hurlburt

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Author name code: hurlburt
ADS astronomy entries on 2022-09-14
author:"Hurlburt, Neal E."

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Title: Heliophysics Events Knowledgebase for FAIR and citable data
Authors: Hurlburt, Neal; Timmons, MR. Ryan
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.

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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.
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.

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Title: Laboratory prototype for a photonic magnetograph
Authors: Hurlburt, Neal; Vasudevan, Gopal; Shing, Lawrence; Chen,
Humphry; Yoo, Ben; Hoeksema, J.
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.

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Title: Heliophysics Events Knowledgebase: Cyber Infrastructure for
Heliophysics and Space Weather
Authors: Hurlburt, Neal; Timmons, Ryan
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.

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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
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.

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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
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.

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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
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.

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Title: Heliophysics Events Knowledgebase Support For Heliophysics
And Space Weather Research
Authors: Timmons, R.; Hurlburt, N.
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.

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Title: The Future Of SolarSoft
Authors: Hurlburt, N.; Freeland, S. L.; Timothy, S.; Shirts, P.;
Slater, G.
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

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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
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.

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Title: Heliophysics Events Knowledgebase support for Space Weather
Research
Authors: Hurlburt, Neal; Timmons, Ryan
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.

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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.
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.

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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.
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.

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Title: The Heliophysics Coverage Registry: An Integrated Metadata
System for Coordinated, Multi-mission Solar Observatories
Authors: Hurlburt, Neal; Timmons, Ryan; Seguin, Ralph
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.

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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.
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.

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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.
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.
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
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.
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
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
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
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
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
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
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
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.
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.
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.
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
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.
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
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.
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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
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
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.
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.
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.
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.
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.
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
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.
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
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
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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.
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.
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 &amp; 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
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.
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.
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.
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.
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.
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.
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 &amp; 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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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&amp;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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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 = &lt;|v|2&gt;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.
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.
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.
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.
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.
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 &lt; θ
&lt; 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.
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.
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.
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.
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.
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.
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&lt; phi &lt; 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
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
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.
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.
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.
1993BAAS...25R1219H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Turbulent Compressible Convection with Rotation
Authors: Brummell, N. H.; Toomre, J.; Hurlburt, N. E.
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.
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.
1993BAAS...25.1188H 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.
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.
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.
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.
1991BAAS...23.1389H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Granulation: Simulations versus Observations
Authors: Hurlburt, N. E.
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.
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.
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.
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 &gt; 1 throughout the layer we find steady overturning convection
with an asymmetry between rising and falling plumes. For ξ &gt; 1
we obtain oscillatory convection with reversals of the flow. When ξ
&gt; 1 at the top of the layer but ξ &gt; 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, &gt; 1 but ξ &gt; 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 &gt; 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.
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
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.
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.
1989ASIC..263..415C Altcode: 1989ssg..conf..415C
No abstract at ADS

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Title: Magnetic Fields Interacting with Nonlinear Compressible
Convection
Authors: Hurlburt, Neal E.; Toomre, Juri
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.
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.
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.
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.
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.
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.
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.
1985tphr.conf..198H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Oscillatory convection in flux tubes, pores and sunspots.
Authors: Hurlburt, N. E.; Weiss, N. O.
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.
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.
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
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.
1982BAAS...14..938H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nonlinear Penetrative Convection in a Compressible Medium
Authors: Hurlburt, N.; Toomre, J.; Massaguer, J. M.
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.
1980BAAS...12S.894H Altcode:
No abstract at ADS