Author name code: hurlburt ADS astronomy entries on 2022-09-14 author:"Hurlburt, Neal E." ------------------------------------------------------------------------ Title: Heliophysics Events Knowledgebase for FAIR and citable data Authors: Hurlburt, Neal; Timmons, MR. Ryan Bibcode: 2022cosp...44.3491H Altcode: The Heliophysics Events Knowledgebase (HEK) began full operations in 2010 in support of the Solar Dynamics Observatory (SDO) with the purpose of helping researchers navigate the daily 2TB flood of data from its 3 instruments. It was built along the lines of what is now known as FAIR (Findable, Accessible, Interoperable, Reusable) principles prior to their codification in 2016 and anticipated the need for improved data citation. The HEK consisted of three main components, along with the associated hardware and software infrastructure: an automated Event Detection System (EDS) for identifying features and events in the (primarily) SDO data stream; the Heliophysics Event Registry (HER) for capturing the metadata extracted by the EDS; and the Heliophysics Coverage Registry (HCR) for tracking subsets of the SDO datasets requested by users. The infrastructure underlying the HER and HCR had previously been prototyped as the Hinode Observation system for the Hinode/Solar-B mission; it was based on an implementation of the VOEvent XML standard developed by the International Virtual Observatory Alliance (IVOA). The HEK team spent considerable effort to design the HEK to be an expandable community resource. The HER can support new event classes, data sources, human annotators, and algorithms, and provides tools to make unique IVOA Resource Identifiers (IVORNs) for each entry which serve a similar role to Digital Object Identifiers (DOIs). It support relations and citations between entries such as "hypotheses" or meta-events connecting other HER events as well as integrate search capabilities across both registries simultaneously. Here we demonstrate the HEK aligns with FAIR principles and highlight our recent efforts and plans to enable fuller adaptation of FAIR principles and improved its support for data citation. Title: Revisiting the Solar Research Cyberinfrastructure Needs: A White Paper of Findings and Recommendations Authors: Nita, Gelu; Ahmadzadeh, Azim; Criscuoli, Serena; Davey, Alisdair; Gary, Dale; Georgoulis, Manolis; Hurlburt, Neal; Kitiashvili, Irina; Kempton, Dustin; Kosovichev, Alexander; Martens, Piet; McGranaghan, Ryan; Oria, Vincent; Reardon, Kevin; Sadykov, Viacheslav; Timmons, Ryan; Wang, Haimin; Wang, Jason T. L. Bibcode: 2022arXiv220309544N Altcode: Solar and Heliosphere physics are areas of remarkable data-driven discoveries. Recent advances in high-cadence, high-resolution multiwavelength observations, growing amounts of data from realistic modeling, and operational needs for uninterrupted science-quality data coverage generate the demand for a solar metadata standardization and overall healthy data infrastructure. This white paper is prepared as an effort of the working group "Uniform Semantics and Syntax of Solar Observations and Events" created within the "Towards Integration of Heliophysics Data, Modeling, and Analysis Tools" EarthCube Research Coordination Network (@HDMIEC RCN), with primary objectives to discuss current advances and identify future needs for the solar research cyberinfrastructure. The white paper summarizes presentations and discussions held during the special working group session at the EarthCube Annual Meeting on June 19th, 2020, as well as community contribution gathered during a series of preceding workshops and subsequent RCN working group sessions. The authors provide examples of the current standing of the solar research cyberinfrastructure, and describe the problems related to current data handling approaches. The list of the top-level recommendations agreed by the authors of the current white paper is presented at the beginning of the paper. Title: Laboratory prototype for a photonic magnetograph Authors: Hurlburt, Neal; Vasudevan, Gopal; Shing, Lawrence; Chen, Humphry; Yoo, Ben; Hoeksema, J. Bibcode: 2021AGUFMSH35D2108H Altcode: We present recent progress in developing an ultra-compact magnetograph that leverages advances in photonics integrated circuits (PICs), low noise lasers and efficient electronics that have come available from developments in the telecommunications industry. A single PIC, which replaces the traditional optical components, processes incoming near infrared signals via two, independent waveguide circuits for each of the two circular polarizations. These signals are heterodyning against a common local oscillator provided by a tunable laser to bring the signals into the RF range. The GHz signals are then digitized using Systems on a Chip (SoCs) developed for 5G communications. Afterwards they are converted to images and magnetograms using methods developed for computational imaging in astronomy and solar magnetometry. Our laboratory prototype observes the full disk of the sun, achieving 20 arc second resolution with a 2cm wafer. Here we will discuss the prototype and present preliminary results. Title: Heliophysics Events Knowledgebase: Cyber Infrastructure for Heliophysics and Space Weather Authors: Hurlburt, Neal; Timmons, Ryan Bibcode: 2021AGUFMSH53A..04H Altcode: The Heliophysics Events Knowledgebase (HEK) began full operations over a decade ago in support of the Solar Dynamics Observatory (SDO) with the purpose of helping researchers navigate the daily 2TB flood of data from its 3 instruments. It consisted of three main components, along with the associated hardware and software infrastructure: an automated Event Detection System (EDS) for identifying features and events in the (primarily) SDO data stream; the Heliophysics Event Registry (HER) for capturing the metadata extracted by the EDS; and the Heliophysics Coverage Registry (HCR) for tracking subsets of the SDO datasets requested by users. The infrastructure underlying the HER and HCR had previously been prototyped as the Hinode Observation system for the Hinode/Solar-B mission based on the VOEvent XML standard of the International Virtual Observatory Alliance. The HEK team realized that the issues they were addressing for SDO and Hinode would be shared by new missions as Heliophysics entered the era of Big Data and as the Heliophysics System Observatory came into being. They spent considerable effort to design the HEK to be an expandable community resource. The HER can support new event classes, data sources and algorithms, as well as support concepts such as hypotheses or meta-events connecting other HEK events and community annotation and cross-linking similar to Facebook and DOIs. These were first put to the test with the addition of the IRIS mission launched in 2013. The HCR was revamped to support the more complex datasets and to enhance and better integrate the HCR search capabilities. In recent years the HEK team has seen an opportunity to transition from a service focused on missions involving the Lockheed Martin Solar and Astrophysics Laboratory to a wider community-oriented resource. The launch of the next generation of heliospheric missions, including Parker Solar Probe and Solar Orbiter, are revealing challenges in event management and mission coordination for which the HEK approach offers a straightforward solution. The completion of new ground-based observatories such as DKIST present opportunities to broaden the range of datasets in this common resource as well. Here we present our recent efforts and plans to support these new missions as well as the broader needs of heliophysics and space weather research. Title: The Multiview Observatory for Solar Terrestrial Science (MOST) Authors: Gopalswamy, Nat; Kucera, Therese; Leake, James; MacDowall, Robert; Wilson, Lynn; Kanekal, Shrikanth; Shih, Albert; Christe, Steven; Gong, Qian; Viall, Nicholeen; Tadikonda, Sivakumar; Fung, Shing; Yashiro, Seiji; Makela, Pertti; Golub, Leon; DeLuca, Edward; Reeves, Katharine; Seaton, Daniel; Savage, Sabrina; Winebarger, Amy; DeForest, Craig; Desai, Mihir; Bastian, Tim; Lazio, Joseph; Jensen, P. E., C. S. P., Elizabeth; Manchester, Ward; Wood, Brian; Kooi, Jason; Wexler, David; Bale, Stuart; Krucker, Sam; Hurlburt, Neal; DeRosa, Marc; Pevtsov, Alexei; Tripathy, Sushanta; Jain, Kiran; Gosain, Sanjay; Petrie, Gordon; Kholikov, Shukirjon; Zhao, Junwei; Scherrer, Philip; Woods, Thomas; Chamberlin, Philip; Kenny, Megan Bibcode: 2021AGUFMSH12A..07G Altcode: The Multiview Observatory for Solar Terrestrial Science (MOST) is a comprehensive mission concept targeting the magnetic coupling between the solar interior and the heliosphere. The wide-ranging imagery and time series data from MOST will help understand the solar drivers and the heliospheric responses as a system, discerning and tracking 3D magnetic field structures, both transient and quiescent in the inner heliosphere. MOST will have seven remote-sensing and three in-situ instruments: (1) Magnetic and Doppler Imager (MaDI) to investigate surface and subsurface magnetism by exploiting the combination of helioseismic and magnetic-field measurements in the photosphere; (2) Inner Coronal Imager in EUV (ICIE) to study large-scale structures such as active regions, coronal holes and eruptive structures by capturing the magnetic connection between the photosphere and the corona to about 3 solar radii; (3) Hard X-ray Imager (HXI) to image the non-thermal flare structure; (4) White-light Coronagraph (WCOR) to seamlessly study transient and quiescent large-scale coronal structures extending from the ICIE field of view (FOV); (5) Faraday Effect Tracker of Coronal and Heliospheric structures (FETCH), a novel radio package to determine the magnetic field structure and plasma column density, and their evolution within 0.5 au; (6) Heliospheric Imager with Polarization (HIP) to track solar features beyond the WCOR FOV, study their impact on Earth, and provide important context for FETCH; (7) Radio and Plasma Wave instrument (M/WAVES) to study electron beams and shocks propagating into the heliosphere via passive radio emission; (8) Solar High-energy Ion Velocity Analyzer (SHIVA) to determine spectra of electrons, and ions from H to Fe at multiple spatial locations and use energetic particles as tracers of magnetic connectivity; (9) Solar Wind Magnetometer (MAG) to characterize magnetic structures at 1 au; (10) Solar Wind Plasma Instrument (SWPI) to characterize plasma structures at 1 au. MOST will have two large spacecraft with identical payloads deployed at L4 and L5 and two smaller spacecraft ahead of L4 and behind L5 to carry additional FETCH elements. MOST will build upon SOHO and STEREO achievements to expand the multiview observational approach into the first half of the 21st Century. Title: Solar Jet Hunter: a citizen science investigation of coronal solar jets Authors: Musset, Sophie; Glesener, Lindsay; Fortson, Lucy; Kapsiak, Charles; Ostlund, Erik; Alnahari, Suhail; Jeunon, Mariana; Zhang, Yixian; Panesar, Navdeep; Fleishman, Gregory; Hurlburt, Neal Bibcode: 2021AGUFMSA32A..07M Altcode: The Sun is the source of energetic particles that fill the heliosphere, interact with planets magnetospheres, and impact human activities. The origins of those energetic particles are still under investigation, as well as the mechanisms responsible for their escape from the solar atmosphere where they are energized. Solar jets, collimated ejections of solar plasma along magnetic field lines extending to the interplanetary medium, offer a possible route for particle escape. Coronal solar jets are commonly observed in soft X-rays and extreme ultraviolet (EUV) and are ubiquitous in the solar atmosphere, assuming various shapes, sizes and velocities. To date, autonomous algorithms are not detecting solar jets reliably, and they are usually reported manually by human observers, resulting in an incomplete and inhomogeneous database of jets. In order to produce a reliable, extensive, and consistent database of jets, that will be used to statistically study the jet phenomenon and its relationship to solar energetic particles, we initiated a citizen science project called Solar Jet Hunter whose goal is to explore the huge amount of EUV observations of the Sun in order to identify and characterize the solar jets in the dataset. The resulting database will also be used to train algorithms to identify solar jets in the EUV data. We will present here the preliminary results of this Zooniverse project. Title: The Sun's dynamic extended corona observed in extreme ultraviolet Authors: Seaton, Daniel B.; Hughes, J. Marcus; Tadikonda, Sivakumara K.; Caspi, Amir; DeForest, Craig E.; Krimchansky, Alexander; Hurlburt, Neal E.; Seguin, Ralph; Slater, Gregory Bibcode: 2021NatAs...5.1029S Altcode: 2021arXiv210508028S; 2021NatAs.tmp..141S The `middle corona' is a critical transition between the highly disparate physical regimes of the lower and outer solar coronae. Nonetheless, it remains poorly understood due to the difficulty of observing this faint region (1.5-3 R). New observations from the Solar Ultraviolet Imager of a Geostationary Operational Environmental Satellite in August and September 2018 provide the first comprehensive look at this region's characteristics and long-term evolution in extreme ultraviolet. Our analysis shows that the dominant emission mechanism here is resonant scattering rather than collisional excitation, consistent with recent model predictions. Our observations highlight that solar wind structures in the heliosphere originate from complex dynamics manifesting in the middle corona that do not occur at lower heights. These data emphasize that low-coronal phenomena can be strongly influenced by inflows from above, not only by photospheric motion, a factor largely overlooked in current models of coronal evolution. This study reveals the full kinematic profile of the initiation of several coronal mass ejections, filling a crucial observational gap that has hindered understanding of the origins of solar eruptions. These new data uniquely demonstrate how extreme ultraviolet observations of the middle corona provide strong new constraints on models seeking to unify the corona and heliosphere. Title: Heliophysics Events Knowledgebase Support For Heliophysics And Space Weather Research Authors: Timmons, R.; Hurlburt, N. Bibcode: 2021AAS...23821608T Altcode: The Heliophysics Events Knowledgebase (HEK) began full operations in 2010 in support of the Solar Dynamics Observatory (SDO) with the purpose of helping researchers navigate the daily 2TB flood of data from its 3 instruments. It consisted of three main components, along with the associated hardware and software infrastructure: an automated Event Detection System (EDS) for identifying features and events in the (primarily) SDO data stream; the Heliophysics Event Registry (HER) for capturing the metadata extracted by the EDS; and the Heliophysics Coverage Registry (HCR) for tracking subsets of the SDO datasets requested by users. The infrastructure underlying the HER and HCR had previously been prototyped as the Hinode Observation system for the Hinode/Solar-B mission; it was based on an implementation of the VOEvent XML standard developed by the International Virtual Observatory Alliance (IVOA). The HEK team realized that the issues they were addressing for SDO and Hinode would continue to be issues for new missions as Heliophysics entered the era of Big Data and as the Heliophysics System Observatory came into being. They spent considerable effort to design the HEK to be an expandable community resource. The HER can support new event classes, data sources and algorithms, as well as support concepts such as "hypotheses" or meta-events connecting other HEK events and community annotation and cross-linking similar to Facebook and DOIs. These were first put to the test with the addition of the IRIS mission launched in 2013. The HCR was revamped to support the more complex datasets and to enhance and better integrate the HCR search capabilities. In recent years the HEK team has seen an opportunity to transition from a service focused on missions where the Lockheed Martin Solar and Astrophysics Laboratory has been a core team member to a broader, community-oriented resource for heliophysics. The launch of the next generation of heliospheric missions, including Parker Solar Probe and Solar Orbiter, are revealing challenges in event management and mission coordination for which the HEK approach offers a straightforward solution. The completion of new ground-based observatories such as DKIST present opportunities to broaden the range of datasets in this common resource as well. Here we present our recent efforts and plans to support these new missions as well as the broader needs of heliophysics and space weather research. Title: The Future Of SolarSoft Authors: Hurlburt, N.; Freeland, S. L.; Timothy, S.; Shirts, P.; Slater, G. Bibcode: 2021AAS...23821301H Altcode: The IDL-based SolarSoft (SSW, SSWIDL) software library and distribution framework continues to be used by a substantial fraction of solar physics researchers, even as other solar physics software packages such as Python-based SunPy grow in usage. In a 2020 survey of researchers in the field of solar physics, 73% of respondents reported using IDL compared to 66% who use Python*. The overwhelming majority of solar physicists using IDL use SolarSoft. In particular, SolarSoft now supports the latest missions in the Heliophysics System Observatory, including the Parker Solar Probe, Solar Orbiter, and GOES 16 and 17 missions. In addition, SolarSoft is used in the data production pipelines of many current missions, including SDO, IRIS, and Hinode. SolarSoft is used for generating much of the content of the Heliospheric Events Knowledgebase (HEK). Given the field's enduring embrace of solarsoft and the value it provides, we are working to provide additional tools to integrate SolarSoft with the latest developments in scientific data analysis, image processing, and software package distribution systems. SSWIDL versions for reading and writing imagery, data, and metadata in the latest and most efficient formats are being developed. The current software distribution system is being augmented to use Git. Seamless access to both SolarSoft and SunPy tools in one interface will allow researchers to work in a single environment. SSWIDL support for running on Jupyter notebooks, and Jupyter-based interactive tutorials are being developed. Here we present the current status of these and other tools.

*Bobra et al, 2020, 'A Survey of Computational Tools in Solar Physics', 10.1007/s11207-020-01622-2 10.1007/s11207-020-01622-2 Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Heliophysics Events Knowledgebase support for Space Weather Research Authors: Hurlburt, Neal; Timmons, Ryan Bibcode: 2021cosp...43E2389H Altcode: The Heliophysics Events Knowledgebase (HEK) began full operations in 2010 in support of the Solar Dynamics Observatory (SDO) with the purpose of helping researchers navigate the daily 2TB flood of data from its 3 instruments. It consisted of three main components, along with the associated hardware and software infrastructure: an automated Event Detection System (EDS) for identifying features and events in the (primarily) SDO data stream; the Heliophysics Event Registry (HER) for capturing the metadata extracted by the EDS; and the Heliophysics Coverage Registry (HCR) for tracking subsets of the SDO datasets requested by users. The infrastructure underlying the HER and HCR had previously been prototyped for the Hinode mission, where it was known as the Hinode Observation system, which was, at its base, an implementation of the VOEvent XML standard developed by the International Virtual Observatory Alliance (IVOA). The HEK team realized that the issues they were addressing for SDO and Hinode would continue to be issues for new missions as Heliophysics entered the era of Big Data and as the Heliophyiscs System Observatory came into being. They spend considerable effort to design the HEK to be an expandable, community resource. The HER can support new event classes, data sources and algorithms, as well as support concepts such as "hypotheses" or meta-events connecting other HEK events and community annotation and cross-linking similar to Facebook and DOIs. This was first put to the test with the addition of the IRIS mission launched in 2013. The HCR was revamped to support the more complex datasets and to enhance and better integrate the HCR search capabilities. The launch of the next generation of heliospheric missions, including Parker Solar Probe and Solar Obiter are revealing challenges in event management and mission coordination for which the HEK approach offers a straight-forward solution. Here we present our recent efforts and plans to support these new heliophysics missions as well as the broader needs of space weather research. Title: Citizen science to identify and analyze coronal jets in SDO/AIA data Authors: Musset, S.; Glesener, L.; Fortson, L.; Wright, D.; Kapsiak, C.; Hurlburt, N. E.; Panesar, N. K.; Fleishman, G. D. Bibcode: 2020AGUFMSH0240006M Altcode: Coronal jets are collimated ejections of plasma that are found to be ubiquitous in the solar atmosphere, at different scales and in different regions of the Sun. They are interpreted as the result of energy release in the solar atmosphere when magnetic reconnection involves both closed and open magnetic field lines. Jets are therefore suspected to be associated with the escape of energetic particles from the solar atmosphere and possibly with perturbations of the solar wind. The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) provides high-cadence and high-resolution images of the solar atmosphere in which coronal jets can be identified and studied. However, the detection of such events via automatic algorithms has been limited and is better achieved by human annotation of the data. In order to detect and catalog coronal jets in the AIA data set, we designed a citizen science project on the Zooniverse platform, where participants can report the precise position and timing of solar jets, along with an indication of their extent. The use of citizen science provides the opportunity to perform this kind of analysis on a large amount of data, and to derive the average values of the jet properties reported by multiple volunteers, removing some of the bias inherent in a single expert observer reporting such properties. This catalog of jet events will provide a useful database for future jet studies, including statistical studies, and a training set for a machine learning approach to the problem of the detection of coronal jets in EUV data sets. Title: Enabling polar coverage of solar photospheric fields with miniature, photonic magnetographs Authors: Hurlburt, N. E.; Vasudevan, G.; Yoo, B.; Chen, H.; Shing, L.; Mobilia, J. Bibcode: 2020AGUFMSH0110007H Altcode: We present progress on developing a novel magnetograph that leverages advances in photonics integrated circuits (PICs) and low noise lasers which have been driven largely by the needs of the telecommunications industry. In our design, a single PIC replaces the traditional optical components by exploiting interferometric imaging techniques developed as part of the SPIDER project, a collaboration with LM and UC Davis. Our PIC processes incoming near infrared signals via two, independent waveguide circuits to capture each circular polarization. Narrow band spectroscopy is achieved by heterodyning the signals with a common local oscillator provided by a tunable laser. The resulting RF signals are processed using standard techniques from radio astronomy and solar magnetometry.

The optics package for our laboratory prototype observes the full disk of the sun, achieving 16 arc second resolution with a square, 2cm wafer. The technology is scalable to sub-arc second resolution using larger wafers, resulting in 100x reductions in volume and mass when compared to traditional designs. The cost of these wafers leads to a comparable reduction in the overall instrument cost since they are printed on silicon wafers using lithographic methods developed for microelectronics rather than by precise manual assembly. Small, solid wafers do not need expensive structures to maintain precise optical alignments during launch or on orbit, which further reduced size and cost.

The penalty for this compactness is an increase in computational and data management requirements. The objectives of our project are threefold:

Produce a set of PICs to capture the infrared solar signal and transform it into the RF domain where it can be processed using standard radio astronomy and helioseismology methods.

Assess the performance of the system and explore alternative processing strategies.

Develop the next generation PIC design and RF processing concept based on our results in preparation for a future flight opportunity.

Our single-wafer magnetographs could be deployed throughout the heliosphere to form cost effective small-sat constellations with resolutions comparable to existing space-borne instruments. Title: The Heliophysics Coverage Registry: An Integrated Metadata System for Coordinated, Multi-mission Solar Observatories Authors: Hurlburt, Neal; Timmons, Ryan; Seguin, Ralph Bibcode: 2020ASPC..522..615H Altcode: 2020adass..27..615H Modern studies of the Sun involve coordinated observations collected from a collage of instruments on the ground and in orbit. Each instrument has its own constraints, such as field of view, duty cycle, and scheduling and commanding windows, that must both be coordinated during operations and be discoverable for analyses of the resulting data. Details on the observed solar features, i.e. sunspots or filaments, and solar events, i.e. flares or coronal mass ejections, are also incorporated to help guide data discovery and data analysis pipelines. The Heliophysics Coverage Registry (HCR) provides a standards-based system for collecting and presenting observations collected by distributed, ground and space based solar observatories which form an integrated Heliophysics system. The HCR currently supports all instruments on the Interface Region Imaging Spectrograph (IRIS) and Hinode missions as well as associated ground-based observatories. Here we present an overview of the HCR along with details on how it provides scientists with tools to make flexible searches on observation metadata in coordination with searches of solar features and events. Title: Ubiquitous imaging of solar photospheric fields using miniature, photonic magnetographs Authors: Hurlburt, N. E.; Chriqui, G.; Thurman, S.; Vasudevan, G.; Shing, L.; Chen, H.; Mobilia, J.; Yoo, B.; Hoeksema, J. T. Bibcode: 2019AGUFMSH41B..08H Altcode: We present progress on developing a novel magnetograph that leverages advances in photonics integrated circuits (PICs) and low noise lasers driven by the needs of the telecommunications industry. In our design, a single PIC replaces the traditional optical components by exploiting interferometric imaging techniques developed as part of the SPIDER project, a collaboration with LM and UC Davis. The resulting signal is processed using standard techniques from radio astronomy and solar magnetometry.

The optics package for our prototype full-disk imager achieves 30 arc second resolution within a few tens of cubic centimeters — compared to tens of thousands needed for traditional designs — with comparable savings in mass. Such devices could easily be deployed throughout the heliosphere on small-sat constellations. Title: The Solar Polar Observing Constellation (SPOC) Mission: research and operational monitoring of space weather from polar heliocentric orbits Authors: Berger, T. E.; Bosanac, N.; Smith, T. R.; Duncan, N. A.; Wu, G.; Turner, E.; Hurlburt, N.; Korendyke, C. Bibcode: 2019AGUFMSH43F3352B Altcode: The Sun's polar regions remain largely unobserved and yet understanding and monitoring of the magnetic field, convective flows, and coronal outflow conditions in the solar polar regions are the keys to accurately modeling and forecasting the solar cycle, solar wind conditions, and CME arrival times at Earth. We describe the Solar Polar Observing Constellation (SPOC), a mission to establish continuous high-resolution imaging of solar magnetic field dynamics, high-latitude surface and sub-surface convective flows, and coronal mass ejection tracking from a low-eccentricity polar heliocentric orbit. SPOC will consist of two identical spacecraft, each equipped with a Lockheed Martin Compact Magnetic Imager (CMI, derived from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager), the Naval Research Laboratory (NRL) Compact Coronagraph (CCOR), and in-situ solar wind and energetic particle instruments. Falcon Heavy launch vehicles will place the SPOC spacecraft into a Jupiter gravitational assist (JGA) heliocentric orbit, achieving an 88-degree ecliptic inclination, with the spacecraft passing over the solar poles within 4 years after launch. Ion engines will subsequently reduce the eccentricity of the orbits to below 0.05 at approximately 0.9 AU within 6 years after launch. Orbital phasing will place the spacecraft over alternate poles to enable continuous monitoring of the polar regions with operational-level redundancy of systems. The inclusion of CCOR will enable visualization and tracking of coronal mass ejections from above (or below) the ecliptic for the first time, greatly enhancing our ability to forecast CME arrival times at Earth and other planets such as Mars. SPOC combines polar region exploration, high-latitude helioseismology and magnetic imaging, and operational space weather monitoring in a single mission. Along with planned missions to the L1 and L5 Lagrangian points in the ecliptic, SPOC will enable an approach to the long-sought goal of continuous full-sphere measurements of the solar magnetic field, solar wind and CME outflow, and energetic particle flux - a goal that cannot be achieved with observations from the ecliptic plane alone. Title: The Structure and Dynamics of the Middle Corona Observed by the GOES Solar Ultraviolet Imager Authors: Seaton, D. B.; Tadikonda, S.; Hurlburt, N.; Seguin, R.; Krimchansky, A.; Hill, S. Bibcode: 2019AGUFMSH11C3407S Altcode: Neither the structure nor the nature of dynamic events in the middle corona — the region of the corona between about 1.5 and 4 RSun — are well known, in large part because this region is extremely challenging to observe for both visible light coronagraphs and EUV imagers. However, a series of new campaigns with the GOES Solar Ultraviolet Imager (SUVI) have shed new light on the nature of this region, its structure and long-term evolution, and, more generally, the nature of observations required to capture the dynamics of this region. Observations such as those we report here demonstrate the potential of studying of this region for space weather forecasts, particularly of CMEs, and more generally reveal how this region plays an important role in determining and modulating both the structure and dynamics of the corona as a whole. We report on the results of this campaign and discuss the implications for upcoming and proposed space missions and ground-based instruments that will observe this region as well as the potential for breakthrough science via coordinated campaigns with Parker Solar Probe. Title: An Evolving Solar Data Environment Authors: Hurlburt, Neal; Freeland, Sam; Timmons, Ryan Bibcode: 2019ASPC..521..687H Altcode: 2018arXiv180611210H The rapid growth of solar data is driving changes in the typical workflow and algorithmic approach to solar data analysis. We present recently deployed tools to aid this evolution and layout the path for future development. The majority of space-based datasets including those from the multi-petabyte Solar Dynamics Observatory and the Hinode and Interface Region Imaging Spectrograph (IRIS) missions are made available to the community through a common API with support in IDL (via SolarSoft), Python/SunPy and other emerging languages. Stellar astronomers may find the IRIS data particularly useful for research into stellar chromospheres and for interpreting UV spectra. Title: Capturing CMEs in SUVI-ECI data Authors: Hurlburt, Neal E. Bibcode: 2019AAS...23411103H Altcode: The SUVI instrument on GOES-17 (now GOES-West) spent a month between August and September, 2018 conducting an extended coronal imaging campaign. Composite images constructed from interleaved image sets that scanned ±4 solar radii across the Sun every 6 minutes were processed to create a consistent dataset for analysis. An optical flow method (opflow3d) was applied to this set to estimate velocities of moving features. The results were then compared to CMEs detected by the CACTUS algorithm operating on co-temporal LASCO images. While the peak speeds reported by opflow3d were significantly lower than the CMEs found further out in the corona by CACTUS, the time intervals of enhanced motions correlate well between the two sets. Here we present the data and discuss the processing, analysis and future work. A new set of observations are scheduled to begin in mid-April. If they begin on time we may report on those results too. Title: Chapter 13 - Solar Data and Simulations Authors: Hurlburt, Neal Bibcode: 2019sgsp.book..443H Altcode: Data collected from instruments observing the Sun and simulations of solar phenomenon have historically been difficult to connect owing to the richness of the observations. Here we review the progress that has been made in bringing them together. We begin by reviewing the life cycle of solar data, from the initial collection, calibration, and processing through the discovery and retrieval of archival data, recent applications of modern statistical and machine learning methods. We then review the evolution of numerical simulations from idealized investigations that could only give general guidance on interpreting solar data to high-resolution simulations that are hard to distinguish from reality. Here we focus on simulations that attempt to capture the essential (magneto-)hydrodynamics of solar phenomena from first principles rather than models based on more heuristic assumptions. With that constraint, the range of simulations is still broad, so we have concentrated on those addressing observations of the Sun and corona while neglecting those focused on stellar evolution and the solar cycle or focused on the solar wind and heliospheric dynamics. Title: Convection-driven Generation of Ubiquitous Coronal Waves Authors: Aschwanden, Markus J.; Gošic, Milan; Hurlburt, Neal E.; Scullion, Eamon Bibcode: 2018ApJ...866...73A Altcode: We develop a new method to measure the 3D kinematics of the subphotospheric motion of magnetic elements, which is used to study the coupling between the convection-driven vortex motion and the generation of ubiquitous coronal waves. We use the method of decomposing a line-of-sight magnetogram from MDI/SDO into unipolar magnetic charges, which yields the (projected) 2D motion [x(t), y(t)] and the (half) width evolution w(t) of an emerging magnetic element from an initial depth of d ≲ 1500 km below the photosphere. A simple model of rotational vortex motion with magnetic flux conservation during the emergence process of a magnetic element predicts the width evolution, i.e., w(t)/w 0 = [B(t)/B 0]-1/2, and an upper limit of the depth variation d(t) ≤ 1.3 w(t). While previous 2D tracing of magnetic elements provided information on advection and superdiffusion, our 3D tracing during the emergence process of a magnetic element is consistent with a ballistic trajectory in the upward direction. From the estimated Poynting flux and lifetimes of convective cells, we conclude that the Coronal Multi-channel Polarimeter-detected low-amplitude transverse magnetohydrodynamic waves are generated by the convection-driven vortex motion. Our observational measurements of magnetic elements appear to contradict the theoretical random-walk braiding scenario of Parker. Title: Imaging the high corona in EUV: More Extended Corona Observations by SUVI Authors: Hurlburt, Neal; Seaton, Dan; Shing, Lawrence; Slater, Greg; Shaw, Margaret; Seguin, Ralph; Minor, Robin; Nwachuku, Calvin Bibcode: 2018shin.confE...2H Altcode: Direct imaging of the solar corona well beyond the fields of views of existing EUV instruments has recently been demonstrated by SDO/AIA and Proba/SWAP off-pointings. They demonstrate that there is a measurable signal out to almost 2.5 Rsun. These encouraging results inspired the SUVI team to investigate even wider fields of view, to over 4 Rsun. The Lockheed Martin SUVI team in conjunction with NOAA and NASA collected data using the SUVI instrument on GOES-16 and -17 at different pointings to assess the feasibility of directly imaging the outer corona. This was initially done twice during the week of February 12, 2018, with two programs involving different patterns and exposures. Significant signal was found in the longer exposures out to the edge of the extended FOV, even though the Sun and its corona were in quiet states at the time. This initial study informed a series of more extensive and higher-performing sequences that are being carried out with the SUVI instrument on the GOES-17 satellite. Here we present results from these various experiments and discuss how such observations may fit in to future space weather missions. Title: The Heliophysics Coverage Registry: An integrated metadata system for coordinated, multi-mission solar observatories Authors: Hurlburt, Neal; Timmons, Ryan; Seguin, Ralph Bibcode: 2018arXiv180611207H Altcode: Modern studies of the Sun involve coordinated observations collected from a collage of instruments on the ground and in orbit. Each instrument has its own constraints, such as field of view, duty cycle, and scheduling and commanding windows, that must both be coordinated during operations and be discoverable for analyses of the resulting data. Details on the observed solar features, i.e. sunspots or filaments, and solar events, i.e. flares or coronal mass ejections, are also incorporated to help guide data discovery and data analysis pipelines. The Heliophysics Coverage Registry (HCR) provides a standards-based system for collecting and presenting observations collected by distributed, ground and space based solar observatories which form an integrated Heliophysics system. The HCR currently supports all instruments on the Interface Region Imaging Spectrograph (IRIS) and Hinode missions as well as associated ground-based observatories. Here we present an overview of the HCR along with details on how it provides scientists with tools to make flexible searches on observation metadata in coordination with searches of solar features and events. Title: Possible Scenario to Effectively Improve Space Weather Predictions from Space-based Observations Authors: Nitta, Nariaki; Hurlburt, Neal E.; Jin, Meng Bibcode: 2018tess.conf41605N Altcode: We discuss how distributed remote-sensing and in situ observations from space will alleviate the two factors below that pose severe limitations on today's space weather forecasting capability. First, we only have incomplete knowledge of the photospheric magnetic field that has been used for computing the coronal magnetic field. This impacts the capability of accurately modeling solar wind, which then makes it hard to know how and when interplanetary coronal mass ejections (ICMEs) affect the geo-space. A number of efforts have been made to correct the polar field measurements, but we may not know its properties unless we directly and routinely measure it clear of foreshortening. EUV and microwave images suggest that the polar regions may be more dynamic than usually assumed. At present we still need to wait for the technology to mature that facilitates high-inclination heliocentric orbits, but eventually we should place several small satellites with a compact magnetograph in such orbits to constantly observe both poles. Second, we have only limited understanding of the solar wind structures at 1 AU that directly cause geomagnetic disturbances. After the arrival of the shock wave from a CME that occurred typically 2-3 days earlier, we cannot predict how the solar wind will evolve during the next day or two. This is because we characterize the solar wind structures on the basis of single measurements, i.e. at L1. Multiple cubesats or small satellites in sub-L1 orbits (covering ranges of distance from the Sun and angle from the Sun-Earth line) will not only improve our nowcasting capability but also advance our understanding of the structure of the ICME and its interaction with solar wind, as shown in examples of state-of-the-arts numerical simulations such as the University of Michigan Alfven Wave Solar Model (AWSoM). This sub-L1 concept may be easily executed even now, and it should represent an important first step toward larger constellations that include a polar mission. Title: Ten years of data discovery using the Heliophysics Coverage Registry Authors: Hurlburt, Neal E.; Timmons, Ryan; Seguin, Ralph Bibcode: 2018tess.conf32002H Altcode: Modern studies of the Sun increasingly involve coordinated observations collected from a collage of instruments on the ground and in orbit. Each instrument has its own constraints, such as field of view, duty cycle, and scheduling and commanding windows that must both be coordinated during operations and be discoverable for analyses of the resulting data. To enable fruitful searches for archival studies, details on solar features, i.e. sunspots or filaments, and solar events, i.e. flares or coronal mass ejections, captured during observations must also available to guide data discovery and automated data analysis pipelines. The Heliophysics Coverage Registry (HCR) provides a standards-based system for collecting and presenting observations collected by distributed, ground and space based solar observatories as part of the integrated Heliophysics Events Knowledgebase (HEK). We present an overview of the HCR and HEK; examples on how it enables flexible searches on observation metadata in coordination with searches of solar features and events; and a statistical analysis of ten years of usage.

The HCR currently supports all instruments on the Interface Region Imaging Spectrograph (IRIS) and Hinode missions as well as associated ground-based observatories. The HCR and its concepts is extensible and we continue supporting new missions as the opportunity arises. Events from external missions are already supported and new ones can be added by creating or exchanged as HCR-compliant VOEvents. Title: First look at the far corona in EUV: SUVI Extended Corona Observations Authors: Hurlburt, Neal E.; Seaton, Daniel B.; Shing, Lawrence; Slater, Gregory L.; Shaw, Margaret; Seguin, Ralph Bibcode: 2018tess.conf40135H Altcode: Our ability to directly image the solar corona well beyond the fields of views of existing EUV instruments has recently been demonstrated by SDO/AIA and Proba/SWAP off-pointings. They demonstrate that there is a measurable signal out to almost 2.5 Rsun. These encouraging results inspired the SUVI team to investigate even wider fields of view, to over 4 Rsun. The Lockheed Martin SUVI team in conjunction with NOAA and NASA collected data using the SUVI instrument on GOES-16 at six different pointings over approximately one hour to assess the feasibility of direct imaging the outer corona. This was done twice during the week of February 12, 2018, with two programs involving different patterns and exposures. A preliminary analysis shows that there is signal in the longer exposures out to the edge of the extended FOV, even though the Sun and its corona were in quiet states at the time. Title: A simplfied MHD model of solar surface flows Authors: Hurlburt, Neal E. Bibcode: 2017SPD....48.0502H Altcode: Recent work on modeling solar photospheric flows has replaced those based on random-walks with kinematic models based upon observed convective properties. These models have successfully reproduced many aspects of the solar cycle. Here we present a dynamic model of surface flows based upon simplified MHD driven by supergranular-scale sources, along with global-scale differential rotation and meridonal flow. This approach can be used to investigate a variety of stellar and could supplant random walk methods in projecting solar fields outside the visible range of current magnetographs. The resulting self-consistent solutions are compared against observations and other models. Title: Timing signatures of solar flares Authors: Balasubramaniam, K. S.; Lynch, C.; Henry, T.; Nitta, N.; Hurlburt, N. E.; Slater, G. L. Bibcode: 2016AGUFMSH43E..02B Altcode: We compare the timing signatures of solar flares observed with the GOES X-ray and the SDO/AIA instruments between the years 2010-2015. From this comparison we find that: (i) the rise-time of flares (time difference from the background to peak) is inversely correlated with the solar cycle, i.e. longer lasting rise times occur during the solar minimum. This implies that a higher thermal state of the outer solar atmosphere, during solar maximum, is far more receptive to being heated than during a solar minimum. (ii) From an analysis of rise-times, statistically, we find that 171 A appears to detect the earliest flares, providing clues to fact that this might be layer where reconnections are first triggered. We discuss the implications of these and other statistical results in terms of forecasting of solar flares. Title: Statistics of eruptions characterized by automated spatiotemporal analysis of SDO/AIA images Authors: Hurlburt, N. E. Bibcode: 2016AGUFMSH34A..06H Altcode: Automatic identification of eruptions near the solar surface (either from filaments or otherwise) has recently been integrated into the Heliophysics Events Knowledgebase (HEK). Here we present a survey of eruptions identified by the EruptionCharacterize module run over six years of SDO/AIA images. Over twenty-thousand distinct eruptions were identified with velocities ranging from 4-120km/sec, sizes from 20 to 1,000Mm and durations from 2 to 180 minutes. The relationships between these eruptions and other features and events available in the HEK are investigated. Title: Coordinated Solar Observation and Event Searches using the Heliophysics Events Knowledgebase (HEK) Authors: Timmons, Ryan; Hurlburt, Neal E.; De Pontieu, Bart Bibcode: 2016SPD....4730903T Altcode: We present capabilities of the HEK for joint searches, returning overlapping data from multiple instruments (IRIS, Hinode) that also include particular solar features and events (active regions, (large) flares, sunspots, etc.). The new search tools aid the process of finding observations of particular interest from non-synoptic instruments. They also include new data products: processed cutout cubes of SOT-FG and AIA data co-aligned with IRIS. Title: Statistical analysis of eruptions detected and characterized by spatiotemporal data mining of SDO/AIA images Authors: Hurlburt, Neal E. Bibcode: 2016SPD....47.0303H Altcode: Identifying and characterizing motions near the solar surface are essential to advance our understanding the drivers of space weather. A method for automatically identifying eruptions near the solar surface (either from filaments or otherwise) has recently been developed and integrated into the Heliophysics Events Knowledgebase. Here we present a survey of eruptions identified by the EruptionPatrol and EruptionCharacterize modules run over six years of SDO/AIA 30.4 nm images. Over twenty-thousand distinct eruptions were identified with velocities ranging from 4-120km/sec, sizes from 20 to 1,000Mm and durations from 2 to 180 minutes. Title: A spectral optical flow method for determining velocities from digital imagery Authors: Hurlburt, Neal; Jaffey, Steve Bibcode: 2015ESInf...4..959H Altcode: 2015arXiv150404660H We present a method for determining surface flows from solar images based upon optical flow techniques. We apply the method to sets of images obtained by a variety of solar imagers to assess its performance. The opflow3d procedure is shown to extract accurate velocity estimates when provided perfect test data and quickly generates results consistent with completely distinct methods when applied on global scales. We also validate it in detail by comparing it to an established method when applied to high-resolution datasets and find that it provides comparable results without the need to tune, filter or otherwise preprocess the images before its application. Title: Automated detection of solar eruptions Authors: Hurlburt, N. Bibcode: 2015JSWSC...5A..39H Altcode: 2015arXiv150403395H Observation of the solar atmosphere reveals a wide range of motions, from small scale jets and spicules to global-scale coronal mass ejections (CMEs). Identifying and characterizing these motions are essential to advancing our understanding of the drivers of space weather. Both automated and visual identifications are currently used in identifying Coronal Mass Ejections. To date, eruptions near the solar surface, which may be precursors to CMEs, have been identified primarily by visual inspection. Here we report on Eruption Patrol (EP): a software module that is designed to automatically identify eruptions from data collected by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (SDO/AIA). We describe the method underlying the module and compare its results to previous identifications found in the Heliophysics Event Knowledgebase. EP identifies eruptions events that are consistent with those found by human annotations, but in a significantly more consistent and quantitative manner. Eruptions are found to be distributed within 15 Mm of the solar surface. They possess peak speeds ranging from 4 to 100 km/s and display a power-law probability distribution over that range. These characteristics are consistent with previous observations of prominences. Title: Internetwork Chromospheric Bright Grains Observed With IRIS and SST Authors: Martínez-Sykora, Juan; Rouppe van der Voort, Luc; Carlsson, Mats; De Pontieu, Bart; Pereira, Tiago M. D.; Boerner, Paul; Hurlburt, Neal; Kleint, Lucia; Lemen, James; Tarbell, Ted D.; Title, Alan; Wuelser, Jean-Pierre; Hansteen, Viggo H.; Golub, Leon; McKillop, Sean; Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Jaeggli, Sarah; Kankelborg, Charles Bibcode: 2015ApJ...803...44M Altcode: 2015arXiv150203490M The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen with the IRIS 1330, 1400, and 2796 Å slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1 m Solar Telescope (SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H 3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å, Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps in Fe i 6302 Å at high spatial (0\buildrel{\prime\prime}\over{.} 33), temporal, and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a non-magnetic environment. We compare slit-jaw images (SJIs) with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 Å slit-jaw filter comes from both the Mg ii k core and wings. The signal in the C ii and Si iv lines is too weak to explain the presence of grains in the 1300 and 1400 Å SJIs and we conclude that the grain signal in these passbands comes mostly from the continuum. Although weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C ii spectra. For some grains, a spectral signature can be found in IRIS Si iv. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region. Title: Characterization of Solar Eruptions reported by EruptionPatrol Authors: Hurlburt, Neal Bibcode: 2015TESS....131104H Altcode: Observation of the solar atmosphere reveals a wide range of real and apparent motions, from small scale jets and spicules to global-scale coronal mass ejections. Identifying and characterizing these motions are essential to advance our understanding the drivers of space weather. A method for automatically identifying eruptions near the solar surface (either from filaments or otherwise) has recently been developed and integrated into the Heliophysics Events Knowledgebase. Here we report on the EruptionPatrol module for identifying eruptions in data collected by the SDO/AIA instrument and on the characterization and analysis of its output. A cluster analysis on the time periods reported by EruptionPatrol demarcates several large-scale events spanning significant portions of the solar disk with lifetimes of up to six hours. Title: Homologous Helical Jets: Observations By IRIS, SDO, and Hinode and Magnetic Modeling With Data-Driven Simulations Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.; Tian, H.; Testa, P.; Reeves, K. K.; Martínez-Sykora, J.; Boerner, P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.; Carlsson, M.; Hansteen, V. Bibcode: 2015ApJ...801...83C Altcode: 2015arXiv150101593C We report on observations of recurrent jets by instruments on board the Interface Region Imaging Spectrograph, Solar Dynamics Observatory (SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21, recurrent coronal jets were observed to emanate from NOAA Active Region 11793. Far-ultraviolet spectra probing plasma at transition region temperatures show evidence of oppositely directed flows with components reaching Doppler velocities of ±100 km s-1. Raster Doppler maps using a Si iv transition region line show all four jets to have helical motion of the same sense. Simultaneous observations of the region by SDO and Hinode show that the jets emanate from a source region comprising a pore embedded in the interior of a supergranule. The parasitic pore has opposite polarity flux compared to the surrounding network field. This leads to a spine-fan magnetic topology in the coronal field that is amenable to jet formation. Time-dependent data-driven simulations are used to investigate the underlying drivers for the jets. These numerical experiments show that the emergence of current-carrying magnetic field in the vicinity of the pore supplies the magnetic twist needed for recurrent helical jet formation. Title: An Analysis of Eruptions Detected by the LMSAL Eruption Patrol Authors: Hurlburt, N. E.; Higgins, P. A.; Jaffey, S. Bibcode: 2014AGUFMSH21A4088H Altcode: Observations of the solar atmosphere reveals a wide range of real and apparent motions, from small scale jets and spicules to global-scale coronal mass ejections. Identifying and characterizing these motions are essential to advance our understanding the drivers of space weather. Automated and visual identifications are used in identifying CMEs. To date, the precursors to these — eruptions near the solar surface — have been identified primarily by visual inspection. Here we report on an analysis of the eruptions detected by the Eruption Patrol, a data mining module designed to automatically identify eruptions from data collected by Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA). We describe the module and use it both to explore relations with other solar events recorded in the Heliophysics Event Knowledgebase and to identify and access data collected by the Interface Region Imaging Spectrograph (IRIS) and Solar Optical Telescope (SOT) on Hinode for further analysis. Title: Hot explosions in the cool atmosphere of the Sun Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.; De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V. Bibcode: 2014Sci...346C.315P Altcode: 2014arXiv1410.5842P The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection. Title: The unresolved fine structure resolved: IRIS observations of the solar transition region Authors: Hansteen, V.; De Pontieu, B.; Carlsson, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Pereira, T. M. D.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.; Martínez-Sykora, J. Bibcode: 2014Sci...346E.315H Altcode: 2014arXiv1412.3611H The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle. Title: Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale, F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli, S. Bibcode: 2014Sci...346B.315T Altcode: 2014arXiv1410.6130T The physical processes causing energy exchange between the Sun’s hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds) of intensity and velocity on small spatial scales (≲500 kilometers) at the footpoints of hot and dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of nonthermal electrons, which are generated in small impulsive (≲30 seconds) heating events called “coronal nanoflares.” The accelerated electrons deposit a sizable fraction of their energy (≲1025 erg) in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona. Title: Prevalence of small-scale jets from the networks of the solar transition region and chromosphere Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.; Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves, K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber, M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W. Bibcode: 2014Sci...346A.315T Altcode: 2014arXiv1410.6143T As the interface between the Sun’s photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~105 kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind. Title: On the prevalence of small-scale twist in the solar chromosphere and transition region Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.; Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.; Martinez-Sykora, J. Bibcode: 2014Sci...346D.315D Altcode: 2014arXiv1410.6862D The solar chromosphere and transition region (TR) form an interface between the Sun’s surface and its hot outer atmosphere. There, most of the nonthermal energy that powers the solar atmosphere is transformed into heat, although the detailed mechanism remains elusive. High-resolution (0.33-arc second) observations with NASA’s Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere and TR that are replete with twist or torsional motions on sub-arc second scales, occurring in active regions, quiet Sun regions, and coronal holes alike. We coordinated observations with the Swedish 1-meter Solar Telescope (SST) to quantify these twisting motions and their association with rapid heating to at least TR temperatures. This view of the interface region provides insight into what heats the low solar atmosphere. Title: An Interface Region Imaging Spectrograph First View on Solar Spicules Authors: Pereira, T. M. D.; De Pontieu, B.; Carlsson, M.; Hansteen, V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Tian, H.; Jaeggli, S.; Kankelborg, C. Bibcode: 2014ApJ...792L..15P Altcode: 2014arXiv1407.6360P Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere remains unknown. Here we give a first glimpse of what quiet-Sun spicules look like when observed with NASA's recently launched Interface Region Imaging Spectrograph (IRIS). Using IRIS spectra and filtergrams that sample the chromosphere and transition region, we compare the properties and evolution of spicules as observed in a coordinated campaign with Hinode and the Atmospheric Imaging Assembly. Our IRIS observations allow us to follow the thermal evolution of type II spicules and finally confirm that the fading of Ca II H spicules appears to be caused by rapid heating to higher temperatures. The IRIS spicules do not fade but continue evolving, reaching higher and falling back down after 500-800 s. Ca II H type II spicules are thus the initial stages of violent and hotter events that mostly remain invisible in Ca II H filtergrams. These events have very different properties from type I spicules, which show lower velocities and no fading from chromospheric passbands. The IRIS spectra of spicules show the same signature as their proposed disk counterparts, reinforcing earlier work. Spectroheliograms from spectral rasters also confirm that quiet-Sun spicules originate in bushes from the magnetic network. Our results suggest that type II spicules are indeed the site of vigorous heating (to at least transition region temperatures) along extensive parts of the upward moving spicular plasma. Title: The Interface Region Imaging Spectrograph (IRIS) Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.; Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou, C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman, C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish, D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.; Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons, R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.; Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.; Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.; Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski, W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.; Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.; Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.; Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson, M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu, K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora, J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.; Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N. Bibcode: 2014SoPh..289.2733D Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 - 0.4 arcsec spatial resolution, two-second temporal resolution, and 1 km s−1 velocity resolution over a field-of-view of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å, 1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw images in four different passbands (C II 1330, Si IV 1400, Mg II k 2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiative-MHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation. Title: Detection of Supersonic Downflows and Associated Heating Events in the Transition Region above Sunspots Authors: Kleint, L.; Antolin, P.; Tian, H.; Judge, P.; Testa, P.; De Pontieu, B.; Martínez-Sykora, J.; Reeves, K. K.; Wuelser, J. P.; McKillop, S.; Saar, S.; Carlsson, M.; Boerner, P.; Hurlburt, N.; Lemen, J.; Tarbell, T. D.; Title, A.; Golub, L.; Hansteen, V.; Jaeggli, S.; Kankelborg, C. Bibcode: 2014ApJ...789L..42K Altcode: 2014arXiv1406.6816K Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0.''33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km s-1 and weaker, slightly slower upflows in the spectral lines Mg II h and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated with brightenings in the slitjaw images (SJIs). The bursty behavior lasts throughout the 2 hr observation, with average burst durations of about 20 s. The locations of these short-lived events appear to be the umbral and penumbral footpoints of EUV loops. Fast apparent downflows are observed along these loops in the SJIs and in the Atmospheric Imaging Assembly, suggesting that the loops are thermally unstable. We interpret the observations as cool material falling from coronal heights, and especially coronal rain produced along the thermally unstable loops, which leads to an increase of intensity at the loop footpoints, probably indicating an increase of density and temperature in the TR. The rain speeds are on the higher end of previously reported speeds for this phenomenon, and possibly higher than the free-fall velocity along the loops. On other observing days, similar bright dots are sometimes aligned into ribbons, resembling small flare ribbons. These observations provide a first insight into small-scale heating events in sunspots in the TR. Title: Coordinated IRIS science using the Heliophysics Event Knowledgebase Authors: Hurlburt, Neal E.; Freeland, Sam; Timmons, Ryan; De Pontieu, Bart Bibcode: 2014AAS...22431301H Altcode: We have recently enhanced the capabilities of the Heliophysics Event Knowledgebase (HEK) to support the complex datasets being produced by the Interface Region Imaging Spectrograph (IRIS). This includes tools to incorporate observations from the Solar Dynamics Observatory and ground-based facilities to generate composite data products. We will discuss the system and its recent evolution and demonstrate its ability to support coordinated science investigations. Title: High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph Authors: Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu, B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.; Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kankelborg, C.; Jaeggli, S.; McIntosh, S. W. Bibcode: 2014ApJ...786..137T Altcode: 2014arXiv1404.6291T We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ~30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ~10 km s-1 in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and ~12 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves. Title: Data integration and analysis using the Heliophysics Event Knowledgebase Authors: Hurlburt, Neal; Reardon, Kevin Bibcode: 2014cosp...40E1250H Altcode: The Heliophysics Event Knowledgebase (HEK) system provides an integrated framework for automated data mining using a variety of feature-detection methods; high-performance data systems to cope with over 1TB/day of multi-mission data; and web services and clients for searching the resulting metadata, reviewing results, and efficiently accessing the data products. We have recently enhanced the capabilities of the HEK to support the complex datasets being produced by the Interface Region Imaging Spectrograph (IRIS). We are also developing the mechanisms to incorporate descriptions of coordinated observations from ground-based facilities, including the NSO's Dunn Solar Telescope (DST). We will discuss the system and its recent evolution and demonstrate its ability to support coordinated science investigations. Title: Dependence of solar plasma flows on magnetic field obliquity Authors: Zita, E. J.; Smith, C.; Hurlburt, N. E. Bibcode: 2013arXiv1309.4468Z Altcode: Interactions between flows and magnetic fields in the Sun's plasma can change surface waves and flows near active regions, are evident in cyclic changes of large-scale phenomena such as the meridional circulation, and contribute to dynamics in the long-term solar magnetic cycle, e.g. during the recent prolonged solar minimum. We investigate possible relationships between these phenomena. We have observed changes in solar surface flow patterns in active regions, dependent on magnetic field strength and orientation, consistent with the theoretically predicted Proctor Effect. Other researchers have observed relationships between changes in solar magnetic fields and meridional circulation flows. We explore similarities between the Proctor Effect and the observed interdependence of larger-scale magnetic fields and flows. This may contribute to understanding of fundamental solar convection and dynamo processes, e.g. the prolonged magnetic minimum of the most recent cycle. Title: Illusions in solar photosphere Authors: Hurlburt, Neal E.; Cheung, M. Bibcode: 2013SPD....4440306H Altcode: An array of methods have been developed over the past few decades aimed at inferring the surface motion in the solar photosphere. These methods are generally based on tracking the apparent motion of features seen in the data which are, for the most part, manifestations of the thermal or magnetic structuring generated by solar magnetoconvection. Patterns formed by nonlinear magnetoconvection are known change dramatically depending on the configuration and strength of the magnetic field. These changes should be taken into account in assessing the performance of any flow-tracking method. Here we assess one method using high-fidelity numerical models of the magnetoconvection in the presence of a large-scale region of emerging flux. We compare the flow structure derived from the opflow3d method against the surface velocities contained within the simulation and investigate systematic errors introduced by local variations in field strength and inclination. Title: Formation of magnetic flux tubes in cylindrical wedge geometry Authors: Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. Bibcode: 2012GApFD.106..701B Altcode: Three-dimensional (3D) MHD numerical simulations have not been able to demonstrate convincingly the spontaneous formation of large vertical flux tubes. Two-dimensional (2D) magnetoconvection in axisymmetric cylinders forms a central magnetic flux tube surrounded by annular convection rings. To study the robustness of this type of solution in three dimensions, the nonlinear resistive MHD equations are solved numerically in a 3D cylindrical wedge from an initially uniform vertical magnetic field. It is shown that the 2D result is retrieved for small domain radii. However, for larger radii the central axis loses its importance and in this case many convection cells form in the numerical domain. Magnetic flux is captured between cells where flow converges and the reduced amount of flux that congregates at the central axis is eroded by the surrounding convection. Title: Effects of Granulation upon Larger-Scale Convection Authors: Hurlburt, N. E.; DeRosa, M. L.; Augustson, K. C.; Toomre, J. Bibcode: 2012ASPC..454...13H Altcode: 2012arXiv1201.4809H We examine the role of small-scale granulation in helping to drive supergranulation and even larger scales of convection. The granulation is modeled as localized cooling events introduced at the upper boundary of a 3-D simulation of compressible convection in a rotating spherical shell segment. With a sufficient number of stochastic cooling events compared to uniform cooling, we find that supergranular scales are realized, along with a differential rotation that becomes increasingly solar-like. Title: Simulations of Buoyant Plumes in Solar Prominences Authors: Hurlburt, N.; Berger, T. Bibcode: 2012ASPC..454..137H Altcode: 2012arXiv1201.4352H Observations of solar prominences reveal a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long "threads" and dark "bubbles" that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. We present results of various configurations and discuss the nonlinear behavior of the resulting dynamics. Title: Enabling systematic Heliophysics research with the Heliophysics Events Knowledgebase Authors: Hurlburt, Neal E. Bibcode: 2012AAS...22032304H Altcode: Understanding the heliophysical systems involved in space weather requires tools for conducting surveys of data and metadata to discern trends, correlations and causation. Virtual Observatories, data systems using web services and event-based systems such as the Heliophysics Events Knowledgebase (HEK) and Heliophysics Integrated Observatory (HELIO), makes it possible to carryout integrated studies that span the full range of Heliophysics. I present recent developments of the HEK that aid such studies and discuss future plans. Title: Interdependence of Solar Plasma Flows and Magnetic Fields Authors: Zita, E. J.; Smith, C.; Hurlburt, N. Bibcode: 2012AAS...22020209Z Altcode: Interactions between flows and magnetic fields in the Sun’s plasma can affect surface phenomena such as sunspots, can reveal deeper magnetic connections via changes in solar flows and oscillations, and drive dynamics in the long-term solar magnetic cycle, e.g. the recent “weird solar minimum.”

We have observed changes in solar surface flow patterns consistent with the Proctor effect, which depends on magnetic field strength / orientation in active regions. Other investigators have observed relationships between solar torsional oscillations and mean field strengths. Zonal flow velocities correlate roughly with field strengths, and may serve as diagnostics or predictors of solar cycles. We explore a possible relationship between the Proctor effect and the magnetic interdependence of zonal flows. Our study potentially deepens understanding of fundamental solar magnetic dynamics underlying convection and dynamo processes.

This work was supported by NSF grant 0807651, NASA grants NAS5-38099, NNM07AA01C, NNG04EA00C, and Lockheed Martin Internal Research Funds. Title: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) Authors: Lemen, James R.; Title, Alan M.; Akin, David J.; Boerner, Paul F.; Chou, Catherine; Drake, Jerry F.; Duncan, Dexter W.; Edwards, Christopher G.; Friedlaender, Frank M.; Heyman, Gary F.; Hurlburt, Neal E.; Katz, Noah L.; Kushner, Gary D.; Levay, Michael; Lindgren, Russell W.; Mathur, Dnyanesh P.; McFeaters, Edward L.; Mitchell, Sarah; Rehse, Roger A.; Schrijver, Carolus J.; Springer, Larry A.; Stern, Robert A.; Tarbell, Theodore D.; Wuelser, Jean-Pierre; Wolfson, C. Jacob; Yanari, Carl; Bookbinder, Jay A.; Cheimets, Peter N.; Caldwell, David; Deluca, Edward E.; Gates, Richard; Golub, Leon; Park, Sang; Podgorski, William A.; Bush, Rock I.; Scherrer, Philip H.; Gummin, Mark A.; Smith, Peter; Auker, Gary; Jerram, Paul; Pool, Peter; Soufli, Regina; Windt, David L.; Beardsley, Sarah; Clapp, Matthew; Lang, James; Waltham, Nicholas Bibcode: 2012SoPh..275...17L Altcode: 2011SoPh..tmp..106L; 2011SoPh..tmp..172L; 2011SoPh..tmp..241L; 2011SoPh..tmp..115L The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous high-resolution full-disk images of the corona and transition region up to 0.5 R above the solar limb with 1.5-arcsec spatial resolution and 12-second temporal resolution. The AIA consists of four telescopes that employ normal-incidence, multilayer-coated optics to provide narrow-band imaging of seven extreme ultraviolet (EUV) band passes centered on specific lines: Fe XVIII (94 Å), Fe XVII, XXI (131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211 Å), He II (304 Å), and Fe XVI (335 Å). One telescope observes C IV (near 1600 Å) and the nearby continuum (1700 Å) and has a filter that observes in the visible to enable coalignment with images from other telescopes. The temperature diagnostics of the EUV emissions cover the range from 6×104 K to 2×107 K. The AIA was launched as a part of NASA's Solar Dynamics Observatory (SDO) mission on 11 February 2010. AIA will advance our understanding of the mechanisms of solar variability and of how the Sun's energy is stored and released into the heliosphere and geospace. Title: Heliophysics Event Knowledgebase for the Solar Dynamics Observatory (SDO) and Beyond Authors: Hurlburt, N.; Cheung, M.; Schrijver, C.; Chang, L.; Freeland, S.; Green, S.; Heck, C.; Jaffey, A.; Kobashi, A.; Schiff, D.; Serafin, J.; Seguin, R.; Slater, G.; Somani, A.; Timmons, R. Bibcode: 2012SoPh..275...67H Altcode: 2010arXiv1008.1291H The immense volume of data generated by the suite of instruments on the Solar Dynamics Observatory (SDO) requires new tools for efficient identifying and accessing data that is most relevant for research. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The HEK system combines automated data mining using feature-detection methods and high-performance visualization systems for data markup. In addition, web services and clients are provided for searching the resulting metadata, reviewing results, and efficiently accessing the data. We review these components and present examples of their use with SDO data. Title: Magnetohydrodynamic simulations of flows around rotating and non-rotating axisymmetric magnetic flux concentrations Authors: Hartlep, T.; Busse, F. H.; Hurlburt, N. E.; Kosovichev, A. G. Bibcode: 2012MNRAS.419.2325H Altcode: 2011MNRAS.tmp.1880H We present results on modelling magnetic flux tubes in an unstably stratified medium and the flows around them using 2D axisymmetric magnetohydrodynamic (MHD) simulations. The study is motivated by the formation of magnetic field concentrations at the solar surface in sunspots and magnetic pores and the large-scale flow patterns associated with them. The simulations provide consistent, self-maintained models of concentrated magnetic field in a convective environment, although they are not fully realistic or directly applicable to the solar case. In this paper, we explore under which conditions the associated flows near the surface are converging (towards the spot centre) or diverging (away from the axis) in nature. It is found that, depending on the parameters of the problem, the results can depend on the initial conditions, in particular for zero or low rotation rates and Prandtl numbers smaller than unity. The solutions with a converging flow generally produce more strongly confined magnetic flux tubes. Title: Data Discovery and Access via the Heliophysics Events Knowledgebase (HEK) Authors: Somani, A.; Hurlburt, N. E.; Schrijver, C. J.; Cheung, M.; Freeland, S.; Slater, G. L.; Seguin, R.; Timmons, R.; Green, S.; Chang, L.; Kobashi, A.; Jaffey, A. Bibcode: 2011AGUFMSM21A1989S Altcode: The HEK is a integrated system which helps direct scientists to solar events and data from a variety of providers. The system is fully operational and adoption of HEK has been growing since the launch of NASA's SDO mission. In this presentation we describe the different components that comprise HEK. The Heliophysics Events Registry (HER) and Heliophysics Coverage Registry (HCR) form the two major databases behind the system. The HCR allows the user to search on coverage event metadata for a variety of instruments. The HER allows the user to search on annotated event metadata for a variety of instruments. Both the HCR and HER are accessible via a web API which can return search results in machine readable formats (e.g. XML and JSON). A variety of SolarSoft services are also provided to allow users to search the HEK as well as obtain and manipulate data. Other components include - the Event Detection System (EDS) continually runs feature finding algorithms on SDO data to populate the HER with relevant events, - A web form for users to request SDO data cutouts for multiple AIA channels as well as HMI line-of-sight magnetograms, - iSolSearch, which allows a user to browse events in the HER and search for specific events over a specific time interval, all within a graphical web page, - Panorama, which is the software tool used for rapid visualization of large volumes of solar image data in multiple channels/wavelengths. The user can also easily create WYSIWYG movies and launch the Annotator tool to describe events and features. - EVACS, which provides a JOGL powered client for the HER and HCR. EVACS displays the searched for events on a full disk magnetogram of the sun while displaying more detailed information for events. Title: Co-evolution of long-lived coronal structures and photospheric flow fields Authors: Hurlburt, Neal Bibcode: 2011sdmi.confE..57H Altcode: Large-scale flows in the vicinity of filaments, coronal holes and active regions are investigated. We identify sets of each over the year of past year using the Heliophysics Events Knowledgebase (HEK). Surface velocities are extracted from a set of HMI data cubes using a spectral optical flow method that sample the structures disk passage. We then investigate the co-evolution of the flow patterns and coronal structures as seen by AIA. Title: HELIO: The Heliophysics Integrated Observatory Authors: Bentley, R. D.; Csillaghy, A.; Aboudarham, J.; Jacquey, C.; Hapgood, M. A.; Bocchialini, K.; Messerotti, M.; Brooke, J.; Gallagher, P.; Fox, P.; Hurlburt, N.; Roberts, D. A.; Duarte, L. Sanchez Bibcode: 2011AdSpR..47.2235B Altcode: Heliophysics is a new research field that explores the Sun-Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.HELIO, the Heliophysics Integrated Observatory, will facilitate this study by creating an integrated e-Infrastructure that has no equivalent anywhere else. It will be a key component of a worldwide effort to integrate heliophysics data and will coordinate closely with international organizations to exploit synergies with complementary domains.HELIO was proposed under a Research Infrastructure call in the Capacities Programme of the European Commission’s 7th Framework Programme (FP7). The project was selected for negotiation in January 2009; following a successful conclusion to these, the project started on 1 June 2009 and will last for 36 months. Title: SDO Data Access and Analysis using the Heliophysics Events Knowledgebase Authors: Hurlburt, Neal E.; HEK Team; Somani, A. Bibcode: 2011SPD....42.2128H Altcode: 2011BAAS..43S.2128H The immense volume of data generated by the suite of instruments on the Solar Dynamics Observatory (SDO) requires new tools for efficient identifying and accessing data that is most relevant for research. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The solar and spacecraft events captured in the HEK can be searched and downloaded through web services and web clients and used to efficiently access relevant SDO data. We review the HEK system, which combines automated data mining using feature-detection methods and high-performance visualization systems, and discuss recent updates, improvements and future plans. Title: Nonlinear Three-dimensional Magnetoconvection around Magnetic Flux Tubes Authors: Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. Bibcode: 2011ApJ...731..108B Altcode: Magnetic flux in the solar photosphere forms concentrations from small scales, such as flux elements, to large scales, such as sunspots. This paper presents a study of the decay process of large magnetic flux tubes, such as sunspots, on a supergranular scale. Three-dimensional nonlinear resistive magnetohydrodynamic numerical simulations are performed in a cylindrical domain, initialized with axisymmetric solutions that consist of a well-defined central flux tube and an annular convection cell surrounding it. As the nonlinear convection evolves, the annular cell breaks up into many cells in the azimuthal direction, allowing magnetic flux to slip between cells away from the central flux tube (turbulent erosion). This lowers magnetic pressure in the central tube, and convection grows inside the tube, possibly becoming strong enough to push the tube apart. A remnant of the central flux tube persists with nonsymmetric perturbations caused by the convection surrounding it. Secondary flux concentrations form between convection cells away from the central tube. Tube decay is dependent on the convection around the tube. Convection cells forming inside the tube as time-dependent outflows will remove magnetic flux. (This is most pronounced for small tubes.) Flux is added to the tube when flux caught in the surrounding convection is pushed toward it. The tube persists when convection inside the tube is sufficiently suppressed by the remaining magnetic field. All examples of persistent tubes have the same effective magnetic field strength, consistent with the observation that pores and sunspot umbrae all have roughly the same magnetic field strength. Title: The Heliophysics Event Knowledgebase in Action Authors: Hurlburt, Neal E. Bibcode: 2011AAS...21715507H Altcode: 2011BAAS...4315507H The Heliophysics Events Knowledgebase (HEK) system is being developed to help solar and heliospheric researchers locate features and events of interest to their science topics. After 9 months of operations using data from SDO we present an overview of the HEK system In action. Title: The Collaborative Heliophysics Events Knowledgebase Authors: Hurlburt, N. E.; Schuler, D.; Cheung, C. Bibcode: 2010AGUFMIN52A..07H Altcode: The Collaborative Heliophysics Events Knowledgebase (CHEK) leverages and integrates the existing resources developed by HEK for SDO (Hurlburt et al. 2010) to provide a collaborative framework for heliophysics researchers. This framework will enable an environment were researches can not only identify and locate relevant data, but can deploy a social network for sharing and expanding knowledge about heliophysical events. CHEK will expand the HEK and key HEK clients into the heliosphere and geospace, and create a heliophysics social network. We describe our design and goals of the CHEK project and discuss its relation to Citizen Science in the heliosphere. Hurlburt, N et al. 2010, “A Heliophysics Event Knowledgebase for Solar Dynamics Observatory,” Sol Phys., in press Title: SDO Data Access And Analysis Authors: Somani, A.; Hurlburt, N. E.; Schrijver, C. J.; Cheung, C.; Freeland, S. L.; Slater, G. L.; Seguin, R.; Timmons, R.; Green, S.; Chang, L.; Kobashi, A.; Jaffey, A. Bibcode: 2010AGUFMSH23C1870S Altcode: The Heliophysics Event Knowledgebase (HEK), Event Detection System (EDS), iSolSearch, Panorama, Event Viewer and Control Software (EVACS), and a variety of SolarSoft routines all work together to provide a suite of tools to facilitate access and analysis of SDO data. The HEK, which consists of the Heliophysics Event Registry (HER) and the Heliophysics Coverage Registry (HCR), uses XML formats built upon the IVOA VOEvent specification to ingest, store, and search events. Web services and SolarSoft routines are available to make use of these functions. The EDS is one of the sources that provides events for ingest into the HEK. The EDS continuously runs feature finding modules on SDO data. It's a distributed system that allows it to keep up with SDO's data rate. iSolSearch allows the user to browse the events in the HER and search for events given a specific time interval and other constraints. Panorama is the software tool used for rapid visualization of large volumes of solar image data in multiple channels/wavelengths. With the EVACS front-end GUI tool, Panorama allows the user to, in real-time, change channel pixel scaling, weights, alignment, blending and colorization of data. The user can also easily create WYSIWYG movies and launch the Annotator tool to describe events and features the user observes in the data. Panorama can also be used to drive clustered HiperSpace walls using the CGLX toolkit. Panorama harnesses the power of the GPU and OpenGL fragment shaders to enable stunning visualization. EVACS provides a JOGL powered GUI that the user can search both the HER and HCR with. EVACS displays the searched for events on a full disk magnetogram of the sun while displaying more detailed information for events. EVACS can also be used to launch Panorama with a selected set of FITS or PRGB files, as well as control many aspects of Panorama. A host of SolarSoft routines are available to not only access functions of the HEK, but to also access metadata and/or image data from the Joint Science Operations Center (JSOC). Routines are also provided to create cutout images and movies of SDO data. A data order web page is provided to allow a casual user to order cutouts or full disk images. This page will make use of both the SSW cutout service as well as the JSOC cutout service. Title: Guided searches to SDO Data using the Heliophysics Events Knowledgebase (Invited) Authors: Hurlburt, N. E.; Cheung, C.; Schrijver, C. J.; Hek Team Bibcode: 2010AGUFMSH22A..02H Altcode: The immense volume of data generated by the suite of instruments on SDO requires new tools for efficiently identifying and accessing data that are most relevant to research investigations. We have developed a set of tools and web services to fill this need. The central element to these is the Heliophysics Events Knowledgebase (HEK). We present an overview of the HEK and describe how our tools and services can be used to guide you to the most useful data for your research. With guidance from the HEK, you can access data by specifying cutouts, wavelengths, and sampling rates in space and time. It also encourages reuse of the extract data and can suggest datasets that are immediately available that might satisfy your requirements, or pass the information on to the VSO, Helioviewer and other services to search for associated data products. Title: Physics of the weird solar minimum: New observations of the Sun Authors: Zita, E.; Smith, C.; Ballou, C.; Friedman, B.; Showalter, C.; Rex, R.; Hurlburt, N. Bibcode: 2010APS..NWS.H1005Z Altcode: While solar physicists expected more sunspots, flares, and coronal mass ejections by now, the Sun has defied most predictions by persisting in a relatively quiet state for an unusually long time. Can we tell whether this solar minimum is likely to ease in the next decade, or if it may become a Maunder-type minimum? What evidence is there for mechanisms that might explain the observed delayed and low-amplitude magnetic activity? What effects could decreased solar activity have on Earth's climate? Evergreen undergraduates study the Sun with colleagues who built the new Solar Dynamics Observatory (SDO). Students analyzed flow velocities with respect to magnetic field tilts; analyzed waves of UV light in active regions; developed a software suite to enable the public to engage with solar dynamics; and cataloged movies of solar events for public release. We use data from the high-resolution HINODE satellite and from the new full-disk SDO. Zita studied the solar dynamo, and found that resistivity gradients can drive magnetic advection. We summarize our work and the light it may shed on questions such as those above. Title: Solar Plasma Flows and Convection in Oblique Magnetic Fields Authors: Smith, Christina; Zita, E. J.; Hurlburt, Neal Bibcode: 2010APS..NWS.D1005S Altcode: Moving charges in the Sun's plasma create a complex network of magnetic fields. This is at the heart of dynamic solar events, such as active regions, sunspots, and coronal mass ejections. We study magnetoconvection, the motion of magnetized ionized fluids (plasmas), to better understand the Sun. Models of solar magnetoconvection often assume simplified magnetic fields that are either completely vertical or horizontal. Realistic fields, however, are often inclined at oblique angles. We analyze high resolution data from the Solar Optical Telescope on the Hinode spacecraft, and compare velocities with magnetic field inclinations. We then compare results with predictions from a numerical model of nonlinear compressible convection in oblique magnetic fields. Title: Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. I. Turbulent Upflow Plumes Authors: Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine, Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya; Suematsu, Yoshinori; Shimizu, Toshifumi Bibcode: 2010ApJ...716.1288B Altcode: Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) "arches" or "bubbles" that "inflate" from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex "roll-up" of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) "optical flow" code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s-1, which is supersonic for a ~10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s-1. Typical lifetimes range from 300 to 1000 s (~5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km2 s-1 reaching maximum projected areas from 2 to 15 Mm2. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images is negative and ranges from -10% for smaller flows to -50% for larger flows. Passive scalar "cork movies" derived from NAVE measurements show that prominence plasma is entrained by the upflows, helping to counter the ubiquitous downflow streams in the prominence. Plume formation shows no clear temporal periodicity. However, it is common to find "active cavities" beneath prominences that can spawn many upflows in succession before going dormant. The mean flow recurrence time in these active locations is roughly 300-500 s (5-8 minutes). Locations remain active on timescales of tens of minutes up to several hours. Using a column density ratio measurement and reasonable assumptions on plume and prominence geometries, we estimate that the mass density in the dark cavities is at most 20% of the visible prominence density, implying that a single large plume could supply up to 1% of the mass of a typical quiescent prominence. We hypothesize that the plumes are generated from a Rayleigh-Taylor instability taking place on the boundary between the buoyant cavities and the overlying prominence. Characteristics, such as plume size and frequency, may be modulated by the strength and direction of the cavity magnetic field relative to the prominence magnetic field. We conclude that buoyant plumes are a source of quiescent prominence mass as well as a mechanism by which prominence plasma is advected upward, countering constant gravitational drainage. Title: An Introduction to the Heliophysics Event Knowledgebase Authors: Hurlburt, Neal E.; Cheung, M.; Schrijver, C.; Chang, L.; Freeland, S.; Green, S.; Heck, C.; Jaffey, A.; Kobashi, A.; Schiff, D.; Serafin, J.; Seguin, R.; Slater, G.; Somani, A.; Timmons, R. Bibcode: 2010AAS...21640222H Altcode: 2010BAAS...41T.876H The immense volume of data generated by the suite of instruments on SDO requires new tools for efficiently identifying and accessing data that are most relevant to research investigations. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The system developed to support the HEK combines automated datamining using feature detection methods; high-performance visualization systems for data markup; and web-services and clients for searching the resulting metadata, reviewing results and efficient access to the data. We will review these components and present examples of their use with SDO data. Title: Mechanisms of Sunspot Formation Authors: Hurlburt, Neal E. Bibcode: 2010AAS...21621104H Altcode: There has been significant recent progress in observing the fine details of sunspots in the photosphere and in interpreting them through numerical modeling. However the large-scale mechanisms that lead to sunspot formation and provide for long-term stability remains vague. I will review recent efforts aimed at identifying and reproducing these mechanisms in numerical simulations of magnetoconvection around active regions and sunspots. This work has been supported by NASA through contract NNM07AA01C. Title: Modeling the Near-Surface Shear Layer Through Coupled Simulations of Surface and Deep Convection Authors: Augustson, Kyle; Hurlburt, N.; DeRosa, M.; Toomre, J. Bibcode: 2010AAS...21640008A Altcode: 2010BAAS...41..855A We examine the role of small-scale granulation in helping to drive supergranulation and even larger scales of convection. The granulation is modeled as localized plumes with statistics taken from surface convection simulations introduced at the upper boundary of a 3-D simulation of compressible convection in a rotating spherical shell segment. With a sufficient number of stochastic plume events compared to a uniform cooling, we find that supergranular scales are realized, along with a differential rotation that becomes increasingly solar-like. Title: Diverging And Converging Flows Around Sunspot Structures In Axisymmetric Mhd Simulations Authors: Hartlep, Thomas; Busse, F. H.; Kosovichev, A. G.; Hurlburt, N. E. Bibcode: 2010AAS...21640005H Altcode: 2010BAAS...41..855H We present results on modeling solar pores and sunspots using 2D axisymmetric magneto-hydrodynamic (MHD) simulations. These models are helpful for understanding the mechanisms of magnetic field concentration in sunspots, and the large-scale flow patterns associated with them. The simulations provide consistent, self-maintained, even if not fully realistic, models of concentrated magnetic field near the solar surface. We explore under which conditions the associated flows are converging or diverging in nature near the surface. Title: The Heliophysics Event Knowledgebase for the Solar Dynamics Observatory - A User's Perspective Authors: Slater, Gregory L.; Cheung, M.; Hurlburt, N.; Schrijver, C.; Somani, A.; Freeland, S. L.; Timmons, R.; Kobashi, A.; Serafin, J.; Schiff, D.; Seguin, R. Bibcode: 2010AAS...21641505S Altcode: 2010BAAS...41S.825S The recently launched Solar Dynamics Observatory (SDO) will generated over 2 petabytes of imagery in its 5 year mission. The Heliophysics Events Knowledgebase (HEK) system has been developed to continuously build a database of solar features and events contributed by a combination of machine recognition algorithms run on every single image, and human interactive data exploration. Access to this growing database is provided through a set of currently existing tools as well as an open source API. We present an overview of the user interface tools including illustrative examples of their use. Title: Detailed Design of the Heliophysics Event Knowledgebase (HEK) Authors: Somani, Ankur; Seguin, R.; Timmons, R.; Freeland, S.; Hurlburt, N.; Kobashi, A.; Jaffey, A. Bibcode: 2010AAS...21641504S Altcode: 2010BAAS...41R.825S We present the Heliophysics Event Registry (HER) and the Heliophysics Coverage Registry (HCR), which serve as two components of the Heliophysics Event Knowledgebase (HEK). Using standardized XML formats built upon the IVOA VOEvent specification, events can be ingested, stored, and later searched upon. Various web services and SolarSoft routines are available to aid in these functions.

One source of events for the HEK is an automated Event Detection System (EDS) that continuously runs feature finding modules on SDO data. Modules are primarily supplied by the Smithsonian Astrophysical Observatory-led Feature Finding Team. The distributed system will keep up with SDO's data rate and issue space weather alerts in near-real time. Some modules will be run on all data while others are run in response to certain solar phenomena found by other modules in the system.

Panorama is a software tool used for rapid visualization of large volumes of solar image data in multiple channels/wavelengths. With the EVACS front-end GUI tool, Panorama allows the user to, in real-time, change channel pixel scaling, weights, alignment, blending and colorization of the data. The user can also easily create WYSIWYG movies and launch the Annotator tool to describe events and features the user observes in the data. Panorama can also be used to drive clustered HiperSpace walls using the CGLX toolkit.

The Event Viewer and Control Software (EVACS) provides a GUI that the user can search both the HER and HCR with. By specifying a start and end time and selecting the types of events and instruments that are of interest, EVACS will display the events on a full disk image of the sun while displaying more detailed information for the events. As mentioned, the user can also launch Panorama via EVACS. Title: An Introduction to the Heliophysics Event Knowledgebase for SDO Authors: Hurlburt, Neal; Schrijver, Carolus; Cheung, Mark Bibcode: 2010cosp...38.2879H Altcode: 2010cosp.meet.2879H The immense volume of data generated by the suite of instruments on SDO requires new tools for efficient identifying and accessing data that is most relevant to research investigations. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The system developed in support of the HEK combines automated datamining using feature detection methods; high-performance visualization systems for data markup; and web-services and clients for searching the resulting metadata, reviewing results and efficient access to the data. We will review these components and present examples of their use with SDO data. Title: Automated Feature and Event Detection with SDO AIA and HMI Data Authors: Davey, Alisdair; Martens, P. C. H.; Attrill, G. D. R.; Engell, A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar, S. H.; Su, Y.; Testa, P.; Wills-Davey, M.; Savcheva, A.; Bernasconi, P. N.; Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F. .; Cirtain, J. W.; Deforest, C. E.; Angryk, R. A.; de Moortel, I.; Wiegelmann, T.; Georgouli, M. K.; McAteer, R. T. J.; Hurlburt, N.; Timmons, R. Bibcode: 2010cosp...38.2878D Altcode: 2010cosp.meet.2878D The Solar Dynamics Observatory (SDO) represents a new frontier in quantity and quality of solar data. At about 1.5 TB/day, the data will not be easily digestible by solar physicists using the same methods that have been employed for images from previous missions. In order for solar scientists to use the SDO data effectively they need meta-data that will allow them to identify and retrieve data sets that address their particular science questions. We are building a comprehensive computer vision pipeline for SDO, abstracting complete metadata on many of the features and events detectable on the Sun without human intervention. Our project unites more than a dozen individual, existing codes into a systematic tool that can be used by the entire solar community. The feature finding codes will run as part of the SDO Event Detection System (EDS) at the Joint Science Operations Center (JSOC; joint between Stanford and LMSAL). The metadata produced will be stored in the Heliophysics Event Knowledgebase (HEK), which will be accessible on-line for the rest of the world directly or via the Virtual Solar Observatory (VSO) . Solar scientists will be able to use the HEK to select event and feature data to download for science studies. Title: Addressing Science Use Cases with HELIO Authors: Bentley, R. D.; Aboudarham, J.; Csillaghy, A.; Jacquey, C.; Hapgood, M. A.; Messerotti, M.; Gallagher, P.; Bocchialini, K.; Hurlburt, N. E.; Roberts, D.; Sanchez Duarte, L. Bibcode: 2009AGUFMSH54A..06B Altcode: The Heliophysics Integrated Observatory (HELIO) is a new VO project funded under the EC's Seventh Framework Programme (FP7). It includes thirteen partners scattered over six countries and is led by University College London. HELIO is designed to support the heliophysics community and is based on a Service Oriented Architecture. The services developed by and integrated into HELIO can be used to address a wide range of science problems; they can be used individually or as part of a work-flow driven search engine that can use a propagation (or other) model to help locate obervations that describe interesting phenomena. We will describe and discuss how the components of HELIO could be used to address science use cases, particularly how a user can adapt the work flow to their own science interests. Networking is one of the three Activities of the HELIO Integrated Infrastructure Initiatives (I3) project. Within this activity we plan to involve the community in all aspects of the design and testing of the HELIO system, including determining which data and metadata should be included, how the quality and content of metadata can be included, etc. We are investigating ways of making HELIO "domain-aware" so that researchers who are specialists in one of the communities that constitute heliophysics can easily identify, access and use data they need from the other communities. We will discuss how the community can help us develop this capability. Title: Modeling of sunspot structures using simulations of axisymmetric MHD convection Authors: Hartlep, T.; Hurlburt, N. E.; Busse, F. H.; Kosovichev, A. G. Bibcode: 2009AGUFMSH23B1538H Altcode: We present our efforts on modeling solar pores and sunspots in 2D and 2.5D axisymmetric magneto-hydrodynamic (MHD) simulations of the upper layers of the Sun's convection zone. One goals of this work is to produce consistent, self-maintained, even if not fully realistic, models of concentrated, strong magnetic field in subsurface layers of the Sun. These models are important for understanding the mechanisms of magnetic field concentration in sunspots, and associated large-scale flow patterns. Also, these can be used as background models in acoustic wave propagation simulations for testing local helioseismology techniques and their performance and problems in magnetic regions. This study explores the parameters under which magnetic field can spontaneously concentrate, and the kind of flow patterns that form in these cases (for instance if there are inflows or outflow at the surface). Title: Solar Tutorial and Annotation Resource (STAR) Authors: Showalter, C.; Rex, R.; Hurlburt, N. E.; Zita, E. J. Bibcode: 2009AGUFMSH13B1512S Altcode: We have written a software suite designed to facilitate solar data analysis by scientists, students, and the public, anticipating enormous datasets from future instruments. Our “STAR" suite includes an interactive learning section explaining 15 classes of solar events. Users learn software tools that exploit humans’ superior ability (over computers) to identify many events. Annotation tools include time slice generation to quantify loop oscillations, the interpolation of event shapes using natural cubic splines (for loops, sigmoids, and filaments) and closed cubic splines (for coronal holes). Learning these tools in an environment where examples are provided prepares new users to comfortably utilize annotation software with new data. Upon completion of our tutorial, users are presented with media of various solar events and asked to identify and annotate the images, to test their mastery of the system. Goals of the project include public input into the data analysis of very large datasets from future solar satellites, and increased public interest and knowledge about the Sun. In 2010, the Solar Dynamics Observatory (SDO) will be launched into orbit. SDO’s advancements in solar telescope technology will generate a terabyte per day of high-quality data, requiring innovation in data management. While major projects develop automated feature recognition software, so that computers can complete much of the initial event tagging and analysis, still, that software cannot annotate features such as sigmoids, coronal magnetic loops, coronal dimming, etc., due to large amounts of data concentrated in relatively small areas. Previously, solar physicists manually annotated these features, but with the imminent influx of data it is unrealistic to expect specialized researchers to examine every image that computers cannot fully process. A new approach is needed to efficiently process these data. Providing analysis tools and data access to students and the public have proven efficient in similar astrophysical projects (e.g. the “Galaxy Zoo.”) For “crowdsourcing” to be effective for solar research, the public needs knowledge and skills to recognize and annotate key events on the Sun. Our tutorial can provide this training, with over 200 images and 18 movies showing examples of active regions, coronal dimmings, coronal holes, coronal jets, coronal waves, emerging flux, sigmoids, coronal magnetic loops, filaments, filament eruption, flares, loop oscillation, plage, surges, and sunspots. Annotation tools are provided for many of these events. Many features of the tutorial, such as mouse-over definitions and interactive annotation examples, are designed to assist people without previous experience in solar physics. After completing the tutorial, the user is presented with an interactive quiz: a series of movies and images to identify and annotate. The tutorial teaches the user, with feedback on correct and incorrect answers, until the user develops appropriate confidence and skill. This prepares users to annotate new data, based on their experience with event recognition and annotation tools. Trained users can contribute significantly to our data analysis tasks, even as our training tool contributes to public science literacy and interest in solar physics. Title: Stochastic Effects of Granulation and Supergranulation Upon Deep Convection Authors: Augustson, Kyle; De Rosa, M. L.; Hurlburt, N. E.; Toomre, J. Bibcode: 2009SPD....40.0805A Altcode: Vigorous fluid motions associated with the observed patterns of supergranulation, mesogranulation, and granulation play a large role in the turbulent transport of heat to the solar surface. The downflows associated with these convective motions plunge from the surface into the near-surface layers of the Sun bringing cooler, low entropy material with them. These flow structures may provide some stochastic effects upon the dynamics of the giant cells of deep convection that extend into the near-surface regions. To investigate such dynamics, we have carried out several 3-D numerical simulations of fully compressible fluids within curved, spherical segments that, at this stage, approximate conditions near the top of the rotating solar convection zone. The upper boundary of the segment is stochastically driven with cool plumes that approximate the spatial and temporal scales of supergranular cell downflows, in essence creating a network of supergranular cells. The segment spans 30° in latitude and 30° in longitude, and has a radial extent of 15% of the solar radius. We explore the formation and evolution of the boundary layer resulting from such stochastic driving, and discuss these dynamics in the context of the near-surface shear layer of the solar convection zone. Title: The Heliophysics Event Knowledgebase for the Solar Dynamics Observatory Authors: Hurlburt, Neal E.; Cheung, M.; Schrijver, K.; HEK development Team Bibcode: 2009SPD....40.1511H Altcode: The Solar Dynamics Observatory will generated over 2 petabytes of imagery in its 5 year mission. In order to improve scientific productivity and to reduce system requirements , we have developed a system for data markup to identify "interesting” datasets and direct scientists to them through an event-based querying system. The SDO Heliophysics Event Knowledgebase (HEK) will enable caching of commonly accessed datasets within the Joint Science Operations Center (JSOC) and reduces the (human) time spent searching for and downloading relevant data. We present an overview of our HEK including the ingestion of images, automated and manual tools for identifying and annotation features within the images, and interfaces and web tools for querying and accessing events and their associated data. Title: Prominence Bubbles and Plumes: Thermo-magnetic Buoyancy in Coronal Cavity Systems Authors: Berger, Thomas; Hurlburt, N. Bibcode: 2009SPD....40.1007B Altcode: The Hinode/Solar Optical Telescope continues to produce high spatial and temporal resolution images of solar prominences in both the Ca II 396.8 nm H-line and the H-alpha 656.3 nm line. Time series of these images show that many quiescent prominences produce large scale (50 Mm) dark "bubbles" that "inflate" into, and sometimes burst through, the prominence material. In addition, small-scale (2--5 Mm) dark plumes are seen rising into many quiescent prominences. We show typical examples of both phenomena and argue that they originate from the same mechanism: concentrated and heated magnetic flux that rises due to thermal and magnetic buoyancy to equilibrium heights in the prominence/coronal-cavity system. More generally, these bubbles and upflows offer a source of both magnetic flux and mass to the overlying coronal cavity, supporting B.C. Low's theory of CME initiation via steadily increasing magnetic buoyancy breaking through the overlying helmut streamer tension forces. Quiescent prominences are thus seen as the lowermost parts of the larger coronal cavity system, revealing through thermal effects both the cooled downflowing "drainage" from the cavity and the heated upflowing magnetic "plasmoids" supplying the cavity. We compare SOT movies to new 3D compressible MHD simulations that reproduce the dark turbulent plume dynamics to establish the magnetic and thermal character of these buoyancy-driven flows into the corona. Title: Simulations Of Buoyant Plumes In Solar Prominences Authors: Hurlburt, Neal E.; Berger, T. Bibcode: 2009SPD....40.1009H Altcode: Recent observations of solar prominences have revealed a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long ``threads'' and dark ``bubbles'' that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. The system is the subjected to to localized heating to trigger a variety of modes and instabilities. Title: Developing a Heliophysics Event Knowledgebase for Solar Dynamics Observatory Authors: Schrijver, K.; Hurlburt, N.; Mark, C.; Freeland, S.; Green, S.; Jaffey, A.; Kobashi, A.; Schiff, D.; Seguin, R.; Slater, G.; Somani, A.; Timmons, R. Bibcode: 2008AGUFMSM11B1619S Altcode: The Solar Dynamics Observatory will generated over 2 petabytes of imagery in its 5 year mission. In order to improve scientific productivity and to reduce system requirements , we have developed a system for data markup to identify -interesting" datasets and direct scientists to them through an event-based querying system. The SDO Heliophysics Event Knowledgebase (HEK) will enable caching of commonly accessed datasets within the Joint Science Operations Center (JSOC) and reduces the (human) time spent searching for and downloading relevant data. We present an overview of our HEK including the ingestion of images, automated and manual tools for identifying and annotation features within the images, and interfaces and webtools for querying and accessing events and their associated data.

informatcs/hpkb Title: A Distributed Processing and Analysis System for Heliophysic Events Authors: Hurlburt, N.; Cheung, M.; Bose, P. Bibcode: 2008AGUFMSA53A1580H Altcode: With several Virtual Observatories now under active development, the time is ripe to consider how they will interact to enable integrated studies that span the full range of Heliophysics. We present a solution that builds upon components of the Heliophysics Event Knowledgebase (HEK) being developed for the Solar Dynamics Observatory and the Heliophysics Event List Manager (HELMS), recently selected as part of the NASA VxO program. A Heliophysics Event Analysis and Processing System (HEAPS) could increase the scientific productivity of Heliophysics data by increasing the visibility of relevant events contained within them while decreasing the incremental costs of incorporating more events in research studies. Here we present the relevant precursors to such a system and show how it could operate within the Heliophysics Data Environment. Title: On the Stability of Active Regions and Sunspots Authors: Hurlburt, Neal; DeRosa, Marc Bibcode: 2008ApJ...684L.123H Altcode: Recent helioseismic measurements of large-scale subsurface flows indicate that systematic horizontal inflows near the photosphere surround many active regions. Such active-region inflows are likely to impede the dispersal of magnetic flux into the surrounding network and thus can influence larger-scale and longer-term patterns and evolution of the surface magnetic field throughout the course of a solar activity cycle. We present results of numerical simulations of compressible magnetoconvection in which an initial unipolar magnetic field undergoes evolution resulting from convectively driven motions. Inflows surrounding regions of concentrated magnetic flux are driven by reducing the surface temperature as a function of local magnetic flux. We find flow patterns that are consistent with observations of those observed around active regions and sunspots. Title: Numerical simulations of rotating axisymmetric sunspots Authors: Botha, G. J. J.; Busse, F. H.; Hurlburt, N. E.; Rucklidge, A. M. Bibcode: 2008MNRAS.387.1445B Altcode: 2008MNRAS.tmp..702B; 2008arXiv0804.4429B A numerical model of axisymmetric convection in the presence of a vertical magnetic flux bundle and rotation about the axis is presented. The model contains a compressible plasma described by the non-linear MHD equations, with density and temperature gradients simulating the upper layer of the Sun's convection zone. The solutions exhibit a central magnetic flux tube in a cylindrical numerical domain, with convection cells forming collar flows around the tube. When the numerical domain is rotated with a constant angular velocity, the plasma forms a Rankine vortex, with the plasma rotating as a rigid body where the magnetic field is strong, as in the flux tube, while experiencing sheared azimuthal flow in the surrounding convection cells, forming a free vortex. As a result, the azimuthal velocity component has its maximum value close to the outer edge of the flux tube. The azimuthal flow inside the magnetic flux tube and the vortex flow is prograde relative to the rotating cylindrical reference frame. A retrograde flow appears at the outer wall. The most significant convection cell outside the flux tube is the location for the maximum value of the azimuthal magnetic field component. The azimuthal flow and magnetic structure are not generated spontaneously, but decay exponentially in the absence of any imposed rotation of the cylindrical domain. Title: The Atmospheric Imaging Array Feature and Event System (AFES) for SDO Authors: Hurlburt, N.; Freeland, S.; Cheung, M.; Schrijver, C. Bibcode: 2008AGUSMSM21A..07H Altcode: The great data volumes involved in Solar Dynamics Observatory impose the need to have efficient means to access, process and transport data products that goes beyond basic data discovery. In order to reduce system requirements and to improve scientific productivity, we pre-package Ðinterestingî datasets and direct scientists to them through an event-based querying system. This will enable caching of commonly accessed datasets within the Joint Science Operations Center (JSOC) and reduces the (human) time spent searching for and downloading relevant data. This system leverages the infrastructure developed for the Hinode Observation System (http://sot.lmsal.com/sot-data) and incorporates elements of the evolving heliophysics knowledgebase (http://www.lmsal.com/helio-informatics/hpkb). We present the details of the AFES including the ingestion of images, automated and manual tools for identifying and annotation features within the images, and interfaces and webtools for querying and accessing events and their associated data. This work has been supported by NASA through contract NNG04AE00C and Lockheed Martin Research Funds. Title: Quiescent Prominence Structure and Dynamics: a new View From the Hinode/SOT Authors: Berger, T.; Okamoto, J.; Slater, G.; Magara, T.; Tarbell, T.; Tsuneta, S.; Hurlburt, N. Bibcode: 2008AGUSMSP53A..01B Altcode: To date the Hinode/Solar Optical Telescope (SOT) has produced over a dozen sub-arcsecond, multi-hour movies of quiescent solar prominences in both the Ca II 396.8~nm H-line and the H-alpha 656.3~nm line. These datasets have revealed new details of the structure and dynamics of quiescent prominences including a new form of mass transport in the form of buoyant plume upflows from the chromosphere. We review the SOT prominence datasets to show that quiescent prominences appear in two major morphological categories: "vertically" and "horizontally" structured. The vertically structured prominences all show ubiquitous downflows in 400--700~km wide "streams" with velocities of approximately 10~km~s-1. Most of the vertically structured prominences also show episodic upflows in the form of dark turbulent plumes with typical velocities of 20~km~s-1. Large-scale oscillations are frequently seen in vertical prominences with periods on the order of 10 min and upward propagation speeds of approximately 10~km~s-1. In addition, "bubble" events in which large voids 10--30~Mm across inflate and then burst are seen in some of the vertical prominences. In contrast, the horizontally structured quiescent prominences exhibit only limited flows along the horizontal filaments. We speculate on the origin of the distinction between the vertically and horizontally structured prominences, taking into account viewing angle and the underlying photospheric magnetic flux density. We also discuss the nature of the mysterious dark plumes and bubble expansions and their implications for prominence mass balance in light of recent models of prominence magnetic structure that find vertical flows along some field lines. Title: Searching for Large-scale flows around Active Regions with Hinode Authors: Hurlburt, N.; Derosa, M.; Hagenaar, M. Bibcode: 2008AGUSMSP43C..08H Altcode: Heliosiemic studies have suggested that active regions are surrounded by large-scale inflows (Haber et al. 2004), and it has recently been hypothesized by Hurlburt and DeRosa (2008,HD) that these are due to the enhanced surface cooling resulting from plage and faculae. We seek confirmation of these results using Hinode observations of Active Regions using a variety of methods to infer inflow velocities from of continuum images and Dopplergrams. These flow patterns are then compared to the HD hypothesis. This work has been supported by NASA through contracts NNM07AA01C and NNG06GD45G. References: Haber, D., Hindman, B., Toomre, J. and Thompson, M. 2004, ÐOrganized Subsurface Flows near Active Regions,î Sol. Phys. 220,371. Hurlburt & DeRosa, 2008 ÐOn the longevity of Active Regions,î Ap.J. Lett., submitted Title: Numerical simulations of convection around magnetic features in the solar convection zone Authors: Botha, Gert; Rucklidge, Alastair; Hurlburt, Neal Bibcode: 2008cosp...37..354B Altcode: 2008cosp.meet..354B On the solar surface, magnetic flux elements collect in regions of converging flow and grow in field strength to become pores. In order to investigate convection around these magnetic flux tubes, we initialize a cylindrical simulation with an axisymmetric solution consisting of a flux tube surrounded by an inflowing collar flow. This is allowed to evolve using the 3D nonlinear magnetohydrodynamic equations for compressible resistive flow. The axisymmetric collar flow breaks into convection cells around the flux tube that are highly dynamic. Through vigorous convection they change the shape of the central magnetic flux tube, but do not succeed in destroying its integrity. We relate our calculation to recent helioseismic measurements of subsurface flows. Title: The Collaborative Heliophysics Observatory Authors: Hurlburt, N.; Freeland, S.; Cheung, M.; Bose, P. Bibcode: 2007AGUFMSH51A0256H Altcode: The Collaborative Heliophysics Observatory (CHO) would provide a robust framework and enabling tools to fully utilize the VOs for scientific discovery and collaboration. Scientists across the realm of heliophysics would be able to create, use and share applications -- either as services using familiar tools or through intuitive workflows -- that orchestrate access to data across all virtual observatories. These applications can be shared freely knowing that proper recognition of data and processing components are acknowledged; that erroneous use of data is flagged; and that results from the analysis runs will in themselves be shared Ð all in a transparent and automatic fashion. In addition, the CHO would incorporate cross-VO models and tools to weave the various virtual observatories into a unified system. These provide starting points for interactions across the solar/heliospheric and heliospheric/magnetospheric boundaries. Title: Nonaxisymmetric Instabilities of Convection around Magnetic Flux Tubes Authors: Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. Bibcode: 2007ApJ...662L..27B Altcode: On the surface of the Sun, magnetic flux elements collect in regions of converging flow, grow in field strength, and become pores, which have been observed to exhibit nonaxisymmetric structure over a range of scales. Around a fully developed sunspot, as well as the fine scale of the penumbra, the moat sometimes shows a clearly observable spokelike structure at low azimuthal wavenumbers. We investigate the formation of azimuthal structure by computing the linear stability properties of fully nonlinear axisymmetric magnetoconvection, which takes the form of a central flux tube surrounded by a convecting field-free region. We find steady and oscillatory instabilities with a preferred azimuthal wavenumber. The unstable modes are concentrated in the convecting region close to the outer edge of the flux tube. The instability is driven by convection and is not a magnetic fluting instability. Title: Numerical simulations of sunspots Authors: Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. Bibcode: 2007IAUS..239..507B Altcode: No abstract at ADS Title: Helio-informatics: Preparing For The Future Of Heliophysics Research. Authors: Schrijver, Carolus J.; Hurlburt, N. E.; Cheung, M. C.; Title, A. M.; Delouille, V.; Hochedez, J.; Berghmans, D. Bibcode: 2007AAS...210.2514S Altcode: 2007BAAS...39..133S The rapidly growing data volumes for space- and ground-based observatories for Sun and heliosphere will soon make it impractical, costly, and perhaps effectively impossible for researchers to download and locally inspect substantial portions of the data archives. By the end of 2008, for example, the Solar Dynamics Observatory will downlink over 2TB/day of compressed data; such a large volume would readily saturate internet connections to the archive site if it were exported to a handful of researchers around the world. We envision a revolution in research methodology towards a mode in which researchers run autonomous event-finding algorithms at a primary data archive in order to pre-select relatively small subsets of the data that can subsequently be inspected and analyzed in detail at a researcher's home institution. Teams from the SDO, Hinode, STEREO, and TRACE missions are developing the infrastructure that is needed to make this into a useful research tool: we are (1) defining standardized event attributes compatible with the Virtual Observatory and EGSO concepts, (2) developing a knowledge base supported by a web-based tool for compound queries based on the contents of solar and heliospheric observations, and (3) assembling a group of researchers who are interested in helping us develop a prototype system while beta-testing it in real scientific studies. We invite you to contact us (a) if you have feature-finding algorithms that you would like to see applied to existing data archives, (b) if you would like to contribute expertise in developing the knowledge-base system, or (c) if you would like to participate in the testing of the system for scientific use. More information on our plans, target dates, and contact information can be found at http://www.lmsal.com/helio-informatics/hpkb/.

The helio-informatics project is being developed with support from the HINODE/SOT (NNM07AA01C), SDO/AIA (NNG04EA00C), STEREO/SECCHI (N00173-02-C-2035), and TRACE (NAS5-38099) science investigations. Title: Simulations of Large-Scale Solar Surface Inflows Surrounding Magnetic Fields Authors: De Rosa, Marc L.; Hurlburt, N. E. Bibcode: 2007AAS...210.2211D Altcode: 2007BAAS...39..126D Recent helioseismic measurements of large-scale subsurface flows have indicated that systematic horizontal inflows near the photosphere surround many active regions. Such active-region inflows are likely to impede the dispersal into the surrounding network, and thus can influence larger-scale and longer-term patterns of magnetic field throughout the course of a solar activity cycle. We present preliminary results of numerical simulations of compressible magnetoconvection, in which an initial unipolar magnetic field undergoes evolution resulting from convectively driven motions. Inflows surrounding regions of concentrated magnetic flux are driven by reducing the surface temperature in regions where the magnetic flux is strong. The effects of these resulting inflows on the dynamics are then studied. Title: Panorama - A High-Performance, Multi-Channel Visualization Tool for Astronomical Image Data Authors: Seguin, Ralph; Hurlburt, N. Bibcode: 2007AAS...210.9403S Altcode: 2007BAAS...39R.217S Panorama is being developed as a standards-based, cross-platform, high-performance visualization tool for inspecting large volumes of time-series astronomical image data. Panorama utilizes the massive processing power of today's computer graphics hardware to quickly and dynamically visualize very large volumes of image data, combine and register multiple wavelengths/channels, create inset movies within larger field of view movies and much more, straight from the FITS science files. Examples of SOT and XRT data from Hinode as well as EUVI data from STEREO A & B will be shown using Panorama. Panorama will be used for visualizing HMI and AIA data from Solar Dynamics Observatory (SDO) as well.

Panorama enables real-time navigation, transformation and manipulation of multiple wavelengths/data channels simultaneously. Users can interactively pan in space, time and wavelength, rotate views, adjust colorization and channel blending on the fly. Panorama can be used to generate VOEvents to report detailed feature and event findings into a knowledge base system also being developed by LMSAL (see Schrijver et al, 2007). Panorama is available standalone for multiple platforms (OS/X, Linux, Solaris, IRIX) and is distributed as part of SolarSoft. Title: Hinode Observations of Umbral Dots Authors: Hurlburt, Neal E.; Berger, T.; Ichimoto, K.; SOT Team Bibcode: 2007AAS...210.9409H Altcode: 2007BAAS...39..218H We analyze observations of sunspot umbra taken by the Solar Optical Telescope (SOT) on Hinode to ascertain the properties of umbral dots. The observations consist of coordinated, multi-wavelength observing sequences spanning several hours for each spot considered. Typically these multi-wavelength observations include longitudinal magnetograms in 6302, and filtergrams in Calcium II H, G-band and blue continuum. We report on the spatial and temporal properties of the umbral dots and their relation to the umbral field and overlying chromosphere.

This work was supported in part by NASA in part under the Hinode/SOT contract NNM07AA01C. Title: An Observation Knowledgebase for Hinode Data Authors: Hurlburt, Neal E.; Freeland, S.; Green, S.; Schiff, D.; Seguin, R.; Slater, G.; Cirtain, J. Bibcode: 2007AAS...210.7203H Altcode: 2007BAAS...39..179H We have developed a standards-based system for the Solar Optical and X Ray Telescopes on the Hinode orbiting solar observatory which can serve as part of a developing Heliophysics informatics system. Our goal is to make the scientific data acquired by Hinode more accessible and useful to scientists by allowing them to do reasoning and flexible searches on observation metadata and to ask higher-level questions of the system than previously allowed. The Hinode Observation Knowledgebase relates the intentions and goals of the observation planners (as-planned metadata) with actual observational data (as-run metadata), along with connections to related models, data products and identified features (follow-up metadata) through a citation system. Summaries of the data (both as image thumbnails and short "film strips") serve to guide researchers to the observations appropriate for their research, and these are linked directly to the data catalog for easy extraction and delivery.

The semantic information of the observation (Field of view, wavelength, type of observable, average cadence etc.) is captured through simple user interfaces and encoded using the VOEvent XML standard (with the addition of some solar-related extensions). These interfaces merge metadata acquired automatically during both mission planning and an data analysis (see Seguin et. al. 2007 at this meeting) phases with that obtained directly from the planner/analyst and send them to be incorporated into the knowledgebase. The resulting information is automatically rendered into standard categories based on planned and recent observations, as well as by popularity and recommendations by the science team. They are also directly searchable through both and web-based searches and direct calls to the API. Observations details can also be rendered as RSS, iTunes and Google Earth interfaces. The resulting system provides a useful tool to researchers and can act as a demonstration for larger, more complex systems. Title: The Search: for Life Beyond Earth Authors: Hurlburt, Neal E.; Blair, J.; Lubbs, S.; Miller, D. Bibcode: 2006AAS...209.9601H Altcode: 2006BAAS...38.1034H Are we alone in the universe? This educational unit approaches this question through scientific observations outlined by the Drake Equation. The Drake Equation, named after Frank Drake of SETI, can be used to calculate the number of advanced civilizations that are willing to communicate with us. Through this unit students determine values for each term of the equation and site evidence for their values. This unit provides a holistic view of science by combining chemistry, physics, astronomy, biology, and sociology. Title: CoSEC: Connecting Living With a Star Research Authors: Hurlburt, N.; Freeland, S.; Bose, P.; Zimdars, A.; Slater, G. Bibcode: 2006AGUFMSH11A0372H Altcode: The Collaborative Sun-Earth Connector (CoSEC) provide the means for heliophysics researchers to compose the data sources and processing services published by their peers into processing workflows that reliably generate publication-worthy data. It includes: composition of computational and data services into easy-to- read workflows with data quality and version traceability; straightforward translation of existing services into workflow components, and advertisement of those components to other members of the CoSEC community; annotation of published services with functional attributes to enable discovery of capabilities required by particular workflows and identify peer subgroups in the CoSEC community; and annotation of published services with nonfunctional attributes to enable selection on the basis of quality of service (QoS). We present an overview and demonstration of the CoSEC system, discuss applications, the lessons learned and future developments. Title: Computational Acoustics in Spherical Geometry: Steps toward Validating Helioseismology Authors: Hanasoge, S. M.; Larsen, R. M.; Duvall, T. L., Jr.; De Rosa, M. L.; Hurlburt, N. E.; Schou, J.; Roth, M.; Christensen-Dalsgaard, J.; Lele, S. K. Bibcode: 2006ApJ...648.1268H Altcode: Throughout the past decade, detailed helioseismic analyses of observations of solar surface oscillations have led to advances in our knowledge of the structure and dynamics of the solar interior. Such analyses involve the decomposition of time series of the observed surface oscillation pattern into its constituent wave modes, followed by inversion procedures that yield inferences of properties of the solar interior. While this inverse problem has been a major focus in recent years, the corresponding forward problem has received much less attention. We aim to rectify this situation by taking the first steps toward validating and determining the efficacy of the helioseismic measurement procedure. The goal of this effort is to design a means to perform differential studies of various effects such as flows and thermal perturbations on helioseismic observables such as resonant frequencies, travel-time shifts, etc. Here we describe our first efforts to simulate wave propagation within a spherical shell, which extends from 0.2 to about 1.0004 Rsolar (where Rsolar is the radius of the Sun) and which possesses a solar-like stratification. We consider a model containing no flows that will serve as a reference model for later studies. We discuss the computational procedure, some difficulties encountered in a simulation of this kind, and the means to overcome them. We also present techniques used to validate the simulation. Title: Numerical Simulations of Rotating Sunspots Authors: Botha, G. J. J.; Rucklidge, A. M.; Busse, F. H.; Hurlburt, N. E. Bibcode: 2006ESASP.617E..53B Altcode: 2006soho...17E..53B No abstract at ADS Title: Converging and diverging convection around axisymmetric magnetic flux tubes Authors: Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. Bibcode: 2006MNRAS.369.1611B Altcode: 2006MNRAS.tmp..605B A numerical model of idealized sunspots and pores is presented, where axisymmetric cylindrical domains are used with aspect ratios (radius versus depth) up to 4. The model contains a compressible plasma with density and temperature gradients simulating the upper layer of the Sun's convection zone. Non-linear magnetohydrodynamic equations are solved numerically and time-dependent solutions are obtained where the magnetic field is pushed to the centre of the domain by convection cells. This central magnetic flux bundle is maintained by an inner convection cell, situated next to it and with a flow such that there is an inflow at the top of the numerical domain towards the flux bundle. For aspect ratio 4, a large inner cell persists in time, but for lower aspect ratios it becomes highly time dependent. For aspect ratios 2 and 3 this inner convection cell is smaller, tends to be situated towards the top of the domain next to the flux bundle, and appears and disappears with time. When it is gone, the neighbouring cell (with an opposite sense of rotation, i.e. outflow at the top) pulls the magnetic field away from the central axis. As this happens a new inner cell forms with an inflow which pushes the magnetic field towards the centre. This suggests that to maintain their form, both pores and sunspots need a neighbouring convection cell with inflow at the top towards the magnetic flux bundle. This convection cell does not have to be at the top of the convection zone and could be underneath the penumbral structure around sunspots. For an aspect ratio of 1, there is not enough space in the numerical domain for magnetic flux and convection to separate. In this case the solution oscillates between two steady states: two dominant convection cells threaded by magnetic field and one dominant cell that pushes magnetic flux towards the central axis. Title: The Consequences Of Active-region Inflows On The Large-scale Dispersal Of Magnetic Field Across The Solar Surface. Authors: Schrijver, Carolus J.; De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2006SPD....37.0716S Altcode: 2006BAAS...38..230S Helioseismic analysis of near-surface modes recently revealed horizontal flows near the solar surface towards regions with enhanced magnetic activity. The magnitude of these flows appears to increase with the magnetic flux contained within them. Such flows help to confine magnetic flux to the activity belt and perhaps even to theactive regions within which the field emerges, and will likely slow the random-walk dispersal of the field. We report on experiments witha surface flux dispersal model to study the consequences of such inflows towards strong-flux regions. We constrain the flow magnitudeby comparing results of a flux assimilation model to solar observations over six-month intervals throughout the last solar cycle. The best-fit model is then used to quantify the effects of these flows on the Sun's global dipole and quadrupole fields on time scales of multiple centuries. Title: Virtual Science Operations for the Sun Solar System Great Observatory Authors: Hurlburt, N.; Bose, P. Bibcode: 2005AGUFMSH51C1226H Altcode: NASA's current and future space science missions create greater opportunities to observe the sun and understand its processes and impact on the space weather through a range of distributed instruments. The joint assets of these missions has recently been coined a "Great Observatory". A key challenge in realizing the Great Observatory concept is harnessing such distributed instruments and the associated continuous complex data sets for enhanced science productivity and reliability. Autonomous science operations and control will enable these goals in spite of tight budgets, evolving science models (evolving understanding and theory) and changing mission goals. The Virtual Science Operations Framework (VSOF) enables the formation of the Great Observatory through the combination of novel data naming systems and middleware services for closed-loop observations planning, analysis and execution with established operational systems. We introduce innovative ideas of instrument and data abstractions, and a uniform substrate for automating coordinated and continuous science observation and analysis operations. These concepts allow space scientists to take advantage of a range of heterogeneous (commandable and preset) and distributed instruments and analysis services to meet the needs of future science missions and analysis tasks in a cost-effective manner. The project exploits current advances in collaboration architectures and information technologies to create a scalable plug-and-play substrate for cooperative space science operations. Title: SolarSoft Web Services Authors: Freeland, S.; Hurlburt, N. Bibcode: 2005AGUFMIN31B1152F Altcode: The SolarSoft system (SSW) is a set of integrated software libraries, databases, and system utilities which provide a common programming and data analysis environment for solar physics. The system includes contributions from a large community base, representing the efforts of many NASA PI team MO&DA teams,spanning many years and multiple NASA and international orbital and ground based missions. The SSW general use libraries include Many hundreds of utilities which are instrument and mission independent. A large subset are also SOLAR independent, such as time conversions, digital detector cleanup, time series analysis, mathematics, image display, WWW server communications and the like. PI teams may draw on these general purpose libraries for analysis and application development while concentrating efforts on instrument specific calibration issues rather than reinvention of general use software. By the same token, PI teams are encouraged to contribute new applications or enhancements to existing utilities which may have more general interest. Recent areas of intense evolution include space weather applications, automated distributed data access and analysis, interfaces with the ongoing Virtual Solar Observatory efforts, and externalization of SolarSoft power through Web Services. We will discuss the current status of SSW web services and demonstrate how this facilitates accessing the underlying power of SolarSoft in more abstract terms. In this context, we will describe the use of SSW services within the Collaborative Sun Earth Connector environment. Title: A Generalized Framework For Combining Statistical Measures of Flare Likelihood Authors: Slater, G. L.; Hurlburt, N. Bibcode: 2005AGUSMSP23B..09S Altcode: There are many parameters which have been found to have varying degrees of correlation with solar flares. We present a framework for combining multiple sources of predictive information to produce a single likelihood value for flare occurrence. The framework is intended as a development tool for flare prediction studies and makes use of the Collaborative Sun-Earth Connector (CoSEC). Title: Simulations Of Acoustic-Flow Interaction In Spherical Geometry: Steps Toward Validating Helioseismology Authors: Hanasoge, S. M.; Duvall, T. L.; De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2005AGUSMSP11B..11H Altcode: We simulate acoustic wave interaction with flows in spherical geometry with the specific intent of using them as artificial data for validation of helioseismology. The numerical procedure is pseudo-spectral; we employ a spherical harmonic representation of the spherical surface, compact finite differences in the radial direction and a fourth order Runge-Kutta time stepping scheme. We also excite surface gravity modes, modeling all waves as linear perturbations to the background state so as to gain further insight into wave-flow interaction. Towards validation, we apply techniques of helioseismology to the artificial data to determine the efficacy of the helioseismic inversion procedure. In other words, we are attempting the forward problem. Title: Numerical Simulations of Bipolar Magnetic Field Decay in Turbulent Convection Authors: De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2005AGUSMSP11C..02D Altcode: We present numerical simulations of compressible magnetoconvection in spherical segments, seeking to examine the decay of active region magnetic fields on the sun. It is surprising that after their emergence, active regions are observed to persist in relative stasis for long periods of time (weeks to months) before suddenly disintegrating. We perform a series of calculations to investigate this process, in which we drive turbulent convection (Rayleigh numbers of order 107) within two- and three-dimensional spherical segments, and measure the decay rates of the embedded bipolar magnetic fields. Title: Using the Collaborative Sun-Earth Connector for integrating data systems Authors: Hurlburt, N.; Freeland, S.; Slater, G.; Bentley, R.; Hill, F.; Bose, P. Bibcode: 2005AGUSMSH43B..05H Altcode: We demonstrate the coupling of disjoint data systems into virtual collaborative operations using the Collaborative Sun-Earth Connector (CoSEC). In addition to demonstrating possible interactions between Virtual observatories, we will present how individual missions and researchers can integrate their systems with space science services already incorporated into CoSEC. We present more advanced concepts of how to create collaborative data environments using upcoming solar missions as examples. This research has been supported through NASA contract NNH04CC00C. Title: Virtual Solar Inc. Authors: Bentley, R. D.; Hill, F.; Hurlburt, N. Bibcode: 2004ASPC..314..311B Altcode: 2004adass..13..311B The need to develop new ways of accessing solar observations, coupled with rapidly increasing volumes of data and the desire to share data with other communities, has led to several projects intended to create virtual solar observatories. We outline the three main initiatives, EGSO, VSO and CoSEC, and describe how the the combined effort will result in a facility that will better match the needs of the community. Interaction with related communities are discussed, including similarities and differences with the IVOA and interoperability. Title: Numerical Models of solar Magnetoconvection: Toward a Coupling to the Corona Authors: De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2004AAS...204.3908D Altcode: 2004BAAS...36..715D We present numerical simulations of a stratified magnetized fluid, confined to a spherical shell, that approximates the transition from a high- to low-beta regime, similar to the conditions present at the solar photosphere. In these simulations, a model corona atmosphere is situated above a convectively unstable, high-beta fluid layer. As a result, the dynamics associated with evolving magnetic features in the solar atmosphere can be modeled in a manner that is self-consistent with the convective motions that provide the driving. Our simulations exhibit arcade-like structures that undergo reconnection as a result of the supergranular-scale fluid motions in the convective layer below, and discuss possible observational consequences. Title: Collaborative Virtual Observatories using CoSEC Authors: Hurlburt, N.; Bose, P.; Freeland, S.; Woodward, M.; Slater, G. Bibcode: 2004AAS...204.5208H Altcode: 2004BAAS...36..755H The ``Virtual Observatories" (VOs) movement is underway to organize space science data into discipline-based VOs. These would provide easy, online access to large volumes of data. We extend this idea to include interactions between these VOs, creating collaborative virtual observatories. The Collaborative Sun-Earth Connector (CoSEC) is used as a test bed for this concept. We demonstrate possible interactions between Virtual observatories by integrating the prototype Virtual Solar Observatory (VSO) and European Grid of Solar Observations (EGSO) with space science services already incorporated into CoSEC. In addition we present more advanced concepts of how Collaborative Observatories might increase the scientific productivity.

This research has been supported through NASA contract NNH04CC00C. Title: IAU Working Group on International Data Access for Solar and Heliospheric data Authors: Bentley, R. D.; Hill, F.; Hurlburt, N.; Roberts, A. Bibcode: 2004AAS...204.5207B Altcode: 2004BAAS...36S.754B Division II (Sun and Heliosphere) of the IAU has initiated a Working Group to study the archiving, retrieval and distribution of solar and heliospheric data. The goal of the Working Group is to facilitate the use of available solar and heliospheric data that are archived in a large number of computers scattered all over the world.

The intent of the Working Group is to help coordinate the existing and growing data exchange through the Internet and work with the virtual observatory initiatives to propose guidelines for exchange at an international level and encourage participation in the projects.

The Working Group is working with the virtual observatory initiatives to ensure that they develop standards and employ techniques that are acceptable to the worldwide solar and heliospheric communities and to encourage interoperability between the projects. The EGSO, VSO, CoSEC and VSPO projects are all part of the Working Group and would also like to encourage the communities to help develop standards and participate in the virtual observatory projects.

The aims of and objectives the Working Group will be discussed and feedback from the audience is encouraged. Title: Solar-like convective and coronal layers in a single numerical model Authors: Hurlburt, N.; De Rosa, M. Bibcode: 2004cosp...35.3551H Altcode: 2004cosp.meet.3551H We investigate the coupling between turbulent magnetoconvection and an atmospheric layer on the sun using numerical simulations of compressible fluids. The model consists of a stratified MHD fluid spanning multiple scale heights, encompassing the transition of the plasma beta from high to low values. Although a heat flux is imposed at the lower boundary, only the lower portion of the domain where the beta is high is convectively unstable. The upper portions are stabilized by a parameterized heating function and the presence of a strong magnetic field and, similar to the solar chromosphere and corona. As a result, the dynamics associated with evolving magnetic features in the solar atmosphere can be modeled in a manner that is self-consistent with the convective motions that provide the driving. We present simulations of arcade-like reconnection in the presence of supergranular-scale flows and discuss possible observational consequences. Title: Collaborative Observatories for ILWS Authors: Hurlburt, N.; Bose, P.; Freeland, S.; Slater, G.; Woodward, M. Bibcode: 2004cosp...35.3217H Altcode: 2004cosp.meet.3217H The success of the ILWS program depends upon the successful integration of data from a wide variety of sources which span the heliosphere, electromagnetic spectrum and physics. A motion is underway to organize these data into discipline-based "Virtual Observatories" (V0s), which would provide easy, online access to large volumes of data. We extend this idea to include interactions between these VOs,creating collaborative observatories. The Collaborative Sun-Earth Connector (CoSEC) is used as a testbed for this concept. We demonstrate possible interactions between Virtual observatories by integrating the prototype Virtual Solar Observatory (VSO) and European Grid of SOlar Obseravtions (EGSO) with space science services already incorporated into CoSEC. In addition we present more advanced concepts of how Collaborative Observatories might increase the scientific productivity of the ILWS program. This research has been supported through NASA contract NNH04CC00C. Title: Modeling solar magnetoconvection and coronal structures Authors: Hurlburt, Neal E.; De Rosa, Marc L. Bibcode: 2004IAUS..223..253H Altcode: 2005IAUS..223..253H We present results of an investigation into the coupling between solar-like magnetoconvection and coronal structures using self-consistent numerical simulations of compressible fluids. The model consists of a stratified MHD fluid spanning multiple scale heights, encompassing the transition of the plasma beta from high to low values. The lower portion of the domain, where the beta is high, is convectively unstable while the upper portion is stabilized by the presence of a strong magnetic field and energy losses. As a result, the dynamics associated with evolving magnetic features in the solar atmosphere can be modelled in a manner that is self-consistent with the convective motions that provide the driving. We present simulations of arcade-like reconnection in the presence of supergranular-scale flows. Title: MHD Simulations Spanning the Convection Zone, Chromosphere, and Corona Authors: De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2003SPD....34.0407D Altcode: 2003BAAS...35..811D The dynamics associated with evolving magnetic structures in the solar atmosphere are ultimately driven by vigorous convective motions below the photosphere. There, nonlinear interactions between the flows and fields lead to the transport of energy up into the atmosphere, which is later converted to heat in the chromosphere and corona and radiated into space. To investigate such dynamics, we have constructed a self-consistent model of the sun encompassing the upper layers of the convection zone, chromosphere, transition region, and lower corona. The fully compressible magnetized fluid comprising the convective layer is dynamically coupled to the atmosphere through the magnetic field. These models allow us to investigate the dynamics associated with waves, magnetic fields, and fluid motions within the solar atmosphere. Title: CoSEC: Coordinated Web Services and Infrastructure for Living with a Star Authors: Hurlburt, N.; Freeland, S.; Bose, P.; Woodward, M. Bibcode: 2003SPD....34.0309H Altcode: 2003BAAS...35..809H The Collaborative Sun-Earth Connector (CoSEC) will offer a testbed for developing and deploying data and modeling services for the space science community. We will demonstrate the concept using the current prototype, www.lmsal.com/cosec, and offer templates and tools for expanding the prototype with existing space science data and models using the SolarSoft framework. In addition we will discuss how CoSEC to relates to other projects, including the Virtual Solar Observatory and the European Grid of Solar Observations.

This research has been supported through NASA grant NAG5-10784. Title: Simulations of Near-Surface Solar Magnetoconvection Within Localized Spherical Segments Authors: De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2003ASPC..293..229D Altcode: 2003tdse.conf..229D Turbulent fluid motions near the surface of the sun, such as those associated with the observed pattern of supergranulation, are thought to play a role in the decay of the magnetic field within plage and active regions on the sun. To investigate such dynamics, we have constructed two related numerical simulations of fully compressible magnetoconvecting fluids, each contained within a curved, spherical segment that approximates the conditions within the upper part of the solar convection zone. The spherical segment domains span 30 degrees in latitude and 60 degrees in longitude, and have a radial extent of 4% of the solar radius. We find that bipolar field configurations decay on diffusive (Ohmic) time scales, rather than on turbulent decay time scales, despite the network of convection cells around and within the magnetized regions. Title: The Collaborative Sun-Earth Connector Authors: Hurlburt, N.; Freeland, S.; Bose, P. Bibcode: 2002AGUFMSH51A0420H Altcode: The Collaborative Sun-Earth Connector fuses data from a variety of instruments, including images, spectra and in situ measurements, to unveil the essential elements of space weather. We demonstrate a prototype system for such coordinated, distributed data analysis based upon software agent technologies and SolarSoft (Freeland and Handy 1998). Researchers use the system to develop process maps which merge distributed data archives and servers into a virtual data analysis system. Sophisticated image and time-series processing can be coordinated between data centers while minimizing the amount of data transferred between them and optimizing the delivery of pertinent and refined data to the requestor. We describe how CoSEC relates to and can leverage related efforts from the Virtual Solar Observatory and the European Grid of Solar Observatories and examine how it can transition to a comprehensive data analysis system for upcoming LWS and SEC missions. Freeland, S. and Handy, B., 1998 Sol. Phys. 182,497 This research is funded by NASA through grant NAG5-10784. Title: Visualizing and Interpreting Very High Resolution Solar Movies Authors: Shine, R. A.; Hurlburt, N.; Title, A. M.; Nightingale, R. W. Bibcode: 2002AGUFMSH52A0498S Altcode: Benefiting from advances in detector technology, image compression, and data storage capacities, current and upcoming solar instruments, especially the Solar Dynamics Observatory (SDO) due to be launched in 2007, will produce immense amounts of data in the form of movies with individual images in the 2048x2048 (4 Mpixel) to 4096x4096 (16 Mpixel) range. This is beyond the capability of most contemporary computer or video displays but several are now becoming available. In order to develop concepts and software for working with existing and future data sets, we have been working with a 9 Mpixel IBM T221 LCD display driven by an SGI Octane 2 workstation. This is a desktop display with a 22 inch diagonal screen. We will demonstrate our prototype system using several combinations of movies from the Swedish Vacuum Solar Tower (SVST) at La Palma, and the TRACE and SOHO satellites and discuss some approaches for the more challenging SDO data products. Title: Numerical Simulations of Solar Active Region Magnetoconvection Authors: De Rosa, M. L.; Hurlburt, N. E. Bibcode: 2002AGUFMSH52A0495D Altcode: Vigorous fluid motions associated with the observed patterns of supergranulation, mesogranulation, and granulation on the sun are likely to play a large role in the continual emergence, evolution, and redistribution of magnetic field within solar active regions. To investigate such non-linear dynamics, we have constructed numerical simulations of fully compressible magnetized fluids, each contained within curved, spherical segments nominally located near the top of the solar convection zone. Overturning motions having length scales comparable to that of solar supergranulation are driven by imposing a solar-like heat flux through the bottom of the domain. We present recent results of several idealized active region simulations within thin spherical segments, each spanning 60°x 30° in longitude and latitude and extending up to 0.04~Rsun in radius. We are able to investigate the analogs of both plage and active regions by varying the amount of magnetic flux that permeates the layer. Simplified field-line extrapolations into the volume above the spherical segments are then used to assess how the corona might respond to the structure and evolution of magnetic field emerging through the solar photosphere. This work was supported by NASA through grant NAG 5-3077 to Stanford University and by Lockheed Martin Independent Research and Development funds. Title: Simulations of near-photospheric magnetoconvection within localized spherical segments Authors: De Rosa, M. L.; Hurlburt, N. E.; Alexander, D. Bibcode: 2002ESASP.505..385D Altcode: 2002IAUCo.188..385D; 2002solm.conf..385D Vigorous fluid motions associated with the observed patterns of supergranulation, mesogranulation, and granulation are likely to play a large role during the evolution of magnetic field within solar active regions. To investigate such dynamics, we have constructed numerical simulations of fully compressible, magnetized fluids, each contained within curved, spherical segments that approximate conditions near the top of the solar convection zone. We present recent results of one three-dimensional simulation of an idealized bipolar active region contained within a thin spherical segment. The segment nominally spans 30° in latitude and 60° in longitude, and has a radial extent of 4% of the solar radius. Upon initialization, the domain is threaded by a bipolar radial magnetic field, which subsequently cancels as the ensuing convection advects field horizontally across the segment. We find that the time scale at which the field decays is slower than the expected turbulent decay time scale, and is much closer to the diffusive (Ohmic) decay time scale, despite the network of convection cells surrounding the magnetized regions. We suggest that this convection serves to confine field of like polarity and thus suppresses the turbulent decay of magnetic field. Title: Complete Models of Axisymmetric Sunspots: Magnetoconvection with Coronal Heating Authors: Hurlburt, Neal E.; Alexander, David; Rucklidge, Alastair M. Bibcode: 2002ApJ...577..993H Altcode: We present detailed results of numerical experiments into the nature of complete sunspots. The models remain highly idealized but include fully nonlinear compressible magnetoconvection in an axisymmetric layer that drives energy into an overlying, low-β plasma. We survey a range of parameters in which the resulting magnetoconvection displays the formation of pore- and sunspot-like behavior and assess the coronal signatures resulting from the energy generated by the magnetoconvection. The coronal heating is assumed to be a result of the dissipation by an unspecified means of a fraction of the Poynting flux entering the corona. The expected signatures in the EUV and soft X-ray bandpasses of the Transition Region and Coronal Explorer and Yohkoh/SXT, respectively, are examined. This ad hoc coupling of the corona to the subphotospheric region results in a dynamical behavior that is consistent with recent observational results. This agreement demonstrates that even simple coupled modeling can lead to diagnostics for investigations of both subphotospheric sunspot structures and coronal heating mechanisms. Title: Numerical Simulations of Supergranular Magnetoconvection Authors: De Rosa, M. L.; Hurlburt, N. E.; Alexander, D.; Rucklidge, A. M. Bibcode: 2002AAS...200.0418D Altcode: 2002BAAS...34..646D The complex interactions between the turbulent fluid motions within the solar convection zone and the related processes of emergence, evolution, and cancellation of magnetic field at the photosphere have received much recent attention. It is likely that such interactions depend on the relative magnitudes of the field and of the flows, but the details of this coupling are not well understood. To further investigate the magnetohydrodynamics within such turbulent convection, we have constructed several idealized simulations of fully compressible MHD fluids, each contained within a curved, spherical segment that approximates a localized volume of subphotospheric convection on the sun. In some cases, the horizontal extent of the computational volume spans 30 heliographic degrees in both latitude and longitude, thereby enabling the dynamics within a large field containing approximately 100 supergranular-sized cells to be studied. By varying the amount of total (unsigned) flux permeating the domain, we are able to investigate analogs to patches of subsurface convection that generally resemble either quiet-sun or active regions when viewed from above. In addition, simplified potential-field extrapolations into the volume above the computational domain are used to illustrate how the coronal field topology might behave in response to the continually evolving magnetic field within the convecting layers. This work was supported by NASA through grant NAG 5-3077 to Stanford University and by Lockheed Martin Independent Research and Development funds. Title: Modeling Solar Magnetoconvection: What we can't see and why it might help us Authors: Hurlburt, N. E. Bibcode: 2002AAS...200.3402H Altcode: 2002BAAS...34..690H Theoretical and numerical models of solar magnetoconvection indicate that much of the essential physics involved escapes detection today. Magnetic brightpoints and their interaction with granulation is at the limit of current telescope resolution. Understanding the details of sunspot formation and structure depends upon high resolution and stable movies of the vector magnetic field and flow velocities that are currently unattainable. While the physics of the fine-scale magnetoconvection may be invisible to us, their possible consequences include irradiance variations and the structuring and heating of the corona. The state of recent mangetoconvection studies will be presented to shed light on what new telescopes may be able to find. This work has been supported by NASA through grant NAG5-7376 and Lockheed Martin Independent Research Funds. Title: Semantic Composition of Distributed Solar Data and Analysis Services For Coordinated E-Science Authors: Hurlburt, N. E.; Freeland, S.; Bose, P.; Woodward, M. Bibcode: 2002AAS...200.6002H Altcode: 2002BAAS...34..742H The success of NASA's Living with a Star Program depends upon coordinated, distributed data systems which share many features with the Virtual Observatory. Data from a variety of instruments including images, spectra and in situ measurements must be fused to unveil the complexities of space weather. We demonstrate a prototype system for such coordinated, distributed data analysis based upon software agents technologies and SolarSoft (Freeland and Handy 1998). Researchers use the system to develop process maps which merge distributed data archives and servers into a virtual data analysis system. Sophisticated image and time-series processing can be coordinated between data centers while minimizing the amount of data transferred between them and optimizing the delivery of pertinent and refined data to the requestor. Freeland, S. and Handy, B., 1998 Sol. Phys. 182,497 Title: Sunspot Dynamics and Coronal Heating Authors: Hurlburt, N.; Alexander, D. Bibcode: 2002stma.conf...19H Altcode: No abstract at ADS Title: Coupled modeling of photospheric and coronal dynamics Authors: Alexander, D.; Hurlburt, N. E.; Rucklidge, A. M.; De Rosa, M. Bibcode: 2001AGUFMSH11C0718A Altcode: The coupling of the motions within and below te photosphere to the chromosphere and corona is one of the fundamental issues in solar physics. We have developed a model coupling the simulated dynamics of sunspots to the simulated heating of coronal loops. In this paper we present an extension of our earlier work to the inclusion of (a) fully three dimensional magnetoconvection, (b) new analytical representations of hydrostatic loops with spatially-dependent heating rates and (c) fully time-dependent hydrodynamic coronal modeling. The dynamic loop model uses the same numerical scheme as the magnetoconvective model used to simulate the photospheric behavior in this sunspot system, making it possible to more fully integrate the two regimes. We present the first results of a hybrid model utilizing a time-dependent coronal model and a fully three-dimensional magnetoconvective model. Title: A Prototype Problem-Solving Environment for Living With a Star Data Authors: Hurlburt, N.; Freeland, S.; Shine, R.; Bose, P. Bibcode: 2001AGUFMSH31A0702H Altcode: The Living With a Star program aims to understanding our space environment as a unified system. For this approach to be successful, the scientific working environment must present the LWS components as a unified whole. We present an architecture and data assimilation environment which addresses this critical issue. The goal of our Problem-Solving Environment for Living With a Star (PSELWS) project is to place the users of the data at center stage -- providing a virtual workbench with the tools, and infrastructure needed for seamless, timely and efficient access to the various data sources. Title: Nonlinear Instability of Compressible Starting Plumes Authors: Rast, Mark; Hurlburt, Neal Bibcode: 2001APS..DFD.DG010R Altcode: The structure and dynamics of stellar convective envelopes and giant planet atmospheres is thought to be controlled by narrow buoyantly driven plumes spanning the convectively unstable region and penetrating the over or underlying stably stratified layers. The stability and entrainment properties of such plumes are poorly understood. When the background state is significantly stratified, downward directed thermal starting plumes are subject to a nonlinear pinch instability not realized in their incompressible counterparts. It results from finite amplitude pressure perturbations dynamically induced in the wake of the plume head. We examine this instability mechanism utilizing two-dimensional planar and axisymmetric as well as fully three-dimensional numerical simulations, and discuss its sensitivity to geometry and dissipation. Title: Coronal Heating and the dynamics of subphotospheric magnetic fields Authors: Hurlburt, N.; Alexander, D. Bibcode: 2001AGUSM..SH31D05H Altcode: Simultaneous observations of sunspots in the photosphere and in the coronal regions above them reveal a close coupling between the dynamics of the photospheric motion and structure and the heating of coronal loops. We investigate this relationship through detailed three-dimensional simulations of dynamic, small-scale structures in sunspot penumbra and umbra in conjunction with models of coronal excitation and emission. The numerical models incorporate a fully three-dimensional magnetoconvection calculation, potential field extrapolations from the sunspot model boundary conditions, steady-state and dynamic coronal loops powered by the convective motions at the surface, EUV and X-ray instrument response functions, and a fieldline rendering. The result is a simulated dynamical active region in three dimensions which can be compared directly with observations and enables us to explore coronal heating and its relationship to the dynamics of the photosphere and convection zone. We present results of recent calculations exploring the dynamics of penumbra grains and their possible influence on the overlying corona. Title: Magnetic Diffusion in Stratified Atmospheres Authors: DeLuca, E. E.; Hurlburt, N. E. Bibcode: 2001ApJ...548.1093D Altcode: The predictions from mean field electrodynamics have been questioned because of the strong feedback of small-scale magnetic structure on the velocity fields. In two dimensions, this nonlinear feedback results in a lengthening of the turbulent decay time. In three dimensions α-quenching is predicted. Previous studies assumed a homogeneous fluid. We will present recent results from two-dimensional compressible MHD decay simulations in a highly stratified atmosphere that more closely resembles the solar convection zone. Our results show that the field geometry has a strong influence on the decay rate: vertical fields remain fairly constant for a period of time and then rapidly decay on the turbulent timescale; horizontal fields decay at an intermediate rate with strong fields persisting near the top and bottom boundaries. The implication of our results for understanding solar active region decay is discussed. Title: Development of structure in pores and sunspots: flows around axisymmetric magnetic flux tubes Authors: Hurlburt, N. E.; Rucklidge, A. M. Bibcode: 2000MNRAS.314..793H Altcode: Flux elements, pores and sunspots form a family of magnetic features observed at the solar surface. As a first step towards developing a fully non-linear model of the structure of these features and of the dynamics of their interaction with solar convection, we conduct numerical experiments on idealized axisymmetric flux tubes in a compressible convecting atmosphere in cylindrical boxes of radius up to 8 times their depth. We find that the magnetic field strength of the flux tubes is roughly independent of both distance from the centre and the total flux content of the flux tube, but that the angle of inclination from the vertical of the field at the edge of the tube increases with flux content. In all our calculations, fluid motion converges on the flux tube at the surface. The results compare favourably with observations of pores; in contrast, large sunspots lie at the centre of an out-flowing moat cell. We conjecture that there is an inflow hidden beneath the penumbrae of large spots, and that this inflow is responsible for the remarkable longevity of such features. Title: The Influence of Internal Heating on Nonlinear Compressible Convection Authors: Hurlburt, N. E.; Weiss, N. O. Bibcode: 2000SPD....31.0506H Altcode: 2000BAAS...32..837H In the bulk of the solar convection zone we expect convection to be efficient and therefore maintain an adiabatic temperature gradient. In most numerical simulations of solar convection the total energy flux within this region is due to the conduction down this gradient (which is small) and the various contributions due to the convective motions. What has often been neglected is the contribution that is transported by radiation. The contribution of this flux decreases across the layer and thereby deposits a significant amount of thermal energy in the midst of the convection zone. This is in contrast to most simulations of the convection where the input of energy is supplied exclusively by conduction from the boundaries. Mixing length models predict that approximately half of the total energy input to the solar convection zone is deposited, more-or-less uniformly over the convection zone, with the remaining half being conducted from the lower boundary. Thus the study of the behavior of internally-heated compressible convection is warranted. Previous studies of internally heated compressible convection have been inconclusive due to the shearing instabilities that arise in simple, periodic domains. Here we suppress these instabilities by considering flows in axisymmetric geometries. We conduct surveys of the structure and dynamics of the resulting flows and present possible applications to observed solar and stellar phenomena. Title: Supergranule and Mesogranule Evolution Authors: Shine, R. A.; Simon, G. W.; Hurlburt, N. E. Bibcode: 2000SoPh..193..313S Altcode: The MDI instrument on the SOHO satellite obtained a nearly continuous 45.5-hr run in high-resolution mode on 17-18 January 1997, collecting continuum, Dopplergram, and magnetogram images once per minute. This is one of the longest data sets yet obtained in this mode and shows significant evolution of the supergranulation pattern. After allowing for solar rotation within the fixed field of view, an area spanning 17° in latitude and 11° in longitude was extracted that covers the same area of the solar surface for the entire run. From the de-rotated continuum images, we computed flow maps of photospheric motions using local correlation techniques (LCT). Horizontal divergence maps constructed from the flow maps show local maxima of the size of mesogranules (5-10''). We interpret these as mesogranules although the LCT flow map resolution (4.8'' FWHM) may not completely resolve smaller mesogranules. Movies made from the divergence maps clearly show the outward convection (advection) of these mesogranules within each supergranule, and narrow boundaries of negative divergence outlining the supergranules. Several new supergranules are observed forming. These appear as areas of strong divergence that pop up between pre-existing supergranules and grow, pushing their neighbors apart. Others seem to perish between growing neighbors. We also computed the vertical component of vorticity from the flow maps. Movies of this vorticity do not show any obvious patterns. Title: Physics of the Solar Corona and Transition Region Authors: Schrijver, C. J.; Hurlburt, N. E. Bibcode: 2000PASP..112..427S Altcode: Conference was held in Monterey, CA, on 1999 August 24-27. Proceedings are published in the topical issues of Solar Physics of 1999 December and 2000 April. Title: Three-dimensional Stereoscopic Analysis of Solar Active Region Loops. II. SOHO/EIT Observations at Temperatures of 1.5-2.5 MK Authors: Aschwanden, Markus J.; Alexander, David; Hurlburt, Neal; Newmark, Jeffrey S.; Neupert, Werner M.; Klimchuk, J. A.; Gary, G. Allen Bibcode: 2000ApJ...531.1129A Altcode: In this paper we study the three-dimensional structure of hot (Te~1.5-2.5 MK) loops in solar active region NOAA 7986, observed on 1996 August 30 with the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO). This complements a first study (Paper I) on cooler (Te~1.0-1.5 MK) loops of the same active region, using the same method of Dynamic Stereoscopy to reconstruct the three-dimensional geometry. We reconstruct the three-dimensional coordinates x(s), y(s), z(s), the density ne(s), and temperature profile Te(s) of 35 individual loop segments (as a function of the loop coordinate s) using EIT 195 and 284 Å images. The major findings are as follows. (1) All loops are found to be in hydrostatic equilibrium, in the entire temperature regime of Te=1.0-2.5 MK. (2) The analyzed loops have a height of 2-3 scale heights, and thus only segments extending over about one vertical scale height have sufficient emission measure contrast for detection. (3) The temperature gradient over the lowest scale height is of order dT/ds~1-10 K km-1. (4) The radiative loss rate is found to exceed the conductive loss rate by about two orders or magnitude in the coronal loop segments, implying that the loops cannot be in quasi-static equilibrium, since standard steady-state loop models show that radiative and conductive losses are comparable. (5) A steady state could only be maintained if the heating rate EH matches exactly the radiative loss rate in hydrostatic equilibrium, requiring a heat deposition length λH of the half density scale height λ. (6) We find a correlation of p~L-1 between loop base pressure and loop length, which is not consistent with the scaling law predicted from steady-state models of large-scale loops. All observational findings indicate consistently that the energy balance of the observed EUV loops cannot be described by steady-state models. Title: Solar Magnetoconvection - (Invited Review) Authors: Hurlburt, N. E.; Matthews, P. C.; Rucklidge, A. M. Bibcode: 2000SoPh..192..109H Altcode: In recent years the study of how magnetic fields interact with thermal convection in the Sun has made significant advances. These are largely due to the rapidly increasing computer power and its application to more physically relevant parameters regimes and to more realistic physics and geometry in numerical models. Here we present a survey of recent results following one line of investigations and discuss and compare the results of these with observed phenomena. Title: Time Variability of EUV Brightenings in Coronal Loops Observed with TRACE Authors: Nightingale, Richard W.; Aschwanden, Markus J.; Hurlburt, Neal E. Bibcode: 1999SoPh..190..249N Altcode: We analyze coronal loops in active region 8272, observed with TRACE on 23 July 1998 during a 70-min interval with a cadence of 1.5 min, in the temperature range of T≈0.9-1.6 MK. We focus on a compact dipolar loop system with a linear size of ≈30 000 km. In this compact loop system we detect about 20 EUV brightenings at any instant of time and in each wavelength. We measure the centroid position of these EUV brightenings and determine their cospatiality in subsequent time frames. We find that EUV brightenings are not cospatial in subsequent time intervals (Δt=90 s), but are almost randomly distributed in space and time. Title: Heating The Atmosphere Above Sunspots Authors: Alexander, David; Hurlburt, Neal E.; Rucklidge, Alastair Bibcode: 1999ESASP.446..117A Altcode: 1999soho....8..117A We present our results of a hybrid model of sunspots and their overlying corona. The two-layer model considers both the nonlinear, compressible magnetoconvection beneath the photosphere and potential, or linear force-free, models of the coronal fields. Heating of the plasma along the field lines is then consider using quasi-static and steady-state model with the heating rate being specified by the dynamics of the magnetoconvection. Two distinct magnetoconvection scenarios are considered. The first describes magnetoconvection in a 2D axisymmetric geometry and considers the time development of the overlying coronal field. The second describes a 3D cylindrical geometry with a static coronal field configuration. Both scenarios diverge from the standard practice of assuming constant temperature and vertical magnetic field conditions at the top surface. Instead a radiative linear force-free field condition is adopted. Extrapolation of the top surface boundary conditions results in a coronal field configuration which is assumed to be filled with plasma heated to coronal temperatures. The heating rate and thermodynamic behavior of the plasma is related to the sub-surface model by assuming that individual fluxtubes are heated uniformly with the necessary energy being generated from the dissipation of the Poynting flux entering the coronal volume. Radiation and conductive losses are included. The combination of a sunspot model, whereby the surface field is completely specified, with a coronal heating model, in which the plasma parameters are specified for a given energy input allows us to explore a broad class of heating paradigms. Title: A new view of the solar outer atmosphere by the Transition Region and Coronal Explorer Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.; Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.; Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen, R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B. Bibcode: 1999SoPh..187..261S Altcode: The Transition Region and Coronal Explorer (TRACE) - described in the companion paper by Handy et al. (1999) - provides an unprecedented view of the solar outer atmosphere. In this overview, we discuss the initial impressions gained from, and interpretations of, the first million images taken with TRACE. We address, among other topics, the fine structure of the corona, the larger-scale thermal trends, the evolution of the corona over quiet and active regions, the high incidence of chromospheric material dynamically embedded in the coronal environment, the dynamics and structure of the conductively dominated transition region between chromosphere and corona, loop oscillations and flows, and sunspot coronal loops. With TRACE we observe a corona that is extremely dynamic and full of flows and wave phenomena, in which loops evolve rapidly in temperature, with associated changes in density. This dynamic nature points to a high degree of spatio-temporal variability even under conditions that traditionally have been referred to as quiescent. This variability requires that coronal heating can turn on and off on a time scale of minutes or less along field-line bundles with cross sections at or below the instrumental resolution of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through the coronal volume, but it is unclear whether this is caused by the evolution of the field or by the weaving of the heating through the coronal volume, shifting around for periods of up to a few tens of minutes and lighting up subsequent field lines. We discuss evidence that the heating occurs predominantly within the first 10 to 20 Mm from the loop footpoints. This causes the inner parts of active-region coronae to have a higher average temperature than the outer domains. Title: The transition region and coronal explorer Authors: Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.; Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier, R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.; Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich, B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren, R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.; Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.; Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.; Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets, P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.; Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C. Bibcode: 1999SoPh..187..229H Altcode: The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ∼700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min. Title: Cylindrical Compressible Magnetoconvection and Model Sunspots Authors: Hurlburt, N.; Alexander, D.; Rucklidge, A. Bibcode: 1999AAS...194.5502H Altcode: 1999BAAS...31..910H We present results of hybrid models of sunspots and pores which encompasses both the nonlinear, compressible magnetoconvection beneath the photosphere, potential models of the coronal fields and includes quasistatic coronal heating models. We solve the equations that describe compressible magnetoconvection in 2D axisymmetric and 3D cylindrical geometries using compact finite difference scheme. The convecting layer consists of electrically conducting gas which experiences a uniform gravitational acceleration directed downwards. The gas possesses a shear viscosity, a thermal conductivity, a magnetic diffusivity, and a magnetic permeability which are all assumed to be constant. We assume that the fluid satisfies the equation of state for a perfect monatomic gas with constant heat capacities. At the bottom of the cylinder, we impose a constant temperature and vertical magnetic field. On the top surface apply instead a radiative, and linear force-free field condition. The outer boundary is insolating and perfectly conducting. The magnetic fields above the computational domain are then extrapolated and heated using a quasistatic model. The heating problem is solved in an empirical way by assuming that individual fluxtubes are heated in a manner that is proportional to one or more of the parameters defining the fluxtube, e.g. pressure, length, field strength, current density etc. The combination of a sunspot model, whereby the surface field is completely specified, with a coronal heating model, in which the plasma parameters are specified for a given energy input allows us to explore a broad class of heating paradigms. We present result of 2D simulations with no net magnetic flux which display phenomena similar to that observed in sunspot moats, and 3D simulations which develop penumbral-like structure. This work was supported by NASA contract NAG5-7376. Title: Nonlinear Compressible Dynamos Authors: Deluca, E. E.; Hurlburt, N. E. Bibcode: 1999AAS...194.5616D Altcode: 1999BAAS...31..914D The predictions of Mean Field Electrodynamics have been questioned because of the strong feedback of small scale magnetic structure on the velocity fields. In 2-D, this nonlinear feedback results in a lengthening of the turbulent decay time. In 3-D alpha-quenching is predicted. Previous studies assumed a homogeneous fluid. Here we present result of numerical solutions of fully compressible, nonlinear dynamos in two and three dimensions. In two dimensions, we consider an adiabatically stratified layer which experiences a constant shear. A mean-field alpha effect is introduced which is uniform over the layer. This system admits dynamo solutions of both the alpha -omega and alpha (2) varieties. This system also experiences a random thermal forcing which generates an additional turbulent diffusion. We seek to understand both the nonlinear actions of this system and the impact of the turbulent motions upon it. The magnetic flux in the convecting region above has a strong influence on the evolution of the dynamo. In three dimensions we model the generation of magnetic field in an adiabatic, stratified layer with random thermal forcing and an imposed velocity shear across the layer. Rather than introduce an artificial alpha effect, we seek a fully self consistent periodic dynamo. We therefore introduce a uniform rotation to the system which, in conjunction with the random forcing produces a mean helicity to the flows. We present the results of these calculations and their implications for the solar cycle. This work is supported by NASA grant: NAGW-5154 Title: Time Variability of Coronal Loops observed by TRACE Authors: Nightingale, R. W.; Aschwanden, M. J.; Hurlburt, N. E. Bibcode: 1999AAS...194.7802N Altcode: 1999BAAS...31..961N We attempt the 3-dimensional reconstruction of a set of coronal loops during the period of July 18 - 23, 1998, which has been observed by TRACE with a cadence of a few minutes in the temperature range of 1-1.5 MK. Using the method of ``Dynamic Stereoscopy'' and a filter-ratio technique we obtain density n_e(s,t) and temperature T_e(s,t) profiles along the loop length s with respect to time t. Based on these measurements we calculate the radiative E_R(s,t) and conductive E_C(s,t) losses, and attempt to constrain the heating function E_H(s,t) as a function of loop coordinate and time. We test whether the required heating function corresponds to a steady-state or is governed by episodic heating. In particular we investigate which time intervals are subject to continuous (or recurrent) heating and which are dominated by radiative cooling. From this study we shed some light on theoretical loop models (e.g., Rosner-Tucker-Vaiana steady-state model) and the resulting scaling laws. Title: A Spectral Optical-Flow Method for Determining Velocities in the Solar Photosphere Authors: Hurlburt, Neal E. Bibcode: 1999soho....9E..66H Altcode: A method for determining surface flows from solar images based upon optical flow techniques is presented and applied to MDI data. Unlike other, previously proposed methods, we assume the flow field is smooth and can be represented by relatively few Fourier coefficients, which are determined by a least-squares fit. The results of this method are compared to correlation tracking and other methods. Extensions to the method and other applications are discussed. Title: Supergranule and Mesogranule Evolution Authors: Shine, Richard; Simon, George; Hurlburt, Neal Bibcode: 1999soho....9E..15S Altcode: The MDI instrument on the SoHO satellite obtained a nearly continuous 46-hour run in high resolution mode on January 17 to 18, 1997, collecting continuum, dopplergram, and magnetogram images once per minute. This is one of the longest data sets yet obtained in this mode and shows significant evolution of the supergranulation pattern. After allowing for solar rotation within the fixed field of view, an area spanning 13 degrees in latitude and 10 degrees in longitude was extracted that covers the same area of the solar surface for the 46 hours. Using the derotated continuum images, we computed flow maps of photospheric motions using local correlation techniques (LCT). The accuracy of these LCT's has been verified by comparison with La Palma ground based data using other data sets (Shine, et al, 1997, B.A.A.S., 29, 02.62). Horizontal divergence maps constructed from the flow maps show local maxima of about the size of mesogranules. We interpret these as mesogranules although the LCT flow map resolution (4.8 arc seconds FWHM) may not completely resolve all mesogranules. Movies made from the divergence maps clearly show the outward convection of these "mesogranules" within each supergranule and narrow boundaries of negative divergence outlining the supergranules. Several new supergranules are observed forming as areas of strong divergence that pop up between pre-existing supergranules and grow, pushing their neighbors apart. Others seem to perish between growing neighbors. Movies of the derived vertical curl do not show any obvious patterns. Videos of these movies and the continuum, dopplergram, and magnetogram images will be shown. This work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin. Title: Solar Magnetoconvection Authors: Hurlburt, N. E. Bibcode: 1999soho....9E...7H Altcode: The structure and dynamics of pores and sunspots have defied simple theoretical descriptions. Over the past century, and particularly the past few decades, two competing and somewhat disjoint models have developed. One envisions sunspots to be the surface manifestation of a set of magnetic flux tubes, which form a distinct set, separate from the surrounding field-free plasma. The other again has them consisting of a single large flux concentration, which exists within a continuum of plasma and magnetic fields and in which normal fluid dynamical processes occur. Here I review recent progress in explaining the structure and dynamics of sunspots based upon the latter model. Several series of highly idealized numerical simulations suggest that this model can indeed explain a large number of the fundamental behaviors observed in sunspots including heating of the umbra, umbral dots, penumbra grains, the Evershed effect, "fluted" and "spined" penumbra, the formation of penumbra and sunspot moats and the formation of X-ray anemonae. Title: Large-scale coronal heating by the small-scale magnetic field of the Sun Authors: Schrijver, C. J.; Title, A. M.; Harvey, K. L.; Sheeley, N. R.; Wang, Y. -M.; van den Oord, G. H. J.; Shine, R. A.; Tarbell, T. D.; Hurlburt, N. E. Bibcode: 1998Natur.394..152S Altcode: Magnetic fields play a crucial role in heating the outer atmospheres of the Sun and Sun-like stars, but the mechanisms by which magnetic energy in the photosphere is converted to thermal energy in the corona remain unclear. Observations show that magnetic fields emerge onto the solar surface as bipolar regions with a broad range of length scales. On large scales, the bipolar regions survive for months before dispersing diffusively. On the smaller scales, individual bipolar regions disappear within days but are continuously replenished by new small flux concentrations, resulting in a sustained state of mixed polarity. Here we determine the rate of emergence of these small bipolar regions and we argue that the frequent magnetic reconnections associated with these regions (an unavoidable consequence of continued flux replacement) will heat the solar atmosphere. The model that describes the details of these mixed-polarity regions is complementary to the traditional diffusion model for large-scale flux dispersal and a combination of the two should lead to a more complete understanding of the role of magnetic fields in stellar atmospheres. Title: First Results from the TRACE Mission Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine, R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.; Acton, L.; Harrison, R.; Delaboudinere, J. -P. Bibcode: 1998AAS...192.1507T Altcode: 1998BAAS...30..841T The TRACE spacecraft was launched on 1 April and all systems are functioning as designed. The initial outgassing period will conclude on 20 April and the science program will then begin. TRACE is a UV-EUV imager with one arc second spatial resolution and is capable of taking images with a cadence as high as two seconds. We will present images and image sequences. We hope to present initial comparisons of magnetic evolution and transition region and coronal brightenings. Title: Chinks in Solar Dynamo Theory: Turbulent Diffusion, Dynamo Waves and Magnetic Helicity Authors: Deluca, E. E.; Hurlburt, N. Bibcode: 1998nasa.reptV....D Altcode: In this first year of our investigation we explored the role of compressibility and stratification in the dissipation of magnetic fields. The predictions of Mean Field Electrodynamics have been questioned because of the strong feedback of small scale magnetic structure on the velocity fields. In 2-D, this nonlinear feedback results in a lengthening of the turbulent decay time. In 3-D alpha-quenching is predicted. Previous studies assumed a homogeneous fluid. This first year we present recent results from 2-D compressible MHD decay simulations in a highly stratified atmosphere that more closely resembles to solar convection zone. We have applied for NCCS T3E time to assist in the performance of our 3-D calculations. Title: Turbulent Compressible Convection with Rotation. II. Mean Flows and Differential Rotation Authors: Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri Bibcode: 1998ApJ...493..955B Altcode: The effects of rotation on turbulent, compressible convection within stellar envelopes are studied through three-dimensional numerical simulations conducted within a local f-plane model. This work seeks to understand the types of differential rotation that can be established in convective envelopes of stars like the Sun, for which recent helioseismic observations suggest an angular velocity profile with depth and latitude at variance with many theoretical predictions. This paper analyzes the mechanisms that are responsible for the mean (horizontally averaged) zonal and meridional flows that are produced by convection influenced by Coriolis forces. The compressible convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers encompassing both laminar and turbulent flow conditions under weak and strong rotational constraints.

When the nonlinearities are moderate, the effects of rotation on the resulting laminar cellular convection leads to distinctive tilts of the cell boundaries away from the vertical. These yield correlations between vertical and horizontal motions that generate Reynolds stresses that can drive mean flows, interpretable as differential rotation and meridional circulations. Under more vigorous forcing, the resulting turbulent convection involves complicated and contorted fluid particle trajectories, with few clear correlations between vertical and horizontal motions, punctuated by an evolving and intricate downflow network that can extend over much of the depth of the layer. Within such networks are some coherent structures of vortical downflow that tend to align with the rotation axis. These yield a novel turbulent alignment mechanism, distinct from the laminar tilting of cellular boundaries, that can provide the principal correlated motions and thus Reynolds stresses and subsequently mean flows. The emergence of such coherent structures that can persist amidst more random motions is a characteristic of turbulence with symmetries broken by rotation and stratification. Such structure is here found to play a crucial role in defining the mean zonal and meridional flows that coexist with the convection. Though they are subject to strong inertial oscillations, the strength and type of the mean flows are determined by a combination of the laminar tilting and the turbulent alignment mechanisms. Varying the parameters produces a wide range of mean motions. Among these, some turbulent solutions exhibit a mean zonal velocity profile that is nearly constant with depth, much as deduced by helioseismology at midlatitudes within the Sun. The solutions exhibit a definite handedness, with the direction of the persistent mean flows often prescribing a spiral with depth near the boundaries, also in accord with helioseismic deductions. The mean helicity has a profile that is positive in the upper portion of the domain and negative in the lower portion, a property bearing on magnetic dynamo processes that may be realized within such rotating layers of turbulent convection. Title: Differential rotation in turbulent compressible convection Authors: Brummell, N. H.; Toomre, J.; Hurlburt, N. Bibcode: 1997ASSL..225..223B Altcode: 1997scor.proc..223B Numerical simulations of 3D compressible convection in a local rectilinear geometry show that zonal and meridional mean flows, $\overline{u}(z)$ and $\overline{v}(z)$, can be produced when rotation is included. A wide variety of mean profiles can be achieved depending upon the parameters, including behaviour equivalent (within the limitations of the model) to that inferred from helioseismic solar observations. Title: Photospheric flows as measured by SOI/MDI Authors: Hurlburt, N.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Simon, G. Bibcode: 1997ASSL..225..285H Altcode: 1997scor.proc..285H On 2 February and 7 March 1996, MDI on the SOHO spacecraft ran several hours to provide high resolution continuum images to map the horizontal flows near the equator and pole by correlation tracking. Here we present preliminary results on the performance of the tracking technique in measuring the differential rotation profile. These preliminary results are compared with each other and with corresponding results of previous studies. Title: Magnetic Diffusion in Stratified Atmospheres Authors: Deluca, Edward E.; Hurlburt, Neal Bibcode: 1997SPD....28.0251D Altcode: 1997BAAS...29..902D The predictions from of Mean Field Electrodynamics have been questioned because of the strong feedback of small scale magnetic structures on the velocity fields. In 2-D, this nonlinear feedback results in a lengthening of the turbulent decay time. In 3-D alpha -quenching is predicted. Previous studies assumed a homogeneous fluid. We will present recent results from 2-D compressible MHD decay simulations in a highly stratified atmosphere that more closely resembles to solar convection zone. Title: Comparison of Granulation Correlation Tracking (CT) and Feature Tracking (FT) Results from SOHO/MDI and the Swedish Vacuum Solar Telescope on La Palma Authors: Shine, R.; Strous, L.; Simon, G.; Berger, T.; Hurlburt, N.; Tarbell, T.; Title, A.; Scharmer, G. Bibcode: 1997SPD....28.0262S Altcode: 1997BAAS...29Q.904S We have computed photospheric velocity flow maps from simultaneous observations taken with MDI and at the Swedish Vacuum Solar Tower (SVST) on La Palma on August 15, 1996. Both sets consist of a series of photospheric images, and flow maps are computed by following the local motions of granules. The MDI data have the important advantages of very stable images and longer continuous coverage of the same area of the solar surface. This longer coverage is necessary to study the evolution of mesogranules, supergranules, and to detect possible low amplitude motions on scales larger than supergranules. However, the high resolution mode of MDI is limited by the small telescope size to about 1.2 arc seconds angular resolution and uses a 0.6 arc second pixel size. This is adequate to show granulation but has the rms constrast significantly reduced to about 2%. Early efforts adapting techniques that were successful with higher resolution ground based images gave poor results and although new methods have now been developed, there are still some problems with accuracy. On the other hand, the SVST images have much higher angular resolution (as good as 0.2 arc second) but suffer from variable atmospheric distortion. They also have a much smaller field of view. By detailed comparison of the two data sets and by using CT and FT techniques to track the motions, we hope to understand the sources of any differences between them and to develop credible correction parameters to the MDI data sets if necessary. This work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin, by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP, and by the Swedish Royal Academy of Sciences. Title: Horizontal Velocity Structure of Supergranules near Disk Center from High-Resolution SoHO/MDI Observations Authors: Strous, L. H.; Simon, G. W.; Shine, R. A.; Hurlburt, N. Bibcode: 1997SPD....28.0265S Altcode: 1997BAAS...29S.904S We determine the average surface flows in supergranules from high-resolution SoHO/MDI observations near disk center, using local correlation and feature tracking methods. We present results as a function of distance to the supergranule center and of supergranule size, and as a function of normalized distance to the supergranule center. This work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin, and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP. Title: A search for interaction between magnetic fields and supergranular flows in the network based on MDI observations Authors: Schrijver, C. J.; Shine, R. A.; Title, A. M.; Hagenaar, H. J.; Hurlburt, N. E.; Tarbell, T. D.; Simon, G. W. Bibcode: 1997SPD....28.0243S Altcode: 1997BAAS...29..901S We study the supergranular flow field and its temporal evolution in the quiet Sun as observed with the Michelson Doppler Imager on board SOHO. We use the intensity images to derive the flow fields using local correlation tracking. The data sets span one to two days with a one--minute cadence. We separate areas with a relatively high filling factor for magnetic concentrations from areas with a low magnetic filling factor in order to study to what extent the flows influence the magnetic network in the quiet Sun and vice versa. This work is supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin, and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP Title: Continuous Observations of Solar Magnetic Fields from SOI/MDI on SOHO Authors: Hoeksema, J. T.; Bush, R. I.; Scherrer, P. H.; Heck, C.; Hurlburt, N.; Shine, R.; Tarbell, T.; Title, A. Bibcode: 1997SPD....28.0127H Altcode: 1997BAAS...29..884H The Solar Oscillations Investigation's Michelson Doppler Imager instrument (SOI/MDI) on SOHO measures the photospheric magnetic field over the whole disk nearly every 96 minutes with 4" resolution and a noise level of a few Gauss. Beginning in April 1996, this unprecedented continuous series of frequent, uniform quality magnetograms provides a striking view of the continual emergence, motion, evolution, and interaction of magnetic flux everywhere on the visible solar surface near solar minimum. These evolving photospheric fields ultimately drive the variations of the corona and solar wind that affect the terrestrial environment. Knowledge of the rapidly evolving photospheric field provides a crucial input for forecasting conditions in the corona, heliosphere, and geospace. A few magnetograms are available each day within hours of observation through the SOHO web site at http://sohowww.nascom.nasa.gov/. These may be used for planning and forecasting, e.g. to compute models of the solar corona. The remainder are generally available within a few weeks. Sometimes more focused campaigns provide magnetic observations as often as once each minute for up to 8 hours. Campaigns can be run with either the full disk resolution or with 0.6" pixels in a limited field near the center of the disk. The SOI project welcomes collaborations. More information can be found at http://soi.stanford.edu/. Title: Magnetoconvection and Sunspot Dynamics Authors: Hurlburt, N.; Rucklidge, A. Bibcode: 1997SPD....28.0252H Altcode: 1997BAAS...29..902H Observations of sunspots provide a wealth of dynamical phenomena which have long confounded and perplexed theoreticians. Recent work with highly idealized numerical experiments suggests that many of the observed phenomena can be explained, or at least reproduced, within a single "unified theory" of magnetoconvection. We present a series of numerical simulations of compressible magnetoconvection which mimic Evershed flow, umbral dots, penumbral grains, and the formation of fluted penumbra and sunspot moats. Title: Comparison of supergranular flows from doppler and local correlation tracking velocities Authors: Frank, Z.; Hurlburt, N.; Shine, R.; Tarbell, T.; Simon, G.; Strous, L.; Matt, S. Bibcode: 1997SPD....28.0259F Altcode: 1997BAAS...29..903F Measurements of the flows in the solar photosphere rely upon two techniques: doppler measurements of the line-of-sight velocity or tracking of features or patterns moving perpendicular to the line-of-sight. These methods have differing characteristics. Doppler measurements can easily measure surface flows near the limb which are not seriously contaminated by p-modes or other solar sources. However, they require excellent instrument calibration over the full field of view. Even then vertical flows within supergranules are barely detectable. Correlation and feature tracking have proven useful for estimating transverse velocity using granules and other tracers. Nevertheless, they can be degraded by the intensity variations of p-modes and possibly other oscillatory motions, as well as by effects of limb darkening and foreshortening. The two methods would both be strengthened through detailed comparisons. Data collected by MDI/SOHO is ideal for this purpose. The data is co-spatial and co-temporal, and is all obtained through the same instrument. We compare Doppler velocities with those obtained through correlation tracking using high-resolution MDI/SOHO images. We focus on motions at positions exceeding 30 degrees from disk center. After taking projection effects into account, we combine the two measurements to form a three-dimensional picture of the flows in the average supergranule. This work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin, and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP. Title: The Dynamic Quiet Solar Corona: 4 Days of Joint Observing with MDI and EIT Authors: Schrijver, C. J.; Shine, R. A.; Hurlburt, N. E.; Tarbell, T. D.; Lemen, J. R. Bibcode: 1997ESASP.404..669S Altcode: 1997cswn.conf..669S No abstract at ADS Title: Turbulent Compressible Convection with Rotation. I. Flow Structure and Evolution Authors: Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri Bibcode: 1996ApJ...473..494B Altcode: The effects of Coriolis forces on compressible convection are studied using three-dimensional numerical simulations carried out within a local modified f-plane model. The physics is simplified by considering a perfect gas occupying a rectilinear domain placed tangentially to a rotating sphere at various latitudes, through which a destabilizing heat flux is driven. The resulting convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers, evaluating conditions where the influence of rotation is both weak and strong. Given the computational demands of these high-resolution simulations, the parameter space is explored sparsely to ascertain the differences between laminar and turbulent rotating convection. The first paper in this series examines the effects of rotation on the flow structure within the convection, its evolution, and some consequences for mixing. Subsequent papers consider the large-scale mean shear flows that are generated by the convection, and the effects of rotation on the convective energetics and transport properties.

It is found here that the structure of rotating turbulent convection is similar to earlier nonrotating studies, with a laminar, cellular surface network disguising a fully turbulent interior punctuated by vertically coherent structures. However, the temporal signature of the surface flows is modified by inertial motions to yield new cellular evolution patterns and an overall increase in the mobility of the network. The turbulent convection contains vortex tubes of many scales, including large-scale coherent structures spanning the full vertical extent of the domain involving multiple density scale heights. Remarkably, such structures align with the rotation vector via the influence of Coriolis forces on turbulent motions, in contrast with the zonal tilting of streamlines found in laminar flows. Such novel turbulent mechanisms alter the correlations which drive mean shearing flows and affect the convective transport properties. In contrast to this large-scale anisotropy, small-scale vortex tubes at greater depths are randomly orientated by the rotational mixing of momentum, leading to an increased degree of isotropy on the medium to small scales of motion there. Rotation also influences the thermodynamic mixing properties of the convection. In particular, interaction of the larger coherent vortices causes a loss of correlation between the vertical velocity and the temperature leaving a mean stratification which is not isentropic. Title: Dynamics of the Chromospheric Network: Mobility, Dispersal, and Diffusion Coefficients Authors: Schrijver, Carolus J.; Shine, Richard A.; Hagenaar, Hermance J.; Hurlburt, Neal E.; Title, Alan M.; Strous, Louis H.; Jefferies, Stuart M.; Jones, Andrew R.; Harvey, John W.; Duvall, Thomas L., Jr. Bibcode: 1996ApJ...468..921S Altcode: Understanding the physics behind the dispersal of photo spheric magnetic flux is crucial to studies of magnetoconvection, dynamos, and stellar atmospheric activity. The rate of flux dispersal is often quantified by a diffusion coefficient, D. Published values of D differ by more than a factor of 2, which is more than the uncertainties allow. We propose that the discrepancies between the published values for D are the result of a correlation between the mobility and flux content of concentrations of magnetic flux. This conclusion is based on measurements of displacement velocities of Ca II K mottles using an uninterrupted 2 day sequence of filtergrams obtained at the South Pole near cycle minimum. We transform the Ca II K intensity to an equivalent magnetic flux density through a power-law relationship defined by a comparison with a nearly simultaneously observed magnetogram. One result is that, wherever the network is clearly defined in the filtergrams, the displacement vectors of the mottles are preferentially aligned with the network, suggesting that network-aligned motions are more important to field dispersal than deformation of the network pattern by cell evolution. The rms value of the inferred velocities, R = <|v|2>½, decreases with increasing flux, Φ, contained in the mottles, from R ≍ 240 m s-1 down to 140 s-1. The value of R(Φ) appears to be independent of the flux surrounding the concentration, to the extreme that it does not matter whether the concentration is in a plage or in the network. The determination of a proper effective diffusion coefficient requires that the function R(Φ) be weighted by the number density n(Φ) of mottles that contain a total flux. We find that n(Φ) decreases exponentially with Φ and propose a model of continual random splitting and merging of concentrations of flux to explain this dependence. Traditional methods used to measure D tend to be biased toward the larger, more sluggish flux concentrations. Such methods neglect or underestimate the significant effects of the relatively large number of the more mobile, smaller concentrations. We argue that the effective diffusion coefficient for the dispersal of photo spheric magnetic flux is ∼600 km2 s-1. Title: Angular Momentum Transport in Turbulent Compressible Convection Authors: Hurlburt, N. E.; Brummell, N. H.; Toomre, J. Bibcode: 1996AAS...188.6907H Altcode: 1996BAAS...28R.936H We consider the dynamics of compressible convection within a curved local segment of a rotating spherical shell, aiming to resolve the disparity between the differential rotation profiles predicted by previous laminar simulations (angular velocity constant on cylinders) and those deduced from helioseismic inversion of the observed frequency splitting of p modes. By limiting the horizontal extent of the domain under study, we can utilize the available spatial degrees of freedom on current supercomputers to attain more turbulent flows than in the full shell. Our previous study of three-dimensional convection within a slab geometry of an f-plane neglected the effects of curvature, and thus did not admit the generation of Rossby waves. These waves propagate in the longitudinal direction and thus produce rather different spectral characteristics and mean flows in the north-south and east-west directions. By considering motions in a curvilinear geometry in which the Coriolis parameter varies with latitude, we admit the possibility of Rossby waves which couple to the turbulent convection. Here we present simulations with Rayleigh numbers in excess of 10(6) , and Prandtl numbers less than 0.1 in such a curved local segment of a spherical shell using a newly developed code based on compact finite differences. This computational domain takes the form of a curved, periodic channel in longitude with stress-free sidewalls in latitude and radius. Despite the differences in geometry and boundary conditions, the flows maintain similarities with those of our previous f-plane simulations. The surface flows form broad, laminar networks which mask the much more turbulent flows of the interior. The dynamics within this turbulent region is controlled by the interactions of a tangled web of strong vortex tubes. These interactions are further complicated by the effects of curvature. The differential rotation generated by the turbulent convection typically increases with depth and attains a maximum at the base of the layer of about 10 % over the imposed rotation rate. Title: An Analytical Model for Fluted Sunspots and a New Interpretation of Evershed Flow and X-Ray Anemones Authors: Martens, Petrus C. H.; Hurlburt, Neal E.; Title, Alan M.; Acton, Loren W. Bibcode: 1996ApJ...463..372M Altcode: We present a force-free constant-α model for the magnetic field in and above so-called "fluted" sunspots. This model is motivated by recent high-resolution observations of Title et al. at the Swedish Solar Observatory in La Palma. They observed that the inclination angle of the magnetic field in the penumbra of sunspots oscillates rapidly with azimuth, with a period of about 60 and an amplitude of about 18°. They further find that there is little variation in the radial direction and in absolute field strength. The resulting phenomenon of interlocking high- and low-inclination field lines was called "flutedness.

In our model, the parameters are chosen to reproduce the La Palma magnetograms, and an analytical expression is obtained for the three-dimensional magnetic field emanating from the sunspot's umbra and penumbra. The model correctly reproduces the azimuthal variation in inclination angle, as well as the mean constancy of the magnetic field strength, and the appearance of a highly corrugated neutral line on the limb side of off-center sunspots. We find that the "flutedness" results in a highly complex topology in a boundary layer extending from the photo sphere into the chromosphere, while the coronal field is uniform.

Title et al. demonstrated that the Evershed flow occurs in regions of nearly horizontal magnetic field, and tacitly assumed, as is done in most of the literature, that the dark filaments in which the flow is observed form individual magnetic flux tubes. Our magnetic field solution suggests that the regions of nearly horizontal field at the photo spheric boundary may not form individual magnetic flux tubes, but rather a series of short horizontal loops bridging a neutral line that is stretched in the radial direction along the penumbra, up to the outer penumbral boundary. Hence, the Evershed flow could not be a simple siphon flow in the radial direction, but would consist of phase-coordinated flows along the many short loops bridging the neutral line. However, the assumption of a force-free field breaks down in this region of the atmosphere, and the topology suggested by it may not materialize in reality.

We further demonstrate that there are large variations in the photospheric cross sections of coronal loops, due to the complexity of the field near their photospheric footpoints. Under the assumption of constant energy input per unit surface area into these loops, the variation in cross section is qualitatively consistent with the variation in X-ray brightness of loops in penumbral "anemones" observed by Yohkoh. Title: Preliminary SOI/MDI Observations of Surface Flows by Correlation Tracking in the Quiet Solar Photosphere and an Emerging Active Region Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Saba, J.; Schrijver, C.; Shine, R.; Title, A.; Simon, G.; Strous, L. Bibcode: 1996AAS...188.6914T Altcode: 1996BAAS...28..937T The extended observation of the solar surface with frequent sampling provided by MDI on SoHO offers the chance to observe the evolution of supergranules and to measure surface flows associated with active regions and perhaps larger scale zonal and meridonal flows. We have used local correlation tracking of the granulation pattern for measuring surface flows from MDI high resolution continuum images. The datasets consist of 1024 x 1024 pixel images collected with a cadence of one minute and extending many hours each. The images are typically centered upon the central meridian of the sun and offset to the north of sun center, spanning roughly 40 degrees of solar longitude and from approximately -10 to +30 degrees of solar latitude. The latitude dependence of the differential rotation is evident. We present preliminary results of our search for signatures of mesogranules, supergranules and giant cells. On 23 Feb. 1996, we obtained a 12-hour continuous sequence including quiet sun near disk center and NOAA region 7946 at about N08 E30. The active region grew rapidly over this interval, forming several sunpots. We show preliminary comparisons of the measured flow fields with coaligned SOI/MDI magnetograms taken at 15-minute intervals. The SOI/MDI program is supported by NASA grant NAG5-3077. Title: SOI/MDI Measurements of Horizontal Flows in the South Polar Region of the Sun by Correlation Tracking and Doppler Shifts Authors: Simon, G.; Frank, Z.; Hurlburt, N.; Schrijver, C.; Shine, R.; Tarbell, T.; Title, A.; Deforest, C. Bibcode: 1996AAS...188.6913S Altcode: 1996BAAS...28R.937S On 7 March 1996, the SOHO spacecraft was offset from its usual disk center pointing for an 11-hour observation of the South Polar region. MDI took a continuous time series of high resolution longitudinal magnetograms during this period, in support of the SOHO-wide Joint Observing Program on polar plumes. It also ran several hours each of two other programs: one to map the horizontal flows near the pole by correlation tracking and Doppler shifts, and another to study wave propagation (e.g., by time-distance helioseismology) at these high latitudes. In this poster we present preliminary results from the first program. Both techniques yield measurements of the differential rotation profile near the pole and of horizontal flows of supergranulation. These results are compared with each other and with corresponding measurements in low latitudes. The location of magnetic features in the horizontal flows is also shown. The SOI/MDI program is supported by NASA grant NAG5-3077. Title: Nonlinear Compressible Convection in Oblique Magnetic Fields Authors: Hurlburt, Neal E.; Matthews, Paul C.; Proctor, Michael R. E. Bibcode: 1996ApJ...457..933H Altcode: Magnetoconvection in the Sun does not take place in the idealized situation in which the imposed field is vertical or horizontal. Instead, fields in sunspots and other active region features are inclined to the vertical, and so the system does not possess the left-right symmetry that is a feature of many analytical and numerical studies. As a first step toward the understanding of convection in general field configurations, we consider the nonlinear behavior of compressible convection in the presence of a uniform, externally imposed, oblique magnetic field. Numerical simulations demonstrate that all solutions take the form of traveling waves, regardless of the degree of nonlinearity or field intensity, for angles of obliquity 0 < θ < π/2. However, the structure of the convection cells, their wave speed, and direction depend sensitively upon the degree of nonlinearity, field angle, and field strength. For sufficiently vigorous convection, we find that all solutions have a net horizontal velocity at the upper surface of the computational domain that is in the direction of the field tilt from vertical (whereas the total horizontal momentum is zero). In cases where the convection dominates over the magnetic field, we find the waves propagating in the same direction as the net surface velocity but with phase velocities that are typically an order of magnitude smaller. In cases where the field dominates over the convection, we find a similar relation in speeds but with waves propagating in the opposite direction. The results appear to be qualitatively independent of the precise boundary conditions applied to the field, as long as the latter do not impart a net horizontal momentum to the layer. Title: Local-Area Simulations of Rotating Compressible Convection and Associated Mean Flows Authors: Hurlburt, N. E.; Brummel, N. H.; Toomre, J. Bibcode: 1995ESASP.376b.245H Altcode: 1995soho....2..245H; 1995help.confP.245H No abstract at ADS Title: Simulated MDI Observations of Convection Authors: Hurlburt, N. E.; Schrijver, C. J.; Shine, R. A.; Title, A. M. Bibcode: 1995ESASP.376b.239H Altcode: 1995soho....2..239H; 1995help.confP.239H No abstract at ADS Title: Turbulent Rotating Compressible Convection in Spherical Domains Authors: Hurlburt, N. E.; Brummell, N. H.; Toomre, J. Bibcode: 1995SPD....26..406H Altcode: 1995BAAS...27..955H No abstract at ADS Title: Observations of Convection Authors: Title, A. M.; Hurlburt, N.; Schrijver, C.; Shine, R.; Tarbell, T. Bibcode: 1995ESASP.376a.113T Altcode: 1995heli.conf..113T; 1995soho....1..113T The primary goal of the Solar Oscillations Investigation is to understand the interior of the Sun using the techniques of helioseismology. In addition the Michelson Doppler Imager produces images of the solar surface with sufficient resolution to measure surface flows via the technique of local correlation tracking and magnetograms which allow feature tracking of magnetic fields. It will be possible to measure the evolution of meso and supergranulation, the evolution of the meso and supergranulation patterns, and the motion of magnetic elements in the flow field. With observing periods of 8 hours one should be able to detect large scale flow fields of 10 m/s second or less. The magnetograms will provide the data to understand how the cell patterns evolve as a function of magnetic field configuration. Title: Working Group 7 - Surface Flows and Feature Tracking Authors: Hathaway, D.; Hurlburt, N.; Jones, H.; Simon, G. Bibcode: 1995ESASP.376a.205H Altcode: 1995heli.conf..205H No abstract at ADS Title: Three Dimensional Compressible Convection in Oblique Magnetic Fields Authors: Hurlburt, N. E.; Matthews, P. C.; Proctor, M. R. E. Bibcode: 1994AAS...185.8601H Altcode: 1994BAAS...26.1464H Magnetoconvection in the Sun does not take place in the idealized situation in which the imposed field is vertical or horizontal. Instead fields in sunspots and other active region features are inclined to the vertical, and so the system does not possess the left-right symmetry that is a part of many analytical and numerical studies. As a step towards the understanding of convection in general field configurations, we consider the nonlinear behavior of three-dimensional compressible convection in the presence of a uniform, externally-imposed, oblique magnetic field and in a rectangular geometry. As in previous two-dimensional simulations, we find that all solutions take the form of traveling waves for angles of obliquity 0< phi < pi /2, although the convection cells possess definite three-dimensional structures. The resulting traveling patterns heighten the impression that many of the dynamics observed within sunspot penumbra may be a consequence of magnetoconvection in oblique fields. This work was supported in part by NASA contracts NASW-4612 and NAS8-3974 and Lockheed Independent Research Funds. Title: Penetration below a Convection Zone Authors: Hurlburt, Neal E.; Toomre, Juri; Massaguer, Josep M.; Zahn, Jean-Paul Bibcode: 1994ApJ...421..245H Altcode: Two-dimensional numerical simulations are used to investigate how fully compressible nonlinear convection penetrates into a stably stratified zone beneath a stellar convection zone. Estimates are obtained of the extent of penetration as the relative stability S of the stable to the unstable zone is varied over a broad range. The model deals with a perfect gas possessing a constant dynamic viscosity. The dynamics is dominated by downward-directed plumes which can extend far into the stable material and which can lead to the excitation of a broad spectrum of internal gravity waves in the lower stable zone. The convection is highly time dependent, with the close coupling between the lateral swaying of the plumes and the internal gravity waves they generate serving to modulate the strength of the convection. The depth of penetration delta, determined by the position where the time-averaged kinetic flux has its first zero in the stable layer, is controlled by a balance between the kinetic energy carried into the stable layer by the plumes and the buoyancy braking they experience there. A passive scalar is introduced into the unstable layer to evaluate the transport of chemical species downward. Such a tracer is effectively mixed within a few convective overturning times down to a depth of delta within the stable layer. Analytical estimates based on simple scaling laws are used to interpret the variation of delta with S, showing that it first involves an interval of adiabatic penetration if the local Peclet number of the convection exceeds unity, followed by a further thermal adjustment layer, the depths of each interval scaling in turn as S-1 and S-1/4. These estimates are in accord with the penetration results from the simulations. Title: An Analytical Model for Fluted Sunspots and its Relation with Evershed Flow and X-Ray Anemone Authors: Hurlburt, Neal E.; Martens, Petrus C.; Title, Alan M.; Acton, Loren Bibcode: 1994ASPC...68..300H Altcode: 1994sare.conf..300H No abstract at ADS Title: Volume Reconstruction of Magnetic Fields using Solar Imagery Authors: Hurlburt, Neal E.; Martens, Petrus C. H.; Slater, Gregory L.; Jaffey, Steven M. Bibcode: 1994ASPC...68...30H Altcode: 1994sare.conf...30H No abstract at ADS Title: An analytical model for fluted sunspots and a new interpretation of Evershed flow Authors: Martens, P. C.; Hurlburt, N.; Title, A. M.; Acton, L. A. Bibcode: 1994ASIC..433..237M Altcode: No abstract at ADS Title: Invited Talk: (The Structure of Convection Beneath the Photosphere: Recent Simulations of Compressible Convection) Authors: Hurlburt, N. Bibcode: 1993BAAS...25R1219H Altcode: No abstract at ADS Title: Turbulent Compressible Convection with Rotation Authors: Brummell, N. H.; Toomre, J.; Hurlburt, N. E. Bibcode: 1993BAAS...25.1192B Altcode: No abstract at ADS Title: A Force-Free Model for Fluted Sunspots Authors: Martens, P. C. H.; Hurlburt, N.; Title, A. M. Bibcode: 1993BAAS...25R1218M Altcode: No abstract at ADS Title: Computed Tomographic Reconstruction of the Soft X-ray Corona Authors: Hurlburt, N. E.; Martens, P. C. H.; Jaffey, S. M.; Slater, G. L. Bibcode: 1993BAAS...25.1188H Altcode: No abstract at ADS Title: Solar Coronal Magnetic Field Topology Inferred from High Resolution Optical and X-ray Movies Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine, R.; Title, A.; Acton, L. Bibcode: 1993BAAS...25.1208T Altcode: No abstract at ADS Title: ``The Active Sun'': Educational Videotapes on Solar Physics for College Astronomy Authors: Hurlburt, N.; Title, A.; Tarbell, T.; Frank, Z.; Topka, K.; Shine, R. Bibcode: 1993AAS...182.1002H Altcode: 1993BAAS...25..809H We present a series of short, educational documentaries on solar physics aimed at college-level general astronomy courses. These tapes highlight recent advances in high-resolution solar astronomy and in theoretical and computational modeling of solar physics with particular focus on dynamical phenomena. The relevant physical mechanisms, theoretical interpretations and observational techniques are discussed. These include granulation, the theory of convection, five-minute oscillations, sunspots, magnetic fields, seeing and dopplergrams. VHS tapes are available to researchers and educators through a variety of distributors. This work supported by Lockheed Independent Research Funds. Title: Solar Coronal Magnetic Field Topology Inferred from High Resolution Optical and X-ray Movies Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine, R.; Title, A.; Acton, L. Bibcode: 1993AAS...182.4805T Altcode: 1993BAAS...25R.880T We are using high resolution digital movies of solar active regions in optical and X-ray wavelengths to study solar flares and other transients. The optical movies were collected at the Swedish Solar Observatory on La Palma using the Lockheed tunable filtergraph system, in May - July, 1992. They include longitudinal and transverse magnetograms, H-alpha Doppler and intensity images at many wavelengths, Ca K, Na D, and white light images. Simultaneous X-ray images from Yohkoh are available much of the time. We are learning several ways to establish the connectivity of some coronal magnetic field lines. Some of the clues available are: magnetic footpoint polarities and transverse field directions; H-alpha fibrils and loops seen in several wavelengths; proper motion and Doppler shifts of blobs moving along field lines; footpoint brightening in micro-flares; spreading of flare ribbons during gradual phases of flares; X-ray morphology and correlations with H-alpha; and draining of flare loops. Examples of each of these will be shown on video. This work is supported by NASA Contracts NASW-4612 and NAS8-37334 and by Lockheed Independent Research Funds. Title: Turbulent Compressible Convection with Rotation Authors: Brummell, N. H.; Hurlburt, N. E.; Toomre, J. Bibcode: 1993ASPC...42...61B Altcode: 1993gong.conf...61B No abstract at ADS Title: Compressible Magnetoconvection in Oblique Fields: Numerical Simulations of Nonlinear Traveling Waves Authors: Hurlburt, N. E.; Matthews, P. C.; Proctor, M. R. E. Bibcode: 1991BAAS...23.1389H Altcode: No abstract at ADS Title: Solar Granulation: Simulations versus Observations Authors: Hurlburt, N. E. Bibcode: 1991BAAS...23.1048H Altcode: No abstract at ADS Title: Turbulent Compressible Convection Authors: Cattaneo, Fausto; Brummell, Nicholas H.; Toomre, Juri; Malagoli, Andrea; Hurlburt, Neal E. Bibcode: 1991ApJ...370..282C Altcode: Numerical simulations with high spatial resolution (up to 96-cubed gridpoints) are used to study three-dimensional, compressible convection. A sequence of four models with decreasing viscous dissipation is considered in studying the changes in the flow structure and transport properties as the convection becomes turbulent. Title: The Organization of Turbulent Convection Authors: Brummell, Nicholas; Cattaneo, Fausto; Malagoli, Andrea; Toomre, Juri; Hurlburt, Neal E. Bibcode: 1991LNP...388..187B Altcode: 1991ctsm.conf..187B Highly resolved numerical simulations are used to study three-dimensional, compressible convection. The viscous dissipation is sufficiently low that the flow divides itself in depth into two distinct regions: (i) an upper thermal boundary layer containing a smooth flow with a granular appearance, and (ii) a turbulent interior pierced by the strongest downflows from the surface layer. Such downflows span the whole depth of the unstable layer, are temporally coherent, and are thermodynamically well correlated. A remarkable property of such convection, once it becomes turbulent, is that the enthalpy and kinetic fluxes carried by the strong downflows nearly cancel, for they are of opposite sense and nearly equal in amplitude. Thus, although the downflows serve to organize the convection and are the striking feature that emerges from effects of compressibility, it is the small-scale, disorganized turbulent motions (between the coherent downflow structures that serve as the principal carriers of net convected flux. Title: Oscillatory convection in sunspot umbrae Authors: Weiss, N. O.; Brownjohn, D. P.; Hurlburt, N. E.; Proctor, M. R. E. Bibcode: 1990MNRAS.245..434W Altcode: Subphotospheric convection is partially inhibited by the strong vertical magnetic field at the centre of a sunspot. We investigate the effects of stratification on non-linear magnetoconvection in a fully compressible perfect gas by means of two-dimensional numerical experiments. Behaviour depends critically on the ratio ξ of the magnetic to the thermal diffusivity, which increases with depth. If ξ > 1 throughout the layer we find steady overturning convection with an asymmetry between rising and falling plumes. For ξ > 1 we obtain oscillatory convection with reversals of the flow. When ξ > 1 at the top of the layer but ξ > 1 at its base, convection sets in as steady motion but there is a transition (involving several bifurcations) to mixed-mode periodic solutions as the Rayleigh number is increased. The flow at the bottom of the layer does not reverse but adjacent rising plumes alternate between active and quiescent states. In the umbral photosphere t, > 1 but ξ > 1 at depths below 1500 km owing to the increase in opacity. Our results imply that time-dependent convection immediately below the photosphere is coupled to motion at levels where ξ > 1. They also explain the existence of umbral dots with a lifetime corresponding to the Alfven time for the converting layer. Title: Three-dimensional compressible convection at low Prandtl numbers. Authors: Toomre, Juri; Brummell, Nicholas; Cattaneo, Fausto; Hurlburt, Neal E. Bibcode: 1990CoPhC..59..105T Altcode: Numerical simulations are used to study fully compressible thermal convection at large Rayleigh numbers. The authors present results from a sequence of three-dimensional simulations that reveal a transition from gradually-evolving laminar convection to nearly turbulent convection as the Prandtl number is reduced from a value of unity to one-tenth. Title: Supersonic Convection Authors: Cattaneo, Fausto; Hurlburt, Neal E.; Toomre, Juri Bibcode: 1990ApJ...349L..63C Altcode: Numerical simulations with high spatial resolution are used to study that the combined effects of stratification, pressure gradients, and nonadiabatic processes can lead to the formation of regions of supersonic motions near the upper thermal boundary layer. Within these regions, the dynamics is dominated by nonstationary shock structures. These form near the downflow sites and propagate upstream along the boundary layer to the upflow regions where they weaken and eventually disappear. The shock cycle, consisting of the formation, propagation, and disappearance of shock structures, has a time scale comparable to the sound crossing time over a portion of the convective cell, giving rise to vigorous time dependence in the convection. Title: Nonlinear compressible magnetoconvection. I - Travelling waves and oscillations Authors: Hurlburt, N. E.; Proctor, M. R. E.; Weiss, N. O.; Brownjohn, D. P. Bibcode: 1989JFM...207..587H Altcode: Two-dimensional compressible convection in a polytropic layer with an imposed vertical magnetic field is studied in a series of numerical experiments which consider a shallow layer, spanning only a fraction of a scale height in density, and increase the ratio (1/beta) of the magnetic to the thermal pressure in a regime where convection sets in at an oscillatory bifurcation. Initially, there are stable periodic oscillations (standing wave solutions). For moderate values of beta the only deviations from Boussinesq behavior are where the field is locally intense but as beta is decreased magnetic pressure fluctuations become increasingly important. When beta is of order unity at the top of the layer standing waves become unstable at higher Rayleigh numbers and traveling waves are preferred. This is an essentially compressible effect in which magnetic pressure plays a crucial role. The associated bifurcation structure is investigated in some detail. Title: Two and Three-Dimensional Simulations of Compressible Convection Authors: Cattaneo, F.; Hurlburt, N. E.; Toomre, J. Bibcode: 1989ASIC..263..415C Altcode: 1989ssg..conf..415C No abstract at ADS Title: Magnetic Fields Interacting with Nonlinear Compressible Convection Authors: Hurlburt, Neal E.; Toomre, Juri Bibcode: 1988ApJ...327..920H Altcode: Two-dimensional numerical simulations are used to study fully compressible convection in the presence of an imposed magnetic field. Highly nonlinear flows are considered that span multiple density scale heights. The convection tends to sweep the initially uniform vertical magnetic field into concentrated flux sheets with significant magnetic pressures. These flux sheets are partially evacuated, and effects of buoyancy and Lorentz forces there can serve to suppress motions. The flux sheets can be surrounded by a sheath of descending flow. If the imposed magnetic field is sufficiently strong, the convection can become oscillatory. The unstably stratified fluid layer has an initial density ratio (bottom to top of layer) of 11. Surveys of solutions at fixed Rayleigh number sample Chandrasekhar numbers from 1 to 1000 and magnetic Prandtl numbers from 1/16 to 1. These nonlinear simulations utilize a two-dimensional numerical scheme based on a modified two-step Lax-Wendroff method. Title: Topology of Plumes in Nonlinear Compressible Convection Authors: Toomre, J.; Cattaneo, F.; Hurlburt, N. E. Bibcode: 1988BAAS...20..678T Altcode: No abstract at ADS Title: A laboratory model of planetary and stellar convection Authors: 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. Bibcode: 1987STIN...8722108H Altcode: Experiments on thermal convection in a rotating, differentially-heated spherical 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 in agreement with numerical simulations that can be conducted at modest parameter values, and suggest possible regimes of motion in rotating planets and stars. Title: Nonlinear Compressible Convection in Regions of Intense Magnetic Fields Authors: Hurlburt, N. E. Bibcode: 1987rfsm.conf..210H Altcode: Two-dimensional numerical simulations are used to explore the behaviour of nonlinear compressible convection extending over multiple scale heights within regions of intense magnetic fields, e.g. sunspots and pores. The large magnetic pressures possessed by such magnetic fields give rise to buoyancy forces which can dramatically alter the behaviour of both oscillatory and steady types of convection. Title: Interaction between Magnetic Fields and Convection Authors: Hurlburt, N. E.; Weiss, N. O. Bibcode: 1987rfsm.conf...35H Altcode: The authors discuss nonlinear convection in the presence of an imposed vertical magnetic field and its influence on the fine structure of the resulting field. They contrast recent results of numerical experiments on steady and oscillatory magnetoconvection with those obtained in the Boussinesq approximation. An attempt is also made to relate idealized model calculations to the structure of observed magnetic fields in the solar photosphere. Title: Nonlinear Compressible Convection Penetrating into Stable Layers and Producing Internal Gravity Waves Authors: Hurlburt, Neal E.; Toomre, Juri; Massaguer, Josep M. Bibcode: 1986ApJ...311..563H Altcode: Penetrative convection spanning multiple scale heights is studied within a simple stellar envelope consisting of three layers: a convectively unstable middle layer bounded above and below by stably stratified polytropes. Two-dimensional numerical simulations are used to investigate the fully compressible nonlinear motions that ensue. The cellular flows display prominent downward-directd plumes surrounded by broader regions of upflow. Such asymmetry arises because pressure fluctuations accentuate buoyancy driving in the concentrated plumes and can even lead to weak buoyancy braking in the surrounding ascending flows. As the plumes plunge downward into a region of stable stratification, they serve to excite a broad spectrum of internal gravity waves there. The induced waves are not passive, for they feed back upon the plumes by deflecting them sideways, thereby modulating the amplitude of the convection in time even in the unstable layer. The penetrative motions that billow upward into the upper stable zone are distinctly weaker, and they cascade back downward toward the unstable zone over a broad horizontal scale. The strong excitation of gravity waves by the convection has implications for gradual mixing deep within a star. Title: Laboratory Experiments on Planetary and Stellar Convection Performed on Spacelab 3 Authors: 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. Bibcode: 1986Sci...234...61H Altcode: 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. Title: Oscillatory Convection in Flux Tubes Pores and Sunspots Authors: Hurlburt, N.; Weiss, N. O. Bibcode: 1985tphr.conf..198H Altcode: No abstract at ADS Title: Oscillatory convection in flux tubes, pores and sunspots. Authors: Hurlburt, N. E.; Weiss, N. O. Bibcode: 1985MPARp.212..198H Altcode: High-resolution images of the solar surface provide a means for probing sub-photospheric structures. The authors combine simple conceptual arguments with numerical models to consider the different flow regimes possible within flux tubes, pores and sunspots which should be found in detailed observations. In the presence of a strong magnetic field convection near the photosphere is likely to be oscillatory. The authors have carried out a series of numerical experiments involving simple atmospheres (polytropic in the absence of convection). Title: Two-dimensional compressible convection extending over multiple scale heights Authors: Hurlburt, N. E.; Toomre, J.; Massaguer, J. M. Bibcode: 1984ApJ...282..557H Altcode: The theoretical description of the dynamics of a stellar convection zone is considered, taking into account one of the most basic issues by studying compressible convection extending over multiple scale heights. A revised version of a code reported by Graham (1975) is employed. Two-dimensional simulations show that nonlinear compressible convection possesses cellular structures with strong localized downward-directed plumes and broader upflows. The horizontal flows which close the circulation within the cell satisfy an approximate Bernoulli integral along a considerable portion of the horizontal trajectory. Attention is given to details regarding the numerical methods, the properties of the numerical solutions, the overall effects of compressibility on nonlinear convection, and a comparison with anelastic modal solutions. Title: Strong Downward Plumes Resulting from Compressibility in Nonlinear Convection and Their Coupling to Gravity Waves Authors: Toomre, J.; Hurlburt, N. E.; Massaguer, J. M. Bibcode: 1984ssdp.conf..222T Altcode: Two-dimensional numerical simulations are used to model fully compressible nonlinear convection spanning multiple scale heights within a stellar envelope. Title: Compressible convection with penetration Authors: Hurlburt, Neal Bibcode: 1983PhDT.......152H Altcode: No abstract at ADS Title: The Lateral Deflection of Large-Scale Convective Flows by Scale Height Effects below the Solar Surface Authors: Hurlburt, N.; Toomre, J. Bibcode: 1982BAAS...14..938H Altcode: No abstract at ADS Title: Nonlinear Penetrative Convection in a Compressible Medium Authors: Hurlburt, N.; Toomre, J.; Massaguer, J. M. Bibcode: 1981BAAS...13..912H Altcode: No abstract at ADS Title: Two Dimensional Compressible Convection Extending Over Multiple Scale Heights Authors: Hurlburt, N. E.; Toomre, J.; Massaguer, J. M.; Graham, E. Bibcode: 1980BAAS...12S.894H Altcode: No abstract at ADS