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Author name code: brueckner
ADS astronomy entries on 2022-09-14
author:"Brueckner, Gunther"
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Title: Calibration of the Soho/Lasco C3 White Light Coronagraph
Authors: Morrill, J. S.; Korendyke, C. M.; Brueckner, G. E.; Giovane,
F.; Howard, R. A.; Koomen, M.; Moses, D.; Plunkett, S. P.; Vourlidas,
A.; Esfandiari, E.; Rich, N.; Wang, D.; Thernisien, A. F.; Lamy, P.;
Llebaria, A.; Biesecker, D.; Michels, D.; Gong, Q.; Andrews, M.
2006SoPh..233..331M Altcode:
We present a detailed review of the calibration of the LASCO C3
coronagraph on the SOHO satellite. Most of the calibration has been
in place since early in the mission and has been utilized to varying
degrees as required by specific analysis efforts. However, using
observational data from the nearly decade-long database of LASCO images,
we have re-evaluated and improved many aspects of the calibration. This
includes the photometric calibration, vignetting function, geometric
distortion, stray light, and exposure and observation times. Using this
comprehensive set of corrections we have generated and made available a
set of calibrated coronal images along with a set of periodic background
images to ease the accessibility and use of the LASCO database.
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Title: New insights on the onsets of coronal mass ejections from soho
Authors: Plunkett, S. P.; Michels, D. J.; Howard, R. A.; Brueckner,
G. E.; St. Cyr, O. C.; Thompson, B. J.; Simnett, G. M.; Schwenn, R.;
Lamy, P.
2002AdSpR..29.1473P Altcode:
Coronal mass ejections (CMES) are among the most dramatic forms of
transient activity occurring in the solar atmosphere. Despite over
twenty years of research, many basic questions related to the physics
of CMEs have remained unanswered. Observations with the LASCO and EIT
experiments on SOHO, combined with recent theoretical modeling, have
provided new insights on some of these outstanding questions and have
also raised many new ones that need to be addressed in the future. In
this paper, we present some of the new results from SOHO pertaining
to the source regions and onsets of CMEs, and their evolution in the
corona. We emphasize the important role that studies of CMEs will play
in the International Solar Cycle Studies program.
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Title: Magnetic Geometry and Dynamics of the Fast Coronal Mass
Ejection of 1997 September 9
Authors: Chen, J.; Santoro, R. A.; Krall, J.; Howard, R. A.; Duffin,
R.; Moses, J. D.; Brueckner, G. E.; Darnell, J. A.; Burkepile, J. T.
2000ApJ...533..481C Altcode:
A coronal mass ejection (CME) was observed on 1997 September 9
by the Mauna Loa Solar Observatory Mark III K-coronameter (MK3)
and by the LASCO C2/C3 and EIT instruments on board the SOHO
spacecraft. Magnetograms and EIT images obtained on days leading
up to the eruption show a neutral line that appears to correspond
to the site of the eruption. Taken together, the data from these
instruments provide a comprehensive, beginning-to-end record of the
event within the 32 R<SUB>solar</SUB> field of view. The motion of
several features are tracked through the fields of view of MK3, C2, and
C3. The CME exhibits the previously identified morphological features
and dynamical properties consistent with those of an erupting magnetic
flux rope with its legs connected to the Sun. The LASCO images and
magnetograms indicate that the flux rope axis was aligned with the
neutral line approximately 2 days behind the west limb. Its apparent
orientation provides an oblique view of an erupting flux rope, a view
that has not been discussed previously. A theoretical flux rope model
is used to understand the forces responsible for the observed CME
dynamics. Synthetic coronagraph images based on the model flux rope
are constructed.
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Title: Coronal Mass Ejections and the Solar Wind: New Results
from LASCO
Authors: Dere, K. P.; Howard, R. A.; Brueckner, G. E.
2000AdSpR..25.1837D Altcode:
The LASCO and EIT experiments on SOHO have provided a revolutionary
picture of coronal dynamics. In the past, the corona has largely been
thought to be a region where the evolution of the coronal structures
occurred on relatively large time scales, aside from the intermittent
coronal mass ejection. The outflows in the polar coronal holes were
largely considered to be time-independent. The picture now presented by
the LASCO and EIT observations are of a highly dynamic corona. Continual
small scale sporadic outflows are observed in quiet streamers and
in the polar coronal holes. The LASCO images of CMEs shows that many
appear to have circular structures that indicate that they consist of
helical magnetic flux ropes. In addition, a new class of CMEs has been
observed and are called `global' CMEs since they appear to involve
regions of the corona separated by as much as 180°
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Title: Search for Velocity Variations in Fe XIV 5304 A&ring
Coronagraph Observations Near Activity Minimum
Authors: Cook, J. W.; Socker, D. G.; Korendyke, C. M.; Howard, R. A.;
Brueckner, G. E.; Karovska, M.; Wood, B. E.
2000AdSpR..25.1883C Altcode:
The LASCO C1 coronagraph on the SOHO satellite observes the solar
corona from 1.1 to 3.0 Ro, and contains a Fabry-Perot interferometer
which can image the corona in the 1.8 million K Fe XIV green line. We
designed an observing program with reduced spatial coverage and reduced
profile coverage at only three wavelengths to study coronal heating
in off-limb structures at high temporal resolution. We illustrate the
observations from 31 March 1997 of a bright loop system above an active
region off the northeast limb
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Title: Kinematic Measurements of Polar Jets Observed by the
Large-Angle Spectrometric Coronagraph
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Howard, R. A.;
Brueckner, G. E.
1999ApJ...523..444W Altcode:
We analyze polar jets observed by the Large-Angle Spectrometric
Coronagraph (LASCO) instrument aboard the Solar and Heliospheric
Observatory. The events studied here are from 1997 March 24 and
August 5. The main objective of our analysis is to determine whether
the jets' motions are consistent with ballistic behavior. Although
ballistic trajectories have some success in fitting the observed
kinematic motions, there is substantial evidence that gravity alone
is not regulating the movement of the jets. First of all, the August 5
events appear to exhibit slight accelerations rather than decelerations
above 3 R<SUB>solar</SUB>. Second, all the events studied here have
very similar velocities, suggesting that by the time the jets reach
the LASCO field of view, the jets have been incorporated into the
ambient solar wind. If this is the case, the jets could be very useful
as tracers of the solar wind at low heights in the Sun's polar regions.
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Title: Comparing the kinematic properties of CMEs observed by LASCO
and EIT with models of erupting flux ropes
Authors: Wood, B. E.; Karovska, M.; Chen, J.; Brueckner, G. E.; Cook,
J. W.; Howard, R. A.
1999AIPC..471..633W Altcode: 1999sowi.conf..633W
We present observations of three coronal mass ejections (CMEs) observed
by the LASCO and EIT instruments aboard the Solar and Heliospheric
Observatory. The three CMEs are from 1997 February 23, 1997 April 30,
and 1998 March 6. The February 23 CME is accompanied by a spectacular
prominence eruption and its leading edge reaches velocities of about
900 km s-1. The April 30 and March 6 CMEs have no apparent accompanying
prominence eruptions and attain more modest velocities of about 300
and 600 km s-1, respectively. Despite their kinematic differences, all
three CMEs have bright, roughly circular rims which can be interpreted
as marking the apexes of expanding magnetic flux ropes, and all three
can be tracked from their origins near the surface of the Sun out to
great distances. We compare the kinematic and morphological properties
of these CMEs with an MHD model of an erupting flux rope, and we find
that the CMEs can be successfully modeled in this manner.
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Title: LASCO observations of the solar polar regions
Authors: Karovska, M.; Wood, B. E.; Brueckner, G. E.; Cook, J. W.;
Howard, R. A.
1999AIPC..471..309K Altcode: 1999sowi.conf..309K
We describe our study of the dynamical properties of coronal structures
in the polar regions of the Sun using a sequence of 200 LASCO/C2
images. This sequence was designed to study polar outflows in general,
in both polar plumes and in interplume regions. The results of our
analyses show that such studies are complicated by the existence of
foreground material, especially when high latitude streamer material
rotates into the field of view. We also describe our analysis of the
kinematic properties of several polar jets. The results suggest that
polar jets might be used for studies of the outflow wind velocities
in coronal holes at heights above several solar radii.
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Title: Magnetic Geometry and Dynamics of the Fast CME of 1997
September 9
Authors: Chen, J.; Santoro, R. A.; Krall, J.; Howard, R. A.; Duffin,
R.; Moses, J. D.; Brueckner, G. E.; Darnell, J. A.; Burkepile, J.
1999AAS...19410105C Altcode: 1999BAAS...31R.998C
A coronal mass ejection (CME) was observed on 1997 September 9 by
the MLSO Mark III K-coronameter (MK3) and by the LASCO C2/C3 and EIT
instruments onboard the SOHO spacecraft. Magnetograms and EIT images
obtained on days leading up to the eruption show a neutral line that
appears to correspond to the site of the eruption. Hα images show
the presence of a filament along the neutral line which subtends an
angle of approximately 45(deg) with the local north-south meridional
direction. Taken together, the data from these instruments provide
a comprehensive, beginning-to-end record of the event within the 32
R_sun field of view. The motion of several features are tracked through
the fields of view of MK3, C2, and C3. The CME exhibits the previously
identified morphological features and dynamical properties consistent
with those of an erupting magnetic flux rope. The LASCO images and
magnetograms indicate that the flux rope axis was aligned with the
neutral line approximately two days behind the west limb. Its apparent
orientation provides an oblique view of an erupting flux rope, a view
that has not been discussed previously. A theoretical flux rope model
is used to understand the observed CME dynamics. Synthetic coronagraph
images based on the model flux rope are constructed. Work supported
by ONR, NASA, and NSF.
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Title: LASCO and EIT Observations of Helical Structure in Coronal
Mass Ejections
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Michels, D. J.;
Delaboudiniere, J. P.
1999ApJ...516..465D Altcode:
Observations of coronal mass ejections (CMEs) by the Large Angle
Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric
Observatory (SOHO) show a significant fraction with circular intensity
patterns. In the past, these would have been called “disconnection”
events, but we suggest that these are evidence of CMEs containing
helical magnetic flux ropes that are often central to many theoretical
models of CMEs and have been observed in magnetic clouds near
1 AU. Three examples are examined in detail with the LASCO and
Extreme-Ultraviolet Imaging Telescope (EIT) data sets, which provide
observations from their initiation through 30 R<SUB>solar</SUB>.
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Title: LASCO observations of the coronal rotation
Authors: Lewis, D. J.; Simnett, G. M.; Brueckner, G. E.; Howard,
R. A.; Lamy, P. L.; Schwenn, R.
1999SoPh..184..297L Altcode:
The near-rigid rotation of the corona above the differential rotation
of the photosphere has important implications for the form of the
global coronal magnetic field. The magnetic reconfiguring associated
with the shear region where the rigidly-rotating coronal field lines
interface with the differentially-rotating photospheric field lines
could provide an important energy source for coronal heating. We present
data on coronal rotation as a function of altitude provided by the Large
Angle Spectrometric Coronagraph (LASCO) instrument aboard the Solar and
Heliospheric Observatory (SOHO) spacecraft. LASCO comprises of three
coronagraphs (C1, C2, and C3) with nested fields-of-view spanning 1.1
R⊙ to 30 R⊙. An asymmetry in brightness, both of the Fe xiv emission
line corona and of the broad-band electron scattered corona, has been
observed to be stable over at least a one-year period spanning May
1996 to May 1997. This feature has presented a tracer for the coronal
rotation and allowed period estimates to be made to beyond 15 R⊙,
up to 5 times further than previously recorded for the white-light
corona. The difficulty in determining the extent of differential motion
in the outer corona is demonstrated and latitudinally averaged rates
formed and determined as a function of distance from the Sun. The
altitude extent of the low latitude closed coronal field region is
inferred from the determined rotation periods which is important to the
ability of the solar atmosphere to retain energetic particles. For the
inner green line corona (<2 R⊙) we determine a synodic rotation
period of (27.4±0.1) days, whereas, for the outer white- light corona,
(>2.5 R⊙) we determine a rotation period of (27.7±0.1) days.
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Title: Comparison of Two Coronal Mass Ejections Observed by EIT and
LASCO with a Model of an Erupting Magnetic Flux Rope
Authors: Wood, B. E.; Karovska, M.; Chen, J.; Brueckner, G. E.; Cook,
J. W.; Howard, R. A.
1999ApJ...512..484W Altcode:
We present observations of two coronal mass ejections (CMEs) observed
by the LASCO and EIT instruments on board the Solar and Heliospheric
Observatory. One was observed on 1997 April 30 and the other on 1997
February 23. The latter CME is accompanied by a spectacular prominence
eruption and reaches velocities of about 900 km s<SUP>-1</SUP>, while
the former has no apparent accompanying prominence eruption and attains
velocities of only about 300 km s<SUP>-1</SUP>. However, the two CMEs
are similar in appearance, having bright circular rims that can be
interpreted as marking the apexes of expanding magnetic flux ropes,
and both can be tracked from their origins near the surface of the Sun
out to great distances. We compare the kinematic and morphological
properties of these CMEs with an MHD model of an erupting flux rope
and find that the CMEs can be successfully modeled in this manner.
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Title: SUSIM UARS measurements of solar UV irradiance
Authors: Floyd, L. E.; Prinz, D. K.; Crane, P. C.; Herring, L. C.;
Brueckner, G. E.
1999AdSpR..24..225F Altcode:
Solar ultraviolet spectral irradiances for wavelengths 115-410 nm were
measured by the Solar Ultraviolet Spectral Irradiance Monitor during
most of the decline of solar cycle 22. New algorithms implemented for
the current data version (V19) are described. The wavelength-dependent
variability during solar cycle 22 is estimated to be over a factor of
2 at H I Ly-α and less than 1-2% above 290 nm.
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Title: Observations of Correlated White-Light and Extreme-Ultraviolet
Jets from Polar Coronal Holes
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Socker, D. G.; Howard,
R. A.; Brueckner, G. E.; Michels, D. J.; Moses, D.; St. Cyr, O. C.;
Llebaria, A.; Delaboudinière, J. -P.
1998ApJ...508..899W Altcode:
Time-lapse sequences of white-light images recorded with the Large
Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric
Observatory (SOHO) frequently show long, narrow structures moving
outward over the Sun's polar regions at high apparent speeds. By
comparing the LASCO observations with Fe XII λ195 spectroheliograms
made with the Extreme-ultraviolet Imaging Telescope (EIT) on SOHO
between 1997 April and 1998 February, we have identified 27 correlated
white-light and extreme-ultraviolet (EUV) jet events. In each case,
the EUV jet was observed near the limb of the polar coronal hole 20-60
minutes before the corresponding white-light jet was registered in the
coronagraph's 2-6 R<SUB>⊙</SUB> field of view. The jets originate
near flaring EUV bright points and are presumably triggered by field
line reconnection between magnetic bipoles and neighboring unipolar
flux. The leading edges of the white-light jets propagate outward at
speeds of 400-1100 km s<SUP>-1</SUP>, whereas the bulk of their material
travels at much lower velocities averaging around 250 km s<SUP>-1</SUP>
at heliocentric distances of 2.9-3.7 R<SUB>⊙</SUB>. These lower
velocities may reflect the actual outflow speeds of the background
polar wind.
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Title: Search for Brightness Variations in Fe XIV Coronagraph
Observations of the Quiescent Solar Corona
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Brueckner, G. E.;
Howard, R. A.; Korendyke, C. M.; Socker, D. G.
1998ApJ...505..432W Altcode:
We use Fe XIV 5303 Å green line images obtained by the Large
Angle Spectrometric Coronagraph (LASCO) on board SOHO to search for
variability in the quiescent solar corona in the shortest observable
timescales. The observing program obtained Fe XIV images of a small
area of the inner corona every 2 minutes over a period of 1 hr. We
present results from two executions of this program taken several months
apart. The most obvious variability observed in the two sequences is
in the form of quasi-steady brightening on timescales of at least an
hour. Of particular interest are two compact loops that are observed to
vary significantly during the course of the observations. Superposed on
the long-term brightening in these loops are statistically significant
variations on timescales of about 30 minutes. In both loops, the overall
brightening is greatest at the apparent loop tops, where the intensity
increases by at least 25%. In one loop there appears to be a flow up
one of the legs of the loop. We place these observations in context with
earlier observations of coronal variability, and we discuss the energy
requirements for the observed brightening. Emission measures computed
from Fe XIV intensities measured within the two brightening loops are
over an order of magnitude lower than those typically found for active
regions on the solar disk, which suggests significantly lower average
densities. For one of the loops, we measure densities in the range
n<SUB>e</SUB> = (5.0-7.4) × 10<SUP>8</SUP> cm<SUP>-3</SUP>. Lower
than average densities are expected for the two loops, given that they
reach more than 1 pressure scale height above the solar limb.
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Title: Joint Nancay Radioheliograph and LASCO Observations of Coronal
Mass Ejections - II. The 9 July 1996 Event
Authors: Pick, M.; Maia, D.; Kerdraon, A.; Howard, R.; Brueckner,
G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Simnett, G.; Lanzerotti, L. J.; Aurass, H.
1998SoPh..181..455P Altcode:
The development of a coronal mass ejection on 9 July 1996 has been
analyzed by comparing the observations of the LASCO/SOHO coronagraphs
with those of the Nancay radioheliograph. The spatial and temporal
evolution of the associated radioburst is complex and involves a
long-duration continuum. The analysis of the time sequence of the
radio continuum reveals the existence of distinct phases associated
with distinct reconnection processes and magnetic restructuring
of the corona. Electrons are accelerated in association with these
reconnection processes. An excellent spatial association is found
between the position and extension of the radio source and the CME seen
by LASCO. Furthermore, it is shown that the topology and evolution
of the source of the radio continuum involve successive interactions
between two systems of loops. These successive interactions lead to
magnetic reconnection, then to a large scale coronal restructuring. Thus
electrons of coronal origin may have access to the interplanetary
medium in a large range of heliographic latitudes as revealed by the
Ulysses observations.
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Title: Geomagnetic storms caused by coronal mass ejections (CMEs):
March 1996 through June 1997
Authors: Brueckner, G. E.; Delaboudiniere, J. -P.; Howard, R. A.;
Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.; Simnett,
G. M.; Thompson, B.; Wang, D.
1998GeoRL..25.3019B Altcode:
(1) All but two geomagnetic storms with Kp ≥ 6 during the operating
period (March 1996 through June 1997) of the Large Angle Spectroscopic
Coronagraph (LASCO) experiment on the Solar and Heliospheric Observatory
(SOHO) spacecraft can be traced to Coronal Mass Ejections (CMEs). (2)
These geomagnetic storms are not related to high speed solar wind
streams. (3) The CMEs which cause geomagnetic effects, can be classified
into two categories: Halo events and toroidal CMEs. (4) The CMEs are
accompanied by Coronal Shock Waves as seen in the Extreme Ultraviolet
Imaging Telescope (EIT) Fe XII images. (5) Some CMEs are related to
flares, others are not. (6) In many cases, the travel time between
the explosion on the Sun and the maximum geomagnetic activity is about
80 hours.
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Title: The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME,
and Interplanetary Shock Propagation of 9 July 1996
Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Galvin,
A. B.; Garcia, H.; Ipavich, F. M.; Karlický, M.; Kiplinger, A.;
Klassen, A.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappin,
S. J.; Thompson, B. J.; Watari, S. I.; Michels, D. J.; Brueckner,
G. E.; Howard, R. A.; Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.;
Schwenn, R.
1998SoPh..181..159D Altcode:
The first X-class flare in four years occurred on 9 July 1996. This
X2.6/1B flare reached its maximum at 09:11 UT and was located in active
region 7978 (S10° W30°) which was an old-cycle sunspot polarity
group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before
and after this event together with Yohkoh SXT images of the flare,
radio observations of the type II shock, and GOES disk-integrated soft
X-ray flux during an extended period that included energy build-up in
this active region.
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Title: Joint Nançay Radioheliograph and LASCO Observations of
Coronal Mass Ejections - I. The 1 July 1996 Event
Authors: Maia, D.; Pick, M.; Kerdraon, A.; Howard, R.; Brueckner,
G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Simnett, G.; Aurass, H.
1998SoPh..181..121M Altcode:
The development of a coronal mass ejection on 1 July 1996 has been
analyzed by comparing the observations of the LASCO/SOHO coronagraph
with those of the Nançay radioheliograph. This comparison brings new
insight and very useful diagnosis for the study of CME events. It
is shown that the initial instability took place in a small volume
located above an active region and that the occurrence of short radio
type III bursts implies a triggering process due to magnetic field
interactions. The subsequent spatial and temporal evolution of the
radio emission strongly suggests that the large scale structure becomes
unstable within the first minute of the event.
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Title: Origin of Streamer Material in the Outer Corona
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Walters, J. H.; Brueckner,
G. E.; Howard, R. A.; Michels, D. J.; Lamy, P. L.; Schwenn, R.;
Simnett, G. M.
1998ApJ...498L.165W Altcode:
We investigate the nature and origin of the outward-moving density
inhomogeneities (“blobs”) detected previously with the Large Angle and
Spectrometric Coronagraph on the Solar and Heliospheric Observatory. The
blobs are concentrated around the thin plasma layer that surrounds
the heliospheric current sheet and that constitutes the outer streamer
belt; they represent only a small, fluctuating component of the total
density within the plasma sheet. As noted before in Sheeley et al.,
blobs are characterized by low speeds and are continually emitted
from the elongated tips of helmet streamers at 3-4 R<SUB>solar</SUB>
from Sun center. We suggest that both the blobs and the plasma sheet
itself represent closed-field material injected into the solar wind as
a result of footpoint exchanges between the stretched helmet-streamer
loops and neighboring open field lines. The plasma sheet is thus
threaded by newly reconnected, open magnetic field lines, which lend
the white-light streamer belt its filamentary appearance. Since in
situ observations at 1 AU show that the slow wind (with speeds below
500 km s<SUP>-1</SUP>) spreads over an angular extent much greater
than the <~3° width of the plasma sheet, we deduce that a major
component of this wind must originate outside the helmet streamers
(i.e., from just inside coronal holes).
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Title: LASCO/EIT Observations of Coronal Mass Ejections from
Large-Scale Filament Channels
Authors: Plunkett, S. P.; Dere, K. P.; Howard, R. A.; Michels, D. J.;
Brueckner, G. E.; Thompson, B. J.; Delaboudiniere, J. -P.
1998ASPC..150..475P Altcode: 1998npsp.conf..475P; 1998IAUCo.167..475P
No abstract at ADS
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Title: Solar Cycle 22 UV Spectral Irradiance Variability: Current
Measurements by SUSIM UARS
Authors: Floyd, L. E.; Reiser, P. A.; Crane, P. C.; Herring, L. C.;
Prinz, D. K.; Brueckner, G. E.
1998sers.conf...79F Altcode:
No abstract at ADS
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Title: Solar Cycle 22 UV Spectral Irradiance Variability: Current
Measurements by SUSIM UARS
Authors: Floyd, L. E.; Reiser, P. A.; Crane, P. C.; Herring, L. C.;
Prinz, D. K.; Brueckner, G. E.
1998SoPh..177...79F Altcode:
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) has
measured the solar spectral irradiance for wavelengths 115-410 nm on
a daily basis since October 11, 1991. The absolutely calibrated solar
UV irradiances through January 8, 1996 have been produced. Their
time-dependent behavior is similar to that of the Mgii index as
measured both by NOAA-9 SBUV and by SUSIM itself. The maximum long-term
variation observed by SUSIM is at Lα and is measured to be in excess
of a factor of 2. This maximum variation decreases with increasing
wavelength until about 300 nm where no significant long-term variation
is directly measured above SUSIM's estimated 1-2% relative accuracy. The
wavelength dependence of the measured UV variability is found to roughly
correspond to the mean emission height given by solar atmospheric
radiative transfer models. Because SUSIM observations began when solar
activity was near its peak and now extend to very near its minimum,
estimates of the solar cycle 22 UV variability are generated from a
combination of these measurements and solar activity proxy indices.
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Title: LASCO and EIT Observations of the Dynamic Corona
Authors: Dere, K. P.; Brueckner, G. E.
1998HiA....11..861D Altcode:
No abstract at ADS
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Title: Correlations of Solar Cycle 22 UV Irradiance
Authors: Floyd, L.; Brueckner, G.; Crane, P.; Prinz, D.; Herring, L.
1997ESASP.415..235F Altcode: 1997cpsh.conf..235F
No abstract at ADS
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Title: Solar Energetic Particle Events and Coronal Mass Ejections:
New Insights from SOHO
Authors: Bothmer, V.; Posner, A.; Kunow, H.; Müller-Mellin, R.;
Herber, B.; Pick, M.; Thompson, B. J.; Delaboudinière, J. -P.;
Brueckner, G. E.; Howard, R. A.; Michels, D. J.; Cyr, C. St.; Szabo,
A.; Hudson, H. S.; Mann, G.; Classen, H. -T.; McKenna-Lawlor, S.
1997ESASP.415..207B Altcode: 1997cpsh.conf..207B
No abstract at ADS
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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.
1997ESASP.415..103S Altcode: 1997cpsh.conf..103S
No abstract at ADS
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Title: LASCO Observations of Variability in the Quiescent Solar Corona
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Brueckner, G. E.;
Howard, R. A.
1997AAS...191.7303W Altcode: 1997BAAS...29Q1321W
We discuss the localized small scale coronal variability detected
in observations made by the Large Angle Spectrometric Coronagraph
(LASCO) onboard SOHO. The LASCO C1 coronagraph was used to take images
of small portions of the solar corona located in the streamer belt
between roughly 1.1 and 2.0 R<SUB>sun</SUB>. Two sets of images were
obtained several months apart. Each set contains images taken with
LASCO's Fabry-Perot interferometer centered on the Fe XIV lambda 5303
line, and in the nearby continuum. The images were obtained about once
every minute. Significant variability was detected in two compact loops,
one in each sequence, which brighten at their tops by about 10% in one
hour. In one of the loops, there appears to be a flow up one leg of
the loop with a velocity of 100--200 km s(-1) . The quiescent loop-top
brightenings are reminiscent of transient loop-top brightenings seen in
Yohkoh soft X-ray observations of the quiescent Sun and during flares.
---------------------------------------------------------
Title: Ultraviolet Irradiance at Solar Minimum
Authors: Floyd, L. E.; Crane, P. C.; Herring, L. C.; Cook, J. W.;
Prinz, D. K.; Brueckner, G. E.
1997AAS...191.7409F Altcode: 1997BAAS...29.1325F
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
Upper Atmosphere Research Satellite has been measuring the sun's UV
spectral irradiance for wavelengths from 115 to 410 nm since October
1991. We describe the behavior of the solar UV spectral irradiance
during the decline of solar cycle 22 with special emphasis on the
recent solar minimum period. Although the time series of the spectral
irradiances have behavior similar to that of the Mg II core-to-wing
ratio, there are differences among them. We describe the behavior
near solar minimum of both the irradiance in selected UV wavelength
intervals, the the Mg II core-to-wing ratio, and the integrated Ly-alpha
line irradiance. Overall, each of these time series follows a similar
pattern: a broad and flat minimum, with some 27-day solar rotation
modulation still evident at nearly all times. The date found for
solar minimum is often used as an input parameter used in predicting
the timing of the following solar cycle maximum. The minimum strongly
depends on both the algorithm and the averaging time period used. For
sunspot number, the generally accepted minimum is defined as the
lowest value of a 12-month running average of monthly averages of daily
values. We analyze various methods for finding the solar minimum in the
UV including that used for sunspot number. For wavelengths longer than
the Al edge at 208 nm, systematic errors due to instrument responsivity
degradation ( ~ +/-1%) become a significant fraction of the long-term
variation during the minimum, making determination of the date of the
minimum increasingly uncertain. We find that the minimum for Mg II
occurs during April 1996 while that for Ly-alpha occurs later, during
October 1996. These results are compared with solar minimum behavior
of other solar indices to better understand the relationship among
the regions of the solar atmosphere where each emission originates.
---------------------------------------------------------
Title: Analysis of Coronal Mass Ejections observed by LASCO
Authors: Subramanian, P.; Dere, K. P.; Howard, R. A.; St. Cyr, C.;
Brueckner, G. E.
1997AAS...191.7306S Altcode: 1997BAAS...29.1321S
The LASCO instrument on the SOHO spacecraft has been observing
coronal mass ejections from the sun from February 1996 to the present
time. This covers a range of solar activity ranging from near-minimum
activity to increasing activity. We present a database of coronal mass
ejection locations, times and velocities. These are then compared
with photospheric magnetic field patterns and large scale coronal
structures. We hope to gain an understanding of coronal mass ejection
initiation mechanisms through these observations. Preliminary results
from our analyses will be presented here.
---------------------------------------------------------
Title: A New View of the Solar Corona and the Solar Wind
Authors: Brueckner, G. E.
1997AAS...19110101B Altcode: 1997BAAS...29.1371B
The Large Angle Spectroscopic Coronagraph (LASCO) experiment on the SOHO
satellite images continuously the solar corona from the surface of the
Sun to 32 solar radii. Motion pictures show the dynamics of the corona
from the surface of the Sun into the interplanetary medium. Three
different electrodynamic processes seem to be responsible for the
dynamic state of the corona: Newly emerging magnetic flux from the
solar convection zone, conversion of magnetic into mechanical energy
by reconnection, and an electrodynamic circuit which couples these
processes on a global scale. In the lower corona newly emerging
magnetic flux drives the expansion of loop structures into the
upper corona, where they react with the global quadrupole magnetic
field by reconnection, depositing mass and energy into the global
current sheet. Excess energy is released as coronal mass ejections
(CMEs). A string of CMEs forms the low latitude, slow speed solar wind,
which is accelerated in the equatorial current sheet. The high speed
solar wind is accelerated in open, straight magnetic fields at higher
latitudes. Reconnections of local magnetic fields can drive supersonic
shock waves, which are the forefront of large, high speed CMEs. Global
energy release inside the equatorial current sheet cause global toroidal
CMEs all around the Sun. They require a global energy coupling mechanism
in the corona. Large local coronal energy releases-CMEs, flares-seem
to change the global structure of the corona.
---------------------------------------------------------
Title: Evidence of an Erupting Magnetic Flux Rope: LASCO Coronal
Mass Ejection of 1997 April 13
Authors: Chen, J.; Howard, R. A.; Brueckner, G. E.; Santoro, R.;
Krall, J.; Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.;
Simnett, G. M.
1997ApJ...490L.191C Altcode:
A coronal mass ejection (CME) observed by LASCO exhibits evidence
that its magnetic field geometry is that of a flux rope. The dynamical
properties throughout the fields of view of C2 and C3 telescopes are
examined. The results are compared with theoretical predictions based
on a model of solar flux ropes. It is shown that the LASCO observations
are consistent with a two-dimensional projection of a three-dimensional
magnetic flux rope with legs that remain connected to the Sun.
---------------------------------------------------------
Title: LASCO Observations of Disconnected Magnetic Structures Out
to Beyond 28 Solar Radii During Coronal Mass Ejections
Authors: Simnett, G. M.; Tappin, S. J.; Plunkett, S. P.; Bedford,
D. K.; Eyles, C. J.; St. Cyr, O. C.; Howard, R. A.; Brueckner, G. E.;
Michels, D. J.; Moses, J. D.; Socker, D.; Dere, K. P.; Korendyke,
C. M.; Paswaters, S. E.; Wang, D.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Bout, M. V.
1997SoPh..175..685S Altcode:
Two coronal mass ejections have been well observed by the LASCO
coronagraphs to move out into the interplanetary medium as disconnected
plasmoids. The first, on July 28, 1996, left the Sun above the west
limb around 18:00 UT. As it moved out, a bright V-shaped structure
was visible in the C2 coronagraph which moved into the field-of-view
of C3 and could be observed out to beyond 28 solar radii. The derived
average velocity in the plane of the sky was 110 ± 5 km s<SUP>-1</SUP>
out to 5 solar radii, and above 15 solar radii the velocity was 269
± 10 km s<SUP>-1</SUP>. Thus there is evidence of some acceleration
around 6 solar radii. The second event occurred on November 5, 1996
and left the west limb around 04:00 UT. The event had an average
velocity in the plane of the sky of ∼54 km s<SUP>-1</SUP> below
4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km
s<SUP>-1</SUP>. In both events the rising plasmoid is connected back
to the Sun by a straight, bright ray, which is probably a signature of
a neutral sheet. In the November event there is evidence for multiple
plasmoid ejections. The acceleration of the plasmoids around a projected
altitude of 5 solar radii is probably a manifestation of the source
surface of the solar wind.
---------------------------------------------------------
Title: First View of the Extended Green-Line Emission Corona At
Solar Activity Minimum Using the Lasco-C1 Coronagraph on SOHO
Authors: Schwenn, R.; Inhester, B.; Plunkett, S. P.; Epple, A.;
Podlipnik, B.; Bedford, D. K.; Eyles, C. J.; Simnett, G. M.; Tappin,
S. J.; Bout, M. V.; Lamy, P. L.; Llebaria, A.; Brueckner, G. E.;
Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels,
D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.;
St. Cyr, O. C.; Wang, D.
1997SoPh..175..667S Altcode:
The newly developed C1 coronagraph as part of the Large-Angle
Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has
been operating since January 29, 1996. We present observations
obtained in the first three months of operation. The green-line
emission corona can be made visible throughout the instrument's full
field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun
center). Quantitative evaluations based on calibrations cannot yet be
performed, but some basic signatures show up even now: (1) There are
often bright and apparently closed loop systems centered at latitudes
of 30° to 45° in both hemispheres. Their helmet-like extensions
are bent towards the equatorial plane. Farther out, they merge into
one large equatorial `streamer sheet' clearly discernible out to 32
R⊙. (2) At mid latitudes a more diffuse pattern is usually visible,
well separated from the high-latitude loops and with very pronounced
variability. (3) All high-latitude structures remain stable on time
scales of several days, and no signature of transient disruption of
high-latitude streamers was observed in these early data. (4) Within
the first 4 months of observation, only one single `fast' feature was
observed moving outward at a speed of 70 km s<SUP>-1</SUP> close to
the equator. Faster events may have escaped attention because of data
gaps. (5) The centers of high-latitude loops are usually found at the
positions of magnetic neutral lines in photospheric magnetograms. The
large-scale streamer structure follows the magnetic pattern fairly
precisely. Based on our observations we conclude that the shape
and stability of the heliospheric current sheet at solar activity
minimum are probably due to high-latitude streamers rather than to
the near-equatorial activity belt.
---------------------------------------------------------
Title: The Relationship of Green-Line Transients to White-Light
Coronal Mass Ejections
Authors: Plunkett, S. P.; Brueckner, G. E.; Dere, K. P.; Howard,
R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Paswaters, S. E.; St. Cyr, O. C.; Socker, D. G.;
Wang, D.; Simnett, G. M.; Bedford, D. K.; Biesecker, D. A.; Eyles,
C. J.; Tappin, S. J.; Schwenn, R.; Lamy, P. L.; Llebaria, A.
1997SoPh..175..699P Altcode:
We report observations by the Large Angle Spectrometric Coronagraph
(LASCO) on the SOHO spacecraft of three coronal green-line transients
that could be clearly associated with coronal mass ejections (CMEs)
detected in Thomson-scattered white light. Two of these events, with
speeds >25 km s<SUP>-1</SUP>, may be classified as `whip-like'
transients. They are associated with the core of the white-light
CMEs, identified with erupting prominence material, rather than with
the leading edge of the CMEs. The third green-line transient has a
markedly different appearance and is more gradual than the other two,
with a projected outward speed <10 km s<SUP>-1</SUP>. This event
corresponds to the leading edge of a `streamer blowout' type of CME. A
dark void is left behind in the emission-line corona following each of
the fast eruptions. Both fast emission-line transients start off as a
loop structure rising up from close to the solar surface. We suggest
that the driving mechanism for these events may be the emergence of new
bipolar magnetic regions on the surface of the Sun, which destabilize
the ambient corona and cause an eruption. The possible relationship of
these events to recent X-ray observations of CMEs is briefly discussed.
---------------------------------------------------------
Title: MHD Interpretation of LASCO Observations of a Coronal Mass
Ejection as a Disconnected Magnetic Structure
Authors: Wu, S. T.; Guo, W. P.; Andrews, M. D.; Brueckner, G. E.;
Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses,
J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout,
M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.
1997SoPh..175..719W Altcode:
We present a qualitative and quantitative comparison of a single
coronal mass ejection (CME) as observed by LASCO (July 28-29, 1996)
with the results of a three-dimensional axisymmetric time-dependent
magnetohydrodynamic model of a flux rope interacting with a helmet
streamer. The particular CME considered was selected based on the
appearance of a distinct `tear-drop' shape visible in animations
generated from both the data and the model.
---------------------------------------------------------
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.
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<SUP>-1</SUP> 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<SUP>-1</SUP>. 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 10<SUP>4</SUP> 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: Origin and Evolution of Coronal Streamer Structure During
the 1996 Minimum Activity Phase
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Kraemer,
J. R.; Rich, N. B.; Andrews, M. D.; Brueckner, G. E.; Dere, K. P.;
Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.;
Paswaters, S. E.; Socker, D. G.; Wang, D.; Lamy, P. L.; Llebaria,
A.; Vibert, D.; Schwenn, R.; Simnett, G. M.
1997ApJ...485..875W Altcode:
We employ coronal extrapolations of solar magnetograph data to interpret
observations of the white-light streamer structure made with the LASCO
coronagraph in 1996. The topological appearance of the streamer belt
during the present minimum activity phase is well described by a model
in which the Thomson-scattering electrons are concentrated around a
single, warped current sheet encircling the Sun. Projection effects
give rise to bright, jet-like structures or spikes whenever the current
sheet is viewed edge-on multiple spikes are seen if the current sheet is
sufficiently wavy. The extreme narrowness of these features in polarized
images indicates that the scattering layer is at most a few degrees
wide. We model the evolution of the streamer belt from 1996 April to
1996 September and show that the effect of photospheric activity on
the streamer belt topology depends not just on the strength of the
erupted magnetic flux, but also on its longitudinal phase relative
to the background field. Using flux transport simulations, we also
demonstrate how the streamer belt would evolve during a prolonged
absence of activity.
---------------------------------------------------------
Title: The Green Line Corona and Its Relation to the Photospheric
Magnetic Field
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Hawley, S. H.; Kraemer,
J. R.; Brueckner, G. E.; Howard, R. A.; Korendyke, C. M.; Michels,
D. J.; Moulton, N. E.; Socker, D. G.; Schwenn, R.
1997ApJ...485..419W Altcode:
Images of the green line corona made with the LASCO C1 coronagraph
on SOHO are analyzed by applying current-free extrapolations to the
observed photospheric field. The Fe XIV λ5303 emission is shown to
be closely related to the underlying photospheric field strength. By
modeling the observed intensity patterns as a function of latitude and
height above the solar limb, we derive an approximate scaling law of the
form n<SUB>foot</SUB> ~ <B<SUB>foot</SUB>><SUP>0.9</SUP>, where
n<SUB>foot</SUB> is the density of the green line-emitting plasma and
<B<SUB>foot</SUB>> is the average field strength at the footprints
of the coronal loop. The observed high-latitude enhancements in the
green line corona are attributed to the poleward concentration of the
large-scale photospheric field. The strongest such enhancements occur
where the high-latitude unipolar fields become reconnected to active
region flux at lower latitudes; the global emission pattern rotates
quasi-rigidly at the rate of the dominant active region complex. The
validity of the current-free approximation is assessed by comparing
the topology of the observed and simulated green line structures.
---------------------------------------------------------
Title: Measurements of Flow Speeds in the Corona Between 2 and 30
R<SUB>⊙</SUB>
Authors: Sheeley, N. R.; Wang, Y. -M.; Hawley, S. H.; Brueckner,
G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.;
Michels, D. J.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.;
Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M.;
Plunkett, S.; Biesecker, D. A.
1997ApJ...484..472S Altcode:
Time-lapse sequences of white-light images, obtained during sunspot
minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph
on the Solar and Heliospheric Observatory, give the impression of
a continuous outflow of material in the streamer belt, as if we
were observing Thomson scattering from inhomogeneities in the solar
wind. Pursuing this idea, we have tracked the birth and outflow of
50-100 of the most prominent moving coronal features and find that:
<P />1. They originate about 3-4 R<SUB>⊙</SUB> from Sun center as
radially elongated structures above the cusps of helmet streamers. Their
initial sizes are about 1 R<SUB>⊙</SUB> in the radial direction and
0.1 R<SUB>⊙</SUB> in the transverse direction. <P />2. They move
radially outward, maintaining constant angular spans and increasing
their lengths in rough accord with their speeds, which typically
double from 150 km s<SUP>-1</SUP> near 5 R<SUB>⊙</SUB> to 300 km
s<SUP>-1</SUP> near 25 R<SUB>⊙</SUB>. <P />3. Their individual speed
profiles v(r) cluster around a nearly parabolic path characterized
by a constant acceleration of about 4 m s<SUP>-2</SUP> through most
of the 30 R<SUB>⊙</SUB> field of view. This profile is consistent
with an isothermal solar wind expansion at a temperature of about
1.1 MK and a sonic point near 5 R<SUB>⊙</SUB>. <P />Based on their
relatively small initial sizes, low intensities, radial motions, slow
but increasing speeds, and location in the streamer belt, we conclude
that these moving features are passively tracing the outflow of the
slow solar wind.
---------------------------------------------------------
Title: Image Processing of December 23 1997 LASCO CME Observations
Authors: Karovska, M.; Wood, B. E.; Brueckner, G. E.; Cook, J. W.;
Howard, R. A.; Andrews, M. D.
1997SPD....28.0126K Altcode: 1997BAAS...29..884K
The Large Angle Spectrometric Coronagraph (LASCO) onboard SOHO contains
three individual coronagraphs, C1, C2, and C3, that image the solar
corona from 1.1 R_sun to 32 R_sun. Since January 1996, LASCO has
detected a number of CMEs. Starting on December 23 1996 several
spectacular CME events were observed with all LASCO coronagraphs. The
onset was detected with both EIT and LASCO/C1 instruments. The images
of the developing CMEs contain many complex components with different
spatial scales and a wide range of contrast levels. Spatial and
temporal characterization of these structures is extremely important
for understanding the origin and the early evolution of CMEs. To
extract information on the low contrast small-scale structures in the
CMEs we applied image processing techniques to several time sequences
of images. Our study of the movies made from these contrast and/or
resolution enhanced images leads to a better knowledge of the morphology
and temporal evolution of the small scale structures, especially at the
onset of the CME as observed with the C1 and EIT. LASCO is a cooperative
project of an international group of scientists at the Naval Research
Laboratory, Washington, DC, the Max-Planck Institut fur Aeronomie,
Germany, the Laboratoire d'Astronomie Spatiale, France, and the Space
Research Group at the University of Birmingham, Great Britain.
---------------------------------------------------------
Title: The Origin and Acceleration of the Solar Wind
Authors: Brueckner, G. E.
1997SPD....28.0129B Altcode: 1997BAAS...29..884B
The two distinctly different types of solar wind, the slow, low latitude
and the fast polar wind have been identified in LASCO movies: The slow,
low latitude solar winds originates in the equatorial current sheet
of the Sun. Mass and energy are supplied by expanding loops in the
lower corona. Emerging magnetic flux must be the driver of the loop
expansion. The expanding loops are confined inside the current sheet,
which is formed by equatorially bend magnetic field of opposite polarity
from the edges of the north and south polar coronal holes. The current
sheet serves as a mass and energy reservoir. Plasmoids are ejected after
the current sheet cannot anymore reconnect newly injected magnetic field
from the ascending loops. These plasmoids are accelerated from the lower
corona to the edge of the field of view at 32 solar radii. They form
the irregular structure of the slow solar wind, as it is observed at
the Earth and beyond. Faster outflow can be observed in the straight
structures of the polar plumes. Flows are steady because of the open
magnetic fields over the solar poles. A reservoir effect does not exist
there. The acceleration takes place closer to the surface of the Sun,
than at the equator. Gusts exists, but they are much less pronounced,
compared with the equatorial wind. They can be used to measure the
wind speed.
---------------------------------------------------------
Title: Sungrazing Comets
Authors: Brueckner, G. E.; Williams, G. V.; Biesecker, D. A.; St. Cyr,
O. C.; Lewis, D. J.; Stezelberger, S. T.; Marsden, B. G.
1997IAUC.6669....1B Altcode:
G. E. Brueckner reports, for the SOHO-LASCO Consortium (which
consists of the Naval Research Laboratory, Laboratoire d'Astronomie
Spatiale, Max-Planck-Institut fur Aeronomie, and the University of
Birmingham), the discovery of four more comets (cf. IAUC 6650, 6653)
in images obtained by the LASCO white-light coronagraphs aboard the
ESA/NASA Solar and Heliospheric Observatory (SOHO) spacecraft. The
following approximate discovery positions are summarized from the
more complete reductions by G. V. Williams on MPEC 1997-K10 to
1997-K13 from measurements by D. A. Biesecker and O. C. St. Cyr:
UT R.A. (2000) Decl. 1996 Jan. 27.971 20 56.4 -20 01 C/1996 B3
1996 Dec. 11.056 17 15.8 -27 03 C/1996 X1 11.802 17 19.4 -27 11
C/1996 X2 1997 Jan. 26.179 20 54.2 -20 33 C/1997 B2 C/1996 B3 was
discovered only recently using automated search software written by
Biesecker. The others were discovered in real time by D. J. Lewis and
Biesecker; S. T. Stezelberger; and Biesecker, respectively. The final
analysis of the brightness of each object has not been completed,
but preliminary results (based on comparisons with stars in the same
coronagraphic field) by Biesecker and St. Cyr suggest that C/1996
X2 had m1 = 7.5 and the others m1 > 8.0, with variations evident
for each object. Orbital computations by the undersigned on the same
above-mentioned MPECs suggest that all these SOHO comets are Kreutz
sungrazers. with T = 1996 Jan. 28.71, Dec. 12.10, Dec. 12.88 and 1997
Jan. 27.08 UT, respectively. None of the four comets was detected
receding from the sun, in spite of continuing observations in each case.
---------------------------------------------------------
Title: SUSIM Measurements of UV Variations During the Decline of
Solar Cycle 22
Authors: Floyd, L. E.; Crane, P. C.; Herring, L. C.; Prinz, D. K.;
Brueckner, G. E.
1997SPD....28.0275F Altcode: 1997BAAS...29..906F
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
Upper Atmosphere Research Satellite (UARS) has measured the solar
spectral irradiance for wavelengths 1150-4100 { Angstroms} on every
available day from October 11, 1991 to the present. The record of
spectral irradiances obtained during this period clearly shows the
decline associated with the last half of solar cycle 22. Superimposed
on this solar cycle variation is a 27-day solar rotation modulation
which, for the most part, maintains coherence across the wavelength
spectrum and with SUSIM's own Mg II core-to-wing ratio index. However,
for wavelengths between the Si I edge at 1682 { Angstroms} and the
Mg I edge at 2513 { Angstroms} and for some time periods, 13.5-day
variations dominate. SUSIM observations began when solar activity was
near maximum and now extend through minimum. Generally, the measured
peak-to-peak variations are larger for shorter wavelengths and for
emission or absorption lines. The wavelength dependence of the UV
variability apparently corresponds to the solar atmospheric emission
heights given by radiative transfer models. The largest measured
variation, that for H I Ly-alpha , exceeds a factor of two. The
variation in the continuum just shortward of the Al I edge at 2076 {
Angstroms} is about 10%; just longward, about 5%. This latter variation
continues up to the Mg I edge and then declines to approximately zero
measured variation at about 3000 { Angstroms} and above. Based on
common proxies of solar UV variation, such as the Mg II core-to-wing
ratio and He I 10830 { Angstroms} equivalent width, SUSIM irradiance
measurements have ranged over more than 85% of the entire solar cycle
22 variation. Through the separate use of each index as a UV proxy,
we extend the SUSIM measurements to estimate the wavelength-dependent
peak-to-peak UV variability over the whole of solar cycle 22. SUSIM
is supported under NASA-Defense Purchase Request S14798D.
---------------------------------------------------------
Title: Using LASCO Observations to Infer Solar Wind Flow Near the Sun
Authors: Sheeley, N. R., Jr.; Brueckner, G. E.; Dere, K. P.; Howard,
R. A.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Koomen, M. J.;
Paswaters, S. E.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.;
St Cyr, O. C.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A.
1997SPD....28.0301S Altcode: 1997BAAS...29..907S
We have continued to track individual coronal features as they become
detached from helmet streamers and move outward from the Sun. The
composite speed profile for 50-100 features has a parabolic shape
with a constant acceleration of about 4 m/s(2) over the 2-30 R field
of view. This well-determined speed profile contrasts strongly with
the nearly uniform scatterplot obtained for about 50 nominal coronal
mass ejections (CMEs), and suggests that these detached bits of coronal
“debris” are passively tracing the speed of the slow solar wind. We
have also begun the more difficult task of tracking outflow along
polar plumes and will summarize these results as of June 1997.
---------------------------------------------------------
Title: EIT and LASCO observations of the initiation of a coronal
mass ejection
Authors: Dere, K.; Brueckner, G. E.; Delaboudiniere, J. -P.
1997SPD....28.0502D Altcode: 1997BAAS...29R.908D
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 200 kms and was preceded by
a bright loop-like structure, which surrounded an emission void,
that traveled out into the corona at a velocity of 400 kms. 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 degrees in latitude, originated
in a volume with dimensions of roughly 35" (2.5 x 10(4) 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: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996;
Part 1: Solar Data
Authors: Andrews, M. D.; Dryer, M.; Aurass, H.; DeForest, C.;
Kiplinger, A. L.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappipn,
S. J.; Thompson, B. J.; Watari, S. I.; Lamy, P.; Mann, G.; Schwenn,
R.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M.
1997ESASP.404..169A Altcode: 1997cswn.conf..169A
No abstract at ADS
---------------------------------------------------------
Title: The April 7, 1997 Event: LASCO and Nancay Radioheliograph
Joint Observations
Authors: Maia, D.; Pick, M.; Howard, R.; Brueckner, G. E.; Lamy, P.
1997ESASP.404..539M Altcode: 1997cswn.conf..539M
No abstract at ADS
---------------------------------------------------------
Title: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996;
Part 2: Propagation
Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Karlicky,
M.; Kiplinger, A.; Klassen, A.; Meisner, R.; Ipavich, F. M.; Galvin,
A. B.; Paswaters, S. E.; Smith, Z.; Tappin, S. J.; Thompson, B. J.;
Watari, S. -I.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.;
Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.; Schwenn, R.
1997ESASP.404..331D Altcode: 1997cswn.conf..331D
No abstract at ADS
---------------------------------------------------------
Title: Acceleration of Coronal Mass Ejections in the Upper Corona:
Observations from Lasco/Soho
Authors: Simnett, G. M.; Tappin, S. J.; Brueckner, G. E.; Howard,
R. A.; Lamy, P.; Michels, D. J.; Schwenn, R.
1997ICRC....1..181S Altcode: 1997ICRC...25a.181S
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Evolution of a Coronal Mass Ejection (CME) to
Magnetic Cloud: A Preliminary Analysis of the January 6-10, 1997
CME Observed by LASCO/SOHO
Authors: Wu, S. T.; Guo, W. P.; Michels, D. J.; Andrews, M. D.;
Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.;
Moses, J. D.; Socker, D. G.; Dere, K. P.; Bougeret, Jean-Louis; Lamy,
P. L.; Schwenn, R.; Simnett, G. M.
1997ESASP.404..739W Altcode: 1997cswn.conf..739W
No abstract at ADS
---------------------------------------------------------
Title: Joint Radioheliograph and LASCO Observations of Coronal
Mass Ejections
Authors: Pick, M.; Maia, D.; Howard, R.; Kerdraon, A.; Brueckner,
G. E.; Lamy, P.; Schwenn, R.; Aurass, H.
1997ESASP.404..601P Altcode: 1997cswn.conf..601P
No abstract at ADS
---------------------------------------------------------
Title: Visibility of Earth-Directed Coronal Mass Ejections
Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Plunkett, S.;
Brueckner, G. E.; Lamy, Ph.; Schwenn, R.; Biesecker, D. A.
1997ESASP.404..567M Altcode: 1997cswn.conf..567M
No abstract at ADS
---------------------------------------------------------
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.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker,
D. G.; Delaboudiniere, J. P.; Hochedez, J. F.; Lamy, P. L.; Schwenn,
R.; Simnett, G. M.; Defise, J. M.; Catura, R. C.
1997IAUJD..19E..18D Altcode:
We present the first observations of the initiation of a corona mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
and LASCO experiments on SOHO show that the CME starts in a small volume
and is associated with slow motions of prominence material. At about
the same time, a shock wave is created that travels out into the corona
at a velocity of 400 km s^{-1} ahead of an eruptive prominence. This
shock wave is clearly the event that is later seen as a classical CME
when observed in the coronagraph above 1.5 solar radii. Although the
CME clearly starts in a small region, a chain of activity near the
limb may also be associated with this event.
---------------------------------------------------------
Title: Enhancing the Spatial Resolution of Solar Coronagraph
Observations Using Dynamic Imaging
Authors: Zaccheo, T. S.; Karovska, M.; Cook, J. W.; Howard, R. A.;
Brueckner, G. E.; Korendyke, C. M.; Schwenn, R.
1996ApJ...471.1058Z Altcode:
The Large Angle Spectrometric Coronagraph (LASCO) Cl coronagraph on
board the Solar and Heliospheric Observatory (SOHO) is designed to
image the corona from 1.1 to 3.0 R<SUB>sun</SUB>. The resolution of
C1 is defined by the size of its CCD pixels, which correspond to 5".6,
and not by the diffraction limit of the optical system, which may be as
small as 3". The resolution of Cl can be improved using the technique of
"dynamic imaging" the process of acquiring successive images of the same
scene using sub- pixel displacements of the steerable primary mirror. We
developed a technique we call the fractional pixel restoration (F PR)
algorithm that utilizes these observations to construct an image with
improved resolution. Simulations were used to test this algorithm and
to explore its limitations. We also applied the direct co-addition
and FPR algorithms to laboratory preffight images of a wire mesh
grid. These results show that the resolution of the C1 coronagraph can
be significantly enhanced, even in the presence of noise and modest
differences between successive images. In some cases, the results can
even reach the diffraction limit of the telescope.
---------------------------------------------------------
Title: Ozone variability in the upper stratosphere during the
declining phase of the solar cycle 22
Authors: Chandra, S.; Froidevaux, L.; Waters, J. W.; White, O. R.;
Rottman, G. J.; Prinz, D. K.; Brueckner, G. E.
1996GeoRL..23.2935C Altcode:
Recent studies of the solar cycle variation of ozone have shown
that the response of ozone in the upper stratosphere to solar UV
variation, as inferred from the SBUV (Solar Backscatter Ultraviolet)
type measurements, is about a factor of two greater than estimated from
2-D photochemical models. Because of potential errors in accounting
for the long term instrument drift in the SBUV type of measurements,
the significance of this discrepancy is difficult to quantify. In this
paper, ozone measurements from the Microwave Limb Sounder (MLS) and
the solar irradiance measurements from the Solar Stellar Irradiance
Comparison Experiment (SOLSTICE) and the Solar Ultraviolet Irradiance
Monitor (SUSIM) onboard the Upper Atmosphere Research Satellite (UARS)
are analyzed to estimate the upper stratosphere ozone response to
changes in the solar UV irradiance. During the three year period of UARS
measurements, analyzed here for the declining phase of the solar cycle
22, the solar irradiance in the 200-205 nm range decreased by about 5 %
from a near solar maximum to a near solar minimum level. During the same
period, ozone mixing ratio measured from the MLS instrument decreased
by about 2-4% in the 0.7-3 hPa region. In the upper stratosphere, the
general characateristics of the MLS time series are similar to those
inferred from the NOAA-11 SBUV/2 measurements. The SBUV/2 trends above
1.5 hPa, however, are significantly greater than those derived from the
MLS data. The UARS data suggest that the long term solar UV response of
ozone in the upper stratosphere is underestimated by 2-D photochemical
models as in previous studies based on the SBUV type measurements.
---------------------------------------------------------
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.
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: LASCO Observations of the 03Feb96 Streamer Blow-out
Authors: Andrews, M. D.; Korendyke, C. M.; Koomen, M. J.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses,
J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.;
St. Cyr, O. C. St.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.;
Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles,
C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3716A Altcode: 1996BAAS...28..880A
The C2 and C3 telescopes on the Large Angle Spectrometric Coronograph
(LASCO) have recorded images of a Streamer Blow-out which occured
on 03Feb96. We will present a series of images produces by combining
data from the 2 coronographs. These images show a rapid evolution of
the coronal streamer belt over projected distances of 2 to 20 solar
radii. The streamer belt shows a dramatic brightening, which is seen to
propagate outward. A bubble-like structure is seen to move away from
the Sun and expand. At the end of this event, the equatorial corona
is significantly less bright than prior to the event.
---------------------------------------------------------
Title: LASCO Observations of the Solar Corona to 32 R<SUB>sun</SUB>
Authors: Cook, J. W.; Koomen, M. J.; Korendyke, C. M.; Brueckner,
G. E.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Morrill, J. S.;
Moses, J. D.; Socker, D. G.; Paswaters, S. E.; Wang, D.; Moulton,
N. E.; Cyr, O. C. St.; Andrews, M. D.; Schwenn, R.; Podlipnik, B.;
Lamy, P. L.; Llebaria, A.; Bout, M. V.; Simnett, G. M.; Bedford,
D. K.; Eyles, C. J.; Plunkett, S.; Biesecker, D. A.
1996AAS...188.3717C Altcode: 1996BAAS...28..880C
The Large Angle Spectrometric Coronagraph (LASCO) was launched on
board the SOHO satellite on 2 December 1995. The C3 externally-occulted
coronagraph of LASCO observes the solar corona over a field from 3.7-32
R_ ⊙, using a 1024x1024 CCD detector with a pixel size corresponding
to 56 arc sec. Observations can be made using color filters ranging
from the blue (420-520 nm) to the near-IR (860-1050 nm), and through
polarizing filters. We report on early observations of the solar corona
out to 32 R<SUB>sun</SUB>.
---------------------------------------------------------
Title: Solar ultraviolet spectral-irradiance observations from the
SUSIM-UARS experiment.
Authors: Brueckner, G. E.; Floyd, L. E.; Lund, P. A.; Prinz, D. K.;
Vanhoosier, M. E.
1996Metro..32..661B Altcode:
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument
on board the Upper Atmosphere Research Satellite (UARS) has measured
solar ultraviolet spectral-irradiance values since October 1991. The
calibration and tracking methods are described. The intensity values
have a precision of 1% at wavelengths longer than 200 nm. Short-term
ultraviolet (UV) variability is correlated with other chromospheric
indices at wavelengths shorter than 280 nm. At longer wavelengths, this
correlation changes gradually into an anticorrelation. There exists
a long-term solar-cycle component at all wavelengths, which seems to
be independent of the rotational modulation. The variability in the
integrated UV from 110 nm to 300 nm amounts to 33% of the variability
in the total solar irradiance.
---------------------------------------------------------
Title: Preliminary Photometric Calibration of LASCO C3 Coronagraph
Images using Pre-Flight Laboratory Images of Standard Sources and
In-Flight Images of Standard Stars
Authors: Korendyke, C. M.; Koomen, M. J.; Andrews, M. D.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.;
Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.;
Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.;
Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker,
D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3621K Altcode: 1996BAAS...28..876K
The C3 coronagraph is a wide field (+/-8.0 degrees), externally
occulted, white light coronagraph. The instrument is one of three
coronagraphs comprising the Large Angle Spectrometric COronagraph
(LASCO) experiment mounted on the Solar Heliospheric Observatory
satellite. The satellite was launched on Dec. 2, 1996; C3 observations
began in early Jan. 1997. The coronagraph optical train includes a set
of five broadband color filters mounted in a wheel. Prior to flight,
an image was obtained through each color filter of a well characterized,
rear-illuminated, opal glass diffusing screen. The C3 in-flight images,
in addition to the coronal structures, also contain several hundred
bright stars. We present a comparison of the photometric calibration
derived from standard stars with the laboratory measurements. The
resulting calibration is then used to examine color variations in the
white light corona over the field of view. The LASCO experiment was
developed by a scientific consortium of members from NRL (USA), MPAe
(Germany), LAS (France) and U. Birmingham (United Kingdom).
---------------------------------------------------------
Title: Validation of the UARS solar ultraviolet irradiances:
Comparison with the ATLAS 1 and 2 measurements
Authors: Woods, T. N.; Prinz, D. K.; Rottman, G. J.; London, J.; Crane,
P. C.; Cebula, R. P.; Hilsenrath, E.; Brueckner, G. E.; Andrews, M. D.;
White, O. R.; VanHoosier, M. E.; Floyd, L. E.; Herring, L. C.; Knapp,
B. G.; Pankratz, C. K.; Reiser, P. A.
1996JGR...101.9541W Altcode:
The measurements of the solar ultraviolet spectral irradiance
made by the two Upper Atmosphere Research Satellite (UARS) solar
instruments, Solar Ultraviolet Spectral Irradiance Monitor (SUSIM)
and SOLar STellar Irradiance Comparison Experiment (SOLSTICE), are
compared with same-day measurements by two solar instruments on the
shuttle ATmospheric Laboratory for Applications and Science (ATLAS)
missions, ATLAS SUSIM and Shuttle Solar Backscatter Ultra Violet (SSBUV)
experiment. These measurements from the four instruments agree to within
the 2σ uncertainty of any one instrument, which is 5 to 10% for all
wavelengths above 160 nm and for strong emission features below 160
nm. Additionally, the long-term relative accuracy of the two UARS data
sets is better than the original 2% goal, especially at wavelengths
greater than 160 nm. This level of agreement is credited to accurate
preflight calibrations coupled with comprehensive inflight calibrations
to track instrument degradation. Two solar irradiance spectra, 119 to
410 nm, are presented; the first combines observations from UARS SUSIM
and UARS SOLSTICE taken on March 29, 1992, during the ATLAS 1 mission,
and the second combines spectra for April 15, 1993, during the ATLAS
2 mission. The ATLAS 1 mission coincided with the initial decline
from the maximum of solar cycle 22 when solar activity was relatively
high. The ATLAS 2 mission occurred somewhat later during the declining
phase of the solar cycle 22 when solar activity was more moderate.
---------------------------------------------------------
Title: Observations of the solar irradiance in the 200-350 nm
interval during the ATLAS-1 Mission: A comparison among three sets
of measurements-SSBUV, SOLSPEC, and SUSIM
Authors: Cebula, R. P.; Thuillier, G. O.; Vanhoosier, M. E.;
Hilsenrath, E.; Herse, M.; Brueckner, G. E.; Simon, P. C.
1996GeoRL..23.2289C Altcode:
The SOLSPEC, SSBUV, and SUSIM spectrometers simultaneously observed
the solar spectral irradiance during the ATLAS-1 mission flown on
board the Space Shuttle Atlantis in March 1992. The three instruments
use different methods and means of absolute calibration and were each
calibrated preflight and postflight. The three data sets are reported
from 200 to 350 nm at 1.1 nm resolution. The method of comparing
the three independent data sets is discussed. The importance of a
common, precise wavelength scale is shown when comparing the data
in wavelength regions of strong Fraunhofer lines. The agreement
among the solar irradiance measurements is better than ±5%. The
fact that the calibrations of the three instruments were based on
three independent standards provides confidence that the absolute
solar spectral irradiance in the range 200-350 nm is now known with an
accuracy better than ±5%. The mean ATLAS-1 solar spectrum is compared
with simultaneous solar observations from the UARS SOLSTICE and UARS
SUSIM instruments. The two mean solar spectra agree to within ±3%.
---------------------------------------------------------
Title: Structure and dynamics of the corona approaching the minimum
of the solar cycle.
Authors: Brueckner, G. E.
1996BAAS...28.1194B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of the comet Hyakutake by the LASCO coronagraph
on the SOHO satellite.
Authors: Andrews, M. D.; Paswaters, S. E.; Brueckner, G. E.; Korendyke,
C. M.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.;
Morril, J. S.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Wang,
D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik,
B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunket, S.;
Simnet, G. M.
1996BAAS...28.1195A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Enhancing the Spatial Resolution of LASCO/C1 Observations
Authors: Zaccheo, T. S.; Karovska, M.; Brueckner, G.; Cook, J. W.;
Howard, R.
1995AAS...18712208Z Altcode: 1995BAAS...27.1454Z
The LASCO C1 coronagraph was designed to examine the fine structure of
the solar corona in the region from 1.1R_sun to 3R_sun. Even though the
diffraction limit of the telescope is ~ 3\arcsec, the nominal resolution
is set by the CCD pixels (5.6”/). A pixel size of 1.5”/ or smaller is
needed in order to obtain diffraction limited observations (according to
the Nyquist criterium). Therefore, the resulting images are undersampled
by a factor of approximately 4. Some of this lost resolution can
be recovered by acquiring successive observations using sub-pixel
displacements of the steerable primary mirror incorporated into the
LASCO/C1 design (“Dynamic Imaging”). The spatial resolution of the
LASCO/C1 coronagraph can be enhanced by combining or co-adding multiple
observations separated by fractions of a pixel. We have identified
several methods for constructing sub-pixel estimates, evaluated the
performance of simple co-addition techniques, and developed an improved
algorithm for obtaining fractional pixel restorations. Simulations
were used to test this algorithm and to explore its limitations. In
this presentation, we describe the algorithm and the results of these
simulations. The results show that the resolution of the C1 coronagraph
can be enhanced, even in the presence of significant noise and modest
differences between successive observations.
---------------------------------------------------------
Title: The Large Angle Spectroscopic Coronagraph (LASCO)
Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke,
C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.;
Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.;
Bedford, D. K.; Eyles, C. J.
1995SoPh..162..357B Altcode:
The Large Angle Spectroscopic Coronagraph (LASCO) is a three
coronagraph package which has been jointly developed for the Solar
and Heliospheric Observatory (SOHO) mission by the Naval Research
Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France),
the Max-Planck-Institut für Aeronomie (Germany), and the University
of Birmingham (UK). LASCO comprises three coronagraphs, C1, C2, and C3,
that together image the solar corona from 1.1 to 30 R<SUB>⊙</SUB> (C1:
1.1 - 3 R<SUB>⊙</SUB>, C2: 1.5 - 6 R<SUB>⊙</SUB>, and C3: 3.7 - 30
R<SUB>⊙</SUB>). The C1 coronagraph is a newly developed mirror version
of the classic internally-occulted Lyot coronagraph, while the C2 and
C3 coronagraphs are externally occulted instruments. High-resolution
imaging spectroscopy of the corona from 1.1 to 3 R<SUB>⊙</SUB> can
be performed with the Fabry-Perot interferometer in C1. High-volume
memories and a high-speed microprocessor enable extensive on-board image
processing. Image compression by a factor of about 10 will result in
the transmission of 10 full images per hour.
---------------------------------------------------------
Title: Solar wind research with the Large Angle Spectroscopic
Coronagraph (LASCO) experiment onboard the Solar and Heliospheric
Observatory (SOHO) satellite
Authors: Brueckner, G. E.
1995sowi.conf...70B Altcode:
The ESA-NASA satellite, to be launched in October 1995, carries three
nested coronagraphs, which will image the solar corona from 1.1 R(solar
mass) to 30 R(solar mass). Super polished mirrors have been developed
for the design of a mirror Lyot coronagraph which has a straylight
level comparable with the coronal intensity from 1.1 R, to 30 R(solar
mass) Coronal details can be imaged with a spatial resolution of 6 arc
seconds. A Fabry Perot interferometer with a spectral resolution of
0.7 A at the wavelength of the green coronal emission line will allow
the simultaneous construction of spectra over the entire field of view
of 10<SUP>6</SUP> pixels. The middle coronagraph (1.5 R(solar mass)
- 6 R(solar mass)) and the outer coronagraph (3 R(solar mass) - 30
R(solar mass)) are externally occulted lens Lyot coronagraphs. Their
straylight level 10<SUP>-11</SUP> B(solar mass) and 10<SUP>-12</SUP>
B(solar mass) respectively is an order of magnitude smaller than
the intensity of the corona. The sensitivity of LASCO to distinguish
between different solar wind acceleration mechanisms will be discussed
as well as its ability to discern different CME models.
---------------------------------------------------------
Title: Ultraviolet Observations of the Structure and Dynamics of an
Active Region at the Limb
Authors: Korendyke, C. M.; Dere, K. P.; Socker, D. G.; Brueckner,
G. E.; Schmieder, B.
1995ApJ...443..869K Altcode:
The structure and dynamics of active region NOAA 7260 at the limb have
been studied using ultraviolet spectra and spectroheliograms obtained
during the eighth rocket flight of the Naval Research Laboratory's
High Resolution Telescope an Spectrograph (HRTS). The instrument
configuration included a narrow-bandpass spectroheliograph to observe
the Sun in the lines of C IV lambda 550 and a tandem-Wadsworth mount
spectrograph to record the profiles of chromospheric transition
region and coronal lines in the 1850-2670 A region. The combination
of high spatial resolution and high spectral purity C IV slit jaw
images with ultraviolet emission-line spectra corresponding allows
examination of a variety of active region phenomena. A time series
of spectroheliograms shows large-scale loop systems composed of
fine-scale threads with some extending up to 100 Mm above the
limb. The proper motion of several supersonic features, including
a surge were measured. The accelerated plasmas appear in several
different geometries and environments. Spectrograph exposures were
taken with the slit positioned at a range of altitudes above the limb
and provide a direct comparison between coronal, transition region
and chromospheric emission line profiles. The spectral profiles of
chromospheric and transition region emission lines show line-of-sight
velocities up to 70 km/s. These lower temperature, emission-line spectra
show small-scale spatial and velocity variations which are correlated
with the threadlike structures seen in C IV. Coronal lines of Fe XII
show much lower velocities and no fine structure.
---------------------------------------------------------
Title: SUSIM UARS Measurements of Solar UV Spectral Irradiance During
the Declining Phase of Solar Cycle 22
Authors: Brueckner, G. E.; Prinz, D. K.; Vanhoosier, M. E.; Crane,
P. C.; Floyd, L. E.; Reiser, P. A.; Lund, P. A.
1995SPD....26..510B Altcode: 1995BAAS...27..958B
No abstract at ADS
---------------------------------------------------------
Title: The Evolution of Periodicities in the Solar UV Spectral
Irradiance
Authors: Crane, P. C.; Floyd, L. E.; Prinz, D. K.; Brueckner, G. E.
1995SPD....26..307C Altcode: 1995BAAS...27..953C
No abstract at ADS
---------------------------------------------------------
Title: Correlations Between Total Solar Irradiance Variations and
Solar Ultraviolet Spectral Irradiance Changes
Authors: Lund, P. A.; Brueckner, G. E.; Prinz, D. K.; Vanhoosier,
M. E.; Crane, P. C.; Floyd, L. E.; Reiser, P. A.
1995SPD....26..509L Altcode: 1995BAAS...27..958L
No abstract at ADS
---------------------------------------------------------
Title: Model For Variability of the Solar Far Ultraviolet Flux Using
Full Disk Magnetograms
Authors: Cook, J. W.; Brueckner, G. E.; Prinz, D. K.; Floyd, L. E.;
Lund, P. A.
1994AAS...18512307C Altcode: 1994BAAS...26R1523C
The variability of the solar full disk flux in the 1175-2100 Angstroms
wavelength range is largely determined from the surface distribution on
the Sun of active regions, whose increase and decrease over the solar
cycle, and passage across the disk, is the main source of long term,
and 27 day, variability. Variations in the distribution of brightness in
quiet areas, perhaps from decay of active regions causing an enhanced
network (“third component"), could also affect variability. While
earlier models of the full disk variability have relied on proxy
activity indicators, such as the Ca II plage area, a more direct
indicator of activity may be full disk photospheric magnetograms. We
have recast our earlier model (1980, J.G.R., 85, 2257) of ultraviolet
variability to base it upon Kitt Peak full disk magnetograms, using
the work of Cook and Ewing (1990, Ap. J., 355, 719) on the observed
relationship of brightness at 1600 Angstroms with magnetic field
strength. We compare our model results with observations of the solar
irradiance from the SUSIM experiment flown on the UARS satellite.
---------------------------------------------------------
Title: Solar Fine-Scale Structures in the Corona, Transition Region,
and Lower Atmosphere
Authors: Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.;
Martin, S. F.; Zirin, H.
1994ApJ...430..913M Altcode:
The American Science and Engineering Soft X-ray Imaging Payload and the
Naval Research Laboratory High Resolution Telescope and Spectrograph
(HRTS) were launched from White Sands on 1987 December 11 in coordinated
sounding rocket flights. The goal was to investigate the correspondence
of fine-scale structures from different temperature regimes in the
solar atmosphere, and particularly the relationship between X-ray bright
points (XBPs) and transition region explosive events. We present results
of the analysis of co-aligned X-ray images, maps of sites of transition
region explosive events observed in C IV 10<SUP>5</SUP>, HRTS 1600
A spectroheliograms of the T<SUB>min</SUB> region, and ground-based
magnetogram and He I 10830 A images. We examined the relationship
of He I 10830 A dark features and evolving magnetic features which
correspond to XBPs. We note a frequent double ribbon pattern of the
He I dark feature counterparts to XBPs. We discuss an analysis of the
relationship of XBPs to evolving magnetic features by Webb et al.,
which shows that converging magnetic features of opposite polarity are
the most significant magnetic field counterparts to XBPs. The magnetic
bipolar features associated with XBPs appear as prominent network
elements in chromospheric and transition region images. The features
in C IV observations corresponding to XBP sites are in general bright,
larger scale (approximately 10 arcsec) regions of complex velocity
fields of order 40 km/s, which is typical of brighter C IV network
elements. These C IV features do not reach the approximately 100 km/s
velocities seen in the C IV explosive events. Also, there are many
similar C IV bright network features without a corresponding XBP in the
X-ray image. The transition region explosive events do not correspond
directly to XBPs. The explosive events appear to be concentrated in
the quiet Sun at the edges of strong network, or within weaker field
strength network regions. We find a greater number of C IV events than
expected from the results of a previous Spacelab 2 HRTS disk survey. We
attribute this at least partly to better spatial resolution with the
newer HRTS data. The full-disk X-ray image shows a pattern of dark
lanes in quiet Sun areas. The number density of C IV events is twice
as large inside as outside a dark lane (4.6 x 10<SUP>-3</SUP> vs. 2.3
x 10<SUP>-3</SUP> explosive events per arcsec <SUP>2</SUP>). The dark
lane corresponds to an old decaying magnetic neutral line. We suggest
that this provides an increased opportunity for small-scale convergence
and reconnection of opposite polarity magnetic field features, in
analogy with the results of Webb et al. for XBPs but at a reduced
scale of reconnection.
---------------------------------------------------------
Title: Combined HRTS-8 Sounding Rocket Observations and YOHKOH Soft
X-ray Observations of NOAA Active Region 7260 at the Solar Limb
Authors: Korendyke, C. M.; Dere, K. P.; Brueckner, G. E.; Waljeski,
K.; Lemen, J. R.
1994kofu.symp..293K Altcode:
On 24 August 1992, the Naval Research Laboratory (NRL) High Resolution
Telescope and Spectrograph (HRTS) was launched aboard a Black Brant
sounding rocket from White Sands, New Mexico. During the flight, the
instrument recorded a unique set of near ultraviolet slit spectra and
1550 A spectroheliograms of an active region at the solar limb. An
extensive set of observations of this region were obtained with the
Yohkoh Soft X-ray Telescope (SXT) near the time of the flight. The C IV
spectroheliograms obtained during this flight are some of the highest
resolution images of the solar transition region ever obtained. The
spectra and spectroheliograms dramatically demonstrate the fundamental
difference between coronal and chromospheric/transition-region plasmas
at 700 km spatial scales. The cooler plasmas exhibit a great deal of
dynamic, fine scale structure with significant flows or proper motion
particularly in the transition zone loops. The coronal emission lines
in the spectra! are relatively uniform and quiescent. The Yohkoh data
during the period before and after the flight show a set of diffuse
high temperature coronal loops with only minimal correspondence to
the structures visible in the C IV spectroheliograms.
---------------------------------------------------------
Title: Status of the LASCO Instrument Development Program
Authors: Moses, D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Lamy, P.; Schwenn,
R.; Simnett, G. M.
1993BAAS...25.1192M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Description of the HRTS-8 Instrument Configuration
Authors: Korendyke, C. M.; Dere, K. P.; Brueckner, G. E.; Socker, D. G.
1993BAAS...25.1182K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Untraviolet Observations of the Chromosphere Transition
Region and Corona of a Solar Active Region
Authors: Dere, K. P.; Korendyke, C. M.; Brueckner, G. E.
1993BAAS...25.1182D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transition Region Explosive Events in an X-Ray Dark Lane
Region of the Quiet Sun
Authors: Cook, J. W.; Moses, D.; Brueckner, G. E.; Dere, K. P.;
Bartoe, J. -D. F.; Webb, D.; Davis, J. M.; Harvey, J. W.; Recely,
F.; Martin, S. F.; Zirin, H.
1993BAAS...25.1181C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar ultraviolet spectral irradiance monitor (SUSIM)
experiment on board the Upper Atmosphere Research Satellite (UARS)
Authors: Brueckner, G. E.; Edlow, K. L.; Floyd, L. E., IV; Lean,
J. L.; Vanhoosier, M. E.
1993JGR....9810695B Altcode:
The state of solar ultraviolet irradiance measurements in 1978, when
NASA requested proposals for a new generation of solar ultraviolet
monitors to be flown on the Upper Atmosphere Research Satellite (UARS),
is described. To overcome the radiometric uncertainties that plagued
the measurements at this time, the solar ultraviolet spectral irradiance
monitor (SUSIM) instrument design included in-flight calibration light
sources and multichannel photometers. Both are aimed at achieving
a maximum precision of the SUSIM measurements over a long period of
time, e.g., one solar cycle. The design of the SUSIM-UARS instrument
is compared with the original design specifications for the UARS
instruments. Details including optical train, filters, detectors,
and contamination precautions are described. Also discussed are the
SUSIM-UARS preflight calibration and characterization, as well as the
results of the inflight performance of the instrument during the first
3 months of operation. Finally, flight operations, observation strategy,
and data reduction schemes are outlined.
---------------------------------------------------------
Title: Multiple Flows and the Fine Structure of the Transition Region
around Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.;
Brueckner, G. E.
1993SoPh..145..257K Altcode:
The fine structure in the flow field in the transition region above
and surrounding a sunspot is determined fromCIV 1548 å line profiles,
observed with the High Resolution Telescope and Spectrograph (HRTS)
during the Spacelab 2 mission. The observed line profiles show one, two,
or three distinct velocity components within the resolution element of
1″ × 1″. Supersonic flows occur in small regions where the line
profile has two or three components. The line component that shows
supersonic speed often is weaker than the subsonic line component,
which may explain why some observers have been unable to detect the
supersonic flow component. The broadening of individual line components
shows non-thermal velocities close to 20 km s<SUP>−1</SUP>. This
suggests that turbulence is less important than usually considered.
---------------------------------------------------------
Title: Description and Performance of the Recently Completed Naval
Research Laboratory Solar Instrument Test Facility
Authors: Korendyke, C. M.; Brueckner, G. E.; Koomen, M. J.; Michels,
D. J.
1993BAAS...25.1191K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Requirements for future solar-physics missions that include
UV instrumentation.
Authors: Brueckner, G. E.
1993ESASP1157..171B Altcode: 1993srfs.book..171B
UV solar physics has always been the centerpiece of solar research
from space. It can be divided into two categories: (1) the measurement
of solar ultraviolet irradiance with no spatial resolution for Earth
atmosphere applications: and (2) high spatial and spectral spectroscopy
and imaging of the solar atmosphere for diagnostics of the solar plasma.
---------------------------------------------------------
Title: The Large Angle Spectroscopic Coronagraph (LASCO): visible
light coronal imaging and spectroscopy.
Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke,
C.; Michels, D. J.; Socker, D. G.; Lamy, P.; Llebaria, A.; Maucherat,
J.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.
1992ESASP.348...27B Altcode: 1992cscl.work...27B
The Large Angle Spectroscopic Coronagraph (LASCO) is a triple
coronagraph being jointly developed for the SOlar and Heliospheric
Observatory (SOHO) mission by the Naval Research Laboratory (USA),
the Laboratoire d'Astronomie Spatiale (France), the Max Planck
Institut für Aeronomie (Germany), and the University of Birmingham
(UK). LASCO comprises three nested coronagraphs (C1, C2, and C3)
that image the solar corona from 1.1 R<SUB><SUB>sun</SUB></SUB> to
30 R<SUB><SUB>sun</SUB></SUB>.
---------------------------------------------------------
Title: Multiple flows in the solar transition region.
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Brueckner, G. E.
1992ESASP.346..211B Altcode: 1992ssts.rept..211B
The solar transition region between the chromosphere and the corona
shows clear evidence of a fine scale structure that is much smaller
than the best available instrumental resolution in the UV of 1×1
arcsec. Previous studies have suggested filling factors of 0.01
- 0.001, with the solar gas being restricted to thin, extended
fibrills. New evidence of the fine scale structure is found from
its dynamical characteristics, the presence of multiple flows. In
multiple flows the solar gas in small volumes show several distinct
velocities, resulting in line profiles with more than one velocity
component within the spatial resolution element. Multiple velocities
are particularly prominent above sunspots, but by no means restricted
to these regions. Instead they are clearly a general feature in the
solar transition region, occurring in quiet as well as active regions.
---------------------------------------------------------
Title: LASCO - Large Angle Spectrometric Coronagraph for SOHO
Authors: Howard, R. A.; Brueckner, G. E.; Dere, K. P.; Korendyke,
C. M.; Koomen, M. J.; Michels, D. J.; Moses, D.; Socker, D. G.;
Schwenn, R.; Inhester, B.; Lamy, P.; Maucherat, A.; Simnett, G. M.;
Eyles, C.
1992AAS...180.3307H Altcode: 1992BAAS...24..781H
No abstract at ADS
---------------------------------------------------------
Title: The chromospheric and transition region manifestations of an
Ellerman bomb.
Authors: Cook, J. W.; Brueckner, G. E.; Dere, K. P.; Martin, S. F.;
Gayley, K. G.
1992BAAS...24.1074C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Diamond Based UV Detectors for Space Missions
Authors: Moses, D.; Marchywka, M.; Brueckner, G. E.; Socker, D. G.;
Hochedez, J. -F.
1991BAAS...23.1318M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparision of Solar Flare Emission Measures from Broadband
Soft X-Ray and Ultraviolet Spectrograph Observations
Authors: Waljeski, K.; Cook, J. W.; Moses, D.; Brueckner, G. E.
1991BAAS...23.1468W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Explosive events and magnetic reconnection in the solar
atmosphere
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Ewing,
J.; Lund, P.
1991JGR....96.9399D Altcode:
Explosive events are highly energetic, small-scale phenomena which are
frequently detected throughout the quiet and active Sun. They are seen
in profiles of spectral lines formed at transition zone temperatures
as exceptionally Doppler-shifted features, typically at 100 km
s<SUP>-1</SUP> to the red and/or blue of the rest wavelength. Sufficient
observational evidence has now been developed to demonstrate that some
explosive events are associated with the emergence of new magnetic
flux. In these cases it is likely that the acceleration of plasma is
caused by the magnetic reconnection resulting from flux emergence. We
take as a working hypothesis the proposal that all explosive events
are the result of magnetic reconnection. Since explosive events tend
to occur on the edges of high photospheric magnetic field regions,
we identify them with reconnection that occurs during the cancellation
of photospheric magnetic flux (Martin, 1984; Livi et al., 1985). The
combined observational characteristics of photospheric flux cancellation
and transition zone explosive events provide powerful diagnostic
information concerning the nature of magnetic reconnection. Reconnection
in the quiet solar atmosphere apparently proceeds in bursts at sites
much smaller than the boundary between opposite polarity flux elements
that are observed to cancel in magnetograph sequences. Equating the
velocity of the expelled transition zone plasma with the Alfvén speed
yields magnetic field strengths of 20 G at the site of reconnection. The
speed at which the reconnection proceeds is commensurate with the rapid
rates predicted by Petschek (1964). ©1991 American Geophysical Union
---------------------------------------------------------
Title: An Ultraviolet Spectral Atlas of a Sunspot and an Active
Region 1190--1730 Angstrom
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
1991ApJS...75.1337B Altcode:
An ultraviolet spectral atlas of a sunspot with high spectral
and spatial resolution in the wavelength region 1190-1730 A is
presented. The atlas contains spectra of three different areas in the
sunspot and also of an active region and a quiet region. The selected
areas are averaged over several arcsec, ranging from 3.5 arcsec in the
sunspot to 18 arcsec in the quiet region. Brief descriptions of the data
reduction and calibration procedures are given. The absolute intensities
are determined with an accuracy of + or - 30 percent and the wavelength
scale is accurate to better than 0.01 A. The transition region lines
show the most extreme example known of downflowing gas above a sunspot,
a phenomenon which seems to be commonly connected to sunspots.
---------------------------------------------------------
Title: The Prime Energy Release of a Solar Flare
Authors: Brueckner, G. E.; Moses, D.; Cook, J. W.; Dere, K. P.;
Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F.
1991BAAS...23.1026B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SUSIM: A Program to Measure Changes in the Sun's Ultraviolet
(UV) Spectral Irradiance over Solar Cycle Time Scales
Authors: Lean, J. L.; Vanhoosier, M. E.; Brueckner, G. E.
1991BAAS...23.1068L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Solar UV Continuum 1440 - 1680 Å
Authors: Kjeldseth-Moe, O.; Brekke, P.; Bartoe, J. -D. F.; Brueckner,
G. E.
1991BAAS...23.1060K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flaring Active Region Structures in the Corona, Transition
Region, and Lower Atmosphere Observed in the SAROC
Authors: Moses, D.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.;
Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F.
1991BAAS...23.1026M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Evidence of Fine Structure in the Solar Transition
Region
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
1991BAAS...23.1060B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multiple flow velocities in the transition region
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
1991AdSpR..11e.251B Altcode: 1991AdSpR..11..251B
Observations with the High Resolution Telescope and Spectrograph (HRTS)
of the C IV lines at 1550 Å above sunspots reveal the co-existence
of several distinct high velocity gas components within the instrument
resolution element of 1 × 1 arc second. A further investigation of the
HRTS material demonstrates that such multiple gas velocities are not
restricted to the temperature region around 10<SUP>5</SUP> K, where the
C IV lines are formed, but that the gas flows with essentially unchanged
speed through all temperature layers from 2.5 × 10<SUP>5</SUP> K
to 10<SUP>4</SUP> K. Furthermore the phenomenon is not restricted to
sunspots, but occurs also in other solar regions, often most easily
distinguished in active regions. We describe the characteristics of the
velocity fields, analyze the mass fluxes and discuss the requirements
they place on the resolving power of future space instruments.
---------------------------------------------------------
Title: Fine structure of the solar transition region: observations
and interpretation.
Authors: Cook, J. W.; Brueckner, G. E.
1991sia..book..996C Altcode:
The authors review recent observations of the solar transition region
and the temperature minimum obtained with high spatial resolution,
primarily ultraviolet spectra and spectroheliograms from sounding
rocket and Spacelab 2 flights of the High Resolution Telescope and
Spectrograph. Information on intensities, velocities, emission
measures and electron densities can be determined. The authors
discuss observational results and the implications of observed
fine structure for our ideas of the structure and physics of the
solar atmosphere. Inclusion of fine structure in our ideas about the
transition region affects the plausibility of one-dimensional average
models of the atmosphere, the determination of temperature gradients,
possible mechanisms for nonradiative heating, and the comparison
of transition region structures with corresponding high-resolution
observations from the photosphere and corona.
---------------------------------------------------------
Title: An Ultraviolet Spectral Atlas of a Prominence
Authors: Engvold, Oddbjorn; Hansteen, V.; Kjeldseth-Moe, O.; Brueckner,
G. E.
1990Ap&SS.170..179E Altcode:
The ultraviolet spectrum of a large prominence has been observed with
the High Resolution Telescope and Spectrograph (HRTS) on SPACELAB 2,
5 August, 1985. The spectrum covers the wavelength range λλ1335 1670
Å and shows numerous emission lines from gas at chromospheric and
transition region temperatures. An Atlas of the prominence spectrum
has been made showing absolute calibrated intensities on an accurate
wavelength scale. The Atlas includes for comparison the corresponding
UV-spectrum from an average quiet solar region.
---------------------------------------------------------
Title: Multiple downflow velocities above sunspotss
Authors: Brekke, P.; Kjeldseth-Moe, O.; Brueckner, G. E.
1990Ap&SS.170..135B Altcode:
Supersonic transition zone downflow appears to be commonly occurring
above sunspots. The downflow has been observed in 29 emission lines
in the ultra-violet spectrum with the High Resolution Telescope and
Spectrograph (HRTS) on two rocket flights and on 5 consecutive days
during the Spacelab-2 mission. Spectra from the second rocket flight,
contain the most extreme example of downflow, showing speeds up to 180
km s<SUP>-1</SUP> and extending over 60 are sec along the slit. The
observations demonstrate the existence of several different distinctive
flow speeds within the 1 arc sec resolution element throughout the
temperature range 7000 240 000 K.
---------------------------------------------------------
Title: Mass Transport above Sunspots
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Brueckner, G. E.
1990Ap&SS.170..149B Altcode:
Mass transport in the transition zone above a sunspot has been
studied in the Civ line at 1548 Å, formed at 100 000 K. Four spectral
rasters have been used, each covering 60×50 are sec. These have been
observed with the High Resolution Telescope and Spectrograph during
the Spacelab-2 mission in 1985. Flow velocities are derived from
multiple Gaussian components fitted to the observed line intensity
profiles. Density sensitive lines were used to find a relation between
the Civ line intensity and the particle density. This relation is used
in the mass flux calculations. The investigation indicates a clear
net downward mass flux above sunspots.
---------------------------------------------------------
Title: An Ultraviolet Spectral Atlas of a Sunspot and an Active
Region 1190-1730Å
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
1990BAAS...22..793B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The High Resolution Telescope and Spectrograph (HRTS) on
Board the Orbiting Solar Laboratory (OSL)
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Dere, K. P.; Socker,
D. G.
1990BAAS...22..845B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal Dark Lanes and the Location of Transition Region
Explosive Events
Authors: Moses, D.; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Davis, J. M.
1990BAAS...22..899M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Return of the Hard Solar Flares' 154 Day Periodicity in Solar
Cycle 22 and Evidence for a Phase Relationship of This Periodicity
between Cycles 21 and 22
Authors: Brueckner, G. E.; Cook, J. W.
1990ApJ...350L..21B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic energy conversion in the solar transition zone
Authors: Brueckner, G. E.
1990AdSpR..10i.161B Altcode: 1990AdSpR..10..161B
Newly emerging magnetic flux can be the energy source for the solar
corona and the solar wind. Plasma bulk motions and oscillations
are observed by means of UV spectroscopy at transition zone
(t.z.) temperatures (~ 20.000 K < T < 250,000 K). The particular
conditions in the transition zone plasma facilitate the conversion
of magnetic into kinetic energy: (1) The β-value in the transition
zone can change rapidly from β<<1 to β>>1. (2) Radiation
losses change rapidly with temperature to create instabilities. (3) The
small spatial filling factor (<0.01) indicates a highly filamented
plasma. Large fluctuations in density, magnetic field strength and
currents may facilitate fast reconnection. The areas of strong plasma
oscillations in the transition zone may be the origin of coronal
heating and particle acceleration.
---------------------------------------------------------
Title: Magnetic energy conversion. Proceedings. Symposium 13 of
the COSPAR 27. Plenary Meeting: Magnetic energy conversion, Espoo
(Finland), 18 - 29 Jul 1988.
Authors: Brueckner, G. E.; Somov, B. V.
1990AdSpR..10i....B Altcode: 1990AdSpR..10R....B
Contents: 1. Basic physical processes; stellar atmospheres and the
interstellar medium. 2. Magnetic energy conversion in the laboratory and
on the Sun. 3. Magnetic energy conversion in solar flares. 4. Magnetic
energy conversion in the terrestrial environment. 5. Magnetic energy
conversion on the Sun.
---------------------------------------------------------
Title: The Prominence/corona Transition Region Analyzed from SL-2 HRTS
Authors: Engvold, O.; Hansteen, V.; Kjeldseth-Moe, O.; Brueckner, G. E.
1990LNP...363..250E Altcode: 1990IAUCo.117..250E; 1990doqp.coll..250E
The ultraviolet spectrum of a large prominence has been observed with
the High Resolution Telescope and Spectrograph (HRTS) on Spacelab 2
August 5, 1985. The spectrum covers the wavelength range 1335-1670Å and
shows numerous emission lines from gas at chromospheric and transition
region temperatures. A spectral atlas of these data is available. The
data reveals a variation with height of the line intensities. The
prominence becomes hotter with height. A value of ~ 0.12 dyn cm-2 for
the gas pressure in the prominence-corona transition region is obtained
from line ratios. The resolved fine structure of the He II 1640.400Å
line indicates that a major part of this emission comes from cold gas. A
broad Fe XI 1467.080Å suggests high velocities in the coronal cavity
region. The Fe XI line in the cavity region is a factor ~ 5 less bright
in the normal corona at the same height. Assuming that the temperature
is the same in the two regions the present obervations suggest that
the pressure in the cavity region is lower by a similar factor.
---------------------------------------------------------
Title: Observed Line Profiles and Mass Fluxes in the Transition
Region above Sunspots
Authors: Maltby, P.; Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.;
Bartoe, J. -D. F.; Brueckner, G. E.
1990PDHO....7..244M Altcode: 1990dysu.conf..244M; 1990ESPM....6..244M
Spectrograms obtained with the HRTS show strong mass flows through
the transition zone that are particularly prominent above sunspot
regions. Most characteristic for the flow associated with sunspots
are regions with supersonic downflows, but upward flowing gas is
also observed with generally smaller velocities. The flow pattern
changes from one day to the next and even within a time span of
minutes. An apparent lack of balance between up- and downflowing
massfluxes is found. Generally the net massflux appears to be directed
downward. Possible reasons for this result are briefly discussed in
terms of observability and line emission area filling factor.
---------------------------------------------------------
Title: The Relationship of C IV Transition Region Structures to the
Photospheric Magnetic Field
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1990BAAS...22..744D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The energy source of the solar chromosphere, transition region
and corona.
Authors: Brueckner, G. E.
1990ppst.conf...23B Altcode:
New high resolution observations show that individual transition region
structures have dimensions of several thousand kilometers. Discrete,
Doppler shifted transition region elements called "explosive events"
exhibit superthermal velocities. The largest velocities can be found
above newly emerging magnetic flux. It is assumed, that magnetic
reconnection processes are causing the dynamics of the transition
region and are its energy source. Unique physical parameters in the
transition region make it the only layer of the solar atmosphere, where
reconnection is facilitated. It is proposed, that the corona becomes
a by-product of the reconnection heating of the transition region and
that the cooling transition region plasma forms the chromosphere. The
reconnection of newly emerging flux must be a universal process in
the solar atmosphere, which is responsible for all observed nonthermal
energy in the chromosphere, transition region and corona.
---------------------------------------------------------
Title: Transition Zone Flows Observed in a Coronal Hole on the
Solar Disk
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Recely, F.
1989ApJ...345L..95D Altcode:
A rocket flight of the NRL High Resolution Telescope and Spectrograph
(HRTS) was performed to obtain ultraviolet spectra of a well-defined
coronal hole on the solar system. Observed emission lines included
strong transition zone lines of C IV at 1548 and 1550 A, strong
chromospheric lines of C I near 1560 A, and chromospheric lines of Fe
(II) at 1563 A. Continuum radiation formed in the temperature minimum
was also recorded. The cumulative histogram of the C IV velocities in
the coronal hole shows an average Doppler shift of 2 km/sec to the red
(downflow) with 26 percent of the profiles having blueshifts (outflows)
compared to 7 percent in the quiet sun. The present observations have
the advantages of higher spatial resolution and a nearly absolute
wavelength scale determined from narrow chromospheric lines of Si I
with an accuracy of about 1 km/sec. The nonthermal velocities, derived
from the C IV line widths, are only marginally larger inside the coronal
hole than those in the quiet sun, thus indicating that the magnitude of
small-scale motions, which may represent energy available for coronal
heating and solar wind acceleration, is equal in the two regions.
---------------------------------------------------------
Title: Transition Region Massflows Associated with Sunspots
Authors: Kjeldseth-Moe, O.; Brekke, P.; Brynildsen, N.; Maltby, P.;
Brueckner, G. E.; Bartoe, J. -D. F.
1989BAAS...21.1178K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Report from solar physics
Authors: Walker, A. B. C.; Acton, L.; Brueckner, G.; Chupp, E. L.;
Hudson, H. S.; Roberts, W.
1989stss.work...31W Altcode:
A discussion of the nature of solar physics is followed by a brief
review of recent advances in the field. These advances include: the
first direct experimental confirmation of the central role played
by thermonuclear processes in stars; the discovery that the 5-minute
oscillations of the Sun are a global seismic phenomenon that can be
used as a probe of the structure and dynamical behavior of the solar
interior; the discovery that the solar magnetic field is subdivided into
individual flux tubes with field strength exceeding 1000 gauss. Also
covered was a science strategy for pure solar physics. Brief discussions
are given of solar-terrestrial physics, solar/stellar relationships,
and suggested space missions.
---------------------------------------------------------
Title: Correspondence between solar fine-scale structures in the
corona, transition region, and lower atmosphere from collaborative
observations
Authors: Moses, J. Daniel; Cook, J. W.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.; Webb, D. F.; Davis, John M.; Recely, F.; Martin,
S. F.; Zirin, H.
1989sxsr.reptR....M Altcode:
The Soft X-Ray Imaging Payload and the High Resolution Telescope and
Spectrograph (HRTS) instrument were launched from White Sands on 11
December 1987 in coordinated sounding rocket flights to investigate the
correspondence of coronal and transition region structures, especially
the relationship between X-ray bright points (XBPs) and transition
region small spatial scale energetic events. The coaligned data from
X-ray images are presented along with maps of sites of transition
region energetic events observed in C IV (100,000 K), HRTS 1600 A
spectroheliograms of the T<SUB>min</SUB> region and ground based
magnetogram and He I 10830 A images.
---------------------------------------------------------
Title: The High Resolution Telescope and Spectrograph (HRTS)
Experiment on the Orbiting Solar Laboratory (OSL) Mission
Authors: Brueckner, G. E.; Socker, D. G.
1989BAAS...21..832B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The HRTS Guest Investigator Program
Authors: Lund, P.; Ewing, J.; Cook, J.; Dere, K.; Brueckner, G.
1989BAAS...21..841L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of HRTS Sounding Rocket Observations at 1600 Å
and Hα with Groundbased Magnetograms and He I 10830 Å Images
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.
1989BAAS...21..840C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet Observations of Macrospicules at the Solar Limb
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.; Ewing, J. W.
1989SoPh..119...55D Altcode:
During the Spacelab 2 mission, the NRL High Resolution Telescope and
Spectrograph (HRTS) obtained a time-series of broad-band ultraviolet
images of macrospicules at the solar limb inside a polar coronal
hole with a temporal resolution of 20 and 60 s. The properties of the
macrospicules observed in the Spacelab data are measured and compared
with the properties reported for EUV macrospicules observed during
Skylab (Bohlin et al., 1975; Withbroe et al., 1976). There is a general
agreement between the data sets but several differences. Because of
the higher temporal resolution of the Spacelab data, it is possible
to see macrospicules with shorter lifetimes than seen during Skylab,
as well as variations on faster timescales. The largest (30-60') and
fastest (150 km s <SUP>-1</SUP>) macrospicules seen during Skylab were
not found in the Spacelab observations. The Spacelab data support the
conclusion that many macrospicules decay by simply fading away.
---------------------------------------------------------
Title: Explosive Events in the Solar Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1989SoPh..123...41D Altcode:
The properties of explosive events in the solar transition zone are
presented by means of detailed examples and statistical analyses. These
events are observed as regions of exceptionally high velocity (∼
100 km s<SUP>−1</SUP>) in profiles of CIV, formed at 10<SUP>5</SUP>
K, observed with the High Resolution Telescope and Spectrograph
(HRTS). The following average properties have been determined from
observations obtained during the third rocket flight of the HRTS: full
width at half maximum extent along the slit - 1.6 × 10<SUP>3</SUP> km;
maximum velocity - 110 km s<SUP>−1</SUP>; peak emission measure -
4 × 10<SUP>41</SUP> cm<SUP>−3</SUP>; lifetime - 60 s; birthrate -
4 × 10<SUP>−21</SUP> cm<SUP>−2</SUP> s<SUP>−1</SUP> in a coronal
hole and 1 × 10<SUP>−20</SUP> cm<SUP>−2</SUP> s<SUP>−1</SUP>
in the quiet Sun; mass - 6 × 10<SUP>8</SUP> g; and, kinetic energy - 6
× 10<SUP>22</SUP> erg. The 6 examples show that there are considerable
variations from these average parameters in individual events. Although
small, the events show considerable spatial structure and are not
point-like objects. A spatial separation is often detected between the
positions of the red and blue shifted components and consequently the
profile cannot be explained by turbulence alone. Mass motions in the
events appear to be isotropic because the maximum observed velocity
does not show any correlation with heliographic latitude. Apparent
motions of the 100 km s<SUP>−1</SUP> plasmas during their 60 s
lifetime should be detected but none are seen. The spatial frequency
of occurrence shows a maximum near latitudes of 40-50°, but otherwise
their sites seem to be randomly distributed. There is enough mass in
the explosive events that they could make a substantial contribution
to the solar wind. It is hard to explain the heating of typical quiet
structures by the release of energy in explosive events.
---------------------------------------------------------
Title: HRTS Transition Region Observations of a Coronal Hole on the
Solar Disk
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1989BAAS...21..841D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Intermediate-Term Solar Periodicities: 100--500 Days
Authors: Lean, J. L.; Brueckner, G. E.
1989ApJ...337..568L Altcode:
Periodogram analyses of time series of ground-based solar observations
during the past three solar cycles confirm that a periodicity near
155 days, originally detected in the occurrence rate of major solar
flares, is also present in the sunspot blocking function, the 10.7 cm
radio flux, and the sunspot number, but not in the plage index. This
indicates that the 155 day solar periodicity is not simply a feature
of flare activity alone and suggests that it is associated with those
regions on the sun where magnetic fields are concentrated into small
areas, such as in sunspots, but not where they are more dispersed,
as in plages. The periodogram of the sunspot blocking function, 10.7
cm radio flux, sunspot number, and plage index daily data during the
entire three-cycle time span each has a peak near 323 days, which
supports previous suggestions that this, too, may be a real solar
period. However, this period is a prominent feature only in solar
cycle 21.
---------------------------------------------------------
Title: Plasma Motions in an Emerging Flux Region
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D.; Kurokawa, H.; McCabe, M.
1988ApJ...335..986B Altcode:
Ultraviolet spectra of C IV show large nonthermal broadening in an
area of emerging flux. These nonthermal motions are observed at a very
early stage of reconnecting field lines. The spectra can be traced
to small, rapidly changing surge or filament-like features which
are seen in the center, blue, and red wing of H-alpha. They seem to
have the characteristics of macrospicules or explosive events. They
are precursors of the reconnection process. Plasma turbulence and/or
plasma waves in the reconnecting plasma may cause the broad C IV line
profiles. The activity in the transition zone precedes the formation
of a bright chromospheric loop system.
---------------------------------------------------------
Title: LASCO: A wide-field white light and spectrometric coronagraph
for SOHO
Authors: Michels, D. J.; Schwenn, R.; Howard, R. A.; Bartoe, J. -D. F.;
Antiochos, S. K.; Brueckner, G. E.; Cheng, C. -C.; Dere, K. P.;
Doschek, G. A.; Mariska, J. T.
1988sohi.rept...55M Altcode:
The scientific objectives of the LASCO (light and spectrometric
coronagraph) project in the SOHO (solar and heliospheric observatory)
mission are described. These include investigation of mechanisms
for heating of the corona and acceleration of the solar wind, causes
of coronal transients, and their role in development of large scale
coronal patterns and interplanetary disturbances. The distribution
and properties of dust particles, including those released from
sun-grazing comets are investigated. Interactions of coronal plasma
with the dust are studied. The corona is analyzed spectroscopically
by a high-resolution scanning, imaging interferometer. The spectral
profiles of three emission lines and one Fraunhofer line are measured
for each picture point, giving temperatures, velocities, turbulent
motions and volume densities. Polarization analysis yields the direction
of coronal magnetic fields.
---------------------------------------------------------
Title: Gas Flows in the Transition Region above Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.;
Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1988ApJ...334.1066K Altcode:
Strong downflows and moderate upflows in the transition region over
a sunspot have been observed with the HRTS on Spacelab 2 in 1985. The
flows are persistent in the sense that they are seen in the same spot
for 5 days. The downflows are prominent in regions of limited extent
(4arcsec - 6arcsec), and flow velocities are in the range 40 - 80 km
s<SUP>-1</SUP> and are thus supersonic. Upward flows have smaller
velocities, 5 - 20 km s<SUP>-1</SUP>, but may extend over a larger
area. In the downflowing regions there is always an appreciable amount
of gas at rest in the line of sight. Flow speeds derived from the
profiles of different lines formed in the transition region between
30,000 and 230,000K are very similar implying constant downflow in
this temperature range.
---------------------------------------------------------
Title: The Correspondence Between Fine-Scale Structures in the Solar
Corona and Transition Region
Authors: Moses, J. D.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Dere, K. P.; Davis, J. M.; Webb, D.
1988BAAS...20..722M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Correlation of Transition Region C IV High-Velocity Events
With Magnetogram and He I 10830 Å Data
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere,
K. P.; Recely, F.; Martin, S.; Zirin, H.
1988BAAS...20..722C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from the High Resolution Telescope and Spectrograph
(HRTS) Experiment on Board Spacelab 2
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1988ApL&C..27..151B Altcode:
Several papers including reviews have been published during different
stages of the data analysis after the SL-2 flight. In order to avoid
repetition, this article lists all publications and briefly mentions
some of the highlights.
---------------------------------------------------------
Title: Discrete Subresolution Structures in the Solar Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.
1987SoPh..114..223D Altcode:
During operations on the Spacelab-2 Shuttle mission, the NRL High
Resolution Telescope and Spectrograph (HRTS) recorded spectra of a
variety of solar features in the 1200-1700 Å wavelength region which
contains spectral lines and continua well suited for investigating
the temperature minimum, the chromosphere and transition zone. These
data show that, at the highest spatial resolution, the transition zone
spectra are broken up from a continuous intensity distribution along
the slit into discrete emission elements. The average dimensions
of these discrete transition zone structures is 2400 km along the
slit, but an analysis of their emission measures and densities shows
that the dimensions of the actual emitting volume is conciderably
less. If these structures are modelled as an ensemble of subresolution
filaments, we find that these filaments have typical radii of from
3 to 30 km and that the cross-sectional fill factor is in the range
from 10<SUP>−5</SUP> to 10<SUP>−2</SUP>. The transport of mass
and energy through these transition zone structures is reduced by
this same factor of 10<SUP>−5</SUP> to 10<SUP>−2</SUP> which has
significant consequences for our understanding of the dynamics of the
solar atmosphere. Because the HRTS transition zone line profiles are
not broadened by resolved large-spatial-scale solar velocity fields,
the line widths of the CIV lines have been analyzed. The average line
width is 0.195 Å (FWHM) and requires an average nonthermal velocity
of 16 km s<SUP>−1</SUP> (most-probable) or 19 km s<SUP>−1</SUP>
(root-mean-square) which is lower than previously observed values.
---------------------------------------------------------
Title: Emerging flux, magnetic reconnection, plasma turbulence and
waves in the transition zone of the solar atmosphere.
Authors: Brueckner, G. E.
1987ESASP.275...95B Altcode: 1987sspp.symp...95B
Ultraviolet spectroscopy of the solar transition zone, especially
Spacelab 2 results, is reviewed. Emerging magnetic flux is considered as
the energy source of the solar corona and the solar wind. The conversion
of magnetic into kinetic energy is facilitated in the transition zone
because of unique conditions. Radiation losses are sufficient to create
fast instabilities. Observed nonthermal velocities in spectra of the
transition zone indicate the existence of strong plasma oscillations and
turbulence. The small filling factor of the transition zone indicates
a highly filamentary structure of density, magnetic field strength,
and currents, which results in rapid reconnection time scales. Particle
acceleration and the heating of the corona are placed in the areas of
strong plasma oscillations of the transition zone.
---------------------------------------------------------
Title: Observations and modelling of the prominence/corona transition
region.
Authors: Engvold, O.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
1987ESASP.275...21E Altcode: 1987sspp.symp...21E
The construction of inhomogeneous temperature transition region
models for solar prominences is considered. Models based on UV line
intensities from SO82B on Apollo Telescope Mount (ATM)/Skylab and the
High Resolution Telescope and Spectrograph (HRTS) on Spacelab 2 are
derived. The modeled structures of the transition region are in the
form of thin tubes, similar to the prominence structures seen in the
cool core. An expression for the thickness of the transition region
around prominences is given, and mechanisms for energy transport are
discussed. Uncertainties and possible improvements in the modeling
are pointed out.
---------------------------------------------------------
Title: Ultraviolet Rocket-Spectra of a Sunspot
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
1987ESASP.270..341B Altcode: 1987erbp.symp..341B
Downflows in the transition zone above a sunspot were observed with
a high resolution telescope and spectrograph on a rocket. The rocket
spectra on photographic film were digitized. Noise caused by film grains
was removed by Fourier filtering. The spectral images were corrected
for geometrical distortions and calibrated to give the solar intensity
as a function of wavelength. Maximum speeds of 200 km/sec are reached
in the flows which extend over 60 arc-sec along the slit. Components
with distinct, but lower velocities also appear. The variations with
temperature of the characteristic flow speeds are studied.
---------------------------------------------------------
Title: Gasflows in the transition region above sunspots.
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Bartoe,
J. -D. F.; Brueckner, G. E.
1987ESASP.275...27K Altcode: 1987sspp.symp...27K
Gas flows in the transition region in and above sunspots were observed
with the High Resolution Telescope and Spectrograph on two rocket
flights and during the Spacelab 2 mission. Supersonic downflows of
mass from the corona appear to be generally occurring in sunspots. The
downflows are often concentrated in regions with typical diameters of
4000 km on the Sun, suggesting a flow in a looplike structure. However,
the total flow pattern often has an elongated sheetlike structure
of much larger extent. Flow speeds are typically 80 km/sec and show
small variation with the temperature of the radiating gas. Much higher
flow-speeds (180 km/sec) also occur. Studies of the areas surrounding
the sunspot in the Spacelab material reveal the presence of upflows over
extended regions with flow-speeds of 10 to 30 km/sec. It is not clear
whether the amount of upward flowing gas is sufficient to compensate
for the mass flux in the downflows.
---------------------------------------------------------
Title: Magnetic Reconnection in the Solar Transition Zone
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dare,
K. P.; Socker, D. G.
1987BAAS...19..942B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transition Zone Flow Patterns in Sunspots
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.
1987BAAS...19..639D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transition Zone Flows in Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Engvold, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
1987rfsm.conf..317K Altcode:
Downflow in the transition region over sunspots first detected on HRTS
rocket flights, seems to be a general phenomenon. Although details
in the flow pattern appear to change over a period of minutes, the
phenomenon itself persists for days. While the mechanism producing the
observed redshifts is not understood it seems most likely that they are
produced by actual downflow of gas in thin filamentary structures. This
may be inferred from the co-existence within the same spatial resolution
element of tubes with strong downflows and tubes where the gas is at
rest. Thus the line profiles result from an unresolved fine structure
in a similar fashion that Evershed effect in the photosphere produces
"flag"-like line profiles in visual lines.
---------------------------------------------------------
Title: Statistical Properties of Small High-Velocity Events in the
Solar Transition Region
Authors: Cook, J. W.; Lund, P. A.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.; Socker, D. G.
1987LNP...291..150C Altcode: 1987csss....5..150C
We discuss the energy contribution of small high-velocity events
observed in the solar transition region to atmospheric heating. These
events do not directly provide enough energy to heat the atmosphere,
but are instead after-products of turbulent energy dissipation at the
sites of the actual primary nonthermal heating process.
---------------------------------------------------------
Title: Identification of [Fe III] in the solar ultraviolet spectrum
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.
1986Natur.324..444J Altcode:
Solar ultraviolet spectra have been obtained with high spectral and
spatial resolution using the Naval Research Laboratory's high-resolution
telescope and spectrograph<SUP>1</SUP> (HRTS) flown on rockets since
1975 and most recently on the Spacelab 2 Shuttle flight. Because the
solar spectrum between ~1,170 and 1,719 Å has been well observed for
some years, few lines of substantial intensity remain unidentified. (See
for example the recent compilation by Sandlin et al.<SUP>2</SUP>). The
longest exposures during the first rocket flight of the HRTS, which
obtained spectra with a spatial resolution of ~ 1 arc s along the slit,
of length ~ 1 solar radius, and a spectral resolution of ~0.05 Å,
showed a number of weak emission lines at the solar limb, in particular
between 1,570 and 1,600 Å (see Plates 16 and 17 in ref. 3), that could
not readily be identified. Improved observations of these lines were
obtained during the flight of HRTS on the Spacelab 2 Shuttle flight in
July-August 1985, by making longer exposures (60,100 and 250 s). The
scope of the data obtained has been described<SUP>4</SUP>. We have
now identified the emission lines concerned as forbidden (electric
quadrupole and magnetic dipole) transitions in Fe III, the first
detection of these particular transitions in any source. They must now
be considered potential candidates for previously unidentified lines in
other low-density (N<SUB>e</SUB> <~ 10<SUP>10</SUP> cm<SUP>-3</SUP>)
astrophysical sources.
---------------------------------------------------------
Title: Outflows and Ejections in the Solar Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1986ApJ...310..456D Altcode:
Time series images of C IV transition zone intensities and velocities
are analyzed to study the uncommon patterns of blueshifted emission. The
images are constructed from stigmatic spectra obtained during the third
flight of the NRL High Resolution Telescope and Spectrograph. A sample
of 11 blueshifted events with near-Gaussian profiles are analyzed. Of
these 11 cases, three are expulsions of material from the network, two
are spicular flows, one is a simple jet, another is associated with
a filament, and four are unexplained. It is not possible to identify
a simple mechanism whereby upflows return to form the predominant
downflows observed in the transition zone, and the upward mass flux
is three orders of magnitude lower than the downward mass flux.
---------------------------------------------------------
Title: Observation of the Density Sensitive Line Mg V 1324 Å in a
Solar Sunspot
Authors: Cook, J. W.; Socker, D. G.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.
1986BAAS...18R.991C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The High-Resolution Solar Spectrum, 1175--1710 Angstrom
Authors: Sandlin, G. D.; Bartoe, J. -D. F.; Brueckner, G. E.; Tousey,
R.; Vanhoosier, M. E.
1986ApJS...61..801S Altcode:
A compendium of new ultraviolet data on specific solar features
observed at high spatial and spectral resolution has been prepared
from the 1175-1710 A spectra of the High Resolution Telescope and
Spectrograph and the Skylab Apollo Telescope Mount. The observations
have included a sunspot, plages, flares, quiet regions, coronal holes,
and the limb. Rest wavelengths with uncertainties from + or - 0.005
to + or - 0.04 A, have been determined from averages of disk, limb,
and off-limb spectra for 3250 lines. Absolute intensities for lines
and continuum, as well as half-widths, are presented for a plage,
a sunspot umbra, a supergranular cell center in a quiet region, and
the limb. A variety of identification techniques, including visual
spectral signatures, has been used to classify spectral lines of atoms,
ions, and molecules. New identifications include an extension of the
nf series of Ca II and 80 additional lines of H2.
---------------------------------------------------------
Title: Culgoora Radio and SKYLAB Extreme Ultraviolet Observations
of Emerging Magnetic Flux in the Lower Corona
Authors: Stewart, R. T.; Brueckner, G. E.; Dere, K. P.
1986SoPh..106..107S Altcode:
Detailed comparisons of Culgoora 160 MHz radioheliograms of solar noise
storms and Skylab EUV spectroheliograms of coronal loop structures
are presented. It is concluded that: (1) there is a close association
between changes in large-scale magnetic fields in the corona and
the onset or cessation of noise storms; (2) these coronal changes
result from the emergence of new magnetic flux at the photospheric
level; (3) although new magnetic flux at the photospheric level is
often accompanied by an increase in flare activity the latter is
not directly responsible for noise storm activity; rather the new
magnetic flux diffuses slowly outwards through the corona at rates
∼1-2 km s<SUP>−1</SUP> and produces noise storms at 160 MHz 1-2
days later; (4) the coronal density above or in large-scale EUV loop
systems is sufficiently dense to account for noise storm emission
at the fundamental plasma frequency; (5) the scatter in noise storm
positions can be accounted for by the appearance and disappearance of
individual loops in a system.
---------------------------------------------------------
Title: High-Resolution Telescope and Spectrograph Images of the
Solar Chromosphere and Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1986ApJ...305..947D Altcode:
Observations of a 10-arcsec-wide 800-arcsec-long region of the
southern solar hemisphere, obtained at 150-160 nm by the rocket-borne
High-Resolution Telescope and Spectrograph on March 1, 1979, are
reported and analyzed. Rastered stigmatic spectra are reduced to create
color images of intensity, Doppler shift, and line width providing
information on the UV structure of the solar atmosphere. Characteristics
discussed include temperature stratification in quiet-sun network
elements; chromospheric jets appearing at supergranular cell centers;
general redshift of 5 km/s in quiet-sun C IV; downflow patterns in C
IV, Fe II, and C I; plage structures with temperature stratification
and 6-km/s C IV downflow; and faint filament emission with blueshifts
near the top and redshifts at the sides in the C IV images.
---------------------------------------------------------
Title: Discrete Components of Solar Transition Zone Emission
Authors: Dere, K. P.; Brueckner, G. E.; Bartoe, J. -D. F.; Cook,
J. W.; Socker, D. G.
1986BAAS...18Q.662D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from the Solar Ultraviolet Spectral Irradiance Monitor
Flown on Spacelab 2
Authors: Vanhoosier, M. E.; Bartoe, J. -D. F.; Brueckner, G. E.;
Prinz, D. K.
1986BAAS...18..675V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Statistical Properties of Small High-Velocity Transition
Region Events on the Sun Observed by HRTS on Spacelab 2
Authors: Cook, J. W.; Lund, P. A.; Brueckner, G. E.; Bartoe, J. -D. F.;
Dere, K. P.; Socker, D. G.
1986BAAS...18..662C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from the High Resolution Telescope and Spectrograph
(HRTS) Experiment
Authors: Brueckner, G. E.; Cook, J. W.; Dere, K. P.
1986BAAS...18..675B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Spacelab 2 Observations of the Temporal Development of
the C IV Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Lund, P.; Socker, D. G.
1986BAAS...18..633D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS results from spacelab 2
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1986AdSpR...6h.263B Altcode: 1986AdSpR...6..263B
The HRTS instrument flew on the Spacelab 2 mission from 29 July -
6 August 1985. HRTS consisted of a 30 cm Gregorian telescope, a slit
spectrograph covering the 1190-1680 Å region with 0.05 Å spectral
resolution, a broadband (90 Å FWHM) spectroheliograph tuned to 1550
Å, and an H-alpha filter system. The spectrograph slit was 920 arc
sec, approximately 1 R<SUB>0</SUB>, in length. Sub arc second spatial
resolution along the slit is possible, but because of jitter in the
Spacelab Instrument Pointing System (IPS) good exposures actually
achieved 1-2 arc sec resolution. We describe the scientific results
from HRTS.
---------------------------------------------------------
Title: Results from the NRL instruments on Spacelab 2
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Morrison, M. D.
1986aiaa.meetZ....B Altcode:
The instrumental features of the high resolution Telescope and
spectrograph (HRTS) and the solar UV spectral irradiance monitor
(SUSIM) used for solar observations on the Spacelab 1 mission are
described. The HRTS has three focal plane instruments receiving light
from a 30 cm aperture furnishing at 15 X 15 arcmin FOV which can
be modified for slit photography and raster scans. The focal plane
instruments are a spectrograph, spectroheliograph and a television
camera and photographic film fronted by a mica Fabry-Perot filter. About
13 hr of solar observations were made with the HRTS during the 8
day mission. Sample spectral and photographic data are provided and
discussed. SUSIM is an UV spectrometer with redundant optical paths for
in-flight calibration with a D2 lamp. It is sensitive in the 1200-4000
A range. Several wavelength ranges are evaluated. Particular attention
is given to multitemporal Ly-alpha recordings.
---------------------------------------------------------
Title: HRTS Spacelab 2 Observations of Spicular Emission at the
Solar Limb
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere,
K. P.; Socker, D. G.
1985BAAS...17..834C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time Series Images of the UV Chromosphere and Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1985BAAS...17..630D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The energy balance in the solar chromosphere-corona transition
zone.
Authors: Moe, O. K.; Andreassen, T.; Andreassen, O.; Maltby, P.;
Bartoe, J. D. F.; Brueckner, G. E.
1985ESASP.229..145M Altcode: 1985ESASP.229..145K; 1985erbp.symp..145M
The significance of high resolution studies of the solar chromosphere
and transition zone in order to understand the transport of energy and
momentum to the corona is pointed out. The various terms of the energy
equation are discussed in relation to observable quantities such as UV
line intensities and wavelength shifts. Finally an example is given
of an observation of the fine structure of the transition zone in an
active region using the best solar UV instrument presently available,
the "High Resolution Telescope and Spectrograph" - HRTS - constructed
at the US Naval Research Laboratory.
---------------------------------------------------------
Title: High-resolution telescope and spectrograph observations of
the quiet solar chromosphere and transition zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1984ApJ...281..870D Altcode:
A systematic program to observe the two-dimensional structure of the
solar atmosphere and its temporal variation was conducted in connection
with the third rocket flight of the High Resolution Telescope and
Spectrograph (HRTS). A description is presented of the manner in which
line intensities, Doppler shifts (velocities), and line widths are
obtained from HRTS spectra. These quantities are derived for a single
stigmatic slit spectra of the quiet sun. It is pointed out that an
accurate wavelength scale can be derived from narrow Si I lines in
the spectra. The intensity of chromospheric lines such as C I lambda
1560 is found to be largely the result of the structures forming the
chromospheric network. A number of conclusions are drawn about quiet
transition zone Doppler shifts (flows).
---------------------------------------------------------
Title: HRTS II EUV observations of a solar ephemeral region
Authors: Roussel-Dupre, R.; Wrathall, J.; Nicolas, K. R.; Bartoe,
J. D. F.; Brueckner, G. E.
1984ApJ...278..428R Altcode:
HRTS II has been used to observe the EUV emission of a small bipolar
magnetic feature or ephemeral region, where strong EUV line enhancement
exhibits contrasts (measured relative to the quiet sun) which range
from 10 to 70. The substantiality of the Lyman-alpha and C II-O
V emission, and the absence of any measurable emission in coronal
forbidden lines, sets a temperature range for the loop's active part
of the order of 16,000-300,000 K. The use of the ratios of allowed
lines as temperature diagnostics yields temperatures that are very
near ionization equilibrium temperatures, and the use of chromospheric
lines to form a wavelength standard yields absolute velocities ranging
in magnitude from zero to 12 km/sec for C IV, N IV, and O V. This flow
is interpreted as a siphon flow.
---------------------------------------------------------
Title: HRTS observations of spicular emission at transition region
temperatures above the solar limb
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.; Socker,
D. G.
1984AdSpR...4h..59C Altcode: 1984AdSpR...4...59C
Slit spectra and spectroheliograph observations were obtained
during the fourth rocket flight of the High Resolution Telescope
and Spectrograph (HRTS) on 7 March 1983. A curved slit 900 arc sec
in length was placed at the solar limb on the western edge of the
south polar coronal hole, giving both coronal hole and quiet region
coverage. In addition, spectroheliograph images tuned to cover a
passband around 1550 Å (primarily C IV at 10<SUP>5</SUP> K) were
taken over an 8 × 15 arc min field. Simultaneous Hα images were
obtained at Sac Peak Observatory. The C IV spectroheliograms show
general spiked emission above the limb, and also several small loo-
or prominence-like events. Slit spectra along the tops of several of
these structures show tilted features which could be interpreted as
rotational velocities of approximately 50 km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: HRTS Ultraviolet Images of the Solar Chromosphere and
Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1984LNP...193..180D Altcode: 1984csss....3..180D
No abstract at ADS
---------------------------------------------------------
Title: The chromosphere-corona transition zone above an active region
Authors: Kjeldseth-Moe, O. .; Andreassen, O.; Maltby, P.; Bartoe,
J. -D. F.; Brueckner, G. E.; Nicolas, K. R.
1984AdSpR...4h..63K Altcode: 1984AdSpR...4...63K
Intensities and profiles of ion emission lines between 1170 A and 1700
A from an active region on the Sun are measured from spectra obtained
with the Naval Research Laboratory's High Resolution Telescope and
Spectrograph - HRTS. The measurements provide simultaneous determination
of line intensities, wavelength shifts and Doppler widths at 50 separate
positions in the active region, with spatial resolution of 1 arc second
and spectral resolution 0.07 A. Fine structure variation of intensities
and gas flow velocities in the temperature range 20,000-200,000 K
are determined. The density sensitive line pair I(1486 N IV)/I(1548
C IV) has been used to measure electron pressures. Derived emission
measures imply filling factors of 0.05-0.1 to balance the divergence
of conductive flux width radiative losses above 60,000 K.
---------------------------------------------------------
Title: Non-radio observations of fast fluctuations.
Authors: Brueckner, G. E.
1984ost1.conf...87B Altcode:
High spatial (≡1arcsec) resolution spectroscopic observations of the
transition zone plasma (≡100,000K) reveal high energetic events in
the quiet sun which show very fast fluctuations. These phenomena fall
into two categories: (1) explosive events, and (2) jets.
---------------------------------------------------------
Title: HRTS Evidence for Rotation of Transition Region Temperature
Spicules
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.; Socker,
D. G.
1984uxsa.coll...32C Altcode: 1984uxsa.conf...32C; 1984IAUCo..86...32C
No abstract at ADS
---------------------------------------------------------
Title: Observations of high-energy jets in the corona above the quiet
sun, the heating of the corona, and the acceleration of the solar wind
Authors: Brueckner, G. E.; Bartoe, J. -D. F.
1983ApJ...272..329B Altcode:
High spatial resolution observations of the ultraviolet solar spectrum
which reveal high-energy events in the quiet sun are presented. The
tandem Wadsworth spectrograph used to make the observations is described
along with the observing techniques, and a brief description of the
characteristics of high-resolution transition zone spectra is given. The
sizes, velocities, line profiles, time behavior, temperature range,
differential emission measures, densities, masses, energies, and
birthrates of turbulent events and jets in the quiet sun are derived
from the observations and discussed. Possible accelerating mechanisms
for these events are discussed, and the consequences of these events
for the heating of the solar corona are discussed. A cloud model of the
solar wind is proposed and possible correlations between the high-energy
events and other solar fine-structure features are discussed.
---------------------------------------------------------
Title: A Comparison of High Energy Events in the Quiet Sun with
Solar Flares
Authors: Brueckner, G. E.
1983SoPh...86..259B Altcode:
Observations of high-speed coronal clouds (OSO-7), flare ejecta (Skylab)
and high-energy jets (HRTS) are compared. It is possible that the same
physical mechanism - an expanding loop - which is responsible for the
high speed jets (400 km sec<SUP>−1</SUP>, 2.5 × 10<SUP>26</SUP>
ergs) can also account for the high-speed coronal clouds (1300 km
sec<SUP>−1</SUP>, 4 × 10<SUP>30</SUP> ergs), which were correlated
with a flare-connected spray. Field strength of 15 gauss and 2500
gauss are required for the jets and the sprays, respectively.
---------------------------------------------------------
Title: High resolution telescope and spectrograph observations of
solar fine structure in the 1600 A region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1983ApJ...270L..89C Altcode:
High spatial resolution spectroheliograms of the 1600 A region obtained
during the HRTS rocket flight of 1978 February 13 are presented. The
morphology, fine structure, and temporal behavior of emission bright
points (BPs) in active and quiet regions are illustrated. In quiet
regions, network elements persist as morphological units, although
individual BPs may vary in intensity while usually lasting the flight
duration. In cell centers, the BPs are highly variable on a 1 minute
time scale. BPs in plages remain more constant in brightness over
the observing sequence. BPs cover less than 4 percent of the quiet
surface. The lifetime and degree of packing of BPs vary with the local
strength of the magnetic field.
---------------------------------------------------------
Title: TYPE-1 Noise Storms and the Structure of the Extreme
Ultraviolet Corona
Authors: Brueckner, G. E.
1983SoPh...85..243B Altcode:
The spatial fine structure of the solar corona as observed in the EUV
line FeXV is compared with the occurrence of major type I metric noise
storms. In all cases, strong changes in the loop structure of the corona
are observed. On the disk, these coronal changes are correlated to the
emergence of new magnetic flux in the vicinity of existing large active
regions. The reverse is demonstrated: during noise storm free periods
no coronal changes can be observed. Noise storms at the limb seem to
originate in open field configurations over active regions. In all
cases, reconnection of coronal magnetic fields over large distances
are the cause of noise storms rather than changes of magnetic fields
within an active region. Noise storms disappear or are weak at the
limb because of foreground absorption in chains of active regions. The
observed intensities of active region loops at the limb show that a
density of 1.3 × 10<SUP>9</SUP> cm<SUP>−3</SUP> which corresponds to
a plasma frequency of 100 MHz can occur over a wide variety of altitudes
because active region loops are not in hydrostatic equilibrium.
---------------------------------------------------------
Title: Chromospheric jets - Possible extreme-ultraviolet observations
of spicules
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1983ApJ...267L..65D Altcode:
Stigmatic EUV spectra of chromospheric lines obtained by the Naval
Research Laboratory High Resolution Telescope and Spectrograph (HRTS)
show small arc second regions with strong (10-20 km/s) Doppler shifts
which are called 'chromospheric jets'. Because of the strong resemblance
of their physical and statistical properties, such as temperature,
density, velocity, size, and birthrate, to those of visible light
spicules, it is highly likely that they are different manifestations
of the same phenomena, although a one-to-one identification has not yet
been made. The main difference is the 40 s lifetime of the chromospheric
jets which is shorter than the 5 minute lifetime of visible light
spicules. The chromospheric jets are found in the supergranular cell
interiors where chromospheric and transition zone line intensities
are weak. Dark H-alpha mottles found in the cell boundaries are well
correlated with intense, symmetric chromospheric EUV line profiles
and are only weakly related to the chromospheric jets.
---------------------------------------------------------
Title: HRTS II EUV Observations of the Lyman α Wing and Transition
Zone Lines of C-IV and O-V
Authors: Roussel-Dupre, R.; Roussel-Dupre, D.; Nicolas, K. R.; Bartoe,
J. D. F.; Brueckner, G. E.
1983BAAS...15R.643R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Images of the Quiet Solar Chromosphere and Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1983BAAS...15..702D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Observations of a Coronal Hole and Quiet Region at the
Solar Limb
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Socker,
D. G.
1983BAAS...15..703B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Type I noise storms and the structure of the extreme
ultraviolet corona.
Authors: Brueckner, G. E.
1983srs..work..255B Altcode:
The spatial fine structure of the solar corona as observed in the EUV
line Fe XV is compared with the occurrence of major type I metric noise
storms. In all cases, strong changes in the loop structure of the corona
are observed. On the disk, these coronal changes are correlated to
the emergence of new magnetic flux in the vicinity of existing large
active regions. Noise storms at the limb seem to originate in open
field configurations over active regions. In all cases, reconnection
of coronal magnetic fields over large distances are the cause of noise
storms rather than changes of magnetic fields within an active region.
---------------------------------------------------------
Title: High Resolution Extreme Ultraviolet Structure of the
Chromosphere Corona Transition Region above a Sunspot
Authors: Nicolas, K. R.; Bartoe, J. -D. F.; Brueckner, G. E.;
Kjeldseth-Moe, O.
1982SoPh...81..253N Altcode:
Ion emission line intensities between 1170 and 1700 Å allow one
to determine the differential emission measure (DEM) and electron
pressure of the plasma in the solar transition region (TR). These
line intensities together with their Doppler shifts and line widths
are measured simultaneously for the first time above a sunsport from
data obtained with the NRL High Resolution Telescope and Spectrograph
with 0.06 Å spectral and 1″ spatial resolution.
---------------------------------------------------------
Title: The dynamics of accelerating coronal bullets
Authors: Karpen, J. T.; Oran, E. S.; Mariska, J. T.; Boris, J. P.;
Brueckner, G. E.
1982ApJ...261..375K Altcode:
Results are presented of computer simulations of the jets
that accelerate through the corona at velocities of 50 to 400
km/s. Particular emphasis is placed on the sensitivity of the induced
acceleration to the form in which energy is put into the system. A
comparison is made between the observed and predicted physical
characteristics of the high-velocity bullets; the potential contribution
of the bullets to the mass and energy balance of the solar corona is
considered. It is found that the velocity and temperature evolution
of the bullets can be modeled successfully by assuming energy input
in the form of an external force, pushing continuously on the ejected
material. From the physical characteristics of the model bullets and the
energy input required to reproduce the observations, it is concluded
that the bullets may constitute a significant fraction of the coronal
mass flux but only a negligible component of the coronal energy budget.
---------------------------------------------------------
Title: Temporal Behavior of Quiet Sun Emission in the T<SUB>min</SUB>
Region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1982BAAS...14..938C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of Extreme Ultraviolet Spicules
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1982BAAS...14..939D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar transition zone pressures from EUV observations of O
IV and N IV
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1982ApJ...259..366D Altcode:
NRL High Resolution Telescope and Spectrograph observations of the O
IV and N IV EUV lines emitted from the Sun are examined. The instrument
provides stigmatic spectra with a spatial resolution of 1 arcsec and a
spectral resolution of 0.05 A in the range 1170-1710 A. Intensity ratios
of the intersystem lines of O IV near 1400 A are used as the primary
diagnostic to measure electron pressures in a sunspot and plage. These
ratios are strongly sensitive to electron pressure but are insensitive
to the temperature structure of the emitting plasma. Average electron
pressures of 9 x 10 to the 15th per cu cm K (1.2 dyn/sq cm) in a plage,
4 x 10 to the 15th per cu cm K (0.6 dyn/sq cm) in a sunspot and 2.2 x 10
to the 15th per cu cm K (0.3 dyn/sq cm) in high speed sunspot downflows
are found. The ratio of I(Nv) + I(C IV) to I(N IV 1486A) is shown to
be relatively insensitive to temperature and gives pressures consistent
with those obtained from the O IV ratio. It is demonstrated that ratios
of allowed lines such as C IV and Si IV to the O IV intersystem lines
are temperature sensitive and hence are unreliable pressure diagnostics.
---------------------------------------------------------
Title: Science on the Space Shuttle
Authors: Neupert, W. M.; Banks, P. M.; Brueckner, G. E.; Chipman,
E. G.; Cowles, J.; McDonnell, J. A. M.; Novick, R.; Ollendorf, S.;
Shawhan, S. D.; Triolo, J. J.; Weinberg, J. L.
1982Natur.296..193N Altcode:
On the Space Shuttle's third flight, scientific instruments will
study the electromagnetic environment with charging and electron
beams. Beam plasma discharge will be studied. The plasma diagnostics
package contains electromagnetic and particle sensors to study the
ionosphere. An attempt will be made to establish a more accurate base of
solar UV irradiance measurements with an absolute error of 10 percent
or less over the wavelength region 120-400 nm. The solar flare X-ray
polarimeter will observe flare X-rays emitted between 5 and 30 keV and
measure their polarization as a function of time and photon energy. A
photopolarimeter will help study zodiacal light, and interplanetary
dust will be sampled by a section of thick aluminum foil. Plant
seedlings will be grown to research the effect of near-zero gravity
on lignification. A thermal canister experiment will help determine
whether instruments can be maintained at a fixed temperature under
varying thermal loads.
---------------------------------------------------------
Title: Solar radiometry: Spectral irradiance measurements
Authors: Brueckner, G. E.
1982AdSpR...2d.177B Altcode: 1982AdSpR...2..177B
The present measurement accuracy of the solar spectral irradiance
is insufficient to derive the real long-term solar spectral
irradiance variability at all wavelengths. Possible error sources
are discussed. A series of new second generation solar irradiance
photometers are now under construction which should considerably improve
these measurements. At the same time, efforts are made to improve the
absolute UV calibration methods to derive a unified UV radiation scale.
---------------------------------------------------------
Title: Solar Physics Branch, E. O. Hulburt Center for Space Research,
Naval Research Laboratory, Washington, D.C. 20375. Report for the
period 1 January 1980 - 30 September 1981.
Authors: Brueckner, G. E.
1982BAAS...14..411B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Type I noise storms and the structure of the extreme
ultraviolet corona
Authors: Brueckner, G. E.
1982srs..work..255B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High-Resolution Ultraviolet Solar Observations from Sounding
Rockets and Spacelab
Authors: Brueckner, G. E.
1981SSRv...29..407B Altcode:
High spatial (∼1″) and temporal (20 s) resolution UV spectroscopy
of the Sun has been carried out with a new instrument flown on sounding
rockets. These observations reveal a multitude of new highly energetic
phenomena in the outer solar atmosphere which may play a decisive rôle
in the mechanical energy balance of the chromosphere, transition zone
and corona.
---------------------------------------------------------
Title: A high precision Solar Ultraviolet Spectral Irradiance Monitor
for the wavelength region 120 400 nm
Authors: Vanhoosier, M. E.; Bartoe, J. -D. F.; Brueckner, G. E.;
Prinz, D. K.; Cook, J. W.
1981SoPh...74..521V Altcode:
There exists a growing need to improve the accuracy of measurement
of the absolute solar flux within the wavelength range 120-400
nm. Although full-disk solar fluxes and variations thereof in the
120-400 nm region are required to model the solar atmosphere, current
increased interest in the measurements arises from their importance in
modeling the terrestrial atmosphere. We describe the Solar Ultraviolet
Spectral Irradiance Monitor (SUSIM) experiment under development at the
Naval Research Laboratory (NRL) for flight aboard the Space Shuttle and
the Upper Atmospheric Research Satellite (UARS). SUSIM will monitor
the solar flux in the 120-400 nm region with high precision, using
an in-flight calibration system to reduce absolute error to < 10%,
and error relative to the 400 nm continuum to < 1%.
---------------------------------------------------------
Title: Transient plasmas in the solar transition zone
Authors: Dere, K. P.; Bartoe, J. -D.; Brueckner, G. E.; Vanhoosier,
M. E.; Dykton, M. D.
1981ApJ...249..333D Altcode:
Observations of C IV emission from the transition zone of the quiet
sun have been obtained with high spatial (1 arcsec), spectral (0.1
A), and temporal (20 s) resolution by a high resolution telescope
and spectrograph. Over spatial scales of several arc seconds, the C
IV profile often exhibits dramatic changes in either the red or blue
wing or in the overall profile at the 20 s temporal resolution of the
observations. It is suggested that some of the rapidly varying emission
may be produced by radiatively cooling plasmas that result from the
thermal instability of coronal plasma. It is shown that such plasmas,
which are in transient ionization, can emit 35 s pulses of C IV emission
for reasonable pressure values. It is also shown that, because of the
limited ability of coronal plasma to maintain ionization equilibrium,
the criteria for the thermal radiative instability must be evaluated
in a manner different from the standard treatment in the case of rapid
perturbations or growth times. From a consideration of length scales
it is determined that these instabilities are most likely to occur in
the upper transition zone.
---------------------------------------------------------
Title: Latitudinal anisotropy of the solar far ultraviolet flux -
Effect on the Lyman alpha sky background
Authors: Cook, J. W.; Meier, R. R.; Brueckner, G. E.; van Hoosier,
M. E.
1981A&A....97..394C Altcode:
An estimate is given for the anisotropy of the solar full disk flux in
the far ultraviolet, as it would be observed for lines of sight within
and above the ecliptic plane through the predominant influence of plages
at low heliocentric latitudes. The flux anisotropy for Lyman alpha,
at a level of solar activity with a sunspot number of roughly 160,
is approximately 0.88 for the integrated flux over the Lyman alpha
profile and 0.83 for the flux at line center. The effect of this Lyman
alpha flux anisotropy on the Lyman alpha sky background intensity,
resonantly backscattered from the local interstellar medium that
is streaming through the solar system, is examined. It is concluded
that the solar Lyman alpha anisotropy should be included in models
of the interplanetary background during periods of moderate to high
solar activity.
---------------------------------------------------------
Title: Coronal Jets, Strong Shock Wave Heating of the Corona and a
Cloud Model of the Solar Wind
Authors: Brueckner, G. E.; Bartoe, J. -D. F.
1981BAAS...13..913B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Dynamics of Accelerating Coronal Bullets
Authors: Karpen, J. T.; Oran, E. S.; Boris, J. P.; Mariska, J. T.;
Brueckner, G. E.
1981BAAS...13..913K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Observations of the Solar Chromosphere and Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1981BAAS...13..845D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS II Observations of a Solar Bi-Polar Region
Authors: Roussel-Dupre, R.; Wrathall, J.; Nicolas, K.; Bartoe,
J. D. F.; Brueckner, G. E.
1981BAAS...13..889R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Extreme Ultraviolet Emission of O IV and N IV from the Sun
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.
1981BAAS...13R.542D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The variability of the sun's ultraviolet radiation
Authors: Brueckner, G. E.
1981AdSpR...1i.101B Altcode: 1981AdSpR...1..101B
The intensity of continua and emission lines which form the solar
UV spectrum below 2100 Å is variable. Continua and emission lines
originating from different layers in the solar atmosphere show a
different degree of variability. Coronal emission lines at short
wavelengths are much more variable than continua at longer wavelengths
which originate in lower layers of the solar atmosphere. Typical
time-scales of solar UV variability are minutes (flare induced),
days (birth of active regions), 27 days (solar rotation), 11 years
(solar cycle) and perhaps centuries, caused by long-term changes of
the solar activity. UV intensity variations have been determined by
either absolute irradiance measurements or by contrast measurements
of plages vs. the quiet sun. Plages are the main contributor to the
solar UV variability. Typical values for the solar UV variability over
a solar cycle are: <1% at wavelengths longer than 2100 Å, 8% at
2080 Å (continuum), 20% at 1900 Å (continuum), 70% at H Lyα, 200%
in certain emission lines 1200 < λ < 1800 Å and more than a
factor of 4 in coronal lines λ < 1000 Å. Plage models predict the
variable component of the solar UV radiation within +/-50%. Absolute
fluxes are known within +/-30%. Several efforts are underway to monitor
the solar UV irradiance with a precision better than a few percent
over a solar activity cycle.
---------------------------------------------------------
Title: The EUV fine structure of the chromosphere-corona transition
zone above a sunspot.
Authors: Nicolas, K. R.; Kjeldseth Moe, O.; Bartoe, J. -D. F.;
Brueckner, G. E.
1981BAAS...13..491N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The sunspot chromosphere-corona transition region
Authors: Nicolas, K. R.; Bartoe, J. -D. F.; Brueckner, G. E.;
Kjeldseth-Moe, D.
1981phss.conf..167N Altcode:
Data from simultaneous readings of the line intensities, Doppler shifts,
and line widths of a sunspot ion emission lines between 1170-1700
A are reported. Subsonic and supersonic flows were observed in the
same line of sight above the umbra. A reduction of coronal plasma
over sunspots with an electron temperature exceeding 1,000,000 K was
confirmed, concurrent with enhanced emission from the transition region
plasma in the temperature range 200,000-1,000,000 K. The differential
emission measure is noted to have been caused to shift because of the
enhancement of the transition region plasma emission, where radiative
losses dominated the energy balance. Calculations of the energy balance
also indicated that a detected divergence in the enthalpy flux for the
umbral downflows could balance the radiative losses in the electron
temperature range 30,000-200,000 K.
---------------------------------------------------------
Title: The dynamics of active regions.
Authors: Brueckner, G. E.
1981sars.work..113B Altcode:
High-resolution, rocket-borne spectral observations of the dynamics
of solar active regions are presented. Spectra were taken in
the region 1175-1710 A at a spatial resolution of 1 arcsec and a
spectral resolution of 0.06 A by the NRL High Resolution Telescope
and Spectrograph during 1975 and 1978. Time sequences of active
region spectra in C I and C IV indicate systematic downflows over a
sunspot and plage, and explosive events characterized by supersonic
flow velocities. Coronal Doppler velocities measured over plages
and sunspots are found to average 13 km/sec downwards and 2.5 km/sec
upwards, respectively. Analysis of the gasdynamics of the active regions
indicates that the spectral lines are formed in the area of free fall,
and in the splashdown layer. Variations in the relative intensity
of the He 1640 emission are explained by a separation of light from
heavy elements as downflows encounter the dense chromospheric layers. A
qualitative evaluation is presented of the mass and energy balance of
an active region.
---------------------------------------------------------
Title: The variability of the sun's ultraviolet radiation.
Authors: Brueckner, G. E.
1981paa..conf..101B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comment on 'Variability of the far-infrared solar temperature
minimum with the solar cycle'
Authors: Cook, J. W.; Brueckner, G. E.; Vanhoosier, M. E.
1980A&A....92L...7C Altcode:
We compare the solar cycle variation of the full disk brightness
temperature minimum in the far-infrared reported by Müller
et al. (1980) to the variation found in the far-ultraviolet
T<SUB>min</SUB> continuum. The far-ultraviolet observations suggest
that the far-infrared variability should be nearer 9,-60 K than the
value of 200 K reported by Müller et al. (1980), whose solar cycle
variation is comparable to their measurement error.
---------------------------------------------------------
Title: Solar physics in the VUV: the importance of high resolution
observations.
Authors: Brueckner, G. E.
1980ApOpt..19.3994B Altcode:
Newly developed space instrumentation has made it possible to explore
the ultraviolet spectrum of the sun with high spatial, spectral,
and temporal resolution. Improvements of VUV observation capability
are discussed with reference to the plane-parallel global model
of the solar atmosphere and refinements that introduce horizontal
inhomogeneities. It is suggested that the global existence of a hot
corona and the outstreaming solar wind may be caused by high-energy
events occurring in the quiet sun. These events are extremely localized
and cover only a small fraction of the solar disk.
---------------------------------------------------------
Title: Stark effect at the SI I series limit
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.
1980ApJ...240..702J Altcode:
Small redshifts and weakenings of high n lines in members of the
Si series observed over a sunspot are interpreted as due to the
Stark effect. Other origins, including Doppler motions, appear to
be excluded. The spectra were obtained with high spatial resolution
using the NRL high-resolution telescope and spectrograph. The origin
of the Stark effect is not yet certain. An interpretation in terms of
a quasi-static quadratic effect would require rather high perturber
densities. An alternative interpretation would be a motional Stark
effect, arising perhaps through the presence of magnetohydrodynamic
waves.
---------------------------------------------------------
Title: HRTS Observations of Solar Fine Structure in the
T<SUB>min</SUB> Region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1980BAAS...12..916C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mass and Energy Flux in the Solar Transition Zone
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Dykton, M.
1980BAAS...12..907B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Are Highly Energetic Coronal Spikes the Source of Coronal
Heating and the Propulsion of the Solar Wind?
Authors: Brueckner, G. E.; Bartoe, J. -D. F.
1980BAAS...12..793B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variability of the solar flux in the far ultraviolet
1175-2100 Å
Authors: Cook, J. W.; Brueckner, G. E.; Vanhoosier, M. E.
1980JGR....85.2257C Altcode:
We examine the expected range of variability over the solar cycle
of the far UV flux (irradiance) in selected lines and continua
within the wavelength range 1175-2100 Å which results from a simple
two-component model of the full-disk flux. We determine contrast factors
I(plage)/I(quiet region) for various lines and continua and estimate
the fraction of the disk that is covered by plages at various times in
the solar 11-year cycle. We assume (1) that enhanced far UV emission
arises from the same plage areas visible in Ca II emission, (2) that
our contrast values are typical, and (3) that both the plage and quiet
region intensities per unit surface area remain constant over the solar
cycle, so that flux variability is caused only by a greater or lesser
fraction of surface area covered by plages. We discussed available
observational evidence for these assumptions. Our results are in good
agreement with the Lα fluxes published by Vidal-Madjar [1975] and the
recent broadband observations by Hinteregger (private communication,
1979), but they are in disagreement with the flux variability reported
by Health and Thekaekara [1977] over the 1700-3000-Å range.
---------------------------------------------------------
Title: Density and Temperature Measurements for Short Lived Transition
Zone Phenomena
Authors: Nicolas, K. R.; Dere, K. P.; Bartoe, J. -D. F.; Brueckner,
G. E.
1980BAAS...12R.530N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transient Plasmas in the Solar Transition Zone
Authors: Dere, K. P.; Nicolas, K. R.; Brueckner, G. E.
1980BAAS...12R.518D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Latitudinal Anisotropy of the Solar Far Ultraviolet Flux:
Effect on the Lα Sky Background
Authors: Cook, J. W.; Meier, R. R.; Brueckner, G. E.; Vanhoosier, M. E.
1980BAAS...12..544C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A high-resolution view of the solar chromosphere and corona.
Authors: Brueckner, G. E.
1980HiA.....5..557B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The chromosphere and transition region
Authors: Canfield, R. C.; Brown, J. C.; Craig, I. J. D.; Brueckner,
G. E.; Cook, J. W.; Doschek, G. A.; Emslie, A. G.; Machado, M. E.;
Henoux, J. -C.; Lites, B. W.
1980sfsl.work..231C Altcode: 1980sofl.symp..231C
The physical processes occurring as a result of the transfer of
energy and momentum from the primary solar flare energy release site
in the corona to the underlying chromosphere and transition region
during the course of the flare are investigated through a comparison
of theoretical models and observational data. Static, dynamic and
hydrodynamic models of the lower-temperature chromospheric flare are
reviewed. The roles of thermal conduction, radiation, fast particles
and mass motion in chromosphere-corona interactions are analyzed on
the basis of Skylab UV, EUV and X-ray data, and empirical and synthetic
models of the chromospheric and upper photospheric responses to flares
are developed. The canonical model of chromospheric heating during
flares as a result of primary energy release elsewhere is found to be
justified in the chromosphere as a whole, although not entirely as the
temperature minimum, and a simplified model of horizontal chromospheric
flare structure based on results obtained is presented.
---------------------------------------------------------
Title: The energy balance and pressure in the solar transition zone
for network and active region features.
Authors: Nicolas, K. R.; Bartoe, J. -D. F.; Brueckner, G. E.;
Vanhoosier, M. E.
1979ApJ...233..741N Altcode:
The electron pressure and energy balance in the solar transition zone
are determined for about 125 network and active region features on
the basis of high spectral and spatial resolution extreme ultraviolet
spectra. Si III line intensity ratios obtained from the Naval Research
Laboratory high-resolution telescope and spectrograph during a rocket
flight are used as diagnostics of electron density and pressure
for solar features near 3.5 x 10 to the 4th K. Observed ratios are
compared with the calculated dependence of the 1301 A/1312 A and
1301 A/1296 A line intensity ratios on electron density, temperature
and pressure. Electron densities ranging from 2 x 10 to the 10th/cu
cm to 10 to the 12th/cu cm and active region pressures from 3 x 10
to the 15th to 10 to the 16th/cu cm K are obtained. Energy balance
calculations reveal the balance of the divergence of the conductive
flux and turbulent energy dissipation by radiative energy losses in
a plane-parallel homogeneous transition zone (fill factor of 1),
and an energy source requirement for a cylindrical zone geometry
(fill factor less than 0.04).
---------------------------------------------------------
Title: Lyman-alpha rocket spectra and models of the quiet and active
solar chromosphere based on partial redistribution diagnostics.
Authors: Basri, G. S.; Linsky, J. L.; Bartoe, J. -D. F.; Brueckner,
G.; van Hoosier, M. E.
1979ApJ...230..924B Altcode:
Absolute intensity Lyman-alpha profiles with a spatial resolution
of 0.8 min and a spectral resolution of 50 mA were obtained for
network and cell regions in the quiet sun, umbral and penumbral
areas of a sunspot, two plages, and a quiescent prominence of the
limb. Weak limb brightening shown by the Lyman-alpha cores and wings
are consistent with predictions derived from partial redistribution
line transfer calculations. Through use of a comoving two-level partial
redistribution code which conserves mass flux, unequal red and blue
Lyman-alpha peak intensities may be interpreted as flow velocities
near 20,000 K. Outflows in the plages and downflows in the network
are also noted. A model of a mean quiet sun chromosphere consistent
with the Lyman-alpha integrated intensity, the Lyman continuum slope,
and the millimeter continuum is presented.
---------------------------------------------------------
Title: CO emission lines in the solar atmosphere.
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas,
K. R.; Sandlin, G. D.; Vanhoosier, M. E.
1979MNRAS.187..473J Altcode:
New identifications of CO emission lines in the EUV spectrum of a
sunspot are reported. The spectra were obtained with the Naval Research
Laboratory's High Resolution Telescope and Spectrograph. The emission is
from the CO fourth positive system and is excited by the strong lines of
C IV, Si IV and O IV. Transitions in the 0-3 band which lie above 1700
A and other lines at shorter wavelengths have been identified from the
spectrum of the June 15, 1973 flare, obtained with the Naval Research
Laboratory's normal incidence spectrograph on Skylab. The observed
intensities in the sunspot are used to derive the CO column density.
---------------------------------------------------------
Title: H<SUB>2</SUB> emission in the solar atmosphere.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas, K. R.; Sandlin,
G. D.; Vanhoosier, M. E.; Jordan, C.
1979MNRAS.187..463B Altcode:
New identifications of emission lines of molecular hydrogen in the EUV
spectrum of sunspots are reported. The spectra were obtained during
the first and second flights of the Naval Research Laboratory's High
Resolution Telescope and Spectrograph (HRTS). While most of the lines
originate in the Lyman bands, fluorescence from the Werner bands has
been found for the first time in the solar atmosphere. H2 fluorescent
emission has also been identified in the spectra of a solar flare
observed with NRL's normal incidence spectrograph on Skylab. Column
densities for H2 are derived from intensities of lines in the sunspot
spectra.
---------------------------------------------------------
Title: Measurements of spectrally integrated atmospheric transmittance
in the O<SUB>2</SUB> Schumann-Runge bands and derived oxygen column
densities: 76-102 km
Authors: Longmire, M. S.; Bartoe, J. -D. F.; Brown, C. M.; Brueckner,
G. E.; Tousey, R.
1979JGR....84.1277L Altcode:
Atmospheric transmittances integrated over wavelength intervals
corresponding approximately to the (15-0) through (4-0) Schumann-Runge
bands of O<SUB>2</SUB> have been determined from EUV solar spectra
(1768 Å<λ<1948 Å) photographed at seven altitudes between
102 and 76 km with a rocket-borne spectrograph having a resolution of
0.07 Å. The observed transmittances are compared with atmospheric
transmittances predicted from three models of the O<SUB>2</SUB>
absorption cross section. The predicted transmittances have also been
used to derive column densities of atmospheric O<SUB>2</SUB> from the
observations. The results are compared with values calculated from
the U.S. Standard Atmosphere (1976) and with oxygen column densities
determined by Prinz and Brueckner (1977) from EUV solar spectra of the
Schumann-Runge continuum (λ<1750 Å) and of the H-Lyman alpha line
(1216 Å) recorded on the same films used in the present research. The
comparisons test the utility of the models for studies of atmospheric
photochemistry, suggest which models may be best for this purpose,
and indicate how the models can be improved.
---------------------------------------------------------
Title: An Analysis of High Spatial and Time Resolution C IV Line
Profiles
Authors: Brueckner, G. E.; Vanhoosier, M. E.; Bartoe, J. -D. F.
1979BAAS...11Q.397B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Variability of the Solar Ultraviolet Radiation in the
Wavelength Region 1200-2100 Å
Authors: Vanhoosier, M. E.; Cook, J.; Brueckner, G. E.
1979BAAS...11..421V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamics of the Solar Transition Zone.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Vanhoosier, M. E.
1979BAAS...11R.397B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: EUV continua of solar flares 1420 - 1960 Å.
Authors: Cook, J. W.; Brueckner, G. E.
1979ApJ...227..645C Altcode:
Measurements of absolute continuum intensities in the wavelength
range 1420-1960 A are presented for the SN subflare of 1973 August
9 and the 2B flare of 1973 September 7, observed from the NRL
spectrograph aboard Skylab. Continuum measurements are also given for
two active-region plages, which are used for background nonflaring
levels. Major enhancement of the flare continuum intensity above the
plage backgrounds occurs in the Si I 3P and 1D continua. The observed
brightness-temperature minimum of the plages is approximately 310
K above the quiet-sun minimum, and occurs at longer wavelength. The
earliest flare brightness-temperature minima are approximately 200 K
above the plage minimum, and also at longer wavelength. The observed
decay time of the flare brightness temperature, which is comparable
to the Solrad 9 X-ray decay time, is much longer than the Ulmschneider
radiative relaxation time for the 1973 September 7 flare and marginally
longer for the 1973 August 9 flare, suggesting continuous excess heating
of the plage temperature minimum region throughout the period of our
flare observations.
---------------------------------------------------------
Title: Emission lines of H<SUB>2</SUB> in the extreme-ultraviolet
solar spectrum.
Authors: Jordan, C.; Brueckner, G. E.; Bartoe, J. -D. F.; Sandlin,
G. D.; Vanhoosier, M. E.
1978ApJ...226..687J Altcode:
A sunspot EUV spectrum covering the wavelength range from 1175 to 1714
A with high spatial and spectral resolution is examined which contains
about 200 lines not previously reported in solar spectra. Many of
the lines are identified as transitions in the Lyman bands of H2. It
is shown that the H2 lines are photoexcited not only by H L-alpha, as
reported previously, but also by the strong transition-region lines of
C II, Si IV, and O IV. The line intensities are analyzed as far as is
possible at present, and differences between the quiet chromosphere
and the sunspot chromosphere are deduced. The polarization of the
observed lines is briefly discussed, the importance of the H L-alpha
fluorescence mechanism for the excitation of the H2 Lyman bands is
demonstrated, and it is concluded that the H2 lines could also be
observable in stars of spectral type later than the sun.
---------------------------------------------------------
Title: CO fluorescence in the extreme-ultraviolet solar spectrum.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Sandlin, G. D.;
Vanhooster, M. E.; Jordan, C.
1978ApJ...223L..51B Altcode:
Emission lines in the fourth positive system of CO have been identified
in the extreme-ultraviolet solar spectrum 1540-1660 A. These lines
are excited by the C IV transition-zone lines at 1548 and 1551 A. They
are strong in the spectrum of a sunspot and in parts of the adjacent
active region. Some of them appear as weak, broad emission features
in the quiet sun.
---------------------------------------------------------
Title: High Spatial Resolution Cinematography of the 1600 Å Solar
Continuum.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.
1978BAAS...10..417B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Energy Balance and Pressure in the Solar Transition Zone.
Authors: Nicolas, K. R.; Bartoe, J. -D. F.; Brueckner, G. E.;
Vanhoosier, M. E.
1978BAAS...10..432N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High Velocity Jets in the "Quiet" Sun as a Possible Source
of the Solar Wind and the Heating of the Corona
Authors: Brueckner, G. E.; Bartoe, J. -D. F.
1978BAAS...10R.416B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Applications of new high spatial and spectral resolution
spectrography. Design principle to solar and stellar ultraviolet
spectroscopy.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.
1978nisa.symp...81B Altcode: 1978nisa.conf...81B
No abstract at ADS
---------------------------------------------------------
Title: Solar EUV emission line profiles of Si ii and Si iii and
their center to limb variations
Authors: Nicolas, K. R.; Brueckner, G. E.; Tousey, R.; Tripp, D. A.;
White, O. R.; Athay, R. G.
1977SoPh...55..305N Altcode:
Spectral line profiles of Si II and Si III are presented which were
observed both at solar center and near the quiet solar limb with the
Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute
intensities and line profiles are derived from the photographic data. A
brief discussion is given of their center-to-limb variations and of
the optical thickness of the chromosphere in these lines. Nonthermal
broadening velocities are found for the optically thin lines from
their full width at half maximum intensity (FWHM).
---------------------------------------------------------
Title: Lines of H2 in extreme-ultraviolet solar spectra
Authors: Jordan, C.; Brueckner, G. E.; Bartoe, J. -D. F.; Sandlin,
G. D.; van Hoosier, M. E.
1977Natur.270..326J Altcode:
The first detection of molecular hydrogen in the sun is reported. The
observations were made with the aid of a high resolution telescope
and spectrograph flown in a rocket on July 21, 1975. A short stretch
of a spectrum obtained with a 51-sec exposure time is presented in a
graph. It has been found that at least 30 of the new lines are related
to known transitions in the Lyman bands of H2. The H2 molecules in
the sunspot, or pore, can be excited by photons in the red wing of H
L-alpha as they travel down towards the photosphere.
---------------------------------------------------------
Title: Molecular Hydrogen in the Solar Atmosphere.
Authors: Brueckner, G.; Bartoe, J. -D. F.; Sandlin, G. D.; Vanhoosier,
M. E.; Jordan, C.
1977BAAS....9..568B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Prime Energy Release and Flare Development (Proceedings
of the Meeting `How Can Flares be Understood?', held during the 16th
General Assembly of the IAU in Grenoble, France, on 27 August, 1976.)
Authors: Brueckner, G. E.
1977SoPh...53..269B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Forbidden lines of the solar corona and transition zone:
975 - 3000 Å.
Authors: Sandlin, G. D.; Brueckner, G. E.; Tousey, R.
1977ApJ...214..898S Altcode:
Forbidden lines characteristic of plasmas at temperatures of 50,000 to
3 million K are observed in ATM UV spectra. Identifications, accurate
wavelengths, ionization classes, intensities, and half-widths are
presented. Coronal blends with He II at 1640 A are noted. Variations in
nonthermal velocities with limb distance are observed. Doppler shifts
in the coronal lines observed on the disk may be related to the solar
wind. The coincidence of two lines with F IV(3P-5S) is evidence for
atomic fluorine in the sun.
---------------------------------------------------------
Title: Applications of a new high spatial and spectral resolution
spectrograph design principle to solar and stellar ultraviolet
spectroscopy
Authors: Bartoe, J. -D. F.; Brueckner, G. E.
1977cosp.meetY....B Altcode:
Schemes for double-dispersion spectrographs and spectrometers are
described which make use of two classical concave gratings in tandem. In
the tandem Wadsworth mount, one grating is positioned so that the slit
is on the grating normal and at the grating focus; the second grating
has the same radius and ruling density and is arranged coincident
with the radius of the first grating. The recorded solar spectra
have high spectral resolution throughout the 1200-1700 A range. By
arranging the two concave gratings so that their normals are parallel,
a zero-dispersion broadband spectroheliograph can be constructed. A
tunable narrow-band spectroheliograph is obtained by adding a grid
collimator between the first and second grating. A variation of
the symmetric tandem Wadsworth mount can be employed to construct a
double-dispersion stigmatic, coma-free scanning spectrometer.
---------------------------------------------------------
Title: Extreme ultraviolet spectroheliograph ATM experiment S082A.
Authors: Tousey, R.; Bartoe, J. -D. F.; Brueckner, G. E.; Purcell,
J. D.
1977ApOpt..16..870T Altcode:
The XUV spectroheliograph, Apollo Telescope Mount experiment S082A, is
described. The instrument was a slitless Wadsworth grating spectrograph
that employed photographic recording. The grating was of 4-m radius,
ruled with 3600 grooves/mm. By rotating the grating to positions
where the normal was at 255 A or 400 A, the spectral ranges 175-335
A and 320-480 A, respectively, were covered with 2-sec of arc spatial
resolution. Close to the normal the resolution reached 2 sec of arc,
but at the extreme limit, 630 A, it was 10 sec of arc or worse. The
aberrations of the instrument are discussed in detail as are the
provisions necessary to maintain optimum imagery and reliability in a
space environment. During the mission about 1020 exposures were made
covering 171-335 A or 320-630 A.
---------------------------------------------------------
Title: Extreme ultraviolet spectrograph ATM experiment S082B.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Purcell, J. D.;
Tousey, R.
1977ApOpt..16..879B Altcode:
The extreme-ultraviolet double-dispersion photographic spectrograph
for the Apollo Telescope Mount (ATM) experiment S082B on Skylab is
described. Novel features were the use of a predisperser grating with
a ruling whose spacing varied approximately linearly with distance
for the purpose of increasing the instrument speed by reducing the
astigmatism and a photoelectric servosystem to stabilize to 1 sec of
arc the solar image at various near-limb positions. The 970-3940-A
range was covered in two sections with effective resolving power of
approximately 30,000 from 1100 A to 1970 A. The spatial resolution
was 2 x 60 solar sec of arc. During the Skylab mission 6400 exposures
were made with the instrument pointed by an astronaut at selected and
recorded solar positions.
---------------------------------------------------------
Title: Observations of the O<SUB>2</SUB> column density between
120 and 70 km and absorption cross section in the vicinity of H
Lyman alpha
Authors: Prinz, D. K.; Brueckner, G. E.
1977JGR....82.1481P Altcode:
From solar spectra obtained during the reentry of Calroc 4 the optical
depth of the atmosphere in the wavelength interval 1213-1219 Å has
been obtained for altitudes between ∼120 and ∼70 km. The data
are consistent with the interpretation that molecular oxygen is the
primary absorbing species under these conditions if the values of
the O<SUB>2</SUB> cross section in the 1216.2- to 1217.2-Å region
are approximately those of Ogawa (1968) and the O<SUB>2</SUB> column
densities in the 80-km region are approximately those derived from
the 8-0 and 11-0 Schumann-Runge bands observed during the same flight.
---------------------------------------------------------
Title: Fine Structure and Dynamics of the Inner Corona.
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Vanhoosier, M. E.
1977BAAS....9..370B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fine Structure and Dynamics of the Inner Corona.
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; van Hoosier, M. E.
1977uxsa.coll....9B Altcode: 1977IAUCo..43....9B
No abstract at ADS
---------------------------------------------------------
Title: Current Instrumental Highlights".
Authors: Brueckner, G. E.; Sandford, P.; Speer, R. J.
1977uxsa.collE...2B Altcode: 1977IAUCo..43R....B
No abstract at ADS
---------------------------------------------------------
Title: Absolute solar ultraviolet intensities and their variations
with solar activity. I. The wavelength region 1750 - 2100 Å.
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Moe, O. K.; Vanhoosier,
M. E.
1976ApJ...209..935B Altcode:
Absolute-calibrated high-resolution ultraviolet spectra from 1750
to 2100 A of the quiet Sun and a plage are presented. From these
spectra, the intensity at the center of the disk, the average disk
intensities, and the solar flux at 1 AU are derived. A comparison
with other measurements shows that in this wavelength region most of
the solar intensity measurements fall within an error limit of 120
percent. The variability of the solar flux in the band 1750-2050 A
caused by active regions is estimated. A change of the sunspot number
from 0 to 120 causes an approximate flux variation of 3 percent. The
blackbody radiation temperature of a plage averaged over 2 x 60 arcsec
in this wavelength region is 200 K higher than that of the quiet
Sun. Subject headings: Sun: activity - Sun: plages - Sun: spectra -
ultraviolet: spectra
---------------------------------------------------------
Title: Models of Solar Chromosphere Structures Implied by Lyman-α
Rocket Spectra.
Authors: Basri, G.; Linsky, J. L.; Bartoe, J. -D. F.; Brueckner, G.;
van Hoosier, M. E.
1976BAAS....8..534B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A.t.m. Observations on the X u.v. Emission from Solar Flares
Authors: Brueckner, G. E.
1976RSPTA.281..443B Altcode: 1976RSLPT.281..443B
Far ultraviolet spectroheliograms (190-465 angstrom) and ultraviolet
spectra (900-1900 angstrom) of selected flares obtained on board Skylab
by two instruments of the Naval Research Laboratory are presented. Time
sequences of three events are discussed in detail; they are compared
with simultaneous X-ray measurements from the N.R.L.'s Solrad 9 and
from the OSO-7 X-ray spectrometer of the University of California,
San Diego. In all events, where proper observational coverage was
obtained, a small kernel seems to be the source of the prime energy
release of a flare. The size of this kernel is determined by the
spatial resolution of the spectroheliograph, which is approximately
2<SUP>' '</SUP>. Densities in this kernel exceed 3 × 10<SUP>12</SUP>
cm<SUP>-3</SUP>. Ion temperatures in a subflare kernel are determined
to be larger than 20 MK. It is very likely, that these temperatures are
much higher in the flare kernel of more energetic events. Hot clouds
of coronal gas at 20 MK surround the kernel. These clouds are trapped
below high magnetic structures, and subsequently seem to be the energy
reservoir for heating the post flare loops. During the explosive phase,
strong Doppler broadening can be seen, especially in transition zone
lines of the brightened plages. These can be interpreted as impact
of high energetic particles guided down to the solar surface along
the loops. The observations suggest that high speed mass motions have
their origin in the exploding flare kernel.
---------------------------------------------------------
Title: High-temperature flare lines in the solar spectrum 171 Å -
630 Å.
Authors: Sandlin, G. D.; Brueckner, G. E.; Scherrer, V. E.; Tousey, R.
1976ApJ...205L..47S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic far ultraviolet observations of transition zone
instabilities and their possible role in a pre-flare energy build-up.
Authors: Brueckner, G. E.; Patterson, N. P.; Scherrer, V. E.
1976SoPh...47..127B Altcode:
(1) Highly flare-productive new emerging active regions are
characterized by numerous small low-lying loops which frequently
show a chaotic pattern. (2) Flare activity in such a region subsides
as the chaotic loop structures relax and expand into a bipolar
configuration. (3) The transition zone in such an active region is
highly unstable as shown by broadened and shifted non-thermal line
profiles of medium ionized elements like Si III, Si IV, C IV, etc. (4)
These transition zone instabilities which occur as isolated events
in active regions of low flare productivity are often observed prior
to flares. (5) Transition zone instabilities can be traced to the
footpoints of active loops, and seem to be accompanied by heating of
the loop. (6) The loops vary in size and show differing degrees of
activity, with the brightest and most compact ones seemingly being
in a pre-flare state which results in the catastrophic energy release
along the loop during a flare.
---------------------------------------------------------
Title: The UV Spectrum of a Sunspot (1175 to 1700 Å) Observed with
High Spatial and Spectral Resolution
Authors: Brueckner, G. E.; Nicolas, K. R.; Bartoe, J. -D. F.;
Vanhoosier, M. E.
1976BAAS....8..345B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preliminary Analysis of NRL Rocket Spectra of the Lα Line
Wings
Authors: Basri, G.; Bartoe, J. -D. F.; Brueckner, G.; Linsky, J.;
van Hoosier, M. E.
1976BAAS....8..331B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometry of the Photospheric and Chromospheric
Granulation in the UV Region 1240-1650Å
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Moe, O. K.; Nicolas,
K. R.; Vanhoosier, M. E.
1976BAAS....8..312B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Pre-Flare Observations During the Evolution of McMath Region
12474 August 7-9, 1973
Authors: Scherrer, V.; Brueckner, G.; Sandlin, G.; Tousey, R.
1976BAAS....8R.373S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal Lines in ATM Spectra 1100Å - 3000Å
Authors: Sandlin, G. D.; Brueckner, G. E.; Tousey, R.
1976BAAS....8..339S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal Changes Associated with a Disappearing Filament
Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V. E.; Tousey, R.; Smith, J. B., Jr.; Speich, D. M.;
Tandberg Hanssen, E.; Wilson, R. M.; de Loach, A. C.; Hoover, R. B.;
McGuire, J. P.
1975SoPh...45..377S Altcode:
This paper describes Skylab/ATM observations of the events associated
with a disappearing filament near the center of the solar disk on
January 18, 1974. As the filament disappeared, the nearby coronal
plasma was heated to a temperature in excess of 6 × 10<SUP>6</SUP>K. A
change in the pattern of coronal emission occurred during the 11/3 hr
period that the soft X-ray flux was increasing. This change seemed to
consist of the formation and apparent expansion of a loop-like coronal
structure which remained visible until its passage around the west limb
several days later. The time history of the X-ray and microwave radio
flux displayed the well-known gradual-rise-and-fall (GRF) signature,
suggesting that this January 18 event may have properties characteristic
of a wide class of X-ray and radio events.
---------------------------------------------------------
Title: A New, High Resolution Ultraviolet Solar Spectrograph for
Rocket and Satellite Applications.
Authors: Bartoe, J. D. F.; Brueckner, G. E.
1975BAAS....7..432B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hydrodynamics of Electron Beam Deposition in Solar Flares.
Authors: Bloomberg, H.; Kepple, P. C.; Davis, J.; Boris, J.;
Brueckner, G.
1975BAAS....7..398B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Plasma Heating and Flare X-rays.
Authors: Davis, J.; Kepple, P.; Strickland, D.; Brueckner, G.
1975BAAS....7..398D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Line Profiles of the Fe XXIV Emission at 192 Å and 255 Å
in Solar Flares
Authors: Brueckner, G. E.; Moe, O. K.; van Hoosier, M. E.
1975BAAS....7..357B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: White light coronagraph in OSO - 7
Authors: Koomen, M. J.; Detwiler, C. R.; Brueckner, G. E.; Cooper,
H. W.; Tousey, R.
1975ApOpt..14..743K Altcode:
A small, externally occulted Lyot-type coronagraph, designed for
use in the seventh unmanned Orbiting Solar Observatory (OSO-7), is
described. The optical configuration, suppression of stray light, SEC
vidicon detector, and data system are discussed, as well as integration
of the instrument into the spacecraft and operation in orbit. Orbital
operation produced daily images of the white-light corona, from 2.8 to
10 solar radii, at least once per day for 2.75 yr. The first records
of white-light coronal transient events were obtained, and the corona
was shown to be constantly changing.
---------------------------------------------------------
Title: The reconnection of magnetic field lines in the solar corona.
Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V. E.; Tousey, R.
1975ApJ...196L.129S Altcode:
Skylab XUV coronal spectroheliograms and photospheric magnetograms
are compared. This comparison shows that, as new bipolar magnetic
fields emerge through the solar surface into the corona, the new
coronal fields interact with the old ones in a manner that suggests
the reconnection of the field lines.
---------------------------------------------------------
Title: Observations from Skylab of the Density Dependent C III
Multiplet at 1175 Å in Active and Quiet Regions and above the Limb
Authors: Nicolas, K.; Brueckner, G.
1975BAAS....7..353N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Forbidden lines of highly ionized iron in solar flare spectra.
Authors: Doschek, G. A.; Feldman, U.; Dere, K. P.; Sandlin, G. D.;
Vanhoosier, M. E.; Brueckner, G. E.; Purcell, J. D.; Tousey, R.
1975ApJ...196L..83D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpreting XUV Spectroheliograms in Terms of Coronal Magnetic
Field Structures
Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V. E.; Tousey, R.
1975BAAS....7Q.346S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Solar UV Intensities 1680 Å to 2100 Å
Authors: Kjeldseth Moe, O.; Brueckner, G. E.; Bartoe, J. D. F.;
van Hoosier, M. E.
1975BAAS....7Q.360K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute solar UV intensities 1680 Å to 2100 Å.
Authors: Moe, O. K.; Brueckner, G. E.; Bartoe, J. -D. F.; van Hoosier,
M. E.
1975BAAS....7..360M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: XUV Observations of Coronal Magnetic Fields
Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V.; Tousey, R.
1975SoPh...40..103S Altcode:
Spectroheliograms obtained with the Naval Research Laboratory's
Extreme Ultraviolet Spectrograph (S082A) on Skylab are compared with
Kitt Peak National Observatory magnetograms. A principal result is
the characteristic reconnection of flux from an emerging bipolar
magnetic region to previously existing flux in its vicinity. Examples
of the disappearance of magnetic flux from the solar atmosphere are
also shown. The results of a particularly simple, potential field
calculation are shown for comparison with the Skylab observations.
---------------------------------------------------------
Title: Ultraviolet Emission Line Profiles of Flares and Active Regions
Authors: Brueckner, G. E.
1975IAUS...68..135B Altcode:
A preliminary description of ultraviolet spectra of active regions and
flares, photographed from Skylab by the Naval Research Laboratory's UV
spectrograph, is given. The findings can be summarized as follows: (1)
Line profiles of medium-ionized lines (transition-zone lines) show the
most pronounced broadenings and shifts in flares and flare-like events;
(2) typical full widths at half maximum of these lines correspond to
Doppler velocities of 70 km/s; (3) shifts of the same magnitude can
be observed; (4) intersystem lines are not broadened or shifted; (5)
forbidden coronal lines and intersystem lines become enhanced in the
flare spectrum at the moment when the turbulence seen in the allowed
transitions disappears; and (6) a very broad line at 1354.2 A, which
appears only in flare spectra, seems to be the forbidden transition
3P(1)-3P(0) of Fe XXI.
---------------------------------------------------------
Title: Flare-Like Ultraviolet Spectra of Active Regions
Authors: Brueckner, G. E.
1975IAUS...68..105B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Solar Intensities 1750 AÅ - 2100 AÅ and Their
Variations with Solar Activity
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Moe, O. K.; van Hoosier,
M. E.
1975scea.conf...71B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New stigmatic, coma-free, concave-grating spectrograph.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.
1975JOSA...65...13B Altcode: 1975OSAJ...65...13B
No abstract at ADS
---------------------------------------------------------
Title: The Fine Structure of the Solar Atmosphere in the Far
Ultraviolet
Authors: Brueckner, G. E.; Bartoe, J. -D. F.
1974SoPh...38..133B Altcode:
High resolution spectroheliograms in the ultraviolet emission lines He
I, He II, O IV, O V, and Ne VII have been photographed during a sounding
rocket flight. Simultaneously, broad band filtergrams of the far
ultraviolet solar corona were obtained from the same flight. This paper
describes qualitatively the spatial distribution of the UV emission. A
comparison with an Hα filtergram is made. The most significant results
can be summarized as follows: We find most of the ultraviolet emission
concentrated around spicules, with different degree of concentration,
decreasing with higher temperatures. 4 different areas of ultraviolet
emission can be distinguished. (1) The normal network, bright in all UV
emission lines from the chromosphere into the corona. (2) The coronal
holes, bright in all UV emission lines up to 600 000 K but depressed in
coronal lines from 1 million degrees upward. (3) The coronal depressions
near active centers, absence of all ultraviolet emissions and (4)
Active regions, where ultraviolet emission comes from plages, sunspots
and coronal loops. High non-thermal Doppler velocities can be found
in certain plage kernels around 10<SUP>5</SUP> to 2 × 10<SUP>5</SUP>
K. Sunspots are bright in the ultraviolet, but do not exhibit He I or
He II emission. The corona above sunspots is weak. Sunspots do not show
high non-thermal Doppler velocities. The He I and He II emission does
not follow either chromospheric, transition zone or coronal pattern;
one can recognize some typical behavior of each.
---------------------------------------------------------
Title: The 1175 Å to 1900 Å Ultraviolet Spectrum of Solar Flares
Authors: Brueckner, G. E.; Bohlin, J. D.; Moe, O. K.; Nicolas, K. R.;
Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R., Jr.; Tousey, R.
1974BAAS....6..285B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Preliminary Study of Coronal Structures by Means of
Time-Lapse Photography
Authors: Sheeley, N. R.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V.; Tousey, R.
1974BAAS....6Q.294S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Cinematographic Observations for ATM and their Comparison
with some ATM Results
Authors: Zirin, H.; Holt, J.; Brueckner, G. E.; Bohlin, J. D.; Purcell,
J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R.
1974BAAS....6R.298Z Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The extreme ultraviolet spectrograph
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Purcell, J. D.;
Tousey, R.
1974SPIE...44..153B Altcode:
The extreme ultraviolet spectrograph system consists of two major
systems, including the telescope and the spectrograph. The telescope is
an off axis paraboloidal mirror. The spectrograph is modified crossed
dispersion double Rowland Mount. The optical coatings are discussed
along with the film, the film camera, and the flight results. It is
pointed out that about six thousand spectra were obtained from the
three Skylab missions.
---------------------------------------------------------
Title: Preliminary Results from the Nrl/atm Instruments from
SKYLAB SL/2
Authors: Tousey, R.; Bartoe, J. D. F.; Bohilin, J. D.; Brueckner,
G. E.; Purcell, J. D.; Scherrer, V. E.; Schumacher, R. J.; Sheeley,
N. R.; Vanhoosier, M. E.
1974IAUS...57..491T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Behaviour of the Outer Solar Corona (3 R<SUB>sun</SUB>
to 10 R<SUB>sun</SUB> during a Large Solar Flare Observed from OSO-7
in White Light
Authors: Brueckner, G. E.
1974IAUS...57..333B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The eruptive prominence of August 21, 1973 observed from
Skylab in the white light corona and in the He II 304 Å chromosphere.
Authors: Poland, A. I.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R.
1974BAAS....6..219P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometry of the solar UV line spectrum with the NRL
spectrograph on board Skylab.
Authors: Brueckner, G.
1974JOSA...64.1375B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Eruptive Prominence of August 21, 1973 Observed from
Skylab in the White Light Corona and in the He II 304Å Chromosphere.
Authors: Poland, A. I.; Bohlin, J. D.; Brueckner, G. E.; Purcell,
J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R.
1974BAAS....6..220P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The extreme ultraviolet spectrograph.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Purcell, J. D.;
Tousey, R.
1974inas.conf..153B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Preliminary Study of the Extreme Ultraviolet
Spectroheliograms from Skylab
Authors: Tousey, R.; Bartoe, J. D. F.; Bohlin, J. D.; Brueckner, G. E.;
Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R., Jr.; Schumacher,
R. J.; Vanhoosier, M. E.
1973SoPh...33..265T Altcode:
Some of the first observations obtained with the Naval Research
Laboratory's Extreme Ultraviolet Spectrograph (S082A) during the first
Skylab mission are presented and compared with magnetograms and other
ground-based data. The instrument is a slitless objective-type grating
spectrograph covering 170-630 Å and described in Solar Phys.27, 251
(1972). Chromospheric network, loop prominences, active regions,
a flare, limb brightening, XUV bright points, and `coronal holes'
are among the phenomena shown and discussed.
---------------------------------------------------------
Title: Extreme Ultraviolet Emission from Chromospheric
Inhomogeneities. An Analysis of the Extreme Ultraviolet Flash Spectrum
of the Sun
Authors: Brueckner, G. E.; Nicolas, K. R.
1973SoPh...29..301B Altcode:
An Aerobee 170 rocket carried five slitless extreme ultraviolet (XUV)
spectroheliographs into the March 7, 1970, solar eclipse. Salt water
damage left latent images on 16 exposures of the XUV camera covering the
wavelength range from 1390 Å to 1945 Å. The salt water damage made the
absolute calibration of the spectroheliograms uncertain. Therefore, the
analysis in this paper is based on a comparison of the extent of flash
spectrum crescents from emission lines formed in the chromosphere-corona
transition zone with two simple but fundamentally different models
describing this region. The observations can be satisfactorily described
by an inhomogeneous model where cool spicules are surrounded by a
transition zone which has the same temperature and density structure
as the chromospheric coronal transition zone customarily used in
spherically symmetric models of the quiet Sun.
---------------------------------------------------------
Title: Absolute Intensity of the Solar Spectrum from 1200 Å to 1790
Å Derived from New Rocket Spectra
Authors: Brueckner, G. E.; Nicolas, K.
1972BAAS....4T.378B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Coronal Origin of a Solar Flare
Authors: Brueckner, G. E.
1972BAAS....4U.378B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Major solar eruption observed.
Authors: Tousey, R.; Brueckner, G. E.; Koomen, M. J.; Michels, D. J.
1972NRRv...25....8T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High angular resolution absolute intensity of the solar
continuum from 1400 Å to 1790 Å.
Authors: Brueckner, G. E.; Moe, O. K.
1972spre.conf.1595B Altcode: 1972spre....2.1595B
No abstract at ADS
---------------------------------------------------------
Title: The Sun's Changing White Light Corona, Viewed from OSO-7.
Authors: Koomen, M. J.; Brueckner, G. E.; Tousey, R.
1971BAAS....3..440K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute intensity of the continuum in the ultraviolet spectrum
of the sun between 1650 - 1800 Å.
Authors: Brueckner, G.; Moe, O.; Pitz, E.
1971BAAS....3..260B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High spectral and spatial resolution ultraviolet spectroscopy
of the sun in the region 1170 - 1800 Å.
Authors: Brueckner, G.
1971BAAS....3Q.259B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A New Completely Digitized Filter Magnetograph
Authors: Brueckner, G. E.
1971IAUS...43...84B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Ultraviolet Flash Spectrum of the Sun from 1400 to 1960 Å
Authors: Brueckner, G. E.; Bartoe, J. D. F.; Nicolas, K. R.; Tousey, R.
1970BAAS....2S.299B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Profile and polarization of the Zeeman triplet 5250.22 Å.
Authors: Moe, O. K.; Brueckner, G. E.; Hagyard, M. J.
1970BAAS....2..331M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar UV Flash Spectrum 1400 Å-1960 Å
Authors: Brueckner, G. E.; Bartoe, J. F.; Nicolas, K. R.; Tousey, R.
1970Natur.226.1132B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Theoretical and Practical Limitations of Solar Magnetic
Field Measurements.
Authors: Brueckner, G.; Hulbert, O. E.
1968AJS....73S..56B Altcode:
Solar magnetic field measurements are closely correlated to line
polarization measurements. To obtain a magnetic picture of an active
region on the sun one has to determine a two- dimensional distribution
of three Stokes parameters Q, U, and V. The accuracy is given by the
necessary spatial and time resolution, by the telescope aperture,
the spectral resolution, and the receiver. Unno's theory of the line
formation of a Zeeman triplet in the sun's atmosphere has been applied
to calculate the polarization as a function of the magnetic field
strength. The calculations show that magnetic field measurements with
spatial resolution limited by the seeing and field strength accuracy to
detect weak fields in active regions are limited only by the properties
of now-available detectors. The recently developed SEC vidicon image
tube, together with the now available narrow-band birefringent filters
open new possibilities to develop magneto- graphs with high time and
spatial resolution combined with high field strength measurement accu-
racy. A new magnetograph which uses the mentioned components will
be described. By using a birefringent filter one avoids technical
difficulties which occur with a Fabry-Perot interferomenter. By
applying the newly developed SEC vidicons one is able to collect,
simultaneously, polarization information of all picture elements. The
accuracy of the field measurements is limited by the signal to noise
ratio of the tube. A further improvement is possible by integrating
several magnetic pictures using digital data reduction.
