Author name code: gurman
ADS astronomy entries on 2022-09-14
author:"Gurman, Joseph B."
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Title: The Virtual Solar Observatory: Progress and Diversions
Authors: Gurman, Joseph B.; Bogart, R. S.; Amezcua, A.; Hill, Frank;
Oien, Niles; Davey, Alisdair R.; Hourcle, Joseph; Mansky, E.; Spencer,
Jennifer L.
Bibcode: 2017SPD....4811501G
Altcode:
The Virtual Solar Observatory (VSO) is a known and useful method for
identifying and accessing solar physics data online. We review current
"behind the scenes" work on the VSO, including the addition of new
data providers and the return of access to data sets to which service
was temporarily interrupted. We also report on the effect on software
development efforts when government IT “security” initiatives
impinge on finite resoruces. As always, we invite SPD members to
identify data sets, services, and interfaces they would like to see
implemented in the VSO.
Title: Organization of Solar and Heliospheric Data for Scientific
Discovery
Authors: Gurman, J. B.
Bibcode: 2016AGUFMSH34A..01G
Altcode:
"Big data" methods are the subject of much interest in the IT
community. ("Big" in this sense refers to data sets with certain
characteristics including, but far from limited to, high volume
and significant variety.) In practice, big data is defined by
requirements for relatively novel methods for effective analysis. I
will discuss briefly standard definitions of big data, whether solar
and heliospheric data fall within those definitions, a possible set
of minimum requirements for data organization for the effective use
of such tools, and the tradeoffs with more traditional models of data
organization, discovery, and service. I will draw upon a small number
of examples of data organization outside our field as well as within
it to illuminate some of the principles. Finally, I will discuss some
of the step necessary to move toward optimizing our data organization
for big data analytics.
Title: The Virtual Solar Observatiory: Where Do We Go From Here?
Authors: Gurman, Joseph B.; Bogart, R. S.; Amezcua, A.; Hill, Frank;
Oien, Niles; Hourcle, Joseph; Spencer, Jennifer L.; Davey, Alisdair R.
Bibcode: 2016SPD....47.0202G
Altcode:
The Virtual Solar Observatory (VSO) is a known and useful method for
identifying and accessing solar phsyics data online. We review current
"behind the scenes" work on the VSO and invite SPD members to identify
data sets, services, and interfaces they would like to see implemented
in the VSO.
Title: Estimating Coronagraph Visibility Functions - Progress Report
Authors: St Cyr, O. C.; Xie, H.; Duncan, D.; Webb, D. F.; Howard,
R.; Gurman, J. B.
Bibcode: 2015AGUFMSH31C2425S
Altcode:
Annual estimates of the coronal mass ejection (CME) rate have been
well-documented and are quasi-continuous since the mid-1970s based on
both groundbased and spacebased observations. However, coronagraphic
observations from a single viewpoint are unable to detect all CMEs
because they are limited by the properties of Thomson-scattered
photospheric radiation by coronal electrons. To overcome this limitation
and to extend the CME rate estimates beyond a single instrument,
Webb & Howard (1994) formulated the "visibility function" as an
instrument-specific calibration factor. Recently we have begun an
investigation comparing visibility functions for SOHO LASCO, STEREO
COR1/COR2, and the groundbased Mauna Loa Solar Observatory Mk3/Mk4
coronagraphs in order to extend the historical record of the CME
rate. With the launch of the twin STEREO spacecraft in late 2006,
we are able to use the combination of multiple instruments viewing
from longitudinally-separated locations to obtain new estimates of
the global CME rate. We provide a progress report on this activity.
Title: Current STEREO Status on the Far Side of the Sun
Authors: Thompson, William T.; Gurman, Joseph; Ossing, Daniel; Luhmann,
Janet; Curtis, David; Schroeder, Peter; Mewaldt, Richard; Davis,
Andrew; Wortman, Kristin; Russell, Christopher; Galvin, Antoinette;
Kistler, Lynn; Ellis, Lorna; Howard, Russell; Vourlidas, Angelos; Rich,
Nathan; Hutting, Lynn; Maksimovic, Milan; Bale, Stuart D.; Goetz, Keith
Bibcode: 2015TESS....140205T
Altcode:
The current positions of the two STEREO spacecraft on the opposite side
of the Sun from Earth (superior solar conjunction) has forced some
significant changes in the spacecraft and instrument operations. No
communications are possible when the spacecraft is within 2 degrees
of the Sun, requiring that the spacecraft be put into safe mode until
communications can be restored. Unfortunately, communications were lost
with the STEREO Behind spacecraft on October 1, 2014, during testing
for superior solar conjunction operations. We will discuss what is
known about the causes of loss of contact, the steps being taken
to try to recover the Behind spacecraft, and what has been done to
prevent a similar occurrence on STEREO Ahead.We will also discuss the
effect of being on the far side of the Sun on the science operations
of STEREO Ahead. Starting on August 20, 2014, the telemetry rate from
the STEREO Ahead spacecraft has been tremendously reduced due to the
need to keep the temperature of the feed horn on the high gain antenna
below acceptable limits. However, the amount of telemetry that can be
brought down has been highly reduced. Even so, significant science is
still possible from STEREO's unique position on the solar far side. We
will discuss the science and space weather products that are, or will
be, available from each STEREO instrument, when those products will be
available, and how they will be used. Some data, including the regular
space weather beacon products, are brought down for an average of a
few hours each day during the daily real-time passes, while the in
situ and radio beacon data are being stored on the onboard recorder
to provide a continuous 24-hour coverage for eventual downlink once
the spacecraft is back to normal operations.
Title: Results of a Survey of Long-Term Archiving Implementations
Authors: Gurman, Joseph B.; Spencer, Jennifer L.
Bibcode: 2015TESS....140316G
Altcode:
NASA’s Heliophysics Data Management Policy calls for
discipline-specific “final archives,” which will be responsible
for the long-term archiving and service of Heliophysics mission
data. Long-term archival functions, such as periodic revalidation of
the data and migration to newer storage media when appropriate, have
never been part of the Solar Data Analysis Center core capabilities. We
also recognize that the largest space solar physics data set, the SDO
AIA and HMI data at the Stanford Joint Science and Operations Center
(JSOC), will eventually need preservation and long-term access, as will
the potentially much larger data archive of DKIST observations. We
have carried out a study of data archiving best practices in other
disciplines and organizations, including NASA’s Space Physics Data
Facility (SPDF), the National Institute of Standards and Technology
(NIST), and private industry, and report on the lessons learned and
possible cost models. We seek input from the broader solar physics
community on the relative value of various levels of preservation
effort.
Title: When the Sun Gets in the Way: Stereo Science Observations on
the Far Side of the Sun
Authors: Vourlidas, A.; Thompson, W. T.; Gurman, J. B.; Luhmann,
J. G.; Curtis, D. W.; Schroeder, P. C.; Mewaldt, R. A.; Davis, A. J.;
Wortman, K.; Russell, C. T.; Galvin, A. B.; Popecki, M.; Kistler,
L. M.; Ellis, L.; Howard, R.; Rich, N.; Hutting, L.; Maksimovic, M.;
Bale, S. D.; Goetz, K.
Bibcode: 2014AGUFMSH53A4202V
Altcode:
With the two STEREO spacecraft on the opposite side of the Sun from
Earth, pointing the high gain antenna at Earth means that it's also
pointed very close to the Sun. This has resulted in unexpectedly
high temperatures in the antenna feed horns on both spacecraft, and
is forcing the mission operations team to take corrective action,
starting in August 2014 for STEREO Ahead, and December 2014 for STEREO
Behind. By off-pointing the antennas to use one of the lower power side
lobes instead of the main lobe, the feed horn temperatures can be kept
at a safe level while still allowing reliable communication with the
spacecraft. However, the amount of telemetry that can be brought down
will be highly reduced. Even so, significant science will still be
possible from STEREO's unique position on the solar far side. We will
discuss the science and space weather products that will be available
from each STEREO instrument, when those products will be available,
and how they will be used. Some data, including the regular space
weather beacon products, will be brought down for an average of a
few hours each day during the daily real-time passes, while the in
situ and radio beacon data will be stored on the onboard recorder to
provide a continuous 24-hour coverage for eventual downlink once the
spacecraft is back to normal operations.
Title: Deciphering Solar Magnetic Activity. I. On the Relationship
between the Sunspot Cycle and the Evolution of Small Magnetic Features
Authors: McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Davey,
Alisdair R.; Howe, Rachel; Krista, Larisza D.; Malanushenko, Anna V.;
Markel, Robert S.; Cirtain, Jonathan W.; Gurman, Joseph B.; Pesnell,
William D.; Thompson, Michael J.
Bibcode: 2014ApJ...792...12M
Altcode: 2014arXiv1403.3071M
Sunspots are a canonical marker of the Sun's internal magnetic
field which flips polarity every ~22 yr. The principal variation of
sunspots, an ~11 yr variation, modulates the amount of the magnetic
field that pierces the solar surface and drives significant variations
in our star's radiative, particulate, and eruptive output over that
period. This paper presents observations from the Solar and Heliospheric
Observatory and Solar Dynamics Observatory indicating that the 11
yr sunspot variation is intrinsically tied to the spatio-temporal
overlap of the activity bands belonging to the 22 yr magnetic activity
cycle. Using a systematic analysis of ubiquitous coronal brightpoints
and the magnetic scale on which they appear to form, we show that the
landmarks of sunspot cycle 23 can be explained by considering the
evolution and interaction of the overlapping activity bands of the
longer-scale variability.
Title: Final (or Maybe Not So Final) Archiving of Solar Physics Data:
Assuring the Validity of and Access to Data in the Post-NSSDC Epoch
Authors: Gurman, Joseph B.; Spencer, Jennifer L
Bibcode: 2014AAS...22421841G
Altcode:
Historically, NASA's National Space Science Data Center was
responsible for the long-term preservation, periodic revalidation
and recording medium transfer of, and access to, older space solar
physics data sets. The NSSDC is fading from view, however, and the
Heliophysics Data Management Policy calls for discipline-specific
“final archives,” where “final” somehow means less final
than a “long-term archive.”The Solar Data Analysis Center may be
tasked with the “final” archiving of space solar physics data
sets, but we have no expertise in the data preservation activities
traditionally carried out by the NSSDC. We also recognize that the
largest space solar physics data set, the SDO AIA and HMI data at the
Stanford Joint Science and Operations Center (JSOC), will also need
preservation and long-term access, as will the potentially much larger
data archive of DKIST observations. We have therefore begun a study of
data archiving best practices in other disciplines and organizations,
including NASA’s Space Physics Data Facility (SPDF), the National
Institute of Standard and Technology (NIST), and private industry. We
report on the lessons learned so far, and possible cost models. We
seek input from the broader solar physics community on the relative
value of various levels of preservation effort.
Title: A Change in the Solar He II EUV Global Network Structure as
an Indicator of the Geo-Effectiveness of Solar Minima
Authors: Didkovsky, L.; Gurman, J. B.
Bibcode: 2014SoPh..289..153D
Altcode: 2013arXiv1305.2230D
Solar activity during 2007 - 2009 was very low, causing anomalously low
thermospheric density. A comparison of solar extreme ultraviolet (EUV)
irradiance in the He II spectral band (26 to 34 nm) from the Solar
Extreme ultraviolet Monitor (SEM), one of instruments on the Charge
Element and Isotope Analysis System (CELIAS) on board the Solar and
Heliospheric Observatory (SOHO) for the two latest solar minima showed
a decrease of the absolute irradiance of about 15±6 % during the solar
minimum between Cycles 23 and 24 compared with the Cycle 22/23 minimum
when a yearly running-mean filter was used. We found that some local,
shorter-term minima including those with the same absolute EUV flux in
the SEM spectral band show a higher concentration of spatial power in
the global network structure from the 30.4 nm SOHO/Extreme ultraviolet
Imaging Telescope (EIT) images for the local minimum of 1996 compared
with the minima of 2008 - 2011. We interpret this higher concentration
of spatial power in the transition region's global network structure as
a larger number of larger-area features on the solar disk. These changes
in the global network structure during solar minima may characterize,
in part, the geo-effectiveness of the solar He II EUV irradiance in
addition to the estimations based on its absolute levels.
Title: The Virtual Solar Observatory: What Needs Fixing
Authors: Gurman, Joseph B.
Bibcode: 2013SPD....44..137G
Altcode:
I report on the current status of the Virtual Solar Observatory
(VSO), and specifically on its shortcomings, backlogs, and plans
for resolving them, including, but not limited to additional data
providers, the aging web GUI, and performance. I solicit suggestions
from the community on other improvements, and prioritization of our
efforts.Abstract (2,250 Maximum Characters): I report on the current
status of the Virtual Solar Observatory (VSO), and specifically on
its shortcomings, backlogs, and plans for resolving them, including,
but not limited to additional data providers, the aging web GUI,
and performance. I solicit suggestions from the community on other
improvements, and prioritization of our efforts.
Title: Hemispheric Asymmetries of Solar Photospheric Magnetism:
Radiative, Particulate, and Heliospheric Impacts
Authors: McIntosh, Scott W.; Leamon, Robert J.; Gurman, Joseph B.;
Olive, Jean-Philippe; Cirtain, Jonathan W.; Hathaway, David H.;
Burkepile, Joan; Miesch, Mark; Markel, Robert S.; Sitongia, Leonard
Bibcode: 2013ApJ...765..146M
Altcode: 2013arXiv1302.1081M
Among many other measurable quantities, the summer of 2009 saw
a considerable low in the radiative output of the Sun that was
temporally coincident with the largest cosmic-ray flux ever measured
at 1 AU. Combining measurements and observations made by the Solar and
Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO)
spacecraft we begin to explore the complexities of the descending phase
of solar cycle 23, through the 2009 minimum into the ascending phase of
solar cycle 24. A hemispheric asymmetry in magnetic activity is clearly
observed and its evolution monitored and the resulting (prolonged)
magnetic imbalance must have had a considerable impact on the structure
and energetics of the heliosphere. While we cannot uniquely tie the
variance and scale of the surface magnetism to the dwindling radiative
and particulate output of the star, or the increased cosmic-ray flux
through the 2009 minimum, the timing of the decline and rapid recovery
in early 2010 would appear to inextricably link them. These observations
support a picture where the Sun's hemispheres are significantly out
of phase with each other. Studying historical sunspot records with
this picture in mind shows that the northern hemisphere has been
leading since the middle of the last century and that the hemispheric
"dominance" has changed twice in the past 130 years. The observations
presented give clear cause for concern, especially with respect to
our present understanding of the processes that produce the surface
magnetism in the (hidden) solar interior—hemispheric asymmetry is the
normal state—the strong symmetry shown in 1996 was abnormal. Further,
these observations show that the mechanism(s) which create and transport
the magnetic flux are slowly changing with time and, it appears, with
only loose coupling across the equator such that those asymmetries can
persist for a considerable time. As the current asymmetry persists and
the basal energetics of the system continue to dwindle we anticipate
new radiative and particulate lows coupled with increased cosmic-ray
fluxes heading into the next solar minimum.
Title: The Virtual Solar Observatory: What Are We Up To Now?
Authors: Gurman, Joseph B.; Hill, F.; Suàrez-Solà, F.; Bogart, R.;
Amezcua, A.; Martens, P.; Hourclé, J.; Hughitt, K.
Bibcode: 2012AAS...22020124G
Altcode:
In the nearly ten years of a functional Virtual Solar Observatory (VSO),
http://virtualsolar.org/, we have made it possible to query and access
sixty-seven distinct solar data products and several event lists from
nine spacecraft and fifteen observatories or observing networks. We
have used existing VSO technology, and developed new software, for
a distributed network of sites caching and serving SDO HMI and/or
AIA data. We have also developed an application programming interface
(API) that has enabled VSO search and data access capabilities in IDL,
Python, and Java. We also have quite a bit of work yet to do,
including completion of the implementation of access to SDO EVE data,
and access to some nineteen other data sets from space- and ground-based
observatories. In addition, we have been developing a new graphic user
interface that will enable the saving of user interface and search
preferences. We solicit advice from the community input prioritizing
our task list, and adding to it.
Title: The highest cosmic ray fluxes ever recorded: What happened
to the earth's deflector shield?
Authors: Leamon, R. J.; Mcintosh, S. W.; Burkepile, J.; Sitongia,
L.; Markel, R. S.; Gurman, J. B.; Olive, J.
Bibcode: 2011AGUFMSH23D..08L
Altcode:
The summer of 2009 saw the largest cosmic ray flux ever measured
at 1AU. Observed by neutron monitors this solar minimum flux was
6% larger than that of the last solar minimum in 1996, and 4%
larger than the previous high of the space age. Clearly, something
dramatically affected the cosmic ray "deflector shield" of the Earth
this time around, but what was it? Using a combination of serendipitous
observations made by the solid state recorder of the SOHO spacecraft,
an analysis of SOHO/MDI magnetograms combined with SOHO/EIT and SDO/AIA
coronal imaging, we deduce that a pronounced north-south asymmetry
in the meridional circulation flow resulted in the evolution of
the photospheric magnetic to a prolonged prevalence of the negative
magnetic polarity in the equatorial region that were the root cause
of the observed cosmic ray flux increase. The negative sign, weakness
and low rigidity of the interplanetary magnetic field, driven by the
excess of open magnetic flux resulting from the flow asymmetry in the
solar interior, enabled more cosmic rays of the energy range measured
at Earth to creep into our atmosphere than previously measured.
Title: Viewing The Entire Sun With STEREO And SDO
Authors: Thompson, William T.; Gurman, J. B.; Kucera, T. A.; Howard,
R. A.; Vourlidas, A.; Wuelser, J.; Pesnell, D.
Bibcode: 2011SPD....42.1835T
Altcode: 2011BAAS..43S.1835T
On 6 February 2011, the two Solar Terrestrial Relations Observatory
(STEREO) spacecraft were at 180 degrees separation. This allowed the
first-ever simultaneous view of the entire Sun. Combining the STEREO
data with corresponding images from the Solar Dynamics Observatory
(SDO) allows this full-Sun view to continue for the next eight years. We
show how the data from the three viewpoints are combined into a single
heliographic map. Processing of the STEREO beacon telemetry allows
these full-Sun views to be created in near-real-time, allowing tracking
of solar activity even on the far side of the Sun. This is a valuable
space-weather tool, not only for anticipating activity before it rotates
onto the Earth-view, but also for deep space missions in other parts of
the solar system. Scientific use of the data includes the ability to
continuously track the entire lifecycle of active regions, filaments,
coronal holes, and other solar features. There is also a significant
public outreach component to this activity. The STEREO Science Center
produces products from the three viewpoints used in iPhone/iPad and
Android applications, as well as time sequences for spherical projection
systems used in museums, such as Science-on-a-Sphere and Magic Planet.
Title: Accessing SDO Data Through the VSO IDL Client (updated)
Authors: Gurman, J. B.; Hourcle, J. A.; Amezcua, A.; Davey, A. R.;
Hughitt, V. K.; Suarez Sola, F. I.; Somani, A.; Spencer, J.; Vso Team
Bibcode: 2010AGUFMSH23C1866G
Altcode:
At the spring AAS meeting, we presented a poster on how to access SDO
data through the Virtual Solar Observatory's IDL client in SolarSoft,
and solicited comments on additional features that scientists would
like to see. With the data* now flowing, we have had a number of
suggestions from the science community, and have added new keywords,
clarified documentation, and hopefully improved the client overall. We
will present information both on the current status and future planned
updated for the VSO IDL client, as well as solicit for additional
comments on how to improve it. * only test data at the time of this
abstract submission, hopefully fully vetted data at the time of
presentation.
Title: Accessing SDO data in a pipeline environment using the VSO
WSDL/SOAP interface
Authors: Suarez Sola, F. I.; Hourcle, J. A.; Amezcua, A.; Bogart,
R.; Davey, A. R.; Gurman, J. B.; Hill, F.; Hughitt, V. K.; Martens,
P. C.; Spencer, J.; Vso Team
Bibcode: 2010AGUFMSH23C1869S
Altcode:
As part of the Virtual Solar Observatory (VSO) effort to support the
Solar Dynamics Observatory (SDO) data, the VSO has worked on bringing
up to date its WSDL document and SOAP interface to make it compatible
with most widely used web services core engines. (E.g. axis2, jws,
etc.) In this presentation we will explore the possibilities available
for searching and/or fetching data within pipeline code. We will explain
some of the WSDL/VSO-SDO interface intricacies and show how the vast
amount of data that is available via the VSO can be tapped via IDL,
Java, Perl or C in an uncomplicated way.
Title: The Highest Cosmic Ray Fluxes Ever Recorded: What Happened
to the Earth's Deflector Shield?
Authors: Burkepile, J.; McIntosh, S. W.; Gurman, J. B.; Leamon, R. J.
Bibcode: 2010AGUFMSH51B1676B
Altcode:
The summer of 2009 saw the largest cosmic ray flux ever measured at
Earth. Cosmic ray intensities in the 270-450 MeV/nucleon range were
nearly 20% larger than anything previously recorded. Clearly, something
dramatically affected the cosmic ray 'deflector shield' of the Earth
during the most recent solar activity minimum. We explore the cause
of this marked increase by examining properties of the global solar
magnetic field and conditions in the solar wind during the previous
solar minimum and compare these to previous solar cycles using in-situ
and remote sensing observations.
Title: SDO Data Access Via The Virtual Solar Observatory
Authors: Hill, Frank; Gurman, J.; Martens, P.; Bogart, R.; Davey, A.;
Hourcle, J.; Suarez Sola, F.; Hughitt, K.; Spencer, J.; Reardon, K.;
Amezcua, A.
Bibcode: 2010AAS...21640218H
Altcode: 2010BAAS...41Q.876H
The launch of SDO brings not only the prospect of new solar physics
discoveries, but also a flood of data. The sustained data rate of
150 Mbs (about 1.6 TB per day) is the highest yet produced by a
solar physics observatory, and the handling of the data requires new
methods. One approach is to distribute the data storage and request
system over a number of distinct sites to reduce the bandwidth
requirements at a single location. The VSO, in conjunction with the
Joint Science and Operations Center (JSOC) at Stanford and a network of
partial archive sites currently at CfA, NSO, ROB, and MPIS, is now able
to provide metadata search and data retrieval services for the SDO AIA
and HMI instruments. EVE data will also be included in the future. This
talk will describe how SDO data can be accessed via the VSO.
Title: Enabling Distributed Search and Access to SDO Data with the
Virtual Solar Observatory
Authors: Davey, Alisdair; Martens, P.; Gurman, J.; Hourcle, J.; Hill,
F.; Suarez-Sola, F.; Amezcua, A.; Bogart, R.; Spencer, J.
Bibcode: 2010cosp...38.2881D
Altcode: 2010cosp.meet.2881D
The Virtual Solar Observatory (VSO) will be an integral part of
distributing Solar Dynamics Observatory (SDO) data to the Solar Physics
community and in enabling it to be searched by scientists. A daily
data volume of 1.5TB presents unique challenges, and the VSO has been
working on enhancing various aspects of its infrastructure to deal with
them. The VSO will provide a dedicated interface to SDO data, providing
common methods users of VSO already know, as well as new methods that
reflect the needs of interacting with AIA, HMI and EVE data. VSO has
created a data distribution architecture based up the Joint Science
Operations Center (JSOC) infrastructure, that in partnership with
NASA Solar Data Analysis Center, National Solar Observatory, Royal
Observatory Belgium, University College Lancashire, Max Planck Institute
for Solar System Research and the Institute d'Astrophysique Spatiale
(Orsay) will enable scientists to retrieve SDO data of interest in
the fastest possible way. VSO is working closely with the Helioviewer
and Heliophysics Event Knowledgebase (HEK) teams to ensure we will
be able to use their efforts and be used by their efforts for data
retrieval. In this manner, graphical, IDL-based and event approaches
to data discovery will be fully supported by the VSO.
Title: Recent STEREO Observations of Coronal Mass Ejections
Authors: St Cyr, O. C.; Xie, H.; Mays, M. L.; Davila, J. M.; Gilbert,
H. R.; Jones, S. I.; Pesnell, W. D.; Gopalswamy, N.; Gurman, J. B.;
Yashiro, S.; Wuelser, J.; Howard, R. A.; Thompson, B. J.; Thompson,
W. T.
Bibcode: 2009AGUFMSH11A1491S
Altcode:
Over 400 CMEs have been observed by STEREO SECCHI COR1 during
the mission's three year duration (2006-2009). Many of the solar
activity indicators have been at minimal values over this period,
and the Carrington rotation-averaged CME rate has been comparable to
that measured during the minima between Cycle 21-22 (SMM C/P) and
Cycle 22-23 (SOHO LASCO). That rate is about 0.5 CMEs/day. During
the current solar minimum (leading to Cycle 24), there have been
entire Carrington rotations where no sunspots were detected and the
daily values of the 2800 MHz solar flux remained below 70 sfu. CMEs
continued to be detected during these exceptionally quiet periods,
indicating that active regions are not necessary to the generation of
at least a portion of the CME population. In the past, researchers were
limited to a single view of the Sun and could conclude that activity
on the unseen portion of the disk might be associated with CMEs. But
as the STEREO mission has progressed we have been able to observe an
increasing fraction of the Sun's corona with STEREO SECCHI EUVI and
were able to eliminate this possibility. Here we report on the nature
of CMEs detected during these exceptionally-quiet periods, and we
speculate on how the corona remains dynamic during such conditions.
Title: The Virtual Solar Observatory: Where Do We Go from Here?
Authors: Gurman, Joseph B.; Bogart, R.; Spencer, J.; Hill, F.; Suarez
Sola, I.; Reardon, K.; Hourcle, J.; Hughitt, K.; Martens, P.; Davey, A.
Bibcode: 2009SPD....40.1508G
Altcode:
The Virtual Solar Observatory (VSO) continues to add features in an
effort to broaden the ways in which it can be used to aid research. We
describe and demonstrate plans for SDO data access (see also the poster
Suarez-Sola et al.), multiple catalog access (Hourclé et al.), and
new capabilities of the IDL VSO_SEARCH function, as well as describing
future capabilities in development and under consideration. Since
the VSO is funded by the Solar Data Analysis Center (SDAC), which will
be undergoing a NASA Senior Review in July, we solicit community input
to help us prioritize this new work: what should we do with the limited
resources available?
Title: The Virtual Solar Observatory—A Resource for International
Heliophysics Research
Authors: Hill, Frank; Martens, Piet; Yoshimura, Keji; Gurman, Joseph;
Hourclé, Joseph; Dimitoglou, George; Suárez-Solá, Igor; Wampler,
Steve; Reardon, Kevin; Davey, Alisdair; Bogart, Richard S.; Tian,
Karen Q.
Bibcode: 2009EM&P..104..315H
Altcode: 2008EM&P..tmp...47H
The Virtual Solar Observatory (VSO) has been developed to allow
researchers, educators, and the general public to access data
and images from the major sources of on-line solar data. The VSO
substantially reduces the effort required to locate disparate data
sets, and removes the need for the user to locate the data and
learn multiple interfaces. The VSO provides a single interface to
about 60 geographically distributed data sets including space- and
ground-based sources. These data sets incorporate several physical
variables including magnetic field, intensity, Doppler velocity, etc.,
and all wavelengths from X-ray to radio. All layers of the sun, from
the interior to the corona, are included. In this paper we describe
the system and present the interface that the user will encounter. We
also discuss future enhancements planned for the system.
Title: Preface: SOHO 20 - Transient events on the Sun and in the
heliosphere
Authors: Robbrecht, E.; Hochedez, J. -F.; Fleck, B.; Gurman, J.;
Forsyth, R.
Bibcode: 2008AnGeo..26.2953R
Altcode:
No abstract at ADS
Title: Moving Beyond Time: New VSO Searches
Authors: Davey, A.; Bogart, R.; Gurman, J.; Hill, F.; Hourcle, J.;
Martens, P.; Suarez Sola, I.; VSO Team
Bibcode: 2008AGUSMSP54A..06D
Altcode:
Since its inception the Virtual Solar Observatory (VSO) has supported
a standard set of search parameters for finding data sets of interest,
including instrument, spectral range and observable, all keyed on
a defined time range. The VSO also allows users to derive search
periods based on feature or event catalogs. Recent work on the catalog
infrastructure will enable far more complex science based queries to
derive both stand alone results and also starting points for querying
other data sets. The technical side of this work is presented at
this meeting in 'Event and Feature Catalogs in the Virtual Solar
Observatory' by Joe Hourcle et al. This abstract focuses on the
science made possible by this catalog work and from work to extend
the standard query mechanisms. In the future we will be able to answer
queries such as 'show me data sets suitable for DEM analysis' or 'give
me an image every ten minutes from this instrument.' This effort has
obvious application to handling SDO data.
Title: Still Virtual After All These Years: Recent Developments in
the Virtual Solar Observatory
Authors: Gurman, J. B.; Bogart, R. S.; Davey, A. R.; Hill, F.; Martens,
P. C.; Zarro, D. M.; Team, T. v.
Bibcode: 2008AGUSMSP51B..17G
Altcode:
While continuing to add access to data from new missions, including
Hinode and STEREO, the Virtual Solar Observatory is also being enhanced
as a research tool by the addition of new features such as the unified
representation of catalogs and event lists (to allow joined searches
in two or more catalogs) and workable representation and manipulation
of large numbers of search results (as are expected from the Solar
Dynamics Observatory database). Working with our RHESSI colleagues,
we have also been able to improve the performance of IDL-callable
vso_search and vso_get functions, to the point that use of those
routines is a practical alternative to reproducing large subsets of
mission data on one's own LAN.
Title: Callable Virtual Observatory Functionality: Sample Use Cases
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
Hill, F.; Suárez-Solá, I.; Zarro, D. M.; Davey, A. R.; Martens,
P. C.; Yoshimura, K.
Bibcode: 2007AGUFMSH51A0259G
Altcode:
A virtual observatory with an Application Programming Interface
(API) can become a powerful tool in analysis and modeling. In
particular, an API that integrates time selection on such criteria
as "most recent" and closest to a given absolute time simplifies the
user-end programming considerably. We examine three types of use cases
(nowcasting, data assimilation input, and user-defined sampling rates)
for such functionality in the Virtual Solar Observatory (VSO).
Title: Design Considerations for Data Catalogs
Authors: Hourcle, J.; Suarez-Sola, I.; Davey, A.; Tian, K.; Yoshimura,
K.; Martens, P.; Gurman, J.; Hill, F.; Bogart, R.
Bibcode: 2007AGUFMSH51A0261H
Altcode:
Mission data catalogs are typically built with the specific mission in
mind. This can create challenges when trying to abstract the metadata
to make it useful to other researchers. The deluge of data from new
missions such as STEREO and Hinode have brought in not only issues
in scale, but also complexities due to the difference in these new
experiments in the context of existing norms. We will discuss issues
and use cases to be considered in designing a mission's data systems
in order to better serve the Heliospheric community.
Title: Dealing with Large Dataset Queries in the Virtual Solar
Observatory
Authors: Suarez-Sola, F. I.; Bogart, R.; Davey, A.; Gurman, J. B.;
Hill, F.; Hourcle, J.; Martens, P. C.; Tian, K.; Yoshimura, K.
Bibcode: 2007AGUFMSH51A0260S
Altcode:
The Virtual Solar Observatory (VSO) project presents a solution for
dealing with large dataset queries. One of the main problems arising
from the VSO user community has been managing queries that generate
a large amount of metadata records spanning several providers. Until
now the only way to do this was through painstakingly repeating the
same query for smaller time periods and collecting the information
at each pass. With the solution presented here we are making possible
for users to access data over any arbitrary time period in one single
query, minimizing the metadata generated, and yet allowing the user
to sample either a small subset or the whole.
Title: Science With the Virtual Solar Observatory: Today and Tomorrow
Authors: Hill, F.; Bogart, R. S.; Davey, A. R.; Gurman, J. B.; Hourcle,
J. A.; Martens, P. C.; Reardon, K. M.; Suarez-Sola, I.; Tian, K. Q.;
Yoshimura, K.
Bibcode: 2007AGUSMSM33D..05H
Altcode:
The Virtual Solar Observatory (VSO) was released to the community in
December 2004. It is designed to provide solar physicists with a tool
that allows them to locate and access solar data in an efficient manner,
thus facilitating science studies involving multiple data sets. Examples
of science projects that have been done with the VSO are a study of
halo CME speeds and their visibility in a variety of SOHO data sets,
and the calibration between helioseismic farside signals and the
characteristics of active regions. Future possible projects include
studies of farside coronal mass ejections; the relationship between
subsurface flows and solar wind speeds; statistics of the active region
life cycle; sunspot energetics, and space weather predictors.
Title: Early Results from STEREO SECCHI COR1
Authors: St. Cyr, Orville C.; Davila, J. M.; Thompson, W.; Thompson,
B. J.; Gurman, J. B.; Burkepile, J. T.; de Toma, G.
Bibcode: 2007AAS...21011903S
Altcode: 2007BAAS...39..243S
With the successful launch and commissioning of STEREO, routine
observations of the Sun's corona by the payload began in early 2007. The
COR1 internally-occulted coronagraphs, which are classically-designed
Lyot instruments covering 1.4-4.0 Rsun, are performing extremely
well. More than two dozen coronal mass ejections (CMEs) were detected
by COR1 in the first month of observations. As the STEREO spacecraft
separate away from Earth, the MK4 coronameter at MLSO will provide
a third vantage point for observations of the low corona. In this
presentation we will show CME observations from COR1 and MK4, and we
will describe the context of these new observations.
Title: The current and future roles of virtual observatories serving
the heliophysical data environment
Authors: Davey, A. R.; Bogart, R. S.; Dimitoglou, G.; Gurman, J. B.;
Hill, F.; Hourcle, J. A.; Martens, P. C.; Suarez-Sola, I.; Tian, K.;
Yoshimura, K.
Bibcode: 2006AGUFMSM11C..05D
Altcode:
The Virtual Solar Observatory is just one of a growing number of
virtual observatories that serve heliophysics data. We discuss the
current capabilities of these virtual observatories, their roles in
data archiving, discovery, quality assurance, assimilation, encouraging
standards and in facilitating science. We also discuss the realistic
goals virtual observatories should have, in fulfilling the demands of
the current and near future heliophysics data environment.
Title: The Virtual Solar Observatory and the Heliophysics Meta-Virtual
Observatory
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
Hill, F.; Suàrez-Sola, I.; Zarro, D. M.; Davey, A. R.; Martens,
P. C.; Yoshimura, K.; Reardon, K. M.
Bibcode: 2006AGUFMSM21A0246G
Altcode:
The Virtual Solar Observatory (VSO) has survived its infancy and
provides metadata search and data identification for measurements from
45 instrument data sets held at 12 online archives, as well as flare
and coronal mass ejection (CME) event lists. Like any toddler, the VSO
is good at getting into anything and everything, and is now extending
its grasp to more data sets, new missions, and new access methods
using its application programming interface (API). We discuss and
demonstrate recent changes, including developments for STEREO and SDO,
and an IDL-callable interface for the VSO API. We urge the heliophysics
community to help civilize this obstreperous youngster by providing
input on ways to make the VSO even more useful for system science
research in its role as part of the growing cluster of Heliophysics
Virtual Observatories.
Title: The Virtual Solar Observatory and the Heliophysics Meta-Virtual
Observatory
Authors: Gurman, Joseph B.; Bogart, R.; Tian, K.; Hill, F.;
Suárez-Sola, I.; Martens, P. C.; Yoshimura, K.; Davey, A.; Dimitoglou,
G.; Hourclé, J.
Bibcode: 2006SPD....37.0305G
Altcode: 2006BAAS...38..222G
The Virtual Solar Observatory (VSO) is now able to search for solar
data ranging from the radio to gamma rays, obtained from space and
groundbased observatories, from 26 sources at 12 data providers, and
from 1915 to the present. The solar physics community can use a Web
interface or an Application Programming Interface (API) that allows
integrating VSO searches into other software, including other Web
services. Over the next few years, this integration will be especially
obvious as the NASA Heliophysics division sponsors the development of
a heliophysics-wide virtual observatory (VO), based on existing VO's
in heliospheric, magnetospheric, and ionospheric physics as well as
the VSO. We examine some of the challenges and potential of such a
"meta-VO."
Title: The VSO at Two and a Half
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
Hill, F.; Suarez-Sola, I.; Wampler, S.; Davey, A. R.; Martens, P. C.;
Yoshimura, K.; Zarro, D. M.
Bibcode: 2006AGUSMSM31B..03G
Altcode:
The Virtual Solar Observatory (VSO) has survived its infancy and
provides metadata search and data identification for 26 data sets
held at 12 online archives, as well as flare and coronal mass ejection
(CME) event lists. Like any toddler, the VSO is good at getting into
anything and everything, and is now extending its grasp to more data
sets and providers, new missions, and new access methods using its
application programming interface (API). We discuss recent changes,
including developments for STEREO and SDO, and an IDL-callable interface
for the VSO API. We urge the heliophysics community to help civilize
this obstreperous youngster by providing input on ways to make the
VSO even more useful for system science research.
Title: Measuring proton energies and fluxes using EIT (SOHO) CCD
areas outside the solar disk images
Authors: Didkovsky, L. V.; Judge, D. L.; Jones, A. R.; Rhodes, E. J.,
Jr.; Gurman, J. B.
Bibcode: 2006AN....327..314D
Altcode: 2006astro.ph..4436D
An indirect proton flux measuring tool based on discrimination of the
energy deposited by protons in 128×128 pixel EIT CCD areas outside
the solar disk images is presented. Single pixel intensity events
are converted into proton incident energy flux using modeled energy
deposition curves for angles of incidence ± 60° in four EIT spatial
areas with different proton stopping power. The extracted proton flux
is corrected for both the loss of one-pixel events in the range of
angles of incidence as well as for the contribution to the single pixel
events resulting from scattered middle-energy protons (low-energy or
high-energy particles are stopped by the EIT components or pass through
them, accordingly). A simple geometrical approach was found and applied
to correct for a non-unique relation between the proton-associated CCD
output signal and the incident proton energy. With this geometrical
approximation four unique proton incident energy ranges were determined
as 45-49, 145-154, 297-335, and 390-440 MeV. The indirect proton flux
measuring tool has been tested by comparing Solar Energetic Particles
(SEP) flux temporal profiles extracted from the EIT CCD frames and
downloaded from the GOES database for the Bastille Day (BD) of 2000
July 14 and the more recent 2005 January 20 events. The SEP flux
temporal profiles and proton spectra extracted from the EIT in the
relatively narrow energy ranges between 45 and 440 MeV reported here
are consistent with the related GOES profiles. The four additional
EIT extracted ranges provide higher energy resolution of the SEP data.
Title: 10 years of SOHO
Authors: Fleck, Bernhard; Müller, Daniel; Haugan, Stein; Sánchez
Duarte, Luis; Siili, Tero; Gurman, Joseph B.
Bibcode: 2006ESABu.126...24F
Altcode:
Since its launch on 2 December 1995, SOHO has revolutionised
our understanding of the Sun. It has provided the first images of
structures and flows below the Sun's surface and of activity on the
far side. SOHO has revealed the Sun's extremely dynamic atmosphere,
provided evidence for the transfer of magnetic energy from the surface
the outer solar atmosphere, the corona, through a "magnetic carpet",
and identified the source regions of the fast solar wind. It has
revolutionised our understanding of solar-terrestrial relations and
dramatically improved our space weather-forecasting by its continuous
stream of images covering the atmosphere, extended corona and far
side. The findings are documented in an impressive number of scientific
publications: over 2500 papers in refereed journals since launch,
representing the work of over 2300 individual scientists. At the
same time, SOHO's easily accessible, spectacular data and fundamental
scientific results have captured the imagination of the space science
community and the general public alike. As a byproduct of the efforts
to provide real-time data to the public, amateurs now dominate SOHO's
discovery of over 1100 Sungrazing comets.
Title: The virtual solar observatory
Authors: Young, C. A.; Gurman, J. B.; Dimitoglou, G.; Hourcle, J.;
Bogart, R. S.; Tian, K.; Hill, F.; Suarz-Sola, I.; Wampler, S.;
Martens, P.; Yoshimura, S.; Davey, A.
Bibcode: 2006ilws.conf..226Y
Altcode:
The recent explosion of data quantity and complexity has lead to the
need for a new way to make data available, the virtual observatory. The
Virtual Solar Observatory (VSO) provides a versatile means for solar
physicists to discover and share the growing sources of data. We present
the development of the VSO, show the system in action and discuss how
data users and data providers can benefit from it.
Title: EGSO - A maturing VO for Solar Physics
Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham, J.;
Antonucci, E.; Gurman, J.; Hill, F.; Pike, D.; Vial, J.; Zharkova, V.
Bibcode: 2005AGUSMSH43B..01B
Altcode:
The European Grid of Solar Observations, EGSO, is a Grid test-bed
funded under the Information Societies Thematic Priority of the European
Commission's Fifth Framework Programme (FP5). In the case of EGSO, the
application chosen was the use of Grid technology to establish a virtual
observatory for solar physics, and the project addresses the generic
problem of how to provide access to a distributed, heterogeneous data
set for a scattered user community. In order to identify observations
that match a user's search criteria, EGSO has been building an
environment that will support complex searches. Because of the absence
of the metadata needed to tie the heterogeneous data together, EGSO has
placed emphasis on the provision of databases that can be accessed from
the Internet through special providers. The provision of appropriate
metadata is of extreme importance in establishing a virtual observatory,
and the approach used can be adapted to facilitate the inclusion of
any data, including non-solar data. We report on the capabilities of
EGSO and discuss experience gained in creating the facility. We also
discuss how EGSO has been working with other virtual observatories that
support the solar, heliospheric and space plasma communities in order
to try to achieve interoperability between the numerous data sets. We
highlight what we consider are the most profitable ways of doing this.
Title: CME Population Distributions: Science Facilitated by the VSO
Authors: Davey, A.; Wills-Davey, M.; Gurman, J.; Bogart, R.;
Dimitoglou, G.; Hill, F.; Hourcle, J.; Martens, P.; Suarez Sola, I.;
Tian, K.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSP23A..09D
Altcode:
The Virtual Solar Observatory (VSO) exists to simplify and unify
access to Solar Physics data. It provides a single interface to
a broad spectrum of data types and sources which previously would
have required considerable effort to collect. Using this ability to
combine data sources, we access the entire SOHO/LASCO CME catalog and
compare it with GOES observations of X-ray flares. Because we consider
these data in their entirety, we find several instances where the
results of less extensive studies may show unintentional selection
effects. As a subpopulation, we specifically consider LASCO-observed
halo CMEs. In agreement with previous studies, we find halo CMEs are
the bulk of the fastest events. This selection effect is consistent
with randomly-distributed CMEs extending over wide angles (>120
degrees). We also examine the lack of slower halo CMEs; otherwise
randomly-distributed events are rarely Earth-directed. While geometric
and Thomson scattering issues make less-energetic halo CMEs hard to
detect, this dearth of slow observations may represent an additional
seeing threshold. The lack of low-energy detections may account for the
disparity in LASCO.s prediction of Kp ≥ 6 vs. Kp ≥ 5 geomagnetic
storms.
Title: The Virtual Solar Observatory: Still a Small Box
Authors: Gurman, J. B.; Bogart, R. S.; Davey, A. R.; Dimitoglou, G.;
Hill, F.; Hourclé, J. A.; Martens, P. C.; Suárez-Sola, I.; Tian,
K. Q.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSH43B..03G
Altcode:
Two and a half years after a design study began, and a year and a
half after development commenced, version 1.0 of the Virtual Solar
Observatory (VSO) was released at the 2004 Fall AGU meeting. Although
internal elements of the VSO have changed, the basic design has
remained the same, reflecting the team's belief in the importance of
a simple, robust mechanism for registering data provider holdings,
initiating queries at the appropriate provider sites, aggregating the
responses, allowing the user to iterate before making a final selection,
and enabling the delivery of data directly from the providers. In
order to make the VSO transparent, lightweight, and portable, the
developers employed XML for the registry, SOAP for communication
between a VSO instance and data services, and HTML for the graphic
user interface (GUI's). We discuss the internal data model, the API,
and user responses to various trial GUI's as typical design issues for
any virtual observatory. We also discuss the role of the "small box"
of data search, identification, and delivery services provided by the
VSO in the larger, Sun-Solar System Connection virtual observatory
(VxO) scheme.
Title: Nine Years Of Euv Bright Points
Authors: McIntosh, Scott W.; Gurman, Joseph B.
Bibcode: 2005SoPh..228..285M
Altcode:
We discuss early results derived from an algorithm that automates the
detection, cataloging, and analysis of extreme-ultraviolet (EUV) "bright
points" (BP) from 9 years of data acquired by the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). The algorithm relies upon the computation of a map of
"intensity significance"; this then contains the location of the EUV
BPs. By mapping the location of BPs in each image and linking them
through long sequences of EIT images we can describe the temporal
and spatial variations of the 1.3× 108 EUV BPs observed
by SOHO to date. We suggest that there is a considerable amount of
physical information about the solar coronal plasma that can be readily
gleamed from the BP detection database. In this paper we discuss only
a small portion of the possible correlations, but we point to the
possibility of BP lifetime distributions that are well described by
modified power-laws; the components of which vary with the different
temperature filters and with time over the present solar cycle.
Title: A Search for Relativistic High-Energy Protons From the Extreme
Solar Flares of 2000-03
Authors: Didkovsky, L. V.; Jones, A. R.; Judge, D. L.; Gurman, J.;
Gangopadhyay, P.; Rhodes, E.; Tsurutani, B. T.
Bibcode: 2005AGUSMSH33A..05D
Altcode:
We applied a high-energy proton flux-measuring tool based on detection
of the energy deposited by post-flare protons in the active silicon
layers of the SOHO/EIT and TRACE CCDs to extract individual proton
events from the Fe XII (19.5~ nm) spectral line solar images. Temporal
profiles of proton flux for extreme solar flares of 2000--03,
including their pre-flare, impulsive phase, and near-post-flare
intervals were analyzed in proton energy ranges 40--400 MeV. Both time
and energy distributions of post-flare protons may be interpreted as
the presence of relativistic (c/3 -- c/2 velocity at 1 A.U.) protons
in some post-flare fluxes.
Title: Building a Virtual Solar Observatory: Lessons Learned
Authors: Bogart, R. S.; Tian, K. Q.; Davey, A.; Dimitoglou, G.;
Gurman, J. B.; Hill, F.; Hourclé, J.; Martens, P. C.; Suárez-Sola,
I.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSH51B..05B
Altcode:
Two years into its development, the VSO has emerged from a drawing board
concept into a full-fledged data query and data delivery system serving
the Solar Physics community. Throughout its development, the VSO has
lived up to its `small box' motto and has built light-weight servers
that can easily run on a desktop or laptop. The two basic functions
of the VSO are data query and data delivery. For these functions, the
VSO servers act like switchboards, dispatching query/data requests
to relevant data providers. More important, these servers present
an abstraction that integrates diverse data archives, thus reducing
complexity. The design of the VSO has evolved during its implementation
in response to difficulties and user feedback. We discuss the changes
in areas such as the data model, user interface, and performance. These
lessons should be of interest to people designing and building other
virtual observatories. We also discuss challenges and opportunities
we foresee as the VSO becomes a significant and enabling research tool.
Title: Nine Years of EIT Bright Points
Authors: McIntosh, S. W.; Gurman, J. B.
Bibcode: 2005AGUSMSP22A..03M
Altcode:
We discuss early results derived from an algorithm that automates the
detection, cataloging, and analysis of Extreme-ultraviolet (EUV) "Bright
Points" (BP) from nine years of data acquired by the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). In particular, we describe the temporal and spatial variations
of the 1.3x108 EUV BPs observed by SOHO to date.
Title: EIT &EUV Brightpoints Over the SOHO Mission so Far
Authors: McIntosh, S. W.; Gurman, J. B.
Bibcode: 2004ESASP.575..235M
Altcode: 2004soho...15..235M
No abstract at ADS
Title: Doing Science with the VSO: Signatures of CME Initiation
Authors: Davey, A. R.; Wills-Davey, M.; Gurman, J. B.; Bogart, R.;
Tian, K. Q.; Martens, P.; Yoshimura, K.; Hill, F.; Suarez-Sola, I.;
Hourclé, J.; Dimitoglou, G.; Wampler, S.
Bibcode: 2004AGUFMSH21B0414D
Altcode:
The Virtual Solar Observatory (VSO) was designed to simplify and unify
access to solar physics data. It provides a single interface to a broad
range of data types and sources which previously would have required
considerable effort to collect one by one. By combining access to online
data sources with published scientific catalogs, the VSO can facilitate
new science. This study seeks to investigate whether signatures of
coronal mass ejection (CME) initiation can be used to constrain CME
initiation models. We selected events from the SOHO/LASCO CME catalog,
generated a time window between the calculated CME ``start time" and
the first observation of the CME in LASCO C2, and examined EIT ``CME
Watch" and H-alpha observations identified by a VSO query as falling in
the specified time windows. We prioritized the EUV data by selecting
those events for which GOES data indicated a flare, and identified
flare sites and dimming regions in the EUV data, with the aim of more
precisely determining CME initiation locations and times. In addition,
we used H-alpha data to investigate CME's associated with by filament
eruptions. The results allow us to calculate minimum acceleration rates,
and determine correlations between coronal structures, ejection events,
and acceleration rates. We use these correlations in turn to identify
viable CME initiation mechanisms.
Title: Evaluation of the Amplitude and Restoring the Temporal Profile
of the Bastille Day Solar Flare in the 19.5 nm from the Saturated
EIT Images
Authors: Didkovsky, L. V.; Jones, A. R.; Judge, D. L.; Gurman, J. B.;
Tsurutani, B. T.
Bibcode: 2004AAS...205.4303D
Altcode: 2004BAAS...36.1411D
SOHO/EIT images taken during extreme solar flares show bright areas
stretched mainly along the E-W direction with the signals close to
the saturation level (blooming) of the CCD camera. A comparison of
a pre-flare and flare images allows us to see both pre-flare and
flare's distinctive features. Pre-flare sources correspond to areas
between strong magnetic fields on the SOHO/MDI magnetic field images. A
location of the modeled flare 'center' was found as a center of gravity
of an unsaturated widening area of the flare. The amplitude of
the peak in the 19.5 nm passband for the extreme Bastille Day flare
of July 14, 2000 was modeled on the assumption that the CCD blooming
had redistributed some of the EUV photo-electrons above the pixel
capacity level from the center of the flare position on the CCD to
other pixels. This assumption allows us to determine the lower limit
for the amplitude of the peak if some electrons were lost during the
blooming and the peak shape corresponds to the modeled one. For the
simplest case we interpreted the flare's peak intensity distribution
as a symmetrical paraboloid. Any other shape of the peak may change the
modeled amplitude, leaving the same number for the total photoelectrons
from the bloomed area as an integral characteristic of the flare. The modeled peak amplitude of the Bastille Day flare is about 256 K
DNs compare to about 16 K DNs of the EIT camera top limit. The restored
flare's temporal profile in the 19.5 nm spectral window was determined
for a sequence of observed images with the cadence of about 12 min
at the time of the flare by counting photoelectrons trapped in the
blooming areas of the flare.
Title: Solving Science Use Cases that relate to the Sun and
Heliosphere with EGSO
Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham,
J.; Antonucci, E.; Gurman, J. B.; Hill, F.; Pike, D.; Vial, J.;
Zharkova, V.
Bibcode: 2004AGUFMSH21B0415B
Altcode:
The European Grid of Solar Observations (EGSO) is a grid testbed
funded by the European Commission's Fifth Framework Programme under
its Information Society Technologies (IST) thematic priority. The
project started in 2002 and is designed to provide enhanced access to
solar and related data around the world. The EGSO grid is composed
of two main components, Roles to set up the grid and, catalogs and
registries to allow roles to answer users queries. Catalogs are made
of lists of observations, events and features (a new service provided
by EGSO). Registries are built from these catalogs and organized in
order to enhance search capabilities. EGSO is working closely with
other virtual observatory (VO) projects in the solar physics and
related domains. This includes the US Virtual Solar Observatory (VSO)
and the Collaborative Sun-Earth Connector (CoSEC). More recently we
have been working with the Virtual Space Plasma Observatory (VSPO) and
have contact with the Virtual Heliospheric Observatory (VHO). Through
discussions with future missions, and within the new IAU Working
Group on ``International Data Access'' (Solar and Heliospheric),
the VOs are studying ways of ensuring interoperability from the
``sun to dirt''. This type of integrated access will be particularly
important to missions such as STEREO and Living Witha Star. In this
paper we will report the current status of EGSO, demonstrate how the
catalogs and registries model serves within the user interface, and
show how the user can retrieve solar and heliospheric data to match
a scientific query. EGSO Release 4 is now being Beta-tested by users
and anyone interested should view the Web page detailing all the EGSO
capabilities under http://www.egso.org/demo
Title: Future Mission Data Environment: Virtualizing Access to Solar
Physics Data
Authors: Gurman, J. B.; Davey, A. R.
Bibcode: 2004ESASP.575..583G
Altcode: 2004soho...15..583G
No abstract at ADS
Title: STEREO in the Virtual Solar Observatory Context
Authors: Hourcle, J. A.; Bogart, R.; Davey, A.; Gurman, J. B.; Hill,
F.; Martens, P.; Suarez-Sola, I.; Tian, K.; Yoshimura, K.
Bibcode: 2004AGUFMSH21B0413H
Altcode:
The Virtual Solar Observatory (VSO) was designed with the goal that it
handle heterogeneous data sets from multiple observatories. With its
two spacecraft and multiple instruments, the STEREO mission provides
an excellent example of solar physics research based on multiple data
sets, and a good test of the abilities of the VSO. Here we will discuss
how the VSO will meet the key challenges that STEREO presents. In
particular, the wide range of data classes and the non-stationary
viewpoints of the two spacecraft demand a flexible underlying data
model of the VSO.
Title: The Virtual Solar Observatory: status and initial operational
experience
Authors: Hill, Frank; Bogart, Richard S.; Davey, Alisdair; Dimitoglou,
George; Gurman, Joseph B.; Hourcle, Joseph A.; Martens, Petrus C.;
Suarez-Sola, Igor; Tian, Karen; Wampler, Steven; Yoshimura, Keiji
Bibcode: 2004SPIE.5493..163H
Altcode:
The Virtual Solar Observatory (VSO) is a bottom-up grassroots approach
to the development of a distributed data system for use by the solar
physics community. The beta testing version of the VSO was released in
December 2003. Since then it has been tested by approximately 50 solar
physicists. In this paper we will present the status of the project,
a summary of the community's experience with the tool, and an overview
of the lessons learned.
Title: Virtual Observatories: Are We Virtually There Yet?
Authors: Gurman, J. B.
Bibcode: 2004AAS...204.5201G
Altcode: 2004BAAS...36R.753G
Virtual observatories are tools for simplifying access to and use of
astronomical data from an increasing number of data sources of rapidly
growing volume. Now that a variety of virtual observatory development
efforts are under way around the world, a cursory review of the efforts
outside solar physics, and an only slightly more detailed consideration
of those within, demonstrates a commonality of conceptual model if not
of approach or application. The linkages among virtual observatories
optimized for different scientific communities present an interesting
challenge to the designers: should virtual observatories be designed
for the most expert users? For the least? For everyone? It is too early
to provide definitive answers, but examination of current efforts does
offer some clues.
Title: Evidence for Coexisting Hot and Cool Polar Coronal Jets -
Coordinated Observations of SOHO and TRACE
Authors: Dobrzycka, D.; Raymond, J. C.; Deluca, E. E.; Gurman, J.;
Biesecker, D.; Fludra, A.
Bibcode: 2004AGUSMSH52A..05D
Altcode:
The polar coronal jets were first observed by SOHO instruments
(EIT, LASCO, UVCS) during the last solar minimum. They were small,
fast ejections originating from flaring UV bright points within large
polar coronal holes. The polar holes disappeared at solar maximum and
the jets were not visible anymore. Currently, however, as the Sun's
activity declines, the polar holes again became permanent structures
and new polar coronal jets were observed by specially designed SOHO
Joint Observing Program (JOP 155). Their frequency of several events per
day appear comparable to the frequency from last solar minimum. Also,
the speed of ∼ 400~km~s-1 at 1.6~R⊙ is consistent
with typical velocities of polar jets in 1996-1998. The ejections are
believed to be triggered by the field line reconnection between the
emerging magnetic dipole and pre-existing unipolar field. Existing
models predict that the hot jet is ejected together with another jet
made of cool material. The coordinated SOHO and TRACE observations
within JOP 155 provide unique opportunity to test this prediction. We
will present observations and discuss evidence supporting the model.
Title: EUV Brightpoints over the cycle to date as observed by SOHO/EIT
Authors: McIntosh, S. W.; Young, C. A.; Gurman, J. B.
Bibcode: 2004AAS...204.9507M
Altcode: 2004BAAS...36..827M
We investigate the multi-wavelength, multiple timescale appearance of
Extreme Ultraviolet (EUV) brightpoints over the current solar cycle
through the eyes of SOHO's Extreme Ultraviolet Imaging Telescope
(EIT). Over the past 8 years EIT has built up an unprecidented dataset
to facilitate the study of these ubiquitous coronal phenomena. Using an
automated detection algorithm we explore their physical and statistical
characteristics over the cycle to-date and ponder the mechanism behind
their generation in several specific instances of note.
Title: Implementation of the Virtual Solar Observatory
Authors: Davey, A. R.; Bogart, R. S.; Gurman, J. B.; Hill, F.; Hourcle,
J.; Martens, P. C.; Suarez-Sola, I.; Tian, K. Q.; Yoshimura, K.
Bibcode: 2004AAS...204.7002D
Altcode: 2004BAAS...36..796D
The Virtual Solar Observatory (VSO) integrates diverse solar data
archives into a virtual collection providing common search and delivery
services. Having developed from a prototype installation involving
four major archives, it is now in the process of expanding to include
a larger variety of archives and data types. We are also refining and
expanding its services and user interfaces and defining an API. We
have defined a working extensible data model enabling us to provide
more detailed and comprehensive search capabilities and to incorporate
additional data products. The API will allow people to construct their
own interfaces to the core VSO functionality and integrate with other
web services and other virtual observatories. Here we describe the
structure of VSO as currently implemented and what is required to
incorporate additional archives.
Title: Origins of the Solar Polar Jets - Coordinated SOHO and TRACE
Observations
Authors: Dobrzycka, D.; Raymond, J. C.; Deluca, E. E.; Gurman, J. B.;
Biesecker, D.; Fludra, A.
Bibcode: 2003AGUFMSH22A0187D
Altcode:
The polar jets are dynamic coronal eruptions originating in the low
solar atmosphere, in flaring UV bright points within polar coronal
holes. They were first observed by SOHO instruments (EIT, LASCO)
during last solar minimum in 1996 when the polar holes were dominating
coronal structures. UVCS/SOHO obtained ultraviolet spectroscopy of
the jet providing us with estimates of the jet plasma conditions,
evolution of the electron temperature and heating rate required to
reproduce the observed ionization state. As the Sun is currently at
the declining phase of its activity, the polar holes again became
permanent structures. The SOHO Joint Observing Program (JOP 155)
was designed to identify and study the jet phenomena that would be
counterparts of the solar minimum polar jets. The jets are believed
to be triggered by field line reconnection between emerging magnetic
dipole and pre-existing unipolar field. Existing models predict that the
hot jet is ejected together with another jet of a cool material. The
particular goal of the coordinated SOHO and TRACE observations was to
look for possible association of the hot and cool plasma ejections. We
present first results of the campaign and discuss their implications.
Title: The Virtual Solar Observatory -- the Why, What, How and Where
Authors: Hill, F.; Bogart, R. S.; Davey, A.; Dimitoglou, G.; Gurman,
J. B.; Martens, P. C.; Tian, K.; Wampler, S.
Bibcode: 2003AGUFM.U22A0012H
Altcode:
Observational solar physics almost always involves the comparison of
several data sets obtained by different instruments and stored in a
variety of archives. Currently a researcher must laboriously locate
the relevant archives, search them with idiosyncratic interfaces,
and retrieve the data by a number of methods. The VSO is a tool to
streamline this process by providing a single unified interface and
search tool for solar archives. Eventually this will be supplemented
by distributed computing tools which will enable queries based on
data itself, in addition to standard queries on metadata. The VSO
will enable a new class of solar research -- large-scale correlative
statistical studies on many data sets, thereby facilitating space
weather studies. An example of a use case is a helioseismic study of the
subsurface structure of cornal hole boundaries and possible predictive
links between the solar interior and the solar wind. An intital
prototype has been built linking archives at GSFC, Stanford, MSU, and
NSO. This prototype has been constructed using a combination of XML,
SOAP, and Perl technologies, and a beta release is available now. The
initial set of archives will soon be expanded to include archives at
HAO, NGDC, and selected NOAA feature and event catalogues. In the
next 2 years, additonal service providers will be added, the user
interface will be fully developed, and distributed computing tools
will be initiated.
Title: Data Integration in the Virtual Solar Observatory
Authors: Bogart, R. S.; Davey, A.; Dimitoglou, G.; Gurman, J. B.;
Hill, F.; Martens, P. C.; Tian, K. Q.; Wampler, S.
Bibcode: 2003AGUFMSH42A0503B
Altcode:
The aim of the Virtual Solar Observatory (VSO) is the integration of
diverse data archives relevant to the study of Solar Physics into a
virtual collection providing common search and delivery services. The
back-end query services are implemented as Web Services and accessible
via the Simple Object Access Protocol (SOAP). SOAP defines a remote
procedure call mechanism that employs HTTP as its transport and
encodes the client-server interactions in XML documents. In addition
to its core function in identifying relevant datasets locally, a SOAP
server at each data provider acts as a wrapper that maps descriptions
in an abstract data model to those in the provider's specific model,
and vice versa. Heterogeneous data search services can thereby be
integrated with a common interface. This allows scientists to access
multiple archives with differing data organizations at once, enhancing
their ability to discover and and analyze correlative data from multiple
sources. We have chosen two SOAP implementations for the VSO: SOAP::Lite
and OpenSOAP. The former, written in Perl, is suitable for fast and
flexible prototyping in data search applications. SOAP::Lite servers
have been set up at each of the VSO archives, and can be readily
installed at other servers. OpenSOAP, written in C with built-in
support for service description and dispatch, may prove useful in
transforming current computing utilities into Web Services. We report
on initial experiments using OpenSOAP to provide additional services
to the basic query functionality of VSO.
Title: Spatial and Temporal Properties of Hot and Cool Coronal Loops
Authors: Nagata, Shin'ichi; Hara, Hirohisa; Kano, Ryouhei; Kobayashi,
Ken; Sakao, Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida, Tsuyoshi;
Gurman, Joseph B.
Bibcode: 2003ApJ...590.1095N
Altcode:
A suite of images from the XUV Doppler Telescope (XDT), the Yohkoh Soft
X-ray Telescope (SXT), and the Extreme-Ultraviolet Imaging Telescope
(EIT) on the Solar and Heliospheric Observatory (SOHO) allow us to
see the whole (T>1 MK) temperature evolution of coronal loops. The
detailed morphological comparison of an active region shows that hot
loops seen in SXT (T>3 MK) and cool loops seen in the the EIT 195
Å band (T~1.5 MK) are located in almost alternating manner. The
anticoincidence of the hot and the cool loops is conserved for a
duration much longer than the estimated cooling timescale. However, both
hot and cool loops have counterparts in the intermediate-temperature
images. The cross-correlation coefficients are higher for neighboring
temperature pairs and lower for pairs with larger temperature
differences. These results suggest that loops are not isothermal but
rather have a differential emission measure distribution of modest but
finite width that peaks at different temperatures for different loops.
Title: The Virtual Solar Observatory: The Best-Laid Schema
Authors: Gurman, J. B.; Dimitoglou, G.; Hill, F.; Wampler, S.; Bogart,
R. S.; Tian, K.; Martens, P.; Davey, A.
Bibcode: 2003SPD....34.0203G
Altcode: 2003BAAS...35..807G
Work on a protoype Virtual Solar Observatory (VSO) is now under way. The
prototype will offer access to data from online solar archives at
Stanford, NSO, Montana State, and the SDAC. We discuss some of the
features of the VSO for users, as well as the basic design and some
of the technical aspects, including the use of XML schemas and SOAP
to allow users a single access method for disparate data services.
Title: First Steps Towards a VSO
Authors: Davey, A. R.; Bogart, R. S.; Dimitoglou, G.; Gurman, J. B.;
Hill, F.; Martens, P. C.; Tian, K. Q.; Wampler, S.
Bibcode: 2003SPD....34.0311D
Altcode: 2003BAAS...35..810D
Work has started on constructing the Virtual Solar Observatory. This
poster describes some of the components of the VSO and the first steps
that have been taken to implement these components. A description of
the overall VSO structure is given, along with descriptions of data
and meta-data models, methods by which these data model are used by
the VSO, details of how VSO nodes are interconnected *
and ideas on the likely format of the VSO API. As an example, the
inclusion of Yohkoh-SXT data at MSU and the future inclusion of the
Yohkoh-Galileo project data will be discussed. *
See also ``Data Integration Using SOAP in the VSO" by Tian et al.
Title: Data Integration Using SOAP in the VSO
Authors: Tian, K. Q.; Bogart, R. S.; Davey, A.; Dimitoglou, G.;
Gurman, J. B.; Hill, F.; Martens, P. C.; Wampler, S.
Bibcode: 2003SPD....34.0312T
Altcode: 2003BAAS...35..810T
The Virtual Solar Observatory (VSO) project has implemented a time
interval search for all four participating data archives. The back-end
query services are implemented as web services, and are accessible
via SOAP. SOAP (Simple Object Access Protocol) defines an RPC (Remote
Procedure Call) mechanism that employs HTTP as its transport and encodes
the client-server interactions (request and response messages) in XML
(eXtensible Markup Language) documents. In addition to its core
function of identifying relevant datasets in the local archive, the SOAP
server at each data provider acts as a "wrapper" that maps descriptions
in an abstract data model to those in the provider-specific data model,
and vice versa. It is in this way that VSO integrates heterogeneous
data services and allows access to them using a common interface. Our
experience with SOAP has been fruitful. It has proven to be a better
alternative to traditional web access methods, namely POST and GET,
because of its flexibility and interoperability.
Title: Solar, Interplanetary, and Geospace Disturbances Associated
with the April 2002 Coronal Mass Ejections
Authors: Gopalswamy, N.; Yashiro, S.; St. Cyr, O.; Lawrence, G.;
Kaiser, M. L.; Gurman, J. B.; Howard, R. A.
Bibcode: 2002AGUFMSA12A..02G
Altcode:
The Solar and Heliospheric Observatory (SOHO) detected a large number of
coronal mass ejections (CMEs) during the April 14-24, 2002 period. We
describe the properties of these CMEs and contrast them with those of
the general population of CMEs. We explore the connection of these
CMEs to the interplanetary shocks and the solar energetic particles
events using Wind and GOES data, respectively. We assess the extent of
preconditioning of the corona by repeated flaring and mass ejections
from the active regions involved. Based on the arrival times of the
interplanetary CMEs and shocks, we discuss the evolution of these
disturbances as they propagated between the Sun and Earth. We compare
the extended nature of the main phase of the complex geomagnetic storm
to other other similar extended storm periods
Title: Strawman Concept for A Virtual Solar Observatory
Authors: Martens, P. C. H.; Gurman, J. B.; Hill, F.; Bogart, R. S.;
Davey, A.; Dimitoglou, G.; Tian, K.; Wampler, S.
Bibcode: 2002AAS...20114103M
Altcode: 2003BAAS...35..567M
We propose here an architecture and feature set for a prototype Virtual
Solar Observatory (VSO). The prototype will not include all the features
that might eventually become part of the VSO, nor even all the features
that are concurrently under development elsewhere that should become
parts of the VSO's functionality. It is possible to approach the design
of such a system in at least two different ways. In one (top-down),
all possible features and uses of a system are studied, and the best
solution for as many as possible is proposed. This is the approach
taken by the European Grid of Solar Observations (EGSO). Alternately,
one can approach a system design from the bottom up, and ask what the
essential element or elements of the design have to be in order to have
a functioning and useful system. The VSO study group decided, after
examining different approaches to abstracting the procedures for solar
data identification and access, to build the “smallest box” possible
around that problem, rather than attempting to draw a box around all
possible aspects of a VSO. This design will be presented in the poster.
Title: The Right Amount of Glue: Technologies and Standards Relevant
to a Future Solar-Terrestrial Data Environment
Authors: Gurman, J. B.; Dimitoglou, G.; Bogart, R. S.; Tian, K. Q.;
Hill, F.; Wampler, S.; Martens, P. C.; Davey, A.
Bibcode: 2002AGUFMSH52C..03G
Altcode:
In order to meet the challenge of developing a new system science, we
will need to employ technology that enables researchers to access data
from fields with which they are at least initially unfamiliar as well as
from sources they use more regularly. At the same time, the quantity of
data to be obtained by missions such as the Solar Dynamics Observatory
demands ease and simplicity of data access. These competing demands
must in turn fit within severely constrained funding for data analysis
in such projects. \p Based on experience in only a single discipline
but with a diversity of data types and sources, we will give examples
of technology that have made a significant difference in the way people
do science. Similarly, we will show how adoption of a well-dcoumented
data format has made it easier for one community to search, reduce,
and analyze data. We will also describe a community-supported data
reduction and analysis software tree with useful features.\p We will
attempt to generalize the lessons learned in these instances to features
the broader, solar-terrestrial community might find compelling, while
avoiding overdesign of a common data environment.\p
Title: EGSO in need for a global schema
Authors: Hill, Frank; Csillaghy, Andre; Bentley, Robert D.; Aboudarham,
Jean; Antonucci, Ester; Finkelstein, Anthony; Ciminiera, Luigi;
Gurman, Joseph B.; Scholl, Isabelle; Pike, Dave; Zharkova, Valentin
Bibcode: 2002SPIE.4846...35H
Altcode:
The European Grid of Solar Observations (EGSO) is a project to develop
a virtual observatory for the solar physics community. Like in all
such projects, a vital component is a schema that adequately describes
the data in the distributed data sets. Here, we discuss the schema in
general terms, and present a draft example of a portion of a possible
XML schema.
Title: Toward a Virtual Solar Observatory
Authors: Gurman, J. B.
Bibcode: 2002ESASP.508..525G
Altcode: 2002soho...11..525G
NASA is currently engaged in the study phase of a modest effort to
establish a Virtual Solar Observatory (VSO). The VSO would serve
ground- and spacebased solar physics data sets from a distributed
network of archives through a small number of interfaces to the
scientific community. The basis of this approach, as of all planned
virtual observatories, is the translation of metadata from the various
sources via source-specific dictionaries so the user will not have to
distinguish among keyword usages. A single Web interface should give
access to all the distributed data. We present the current status of the
VSO, its initial scope, and its relation to the European EGSO effort.
Title: Building a Virtual Solar Observatory: I Look Around and
There's a Petabyte Following Me
Authors: Gurman, J. B.; Bogart, R.; Hill, F.; Martens, P.
Bibcode: 2002AAS...200.5805G
Altcode: 2002BAAS...34..740G
The 2001 July NASA Senior Review of Sun-Earth Connections missions
and data centers directed the Solar Data Analysis Center (SDAC) to
proceed in studying and implementing a Virtual Solar Observatory (VSO)
to ease the identification of and access to distributed archives of
solar data. Any such design (cf. the National Virtual Observatory
and NASA's Planetary Data System) consists of three elements: the
distributed archives, a "broker" facility that translates metadata
from all partner archives into a single standard for searches,
and a user interface to allow searching, browsing, and download of
data. Three groups are now engaged in a six-month study that will
produce a candidate design and implementation roadmap for the VSO. We
hope to proceed with the construction of a prototype VSO in US fiscal
year 2003, with fuller deployment dependent on community reaction to
and use of the capability. We therefore invite as broad as possible
public comment and involvement, and invite interested parties to a
`birds of a feather' session at this meeting. VSO is partnered with
the European Grid of Solar Observations (EGSO), and if successful, we
hope to be able to offer the VSO as the basis for the solar component
of a Living With a Star data system.
Title: Variability and dynamic state of active region loops
Authors: Fredvik, T.; Kjeldseth-Moe, O.; Haugan, S. V. H.; Brekke,
P.; Gurman, J. B.; Wilhelm, K.
Bibcode: 2002AdSpR..30..635F
Altcode:
A set of 218 consecutive CDS rasters taken at the solar limb on October
26-28 1999 has been used to investigate the variability and plasma
dynamics of active region loops. Each raster contains simultaneous
images in 6 different lines, covering the full temperature range of
CDS, 10 000 K (He I) to 2.7 MK (Fe XVI). Activity is seen to go on
without breaks at temperatures below 1 MK for the full 39 hours of the
series. Transition region loops or extended sections of loops, 50-200
Mm long, appear and disappear in intervals as short as 11 minutes,
the observing cadence. In the corona the emission is less variable,
but significant changes are seen. Measured Doppler shifts correspond
to typical plasma velocities of 20 km s -1 to 100 km
s -1, at temperatures 10 000 K to 450 000 K, and siphon
flows may occur in some of the loops. High velocities are frequently
seen where the emitted intensities are weak, often on the outer edges
of loops as defined in that particular spectral line. At coronal
temperatures, 1 MK and higher, systematic loop velocities occur only
occasionally. Simultaneous observations with EIT and SUMER were made
during part of the raster series and are compared with the CDS result.
Title: Polar Coronal Jets at Solar Minimum
Authors: Dobrzycka, D.; Cranmer, S. R.; Raymond, J. C.; Biesecker,
D. A.; Gurman, J. B.
Bibcode: 2002ApJ...565..621D
Altcode:
We present an analysis of six polar coronal jets observed by
the Ultraviolet Coronagraph Spectrometer (UVCS) at solar minimum
(1996). Four of the events were also recorded by the Extreme-Ultraviolet
Imaging Telescope (EIT) and/or the Large Angle Spectrometric Coronagraph
(LASCO) C2 coronagraph. We compared the jets with others recorded in
1997. We modeled the observable properties of the jet from 1996 June 11,
detected at 1.5 Rsolar. It represents a type of polar jet
in which H I Lyα and O VI get brighter at the same time. The model
reproduced the line properties with an electron density enhancement
of a factor of 2 (with a resulting density of 4.8×106
cm-3), an outflow velocity enhancement of a factor of
3 (yielding a velocity of 200 km s-1), and an electron
temperature decrease of a factor of 0.36 (with a resulting temperature
of 5.3×105 K). We derived the jet's electron densities
from the LASCO C2 white-light observations. They are a factor of 1.5
higher than in the interplume corona and comparable to those in plume
regions within the C2 field of view. We developed a model for the origin
of polar jets based on Wang's model for plumes. We envisioned that
jets may be the result of short-lived bursts of base heating, while
plumes may be the result of base-heating events that last longer than
several hours. Models with the base heat flux near 3×105
ergs cm-2 s-1 come closest to matching the
observations, though they are not entirely consistent.
Title: Toward a Virtual Solar Observatory: Starting Before the
Petabytes Fall
Authors: Gurman, J. B.
Bibcode: 2001AAS...19911203G
Altcode: 2001BAAS...33.1478G
Although a few, large, space- and groundbased solar physics
databases exist at selected locations, there is as yet only limited
standardization or interoperability. I describe the outline of a plan
to facilitate access to a distributed network of online solar data
archives, both large and small. The underlying principle is that the
user need not know where the data are, only how to specify which data
are desired. At the least, such an approach could considerably simplify
the scientific user's access to the enormous amount of solar physics
data to be obtained in the next decade. At best, it might mean the
withering away of traditional data centers, and all the bureaucracy
they entail. This work is supported by the Sun-Earth Connections
Division of NASA Office of Space Science, thanks to an anomalous act
of largess on the part of the 2001 SEC Senior Review.
Title: Eruption and acceleration of flare-associated coronal mass
ejection loops in the low corona
Authors: Neupert, W. M.; Thompson, B. J.; Gurman, J. B.; Plunkett,
S. P.
Bibcode: 2001JGR...10625215N
Altcode:
Observations made by the EUV imaging telescope (EIT) and the Large-Angle
Spectrometric Coronagraph (LASCO) on board the Solar Heliospheric
Observatory (SOHO) have been used to characterize the eruption and
acceleration of flare-associated coronal mass ejections (CMEs) in the
low corona. For three well-observed limb events we tracked CME loops
back to preexisting but faint EUV-emitting loops at heights of 100-250
Mm that initially brightened slowly and possibly increased slowly in
height, apparently in response to filament activity and eruption in the
associated active regions. Subsequent CME acceleration coincided with
a rapid rise of the soft X-ray flux, occurred between 100 and 350 Mm
above the surface, and may have been as high as 0.5 km s-1
s-1, consistent with an impulsive acceleration of the CME
to the speeds observed in subsequent white-light observations. The
existence of a delay of up to 30 min observed between initial filament
eruption in H alpha and subsequent high acceleration of the CME in
one event implies that there may have been two separate phases of
magnetic reconnection, with the initial filament activity acting as
a trigger for subsequent CME and energetic particle acceleration in
the impulsive stage of the flare. The presence or absence of this
impulsive phase may provide a basis for the two types of CMEs that
have been discussed in the literature.
Title: Ultraviolet Spectroscopy of Coronal Jets Within the Fast
Solar Wind
Authors: Dobrzycka, D.; Cranmer, S. R.; Raymond, J. C.; Biesecker,
D. A.; Gurman, J. B.
Bibcode: 2001AGUSM..SH41B09D
Altcode:
The coronal jets are spectacular dynamic events originating from
different structures in the solar corona. We present UVCS/SOHO
observations of polar coronal jets. They appear to originate near
flaring ultraviolet bright points within polar coronal holes that are
source regions of the fast solar wind. UVCS recorded the jets as a
significant enhancement in the integrated intensities of the strongest
coronal emission lines: mostly H~I Lyα and O~VI λ λ 1032,1037. A
number of detected jets are correlated with the EIT Fe~XII 195~Å
and LASCO C2 white-light events. Typically, the observed H~I Lyα
enhancement was up to a factor of 1.3-1.7 over the ambient corona and
lasted for 20-30 minutes. The narrow profiles of the emission lines
indicate that the material in the jets is cooler than the underlying
corona. We modeled the observable properties of the jets to get
estimates on jet plasma conditions. We discuss the model results, the
initial electron temperature and the heating rate required to reproduce
the observed O~VI ionization state. We also discuss connection of
the polar jets to the fast solar wind. This work is supported by the
National Aeronautics and Space Administration under grant NAG5--7822 to
the Smithsonian Astrophysical Observatory, by Agenzia Spaziale Italiana,
and by the ESA PRODEX program (Swiss contribution).
Title: Did I Say Terabyte? I Meant Petabyte: Data Archiving in the
Era of SDO
Authors: Gurman, J. B.
Bibcode: 2001AGUSM..SP21B01G
Altcode:
Even solar missions of modest size in the next half decade will produce
terabytes (Tbyte = 1012 byte) of data. The Solar Data
Analysis Center is already dealing with mission archives of similar
volumes, and is serving the entire archives to the community over the
Internet (Gurman 1999). With the Solar Dynamics Observatory (SDO)
scheduled for launch at the end of 2006, archiving and serving the
data from a primarily solar physics mission begins to get interesting:
one Tbyte of data a day, or over a petabyte (Pbyte) of data in three
years.We examine whether current data archiving and service strategies
can be scaled to such volumes,and enumerate other challenges associated
with distributed access to so much data.
Title: Recent insights into the physics of the sun and heliosphere
: highlights from SOHO and other space missions : IAU Symposium
203, proceedings of the 24th General Assembly of the IAU held at
Manchester, United Kingdom, 7-11 August 2000
Authors: Brekke, Pål; Fleck, Bernhard; Gurman, Joseph B.
Bibcode: 2001IAUS..203.....B
Altcode:
No abstract at ADS
Title: Comparison of the 1998 April 29 M6.8 and 1998 November 5
M8.4 Flares
Authors: Wang, Haimin; Goode, Philip R.; Denker, Carsten; Yang, Guo;
Yurchishin, Vasyl; Nitta, Nariaki; Gurman, Joseph B.; St. Cyr, Chris;
Kosovichev, Alexander G.
Bibcode: 2000ApJ...536..971W
Altcode:
We combined, and analyzed in detail, the Hα and magnetograph data
from Big Bear Solar Observatory (BBSO), full-disk magnetograms from
the Michelson Doppler Imager (MDI) on board Solar and Heliospheric
Observatory (SOHO), coronagraph data from the Large Angle Spectrometric
Coronagraph (LASCO) of SOHO, Fe XII 195 Å data from the Extreme
ultraviolet Imaging Telescope (EIT) of SOHO, and Yohkoh soft X-ray
telescope (SXT) data of the M6.8 flare of 1998 April 29 in National
Oceanic and Atmospheric Administration (NOAA) region 8375 and the
M8.4 flare of 1998 November 5 in NOAA region 8384. These two flares
have remarkable similarities:1. Partial halo coronal mass ejections
(CMEs) were observed for both events. For the 1998 April 29 event,
even though the flare occurred in the southeast of the disk center,
the ejected material moved predominantly across the equator, and the
central part of the CME occurred in the northeast limb. The direction
in which the cusp points in the postflare SXT images determines the
dominant direction of the CMEs.2. Coronal dimming was clearly observed
in EIT Fe XII 195 Å for both but was not observed in Yohkoh SXT for
either event. Dimming started 2 hr before the onset of the flares,
indicating large-scale coronal restructuring before both flares.3. No
global or local photospheric magnetic field change was detected from
either event; in particular, no magnetic field change was found in the
dimming areas.4. Both events lasted several hours and, thus, could be
classified as long duration events (LDEs). However, they are different
in the following important aspects. For the 1998 April 29 event,
the flare and the CME are associated with an erupting filament in
which the two initial ribbons were well connected and then gradually
separated. SXT preflare images show the classical S-shape sheared
configuration (sigmoid structure). For the 1998 November 5 event, two
initial ribbons were well separated, and the SXT preflare image shows
the interaction of at least two loops. In addition, no filament eruption
was observed. We conclude that even though these two events resulted
in similar coronal consequences, they are due to two distinct physical
processes: eruption of sheared loops and interaction of two loops.
Title: Observed Variability and Dynamics of Active Region Loops
Authors: Haugan, S. V. H.; Brekke, P.; Fredvik, T.; Kjeldseth-Moe,
O.; Wilhelm, K.; Gurman, J. B.
Bibcode: 2000SPD....31.0205H
Altcode: 2000BAAS...32..811H
A series of 218 rasters taken with the Coronal Diagnostic Spectrometer
(CDS) on SOHO demonstrates the strong time variability and
dynamical state of the plasma in active region loops at transition
region temperatures, i.e. 10 000 K to 500 000 K, first reported
by Kjeldseth-Moe and Brekke (1998). The continuous raster series,
which covered 39 hours, show how transition region loops or sections
of loops, 50-200 Mm in length, appear and disappear in intervals as
short as 10 minutes, the observing cadence. At the same temperatures
plasma velocities of 20 km s-1 to 100 km s-1
are indicated from observed Doppler shifts. Siphon flows may occur in
some of the loops, but in other loops patterns are less obvious. High
velocities are frequently seen where the emitted intensities are weak,
often on the ``outside'' of the loops as defined by the emission in
that particular spectral line. At coronal temperatures the emission
is less time variable, but significant changes are seen. Systematic
loop velocities occur only occasionally in the corona. Simultaneous
observations with EIT and SUMER were made during part of the raster
series and is compared with the CDS result.
Title: Four years of SOHO discoveries - some highlights.
Authors: Fleck, B.; Brekke, P.; Haugan, S.; Duarte, L. S.; Domingo,
V.; Gurman, J. B.; Poland, A. I.
Bibcode: 2000ESABu.102...68F
Altcode:
Analysis of the helioseismic data from SOHO has shed new light on
solar and heliosheric physics: the structure and dynamics of the
solar interior, the heating and dynamics of the solar corona, and the
acceleration and composition of the solar wind.
Title: Eruptive Events at 304 Angstroms: A Sample from SOHO EIT
Authors: Gurman, J. B.
Bibcode: 2000SPD....31.0272G
Altcode: 2000BAAS...32..824G
Although the SOHO Extreme ultraviolet Imaging Telescope (EIT) is
normally used to monitor the full disk at 195 Angstroms with a 12-minute
cadence, we make use of occasional opportunities to observe in the He II
Ly α resonance line at 303.7 Angstroms (with some contribution from Si
XI 303.4 Angstroms) at a somewhat higher cadence. At the current phase
of the solar cycle, this affords us the opportunity of amassing some
statistics on various kinds of activity observable at 304 Angstroms. I
report here on the limb activity visible in these data, including
surges, sprays, eruptive prominences, and two classes of phenomena
which may not correspond to the classical H I Ba α nomenclature for
eruptive events: loop sprays and fan jets. The former resemble flare
sprays but appear to travel along pre-existing coronal loops, while
the latter are not clearly associated with flares, and may represent
a manifestation of coronal mass ejections at chromospheric temperatures.
Title: Observations of the 24 September 1997 Coronal Flare Waves
Authors: Thompson, B. J.; Reynolds, B.; Aurass, H.; Gopalswamy, N.;
Gurman, J. B.; Hudson, H. S.; Martin, S. F.; St. Cyr, O. C.
Bibcode: 2000SoPh..193..161T
Altcode:
We report coincident observations of coronal and chromospheric `flare
wave' transients in association with a flare, large-scale coronal
dimming, metric radio activity and a coronal mass ejection. The two
separate eruptions occurring on 24 September 1997 originate in the
same active region and display similar morphological features. The
first wave transient was observed in EUV and Hα data, corresponding
to a wave disturbance in both the chromosphere and the solar corona,
ranging from 250 to approaching 1000 km s−1 at different
times and locations along the wavefront. The sharp wavefront had a
similar extent and location in both the EUV and Hα data. The data did
not show clear evidence of a driver, however. Both events display a
coronal EUV dimming which is typically used as an indicator of a coronal
mass ejection in the inner corona. White-light coronagraph observations
indicate that the first event was accompanied by an observable coronal
mass ejection while the second event did not have clear evidence of a
CME. Both eruptions were accompanied by metric type II radio bursts
propagating at speeds in the range of 500-750 km s−1,
and neither had accompanying interplanetary type II activity. The
timing and location of the flare waves appear to indicate an origin
with the flaring region, but several signatures associated with coronal
mass ejections indicate that the development of the CME may occur in
concert with the development of the flare wave.
Title: Properties of coronal mass ejections: SOHO LASCO observations
from January 1996 to June 1998
Authors: St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J.; Paswaters,
S. E.; Koomen, M. J.; Simnett, G. M.; Thompson, B. J.; Gurman, J. B.;
Schwenn, R.; Webb, D. F.; Hildner, E.; Lamy, P. L.
Bibcode: 2000JGR...10518169S
Altcode: 2000JGR...105.8169S; 2000JGRA..105.8169S
We report the properties of all the 841 coronal mass ejections (CMEs)
observed by the Solar and Heliospheric Observatory (SOHO) Large Angle
Spectroscopic Coronagraph (LASCO) C2 and C3 white-light coronagraphs
from January 1996 through June 1998, and we compare those properties to
previous observations by other similar instruments. Both the CME rate
and the distribution of apparent locations of CMEs varied during this
period as expected based on previous solar cycles. The distribution
of apparent speeds and the fraction of CMEs showing acceleration were
also in agreement with earlier reports. The pointing stability provided
by an L-1 orbit and the use of CCD detectors have resulted in superior
brightness sensitivity for LASCO over earlier coronagraphs; however, we
have not detected a significant population of fainter (i.e., low mass)
CMEs. The general shape of the distribution of apparent sizes for LASCO
CMEs is similar to those of earlier reports, but the average (median)
apparent size of 72° (50°) is significantly larger. The larger
average apparent size is predominantly the result of the detection of
a population of partial and complete halo CMEs, at least some of which
appear to be events with a significant longitudinal component directed
along the Sun-Earth line, either toward or away from the Earth. Using
full disk solar images obtained by the Extreme ultraviolet Imaging
Telescope (EIT) on SOHO, we found that 40 out of 92 of these events
might have been directed toward the Earth, and we compared the timing
of those with the Kp geomagnetic storm index in the days following
the CME. Although the ``false alarm'' rate was high, we found that 15
out of 21 (71%) of the Kp>=6 storms could be accounted for as SOHO
LASCO/EIT frontside halo CMEs. If we eliminate three Kp storms that
occurred following LASCO/EIT data gaps, then the possible association
rate was 15 out of 18 (83%).
Title: Dynamics of polar plumes observed at the 1998 February
26 eclipse
Authors: Lites, B. W.; Card, G.; Elmore, D. F.; Holzer, T.; Lecinski,
A.; Streander, K. V.; Tomczyk, S.; Gurman, J. B.
Bibcode: 1999SoPh..190..185L
Altcode:
This paper presents first observations of dynamics of the white-light
solar corona detected during the few minutes of totality of a solar
eclipse. Perturbations of a polar plume associated with an embedded
`jet' structure observed simultaneously at 195 Å with the EUV
Imaging Telescope (EIT) aboard the SOHO spacecraft lead to estimates
of the electron density fluctuations accompanying the jet: ±15%. The
morphological behavior of the jet, its apparent upward propagation speed
of ≈200 km s−1, and the inferred density perturbations
suggest that the jet is led by a weak, outward-propagating shock
resulting from the injection of material at high velocity at the base of
the corona. Smaller perturbations of the white-light corona are apparent
at many other locations, sustaining hope that propagating Alfvén waves
may be measurable in the solar corona. Density perturbations associated
with the jet follow from empirical electron density models of the polar
inter-plume and plume regions, as derived from the ground-based eclipse
measurements of coronal polarization brightness. These models indicate
polar plume densities 4-6 times that of the interplume low corona.
Title: Is the chromosphere hotter in coronal holes?
Authors: Gopalswamy, N.; Shibasaki, K.; Thompson, B. J.; Gurman,
J. B.; Deforest, C. E.
Bibcode: 1999AIPC..471..277G
Altcode: 1999sowi.conf..277G
Coronal holes are brighter than the quiet Sun in microwaves. Microwave
emission from the quiet Sun is optically thick thermal bremsstrahlung
from the upper chromosphere. Therefore, the optically thick layer in the
coronal hole chromosphere must be hotter than the corresponding layer
in the quiet chromosphere. We present microwave and SOHO observations
in support of this idea. Because of the availability of simultaneous
EUV and microwave images it is now possible to obtain more details
of this enigmatic phenomenon. In this paper, we highlight the primary
properties of the microwave enhancement in coronal holes and point out
some related phenomena. Finally, we summarize the possible explanations
of the radio enhancement.
Title: SOHO/EIT Observations of the 1997 April 7 Coronal Transient:
Possible Evidence of Coronal Moreton Waves
Authors: Thompson, B. J.; Gurman, J. B.; Neupert, W. M.; Newmark,
J. S.; Delaboudinière, J. -P.; Cyr, O. C. St.; Stezelberger, S.;
Dere, K. P.; Howard, R. A.; Michels, D. J.
Bibcode: 1999ApJ...517L.151T
Altcode:
We report observations obtained with the Extreme ultraviolet
Imaging Telescope (EIT) on board SOHO of a large-scale coronal
transient propagating across the disk of the Sun at a speed of 250 km
s-1, in apparent association with a flare and coronal mass
ejection. The observations consist of a series of images taken in the
Fe XII 195 Å bandpass at an average cadence of 15 minutes. A visible
increase in coronal emission propagates away from the erupting region,
traveling across most of the solar disk in less than an hour. As the
wave propagates through the ambient corona, its path is not homogeneous,
and it is less observable near strong magnetic features such as
active regions and magnetic neutral lines. The characteristics of
this event appear to be representative of several other ``EIT waves,''
which we identify as strong candidates for the coronal manifestation
of Moreton waves.
Title: A Transition Region Eruption Observed with CDS, TRACE and EIT
Authors: Brekke, P.; Kjeldseth-Moe, O.; Fredvik, T.; Haugan, S. V. H.;
Tarbell, T. D.; Gurman, J. B.
Bibcode: 1999AAS...194.5905B
Altcode: 1999BAAS...31..918B
An ejection of plasma on the west limb has been observed with CDS,
TRACE and EIT on 19 May 1998. The start of the eruption coincided
with a weak flare observed with GOES. Erupting material rose to 120
Mm above the solar surface in 17 min, and then fell back to the solar
surface. Vertical velocities of 200 km s(-1) are estimated from a series
of TRACE images in the C(+3) resonance lines at 155 nm and from EIT
images in the 19.5 nm band, while Doppler shifts of the transition
region lines observed with CDS yield maximum horizontal velocities
of 300 km s(-1) at the top of the plasma trajectories. The similar
appearance and time variation of the eruption as seen with all three
instruments indicate the presence of a multi-temperature plasma in
spatial regions less than 1-2 arc seconds, with temperatures ranging
from 10(5) K to 1.5 MK. The material did not have the momentum to break
loose from the Sun and was not associated with any CME observed with
LASCO. However, we may speculate that CMEs are similar to the eruption
observed, with even higher speeds involved.
Title: Microwave enhancement and variability in the elephant's trunk
coronal hole: Comparison with SOHO observations
Authors: Gopalswamy, N.; Shibasaki, K.; Thompson, B. J.; Gurman, J.;
DeForest, C.
Bibcode: 1999JGR...104.9767G
Altcode:
We report on an investigation of the microwave enhancement and its
variability in the elephant's trunk coronal hole observed during the
Whole Sun Month campaign (August 10 to September 9, 1996). The microwave
images from the Nobeyama radioheliograph were compared with magnetograms
and EUV images obtained simultaneously by the Michelson Doppler imager
and the extreme ultraviolet imaging telescope (EIT) on board the SOHO
spacecraft. The combined data set allowed us to understand the detailed
structure of the microwave enhancement in the spatial and temporal
domains. We find that the radio enhancement is closely associated
with the enhanced unipolar magnetic regions underlying the coronal
hole. The radio enhancement consists of a smooth component originating
from network cell interiors and a compact component associated with
network magnetic elements. When a minority polarity is present near
a majority polarity element, within the coronal hole, the resulting
mixed polarity region is associated with a bright-point-like emission
in coronal EUV lines such as the Fe XII 195 Å. These coronal bright
points are also observed distinctly in the EIT 304 Å band, but not
in microwaves. On the other hand, the lower-temperature line emission
(304 Å) and the microwave enhancement are associated with the unipolar
magnetic flux elements in the network. We found strong time variability
of the radio enhancement over multiple timescales, consistent with the
initial results obtained by SOHO instruments. The microwave enhancement
is most probably due to temperature enhancement in the chromosphere
and may be related to the origin of solar wind.
Title: How Many Terabytes Was That? Archiving and Serving Solar
Space Data Without Losing Your Shirt
Authors: Gurman, J. B.
Bibcode: 1999AAS...194.7601G
Altcode: 1999BAAS...31..955G
Even solar missions of modest size in the next decade will produce
terabytes (10(12) bytes) of data. The Solar Data Analysis Center
is already dealing with mission archives of similar volumes, and is
serving the entire archives to the community over the Internet. We
examine present and near-term archiving strategies and media, and
conclude rather surprisingly that online storage on network-attached
RAID arrays is the most cost-effective, as well as the most usable,
archiving method likely to be available over the next decade for keeping
and serving scientifically useful data for a period of 10 years or more.
Title: Jets and Eruptions in the Transition Region Observed with CDS,
EIT and TRACE
Authors: Brekke, P.; Kjeldseth-Moe, O.; Tarbell, T.; Gurman, J.
Bibcode: 1999ASPC..183..357B
Altcode: 1999hrsp.conf..357B
No abstract at ADS
Title: Active Regions
Authors: Holman, G. D.; Cheng, C. -C.; Gurman, J. B.; Haisch, B. M.;
Poland, A. I.; Porter, J. G.; Saba, J. L. R.; Schmieder, B.; Strong,
K. T.
Bibcode: 1999mfs..conf...41H
Altcode:
Magnetic Field Strength and Strucutre Results Prior to SMM First Results
with SMM Subsequent Results: 1983-1987 The Coronal Magnetic Structures
Observing Campaign Coronal Magnetic Field Studies after SMM Dynamics
and Heating of the Solar Corona FCS Line-Broadening Measurements
Large Nonthermal Velocities Spatial Variations Correlation Studies FCS
Line-Broadening Data Interpreting the FCS Line Broadening Constraints
on Mass Motions Link to Heating Discussion Coronal Heating, Magnetic
Fields, and Flares UVSP Obervations of Active Regions Transition Region
Brightenings: UV Microflares Sunspots Magnetic Field and Height of the
Transition Region Sunspot Plumes Sunspot Flows Horizontal Flows Vertical
Flows Nonthermal Line Broadening Umbral Oscillations A Look Backward,
a Look Forward Prominences and Filaments Prominence Environment and
Structure Steady Flows in Prominence Material Activity in Prominences
Postflare Loops and Surges Conclusion
Title: Observations of Coronal Structures Above an Active Region by
EIT and Implications for Coronal Energy Deposition
Authors: Neupert, W. M.; Newmark, J.; Delaboudinière, J. -P.;
Thompson, B. J.; Catura, R. C.; Moses, J. D.; Gurman, J. B.;
Portier-Fozzani, F.; Gabriel, A. H.; Artzner, G.; Clette, F.; Cugnon,
P.; Maucherat, A. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Dere,
K. P.; Howard, R. A.; Michels, D. J.; Freeland, S.; Lemen, J. R.;
Stern, R. A.
Bibcode: 1998SoPh..183..305N
Altcode:
Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO
have been used to evaluate temperature and density as a function of
position in two largescale features in the corona observed in the
temperature range of 1.0-2.0 MK. Such observations permit estimates
of longitudinal temperature gradients (if present) in the corona and,
consequently, estimates of thermal conduction and radiative losses
as a function of position in the features. We examine two relatively
cool features as recorded in EIT's Fe ix/x (171 Å) and Fe xii (195 Å)
bands in a decaying active region. The first is a long-lived loop-like
feature with one leg, ending in the active region, much more prominent
than one or more distant footpoints assumed to be rooted in regions of
weakly enhanced field. The other is a near-radial feature, observed
at the West limb, which may be either the base of a very high loop
or the base of a helmet streamer. We evaluate energy requirements to
support a steady-state energy balance in these features and find in
both instances that downward thermal conductive losses (at heights
above the transition region) are inadequate to support local radiative
losses, which are the predominant loss mechanism. The requirement that a
coronal energy deposition rate proportional to the square of the ambient
electron density (or pressure) is present in these cool coronal features
provides an additional constraint on coronal heating mechanisms.
Title: Comparison of Prominences in Hα and He II 304 Å
Authors: Wang, Haimin; Chae, Jongchul; Gurman, Joseph B.; Kucera,
Therese A.
Bibcode: 1998SoPh..183...91W
Altcode:
In this letter, we bring attention to prominences which show different
morphology in Hα and He ii 304 Å, as observed simultaneously by
BBSO and EIT on board SOHO. Those two lines have been thought to
represent similar chromospheric structures although they are formed at
significantly different temperatures. We give two examples representing
two kinds of anomaly: (1) prominences showing strong Hα emissions in
the lower part and strong He ii emissions in the upper part, and (2)
erupting prominences showing extensive He ii emission, but nothing in
Hα. Our results indicate that a part or the whole of a prominence may
be too hot to emit Hα radiation, possibly due to heating or thermal
instability. Please note that these are not just two isolated cases,
many other prominences show the similar differences in Hα and He ii
304 Å.
Title: The prolate solar chromosphere
Authors: Auchere, F.; Boulade, S.; Koutchmy, S.; Smartt, R. N.;
Delaboudiniere, J. P.; Georgakilas, A.; Gurman, J. B.; Artzner, G. E.
Bibcode: 1998A&A...336L..57A
Altcode:
We present a comparative analysis of the chromospheric solar
limb prolateness, using strictly simultaneous H_alpha ground-based
observations and Heriptsize{II} space-based observations. The typical
prolateness is found to be Delta D/D=5.5*E(-3) in Heriptsize{II}
and 1.2*E(-3) in H_alpha . The first measurements in the 30.4 nm
Heriptsize{II} line over a period of two years, as well as coronal
data, are discussed to explore further the origin of the prolateness
and its possible consequences.
Title: On the relationship between coronal mass ejections and
magnetic clouds
Authors: Gopalswamy, N.; Hanaoka, Y.; Kosugi, T.; Lepping, R. P.;
Steinberg, J. T.; Plunkett, S.; Howard, R. A.; Thompson, B. J.;
Gurman, J.; Ho, G.; Nitta, N.; Hudson, H. S.
Bibcode: 1998GeoRL..25.2485G
Altcode:
We compare the substructures of the 1997 February 07 coronal mass
ejection (CME) observed near the Sun with a corresponding event in
the interplanetary medium to determine the origin of magnetic clouds
(MCs). We find that the eruptive prominence core of the CME observed
near the Sun may not directly become a magnetic cloud as suggested by
some authors and that it might instead become the ”pressure pulse”
following the magnetic cloud. We substantiate our conclusions using time
of arrival, size and composition estimates of the CME-MC substructures
obtained from ground based, SOHO and WIND observations.
Title: Observation of Quasi-periodic Compressive Waves in Solar
Polar Plumes
Authors: DeForest, C. E.; Gurman, J. B.
Bibcode: 1998ApJ...501L.217D
Altcode:
On 1996 March 7, the Solar and Heliospheric Observatory spacecraft
conducted a multi-instrument campaign to observe polar plumes in the
south polar coronal hole. Recent time-domain analyses of EUV Imaging
Telescope images from that campaign show filamentary substructure in
the plumes, on a length scale of ~5", which changes on timescales
of a few minutes, and coherent quasi-periodic perturbations in
the brightness of Fe IX and Fe X line emission at 171 Å from the
plumes. The perturbations amount to 10%-20% of the plumes' overall
intensity and propagate outward at 75-150 km s-1, taking
the form of wave trains with periods of 10-15 minutes and envelopes
of several cycles. We conclude that the perturbations are compressive
waves (such as sound waves or slow-mode magnetosonic waves) propagating
along the plumes. Assuming that the waves are sonic yields a mechanical
energy flux of 150-400 W m-2 (1.5-4 ×105 ergs
cm-2 s-1) in the plumes.
Title: SOHO/EIT observations of an Earth-directed coronal mass
ejection on May 12, 1997
Authors: Thompson, B. J.; Plunkett, S. P.; Gurman, J. B.; Newmark,
J. S.; St. Cyr, O. C.; Michels, D. J.
Bibcode: 1998GeoRL..25.2465T
Altcode:
An earth-directed coronal mass ejection (CME) was observed on May 12,
1997 by the SOHO Extreme ultraviolet Imaging Telescope (EIT). The CME,
originating north of the central solar meridian, was later observed by
the Large Angle Spectrometric Coronagraph (LASCO) as a “halo” CME:
a bright expanding ring centered about the occulting disk. Beginning at
about 04:35 UT, EIT recorded several CME signatures, including dimming
regions close to the eruption, post-eruption arcade formation, and a
bright wavefront propagating quasi-radially from the source region. Each
of these phenomena appear to be associated with the same eruption, and
the onset time of these features corresponds with the estimated onset
time observed in LASCO. We discuss the correspondence of these features
as observed by EIT with the structure of the CME in the LASCO data.
Title: Sunspot Oscillations from SUMER Spectra
Authors: Rendtel, J.; Staude, J.; Innes, D.; Wilhelm, K.; Gurman, J. B.
Bibcode: 1998ESASP.417..277R
Altcode: 1998cesh.conf..277R
No abstract at ADS
Title: Helio-Atmospheric Links Explorer (HALE): A MIDEX Experiment
for Exploring the Emergence of Magnetic Flux from Below the Solar
Photosphere through the Corona
Authors: Scherrer, P. H.; Title, A. M.; Bush, R. I.; Duvall, T. L.,
Jr.; Gurman, J. B.; Kosovichev, J. T.; Hoeksema, A. G.; Poland, A. I.;
Tarbell, T. D.
Bibcode: 1998ESASP.417..285S
Altcode: 1998cesh.conf..285S
No abstract at ADS
Title: Birth Place of the 1998 January 21 CME
Authors: Gopalswamy, N.; Hanaoka, Y.; Kaiser, M.; Gurman, J.; Hudson,
H.; Howard, R. A.
Bibcode: 1998cee..workE..40G
Altcode:
The 1998 January 21 halo coronal mass ejection was launched
from high southern latitudes in association with a filament
disappearance observed by the Nobeyama Radioheliograph. Signatures
of the initial destabilization of the filament were observed by
the Extreme-ultraviolaet Imaging Telescope (EIT) on board the SOHO
spacecraft and by the Soft X-ray Telescope (SXT) on board Yohkoh. The
Wind/WAVES experiment observed a type II burst in the 600-300 kHz
range. The data coverage for this event is unusually high and we make
use of it to understand the origin and evolution of the eruption. We
address several issues based on these data: (i) relation between
filament eruption and arcade formation beneath the filament, (ii)
comparison between the hot arcade formation in X-rays and EUV, (iii)
relation between the filament eruption and the white light CME, (iv)
relation between the CME and the interplanetary shock inferred from the
WAVES data. A summary of near-surface activities associated with the
eruption can be seen in the Figure 1. Figure 1. SOHO/MDI longitudinal
magnetogram, with radio filament (white contours) and X-ray emission
(enclosed by dark lines) are overlaid. The thick white line from E to
W is the neutral line over which the eruption took place. North is to
the top and east is to the left. F is the location where the filament
split at the time of eruption.
Title: Oscillations in a Sunspot Transition Region Observed with SOHO
Authors: Staude, J.; Rendtel, J.; Innes, D.; Wilhelm, K.; Gurman, J. B.
Bibcode: 1998ESASP.418..651S
Altcode: 1998soho....6..651S
Measurements of oscillations in the chromosphere-corona transition
region (TR) above sunspots are of fundamental importance for
investigating sunspot structure and dynamics; for instance, resonator
models of magneto-atmospheric waves and their non-adiabatic behavior
can be tested in this way (Staude et al., 1985). UV spectroscopic
data obtained with the SUMER spectrograph aboard SOHO have been
analyzed to detect such oscillations. The longest time series was
obtained on August 29, 1996, between 09:08 UT and 13:31 UT. During
this period, scans were made over the active region NOAA 7986 in the
wavelength bands around 770.4 AA (Ne VIII line, formed at T ~6 times
105 K) and 1548.1 AA (C IV line, T ~7 times 104
dots 1.3 times 105 K). The large dominating sunspot of this
active region was close to the disk centre. Simultaneous observations
with the Normal Incidence Spectrometer of CDS aboard SOHO have shown,
that the spot had a bright EUV plume at TR temperatures (Maltby et al.,
1998). For compensating possible instrumental and exposure effects,
we extract background information from each image. A preliminary
data analysis indicates intensity oscillations in the 2-minute range
(at 7.4 dots 7.7 mHz) in both spectral lines and a slow temporal
decrease of oscillatory power in the Ne VIII line, but an increase
in the C IV line. These results hint at a non-adiabatic behavior of
the oscillations and a slow cooling of the emitting sunspot plume
region. Further supplementary observations of the active region NOAA
7986 are from EIT aboard SOHO (in the Fe IX/X lines at 171 AA ---
T ~1.3 times 106 K --- a time series of 2 hours has been
obtained simultaneous to the first part of the SUMER series, moreover,
single high-resolution pictures in 4 UV lines exist) as well as from
the magnetograph of the Einsteinturm observatory at Potsdam showing
a rather complex polarity distribution. It is planned to extend the
study towards velocity variations and to correlations between the
oscillations in the two SUMER lines. Furthermore, correlations will
be investigated towards the EIT time series.
Title: New Images of the Solar Corona
Authors: Gurman, Joseph B.; Thompson, Barbara J.; Newmark, Jeffrey A.;
Deforest, Craig E.
Bibcode: 1998ASPC..154..329G
Altcode: 1998csss...10..329G
In 1.5 years of operation, The Extreme Ultraviolet Imaging Telescope
(EIT) on SOHO has obtained over 40,000 images of the Sun in four
wavebands between 171 Angstroms and 304 Angstroms, with spatial
resolution limited only by the pixel scale of 2.59 arcsec. These
images, and in particular compilations of time series of images into
digital movies, have changed several of our ideas about the corona
at temperatures of 0.9 - 2.5 MK. For the first time, we are able to
see outflow in polar plumes and microjets inputting momentum into the
high-speed, polar wind flow. For the first time, in conjunction with the
LASCO coronagraphs and ground-based He I imagers, we have been able to
see all the structures involved in coronal mass ejections (CMEs), from
the surface of the Sun to 30 solar radii above it. In several cases, we
have been able to observe directly the dramatic Moreton waves emanating
from the active region where the CMEs originate, and radiating across
virtually the entire visible hemisphere of the Sun. We interpret these
large-scale coronal disturbances as fast-mode waves. Such events appear
in the SOHO-LASCO coronagraphs as earthward-directed, and several have
been detected by solar wind monitoring experiments on SOHO and other
spacecraft. We have been able to view a variety of small-scale phenomena
as well, including motions in prominences and filaments, macrospicular
and polar microjet eruptions, and fine structures in the polar crown
filament belt. The multi-wavelength capability of EIT makes it possible
to determine the temperature of the coronal plasma and, here, too,
we have been afforded a novel view: the heating in coronal active
regions occurs over a considerably larger area than the high-density
loops structures alone (i.e., bright features) would indicate.
Title: White-Light Coronal Mass Ejections: A New Perspective from
LASCO
Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.;
Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner,
G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere,
K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis,
D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark,
J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker,
D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D.
Bibcode: 1997ESASP.415..103S
Altcode: 1997cpsh.conf..103S
No abstract at ADS
Title: Solar Active Region Movies seen by the SOHO Extreme-ultraviolet
Telescope
Authors: Newmark, J. S.; Thompson, B.; Gurman, J. B.; Delaboudiniere,
J. P.; Aschwanden, Markus; Mason, Helen
Bibcode: 1997AAS...191.7307N
Altcode: 1997BAAS...29.1321N
The Extreme-ultraviolet Imaging Telescope (EIT) on board the SOHO (SOlar
and Heliospheric Observatory) satellite provides wide-field images of
the corona and transition region on the solar disc and up to 1.4 solar
radii above the limb. Its normal incidence multilayer-coated optics
select spectral emission lines from FeIX (171 Ang), FeXII (195 Ang),
FeXV (284 Ang), and HeII (304 Ang) with 2.6 arcsecond resolution which
allow us to describe Solar activity over a wide temperature range. EIT
is providing unique EUV observations of the structure and evolution of
active regions. Here we show movies of active region 8059 from July
3-10, 1997. The high temporal variability of the AR loops is very
evident. Initial temperature and density diagnostics are explored as
well as a comparison with diagnostics from the SOHO-CDS instrument.
Title: Polar Plume Anatomy: Results of a Coordinated Observation
Authors: DeForest, C. E.; Hoeksema, J. T.; Gurman, J. B.; Thompson,
B. J.; Plunkett, S. P.; Howard, R.; Harrison, R. C.; Hasslerz, D. M.
Bibcode: 1997SoPh..175..393D
Altcode:
On 7 and 8 March 1996, the SOHO spacecraft and several other space-
and ground-based observatories cooperated in the most comprehensive
observation to date of solar polar plumes. Based on simultaneous
data from five instruments, we describe the morphology of the plumes
observed over the south pole of the Sun during the SOHO observing
campaign. Individual plumes have been characterized from the photosphere
to approximately 15 R⊙ yielding a coherent portrait of the features
for more quantitative future studies. The observed plumes arise from
small (∼ 2-5 arc sec diameter) quiescent, unipolar magnetic flux
concentrations, on chromospheric network cell boundaries. They are
denser and cooler than the surrounding coronal hole through which they
extend, and are seen clearly in both Feix and Fexii emission lines,
indicating an ionization temperature between 1.0-1.5 x 106
K. The plumes initially expand rapidly with altitude, to a diameter of
20-30 Mm about 30 Mm off the surface. Above 1.2 R⊙ plumes are observed
in white light (as `coronal rays') and extend to above 12 R⊙. They
grow superradially throughout their observed height, increasing their
subtended solid angle (relative to disk center) by a factor of ∼10
between 1.05 R⊙ and 4-5 R⊙ and by a total factor of 20-40 between
1.05 R⊙ and 12 R⊙. On spatial scales larger than 10 arc sec,
plume structure in the lower corona (R < 1.3 R⊙) is observed to
be steady-state for periods of at least 24 hours; however, on spatial
scales smaller than 10 arc sec, plume XUV intensities vary by 10-20%
(after background subtraction) on a time scale of a few minutes.
Title: EIT Observations of the Extreme Ultraviolet Sun
Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner,
G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.;
Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard,
R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus,
P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.;
Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark,
J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.;
Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R.
Bibcode: 1997SoPh..175..571M
Altcode:
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO
spacecraft has been operational since 2 January 1996. EIT observes
the Sun over a 45 x 45 arc min field of view in four emission line
groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination
of the instrument flatfield, the instrument scattering function, and
the instrument aging were necessary for the reduction and analysis
of the data. The observed structures and their evolution in each
of the four EUV bandpasses are characteristic of the peak emission
temperature of the line(s) chosen for that bandpass. Reports on the
initial results of a variety of analysis projects demonstrate the range
of investigations now underway: EIT provides new observations of the
corona in the temperature range of 1 to 2 MK. Temperature studies of
the large-scale coronal features extend previous coronagraph work
with low-noise temperature maps. Temperatures of radial, extended,
plume-like structures in both the polar coronal hole and in a low
latitude decaying active region were found to be cooler than the
surrounding material. Active region loops were investigated in detail
and found to be isothermal for the low loops but hottest at the loop
tops for the large loops.
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.;
Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier,
F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.;
Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.;
Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.;
Llebaria, A.; Schwenn, R.; Simnett, G. M.
Bibcode: 1997SoPh..175..601D
Altcode:
We present the first observations of the initiation of a coronal mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
experiment on SOHO show that the CME began in a small volume and was
initially associated with slow motions of prominence material and a
small brightening at one end of the prominence. Shortly afterward,
the prominence was accelerated to about 100 km s-1 and
was preceded by a bright loop-like structure, which surrounded an
emission void, that traveled out into the corona at a velocity of
200-400 km s-1. These three components, the prominence,
the dark void, and the bright loops are typical of CMEs when seen at
distance in the corona and here are shown to be present at the earliest
stages of the CME. The event was later observed to traverse the LASCO
coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest
is the fact that this large-scale event, spanning as much as 70 deg in
latitude, originated in a volume with dimensions of roughly 35" (2.5
x 104 km). Further, a disturbance that propagated across
the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the
west limb.
Title: Association of Extreme-Ultraviolet Imaging Telescope (EIT)
Polar Plumes with Mixed-Polarity Magnetic Network
Authors: Wang, Y. -M.; Sheeley, N. R.; Dere, K. P.; Duffin, R. T.;
Howard, R. A.; Michels, D. J.; Moses, J. D.; Harvey, J. W.; Branston,
D. D.; Delaboudinière, J. -P.; Artzner, G. E.; Hochedez, J. F.;
Defise, J. M.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert,
W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Clette, F.
Bibcode: 1997ApJ...484L..75W
Altcode:
SOHO EIT spectroheliograms showing the polar coronal holes during the
present sunspot minimum are compared with National Solar Observatory
(Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The
chromospheric λ8542 magnetograms, obtained on a routine, near-daily
basis since 1996 June, reveal the Sun's strong polar fields with
remarkable clarity. We find that the Fe IX λ171 polar plumes occur
where minority-polarity flux is in contact with flux of the dominant
polarity inside each polar hole. Moreover, the locations of ``plume
haze'' coincide approximately with the patterns of brightened He
II λ304 network within the coronal hole. The observations appear
to be consistent with mechanisms of plume formation involving
magnetic reconnection between unipolar flux concentrations and nearby
bipoles. The fact that minority-polarity fields constitute only a small
fraction of the total magnetic flux within the polar holes suggests
that plumes are not the main source of the high-speed polar wind.
Title: Tracking a CME from Cradle to Grave: A Multi-wavelength
Analysis of the February 6-7, 1997 Event
Authors: Gopalswamy, N.; Kundu, M. R.; Hanaoka, Y.; Kosugi, T.; Hudson,
H.; Nitta, N.; Thompson, B.; Gurman, J.; Plunkett, S.; Howard, R.;
Burkepile, J.
Bibcode: 1997SPD....28.0501G
Altcode: 1997BAAS...29..908G
The partially earth-directed coronal mass ejection (CME) event of 1997
February 6-7 originated from the southwest quadrant of the sun. The
CME accelerated from 170 km/s to about 830 km/s when it reached a
distance of 25 solar radii. The CME was an arcade eruption followed
by bright prominence core structures. The prominence core was tracked
continuously from the solar surface to the interplanetary medium by
combining data from the Nobeyama radioheliograph (microwaves), Mauna Loa
Solar Observatory (He 10830 { Angstroms}), SOHO/EIT (EUV) and SOHO/LASCO
(white light). The CME was accompanied by an arcade formation, fully
observed by the YOHKOH/SXT (soft X-rays) and SOHO/EIT (EUV). The X-ray
and EUV observations suggest that the reconnection proceeded from
the northwest end to the southeast end of a filament channel. In the
SOHO/EIT images, the the feet of the soft X-ray arcade were observed
as EUV ribbons. The CME event also caused a medium sized geomagnetic
storm: The hourly equatorial Dst values attained storm level during
18:00-19:00 UT on February 09. This means the disturbance took about
2.25 days to reach the Earth. The first signatures of an IP shock was
a pressure jump in the WIND data around 13:00 UT on Feb 09, 1997 which
lasted for about 14 hours, followed by flux rope signatures. This CME
event confirms a number of ideas about CMEs: The three part structure
(frontal bright arcade, dark cavity and prominence core), disappearing
filament, elongated arcade formation, and terrestrial effects. We make
use of the excellent data coverage from the solar surface to the Earth
to address a number of issues regarding the origin and propagation of
the geoeffective solar disturbances. We benefited from discussions at
the first SOHO-Yohkoh Coordinated Data Analysis Workshop, held March
3-7, 1997, at Goddard Space Flight Center.
Title: Nobeyama/SOHO/BBSO Comparison of Solar Polar Coronal Holes
Authors: Gary, D. E.; Enome, S.; Shibasaki, K.; Gurman, J. B.; Shine,
R. A.
Bibcode: 1997SPD....28.0801G
Altcode: 1997BAAS...29..912G
Although it is not widely known outside the discipline of solar
radiophysics, a long-standing puzzle exists: the poles of the Sun
appear brighter than the rest of the quiet Sun in a restricted range
of wavelengths roughly from 15 GHz to about 48 GHz (cf. Kosugi et
al. 1986). At somewhat lower radio frequencies the poles appear darker
than the quiet Sun due to a deficit of coronal material, while at
mm-wavelengths the polar and non-polar quiet Sun appear quite uniform
due to the similarity of the atmospheric structure at lower heights
in the chromosphere. The excess brightness at the poles has also been
reported in coronal holes on the disk, and so is apparently related to
the phenomenon of coronal holes. The brightening likely corresponds to
an elevated temperature in the upper chromosphere in coronal holes
relative to normal quiet Sun. The phenomenon is especially well
suited to study via radio emission due to the unique sensitivity of
radio waves to this height range in the chromosphere. The possibility
exists that the different chromospheric structure for coronal holes
implied by the radio brightening may offer some clue to the origin of
the fast solar wind, which is now well established to arise in coronal
holes. Radio brightening of coronal holes is a difficult observational
problem because an instrument is needed that can image large areas of
the Sun at relatively high resolution. The Nobeyama Radioheliograph
has the required capability and operates at 17 and 34 GHz, nicely
within the frequency range where the brightening occurs. We compare
Nobeyama radio synthesis images on several days in 1996 with images
from the EIT, CDS, and MDI experiments on the Solar and Heliospheric
Observatory (SOHO) spacecraft, and with high resolution images from
the Big Bear Solar Observatory, with the aim of determining the spatial
and temporal characteristics of the brightening. We compare the extent
of the radio brightening with the boundaries of the coronal holes seen
from the SOHO data, to establish the previously suggested identity of
the polar brightening with coronal holes. We investigate whether the
brightening is primarily associated with network features, faculae,
or perhaps bipolar magnetic elements, or whether it is instead a
diffuse brightening more-or-less uniformly covering the coronal hole
area. We look for temporal variations, and their correlation with
changing features seen from SOHO. We conclude with some ideas for how
the chromospheric structure may be different in coronal holes than in
normal quiet Sun, and speculate on the implications for acceleration
of the fast solar wind.
Title: Wave Propagation in the Chromosphere and Transition Region:
Where Have All the Shock Waves Gone?
Authors: Fleck, B.; Steffens, S.; Deubner, F. -L.; Wilhelm, K.;
Harrison, R.; Gurman, J.
Bibcode: 1997SPD....28.0120F
Altcode: 1997BAAS...29..882F
We present first results from a joint observing program (SOHO JOP 26)
involving SUMER, CDS and EIT on SOHO, coordinated with ground-based
observations at the Vacuum Tower Telescope at Iza{\ n}a, Tenerife. The
objective of this study is to characterize the wave propagation
properties in the solar atmosphere, from the photosphere through the
chromosphere up into the transition region. Particular emphasis is laid
on the 3-min shock waves observed in the Ca II K line. How do they
impact the transition region and what signature do they leave there
and in the lower corona? The ground-based measurements comprise high
resolution time series (both filtergrams and spectrograms) in Ca II K,
Hα and Mgb_2. With SUMER we ran four sequences covering different
temperature regimes: a) O I 1302, O I 1306, Si II 1309, C I 1311,
C II 1334, C II 1335, b) Si I 1256, N V 1242, O V 629 c) He I 584,
C III 1175, O I 1152, d) H I 1025, O VI 1031, O VI 1037. With CDS we
took spectral time series in O VI 554, He I 584, He II 607, Mg IX 368,
and O V 629 as well as wide-slit (90x240'') ``movies'' in He I 584,
Mg IX 368 and O V 629, while EIT ran sub-field high cadence sequences
in He II 304.
Title: SOHO/EIT and SOHO/LASCO Observations of the April 1 1997 Event:
Coronal Observations of a Moreton Wave
Authors: Thompson, B. J.; Newmark, J. S.; Gurman, J. B.; St. Cyr,
O. C.; Stezelberger, S.
Bibcode: 1997SPD....28.0130T
Altcode: 1997BAAS...29..884T
The SOHO Extreme ultraviolet Imaging Telescope (EIT) recorded a series
of events on April 1, 1997 with a 12-minute cadence of 195 Angstrom
(Fe XII) images. A Moreton wave was observed emanating from a flaring
active region beginning at 13:56 UT 1-April-1997. The wave travelled
at initial speeds of approximately 300 km/sec, spreading across the
solar disk radially from the flare. The CME observed by SOHO/LASCO was
observable at both the east and west limbs in the C2 (2-6 solar radii)
and C3 (3.7-30 solar radii) coronagraphs. The event was the site of
strong emerging flux, and a number of explosive jet-like surges were
observed at the east edge of the region prior to, throughout, and
following the event. The discussion will include topology, comparison
to Moreton wave/MHD theory predictions, and solar wind signatures.
Title: Time Variability of Polar Plumes as observed with SoHO/EIT
and SoHO/MDI
Authors: Deforest, C. E.; Gurman, J. B.; Moses, J. D.
Bibcode: 1997SPD....28.0803D
Altcode: 1997BAAS...29..912D
Polar plumes are magnetically open high density structures that are
observed in the polar coronal holes. They arise from unipolar magnetic
footpoints in between chromospheric network cells, and expand as they
rise through the corona to altitudes of at least 15-20 solar radii. On
timescales of hours, plumes are remarkably stable, quiescent structures;
however, we find that plumes vary significantly in XUV intensity
on time scales of a few minutes and length scales of about an arc
minute, based on high cadence observations in the EIT 171A and 195A
passbands. The observed variations propagate outward with speeds of
about 300 km/sec. We demonstrate this effect in several plumes observed
during different EIT high cadence pole observations; compare observed
variations in the photospheric field, as measured simultaneously by
MDI, to the intensity variations in the plumes; and suggest whether
the outward motions represent physical structures or wave motion.
Title: Observations of Coronal Features by EIT above an Active Region
by EIT and Implications for Coronal Heating
Authors: Neupert, W. M.; Newmark, J.; Thompson, B. J.; Catura, R.;
Moses, J. D.; Portier-Fozzani, F.; Delaboudiniere, J. P.; Gabriel, A.;
Artzner, G.; Clette, F.; Cugnon, P.; Maucherat, A.; Defise, J. M.;
Jamar, C.; Rochus, P.; Howard, R.; Michels, D.; Dere, K.; Freeland,
S.; Lemen, J.; Stern, R.; Gurman, J.
Bibcode: 1997SPD....28.0115N
Altcode: 1997BAAS...29..881N
The EUV Imaging Telescope (EIT) on the SOHO provides the capability
for multi-wavelength imaging of the corona in four spectral bands,
centered at 171, 195, 284, and 304 Angstroms, using multilayer telescope
technology. These bands encompass coronal temperatures from 1 MK
to 2.5 MK as well as the upper chromosphere, at about 60,000 K. In
particular, nearly simultaneous imaging in the 171 and 195 Angstrom
bands, the former including major Fe IX and Fe X emission lines, the
latter including a strong Fe XII line, provides a capability to infer
the morphology and characteristics of the corona at temperatures of
1.0 - 1.7 MK. We have examined the corona in this temperature range
over an active region observed from SOHO from May - September, 1996 and
find that low-lying loops (below a density scale height of 75,000 km,
characteristic of Fe X) vary little in brightness and temperature along
their length. For features extending to greater heights, however, both
brightness gradients and temperature gradients are observed. Preliminary
analysis of the observations when the region was on the West limb
on September 30 indicates a small positive temperature gradient of
approximately 0.5 K/km in one loop system that extended above 100,000
km. On the other hand, a nearly radial feature extending to the edge of
the EIT FOV was isothermal or had at most a slight negative temperature
gradient. Such measurements may have application to the modeling of
coronal loops and streamers and the processes of coronal heating and
solar wind acceleration.
Title: A Multi-Wavelength Analysis of the February 6/7, 1997 Coronal
Mass Ejection
Authors: Plunkett, S. P.; Gopalswamy, N.; Kundu, M. R.; Howard, R. A.;
Thompson, B. J.; Gurman, J. B.; Lepping, R. P.; Hudson, H. S.; Nitta,
N.; Hansoka, Y.; Kosugi, T.; Burkepile, J. T.
Bibcode: 1997ESASP.404..615P
Altcode: 1997cswn.conf..615P
No abstract at ADS
Title: Imaging the solar corona in the EUV
Authors: Delaboudiniere, J. -P.; Stern, R. A.; Maucherat, A.;
Portier-Fozzani, F.; Neupert, W. M.; Gurman, J. B.; Catura, R. C.;
Lemen, J. R.; Shing, L.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.;
Michels, D. J.; Moses, J. D.; Au, B.; Dere, K. P.; Howard, R. A.;
Kreplin, R.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.;
Marioge, J. P.; Clette, F.; Cugnon, P.; van Dessel, E. L.
Bibcode: 1997AdSpR..20.2231D
Altcode:
The SOHO (SOlar and Heliospheric Observatory) satellite was launched on
December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point
on February 14th 1996, it began to continuously observe the Sun. As
one of the instruments onboard SOHO, the EIT (Extreme ultraviolet
Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The
He II filter at 304 A˚ images the chromosphere and the base of the
transition region at a temperature of 5 - 8 x 10^4 K; the Fe IX-X
filter at 171 A˚ images the corona at a temperature of ~ 1.3 x 10^6 K;
the Fe XII filter at 195 A˚ images the quiet corona outside coronal
holes at a temperature of ~ 1.6 x 10^6 K; and the Fe XV filter at 284
A˚ images active regions with a temperature of ~ 2.0 x 10^6 K. About
5000 images have been obtained up to the present. In this paper,
we describe also some aspects of the telescope and the detector
performance for application in the observations. Images and movies
of all the wavelengths allow a look at different phenomena present in
the Sun's corona, and in particular, magnetic field reconnection.
Title: Quasi-Periodic Compressive Waves in Polar Plumes
Authors: Deforest, C. E.; Gurman, J. B.
Bibcode: 1997ESASP.404..775D
Altcode: 1997cswn.conf..775D
No abstract at ADS
Title: First Results from SOHO on Waves Near the Solar Transition
Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.;
Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten,
R. J.
Bibcode: 1997ASPC..118..284S
Altcode: 1997fasp.conf..284S
We present first results from simultaneous observations with the
CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995)
for a description of the instruments} onboard SOHO and the VTT at
Tenerife. Our aim is to study the wave propagation, shock formation,
and transmission properties of the upper chromosphere and transition
region. The preliminary results presented here include the variation
of velocity power spectra with height, difference in power between
internetwork and network regions, and variations in mean flows displayed
by different spectral lines.
Title: SOHO EIT Carrington Maps from Synoptic Full-Disk Data
Authors: Thompson, B. J.; Newmark, J. S.; Gurman, J. B.;
Delaboudiniere, J. P.; Clette, F.; Gibson, S. E
Bibcode: 1997ESASP.404..779T
Altcode: 1997cswn.conf..779T
No abstract at ADS
Title: SOHO observations of the north polar solar wind
Authors: Peres, G.; Ciaravella, A.; Betta, R.; Orlando, S.; Reale,
F.; Kohl, J.; Noci, G.; Fineschi, S.; Romoli, M.; Brekke, P.; Fludra,
A.; Gurman, J. B.; Lemaire, P.; Schuhle, U.
Bibcode: 1997ESASP.404..587P
Altcode: 1997cswn.conf..587P
No abstract at ADS
Title: Wave Propagation in the Chromosphere and Transition Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Harrison, R.; Gurman, J.
Bibcode: 1997ESASP.404..679S
Altcode: 1997cswn.conf..679S
No abstract at ADS
Title: First Results from EIT
Authors: Clette, F.; Delaboudiniere, J. -P.; Artzner, G. E.; Brunaud,
J.; Gabriel, A. H.; Hochedez, J. -F.; Millier, F.; Song, X. Y.; Au, B.;
Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.;
Defise, J. -M.; Jamar, C.; Rochus, P.; Chauvineau, J. -P.; Marioge,
J. -P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman,
J. B.; Neupert, W. M.; Maucherat, A.; Cugnon, P.; van Dessel, E. L.
Bibcode: 1997ASPC..118..268C
Altcode: 1997fasp.conf..268C
The Extreme-UV Imaging telescope has already produced more than 15000
wide-field images of the corona and transition region, on the disk
and up to 1.5R_⊙ above the limb, with a pixel size of 2.6\arcsec. By
using four different emission lines, it provides the global temperature
distribution in the quiet corona, in the range 0.5 to 3*E(6) K. Its
excellent sensitivity and wide dynamic range allow unprecedented views
of low emission features, even inside coronal holes. Those so-called
``quiet'' regions actually display a wide range of dynamical phenomena,
in particular at small spatial scales and at time scales going down
to only a few seconds, as revealed by all EIT time sequences of
full- or partial-field images. The initial results presented here
demonstrate the importance of this wide-field imaging experiment for
a good coordination between SOHO and ground-based solar telescopes,
as well as for science planning.
Title: Coordinated SOHO Observations of Polar Plumes
Authors: Deforest, C. E.; Scherrer, P. H.; Tarbell, T.; Harrison,
R. A.; Fludra, A.; Delaboudiniere, J. P.; Gurman, J. B.; Wilhelm,
K.; Lemaire, P.; Hassler, D. M.; Kohl, J. L.; Noci, G.; Fineschi,
S.; Brueckner, G. E.; Howard, R. A.; Cyr, O. C. St.
Bibcode: 1996AAS...188.4909D
Altcode: 1996BAAS...28R.898D
On 7 and 8 March 1996, SOHO instruments engaged in their first
joint science operation, a 12-hr observation of polar plumes
over the South polar coronal hole. The observing mini-campaign
included observations from SOHO, other spacecraft, and ground-based
observatories. Contributing SOHO instruments -- in order of altitude,
MDI, CDS, SUMER, EIT, UVCS, and LASCO -- made overlapping, simultaneous
observations of plume structures from the photosphere out to the
LASCO C3 limit of 32 solar radii. MDI provided line-of-sight surface
magnetograms with a one-min cadence and 0.6 arcsec resolution;
CDS, SUMER, and EIT supplied temperature-sensitive images of the
lower corona with varying cadences and resolutions; UVCS measured
fluctuations in Ly B intensity across the coronal hole with a one-min
cadence at 1.4 R0; and LASCO imaged the entire corona out to 30 R0 in
various visible passbands. Plume footpoints in the lower corona are
observed by EIT and CDS to vary by a factor of two in EUV brightness
with a timescale of tens of minutes, while the structures above are
(as as been previously observed) quiescent on at least a ten-hr time
scale. We present preliminary results of cross-instrument analysis
of the observed plumes, and suggest how this and similar future data
sets can be used to constrain quiet-sun wind acceleration and coronal
heating models for the coronal hole. This research is supported by
the SOI-MDI NASA contract NAG5-3077 at Stanford University. SOHO is
project of international cooperation between NASA and ESA.
Title: Observations of the South coronal hole from EIT and YOHKOH
Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern,
R.; Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel, A.;
Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr,
O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert,
W.; Einfalt, E.; Newmark, J.
Bibcode: 1996AAS...188.0206H
Altcode: 1996BAAS...28..821H
The Extreme ultraviolet Imaging Telescope (EIT) on board the
SOHO spacecraft is capable of studying solar transition region,
chomospheric and coronal plasmas over bandpasses optimized for He II
304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 - 1.0 MK),
Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 - 2.5
MK) with 2.5 arcsecond spatial resolution. This telescope in concert
with the Yohkoh/SXT instrument allows us to simultaneously observe
solar structures at temperatures ranging from less than 0.1MK in the
transition region to over 3MK in the solar corona. EIT has had several
opportunities to observe the South coronal hole with high spatial and
temporal resolution. We compare observations from EIT and SXT with
an eye towards correlating temporal variations over the range of
wavelengths, activity of polar crown filament systems and relating
large-scale morphology of the X-ray corona to the transition region
in He II.
Title: There's No Such Thing as the Quiet Sun: EUV Movies from SOHO
Authors: Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel,
A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr,
O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert,
W.; Einfalt, E.; Newmark, J.
Bibcode: 1996AAS...188.3718G
Altcode: 1996BAAS...28..880G
We present unique time series of high-resolution solar images from the
normal-incidence Extreme ultraviolet Imaging Telescope (EIT) on board
the SOHO spacecraft. With a pixel scale of 2.6 arc sec and a detector
dynamic range of > 10(4) , the EIT can be used to study the dynamics
of chromospheric and coronal features in multilayer bandpasses optimized
for He II 304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 -
1.0 MK), Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 -
2.5 MK). Among the most striking features of the digital movies we will
display are: the dynamic nature of small-scale loop features in the
polar coronal holes, the constant activity of the polar crown filament
systems, the locations of the bases of polar plumes, the presence
of dark (scattering) filament material in the coronal emission line
images, and the evolution of a unique, linear, dark feature in a young
active region. The latter feature is suggestive of the ``coronal void''
observed in the electron scattering corona by Macqueen et al./ (1983).
Title: Observations of the south coronal hole from EIT and Yohkoh.
Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern,
R.; Gurman, J. B.; Delaboudinière, J. P.; Artzner, G.; Gabriel,
A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.;
Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; St. Cyr,
O. C.; Neupert, W.; Einfalt, E.; Newmark, J.
Bibcode: 1996BAAS...28Q.821H
Altcode:
No abstract at ADS
Title: EIT Images of the EUV Solar Atmosphere
Authors: Portier-Fozzani, F.; Moses, J. D.; Delaboudiniere, J. P.;
Gurman, J. B.; Clette, F.; Maucherat, A.
Bibcode: 1996ASPC..111..402P
Altcode: 1997ASPC..111..402P
The Extreme-ultraviolet Imaging Telescope (EIT) was one of several
instruments launched on board SOHO on 1995 Dec 2. It has already
produced thousands of wide-field images of the low corona at 4
wavelengths (171, 195, 284 and 304 Å). These wavelengths correspond
to different emission lines, formed over a wide range of plasma
temperatures. The first EIT images and movies reveal how this sensitive
instrument will provide unprecedented information about the dynamics
of small scale phenomena in the quiet solar corona and inside coronal
holes. Results of a local deconvolution method, used to correct a grid
pattern present in raw EIT images, are also presented.
Title: SOHO Ground Segment, Science Operations, and Data Products
Authors: St. Cyr, O. C.; Sánchez-Duarte, L.; Martens, P. C. H.;
Gurman, J. B.; Larduinat, E.
Bibcode: 1995SoPh..162...39S
Altcode:
We describe the ground segment, pre-launch operations concepts, and
data products supporting the SOHO mission. Our goal is threefold:
first, we provide a historical view of the design and development of
the systems described here, as a background perspective to those who
will use the system and those who may build such systems for future
missions. Second, because we hope that many researchers from the solar
and space physics communities will visit these facilities during the
mission, we provide an overview for the benefit of the end-user. We
anticipate that visitors to GSFC may plan observations for one or more
of SOHO's complement of instruments, and such researchers may use the
facilities to analyze data gathered by the SOHO instruments. Third,
we present the working plan for investigators with groundbased or
other spacebased instruments to collaborate with SOHO.
Title: EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission
Authors: Delaboudinière, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel,
A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.;
Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise,
J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.;
Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.;
Neupert, W. M.; Maucherat, A.; Clette, F.; Cugnon, P.; Van Dessel,
E. L.
Bibcode: 1995SoPh..162..291D
Altcode:
The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field
images of the corona and transition region on the solar disc and up to
1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated
optics will select spectral emission lines from Fe IX (171 å), Fe
XII (195 å), Fe XV (284 å), and He II (304 å) to provide sensitive
temperature diagnostics in the range from 6 × 104 K to 3
× 106 K. The telescope has a 45 x 45 arcmin field of view
and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial
resolution. The EIT will probe the coronal plasma on a global scale,
as well as the underlying cooler and turbulent atmosphere, providing
the basis for comparative analyses with observations from both the
ground and other SOHO instruments. This paper presents details of the
EIT instrumentation, its performance and operating modes.
Title: NASA Solar Eclipse Bulletins and Electronic Access via Internet
Authors: Espenak, F.; Gurman, J.; Anderson, J.
Bibcode: 1995pist.conf...92E
Altcode:
No abstract at ADS
Title: The Sunspot Transition Region: Where Are the Bright Plumes
and the Downflows?
Authors: Gurman, Joseph B.
Bibcode: 1993ApJ...412..865G
Altcode:
Measurements of umbral-to-quiet sun and umbral-to-plage contrast
in five active regions have been obtained in the transition region
emission lines Si IV 1402.77 A, C IV 1548.19 A, and O V 1371.29 A,
using the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum
Mission. The umbral transition region in these lines appears generally
indistinguishable from the quiet transition region. In addition,
high-resolution profiles of the C IV lines 1548.19 A, 1550.77 A in the
umbrae of eight individual sunspots in different active regions show
only weak, mostly subsonic, redshifted components. This result differs
sharply from the observations of multiple, strong, often supersonic
downflows observed with the HRTS instrument (e.g., Brekke et al., 1987).
Title: A Graphical User Interface for Solar Data Analysis
Authors: Einfalt, E.; Zarro, D.; Tolbert, A.; Gurman, J.; Schwartz,
R.; Nakatsuka, R.
Bibcode: 1993BAAS...25.1190E
Altcode:
No abstract at ADS
Title: Solar corona synoptic observations from SOHO with an Extreme
Ultraviolet Imaging Telescope.
Authors: Delaboudinière, J. P.; Gabriel, A. H.; Artzner, G. E.;
Dere, K.; Howard, R.; Michels, D.; Catura, R.; Lemen, J.; Stern, R.;
Gurman, J.; Neupert, W.; Cugnon, P.; Koeckelenbergh, A.; van Dessel,
E. L.; Jamar, C.; Maucherat, A.
Bibcode: 1992ESASP.348...21D
Altcode: 1992cscl.work...21D
The major scientific objective of the EUV Imaging Telescope (EIT)
is to study the evolution of coronal structure over a wide range
of spatial and temporal scales and temperatures. A second strategic
objective is to provide full disk synoptic maps of the global corona
to aid in unifying SOHO (Solar and Heliospheric Observatory)/Cluster
investigations. EIT will also provide images to support the planning
of detailed spectroscopic investigations by the CDS (Coronal Diagnostic
Spectrometer) and SUMER spectrometers in SOHO. EIT observations will be
made in four narrow spectral bands, centered at 171 A (Fe 9), 195 A(Fe
12), 284 A (Fe 15), and 304 A (He 2) representing restricted temperature
domains within a wide temperature range from 40,000 to 3,000,000
K. The results will be images of the solar atmosphere from the upper
chromosphere and transition region to the active region corona. These
maps, made at appropriate time intervals, will be used to study the fine
structures in the solar corona and to relate their dynamic properties
to the underlying chromosphere and photosphere. Dynamic events in the
inner corona will be related to white light transients in the outer
corona, and observations of the internal structure of coronal holes
will be used to investigate origins of the solar wind.
Title: Chromospheric Structure
Authors: Gurman, J. B.
Bibcode: 1992ASIC..373..245G
Altcode: 1992sla..conf..245G
A brief introduction is given to the variety of chromospheric
features seen in Hα images. Despite their wealth of detail, images
obtained in a single, narrow band in Hα also suffer from a surfeit
of missing information. The most basic chromospheric structures are
the supergranular network and spicules; these are visible in lines
formed higher in the chromosphere, as well, which also show evidence
for small-scale heating. The heating of even the lower chromosphere is
still problematic, but may be explained by large-amplitude acoustic
wave dissipation. A current challenge is understanding the apparent
thermal bifurcation of the chromosphere into regimes of distinctly
different scale heights. Finally, the possibility of chromospheric
wave cavities is briefly discussed.
Title: UV Observations of Sunspots (Invited)
Authors: Gurman, J. B.
Bibcode: 1992LNP...397..147G
Altcode: 1992sils.conf..147G
No abstract at ADS
Title: Solar Ultraviolet Instrumentation
Authors: Gurman, J. B.
Bibcode: 1992ASIC..373..395G
Altcode: 1992sla..conf..395G
No abstract at ADS
Title: Sunspots: a Laboratory for Solar Physics
Authors: Gurman, J. B.
Bibcode: 1992ASIC..373..221G
Altcode: 1992sla..conf..221G
No abstract at ADS
Title: The Solar Maximum Mission Data Analysis Center
Authors: Gurman, J. B.
Bibcode: 1991BAAS...23.1063G
Altcode:
No abstract at ADS
Title: The UVSP Data Archive
Authors: Gurman, J. B.
Bibcode: 1991BAAS...23..925G
Altcode:
No abstract at ADS
Title: The Sunspot Transition Region: Where are the Plumes and
Supersonic Downflows?
Authors: Gurman, J. B.
Bibcode: 1990BAAS...22..809G
Altcode:
No abstract at ADS
Title: Extreme ultraviolet imaging telescope on board the Solar
Heliospheric Observatory
Authors: Delaboudiniere, Jean-Pierre; Gabriel, Alan H.; Artzner,
Guy E.; Millier, F.; Michels, Donald J.; Dere, Kenneth P.; Howard,
Russell A.; Kreplin, Robert W.; Catura, Richard C.; Stern, Robert A.;
Lemen, James R.; Neupert, Werner M.; Gurman, Joseph B.; Cugnon, P.;
Koeckelenbergh, A.; van Dessel, E. L.; Jamar, Claude A.; Maucherat,
Andre J.; Chauvineau, Jean-Pierre; Marioge, Jean-Paul
Bibcode: 1989SPIE.1160..518D
Altcode: 1989xeoa.conf..518D
The design of the multibandpass Extreme-Ultraviolet Imaging Telescope
designed for 1996 launch on board the Solar Heliospheric Observatory
is described. The telescope will observe simultaneously distinct
temperature ranges in the solar corona, defined by well chosen emission
lines. Images in four narrow bandpasses at wavelengths ranging from 17
to 31 nm will be obtained using normal-incidence multilayered optics
deposited on quadrants of a Ritchey-Chretien telescope. Results are
presented on the performances measured on a 2/3 scale mock-up. The
bandpasses could be adjusted to better than 1 percent in wavelength.
Title: Chromospheric 300 s Oscillations in Flaring Regions
Authors: Gurman, J. B.; Drake, S. A.
Bibcode: 1989BAAS...21..837G
Altcode:
No abstract at ADS
Title: Flare Dynamics
Authors: Zarro, D.; Alexander, D.; Fludra, A.; Emslie, G.; Gurman, J.;
Graeter, M.; Li, P.; Phillips, K.; Saba, J.; Schmieder, B.; Slater,
G.; Wulser, J. P.; Watanabe, T.; Dulk, G.; MacKinnon, A.; McClements,
K.; Spicer, D.
Bibcode: 1989tnti.conf....2Z
Altcode:
No abstract at ADS
Title: SMM observations of the variability of active regions in the
UV: flares, bursts, and oscillations.
Authors: Drake, S. A.; Gurman, J. B.; Orwig, L. E.
Bibcode: 1989sasf.confP.235D
Altcode: 1988sasf.conf..235D; 1989IAUCo.104P.235D
The authors have made extensive observations of the time-variability of
solar active regions in the far-UV using the ultraviolet spectrometer
on SMM. They describe the three different modes of solar variability
(impulsive events, bursts and oscillations) that are evident in the
data and discuss their physical implications.
Title: The SMM UV observations of Active Region 5395
Authors: Drake, Stephen A.; Gurman, Joseph B.
Bibcode: 1989dots.work..248D
Altcode:
The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum
Mission (SMM) spacecraft was used extensively to study the spatial
morphology and time variability of solar active regions in the far UV
(at approx. wavelength of 1370 A) since July 1985. The normal spatial
resolution of UVSP observations in this 2nd-order mode is 10 sec.,
and the highest temporal resolution is 64 milliseconds. To make a
full-field, 4 min. by 4 min. image this wavelength using 5 sec. raster
steps takes about 3 minutes. UVSP can also make observations of the
Sun at approx. wavelength of 2790 with 3 sec. spatial resolution when
operated in its 1st-order mode; a full-field image at this wavelength
(a so-called SNEW image) takes about 8 minutes. UVSP made thousands of
observations (mostly in 2nd-order) of AR 5395 during its transit across
the visible solar hemisphere (from 7 to 19 March, inclusive). During
this period, UVSP's duty cycle for observing AR 5395 was roughly
40 percent, with the remaining 60 percent of the time being fairly
evenly divided between aeronomy studies of the Earth's atmosphere and
dead time due to Earth occultation of the Sun. UVSP observed many of
the flares tagged to AR 5395, including 26 GOES M-level flares and
3 X-level flares, one of which produced so much UV emission that the
safety software of UVSP turned off the detector to avoid damage due
to saturation. Images and light curves of some of the more spectacular
of the AR 5395 events are presented.
Title: Solar Activity and Flare Observations from the Swedish Solar
Observatory on La Palma
Authors: Wolfson, J.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell,
T.; Title, A.; Topka, K.; Scharmer, G.; Brandt, P.; Gurman, J.
Bibcode: 1988BAAS...20..978W
Altcode:
No abstract at ADS
Title: NASA's Solar Maximum Mission : a look at a new sun
Authors: Gurman, Joseph B.
Bibcode: 1987nsmm.book.....G
Altcode: 1987QB526.F6N37....
As part of the ongoing process of trying to understand the physical
processes at work in the Sun, the Solar Maximum Mission (SMM)
spacecraft was launched on February 14, 1980, near the height of the
solar cycle, to enable the solar physics community to examine, in
more physically meaningful detail than ever before, the most violent
aspect of solar activity: flares. The scientific products of SMM
are substantial: by 1986, over 400 papers based on SMM observations
and their interpretations had appeared in scientific journals. More
important than such numerical measures of success is the significance
of the science that has come from SMM. The following topics, the Sun
as a star, solar flares, and the active solar atmosphere, as well as
other findings of SMM investigators are described. The instruments on
the SMM are also described.
Title: Sunspot umbral oscillations in Mg ii k
Authors: Gurman, Joseph B.
Bibcode: 1987SoPh..108...61G
Altcode:
Time series observations of the profile of the MgII k line λ2795.52
have been obtained in five sunspots with the Ultraviolet Spectrometer
and Polarimeter (UVSP) on the Solar Maximum Mission. The three sunspots
with umbrae larger than the 3″ × 3″ pixel size show significant
oscillations in integrated line intensity and line centroid, with
frequencies in the range 5.29-7.55 mHz (periods of 132-190 s).
Title: Simultaneous Measurements of Sunspot Umbral Oscillations in
the Photosphere, Chromosphere, and Transition Region
Authors: Thomas, John H.; Lites, Bruce W.; Gurman, Joseph B.; Ladd,
Edwin F.
Bibcode: 1987ApJ...312..457T
Altcode:
Measurements of umbral oscillations in a sunspot were made
simultaneously from space (with the SMM/UVSP instrument) in the
C IV transition-region line and from the ground (with the tower
telescope at NSO/sunspot) in spectral lines formed in the photosphere
and chromosphere. The power spectra of velocity and intensity
variations show multiple peaks in the 3 min band (4.5-10 mHz). A
strong oscillation at 5.5 mHz is coherent between the chromosphere
and transition region. Another strong oscillation mode at 7.5 mHz is
coherent between the photosphere and transition region and appears to
have a node in the chromosphere. The rms velocity in the 3 min band is
a little over 12 km/sec in both the chromosphere and transition region,
but the kinetic energy density is lower in the transition region (by
a factor of 10 or more) due to the lower mass density there. These
measurements of amplitude and phase of the waves at different heights
provided a new, independent method of testing or fitting models of
the vertical temperature distribution in the umbral chromosphere and
transition regions.
Title: Spectral Line Profiles of Fe XXI 1354.1 Angstrom from the
Solar Maximum Mission
Authors: Mason, H. E.; Shine, R. A.; Gurman, J. B.; Harrison, R. A.
Bibcode: 1986ApJ...309..435M
Altcode:
Observations of the Fe XXI 1354.1 A line were obtained for several
flares using the SMM-UVSP instrument with varying spectral and spatial
resolution. Of special interest are spectral line profiles from the
footpoints of flare loops taken during the impulsive phase. These
data show blueshifted Fe XXI profiles coincident and cospatial with
the impulsive brightening of chromospheric material. The present
analysis supports the hypothesis that the blueshifted component of the
high temperature emission is an integral part of the flare, possibly
associated with chromospheric evaporation.
Title: Sunspot Umbral Oscillations in the Photosphere, Chromosphere,
and Transition Region
Authors: Thomas, J. H.; Lites, B. W.; Gurman, J. B.; Ladd, E. F.
Bibcode: 1986BAAS...18..678T
Altcode:
No abstract at ADS
Title: A Search for Chromospheric P-Mode Oscillations in Late-Type
Giants
Authors: Gurman, Joseph B.
Bibcode: 1986iue..prop.2456G
Altcode:
We propose to obtain time series of long-wavelength, high-dispersion
spectra of a late G giant to determine whether there is evidence of
periodic variations in the Mg II k and h lines (in intensity, centroid,
and / or relative blue- and red-emission peak strengths). Periods on
the order of 2 hours could be interpreted as evidence for the trapping
of acoustic waves - a p-mode - in the stellar chromosphere. We would
also obtain similar observations of a K5 giant as a "control," since
the latter star, without a steep temperature rise to a hot corona,
should not have an effective chromospheric cavity in which to trap
acoustic waves.
Title: Linear models of acoustic waves in sunspot umbrae.
Authors: Gurman, J. B.; Leibacher, J. W.
Bibcode: 1984ESASP.220..205G
Altcode: 1984ESPM....4..205G
The authors interpret the 5.5 to 8.5 mHz oscillations observed in umbral
chromospheres and transition regions as acoustic waves propagating
parallel, or nearly parallel, to the temperature gradient.
Title: Center-to-Limb Variation of Transition Region Redshift
Authors: Shine, R. A.; Woodgate, B. E.; Gurman, J. B.
Bibcode: 1984BAAS...16..992S
Altcode:
No abstract at ADS
Title: Linear models of acoustic waves in sunspot umbrae
Authors: Gurman, J. B.; Leibacher, J. W.
Bibcode: 1984ApJ...283..859G
Altcode:
The two-dimensional, linear hydrodynamics of quiet solar and umbral
model atmospheres in a plane-parallel, adiabatic approximation
are investigated. The 5.5-8.5 mHz oscillations observed in umbral
chromospheres and transition regions are interpreted as acoustic
waves propagating parallel, or nearly parallel, to the temperature
gradient. These waves are not totally internally reflected by the steep
temperature gradient and, thus, are not trapped. Partial reflections,
however, are effective in modulating the transmission as a function
of frequency. The resonant transmission mechanism of Zugzda, Locans,
and Staude (1983) is found to produce a spectrum of resonances in the
transmission of acoustic waves in any atmosphere with a temperature
minimum. Since the observed umbral oscillations display power in only
a narrow range of frequencies, characteristics of the umbral models,
wave propagation, and observations that would tend to suppress the
higher frequency resonances are examined.
Title: The Mg ii h line in sunspot umbrae
Authors: Gurman, J. B.
Bibcode: 1984SoPh...90...13G
Altcode:
Observations of the MgII h line in the umbrae of five sunspots show a
spread of a factor of 3 in peak intensity. This range is larger than,
and brackets, the range found in a single umbra by Lites and Skumanich
(1982).
Title: Erratum - the Mghii Line in Sunspot Umbrae
Authors: Gurman, J. B.
Bibcode: 1984SoPh...92..391G
Altcode:
No abstract at ADS
Title: Fluid motions in the solar chromosphere-corona transition
region. IV - Mass motions over sunspot umbrae
Authors: Gurman, J. B.; Athay, R. G.
Bibcode: 1983ApJ...273..374G
Altcode:
Doppler velocity measurements in the C IV resonance line λ1548.19 have
been obtained over the umbrae of eight sunspots with the Ultraviolet
Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission. The
velocity bandpass of these observations is approximately ±30 km
s-1, and their spatial resolution is 3" × 3". Although a
few individual resolution elements display flow velocities ∼ ±15
km s-1 relative to the quiet network, we measure a mean
upflow of (1.2 ± 5.6) km s-1 when averaged over all the
resolution elements. Means over individual umbrae frequently show
smaller variances, which is evidence for a real distribution of umbral
transition region velocity fields. We also examine two possible
explanations for the smaller nonthermal broadening of the sunspot C
IV line.
Title: The Magnetic Field as a Function of Depth in a Sunspot Umbra
Authors: Gurman, J. B.
Bibcode: 1983BAAS...15..994G
Altcode:
No abstract at ADS
Title: Fluid motions in the solar chromosphere-corona transition
region. III - Active region flows from wide slit Dopplergrams
Authors: Athay, R. G.; Gurman, J. B.; Henze, W.
Bibcode: 1983ApJ...269..706A
Altcode:
Large-scale velocity patterns observed in C IV in active regions show
close correspondence with photospheric magnetic field patterns. In a
large majority of cases, magnetic neutral lines show blueshift on their
sun center side and redshift on their limbward side. The large-scale
flow is consistent with widespread loop structure having downflow in
both legs of the loops. Studies of individual bright loops, confirm
that the flow is downward in most cases. However, an important subset
of loops show flow from one end of the loop to the other.
Title: Is There a Chromospheric p-mode in β Ceti?
Authors: Gurman, J. B.
Bibcode: 1983BAAS...15..656G
Altcode:
No abstract at ADS
Title: Fluid motions in the solar chromosphere-corona transition
region. I - Line widths and Doppler shifts for C IV
Authors: Athay, R. G.; Gurman, J. B.; Henze, W.; Shine, R. A.
Bibcode: 1983ApJ...265..519A
Altcode:
Matrices of line profiles for C IV, λ1548, observed with a 3" aperture
and sampled in 3" intervals in active and quiet solar regions, show
a pronounced tendency for line width to increase with increasing
redshift. The correlation between increasing central intensity of the
line and increasing redshift demonstrated by some authors is clearly
present in these data but is weakened by the not infrequent occurrence
of regions of strong redshift but with low intensity. Sunspots show
both systematically narrower line profiles over umbral areas and strong
redshifts on their Sun-center side. The latter result is consistent
with a reverse Evershed effect.
Title: An Emission Measure Analysis of Two Sunspots Observed by the
UVSP Instrument on the SMM Spacecraft
Authors: Kingston, A. E.; Doyle, J. G.; Dufton, P. L.; Gurman, J. B.
Bibcode: 1982SoPh...81...47K
Altcode:
The EUV observations from the SMM satellite of two sunspots are
presented here. These observations show the sunspots (a) to be
regions of lower intensity than the surrounding plage, contrary to
that found by previous authors, and (b) to have line intensities
which vary little over a period of several hours. An upper limit to
mass flows of 2km s-1 is derived, indicating a relatively
simple energy balance for the chromosphere-corona transition zone
with thermal conduction being balanced by radiative losses. Electron
densities derived from NIV to CIV line ratios imply electron pressures
(log NeTe) of 15.0 to 15.3.
Title: Fluid motions the solar chromosphere-corona transition
region. II Active region flows in C IV from narrow slit Dopplergrams
Authors: Athay, R. G.; Gurman, J. B.; Shine, R. A.; Henze, W.
Bibcode: 1982ApJ...261..684A
Altcode:
From a study of Dopplergrams made with two narrow slits in the opposite
wings of the C IV line, N λ1548, we find widespread evidence for
steady flow patterns associated with large sunspots and, on a larger
scale, with active region magnetic field patterns. The characteristic
sunspot flow is in the reverse Evershed sense with a substantial
vertical component. Active region flows indicate oppositely directed
velocities with mainly horizontal components on either side of magnetic
neutral lines. Some neutral lines show flow toward the neutral line,
whereas others show flow away from the neutral line.
Title: Relation of Ephemeral Magnetic Regions to the Low Amplitude
Branch of Persistent Vertical Velocities
Authors: Gebbie, K. B.; Toomre, J.; Haber, D. A.; Hill, F.; Simon,
G. W.; November, L. J.; Gurman, J. B.; Shine, R. A.
Bibcode: 1982BAAS...14R.939G
Altcode: 1982BAAS...14..939G
No abstract at ADS
Title: The Transmission and Trapping of Acoustic Waves in the Umbral
Chromosphere
Authors: Gurman, J. B.; Leibacher, J. W.
Bibcode: 1982BAAS...14Q.939G
Altcode:
No abstract at ADS
Title: Transition region oscillations in sunspots.
Authors: Gurman, J. B.; Leibacher, J. W.; Shine, R. A.; Woodgate,
B. E.; Henze, W.
Bibcode: 1982ApJ...253..939G
Altcode:
Time series observations of the profile of the C IV resonance
line 1548.19 A obtained in eight sunspots with the Ultraviolet
Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission are
discussed. All of the sunspots exhibit significant oscillations in
line-of-sight velocity with frequencies in the range from 5.8 mHz to
7.8 mHz (periods of 129-173 s). Significant intensity oscillations
are observed at the same periods in four of the time series; the
maximum intensity is in phase with maximum blueshift. Difference
spectroheliograms ('Dopplergrams') of the two halves of the C IV line,
as well as observations in the Si IV resonance line 1402.77 A and the
O IV intersystem line 1401.16 A, also reveal velocity oscillations at
similar frequencies but only over sunspots.
Title: Steady flows in the solar transition region observed with SMM
Authors: Gebbie, K. B.; Hill, F.; November, L. J.; Gurman, J. B.;
Shine, R. A.; Woodgate, B. E.; Athay, R. G.; Tandberg-Hanssen, E. A.;
Toomre, J.; Simon, G. W.
Bibcode: 1981ApJ...251L.115G
Altcode:
Steady flows in the quiet solar transition region have been observed
with the Ultraviolet Spectrometer and Polarimeter experiment on the
Solar Maximum Mission (SMM) satellite. The persistent vertical motions
seen at disk center have spatial rms amplitudes of 1.4 km/s in the C
II line, 3.9 km/s in Si IV, and 4.2 km/s in C IV. The amplitudes of
the more horizontal flows seen toward the limb tend to be somewhat
higher. Plots of steady vertical velocity versus intensity seen at
disk center in Si IV and C IV show two distinct branches.
Title: Vector Magnetic Fields in Sunspots - Part One - Weak-Line
Observations
Authors: Gurman, J. B.; House, L. L.
Bibcode: 1981SoPh...71....5G
Altcode:
Observations of a round, unipolar sunspot in the Zeeman triplet Fe I
λ6302.5 with the High Altitude Observatory Stokes Polarimeter are used
to derive the vector magnetic field in the spot. The behavior of the
magnitude, inclination, and azimuth of the field vector B across the
spot is discussed. A linear relation is found between the continuum
intensity Ic and the field magnitude B.
Title: Preliminary observations and results obtained with the
ultraviolet spectrometer and polarimeter
Authors: Tandberg-Hanssen, E.; Cheng, C. C.; Athay, R. G.; Beckers,
J. M.; Brandt, J. C.; Chapman, R. D.; Bruner, E. C.; Henze, W.; Hyder,
C. L.; Gurman, J. B.
Bibcode: 1981ApJ...244L.127T
Altcode:
New observation with the Ultraviolet Spectrometer and Polarimeter
(UVSP) of a number of manifestations of solar activity obtained
during the first three months of Solar Maximum Mission operations are
presented. Attention is given to polarimetry in sunspots, oscillations
above sunspots, density diagnostics of transition-zone plasmas in
active regions, and the eruptive prominence - coronal transient link.
Title: SMM/UVSP Observations of Oscillations and Other Properties
in a Sunspot
Authors: Henze, W.; Tandberg-Hanssen, E.; Reichmann, E. J.; Shine,
R. A.; Woodgate, B. E.; Gurman, J. B.; Athay, R. G.
Bibcode: 1981BAAS...13..858H
Altcode:
No abstract at ADS
Title: Active Region Flows in the Transition Region
Authors: Athay, R. G.; Gurman, J. B.; Henze, W.
Bibcode: 1981BAAS...13..914A
Altcode:
No abstract at ADS
Title: The Sunspot Atmosphere at 105 K
Authors: Gurman, J. B.; Woodgate, B. E.
Bibcode: 1981BAAS...13..880G
Altcode:
No abstract at ADS
Title: Height Dependence of Steady Flows Determined from Coordinated
SMM and SPO Observations
Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon,
G. W.; Gurman, J. B.; Shine, R. A.; Woodgate, B. E.
Bibcode: 1981BAAS...13..914G
Altcode:
No abstract at ADS
Title: Solar maximum mission experiment: Ultraviolet spectroscopy
and polarimetry on the solar maximum mission
Authors: Tandberg-Hanssen, E.; Cheng, C. C.; Woodgate, B. E.; Brandt,
J. C.; Chapman, R. D.; Kenney, P. J.; Michalitsianos, A. G.; Shine,
R. A.; Athay, R. G.; Beckers, J. M.; Bruner, E. C.; Rehse, R. A.;
Schoolman, S. A.; Gurman, J. B.; Hyder, C. L.; Henze, W.
Bibcode: 1981AdSpR...1m.275T
Altcode: 1981AdSpR...1..275T
We describe the Ultraviolet Spectrometer and Polarimeter (UVSP) on the
Solar Maximum Mission (SMM) spacecraft. The instrument, which operates
in the wavelength range 1150 - 3600 Å, has a spatial resolution of 2-3
arc sec and a spectral resolution of 0.02 Å FWHM in second order. A
Gregorian telescope, focal length 1.8 m, feeds a 1 m Ebert-Fastie
spectrometer. A polarimeter comprising rotating Mg F2
waveplates can be inserted behind the spectrometer entrance slit and
allows all four Stokes parameters to be determined. The observing
modes include rasters, spectral scans, velocity measurements, and
polarimetry. Finally, we present examples of initial observations made
since launch.
Title: Solar Maximum Mission experiment: ultraviolet spectroscopy
and polarimetry on the Solar Maximum Mission.
Authors: Tandberg-Hanssen, E.; Woodgate, B. E.; Athay, R. G.; Beckers,
J. M.; Brandt, J. C.; Bruner, E. C.; Chapman, R. D.; Cheng, C. -C.;
Gurman, J. B.; Hyder, C. L.; Kenney, P. J.; Michalitsianos, A. G.;
Rehse, R. A.; Schoolman, S. A.; Shine, R. A.; Henze, W.
Bibcode: 1981hea..conf..275T
Altcode:
No abstract at ADS
Title: UVSP/SMM observations of transition region oscillations
in sunspots
Authors: Gurman, J. B.; Shine, R. A.; Woodgate, B. E.; Leibacher,
J. W.; Henze, W.
Bibcode: 1981phss.conf..319G
Altcode:
Using Ultraviolet Spectrometer and Polarimeter data obtained in emission
lines formed at temperatures of 70,000 K to 130,000 K, transition
region oscillations in sunspots have been observed. The frequency of
these oscillations lies in the range 5.8 mHz to 7.8 mHz. Their regular
appearance in line-of-sight velocity and their frequent occurrence in
intensity in phase with maximum blue shift leads to the interpretation
of the oscillations as upward-propagating acoustic waves. The presence
in two of the C IV wavelength 1548.19 time series of a phase-shifted
oscillation in the line width may be caused by the presence of
unidentified blends in the line wings. The energy flux carried by the
umbral acoustic waves is less than 2000 erg/sq cm/s, some seven orders
of magnitude smaller than the missing radiative flux of sunspots.
Title: The photospheric vector magnetic field of a sunspot and its
vertical gradient
Authors: Hagyard, M. J.; West, E. A.; Tandberg-Hanssen, E.; Smith,
J. E.; Henze, W., Jr.; Beckers, J. M.; Bruner, E. C.; Hyder, C. L.;
Gurman, J. B.; Shine, R. A.
Bibcode: 1981phss.conf..213H
Altcode:
The results of direct comparisons of photospheric and transition
region line-of-sight field observations of sunspots using the SMM UV
spectrometer and polarimeter are reported. The analysis accompanying
the data is concentrated on demonstrating that the sunspot concentrated
magnetic field extends into the transition region. An observation
of a sunspot on Oct. 23, 1980 at the S 18 E 03 location is used as
an example. Maximum field strengths ranged from 2030-2240 gauss for
large and small umbrae viewed and inclination of the field to the
line-of-sight was determined for the photosphere and transition
region. The distribution of the magnetic field over the sunspot
and variation of the line-of-sight gradient are discussed, as are
the magnitudes and gradients of the photospheric field across the
penumbral-photospheric boundaries.
Title: The Development of Flares Observed in the Spectral Lines OV
1371 Å, FeXXI 1354 Å, and in Hard X-Rays
Authors: Woodgate, B. E.; Bruner, E. C.; Cheng, C. C.; Dennis, B. R.;
Gurman, J. B.; Frost, K. J.; Hyder, C. L.; Kiplinger, A.; Mason,
H. E.; Orwig, L. E.; Poland, A. I.; Schoolman, S. A.; Shine, R. A.;
Tandberg-Hanssen, E. A.
Bibcode: 1980BAAS...12..911W
Altcode:
No abstract at ADS
Title: Steady Flows in the Solar Transition Region Observed with
the UVSP Experiment on SMM
Authors: Gebbie, K. B.; Hill, F.; Toomre, J.; November, L. J.; Simon,
G. W.; Athay, R. G.; Bruner, E. C.; Rehse, R.; Gurman, J. B.; Shine,
R. A.; Woodgate, B. E.; Tandberg-Hanssen, E. A.
Bibcode: 1980BAAS...12..907G
Altcode:
No abstract at ADS
Title: Transition Region Oscillations in Sunspots
Authors: Gurman, J. B.; Shine, R. A.; Woodgate, B. E.;
Tandberg-Hanssen, E. A.; Bruner, E. C.; Schoolman, S. A.; Athay, R. G.
Bibcode: 1980BAAS...12..906G
Altcode:
No abstract at ADS
Title: SMM/UVSP Observations of Magnetic Fields in the Transition
Region above Sunspots
Authors: Henze, W.; Beckers, J. M.; Gurman, J. B.; Hyder, C. L.;
Schoolman, S. A.; Shine, R. A.; Tandberghanssen, E.; Woodgate, B. E.;
Hagyard, M. J.
Bibcode: 1980BAAS...12R.896H
Altcode:
No abstract at ADS
Title: UV Observations of the June 29, 1980 Flare at 18:24UT
Authors: Poland, A. I.; Woodgate, B. E.; Shine, R. A.; Frost, K. J.;
Kenny, P.; Bruner, E. C.; Wolfson, J.; Cheng, C. C.; Tandberg-Hanssen,
E. A.; Gurman, J.; Henze, W.; Machado, M.
Bibcode: 1980BAAS...12..903P
Altcode:
No abstract at ADS
Title: Sunspot Observations with the Ultraviolet Spectrometer and
Polarimeter Experiment on the Solar Maximum Mission
Authors: Gurman, J. B.; Woodgate, B. E.; Shine, R. A.; Brandt, J. C.;
Chapman, R. D.; Michalitsianos, A. G.; Kenny, P. J.; Bruner, E. C.;
Rehse, R.; Schoolman, S. A.; Cheng, C. C.; Tandberg-Hanssen, E. A.;
Athay, G. R.; Beckers, J. M.; Henze, W.; Brown, Teledyne; Hyder, C. L.
Bibcode: 1980BAAS...12..535G
Altcode:
No abstract at ADS
Title: Density Diagnostic of Solar Active Region and Flare Plasmas
from Si IV/O IV Line Ratio as Observed from SMM
Authors: Bruner, E. C.; Rehse, R.; Schoolman, S. A.; Brandt, J. C.;
Chapman, R. D.; Kenny, P. J.; Michalitsianos, A. G.; Shine, R. A.;
Woodgate, B. E.; Cheng, C. C.; Tandberg-Hanssen, E. A.; Athay, G. R.;
Beckers, J. M.; Gurman, J.; Henze, W.; Brown, Teledyne; Hyder, C. L.
Bibcode: 1980BAAS...12R.539B
Altcode:
No abstract at ADS
Title: Density diagnostic of solar active region and flare plasmas
from Si IV/O IV line ratio as observed from SMM (Solar Maximum
Mission).
Authors: Bruner, E. C.; Rehse, R.; Schoolman, S. A.; Brandt, J. C.;
Chapman, R. D.; Kenny, P. J.; Michalitsianos, A. G.; Shine, R. A.;
Woodgate, B. E.; Cheng, C. -C.; Tandberg-Hanssen, E. A.; Athay, G. R.;
Beckers, J. M.; Gurman, J. B.; Henze, W.; Hyder, C. L.
Bibcode: 1980BAAS...12..534B
Altcode:
No abstract at ADS
Title: Solar Flare and Surge Image Sequences as Seen by the
Ultraviolet Spectrometer and Polarimeter on SMM
Authors: Henze, W.; Brown, Teledyne; Brandt, J. C.; Chapman,
R. D.; Kenny, P. J.; Michalitsianos, A. G.; Shine, R. A.; Woodgate,
B. E.; Bruner, E. C.; Rehse, R.; Schoolman, S. A.; Cheng, C. C.;
Tandberg-Hanssen, E. A.; Athay, G. R.; Beckers, J. M.; Gurman, J.;
Hyder, C. L.
Bibcode: 1980BAAS...12..532H
Altcode:
No abstract at ADS
Title: The Ultraviolet Spectrometer and Polarimeter (UVSP) on the
Solar Maximum Mission and Initial Results in Polarimetry
Authors: Tandberg-Hanssen, E.; Athay, R. G.; Bruner, E. C.; Beckers,
J. M.; Brandt, J. C.; Chapman, R. D.; Cheng, C. C.; Gurman, J.;
Henze, W.; Brown, Teledyne; Hyder, C. L.; Michalitsianos, A. G.;
Shine, R. A.; Schoolman, S. A.; Woodgate, B. E.
Bibcode: 1980BAAS...12..534T
Altcode:
No abstract at ADS
Title: The Dynamics of Solar Flares and Surges as Seen at the Solar
Limb in the Transition Zone
Authors: Woodgate, B. E.; Brandt, J. C.; Chapman, R. D.; Kenny,
P. J.; Michalitsianos, A. G.; Shine, R. A.; Bruner, E. C.; Rehse, R.;
Schoolman, S. A.; Cheng, C. C.; Tandbert-Hanssen, E. A.; Athay, G. R.;
Beckers, J. M.; Gurman, J.; Henze, W.; Brown, Teledyne; Hyder, C. L.
Bibcode: 1980BAAS...12Q.535W
Altcode:
No abstract at ADS
Title: Active Region Morphology and Evolution Images from the
Ultraviolet Spectrometer and Polarimeter
Authors: Shine, R. A.; Brandt, J. C.; Chapman, R. D.; Kenny, P. J.;
Michalitsianos, A. G.; Woodgate, B. E.; Bruner, E. C.; Rehse, R.;
Schoolman, S. A.; Cheng, C. C.; Tandberg-Hanssen, E. A.; Athay, G. R.;
Beckers, J. M.; Gurman, J.; Henze, W.; Brown, Teledyne; Hyder, C. L.
Bibcode: 1980BAAS...12R.531S
Altcode:
No abstract at ADS
Title: Sunspot vector magnetic fields and model umbral atmospheres
Authors: Gurman, J. B.
Bibcode: 1979ncar.rept.....G
Altcode:
The Stokes polarimeter of the High Altitude Observatory was used to
observe a round, unipolar sunspot in three absorption lines and the
nearby continua. Observations in the weak Zeeman triplet at 6302.50A
wavelength are used to derive the vector magnetic field across the
spot. Stokes profiles are used to probe the depth variation of the
magnetic field and to obtain a model atmosphere for the umbra. A
linear anticorrelation is found between the continuum intensity and
the magnetic field strength. Model atmospheres determined at four
locations in the umbra represent a significant improvement over the
few existing umbral models in fitting the observed D2 line wings. A
method of determining the longitudinal component of the B field as a
function of depth is derived and tested with synthetic Stokes profiles.
Title: Sunspot Vector Magnetic Fields and Model Umbral Atmospheres.
Authors: Gurman, J. B.
Bibcode: 1979PhDT.........2G
Altcode:
The Stokes parameters provide a complete description of the polarization
of electromagnetic radiation. The Stokes polarimeter of the High
Altitude Observatory, which is capable of measuring all four Stokes
parameters simulataneously across a spectral line profile, was used
to observe a round, unipolar sunspot in three absorption lines and the
nearby continua. Observations in the weak Zeeman triple lambda 6302.50 A
are used to derive the vector magnetic field B across the spot. Doppler
shift measurements in the Zeeman-insensitive line Fe I lambda 5576.10
A show no significant vertical flows in the spot. Finally, Stokes
profiles of the Zeeman-sensitive resonance line Na I D2 lambda 5889.96
A are used to probe the depth variation of the magnetic field and to
obtain a model atmosphere for the umbra. Combination of the weak- and
strong-line results indicates a horizontal variation in the sum of gas
and magnetic pressure in the umbra. Acoustic turbulence is proposed to
prevent the creation of flows which are not observed. Possible scales
of such turbulence are discussed.
Title: Sunspot vector magnetic fields and model umbral atmospheres
Authors: Gurman, Joseph Bearak
Bibcode: 1979PhDT.......148G
Altcode:
No abstract at ADS
Title: Observation of Vector Magnetic Fields in Sunspots
Authors: House, L. L.; Baur, T. G.; Elmore, D. E.; Auer, L. W.;
Gurman, J.; Heasley, J. N.
Bibcode: 1976BAAS....8..346H
Altcode:
No abstract at ADS
Title: A Comparison of EUV Spectroheliograms and Photospheric
Magnetograms
Authors: Gurman, Joseph B.; Withbroe, George L.; Harvey, John W.
Bibcode: 1974SoPh...34..105G
Altcode:
A comparison of EUV data from the Harvard College Observatory
experiment on OSO-6 with photospheric magnetograms from Kitt Peak
National Observatory indicates a bipartite relationship between values
of the longitudinal field strength B and Mg x intensity I averaged over
square areas 35″ × 35″: in quiet regions ¦B¦ ∼ Ik,
where 0.0 ≲ k ≲ 0.3, and in active regions ¦B¦ ∼ I. From these
relationships we infer that ¦B¦ ∼ ne2k
in quiet regions and ¦B¦ ∼ ne2 in active
regions. In addition, the photospheric field beneath a coronal hole
is found to be virtually identical to that beneath normal quiet regions.
Title: Models of the Chromospheric-Coronal Transition Layer and
Lower Corona Derived from Extreme-Ultraviolet Observations
Authors: Withbroe, George L.; Gurman, Joseph B.
Bibcode: 1973ApJ...183..279W
Altcode:
intensities of nine resonance lines from ions in the lithium and
sodium isoelectronic sequences are used to derive models for the
chromospheric-coronal transition layer and the corona in quiet and
active solar regions. The resulting models are combined with models
derived in previous studies to determine how the coronal temperature
and the conductive flux from the corona to the chromosphere vary as
a function of the electron pressure P = n,T in the lower corona. The
coronal temperature ranges from 106 K in coronal "holes" to 2.5 x 106
K in active regions. The conductive flux varies approximately as for P
3.0 >c 1015 and remains constant at a value of about 6 x 106 ergs 1
for P > 3.0 x 1015. Subject headings:chromosphere, solar - corona,
solar - coronal lines - spectra, solar - spectra, ultraviolet