Author name code: dere ADS astronomy entries on 2022-09-14 author:"Dere, K." ------------------------------------------------------------------------ Title: The Temperature and Emission Measure Distribution in the Quiet and Active Solar Corona: A Bayesian Approach Authors: Dere, Kenneth P. Bibcode: 2022ApJ...930...86D Altcode: 2022arXiv220317086D The reconstruction of the differential emission measure (DEM) from observations of spectral line intensities provides information on the temperature distribution of the emission measure in the region observed. The inversion process is known to be highly unstable, and it has been necessary to provide additional constraints, such as requiring that the DEM should be smooth. However, this is a nonphysical constraint. The goal of this analysis is to make an empirical determination of the ability of a set of emission-line intensities to constrain the reconstruction. Here, a simple model is used, by means of a Markov Chain Monte Carlo process, to arrive at solutions that reproduce the observed intensities in a region of the quiet Sun and a solar active region. These solutions are compared by means of the reduced chi-squared. The conclusion from this analysis is that the observations are only capable of constraining a model consisting of four temperature-emission measure pairs plus a determination of the standard deviation of the model from the observed line intensities. A more complex model with five temperature-emission measure pairs does not improve the fit and leads to parameters that are irrelevant. A more general conclusion is that the information content of a set of observed emission lines is limited with respect to the determination of the emission measure distribution. Title: CHIANTI—An Atomic Database for Emission Lines. XVI. Version 10, Further Extensions Authors: Del Zanna, G.; Dere, K. P.; Young, P. R.; Landi, E. Bibcode: 2021ApJ...909...38D Altcode: 2020arXiv201105211D We present version 10 of the CHIANTI package. In this release, we provide updated atomic models for several helium-like ions and for all the ions of the beryllium, carbon, and magnesium isoelectronic sequences that are abundant in astrophysical plasmas. We include rates from large-scale atomic structure and scattering calculations that are in many cases a significant improvement over the previous version, especially for the Be-like sequence, which has useful line diagnostics to measure the electron density and temperature. We have also added new ions and updated several of them with new atomic rates and line identifications. Also, we have added several improvements to the IDL software, to speed up the calculations and to estimate the suppression of dielectronic recombination. Title: Quiet Sun electron densities and their uncertainties derived from spectral emission line intensities Authors: Dere, Kenneth P. Bibcode: 2020MNRAS.496.2334D Altcode: 2020arXiv200604184D; 2020MNRAS.tmp.1785D The goal of this paper is to apply statistical methods to determine electrons densities and their errors from measurements of density-sensitive line intensities in the quiet Sun. Three methods are employed. The first is the use of L-function plots to provide a quick visual assessment of the likelihood that a set of line intensities can provide a robust estimate of these quantities. A second methods involves a χ2 minimization together with a prescription for determining the regions of statistical confidence in addition to the best-fitting value. A third method uses a Bayesian inference technique that employs a Monte Carlo Markov Chain (MCMC) calculation from which an analysis of the posterior distributions provide estimates of the mean and regions of high probability density. Using these three methods, observations of extreme-ultraviolet spectral lines originating from regions of the quiet Sun have been analysed. The quantitative χ2 minimization and MCMC sampling provide results that are generally in good agreement, especially for sets of lines of ions that have L-function plots that suggest that a robust analysis might be possible. Title: Latest updates to the CHIANTI atomic database Authors: Young, Peter R.; Dere, Kenneth P.; Del Zanna, Giulio; Landi, Enrico; Sutherland, Ralph Bibcode: 2019AAS...23431402Y Altcode: CHIANTI is a database of atomic data parameters and a software package for computing the radiative emissions from optically-thin astrophysical plasmas. CHIANTI is freely available to the community (http://chiantidatabase.org), and is very widely used in the Heliophysics and Astrophysics communities. The papers describing CHIANTI have been cited over 3500 times in the 22-year lifetime of the project.

Version 9 of CHIANTI was released in March 2019, and this presentation summarizes the new updates and highlights important applications. The key change for CHIANTI 9 was the implementation of a new method to account for recombination and dielectronic capture in the level balance equations through new, two-ion models that fully capture the state-to-state transitions between ions. The models are needed for the calculation of X-ray satellite lines and, for the first time, enable density sensitivity to be modeled.

A number of the standard atomic data-sets have been updated, including recombination rates for several important coronal iron ions. New software routines have been written for computing the differential emission measure of a plasma, and for computing the response functions of the Atmospheric Imaging Assembly on board NASA's Solar Dynamics Observatory . Title: CHIANTI—An Atomic Database for Emission Lines. XV. Version 9, Improvements for the X-Ray Satellite Lines Authors: Dere, K. P.; Del Zanna, G.; Young, P. R.; Landi, E.; Sutherland, R. S. Bibcode: 2019ApJS..241...22D Altcode: 2019arXiv190205019D CHIANTI contains a large quantity of atomic data for the analysis of astrophysical spectra. Programs are available in IDL and Python to perform calculation of the expected emergent spectrum from these sources. The database includes atomic energy levels, wavelengths, radiative transition probabilities, rate coefficients for collisional excitation, ionization, and recombination, as well as data to calculate free-free, free-bound, and two-photon continuum emission. In Version 9, we improve the modeling of the satellite lines at X-ray wavelengths by explicitly including autoionization and dielectronic recombination processes in the calculation of level populations for select members of the lithium isoelectronic sequence and Fe XVIII-XXIII. In addition, existing data sets are updated, new ions are added, and new total recombination rates for several Fe ions are included. All data and IDL programs are freely available at http://www.chiantidatabase.org or through SolarSoft, and the Python code ChiantiPy is also freely available at https://github.com/chianti-atomic/ChiantiPy. Title: The CHIANTI atomic database Authors: Young, P. R.; Dere, K. P.; Landi, E.; Del Zanna, G.; Mason, H. E. Bibcode: 2016JPhB...49g4009Y Altcode: 2015arXiv151205620Y The freely available CHIANTI atomic database was first released in 1996 and has had a huge impact on the analysis and modeling of emissions from astrophysical plasmas. It contains data and software for modeling optically thin atom and positive ion emission from low density (≲1013 cm-3) plasmas from x-ray to infrared wavelengths. A key feature is that the data are assessed and regularly updated, with version 8 released in 2015. Atomic data for modeling the emissivities of 246 ions and neutrals are contained in CHIANTI, together with data for deriving the ionization fractions of all elements up to zinc. The different types of atomic data are summarized here and their formats discussed. Statistics on the impact of CHIANTI to the astrophysical community are given and examples of the diverse range of applications are presented. Title: CHIANTI - An atomic database for emission lines. Version 8 Authors: Del Zanna, G.; Dere, K. P.; Young, P. R.; Landi, E.; Mason, H. E. Bibcode: 2015A&A...582A..56D Altcode: 2015arXiv150807631D We present version 8 of the CHIANTI database. This version includes a large amount of new data and ions, which represent a significant improvement in the soft X-ray, extreme UV (EUV) and UV spectral regions, which several space missions currently cover. New data for neutrals and low charge states are also added. The data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for most of the new datasets are not spline-fitted as previously, but are retained as calculated. This required a change of the format of the CHIANTI electron excitation files. The format of the energy files has also been changed. Excitation rates between all the levels are retained for most of the new datasets, so the data can in principle be used to model high-density plasma. In addition, the method for computing the differential emission measure used in the CHIANTI software has been changed. Title: ChiantiPy: Python package for the CHIANTI atomic database Authors: Dere, Ken Bibcode: 2013ascl.soft08017D Altcode: ChiantiPy is an object-orient Python package for calculating astrophysical spectra using the CHIANTI atomic database for astrophysical spectroscopy. It provides access to the database and the ability to calculate various physical quantities for the interpretation of astrophysical spectra. Title: CHIANTI 7.1: a new database release for SDO data analysis Authors: Young, P. R.; Landi, E.; Del Zanna, G.; Dere, K. P.; Mason, H. E. Bibcode: 2013enss.confE..58Y Altcode: Version 7.1 of the CHIANTI atomic database was released in October 2012 and contains a number of improvements to better model data returned by the AIA and EVE instruments on board SDO. Specifically the models for the important iron ions Fe VIII to Fe XIV have been greatly expanded, yielding many thousands of new transitions in the 50-170 angstrom range that enable the irradiance spectra obtained by EVE to be modeled more accurately. A lack of available atomic data meant that the AIA 94 angstrom channel was not well modeled at low temperatures in earlier versions of CHIANTI. New data for Fe VIII, Fe X and Fe XIV added to CHIANTI 7.1 give important contributions to the channel and greatly improve comparisons with theory. Title: CHIANTI—An Atomic Database for Emission Lines. XIII. Soft X-Ray Improvements and Other Changes Authors: Landi, E.; Young, P. R.; Dere, K. P.; Del Zanna, G.; Mason, H. E. Bibcode: 2013ApJ...763...86L Altcode: The CHIANTI spectral code consists of two parts: an atomic database and a suite of computer programs in Python and IDL. Together, they allow the calculation of the optically thin spectrum of astrophysical objects and provide spectroscopic plasma diagnostics for the analysis of astrophysical spectra. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, ionization, and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7.1 has been released, which includes improved data for several ions, recombination rates, and element abundances. In particular, it provides a large expansion of the CHIANTI models for key Fe ions from Fe VIII to Fe XIV to improve the predicted emission in the 50-170 Å wavelength range. All data and programs are freely available at http://www.chiantidatabase.org and in SolarSoft, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net. Title: Recent Developments with the CHIANTI Atomic Database for Astrophysical Spectroscopy Authors: Dere, Kenneth P. Bibcode: 2012AAS...22020802D Altcode: The CHIANTI atomic database for astrophysical spectroscopy maintains an assessed set of atomic data that are necessary to calculate emission from ionized plasmas that exist throughout the universe. As new atomic data becomes available, it is added to the CHIANTI database in order to improve the accuracy of data already in the database, to extend the range of spectral lines that can be reproduced or to develop new ions that are not already in the database.

Version 7 of the database was recently released (Landi et al., 2012). This included several new ions and a wide range of updated ions. A Python interface to CHIANTI, ChiantiPy, was developed to complement the existing IDL interface. A web application, based on ChiantiPy, was also developed that allows the user to make spectral calculations using the Chianti database directly from a web browser.

Version 7.1 is expected to be released in 2012 and is expected to include updated atomic data for existing ions and the develop of new ions. Ionization equilibria will be updated based on new calculations of dielectronic recombination for some isoelectronic sequences. Title: CHIANTI—An Atomic Database for Emission Lines. XII. Version 7 of the Database Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason, H. E. Bibcode: 2012ApJ...744...99L Altcode: The CHIANTI spectral code consists of an atomic database and a suite of computer programs to calculate the optically thin spectrum of astrophysical objects and carry out spectroscopic plasma diagnostics. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, and ionization and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7 has been released, which includes several new ions, significant updates to existing ions, as well as Chianti-Py, the implementation of CHIANTI software in the Python programming language. All data and programs are freely available at http://www.chiantidatabase.org, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net. Title: Recent Progress with the CHIANTI Atomic Database for Astrophysical Spectroscopy Authors: Dere, Kenneth P. Bibcode: 2011AAS...21813402D Altcode: 2011BAAS..43G13402D The first version of the CHIANTI atomic database for astrophysical spectroscopy was released in 1997 and the most recent version in 2009. Recent progress with CHIANTI will be described.

Based on the ionization rates developed by Dere (2007) and the radiative and dielectronic recombination rates of Badnell and colleagues, a new set of ionization balance calculations has been calculated. These show some substantial difference from previous calculations.

A suite of Python programs, ChiantiPy, has been developed to allow users to use the CHIANTI database to calculate spectral line and continuum intensities in an object-oriented manner. This package is also the basis for a developmental web server that can show the results of specifically requested calculations through a user web browser.

The direction of future work with CHIANTI will be outlined. Title: CHIANTI - an atomic database for emission lines. IX. Ionization rates, recombination rates, ionization equilibria for the elements hydrogen through zinc and updated atomic data Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G.; Landini, M.; Mason, H. E. Bibcode: 2009A&A...498..915D Altcode: Aims: The goal of the CHIANTI atomic database is to provide a set of atomic data for the interpretation of astrophysical spectra emitted by collisionally dominated, high temperature, optically thin sources.
Methods: A complete set of ground level ionization and recombination rate coefficients has been assembled for all atoms and ions of the elements of H through Zn and inserted into the latest version of the CHIANTI database, CHIANTI 6. Ionization rate coefficients are taken from the recent work of Dere (2007, A&A, 466, 771) and recombination rates from a variety of sources in the literature. These new rate coefficients have allowed the calculation of a new set of ionization equilibria and radiative loss rate coefficients. For some ions, such as Fe VIII and Fe IX, there are significant differences from previous calculations. In addition, existing atomic parameters have been revised and new atomic parameters inserted into the database.
Results: For each ion in the CHIANTI database, elemental abundances, ionization potentials, atomic energy levels, radiative rates, electron and proton collisional rate coefficients, ionization and recombination rate coefficients, and collisional ionization equilibrium populations are provided. In addition, parameters for the calculation of the continuum due to bremsstrahlung, radiative recombination and two-photon decay are provided. A suite of programs written in the Interactive Data Language (IDL) are available to calculate line and continuum emissivities and other properties. All data and programs are freely available at http://wwwsolar.nrl.navy.mil/chianti Title: The Coronal Mass of Solar Active Regions Authors: Dere, Kenneth P. Bibcode: 2009SPD....40.3702D Altcode: The material contained in coronal mass ejections (CMEs) that originate from active regions is believed to be provided by the mass in the active region itself. This loss of mass is exhibited by coronal dimmings. Previous estimates of the lost mass have depended on assumptions about the volume or density of the ejected material. The Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode has the ability to measure both emission measures and electron densities and provide a better measure of the coronal mass in active regions.

The technique for determining the coronal mass from EIS measurements is described and applied to several active regions. The mass lost during a CME eruption is calculated and compared to measurements of the mass of a typical range of CMEs. One of the questions that can be addressed is whether a CME accumulates or loses mass during its passage through the heliosphere. Title: CHIANTI Version 6.0 - Inclusion of Ionization and Recombination Rates Authors: Dere, Kenneth P.; Landi, E.; Young, P.; Del Zanna, G.; Mason, H.; Landini, M. Bibcode: 2009SPD....40.1504D Altcode: A new version of the CHIANTI atomic database for astrophysical spectroscopy is being prepared for imminent release. This will constitute Version 6.0. The main focus of this release is the inclusion of ionization cross-sections and rate coefficients from Dere (2007) and recombination rate coefficients from the literature, in particular, the calculations of Badnell and colleagues. A new set of ionization equilibria have been calculated from these rate coefficients. These show some significant differences from previous calculations. Atomic data for many ions have been revised and new calculations are included that enable the calculation of spectra of ions new to the CHIANTI database. The radiative loss function has been calculated based on the CHIANTI Version 6 database for both coronal and photospheric abundances.

A paper describing CHIANTI Version 6.0 in detail has been accepted for publication in Astronomy and Astrophysics. Title: Chiantipy - The Python Interface To Chianti Authors: Dere, Kenneth P. Bibcode: 2009SPD....40.1505D Altcode: Python is a free, modern, object-oriented programming language that is well suited to scientific data analysis. A command line version for use within the IPython shell is under development and significant progress has already been made. Programmatically, each ion in the CHIANTI database is treated as an object, providing a good match to the structure of the CHIANTI database. Currently, ChiantiPy is able to calculate and plot level populations, spectral line emissivities, contribution functions, G(n,T), and line intensity ratios as functions of temperature and electron and proton density. A GUI version is also planned.

The current capabilities of ChiantiPy will be demonstrated. Title: The plasma filling factor of coronal bright points. II. Combined EIS and TRACE results Authors: Dere, K. P. Bibcode: 2009A&A...497..287D Altcode: Aims: In a previous paper, the volumetric plasma filling factor of coronal bright points was determined from spectra obtained with the Extreme ultraviolet Imaging Spectrometer (EIS). The analysis of these data showed that the median plasma filling factor was 0.015. One interpretation of this result was that the small filling factor was consistent with a single coronal loop with a width of 1-2´´, somewhat below the apparent width. In this paper, higher spatial resolution observations with the Transition Region and Corona Explorer (TRACE) are used to test this interpretation.
Methods: Rastered spectra of regions of the quiet Sun were recorded by the EIS during operations with the Hinode satellite. Many of these regions were simultaneously observed with TRACE. Calibrated intensities of Fe xii lines were obtained and images of the quiet corona were constructed from the EIS measurements. Emission measures were determined from the EIS spectra and geometrical widths of coronal bright points were obtained from the TRACE images. Electron densities were determined from density-sensitive line ratios measured with EIS. A comparison of the emission measure and bright point widths with the electron densities yielded the plasma filling factor.
Results: The median electron density of coronal bright points is 3 × 109 cm-3 at a temperature of 1.6 × 106 K. The volumetric plasma filling factor of coronal bright points was found to vary from 3 × 10-3 to 0.3 with a median value of 0.04.
Conclusions: The current set of EIS and TRACE coronal bright-point observations indicate the median value of their plasma filling factor is 0.04. This can be interpreted as evidence of a considerable subresolution structure in coronal bright points or as the result of a single completely filled plasma loop with widths on the order of 0.2-1.5´´ that has not been spatially resolved in these measurements. Title: The plasma filling factor of coronal bright points. Coronal bright points Authors: Dere, K. P. Bibcode: 2008A&A...491..561D Altcode: Aims: We determine the volumetric plasma filling factor of coronal bright points.
Methods: Rastered spectra of the regions of the quiet Sun were recorded by the Extreme ultraviolet Imaging Spectrometer (EIS) during operations with the Hinode satellite. Calibrated intensities of Fe XII lines were obtained and images of the quiet corona were constructed. From the imaged spectra, the emission measures and geometrical widths of coronal bright points were obtained. Electron densities were determined from density-sensitive line ratios. A comparison of the emission measure and bright point widths with the electron densities yielded the plasma-filling factor.
Results: The median electron density of coronal bright points is 4 × 109 cm-3 at a temperature of 1.6×106 K. The volumetric plasma-filling factor of coronal bright points was found to vary from 4 × 10-5 to 0.2 with a median value of 0.015.
Conclusions: The current set of EIS coronal bright point observations indicates that the median value of their plasma filling-factor is 0.015. This can be interpreted as evidence of a considerable subresolution structure in coronal bright points or as the result of a single completely-filled plasma loop with a width on the order of 1-2 arcsec that has not been spatially resolved in these measurements.

Full Table 2 is only available in electronic form at http://www.aanda.org Title: VizieR Online Data Catalog: Plasma filling factor of coronal bright points (Dere+, 2008) Authors: Dere, K. P. Bibcode: 2008yCat..34910561D Altcode: The data describe the observed and derived properties of a set of corona l bright points. The labeling allows the reader to correlate the data in Table 2 with their images in Figures 2 and 3.

(1 data file). Title: The Plasma Filling Factor of Coronal Bright Points Authors: Dere, K. P. Bibcode: 2008AGUSMSP31D..04D Altcode: Rastered spectra of regions of the quiet Sun were recorded by the Extreme ultraviolet Imaging Spectrometer (EIS) during operations with the Hinode satellite. Calibrated intensities of Fe XII lines were obtained and images of the quiet corona were constructed. From the imaged spectra, the emission measures and geometrical widths of coronal bright points were obtained. From density-sensitive line ratios, electron densities were determined. A comparison of the emission measure and bright point widths with the electron densities yielded the plasma-filling factor. The median electron density of coronal bright points is 2.5 × 109 cm-3 at a temperature of 1.4 × 106K. The volumetric plasma filling factor of coronal bright points was found to vary from 3 × 10-3 to unity with a median value of 0.02. The small filling factors lends support to theories, such as the nanoflare theory of Parker, that suggest coronal heating occurs on small spatial scales. Title: The Structure and Dynamics of the Quiet Corona from Observations with the Extreme ultraviolet Imaging Spectrometer Authors: Dere, K. P.; Doschek, G. A.; Mariska, J. T.; Harra, L. K.; Matsuzaki, K.; Hansteen, V.; Thomas, R. J. Bibcode: 2007AGUFMSH53A1046D Altcode: The goal of the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode satellite is to measure such physical parameters as the velocity and density of the solar corona in order to provide an observational basis to understand how coronal plasmas are heated and accelerated. On 2007 January 20, EIS performed a raster of a 128 x 512 arc-sec. area of a quiet region near Sun center. The observing program recorded spectra of He II λ256, formed at 9 × 104 K, and lines of Fe VIII-XV, formed at temperatures spanning the range from 5 × 105 through 2 × 106 K. Maps of intensities, velocities and electron densities derived from these observations are presented and discussed. Intensity maps in He II λ256 show the chromospheric network. Line intensities of Fe X-XIV show small-scale bright points and more extended structures. The intensity map of Fe VIII shows a transition between the two temperatures. The coronal lines reveal regions of high outflow velocities on the order of 100 km s-1 in a compact region and 12 km s-1 in an extended region. The presence of these high velocities in the quiet corona is an entirely new and unexpected result. Electron densities derived from density sensitive line ratios of Fe XII and XIII are typically about 3 - 20×108 cm-3. The highest densities are found in bright, compact areas. For the first time, explosive events in the quiet sun have been observed in the extreme-ultraviolet in He II λ256 profiles and have properties similar to those previously reported. Title: The Structure and Dynamics of the Quiet Corona from Observations with the Extreme Ultraviolet Imaging Spectrometer on Hinode Authors: Dere, Kenneth P.; Doschek, George A.; Mariska, John T.; Hansteen, Viggo H.; Harra, Louise K.; Matsuzaki, Keiichi; Thomas, Roger J. Bibcode: 2007PASJ...59S.721D Altcode: The goal of the Hinode mission is to provide an observational basis for understanding the heating and acceleration of coronal plasmas. On 2007 January 20, the Extreme ultraviolet Imaging Spectrometer performed a raster of a quiet region near Sun center. Maps of intensities, velocities, and electron densities derived from these observations are presented and discussed. Intensity maps in HeII λ 256, formed at 9 × 104 K, show the chromospheric network. Line intensities of FeX-XIV, formed at temperatures from 1-2 × 106 K, show small-scale bright points and more extended structures. The intensity map of FeVIII shows a transition between the two temperatures. The coronal lines reveal regions of high outflow velocities on the order of 100kms-1 in a compact region and 12kms-1 in an extended region. The presence of such high velocities in the quiet corona is an entirely new and unexpected result. Electron densities derived from density sensitive line ratios of FeXII and XIII are typically 3-20 × 108cm-3. The highest densities are found in bright, compact areas. For the first time, explosive events in the quiet sun have been observed in the extreme-ultraviolet in HeII λ 256 profiles. Title: Hot and Cool Loops Composing the Corona of the Quiet Sun Authors: Matsuzaki, Keiichi; Hara, Hirohisa; Watanabe, Tetsuya; Dere, Kenneth P.; Brown, Charles M.; Culhane, Len Bibcode: 2007PASJ...59S.683M Altcode: We performed a raster scan observation of the quiet Sun with the EUV Imaging Spectrometer (EIS) aboard Hinode and simultaneously analyzed observed emission lines of Fe VIII to XV. From a combined analysis, radiance maps from the observed emission lines were deconvolved into plasma components at five representative temperatures between 0.40MK and 2.63MK. While the lowest temperature component shows network structures on spatial scales of between 10" and 20", the higher temperature components show thread-like patterns on larger scales. A comparison of emission measures at the different temperatures suggests that the lowest temperature component is mainly composed of bodies of small loops, rather than a collection of foot points of the higher temperature loops. The difference in morphologies is interpreted as being due to different magnetic field configurations, loops within super-granule cells and fields extending beyond the boundaries of super-granule cells, with distinct peak temperatures following a loop scaling law. Title: The Temperature and Density Structure of an Active Region Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode Authors: Doschek, George A.; Mariska, John T.; Warren, Harry P.; Culhane, Len; Watanabe, Tetsuya; Young, Peter R.; Mason, Helen E.; Dere, Kenneth P. Bibcode: 2007PASJ...59S.707D Altcode: The Extreme-Ultraviolet Imaging Spectrometer (EIS) on Hinode produces high resolution spectra that can be combined via rasters into monochromatic images of solar structures, such as active regions. Electron temperature and density maps of the structures can be obtained by imaging the structures in different spectral lines with ratios sensitive to either temperature or density. Doppler maps and ion temperature maps can be made from spectral line wavelengths and profiles, respectively. In this paper we discuss coronal temperature and density distributions within an active region, illustrating the power of EIS for solar plasma diagnostics. Title: EUV Emission Lines and Diagnostics Observed with Hinode/EIS Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Dere, Ken P.; Landi, Enrico; Landini, Massimo; Doschek, George A.; Brown, Charles M.; Culhane, Len; Harra, Louise K.; Watanabe, Tetsuya; Hara, Hirohisa Bibcode: 2007PASJ...59S.857Y Altcode: 2007arXiv0706.1857Y Quiet Sun and active region spectra from the Hinode/EIS instrument are presented, and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify the most useful density diagnostics from the ions covered by EIS. Title: Wavelength Determination for Solar Features Observed by the EUV Imaging Spectrometer on Hinode Authors: Brown, Charles M.; Hara, Hirohisa; Kamio, Suguru; Feldman, Uri; Seely, John F.; Doschek, George A.; Mariska, John T.; Korendyke, Clarence M.; Lang, James; Dere, Kenneth P.; Culhane, Len; Thomas, Roger J.; Davila, Joseph M. Bibcode: 2007PASJ...59S.865B Altcode: A wavelength calibration of solar lines observed by the high resolution EUV Imaging Spectrometer (EIS) on the Hinode satellite is reported. Spectral features of the quiet sun and of two mildly active areas were measured and calibrated. A listing of the stronger observed lines with identification of the leading contributor ions is presented. 41 lines are reported, with 90% identified. Wavelength precisions (2σ) of ±0.0031Å for the EIS short band and ±0.0029Å for the EIS long band are obtained. These lines, typical of 1-2 ×106 K plasmas, are recommended as standards for the establishment of EIS wavelength scales. The temperature of EIS varies by about 1D.5 C around the orbit and also with spacecraft pointing. The correlation of these temperature changes with wavelength versus pixel number scale changes is reported. Title: Application of CHIANTI to Solar-B Authors: Dere, K.; Landi, E.; Del Zanna, G.; Young, P.; Mason, H.; Landini, M. Bibcode: 2007ASPC..369...35D Altcode: CHIANTI (http://wwwsolar.nrl.navy.mil/chianti.html) has been developed to support the interpretation of solar and astrophysical spectroscopic measurements. The most recent release, version 5.0 (Landi et al. 2005) presents an improvement over previous versions by including new large scale datasets for Fe ions from Fe XVII to Fe XXIV for X-ray emission and improved atomic data for EUV line emission. We will demonstrate how this can be applied to the analysis of XRT and EIS data, in particular. For example, new excitation rates for Fe XII have resolved a long standing problem in the use of Fe XII line ratios as accurate density diagnostics. Current work involves improvements to ionization and recombination rates which will also be useful in the interpretation of Solar-B data Title: VizieR Online Data Catalog: Ionization rate coefficients for elements H to Zn (Dere+, 2007) Authors: Dere, K. P. Bibcode: 2007yCat..34660771D Altcode: This table contains spline fits to scaled ionization rate coefficient that will allow the computation of ionization rate coefficients of all ions of the elements hydrogen through zinc over a wide range of temperatures.

This file has been modified from the original to correct the values for the calcium-like sequence on September 12, 2007.

(1 data file). Title: The EUV Imaging Spectrometer for Hinode Authors: Culhane, J. L.; Harra, L. K.; James, A. M.; Al-Janabi, K.; Bradley, L. J.; Chaudry, R. A.; Rees, K.; Tandy, J. A.; Thomas, P.; Whillock, M. C. R.; Winter, B.; Doschek, G. A.; Korendyke, C. M.; Brown, C. M.; Myers, S.; Mariska, J.; Seely, J.; Lang, J.; Kent, B. J.; Shaughnessy, B. M.; Young, P. R.; Simnett, G. M.; Castelli, C. M.; Mahmoud, S.; Mapson-Menard, H.; Probyn, B. J.; Thomas, R. J.; Davila, J.; Dere, K.; Windt, D.; Shea, J.; Hagood, R.; Moye, R.; Hara, H.; Watanabe, T.; Matsuzaki, K.; Kosugi, T.; Hansteen, V.; Wikstol, Ø. Bibcode: 2007SoPh..243...19C Altcode: The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona and upper transition region emission lines in the wavelength ranges 170 - 210 Å and 250 - 290 Å. The line centroid positions and profile widths will allow plasma velocities and turbulent or non-thermal line broadenings to be measured. We will derive local plasma temperatures and densities from the line intensities. The spectra will allow accurate determination of differential emission measure and element abundances within a variety of corona and transition region structures. These powerful spectroscopic diagnostics will allow identification and characterization of magnetic reconnection and wave propagation processes in the upper solar atmosphere. We will also directly study the detailed evolution and heating of coronal loops. The EIS instrument incorporates a unique two element, normal incidence design. The optics are coated with optimized multilayer coatings. We have selected highly efficient, backside-illuminated, thinned CCDs. These design features result in an instrument that has significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2 - 5 s exposure times in the brightest lines. EIS can scan a field of 6×8.5 arc min with spatial and velocity scales of 1 arc sec and 25 km s−1 per pixel. The instrument design, its absolute calibration, and performance are described in detail in this paper. EIS will be used along with the Solar Optical Telescope (SOT) and the X-ray Telescope (XRT) for a wide range of studies of the solar atmosphere. Title: Ionization rate coefficients for the elements hydrogen through zinc Authors: Dere, K. P. Bibcode: 2007A&A...466..771D Altcode: Aims:The interpretation of astrophysical spectra depends directly on a knowledge of the ionization state of the emitting plasma. This is determined, in part, from collisional ionization rate coefficients. The most recent assessments of these were performed by Arnaud & Rothenflug (1985, A&AS, 60, 425) and Arnaud & Raymond (1992, ApJ, 398, 394). Since their work, new laboratory measurements of ionization cross sections have become available as well as the Flexible Atomic Code (FAC) which enables theoretical calculations of these rates. Our goal is to provide a complete set of ionization rate coefficients for the elements hydrogen through zinc.
Methods: A scaling law, which assists the analysis of ionization cross sections and rate coefficients, has been developed following the approach of Burgess & Tully (1992, A&A, 254, 436). Essentially all available measured cross sections along each isoelectronic sequence have been examined and compared to cross sections calculated with the Flexible Atomic Code (FAC) and with other calculations. Two approaches has been taken to provide a complete set of ionization cross sections. In the first, fits to scaled measured ionization cross sections, particularly for neutral and singly ionized species, are performed. In the second, fits to scaled calculated direct ionization and excitation-autoionization cross sections are performed to provide the remainder of the set. The fits to the cross sections are then integrated over a Maxwellian velocity distribution to derive ionization rate coefficients.
Results: A complete set of ground level ionization cross sections and rate coefficients has been developed through the combination of these two approaches. A tabulation of parameter fits to ground level ionization rate coefficients for all atoms and ions of the elements of H through Zn is provided.

Full Table [see full text] is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/466/771 Title: Transition Region Explosive Events and their Relation to the Solar Magnetic Field Authors: Muglach, Karin; Dere, K. Bibcode: 2007AAS...210.9118M Altcode: 2007BAAS...39..207M Magnetic field restructuring by reconnection is pervasive in solar physics. It can potentially provide the energy to heat and accelerate the plasma in the solar atmosphere. We will investigate the role of small-scale magnetic reconnection in the formation of transition region explosive events. These events are defined by strong transient enhancements of the wings of spectral lines that form at transition region temperatures (between 20 000 - 200 000 K).Using SUMER data we are able to identify EEs by their spectral signature. With MDI we can continuously map the photospheric magnetic field and search for a manifestation of the reconnection in the lower solar atmosphere. We have analysed several dozens of explosive events and will show how the underlying magnetic field evolves during these events. Title: Two Successive Coronal Mass Ejections Driven by the Kink and Drainage Instabilities of an Eruptive Prominence Authors: Zhou, G. P.; Wang, J. X.; Zhang, J.; Chen, P. F.; Ji, H. S.; Dere, K. Bibcode: 2006ApJ...651.1238Z Altcode: We describe a clear case of the initiation of a propagating bright arc and a CME on 2002 December 28, which were associated with an eruptive prominence. In EIT 304 and 195 Å images, a very long filament showed evidence of severe twisting in one of its fragments, which appeared as a prominence on December 26; then, the prominence showed the conversion of its twist into writhe. Two days later, the prominence displayed a slow rising motion for hours. Internal twisting and mass motion took place before the rapid acceleration and final eruption. The propagating bright arc and the following CME corresponded to the early rising and the subsequently eruptive phases of the prominence, respectively. Signatures of magnetic reconnection, i.e., a cusp structure and postflare loops in EUV wave bands and hard X-ray sources in the corona, were observed after the prominence eruption. It appears that the kink instability and the mass drainage in the prominence played key roles in triggering the initiation of the CME. However, the rather impulsive acceleration of the CME resulted from magnetic reconnection beneath the filament. Title: A Statistical Study of Main and Residual Accelerations of Coronal Mass Ejections Authors: Zhang, J.; Dere, K. P. Bibcode: 2006ApJ...649.1100Z Altcode: In this paper we present the results of a statistical study of the accelerations of coronal mass ejections (CMEs). A CME usually undergoes a multiphased kinematic evolution, with a main acceleration phase characterized by a rapid increase of CME velocity in the inner corona, followed by a relatively smooth propagation phase characterized by a constant speed or a small residual acceleration in the outer corona. We study both the main acceleration and the residual acceleration for 50 CME events based on Large Angle Spectrometric Coronagraph (LASCO) observations. We find that the magnitude of the main acceleration has a wide distribution, from 2.8 to 4464.0 m s-2, with a median (average) value of 170.1 (330.9 m s-2), and a standard deviation of 644.8 m s-2, whereas the magnitude of the residual acceleration ranges only from -131.0 to 52.0 m s-2, with a median (average) value of 3.1 (0.9 m s-2) and a standard deviation of 25.3 m s-2. The duration of the main acceleration is also widely distributed, from 6 to 1200 minutes, with a median (average) value of 54 (180 minutes) and a standard deviation of 286 minutes.We find an intriguing scaling law between the acceleration magnitude (A) and the acceleration duration (T) over the entire parameter range of almost 3 orders of magnitude, which can be expressed as A (m s-2)=10,000T-1 (minutes). The implications of these observational results on the issues of CME classification and CME modelings are discussed. Title: The Extreme Ultraviolet Imaging Spectrometer (EIS) on Solar-B Authors: Doschek, George A.; Brown, C. M.; Korendyke, C. M.; Mariska, J. T.; Myers, S. H.; Seely, J. F.; Dere, K. P.; Lang, J.; Culhane, J. L.; Watanabe, T. Bibcode: 2006SPD....37.3604D Altcode: 2006BAAS...38S.260D The Extreme Ultraviolet Imaging Spectrometer (EIS) for Solar-B is a high throughput state-of-the-art instrument designed to obtain solar spectra and images in two wavelength bands centered near 195 and 270 Angstroms. Traditional spectra can be obtained using narrow slits or images of solar structures can be obtained in individual spectral lines using wide slots. Essentially, the instrument obtains images in wavebands similar to TRACE but in each spectral line within the waveband. This removes electron temperature ambiguities inherent in broadband imagers and allows dynamic effects to be detected via Doppler shifts and densities and other plasma parameters to be measured via spectroscopic plasma diagnostics. After a brief description of how the instrument works and a comparison with previous instrumentation (sensitivity, etc.), the presentation will focus on the science that can be accomplished with EIS, presented in the form of sample observing sequences. The focus will be on active regions and solar flares with a consideration of topics such as temperature and density distributions in active region loops and their evolution, dynamical motions in active region loops, the reconnection site in solar flares, and temperature evolution of multimillion degree flare loops. Title: CMEs driven by an eruptive prominence Authors: Zhou, G. P.; Wang, J. X.; Zhang, J.; Chen, P. F.; Ji, H. S.; Dere, K. Bibcode: 2006IAUS..233..405Z Altcode: A clear case on Dec. 28 2002 is presented. It is about the initiation of two successive CMEs, which were related to an eruptive prominence. In EIT 304 Å and 195 Å observations, we found a long filament severely twisting in a piece of its fragments, which appeared as a prominence on Dec. 26. Then, the prominence converted its twist into writhe. Two days later, the prominence displayed a slow rising motion for hours. There happened internal twisting and mass motion before the prominence rapid acceleration and final eruption. Two successive CMEs recorded by LASCO C2 coronagraph corresponded to the early rising and the subsequently eruptive phases of the prominence, respectively. Evidence of magnetic reconnection, i.e., a cusp structure and post-flare loops in EUV wavebands, and hard X-ray sources in the corona, were observed after the prominence disruption. It appears that the kink instability and the mass drainage in the prominence played important roles in triggering two CMEs' initiation. We suspected that the rather impulsive acceleration of the second CME resulted from magnetic reconnection beneath the prominence. Title: CHIANTI-An Atomic Database for Emission Lines. VII. New Data for X-Rays and Other Improvements Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason, H. E.; Landini, M. Bibcode: 2006ApJS..162..261L Altcode: The CHIANTI atomic database contains atomic energy levels, wavelengths, radiative transition probabilities, and collisional excitation data for a large number of ions of astrophysical interest. CHIANTI also includes a suite of IDL routines to calculate synthetic spectra and carry out plasma diagnostics. Version 5 has been released, which includes several new features, as well as new data for many ions. The new features in CHIANTI are as follows: the inclusion of ionization and recombination rates to individual excited levels as a means to populate atomic levels; data for Kα and Kβ emission from Fe II to Fe XXIV; new data for high-energy configurations in Fe XVII to Fe XXIII; and a complete reassessment of level energies and line identifications in the X-ray range, multitemperature particle distributions, and photoexcitation from any user-defined radiation field. New data for ions already in the database, as well as data for ions not present in earlier versions of the database, are also included. Version 5 of CHIANTI represents a major improvement in the calculation of line emissivities and synthetic spectra in the X-ray range and expands and improves theoretical spectra calculations in all other wavelength ranges. Title: Observing the Solar atmosphere with the Extreme Ultraviolet Imaging Spectrometer on Solar B Authors: Korendyke, C. M.; Brown, C.; Dere, K.; Doschek, G.; Klimchuk, J.; Landi, E.; Mariska, J.; Warren, H.; Lang, J. Bibcode: 2005AGUFMSH41B1124K Altcode: The Extreme Ultraviolet Imaging Spectrometer (EIS) is part of the instrument complement on the Solar B satellite, scheduled for launch in the summer of 2006. The instrument has been calibrated and is presently mounted on the spacecraft. EIS is the most sensitive EUV solar spectrometer to be flown. The instrument is the first of a new generation of two optical element, solar spectrographs. Preliminary results from the laboratory focussing and calibration of the instrument will be shown. The instrument wavelength coverage includes reasonably bright spectral lines emitted by plasmas from 0.1 to 20 MK in temperature. The wavelength range also provides coronal density diagnostics. Temperature, density and velocity diagnostics will be discussed. An example observing program for exploring active region evolution and dynamics will be discussed. Title: Application of CHIANTI to High Resolution Solar Spectra Authors: Dere, K. P.; Landi, E. Bibcode: 2005AGUFMSH44A..02D Altcode: CHIANTI has been developed to support the interpretation of solar and astrophysical spectroscopic measurements. The most recent release, version 5.0 (Landi et al., 2005) presents an improvement over previous versions by including new large scale datasets for Fe ions from Fe XVII to Fe XXIV for X-ray emission and improved atomic data for EUV line emission. We will show examples of its use in the analysis of X-ray spectra from SMM, ultraviolet spectra from SOHO and the interpretation of broadband instruments such as EIT and TRACE. Current work involves the analysis of ionization and recombination rates based on recent laboratory measurements and calculations with the Flexible Atomic Code. The incorporation of ionization and recombination rates into CHIANTI will allow us to explore such effects as the effect of finite densities on ionization balance and transient and nonthermal ionization populations. Title: Coronal and Stellar Mass Ejections, IAU Symposium Proceedings of the International Astronomical Union 226, Authors: Dere, Kenneth; Wang, Jingxiu; Yan, Yihua Bibcode: 2005IAUS..226.....D Altcode: The Sun and other stars eject large clouds of plasma and magnetic fields on a continual basis. They are accelerated to high speeds and then become capable of producing highly energetic charged particles and disrupting the magnetospheres of planets such as the Earth. This proceeding reflects recent attempts to understand these processes as well as how the magnetic evolution at the base of the corona can cause these events, and how stars are capable of rapidly releasing energy in the form of mass ejections. Contributions by leading scientists make it a valuable astronomical resource. Title: Coronal and Stellar Mass Ejections (IAU S226) Authors: Dere, Kenneth; Wang, Jingxiu; Yan, Yihua Bibcode: 2005csme.book.....D Altcode: 1. Historical introduction; 2. Observation of CMES; 3. CME source regions; 4. Theoretical models of CMEs; 5. Comparisons of CME models and observations; 6. CMES and energetic particles; 7. ICMEs in the heliosphere; 8. CMES and geomagnetic storms; 9. Stellar ejections. Title: Recent developments of the CHIANTI database in the X-ray wavelength range Authors: Landi, E.; Dere, K. P.; Young, P. R.; del Zanna, G.; Mason, H. E.; Landini, M. Bibcode: 2005AIPC..774..409L Altcode: CHIANTI is a database of atomic data and transition probabilities that allows the calculation of synthetic spectra and plasma diagnostics of optically thin plasmas. It is primarily suited for wavelengths shorter than 2000 Å but in principle can also be used at longer wavelengths. In the present paper we illustrate the latest development of the CHIANTI database, that include a huge expansion of the database in the X-ray wavelength range, the renewal of several data in the EUV range, and the inclusion of ionization and recombination in the level population calculation. This enhanced database will constitute the Version 5 of CHIANTI. Title: The correlation between features in the solar spectrum near Mg II and photospheric magnetic fields Authors: Morrill, J.; Korendyke, C.; Dere, K. Bibcode: 2005AGUSMSP41B..06M Altcode: During the HRTS-9 flight, spectrograms and spectroheliograms where obtained of the quiet sun, quiet limb, plage, and sunspots. Previous analysis of these observations required the correction of a small set of spectra for instrumental distortions and the absolute intensity calibration. We have applied these corrections to a larger portion of the HRTS-9 observations where the spectrograph slit was rastered across a small region of the sun along the solar equator. This set of corrected spectrograms has allowed us to generate high spatial and spectral resolution spectroheliograms of the observed quiet and active portions of the sun. In addition, with use of a magnetogram taken while the flight was in progress we have examined the relationship between the photospheric magnetic field and both Mg II emission at 280 nm and absorption features in the nearby solar spectrum due to both neutral and singly ionized species. In this presentation we will present our high resolution spectroheliograms as well as results showing the relationship between the magnetic field and several specific spectral features. Title: The Extreme Ultraviolet Imaging Spectrometer on Solar-B Authors: Mariska, J. T.; Brown, C. M.; Doschek, G. A.; Korendyke, C. M.; Myers, S. H.; Seely, J. F.; Dere, K. P.; Lang, J.; Culhane, J. L.; Watanabe, T. Bibcode: 2005AGUSMSP43A..02M Altcode: The Extreme Ultraviolet Imaging Spectrometer (EIS) is currently under development for flight on the Japanese Solar-B satellite. EIS uses a multilayer-coated off-axis telescope mirror and a multilayer-coated toroidal grating spectrometer to produce stigmatic spectra of solar regions isolated by a 1024 arcsec high slit. The instrument produces monochromatic images either by rastering the solar image across a narrow entrance slit or by using a very wide slit. Half of each optic is coated to optimize reflectance at 19.5 nm, and the other half to optimize reflectance at 27.0 nm, with each wavelength range imaged onto a separate CCD detector. EIS can provide key dynamical and density diagnostic information. Combining EIS data with observations from the other instruments on Solar-B should provide a detailed picture of solar atmospheric processes from the visible surface into the corona. In this presentation, we provide details of the instrument's expected performance based on calibration of the individual flight optics and end-to-end testing at the Rutherford Appleton Laboratory in the UK. Title: Three-dimensional Structure of Coronal Mass Ejections from LASCO Polarization Measurements Authors: Dere, Kenneth P.; Wang, Dennis; Howard, Russell Bibcode: 2005ApJ...620L.119D Altcode: The three-dimensional structure of a coronal mass ejection (CME) is essential information for understanding the process by which they are ejected from the Sun. Coronagraphic measurements readily provide information on the structure of CMEs in the plane of the sky. It has been known for some time that polarization measurements can provide information on the position of coronal plasmas out of the plane of the sky. Recently, T. G. Moran & J. M. Davila have shown that polarimetric measurements with the Large Angle and Spectrometric Coronagraph (LASCO) can be used to determine the three-dimensional structure of a CME with considerable definition. We have examined a series of high-cadence (1 hr) LASCO polarization measurements obtained during 2002 and discuss the analysis of two particularly well observed events. One event indicates that the CME structure is that of a rising arcade of loops, while the other appears to consist of a flux-rope type of structure. Because we have examined a large, relatively high cadence set of LASCO observations, we have been able to select events that provide significantly greater definition of CME structure than previously possible. Title: The Three Dimensional Structure of CMEs from LASCO Polarization Measurements Authors: Dere, Kenneth; Wang, Dennis Bibcode: 2005IAUS..226..114D Altcode: The degree of polarization of Compton-scattered photospheric light observed in a coronagraph is dependent on the distance of the scattering electrons from the plane of the sky. Measurements of the polarization of light scattered by CME structures have been observed by LASCO C2. We have reduced and analyzed a month long sequence of such measurements which were taken at a cadence of 1 hour. The CME brightness has been distributed throughout a 3 dimensional cube and visualized at a variety of angles. Several CMEs are found to have considerable fine-structure consistent with expanding loop arcades. The analysis is subject to a variety of assumptions such as a lack of knowledge of whether a source is before or behind the plane of the sky. Nevertheless, the results obtained to date are intriguing. Title: The CHIANTI database Authors: Landi, E.; Dere, K. P.; Young, P. R.; Landini, M.; Mason, H. E.; Del Zanna, G. Bibcode: 2005HiA....13..653L Altcode: CHIANTI is a database of atomic data and transition rates necessary for calculating synthetic spectra and carrying out plasma diagnostics of astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI includes both line and continuum emission from all astrophysically abundant elements in the universe. All data are taken from refereed literature and are critically assessed. CHIANTI also includes a suite of IDL programs that allow spectroscopic analysis to be carried out. CHIANTI data and software are freely distributed over the internet.

In the present talk I will describe the contents of the CHIANTI database its current status and the areas where CHIANTI is being developed and I will also present a comparison of CHIANTI predictions with the X-ray emission from astrophysical sources. Title: The Evolution of Photospheric Source Regions of CMEs Authors: Muglach, K.; Dere, K. Bibcode: 2005IAUS..226..179M Altcode: In this presentation we determine the source regions of CMEs that were observed with SoHO/LASCO during times of solar activity maximum (Feb./Mar. 2000) and during the declining phase of the solar cycle (Nov./Dec. 2002). The CMEs were traced back onto the disk and EIT EUV images were used for identifying the sources. With the help of MDI synoptic magnetograms we follow the evolution of the photospheric magnetic flux about 24h before and 12h after the event. We find that about 87% of the identified CME source regions show small-scale flux changes before the event, usually flux emergence and/or flux disappearance. In 13% of the cases we find no signature of photospheric flux changes. Title: The 3D structure of CMEs from LASCO polarization measurements Authors: Dere, K. P.; Wang, D.; Howard, R. Bibcode: 2004AGUFMSH22A..03D Altcode: The polarization of Compton scattered light from a coronal plasma is a function of the distance of that plasma from the plane of the sky. From an image of the polarization of the corona it is possible to construct a 3D cube of intensity which can be visualized at any angle to study it's three dimensional distribution. For a one month period during July and August 2002, the LASCO C2 coronagraph performed polarization measurements with a one hour cadence. During this period, several CMEs were well observed. Two CMEs give the appearance of an ejecting loop arcade. Another CME is not as easily described but may indicate the presence of a flux tube. There are two main ambiguities in the analysis. First, a given polarization can be produced by scattering from in front of or behind the plane of the sky. This ambiguity can be overcome by selecting CMEs that are completely out of the plane of the sky. Second, in reconstructing the 3D distribution of intensity, it is assumed that the intensity can be visualized as coming from a single point in 3D space. The filamentary structures commonly seen in the 3D visualizations suggest that this is not a significant problem. Title: Solar UV Spectral Radiance from SKYLAB Authors: Morrill, J.; Korendyke, C.; Dere, K. Bibcode: 2004AGUFMSH53A0305M Altcode: As part of an ongoing NASA-LWS sponsored research program, solar UV spectral radiance has been determined for the quiet sun at a variety of center-to-limb positions observed by the SO82B UV spectrograph on SKYLAB. This has been done using a high quality flatbed scanner to digitize the SKYLAB film data. The goal of the present program is to develop a spectral irradiance model that utilizes the full resolution of the SKYLAB spectra (~ 0.010 nm at 300 nm). The model requires detailed knowledge of the center-to-limb variation (CLV) at full resolution over the 200 - 400nm wavelength range. This information is also required to determine the absolute intensity calibration which uses full-disk irradiance measurements from UARS (SOLSTICE and SUSIM) in addition to the CLV. This calibration is then used to derive the disk center radiance. In addition to the quiet sun, spectra of sunspots and active regions are also being digitized and an attempt is underway to derive the CLV for these surface morphologies as well. Further, spectra at shorter wavelength (~120 - 200nm) are being examined in order to extend the wavelength coverage of these radiance and CLV results. In this presentation we will present the details of the analysis methods and results for the quiet sun. Ongoing work on sunspots and active regions will be presented as will results involving work on shorter wavelength spectra. Title: The Evolution of Photospheric Source Regions of CMEs Authors: Muglach, K.; Dere, K. Bibcode: 2004AAS...204.3808M Altcode: 2004BAAS...36..713M In this presentation we determine the source regions of CMEs that were observed with SOHO/LASCO during times of solar activity maximum (Feb./Mar. 2000) and during the declining phase of the solar cycle (Nov./Dec. 2002). The CMEs were traced back onto the disk and EIT EUV images were used for identifying the sources. With the help of MDI synoptic and high cadence magnetograms we follow the evolution of the photospheric magnetic flux about 12 h before and after the event. We find that 80% of the identified CMEs (29 out of a total of 36 events) show small--scale flux changes before the event, usually flux emergence or flux disappearance. In 20% of the cases we find no signature of photospheric flux changes. Title: A Comparison of the Mg II Index Derived from Estimated and Observed Solar Spectra Authors: Morrill, J.; Korendyke, C.; Dere, K. Bibcode: 2004AAS...204.7207M Altcode: 2004BAAS...36..799M We have estimated values of the Mg II index using a model of solar spectral irradiance developed at the Naval Research Laboratory. This model uses Ca II K images and spatially resolved sun spot, quiet sun, and active sun spectra measured by the HRTS-9 rocket to generate the estimated spectra. These spectra are compared to observed spectra such as the UARS-SUSIM and UARS-SOLSTICE data sets. In order to further compare the observed and estimated spectra, a Mg II index is derived from these two sets of spectra. In this presentation we will review the details of the model, discuss the methods of deriving the Mg II index, and compare the Mg II variability resulting from the observed and estimated spectra. Title: Recent development of the CHIANTI database in the X-ray wavelength range Authors: Landi, E.; Dere, K. P.; Mason, H. E.; Del Zanna, G.; Landini, M.; Young, P. R. Bibcode: 2004AAS...204.7310L Altcode: 2004BAAS...36R.801L CHIANTI consists of a database of critically assessed atomic data and transition rates to calculate line and continuum emission from astrophysical plasmas.

During the last year the CHIANTI database has been substantially expanded in the X-ray wavelength region by including a large number of new configurations and lines, and by including ionization and recombination processes in the level population calculations.

We will describe these improvements, the data we used, and illustrate examples of 1) their effects on predicted emissivities and on plasma diagnostics 2) applications to the study of flares in solar active regions Title: A Study of the Kinematic Evolution of Coronal Mass Ejections Authors: Zhang, J.; Dere, K. P.; Howard, R. A.; Vourlidas, A. Bibcode: 2004ApJ...604..420Z Altcode: We report the kinematic properties of a set of three coronal mass ejections (CMEs) observed with the LASCO (Large Angle and Spectrometric Coronagraph) on the Solar and Heliospheric Observatory (SOHO) spacecraft, which showed characteristics of impulsive, intermediate, and gradual acceleration, respectively. The first CME had a 30 minute long fast acceleration phase during which the average acceleration was about 308 m s-2 this acceleration took place over a distance of about 3.3 Rsolar (from 1.3 to 4.6 Rsolar, height measured from disk center). The CME characterized by intermediate acceleration had a long acceleration phase of about 160 minutes during which the average acceleration was about 131 m s-2 the CME traveled a distance of at least 4.3 Rsolar, reaching a height of 7.0 Rsolar at the end of the acceleration phase. The CME characterized by gradual acceleration had no fast acceleration phase. Instead, it displayed a persistent weak acceleration lasting more than 24 hr with an average acceleration of only 4.0 m s-2 throughout the LASCO field of view (from 1.1 to 30 Rsolar). This study demonstrates that the final velocity of a CME is determined by a combination of acceleration magnitude and acceleration duration, both of which can vary significantly from event to event. The first two CME events were associated with soft X-ray flares. We found that in the acceleration phase there was close temporal correlation both between the CME velocity and the soft X-ray flux of the flare and between the CME acceleration and derivative of the X-ray flux. These correlations indicate that the CME large-scale acceleration and the flare particle acceleration are strongly coupled physical phenomena occurring in the corona. Title: Performance of multilayer-coated gratings for the extreme-ultraviolet imaging spectrometer (EIS) for the Solar-B mission Authors: Seely, John F.; Windt, David L.; Donguy, Soizik; Brown, Charles; Holland, Glenn; Hunter, William R.; Kowalski, Michael P.; Kjornrattanawanich, Benjawan; Doschek, George; Mariska, John; Korendyke, Clarence; Dere, Ken Bibcode: 2004SPIE.5168...12S Altcode: The measured efficiencies of two flight gratings and the reflectances of two flight mirrors developed for the Extreme-Ultraviolet Imaging Spectrometer (EIS) for the Japanese Solar-B mission are presented. Each optic has two sectors with Mo/Si multilayers that refelct the 17 - 21 nm and 25 - 29 nm wavebands at normal incidence. The efficiencies that were measured using monochromatic synchrotron radiation are in good agreement with the calculated efficiencies. Title: CHIANTI -- An Atomic Database for UV and X-ray Cool star spectroscopy Authors: Young, P. R.; Landi, E.; Bromage, G. E.; del Zanna, G.; Dere, K. P.; Landini, M.; Mason, H. E. Bibcode: 2003csss...12.1119Y Altcode: The CHIANTI atomic database was first released in 1996 and has since become the standard resource for the interpretation of UV spectra from the transition regions and coronae of the Sun and other cool stars. We describe the contents of the most recent release (v.3) and some of the uses that have been found for the database. Title: Expected Performance of the Extreme Ultraviolet Imaging Spectrometer on Solar-B Authors: Mariska, J. T.; Brown, C. M.; Dere, K. P.; Doschek, G. A.; Korendyke, C. M.; Myers, S. H.; Seely, J. F.; Culhane, J. L.; Watanabe, T. Bibcode: 2003SPD....34.2006M Altcode: 2003BAAS...35..845M The Extreme Ultraviolet Imaging Spectrometer (EIS) is currently under development for flight on the Japanese Solar-B satellite. EIS uses a multilayer-coated off-axis telescope mirror and a multilayer-coated toroidal grating spectrometer to produce stigmatic spectra of solar regions isolated by a 1024 arcsec high slit. The instrument produces monochromatic images either by rastering the solar image across a narrow entrance slit or by using a very wide slit. Half of each optic is coated to optimize reflectance at 19.5 nm, and the other half to optimize reflectance at 27.0 nm, with each wavelength range imaged onto a separate CCD detector.

In this presentation we provide an update on the EIS hardware development and show details of the expected performance of the instrument in solar quiet regions, active regions, and flares. Title: Normal-incidence EXtreme-Ultraviolet imaging Spectrometer - NEXUS Authors: Dere, K. P. Bibcode: 2003SPD....34.2405D Altcode: 2003BAAS...35..853D NEXUS is the result of a breakthrough optical design that incorporates new technologies to achieve high optical throughput at high spatial (1 arcsec) and spectral (1-2 km s-1) resolution over a wide field of view in an optimal extreme-ultraviolet spectral band. This achievement was made possible primarily by two technical developments. First, a coating of boron-carbide deposited onto a layer of iridium provided a greatly enhanced reflectivity at EUV wavelengths that would enable NEXUS to observe the Sun over a wide temperature range at high cadence. The reflectivity of these coatings have been measured and demonstrated in the laboratory.

The second key development was the use of a variable-line-spaced toroidal grating spectrometer. The spectrometer design allowed the Sun to be imaged at high spatial and spectral resolution along a 1 solar radius-long slit and over a wavelength range from 450 to 800 Å, nearly an entire spectral order. Because the spectrograph provided a magnification of about a factor of 6, only 2 optical elements are required to achieved the desired imaging performance. Throughput was enhanced by the use of only 2 reflections. The could all be accomodated within a total instrument length of 1.5m.

We would like to acknowledge support from ONR Title: Association between CME/Flare Events and Enhanced Oxygen Charge States Authors: Reinard, A. A.; Dere, K.; Howard, R. Bibcode: 2003SPD....34.0608R Altcode: 2003BAAS...35..818R We present results from a study of coronal mass ejection (CME) data obtained both optically (from SOHO/LASCO and SOHO/EIT) and in situ (from ACE). Phenomena associated with optical CMEs, such as flares and radio bursts, are compared with heliospheric CME signatures, such as enhanced charge states and elevated helium densities, to determine if there is any correspondence between them. A casual relationship has been seen between CMEs with large flares and ICMEs with enhanced oxygen charge state ratios. This relationship will be further investigated. An understanding of how CME observations at the Sun relate to CME observations in the heliosphere will increase our understanding of CME dynamics and may provide insight into CME origins. Title: High Resolution Limb Darkening Function Near 2800 /AA/ Measured by HRTS Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M. Bibcode: 2003SPD....34.1909M Altcode: 2003BAAS...35..843M We are currently developing an empirical model of solar spectral irradiance varaibility. This model will combine ground based observations of the areas and locations of plage and sunspots with measured wavelength dependent contrast factors in order to estimate the solar spectrum. One important component of this model is the wavelength dependent limb darking function that must be determined at high resolution. Using quiet sun spectra near Mg II at about 2800 /AA/ measured by the NRL HRTS instrument, we have recently determined this function for the quiet sun. This function shows many features similar to those seen in the active region contast that we have reported earlier. In this presentation we will discuss the method of determining the limb darkening function in the 2765 -2885 /AA/ region and it's impact on the irradiance model. Title: CHIANTI-An Atomic Database for Emission Lines. VI. Proton Rates and Other Improvements Authors: Young, P. R.; Del Zanna, G.; Landi, E.; Dere, K. P.; Mason, H. E.; Landini, M. Bibcode: 2003ApJS..144..135Y Altcode: 2002astro.ph..9493Y The CHIANTI atomic database contains atomic energy levels, wavelengths, radiative transition probabilities, and electron excitation data for a large number of ions of astrophysical interest. Version 4 has been released, and proton excitation data are now included, principally for ground configuration levels that are close in energy. The fitting procedure for excitation data, both electrons and protons, has been extended to allow nine-point spline fits in addition to the previous five-point spline fits. This allows higher quality fits to data from close-coupling calculations where resonances can lead to significant structure in the Maxwellian-averaged collision strengths. The effects of photoexcitation and stimulated emission by a blackbody radiation field in a spherical geometry on the level balance equations of the CHIANTI ions can now be studied following modifications to the CHIANTI software. With the addition of H I, He I, and N I, the first neutral species have been added to CHIANTI. Many updates to existing ion data sets are described, while several new ions have been added to the database, including Ar IV, Fe VI, and Ni XXI. The two-photon continuum is now included in the spectral synthesis routines, and a new code for calculating the relativistic free-free continuum has been added. The treatment of the free-bound continuum has also been updated. Title: Identification of Solar Sources of Major Geomagnetic Storms between 1996 and 2000 Authors: Zhang, J.; Dere, K. P.; Howard, R. A.; Bothmer, V. Bibcode: 2003ApJ...582..520Z Altcode: This paper presents identification of solar coronal mass ejection (CME) sources for 27 major geomagnetic storms (defined by disturbance storm timeindex<=-100 nT) occurring between 1996 and 2000. Observations of CMEs and their solar surface origins are obtained from the Large Angle and Spectrometric Coronagraph (LASCO) and the EUV Imaging Telescope (EIT) instruments on the SOHO spacecraft. Our identification has two steps. The first step is to select candidate front-side halo (FSH) CMEs using a fixed 120 hr time window. The second step is to use solar wind data to provide further constraints, e.g., an adaptive time window defined based on the solar wind speed of the corresponding interplanetary CMEs. We finally find that 16 of the 27 (59%) major geomagnetic storms are identified with unique FSH CMEs. Six of the 27 events (22%) are associated with multiple FSH CMEs. These six events show complex solar wind flows and complex geomagnetic activity, which are probably the result of multiple halo CMEs interacting in interplanetary space. A complex event occurs when multiple FSH CMEs are produced within a short period. Four of the 27 (15%) events are associated with partial-halo gradual CMEs emerging from the east limb. The surface origin of these events is not known because of a lack of any EIT signature. We believe that they are longitudinally extended CMEs having a component moving along the Sun-Earth connection line. One of the 27 major geomagnetic storms is caused by a corotating interaction region. We find an asymmetry in the longitudinal distribution of solar source region for the CMEs responsible for major geomagnetic storms. They are more likely to originate from the western hemisphere than from the eastern hemisphere. In terms of latitude, most geoeffective CMEs originate within a latitude strip of +/-30°. The average transit time for a solar CME to arrive at the near-Earth space is found to be 64 hr, while it takes 78 hr on average to reach the peak of the geomagnetic storm. There is a correlation between CME transit time from the Sun to the near-Earth space (T, in hours) and the CME initial velocity (V, in unit of kilometers per second) at the Sun, which can be simply described as T=96-(V/21). We also find that while these geoeffective CMEs are either full-halo CMEs (67%) or partial-halo CMEs (30%), there is no preference for them to be fast CMEs or to be associated with major flares and erupting filaments. Title: In Situ and Heliospheric CME Signature Relations Authors: Reinard, Alysha; Dere, K.; Howard, R.; Zurbuchen, T. Bibcode: 2003IAUJD...7E..31R Altcode: We present results from a study of coronal mass ejection (CME) data obtained both optically (from SOHO/LASCO and SOHO/EIT) and in situ (from ACE). Phenomena associated with optical CMEs such as flares and radio bursts are compared with heliospheric CME signatures such as enhanced charge states and elevated helium densities to determine if there is any correspondence between them. A casual relationship has been seen between CMEs with large flares and ICMEs with enhanced oxygen charge state ratios. This relationship will be further investigated. An understanding of how CME observations at the Sun relate to CME observations in the heliosphere will increase our understanding of CME dynamics and may provide insight into CME origins. Title: Chianti: Inclusion of Ionization and Recombination Rates Authors: Dere, Kenneth P. Bibcode: 2003IAUJD..17E..17D Altcode: The spectrum produced by an astrophysical plasma is directly dependent on the ionization state of the plasma. In order to understand the ionization balance it is necessary to know the ionization and recombination rates of the various ions whether the plasma is in a steady-state ionization state or a transient ionization state.

New and improved measurements and calculations of ionization and recombination rate continue to become available. We have collected the various measurements and calculations for inclusion into the CHIANTI database. We have developed a scaling law for the ionization rates similar to that of Burgess and Tully (1992) for electron excitation rates. We will discuss our progress the adjustments needed for the new rates and the need for more measurements and calculations. Title: CHIANTI - An Atomic Database for XUV Emission Lines Authors: Landi, Enrico; Dere, Ken P.; Landini, Massimo; Young, Peter R.; Mason, Helen E.; del Zanna, Giulio Bibcode: 2003IAUJD..17E..10L Altcode: CHIANTI is a database of atomic data and transition rates necessary for calculating synthetic spectra and carrying out plasma diagnostics of astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI includes both line and continuum emission from all astrophysically abundant elements in the universe. All data are taken from refereed literature and are critically assessed. CHIANTI also includes a suite of IDL programs that allow spectroscopic analysis to be carried out. CHIANTI data and software are freely distributed over the internet.

In the present talk I will describe the contents of the CHIANTI database its current status and the areas where CHIANTI is being developed and I will also present a comparison of CHIANTI predictions with the X-ray emission from astrophysical sources. Title: A Comparison between Coronal Emission Lines from an Isothermal Spectrum Observed with the Coronal Diagnostic Spectrometer and CHIANTI Emissivities Authors: Landi, E.; Feldman, U.; Dere, K. P. Bibcode: 2002ApJ...574..495L Altcode: The present paper compares off-disk spectral observations of the solar corona in the ranges 307-379 and 513-633 Å with theoretical emissivities calculated using the CHIANTI database. The observed spectra were recorded by the Coronal Diagnostic Spectrometer instrument on board the Solar and Heliospheric Observatory using the normal-incidence portion of the instrument. Using line-ratio techniques, we first measure the electron temperature and density in the emitting region, verifying that it is nearly isothermal. Next, we use an emission-measure analysis to compare measured spectral line intensities with predictions from the CHIANTI database. This comparison allows us to assess the quality of the CHIANTI data for the brightest coronal lines in the 307-379 and 513-633 Å spectral ranges. As a result, we are able to (1) select lines and ions for which the agreement between theory and observation is good, (2) identify a few lines that are blended, and (3) stress inconsistencies between a few lines and theory, thus showing where improvements to atomic data and transition probabilities are necessary. Title: Identifying Solar Sources of Major Geomagnetic Storms Authors: Zhang, J.; Dere, K. P.; Howard, R. A. Bibcode: 2002AAS...200.2805Z Altcode: 2002BAAS...34..680Z We identify solar coronal mass ejection (CME) sources for 27 (out of 38) major geomagnetic storm events occurred between 1996 and 2000 based on complete solar and interplanetary observations from SOHO, ACE and WIND spacecrafts. Our search begins with selecting all front-side halo CMEs (FSH CMEs) based on a fixed transition window of 30--120 hours before the Dst peak time. Valid transition window is reduced by using solar wind speed of corresponding ICME (Interplanetary CME) for solar CMEs that are ejected at a speed higher than background solar wind. We find that 15 of the 27 (60%) major geomagnetic storms can be uniquely identified with a single FSH CME. However, 6 of the 27 events (20%) have multiple FSH CME sources. The complex solar wind flow of these events indicate interaction of CMEs in their path toward the Earth. The left 6 events (20%) have no FSH CME in the transition window. It appears that 4 out of the 6 events are caused by partial halo gradual CMEs originated from east limb, which are believed to be longitudinal extended gradual CMEs with intrinsic wide-angle. One event is caused by an impulsive CME from west limb, and another event is caused by corotating interaction region (CIR) associated with a low latitude coronal hole. The average transition time from the Sun to the Earth is 64 hours while it is 78 hours to reach peak of geomagnetic storms. There is a coarse correlation between CME speed (V in km/s) and transition time (to ICME, T in hr.), simply as T=96-V/21. We find that geo-effective CMEs are more likely originated from western hemisphere than from eastern hemisphere. Almost all geo-effective CMEs from western hemisphere are full halo CMEs, while most geo-effective CMEs from eastern hemisphere are partial halo CMEs. Title: CHIANTI-An Atomic Database for Emission Lines. V. Comparison with an Isothermal Spectrum Observed with SUMER Authors: Landi, E.; Feldman, U.; Dere, K. P. Bibcode: 2002ApJS..139..281L Altcode: CHIANTI is a database consisting of critically evaluated atomic data and transition probabilities necessary to analyze spectral observations of optically thin plasmas. Previous papers described the content of the database and compared it to a solar active region spectrum between 170 and 450 Å. The aim of the present paper is to compare CHIANTI predictions to off-disk spectral observations of the solar corona between 500 and 1500 Å. The observed spectra were recorded by the SUMER instrument on board the Solar and Heliospheric Observatory using the full spectral range allowed by the instrument. Earlier works have demonstrated that the particular emitting plasma is isothermal at a temperature of 1.35×106 K, making it ideal for the assessment of the accuracy of the CHIANTI database. This assessment of the CHIANTI database allowed us (1) to select lines and ions for which the agreement between theory and observation is good, (2) to identify several lines which are blended, and (3) to stress inconsistencies between a few lines and theory, thus showing where improvements to atomic data and transition probabilities are necessary. Title: Sun earth connection coronal and heliospheric investigation (SECCHI) Authors: Howard, R. A.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Cook, J. W.; Secchi Consortium Bibcode: 2002AdSpR..29.2017H Altcode: The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the NASA Solar Terrestrial Relations Observatory ( STEREO) mission is a suite of remote sensing instruments consisting of an extreme ultraviolet imager, two white light coronagraphs, and a heliospheric imager. Two spacecraft with identical instrumentation will obtain simultaneous observations from viewpoints of increasing separation in the ecliptic plane. In support of the STEREO mission objectives, SECCHI will observe coronal mass ejections from their birth at the Sun, through the outer corona, to their impact at Earth. The SECCHI program includes a coordinated effort to develope magneto-hydrodynamic models and visualization tools to interpret the images that will be obtained from the two spacecraft viewpoints. The resulting three-dimensional analysis of CMEs will help to resolve some of the fundamental outstanding questions in solar physics. Title: The CHIANTI Atomic Database and Instrument Calibration: a Symbiosis Authors: Mason, H. E.; Del Zanna, G.; Dere, K. P.; Landi, E.; Landini, M.; Young, P. R. Bibcode: 2002ISSIR...2..271M Altcode: 2002ESASR...2..271M; 2002rcs..conf..271M The CHIANTI atomic database comprises a comprehensive, accurate and up-to-date database of atomic parameters, necessary for emission-line spectroscopy. The suite of user-friendly software allows plasma diagnostics to be carried out. Since its release in 1996, CHIANTI has become a standard resource for the analysis of solar spectra. Accurate atomic data can provide the foundation for in-flight instrument calibrations. Conversely, an accurate instrument calibration can provide a check on atomic parameters. The internal consistency of spectral-line intensities can be used to highlight specific anomalies. In this paper, we illustrate how CHIANTI has been used to validate the calibration of solar EUV instruments: SOHO-CDS, -SUMER, -EIT and SERTS. In addition, we show how anomalous spectral-line intensities indicate the need for more accurate atomic calculations. Title: Relationship Between Coronal Mass Ejections and Flares Authors: Zhang, J.; Dere, K.; Howard, R. A. Bibcode: 2001AGUFMSH31C..05Z Altcode: We present the results of our observational study about the relationship between CMEs (Coronal Mass Ejections) and flares. We make use of CME events well observed by the LASCO instrument (Large Angle and Spectrometric Coronagraph), which are suitable for studying their detailed kinematic evolution throughout the lower corona (1.1--3 Rsun, the LASCO C1 field of view) and the upper corona (2--30 Rsun, the LASCO C2/C3 field of view). We make height-time and velocity-time plots for these events, giving special attention to the height range of the lower corona where CME acceleration takes place. We find that the evolution of impulsive CMEs can be divided into three phases: initiation phase characterized by slow ascension (less than 80 km/s), impulsive acceleration phase, and subsequent propagation phase. The initiation phase starts earlier than the onset time of the associated flare. However, the onset time of the impulsive acceleration phase coincides with the onset time of the flare, and the acceleration period of the impulsive acceleration phase coincides with the rise phase of the flare. Gradual CMEs, which are not associated with flares, do not show an impulsive acceleration phase. On the other hand, there exists another class of CMEs, which we call explosive CMEs. Explosive CMEs are accelerated extremely fast to reach a great velocity; the acceleration takes place very low in the corona (less than 0.5 Rsun above the surface). They do not show an initiation phase and are associated with major flares. The Nov. 6, 1997 CME/flare event, which is a great particle event, is a typical explosive one and will be discussed in detail in the presentation Title: Solar Irradiance Variability Modeled Near Mg II Using Plage and Sunspot Contrast Factors Measured by HRTS Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M.; Floyd, L. E. Bibcode: 2001AGUFMSH11C0733M Altcode: Empirical models of solar spectral irradiance varaibility combine areas and locations of plage and sunspots with wavelength dependent contrast factors in order to estimate the solar spectrum. At UV wavelengths, these models have relied on estimated or calculated contrast factors that are often at low resolution. Using quiet sun, plage, and sunspot spectra near Mg II at ~ 2800Å measured by the NRL HRTS instrument, we have recently determined the wavelength dependent contrast factors for plage and sunspots. In this presentation we will discuss the use of measured contrast factors in a spectral irradiance model of the 2765 - 2885Å region and the preliminary comparisons of model results with SUSIM observations. These comparisons will examine spectral irradiance variations on solar rotational and solar cycle time scales. Title: Source Regions of Coronal Mass Ejections Authors: Subramanian, Prasad; Dere, K. P. Bibcode: 2001ApJ...561..372S Altcode: 2001astro.ph..7138S Observations of the solar corona with the Large Angle and Spectrometric Coronagraph Experiment (LASCO) and EUV Imaging Telescope (EIT) instruments on the Solar and Heliospheric Observatory (SOHO) provide an unprecedented opportunity to study coronal mass ejections (CMEs) from their initiation through their evolution out to 30 Rsolar. The objective of this study is to gain an understanding of the source regions from which the CMEs emanate. To this end, we have developed a list of 32 CMEs whose source regions are located on the solar disk and are well observed in EIT 195 Å data during the period from solar minimum in 1996 January through the rising part of the cycle in 1998 May. We compare the EIT source regions with photospheric magnetograms from the Michelson Doppler Imager (MDI) instrument on SOHO and the National Solar Observatory at Kitt Peak and also with Hα data from various sources. The overall results of our study show that 41% of the CME-related transients observed are associated with active regions and have no prominence eruptions, 44% are associated with eruptions of prominences embedded in active regions, and 15% are associated with eruptions of prominences outside active regions. Those CMEs that do not involve prominence eruptions originate in active regions both with and without prominences. We describe six especially well observed events. These case studies suggest that active region CMEs (without eruptive prominences) are associated with active regions with lifetimes between 11 and 80 days. They are also often associated with small-scale emerging or canceling flux over timescales of 6-7 hr. CMEs associated with active region prominence eruptions, on the other hand, are typically associated with old active regions with lifetimes ~6-7 months. Title: Reconciling Extreme-Ultraviolet and Radio Observations of the Sun's Corona Authors: Zhang, J.; Kundu, M. R.; White, S. M.; Dere, K. P.; Newmark, J. S. Bibcode: 2001ApJ...561..396Z Altcode: The Sun's corona, which is composed of plasma at a temperature of a few millions of degrees, can be best viewed in two electromagnetic domains, one from wavelengths of a few angstroms to hundreds of angstroms (in the soft X-ray and EUV domain), the other from wavelengths of a few centimeters to several tens of centimeters (in the radio domain). In this paper, we present a quantitative comparison of coronal observations made in these two domains with high spatial resolution over the full disk of the Sun. The EUV observations were taken with the EIT (Extreme-Ultraviolet Imaging Telescope) on board SOHO (Solar and Heliospheric Observatory), and the radio observations were taken with the VLA (Very Large Array). The two sets of images show very similar morphologies, indicating that the different wavelengths originate from common solar features. We predict radio fluxes using the temperature and emission measure of the corona calculated from EIT observations, adopting Meyer's table of coronal abundances for the calculations. In each of the seven observations investigated, there always exists a good linear correlation in the pixel-by-pixel correlation plot between the predicted and the observed radio flux for coronal features over a wide range of flux variation. Nevertheless, the predicted radio flux is systematically larger than that observed by a factor of 2.0+/-0.2, on average. We attribute the difference to the underestimation of the abundance of Fe relative to H in the abundances adopted by Meyer. On this basis, we place the absolute Fe abundance in the corona at 7.8×10-5, which has an enrichment factor of 2.4 relative to the accepted photospheric Fe abundance. Title: CHIANTI - An atomic database for X-EUV spectral lines Authors: Dere, K. P.; Landi, E. Bibcode: 2001tysc.confE..64D Altcode: CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities and electron excitation data for a large number of ions of astrophysical interest. It also includes a suite of Interactive Data Language (IDL) programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics. This database allows the calculation of theoretical line emissivities necessary for the analysis of optically thin emission line spectra. The first version (1.01) of the CHIANTI database was released in 1996 h paper1. The second version, released in 1999, included continuum emission and data for additional ions (Landi et al. 1999). Both versions of the CHIANTI database have been used extensively by the astrophysical and solar communities to analyze emission line spectra from astrophysical sources. Now the CHIANTI database has been extended to wavelengths shorter than 50Å by including atomic data for the hydrogen and helium isoelectronic sequences, inner-shell transitions and satellite lines and several other ions. In addition, some of the ions already present in the database have been updated and extended with new atomic data from published calculations. Title: On the Temporal Relationship between Coronal Mass Ejections and Flares Authors: Zhang, J.; Dere, K. P.; Howard, R. A.; Kundu, M. R.; White, S. M. Bibcode: 2001ApJ...559..452Z Altcode: The temporal relationship between coronal mass ejections (CMEs) and associated solar flares is of great importance to understanding the origin of CMEs, but it has been difficult to study owing to the nature of CME detection. In this paper, we investigate this issue using the Large Angle and Spectrometric Coronagraph and the EUV Imaging Telescope observations combined with GOES soft X-ray observations. We present four well-observed events whose source regions are close to the limb such that we are able to directly measure the CMEs' initial evolution in the low corona (~1-3 Rsolar) without any extrapolation; this height range was not available in previous space-based coronagraph observations. The velocity-time profiles show that kinematic evolution of three of the four CMEs can be described in a three-phase scenario: the initiation phase, impulsive acceleration phase, and propagation phase. The initiation phase is characterized by a slow ascension with a speed less than 80 km s-1 for a period of tens of minutes. The initiation phase always occurs before the onset of the associated flare. Following the initiation phase, the CMEs display an impulsive acceleration phase that coincides very well with the flares' rise phase lasting for a few to tens of minutes. The acceleration of CMEs ceases near the peak time of the soft X-ray flares. The CMEs then undergo a propagation phase, which is characterized by a constant speed or slowly decreasing in speed. The acceleration rates in the impulsive acceleration phase are in the range of 100-500 m s-2. One CME (on 1997 November 6, associated with an X9.4 flare) does not show an initiation phase. It has an extremely large acceleration rate of 7300 m s-2. The possible causes of CME initiation and acceleration in connection with flares are explored. Title: The Sources of Solar Ultraviolet Variability between 2765 and 2885 Å: Mg I, Mg II, Si I, and Continuum Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M. Bibcode: 2001ApJ...557..854M Altcode: The variation of the solar spectrum between 2000 and 4000 Å is a major component of the total irradiance variability of the Sun. Recent analyses suggest that variations in the solar ultraviolet flux at these wavelengths account for about 30% of the total solar irradiance variability. Most estimates of solar spectral irradiance variability in the ultraviolet are based on the ratio of the intensity of features such as solar plages and sunspots to the intensity of the quiet Sun. These ratios are referred to as contrast factors. To a large degree, contrast factors at ultraviolet wavelengths have not been measured. We present measurements of the average intensities of plage, sunspot, and quiet-Sun regions in the spectral range between 2765 and 2885 Å, derived from high spatial and spectral resolution spectra obtained during the ninth rocket flight of the High Resolution Telescope and Spectrograph in 1995. From these average spectra, plage and sunspot contrast factors are determined. To our knowledge, these are the first contrast factors at these wavelengths derived from measured solar intensities. These spectra show a large contrast in the Mg I, Mg II, and Si I Fraunhofer lines and a much smaller contrast (1.01+/-0.015 to 1.04+/-0.04) in the line-blanketed continuum. Contrast factors are also determined for three intensity levels of the quiet Sun as well as for a single sunspot. Many fine spectral features in the contrast factors can be attributed to weak Fraunhofer lines of Cr II, Fe I, Fe II, and Mg I. Title: CHIANTI-An Atomic Database for Emission Lines. IV. Extension to X-Ray Wavelengths Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G. Bibcode: 2001ApJS..134..331D Altcode: CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities, and electron excitation data for a large number of ions of astrophysical interest. It also includes a suite of Interactive Data Language programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics. This database allows the calculation of theoretical line emissivities necessary for the analysis of optically thin emission-line spectra. The first version (1.01) of the CHIANTI database was released in 1996 and published by Dere et al. in 1997 as Paper I in this series. The second version, released in 1999 by Landi et al., included continuum emission and data for additional ions. Both versions of the CHIANTI database have been used extensively by the astrophysical and solar communities to analyze emission-line spectra from astrophysical sources. Now the CHIANTI database has been extended to wavelengths shorter than 50 Å by including atomic data for the hydrogen and helium isoelectronic sequences, inner-shell transitions and satellite lines, and several other ions. In addition, some of the ions already present in the database have been updated and extended with new atomic data from published calculations. Title: High-resolution Imaging of the Upper Solar Chromosphere: First Light Performance of the Very-high-Resolution Advanced ULtraviolet Telescope Authors: Korendyke, C. M.; Vourlidas, A.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Morrill, J. S.; Moses, J. D.; Moulton, N. E.; Socker, D. G. Bibcode: 2001SoPh..200...63K Altcode: The Very-high-resolution Advanced ULtraviolet Telescope (VAULT) experiment was successfully launched on 7 May 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a two-grating, zero-dispersion spectroheliograph tuned to isolate the solar Lα emission line. During the flight, the instrument successfully obtained a series of images of the upper chromosphere with a limiting resolution of ∼ 0.33 arc sec. The resulting observations are the highest-resolution images of the solar atmosphere obtained from space to date. The flight demonstrated that sub-arc second ultraviolet images of the solar atmosphere are achievable with a high-quality, moderate-aperture space telescope and associated optics. Herein, we describe the payload and its in-flight performance. Title: Solar Origin of Major Geo-magnetic Storms Between 1996 and 2000 Authors: Zhang, J.; Dere, K. P.; Howard, R. A. Bibcode: 2001AGUSM..SH62A11Z Altcode: We investigate the solar origin of major geo-magnetic storms which occurred between 1996 and 2000. Based on the hourly DST index, we identify 39 major geo-magnetic storms (defined as peak DST less than -100) in this period. The solar observations are primarily based on LASCO (Large-Angle and Spectrometric Coronagraph) and EIT (Extreme-ultraviolet Imaging Telescope) instruments on board SOHO spacecraft. Using a six-day time window, we search through all halo/partial-halo CMEs (Coronal Mass Ejections) seen in LASCO and coronal dimmings seen in EIT for each storm to try to identify its solar source. 30 of the 39 storms are in the LASCO/EIT duty cycle (most of the other 9 events occurred during 1998-1999 SOHO failure). We associate these storms to solar sources with three different confidence levels. For 18 of the 30 events, we have reliably determined their solar sources, all of which show both strong halo CME signature and almost simultaneous strong coronal dimming signature; these signatures are usually unique in the time window. For 5 of the 30 events, there are multiple halo CMEs and dimmings found in the time window, and we can not make unambiguous association with a particular solar source. For the other 7 of the 30 events, we find it is difficult to identify solar sources, due to lack of strong signature in either LASCO or EIT observations or both. We investigate various characteristics of solar sources for those 18 major storms with unambiguous association, including CME morphology and kinematics, pre-eruption coronal structure and evolution, coronal dimmings and waves, coronal post-eruption loops, X-ray and optical flares, filaments, photospheric magnetic field structure and distribution of heliocentric position. The purpose is to understand the characteristics of CMEs observed near the Sun which causes major geo-magnetic storms. Title: Ultra-High Resolution Observations of the Upper Chromosphere: First Results From the NRL VAULT Sounding Rocket Payload Authors: Vourlidas, A.; Korendyke, C. M.; Dere, K. P.; Klimchuk, J. A. Bibcode: 2001AGUSM..SP61A03V Altcode: The Very high resolution Advanced ULtraviolet Telescope (VAULT) is a new spectroscopic imaging instrument. The instrument was launched on May 7, 1999 as a sounding rocket payload. The goal of the first VAULT flight was to obtain sub-arcsecond images of the Sun in the light of Lya (1216 Å). VAULT directly imaged an active region plage, fliaments and the fine structures in the supergranule boundaries and network with the unprecented spatial resolution of 0.33 arcseconds. We present the VAULT images and the first results from the comparison of the Lya data to observations from other instruments and in particular with a sequence of TRACE 171 Å images taken during the VAULT flight. Title: CHIANTI - an atomic database for emission lines, Paper 4: Extension to X-ray Wavelengths Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G. Bibcode: 2001AGUSM..SP21B08D Altcode: CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities and electron excitation data for a large number of ions of astrophysical interest. It also includes a suite of Interactive Data Language (IDL) programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics. This database allows the calculation of theoretical line emissivities necessary for the analysis of optically thin emission line spectra. The first version of the CHIANTI database was released in 1996 (Dere et al., 1996). The second version, released in 1999, included continuum emission and data for additional ions (Landi et al. 1999). Both versions of the CHIANTI database have been used extensively by the astrophysical and solar communities to analyze emission line spectra from astrophysical sources. Now the CHIANTI database has been extended to wavelengths shorter than 50Å by including atomic data for the hydrogen and helium isoelectronic sequences, inner-shell transitions and satellite lines and several other ions. In addition, some of the ions already present in the database have been updated and extended with new atomic data from published calculations. Title: The Extreme Ultraviolet Imaging Spectrometer on Solar-B Authors: Mariska, J. T.; Brown, C. M.; Dere, K. P.; Doschek, G. A.; Korendyke, C. M.; Culhane, J. L.; Watanabe, T. Bibcode: 2001AGUSM..SH41A12M Altcode: Emission lines in the extreme ultraviolet spectral region provide a sensitive probe of the high-temperature plasma in the solar transition region and corona. Simultaneously achieving high spatial, spectral, and temporal resolution in this wavelength region has been challenging. We describe the design and capabilities of the Extreme Ultraviolet Imaging Spectrometer (EIS) planned for flight on the Japanese Solar-B satellite. EIS consists of a multilayer-coated off-axis telescope mirror and a multilayer-coated toroidal grating spectrometer. The telescope mirror forms a solar image on the spectrometer entrance slit assembly and the spectrometer forms stigmatic spectra of the solar region isolated by the 1024 arcsec high slit. The instrument includes thin-film aluminum filters to reject longer wavelength radiation and CCD detectors at the focal plane. Articulation of the primary mirror provides roughly 1600 arcsec of east-west coarse pointing freedom and 360 arcsec of fine east-west motion for rastering. Monochromatic images are formed either by rastering the solar image across a narrow entrance slit or by using a very wide slit. Half of each optic is coated to optimize reflectance at 19.5 nm, and the other half to optimize reflectance at 27.0 nm. Each wavelength range is imaged onto a separate CCD detector. The EIS spectral range contains emission lines formed over a temperature range from roughly 0.1 to 20 MK. Bright lines in the selected wavelength bands will yield precision measurements of line-of-sight velocities and nonthermal plasma motions. This spectral range also includes several pairs of density-sensitive lines. Title: High Resolution Observations of Solar Spectral Variability Near Mg II Measured by HRTS Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M. Bibcode: 2001AGUSM..SP32B03M Altcode: The HRTS-9 rocket flight occurred on April 18, 1995 and made measurements of solar spectral variability near the Mg II h and k lines. These observations include high spatial and spectral resolution spectrograms as well as spectroheliograms in four FUV passbands and H-alpha. The spectrograms cover the wavelength range 2665 to 2885Å with a spectral resolution of .2Å and a spatial resolution of 1 arc-second along a 900 arc-second slit. The most prominent features in this spectral range include the strong Mg II h and k lines near 2800 Å, the Mg I and Si I Fraunhofer lines near 2850 and 2880Å, respectively, and the line-blanketed quasi-continuum region. During the HRTS-9 flight, spectrograms and spectroheliograms where obtained of the quiet sun, quiet limb, plage, and sunspots. In addition to instrumental corrections, we have recently applied an absolute intensity calibration to the HRTS-9 data derived from SUSIM/ATLAS-3 and SUSIM/UARS observations. The analysis of these calibrated data has focused on the spectral variability of the above surface features and how these observations impact solar irradiance variability. Specifically, we examine the contrast variation of the plage and sunspot compared to the quiet sun as well as contrast variation within the quiet sun. In this presentation we will discuss the details of the observed spectra and wavelength dependent contrast factors. This will include a comparison of our present results with earlier estimates of plage contrast in this wavelength region and a discussion of the fine structures observed at high spectral resolution. Title: Source Regions of Coronal Mass Ejections Authors: Dere, K. P.; Subramanian, P. Bibcode: 2001IAUS..203..362D Altcode: A set of 32 coronal mass ejections observed with the LASCO and EIT instruments on SOHO have been examined. These events have been selected from the period between May 1997 through May 1998 and includes the period of solar minimum and the rise of solar cycle 23. The criteria for including these events were that they were observed as a CME in LASCO, they were well observed with EIT and they were located near disk center. The sources of these 32 events were active regions without filaments (26 cases),active regions with filaments (7 cases) and quiescent filaments (6 cases). In the EIT, the signature of the initiation of the coronal mass ejection includes flares, EIT waves, coronal dimmings and mass ejections. The characteristics of the photospheric magnetic activity associated with these events, observed with NSO/Kitt Peak and MDI/SOHO magnetograms, indicate that CMEs are associated with a wide range of activity that includes small scale flux emergence and cancellation, large scale flux emergence, and large scale flux decay. During this period of the solar cycle, the solar disk contains few active regions which are generally generally short lives so that there may be a solar cycle dependence to these conclusions. Title: BEPPOSAX Observation of EQ Pegasi (CD-ROM Directory: contribs/landi) Authors: Landi, E.; Landini, M.; Dere, K.; Risaliti, G. Bibcode: 2001ASPC..223..991L Altcode: 2001csss...11..991L No abstract at ADS Title: In-flight performance of the Very high Angular resolution ULtraviolet Telescope sounding rocket payload Authors: Korendyke, Clarence M.; Vourlidas, A.; Cook, John W.; Dere, Kenneth P.; Feldman, R.; Howard, Russell A.; Lilley, D. N.; Morrill, Jeff S.; Moses, J. Daniel; Moulton, Norman E.; Moye, Robert W.; Roberts, D. E.; Shepler, E. L.; Smith, J. K.; Socker, Dennis G.; Spears, T. R.; Waymire, R. S.; Brown, Wayne E.; Tarbell, Theodore D.; Berger, Tom; Handy, Brian N. Bibcode: 2000SPIE.4139..340K Altcode: The Very high Angular Resolution ULtraviolet Telescope experiment was successfully launched on May 7, 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a double grating spectroheliograph tuned to isolate the solar Lyman (alpha) emission line. During the flight, the instrument successfully obtained a series of images of the upper chromosphere with a limiting resolution of approximately 0.33 arc-seconds. The resulting observations are the highest resolution images of the solar atmosphere obtained from space to date. The flight demonstrated that subarc-second ultraviolet images of the solar atmosphere are achievable with a high quality, moderate aperture space telescope and associated optics. Herein, we describe the payload and its in- flight performance. Title: Solar Transition Region Authors: Dere, K. Bibcode: 2000eaa..bookE2021D Altcode: The solar transition region can generally be defined as those plasmas at temperatures between 2×104 and 1×106 K, a temperature regime bridging the CHROMOSPHERE and CORONA. Prior to the space age, the transition region was unobserved although the existence of the higher-temperature corona was known. Spectral lines formed at transition region temperatures are found primarily below 2000 Å where they... Title: The Preflight Photometric Calibration of the Extreme-Ultraviolet Imaging Telescope EIT Authors: Dere, K. P.; Moses, J. D.; Delaboudinière, J. -P.; Brunaud, J.; Carabetian, C.; Hochedez, J. -F.; Song, X. Y.; Catura, R. C.; Clette, F.; Defise, J. -M. Bibcode: 2000SoPh..195...13D Altcode: This paper presents the preflight photometric calibration of the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). The EIT consists of a Ritchey-Chrétien telescope with multilayer coatings applied to four quadrants of the primary and secondary mirrors, several filters and a backside-thinned CCD detector. The quadrants of the EIT optics were used to observe the Sun in 4 wavelength bands that peak near 171, 195, 284, and 304 Å. Before the launch of SOHO, the EIT mirror reflectivities, the filter transmissivities and the CCD quantum efficiency were measured and these values are described here. The instrumental throughput in terms of an effective area is presented for each of the various mirror quadrant and filter wheel combinations. The response to a coronal plasma as a function of temperature is also determined and the expected count rates are compared to the count rates observed in a coronal hole, the quiet Sun and an active region. Title: Solar UV Irradiance Variability Observed at High Spatial and Spectral Resolution by HRTS Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M. Bibcode: 2000SPD....31.0128M Altcode: 2000BAAS...32..806M The HRTS-9 rocket flight occured on April 18, 1995 and was configured to study the sources of solar variablity by observing ultraviolet emission patterns near the Mg II h and k lines. These observations include high spatial and spectral resolution spectrograms as well as spectroheliograms in four FUV passbands and H-alpha. The spectrograms cover the wavelength range 2665 to 2885 Angstroms \ with a spectral resolution of .2 Angstroms \ and a spatial resolution of 1 arc-second along a 900 arc-second slit. Prominent spectral features in this wavelength range include the Mg II h and k lines near 2800 Angstroms, the strong Mg I and Si I Fraunhofer lines near 2850 and 2880 Angstroms, respectively, and the line-blanketed quasi-continuum region. HRTS-9 observations included the quiet sun, quiet limb, plage, and sunspots. The analysis of this data set has focused on the spatial intensity variability of the features as a function of wavelength with particular regard for how these will affect solar variability. Specifically, we examine the contrast variation of the plage and sunspot compared to the quiet sun as well as contrast variation within the quiet sun. The observed sunspot spectrum shows the characteristic decrease in the quasi-continuum, the non-reversed Mg II h and k line shapes as well as the enhancement in the Mg II h and k core emissions over that observed in the quiet sun. In this presentation we will discuss the wavelength dependent contrasts of the plage and quiet sun regions, the characteristics of the observed sunspot spectrum, and the implications on solar variability. Title: Large-Angle Spectrometric Coronagraph Measurements of the Energetics of Coronal Mass Ejections Authors: Vourlidas, A.; Subramanian, P.; Dere, K. P.; Howard, R. A. Bibcode: 2000ApJ...534..456V Altcode: We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit flux-rope morphologies. Assuming flux conservation, we use observations of the magnetic flux in a variety of magnetic clouds near the Earth to determine the magnetic flux and magnetic energy in CMEs near the Sun. We find that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that flux-rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the flux-rope parts of the CMEs can be considered a closed system above ~2 Rsolar. Title: LASCO and EIT observations of CMEs associated with flares Authors: Zhang, J.; Dere, K. P.; Howard, R. A.; Kundu, M. R.; White, S. M. Bibcode: 2000SPD....31.0906Z Altcode: 2000BAAS...32..841Z Coronal mass ejections (CME) and flares are two primary causes of adverse space weather. These two solar eruptive phenomenon are often observed to be associated with each other. Yet the relationship between them is not well known. With unprecedented LASCO (Large-Angle and Spectrometric Coronagraph) and EIT (Extreme-ultraviolet Imaging Telescope) observations combined with simultaneous HXT (Hard X-ray Telescope), GOES and other flare observations, we pursue to make a comprehensive study on the spatial, temporal and energetic relationship between CMEs and flares. In order to make accurate measurement of the onset time of CMEs, we primarily select CME events whose source regions are close to the limb and which are well observed by LASCO/C1 from 1.1 to 3 solar radii. Although a flare occurs in a rather small area of active region, the CME's source region often covers much larger longitudinal and latitudinal extension. Some CMEs occur simultaneously with flare (within only a few minutes), however, some CMEs occur well before the flares (more than 30 minutes earlier). Fast CMEs are associated with strong flares. These studies are aimed to understand the initiation process of solar eruptive phenomenon, and to fit a variety of observational aspects into a consistent picture. Title: LASCO and EIT Observations of Coronal Mass Ejections Authors: Dere, K. P.; Vourlidas, A.; Subramanian, Prasad Bibcode: 2000astro.ph..2061D Altcode: We present a brief overview of LASCO and EIT observations of CMEs. We discuss CME energetics, the relation of CMEs to streamers and conclude with some insights into the source regions of CMEs. Title: Non-Radial Unipolar Coronal Streamers in Magnetically High Latitudes and Radial Bipolar Streamers at the Magnetic Equator of the Sun Authors: Saito, Takao; Shibata, K.; Dere, K. P.; Numazawa, S. Bibcode: 2000AdSpR..26..807S Altcode: The complex structure of coronal streamers can be better understood by their classification into two classes: non-radial unipolar streamers emanating from magnetically high latitudes, and radial bipolar streamers emanating from the magnetic equator. The coronal streamers observed during the total solar eclipses of July 11,1991 and February 26, 1998 are classified into the two types. Various characteristics of the two types are discussed and summarized. Important relations of the two to solar, interplanetary, and terrestrial phenomena are discussed Title: Coronal Mass Ejections and the Solar Wind: New Results from LASCO Authors: Dere, K. P.; Howard, R. A.; Brueckner, G. E. Bibcode: 2000AdSpR..25.1837D Altcode: The LASCO and EIT experiments on SOHO have provided a revolutionary picture of coronal dynamics. In the past, the corona has largely been thought to be a region where the evolution of the coronal structures occurred on relatively large time scales, aside from the intermittent coronal mass ejection. The outflows in the polar coronal holes were largely considered to be time-independent. The picture now presented by the LASCO and EIT observations are of a highly dynamic corona. Continual small scale sporadic outflows are observed in quiet streamers and in the polar coronal holes. The LASCO images of CMEs shows that many appear to have circular structures that indicate that they consist of helical magnetic flux ropes. In addition, a new class of CMEs has been observed and are called `global' CMEs since they appear to involve regions of the corona separated by as much as 180° Title: Commission 10: Solar Activity: (Activite Solaire) Authors: Ai, G.; Benz, A.; Dere, K. P.; Engvold, O.; Gopalswamy, N.; Hammer, R.; Hood, A.; Jackson, B. V.; Kim, I.; Marten, P. C.; Poletto, G.; Rozelot, J. P.; Sanchez, A. J.; Shibata, K.; van Driel-Geztelyi, L. Bibcode: 2000IAUTA..24...67A Altcode: No abstract at ADS Title: Microwave and Extreme Ultraviolet Observations of Solar Polar Regions Authors: Nindos, A.; Kundu, M. R.; White, S. M.; Gary, D. E.; Shibasaki, K.; Dere, K. P. Bibcode: 1999ApJ...527..415N Altcode: The poles of the Sun are brighter than the rest of the quiet Sun's emission in a limited range of radio frequencies from 17 GHz to 87 GHz. We have studied microwave images of the quiet Sun made with the Nobeyama radioheliograph at 17 GHz. They show that the so-called polar-cap brightening consists of two components: a diffuse component of 1500 K excess brightness and patchy compact sources with localized excess brightness of about 3500 K. We test the reality of the compact sources using the maximum entropy method deconvolution. The total flux and the number of compact polar sources as well as the north-south extent of the diffuse polar emission are larger in the pole that is closest to the Earth. We compared the microwave polar emission with nearly simultaneous SOHO EIT images taken in the lines of He II at 304 Å and Fe XII at 195 Å. No one-to-one correlation between the compact radio sources and the bright EUV features was found: most of the radio emission arises between the plumes visible to EIT. The boundaries of the polar-cap brightenings did not match exactly the boundaries of the coronal holes as seen in either the Fe XII 195 Å images or the He II 304 Å images. The temporal variations of the compact microwave sources did not correspond to any significant changes in EUV emission. On the other hand, most He II 304 Å changing features were associated with the diffuse polar microwave emission, which was practically constant. Our data suggest that the origin of the polar brightening is not coronal; it seems that the bulk of the patchy radio emission comes from heights below the 80,000 K layer. Title: LASCO Measurements of the Energetics of Coronal Mass Ejections Authors: Vourlidas, Angelos; Subramanian, Prasad; Dere, K. P.; Howard, R. A. Bibcode: 1999astro.ph.12069V Altcode: We examine the energetics of Coronal Mass Ejections (CMEs) with data from the LASCO coronagraphs on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit a flux-rope morphology. Assuming flux conservation, we use observations of the magnetic flux in a variety of magnetic clouds near the Earth to determine the magnetic flux and magnetic energy in CMEs near the Sun. We find that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that flux rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the flux rope parts of the CMEs can be considered to be a closed system above $\sim$ 2 $R_{\sun}$. Title: CHIANTI: A database for astrophysical emission line spectroscopy Authors: Del-Zanna, Giulio; Young, Peter; Dere, Ken; Landini, Massimo; Landi, Enrico; Mason, Helen Bibcode: 1999ascl.soft11004D Altcode: CHIANTI consists of a critically evaluated set of atomic data necessary to calculate the emission line spectrum of astrophysical plasmas. The data consists of atomic energy levels, atomic radiative data such as wavelengths, weighted oscillator strengths and A values, and electron collisional excitation rates. A set of programs that use these data to calculate the spectrum in a desired wavelength range as a function of temperature and density are also provided. These programs have been written in Interactive Data Language (IDL) and descriptions of these various programs are provided on the website. Title: Concept Study Report: Extreme-Ultraviolet Imaging Spectrometer Solar-B Authors: Doschek, George A.; Brown, Charles M.; Davila, Joseph M.; Dere, Kenneth P.; Korendyke, Clarence M.; Mariska, John T.; Seely, John F. Bibcode: 1999STIN...0011153D Altcode: We propose a next generation Extreme-ultraviolet Imaging Spectrometer (EIS) that for the first time combines high spectral, spatial, and temporal resolution in a single solar spectroscopic instrument. The instrument consists of a multilayer-coated off-axis telescope mirror and a multilayer-coated grating spectrometer. The telescope mirror forms solar images on the spectrometer entrance slit assembly. The spectrometer forms stigmatic spectra of the solar region located at the slit. This region is selected by the articulated telescope mirror. Monochromatic images are obtained either by rastering the solar region across a narrow entrance slit, or by using a very wide slit (called a slot) in place of the slit. Monochromatic images of the region centered on the slot are obtained in a single exposure. Half of each optic is coated to maximize reflectance at 195 Angstroms; the other half to maximize reflectance at 270 Angstroms. The two Extreme Ultraviolet (EUV) wavelength bands have been selected to maximize spectral and dynamical and plasma diagnostic capabilities. Spectral lines are observed that are formed over a temperature range from about 0.1 MK to about 20 MK. The main EIS instrument characteristics are: wavelength bands - 180 to 204 Angstroms; 250 to 290 Angstroms; spectral resolution - 0.0223 Angstroms/pixel (34.3km/s at 195 Angstroms and 23.6 km/s at 284 Angstroms); slit dimensions - 4 slits, two currently specified dimensions are 1" x 1024" and 50" x 1024" (the slot); largest spatial field of view in a single exposure - 50" x 1024"; highest time resolution for active region velocity studies - 4.4 s. Title: The relationship of coronal mass ejections to streamers Authors: Subramanian, Prasad; Dere, K. P.; Rich, N. B.; Howard, R. A. Bibcode: 1999JGR...10422321S Altcode: 1999astro.ph..6207S We have examined images from the Large-Angle and Spectrometric Coronagraph (LASCO) to study the relationship of coronal mass ejections (CMEs) to coronal streamers. We wish to test the suggestion [Low, 1996] that CMEs arise from flux ropes embedded in a streamer erupting and disrupting the streamer. The data span a period of 2 years near Sunspot minimum through a period of increased activity as Sunspot numbers increased. We have used LASCO data from the C2 coronagraph which records Thomson scattered white light from coronal electrons at heights between 1.5 and 6Rs. Maps of the coronal streamers have been constructed from LASCO C2 observations at a height of 2.5Rs at the east and west limbs. We have superposed the corresponding positions of CMEs observed with the C2 coronagraph onto the synoptic maps. We identified the different kinds of signatures CMEs leave on the streamer structure at this height (2.5Rs). We find four types of CMEs with respect to their effect on streamers: 1. CMEs that disrupt the streamer, 2. CMEs that have no effect on the streamer, even though they are related to it, 3. CMEs that create streamer-like structures and 4. CMEs that are latitudinally displaced from the streamer. CMEs in categories 3 and 4 are not related to the streamer structure. This is the most extensive observational study of the relation between CMEs and streamers to date. Previous studies using SMM data have made the general statement that CMEs are mostly associated with streamers and that they frequently disrupt it. However, we find that approximately 35% of the observed CMEs bear no relation to the preexisting streamer, while 46% have no effect on the observed streamer, even though they appear to be related to it. Our conclusions thus differ considerably from those of previous studies. Title: SOHO/EIT Observations of the 1997 April 7 Coronal Transient: Possible Evidence of Coronal Moreton Waves Authors: Thompson, B. J.; Gurman, J. B.; Neupert, W. M.; Newmark, J. S.; Delaboudinière, J. -P.; Cyr, O. C. St.; Stezelberger, S.; Dere, K. P.; Howard, R. A.; Michels, D. J. Bibcode: 1999ApJ...517L.151T Altcode: We report observations obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO of a large-scale coronal transient propagating across the disk of the Sun at a speed of 250 km s-1, in apparent association with a flare and coronal mass ejection. The observations consist of a series of images taken in the Fe XII 195 Å bandpass at an average cadence of 15 minutes. A visible increase in coronal emission propagates away from the erupting region, traveling across most of the solar disk in less than an hour. As the wave propagates through the ambient corona, its path is not homogeneous, and it is less observable near strong magnetic features such as active regions and magnetic neutral lines. The characteristics of this event appear to be representative of several other ``EIT waves,'' which we identify as strong candidates for the coronal manifestation of Moreton waves. Title: Microwave and Extreme Ultraviolet Observations of Solar Polar Regions Authors: Nindos, A.; Kundu, M. R.; White, S. M.; Gary, D. E.; Shibasaki, K.; Dere, K. P. Bibcode: 1999AAS...194.3207N Altcode: 1999BAAS...31..871N The radio emission of solar poles is brighter than the rest of the quiet Sun's emission in a limited range of frequencies from 17 GHz to 87 GHz. We have studied microwave images of the quiet Sun made with the Nobeyama Radioheliograph at 17 GHz. They show that the so-called polar-cap brightening consists of two components: a diffuse component of 1500 K excess brightness, and patchy compact sources with localized excess brightness of about 3500 K. The total flux and the number of compact polar sources as well as the North-South extent of the diffuse polar emission are larger in the pole which is closest to the Earth. We compared the microwave polar emission with nearly simultaneous SoHO EIT images taken in the lines of He ii at 304 Angstroms and Fe xii at 195 Angstroms. No one-to-one correlation between the compact radio sources and the bright EUV features was found: most of the radio emission arises between the plumes visible to EIT. The boundaries of the polar-cap brightenings did not match exactly the boundaries of the coronal holes as seen in the Fe xii 195 Angstroms images. The temporal variations of the compact microwave sources did not correspond to any significant changes in EUV emission. On the other hand, most He ii 304 Angstroms changing features were associated with the diffuse polar microwave emission which was practically constant. Our data suggest that the origin of the polar brightening is not coronal; it seems that the bulk of the patchy radio emission comes from heights below the 80000 K layer. Title: LASCO Measurements of Erupting Flux Ropes Authors: Vourlidas, A.; Subramanian, P.; Dere, K. P.; Howard, R. A. Bibcode: 1999AAS...19410103V Altcode: 1999BAAS...31..998V It is commonly assumed that Coronal Mass Ejections from the Sun are magnetically driven. We address this question with data from the LASCO coronagraphs aboard the SOHO spacecraft. These observations provide fairly direct measurements of the energetics of CMEs. We determine the kinetic and gravitational energies and their evolution for several helical CMEs. We estimate the evolution of the magnetic energy based on the conservation of magnetic flux and observations of magnetic clouds near the Earth. From the magnitude and variation of these three forms of energy, we examine the energetics of CMEs from the perspective that they are driven through their internal magnetic energy. Title: Global Coronal Mass Ejections observed with LASCO Authors: Dere, K. P.; Howard, R. A. Bibcode: 1999AAS...19410101D Altcode: 1999BAAS...31..998D The Large Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) spacecraft has provide nearly continuous observations of the solar corona from January 1996 until the present. This covers periods near minimum solar activity through the rise of the current sunspot cycle. Numerous coronal mass ejections (CMEs) have been observed during this period. Many of these can be characterized as arising from a spatially limited area of the corona. However, there now appears to be a class of CMEs that involve involve coronal structures spanning a hemisphere or more and we refer to these CMEs as global CMEs. In some cases, simultaneous CME activity are seen above the limb on opposite sides of the solar disk. Several examples of global CMEs are presented. The fact that they can occur during periods of relatively low solar activity supports the sugestion that these large scale CMEs are not simply the chance occurence of 2 or more unrelated CMEs at about the same time. Title: HRTS Observations of Solar Fine Scale Structures in the Near-UV Authors: Morrill, J. S.; Dere, K. P.; Korendyke, C. M. Bibcode: 1999AAS...194.9311M Altcode: 1999BAAS...31..990M The NRL High Resolution Telescope and Spectrograph (HRTS) obtains ultraviolet spectra, ultraviolet spectroheliograms and H alpha spectroheliograms at a spatial resolution of about 1 arc-second along a 900 arc-second slit. The HRTS-9 rocket flew on April 18, 1995 during the declining phase of the solar cycle. The HRTS-9 instrument and observing program were tailored to observe emission patterns inthe ultraviolet for the purpose of studying solar variability. Observation targets included the quiet sun, active regions and the quiet limb. The wavelength range of HRTS-9 spectrograph was from 275 nm to 290 nm. Some of the prominent spectral features in this wavelength range are the Mg II h and k lines at 280 nm, the strong Mg I Fraunhofer line at 285 nm, and the continuum. The ultraviolet spectroheliograph obtained images of a portion of the sun at wavelengths corresponding to a range of temperatures: 1550 (C IV), 1540 (Si I), 1560 (C I), and 1600 (continuum). The primary goal of the HRTS-9 rocket program was to examine the origin of the total solar variability in the intensity variations of solar structures in the near ultraviolet on a variety of spatial scales. The HRTS-9 data reveals the fine structure of the quiet sun, plage, and sun spots in the near ultraviolet. In addition, active region contrast factors are determined for comparison with modes of full disk ultraviolet variability based on SUSIM and SOLTICE observations from UARS. Title: The Increase in Mass of CMEs due to Propagation Authors: Howard, R. A.; Dere, K. P.; Sheeley, N. R., Jr.; Subramanian, P.; Vourlidas, A.; Wang, D. Bibcode: 1999AAS...19410102H Altcode: 1999BAAS...31..998H The question we would like to address is whether coronal mass ejections snowplow ambient material. Some of the CMEs observed by the LASCO coronagraph on SOHO have a clearly defined loop-like front, meaning that the trailing edge of the front can be clearly defined. We measure the mass in the front of the CME in this subclass. We find that for some of the events, the mass in the leading edge increases, implying that the CME is indeed "snowplowing" ambient material. If there is a significant increase in mass, then the CME frontal speed might decrease to conserve momentum. We estimate the amount of ambient material, using a model of coronal densities, and find that it is consistent with the mass increase. We can also estimate the height in the corona, below the occulting disk, from where the original material in the CME is released. These concepts as well as conditions for when the mass increases will be discussed. Title: Solar Polar Imager Authors: Moses, D.; Dere, K. P.; Howard, R. A.; Korendyke, C. M.; Socker, D. G.; Wang, Y. -M.; Goldstein, B. E.; Liewer, P. E. Bibcode: 1999AAS...194.7613M Altcode: 1999BAAS...31..958M Observation of the global coronal and magnetic field structure of the Sun requires coronal imaging and magnetograms from a perspective out of the ecliptic. While the upcoming Solar Terrestrial Relations Observatory (STEREO) mission will provide a great advance in the understanding of the three-dimensional structure of the corona and interplanetary medium, the orientation of the Sun's large scale magnetic axis of symmetry with the STEREO spacecraft separation defines the limits of this mission. The global structure of the streamer belts, polar coronal holes and coronal plumes all reflect the symmetry of the large scale solar magnetic field. Observations of Coronal Mass Ejections (CMEs) from the LASCO and EIT instruments on the Solar and Heliospheric Observatory (SOHO) indicate the need for synoptic coronal imaging out of the ecliptic (Solar Polar Imager), as well as in stereo pairs in the ecliptic (STEREO), for advancement in the understanding of the origins and consequences of CMEs. The SOHO MDI has shown the need for observations of the evolution of the polar magnetic fields and convection patterns to understand the generation and transport of the solar magnetic fields. Finally, the Ulysses mission has shown the need for polar coronal imaging and magnetograms for understanding the source of the solar wind. Ulysses has demonstrated the need for on-board in situ particles and fields instruments as a link to the remote sensing observations. Lightweight and compact instrumentation for these observations has already been demonstrated technically. An orbital mission involving a Jupiter assist such as Ulysses is also technically demonstrated, although the duration of the polar observations is limited to the point of degrading the studies of solar cycle evolution. An orbital mission involving a circularized polar orbit is possible with the use of solar-sail propulsion, but this involves technology that has yet to be demonstrated. Title: LASCO and EIT Observations of Helical Structure in Coronal Mass Ejections Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Michels, D. J.; Delaboudiniere, J. P. Bibcode: 1999ApJ...516..465D Altcode: Observations of coronal mass ejections (CMEs) by the Large Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) show a significant fraction with circular intensity patterns. In the past, these would have been called ``disconnection'' events, but we suggest that these are evidence of CMEs containing helical magnetic flux ropes that are often central to many theoretical models of CMEs and have been observed in magnetic clouds near 1 AU. Three examples are examined in detail with the LASCO and Extreme-Ultraviolet Imaging Telescope (EIT) data sets, which provide observations from their initiation through 30 Rsolar. Title: CHIANTI - an atomic database for emission lines. III. Continuum radiation and extension of the ion database Authors: Landi, E.; Landini, M.; Dere, K. P.; Young, P. R.; Mason, H. E. Bibcode: 1999A&AS..135..339L Altcode: CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities and electron excitation data for a large number of ions of astrophysical interest. This database allows the calculation of theoretical line emissivities necessary for the analysis of optically thin emission line spectra, and includes also a suite of IDL (Interactive Data Language) programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics. The first version (1.0) of the CHIANTI database was released in 1996 te[(Dere et al. 1997)]{Der97} and has been extensively used for analysis of line spectra from astrophysical sources by the scientific community. The present paper describes the first major update to the CHIANTI database which will subsequently be labeled version 2.0. The update consists of the addition of a large number of new ions, the revision of existing data for some ions and the inclusion of an IDL procedure to calculate the continuum. The CHIANTI atomic database and supporting IDL routines are freely available through the internet. Title: Observations of Coronal Structures Above an Active Region by EIT and Implications for Coronal Energy Deposition Authors: Neupert, W. M.; Newmark, J.; Delaboudinière, J. -P.; Thompson, B. J.; Catura, R. C.; Moses, J. D.; Gurman, J. B.; Portier-Fozzani, F.; Gabriel, A. H.; Artzner, G.; Clette, F.; Cugnon, P.; Maucherat, A. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Freeland, S.; Lemen, J. R.; Stern, R. A. Bibcode: 1998SoPh..183..305N Altcode: Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO have been used to evaluate temperature and density as a function of position in two largescale features in the corona observed in the temperature range of 1.0-2.0 MK. Such observations permit estimates of longitudinal temperature gradients (if present) in the corona and, consequently, estimates of thermal conduction and radiative losses as a function of position in the features. We examine two relatively cool features as recorded in EIT's Fe ix/x (171 Å) and Fe xii (195 Å) bands in a decaying active region. The first is a long-lived loop-like feature with one leg, ending in the active region, much more prominent than one or more distant footpoints assumed to be rooted in regions of weakly enhanced field. The other is a near-radial feature, observed at the West limb, which may be either the base of a very high loop or the base of a helmet streamer. We evaluate energy requirements to support a steady-state energy balance in these features and find in both instances that downward thermal conductive losses (at heights above the transition region) are inadequate to support local radiative losses, which are the predominant loss mechanism. The requirement that a coronal energy deposition rate proportional to the square of the ambient electron density (or pressure) is present in these cool coronal features provides an additional constraint on coronal heating mechanisms. Title: A new perspective on the sun from SOHO-challenges for atomic physics Authors: Dere, Kenneth; Mason, Helen Bibcode: 1998AIPC..434..213D Altcode: 1998amda.conf..213D The Solar and Heliospheric Observatory (SOHO) carries several ultraviolet spectrometers to diagnose the plasma conditions of the solar atmosphere in order to address several outstanding questions in solar research: why is the corona hot and how is the solar wind accelerated. Diagnostic techniques for determining the magnetohydrodynamic state (magnetic field, density, temperature, velocity) are discussed. We describe the CHIANTI database which has been designed to provide the necessary spectroscopic diagnostics for these data as well as for other spectroscopic missions. The database is built on 3 main files for each ion: atomic energy levels, radiative data, and electron collisional data. The electron collision strengths are assessed and scaled using the Burgess and Tully scaling laws. Analyses of EUV line intensities often reveal discrepancies between observed and predicted line intensities of about of 2 when considering lines of the same ion. A more recent analysis has shown that it is possible to arrive at a subset of EUV spectral lines where the line intensities are reproducible to within about 25%. For X-ray lines, as will be observed by AXAF, there is still considerable need for energy levels, radiative data and collision strengths, particularly for the Δn>=1 transitions. Title: LASCO/EIT Observations of Coronal Mass Ejections from Large-Scale Filament Channels Authors: Plunkett, S. P.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Brueckner, G. E.; Thompson, B. J.; Delaboudiniere, J. -P. Bibcode: 1998ASPC..150..475P Altcode: 1998npsp.conf..475P; 1998IAUCo.167..475P No abstract at ADS Title: CHIANTI - an Atomic Database For Emission Lines Paper I: Wavelengths Greater than 50 Angstroms Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Fossi, B. C. M.; Young, P. R. Bibcode: 1998ASPC..143..390D Altcode: 1998sigh.conf..390D No abstract at ADS Title: LASCO and EIT Observations of the Dynamic Corona Authors: Dere, K. P.; Brueckner, G. E. Bibcode: 1998HiA....11..861D Altcode: No abstract at ADS Title: Important atomic processes in solar physics Authors: Dere, K. Bibcode: 1998sese.conf..283D Altcode: No abstract at ADS Title: White-Light Coronal Mass Ejections: A New Perspective from LASCO Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.; Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner, G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere, K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis, D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark, J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker, D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D. Bibcode: 1997ESASP.415..103S Altcode: 1997cpsh.conf..103S No abstract at ADS Title: The Structure of "halo" Coronal Mass Ejections Authors: Vourlidas, A.; Howard, R. A.; Dere, K. P.; Passwaters, S. E. Bibcode: 1997AAS...191.7305V Altcode: 1997BAAS...29.1321V We investigate the relation between the structure of "halo" coronal mass ejections (CMEs) and the global coronal structure. In particular, we compare two "halo" events which occured on October 21, 1997 and were observed with the SoHO/LASCO coronographs at a high cadence. Although the two CME occured at different locations on the solar disk, they both exhibit similar morphology which appear to be influenced by the global coronal structure. By comparing the data from the coronaraphs, EIT and magnetograms, we will attempt to decipher the interplay between the ejected material and the surrounding corona. Title: LASCO observations of CMEs with helical geometries Authors: Dere, K. Bibcode: 1997AAS...19112005D Altcode: 1997BAAS...29R1402D In the past, many observations of coronal mass ejections (CMEs) have been obtained. Nevertheless, their structure and magnetic topology remains an open question. Previous observations have often been found consistent with simple loop, arcade or bubble geometries. More recently, helical flux rope geometries have been suggested by Low, Chen, Rust and Kumar, and Wu et al. Observations of CMEs with the LASCO coronagraphs on SOHO include events which appear to be consistent with a toroidal geometry. This topology is also that deduced for magnetic clouds observed near the Earth. Examples of helical CMEs observed with LASCO are presented and analyzed. Title: Analysis of Coronal Mass Ejections observed by LASCO Authors: Subramanian, P.; Dere, K. P.; Howard, R. A.; St. Cyr, C.; Brueckner, G. E. Bibcode: 1997AAS...191.7306S Altcode: 1997BAAS...29.1321S The LASCO instrument on the SOHO spacecraft has been observing coronal mass ejections from the sun from February 1996 to the present time. This covers a range of solar activity ranging from near-minimum activity to increasing activity. We present a database of coronal mass ejection locations, times and velocities. These are then compared with photospheric magnetic field patterns and large scale coronal structures. We hope to gain an understanding of coronal mass ejection initiation mechanisms through these observations. Preliminary results from our analyses will be presented here. Title: LASCO Observations of Disconnected Magnetic Structures Out to Beyond 28 Solar Radii During Coronal Mass Ejections Authors: Simnett, G. M.; Tappin, S. J.; Plunkett, S. P.; Bedford, D. K.; Eyles, C. J.; St. Cyr, O. C.; Howard, R. A.; Brueckner, G. E.; Michels, D. J.; Moses, J. D.; Socker, D.; Dere, K. P.; Korendyke, C. M.; Paswaters, S. E.; Wang, D.; Schwenn, R.; Lamy, P.; Llebaria, A.; Bout, M. V. Bibcode: 1997SoPh..175..685S Altcode: Two coronal mass ejections have been well observed by the LASCO coronagraphs to move out into the interplanetary medium as disconnected plasmoids. The first, on July 28, 1996, left the Sun above the west limb around 18:00 UT. As it moved out, a bright V-shaped structure was visible in the C2 coronagraph which moved into the field-of-view of C3 and could be observed out to beyond 28 solar radii. The derived average velocity in the plane of the sky was 110 ± 5 km s-1 out to 5 solar radii, and above 15 solar radii the velocity was 269 ± 10 km s-1. Thus there is evidence of some acceleration around 6 solar radii. The second event occurred on November 5, 1996 and left the west limb around 04:00 UT. The event had an average velocity in the plane of the sky of ∼54 km s-1 below 4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km s-1. In both events the rising plasmoid is connected back to the Sun by a straight, bright ray, which is probably a signature of a neutral sheet. In the November event there is evidence for multiple plasmoid ejections. The acceleration of the plasmoids around a projected altitude of 5 solar radii is probably a manifestation of the source surface of the solar wind. Title: First View of the Extended Green-Line Emission Corona At Solar Activity Minimum Using the Lasco-C1 Coronagraph on SOHO Authors: Schwenn, R.; Inhester, B.; Plunkett, S. P.; Epple, A.; Podlipnik, B.; Bedford, D. K.; Eyles, C. J.; Simnett, G. M.; Tappin, S. J.; Bout, M. V.; Lamy, P. L.; Llebaria, A.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D. Bibcode: 1997SoPh..175..667S Altcode: The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres. Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial `streamer sheet' clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4) Within the first 4 months of observation, only one single `fast' feature was observed moving outward at a speed of 70 km s-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity belt. Title: EIT Observations of the Extreme Ultraviolet Sun Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner, G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.; Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R. Bibcode: 1997SoPh..175..571M Altcode: The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. Title: CHIANTI - an atomic database for emission lines Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Monsignori Fossi, B. C.; Young, P. R. Bibcode: 1997A&AS..125..149D Altcode: A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides a database of atomic energy levels, wavelengths, radiative data and electron excitation data for ions which are abundant in cosmic plasmas. The most recent electron excitation data have been assessed and stored following the method of \cite[Burgess \& Tully (1992)]{bur92}. The current version is essentially complete for specifying the emission spectrum at wavelengths greater than 50 Angstroms. A list of observed lines in the spectral region between 50 and 1100 Angstroms has been compiled and compared with the lines predicted by the CHIANTI database. The CHIANTI database reproduces the vast majority of lines observed at these wavelengths. CHIANTI includes IDL (Interactive Data Language) routines to calculate optically thin synthetic spectra for equilibrium conditions. IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies are also included. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. Title: The Relationship of Green-Line Transients to White-Light Coronal Mass Ejections Authors: Plunkett, S. P.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; St. Cyr, O. C.; Socker, D. G.; Wang, D.; Simnett, G. M.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Tappin, S. J.; Schwenn, R.; Lamy, P. L.; Llebaria, A. Bibcode: 1997SoPh..175..699P Altcode: We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green-line transients that could be clearly associated with coronal mass ejections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds >25 km s-1, may be classified as `whip-like' transients. They are associated with the core of the white-light CMEs, identified with erupting prominence material, rather than with the leading edge of the CMEs. The third green-line transient has a markedly different appearance and is more gradual than the other two, with a projected outward speed <10 km s-1. This event corresponds to the leading edge of a `streamer blowout' type of CME. A dark void is left behind in the emission-line corona following each of the fast eruptions. Both fast emission-line transients start off as a loop structure rising up from close to the solar surface. We suggest that the driving mechanism for these events may be the emergence of new bipolar magnetic regions on the surface of the Sun, which destabilize the ambient corona and cause an eruption. The possible relationship of these events to recent X-ray observations of CMEs is briefly discussed. Title: MHD Interpretation of LASCO Observations of a Coronal Mass Ejection as a Disconnected Magnetic Structure Authors: Wu, S. T.; Guo, W. P.; Andrews, M. D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J. Bibcode: 1997SoPh..175..719W Altcode: We present a qualitative and quantitative comparison of a single coronal mass ejection (CME) as observed by LASCO (July 28-29, 1996) with the results of a three-dimensional axisymmetric time-dependent magnetohydrodynamic model of a flux rope interacting with a helmet streamer. The particular CME considered was selected based on the appearance of a distinct `tear-drop' shape visible in animations generated from both the data and the model. Title: EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.; Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M. Bibcode: 1997SoPh..175..601D Altcode: We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200-400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. Title: Origin and Evolution of Coronal Streamer Structure During the 1996 Minimum Activity Phase Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Kraemer, J. R.; Rich, N. B.; Andrews, M. D.; Brueckner, G. E.; Dere, K. P.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Paswaters, S. E.; Socker, D. G.; Wang, D.; Lamy, P. L.; Llebaria, A.; Vibert, D.; Schwenn, R.; Simnett, G. M. Bibcode: 1997ApJ...485..875W Altcode: We employ coronal extrapolations of solar magnetograph data to interpret observations of the white-light streamer structure made with the LASCO coronagraph in 1996. The topological appearance of the streamer belt during the present minimum activity phase is well described by a model in which the Thomson-scattering electrons are concentrated around a single, warped current sheet encircling the Sun. Projection effects give rise to bright, jet-like structures or spikes whenever the current sheet is viewed edge-on multiple spikes are seen if the current sheet is sufficiently wavy. The extreme narrowness of these features in polarized images indicates that the scattering layer is at most a few degrees wide. We model the evolution of the streamer belt from 1996 April to 1996 September and show that the effect of photospheric activity on the streamer belt topology depends not just on the strength of the erupted magnetic flux, but also on its longitudinal phase relative to the background field. Using flux transport simulations, we also demonstrate how the streamer belt would evolve during a prolonged absence of activity. Title: Nonthermal Velocities in the Solar Transition Zone and Corona Authors: Doyle, J. G.; O'Shea, E.; Erdélyi, R.; Dere, K. P.; Socker, D. G.; Keenan, F. P. Bibcode: 1997SoPh..173..243D Altcode: Nonthermal velocities are presented for spectral lines covering the temperature range 10 4-10 6 K, measured from high-spectral-resolution data for several solar features observed at the limb by the high resolution telescope and spectrograph (HRTS), including a coronal hole, `quiescent regions' and several small-scale active regions. These results are compared with predictions based on acoustic waves and heating via Alfvén waves. It is likely that more than one mechanism is operating simultaneously, in particular, resonant Alfvén wave heating, which is very sensitive to background plasma motions. Title: Measurements of Flow Speeds in the Corona Between 2 and 30 R⊙ Authors: Sheeley, N. R.; Wang, Y. -M.; Hawley, S. H.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997ApJ...484..472S Altcode: Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursuing this idea, we have tracked the birth and outflow of 50-100 of the most prominent moving coronal features and find that:

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

2. They move radially outward, maintaining constant angular spans and increasing their lengths in rough accord with their speeds, which typically double from 150 km s-1 near 5 R⊙ to 300 km s-1 near 25 R⊙.

3. Their individual speed profiles v(r) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s-2 through most of the 30 R⊙ field of view. This profile is consistent with an isothermal solar wind expansion at a temperature of about 1.1 MK and a sonic point near 5 R⊙.

Based on their relatively small initial sizes, low intensities, radial motions, slow but increasing speeds, and location in the streamer belt, we conclude that these moving features are passively tracing the outflow of the slow solar wind. Title: Association of Extreme-Ultraviolet Imaging Telescope (EIT) Polar Plumes with Mixed-Polarity Magnetic Network Authors: Wang, Y. -M.; Sheeley, N. R.; Dere, K. P.; Duffin, R. T.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Harvey, J. W.; Branston, D. D.; Delaboudinière, J. -P.; Artzner, G. E.; Hochedez, J. F.; Defise, J. M.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert, W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Clette, F. Bibcode: 1997ApJ...484L..75W Altcode: SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The chromospheric λ8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable clarity. We find that the Fe IX λ171 polar plumes occur where minority-polarity flux is in contact with flux of the dominant polarity inside each polar hole. Moreover, the locations of ``plume haze'' coincide approximately with the patterns of brightened He II λ304 network within the coronal hole. The observations appear to be consistent with mechanisms of plume formation involving magnetic reconnection between unipolar flux concentrations and nearby bipoles. The fact that minority-polarity fields constitute only a small fraction of the total magnetic flux within the polar holes suggests that plumes are not the main source of the high-speed polar wind. Title: The Solar-B Mission Authors: Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila, Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon; Harvey, John; Hathaway, David; Hudson, Hugh; Moore, Ronald; Lites, Bruce; Rust, David; Strong, Keith; Title, Alan Bibcode: 1997STIN...9721329A Altcode: Solar-B, the next ISAS mission (with major NASA participation), is designed to address the fundamental question of how magnetic fields interact with plasma to produce solar variability. The mission has a number of unique capabilities that will enable it to answer the outstanding questions of solar magnetism. First, by escaping atmospheric seeing, it will deliver continuous observations of the solar surface with unprecedented spatial resolution. Second, Solar-B will deliver the first accurate measurements of all three components of the photospheric magnetic field. Solar-B will measure both the magnetic energy driving the photosphere and simultaneously its effects in the corona. Solar-B offers unique programmatic opportunities to NASA. It will continue an effective collaboration with our most reliable international partner. It will deliver images and data that will have strong public outreach potential. Finally, the science of Solar-B is clearly related to the themes of origins and plasma astrophysics, and contributes directly to the national space weather and global change programs. Title: Using LASCO Observations to Infer Solar Wind Flow Near the Sun Authors: Sheeley, N. R., Jr.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Koomen, M. J.; Paswaters, S. E.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; St Cyr, O. C.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997SPD....28.0301S Altcode: 1997BAAS...29..907S We have continued to track individual coronal features as they become detached from helmet streamers and move outward from the Sun. The composite speed profile for 50-100 features has a parabolic shape with a constant acceleration of about 4 m/s(2) over the 2-30 R field of view. This well-determined speed profile contrasts strongly with the nearly uniform scatterplot obtained for about 50 nominal coronal mass ejections (CMEs), and suggests that these detached bits of coronal ``debris'' are passively tracing the speed of the slow solar wind. We have also begun the more difficult task of tracking outflow along polar plumes and will summarize these results as of June 1997. Title: EIT and LASCO observations of the initiation of a coronal mass ejection Authors: Dere, K.; Brueckner, G. E.; Delaboudiniere, J. -P. Bibcode: 1997SPD....28.0502D Altcode: 1997BAAS...29R.908D We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 200 kms and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 400 kms. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R_⊙. Of particular interest is the fact that this large scale event, spanning as much as 70 degrees in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 10(4) km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. Title: Observations of Coronal Features by EIT above an Active Region by EIT and Implications for Coronal Heating Authors: Neupert, W. M.; Newmark, J.; Thompson, B. J.; Catura, R.; Moses, J. D.; Portier-Fozzani, F.; Delaboudiniere, J. P.; Gabriel, A.; Artzner, G.; Clette, F.; Cugnon, P.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Howard, R.; Michels, D.; Dere, K.; Freeland, S.; Lemen, J.; Stern, R.; Gurman, J. Bibcode: 1997SPD....28.0115N Altcode: 1997BAAS...29..881N The EUV Imaging Telescope (EIT) on the SOHO provides the capability for multi-wavelength imaging of the corona in four spectral bands, centered at 171, 195, 284, and 304 Angstroms, using multilayer telescope technology. These bands encompass coronal temperatures from 1 MK to 2.5 MK as well as the upper chromosphere, at about 60,000 K. In particular, nearly simultaneous imaging in the 171 and 195 Angstrom bands, the former including major Fe IX and Fe X emission lines, the latter including a strong Fe XII line, provides a capability to infer the morphology and characteristics of the corona at temperatures of 1.0 - 1.7 MK. We have examined the corona in this temperature range over an active region observed from SOHO from May - September, 1996 and find that low-lying loops (below a density scale height of 75,000 km, characteristic of Fe X) vary little in brightness and temperature along their length. For features extending to greater heights, however, both brightness gradients and temperature gradients are observed. Preliminary analysis of the observations when the region was on the West limb on September 30 indicates a small positive temperature gradient of approximately 0.5 K/km in one loop system that extended above 100,000 km. On the other hand, a nearly radial feature extending to the edge of the EIT FOV was isothermal or had at most a slight negative temperature gradient. Such measurements may have application to the modeling of coronal loops and streamers and the processes of coronal heating and solar wind acceleration. Title: VizieR Online Data Catalog: CHIANTI - An Atomic Database For Emission Lines I. (Dere+ 1997) Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Monsignori Fossi, B. C.; Young, P. R. Bibcode: 1997yCat..41250149D Altcode: A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides a database of atomic energy levels, wavelengths, radiative data and electron excitation data for ions which are abundant in cosmic plasmas. The most recent electron excitation data have been assessed and stored following the method of Burgess & Tully (1992A&A...254..436B). The current version is essentially complete for specifying the emission spectrum at wavelengths greater than 50Å. A list of observed lines in the spectral region between 50 and 1100Å has been compiled and compared with the lines predicted by the CHIANTI database. The CHIANTI database reproduces the vast majority of lines observed at these wavelengths. CHIANTI includes IDL (Interactive Data Language) routines to calculate optically thin synthetic spectra for equilibrium conditions. IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies are also included. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. (1 data file). Title: Imaging the solar corona in the EUV Authors: Delaboudiniere, J. -P.; Stern, R. A.; Maucherat, A.; Portier-Fozzani, F.; Neupert, W. M.; Gurman, J. B.; Catura, R. C.; Lemen, J. R.; Shing, L.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Michels, D. J.; Moses, J. D.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Clette, F.; Cugnon, P.; van Dessel, E. L. Bibcode: 1997AdSpR..20.2231D Altcode: The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 A˚ images the chromosphere and the base of the transition region at a temperature of 5 - 8 x 10^4 K; the Fe IX-X filter at 171 A˚ images the corona at a temperature of ~ 1.3 x 10^6 K; the Fe XII filter at 195 A˚ images the quiet corona outside coronal holes at a temperature of ~ 1.6 x 10^6 K; and the Fe XV filter at 284 A˚ images active regions with a temperature of ~ 2.0 x 10^6 K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection. Title: Dynamical Evolution of a Coronal Mass Ejection (CME) to Magnetic Cloud: A Preliminary Analysis of the January 6-10, 1997 CME Observed by LASCO/SOHO Authors: Wu, S. T.; Guo, W. P.; Michels, D. J.; Andrews, M. D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Bougeret, Jean-Louis; Lamy, P. L.; Schwenn, R.; Simnett, G. M. Bibcode: 1997ESASP.404..739W Altcode: 1997cswn.conf..739W No abstract at ADS Title: EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker, D. G.; Delaboudiniere, J. P.; Hochedez, J. F.; Lamy, P. L.; Schwenn, R.; Simnett, G. M.; Defise, J. M.; Catura, R. C. Bibcode: 1997IAUJD..19E..18D Altcode: We present the first observations of the initiation of a corona mass ejection (CME) seen on the disk of the Sun. Observations with the EIT and LASCO experiments on SOHO show that the CME starts in a small volume and is associated with slow motions of prominence material. At about the same time, a shock wave is created that travels out into the corona at a velocity of 400 km s^{-1} ahead of an eruptive prominence. This shock wave is clearly the event that is later seen as a classical CME when observed in the coronagraph above 1.5 solar radii. Although the CME clearly starts in a small region, a chain of activity near the limb may also be associated with this event. Title: First Results from EIT Authors: Clette, F.; Delaboudiniere, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. -F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise, J. -M.; Jamar, C.; Rochus, P.; Chauvineau, J. -P.; Marioge, J. -P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Maucherat, A.; Cugnon, P.; van Dessel, E. L. Bibcode: 1997ASPC..118..268C Altcode: 1997fasp.conf..268C The Extreme-UV Imaging telescope has already produced more than 15000 wide-field images of the corona and transition region, on the disk and up to 1.5R_⊙ above the limb, with a pixel size of 2.6\arcsec. By using four different emission lines, it provides the global temperature distribution in the quiet corona, in the range 0.5 to 3*E(6) K. Its excellent sensitivity and wide dynamic range allow unprecedented views of low emission features, even inside coronal holes. Those so-called ``quiet'' regions actually display a wide range of dynamical phenomena, in particular at small spatial scales and at time scales going down to only a few seconds, as revealed by all EIT time sequences of full- or partial-field images. The initial results presented here demonstrate the importance of this wide-field imaging experiment for a good coordination between SOHO and ground-based solar telescopes, as well as for science planning. Title: The Rate of Magnetic Reconnection Observed in the Solar Atmosphere Authors: Dere, Kenneth P. Bibcode: 1996ApJ...472..864D Altcode: The structure of the solar corona is often observed to evolve in a manner that is generally attributed to the process of magnetic field line reconnection. The spatial and temporal scales for a variety of reconnection events have been examined on the basis of descriptions in the scientific literature. These events tend to fall into two general categories. In the first category, reconnection proceeds as the corona adjusts itself to the emergence of new magnetic flux. In the second category, the field lines have been explosively blown open by a flare or mass ejection, and the field lines eventually return to a more potential field configuration by means of reconnection. Estimates of the density, temperature, and magnetic field strength in the reconnection volume provide a basis on which to calculate the reconnection rate expected for resistive diffusion, tearing mode reconnection, and reconnection at the Alfvén speed. The observed temporal and spatial scales of the reconnection events indicate that the rate of reconnection is on the order of 0.001-0.1 of the Alfvén rate, the Alfvén speed divided by the observed length scale. This indicates that the effective Reynolds number for large-scale structures in the corona is of the order of 10- 1000. In none of the cases examined does the reconnection appear to be driven by external flows, but the process is more properly described as the relaxation of nonpotential magnetic field configurations toward a potential configuration. Title: STEREO: a solar terrestrial event observer mission concept Authors: Socker, Dennis G.; Antiochos, S. K.; Brueckner, Guenter E.; Cook, John W.; Dere, Kenneth P.; Howard, Russell A.; Karpen, J. T.; Klimchuk, J. A.; Korendyke, Clarence M.; Michels, Donald J.; Moses, J. Daniel; Prinz, Dianne K.; Sheely, N. R.; Wu, Shi T.; Buffington, Andrew; Jackson, Bernard V.; Labonte, Barry; Lamy, Philippe L.; Rosenbauer, H.; Schwenn, Rainer; Burlaga, L.; Davila, Joseph M.; Davis, John M.; Goldstein, Barry; Harris, H.; Liewer, Paulett C.; Neugebauer, Marcia; Hildner, E.; Pizzo, Victor J.; Moulton, Norman E.; Linker, J. A.; Mikic, Z. Bibcode: 1996SPIE.2804...50S Altcode: A STEREO mission concept requiring only a single new spacecraft has been proposed. The mission would place the new spacecraft in a heliocentric orbit and well off the Sun- Earth line, where it can simultaneously view both the solar source of heliospheric disturbances and their propagation through the heliosphere all the way to the earth. Joint observations, utilizing the new spacecraft and existing solar spacecraft in earth orbit or L1 orbit would provide a stereographic data set. The new and unique aspect of this mission lies in the vantage point of the new spacecraft, which is far enough from Sun-Earth line to allow an entirely new way of studying the structure of the solar corona, the heliosphere and solar-terrestrial interactions. The mission science objectives have been selected to take maximum advantage of this new vantage point. They fall into two classes: those possible with the new spacecraft alone and those possible with joint measurements using the new and existing spacecraft. The instrument complement on the new spacecraft supporting the mission science objectives includes a soft x-ray imager, a coronagraph and a sun-earth imager. Telemetry rate appears to be the main performance determinant. The spacecraft could be launched with the new Med-Lite system. Title: Next-generation EUV imaging spectrometer for solar flare observations Authors: Moses, J. Daniel; Brueckner, Guenter E.; Dere, Kenneth P.; Korendyke, Clarence M.; Moulton, Norman E.; Prinz, Dianne K.; Seely, John F.; Socker, Dennis G.; Bruner, Marilyn E.; Lemen, James R. Bibcode: 1996SPIE.2804..260M Altcode: The Naval Research Laboratory Skylab SO82A slitless spectrograph provided solar flare observations that have never been equaled in diagnostic capabilities for interpreting thermal flare physics. Improvements in detector technology, optics and optical coating technology, and almost two decades of analysis of SO82A data can be combined with the basic concept of an EUV objective grating spectrograph to build an instrument to address many of the remaining mysteries of solar flares. This next generation instrument incorporates two sets of two identical, orthogonally mounted slitless spectrographic Cassegrain telescopes. Each telescope consists of a multilayer coated, Wadsworth mount objective grating and multilayer coated spherical secondary mirror; a backside illuminated CCD detector is installed at the focal plane. The orthogonal mounting changes the dispersion direction by 90 degrees on the disk image; processing on the two resulting images allows recovery of the undispersed disk image and spectral line profiles. The resulting instrument will obtain high time cadence, spectrally-dispersed images with improved spatial resolution, dynamic range, signal-to-noise ratio, and velocity discrimination. Title: A Model for Active Region Emission at Centimeter Wavelengths Authors: Nindos, A.; Alissandrakis, C. E.; Gelfreikh, G. B.; Kundu, M. R.; Dere, K. P.; Korzhavin, A. N.; Bogod, V. M. Bibcode: 1996SoPh..166...55N Altcode: We present multi-frequency observations and model computations of the microwave emission of a solar active region. The radio observations were obtained with the RATAN-600 at several wavelengths between 0.8 and 31.6 cm and with the VLA at 6 and 20 cm. The active region was also observed in the EUV O Iv lines by the HRTS instrument aboard the Space Shuttle Spacelab-2 mission. These lines are formed in the chromosphere-corona transition region and their intensity ratio is sensitive to pressure. Photospheric magnetograms provided both the longitudinal and the transverse component of the magnetic field. The microwave observations were checked against model computations taking into account both the free-free and the gyro-resonance emission mechanisms and using the pressure data from the O IV lines. The magnetic field was computed through constant-α force-free extrapolations of the longitudinal photospheric field. We computed both the flux from 2 to 20 cm and the spatial structure of the microwave emission at 6 and 20 cm. The comparison of the computed and observed flux spectra allowed us to estimate the magnetic field strength at the base of the transition region and in the low corona, as well as the values of the conductive flux and the height of the base of the transition region. The model maps at 6 cm and 20 cm showed that α was not constant above the active region; the same conclusion was reached on the basis of the photospheric observations. The use of pressure measurements allowed us to identify microwave structures which were determined by pressure enhancements. At 6 cm the computations confirmed the fact that the magnetic field is the principal factor that determines the structure of sunspot-associated sources and showed that the effect of pressure variations was small. Pressure variations were more important at 20 cm, where the peak of the emission was associated with the sunspot and a diffuse component was associated with the plage which had an average pressure higher by a factor of 1.54 than the sunspot. Title: CHIANTI - an Atomic Database for Emission Line Spectroscopy: Version 1 - Wavelengths greater than 50 Angstroms Authors: Dere, K. P.; Monsignori-Fossi, B. C.; Landi, E.; Mason, H. E.; Young, P. R. Bibcode: 1996AAS...188.8501D Altcode: 1996BAAS...28..961D A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides an atomic database of energy levels (wavelengths), radiative data and electron excitation data for ions which are abundant in astrophysical plasmas. The most recent electron excitation data have been assessed and stored following the method of Burgess and Tully (1992). CHIANTI includes IDL (Interactive Data Language) routines to produce optically thin synthetic spectra for lambda > 50 Angstroms, assuming equilibrium conditions. It also includes IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. Title: LASCO Observations of the 03Feb96 Streamer Blow-out Authors: Andrews, M. D.; Korendyke, C. M.; Koomen, M. J.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C. St.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M. Bibcode: 1996AAS...188.3716A Altcode: 1996BAAS...28..880A The C2 and C3 telescopes on the Large Angle Spectrometric Coronograph (LASCO) have recorded images of a Streamer Blow-out which occured on 03Feb96. We will present a series of images produces by combining data from the 2 coronographs. These images show a rapid evolution of the coronal streamer belt over projected distances of 2 to 20 solar radii. The streamer belt shows a dramatic brightening, which is seen to propagate outward. A bubble-like structure is seen to move away from the Sun and expand. At the end of this event, the equatorial corona is significantly less bright than prior to the event. Title: LASCO Observations of the Solar Corona to 32 Rsun Authors: Cook, J. W.; Koomen, M. J.; Korendyke, C. M.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Morrill, J. S.; Moses, J. D.; Socker, D. G.; Paswaters, S. E.; Wang, D.; Moulton, N. E.; Cyr, O. C. St.; Andrews, M. D.; Schwenn, R.; Podlipnik, B.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.; Plunkett, S.; Biesecker, D. A. Bibcode: 1996AAS...188.3717C Altcode: 1996BAAS...28..880C The Large Angle Spectrometric Coronagraph (LASCO) was launched on board the SOHO satellite on 2 December 1995. The C3 externally-occulted coronagraph of LASCO observes the solar corona over a field from 3.7-32 R_ ⊙, using a 1024x1024 CCD detector with a pixel size corresponding to 56 arc sec. Observations can be made using color filters ranging from the blue (420-520 nm) to the near-IR (860-1050 nm), and through polarizing filters. We report on early observations of the solar corona out to 32 Rsun. Title: Preliminary Photometric Calibration of LASCO C3 Coronagraph Images using Pre-Flight Laboratory Images of Standard Sources and In-Flight Images of Standard Stars Authors: Korendyke, C. M.; Koomen, M. J.; Andrews, M. D.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M. Bibcode: 1996AAS...188.3621K Altcode: 1996BAAS...28..876K The C3 coronagraph is a wide field (+/-8.0 degrees), externally occulted, white light coronagraph. The instrument is one of three coronagraphs comprising the Large Angle Spectrometric COronagraph (LASCO) experiment mounted on the Solar Heliospheric Observatory satellite. The satellite was launched on Dec. 2, 1996; C3 observations began in early Jan. 1997. The coronagraph optical train includes a set of five broadband color filters mounted in a wheel. Prior to flight, an image was obtained through each color filter of a well characterized, rear-illuminated, opal glass diffusing screen. The C3 in-flight images, in addition to the coronal structures, also contain several hundred bright stars. We present a comparison of the photometric calibration derived from standard stars with the laboratory measurements. The resulting calibration is then used to examine color variations in the white light corona over the field of view. The LASCO experiment was developed by a scientific consortium of members from NRL (USA), MPAe (Germany), LAS (France) and U. Birmingham (United Kingdom). Title: Observations of the South coronal hole from EIT and YOHKOH Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel, A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.; Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr, O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert, W.; Einfalt, E.; Newmark, J. Bibcode: 1996AAS...188.0206H Altcode: 1996BAAS...28..821H The Extreme ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft is capable of studying solar transition region, chomospheric and coronal plasmas over bandpasses optimized for He II 304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 - 1.0 MK), Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 - 2.5 MK) with 2.5 arcsecond spatial resolution. This telescope in concert with the Yohkoh/SXT instrument allows us to simultaneously observe solar structures at temperatures ranging from less than 0.1MK in the transition region to over 3MK in the solar corona. EIT has had several opportunities to observe the South coronal hole with high spatial and temporal resolution. We compare observations from EIT and SXT with an eye towards correlating temporal variations over the range of wavelengths, activity of polar crown filament systems and relating large-scale morphology of the X-ray corona to the transition region in He II. Title: There's No Such Thing as the Quiet Sun: EUV Movies from SOHO Authors: Gurman, J. B.; Delaboudiniere, J. P.; Artzner, G.; Gabriel, A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.; Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; Cyr, O. C. St.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Neupert, W.; Einfalt, E.; Newmark, J. Bibcode: 1996AAS...188.3718G Altcode: 1996BAAS...28..880G We present unique time series of high-resolution solar images from the normal-incidence Extreme ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft. With a pixel scale of 2.6 arc sec and a detector dynamic range of > 10(4) , the EIT can be used to study the dynamics of chromospheric and coronal features in multilayer bandpasses optimized for He II 304 Angstroms (0.08 MK), Fe IX/X 171, 173 Angstroms (0.8 - 1.0 MK), Fe XII 195 Angstroms (1.5 MK), and Fe XV 284 Angstroms (2.0 - 2.5 MK). Among the most striking features of the digital movies we will display are: the dynamic nature of small-scale loop features in the polar coronal holes, the constant activity of the polar crown filament systems, the locations of the bases of polar plumes, the presence of dark (scattering) filament material in the coronal emission line images, and the evolution of a unique, linear, dark feature in a young active region. The latter feature is suggestive of the ``coronal void'' observed in the electron scattering corona by Macqueen et al./ (1983). Title: Coronal structure and heating: comparison between SXT/Yohkoh observations of an active region and magnetogram Authors: Cheng, C. -C.; Dere, K. P.; Wu, S. T.; Hagyard, M. J.; Hiei, E. Bibcode: 1996AdSpR..17d.205C Altcode: 1996AdSpR..17..205C We have studied the magnetic structure in AR 7150 (S09E06) observed on 29 April 1992 by the Soft X-Ray Telescope (SXT) on Yohkoh. The observed X-ray images are compared with force-free magnetic fields with different values of alpha, extrapolated from the MSFC photospheric magnetogram observed at the same time. The results show that the magnetic field of the active region is not potential. Different groups of loops are characterized by different values of alpha. Bright loops correspond to field with large alpha, indicating twisting of the loop. However, there is no obvious correlation between the brightness of individual loops with the amount of twist. Further investigation of the magnetic state of the loop structure requires accurate nonlinear force-free calculations. Title: Observations of the south coronal hole from EIT and Yohkoh. Authors: Handy, B. N.; Catura, R.; Freeland, S.; Lemen, J.; Stern, R.; Gurman, J. B.; Delaboudinière, J. P.; Artzner, G.; Gabriel, A.; Maucherat, A.; Defise, J. M.; Jamar, C.; Rochus, P.; Clette, F.; Cugnon, P.; Howard, R.; Michels, D.; Moses, J. D.; Dere, K.; St. Cyr, O. C.; Neupert, W.; Einfalt, E.; Newmark, J. Bibcode: 1996BAAS...28Q.821H Altcode: No abstract at ADS Title: Nonthermal velocities in the solar transition and coronal region observed with the high-resolution telescope and spectrograph Authors: O'Shea, E.; Doyle, J. G.; Dere, K. P.; Keenan, F. P. Bibcode: 1996ASPC..109..145O Altcode: 1996csss....9..145O No abstract at ADS Title: Observations of the comet Hyakutake by the LASCO coronagraph on the SOHO satellite. Authors: Andrews, M. D.; Paswaters, S. E.; Brueckner, G. E.; Korendyke, C. M.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morril, J. S.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunket, S.; Simnet, G. M. Bibcode: 1996BAAS...28.1195A Altcode: No abstract at ADS Title: EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission Authors: Delaboudinière, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Maucherat, A.; Clette, F.; Cugnon, P.; Van Dessel, E. L. Bibcode: 1995SoPh..162..291D Altcode: The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 å), Fe XII (195 å), Fe XV (284 å), and He II (304 å) to provide sensitive temperature diagnostics in the range from 6 × 104 K to 3 × 106 K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes. Title: The Large Angle Spectroscopic Coronagraph (LASCO) Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J. Bibcode: 1995SoPh..162..357B Altcode: The Large Angle Spectroscopic Coronagraph (LASCO) is a three coronagraph package which has been jointly developed for the Solar and Heliospheric Observatory (SOHO) mission by the Naval Research Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France), the Max-Planck-Institut für Aeronomie (Germany), and the University of Birmingham (UK). LASCO comprises three coronagraphs, C1, C2, and C3, that together image the solar corona from 1.1 to 30 R⊙ (C1: 1.1 - 3 R⊙, C2: 1.5 - 6 R⊙, and C3: 3.7 - 30 R⊙). The C1 coronagraph is a newly developed mirror version of the classic internally-occulted Lyot coronagraph, while the C2 and C3 coronagraphs are externally occulted instruments. High-resolution imaging spectroscopy of the corona from 1.1 to 3 R⊙ can be performed with the Fabry-Perot interferometer in C1. High-volume memories and a high-speed microprocessor enable extensive on-board image processing. Image compression by a factor of about 10 will result in the transmission of 10 full images per hour. Title: Ultraviolet Observations of the Structure and Dynamics of an Active Region at the Limb Authors: Korendyke, C. M.; Dere, K. P.; Socker, D. G.; Brueckner, G. E.; Schmieder, B. Bibcode: 1995ApJ...443..869K Altcode: The structure and dynamics of active region NOAA 7260 at the limb have been studied using ultraviolet spectra and spectroheliograms obtained during the eighth rocket flight of the Naval Research Laboratory's High Resolution Telescope an Spectrograph (HRTS). The instrument configuration included a narrow-bandpass spectroheliograph to observe the Sun in the lines of C IV lambda 550 and a tandem-Wadsworth mount spectrograph to record the profiles of chromospheric transition region and coronal lines in the 1850-2670 A region. The combination of high spatial resolution and high spectral purity C IV slit jaw images with ultraviolet emission-line spectra corresponding allows examination of a variety of active region phenomena. A time series of spectroheliograms shows large-scale loop systems composed of fine-scale threads with some extending up to 100 Mm above the limb. The proper motion of several supersonic features, including a surge were measured. The accelerated plasmas appear in several different geometries and environments. Spectrograph exposures were taken with the slit positioned at a range of altitudes above the limb and provide a direct comparison between coronal, transition region and chromospheric emission line profiles. The spectral profiles of chromospheric and transition region emission lines show line-of-sight velocities up to 70 km/s. These lower temperature, emission-line spectra show small-scale spatial and velocity variations which are correlated with the threadlike structures seen in C IV. Coronal lines of Fe XII show much lower velocities and no fine structure. Title: The Rate of Magnetic Reconnection in the Solar Corona Authors: Dere, K. P. Bibcode: 1995SPD....26..612D Altcode: 1995BAAS...27..963D No abstract at ADS Title: EIT: The Extreme Ultraviolet Imaging Telescope. Synoptic Observations of Small and Large-Scale Coronal Structures Authors: Clette, F.; Delaboudinière, J. P.; Dere, K. P.; Cugnon, P.; EIT Science Team Bibcode: 1995LNP...444..251C Altcode: 1995cmer.conf..251C The EIT will provide wide-field images of the corona and transition region, on the solar disc and up to 1 R⊙ above the limb. Its normal incidence multilayer-coated optics will select the spectral emission lines of four ions (Fe IX, 171 Å; Fe XII, 195 Å; Fe XV, 284 Å; Hell, 304 Å), providing a sensitive temperature diagnostic in the range 6.104 to 3.106K. This SOHO instrument will thus probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere. The EIT's characteristics and performances are presented, and prospects for coordinated observations with ground-based radio observatories are outlined. Title: Magnetic Structure and Heating of an Active Region: Comparison Between SXT/Yohkoh Observations and Magnetogram Authors: Cheng, C. -C.; Dere, K. P.; Wang, Jingxiu; Ai, Guoxiang Bibcode: 1994AAS...185.8604C Altcode: 1994BAAS...26.1464C We have studied the magnetic structure of AR7420 observed on 9 February 1993 by the Soft X-Ray Telescope (SXT) on Yohkoh. The observed X-ray images of the active region are compared with various force-free magnetic fields, extrapolated from the photospheric magnetograms obtained at the same time by the Huairou Station of the Beijing Astronomical Observatory. The results show that the magnetic configuration of the active region is not a potential field. Different groups of loops are characterized by different values of alpha , indicating that the loops are twisted and that there are currents flowing through them. Here alpha is given by nabla times B=alpha B for a force free field, where B is the magnetic field. In particular, we find that there are opposite current systems in the active region, as specified by positive and negative values of alpha . In addition, we find that there is no obvious correlation between the brightness of individual loops with the amount of twist. Implications of the results will be discussed. Title: Hierarchy of spatial scale sin UV prominences Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P. Bibcode: 1994SSRv...70..175S Altcode: Ultraviolet spectra of a quiescent prominence observed with theHigh Resolution Telescope and Spectrograph (HRTS) are analyzed. Different techniques lead to greatly different spatial scales for the prominence structures. The UV spectra show strong variations in intensity and Doppler shift on scales larger than 1700 km. Spectroscopic diagnostics employing line intensity ratios indicate the existence of scales between 400 m to some hundred kilometers. We attempt to interpret various aspects of the prominence intensities and velocities with a multiple thread model. Title: Solar mass flow in fine-scale structures Authors: Dere, K. P. Bibcode: 1994SSRv...70...21D Altcode: Observations of transient and steady velocities at chromospheric, transition region and coronal temperatures in the quiet Sun and coronal holes are reviewed. The relevance of fine-scale structures in governing the mass balance of the solar atmosphere is stressed. At present, a coherent picture of these mass flows does not exist. However, the current observational base of transition region and coronal velocity information is limited but should greatly improve with measurements from the SOHO satellite. Title: Solar Fine-Scale Structures in the Corona, Transition Region, and Lower Atmosphere Authors: Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.; Martin, S. F.; Zirin, H. Bibcode: 1994ApJ...430..913M Altcode: The American Science and Engineering Soft X-ray Imaging Payload and the Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) were launched from White Sands on 1987 December 11 in coordinated sounding rocket flights. The goal was to investigate the correspondence of fine-scale structures from different temperature regimes in the solar atmosphere, and particularly the relationship between X-ray bright points (XBPs) and transition region explosive events. We present results of the analysis of co-aligned X-ray images, maps of sites of transition region explosive events observed in C IV 105, HRTS 1600 A spectroheliograms of the Tmin region, and ground-based magnetogram and He I 10830 A images. We examined the relationship of He I 10830 A dark features and evolving magnetic features which correspond to XBPs. We note a frequent double ribbon pattern of the He I dark feature counterparts to XBPs. We discuss an analysis of the relationship of XBPs to evolving magnetic features by Webb et al., which shows that converging magnetic features of opposite polarity are the most significant magnetic field counterparts to XBPs. The magnetic bipolar features associated with XBPs appear as prominent network elements in chromospheric and transition region images. The features in C IV observations corresponding to XBP sites are in general bright, larger scale (approximately 10 arcsec) regions of complex velocity fields of order 40 km/s, which is typical of brighter C IV network elements. These C IV features do not reach the approximately 100 km/s velocities seen in the C IV explosive events. Also, there are many similar C IV bright network features without a corresponding XBP in the X-ray image. The transition region explosive events do not correspond directly to XBPs. The explosive events appear to be concentrated in the quiet Sun at the edges of strong network, or within weaker field strength network regions. We find a greater number of C IV events than expected from the results of a previous Spacelab 2 HRTS disk survey. We attribute this at least partly to better spatial resolution with the newer HRTS data. The full-disk X-ray image shows a pattern of dark lanes in quiet Sun areas. The number density of C IV events is twice as large inside as outside a dark lane (4.6 x 10-3 vs. 2.3 x 10-3 explosive events per arcsec 2). The dark lane corresponds to an old decaying magnetic neutral line. We suggest that this provides an increased opportunity for small-scale convergence and reconnection of opposite polarity magnetic field features, in analogy with the results of Webb et al. for XBPs but at a reduced scale of reconnection. Title: HRTS Observations of Explosive Events in a Flaring Active Region Authors: Dere, K. P.; Martin, S. F. Bibcode: 1994kofu.symp..289D Altcode: Explosive events are a highly dynamic, small-scale phenomena that are commonly observed on the Sun with the NRL High Resolution Telescope and Spectrograph (HRTS). There is now considerable evidence which suggests that they are signatures of magnetic reconnection during flux emergence and cancellation. Data from the Big Bear Solar Observatory and the HRTS instrument are used to demonstrate the direct correspondence between explosive events and evolving magnetic structures. Title: Combined HRTS-8 Sounding Rocket Observations and YOHKOH Soft X-ray Observations of NOAA Active Region 7260 at the Solar Limb Authors: Korendyke, C. M.; Dere, K. P.; Brueckner, G. E.; Waljeski, K.; Lemen, J. R. Bibcode: 1994kofu.symp..293K Altcode: On 24 August 1992, the Naval Research Laboratory (NRL) High Resolution Telescope and Spectrograph (HRTS) was launched aboard a Black Brant sounding rocket from White Sands, New Mexico. During the flight, the instrument recorded a unique set of near ultraviolet slit spectra and 1550 A spectroheliograms of an active region at the solar limb. An extensive set of observations of this region were obtained with the Yohkoh Soft X-ray Telescope (SXT) near the time of the flight. The C IV spectroheliograms obtained during this flight are some of the highest resolution images of the solar transition region ever obtained. The spectra and spectroheliograms dramatically demonstrate the fundamental difference between coronal and chromospheric/transition-region plasmas at 700 km spatial scales. The cooler plasmas exhibit a great deal of dynamic, fine scale structure with significant flows or proper motion particularly in the transition zone loops. The coronal emission lines in the spectra! are relatively uniform and quiescent. The Yohkoh data during the period before and after the flight show a set of diffuse high temperature coronal loops with only minimal correspondence to the structures visible in the C IV spectroheliograms. Title: The Composition of a Coronal Active Region Authors: Waljeski, K.; Moses, D.; Dere, K. P.; Saba, J. L. R.; Strong, K. T.; Webb, D. F.; Zarro, D. M. Bibcode: 1994ApJ...429..909W Altcode: The relative abundances of iron, oxygen, magnesium, and neon in a coronal active region are determined from measurements of soft X-ray line and broadband intensities. The emission measure, temperature, and column density are derived from these measured intensities and are used to place a constraint on the abundances of the heavier elements relative to hydrogen in the corona. The intensity measurements were made on 1987 December 11, when an active region was observed jointly by the American Science and Engineering (AS&E) High Resolution Soft X-Ray Imaging Sounding-Rocket Payload and the X-Ray Polychromator Flat Crystal Spectrometer (FCS) onboard the Solar Maximum Mission spacecraft. The coordinated observations include images through two broadband filters (8 to 29 A and 8 to 39, 44 to 60 A) and profiles of six emission lines: Fe XVII (15.01 A), FE VIII (15.26 A), O VIII (18.97 A), Mg XI (9.17 A), Ne IX (13.44 A), and Fe XVIII (14.21 A). The effects of resonance scattering are considered in the interpretation of the FCS line intensities. We calculated the expected intensity ratio of the two Fe XVII lines as a function of optical depth and compared this ratio with the observed intensity ratio to obtain the optical depths of each of the lines and the column density. The line intensities and the broadband filtered images are consistent with the emission from a thermal plasma where Fe, O, Mg, and Ne have the 'adopted coronal' abundances of Meyer (1985b) relative to one another, but are not consistent with the emission from a plasma having photospheric abundances: The ratios of the abundances of the low first ionization potential (FIP) elements (Fe and Mg) to the abundances of the high-FIP elements (Ne and O) are higher than the ratios seen in the photosphere by a factor of about 3.5. This conclusion is independent of the assumption of either an isothermal or a multithermal plasma. The column densities derived from the Fe XVII line ratio and the geometry of the active region provide a diagnostic of the abundance of hydrogen relative to the heavier elements. We find that the abundance of iron with respect to hydrogen in the corona is higher than the value given Meyer (1985b) by a factor of 8.2(-5.4, +5.1). This means that, for the observed active region, the absolute abundances of the low-FIP elements (Fe and Mg) are enhanced in the corona relative to the photosphere, while the abundances of the high-FIP elements (Ne and O) are either slightly enhanced in the corona or nearly the same in the photosphere and the corona. Title: Explosive events, magnetic reconnection, and coronal heating Authors: Dere, K. P. Bibcode: 1994AdSpR..14d..13D Altcode: 1994AdSpR..14...13D Signatures of explosive events are prominent in transition region spectra where they display exceptionally large velocities (>100 km s-1) in small areas (1500 km). Their physical properties, deduced from previous analyses of HRTS spectra and more recent work, are summarized here. It now appears that the explosive events are associated with the process of magnetic cancellation and HRTS data obtained during the most recent rocket flight in 1990 provide direct evidence for this assertion. Flux cancellation, which tends to proceed on time-scales of hours, most likely involves magnetic reconnection in a very bursty manner which explains the small, short-lived explosive events. These reconnection events are part of a larger pattern where small flux elements emerge in the supergranule centers and are transported to the boundaries to continually regenerate the network fields on a timescale of about 8 hours. These timescales are also sufficiently short to account for the energetics of the quiet sun. Title: Observational characteristics of explosive events Authors: Hénoux, J. -C.; Dere, K. P. Bibcode: 1994LNP...432..203H Altcode: The characteristics of dynamic phenomena observed in the EUV with the HRTS instruments, chromospheric jets and explosive events, are reviewed here. Most of the review is devoted to explosive events that are short duration explosions involving a plasma at 105 K. These events are characterised by strong Doppler shifts rather than by brightness enhancements, contrary to EUV impulsive brightenings observed by SMM. They are presumably due to magnetic reconnection involving unresolved fine structures of the magnetic field near the network. The role of the density of concentrated magnetic fluxtubes in a reconnection scenario has still to be understood. Title: Observational characteristics of explosive events. Authors: Hénoux, J. C.; Dere, K. P. Bibcode: 1994LNP...432..205H Altcode: 1994LNPM...11..205H The characteristics of dynamic phenomena observed in the EUV with the HRTS instruments, chromospheric jets and explosive events, are reviewed. Most of the review is devoted to explosive events that are short duration explosions involving a plasma at 105K. These events are characterised by strong Doppler shifts rather than by brightness enhancements, contrary to EUV impulsive brightenings observed by SMM. They are presumably due to magnetic reconnection involving unresolved fine structures of the magnetic field near the network. The role of the density of concentrated magnetic fluxtubes in a reconnection scenario has still to be understood. Title: A New Synthetic XUV Spectrum Authors: Dere, K. P.; Mason, H. E.; Fossi, B. C. Monsignori; Waljeski, K. H. Bibcode: 1993AAS...18311203D Altcode: 1993BAAS...25.1459D We have begun a program to develop a synthetic XUV spectrum for the 70 - 2500 /AA wavelength region based on a critical analysis of the most recent calculations of atomic parameters, in particular, atomic collision strengths and their thermal averages. Ultraviolet spectra returned by the EUVE and HST instruments demonstrate a continued need for the most accurate atomic parameters in order to determine the physical conditions in the emitting plasmas. Most previous synthetic spectra has relied heavily on the gaunt factor approximation which can predict excitation rates only for dipole transitions and only to within a factor of 2 to 3. In many cases, direct calculations of the collision strengths are now available. Burgess and Tully (1992) have developed a technique for critically evaluating collision strength calculations and scaling and compacting the data. Different scalings are available for resonance, intercombination and forbidden excitations. This method will be applied in the construction of our spectrum. In the end, we intend to produce a set of critically evaluated atomic parameters from which the nearly optically thin spectrum of a low density astrophysical plasma can be calculated, together with the programs necessary to perform these calculations. We will include the ability to prescribe elemental abundances and to correct for optical depth and populations of metastable levels as a function of density. The data sets and programs will be made available by anonymous ftp. Title: A Description of the HRTS-8 Instrument Configuration Authors: Korendyke, C. M.; Dere, K. P.; Brueckner, G. E.; Socker, D. G. Bibcode: 1993BAAS...25.1182K Altcode: No abstract at ADS Title: HRTS Untraviolet Observations of the Chromosphere Transition Region and Corona of a Solar Active Region Authors: Dere, K. P.; Korendyke, C. M.; Brueckner, G. E. Bibcode: 1993BAAS...25.1182D Altcode: No abstract at ADS Title: UV prominences observed with the HRTS: structure and physical properties Authors: Wiik, J. E.; Dere, K.; Schmieder, B. Bibcode: 1993A&A...273..267W Altcode: Ultraviolet spectra of two quiescent prominences (PL1, PL2) observed with the High Resolution Telescope and Spectrograph (HRTS) are described and analyzed. Meudon synoptic maps and spectroheliograms indicate that prominence PL 1 was extremely active during the flight and that material ejections were likely. PL2 appeared to be a more stable prominence. The significant differences between the spectra of the two prominences can perhaps be explained by their levels of activity. The spectrum of the more active prominence PL1 is dominated by transition zone lines formed near 105 K whereas the second prominence PL2 shows considerable emission of cooler chromospheric lines formed near 2 × 1O4 K. PL 1 also exhibits larger bulk flow velocities (up to ∼ 30 km s-1) and non-thermal velocities (∼20km s-1). From line ratios (O IV, N V, N IV, Si IV) a relatively large electron density (∼1011 cm-3) is derived for the PL1 prominence transition region (PTR). In comparison, PL2 is a relatively quiet prominence with bulk flow velocities generally less than ∼3 km s-1.

Different techniques yield greatly different spatial scales for the prominence. The UV spectra show strong variations in intensity and Doppler shift on scales of about 1700km. The combined density and emission measures indicate path lengths of 400 m or less. The optical depth in C IV requires path lengths of 40 km or less. If, as suggested by these analyses, it is assumed that prominence emission is due to a number of micro-structures with a Gaussian velocity distribution, then spatial scales of the micro-structures of a few hundred kilometers are found. Title: Transition Region Explosive Events in an X-Ray Dark Lane Region of the Quiet Sun Authors: Cook, J. W.; Moses, D.; Brueckner, G. E.; Dere, K. P.; Bartoe, J. -D. F.; Webb, D.; Davis, J. M.; Harvey, J. W.; Recely, F.; Martin, S. F.; Zirin, H. Bibcode: 1993BAAS...25.1181C Altcode: No abstract at ADS Title: Scaling Laws for Coronal Heating: X-ray Loop Observations Authors: Waljeski, K.; Dere, K. P.; Moses, D. Bibcode: 1993BAAS...25.1212W Altcode: No abstract at ADS Title: Nonthermal Velocities in the Solar Transition Zone Observed with the High-Resolution Telescope and Spectrograph Authors: Dere, K. P.; Mason, H. E. Bibcode: 1993SoPh..144..217D Altcode: Data obtained during the first rocket flight of the NRL High Resolution Telescope and Spectrograph (HRTS) have been used to study nonthermal velocities for spectral lines primarily covering the temperature range 104 to 2 × 106 K. The high spectral and spatial resolution, combined with an enhanced dynamic intensity range of the reduced data, has enabled us to study the distribution of the nonthermal velocities for quiet and active regions. Average values of the nonthermal velocities peak at about 27 km s−1 at 105 K for the quiet regions, with a wide distribution of nonthermal velocities for each line. The active region nonthermal velocities have a narrower distribution which is weighted towards higher values. The SiIV and C IV line profiles are not well described by a single Gaussian, indicating that high-velocity components (above 30 km s−1) are present in the quiet-Sun spectra. The radiative losses for all plasma above l05 K have been calculated for the quiet Sun, an active region and a coronal hole. These have been compared with the acoustic wave flux inferred from the nonthermal line widths. There appears to be a sufficient flux of waves to heat these regions of the atmosphere. Title: Observational test of coronal heating models. Authors: Waljeski, Katrina; Dere, Ken P.; Moses, Dan Bibcode: 1992ESASP.348..281W Altcode: 1992cscl.work..281W The properties of coronal loops are measured and used to test the predictions of coronal heating models. The coronal loop temperature, emission measure, geometry, and magnetic field strength are measured from broadband soft X-ray images obtained by the American Science and Engineering High Resolution Soft X-Ray Imaging Sounding Rocket Payload and from coordinated ground-based observations. The radiative energy loss rates for these loops, calculated from the observed plasma properties, are compared to the scalings with loop length or magnetic field strength predicted by various models of coronal heating. The loop scaling laws of Rosner, Tucker, and Vaiana and of Golub et al. are also tested with these observations. Title: Solar corona synoptic observations from SOHO with an Extreme Ultraviolet Imaging Telescope. Authors: Delaboudinière, J. P.; Gabriel, A. H.; Artzner, G. E.; Dere, K.; Howard, R.; Michels, D.; Catura, R.; Lemen, J.; Stern, R.; Gurman, J.; Neupert, W.; Cugnon, P.; Koeckelenbergh, A.; van Dessel, E. L.; Jamar, C.; Maucherat, A. Bibcode: 1992ESASP.348...21D Altcode: 1992cscl.work...21D The major scientific objective of the EUV Imaging Telescope (EIT) is to study the evolution of coronal structure over a wide range of spatial and temporal scales and temperatures. A second strategic objective is to provide full disk synoptic maps of the global corona to aid in unifying SOHO (Solar and Heliospheric Observatory)/Cluster investigations. EIT will also provide images to support the planning of detailed spectroscopic investigations by the CDS (Coronal Diagnostic Spectrometer) and SUMER spectrometers in SOHO. EIT observations will be made in four narrow spectral bands, centered at 171 A (Fe 9), 195 A(Fe 12), 284 A (Fe 15), and 304 A (He 2) representing restricted temperature domains within a wide temperature range from 40,000 to 3,000,000 K. The results will be images of the solar atmosphere from the upper chromosphere and transition region to the active region corona. These maps, made at appropriate time intervals, will be used to study the fine structures in the solar corona and to relate their dynamic properties to the underlying chromosphere and photosphere. Dynamic events in the inner corona will be related to white light transients in the outer corona, and observations of the internal structure of coronal holes will be used to investigate origins of the solar wind. Title: Intensity, velocity and turbulence in prominences observed with the HRTS instrument. Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P. Bibcode: 1992JAF....43...36S Altcode: No abstract at ADS Title: Explosive events and magnetic reconnection in the solar atmosphere Authors: Dere, K. P. Bibcode: 1992AIPC..267...63D Altcode: 1992ecsa.work...63D Explosive events are highly-dynamic, small-scale phenomena commonly observed in spectra of transition zone lines. Their velocities are near 100 km s-1, sizes near 1500 km, and time scales near 60 s. They occur at a height of 1000-2000 km, below typical transition zone structures. It has been demonstrated that some explosive events are caused by emerging magnetic flux and there is good evidence to indicate that the great majority are related to magnetic flux cancellation. The most probable mechanism for their generation is magnetic reconnection. The characteristics of explosive events and flux cancellation taken together show that magnetic reconnection in the quiet sun apparently proceeds readily in rapid bursts along the neutral line separating opposite flux elements that are convected together by photospheric flows. Title: Ultraviolet Explosive Events and Evolving Magnetic Fields Authors: Dere, K. P.; Martin, S. F. Bibcode: 1992AAS...180.5604D Altcode: 1992BAAS...24..821D No abstract at ADS Title: Intensity, velocity and turbulence in prominences observed with the HRTS. Authors: Wiik, J. E.; Dere, K.; Schmieder, B. Bibcode: 1992ESASP.344...65W Altcode: 1992spai.rept...65W The moments of UV emission line profiles between 1206 and 1670 A observed in two quiescent prominences with the High Resolution Telescope and Spectrograph (HRTS) are analysed. Spectral lines in this region of the solar spectrum provide information on plasmas in the 10000K to 200000K range. In both prominences a good correlation is found between the intensities of lines formed at different temperatures. A good correlation is also found between the non-thermal velocities of different lines. Title: LASCO - Large Angle Spectrometric Coronagraph for SOHO Authors: Howard, R. A.; Brueckner, G. E.; Dere, K. P.; Korendyke, C. M.; Koomen, M. J.; Michels, D. J.; Moses, D.; Socker, D. G.; Schwenn, R.; Inhester, B.; Lamy, P.; Maucherat, A.; Simnett, G. M.; Eyles, C. Bibcode: 1992AAS...180.3307H Altcode: 1992BAAS...24..781H No abstract at ADS Title: Transition region dynamics. Authors: Dere, K. P. Bibcode: 1992ESASP.344...43D Altcode: 1992spai.rept...43D The solar transition region has qualities that make it an ideal testing ground for theories of coronal heating and dynamics. Strong diagnostic lines formed at transition region temperatures (2×105 to 106K) are found at VUV wavelengths that are observable with relatively straightforward optical techniques. The transition region is highly dynamic; nonthermal velocities peak at 105K and high velocity explosive events, indicators of magnetic reconnection, are commonly found throughout the quiet and active sun. The fine-scale density and velocity structures indicate that important information will be found at spatial scales below 1″ Title: Dynamics in the Prominence - Corona Transition Region from HRTS Spectra Authors: Schmieder, B.; Dere, K. P.; Wiik, J. E. Bibcode: 1992LNP...399..333S Altcode: 1992esf..coll..333S; 1992IAUCo.133..333S Line profiles of UV emission lines between 1206Å and 1670Å observed in two prominences with the High Resolution Telescope and Spectrograph (HRTS) are analysed. Spectral lines in this region of the solar spectrum such as C I, Fe II, Si IV and C IV, provide information on plasmas in the 10 000 K to 200 000 K range. In the active prominence observed with HRTS-1 a good correlation is found between the intensities and velocities of different lines formed over a range of temperatures. On the contrary, poor cross correlation between the velocities observed in plasmas of cold temperatures indicates the presence of different structures in the SL2 prominence. Microturbulent velocities from 0 to 25km s-1 are found in both prominences. Title: The chromospheric and transition region manifestations of an Ellerman bomb. Authors: Cook, J. W.; Brueckner, G. E.; Dere, K. P.; Martin, S. F.; Gayley, K. G. Bibcode: 1992BAAS...24.1074C Altcode: No abstract at ADS Title: Explosive events and magnetic reconnection in the solar atmosphere Authors: Dere, K. P. Bibcode: 1992sws..coll...11D Altcode: Signatures of explosive events are prominent in transition region spectra where they display large (100 km/s) in small areas (1500 km). Their physical properties, deduced from previous analyses of HRTS spectra and more recent work, are summarized here. It now appears that the explosive events are associated with the process of magnetic cancellation and HRTS data obtained during the most recent rocket flight in 1990 provide direct evidence for this assertion. Flux cancellation, which tends to proceed with timescales of hours, most likely involved magnetic reconnection in a very bursty manner which explains the small, short-lived explosive events. Title: Relative Abundances in the Lower Solar Transition Region Authors: Doschek, G. A.; Dere, K. P.; Lund, P. A. Bibcode: 1991ApJ...381..583D Altcode: Properties of the lower solar transition region as determined from UV spectral lines recorded by the Naval Research Laboratory HRTS are investigated. The spectra were obtained from a rocket flight in July 1975. Variations of intensity ratios of strong lines of C IV, Si IV, C II, Si III, and O IV over the entire field of view of the HRTS instrument, which extends from disk center to the solar limb are discussed. The largest apparent abundance variations appear to be in the active regions surrounding a sunspot. The C/Si ratio is lower in the active regions than anywhere else in the instrument field of view, implying a lower C/Si abundance ratio in the active regions. There is a possible correlation of line intensity variation in the active region with Doppler shift of the lines; the explanation for this is unclear. The magnitude and reality of intensity ratio variations of all observed solar features are discussed, and monotonic center-to-limb intensity ratio variations due to the opacity of some of the spectral lines are measured. Title: Velocity Gradients in the Chromosphere-Corona Transition Region Authors: Athay, R. G.; Dere, K. P. Bibcode: 1991ApJ...381..323A Altcode: Velocity data obtained from Doppler shifts of EUV spectral lines observed with the High Resolution Telescope and Spectrograph flown on Spacelab II are analyzed to determine the properties of the mean velocities V-bar and its spatial variance V(sigma), for chromospheric and transition region lines. The lines studied include the ions O I, C I, Fe II, C II, Si III, Si IV, and C IV. The constancy of V(sigma) from center to limb together with a systematic maximum redshift in V-bar in central disk regions is interpreted to mean that the plasma flow is divergent from the tops of closed field lines and that the cool plasma more or less fills the magnetic loops from which most of the radiation originates. The same is true of the hotter plasma. It is suggested that the crossfield component of Delta T is large and that the alternation from cool loops to hot loops occurs on spatial scales much less than 1 arcsec. Title: Chromospheric and Transition Region Diagnostics Using Emission-Line Intensities Authors: Athay, R. G.; Dere, K. P. Bibcode: 1991ApJ...379..776A Altcode: EUV emission-line intensities from the HRTS experiment on Spacelab 2 are analyzed to determine the causes of intensity variations from point to point on the solar surface. Chromospheric lines of O I and transition region lines of C II, Si IV, and C IV exhibit saturation effects that limit the line intensities in the brighter regions. No such effect is found in lines of C I, Fe II, or Si III. The chromospheric lines saturate because the optical thickness exceeds the thermalization depth, whereas the transition region lines saturate because of the geometry of the unresolved fine structure. The latter is assumed to consist of elongated cylinder-like features oriented along magnetic lines of force that are mainly vertical. Saturation occurs when the optical thickness along the axis of the cylinders exceeds unity. Estimates based on the observed saturation effects give fill factors for the fine structure 0.005 and 0.4 at 100,000 K and 30,000 K, respectively. The corresponding lengths of the cylinders are estimated at 1000 km and 40 km at the two temperatures. Title: Explosive events and magnetic reconnection in the solar atmosphere Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Ewing, J.; Lund, P. Bibcode: 1991JGR....96.9399D Altcode: Explosive events are highly energetic, small-scale phenomena which are frequently detected throughout the quiet and active Sun. They are seen in profiles of spectral lines formed at transition zone temperatures as exceptionally Doppler-shifted features, typically at 100 km s-1 to the red and/or blue of the rest wavelength. Sufficient observational evidence has now been developed to demonstrate that some explosive events are associated with the emergence of new magnetic flux. In these cases it is likely that the acceleration of plasma is caused by the magnetic reconnection resulting from flux emergence. We take as a working hypothesis the proposal that all explosive events are the result of magnetic reconnection. Since explosive events tend to occur on the edges of high photospheric magnetic field regions, we identify them with reconnection that occurs during the cancellation of photospheric magnetic flux (Martin, 1984; Livi et al., 1985). The combined observational characteristics of photospheric flux cancellation and transition zone explosive events provide powerful diagnostic information concerning the nature of magnetic reconnection. Reconnection in the quiet solar atmosphere apparently proceeds in bursts at sites much smaller than the boundary between opposite polarity flux elements that are observed to cancel in magnetograph sequences. Equating the velocity of the expelled transition zone plasma with the Alfvén speed yields magnetic field strengths of 20 G at the site of reconnection. The speed at which the reconnection proceeds is commensurate with the rapid rates predicted by Petschek (1964). ©1991 American Geophysical Union Title: The Magnetic Network Location of Explosive Events Observed in the Solar Transition Region Authors: Porter, J. G.; Dere, K. P. Bibcode: 1991ApJ...370..775P Altcode: Compact short-lived explosive events have been observed in solar transition region lines with the High-Resolution Telescope and Spectrograph (HRTS) flown by the Naval Research Laboratory on a series of rockets and on Spacelab 2. Data from Spacelab 2 are coaligned with a simultaneous magnetogram and near-simultaneous He I 10,380 -A spectroheliogram obtained at the National Solar Observatory at Kitt Peak. The comparison shows that the explosive events occur in the solar magnetic network lanes at the boundaries of supergranular convective cells. However, the events occur away from the larger concentrations of magnetic flux in the network, in contradiction to the observed tendency of the more energetic solar phenomena to be associated with the stronger magnetic fields. Title: The Prime Energy Release of a Solar Flare Authors: Brueckner, G. E.; Moses, D.; Cook, J. W.; Dere, K. P.; Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F. Bibcode: 1991BAAS...23.1026B Altcode: No abstract at ADS Title: Nonthermal Velocities in the Solar Transition Region Authors: Dere, K. P.; Mason, H. E. Bibcode: 1991BAAS...23Q1028D Altcode: No abstract at ADS Title: Flaring Active Region Structures in the Corona, Transition Region, and Lower Atmosphere Observed in the SAROC Authors: Moses, D.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F. Bibcode: 1991BAAS...23.1026M Altcode: No abstract at ADS Title: Coordinated observations with high resolution spectrographs (HRTS, SERTS, MSDP) Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas, R. J.; Dere, K. P. Bibcode: 1991AdSpR..11e.255S Altcode: 1991AdSpR..11R.255S Observations with the High Resolution Telescope Spectrograph (HRTS) aboard Spacelab2 in 1985, and more recently with the Solar Extreme-ultraviolet Rocket Telescope and Spectrometer (SERTS) during the rocket flight of May 5, 1989 were well coordinated with the Meudon instruments, principally with the Multichannel Subtractive Double Pass (MSDP) spectrograph. These instruments allow the study of phenomena in a large temperature range and the determination of the energy budget. MSDP observations coordinated with the SERTS have permitted the analysis of physical parameters of coronal plasma surrounding dynamical chromospheric events, such as preflaring region and a filament. By combining Hα spectrograms and HRTS data, C IV flow (~50 km s-1) detected at the footpoints of a prominence has been interpreted by horizontal velocities along the axis of the arches of the prominence. Title: High resolution solar physics from rockets Authors: Dere, K. P. Bibcode: 1991AdSpR..11e.191D Altcode: 1991AdSpR..11..191D Explosive events are highly energetic phenomena that are frequently seen throughout the quiet and active sun, particularly in spectral lines formed at transition zone temperatures. Sufficient observational evidence has now been developed to conclusively demonstrate that some explosive events are caused by magnetic reconnection in emerging magnetic flux regions. It is also consistent with observations of photospheric magnetic flux cancellation to propose that all explosive events are the result of magnetic reconnection. By combining the observational facts concerning photospheric flux cancellation and transition zone explosive events it can be shown that reconnection in the quiet solar atmosphere proceeds in bursts at sites much smaller than the boundary between opposite polarity flux elements that are observed to cancel in magnetograph sequences. Title: Bifurcation in the Low Chromosphere Authors: Athay, R. Grant; Dere, K. P. Bibcode: 1990ApJ...358..710A Altcode: Bright chromospheric faculae of diameter d(c) covering an area of the solar disk f(c) smaller than 1 yield a predictable level of limb brightening. For a resolution diameter d(r), the combination of f(c) and d(c) leads, also, to a prediction of the fraction, phi(0), of observing pixels (resolution areas) that are free of facular emission. Data from the first flight of the High Resolution Telescope and Spectrograph of the U.S. Naval Research Laboratory with d(r) about 1 arcsec are used to measure both the level of limb brightening and phi(0) in EUV emission lines of O I, C I, and Fe II. The results favor f(c) about 0.9 and d(c) greater than about 2.5 arcssec. It is concluded that the chromospheric temperature rise is present over about 90 percent of the solar surface. Title: Flow patterns in a sunspot region observed in the photosphere, chromosphere and transition region Authors: Dere, K. P.; Schmieder, B.; Alissandrakis, C. E. Bibcode: 1990A&A...233..207D Altcode: The flow patterns around a sunspot at photospheric, chromospheric, and transition zone temperatures is examined. The spiral fibril pattern observed in H-alpha is consistent with a constant alpha force-free field extrapolation of the photospheric magnetic field. Evidence is found for the first time that C IV fibrils near spots follow the field lines parallel to the chromospheric H-alpha fibrils. The observed large-scale pattern of redshifts and blueshifts in the vicinity of the sunspot is stable and conforms to the typical Evershed flow patterns of radial outflow at the photospheric levels and radial inflows at the chromospheric and transition region levels. The three-dimensional velocity vectors associated with this flow are derived assuming an axially symmetric Evershed flow. Title: The High Resolution Telescope and Spectrograph (HRTS) on Board the Orbiting Solar Laboratory (OSL) Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Dere, K. P.; Socker, D. G. Bibcode: 1990BAAS...22..845B Altcode: No abstract at ADS Title: Coronal Dark Lanes and the Location of Transition Region Explosive Events Authors: Moses, D.; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Davis, J. M. Bibcode: 1990BAAS...22..899M Altcode: No abstract at ADS Title: The HRTS/OSL Vacuum Ultraviolet CCD Development Program Authors: Socker, D. G.; Dere, K. P.; Korendyke, C. M. Bibcode: 1990BAAS...22..889S Altcode: No abstract at ADS Title: Ultraviolet Spectra of a Prominence Authors: Dere, K.; Lund, P.; Schmieder, B. Bibcode: 1990BAAS...22R.815D Altcode: No abstract at ADS Title: Relationship between a spot and a filament observed during spacelab 2 mission Authors: Schmieder, B.; Dere, K. P.; Raadu, M. A.; Démoulin, P.; Alissandrakis, C. E. Bibcode: 1990AdSpR..10i.195S Altcode: 1990AdSpR..10..195S During the Spacelab 2 Mission, an active region including a sunspot, plages, fibrils and a filament which disappears during the observation period, was observed in Hα and in the C IV lines. The analysis of the observations leads to several conclusions. Shear in the active region filament is observed before its disappearance. Hα and C IV upflows in the filament are well correlated spatially, but the transition zone (C IV) velocities are an order of magnitude larger than the Hα chromospheric ones. Over the sunspot, the reverse-Evershed effect is observed in Hα and in C IV Dopplershift images while strong downflows are also detected in the C IV profiles.

Magnetograph data for the whole region are used to calculate the linear force-free magnetic field. A single value of the force-free parameter α is found to give a good fit to both the sheared filament structure and the sunspot spiral structures, indicating a causal relationship.

We propose a model based on the inductive coupling between current systems associated with the filament and the sunspot. Relaxation phenomena due to resistive effects in the filament could lead to irreversible conversion of magnetic energy into kinetic energy and heating. Title: Heating of the solar transition region in fine-scale structures Authors: Dere, K. P. Bibcode: 1990AdSpR..10i.169D Altcode: 1990AdSpR..10..169D Studies of the solar transition region with ultraviolet instruments such as the NRL High Resolution Telescope and Spectrograph (HRTS) point out the advantages of this region to understanding nonthermal heating in the solar atmosphere. In contrast to the classical picture where the transition zone is a thin region maintained simply by the dissipation of heat conducted down from the corona, high resolution spectroheliograms show that the transition zone consists of elongated structures that must be heated locally because the field aligned temperature gradients are insufficient to support the necessary conductive flux. An analysis of the observationally determined emission measures (ne2Δ1) and pressures of transition region structures reveals that they consist of fine-scale subresolution structures with dimensions less than 100 km. Further evidence for subresolution structure is found in spectral line widths which are wider than expected from thermal broadening. The velocity power spectrum, derived from both resolved motions evident in net Doppler shifts of line profiles and unresolved motions seen in the nonthermal widths, shows the need for significant power at scales of 10 km or less. The power, because it extends to such high wavenumbers, can be dissipated by viscosity and joule heating at a rate sufficient to maintain transition zone against its radiative losses. Title: A brief scientific history of the NRL HRTS program. Authors: Dere, K. P. Bibcode: 1990ppst.conf...29D Altcode: Since its first flight in 1975, the NRL High Resolution Telescope and Spectrograph (HRTS) has now recorded high quality ultraviolet spectra of the Sun on 6 rocket flights and during extended operations on the Space Shuttle Spacelab 2 mission in 1985. Title: The Relationship of C IV Transition Region Structures to the Photospheric Magnetic Field Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1990BAAS...22..744D Altcode: No abstract at ADS Title: High Resolution Spectrography in Ultraviolet Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas, R. J.; Dere, K. P. Bibcode: 1990PDHO....7..250S Altcode: 1990ESPM....6..250S; 1990dysu.conf..250S The authors point out some of the advantages of coordinated observations with ground-based and space instrumentation. Results obtained during the rocket flight of the Solar Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS) for a preflaring region are presented and the complementarity of observations is pointed out with the High Resolution Telescope and Spectrograph (HRTS) which permits the detection of dynamical structures in hot plasma surrounding cool structures such as prominences and sunspots seen in visible light. Title: Temperature and Center-Limb Variations of Transition Region Velocities Authors: Athay, R. G.; Dere, K. P. Bibcode: 1989ApJ...346..514A Altcode: HRTS data from the Spacelab 2 mission are used to derive the center-limb and temperature variations of the mean velocity and the velocity variance in the solar chromosphere and transition zone. The mean velocity is found to vary much more rapidly from center to limb and with temperature than does the velocity variance. Also, the mean velocity shows a characteristic signature at some magnetic neutral lines in accordance with the findings of Klimchuk (1987) from Solar Maximum Mission (SMM) data. The velocity variance does not show a characteristic signature at the neutral lines but shows an inverse correlation with intensity. The latter is interpreted as reduced velocity variance in strong field regions. The results are discussed in terms of downflow along lines of force in magnetic arcades. Title: Transition Zone Flows Observed in a Coronal Hole on the Solar Disk Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Recely, F. Bibcode: 1989ApJ...345L..95D Altcode: A rocket flight of the NRL High Resolution Telescope and Spectrograph (HRTS) was performed to obtain ultraviolet spectra of a well-defined coronal hole on the solar system. Observed emission lines included strong transition zone lines of C IV at 1548 and 1550 A, strong chromospheric lines of C I near 1560 A, and chromospheric lines of Fe (II) at 1563 A. Continuum radiation formed in the temperature minimum was also recorded. The cumulative histogram of the C IV velocities in the coronal hole shows an average Doppler shift of 2 km/sec to the red (downflow) with 26 percent of the profiles having blueshifts (outflows) compared to 7 percent in the quiet sun. The present observations have the advantages of higher spatial resolution and a nearly absolute wavelength scale determined from narrow chromospheric lines of Si I with an accuracy of about 1 km/sec. The nonthermal velocities, derived from the C IV line widths, are only marginally larger inside the coronal hole than those in the quiet sun, thus indicating that the magnitude of small-scale motions, which may represent energy available for coronal heating and solar wind acceleration, is equal in the two regions. Title: Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations Authors: Moses, J. Daniel; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Webb, D. F.; Davis, John M.; Recely, F.; Martin, S. F.; Zirin, H. Bibcode: 1989sxsr.reptR....M Altcode: The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the Tmin region and ground based magnetogram and He I 10830 A images. Title: Extreme ultraviolet imaging telescope on board the Solar Heliospheric Observatory Authors: Delaboudiniere, Jean-Pierre; Gabriel, Alan H.; Artzner, Guy E.; Millier, F.; Michels, Donald J.; Dere, Kenneth P.; Howard, Russell A.; Kreplin, Robert W.; Catura, Richard C.; Stern, Robert A.; Lemen, James R.; Neupert, Werner M.; Gurman, Joseph B.; Cugnon, P.; Koeckelenbergh, A.; van Dessel, E. L.; Jamar, Claude A.; Maucherat, Andre J.; Chauvineau, Jean-Pierre; Marioge, Jean-Paul Bibcode: 1989SPIE.1160..518D Altcode: 1989xeoa.conf..518D The design of the multibandpass Extreme-Ultraviolet Imaging Telescope designed for 1996 launch on board the Solar Heliospheric Observatory is described. The telescope will observe simultaneously distinct temperature ranges in the solar corona, defined by well chosen emission lines. Images in four narrow bandpasses at wavelengths ranging from 17 to 31 nm will be obtained using normal-incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. Results are presented on the performances measured on a 2/3 scale mock-up. The bandpasses could be adjusted to better than 1 percent in wavelength. Title: Turbulent Power and Dissipation in the Solar Transition Zone Authors: Dere, Kenneth P. Bibcode: 1989ApJ...340..599D Altcode: The power spectrum of the spatial velocity fluctuations of the solar transition zone are determined from high-resolution telescope and spectrograph solar spectra of C IV. It is found that virtually all of the power resides at higher wavenumbers and that the spectrum is flatter than predicted for the inertial range of a turbulent fluid. The results suggest that the small-scale fluctuations are maintained by a driving mechanism such as magnetic reconnection or wave motions produced in the photosphere. Title: Dynamics of a filament at the boundary of a SPOT region with magnetic shear Authors: Schmiedler, B.; Demoulin, P.; Raadu, M. A.; Dere, K. P. Bibcode: 1989A&A...213..402S Altcode: H-alpha (MSDP), magnetograph (Meudon), and C IV (HRTS) observations are used to investigate the relationship between the dynamics of a solar filament and a spot region with vortex structure. Comparisons are made between the structures in H-alpha and C IV intensity and Doppler-shift images. These show filament shearing and a good correlation between H-alpha and C IV upflow, the C IV filament being very dynamic (+ or - 50 km/s). Magnetograph data for the whole region including the sunspot are used to calculate linear force-free fields. The magnetic structure at the filament is found to be favorable for support. Title: The HRTS Guest Investigator Program Authors: Lund, P.; Ewing, J.; Cook, J.; Dere, K.; Brueckner, G. Bibcode: 1989BAAS...21..841L Altcode: No abstract at ADS Title: Comparison of HRTS Sounding Rocket Observations at 1600 Å and Hα with Groundbased Magnetograms and He I 10830 Å Images Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P. Bibcode: 1989BAAS...21..840C Altcode: No abstract at ADS Title: Ultraviolet Observations of Macrospicules at the Solar Limb Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Socker, D. G.; Ewing, J. W. Bibcode: 1989SoPh..119...55D Altcode: During the Spacelab 2 mission, the NRL High Resolution Telescope and Spectrograph (HRTS) obtained a time-series of broad-band ultraviolet images of macrospicules at the solar limb inside a polar coronal hole with a temporal resolution of 20 and 60 s. The properties of the macrospicules observed in the Spacelab data are measured and compared with the properties reported for EUV macrospicules observed during Skylab (Bohlin et al., 1975; Withbroe et al., 1976). There is a general agreement between the data sets but several differences. Because of the higher temporal resolution of the Spacelab data, it is possible to see macrospicules with shorter lifetimes than seen during Skylab, as well as variations on faster timescales. The largest (30-60') and fastest (150 km s -1) macrospicules seen during Skylab were not found in the Spacelab observations. The Spacelab data support the conclusion that many macrospicules decay by simply fading away. Title: Explosive Events in the Solar Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1989SoPh..123...41D Altcode: The properties of explosive events in the solar transition zone are presented by means of detailed examples and statistical analyses. These events are observed as regions of exceptionally high velocity (∼ 100 km s−1) in profiles of CIV, formed at 105 K, observed with the High Resolution Telescope and Spectrograph (HRTS). The following average properties have been determined from observations obtained during the third rocket flight of the HRTS: full width at half maximum extent along the slit - 1.6 × 103 km; maximum velocity - 110 km s−1; peak emission measure - 4 × 1041 cm−3; lifetime - 60 s; birthrate - 4 × 10−21 cm−2 s−1 in a coronal hole and 1 × 10−20 cm−2 s−1 in the quiet Sun; mass - 6 × 108 g; and, kinetic energy - 6 × 1022 erg. The 6 examples show that there are considerable variations from these average parameters in individual events. Although small, the events show considerable spatial structure and are not point-like objects. A spatial separation is often detected between the positions of the red and blue shifted components and consequently the profile cannot be explained by turbulence alone. Mass motions in the events appear to be isotropic because the maximum observed velocity does not show any correlation with heliographic latitude. Apparent motions of the 100 km s−1 plasmas during their 60 s lifetime should be detected but none are seen. The spatial frequency of occurrence shows a maximum near latitudes of 40-50°, but otherwise their sites seem to be randomly distributed. There is enough mass in the explosive events that they could make a substantial contribution to the solar wind. It is hard to explain the heating of typical quiet structures by the release of energy in explosive events. Title: HRTS Transition Region Observations of a Coronal Hole on the Solar Disk Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1989BAAS...21..841D Altcode: No abstract at ADS Title: A Model for the Heating of the Transition Region Authors: Antiochos, S. K.; Dere, K. P. Bibcode: 1989BAAS...21..841A Altcode: No abstract at ADS Title: Magnetic Associations of Explosive Events Authors: Porter, J. G.; Dere, K. P. Bibcode: 1989BAAS...21..852P Altcode: No abstract at ADS Title: Plasma Motions in an Emerging Flux Region Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere, K. P.; Socker, D.; Kurokawa, H.; McCabe, M. Bibcode: 1988ApJ...335..986B Altcode: Ultraviolet spectra of C IV show large nonthermal broadening in an area of emerging flux. These nonthermal motions are observed at a very early stage of reconnecting field lines. The spectra can be traced to small, rapidly changing surge or filament-like features which are seen in the center, blue, and red wing of H-alpha. They seem to have the characteristics of macrospicules or explosive events. They are precursors of the reconnection process. Plasma turbulence and/or plasma waves in the reconnecting plasma may cause the broad C IV line profiles. The activity in the transition zone precedes the formation of a bright chromospheric loop system. Title: LASCO: A wide-field white light and spectrometric coronagraph for SOHO Authors: Michels, D. J.; Schwenn, R.; Howard, R. A.; Bartoe, J. -D. F.; Antiochos, S. K.; Brueckner, G. E.; Cheng, C. -C.; Dere, K. P.; Doschek, G. A.; Mariska, J. T. Bibcode: 1988sohi.rept...55M Altcode: The scientific objectives of the LASCO (light and spectrometric coronagraph) project in the SOHO (solar and heliospheric observatory) mission are described. These include investigation of mechanisms for heating of the corona and acceleration of the solar wind, causes of coronal transients, and their role in development of large scale coronal patterns and interplanetary disturbances. The distribution and properties of dust particles, including those released from sun-grazing comets are investigated. Interactions of coronal plasma with the dust are studied. The corona is analyzed spectroscopically by a high-resolution scanning, imaging interferometer. The spectral profiles of three emission lines and one Fraunhofer line are measured for each picture point, giving temperatures, velocities, turbulent motions and volume densities. Polarization analysis yields the direction of coronal magnetic fields. Title: Gas Flows in the Transition Region above Sunspots Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.; Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Socker, D. G. Bibcode: 1988ApJ...334.1066K Altcode: Strong downflows and moderate upflows in the transition region over a sunspot have been observed with the HRTS on Spacelab 2 in 1985. The flows are persistent in the sense that they are seen in the same spot for 5 days. The downflows are prominent in regions of limited extent (4arcsec - 6arcsec), and flow velocities are in the range 40 - 80 km s-1 and are thus supersonic. Upward flows have smaller velocities, 5 - 20 km s-1, but may extend over a larger area. In the downflowing regions there is always an appreciable amount of gas at rest in the line of sight. Flow speeds derived from the profiles of different lines formed in the transition region between 30,000 and 230,000K are very similar implying constant downflow in this temperature range. Title: EIT: Solar corona synoptic observations from SOHO with an Extreme-ultraviolet Imaging Telescope Authors: Delaboudiniere, J. P.; Gabriel, A. H.; Artzner, G. E.; Michels, D. J.; Dere, K. P.; Howard, R. A.; Catura, R.; Stern, R.; Lemen, J.; Neupert, W. Bibcode: 1988sohi.rept...43D Altcode: The Extreme-ultraviolet Imaging Telescope (EIT) of SOHO (solar and heliospheric observatory) will provide full disk images in emission lines formed at temperatures that map solar structures ranging from the chromospheric network to the hot magnetically confined plasma in the corona. Images in four narrow bandpasses will be obtained using normal incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. The EIT is capable of providing a uniform one arc second resolution over its entire 50 by 50 arc min field of view. Data from the EIT will be extremely valuable for identifying and interpreting the spatial and temperature fine structures of the solar atmosphere. Temporal analysis will provide information on the stability of these structures and identify dynamical processes. EIT images, issued daily, will provide the global corona context for aid in unifying the investigations and in forming the observing plans for SOHO coronal instruments. Title: The Correspondence Between Fine-Scale Structures in the Solar Corona and Transition Region Authors: Moses, J. D.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Davis, J. M.; Webb, D. Bibcode: 1988BAAS...20..722M Altcode: No abstract at ADS Title: Correlation of Transition Region C IV High-Velocity Events With Magnetogram and He I 10830 Å Data Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Recely, F.; Martin, S.; Zirin, H. Bibcode: 1988BAAS...20..722C Altcode: No abstract at ADS Title: The Power Spectrum of Velocities in the Solar Transition Zone Authors: Dere, K. P. Bibcode: 1988BAAS...20..722D Altcode: No abstract at ADS Title: Solar physics from Spacelab 2. Authors: Dere, K. P. Bibcode: 1988JPhys..49....3D Altcode: 1988IAUCo.102....3D Four instruments were flown aboard the Spacelab 2 shuttle mission to perform systematic observations of the solar atmosphere at high resolution and to measure specific global properties of the sun. The Solar Optical Universal Polarimeter recorded series of white light images with which the evolution of the granulation and sunspot phenomena have been studied. The Coronal Helium Abundace Shuttle Experiment provided measurements of a number of EUV coronal lines, and, in particular, the intensities of He II λ304 and H I λ1216 from which the coronal helium abundance can be determined. The High Resolution Telescope and Spectrograph obtained stigmatic spectra in the 1200 - 1700 Å wavelength range, as well as broad band UV spectroheliograms, to provide diagnostic information on the solar chromosphere and transition zone. The Solar Ultraviolet Spectral Irradiance Monitor measured the total solar irradiance at a resolution of 1.5 and 50 Å in the 1200 to 4000 Å wavelength range to an accuracy of 3%. Title: Results from the High Resolution Telescope and Spectrograph (HRTS) Experiment on Board Spacelab 2 Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere, K. P.; Socker, D. G. Bibcode: 1988ApL&C..27..151B Altcode: Several papers including reviews have been published during different stages of the data analysis after the SL-2 flight. In order to avoid repetition, this article lists all publications and briefly mentions some of the highlights. Title: Ultraviolet Observations of Solar Fine Structure Authors: Dere, Kenneth P.; Bartoe, John-David F.; Brueckner, Guenter E.; Cook, John W.; Socker, Dennis G. Bibcode: 1987Sci...238.1267D Altcode: The High Resolution Telescope and Spectrograph was flown on the Spacelab-2 shuttle mission to perform extended observations of the solar chromosphere and transition zone at high spatial and temporal resolution. Ultraviolet spectroheliograms show the temporal development of macrospicules at the solar limb. The C IV transition zone emission is produced in discrete emission elements that must be composed of exceedingly fine (less than 70 kilometers) subresolution structures. Title: Chromospheric and Transition Zone Flows in a Solar Active Region Authors: Dere, K. P.; Schmieder, B. Bibcode: 1987BAAS...19.1118D Altcode: No abstract at ADS Title: Discrete Subresolution Structures in the Solar Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Socker, D. G. Bibcode: 1987SoPh..114..223D Altcode: During operations on the Spacelab-2 Shuttle mission, the NRL High Resolution Telescope and Spectrograph (HRTS) recorded spectra of a variety of solar features in the 1200-1700 Å wavelength region which contains spectral lines and continua well suited for investigating the temperature minimum, the chromosphere and transition zone. These data show that, at the highest spatial resolution, the transition zone spectra are broken up from a continuous intensity distribution along the slit into discrete emission elements. The average dimensions of these discrete transition zone structures is 2400 km along the slit, but an analysis of their emission measures and densities shows that the dimensions of the actual emitting volume is conciderably less. If these structures are modelled as an ensemble of subresolution filaments, we find that these filaments have typical radii of from 3 to 30 km and that the cross-sectional fill factor is in the range from 10−5 to 10−2. The transport of mass and energy through these transition zone structures is reduced by this same factor of 10−5 to 10−2 which has significant consequences for our understanding of the dynamics of the solar atmosphere. Because the HRTS transition zone line profiles are not broadened by resolved large-spatial-scale solar velocity fields, the line widths of the CIV lines have been analyzed. The average line width is 0.195 Å (FWHM) and requires an average nonthermal velocity of 16 km s−1 (most-probable) or 19 km s−1 (root-mean-square) which is lower than previously observed values. Title: Transition Zone Flow Patterns in Sunspots Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Socker, D. G. Bibcode: 1987BAAS...19..639D Altcode: No abstract at ADS Title: Statistical Properties of Small High-Velocity Events in the Solar Transition Region Authors: Cook, J. W.; Lund, P. A.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Socker, D. G. Bibcode: 1987LNP...291..150C Altcode: 1987csss....5..150C We discuss the energy contribution of small high-velocity events observed in the solar transition region to atmospheric heating. These events do not directly provide enough energy to heat the atmosphere, but are instead after-products of turbulent energy dissipation at the sites of the actual primary nonthermal heating process. Title: Identification of [Fe III] in the solar ultraviolet spectrum Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P. Bibcode: 1986Natur.324..444J Altcode: Solar ultraviolet spectra have been obtained with high spectral and spatial resolution using the Naval Research Laboratory's high-resolution telescope and spectrograph1 (HRTS) flown on rockets since 1975 and most recently on the Spacelab 2 Shuttle flight. Because the solar spectrum between ~1,170 and 1,719 Å has been well observed for some years, few lines of substantial intensity remain unidentified. (See for example the recent compilation by Sandlin et al.2). The longest exposures during the first rocket flight of the HRTS, which obtained spectra with a spatial resolution of ~ 1 arc s along the slit, of length ~ 1 solar radius, and a spectral resolution of ~0.05 Å, showed a number of weak emission lines at the solar limb, in particular between 1,570 and 1,600 Å (see Plates 16 and 17 in ref. 3), that could not readily be identified. Improved observations of these lines were obtained during the flight of HRTS on the Spacelab 2 Shuttle flight in July-August 1985, by making longer exposures (60,100 and 250 s). The scope of the data obtained has been described4. We have now identified the emission lines concerned as forbidden (electric quadrupole and magnetic dipole) transitions in Fe III, the first detection of these particular transitions in any source. They must now be considered potential candidates for previously unidentified lines in other low-density (Ne <~ 1010 cm-3) astrophysical sources. Title: Outflows and Ejections in the Solar Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1986ApJ...310..456D Altcode: Time series images of C IV transition zone intensities and velocities are analyzed to study the uncommon patterns of blueshifted emission. The images are constructed from stigmatic spectra obtained during the third flight of the NRL High Resolution Telescope and Spectrograph. A sample of 11 blueshifted events with near-Gaussian profiles are analyzed. Of these 11 cases, three are expulsions of material from the network, two are spicular flows, one is a simple jet, another is associated with a filament, and four are unexplained. It is not possible to identify a simple mechanism whereby upflows return to form the predominant downflows observed in the transition zone, and the upward mass flux is three orders of magnitude lower than the downward mass flux. Title: Observation of the Density Sensitive Line Mg V 1324 Å in a Solar Sunspot Authors: Cook, J. W.; Socker, D. G.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P. Bibcode: 1986BAAS...18R.991C Altcode: No abstract at ADS Title: Culgoora Radio and SKYLAB Extreme Ultraviolet Observations of Emerging Magnetic Flux in the Lower Corona Authors: Stewart, R. T.; Brueckner, G. E.; Dere, K. P. Bibcode: 1986SoPh..106..107S Altcode: Detailed comparisons of Culgoora 160 MHz radioheliograms of solar noise storms and Skylab EUV spectroheliograms of coronal loop structures are presented. It is concluded that: (1) there is a close association between changes in large-scale magnetic fields in the corona and the onset or cessation of noise storms; (2) these coronal changes result from the emergence of new magnetic flux at the photospheric level; (3) although new magnetic flux at the photospheric level is often accompanied by an increase in flare activity the latter is not directly responsible for noise storm activity; rather the new magnetic flux diffuses slowly outwards through the corona at rates ∼1-2 km s−1 and produces noise storms at 160 MHz 1-2 days later; (4) the coronal density above or in large-scale EUV loop systems is sufficiently dense to account for noise storm emission at the fundamental plasma frequency; (5) the scatter in noise storm positions can be accounted for by the appearance and disappearance of individual loops in a system. Title: High-Resolution Telescope and Spectrograph Images of the Solar Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1986ApJ...305..947D Altcode: Observations of a 10-arcsec-wide 800-arcsec-long region of the southern solar hemisphere, obtained at 150-160 nm by the rocket-borne High-Resolution Telescope and Spectrograph on March 1, 1979, are reported and analyzed. Rastered stigmatic spectra are reduced to create color images of intensity, Doppler shift, and line width providing information on the UV structure of the solar atmosphere. Characteristics discussed include temperature stratification in quiet-sun network elements; chromospheric jets appearing at supergranular cell centers; general redshift of 5 km/s in quiet-sun C IV; downflow patterns in C IV, Fe II, and C I; plage structures with temperature stratification and 6-km/s C IV downflow; and faint filament emission with blueshifts near the top and redshifts at the sides in the C IV images. Title: Discrete Components of Solar Transition Zone Emission Authors: Dere, K. P.; Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Socker, D. G. Bibcode: 1986BAAS...18Q.662D Altcode: No abstract at ADS Title: Statistical Properties of Small High-Velocity Transition Region Events on the Sun Observed by HRTS on Spacelab 2 Authors: Cook, J. W.; Lund, P. A.; Brueckner, G. E.; Bartoe, J. -D. F.; Dere, K. P.; Socker, D. G. Bibcode: 1986BAAS...18..662C Altcode: No abstract at ADS Title: Results from the High Resolution Telescope and Spectrograph (HRTS) Experiment Authors: Brueckner, G. E.; Cook, J. W.; Dere, K. P. Bibcode: 1986BAAS...18..675B Altcode: No abstract at ADS Title: HRTS Spacelab 2 Observations of the Temporal Development of the C IV Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Lund, P.; Socker, D. G. Bibcode: 1986BAAS...18..633D Altcode: No abstract at ADS Title: HRTS results from spacelab 2 Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere, K. P.; Socker, D. G. Bibcode: 1986AdSpR...6h.263B Altcode: 1986AdSpR...6..263B The HRTS instrument flew on the Spacelab 2 mission from 29 July - 6 August 1985. HRTS consisted of a 30 cm Gregorian telescope, a slit spectrograph covering the 1190-1680 Å region with 0.05 Å spectral resolution, a broadband (90 Å FWHM) spectroheliograph tuned to 1550 Å, and an H-alpha filter system. The spectrograph slit was 920 arc sec, approximately 1 R0, in length. Sub arc second spatial resolution along the slit is possible, but because of jitter in the Spacelab Instrument Pointing System (IPS) good exposures actually achieved 1-2 arc sec resolution. We describe the scientific results from HRTS. Title: Results from the NRL instruments on Spacelab 2 Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Morrison, M. D. Bibcode: 1986aiaa.meetZ....B Altcode: The instrumental features of the high resolution Telescope and spectrograph (HRTS) and the solar UV spectral irradiance monitor (SUSIM) used for solar observations on the Spacelab 1 mission are described. The HRTS has three focal plane instruments receiving light from a 30 cm aperture furnishing at 15 X 15 arcmin FOV which can be modified for slit photography and raster scans. The focal plane instruments are a spectrograph, spectroheliograph and a television camera and photographic film fronted by a mica Fabry-Perot filter. About 13 hr of solar observations were made with the HRTS during the 8 day mission. Sample spectral and photographic data are provided and discussed. SUSIM is an UV spectrometer with redundant optical paths for in-flight calibration with a D2 lamp. It is sensitive in the 1200-4000 A range. Several wavelength ranges are evaluated. Particular attention is given to multitemporal Ly-alpha recordings. Title: HRTS Spacelab 2 Observations of Spicular Emission at the Solar Limb Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Socker, D. G. Bibcode: 1985BAAS...17..834C Altcode: No abstract at ADS Title: Ultraviolet Observations of Fine Structure in the Solar Chromosphere and Transition Zone Authors: Dere, K. Bibcode: 1985tphr.conf..233D Altcode: No abstract at ADS Title: Time Series Images of the UV Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1985BAAS...17..630D Altcode: No abstract at ADS Title: Report of the working group on future observations of the sun. Authors: Dere, K.; Kneer, F.; Landman, D. Bibcode: 1985cdm..proc...14D Altcode: No abstract at ADS Title: HRTS observations of the solar chromosphere and transition zone. Authors: Dere, K. P. Bibcode: 1985cdm..proc...50D Altcode: The NRL High Resolution Telescope and Spectrograph (HRTS) consists of a 30 cm Cassegrain telescope which focuses an image of the sun with 1 arcsec resolution, a stigmatic tandem-Wadsworth mount UV spectrograph, a UV broadband spectroheliograph and H-alpha film and video cameras. Images of the UV line and continuum intensities show that they are all strongly associated with the chromospheric network, with an almost one-to-one correspondence found between Fe II intensity images and H-alpha -0.6 A spectroheliograms. The region of C IV emission occurs above the chromospheric mottles at a height of 3900 km when the continuum height is placed at 500 km; significant C IV transition-zone emission was also found at the base of the network elements. C IV profiles are generally near Gaussian, with dimensions on the order of 200 km. Time series and velocity field data are provided, and it is concluded that a steady state heating mechanism is present in the chromosphere. Title: UV observations of fine structure in the solar chromosphere and transition zone. Authors: Dere, K. P. Bibcode: 1985MPARp.212..233D Altcode: The capabilities of the NRL High Resolution Telescope and Spectrograph (HRTS) made it possible to obtain UV spectra at a spatial resolution sufficient to resolve fine structures in the solar chromosphere and transition zone. To date, it has made observations during 4 rocket flights and recently obtained highly successful longer term observations during the Spacelab-2 mission. Obviously, only the rocket spectra have been analyzed in any detail. The author addresses three areas where the understanding of the solar chromosphere and transition zone, based on these HRTS observations, may need reassessment. Title: High-resolution telescope and spectrograph observations of the quiet solar chromosphere and transition zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1984ApJ...281..870D Altcode: A systematic program to observe the two-dimensional structure of the solar atmosphere and its temporal variation was conducted in connection with the third rocket flight of the High Resolution Telescope and Spectrograph (HRTS). A description is presented of the manner in which line intensities, Doppler shifts (velocities), and line widths are obtained from HRTS spectra. These quantities are derived for a single stigmatic slit spectra of the quiet sun. It is pointed out that an accurate wavelength scale can be derived from narrow Si I lines in the spectra. The intensity of chromospheric lines such as C I lambda 1560 is found to be largely the result of the structures forming the chromospheric network. A number of conclusions are drawn about quiet transition zone Doppler shifts (flows). Title: Ultraviolet spectroscopy of the chromosphere and transition zone at high spatial and temporal resolution Authors: Dere, K. P. Bibcode: 1984AdSpR...4h..55D Altcode: 1984AdSpR...4...55D The third rocket flight of the NRL High Resolution Telescope and Spectrograph (HRTS) recorded UV spectra of the quiet Sun in a 10'' × 800'' region. By rastering the slit in 2'' increments, a time series with 20s resolution of two-dimensional spectra with 1'' spatial resolution was obtained. The spectrum includes strong chromospheric diagnostic lines of C I, Si I, and Fe II, transition zone lines of C IV and the continuum which is produced in the temperature minimum. Images of the network show that Fe II emission is well-correlated with dark Hα mottles, that the transition zone is produced in extended structures which are apparently continuations of the mottles, and that the strongest continuum emission is from near the base of the mottles. Time series of C I profiles show little variation in most features aside from the chromospheric jets which develop rapidly over timescales of 30s. The C IV profiles also show only gradual variations over most of the slit except for the numerous small explosive events. Title: HRTS Ultraviolet Images of the Solar Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1984LNP...193..180D Altcode: 1984csss....3..180D No abstract at ADS Title: HRTS Ultraviolet Solar Spectroscopy (invited Paper) Authors: Dere, K. P. Bibcode: 1984uxsa.coll...22D Altcode: 1984IAUCo..86...22D; 1984uxsa.conf...22D No abstract at ADS Title: HRTS observations of the fine structure and dynamics of the solar chromosphere and transition zone. Authors: Dere, K. P. Bibcode: 1983NASCP.2280..33D Altcode: 1983sowi.conf...33D Arc-second UV observations of the Sun by the NRL High Resolution Telescope and Spectrograph (HRTS) have led to the discovery of dynamic fine structures such as 400 km s-1 coronal jets and chromospheric jets (spicules) and have provided new information about the structure and dynamics of the transition zone. These observations are reviewed and their relevance to the origin of the solar wind is discussed. Title: Mass and energy balance in the 1973 August 9 flare Authors: Dere, K. P.; Cook, J. W. Bibcode: 1983A&A...124..181D Altcode: The mass and energy balance of the thermal plasma during the decay phase of the solar flare of August 9, 1973, are studied. The analysis is based on observationally determined values for the differential emission measure, density, turbulent and bulk velocities, and physical dimensions. The total particle content and total thermal energy content of the flare plasmas with temperatures above 100,000 K and their variation with time are calculated. The particle loss and the energy losses through radiation, conduction, and convection are evaluated. The decrease in total particle content can be accounted for by the convective losses through the loop footprints at 100,000 K. Radiation is the dominant energy loss mechanism although convective losses at 100,000 K can be important. Conductive losses at 100,000 K into cooler chromospheric material appear to be negligible. The decrease in the total energy content during the decay phase is equal to the sum of the energy losses over the period of observation. No requirement is found for continued heating during the decay phase. Title: Chromospheric jets - Possible extreme-ultraviolet observations of spicules Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1983ApJ...267L..65D Altcode: Stigmatic EUV spectra of chromospheric lines obtained by the Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) show small arc second regions with strong (10-20 km/s) Doppler shifts which are called 'chromospheric jets'. Because of the strong resemblance of their physical and statistical properties, such as temperature, density, velocity, size, and birthrate, to those of visible light spicules, it is highly likely that they are different manifestations of the same phenomena, although a one-to-one identification has not yet been made. The main difference is the 40 s lifetime of the chromospheric jets which is shorter than the 5 minute lifetime of visible light spicules. The chromospheric jets are found in the supergranular cell interiors where chromospheric and transition zone line intensities are weak. Dark H-alpha mottles found in the cell boundaries are well correlated with intense, symmetric chromospheric EUV line profiles and are only weakly related to the chromospheric jets. Title: HRTS Images of the Quiet Solar Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1983BAAS...15..702D Altcode: No abstract at ADS Title: The NRL SOLRAD 11 Satellites (1976-023C, 1976-023D) description of experiments Authors: Horan, D. M.; Kreplin, R. W.; Dere, K. P. Bibcode: 1982nrl..reptY....H Altcode: The Naval Research Laboratory's SOLRAD 11 satellites were successfully launched on 15 March 1976. The two satellites each carried an identical complement of 25 experiments to measure solar electromagnetic and charged particle emissions, Earth auroral and stellar X-ray emission, terrestrial and interplanetary extreme ultraviolet emission, X-ray and charged particle emission from the anti-solar direction, and gamma ray bursts. This report provides general descriptive information on the satellites and their sensors. Title: Observations of Extreme Ultraviolet Spicules Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1982BAAS...14..939D Altcode: No abstract at ADS Title: Solar transition zone pressures from EUV observations of O IV and N IV Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1982ApJ...259..366D Altcode: NRL High Resolution Telescope and Spectrograph observations of the O IV and N IV EUV lines emitted from the Sun are examined. The instrument provides stigmatic spectra with a spatial resolution of 1 arcsec and a spectral resolution of 0.05 A in the range 1170-1710 A. Intensity ratios of the intersystem lines of O IV near 1400 A are used as the primary diagnostic to measure electron pressures in a sunspot and plage. These ratios are strongly sensitive to electron pressure but are insensitive to the temperature structure of the emitting plasma. Average electron pressures of 9 x 10 to the 15th per cu cm K (1.2 dyn/sq cm) in a plage, 4 x 10 to the 15th per cu cm K (0.6 dyn/sq cm) in a sunspot and 2.2 x 10 to the 15th per cu cm K (0.3 dyn/sq cm) in high speed sunspot downflows are found. The ratio of I(Nv) + I(C IV) to I(N IV 1486A) is shown to be relatively insensitive to temperature and gives pressures consistent with those obtained from the O IV ratio. It is demonstrated that ratios of allowed lines such as C IV and Si IV to the O IV intersystem lines are temperature sensitive and hence are unreliable pressure diagnostics. Title: Extreme Ultraviolet Spectra of Solar Active Regions and Their Analysis Authors: Dere, K. P. Bibcode: 1982SoPh...77...77D Altcode: Extreme ultraviolet spectra of several active regions are presented and analyzed. Spectral intensities of 3 active regions observed with the NRL Skylab XUV spectroheliograph (170-630 Å) are derived. From this data density sensitive line ratios of Mg VIII, Si X, S XII, Fe IX, Fe X, Fe XI, Fe XII, Fe XIII, Fe XIV, and Fe XV are examined and typically yield, to within a factor of 2, electron pressures of 1 dyne cm−2 (neT = 6 × 1015 cm−3 K). The differential emission measure of the brightest 35″ × 35″ portion of an active region is obtained between 1.4 × 104 K and 5 × 106 K from HCO OSO-VI XUV (280-1370 Å) spectra published by Dupree et al. (1973). Stigmatic EUV spectra (1170-1710 Å) obtained by the NRL High Resolution Telescope and Spectrograph (HRTS) are also presented. Doppler velocities as a function of position along the slit are derived in an active region plage and sunspot. The velocities are based on an absolute wavelength scale derived from neutral chromospheric lines and are accurate to ±2 km s−1. Downflows at 105 K are found throughout the plage with typical velocities of 10 km s−1. In the sunspot, downflows are typically 5 to 20 km s−1 over the umbra and zero over the penumbra. In addition localized 90 and 150 km s−1 downflows are found in the umbra in the same 1″ × 1″ resolution elements which contain the lower velocity downflows. Spectral intensities and velocities in a typical plage 1″ resolution element are derived. The velocities are greatest (∼ 10 km s−1) at 105 K with lower velocities at higher and lower temperatures. The differential emission measure between 1.3 × 104 K and 2 × 106 K is derived and is found to be comparable to that derived from the OSO-VI data. An electron pressure of 1.4 dynes cm−2 (neT = 1.0 × 1016 cm−3 K) is determined from pressure sensitive line ratios of Si III, O IV, and N IV. From the data presented it is shown that convection plays a major role in determining the structure and dynamics of the active region transition zone and corona. Title: The XUV structure of solar active regions Authors: Dere, K. P. Bibcode: 1982SoPh...75..189D Altcode: XUV spectroheliograms of 2 active regions are studied. The images are due to lines emitted at temperatures between 8 x 104 K and 2 x 106 K and thus are indicative of transition region and coronal structures. The hot coronal lines are formed solely in loop structures which connect regions of opposite photospheric magnetic polarity but are not observed over sunspots. Transition region lines are emitted in plages overlying regions of intense photospheric magnetic field and in loops or loop-segments connecting such regions. The hot coronal loops are supported hydrostatically while only some of the transition zone loops are. The coronal and transition zone loops are distinctly separated and are not coaxial. A comparison of direct measurements of electron densities using density sensitive line ratios with indirect measurements using emission measures and path lengths shows the existence of fine structures of less than a second of arc in transition region loops. From a similar analysis, hot coronal loops do not have any fine structure below about 2 seconds of arc. Title: Transient plasmas in the solar transition zone Authors: Dere, K. P.; Bartoe, J. -D.; Brueckner, G. E.; Vanhoosier, M. E.; Dykton, M. D. Bibcode: 1981ApJ...249..333D Altcode: Observations of C IV emission from the transition zone of the quiet sun have been obtained with high spatial (1 arcsec), spectral (0.1 A), and temporal (20 s) resolution by a high resolution telescope and spectrograph. Over spatial scales of several arc seconds, the C IV profile often exhibits dramatic changes in either the red or blue wing or in the overall profile at the 20 s temporal resolution of the observations. It is suggested that some of the rapidly varying emission may be produced by radiatively cooling plasmas that result from the thermal instability of coronal plasma. It is shown that such plasmas, which are in transient ionization, can emit 35 s pulses of C IV emission for reasonable pressure values. It is also shown that, because of the limited ability of coronal plasma to maintain ionization equilibrium, the criteria for the thermal radiative instability must be evaluated in a manner different from the standard treatment in the case of rapid perturbations or growth times. From a consideration of length scales it is determined that these instabilities are most likely to occur in the upper transition zone. Title: HRTS Observations of the Solar Chromosphere and Transition Zone Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1981BAAS...13..845D Altcode: No abstract at ADS Title: Extreme Ultraviolet Emission of O IV and N IV from the Sun Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1981BAAS...13R.542D Altcode: No abstract at ADS Title: Mass and Energy Balance in the 1973 August 9 Flare Authors: Cook, J. W.; Dere, K. P. Bibcode: 1981BAAS...13..554C Altcode: No abstract at ADS Title: Spectroscopic diagnostics of the active region: transition zone and corona. Authors: Dere, K. P.; Mason, H. E. Bibcode: 1981sars.work..129D Altcode: Techniques currently used in the analysis of X-ray and UV spectroscopic data on solar features are reviewed with particular emphasis on those used for studies of active regions in the transition zone and corona. Attention is given to temperature and emission measure diagnostics by the use of line emission from a low-density plasma, broadband X-ray diagnostics, and diagnostics specific to various active region structures, and to electron density diagnostics based on metastable levels and the ratio of emission measure to the volume derived from spatially resolved images. Methods used for calculating atomic structure, electron and proton scattering, the ionization equilibrium and the effects on it of diffusion and flows, and the line profiles and optical depths are also considered. Title: Analysis and Interpretation of EUV Emission from Solar Active Regions Authors: Dere, K. P. Bibcode: 1980BAAS...12..908D Altcode: No abstract at ADS Title: Density and Temperature Measurements for Short Lived Transition Zone Phenomena Authors: Nicolas, K. R.; Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E. Bibcode: 1980BAAS...12R.530N Altcode: No abstract at ADS Title: Transient Plasmas in the Solar Transition Zone Authors: Dere, K. P.; Nicolas, K. R.; Brueckner, G. E. Bibcode: 1980BAAS...12R.518D Altcode: No abstract at ADS Title: The thermal X-ray flare plasma Authors: Moore, R.; McKenzie, D. L.; Svestka, Z.; Widing, K. G.; Dere, K. P.; Antiochos, S. K.; Dodson-Prince, H. W.; Hiei, E.; Krall, K. R.; Krieger, A. S. Bibcode: 1980sfsl.work..341M Altcode: 1980sofl.symp..341M Following a review of current observational and theoretical knowledge of the approximately 10 to the 7th K plasma emitting the thermal soft X-ray bursts accompanying every H alpha solar flare, the fundamental physical problem of the plasma, namely the formation and evolution of the observed X-ray arches, is examined. Extensive Skylab observations of the thermal X-ray plasmas in two large flares, a large subflare and several compact subflares are analyzed to determine plasma physical properties, deduce the dominant physical processes governing the plasma and compare large and small flare characteristics. Results indicate the density of the thermal X-ray plasma to be higher than previously thought (from 10 to the 10th to 10 to the 12th/cu cm for large to small flares), cooling to occur radiatively as much as conductively, heating to continue into the decay phase of large flares, and the mass of the thermal X-ray plasma to be supplied primarily through chromospheric evaporation. Implications of the results for the basic flare mechanism are indicated. Title: The Extreme Ultraviolet Structure of Solar Active Regions. Authors: Dere, K. P. Bibcode: 1980PhDT.........2D Altcode: The extreme ultraviolet emissions from solar active regions have been analyzed to determine their temperatures, densities, pressures, emission measures, flow velocities and structures. The accuracy and limitations of the diagnostic techniques are discussed. It is found that the active region structures are well correlated with the inferred and observed magnetic fields and that the electron pressure of the plasma is essentially constant over a wide range of temperatures. Cool (10('5)K (LESSTHEQ) T (LESSTHEQ) 10('6)K) loop structures are shon to be composed of unresolved filaments. Static and steady flow one dimensional hydrodynamical models of active region loops have been constructed and used to interpret the observations. Both models require a loop cross section that diverges with height. This is found by comparing the static model with the observed emission measures and the steady flow model with the observed flow velocities. No local heating is found to be needed in the transition zone. Transition zone downflows in active regions indicate a mass loss from the overlying coronal structures for which there is no know supply. Title: Radiative energy output of the 5 September 1973 flare Authors: Canfield, R. C.; Cheng, C. -C.; Dere, K. P.; Dulk, G. A.; McLean, D. J.; Schmahl, E. J.; Robinson, R. D., Jr.; Schoolman, S. A. Bibcode: 1980sfsl.work..451C Altcode: 1980sofl.symp..451C Measurements of the radiative energy output of the solar flare of Sept. 5, 1973, over a wavelength range of more than ten decades, from below 1 A to above 1 m are presented. Observations of soft X-rays (0.5-20 A), XUV and EUV lines (171-1863 A) and EUV continua (1400-1960 A), H alpha radiation, visible lines and continua (3700-8700 A) and radio emission (centimeter to meter wavelengths) were obtained concurrently by Skylab and ground-based instruments. Estimates of power output at flare maximum are obtained for the observed wavelengths with uncertainty of at least half an order of magnitude, due to corresponding uncertainties in EUV and visible fluxes. Taking into account energy radiated at unobserved wavelengths and the characteristic time of the best-reduced data (the soft X-ray), calculations indicate a total radiated flare energy of approximately 4 x 10 to the 29th erg. Title: Mass Flow and Energy Balance in a Solar Flare Authors: Cook, J. W.; Dere, K. P. Bibcode: 1979BAAS...11..678C Altcode: No abstract at ADS Title: XUV electron density diagnostics for solar flares. Authors: Dere, K. P.; Mason, H. E.; Widing, K. G.; Bhatia, A. K. Bibcode: 1979ApJS...40..341D Altcode: Potential electron-density diagnostics for the high-temperature component of solar flares are studied with reference to the wavelength region from 171 to 630 A. The specific ions discussed include Fe IX through Fe XV, Ni XI through Ni XVII, and ions in the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Line ratios that could be useful as density indicators under solar-flare conditions are indicated, available data for the ions considered are reviewed, and several theoretical intensity ratios are plotted. The results are employed to determine the electron-density distribution as a function of electron temperature for several spectra from two flares. For these flares it is found that the electron density increases from 10 billion to 500 billion per cu cm for a temperature increase from 1 million to 10 million K. Title: The decay of the 1973 August 9 flare. Authors: Dere, K. P.; Cook, J. W. Bibcode: 1979ApJ...229..772D Altcode: The state and evolution of the decay-phase plasma from a compact solar flare that occurred on August 9, 1973, are investigated on the basis of XUV and X-ray observations from Skylab and Solrad 9. Density-sensitive line ratios are used to determine the electron density over the temperature range from 30,000 to 5 million K, and the differential emission measure in the temperature interval from 30,000 to 20 million K is derived for several times in the decay phase. The morphology of the flare is discussed, including its relation to the observed photospheric magnetic field. The sequential formation of new loops during the decay phase is emphasized as an essential element for understanding the decay phase of the flare. This idea is developed further by comparing the observed differential emission measure with that predicted by a semiempirical model which considers the sequential formation of isothermal loops that cool by radiation and thermal conduction. Title: Errors in Differential Emission Measure Solutions Authors: Dere, K. P. Bibcode: 1978A&A....70..439D Altcode: Summary. The possible errors in differential emission measures derived from spectral line intensities of limited accuracy have been examined by direct numerical simulation. The results indicate that if a functional form that is smooth and non-negative is used to approximate the differential emission measure, it is possible to obtain solutions which have errors that are not significantly greater than the errors in the spectral data. Key words: X-ray - XUV - spectra-plasmas Title: Evolution of the coronal and transition-zone plasma in a compact flare: the event of 1973 August 9. Authors: Underwood, J. H.; Antiochos, S. K.; Feldman, U.; Dere, K. P. Bibcode: 1978ApJ...224.1017U Altcode: X-ray and extreme ultraviolet observations of a compact flare were analyzed to determine the relative importance of radiation, thermal conduction, and 'evaporation' in the evolution of the temperature and density structure of the plasma. In the event studied (1973 August 9), the electron density was relatively high (5 x 10 to the eleventh to 1 x 10 to the twelfth) and radiation was evidently an important energy-loss and cooling mechanism. The light curves of ultraviolet lines formed at temperatures between 10 to the fifth to 10 to the seventh K indicate a time-varying emission measure gradient, and hence temperature gradient, during the flare. Radiative instability evidently played an important role in determining the steepness of these gradients during the rise and fall phases, and caused strong downward motions of material during the cooling phase. Toward the end of the event, the coronal electron density decreased and the temperature gradient relaxed toward that expected from a conduction-dominated plasma. For this flare, evaporative cooling did not appear to be a significant factor. Title: Spectral lines observed in solar flares between 171 and 630 Angstroms. Authors: Dere, K. P. Bibcode: 1978ApJ...221.1062D Altcode: Several hundred spectral lines emitted in solar flares between 171 and 630 A have been recorded by the Naval Research Laboratory spectroheliograph aboard Skylab. The wavelengths, identifications, and intensity estimates of these lines are presented, based on measurements of all of the suitable flare plates. Nearly 100 new and unidentified lines have been observed. Identifications of three Fe XXI and two Fe XVII lines are suggested. Title: EUV Observations of a Solar Active Region Authors: Dere, K. P. Bibcode: 1978BAAS...10..440D Altcode: No abstract at ADS Title: Multiple loop activation and continuous energy release in the solar flare of June 15, 1973. Authors: Widing, K. G.; Dere, K. P. Bibcode: 1977SoPh...55..431W Altcode: The spatial and temporal evolution of the high temperature plasma in the flare of 1973 June 15 has been studied using the flare images photographed by the NRL XUV spectroheliograph on Skylab. Title: Structure and dynamics of a solar flare: X-ray and XUV observations. Authors: Dere, K. P.; Horan, D. M.; Kreplin, R. W. Bibcode: 1977ApJ...217..976D Altcode: Results are presented for an analysis of X-ray and XUV emission from the solar flare that occurred on September 5, 1973. X-ray emission was monitored by ionization chambers aboard the Solrad 9 satellite, and the XUV emission in the wavelength range 170-345 A was recorded by a slitless objective-grating spectroheliograph on Skylab. The physical parameters of the flare plasma, including temperature, density, volume, and magnetic-field configuration, are evaluated. A geometrical loop model is used to determine the volumes of the various emitting regions. The structure of the flare in the rise and decay phases is examined in detail, and conclusions about the effect of various dynamic processes in the flare plasma are made. A major finding is that continued energy release is required well into the flare decay phase. In the rise phase, energy is apparently released only along a small portion of a loop, and in the decay phase apparently throughout most of its length. Title: Electron densities in solar flares from line ratios of Ca XVII. Authors: Doschek, G. A.; Feldman, U.; Dere, K. P. Bibcode: 1977A&A....60L..11D Altcode: Summary. We show that the intensity ratios of certain extreme ultraviolet spectral lines of Ca XVII are sensitive to electron density in solar flares. Calculations of the line ratios as functions of density are presented. These calculations are based on published atomic data for Ca XVII and for other ions of the beryllium isoelectronic sequence. For a flare that occurred on 9 August 1973, we derive a density of about 5 x 101 from the Ca XVII line ratios. Key words: solar flares - Be I sequence Title: The Solar Spectrum Below 10Å Authors: Kreplin, R. W.; Dere, K. P.; Horan, D. M.; Meekins, J. F. Bibcode: 1977soiv.conf..287K Altcode: No abstract at ADS Title: Forbidden lines of highly ionized iron in solar flare spectra. Authors: Doschek, G. A.; Feldman, U.; Dere, K. P.; Sandlin, G. D.; Vanhoosier, M. E.; Brueckner, G. E.; Purcell, J. D.; Tousey, R. Bibcode: 1975ApJ...196L..83D Altcode: No abstract at ADS Title: A Multi-Thremal Analysis of Solar X-Ray Emission Authors: Dere, Kenneth P.; Horan, Donald M.; Kreplin, Robert W. Bibcode: 1974SoPh...36..459D Altcode: The NRL SOLRAD 10 satellite carries six ionization chambers to measure solar X-radiation in the 0.5 to 60 Å wavelength band. The X-ray emission spectrum in this range is determined by the derivative of the coronal emission measure (∫ Ne2dV) with respect to temperature when the thermal processes of bremsstrahlung, radiative recombination and line radiation are considered. If a simple model for this differential emission measure is used and detector responses to the calculated spectra are fitted to the SOLRAD data by a least squares method, the differential emission measure can be obtained for temperatures between 2 × 106K and 64 × 106K. Data during quiet and flaring periods are analyzed and the general behavior of the differential emission measure during flares is presented. This analysis is based on experimental measurements of the efficiencies of the SOLRAD detectors. Title: The spectral dependence of solar soft X-ray flux values obtained by SOLRAD 9. Authors: Dere, K. P.; Horan, D. M.; Kreplin, R. W. Bibcode: 1974JATP...36..989D Altcode: The determination of solar energy flux values from ionization chamber experiments is discussed. Procedures and calculations necessary for the correction of SOLRAD 9 0.5-3 Å and 1-8 Å data and for the determination of the flare plasma temperature and emission measure are presented. These calculations are based on the continuum spectrum of CULHANE (1969), the line spectrum of TUCKER and KOREN (1971), and experimental values of the detector efficiencies. Title: Electron temperature and emission measure variations in the solar corona. Authors: Horan, D. M.; Dere, K. P.; Kreplin, R. W. Bibcode: 1974spre.conf..441H Altcode: No abstract at ADS Title: Reduction of solar X-ray flux measurements for use in ionospheric research. Authors: Kreplin, R. W.; Horan, D. M.; Dere, K. P. Bibcode: 1973spre.conf..469K Altcode: 1973spre....1..469K No abstract at ADS