Author name code: brueckner ADS astronomy entries on 2022-09-14 author:"Brueckner, Gunther" ------------------------------------------------------------------------ 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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 Rsolar 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. Title: Coronal Mass Ejections and the Solar Wind: New Results from LASCO Authors: Dere, K. P.; Howard, R. A.; Brueckner, G. E. Bibcode: 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° 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. Bibcode: 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 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. Bibcode: 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 Rsolar. 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. 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. Bibcode: 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. Title: LASCO observations of the solar polar regions Authors: Karovska, M.; Wood, B. E.; Brueckner, G. E.; Cook, J. W.; Howard, R. A. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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 Rsolar. 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. Bibcode: 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. 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. Bibcode: 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-1, while the former has no apparent accompanying prominence eruption and attains velocities of only about 300 km s-1. 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. Title: SUSIM UARS measurements of solar UV irradiance Authors: Floyd, L. E.; Prinz, D. K.; Crane, P. C.; Herring, L. C.; Brueckner, G. E. Bibcode: 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. 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. Bibcode: 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⊙ 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-1, whereas the bulk of their material travels at much lower velocities averaging around 250 km s-1 at heliocentric distances of 2.9-3.7 R⊙. These lower velocities may reflect the actual outflow speeds of the background polar wind. 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. Bibcode: 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 ne = (5.0-7.4) × 108 cm-3. Lower than average densities are expected for the two loops, given that they reach more than 1 pressure scale height above the solar limb. 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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 Rsolar 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-1) 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). 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. Bibcode: 1998ASPC..150..475P Altcode: 1998npsp.conf..475P; 1998IAUCo.167..475P No abstract at ADS 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. Bibcode: 1998sers.conf...79F Altcode: No abstract at ADS 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. Bibcode: 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. Title: LASCO and EIT Observations of the Dynamic Corona Authors: Dere, K. P.; Brueckner, G. E. Bibcode: 1998HiA....11..861D Altcode: No abstract at ADS Title: Correlations of Solar Cycle 22 UV Irradiance Authors: Floyd, L.; Brueckner, G.; Crane, P.; Prinz, D.; Herring, L. Bibcode: 1997ESASP.415..235F Altcode: 1997cpsh.conf..235F No abstract at ADS 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. Bibcode: 1997ESASP.415..207B Altcode: 1997cpsh.conf..207B No abstract at ADS Title: White-Light Coronal Mass Ejections: A New Perspective from LASCO Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.; Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner, G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere, K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis, D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark, J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker, D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D. Bibcode: 1997ESASP.415..103S Altcode: 1997cpsh.conf..103S No abstract at ADS Title: LASCO Observations of Variability in the Quiescent Solar Corona Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Brueckner, G. E.; Howard, R. A. Bibcode: 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 Rsun. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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-1 out to 5 solar radii, and above 15 solar radii the velocity was 269 ± 10 km s-1. 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-1 below 4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km s-1. 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. Bibcode: 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-1 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. Bibcode: 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-1, 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-1. 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. Bibcode: 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. Bibcode: 1997SoPh..175..601D Altcode: We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200-400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. Title: 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. Bibcode: 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. Bibcode: 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 nfoot ~ <Bfoot>0.9, where nfoot is the density of the green line-emitting plasma and <Bfoot> 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⊙ 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. Bibcode: 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:

1. They originate about 3-4 R⊙ from Sun center as radially elongated structures above the cusps of helmet streamers. Their initial sizes are about 1 R⊙ in the radial direction and 0.1 R⊙ in the transverse direction.

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-1 near 5 R⊙ to 300 km s-1 near 25 R⊙.

3. Their individual speed profiles v(r) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s-2 through most of the 30 R⊙ 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⊙.

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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Rsun. 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. Bibcode: 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. Bibcode: 1996AAS...188.4909D Altcode: 1996BAAS...28R.898D On 7 and 8 March 1996, SOHO instruments engaged in their first joint science operation, a 12-hr observation of polar plumes over the South polar coronal hole. The observing mini-campaign included observations from SOHO, other spacecraft, and ground-based observatories. Contributing SOHO instruments -- in order of altitude, MDI, CDS, SUMER, EIT, UVCS, and LASCO -- made overlapping, simultaneous observations of plume structures from the photosphere out to the LASCO C3 limit of 32 solar radii. MDI provided line-of-sight surface magnetograms with a one-min cadence and 0.6 arcsec resolution; CDS, SUMER, and EIT supplied temperature-sensitive images of the lower corona with varying cadences and resolutions; UVCS measured fluctuations in Ly B intensity across the coronal hole with a one-min cadence at 1.4 R0; and LASCO imaged the entire corona out to 30 R0 in various visible passbands. Plume footpoints in the lower corona are observed by EIT and CDS to vary by a factor of two in EUV brightness with a timescale of tens of minutes, while the structures above are (as as been previously observed) quiescent on at least a ten-hr time scale. We present preliminary results of cross-instrument analysis of the observed plumes, and suggest how this and similar future data sets can be used to constrain quiet-sun wind acceleration and coronal heating models for the coronal hole. This research is supported by the SOI-MDI NASA contract NAG5-3077 at Stanford University. SOHO is project of international cooperation between NASA and ESA. Title: 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. Bibcode: 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 Rsun 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. Bibcode: 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 Rsun. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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⊙ (C1: 1.1 - 3 R⊙, C2: 1.5 - 6 R⊙, and C3: 3.7 - 30 R⊙). 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⊙ 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. Bibcode: 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 106 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 10-11 B(solar mass) and 10-12 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 105, HRTS 1600 A spectroheliograms of the Tmin 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 10-3 vs. 2.3 x 10-3 explosive events per arcsec 2). 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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−1. 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. Bibcode: 1993BAAS...25.1191K Altcode: No abstract at ADS Title: Requirements for future solar-physics missions that include UV instrumentation. Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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 Rsun to 30 Rsun. Title: Multiple flows in the solar transition region. Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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-1 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 105 K, where the C IV lines are formed, but that the gas flows with essentially unchanged speed through all temperature layers from 2.5 × 105 K to 104 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. Bibcode: 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. Bibcode: 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. Bibcode: 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-1 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990ApJ...350L..21B Altcode: No abstract at ADS Title: Magnetic energy conversion in the solar transition zone Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990BAAS...22..744D Altcode: No abstract at ADS Title: The energy source of the solar chromosphere, transition region and corona. Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Tmin 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 -1) 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. Bibcode: 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−1) in profiles of CIV, formed at 105 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 × 103 km; maximum velocity - 110 km s−1; peak emission measure - 4 × 1041 cm−3; lifetime - 60 s; birthrate - 4 × 10−21 cm−2 s−1 in a coronal hole and 1 × 10−20 cm−2 s−1 in the quiet Sun; mass - 6 × 108 g; and, kinetic energy - 6 × 1022 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−1 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. Bibcode: 1989BAAS...21..841D Altcode: No abstract at ADS Title: Intermediate-Term Solar Periodicities: 100--500 Days Authors: Lean, J. L.; Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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-1 and are thus supersonic. Upward flows have smaller velocities, 5 - 20 km s-1, 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 10−5 to 10−2. The transport of mass and energy through these transition zone structures is reduced by this same factor of 10−5 to 10−2 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−1 (most-probable) or 19 km s−1 (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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 spectrograph1 (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.2). 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 described4. 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 (Ne <~ 1010 cm-3) astrophysical sources. Title: Outflows and Ejections in the Solar Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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−1 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 R0, 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 105 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-1. Title: HRTS Ultraviolet Images of the Solar Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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−1, 2.5 × 1026 ergs) can also account for the high-speed coronal clouds (1300 km sec−1, 4 × 1030 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. Bibcode: 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. Bibcode: 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 × 109 cm−3 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Tmin Region Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1982srs..work..255B Altcode: No abstract at ADS Title: High-Resolution Ultraviolet Solar Observations from Sounding Rockets and Spacelab Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981BAAS...13R.542D Altcode: No abstract at ADS Title: The variability of the sun's ultraviolet radiation Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Tmin 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. Bibcode: 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. Bibcode: 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 Tmin Region Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1980BAAS...12..544C Altcode: No abstract at ADS Title: A high-resolution view of the solar chromosphere and corona. Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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: H2 emission in the solar atmosphere. Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas, K. R.; Sandlin, G. D.; Vanhoosier, M. E.; Jordan, C. Bibcode: 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 O2 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. Bibcode: 1979JGR....84.1277L Altcode: Atmospheric transmittances integrated over wavelength intervals corresponding approximately to the (15-0) through (4-0) Schumann-Runge bands of O2 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 O2 absorption cross section. The predicted transmittances have also been used to derive column densities of atmospheric O2 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. Bibcode: 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. Bibcode: 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. Bibcode: 1979BAAS...11R.397B Altcode: No abstract at ADS Title: EUV continua of solar flares 1420 - 1960 Å. Authors: Cook, J. W.; Brueckner, G. E. Bibcode: 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 H2 in the extreme-ultraviolet solar spectrum. Authors: Jordan, C.; Brueckner, G. E.; Bartoe, J. -D. F.; Sandlin, G. D.; Vanhoosier, M. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 O2 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. Bibcode: 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 O2 cross section in the 1216.2- to 1217.2-Å region are approximately those of Ogawa (1968) and the O2 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. Bibcode: 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. Bibcode: 1977uxsa.coll....9B Altcode: 1977IAUCo..43....9B No abstract at ADS Title: Current Instrumental Highlights". Authors: Brueckner, G. E.; Sandford, P.; Speer, R. J. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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' '. Densities in this kernel exceed 3 × 1012 cm-3. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 × 106K. 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. Bibcode: 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. Bibcode: 1975BAAS....7..398B Altcode: No abstract at ADS Title: Plasma Heating and Flare X-rays. Authors: Davis, J.; Kepple, P.; Strickland, D.; Brueckner, G. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1975scea.conf...71B Altcode: No abstract at ADS Title: New stigmatic, coma-free, concave-grating spectrograph. Authors: Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 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. Bibcode: 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 105 to 2 × 105 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1974IAUS...57..491T Altcode: No abstract at ADS Title: The Behaviour of the Outer Solar Corona (3 Rsun to 10 Rsun during a Large Solar Flare Observed from OSO-7 in White Light Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1972BAAS....4T.378B Altcode: No abstract at ADS Title: The Coronal Origin of a Solar Flare Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1971BAAS....3Q.259B Altcode: No abstract at ADS Title: A New Completely Digitized Filter Magnetograph Authors: Brueckner, G. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1970Natur.226.1132B Altcode: No abstract at ADS Title: Theoretical and Practical Limitations of Solar Magnetic Field Measurements. Authors: Brueckner, G.; Hulbert, O. E. Bibcode: 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.