Author name code: poland ADS astronomy entries on 2022-09-14 author:"Poland, Arthur I." ------------------------------------------------------------------------ Title: The Importance of Non-Isotropic Conduction in Multi-Dimensional MHD Calculations of Coronal Magnetic Loops Authors: Poland, Arthur I.; Forjan, G. Bibcode: 2009SPD....40.1207P Altcode: Much progress has recently been made in modeling and observations of coronal loops. Most recent modeling has focused on 1-D models to investigate the location of the heating responsible for the high temperatures of these loops and the corona in general. More specifically the focus has been on various forms of pulsed heating with much argument as to whether these pulses arise in the corona or the transition region. There has been very little work done using multi-dimensional models for two reasons: 1) to do this correctly one must treat thermal conduction in a non-isotropic manner, only along the magnetic field lines, and 2) to have the calculations be meaningful one must adequately resolve the transition region, to approximately 12 km resolution. We have addressed both of these problems in using the University of Chicago Flash code to model the solar atmosphere from a temperature of 8,000K to over 1,000,000K. Adequate resolution was achieved by setting the adaptive mesh parameter to a sufficiently large value that dynamic regridding gave the needed 12 km resolution. Thermal conduction was originally handled in the program as an isotropic quantity. However, we have developed new modules for the code such that conduction was calculated as occurring only along the magnetic field lines.

Preliminary results show that the 2-D results with non-isotropic conduction more closely match the 1-D results than the 2-D results with isotropic conduction. This indicates that 1-D calculations are still valuable. We also find that with sufficiently detailed observations one should be able to discriminate between heating originating in the transition region and heating originating in the corona. Title: Automated Detection of CMEs with SOHO and STEREO Coronagraph Observations Authors: Olmedo, O.; Zhang, J.; Wechsler, H.; Poland, A.; Borne, K. Bibcode: 2008AGUSMSP43A..02O Altcode: A Solar Eruptive Event Detection System (SEEDS) has been developed to automatically detect, track, and catalog coronal mass ejections (CMEs) with SOHO and STEREO corona observations. The method developed is based on decomposing 2-D Coronagraph images to 1-D and looking for outstanding bright regions. Thresholds determine these regions, and in time sequences, CMEs can be located and tracked. A complete catalog of CMEs using LASCO C2 coronagraphs has been compiled using the SEEDS software and the results are made available online (http://spaceweather.gmu.edu/seeds). A preliminary catalog has been made using SECCHI COR2 coronagraphs and is also available online. We have been experimenting with real-time detection and make these results available online on a daily basis. We present statistics comparing the detections made with LASCO C2 with the CDAW CME catalog for the whole solar cycle 23. It is found that SEEDS is able to identify approximately 75% of the CMEs found within the CDAW CME catalog (omitting CMEs with quality index of 0 indicating an ill-defined CME). We look into approximately 100% more events detected by SEEDS which were not in CDAW and study the nature of these events. Title: Automatic Detection and Tracking of Coronal Mass Ejections in Coronagraph Time Series Authors: Olmedo, O.; Zhang, J.; Wechsler, H.; Poland, A.; Borne, K. Bibcode: 2008SoPh..248..485O Altcode: 2008SoPh..tmp....6O We present the current capabilities of a software tool to automatically detect coronal mass ejections (CMEs) based on time series of coronagraph images: the solar eruptive event detection system (SEEDS). The software developed consists of several modules: preprocessing, detection, tracking, and event cataloging. The detection algorithm is based on a 2D to 1D projection method, where CMEs are assumed to be bright regions moving radially outward as observed in a running-difference time series. The height, velocity, and acceleration of the CME are automatically determined. A threshold-segmentation technique is applied to the individual detections to automatically extract an approximate shape of the CME leading edge. We have applied this method to a 12-month period of continuous coronagraph images sequence taken at a 20-minute cadence by the Large Angle and Spectrometric Coronagraph (LASCO) instrument (using the C2 instrument only) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft. Our automated method, with a high computational efficiency, successfully detected about 75% of the CMEs listed in the CDAW CME catalog, which was created by using human visual inspection. Furthermore, the tool picked up about 100% more small-size or anomalous transient coronagraph events that were ignored by human visual inspection. The output of the software is made available online at http://spaceweather.gmu.edu/seeds/. The parameters of scientific importance extracted by the software package are the position angle, angular width, velocity, peak, and average brightness. Other parameters could easily be added if needed. The identification of CMEs is known to be somewhat subjective. As our system is further developed, we expect to make the process significantly more objective. Title: The Advancement Of An Automatic Solar Eruptive Event Detection System (seeds) To A Near Real-time System Authors: Olmedo, Oscar; Zhang, J.; Wechsler, H.; Poland, A.; Borne, K. Bibcode: 2007AAS...210.2929O Altcode: 2007BAAS...39..325O We have been working on a tool to automatically detect, track and catalogue Coronal Mass Ejections as observed by the LASCO C2 instrument on board the SOHO spacecraft. The software developed follows a simple algorithm, which is based on decomposing 2-D Coronagraph images to 1-D and looking for outstanding bright regions. Thresholds determine these regions, and in time sequences, CMEs can be located and tracked. Many improvements to the algorithm have been made in recent months dealing with the preprocessing of the input images as well as the tracking of CME detections. Most importantly the system has advanced to the point that it can make detections of CMEs in near real-time. What is meant by near real-time detection is; first, the downloading images, as they are made available by the instrument team, and second, the processing and reporting of CME events as they occur on a daily basis. The true positive rate of detections is over 75% as compared with the CDAW CME catalog, and will continue to improve with further experimentation of threshold values. Output from the SEEDS algorithm can be found at http://solar.gmu.edu/research/autocme/ (Still showing preliminary results). Currently, the software is being adapted to accept STEREO images as input, preliminary test with STEREO COR2 data show promising results. Title: Sentinels of the Sun: Forecasting Space Weather Authors: Poland, Arthur I. Bibcode: 2006SpWea...4.8007P Altcode: The story of humanity's interest in space weather may go back to prehistoric times when people at high latitudes noticed the northern lights. Interest became more acute after the development of electrical technologies such as the telegraph, and certainly during World War II when shortwave radio communication came into practical use. Solar observing actually began to be supported by the military, with the observatory at Climax, Colorado being established to monitor the Sun during the war. With the advent of satellites and manned space travel to the Moon, space weather became a seriously funded endeavor both for basic research and forecasting. In the book, Sentinels of the Sun: Forecasting Space Weather, Barbara Poppe does an excellent job of telling this story for the nonprofessional. Moreover, as a professional who has studied space weather since before humans landed on the Moon, I found the book to be a very enjoyable read. Title: The Development of an Automatic Solar Eruptive Event Detection System (SEEDS) Authors: Olmedo, Oscar A., Jr.; Zhang, J.; Wechsler, H.; Borne, K.; Poland, A. Bibcode: 2006SPD....37.0817O Altcode: 2006BAAS...38..233O We present a software tool that automatically detects Coronal Mass Ejections (CMEs) as observed by the LASCO C2 instrument on board the SOHO spacecraft. The software developed follows a simple algorithm, which is based on decomposing 2-D Coronagraph images to 1-D and looking for outstanding bright regions. Thresholds determine these regions, and in time sequences, CMEs can be located and tracked. We have applied this method on a 12-month period of LASCO C2 data and have found about 75% more events than the NRL-GSFC-CUA CME catalog generated by human visual inspection. The automatic method gives a true positive rate of approximately 75% using the manual catalog as a benchmark. The software being presented is to be part a suite of software tools in the Solar Eruptive Event Detection System (SEEDS), being developed at George Mason University. The main purpose of SEEDS is to make associations of solar transient events observed by different instruments based on high-dimensional temporal and spatial data. An example problem SEEDS may be able to answer is whether or not a CME event seen In a Coronagraph is associated with a flareing/dimming event seen in coronal images. With many future spac missions underway, such as STEREO and SDO, SEEDS hopes to be utilized in aiding to the gain of scientific knowledge in an efficient and effective way, to the ultimate goal of making real time forecasting of space weather events. Title: Automatic detection of Coronal Mass Ejections using Computer Vision. Authors: Olmedo, O. A.; Zhang, J.; Wechsler, H.; Poland, A.; Borne, K. D. Bibcode: 2006AGUSMSH43A..02O Altcode: We present a software tool that automatically detects Coronal Mass Ejections (CMEs) as observed by the LASCO C2 instrument on board the SOHO spacecraft. The software developed follows a simple algorithm, which is based on decomposing 2-D Coronagraph images to 1-D and looking for outstanding bright regions. Thresholds determine these regions, and in time sequences, CMEs can be located and tracked. We have applied this method on a 12-month period of LASCO C2 data and have found about 75% more events than the NRL-GSFC-CUA CME catalog generated by human visual inspection. The automatic method gives a true positive rate of approximately 75% using the manual catalog as a benchmark. The software being presented is to be part a suite of software tools in the Solar Eruptive Event Detection System (SEEDS), being developed at George Mason University. The main purpose of SEEDS is to make associations of solar transient events observed by different instruments based on high-dimensional temporal and spatial data. An example problem SEEDS may be able to answer is whether or not a CME event seen In a Coronagraph is associated with a flareing/dimming event seen in coronal images. With many future spac missions underway, such as STEREO and SDO, SEEDS hopes to be utilized in aiding to the gain of scientific knowledge in an efficient and effective way, to the ultimate goal of making real time forecasting of space weather events. Title: Heating the Solar Corona: Observations for Model Boundary Conditions Authors: Nestlerode, C. M.; Poland, A. I. Bibcode: 2005AAS...20711107N Altcode: 2005BAAS...37.1342N A prominent question in solar physics concerns the sources of coronal heating. This problem can be addressed through observations of closed magnetic loops which have high enough density to provide adequate temporal, spatial, and spectral resolution. Measurements of temperature, density, and velocity throughout the loop can be used for boundary conditions and compared with quantities for model calculations. In this paper, we present Solar Ultraviolet Measurements from Emitted Radiation (SUMER) data from the Solar and Heliospheric Observatory's (SOHO's) JOP 161 program. The SUMER instrument has high spatial and spectral resolution over several different spectral lines and therefore the data cover a large temperature range. The analyzed lines include Mg VIII, Mg IX, N III, N IV, Ne VIII, O IV, O V, S IV, S V, and S X with temperatures ranging from 60,000 K (S IV) to 0.9 MK (Mg IX). The velocity profiles are created using Gaussian fitting with wavelength calibration determined using average quiet Sun velocities from known Doppler velocity shifts. The velocity profiles show important changes in solar foot point plasma speed both spatially and temporally. This analysis builds on previous analysis of solar spectral lines observed with the SOHO Coronal Diagnostic Spectrometer (CDS); the advantage of the SUMER instrument is better resolution, both spectrally and spatially. This work was funded by NASA, Living with a Star Program. Title: Solar Eruptive Event Detection System (SEEDS) Authors: Olmedo, O.; Zhang, J.; Wechsler, H.; Borne, K.; Poland, A. Bibcode: 2005AAS...20711106O Altcode: 2005BAAS...37.1342O We report the progresses in developing a suite of software tools to automatically detect and classify transient astrophysical events. Astrophysical data is being created at the rate beyond human operators capable of analyzing. Our team, composed of scientist in the astronomy and computer science departments at George Mason University (GMU), is particularly interested in tackling this problem. This project is in its early stage and to date we are concentrating on solar eruptive events, calling our analyzing scheme Solar Eruptive Event Detection System (SEEDS). We have successfully developed tools to detect and classify coronal mass ejections (CMEs) observed by LASCO instrument on board the SOHO spacecraft. SEEDS proceeds as follows; firstly advanced image processing techniques are used to detect transient features and a time-dependent causal filter is applied for tracking the features, from here, the detected events are put through a machine learning algorithm where they are classified and event catalogs are created. The next step is to make association of transient events observed by different instruments based on high-dimensinal temporal and spatial data. A scientific question, for example, that may be answered with SEES is whether or not a CME event seen in a Coronagraph is associated with a flareing/dimming event seen in coronal images. With many future space observing missions underway, such as STEREO and SDO, SEEDS hopes to be utilized in aiding to the gain of scientific knowledge in an efficient and effective way, to the ultimate goal of making real time forecasting of space weather events. Title: Space Weather At George Mason University Authors: Poland, A. I.; Zhang, J. Bibcode: 2005AGUSMED11A..04P Altcode: George Mason University (GMU), located in Fairfax, Virginia has an exciting and rapidly growing set of graduate programs in Astrophysics, Space Weather, Planetary Sciences, and Earth Sciences. The faculty members in these programs are affiliated with the Department of Physics and Astronomy and the School of Computational Sciences (SCS). The synergy between these two departments creates opportunities for learning not found in traditional programs. Our curriculum emphasizes multi-disciplinary science that crosses traditional department boundaries. Space Weather/solar terrestrial physics is one of these multi-disciplinary areas. We expect our students to develop a deep understanding of the Sun, the heliosphere, geospace, and their interactions; we emphasize a systems view. The graduate program in Space Weather at GMU offers degrees at the Masters (M.S.) and Doctoral (Ph. D) levels through the School of Computational Sciences (SCS) and the Department of Physics and Astronomy of the College of Arts and Sciences (CAS). A wide variety of relevant courses are offered through (SCS) in partnership with (CAS). Students also have the opportunity to do research associated with the Goddard Space Flight Center and the Navel Research Laboratory. For more information on the program see: http://www.scs.gmu.edu/spaceweather/ Undergraduates and people from local industry are also taking some of our courses to further their education in this area. Many of them are finding the lectures directly relevant to their daily work, such as satellite orbit maintenance. Title: Doppler Shift Velocity Calculations of Multi-Wavelength Coronal Diagnostic Spectrometer Data Using Various Background Corrections Authors: Duffin, R. T.; Poland, A. I.; McIntosh, S. W. Bibcode: 2004ESASP.575..545D Altcode: 2004soho...15..545D No abstract at ADS Title: Detailed SUMER Observations of Coronal Loop Footpoint Dynamics Authors: McIntosh, Scott W.; Poland, Arthur I. Bibcode: 2004ApJ...604..449M Altcode: For the most part, the characteristics of heating in the open corona and in closed coronal loops are determined by observing the emitted plasma intensity as a function of position and comparing this with model calculations. There are also some efforts that include observed velocity and still others that use theoretical physical processes such as electrodynamic or turbulent heating, for example. With a view toward future modeling endeavors, we investigate the temporal behavior of the intensity and velocity of a magnetic loop footpoint as observed by SUMER on the Solar and Heliospheric Observatory (SOHO) spacecraft as part of SOHO/TRACE Joint Observing Program 72. We study these quantities in emission lines that were specifically chosen to span the temperature domain of the upper chromospheric and transition region plasmas (105-106 K). We discuss the implications of these observations, suggest improvements, and present some new avenues of exploration. The most significant result is the demonstration of the importance of including the measurement of velocity as a function of time in the loop footpoint region. Title: International heliophysical year: a program of global research continuing the tradition of previous international years Authors: Davila, Joseph M.; Poland, Arthur I.; Harrison, Richard A. Bibcode: 2004AdSpR..34.2453D Altcode: In 1957 a program of international research, inspired by the International Polar Years of 1882-1883 and 1932-1933, was organized as the International Geophysical Year (IGY) to study global phenomena of the Earth and geospace. The IGY involved about 60,000 scientists from 66 nations, working at thousands of stations from pole to pole, in an effort to obtain simultaneous, global observations on Earth and in space. There had never been anything like it before. The 50th anniversary of the International Geophysical Year will occur in 2007. We propose to organize an international program of scientific collaboration for this time period called the International Heliophysical Year (IHY). Like its predecessors, the IHY will focus on fundamental global questions of Earth science. Title: Nonlinear interactions in coronal heating Authors: Einaudi, G.; Dahlburg, R. B.; Rappazzo, A. F.; Poland, A.; Li, Y. Bibcode: 2004cosp...35.3938E Altcode: 2004cosp.meet.3938E The dynamics of the solar corona as well as its very existence are due to the dynamics of plasmas and magnetic fields which, at the global scales of coronal loops, prominences and helmet streamers may be described by magnetohydrodynamics. Here we will discuss the importance and role of nonlinear interactions in the heating of the solar corona, which relies on the transfer, storage and dissipation of the mechanical energy present in photospheric motion (Einaudi and Velli 1999). Nonlinear interactions including the coupling of coronal fields to the motions and emerging flux through the photosphere determine both the rate of heating and the topology of coronal magnetic fields. The dependence of the heating rate on the time and space scales of the photospheric motions will be considered. In particular we compare the results of the numerical simulations performed using as input the MDI data on the features of the photospheric motions at the base of some coronal loops with the behavior of the loops themselves as deduced from TRACE. G. Einaudi and M. Velli, Phys. Plasmas 6, 4146 (1999). Title: Road Map of Solar-Terrestrial Programs in the USA Authors: Poland, A. I. Bibcode: 2003JKAS...36S.151P Altcode: No abstract at ADS Title: Coronal Loops Heated by Magnetohydrodynamic Turbulence. I. A Model of Isobaric Quiet-Sun Loops with Constant Cross Sections Authors: Chae, Jongchul; Poland, Arthur I.; Aschwanden, Markus J. Bibcode: 2002ApJ...581..726C Altcode: Several recent papers have presented new observational results indicating that many coronal loops in active regions are nearly isothermal. It is expected that quiet-Sun loops may have similar thermal structures, since quiet-Sun differential emission measures look similar to those in active regions. In the quiet Sun, it is well known from observations that the nonthermal velocity inferred from the excess broadening of a line over thermal broadening reaches a peak of about 30 km s-1 around 3×105 K and then decreases with temperature, having a value of about 20 km s-1 at 1×106 K. In the present work, we make the assumption that the observed nonthermal velocities are a manifestation of magnetohydrodynamic (MHD) turbulence and present a model of static, isobaric coronal loops heated by turbulence. Instead of solving the MHD equations, we adopt simple energy spectra in MHD turbulence and infer the heating rate as a function of temperature from the observed nonthermal velocities. By solving the steady state energy equation of a loop in which temperature monotonically increases with height, we obtain the following results: (1) The heating rate is predominantly near the footpoints and decreases with the loop arc length. (2) There is a critical temperature above which the loop cannot be maintained in a steady state. (3) The loop is denser and is more isothermal than uniformly heated loops, being compatible with recent observations. (4) The theoretical differential emission measures are in good agreement with the empirical values at temperatures above 105 K. Below this temperature, we still have a large discrepancy. (5) It is possible to explain the observed strong correlation between intensity and nonthermal velocity of a spectral line in the quiet Sun. Our results support the idea that quasi-statically driven MHD turbulence of the direct current (DC) type in the stratified medium (transition region and corona) is a viable mechanism for coronal heating. Title: The International Heliophysical Year (IHY) Authors: Davila, J. M.; Harrison, R.; Poland, A.; Thompson, B.; Gopalswamy, N. Bibcode: 2002AGUFMSH21A0518D Altcode: In 1957 a program of international research, inspired by the International Polar Years of 1882-83 and 1932-33, was organized as the International Geophysical Year (IGY) to study global phenomena of the Earth and geospace. The IGY involved about 60,000 scientists from 66 nations, working at thousands of stations, from pole to pole to obtain simultaneous, global observations on Earth and in space. There had never been anything like it before. The fiftieth anniversary of the International Geophysical Year will occur in 2007. We propose to organize an international program of scientific collaboration for this time period called the International Heliophysical Year (IHY). Like it predecessors, the IHY will focus on fundamental global questions of Earth science. Title: The International Heliophysical Year Concept Authors: Davila, J.; Harrison, R.; Poland, A.; St-Cyr, O.; Thompson, B. Bibcode: 2002cosp...34E.529D Altcode: 2002cosp.meetE.529D In 1957 a program of international research, inspired by the International Polar Years of 1882-83 and 1932-33, was organized as the International Geophysical Year (IGY) to study global phenomena of the Earth and geospace. The IGY involved about 60,000 scientists from 66 nations, working at thousands of stations, from pole to pole to obtain simultaneous, global observations on Earth and in space. There had never been anything like it before. The fiftieth anniversary of the International Geophysical Year will occur in 2007. We propose to organize an international program of scientific collaboration for this time period called the International Heliophysical Year (IHY). Like its predecessors, the IHY will focus on fundamental global questions of Earth science. Title: The New Solar Corona Authors: Aschwanden, Markus J.; Poland, Arthur I.; Rabin, Douglas M. Bibcode: 2001ARA&A..39..175A Altcode: We focus on new observational capabilities (Yohkoh, SoHO, TRACE), observations, modeling approaches, and insights into physical processes of the solar corona. The most impressive new results and problems discussed in this article can be appreciated from the movies available on the Annual Reviews website and at http://www.lmsal.com/pub/araa/araa.html. "The Sun is new each day." Heraclites (ca 530-475 BC) "Everything flows." Heraclites (ca 530-475 BC) Title: Technology for the SEC Theme at NASA Authors: Poland, A. I. Bibcode: 2000SPD....31.1604P Altcode: 2000BAAS...32..849P Technology advances are essential to achieve a high quality of science in NASA missions. In the past, instrument technology has been funded either through the SR&T program or during development of accepted flight programs. Some changes are occuring in NASA to improve our ability to advance technology for our future programs. I will discuss some of the new program ideas and relate them to the SEC Roadmap and other SEC technology documents being developed at GSFC. Title: Four years of SOHO discoveries - some highlights. Authors: Fleck, B.; Brekke, P.; Haugan, S.; Duarte, L. S.; Domingo, V.; Gurman, J. B.; Poland, A. I. Bibcode: 2000ESABu.102...68F Altcode: Analysis of the helioseismic data from SOHO has shed new light on solar and heliosheric physics: the structure and dynamics of the solar interior, the heating and dynamics of the solar corona, and the acceleration and composition of the solar wind. Title: Modeling of Solar Transition Region Outflows Authors: Poland, A. I.; Chae, J. Bibcode: 1999AAS...194.9312P Altcode: 1999BAAS...31..990P The problem of observing outflow of material from the Sun has been an interesting issue in solar physics for several decades. The problem is that we know material flows from the Sun since there is a solar wind measured at Earth and in interplanetary space. However, observations in the chromosphere, transition region, and lower corona show mostly inflow with almost no outflow. In a recent paper by Hassler and coworkers it was shown that there is a significant outflow at network boundaries as seen in NeVIII (Te 800,000K), but no significant outflows have been observed at other temperatures. In our earlier work we demonstrated why one would expect to see only inflows below 100,000K. The energy balance between conduction, radiation, and enthalpy resulted in gradients being too steep to observe outflowing material. We have extended that work to 1,000,000K and included the observed effects of the spreading magnetic field with temperature. These new calculation results seem to be in agreement with the observations and indicate that outflows should only be observable in the 800,000K range. Title: Observations of Hydrogen and Helium Continua in Solar Prominences Authors: Andretta, V.; Kucera, T. A.; Poland, A. I. Bibcode: 1999ASPC..158..162A Altcode: 1999ssa..conf..162A No abstract at ADS Title: Active Regions Authors: Holman, G. D.; Cheng, C. -C.; Gurman, J. B.; Haisch, B. M.; Poland, A. I.; Porter, J. G.; Saba, J. L. R.; Schmieder, B.; Strong, K. T. Bibcode: 1999mfs..conf...41H Altcode: Magnetic Field Strength and Strucutre Results Prior to SMM First Results with SMM Subsequent Results: 1983-1987 The Coronal Magnetic Structures Observing Campaign Coronal Magnetic Field Studies after SMM Dynamics and Heating of the Solar Corona FCS Line-Broadening Measurements Large Nonthermal Velocities Spatial Variations Correlation Studies FCS Line-Broadening Data Interpreting the FCS Line Broadening Constraints on Mass Motions Link to Heating Discussion Coronal Heating, Magnetic Fields, and Flares UVSP Obervations of Active Regions Transition Region Brightenings: UV Microflares Sunspots Magnetic Field and Height of the Transition Region Sunspot Plumes Sunspot Flows Horizontal Flows Vertical Flows Nonthermal Line Broadening Umbral Oscillations A Look Backward, a Look Forward Prominences and Filaments Prominence Environment and Structure Steady Flows in Prominence Material Activity in Prominences Postflare Loops and Surges Conclusion Title: Neutral Hydrogen Column Depths in Prominences Using EUV Absorption Features Authors: Kucera, T. A.; Andretta, V.; Poland, A. I. Bibcode: 1998SoPh..183..107K Altcode: Observations of prominence regions in hot coronal lines (≳106 K) at wavelengths below the hydrogen Lyman absorption limit show what appear to be absorption features. Other authors have suggested that these observed features may be due to H and He continuum absorption. But there has, as yet, been no conclusive evidence that this is indeed the case. In this paper we present new Solar and Heliospheric Observatory (SOHO) observations that allow us to address this problem in a quantitative manner. We find that continuum absorption is the best explanation for the absorption observed in imaging data from the Coronal Diagnostic Spectrometer (CDS) on board SOHO. Furthermore, we discuss a new technique to measure the column depth of neutral hydrogen in a prominence, and use it to obtain estimates of the prominence filling factors as well. We calculate the column depth of neutral hydrogen, ξH∼1018 cm−2, and the filling factor, f≳0.3. Title: SUMER Observations of the Evolution and the Disappearance of a Solar Prominence Authors: Ofman, L.; Kucera, T. A.; Mouradian, Z.; Poland, A. I. Bibcode: 1998SoPh..183...97O Altcode: The mechanisms that lead to the formation and the disappearance of prominences are poorly understood, at present. An arch-shaped prominence was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory (SOHO) on 31 March-1 April 1996. The observations were performed at three wave-bands in the Lyman continuum. Ten successive images were obtained at 41-minute time intervals. Based on computed models of Gouttebroze, Heinzel, and Vial (1993), we have determined the temperature distribution of the prominence using the intensity ratio of 876 Å and 907 Å. The observed time sequence shows that parts of the prominence disappear possibly by heating, while other parts exhibit heating and cooling with apparent outward motion. We model the heat input with the linearized MHD equations using a prescribed initial density and a broad-band spectrum of Alfvén waves. We find a good qualitative agreement with observations. In the model the prominence is heated by the resonant absorption of Alfvén waves with frequencies that match the resonant condition for a particular flux tube structure that is determined by the magnetic field topology and plasma density. Title: Temperature Dependence of Ultraviolet Line Average Doppler Shifts in the Quiet Sun Authors: Chae, J.; Yun, H. S.; Poland, A. I. Bibcode: 1998ApJS..114..151C Altcode: The existence of prevailing redshifts in the UV lines formed in the solar transition region raises an important question concerning its physical origin and its role in the mass and energy balance of the outer solar atmosphere. A series of UV spectral lines observed by SUMER has been analyzed to obtain the spatial average of Doppler shifts in the quiet Sun as a function of temperature. The UV lines used for the analysis cover temperatures ranging from 104 to 106 K. The wavelength calibration has been done in reference to the coolest chromospheric lines such as neutral lines of silicon and sulfur. The positioning of the line center in blended lines has been made by employing a constrained multi-Gaussian fitting technique. The error in the measured average of the Doppler shifts is estimated to be smaller than 1 km s-1.

Our results show that the average Doppler shift at the base of the transition region is about 1-2 km s-1, increasing with temperature with a peak value of 11 km s-1 near T = 2.3 × 105 K. Then it decreases but remains still above zero (5 km s-1 in Ne VIII lines and 4 km s-1 in Mg X lines). We find that this behavior can be explained by the dominance of emission from plasma flowing downward from the upper hot region to the lower cool region along flux tubes with varying cross section. Assuming that pressure and mass flux are constant along a flux tube, the cross section of a typical flux tube has been estimated as a function of temperature. It turns out that the cross section is nearly constant below T = 105 K and then expands by a factor of about 30 at T = 106 K. This behavior is fairly well represented by an analytical functional form, A(T)/A(Th) = [1 + (Γ2 - 1)(T/Th)ν]1/2/Γ with parameters of Th = 106 K, Γ = 30, and ν = 3.6. Title: Helio-Atmospheric Links Explorer (HALE): A MIDEX Experiment for Exploring the Emergence of Magnetic Flux from Below the Solar Photosphere through the Corona Authors: Scherrer, P. H.; Title, A. M.; Bush, R. I.; Duvall, T. L., Jr.; Gurman, J. B.; Kosovichev, J. T.; Hoeksema, A. G.; Poland, A. I.; Tarbell, T. D. Bibcode: 1998ESASP.417..285S Altcode: 1998cesh.conf..285S No abstract at ADS Title: Helical Structure in an Eruptive Prominence Related to a CME (SUMER, CDS, LASCO) Authors: Kucera, T. A.; Poland, A. I.; Wiik, J. E.; Schmieder, B.; Simnett, G. Bibcode: 1998ASPC..150..318K Altcode: 1998IAUCo.167..318K; 1998npsp.conf..318K SOHO (SUMER/CDS) observed an eruptive prominence on May 1,1996, associated with a CME observed by LASCO. We investigate the physical conditions of this prominence in order to quantify velocity, temperature, and density. SUMER spectra in Si IV and O IV lines are used to obtain Doppler-shift images of the prominence. The prominence shows large-scale red and blueshifted regions, revealing a large helical structure with a global twist. In addition, fine structure analysis shows multiple components in the line profile, suggesting integration of many threads along the line-of-sight with a large dispersion of velocities (∼150 km s-1). Title: Dynamics and Fine Structures in Quiescent Prominences (MSDP/Pic du Midi, SOHO/SUMER and CDS) Authors: Li, K.; Malherbe, J. -M.; Wiik, J. E.; Schmieder, B.; Roudier, Th.; Kucera, T.; Poland, A. Bibcode: 1998ASPC..150...32L Altcode: 1998IAUCo.167...32L; 1998npsp.conf...32L No abstract at ADS Title: Observation of Prominence Heating and the Heating Mechanism Authors: Ofman, L.; Mouradian, Z.; Kucera, T. A.; Poland, A. I. Bibcode: 1998ASPC..150..159O Altcode: 1998IAUCo.167..159O; 1998npsp.conf..159O No abstract at ADS Title: Velocity Fields of a Filament Region Observed with Ground-Based Telescopes and from SOHO Authors: Mein, P.; Schmieder, B.; Malherbe, J. -M.; Wiik, J. E.; Engvold, O.; Brekke, P.; Zirker, J. B.; Poland, A. I.; Delaboudiniere, J. -P.; Staiger, J. Bibcode: 1998ASPC..150..135M Altcode: 1998npsp.conf..135M; 1998IAUCo.167..135M No abstract at ADS Title: Eruptive prominence and associated CME observed with SUMER, CDS and LASCO (SOHO) Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A.; Brekke, P.; Simnett, G. Bibcode: 1997SoPh..175..411W Altcode: Observations of an eruptive prominence were obtained on 1 May 1996, with the SUMER and CDS instruments aboard SOHO during the preparatory phase of the Joint Observing Programme JOP12. A coronal mass ejection observed with LASCO is associated temporally and spatially with this prominence. The main objective of JOP12 is to study the dynamics of prominences and the prominence-corona interface. By analysing the spectra of Oiv and Siiv lines observed with SUMER and the spectra of 15 lines with CDS, Doppler shifts, temperatures and electron densities (ratio of Oiv 1401 to 1399Å) were derived in different structures of the prominence. The eruptive part of the prominence consists of a bubble (plasmoid) of material already at transition region temperatures with red shifts up to 100 km s-1 and an electron density of the order of 1010cm-3. The whole prominence was very active. It developed both a large helical loop and several smaller loops consisting of twisted threads or multiple ropes. These may be studied in the SUMER movie (movie 2). The profiles of the SUMER lines show a large dispersion of velocities (±50 km s-1) and the ratio of the Oiv lines indicates a large dispersion in electron density (3 x 109cm-3 to 3x 1011cm-3). The CME observed by LASCO left the corona some tens of minutes before the prominence erupted. This is evidence that the prominence eruptions are probably the result of the removal of the restraining coronal magnetic fields which are in part responsible for the original stability of the prominence. Title: Effects of Non-LTE Radiative Loss and Partial Ionization on the Structure of the Transition Region Authors: Chae, J.; Yun, H. S.; Poland, A. I. Bibcode: 1997ApJ...480..817C Altcode: In this paper we address the question of how non-LTE radiative losses with partial ionization of hydrogen and helium affects the energetics and structure of the solar transition region. To accomplish this we have constructed theoretical models of a thin rigid magnetic flux tube with a steady material flow, which is embedded vertically in the solar atmosphere. These models include the effects of material flow, conduction, non-LTE radiative transfer in H and He, and partial ionization. We find from this study that the effect of non-LTE radiative transfer with partial ionization is significant near the base of the transition region at temperatures less than 2.5 × 104 K. This leads to a 1 order of magnitude increase in the differential emission measure in comparison with the optically thin approximation with complete ionization in the low (less than 2.5 × 104 K) temperature regime. Above this region the non-LTE and opacity effects are small. In the upflow case the conductive and convective energy processes dominate to such a large extent that non-LTE radiative process and partial ionization are not important.

In this work we also confirm the previous work of other authors who provided the explanation for why downflowing transition region material is much more visible than upflowing material. We present the results in a manner that gives a good physical understanding as to why this occurs. Title: Measuring the He I/H ratio in a prominence using Lyman absorption Authors: Kucera, T. A.; Andretta, V.; Poland, A. I. Bibcode: 1997SPD....28.0112K Altcode: 1997BAAS...29Q.881K We investigate a method for measuring the ratio of neutral helium to hydrogen in solar prominences. The upper limit to the Lyman continuum occurs at 911 Angstroms for H, 504 Angstroms for He I, and 228 Angstroms for He II. Lyman absorption by prominences and other structures is clearly visible in emission of hot coronal lines observed by the Coronal Diagnostic Spectrometer (CDS) and Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). By comparing the absorption in lines absorbed by H only and by H and He I, the ratio of He I to H in prominences can be determined. We attempt to do this by comparing the absorption by a prominence in the Mg X line at 624.9 Angstroms and the Mg IX line at 368.1 Angstroms, both observed by CDS. Title: A New Look at the Quiet Sun Network in the Upper Atmosphere During a Minimum of Activity Cycle Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Poland, A.; Falciani, R. Bibcode: 1997ESASP.404..517L Altcode: 1997cswn.conf..517L No abstract at ADS Title: First Results of the SUMER Telescope and Spectrometer on SOHO - I. Spectra and Spectroradiometry Authors: Wilhelm, K.; Lemaire, P.; Curdt, W.; Schühle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Huber, M. C. E.; Vial, J. -C.; Kühne, M.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M.; Feldman, U.; Hollandt, J.; Brekke, P. Bibcode: 1997SoPh..170...75W Altcode: SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 × 106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona. Title: High resolution solar ultraviolet measurements Authors: Lemaire, P.; Wilhelm, K.; Schühle, U.; Curdt, W.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. -C. Bibcode: 1997AdSpR..20.2249L Altcode: The increase of our understanding of the processes acting in the solar corona and maintaining it is strongly dependent on the quality of the data that are obtained to check theories. The fine structure of the solar atmosphere seen from the photosphere and extending to the hottest parts of the corona requires data with high resolution in all parameter space (angular, spectral and temporal). To constrain the hypotheses that are proposed to describe the solar corona, it is necessary to establish an accurate energy budget taking into account the processes which are acting from the chromosphere to the corona. Some requirements can be established and compared with the data collected so far (or about to be collected) with the present SUMER (Solar Utraviolet Measurements of Emitted Radiations) instrumentation. Title: First Results of the SUMER Telescope and Spectrometer on SOHO - II. Imagery and Data Management Authors: Lemaire, P.; Wilhelm, K.; Curdt, W.; SchÜle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. C.; KÜhne, M.; Huber, M. C. E.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M. Bibcode: 1997SoPh..170..105L Altcode: SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We report on some aspects of the observation programmes that have already led us to a new view of many aspects of the Sun, including quiet Sun, chromospheric and transition region network, coronal hole, polar plume, prominence and active region studies. After an introduction, where we compare the SUMER imaging capabilities to previous experiments in our wavelength range, we describe the results of tests performed in order to characterize and optimize the telescope under operational conditions. We find the spatial resolution to be 1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along the slit. Resolution and sensitivity are adequate to provide details on the structure, physical properties, and evolution of several solar features which we then present. Finally some information is given on the data availability and the data management system. Title: High-Resolution Observations of the Extreme Ultraviolet Sun Authors: Harrison, R. A.; Fludra, A.; Pike, C. D.; Payne, J.; Thompson, W. T.; Poland, A. I.; Breeveld, E. R.; Breeveld, A. A.; Culhane, J. L.; Kjeldseth-Moe, O.; Huber, M. C. E.; Aschenbach, B. Bibcode: 1997SoPh..170..123H Altcode: This paper presents first results of the Coronal Diagnostic Spectrometer (CDS) recently launched aboard the Solar and Heliospheric Observatory (SOHO). CDS is a twin spectrometer, operating in the extreme ultraviolet range 151-785 Å. Thus, it can detect emission lines from trace elements in the corona and transition region which will be used to provide diagnostic information on the solar atmosphere. In this paper, we present early spectra and images, to illustrate the performance of the instrument and to pave the way for future studies. Title: Coordinated Observations of Prominences with SUMER/CDS and Ground Observatories Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A. Bibcode: 1997ASPC..118..278W Altcode: 1997fasp.conf..278W An international campaign for the observation of prominences and filaments was successfully accomplished between June 3 and 9 1996. Several ground observatories took part in the campaign which included the space observatories SOHO and Yohkoh. The main objective of this campaign was to study the dynamics of prominences and the prominence-corona interface, the formation of filaments and the fine structures at different temperatures. We will reported on two Joint Observing Programmes of SUMER and CDS aboard SOHO (JOP 12 and JOP 17), which have been achieved. Finally we will present as an exemple a prominence observed on May 1, 1996 during the tests of the programme JOP 12. This prominence was associated with a CME (observed with LASCO). Very active parts with Dopplershifs up to +/- 36kms(-1) were measured in the SUMER spectra of the prominence, indicating the presence of twisted ropes during the eruption. Mean electron densities have spatial and temporal dispersion of one order of magnitude (10(9) - 10(10) cm(-3) ). Title: The structure of the solar corona as observed by the Solar Extreme Ultraviolet Rocket Telescope and Spectrograph Authors: Davila, Joseph M.; Thomas, Roger J.; Brosius, Jeffrey; Poland, Arthur Bibcode: 1997AdSpR..20.2293D Altcode: Data from the Solar Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS) have been used to address a number of important scientific problems. The primary strength of the SERTS data is the fact that this spectral range is rich with emission lines. Over 270 lines are seen in the SERTS active Sun spectrum, from 57 different ions. For example, multiple (>= 4) lines are observed for all ionization states of iron from Fe IX to Fe XVII. Temperatures and densities have been derived for a number of active and quiet Sun regions, the coronal magnetic field strength has been estimated for both a plage region and an active region. Title: "Prominences, filaments and chromospheric activity" June 1996 campaign with SOHO, YOHKOH and Wrocław. Authors: Wiik, J. E.; Rudawy, P.; Schmieder, B.; Kucera, T.; Rompolt, B.; Poland, A. Bibcode: 1997joso.proc...93W Altcode: No abstract at ADS Title: The sun as never viewed before Authors: Poland, A. I. Bibcode: 1997EOSTr..78..133P Altcode: With the launch of the Solar and Heliospheric Observatory (SOHO), on December 2, 1995, solar physics entered a new era of “viewing” the Sun and heliosphere without interferences from the Earth's atmosphere. SOHO is a mission of international cooperation between the European Space Agency (ESA) and NASA. The most exciting new discoveries from SOHO include the unexpectedly high magnetic activity observed during the very minimum of the solar cycle and the “observation” of the interior structure of the Sun (helioseismology). The coronal instruments are showing that coronal mass ejections (CMEs) leave the Sun more frequently than expected, at the rate of approximately one per day. The helioseismology experiments, with their extremely low noise due to the absence of the Earth's atmospheric interference, are showing that convective cells under the solar surface are shaped like pancakes, not spheres as was previously assumed. Title: Extreme ultraviolet observations of the solar corona: first results from the coronal diagnostic spectrometer on SOHO Authors: Harrison, R. A.; Fludra, A.; Sawyer, E. C.; Culhane, J. L.; Norman, K.; Poland, A. I.; Thompson, W. T.; Kjeldseth-Moe, O.; Aschenbach, B.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E. Bibcode: 1997AdSpR..20.2239H Altcode: We present first results from the Coronal Diagnostic Spectrometer (CDS) aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is a double spectrometer operating in the 151-785 A˚ range. This region of the solar spectrum is rich in emission lines from trace elements in the solar atmosphere, which can be used to derive diagnostic information on coronal and transition region plasma. Early spectra are presented and well identified lines are listed. In addition, examples of images in selected wavelength ranges are shown, for a prominence, a loop system and a bright point, demonstrating well the power of such extreme ultraviolet observations. Title: The first results from SOHO. Authors: Domingo, V.; Fleck, B.; Poland, A. Bibcode: 1996ESABu..87....7D Altcode: SOHO, launched by an Atlas II-AS from Cape Canaveral on 2 December 1995, was inserted into its halo orbit around the L1 Lagrangian point. Typical examples of the unique results being obtained with SOHO's instruments are presented. Title: SOHO-Solar and Heliospheric Observatory Authors: Poland, A. I. Bibcode: 1996AAS...188.4901P Altcode: 1996BAAS...28..896P With the successful launch of SOHO on Dec. 2, 1995 we are beginning a new era of solar and heliospheric observations. SOHO is a space mission of international co-operation between the European Space Agency (ESA) and NASA designed to study the sun and heliosphere from the vicinity of the sun-earth L1 point. In this talk I will give an overview of the first results and planned observations in the three areas of the sun/heliosphere system: the solar interior as studied through the techniques of helioseismology; the solar atmosphere and studies of the heating and acceleration of the solar wind; and in-situ measurements of the solar wind as observed at L1. I will also discuss the framework in which SOHO is operated and how other scientist, not already involved in the SOHO mission, can get involved with the program. Title: A Solar EUV Spectral Atlas Observed with SUMER Authors: Brekke, P.; Wilhelm, K.; Lemaire, P.; Curdt, W.; Schuhle, U.; Poland, A.; Kucera, T.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1996AAS...188.3713B Altcode: 1996BAAS...28..879B We present the first solar EUV spectral atlas in the wavelength range 500 -- 1600 { Angstroms}. The spectra were recorded with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) which is part of the ESA/NASA Solar and Heliospheric Observatory (SOHO). The solar spectrum below 1200 { Angstroms} is not very well known. Thus, the present spectral atlas, and SUMER observations in general, represents a new important diagnostic tool to study essential physical parameters of the solar atmosphere. It includes emission from atoms and ions in the temperature range 10(4) to 2 x 10(6) K. Thus, emission lines and continua emitted from the lower chromosphere to the lower corona can be studied. The atlas is also useful as a planning tool for SUMER studies to determine useful dwell times, possible blends, and to select proper data extraction windows. The angular resolution of SUMER is close to 1 arcsec, but the atlas presented here represents an average along part of the 1-arcsec wide slit, typically 30 arcsec. The spectral resolving power of the instrument is lambda /Delta lambda = 17770-38300. For more details about the SUMER instrument we refer to Wilhelm et al. (Solar Physics, 162, 189, 1995). The spectral data in this atlas were obtained with the spectrometer slit positioned at the center of the solar disk with a dwell time of 300 s to bring up weak lines and continua. The full spectral range was put together from a number of exposures each covering approximately 20 { Angstroms} in 1st order on the coated, and therefore most sensitive, part (KrB) of the detector. 1st and 2nd order spectra are superimposed. The spectral atlas is available in a computer readable format together with a IDL program to read and display the data using a widget interface. The atlas and the programs can be obtained via the World Wide Web (http://hydra.mpae.gwdg.de/mpae_projects/SUMER/sumer.html) or by contacting one of the authors. Title: Preface Authors: Fleck, B.; Domingo, V.; Poland, A. Bibcode: 1995SoPh..162D...9F Altcode: No abstract at ADS Title: The Coronal Diagnostic Spectrometer for the Solar and Heliospheric Observatory Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise, A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang, J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards, A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas, P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe, O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger, H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I. Bibcode: 1995SoPh..162..233H Altcode: The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150 - 800 å. By observing the intensities of selected lines and line profiles, we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Futhermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere. Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schühle, U.; Lemaire, P.; Gabriel, A.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kühne, M.; Timothy, J. G.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1995SoPh..162..189W Altcode: The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 × 106K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations. Title: The SOHO mission. Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1995SoPh..162.....F Altcode: SOHO, the Solar and Heliospheric Observatory, is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona. This special issue is dedicated to the SOHO payload and to its operation. Title: The SOHO Mission: an Overview Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995SoPh..162....1D Altcode: The Solar and Heliospheric Observatory (SOHO) is a space mission that forms part of the Solar-Terrestrial Science Program (STSP), developed in a collaborative effort by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). The STSP constitutes the first "cornerstone" of ESA's long-term programme known as "Space Science — Horizon 2000". The principal scientific objectives of the SOHO mission are a) to reach a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) to gain better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments. SOHO is a three-axis stabilized spacecraft with a total mass of 1850 kg; 1150 W of power will be provided by the solar panels. The payload weighs about 640 kg and will consume 450 W in orbit. SOHO will be launched by an ATLAS II-AS and will be placed in a halo orbit around the Sun-Earth L1 Lagrangian point where it will be continuously pointing to Sun centre with an accuracy of 10 arcsec. Pointing stability will be better than 1 arcsec over 15 min intervals. The SOHO payload produces a continuous science data stream of 40 kbits/s which will be increased by 160 kbits/s whenever the solar oscillations imaging instrument is operated in its highrate mode. Telemetry will be received by NASA's Deep Space Network (DSN). Planning, coordination and operation of the spacecraft and the scientific payload will be conducted from the Experiment Operations Facility (EOF) at NASA's Goddard Space Flight Center (GSFC). Title: Some design and performance features of SUMER: solar ultraviolet measurements of emitted radiation Authors: Wilhelm, Klaus; Curdt, W.; Marsh, E.; Schuehle, Udo H.; Lemaire, Philippe; Gabriel, Alan H.; Vial, J. -C.; Grewing, Michael; Huber, Martin C.; Jordan, S. D.; Poland, Arthur I.; Thomas, Roger J.; Kuehne, Mikhael; Timothy, J. Gethyn; Hassler, Donald M.; Siegmund, Oswald H. Bibcode: 1995SPIE.2517....2W Altcode: The instrument SUMER (solar ultraviolet measurements of emitted radiation) is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 multiplied by 106 K and above. The observations will be performed, on board SOHO (solar and heliospheric observatory) scheduled for launch in November 1995, by a scanning, normal-incidence telescope/spectrometer system in the wavelength range from 500 to 1610 angstrom. Spatial resolution requirements compatible with the pointing stability of SOHO are less than 1000 km corresponding to about 1-arcsec angular resolution. Doppler observations of EUV line shifts and broadenings should permit solar plasma velocity measurements down to 1 km s-1. We report here on some specific features of this instrument related to its pointing as well as its spatial and spectral resolution capabilities. Title: Coronal Diagnostic Spectrometer: an extreme-ultraviolet spectrometer for the Solar and Heliospheric Observatory Authors: Kent, Barry J.; Harrison, Richard A.; Sawyer, Eric C.; Hayes, R. W.; Richards, Anthony G.; Culhane, John L.; Norman, K.; Breeveld, A. A.; Thomas, P. D.; Poland, Arthur I.; Thomas, Roger J.; Thompson, William T.; Aschenbach, Bernd R.; Braeuninger, Heinrich W.; Kjeldseth-Moe, O.; Kuehne, Mikhael; Hollandt, J.; Paustian, W.; Bromage, B. J. Bibcode: 1995SPIE.2517...12K Altcode: The coronal diagnostic spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 15.0 - 80.0 nm. By observing the intensities of selected lines and line profiles, it is possible to derive temperature, density, flow, and abundance information for the plasmas in the solar atmosphere. Spatial resolution down to a few arcseconds and temporal resolution of seconds, allows such studies to be made within the fine-scale structure of the solar corona. Furthermore, coverage of a large wavelength band provides the capability for simultaneously observing the properties of plasma across the wide temperature ranges of the solar atmosphere. The CDS design makes use of a Wolter-Schwarzschild II telescope which simultaneously illuminates two spectrometer systems, one operating in normal incidence the other in grazing incidence. In this paper we describe the salient features of the design of the CDS instrument and discuss the performance characteristics of CDS as established through pre-delivery test and calibration activities. Title: SOHO: The Solar and Heliospheric Observatory Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995SSRv...72...81D Altcode: The Solar and Heliospheric Observatory (SOHO), together with the Cluster mission, constitutes ESA's Solar Terrestrial Science Programme (STSP), the first “Cornerstone” of the Agency's long-term programme “Space Science — Horizon 2000”. STSP, which is being developed in a strong collaborative effort with NASA, will allow comprehensive studies to be made of the both the Sun's interior and its outer atmosphere, the acceleration and propagation of the solar wind and its interaction with the Earth. This paper gives a brief overview of one part of STSP, the SOHO mission. Title: The SOHO mission Authors: Fleck, B.; Domingo, V.; Poland, A. Bibcode: 1995somi.book.....F Altcode: No abstract at ADS Title: SOHO: The Solar and Heliospheric Observatory Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995hlh..conf...81D Altcode: No abstract at ADS Title: The SOHO mission Poland. Authors: Fleck, B.; Domingo, V.; Poland, Arthur I. Bibcode: 1995sohp.book.....F Altcode: 1995QB521.S5828.... No abstract at ADS Title: Coronal fine structure as seen in the Skylab white light coronagraph Authors: Poland, A. I. Bibcode: 1994ESASP.373..227P Altcode: 1994soho....3..227P No abstract at ADS Title: The scientific payload of the space-based Solar and Heliospheric Observatory (SOHO) Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1994SSRv...70....7D Altcode: The space-based Solar and Heliospheric Observatory (SOHO) is a joint venture of ESA and NASA within the frame of the Solar Terrestrial Science Programme (STSP), the first “Cornerstone” of ESA's long-term programme “Space Science — Horizon 2000”. The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here. Title: SOHO operations and ground system Authors: Poland, A. I.; Domingo, V.; Fleck, B. Bibcode: 1994SSRv...70...13P Altcode: SOHO is a joint ESA/NASA mission to study the sun from its interior to, and including, the solar wind in interplanetary space. It is currently scheduled for launch in 1995. After launch SOHO with be operated from the Experiment Operations Facility (EOF) at Goddard Space Flight Center (GSFC). The EOF will consist of facilities for instrument commanding, data reception, data reduction and data analysis. In this paper the operations concepts including instrument ground commanding from the EOF and communications capabilities between the EOF and ground observatories and the public networks in general will be described. Title: Delay-line detectors for the UVCS and SUMER instruments on the SOHO Satellite Authors: Siegmund, Oswald H.; Stock, Joseph M.; Marsh, Daniel R.; Gummin, Mark A.; Raffanti, Richard; Hull, Jeffrey; Gaines, Geoffrey A.; Welsh, Barry Y.; Donakowski, B.; Jelinsky, Patrick N.; Sasseen, Timothy; Tom, James L.; Higgins, B.; Magoncelli, T.; Hamilton, Jon W.; Battel, Steven J.; Poland, Arthur I.; Jhabvala, Murzy D.; Sizemore, K.; Shannon, J. Bibcode: 1994SPIE.2280...89S Altcode: Microchannel plate based detectors with cross delay line image readout have been rapidly implemented for the SUMER and UVCS instruments aboard the Solar Orbiting Heliospheric Observatory (SOHO) mission to be launched in July 1995. In October 1993 a fast track program to build and characterize detectors and detector control electronics was initiated. We present the detector system design for the SOHO UVCS and SUMER detector programs, and results from the detector test program. Two deliverable detectors have been built at this point, a demonstration model for UVCS, and the flight Ly (alpha) detector for UVCS, both of which are to be delivered in the next few weeks. Test results have also been obtained with one other demonstration detector system. The detector format is 26mm x 9mm, with 1024 x 360 digitized pixels,using a low resistance Z stack of microchannel plates (MCP's) and a multilayer cross delay line anode (XDL). This configuration provides gains of approximately equals 2 X 10(superscript 7) with good pulse height distributions (<50% FWHM) under uniform flood illumination, and background levels typical for this configuration (approximately equals 0.6 event cm(superscript -2) sec(superscript -1)). Local counting rates up to approximately equals 400 event/pixel/sec have been achieved with no degradation of the MCP gain. The detector and event encoding electronics achieves approximately equals 25 micrometers FWHM with good linearity (+/- approximately equals 1 pixel) and is stable to high global counting rates (>4 X 10(superscript 5) events sec(superscript -1)). Flat field images are dominated by MCP fixed pattern noise and are stable, but the MCP multifiber modulation usually expected is uncharacteristically absent. The detector and electronics have also successfully passed both thermal vacuum and vibration tests. Title: 'SUMER' - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuhne, M.; Lemaire, P.; Marsch, E.; Poland, A. I.; Schuhle, U.; Thomas, R. J.; Timothy, J. G.; Vial, J. -C. Bibcode: 1994scs..conf..619W Altcode: 1994IAUCo.144..619W SUMER is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. The spatial and spectral resolution capabilities of the instrument are considered in some detail, and a new detector concept is introduced. Title: SOHO Science Opportunities Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994scs..conf..609F Altcode: 1994IAUCo.144..609F The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here. Title: SOHO Operations Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994scs..conf..614F Altcode: 1994IAUCo.144..614F SOHO, the Solar and Heliospheric Observatory, is currently scheduled for launch in 1995. After launch SOHO will be operated from the Experiment Operations Faciliy (EOF) at Goddard Space Flight Center (GSFC). The EOF will consist of facilities for instrument commanding, data reception, data reduction and data analysis. This paper briefly describes the operations concepts. Title: SOHO: science objectives and capabilities Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994ASIC..433..517F Altcode: No abstract at ADS Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G. Bibcode: 1993BAAS...25.1192W Altcode: No abstract at ADS Title: Invited Talk: (SOHO Coronal Observations) Authors: Poland, A. I. Bibcode: 1993BAAS...25.1195P Altcode: No abstract at ADS Title: SUMER: temperatures, densities, and velocities in the outer solar atmosphere. Authors: Lemaire, P.; Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuehne, M.; Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy, J. G.; Vial, J. C. Bibcode: 1992ESASP.348...13L Altcode: 1992cscl.work...13L The SUMER instrumentation, that will be mounted on the SOHO spacecraft, is in development under MPAE leadership. It has some capability to improve the solar angular resolution and the spectral resolution already obtained in the far UV to the extreme UV, corresponding to the temperature range between 104 and a few 106K. The authors give some insights into the SUMER spectrometer that is developed to study the dynamics and to infer temperatures and densities of the low corona and the chromosphere-corona transition zone in using the 50 - 160 nm wavelength range. First, they recall the SUMER scientific goals and the technics used. Then, after a brief description of the instrumentation the expected performances are described. The way the observations can be conducted is emphasized and it is shown how SUMER is operated in coordination with other SOHO instrumentations and in cooperation with ground-based observations. Title: Measurements of an intensified CCD detector for the solar and heliospheric observatory Authors: Thompson, William T.; Poland, Arthur I.; Siegmund, Oswald H.; Swartz, Marvin; Leviton, Douglas B.; Payne, Leslie J. Bibcode: 1992SPIE.1743..464T Altcode: An engineering model intensified CCD detector for the SOHO Coronal Diagnostics Spectrometer has been built and tested at the NASA Goddard Space Flight Center. A windowless MCP intensifier tube converts EUV radiation (30 - 65 nm) into visible light, which is focused via a lens system onto a Tektronix 1024 X 1024 CCD. Tests have been made of this engineering model to determine the following characteristics: quantum efficiency, resolution, throughput, linearity, statistical variation, readout noise, scattering, and flat-field response. In almost all respects, the detector performed as expected. This detector has been delivered, and work is underway on the flight detector. Title: "SUMER" - Solar Ultraviolet Measurements of Emitted Radiation. Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kühne, M.; Lemaire, P.; Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy, J. G.; Vial, J. C. Bibcode: 1992eocm.rept..225W Altcode: The experiment Solar Ultraviolet Measurements of Emitted Radiation (SUMER) is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. Specifically, SUMER will measure profiles and intensities of extreme ultraviolet (EUV) lines emitted in the solar atmosphere ranging from the upper chromosphere to the lower corona; determine line broadenings, spectral positions and Doppler shifts with high accuracy; provide stigmatic images of selected areas of the Sun in the EUV with high spatial, temporal and spectral resolution and obtain full images of the Sun and the inner corona in selectable EUV lines, corresponding to a temperature range from 104 to more than 1.8×106K. Title: SOHO - An Observatory to Study the Solar Interior and the Solar Atmosphere Authors: Poland, A. I. Bibcode: 1992AAS...180.3306P Altcode: 1992BAAS...24..781P No abstract at ADS Title: Opacity Effects on the Radiative Losses of Coronal Loops Authors: Kuin, N. P. M.; Poland, A. I. Bibcode: 1991ApJ...370..763K Altcode: This paper presents calculations of radiative losses, which include the effects of geometry and optical depth, that can be used to improve the energy losses in many flux-tube calculations for loops with constant and variable cross sections. The results include the non-LTE ionization state of hydrogen and helium, thus allowing the determination of the ionization energy in the gas and the relative importance of collisional and radiative processes. These calculations show that optical depth effects are important under solar conditions in the temperature range of 8000-40,000 K. Title: The SOHO Space Satellite: UV instrumentation. Authors: Poland, Arthur I.; Domingo, Vicente Bibcode: 1991SPIE.1343..310P Altcode: The solar and heliospheric observatory, SOHO will be placed into a halo orbit around the L1 sun-earth Lagrangian point in 1995. The authors describe the ultra-violet and EUV instruments designed to study the solar atmosphere from the chromosphere through the corona. The instruments and their basic characteristics are: 1) SUMER - a normal incidence telescope with a normal incidence spherical concave grating for stigmatic imaging to measure line profiles and images in the wavelength range from 500 Å to 1600 Å with a 1.5″resolution; 2) CDS - a grazing incidence telescope with one grazing incidence astigmatic spectrograph and one normal incidence toroidal grating spectrograph to measure line ratios and images in the range from 170 Å to 800 Å with a 2″resolution; 3) EIT - a normal incidence multilayered telescope to produce narrow band pass images in the spectral lines at 171 Å, 195 Å, 284 Å, and 304 Å with a 3″resolution; 4) UVCS - a normal incidence coronagraph with a normal incidence toroidal grating spectrograph to measure line profiles and images of several EUV lines from ≡500 Å to ≡1200 Å with a several arcsecond resolution; and 5) SWAN - a lens with hydrogen absorption cell and interference filter to measure Ly-α profiles in the far corona and heliosphere. Title: An intensified CCD detector using the phosphor TPB. Authors: Thompson, William T.; Swartz, Marvin; Poland, Arthur I. Bibcode: 1990SPIE.1344..415T Altcode: 1990exrg.conf..415T The Research Amplifying Imaging Detector (RAID) consists of a microchannel plate image intensifier with a thin coating (3500 - 10,000 Å) of the phosphor tetraphenyl-butadiene (TPB) on the entrance window to convert EUV radiation to visible, and coupled via a lens to a CCD detector. This design allows great flexibility in selecting the pixel size and field of view, with a simple mechanical design. Tests have been made at visible and EUV (304 Å) wavelengths of the following performance aspects: EUV spectral sensitivity, spatial resolution both of components and of the system as a whole, noise, linearity, and dynamic range. Title: SOHO - an Observatory to Study the Solar Interior and the Solar Atmosphere Authors: Poland, A. I.; Domingo, V. Bibcode: 1990ASSL..166..277P Altcode: 1990oeob.coll..277P; 1990IAUCo.123..277P The Solar and Heliospheric Observatory (SOHO) is described. The two main objectives of SOHO are to improve understanding of solar coronal phenomena and to study solar structure and interior dynamics from its core to the photosphere. The primary goals of the coronal and solar wind studies are to understand the coronal heating mechanism and its expansion into the solar wind. These goals will be achieved both by remote sensing of the solar atmosphere with high resolution spectrometers and telescopes and by in situ measurement of the composition and energy of the resulting solar wind and the energetic particles that propagate through it. The structure and interior dynamics are to be studied by helioseismological methods and the measurement of solar irradiance variations. The SOHO spacecraft will be three-axis stabilized and located in a halo orbit around the L1 Lagrangian point (approximately 1 percent of the distance from the Earth to the Sun). It is currently scheduled for launch in July 1995. Title: Mass and Energy Flow in Prominences Authors: Poland, Arthur I. Bibcode: 1990LNP...363..120P Altcode: 1990doqp.coll..120P; 1990IAUCo.117..120P Mass and energy flow in quiescent prominences is considered based on the hypothesis that active region prominences have a different structure and thus different mass and energy flow characteristics. Several important physical parameters have been plotted using the computational model, representing the evolutionary process after the prominence formation. The temperature, velocity, conductive flux, and enthalpy flux are plotted against distance from the highest point in the loop to the coolest part of the prominence. It is shown that the maximum velocity is only about 5 km/s. The model calculations indicate that the transition region of prominences is dominated by complex processes. It is necessary to take into account mass flow at temperatures below 200,000 K, and both mass flow and optical depth effects in hydrogen at temperatures below 30,000 K. Both of these effects lead to a less steep temperature gradient through the prominence corona interface than can be obtained from the conduction alone. Title: The Eruption of a Quiescent Prominence as Observed in Ultraviolet Lines Authors: Fontenla, J. M.; Poland, A. I. Bibcode: 1989SoPh..123..143F Altcode: We compare observations of an eruptive and a quiescent prominence in order to better understand the energetic processes in an eruptive prominence. Observations of an eruptive prominence were obtained in Hα, several UV emission lines (1215-1640 Å), and coronal white light at approximately 19:00 UT on September 20, 1980. The data we present shows the development of the eruption in the Hα and UV emission lines and is compared with the intensities from similar observations of a quiescent prominence. While the event is coincident with some coronal changes, above 1.2 and up to 1.5 solar radii, it does not result in a true coronal mass ejection event. Title: SUMER - Solar ultraviolet measurements of emitted radiation. Authors: Curdt, W.; Wilhelm, K.; Axford, W. I.; Marsch, E.; Richter, A. K.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Timothy, J. G. Bibcode: 1989AGAb....2...14C Altcode: 1989amt..conf...14C No abstract at ADS Title: Opacity Effects on the Radiative Losses of Coronal Loops Authors: Kuin, N. P. M.; Poland, A. I. Bibcode: 1989BAAS...21Q.711K Altcode: No abstract at ADS Title: Impulsive phase transport. Authors: Canfield, R. C.; Bely-Dubau, E.; Brown, J. C.; Dulk, G. A.; Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose, D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.; Tanaka, K.; Zirin, H. Bibcode: 1989epos.conf..225C Altcode: The work of this group was concerned with how the energy released in a solar flare is transported through the solar atmosphere before escaping in the form of radiant and mechanical energy. Title: SOHO: an observatory to study the solar interior and the solar atmosphere Authors: Domingo, V.; Poland, A. I. Bibcode: 1988sohi.rept....7D Altcode: The Solar and Heliospheric Observatory (SOHO) is described. The two main objectives of SOHO are to improve understanding of solar coronal phenomena and to study solar structure and interior dynamics from its core to the photosphere. The primary goals of the coronal and solar wind studies are to understand the coronal heating mechanism and its expansion into the solar wind. These goals will be achieved both by remote sensing of the solar atmosphere with high resolution spectrometers and telescopes and by in situ measurement of the composition and energy of the resulting solar wind and the energetic particles that propagate through it. The structure and interior dynamics are to be studied by helioseismological methods and the measurement of solar irradiance variations. The SOHO spacecraft will be three-axis stabilized and located in a halo orbit around the L1 Lagrangian point (approximately 1 percent of the distance from the Earth to the Sun). It is currently scheduled for launch in July 1995. Title: SUMER: Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, M. C. E.; Lemaire, P.; Marsch, E.; Poland, A. I. Bibcode: 1988sohi.rept...31W Altcode: The SUMER (solar ultraviolet measurements of emitted radiation) experiment is described. It will study flows, turbulent motions, waves, temperatures and densities of the plasma in the upper atmosphere of the Sun. Structures and events associated with solar magnetic activity will be observed on various spatial and temporal scales. This will contribute to the understanding of coronal heating processes and the solar wind expansion. The instrument will take images of the Sun in EUV (extreme ultra violet) light with high resolution in space, wavelength and time. The spatial resolution and spectral resolving power of the instrument are described. Spectral shifts can be determined with subpixel accuracy. The wavelength range extends from 500 to 1600 angstroms. The integration time can be as short as one second. Line profiles, shifts and broadenings are studied. Ratios of temperature and density sensitive EUV emission lines are established. Title: An Intensified CCD EUV Camera for the SOHO/CDS Experiment Authors: Golub, L.; Kalata, K.; Poland, A. I.; Thomas, R. J. Bibcode: 1988BAAS...20..980G Altcode: No abstract at ADS Title: Hydrogen and Helium Excitation by Extreme Ultraviolet Radiation for the Production of White-Light Flares Authors: Poland, A. I.; Milkey, R. W.; Thompson, W. T. Bibcode: 1988SoPh..115..277P Altcode: White-light flares are defined as those flares that produce significant enhancement of emission in the visible light continuum. The source of energy for this emission has not yet been identified with several possibilities being suggested: heating of the lower chromosphere by some mechanical or magnetic means, or by soft X-ray or extreme ultraviolet radiation from coronal loops being absorbed in the lower chromosphere and re-emitted in the visible. Title: Some dynamical aspects of a quiescent filament Authors: Schmieder, B.; Demoulin, P.; Poland, A.; Thompson, B. Bibcode: 1988A&A...197..281S Altcode: A typical quiescent filament was observed on the disk in the Hα and C IV lines during a period of approximately one hour. Vertical velocities (<2.5 km s-1) with a time scale of 5 min and a spatial scale of a few tens of seconds of arc were detected in Hα, and associated with microturbulence in both lines. The C IV observations correlated well with those in Hα, and showed no indication of material heating from Hα to C IV temperatures. Two mechanisms to explain these observations are proposed: mass motion along twisted magnetic field or instabilities triggering waves along the filament. Title: The SOHO project: helioseismology investigations Authors: Domingo, V.; Poland, A. Bibcode: 1988AdSpR...8k.109D Altcode: 1988AdSpR...8..109D The solar and heliospheric observatory, Soho, will be placed into a halo orbit around the L1 Sun-Earth Lagrangian point in 1995. It will carry a set of instruments to study the physical phenomena in the solar atmosphere that heat the solar corona, the mechanisms by which the solar corona expands into the solar wind, and investigate the structure of the solar interior by the study of solar oscillations, both in velocity and in intensity (Helioseismology).

In this paper we describe the mission and the investigations to be carried out with the helioseismology instruments in the payload. A solar oscillations imager will measure velocity oscillations of degree up to 4000, while two other instruments will measure very long series of low degree modes of oscillation, one of them in velocity and the other in irradiance. The data obtained will be used to study the radial stratification and the longitudinal variation of the physical characteristics of the Sun, as well as many dynamical phenomena of the upper layers of the solar atmosphere. Title: A model for the structure and formation of prominences. Authors: Poland, A. I.; Mariska, J. T. Bibcode: 1988dssp.conf..133P Altcode: The authors present a geometric model for the magnetic structure of a prominence inspired by recent high resolution images and magnetic field measurements of filaments and prominences. In this model the observed prominence structures are a mapping of locations in the magnetic field structure where material can condense without falling to the chromosphere. Vertical structures near the footpoints are a series of near potential fields. Title: Current Understanding and Issues on Electron Beam Injection in Space Authors: Poland, A. I.; Domingo, V. Bibcode: 1988AdSpR...8k.101P Altcode: 1988AdSpR...8Q.101P The Solar and Heliospheric Observatory (SOHO) satellite mission is planned to study the solar interior, to investigate the physical phenomena related to the formation of the solar corona and the solar wind, and to make in situ measurements of the solar wind. The SOHO instruments designed to study the solar atmosphere and the solar wind are described. The experiments include the study of solar UV radiation, a coronal diagnostic spectrometer, an extreme UV imaging telescope, a UV coronagraph spectrometer, a white light and spectrometric coronagraph, and a study of solar wind anisotropies. Title: Soho and Cluster - the scientific instruments. Authors: Domingo, V.; Schmidt, R.; Poland, A. I.; Goldstein, M. L. Bibcode: 1988ESABu..56...24D Altcode: The need to understand the complex processes that control the structure and dynamics of our daylight star and define the Earth's environment in space, has long been widely realised. Its continuing importance is reflected by the fact that twenty-three Principal Investigators and several hundred Co-Investigators from more than eighteen countries are now actively involved in the preparations for and execution of the Soho and Cluster missions. Title: A Model for the Structure and Formation of Prominences Authors: Poland, A. I.; Mariska, J. T. Bibcode: 1987dssp.work..133P Altcode: 1987ASSL..150..133P No abstract at ADS Title: Impulsive Phase Observations and Their Interpretation Authors: Canfield, R. C.; Bely-Dumau, E.; Brown, J. C.; Dulk, G. A.; Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose, D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.; Tanaka, K.; Zirin, H. Bibcode: 1986epos.conf..3.4C Altcode: 1986epos.confC...4C No abstract at ADS Title: Theoretical Studies of Transport Processes Authors: Canfield, R. C.; Bely-Dumau, E.; Brown, J. C.; Dulk, G. A.; Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose, D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.; Tanaka, K.; Zirin, H. Bibcode: 1986epos.conf.3.34C Altcode: 1986epos.confBC.34C No abstract at ADS Title: Coronal and Prominence Plasmas: proceedings of workshops held at Goddard Space Flight Center, April 9-11, 1985, April 8-10, 1986 Authors: Poland, Arthur I. Bibcode: 1986NASCP2442.....P Altcode: 1986copp.nasa.....P No abstract at ADS Title: Numerical simulations of a siphon mechanism for quiescent prominence formation. Authors: Poland, A. I.; Mariska, J. T.; Klimchuk, J. A. Bibcode: 1986NASCP2442...57P Altcode: 1986copp.nasa...57P Quiescent prominences represent a significant challenge to our understanding of the flow of mass and energy in the outer layers of the solar atmosphere. A small number of quiescent prominences contain as much mass as the entire corona (Athay, 1976). The problem then is how to get that much material into the relatively small volume of a prominence and maintain it at a temperature of 10,000 K in close proximity to material at one million K. The thermal insulation to conduction provided by the magnetic field explains the disparate temperatures. The mass source problem is less well understood. One method for supplying mass to the prominence is to siphon it from the chromosphere. The siphon mechanism begins with a magnetic loop that evolves into a configuration with a gravitational well, such as that described by Kippenhahn and Schluter (1957). This could be formed, for example, by a twist in the magnetic field. A gravitational well could also be formed by a condensation induced sag in the field. This could further enhance the condensation process. Once this well has formed, or as it is forming, the material in the well area of the loop must cool and condense to the point where radiative losses exceed any heat input. Additional material must also flow into the well from the underlying chromosphere to supply the mass required to form the prominence. One example from a series of numerical simulations that were performed to study the formation of quiescent prominences is presented. Title: Constraints on filament models deduced from dynamical analysis. Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Malherbe, J. M.; Poland, A. I. Bibcode: 1986NASCP2442..177S Altcode: 1986copp.nasa..177S The conclusions deduced from simultaneous observations with the Ultra-Violet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission satellite, and the Multichannel Subtractive Double Pass (MSPD) spectrographs at Meudon and Pic du Midi observatories are presented. The observations were obtained in 1980 and 1984. All instruments have almost the same field of view and provide intensity and velocity maps at two temperatures. The resolution is approx. 0.5 to 1.5" for H alpha line and 3" for C IV. The high resolution and simultaneity of the two types of observations allows a more accurate description of the flows in prominences as functions of temperature and position. The results put some contraints on the models and show that dynamical aspects must be taken into account. Title: Dynamics of solar filaments. VI - Center-to-limb study of H-alpha and C IV velocities in a quiescent filament Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Poland, A. I. Bibcode: 1986A&A...166..319S Altcode: The rotation of a stable quiescent filament from near disk center to the limb has been observed. Observations of intensity and velocity were made in H-alpha and C IV, and compared with magnetic field measurements. From the H-alpha observations, it is concluded that the filament is made up of many small scale magnetic features that are not coherently aligned along the neutral line. They are especially convoluted at the apparent 'footpoints'. The measured velocities are of the order of a few kilometers per second in both lines. However, the comparison of the standard deviations of the C IV velocities in and out of the filament as it rotates toward the limb shows that the vertical velocities in the filament are greater than the horizontal velocities. Measurements of velocity do not make it possible to distinguish between the Raadu-Kuperus (1973) or Kippenhahn-Schluter (1957) models for prominences because neither theory is adequately developed for this comparison. However, the observation of the many fine loops brings into question the correctness of either model. Title: Hydrogen and Helium Excitation by EUV Radiation for the Production of White-Light Falres Authors: Thompson, W. T.; Poland, A. I.; Milkey, R. W. Bibcode: 1986BAAS...18..899T Altcode: No abstract at ADS Title: Ephemeral active regions and coronal bright points: A solar maximum Mission 2 guest investigator study Authors: Harvey, K. L.; Tang, F. Y. C.; Gaizauskas, V.; Poland, A. I. Bibcode: 1986gsfc.rept.....H Altcode: A dominate association of coronal bright points (as seen in He wavelength 10830) was confirmed with the approach and subsequent disappearance of opposite polarity magnetic network. While coronal bright points do occur with ephemeral regions, this association is a factor of 2 to 4 less than with sites of disappearing magnetic flux. The intensity variations seen in He I wavelength 10830 are intermittent and often rapid, varying over the 3 minute time resolution of the data; their bright point counterparts in the C IV wavelength 1548 and 20 cm wavelength show similar, though not always coincident time variations. Ejecta are associated with about 1/3 of the dark points and are evident in the C IV and H alpha data. These results support the idea that the anti-correlation of X-ray bright points with the solar cycle can be explained by the correlation of these coronal emission structures with sites of cancelling flux, indicating that, in some cases, the process of magnetic flux removal results in the release of energy. That the intensity variations are rapid and variable suggests that this process works intermittently. Title: A Siphon Mechanism for Supplying Prominence Mass Authors: Poland, A. I.; Mariska, J. T. Bibcode: 1986SoPh..104..303P Altcode: We examine a siphon-like mechanism for moving mass from the chromosphere to a gravitational well at the top of a magnetic loop to form a prominence. The calculations assume no apriori flow velocity at the loop base. Instead heating in the loop legs drives the flow. The prominence formation process requires two steps. First, the background heating rate must be reduced to on the order of 1 % of the initial heating rate required to maintain the coronal loop. This forms an initial condensation at the top of the loop. Second, the heating must take place only in the loop legs in order to produce a pressure differential which drives mass up into the well at the top of the loop. The heating rate in the loop must be increased once the prominence has begun to form or full prominence densities can not be achieved in a reasonable time. We conclude that this heating driven siphon-like mechanism is feasible for producing and maintaining prominences. Title: Impulsive phase transport. Authors: Canfield, R. C.; Bely-Dubau, E.; Brown, J. C.; Dulk, G. A.; Emslie, A. G.; Enome, S.; Gabriel, A. H.; Kundu, M. R.; Melrose, D.; Neidig, D. F.; Ohki, K.; Petrosian, V.; Poland, A.; Rieger, E.; Tanaka, K.; Zirin, H. Bibcode: 1986NASCP2439....3C Altcode: Contents: 1. Introduction: motivation for transport studies, historical perspective, overview of the chapter. 2. Impulsive phase observations and their interpretation: gamma-ray emission above 10 MeV, hard X-ray and microwave morphology, combined soft and hard X-ray spectra, iron Kα emission, ultraviolet and hard X-ray emission, white light emission, Hα emission. 3. Theoretical studies of transport processes: electron beams and reverse currents, proton transport, radiative energy transport by amplified decimetric waves. 4. Summary. Title: On V and hard X-rays, observations and model calculations. Authors: Poland, A. I.; Mariska, J. T. Bibcode: 1986NASCP2449..279P Altcode: 1986rfsf.nasa..279P This paper is an amalgamation of two published works that discuss the observation and theoretical calculations of O V (T ≡ 250,000K) and hard X-rays (30 - 100 keV) emitted during flares. The papers are by Poland et al. (1984, see Abstr. 37.073.132) and Mariska and Poland (1985, see Abstr. 39.076.024). The observations of hard X-rays and O V show that the excitation processes for each type of emission are closely coupled. Except for small differences the two types of emission rise and fall together during a flare. Model calculations are able to reproduce this behavior to a large extent, only when conductive processes do not dominate the energy transport processes. Title: Dynamics of solar filaments. IV - Structure and mass flow of an active region filament Authors: Schmieder, B.; Malherbe, J. M.; Simon, G.; Poland, A. I. Bibcode: 1985A&A...153...64S Altcode: An active region filament near the center of the solar disk was observed on September 29-30, 1980, with the Multichannel Subtractive Double Pass Spectrograph of the Meudon solar tower and the UV Spectrograph and Polarimeter aboard the SMM satellite. H-alpha and C IV measurements are presently used to study brightness and material velocity in the 10,000 and 100,000 K temperature ranges, and photospheric magnetograms are used to investigate the underlying magnetic field. Attention is given to the constraints imposed on possible filament structures by observations, as well as the expected MHD relationships. Title: Numerical Simulation of a Siphon Mechanism for Quiescent Prominences Authors: Mariska, J. T.; Poland, A. I. Bibcode: 1985BAAS...17..842M Altcode: No abstract at ADS Title: Energetics of a double flare on November 8, 1980 Authors: Doyle, J. G.; Byrne, P. B.; Dennis, B. R.; Emslie, A. G.; Poland, A. I.; Simnett, G. M. Bibcode: 1985SoPh...98..141D Altcode: Here we complete an energy balance analysis of a double impulsive hard X-ray flare. From spatial observations, we deduce both flares probably occur in the same loop within the resolution of the data. For the first flare, the energy in the fast electrons (assuming a thick-target model) is comparable to the convective up-flow energy, suggesting that these are related successive modes of energy storage and transfer. The total energy lost through radiation and conduction, 2.0 × 1028 erg, is comparable to the energy in fast electrons 2.5 × 1028 erg. For the second flare, the energy in the fast electrons is more than one order of magnitude greater than the energy of the convective up-flow. Total energy losses are within a factor of two lower than the calculated fast electron energy. We interpret the observations as showing that the first flare occurred in a small loop with fast electrons heating the chromosphere and resulting in chromospheric evaporation increasing the density in the loop. For the second flare most of the heating occurred at the electron acceleration site. The two symmetrical components of the Ca XIX resonance line and a high velocity down-flow of 115 km s −1 observed at the end of the second hard X-ray burst are consistent with the flare eruption (reconnection) region being high in the flare loop. The estimated altitude of the acceleration site is 5500 km above the photosphere. Title: The Relation Between Hard X-Ray and Transition Region Line Emission in Solar Flares Authors: Mariska, J. T.; Poland, A. I. Bibcode: 1985SoPh...96..317M Altcode: Observational evidence suggests that both the hard X-ray and ultraviolet emission from the impulsive phase of flares result from an electron beam. We present the results of model calculations that are consistent with this theory. The impulsive phase is envisioned as occurring in many small magnetically confined loops, each of which maintains an electron beam for only a few seconds. This model successfully matches several observed aspects of the impulsive phase. The corona is heated to less than 2 × 106 K, maximum enhanced emission occurs in lines formed near 105 K, and there is only slight enhancement between 105 and 2 × 106 K. The slope of the observed relationship between hard X-ray and OV 1371 Å emission is also matched, but the relative emission is not. The calculations indicate that UV emission lines formed below a temperature of about 105 K will arise predominantly from the chromospheric region heated by the electron beam to transition region temperatures. Emission lines formed at higher temperatures will be produced in the transition region. This should be detectable in density-sensitive line ratios. To account successfully for the impulsive UV emission, the peak temperature in the impulsively heated loops must remain below about 2 × 106 K. Thus our model implies that the impulsive heating takes place in different loops from the hotter gradual phase emission. Title: Performance testing of the high altitude observatory PDS microdensitometer Authors: Poland, A.; Munro, R.; Friend, D. Bibcode: 1984asmd.conf...19P Altcode: High Altitude Observatory HAO microdensitometer undergoes monthly testing to assure its consistent performance. These tests check positional and photometric stability at the 10 micron aperture level. The HAO test procedure is designed to run without operator intervention following initial configuration of the microdensitometer for each subprocedure. Specialized test software is resident in the PDP 8. The operator selects the proper subprocedure by entering commands. Once computer control is established, it is not relinquished until the test is complete. Title: The energy relation between hard X-ray and O V emission in solar flares Authors: Poland, A. I.; Orwig, L. E.; Mariska, J. T.; Auer, L. H.; Nakatsuka, R. Bibcode: 1984ApJ...280..457P Altcode: The relationship between energy emitted in hard X-rays and the ultraviolet during the impulsive phase of solar flares provides an important diagnostic for understanding the energy flow from nonthermal to thermal. Many flares were observed from the Solar Maximum Mission satellite simultaneously in hard X-rays and the O V line at 1371 A formed at 250,000 K, providing information relevant to this problem. Previous work has shown that short time scale peaks in emission of these two types of radiation coincide in time to within 1 s. In this work the energy relation between the two types of emission is investigated and it is found that for any given flare there is a definite relation between hard X-ray and O V emissions throughout the flare, but from one flare to the next this relation varies markedly. These differences are attributed to the initial conditions in the flaring loops and some exploratory model calculations are presented to support this hypothesis. Title: A Multiwavelength Study of a Double Impulsive Flare Authors: Strong, K. T.; Benz, A. O.; Dennis, B. R.; Leibacher, J. W.; Mewe, R.; Poland, A. I.; Schrijver, J.; Simnett, G.; Smith, J. B., Jr.; Sylwester, J. Bibcode: 1984SoPh...91..325S Altcode: Extensive data from the Solar Maximum Mission (SMM) and ground-based observatories are presented for two flares; the first occurred at 12:48 UT on 31 August, 1980 and the second just 3 min later. They were both compact events located in the same part of the active region. The first flare appeared as a typical X-ray flare: the CaXIX X-ray lines were broadened (≡ 190±40 km s-1) and blue shifted (≡ 60±20 km s-1) during the impulsive phase, and there was a delay of about 30 s between the hard and soft X-ray maxima. The relative brightness of the two flares was different depending on the spectral region being used to observe them, the first being the brighter at microwave and hard X-ray wavelengths but fainter in soft X-rays. The second flare showed no significant mass motions, and the impulsive and gradual phases were almost simultaneous. The physical characteristics of the two flares are derived and compared. The main difference between them was in the pre-flare state of the coronal plasma at the flare site: before the first flare it was relatively cool (3 × 106 K) and tenuous (4 × 109 cm-3), but owing to the residual effects of the first flare the coronal plasma was hotter (5 × 106 K) and more dense (3 × 1011 cm-3) at the onset of the second flare. We are led to believe from these data that the plasma filling the flaring loops absorbed most of the energy released during the impulsive phase of the second flare, so that only a fraction of the energy could reach the chromosphere to produce mass motions and turbulence. Title: The Relation Between Hard X-Ray and Transition-Region Line Emission in Solar Flares Authors: Mariska, J. T.; Poland, A. I. Bibcode: 1984BAAS...16R.543M Altcode: No abstract at ADS Title: Development and Plans for a Solar Extreme Ultraviolet Telescope and Spectrograph (SEUTS) Authors: Epstein, G. L.; Neupert, W. M.; Poland, A. I.; Thomas, R. J. Bibcode: 1984BAAS...16..546E Altcode: No abstract at ADS Title: X-Ray Ionization During the Impulsive Phase of A Solar Flare Authors: Waldron, W. L.; Poland, A. I. Bibcode: 1984BAAS...16..545W Altcode: No abstract at ADS Title: Performance testing of the High Altitude Observatory PDS microdensitometer. Authors: Poland, A.; Munro, R.; Friend, D. Bibcode: 1984NASCP2317...19P Altcode: The High Altitude Observatory PDS microdensitometer, purchased in 1972, is one of the earlier machines produced. Particular features of this machine include: PDP-8 control, 12 bit A/D converter, high density log amplifier, updated locking microscope head, auto-loc, teflon drive screws and nuts, and high speed operation (up to 60 mm/sec). The microdensitometer is generally used with 10 or 50 micron apertures on 35 mm and 70 mm film. The HAO microdensitometer undergoes monthly testing to assure its consistent performance. These tests are designed to check positional and photometric stability at the 10 micron aperture level. Title: Performance Testing of the High Altitude Observatory PDS Microdensitometer Authors: Poland, A. I.; Munro, R.; Friend, D. Bibcode: 1984amd..conf...19P Altcode: No abstract at ADS Title: Magnetohydrodynamic simulation of the coronal transient associated with the solar limb flare of 1980, June 29, 18∶21 UT Authors: Wu, S. T.; Wang, S.; Dryer, M.; Poland, A. I.; Sime, D. G.; Wolfson, C. J.; Orwig, L. E.; Maxwell, A. Bibcode: 1983SoPh...85..351W Altcode: Soft X-ray data from the XRP experiment on SMM are used to generate the temperature and density in the flaring region of the 1980, June 29 (18∶21 UT) solar flare. The temporal data (Tmax ∼- 20 × 106 K and nmax ∼- 4 × 1011 cm−3), together with an assumed velocity, are used to simulate mass injection as the input pulse for the MHD model of Wu et al. (1982a, 1983a). The spatial and temporal coronal response is compared with the ground-based, Mark III K-coronameter observations of the subsequent coronal transient. The simulation produces a spatially-wide, large amplitude, temporarily-steepened MHD wave for either of the two `canonical' magnetic topologies (closed and open), but no shock wave. This result appears to be confirmed by the fact that a type II radio event was observed late in the event for only a few minutes, thereby indicating that a steepening wave with temporary, marginal shock formation, was indeed present. The density enhancements produced by the simulation move away from the Sun at the same velocity observed by the K-coronameter. However, the observation of the coronal transient included a rarefaction that does not appear in the simulation. A probable explanation for this discrepancy is the likelihood that the magnitude and temporal profile of the density of the soft X-ray emitting plasma should not have been used as part of the mass injection pulse. We believe that the temperature profile alone, as suggested by earlier simulations, might have been a necessary and sufficient condition to produce both the compression and rarefaction of the ambient corona as indicated by the K-coronameter data. Hence, the dense plasma observed by XRP was probably confined, for the most part, close to the Sun during the ∼ 17 min duration of the observations. Title: Physical Conditions in a Quiescent Prominence Derived from Ultraviolet Spectra Obtained with the UVSP Instrument on the Solar-Maximum Authors: Poland, A. I.; Tandberg-Hanssen, E. Bibcode: 1983SoPh...84...63P Altcode: A quiescent prominence observed above the north-west limb on November 20, 1980, is analyzed using data obtained with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM). The spectral data include the lines 1215 Å of HI, 1401 Å of OIV, 1402 Å of SiIV, 1548 Å of CIV, 1640 Å of HeI, and 1655 Å of CI. From an analysis of these lines and their emission patterns we deduce physical characteristics of the prominence plasma, and suggest in particular that the prominence consisted of flux tubes at various temperatures. In the hotter parts of the plasma the number density reached values of about 3 × 1011 cm#X2212;3. Title: Relation Between Hard X-ray and OV Energy Emitted During Solar Flares Authors: Poland, A. I.; Orwing, L. E.; Mariska, J. T.; Auer, L. H. Bibcode: 1983BAAS...15..713P Altcode: No abstract at ADS Title: Simultaneous ultraviolet line and hard X-ray bursts in the impulsive phase of solar flares Authors: Woodgate, B. E.; Shine, R. A.; Poland, A. I.; Orwig, L. E. Bibcode: 1983ApJ...265..530W Altcode: Several fast impulsive phase solar flare bursts were observed by the Solar Maximum Mission instruments on 1980 November 8. The bursts were seen to be coincident in the O V 1371 Å line formed at 2.5 × 105 K and in 25-300 keV X-rays, to within the resolution time of 1 s. This lack of time difference is inconsistent with models for these flares in which the hard X-rays are produced at the top of a loop, followed by the formation of a thermal conduction front which travels to the footpoint where a UV burst is produced by heating. Models in which both X-rays and UV radiation are produced at the footpoint, or an electron beam transmits energy between loop top and footpoint is less than 1 s, are allowed. Title: Ultraviolet Observations of Solar Flares Authors: Poland, A. I. Bibcode: 1982Obs...102..123P Altcode: No abstract at ADS Title: The Impulsive and Gradual Phases of a Solar Limb Flare as Observed from the Solar Maximum Mission Satellite Authors: Poland, A. I.; Machado, M. E.; Wolfson, C. J.; Frost, K. J.; Woodgate, B. E.; Shine, R. A.; Kenny, P. J.; Cheng, C. C.; Tandberg-Hanssen, E. A.; Bruner, E. C.; Henze, W. Bibcode: 1982SoPh...78..201P Altcode: Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10″ spatial resolution in the lines of O v (Te ∼ 2.5 × 105 K) and Fe XXI (Te ∼ 1.1 × 107 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30 000 km above the solar surface at specific points in the flare loop. The Fe XXI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient. Title: Coronal activity below 2 solar radii - 1980 February 15-17 Authors: Fisher, R. R.; Poland, A. I. Bibcode: 1981ApJ...246.1004F Altcode: Coronal observations concerning the area between the solar surface and 2.0 solar radii can now be conducted by making use of a new ground-based K-coronameter and a prominence monitor on Mauna Loa in Hawaii. Observations made by the K-coronameter on three consecutive days surrounding the eclipse of 1980 February 16 show that the solar corona was very active during this time. Definite changes occurred between each day's observations. During one period of K-coronameter observations (1980 February 15) a coronal transient was observed to move through the coronameter's field of view. A description is presented of the general changes which occurred in the corona during this period, taking into account the coronal transient observed by the prominence monitor and K-coronameter. The most important aspects of these new observations pertain to the relationship between the H alpha prominence and the surrounding coronal material. Title: The Evolution of a Coronal Streamer and the Photospheric Magnetic Field Authors: Poland, A. I.; MacQueen, R. M. Bibcode: 1981SoPh...71..361P Altcode: A large equatorial coronal streamer observed in the outer corona (3R) grew in brightness and size during successive limb passages between October 6, 1973 and January 10, 1974 (solar rotations 1606-1611). Unlike previous studies of streamers and their photospheric associations, no definite surface feature could be identified in the present case. This suggests that the streamer is associated with the large scale photospheric magnetic field. Comparison of the streamer growth with observed underlying photospheric magnetic flux changes indicated that as the streamer increased in brightness, areal extent, and density, the photospheric magnetic flux decreased. Three possible explanations for the streamer's growth are presented; the conceptually simplest being that the decrease in photospheric field results in an opening of the flux tubes under the streamer which permits an increased mass flux through the streamer. Title: New Mauna Loa coronagraph systems Authors: Fisher, R. R.; Lee, R. H.; MacQueen, R. M.; Poland, A. I. Bibcode: 1981ApOpt..20.1094F Altcode: A new set of instruments, consisting of two coronagraph systems, has been installed and is operating at the Mauna Loa Observing Station, Hawaii. The instruments are the 23-cm objective Mark III K-coronameter (K-III) system, a photoelectric instrument used to observe the inner solar corona from 1.2 R0 to 2.2 R0 and the 12.5-cm objective Prominence Monitor system used for the detection of H-alpha limb activity. New features of the K-coronameter system include the use of achromatic wave plates for wide bandpass operation and linear diode array detectors. Raster scans of the coronal image are obtained in 1.5 min for a critical sampling scheme of 20-sec of arc resolution (10 x 10-sec of arc pixels) in the coronal pB image. This represents a 350 information gain factor for each detection channel when compared with the previous Mauna Loa K-coronameters. Title: Coronal Transients Near Sunspot Maximum Authors: Poland, A. I.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr. Bibcode: 1981SoPh...69..169P Altcode: The Naval Research Laboratory's most recent Earth-orbiting coronagraph, called Solwind, has been observing the Sun's outer corona (2.6-10.0 R) at 10-min intervals since March 28, 1979. These observations provide the first comprehensive view of coronal transients near the peak of a sunspot cycle. Six, well-defined transients in our quick-look data have masses ranging from 7 × 1014 g to 2 × 1016 g and outward speeds ranging from 150 km s−1 to 900 km s−1. These values are comparable to the ones that were obtained with the OSO-7 and Skylab observations during the declining phase of the last sunspot cycle. Although the amount of quick-look data is not sufficient to provide meaningful statistics, the coronal transients near sunspot maximum seem to occur with a greater frequency and a wider latitude range than the transients during the declining phase of the cycle. In both eras, there is a good, but imperfect, association between the occurrence of coronal transients and surface phenomena such as eruptive prominences and flares. Title: Changes in the Characteristics of the Coronal Plasma During Two Impulsive Flares Authors: Strong, K. T.; Sylwester, J.; Parmar, A.; Dennis, B.; Poland, A. Bibcode: 1980BAAS...12R.911S Altcode: No abstract at ADS Title: The Development of Flares Observed in the Spectral Lines OV 1371 Å, FeXXI 1354 Å, and in Hard X-Rays Authors: Woodgate, B. E.; Bruner, E. C.; Cheng, C. C.; Dennis, B. R.; Gurman, J. B.; Frost, K. J.; Hyder, C. L.; Kiplinger, A.; Mason, H. E.; Orwig, L. E.; Poland, A. I.; Schoolman, S. A.; Shine, R. A.; Tandberg-Hanssen, E. A. Bibcode: 1980BAAS...12..911W Altcode: No abstract at ADS Title: UV Observations of the June 29, 1980 Flare at 18:24UT Authors: Poland, A. I.; Woodgate, B. E.; Shine, R. A.; Frost, K. J.; Kenny, P.; Bruner, E. C.; Wolfson, J.; Cheng, C. C.; Tandberg-Hanssen, E. A.; Gurman, J.; Henze, W.; Machado, M. Bibcode: 1980BAAS...12..903P Altcode: No abstract at ADS Title: The observation of a high-latitude coronal transient Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Poland, A. I. Bibcode: 1980ApJ...238L.161S Altcode: On 1979 September 27 NRL's earth-orbiting coronagraph (Solwind) observed a coronal mass ejection whose outward direction in the plane of the sky was within 12 deg of the sun's north polar axis. Such high-latitude transients were not observed by the OSO 7 and Skylab coronagraphs during the declining phase of the last sunspot cycle, but may be relatively common near sunspot maximum. Title: K-coronameter observations of the solar corona, 15 - 16 February 1980. Authors: Fisher, R.; Poland, A. I. Bibcode: 1980BAAS...12..750F Altcode: No abstract at ADS Title: Radio and white-light observations of the 1973 August 21 coronal transient. Authors: Gergely, T. E.; Kundu, M. R.; Munro, R. H.; Poland, A. I. Bibcode: 1979ApJ...230..575G Altcode: A coronal transient, which occurred on August 21, 1973, has been observed simultaneously in white light and at decameter radio wavelengths. The radio observations were obtained with a two-dimensional swept-frequency array (called the Teepee Tee). The white-light observations consist of a series of photographs taken by the High Altitude Observatory's coronagraph aboard Skylab. The radio emission associated with the transient was continuum in nature and lasted for almost 5 hours. The source of emission was observed to be cospatial with the lower part of one of the secondary white-light loops. A lower limit of 0.6 solar radius for the depth (extension along the line of sight) of this part of the transient was derived from considerations of radio-wave propagation in the corona. The radio source showed no dispersion of height with frequency, and, therefore, the emission is attributed to gyrosynchrotron radiation. Based on this assumption, the magnetic-field strength in the lower part of the loop is estimated to be in the 2.0-4.5-gauss range at a height of 2.1 solar radii from the center of the sun. Title: The association of coronal mass ejection transients with other forms of solar activity. Authors: Munro, R. H.; Gosling, J. T.; Hildner, E.; MacQueen, R. M.; Poland, A. I.; Ross, C. L. Bibcode: 1979SoPh...61..201M Altcode: Coronal mass ejection transients observed with the white light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass ejection transients and chromospheric Hα activity, with three-quarters of the transients apparently originating in or near active regions. We infer that 40% of transients are associated with flares, 50% are associated with eruptive prominences solely (without flares), and more than 70% are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares which displayed apparent mass ejections of Hα-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection. Title: Mass flow in loop type coronal transients. Authors: Anzer, U.; Poland, A. I. Bibcode: 1979SoPh...61...95A Altcode: The white light coronagraph on Skylab observed many loop type coronal transients. These loops travel through the coronagraph's field of view (2-6R) over a period of a few hours, after which the legs of the loops usually remain visible for a few days. In this paper we investigate the temporal changes in density and mass per unit length measured along the legs of such loops during the several days after the initial eruption. Examination of 8 transients shows that the mass and density in the legs decrease during the few hours after the top of the loop has travelled beyond the coronagraph's field of view. The mass and density then increase slowly, during the next one half to one day, then decrease again over approximately the same period. These changes are generally shown to be too rapid to be explained by solar rotation, indicating that the transient legs have a lifetime of only a few days. Title: Physical Conditions in a Limb Flare Authors: Fisher, R. R.; Poland, A. I. Bibcode: 1978BAAS...10..657F Altcode: No abstract at ADS Title: Motions and mass changes of a persistent coronal streamer. Authors: Poland, A. I. Bibcode: 1978SoPh...57..141P Altcode: A coronal streamer was observed by the white light coronagraph on Skylab during 5 successive limb passages between 1 June, 1973 and 6 August, 1973. The Skylab data give independent measures of coronal brightness and polarization, as functions of time. These permit the distinction between changes in the coronal streamer's appearance due to solar rotation and actual structural changes. The streamer's visual appearance changed slightly between successive limb passages indicating that it was not a steady state feature. Measurements of the streamer's latitude, brightness, and polarization during 3 east limb passages show that: (1) the streamer's axis migrated southward from 25° N at first east limb passage to 11° N at second east limb passage to 8° N latitude at third east limb passage; (2) the streamer's mass (and mass gradient with height), varied by between 20 and 50% from one east limb passage to the next; (3) the streamer's longitudinal extent was also observed to be less on successive east limb passages; and (4) mass changes (distinct from coronal transients) occurring over hours were detected during at least two limb passages. Comparison of the outer coronal observations with observations from lower in the solar atmosphere indicate that the streamer was associated with a complex of solar activity consisting of active regions and filaments. This complex of activity shifted southward by the same amount as the streamer. The variations detected in the streamer preclude the detailed determination of its three-dimensional structure. Title: Expansion and broadening of coronal loop transients: a theoretical explanation. Authors: Mouschovias, T. Ch.; Poland, A. I. Bibcode: 1978ApJ...220..675M Altcode: Consequences are examined of the assumption that an observed coronal loop transient is a twisted rope of magnetic-field lines expanding and broadening in the background coronal plasma and magnetic field. It is shown that the expansion can be accounted for by the azimuthal component of the field; the observed broadening of the loop as it moves outward can be accounted for by the longitudinal component of the field. In order to have a net outward force and at the same time avoid a classical pinch (sausage) instability, the two components of the field must satisfy a certain inequality. It is predicted that, as the loop rises, the width (h) of its top portion should vary proportionally with distance (R) from the sun's center. This is in good agreement with measurements that show h is proportional to the 0.8 power of R. The prediction that the radius of curvature of the top portion of the loop should be proportional to R differs from the measured variation. The difference could be accounted for by a drag due to the background coronal field that flattens the loop's top. Title: Temporal evolution of the equatorial K-corona. Authors: MacQueen, R. M.; Poland, A. I. Bibcode: 1977SoPh...55..143M Altcode: Observations of the equatorialK-coronal radiance at 2.5R from Sun center and its variation with time, on a daily basis, during the Skylab mission (May 1973-February 1974) are presented. The observations are subdivided into three periods, each characterized by a different variation of the radiance pattern with time. During the initial period, encompassing two solar rotations, there are several data gaps, but the radiance pattern shows a more or less smooth variation with time; however, during the second period (also about two solar rotations duration) the radiance signal is neither persistent on the short term nor recurrent from one limb passage to the next. Finally, during the last period, of five solar rotations duration, the radiance signal exhibits an orderly periodic behavior of increasing intensity. These results are interpreted as indicating a general simplification of the coronal magnetic field through the mission and, in comparison with harmonic analysis of the surface magnetic field (Levine, 1977), as indicating a rapid response of equatorial outer coronal structures to abrupt changes in the global surface field structure. Title: A study of the background corona near solar minimum. Authors: Saito, K.; Poland, A. I.; Munro, R. H. Bibcode: 1977SoPh...55..121S Altcode: The white light coronagraph data from Skylab is used to investigate the equatorial and polarK andF coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona is dominated by either streamers or coronal holes seen in projections on the limb approximately 50% and 30% of the time, respectively; (2) despite the domination by streamers and holes, two periods of time were found which were free from the influences of streamers or holes (neither streamers nor holes were within 30° in longitude of the limb); (3) the derived equatorial background density model is less than 15% below the minimum equatorial models of Newkirk (1967) and Saito (1970); (4) a spherically symmetric density model for equatorial coronal holes yields densities one half those of the background density model; and (5) the inferred brightness of theF-corona is constant to within ±10% and ±5% for the equatorial and polar values, respectively, over the observation period. While theF-corona is symmetric at 2R it begins to show increasing asymmetry beyond this radius such that at 5R the equatorialF-coronal brightness is 25% greater than the polar brightness. Title: Radiance calibration of the High Altitude Observatory white-light coronagraph on Skylab. Authors: Poland, A. I.; Gosling, J. T.; MacQueen, R. M.; Munro, R. H. Bibcode: 1977ApOpt..16..926P Altcode: The processing of over 35,000 photographs of the solar corona obtained by the white-light coronograph on Skylab is described. Calibration of the vast amount of data was complicated by temporal effects of radiation fog and latent image loss. These effects were compensated by imaging a calibration step wedge on each data frame. Absolute calibration of the wedge was accomplished through comparison with a set of previously calibrated glass opal filters. Analysis employed average characteristic curves derived from measurements of step wedges from many frames within a given camera half-load. The net absolute accuracy of a given radiance measurement is estimated to be 20%. Title: Measurement of stray radiance in the High Altitude Observatory's Skylab coronagraph. Authors: Csoeke-Poeckh, A.; MacQueen, R. M.; Poland, A. I. Bibcode: 1977ApOpt..16..931C Altcode: The paper outlines two techniques used for determining the instrumental stray radiance from orbital results obtained with the Skylab white light coronagraph. The first technique employs images of the lunar disk made near the time of solar eclipse to compare the apparent contrasts of maria and highlands recorded by the coronograph with those of previous studies and then determine the magnitude of the stray radiance and its variation along a radius. The second method determines the azimuthal variation of the stray radiance by measuring the change in the net radiance of a point in the coronal images as the image is rotated. Title: The Background Corona Near Solar Minimum. Authors: Saito, K.; Poland, A.; Munro, R.; MacQueen, R. Bibcode: 1977BAAS....9Q.371S Altcode: No abstract at ADS Title: Interpretation of broad-band polarimetry of solar coronal transients: importance of the Halpha emission. Authors: Poland, A. I.; Munro, R. H. Bibcode: 1976ApJ...209..927P Altcode: An eruptive prominence and coronal transient was observed in H-alpha, He II 304-A, and coronal white light (3700-7000 A). This event was generically similar to many other coronal transients associated with eruptive prominences in that loops of material propagated outward through the corona. It differed in that some of the prominence material was observed above 1.75 solar radii in both coronal white light and He II. Polarization analysis of the white-light data shows that the observed radiance from the loop-like transient was entirely due to free electron or Thomson scattering, whereas the white-light radiance from the prominence material was dominated by H-alpha emission. By comparing the white-light observations with model calculations, the densities along the loop and limits on the temperature and density of the prominence are obtained. Material observed in both white light and He II is shown to be cool prominence material, whereas analysis indicates that the transient-loop material is hot and coronal in origin. The time sequence of observations leads to the hypothesis that the prominence material is heated as it is ejected from the sun. Title: Expansion and Broadening of Coronal Loop Transients. Authors: Mouschovias, T. Ch.; Poland, A. I. Bibcode: 1976BAAS....8..534M Altcode: No abstract at ADS Title: The Structure and Fluctuations of a Coronal Streamer. Authors: Poland, A. I. Bibcode: 1976BAAS....8Q.532P Altcode: No abstract at ADS Title: The speeds of coronal mass ejection events. Authors: Gosling, J. T.; Hildner, E.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1976SoPh...48..389G Altcode: The outward speeds of mass ejection events observed with the white light coronagraph experiment on Skylab varied over a range extending from less than 100 km s−1 to greater than 1200 km s−1. For all events the average speed within the field of view of the experiment (1.75 to 6 solar radii) was 470 km s−1. Typically, flare associated events (Importance 1 or greater) traveled faster (775 km s−1) than events associated with eruptive prominences (330 km s−1); no flare associated event had a speed less than 360 km s−1, and only one eruptive prominence associated event had a speed greater than 600 km s−1. Speeds versus height profiles for a limited number of events indicate that the leading edges of the ejecta move outward with constant or increasing speeds. Title: Initial Results from the High Altitude Observatory White Light Coronagraph on Skylab - A Progress Report Authors: MacQueen, R. M.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1976RSPTA.281..405M Altcode: 1976RSLPT.281..405M The frequent, periodic observations by the white light coronagraph allow an examination of coronal variations over a broad range of temporal scales. Examples of the slowest and most rapid variations are presented. An example of extremely slow coronal variations is the gradual evolution - to a large equatorial streamer - in association with a marked decrease in solar activity, as the total magnetic flux in one hemisphere decreased. Another example is given of a long-lived quasi-stable coronal streamer, apparently associated with a stable filament channel; comparison of this streamer with coronal potential magnetic field computations show little correlation. The remainder of the paper summarizes some results on coronal transients - the most rapid variations observed. Characteristic mass and energies involved in mass ejection transients, their temporal and spatial distributions, their associations with surface phenomena and possible interplanetary signatures, and finally their role in coronal evolution are briefly noted. Title: Frequency of coronal transients and solar activity. Authors: Hildner, E.; Gosling, J. T.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1976SoPh...48..127H Altcode: The High Altitude Observatory's white light coronagraph aboard Skylab observed some 110 coronal transients - rapid changes in appearance of the corona - during its 227 days of operation. The longitudes of the origins of these transients were not distributed uniformly around the solar surface (51 of the 100 events observed in seven solar rotations arose from a single quadrant of longitude). Further, the frequency of transient production from each segment of the solar surface was well correlated with the sunspot number and Ca II plage (area × brightness) index in the segment, rotation by rotation. This correlation implies that transients occur more often above strong photospheric and chromospheric magnetic fields, that is, in regions where the coronal magnetic field is stronger and, perhaps, more variable. This pattern of occurrence is consistent with our belief that the forces propelling transient material outward are, primarily, magnetic. A quantitative relation between transient production from an area and the Zürich sunspot number appropriate to that area is derived, and we speculate that the relation is independent of phase in the solar activity cycle. If true, the Sun may give rise to as many as 100 white light coronal transients per month at solar cycle maximum. Title: The Speeds of Coronal Mass Ejection Events Authors: Hildner, E.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L.; Gosling, J. T. Bibcode: 1976BAAS....8R.368H Altcode: No abstract at ADS Title: Movie of Comet Kohoutek (1973f) as Observed Near Minimum Elongation by the Hao Coronagraph Aboard SKYLAB Authors: Hildner, E.; Gosling, J. T.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1976NASSP.393..124H Altcode: 1976IAUCo..25..124H No abstract at ADS Title: A search for forward scattering of sunlight from lunar libration clouds Authors: Munro, R. H.; Gosling, J. T.; Hildner, E.; MacQueen, R. M.; Poland, A. I.; Ross, C. L.; Hopfield, A. Bibcode: 1975P&SS...23.1313M Altcode: An attempt to determine the radiance of forward scattered sunlight from particles in lunar libration regions was made with the white light coronagraph on Skylab. The libration regions could not be distinguished against the solar K + F coronal background; an upper limit to the libration cloud radiance is determined to be 2·5 × 10 -11B , where B is the mean radiance of the solar disk. Employing a model of the particle composition and size distribution which has been proposed for the interplanetary medium, we determine upper limits for the density enhancements in the libration region from the upper limit of the forward scattered radiance presented herein. Similarly, the actual spatial density enhancement is calculated using the earlier observations of the libration region backscattered radiance (Roach, 1975). Enhancements of a factor of 10 2-10 3 are thus determined, depending upon material composition and size distribution used. By combining the forward and backscatter observations, it is possible to eliminate from consideration clouds whose power law particle size distribution exponent k is 2·5 and complex index of refraction m is 1·33-0.05 i and 1·50-0.05 i (i.e. absorbing ice and quartz particles, respectively). Finally, the radiance contrast of a possible model libration cloud is calculated with respect to the K- and F-corona/zodiaal light background and is shown to be a maximum in the vicinity of solar elongation angle ∼30 deg. Title: The Emission Sources and Geometry of the Coronal Transient of 21 August 1973. Authors: Poland, A. I.; Munro, R. H. Bibcode: 1975BAAS....7..473P Altcode: No abstract at ADS Title: The Large Coronal Transient of 10 June 1973. I: Observational Description Authors: Hildner, E.; Gosling, J. T.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1975SoPh...42..163H Altcode: During the 8.5 month flight of the High Altitude Observatory's white light coronagraph on board Skylab, over 100 coronal transients were observed. In this paper we present a description of one well observed loop transient, that of 10 June 1973. The transient apparently resulted from the eruption of a quiescent prominence on the limb; the emergence of a new, bipolar active region near the prominence may have caused the eruptior. The transient's leading edge rose from 3.6 to 5.0 solar radii (R) from Sun center at approximately 500 km s−1 during the 32 min of coronagraph observations. Material in a pre-existing streamer was swept away by the transient, causing the streamer to disappear. The mass ejected into the corona above a projected height of 2 R was ≈ 5.4 × 1015 g, the potential energy associated with the ejected transient material was ⩾7.0 × 1030 erg, and the kinetic energy of the ejected material is estimated as 1.7 × 1030 erg. The 10 June 1973 transient was, in most respects, typical of other loop transients observed by Skylab. Title: Observations of a Long Lived Coronal Streamer Authors: Poland, A. I. Bibcode: 1975BAAS....7..356P Altcode: No abstract at ADS Title: Direct Observations of a Flare Related Coronal and Solar Wind Disturbance Authors: Gosling, J. T.; Hildner, E.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1975SoPh...40..439G Altcode: Numerous mass ejections from the Sun have been detected with orbiting coronagraphs. Here for the first time we document and discuss the direct association of a coronagraph observed mass ejection, which followed a 2B flare, with a large interplanetary shock wave disturbance observed at 1 AU. Estimates of the mass (2.4 × 1016 g) and energy content (1.1 × 1032 erg) of the coronal disturbance are in reasonably good agreement with estimates of the mass and energy content of the solar wind disturbance at 1 AU. The energy estimates as well as the transit time of the disturbance are also in good agreement with numerical models of shock wave propagation in the solar wind. Title: Reticulation: effects and cure. Authors: Poland, A. I.; Gosling, J. T. Bibcode: 1975AASPB...9...14P Altcode: No abstract at ADS Title: Photography of comet Kohoutek by Skylab white light coronagraph. Authors: MacQueen, R. M.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Poland, A. I.; Ross, C. L.; Keller, H. U.; Schmidt, H. U. Bibcode: 1975NASSP.355...19M Altcode: 1975coko.conf...19M No abstract at ADS Title: Mass ejections from the Sun: A view from Skylab Authors: Gosling, J. T.; Hildner, E.; MacQueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1974JGR....79.4581G Altcode: More than 30 instances of sudden mass ejections from the sun were observed with the white light coronagraph experiment aboard Skylab during the first 118 days of the mission. Typically, these ejections appear as large magnetic loops rooted at the sun, yet expanding outward through the solar corona at speeds of the order of 400 km s-1. The loops always appear to retain their magnetic connection to the sun. Eighteen of these ejections were associated with active and eruptive prominences and surges; only three ejections appear to have been flare initiated. Associations with ground-detected metric wavelength type 2 and 4 radio bursts occur for about 30% of these events; however, ground-detected type 2 and 4 radio bursts originating near the limb are almost invariably accompanied by coronagraph-observed ejections. Pressure or MHD waves run out ahead of the transient material ejecta; at times these waves can be detected by their effects on nearby coronal structures. For one event, that of August 10, 1973, we make the following estimates: (1) mass content, 4 × 1015 grams; (2) mass flow rate, 1.1 × 1012 grams s-1 (3) energy content, 8.4 × 1030 ergs; and (4) energy flow rate, 7.7 × 1026 ergs s-1. Locally, this represents a significant mass and energy input to the solar wind; we suggest that the ejections are the coronal counterparts of nonrecurrent (including shocks) solar wind disturbances detected near the orbit of the earth. Title: Theoretical Helium i Emission-Line Intensities for Quiescent Prominences Authors: Heasley, J. N.; Mihalas, Dimitri; Poland, A. I. Bibcode: 1974ApJ...192..181H Altcode: Self-consistent solutions of the combined statistical equilibrium and transfer equations have been carried out for a rather complete multilevel, multi-ion model helium atom in model quiescent prominences. The excitation and ionization of both He I and He ii were considered simultaneously, and detailed calculations of the radiative transfer in the resonance lines and ground-state continua of both these ions were made, allowing for the effects of overlapping hydrogen transitions. A large number of excited states have been included in the computation, so that a fairly comprehensive set of predicted subordinate line intensities are now available for comparison with observation. A preliminary comparison of the predicted values with published singleti triplet ratio observations shows good agreement for all the pairs of lines considered. Subject headings: atomic processes - line formation - prominences, solar Title: The High Altitude Observatory White Light Coronagraph Experiment Authors: MacQueen, R. M.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1974IAUS...57..505M Altcode: No abstract at ADS Title: Theoretical helium I emission line intensities for quiescent prominences. Authors: Heasley, J. N.; Mihalas, D.; Poland, A. I. Bibcode: 1974BAAS....6..219H Altcode: No abstract at ADS Title: The High Altitude Observatory white light coronagraph Authors: MacQueen, R. M.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1974SPIE...44..207M Altcode: Most of the instruments of the Apollo Telescope Mount are satellite-borne because they observe in regions of the electromagnetic spectrum where the telluric atmosphere is opaque. For the coronagraph of the High Altitude Observatory, observing in visible light, this is not so. The structure of the solar corona is obscured from ground-based observations by scattered light in the earth's atmosphere, and observations from space are required to reduce this scattered light to a level which is negligible with respect to the brightness of the outer solar corona. 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: Theoretical Helium I Emission Line Intensities for Quiescent Prominences. Authors: Heasley, J. N.; Mihalas, D.; Poland, A. I. Bibcode: 1974BAAS....6..220H Altcode: No abstract at ADS Title: The Outer Solar Corona as Observed from Skylab: Preliminary Results Authors: MacQueen, R. M.; Eddy, J. A.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Newkirk, G. A., Jr.; Poland, A. I.; Ross, C. L. Bibcode: 1974ApJ...187L..85M Altcode: The white-light coronagraph experiment has made frequent, periodic observations of the solar corona from 1.5 R0 to 6.0 R0 during the Skylab mission, and these observations will permit the determination of the three-dimensional extent of coronal forms. There are several time scales on which visual changes in coronal structures occur, ranging from approximately one-half rotation to less than hours. A number of events corresponding to the shortest time scale - coronal transients - cause major restructuring of the corona. Subject headings: corona, solar - solar wind 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 High Altitude Observatory white light coronagraph. Authors: MacQueen, R. M.; Gosling, J. T.; Hildner, E.; Munro, R. H.; Poland, A. I.; Ross, C. L. Bibcode: 1974inas.conf..207M Altcode: No abstract at ADS Title: The Outer Solar Corona as Observed from Skylab: Preliminary Results. Authors: Poland, A. I.; Gosling, J. T.; Hildner, E. G.; MacQueen, R. M.; Munro, R. H.; Ross, C. L. Bibcode: 1973BAAS....5..419P Altcode: No abstract at ADS Title: Observations of Coronal Forms: 7 March - 7 June 1970 Authors: Hansen, R. T.; Hansen, S. F.; Newkirk, G. A.; MacQueen, R. M.; Gosling, J. T.; Poland, A. I. Bibcode: 1972BAAS....4T.383H Altcode: No abstract at ADS Title: Helium in hot stars Authors: Poland, A. I. Bibcode: 1972Obs....92...17P Altcode: No abstract at ADS Title: Energy Balance in Cool Quiescent Prominences Authors: Poland, A.; Anzer, U. Bibcode: 1971SoPh...19..401P Altcode: The energy balance for cool quiescent prominences is examined using a 6000 km, 6000 K isothermal slab model prominence with a density gradient dictated by a modified Kippenhahn-Schlüter model. The model is irradiated from both sides by the coronal, chromospheric, and photospheric radiation fields. The radiative transfer problem is solved in detail for the Lyman continuum and Hα to determine the net radiative energy loss for hydrogen. An estimate of the energy loss for Ca II H and K indicates that this source of energy loss is unimportant when compared with the hydrogen radiation. The radiative energy loss is easily balanced by the conductive energy gain from the corona. Title: Hydrogen Ionization and n=2 Population for Model Spicules and Prominences Authors: Poland, A.; Skumanich, A.; Athay, R. G.; Tandberg-Hanssen, E. Bibcode: 1971SoPh...18..391P Altcode: Using slab model atmospheres that are irradiated from both sides by photospheric, chromospheric, and coronal radiation fields we have determined the ionization and excitation equilibrium for hydrogen. Title: Energy balance in quiescent prominences. Authors: Poland, A.; Anzer, U. Bibcode: 1971BAAS....3..353P Altcode: No abstract at ADS Title: On the Application of the Newton-Raphson Method to the Excitation and Transfer of Continuum Radiation Authors: Domenico, B. A.; Poland, A. I.; Skumanich, A. Bibcode: 1971BAAS....3....9D Altcode: No abstract at ADS Title: -Non-LTE effects for He i in early B type stars Authors: Poland, A.; Skumanich, A. Bibcode: 1971MNRAS.152P..18P Altcode: The contention by Hearn and Leckrone that non-LTE affects helium abundances derived for early main sequence stars is shown to be in error. Although the cores of some lines exhibit non-LTE effects, their equivalent widths, which are dominated by line wings that remain in LTE, are unaffected and yield the same helium abundances as in LTE. The lines A6678 and A587S have weak wings and remain affected by non-LTE. Title: The Ionization Equilibrium and the N = 2 Population of Hydrogen in Quiescent Prominences Authors: Poland, A.; Athay, R. G.; Skumanich, A.; Tandberg-Hanssen, E. Bibcode: 1970BAAS....2R.338P Altcode: No abstract at ADS Title: Neutral Helium Lines and the Helium Anomaly in Hot Stars Authors: Poland, Arthur I. Bibcode: 1970ApJ...160..609P Altcode: Using our previously calculated departures from LTE for He r in hot stars we have calculated nonLTE and LTE line profiles and equivalent widths for the 2SAP, 2P-4S, 2P-5S, and 2P-4D transitions in the singlet and triplet systems of neutral helium in model atmospheres of 20000 and 30000 K with log g = 4. In comparing the LTE and non-LTE calculations we found that: (1) the cores of the stronger lines are deepened by including non-LTE; (2) for some of the weaker lines non-LTE raises the core of the line; (3) the wings of the lines are formed in LTE, as are the forbidden components of the 2P-4D transitions; and (4) the equivalent widths of the lines are almost unaffected by non-LTE. Because the forbidden components of the 2P-4D transitions are formed in LTE and the allowed cores of these lines are strongly affected by non-LTE, we have formed a ratio of line depth in the allowed component to line depth in the forbidden component to compare the non-LTE effect wfth observations. A comparison of LTE, non-LTE, and observed ratios shows that only the non-LTE results agree with the observations. Since the equivalent widths of the lines are not affected by non-LTE, we have calculated LTE widths for a series of model atmospheres and have found that the helium anomaly can be explained by LTE alone. In fact, the helium anomaly is basically a strong line/weak line effect. A comparison of our equivalent widths with observations indicates that the helium abundance in early-type dwarfs is about He/H = 0.12. Title: The rotational temperature of a TiO band in the spectrum of R Hydrae. Authors: Keller, C. F.; Jackson, B. V.; Poland, A. I.; Peery, B. F., Jr. Bibcode: 1970A&A.....4..415K Altcode: A procedure is presented for the determination of a rotational temperature from observations of the (1.0) ?`8 TiO band. The method is based upon comparison between accurately measured wavelengths of blended absorption features in the band and corresponding wavelengths in the computed band proffle. The rotational temperature found from McDonald coude' spectrograms of R Hydrae is Trot = 1430 290 0K. Key words: R Hydrae, long period variable - molecular spectroscopy, TiO-temperature Title: Neutral helium lines and departures from LTE in hot stars Authors: Johnson, Hollis Ralph; Poland, Arthur I. Bibcode: 1970PGLO...94.1151J Altcode: No abstract at ADS Title: Neutral helium lines and the helium anomaly in hot stars Authors: Poland, Arthur I. Bibcode: 1970PGLO...98..609P Altcode: No abstract at ADS Title: Departures from LTE for neutral helium lines in hot stars Authors: Poland, Arthur Ira Art Bibcode: 1969PhDT........91P Altcode: No abstract at ADS Title: Departures from LTE for Neutral Helium Lines in Hot Stars. Authors: Poland, Arthur Ira Bibcode: 1969PhDT.........4P Altcode: No abstract at ADS Title: Neutral helium lines and departures from LTE in hot stars. Authors: Johnson, H. R.; Poland, A. I. Bibcode: 1969JQSRT...9.1151J Altcode: No abstract at ADS Title: Calculations of Solar Hydrogen Lines: Comparative Solutions for a Standard Line Transfer Problem Authors: Athay, R. G.; Avrett, E. H.; Beebe, H. A.; Johnson, H. R.; Poland, A. I.; Cuny, Y. Bibcode: 1968rla..conf..169A Altcode: No abstract at ADS Title: On the Equilibrium of Hydrogen in Early-Type Stars Authors: Beebe, H. A.; Hollis, H. R.; Poland, A. I. Bibcode: 1968rla..conf..393B Altcode: No abstract at ADS Title: Neutral Helium Lines and Departures from LTE in Hot Stars Authors: Johnson, H. R.; Poland, A. I. Bibcode: 1968rla..conf..413J Altcode: No abstract at ADS Title: Departures from Equilibrium in Neutral Helium for Hot Stars. Authors: Johnson, Hollis K.; Poland, Arthur I. Bibcode: 1968AJS....73Q.186J Altcode: Departures from equilibrium for He I are calculated for theoretical models of early-type stars by solving self-consistently the equations for radiative transfer and steady state for a model atom. These calculations are aimed at an understanding of the observations of anomalous singlet/triplet intensity ratios in hot stars. Atmospheric models chosen are: T= 20 0000K, log g =4 (Strom, S., and Avrett, F., A strophys. J. Suppl. 12, 1, 1965) and T=300000K, log g=4 (Mihalas, D., Apstrophys. J. Suppl. 9, 321,1964). Various atomic models have been chosen in order to test their effects on the final result. Extensive calculations show that the singlets and triplets can be effectively decoupled and solved separately. Final solutions for the singlets involved the levels: 1S, 2S, 2P, 3, 4, 5, 6, 7-9,10-14,15-20, with a similar atom for the triplets. All collisional and radiative rates were included for all levels up to n =6. Above n =6, each level was connected radiatively to 2S, 2P, and 3 and collisionally to 1'S, 25, 2P, 3, and the adjacent levels. Actual calculations show that the ignored transitions are unimportant for the observed lines. At the surface of the star (r =0), the non-LTF parameter b1= 180 for the 20 0000K model and bi=3.4 for the 30 0000K. Results for the 20 0000K model at a height where r(43-23P) = 2.4 are listed below. j bj j bj 1'S 1.17 21S 1.41 2~S 1.30 2'P 1.41 2~P 1.22 31 1.02 33 1.05 41 1.00 43 1.00 Thus in the region of formation of the subordinate lines of neutral helium, departures from thermodynamic equilibrium are quite small for a 20 0000K star, in agreement with observations. Calculations are underway for a 30 0000K star, where significant departures from equilibrium are expected. Title: Effects in the Two-Color Diagram of the Rotation of A and F Stars. Authors: Peters, James G.; Poland, Arthur I.; Wrubel, Marshal H. Bibcode: 1966AJ.....71S.174P Altcode: The method described by Collins (Astrophys. J. 138, 1134, 1963) for computing the observed radiation of rotating stars as a function of angular velocity and inclination, has been extended to include departures from grayness. Computed displacements of rotating A and F stars in the two-color diagram are compared with earlier observations (Kraft and Wrubel, Astrophys. J. 142, 703,1965).