ALBERT

Description: 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 Omega 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 Omega 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Howe -- Christensen-Dalsgaard -- Hill -- Komm -- Larsen -- Schou -- Thompson -- Toomre -- New York, N.Y. -- Science. 2000 Mar 31;287(5462):2456-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Solar Observatory, National Optical Astronomy Observatories, Post Office Box 26732, Tucson, AZ 85726-6732, USA. Theoretical Astrophysics Center, Danish National Research Foundation, and Institute of Physics and Astronomy, Aarhus Uni.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10741959" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Toomre, Juri -- New York, N.Y. -- Science. 2002 Apr 5;296(5565):64-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA. jtoomre@jila.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11935010" target="_blank"〉PubMed〈/a〉

Description: Helioseismology requires nearly continuous observations of the oscillations of the solar surface for long periods of time in order to obtain precise measurements of the sun's normal modes of oscillation. The GONG project acquires velocity images from a network of six identical instruments distributed around the world. The GONG network began full operation in October 1995. It has achieved a duty cycle of 89 percent and reduced the magnitude of spectral artifacts by a factor of 280 in power, compared with single-site observations. The instrumental noise is less than the observed solar background.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey -- Hill -- Hubbard -- Kennedy -- Leibacher -- Pintar -- Gilman -- Noyes -- Title -- Toomre -- Ulrich -- Bhatnagar -- Kennewell -- Marquette -- Patron -- Saa -- Yasukawa -- New York, N.Y. -- Science. 1996 May 31;272(5266):1284-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. W. Harvey, F. Hill, R. P. Hubbard, J. R. Kennedy, J. W. Leibacher, and J. A. Pintar are with the National Solar Observatory, National Optical Astronomy Observatories, Post Office Box 26732, Tucson, AZ 85726-6732, USA. P. A. Gilman is with the High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307, USA. R. W. Noyes is with the Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA. A. M. Title is with the Lockheed Solar and Astrophysics Laboratory, Palo Alto, CA 94304, USA. J. Toomre is with JILA, University of Colorado, Boulder, CO 80309, USA. R. K. Ulrich is with the Department of Physics and Astronomy, University of California, Los Angeles, CA 90024, USA. A. Bhatnagar is with the Udaipur Solar Observatory, Physical Research Laboratory, Udaipur, India. J. A. Kennewell is with the Learmonth Solar Observatory, IPS Radio and Space Services, Exmouth, Western Australia, Australia. W. Marquette is with the Big Bear Solar Observatory, Big Bear City, CA 92314, and California Institute of Technology, 264-33, Pasadena, CA 91125, USA. J. Patron is with the Observatorio del Teide, Instituto Astrofisica de Canarias, La Laguna, Tenerife, Spain. O. Saa is with the Cerro Tololo Interamerican Observatory, National Optical Astronomy Observatories, La Serena, Chile. E. Yasukawa is with the Mauna Loa Solar Observatory, Hilo, HI 96720, and High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662455" target="_blank"〉PubMed〈/a〉

Description: Helioseismology is probing the interior structure and dynamics of the sun with ever-increasing precision, providing a well-calibrated laboratory in which physical processes can be studied under conditions that are unattainable on Earth. Nearly 10 million resonant modes of oscillation are observable in the solar atmosphere, and their frequencies need to be known with great accuracy in order to gauge the sun's interior. The advent of nearly continuous imaged observations from the complementary ground-based Global Oscillation Network Group (GONG) observatories and the space-based Solar and Heliospheric Observatory instruments augurs a new era of discovery. The flow of early results from GONG resolves some issues and raises a number of theoretical questions whose answers are required for understanding how a seemingly ordinary star actually operates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gough -- Leibacher -- Scherrer -- Toomre -- New York, N.Y. -- Science. 1996 May 31;272(5266):1281-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. O. Gough is with the Institute of Astronomy, University of Cambridge, Cambridge, CB3 OHA UK. J. W. Leibacher is with the National Solar Observatory, Tucson, AZ, USA. P. H. Scherrer is with the Department of Physics, Stanford University, Stanford, CA, USA. J. Toomre is with JILA, University of Colorado, Boulder, CO, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662454" target="_blank"〉PubMed〈/a〉

Description: Observations of the sun reveal highly complex flows and magnetic structures that must result from turbulent convection in the solar envelope. A remarkable degree of large-scale coherence emerges from the small-scale turbulent dynamics, as seen in the cycles of magnetic activity and in the differential rotation profile of this star. High-performance computing now permits numerical simulations of compressible turbulence and magnetohydrodynamics with sufficient resolution to show that compact structures of vorticity and magnetic fields can coexist with larger scales. Such structured turbulence is yielding transport properties for heat and angular momentum at considerable variance with earlier models. These simulations are elucidating the coupling of turbulent fluid motions with rotation and magnetic fields, which must control the interlinked differential rotation and magnetic dynamo action.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brummell, N -- Toomre, J -- Cattaneo, F -- New York, N.Y. -- Science. 1995 Sep 8;269(5229):1370-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17731146" target="_blank"〉PubMed〈/a〉

Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gough -- Kosovichev -- Toomre -- Anderson -- Antia -- Basu -- Chaboyer -- Chitre -- Christensen-Dalsgaard -- Dziembowski -- Eff-Darwich -- Elliott -- Giles -- Goode -- Guzik -- Harvey -- Hill -- Leibacher -- Monteiro -- Richard -- Sekii -- Shibahashi -- Takata -- Thompson -- Vauclair -- Vorontsov -- New York, N.Y. -- Science. 1996 May 31;272(5266):1296-300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. O. Gough, J. R. Elliott, and T. Sekii are with the Institute of Astronomy, University of Cambridge, CB3 0HA, UK. A. G. Kosovichev and P. R. Giles are with HEPL, Stanford University, Stanford, CA, USA. J. Toomre is at JILA, University of Colorado, Boulder, CO, USA. E. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are at the National Solar Observatory, Tucson, AZ, USA. H. M. Antia and S. M. Chitre are at the Tata Institute for Fundamental Research, Bombay, India. S. Basu and J. Christensen-Dalsgaard are at the Theoretical Astrophysics Centre, Aarhus University, Denmark. B. Chaboyer is at the Canadian Institute for Theoretical Astrophysics, Toronto, Canada. W. A. Dziembowski is at the Copernicus Astronomical Center, Warsaw, Poland. A. Eff-Darwich is at the Instituto Astrofisico de Canarias, Tenerife, Canary Islands. P. R. Goode is at the New Jersey Institute of Technology, Newark, NJ, USA. J. A. Guzik is at the Los Alamos National Laboratory, Los Alamos, NM, USA. M. J. P. F. G. Monteiro is at the University of Oporto, Postugal. O. Richard and S. Vauclair are at the Observatoire Midi-Pyrenees, Toulouse, France. H. Shibahashi and M. Takata are in the Department of Astronomy, University of Tokyo, Tokyo, Japan. M. J. Thompson and S. V. Vorontsov are at Queen Mary and Westfield College, University of London, London, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662458" target="_blank"〉PubMed〈/a〉

Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thompson -- Toomre -- Anderson -- Antia -- Berthomieu -- Burtonclay -- Chitre -- Christensen-Dalsgaard -- Corbard -- DeRosa -- Genovese -- Gough -- Haber -- Harvey -- Hill -- Howe -- Korzennik -- Kosovichev -- Leibacher -- Pijpers -- Provost -- Rhodes Jr -- Schou -- Sekii -- Stark -- Wilson -- New York, N.Y. -- Science. 1996 May 31;272(5266):1300-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉M. J. Thompson and R. Howe are in the Astronomy Unit, Queen Mary and Westfield College, University of London, Mile End Road, London E1 4NS, UK. J. Toomre, M. DeRosa, and D. A. Haber are at the Joint Institute for Laboratory Astrophysics, University of Colorado, Boulder, CO 80309-0440, USA. E. R. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are at the National Solar Observatory (NSO), National Optical Astronomy Observatories (NOAO), Post Office Box 26732, Tucson, AZ 85726-6732, USA. H. M. Antia and S. M. Chitre are at the Tata Institute of Fundamental Research, Bombay 400005, India. G. Berthomieu, T. Corbard, and J. Provost are at the Observatoire de la Cote d'Azur, 06304 Nice Cedex 4, France. D. Burtonclay and P. R. Wilson are in the School of Mathematics, University of Sydney, Sydney, NSW 2006, Australia. J. Christensen-Dalsgaard and F. P. Pijpers are at the Theoretical Astrophysics Center, Aarhus University, DK-8000 Aarhus C, Denmark. C. R. Genovese is in the Department of Statistics, Carnegie Mellon University, Pittsburgh, PA 15213, USA. D. O. Gough and T. Sekii are in the Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK. S. G. Korzennik is at the Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. A. G. Kosovichev and J. Schou are at Hansen Experimental Physics Laboratory Annex, Stanford University, Stanford, CA 94305-4085, USA. E. J. Rhodes Jr. is in the Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA. P. B. Stark is in the Department of Statistics, University of California, Berkeley, CA 94720-3860, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662459" target="_blank"〉PubMed〈/a〉

Description: Oscillations of the sun make it possible to probe the inside of a star. The frequencies of the oscillations have already provided measures of the sound speed and the rate of rotation throughout much of the solar interior. These quantities are important for understanding the dynamics of the magnetic cycle and have a bearing on testing general relativity by planetary precession. The oscillation frequencies yield a helium abundance that is consistent with cosmology, but they reinforce the severity of the neutrino problem. They should soon provide an important standard by which to calibrate the theory of stellar evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Christensen-Dalsgaard, J -- Gough, D -- Toomre, J -- New York, N.Y. -- Science. 1985 Sep 6;229(4717):923-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17782505" target="_blank"〉PubMed〈/a〉

Description: Experiments on thermal convection in a rotating, differentially heated hemispherical shell with a radial buoyancy force were conducted in an orbiting microgravity laboratory. A variety of convective structures, or planforms, were observed, depending on the magnitude of the rotation and the nature of the imposed heating distribution. The results are compared with numerical simulations that can be conducted at the more modest heating rates, and suggest possible regimes of motion in rotating planets and stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hart, J E -- Toomre, J -- Deane, A E -- Hurlburt, N E -- Glatzmaier, G A -- Fichtl, G H -- Leslie, F -- Fowlis, W W -- Gilman, P A -- New York, N.Y. -- Science. 1986 Oct 3;234(4772):61-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17742634" target="_blank"〉PubMed〈/a〉