very high accuracy to which the f-mode frequencies can now be determined, in particular from the SOI/MDI experiment on SOHO, this sensitivity may provide an important diagnostic of the Sun's near-surface structure. We investigate this sensitivity, in terms of numerical kernels and the simple analytical approximation derived by Gough. In addition, we consider the possibilities for investigating time variations and asphericity in solar structure on the basis of f-mode observations. Title: The SOI-MDI High-Latitude Jet: the Evidence For and Against Authors: Howe, R.; Antia, H.; Basu, S.; Christensen-Dalsgaard, J.; Korzennik, S. G.; Schou, J.; Thompson, M. J. Bibcode: 1998ESASP.418..803H Altcode: 1998soho....6..803H The apparent detection of a prograde jet at latitude 75-circ and at a radius of about 0.95Rodot in some inversions of rotation data from SOI--MDI (Schou et al., 1998) has excited considerable interest, but whether the jet really exists in the solar interior is certainly not yet firmly established. The detection of the feature is sensitive both to the inversion techniques used and to the methods of mode parameter estimation used to generate the input data. In particular, the feature is much more apparent in Regularized Least-Squares inversions than in inversions using an Optimally Localized Average approach, and is not detected at all in the present GONG data when analysed with the GONG peakfinding algorithm, or indeed in SOI data when analysed with the GONG algorithm. Therefore in this poster we examine critically the current evidence for the source and existence of this jet in the light of forward and inverse analyses. Title: Solar internal sound speed as inferred from combined BiSON and LOWL oscillation frequencies Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1997MNRAS.292..243B Altcode: 1997astro.ph..2105B Observations of the Sun with the LOWL instrument provide a homogeneous set of solar p-mode frequencies from low to intermediate degree that allow one to determine the structure of much of the solar interior avoiding systematic errors that are introduced when different data sets are combined, i.e., principally the effects of solar cycle changes on the frequencies. Unfortunately, the LOWL data set contains very few of the lowest-degree modes, which are essential for determining reliably the structure of the solar core - in addition, these lowest-degree data have fairly large associated uncertainties. However, observations made by the Birmingham Solar-Oscillations Network (BiSON) in integrated sunlight provide high-accuracy measurements of a large number of low-degree modes. In this paper we demonstrate that the low-degree mode set of the LOWL data can be successfully combined with the more accurate BiSON data, provided the observations are contemporaneous for those frequencies where the solar cycle induced effects are important. We show that this leads to a factor of 2 decrease in the error on the inferred sound speed in the solar core. We find that the solar sound speed is higher than in solar models for r<0.2Rsolar. The density of the solar core is, however, lower than that in solar models. Title: Rotation and Zonal Flows in the Solar Envelope from the SOHO/MDI Observations Authors: Scherrer, P. H.; Schou, J.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Kosovichev, A. G.; Antia, H. M.; Chitre, S. M.; Christensen-Dalsgaard, J.; Larsen, R. M.; Pijpers, F. P.; Eff-Darwich, A.; Korzennik, S. G.; Gough, D. O.; Sekii, T.; Howe, R.; Tarbell, T.; Title, A. M.; Thompson, M. J.; Toomre, J. Bibcode: 1997AAS...191.7310S Altcode: 1997BAAS...29.1322S We report on the latest inferences concerning solar differential rotation that have been drawn from the helioseismic data that are now available from the Solar Oscillations Investigation (SOI) using the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). That spacecraft is positioned in a halo orbit near the Sun-Earth Lagrangian point L_1, in order to obtain continuous Doppler-imaged observations of the sun with high spatial fidelity. Doppler velocity, intensity and magnetic field images are recorded, based on modulations of the 676.8 nm Ni I solar absorption line. The high spatial resolution of MDI thereby permits the study of many millions of global resonant modes of solar oscillation. Determination and subsequent inversion of the frequencies of these modes, including the degeneracy-splitting by the rotation of the sun, enables us to infer how the sun's angular velocity varies throughout much of the interior. The current MDI data are providing substantial refinements to the helioseismic deductions that can be made about differential rotation both within the convection zone and in its transition to the radiative interior. The shearing layer evident in the angular velocity Omega just below the solar surface is becoming better defined, as is the adjustment layer or tachocline near the base of the convection zone. The MDI data are also revealing a prominent decrease in Omega at high latitudes from the rotation rate expressed by a simple three-term expansion in latitude that was originally deduced from surface Doppler measurements. Further, there are indications that a submerged polar vortex involving somewhat faster Omega than its surroundings exists at about 75(deg) in latitudes. Title: SVD preprocessing of helioseismic data for solar structure inversion. Authors: Basu, S.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1997A&A...321..634B Altcode: Helioseismic inversion to determine solar structure is based on the analysis of very substantial numbers of modes and hence may involve considerable computational expense. This is particularly true for inversions using methods of optimally localised averages, which require inversion of matrices whose order is the number of modes in the set; yet such methods are desirable to make the full use of the data. On the other hand, there is considerable redundancy in the data, different modes carrying almost the same information about solar structure. Thus, in the unavoidable presence of data errors, the number of independent pieces of information is generally much less than the number of modes. This suggests that the mode-set can be reduced by forming suitable combinations of the data before the more computationally intensive inversion is performed. We show that such combinations may be based on singular value decomposition (SVD) of the problem, leading to a drastically reduced inverse problem whose solution is essentially indistinguishable from the solution of the original problem. In addition, the results of the SVD provide insight into the information content of the helioseismic data. Title: Structure and Rotation of the Solar Interior: Initial Results from the MDI Medium-L Program Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.; de Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.; Scott, K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard, J.; Dappen, W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.; Thompson, M. J.; Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.; Title, A. M.; Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson, C. J.; Zayer, I.; Milford, P. N. Bibcode: 1997SoPh..170...43K Altcode: The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∽ 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the main component of which is Gaussian-weighted binning, has been optimized to reduce the negative influence of spatial aliasing of the high-degree oscillation modes. The data processing is completed in a data analysis pipeline at the SOI Stanford Support Center to determine the mean multiplet frequencies and splitting coefficients. The initial results show that the noise in the medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. This is important for inferring the Sun's internal structure and rotation. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. The results also confirm the previous finding by the GONG (Gough et al., 1996) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer. This layer is likely to be the place where the solar dynamo operates. In order to understand how the Sun works, it is extremely important to observe the evolution of this transition layer throughout the 11-year activity cycle. Title: Internal structure and rotation of the Sun: First results from MDI data Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.; De Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.; Scott, K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard, J.; Däppen, W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.; Thompson, M. J.; Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.; Title, A. M.; Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson, C. J.; Zayer, I.; Milford, P. N. Bibcode: 1997IAUS..181..203K Altcode: No abstract at ADS Title: Internal rotation and dynamics of the Sun from GONG data Authors: Korzennik, S.; Thompson, M. J.; Toomre, J.; GONG Internal Rotation Team Bibcode: 1997IAUS..181..211K Altcode: No abstract at ADS Title: On solar p-mode frequency shifts caused by near-surface model changes Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1997MNRAS.284..527C Altcode: The effect on p-mode frequencies of changing the near-surface structure of solar models is investigated. As is well known, changes confined to the near-surface region have little effect on the low-frequency p modes: this is as one would expect from a simple asymptotic description which shows that these modes have upper turning points located well beneath the photosphere. However, some examples of structural changes show that, if the changes are viewed at fixed fractional radius (an Eulerian description), the small frequency shifts at low frequency come about through near-cancellation of different contributions which are individually much larger than the resultant shifts themselves; the reason is that even so-called near-surface changes extend substantially below the upper turning points of these modes. We demonstrate that the corresponding changes at fixed fractional mass (a Lagrangian description) are confined much closer to the surface, so that the small frequency shifts come about in a natural way. 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: On the use of the error correlation function in helioseismic inversions Authors: Howe, R.; Thompson, M. J. Bibcode: 1996MNRAS.281.1385H Altcode: A diagnostic of helioseismic inversions that has not so far been greatly used is the correlation function describing how the errors in the solutions at different points in the solar interior are correlated. Even if the errors in the input data are uncorrelated, the solution errors will in general be correlated. We investigate the correlation functions for a variety of inversion methods commonly used in helioseismology, using the estimation of a one-dimensional rotation profile as a prototypical example. As we demonstrate, there are characteristic length scales over which the errors are correlated, which are similar among different inversion methods. However, there can also be dramatic differences in the error correlations among otherwise similar looking inversions if the parameters are chosen inappropriately. It is therefore advisable to consider the correlation function, as well as other diagnostics, when assessing the reliability of an inversion solution. Title: Solar structure as revealed by 1 year LOWL data Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1996BASI...24..147B Altcode: No abstract at ADS Title: Results from the LOWL instrument Authors: Schou, J.; Tomczyk, S.; Thompson, M. J. Bibcode: 1996BASI...24..375S Altcode: No abstract at ADS Title: Low-degree frequency splitting measurements and the rotation rate of the solar core Authors: Tomczyk, S.; Schou, J.; Thompson, M. J. Bibcode: 1996BASI...24..245T Altcode: No abstract at ADS 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: Filtering out near-surface uncertainties from helioseismic inversions Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Perez Hernandez, F.; Thompson, M. J. Bibcode: 1996MNRAS.280..651B Altcode: The differences between observed solar p-mode frequencies and the frequencies of a reference model can be inverted to infer the structure of the Sun using a variety of linear inversion techniques. However, it is well known that the adiabatic description, which is often employed in frequency calculations, breaks down in the outermost layers of the Sun. This and other uncertainties in the treatment of the superficial layers introduce a slowly varying frequency-dependent function into the frequency differences.

We present here a technique to pre-process the frequency differences prior to applying any of the standard inversion techniques in order to eliminate the frequency dependent component which arises from the near-surface uncertainties, suppressing also the corresponding contributions from the kernels relating frequency differences to differences in structure. This is achieved by applying suitable linear filters to the frequency differences and to the mode kernels. We obtain the filtered kernels and demonstrate that the surface contribution can be successfully suppressed. We also present the results of the inversions performed after the data and mode kernels have been filtered. 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: Measurement of the Rotation Rate in the Deep Solar Interior Authors: Tomczyk, S.; Schou, J.; Thompson, M. J. Bibcode: 1996AAS...188.6903T Altcode: 1996BAAS...28..935T We present a measurement of the rotation rate in the interior of the Sun based on two years of observations with the LOWL instrument. LOWL allows the observation of solar oscillations with degrees from 0 to 100, thus providing a homogeneous low- and intermediate-degree dataset. Significantly, it is able to make spatially resolved observations of low degree modes, thereby making it possible to separate the different modes within a given multiplet. This reduces the potential for systematic errors compared to observations using integrated sunlight. We have used observations of the frequency splittings of modes with degrees from 1 to 100 to infer the rotation rate in the solar interior with some radial resolution and without excessive errors. Over most of the interior we have also been able to estimate the latitudinal variation of the rotation rate. We confirm earlier findings that near the base of the convection zone the solar rotation profile undergoes a transition from surface-like differential rotation to a rotation rate that is independent of latitude. Additionally, we find that below the base of the convection zone our measurement is consistent with rigid body rotation at a rate somewhat lower than the surface equatorial rate. This measurement provides strong constraints on the theories of angular momentum transport in solar-type stars. 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: Solar Internal Rotation and Dynamics from GONG Frequency Splittings Authors: Thompson, M. J.; Toomre, J.; GONG Dynamics Inversion Team Bibcode: 1996AAS...188.5305T Altcode: 1996BAAS...28..903T The splitting of the Sun's global mode frequencies by large-scale flows can be used to investigate the rotation profile in both radius and latitude within the convection zone and deeper radiative interior. The inversion of GONG data confirms that the surface latitudinal variation of the rotation rate carries through much of the convection zone. At the base of the convection zone there is a currently unresolved adjustment layer with latitudinally independent rotation at greater depths. A shearing layer just below the surface is discernable at low to mid latitudes. Such global investigations are supplemented by local area analyses via ring diagrams, which enable us to probe the subsurface variation of rotation with depth beneath selected regions of the Sun. 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: The Sun's Hydrostatic Structure from LOWL Data Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1996ApJ...460.1064B Altcode: Recent observations with the LOWL (Low-Degree [l] Oscillations Experiment) instrument have for the first time provided a uniform set of frequencies that allow detailed inversion for the structure of much of the Sun's deep interior. We present the results of inverting the LOWL data and compare them with the corresponding results obtained using inhomogeneous data sets from more than one instrument. Furthermore, improvements in the description of the required physics motivates the calculation of new solar models. Thus, we present results of inversions of the LOWL data against several reference models using up-to-date physics. In models including the gravitational settling of helium, the sound speed and density agree with the Sun to within substantially better than 1%. We test various modifications to the physics of the models in order to see if the remaining small (but significant) discrepancy between the Sun and the models can be removed. We find that none of the modifications tested can adequately account for the remaining discrepancy, though a small increase in helium diffusion in the core gives a modest improvement over the standard diffusion model. Finally, we find that the seismic data support theoretical calculations that indicate that settling of heavier elements has reduced the present surface value of Z by about 8% relative to its mean interior value. Title: The Sun's rotation rate in its equatorial plane. Authors: Antia, H. M.; Chitre, S. M.; Thompson, M. J. Bibcode: 1996A&A...308..656A Altcode: We investigate the Sun's rotation rate in its equatorial plane, as a function of depth, using Big Bear data for the years 1986, 1988, 1989 and 1990. One novel feature of this investigation is that we have used an iterative inversion technique, based upon the regularized least-squares method. Such methods generally have one or more adjustable parameters, and the details of the inferred rotation profile depend upon the values chosen for those parameters. We find that the iterative technique produces results that are much less sensitive to the values of the parameters, which may be seen as one advantage of our procedure. Our results exhibit various features, including a secular decrease in the rotation rate beneath the convection zone, a locally enhanced rotation rate near 0.9Rsun_ (Rsun_ being the photospheric radius), and a local minimum near 0.6Rsun_. Not only are these features apparently fairly robust from year to year, they have all variously been seen in inversions of other datasets. However, we demonstrate that some caution should be exercised in interpreting such features in the Sun's equatorial rotation rate. Title: Seismic properties of the Sun's superadiabatic layer. I. Theoretical modelling and parametrization of the uncertainties. Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1996A&A...307..624M Altcode: Some alternatives to the traditional mixing-length theory (MLT) have recently been proposed for modelling convective heat transport inside stars. The ideal formulation is one that does not involve any free parameters. However, in our present state of ignorance we still need at least one free parameter in order to build solar models with the correct radius. Having adjusted this parameter (e.g. the mixing-length parameter α_c_) to obtain the observed radius, we cannot discriminate non-seismically between different convective theories, regardless of how low-efficiency convection is treated. In this paper we consider how the additional information provided by global p-mode frequencies can be used to investigate low-efficiency convection at the top of the solar convective envelope and discriminate between different theories. We consider a parametrization which in addition to the mixing length has two further parameters: one (β_c_) which regulates the relative degree of overadiabaticity (or inefficiency) of convection, and a second (m) that affects the transition between the regimes of efficient and inefficient convection. Our parametrization includes traditional MLT__ and the theory of Canuto & Mazzitelli as particular cases. We study the effect of varying these parameters by constructing a series of envelope models with the same depth of the convection zone and computing their oscillation frequencies. We discuss our results in terms of kernels relating frequency changes to changes in the structure of the superadiabatic region. Title: A modified R^1∘xR^1 method for helioseismic rotation inversions Authors: Pijpers, F. P.; Thompson, M. J. Bibcode: 1996MNRAS.279..498P Altcode: 1995astro.ph.10143P We present an efficient method for two-dimensional (2D) inversions for the solar rotation rate using the Subtractive Optimally Localized Averages (SOLA) method and a modification of the R^1∘xR^1 technique proposed by Sekii. The SOLA method is based on explicit construction of averaging kernels similar to the Backus-Gilbert method. The versatility and reliability of the SOLA method in reproducing a target form for the averaging kernel, in combination with the idea of the R^1∘xR^1 decomposition, results in a computationally very efficient inversion algorithm. This is particularly important for full 2D inversions of helioseismic data in which the number of modes runs into at least tens of thousands. Title: On constructing seismic models of the Sun. Authors: Basu, S.; Thompson, M. J. Bibcode: 1996A&A...305..631B Altcode: Observed p-mode frequencies have been extensively used to determine the the Sun's radial structure. The results of such inversions are often called "seismic models" of the Sun. In this work we investigate whether one can in fact construct models that match the measured solar frequencies to within observational errors. We invert linearized equations, relating frequency differences between the Sun and a reference model to differences in their structure, using a Regularized Least Squares (RLS) technique with second derivative smoothing. As a test, we first invert frequencies from test models. Random noise is added to these to simulate the observers' quoted errors for solar data. We investigate how the goodness of fit to the data, and the acceptability of the solution, depend upon the number of spline knots in the solution functions and upon the amount of smoothing used. With this artificial data, we can obtain a chi-squared per degree of freedom (χnu_^2^) of order unity even when the differences between the reference and test models are quite large. In contrast, using the most widely used compilation of observed solar frequencies, we are unable to get the value of χnu_^2^ close to one. Replacing the low degree data with recent data from the BISON network, and omitting frequencies determined by the ridge-fitting method (which could be more susceptible to systematic error), the value χnu_^2^ can be reduced substantially. We discuss possible causes for the small remaining excess in χnu_^2^. Title: Filtering in Inversion for Solar Internal Structure Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Pérez Hernández, F.; Thompson, M. J. Bibcode: 1996imie.conf...32B Altcode: No abstract at ADS Title: Averaging Kernels, Error Correlation Functions and Linear Methods in Helioseismology Authors: Howe, Rachel; Thompson, Michael J. Bibcode: 1996imie.conf...40H Altcode: No abstract at ADS Title: Results From the LOWL Instrument Authors: Schou, J.; Tomczyk, S.; Thompson, M. J. Bibcode: 1995AAS...18710101S Altcode: 1995BAAS...27.1426S In this poster we will present various results from one year of observations with the LOWL instrument. The LOWL instrument is designed to observe oscillations with degrees l from 0 to about 100 providing a homogeneous dataset for inversions. Given the spatial resolution of the instrument it is possible to separate different azimuthal orders m even for the lowest degree modes, hopefully giving more accurate splittings than those determined using integrated sunlight for a similar time period. We will show the results of an inversion for the solar rotation rate between 0.1R_sun and 0.95R_sun. Given the long duration and the large number of terms used to describe the m-dependence of the mode frequencies we have been able to obtain very good resolution in both the radial direction and in latitude while keeping the statistical errors low, thereby obtaining more accurate results than previously possible. We will also present results of analyzing different parts of the time-series and compare the temporal variations in mode frequencies and splittings with variations in the solar activity. Title: Helioseismic estimation of convective overshoot in the Sun Authors: Christensen-Dalsgaard, Jorgen; Monteiro, Mario J. P. F. G.; Thompson, Michael J. Bibcode: 1995MNRAS.276..283C Altcode: By using the periodic signal present in the frequencies of oscillation due to the base of the solar convection zone, Monteiro, Christensen-Dalsgaard & Thompson gave an upper limit to the extent of a layer of convective overshooting in the Sun. Alternative studies have suggested that it may not be possible to do so since the amplitude of the signal does not vary monotonically with the extent of the layer.

In this work a new more complete set of models is used to compare the values of the amplitude obtained from the fitting of the signal with the expected amplitudes. These are determined using the assumption that the rapid variation occurring at the base of the convection zone and creating the periodic signal can be described as discontinuities of the sound-speed derivatives. The amplitude of the signal due to the discontinuity of the third derivative of the sound speed is then proportional to the derivative of the radiative gradient, while the amplitude resulting from the discontinuity of the second derivative is proportional to the difference between radiative and adiabatic gradients at the position where the transition occurs. The latter is non-zero only if overshoot is present.

Asymptotic predictions of the amplitudes of the signal in the p-mode frequencies are in good agreement with the values found from fitting models with substantial overshoot regions; as was also found by Monteiro et al., the observed solar frequencies place severe limits on the extent of overshoot of this nature. Title: Linear inversions for the Sun's internal rotation Authors: Thompson, M. J. Bibcode: 1995InvPr..11..709T Altcode: No abstract at ADS Title: Measurement of the Rotation Rate in the Deep Solar Interior Authors: Tomczyk, S.; Schou, J.; Thompson, M. J. Bibcode: 1995ApJ...448L..57T Altcode: We present a measurement of solar internal rotation based on observations obtained over 3 months in early 1994 with a new instrument called LOWL. This instrument allows for the simultaneous observation of low- and intermediate-degree solar oscillations with spatial resolution. We have measured the frequency splitting of 673 multiplets with degrees ranging from 1 to 80 and inverted these to derive an estimate of the solar internal rotation profile between 0.2 and 0.85 R⊙. The accuracy of this measurement ranges from ~1% in the outer regions to ~5% at 0.2 R⊙ and thus places better constraints than hitherto on the rotation in the deep solar interior. We confirm earlier findings that near the base of the convection zone the solar rotation profile undergoes a transition from surface-like differential rotation to a rotation rate that is independent of latitude. In addition, we find that from the base of the convection zone down to 0.2 R⊙ our measurement is consistent with rigid body rotation at a rate somewhat lower than the surface equatorial rate. The accuracy of our measurement in the deep solar interior provides a strong constraint to theories of solar and stellar angular momentum transport. Title: A Measurement of the Rotation Rate in the Deep Solar Interior Authors: Schou, J.; Tomczyk, S.; Thompson, M. J. Bibcode: 1995ESASP.376b.275S Altcode: 1995soho....2..275S; 1995help.confP.275S No abstract at ADS Title: The Sensitivity of Various Mode Sets for Probing Differential Rotation Shear Zones Authors: Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 1995ESASP.376b..41C Altcode: 1995soho....2...41C; 1995help.confP..41C The potential of forthcoming datasets from GONG and SOI for resolving long-lived azimuthal jets and shearing flows is investigated. The authors construct various artificial datasets, containing noise resembling that for a one-year observing run. These are then inverted, using a 2-D regularized least squares (RLS) inversion. In particular, the authors investigate the ability of the RLS method to form well-localized averages of the rotation rate, as measured by the averaging kernels, using an extensive mode set as well as subsets thereof. The authors show that it is possible to keep the noise in the solution down to a few nanohertz in much of the solar interior, while obtaining very reasonable resolution, for a GONG-like dataset. Title: Solar Structure Inversion with LOWL Data Authors: Basu, S.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Tomczyk, S. Bibcode: 1995ESASP.376b..25B Altcode: 1995help.confP..25B; 1995soho....2...25B Presents inversion results for the radial hydrostatic structure of the Sun, using six months of oscillation data obtained with the LOWL instrument. Using modes with degrees from 0 to 90 and frequencies between 1.5 and 3.5 mHz, the authors have inferred the variation with depth of the sound speed, density ρ and u = p/ρ (p being pressure) from r = 0.05 Rsun to 0.85 Rsun. They find that in this region the sound speed in the Sun is within 0.15% of that of a model constructed using the MHD equation of state and OPAL opacities and incorporating helium diffusion. The density difference between Sun and model is less than 0.8%. Given the small error bars on the inversion results these small differences are significant, however. The solar sound speed appears to be higher than in the model for r < 0.2 Rsun . The authors speculate that this might indicate interesting physics in the inner core. Title: Constraining Solar Core Rotation with Genetic Forward Modelling Authors: Tomczyk, S.; Charbonneau, P.; Schou, J.; Thompson, M. J. Bibcode: 1995ESASP.376b.271T Altcode: 1995soho....2..271T; 1995help.confP.271T No abstract at ADS Title: Uncertainties for Two-dimensional Models of Solar Rotation from Helioseismic Eigenfrequency Splitting Authors: Genovese, Christopher R.; Stark, Philip B.; Thompson, Michael J. Bibcode: 1995ApJ...443..843G Altcode: Observed solar p-mode frequency splittings can be used to estimate angular velocity as a function of position in the solar interior. Formal uncertainties of such estimates depend on the method of estimation (e.g., least-squares), the distribution of errors in the observations, and the parameterization imposed on the angular velocity. We obtain lower bounds on the uncertainties that do not depend on the method of estimation; the bounds depend on an assumed parameterization, but the fact that they are lower bounds for the 'true' uncertainty does not. Ninety-five percent confidence intervals for estimates of the angular velocity from 1986 Big Bear Solar Observatory (BBSO) data, based on a 3659 element tensor-product cubic-spline parameterization, are everywhere wider than 120 nHz, and exceed 60,000 nHz near the core. When compared with estimates of the solar rotation, these bounds reveal that useful inferences based on pointwise estimates of the angular velocity using 1986 BBSO splitting data are not feasible over most of the Sun's volume. The discouraging size of the uncertainties is due principally to the fact that helioseismic measurements are insensitive to changes in the angular velocity at individual points, so estimates of point values based on splittings are extremely uncertain. Functionals that measure distributed 'smooth' properties are, in general, better constrained than estimates of the rotation at a point. For example, the uncertainties in estimated differences of average rotation between adjacent blocks of about 0.001 solar volumes across the base of the convective zone are much smaller, and one of several estimated differences we compute appears significant at the 95% level. Title: Results from the LOWL Instrument Authors: Schou, J.; Tomczyk, S.; Thompson, M. J. Bibcode: 1995SPD....26..402S Altcode: 1995BAAS...27..954S No abstract at ADS Title: Optimally Localized Kernels for 2D Helioseismic Inversion Authors: Christensen-Dalsgaard, J.; Larsen, R. M.; Schou, J.; Thompson, M. J. Bibcode: 1995ASPC...76...70C Altcode: 1995gong.conf...70C No abstract at ADS Title: SOLA Inversions for the Radial Structure of the Sun Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1995ASPC...76..144C Altcode: 1995gong.conf..144C No abstract at ADS Title: Some Aspects of Helioseismic Time-Series Analysis Authors: Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1995ASPC...76..528S Altcode: 1995gong.conf..528S No abstract at ADS Title: A Self-Consistent Approach to Filtering Out Near-Surface Uncertainties from Helioseismic Inversions Authors: Basu, S.; Thompson, M. J.; Christensen-Dalsgaard, J.; Perez Hernandez, F. Bibcode: 1995ASPC...76..152B Altcode: 1995gong.conf..152B No abstract at ADS Title: Helioseismic Constraints on Theories of Convection Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1995ASPC...76..128M Altcode: 1995gong.conf..128M No abstract at ADS Title: On Constructing Seismic Models of the Sun's Radial Structure Authors: Basu, S.; Thompson, M. J. Bibcode: 1995ASPC...76..148B Altcode: 1995gong.conf..148B No abstract at ADS Title: Hunting for Azimuthal Jets and Shearing Flows in the Solar Convection Zone Authors: Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.; Toomre, J. Bibcode: 1995ASPC...76..212C Altcode: 1995gong.conf..212C No abstract at ADS Title: A Measurement of the Rotation Rate in the Deep Solar Interior Authors: Schou, J.; Tomczyk, S.; Thompson, M. J. Bibcode: 1994AAS...185.4401S Altcode: 1994BAAS...26Q1377S Measurements of the rotation rate in the deep solar interior using helioseismology have given inconsistent results, presumably due to problems with the algorithms used for the analysis of spatially unresolved observations of the oscillations. Here we present a measurement of the rotation rate in the interior of the Sun based on observations with a new instrument called LOWL. Unlike earlier instruments this instrument allows the observation of oscillations with degrees from 0 to ~ 80. In particular it is able to make spatially resolved observations of low degree modes, thereby making it possible to spatially separate the different modes within a given multiplet. This reduces the potential for systematic errors compared to observations using integrated sunlight. We have used observations of the frequency splittings of modes with degrees from 1 to 80 to infer the rotation rate in the solar interior down to ~ 0.2 R_⊙ with some radial resolution and without excessive errors. Over part of the range we have also been able to estimate the latitudinal variation of the rotation rate. This measurement provides strong constraints on the theories of solar and stellar angular momentum transport. Title: On Comparing Helioseismic Two-dimensional Inversion Methods Authors: Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1994ApJ...433..389S Altcode: We consider inversion techniques for investigating the structure and dynamics of the solar interior as functions of radius and latitude. In particular, we look at the problem of inferring the radial and latitudinal dependence of the Sun's internal rotation, using a fully two-dimensional least-squares inversion algorithm. Concepts such as averaging kernels, measures of resolution, and trade-off curves, which have previously been used in the one-dimensional case, are generalized to facilitate a comparison of two-dimensional methods. We investigate the weighting given to different modes and discuss the implications of this for observational strategies. As an illustration we use a mode set whose properties are similar to those expected for data from the GONG network. Title: Conceptual Astronomy Authors: Thompson, M. J. Bibcode: 1994ConPh..35..289T Altcode: No abstract at ADS Title: Seismic study of overshoot at the base of the solar convective envelope Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1994A&A...283..247M Altcode: Sharp transitions in the internal stratification of a star give rise to a characteristic signature in normal-mode frequencies. In particular, if in the Sun such a feature were located well inside the acoustic cavity of many solar p modes, it would give rise to a signal that was a periodic function of the frequency of the modes. We use this signature to detect the base of the solar convection zone and to investigate the existence of convective overshoot into the radiative interior. Two methods are considered. The 'absolute' method obtains the residuals in the frequencies after making a smooth fit in mode order n, and then uses an asymptotic description of the eigenfunctions to make a fit to the residuals. The 'differential' method makes an asymptotic fit to the differences between solar frequencies and the frequencies of a theoretical model. Various theoretical models of overshoot at the base of the convection zone predict the existence of a rather abrupt transition to subadiabatic stratification at the base of the overshoot region. We find no strong evidence for the existence of an overshoot region of this kind. Indeed if the overshoot consists of an essentially adiabatic extension of the convection zone followed by an abrupt transition to radiative stratification then we may (at the 95% confidence level) put an upper limit of 0.07 local pressure scale heights on the extent of the overshoot layer. Title: Recent results from helioseismology. Authors: Thompson, M. J. Bibcode: 1994LNP...432...19T Altcode: 1994LNPM...11...19T The very accurately measured frequencies of the Sun's global oscillation are providing us with a detailed picture of the solar interior. The adiabatic sound speed is of foremost importance in determining the observed p-mode frequencies and hence is readily accessible to seismic analysis of the frequency data. It has thus been known for some time that the sound speed in the bulk of the radiative interior is greater than in theoretical models. Much of this discrepancy is removed by the latest Livermore opacities, but a significant discrepancy remains. The cause of this discrepancy may be settling and diffusion of helium in the solar interior. This would also explain the discrepancy between seismic measurements of the envelope helium abundance and the abundance required to produce correctly calibrated evolution models. The frequencies also enable to pinpoint the base of the convection zone and to investigate the extent of overshoot into the underlying convectively stable region. The variation of the p-mode frequencies with time is discussed, as are the current helioseismic determinations of the Sun's internal rotation. Finally future prospects are considered. Title: The SOLA method for helioseismic inversion Authors: Pijpers, F. P.; Thompson, M. J. Bibcode: 1994A&A...281..231P Altcode: The Subtractive Optimally Localized Averages (SOLA) method is a versatile and efficient technique for inverting helioseismic data. The SOLA method is based on explicit construction of Backus-Gilbert averaging kernels, but whereas the more usual formulations of the optimally localized averages (OLA) method use a multiplicative penalty function to localize the kernels, the distinctive idea of SOLA is that one specifies a desired target form for the kernels and then minimizes the integrated squared difference between the kernels and the target form. This allows great versatility in the choice of target form, and furthermore SOLA has the significant advantage of being computationally more efficient than the usual OLA formulations. A Gaussian target function is a useful choice, and we use the example of determining the Sun's internal rotation to explore how the parameter values (such as the Gaussian's width) should best be chosen. Some alternatives to using a Gaussian function as target function are discussed and applied to artificial data in a blind experiment. In particular we show that it is possible to invert directly for the gradient of the rotation. This may be of interest if there are localized large gradients in the rotation rate. Title: The Depth of the Solar Convection Zone Authors: Christensen-Dalsgaard, J.; Gough, D. O.; Thompson, M. J. Bibcode: 1994snft.book..427C Altcode: No abstract at ADS Title: Generalized Singular Value Decomposition Analysis of Helioseismic Inversions Authors: Christensen-Dalsgaard, J.; Hansen, P. C.; Thompson, M. J. Bibcode: 1993MNRAS.264..541C Altcode: We present the generalized singular value decomposition (GSVD) as a powerful tool for the analysis of 111-conditioned inversion problems, such as arise in helioseismology and other areas of astronomy. The GSVD provides rather natural bases with which to express the various properties of the inversion, in particular the solution, the inversion coefficients (which relate the solution to the data) and the averaging kernels (which relate the solution to the underlying unknown function). These facilitate an analysis of resolution and error properties. We apply the theory to a helioseismic example and find inter alia that, for our prototypical problem, there is an effective limit to the information content of the mode set in the presence of reasonable data errors which is much less than might have been expected from the number of modes. We show that various popular inversion methods can be analysed using the tools developed here. We find in our helioseismic application that the methods make very similar use of the data. Title: Resonant Alfvén wave excitation in two-dimensional systems: Singularities in partial differential equations Authors: Thompson, Michael J.; Wright, Andrew N. Bibcode: 1993JGR....9815541T Altcode: The resonant excitation of Alfvén waves is considered in a cold plasma embedded in a uniform magnetic field Bẑ. All wave fields are assumed to vary as exp[i(λy-ωt)], and the background medium is invariant in y. The background density distribution ρ0(x,z) is otherwise completely arbitrary. Regular and singular solutions for the waves are derived systematically in the vicinity of a resonance by considering a generalized Frobenius series, and we are able to recover many results found in earlier studies. Some new features of our work include a generalization of the overlap integral determining the efficiency with which any resonance may be excited, and the possibility that ξy~1/xN (N=1,2,3...) at the resonance. Hitherto only the solution with N=1 has been considered. Title: A preprocessing strategy for helioseismic inversions Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993A&A...272L...1C Altcode: Helioseismic inversion in general involves considerable computational expense, due to the large number of modes that is typically considered. This is true in particular of the widely used optimally localized averages (OLA) inversion methods, which require the inversion of one or more matrices whose order is the number of modes in the set. However, the number of practically independent pieces of information that a large helioseismic mode set contains is very much less than the number of modes, suggesting that the set might first be reduced before the expensive inversion is performed. We demonstrate with a model problem that by first performing a singular value decomposition the original problem may be transformed into a much smaller one, reducing considerably the cost of the OLA inversion and with no significant loss of information. Title: Effects of Diffusion on Solar Models and Their Oscillation Frequencies Authors: Christensen-Dalsgaard, J.; Proffitt, C. R.; Thompson, M. J. Bibcode: 1993ApJ...403L..75C Altcode: Settling and diffusion of helium have significant effects on the structure of solar models and their oscillation frequencies. We examine these effects in considerably more detail than has been done before, and we compare the computed frequencies with an extensive set of observed frequencies. We find that inclusion of diffusion results in a significant improvement in the agreement between theory and observations. Title: On Detecting Overshoot Below the Sun's Convective Envelope Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993ASPC...42..253M Altcode: 1993gong.conf..253M No abstract at ADS Title: Two-dimensional helioseismic inversions Authors: Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993ASPC...40...72S Altcode: 1993IAUCo.137...72S; 1993ist..proc...72S No abstract at ADS Title: Detecting convective overshoot in solar-type stars Authors: Monteiro, M. J. P. F. G.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993ASPC...40..557M Altcode: 1993IAUCo.137..557M; 1993ist..proc..557M No abstract at ADS Title: Faster Formulations of the Ola Method Authors: Pijpers, F. P.; Thompson, M. J. Bibcode: 1993ASPC...42..245P Altcode: 1993gong.conf..245P No abstract at ADS Title: Tests and Applications of the SOLA Inversion Method - a New Determination of the Solar Rotation Rate Authors: Pijpers, F. P.; Thompson, M. J. Bibcode: 1993ASPC...42..241P Altcode: 1993gong.conf..241P No abstract at ADS Title: Two-Dimensional Helioseismic Inversions Authors: Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993ASPC...42..205S Altcode: 1993gong.conf..205S No abstract at ADS Title: A Hands-On IDL Program for Helioseismic Inversion Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1993ASPC...42..249C Altcode: 1993gong.conf..249C No abstract at ADS Title: Seismic Investigation of the Sun's Internal Structure and Rotation Authors: Thompson, M. J. Bibcode: 1993ASPC...42..141T Altcode: 1993gong.conf..141T No abstract at ADS Title: Sources of uncertainty in direct seismological measurements of the solar helium abundance Authors: Kosovichev, A. G.; Christensen-Dalsgaard, J.; Daeppen, W.; Dziembowski, W. A.; Gough, D. O.; Thompson, M. J. Bibcode: 1992MNRAS.259..536K Altcode: The methods by which Dappen et al. (1988, 1990, 1991) and Dziembowski et al. (1990, 1991, 1992) recently obtained discrepant estimates of the helium abundance in the solar convection zone are compared. The aim of the investigation reported in this paper is to identify the main source of the discrepancy. Using as proxy data eigenfrequencies of a set of modes of a theoretical solar model, computed with the same physics as were the frequencies of a reference model with which these data are compared, the two methods yield similar results. Thus we ascertain that the principal source of the discrepancy is not in the inversions themselves, which yield essentially a measure of the variation of the adiabatic exponent gamma of the material in the He II ionization zone. Instead it is in the approximations adopted in the treatment of heavy elements in the equation of state used to relate the variation of gamma to chemical composition. We obtain acceptably consistent results when inverting solar data by two methods using the same equation of state. We attempt to identify the likely residual sources of uncertainty. Title: On the rate of destruction of lithium in late-type main-sequence stars Authors: Christensen-Dalsgaard, J.; Gough, D. O.; Thompson, M. J. Bibcode: 1992A&A...264..518C Altcode: It it shown that the rate of destruction of lithium by nuclear reactions in the outer mixed layers of late-type main-sequence stars depends on both the depth of the region where mixing occurs and the stratification within it. The mixed region includes and probably extends beneath the base of the convection zone. As the star evolves on the main sequence, the properties of the convection zone vary in a simple manner. If the mixed layer behaves similarly, then the mean destruction rate can easily be related to the present local value evaluated at the base of the mixed layer. In the case of the sun, it is found that if mixing is rapid compared with the nuclear destruction rate, then the mean destruction rate is approximately equal to one-half the present local value. Title: On the effects of chromospheric magnetic perturbations on solar oscillation frequencies Authors: Wright, A. N.; Thompson, M. J. Bibcode: 1992A&A...264..701W Altcode: A perturbation method is developed for calculating the effect on the frequencies of solar global oscillations of changes in the chromosphere. We show that the frequency perturbation depends on the subphotospheric structure of the solar model only through the mode inertia (or mode mass). The effects of changing the chromosphere can first be calculated independently of any particular model of the solar interior; and the frequency perturbations for any given model then obtained by scaling with mode inertia. In particular we apply the method to changes in chromospheric magnetic field. Title: Faster formulations of the optimally localized averages method for helioseismic inversions Authors: Pijpers, F. P.; Thompson, M. J. Bibcode: 1992A&A...262L..33P Altcode: Much use is made in helioseismology of the optimally localized averages method of inversion, introduced by Backus and Gilbert. However, the method is computationally expensive for large data sets. Here we present a class of alternative formulations of that method which are more efficient computationally and yet they retain the advantages of the method in its usual form. Title: The Effect of an Inclined Magnetic Field on Solar Oscillation Frequencies Authors: Goode, Philip R.; Thompson, Michael J. Bibcode: 1992ApJ...395..307G Altcode: The radiative interior of the sun could be hiding a large-scale magnetic field, which might not be axisymmetric about the observed rotation axis. Using helioseismic data, we estimate that the strength of any such relic field must be less than about 30 MG, if the field is axisymmetric about the rotation axis. The shape oblateness caused by a field at this limiting strength is about 5-10 x 10 exp -6. Stronger fields can be accommodated by the helioseismic data if they are inclined to the rotation axis. We further conclude that the convention zone and at least the outer part of the radiative interior rotate on the same axis. Title: The Resolving Power of Current Helioseismic Inversions for the Sun's Internal Rotation Authors: Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1992ApJ...385L..59S Altcode: An inversion of the currently available rotational splitting data which is representative of other recent inversions for the sun's internal rotation is analyzed. The so-called polar rate is found to be an extrapolation from lower latitudes. The basic conclusion that the average radial gradient of the rotation rate in the solar convection zone is small is corroborated. Title: Does the Sun Rotate on a Single Axis? Authors: Goode, Philip R.; Thompson, Michael J. Bibcode: 1992ASPC...27..182G Altcode: 1992socy.work..182G No abstract at ADS Title: The Depth of the Solar Convection Zone Authors: Christensen-Dalsgaard, J.; Gough, D. O.; Thompson, M. J. Bibcode: 1991ApJ...378..413C Altcode: The transition of the temperature gradient between being subadiabatic and adiabatic at the base of the solar convection zone gives rise to a clear signature in the sound speed. Helioseismic measurements of the sound speed therefore permit a determination of the location of the base of the convection zone. Two techniques were tested by applying them to artifical data, obtained by adding simulated noise to frequencies computed from two different solar models. The determinations appear to be relatively insensitive to uncertainties of the physics of the solar interior. From an analysis of observed frequencies of solar oscillation it is concluded that the depth of the solar convection zone is (0.287 + or - 0.003) solar radii. Title: The Response of the Adiabatic Exponent Gamma 1 to Modifications of Solar Models Authors: Christensen-Dalsgaard, J.; Thompson, M. J. Bibcode: 1991ApJ...367..666C Altcode: Guenther et al. (1989) investigated the effet of varying the abundance of elemental Ne on solar models and found that the changes in some aspects of these models in the ionization zones of helium and hydrogen were nonmonotonic functions of the assumed Ne abundance. In this paper, the results of Guenther et al. are examined, and it is found that the apparent nonmonotonic behavior of the models was caused by slight errors in the radii of their models, combined with the fact that the adiabatic exponent Gamma(1) was compared at fixed distance r from the center of the model. When the models are compared at fixed fractional radius r/R, the differences in the values of Gamma(1) were found to behave in a much more regular way. Title: Helioseismic Inversion Authors: Thompson, M. J. Bibcode: 1991LNP...388...61T Altcode: 1991ctsm.conf...61T The application of inverse theory enables us to use the measured frequencies of normal modes of oscillation of the Sun to make inferences about the structure and dynamics of the solar interior. Some basic concepts and a few inversion techniques are discussed. Results on solar rotation and radial stratification are reviewed, and finally the potential for investigating other moderate-mass stars seismologically is considered. Title: The inversion problem. Authors: Gough, D. O.; Thompson, M. J. Bibcode: 1991sia..book..519G Altcode: The authors discuss some fundamental problems associated with inverting helioseismic data to infer properties of the solar interior, and review various methods used to invert frequencies of normal modes of oscillation. After discussing linear methods, the authors present and compare different asymptotic methods that have been used to infer the internal solar sound speed. They also discuss numerical inversions for solar structure, and address the issue of inverting for more than one function. Methods of inverting for the nonspherically symmetric structure of the Sun are presented. Title: A New Inversion for the Hydrostatic Stratification of the Sun Authors: Däppen, W.; Gough, D. O.; Kosovichev, A. G.; Thompson, M. J. Bibcode: 1991LNP...388..111D Altcode: 1991ctsm.conf..111D Inversions for the spherically symmetric component of the hydrostatic stratification of the Sun are presented. These employ the Backus-Gilbert optimally localized averaging procedure applied to oscillation multiplet frequencies in the range 1.5 - 3 mHz of modes with 4 l 140 determined by Libbrecht et al. (1990) from observations carried out in 1986. We also obtain an estimate of the helium abundance in the solar convective envelope. Title: A comparison of methods for inverting helioseismic data Authors: Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J. Bibcode: 1990MNRAS.242..353C Altcode: Consideration is given to the inversion techniques used to study the properties of the solar interior with observed frequencies of solar oscillation. Linear inversion schemes for helioseismic problems are compared in terms of resolutions and error properties. Measures of the error amplification resulting from the inversion and the resolution achieved are defined. Although the study includes only inversions for a spherically symmetric angular velocity distribution, it is suggested that the methods may be used to study kernels for other properties of the solar interior. Title: The effect of rotation and a buried magnetic field on stellar oscillations Authors: Gough, D. O.; Thompson, M. J. Bibcode: 1990MNRAS.242...25G Altcode: A perturbation method is presented for calculating the frequency modification of stellar oscillations caused by rotation and internal magnetic field. A short-wavelength asymptotic analysis derived from ray theory is also presented. The effects on high-order solar acoustic modes of various hypothetical angular velocity and magnetic field configurations are investigated using both methods of calculation. The asymptotic formulas provide a good estimate for the frequency splitting of five-minute modes when the field and the rotation vary sufficiently smoothly. On the other hand, a localized magnetic field, for example at the base of the convection zone, produces a characteristic oscillatory perturbation to the eigenfrequencies. Title: A New Inversion of Solar Rotational Splitting Data Authors: Thompson, M. J. Bibcode: 1990SoPh..125....1T Altcode: The fine structure of the solar p-mode spectrum is used to obtain an estimate of the Sun's internal rotation rate, as a function of both latitude and depth, for fractional radii in the range 0.55 < r/R < 0.85. Because each piece of data is a weighted average of the rotation rate over an extended region of the solar interior and because the number of such measurements is finite, such an inversion unavoidably has limited resolution and suffers from other systematic errors. Accordingly, the results of the inversion presented here and other published inversions should be interpreted with this in mind. These problems are discussed in detail for the present inversion. Title: What are the Observed High-Frequency Solar Acoustic Modes? Authors: Kumar, P.; Duvall, T. L., Jr.; Harvey, J. W.; Jefferies, S. M.; Pomerantz, M. A.; Thompson, M. J. Bibcode: 1990LNP...367...87K Altcode: 1990psss.conf...87K Jefferies et al. (1988) observe discrete peaks up to 7mHz in the power spectra of their intermediate degree solar intensity oscillation data obtained at South Pole. This is perhaps surprising since waves with frequency greater than the acoustic cut-off frequency at the temperature minimum ( 5.5mHz), unlike their lower frequency counterparts, are not trapped in the solar interior. We propose that the observed peaks are associated with what are principally progressive waves emanating from a broad-band acoustic source. The geometrical effect of projecting observations of these progressive waves onto spherical harmonics then gives rise to peaks in the power spectra. The frequencies and amplitudes of the peaks will depend on the spatial characteristics of the source. Partial reflections in the solar atmosphere modify the power spectra, but in this picture they are not the primary reason for the appearance of the peaks. We estimate the frequency and power which would be expected from this model and compare it with the observations. We argue that these high frequency mock-modes are not overstable, and that they are excited by acoustic emission from turbulent convection. Title: Differential asymptotic sound-speed inversions Authors: Christensen-Dalsgaard, J.; Thompson, M. J.; Gough, D. O. Bibcode: 1989MNRAS.238..481C Altcode: An asymptotic method for determining the internal solar sound speed from the differences between observed p-mode frequencies and those of a standard reference solar model is presented. In order to test the method, it has been applied to the frequency differences between pairs of solar models, where in each case one takes the part of the reference model and the other the role of the sun. The results of these numerical experiments indicate that by using this simple method one may in principle be able to determine the sound speed from the energy-generating core to the helium ionization zone. Title: Determination of the solar internal sound speed by means of a differential asymptotic inversion. Authors: Christensen-Dalsgaard, J.; Gough, Douglas O.; Thompson, M. J. Bibcode: 1988ESASP.286..493C Altcode: 1988ssls.rept..493C The authors present a simple asymptotic inversion method for obtaining an estimate of the difference in internal sound speed from differences between five-minute p-mode oscillation frequencies. Thus, given a known model and a set of frequencies of a model of unknown structure, or of the Sun, the internal sound speed of the latter can be estimated. Numerical experiments with error-free frequencies indicate that this method can provide an estimate of the sound speed, from the energy-generating core to the helium ionization zone, with smaller fractional error than any previously published results. The authors have applied the method to real solar data, and find that the solar sound speed is indeed broadly as determined by an earlier investigation at those depths for which the earlier inversion should be reliable. Title: Evidence for a thin perturbative layer near the base of the solar convection zone. Authors: Thompson, M. J. Bibcode: 1988ESASP.286..321T Altcode: 1988ssls.rept..321T Low-degree solar p-mode frequencies hint at the presence of a thin perturbative layer at the base of the Sun's convection zone. Magnetic flux stored in an overshoot region could constitute such a perturbative layer. Title: Further progress on the helium abundance determination. Authors: Daeppen, W.; Gough, Douglas O.; Thompson, M. J. Bibcode: 1988ESASP.286..505D Altcode: 1988ssls.rept..505D The authors report on further progress in attempting to determine the helium abundance in the solar convection zone by analysing the position and shape of the "helium hump" in a thermodynamic quantity Θ which can be inferred from the sound speed in the vicinity of the He II ionization zone. At present they are estimating the sound speed from frequencies of high-degree oscillations by a differential asymptotic technique. The helium abundance Y is then determined by fitting the hump inferred to one obtained by interpolation in a grid of theoretical model envelopes. They have tested the procedure by carrying out a double-blind experiment on artificial data, and have found that accurate knowledge of the equation of state is essential for a useful determination. The authors have also carried out the procedure on real solar data, but they judge that the frequencies are at present too poorly determined to enable us to obtain a reliable estimate of Y in the sun. Title: On the Implications of the Symmetric Component of the Frequency Splitting Authors: Gough, D. O.; Thompson, M. J. Bibcode: 1988IAUS..123..175G Altcode: The component of the frequency splitting of solar five-minute oscillations observed by Duvall, Harvey and Pomerantz that is even in azimuthal degree measures latitudinal and depth variations in the structure of the sun. The authors indicate how the data hint that there is a shallow perturbation, possibly associated with a magnetic field, that is concentrated at low latitudes. Title: Magnetic Perturbations to Stellar Oscillation Eigenfrequencies Authors: Gough, D. O.; Thompson, M. J. Bibcode: 1988IAUS..123..155G Altcode: Magnetic fields contribute to the splitting of the degeneracy of modes of like order and degree. The splitting is estimated for some simple hypothetical toroidal magnetic field configurations in the sun, and the results are compared with previous asymptotic estimates. Splitting by a field confined to a thin layer at the base of the convection zone is found not to agree with recent measurements. Title: Problems in helioseismology Authors: Thompson, Michael John Bibcode: 1987PhDT........98T Altcode: No abstract at ADS Title: Communication. Enhanced sensitivity in the determination of mercury by inductively coupled plasma atomic-emission spectrometry Authors: Thompson, Michael; Coles, Barry J. Bibcode: 1984Ana...109..529T Altcode: No abstract at ADS Title: Post-Newtonian collapse calculations Authors: Thompson, M. Bibcode: 1983PASA....5..179T Altcode: 1983PASAu...5..179T The dynamical collapse of a rotating body (with a mass less than the critical mass) from white dwarf densities down toward neutron star densities is examined with a view to resolving some of the effects of rotation on the evolution. In the approach used here, the post-Newtonian equations for continuity and momentum (Chandrasekhar, 1964) for a perfect fluid are modeled with the smoothed particle hydrodynamics of Gingold and Monagham (1982). The version of the code used conserves both linear and angular momentum exactly. Collapse calculations are carried out using a 1000-particle code. The results obtained are briefly discussed, and improvements to the code are suggested.