Author name code: curdt ADS astronomy entries on 2022-09-14 author:"Curdt, Werner" ------------------------------------------------------------------------ Title: Multiwavelength quiescent prominence spectroscopic observations Authors: Zhang, Ping; Vial, Jean-Claude; Feng, Li; Curdt, Werner; Zapior, Maciej Bibcode: 2021cosp...43E1770Z Altcode: In the frame of the SUMER-IRIS HOP 334 campaign in March-April 2017, joint prominence observations have been performed with IRIS (Mg II h and k), SUMER (L-alpha) and HSFA2 ( Ondřejov Observatory) in Ca II K, H-beta and H-alpha. We proceeded first with the difficult task of coalignment i.e. identifying the pixels of the different slits corresponding to the same solar region observed at the same time. The selected profiles photometrically calibrated have been found non-reversed.Through the use of the NLTE radiative transfer code PRODOP available at MEDOC/IAS, we tentatively derive the 1D model fitting all observed profiles. The observed Lalpha profile found to be larger than the isothermal modelled one requires the addition of a PCTR. Some basic thermodynamical parameters are consequently derived. Title: The Solar Orbiter SPICE instrument. An extreme UV imaging spectrometer Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.; Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini, K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.; Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.; Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau, J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.; Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest, S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler, D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller, S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall, G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris, N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.; Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.; Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy, B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.; Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial, J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward, S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D. Bibcode: 2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet wavelengths. In this paper, we present the concept, design, and pre-launch performance of this facility instrument on the ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper is to give prospective users a better understanding of the possible types of observations, the data acquisition, and the sources that contribute to the instrument's signal.
Results: The paper discusses the science objectives, with a focus on the SPICE-specific aspects, before presenting the instrument's design, including optical, mechanical, thermal, and electronics aspects. This is followed by a characterisation and calibration of the instrument's performance. The paper concludes with descriptions of the operations concept and data processing.
Conclusions: The performance measurements of the various instrument parameters meet the requirements derived from the mission's science objectives. The SPICE instrument is ready to perform measurements that will provide vital contributions to the scientific success of the Solar Orbiter mission. Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz, W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado, R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.; Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel, V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau, M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar, S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.; Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.; Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.; Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud, A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.; Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.; Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan, K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.; Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.; Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq, S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.; Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining, S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort, F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.; Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.; Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.; Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.; Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane, K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit, S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen, K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.; Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.; Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.; Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N. Bibcode: 2020A&A...642A...8R Altcode: Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the "connection science" between solar activity and the heliosphere.
Aims: With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-α and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft's heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.
Results: In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.
Conclusions: The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs. Title: Initial features of an X-class flare observed with SUMER and TRACE Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2018arXiv180510418W Altcode: A class X1.5 flare started on the solar limb at 00:43 UT on 21 April 2002, which was associated with a CME observed at 01:27 UT by LASCO C2. The coordinated analyses of this flare include TRACE 195 Å images and SUMER spectra in lines of Fe XXI, Fe XII, and C II. We find that: 1) The flare began with a jet seen by TRACE, which was detected by SUMER in the C II line as a strong brightening with blue shifts up to 170 km s$^{-1}$. At that time only weak emission was detected in Fe XII and Fe XXI. 2) Subsequently, a weak looplike brightening started south of the jet, moving outwards with an average speed of about 150 km s$^{-1}$. The SUMER spectra responded this moving loop as separatingly brightenings, visible only in the Fe XXI line. The southwards moving component contains red- and blue-shifted emission features and has an apparent speed of $\sim$120 km s$^{-1}$. The absence of signatures in Fe XII and C II lines indicates that the moving weak loop seen by TRACE corresponds to the emission from very hot plasma, in a blend line in the 195 Å bandpass due to Fe XXIV formed at T > 10 MK. 3) The trigger mechanism of the flare and associated CME can be interpreted in the same way as that proposed by Wang et al. (2002) for an event with similar initial features. Title: An Empirical Model of the Variation of the Solar Lyman-α Spectral Irradiance Authors: Kretzschmar, Matthieu; Snow, Martin; Curdt, Werner Bibcode: 2018GeoRL..45.2138K Altcode: We propose a simple model that computes the spectral profile of the solar irradiance in the hydrogen Lyman alpha line, H Ly-α (121.567 nm), from 1947 to present. Such a model is relevant for the study of many astronomical environments, from planetary atmospheres to interplanetary medium. This empirical model is based on the SOlar Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation observations of the Ly-α irradiance over solar cycle 23 and the Ly-α disk-integrated irradiance composite. The model reproduces the temporal variability of the spectral profile and matches the independent SOlar Radiation and Climate Experiment/SOLar-STellar Irradiance Comparison Experiment spectral observations from 2003 to 2007 with an accuracy better than 10%. Title: An Empirical Model of the Variations of the Solar Lyman-Alpha Spectral Irradiance Authors: Kretzschmar, M.; Snow, M. A.; Curdt, W. Bibcode: 2017AGUFMSH43B2810K Altcode: We propose a simple model that computes the spectral profile of the solar irradiance in the Hydrogen Lyman alpha line, H Ly-α (121.567nm), from 1947 to present. Such a model is relevant for the study of many astronomical environments, from planetary atmospheres to interplanetary medium, and can be used to improve the analysis of data from mission like MAVEN or GOES-16. This empirical model is based on the SOHO/SUMER observations of the Ly-α irradiance over solar cycle 23, which we analyze in details, and relies on the Ly-α integrated irradiance composite. The model reproduces the temporal variability of the spectral profile and matches the independent SORCE/SOSLTICE spectral observations from 2003 to 2007 with an accuracy better than 10%. Title: ASPIICS: a giant, white light and emission line coronagraph for the ESA proba-3 formation flight mission Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.; Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Zhukov, A. Bibcode: 2017SPIE10565E..0TL Altcode: Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observations of the white light corona inside typically 2-2.5 solar radii (Rsun). Formation flying offers and elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters [1, 2]. Such an instrument ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) has been selected by the European Space Agency (ESA) to fly on its PROBA-3 mission of formation flying demonstration which is presently in phase B (Fig. 1). The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.04 solar radii from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to reach the chromosphere and the upper part of the spicules [3]. ASPIICS will perform (i) high spatial resolution imaging of the continuum K+F corona in photometric and polarimetric modes, (ii) high spatial resolution imaging of the E-corona in two coronal emission lines (CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry of the Fe XIV emission line. ASPIICS will address the question of the coronal heating and the role of waves by characterizing propagating fluctuations (waves and turbulence) in the solar wind acceleration region and by looking for oscillations in the intensity and Doppler shift of spectral lines. The combined imaging and spectral diagnostics capabilities available with ASPIICS will allow mapping the velocity field of the corona both in the sky plane (directly on the images) and along the line-of-sight by measuring the Doppler shifts of emission lines in an effort to determine how the different components of the solar wind, slow and fast are accelerated. With a possible launch in 2014, ASPIICS will observe the corona during the maximum of solar activity, insuring the detection of many Coronal Mass Ejections (CMEs). By rapidly alternating high-resolution imaging and spectroscopy, CMEs will be thoroughly characterized. Title: Solar Coronal Jets: Observations, Theory, and Modeling Authors: Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.; Meyer, K.; Dalmasse, K.; Matsui, Y. Bibcode: 2016SSRv..201....1R Altcode: 2016arXiv160702108R; 2016SSRv..tmp...31R Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of "nominal" solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broad range of solar-heliospheric problems. Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun to the Heliosphere Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta, Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo Bibcode: 2016cosp...41E.607F Altcode: The SPICE (Spectral Imaging of the Coronal Environment) instrument is one of the key remote sensing instruments onboard the upcoming Solar Orbiter Mission. SPICE has been designed to contribute to the science goals of the mission by investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. In particular, SPICE will provide quantitative information on the physical state and composition of the solar atmosphere plasma. For example, SPICE will access relative abundances of ions to study the origin and the spatial/temporal variations of the 'First Ionization Potential effect', which are key signatures to trace the solar wind and plasma ejections paths within the heliosphere. Here we will present the instrument and its performance capability to attain the scientific requirements. We will also discuss how different observation modes can be chosen to obtain the best science results during the different orbits of the mission. To maximize the scientific return of the instrument, the SPICE team is working to optimize the instrument operations, and to facilitate the data access and their exploitation. Title: Solar abundances with the SPICE spectral imager on Solar Orbiter Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin, Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany Bibcode: 2016cosp...41E.681G Altcode: Elemental composition of the solar atmosphere and in particular abundance bias of low and high First Ionization Potential (FIP) elements are a key tracer of the source regions of the solar wind. These abundances and their spatio-temporal variations, as well as the other plasma parameters , will be derived by the SPICE (Spectral Imaging of the Coronal Environment) EUV spectral imager on the upcoming Solar Orbiter mission. SPICE is designed to provide spectroheliograms (spectral images) using a core set of emission lines arising from ions of both low-FIP and high-FIP elements. These lines are formed over a wide range of temperatures, enabling the analysis of the different layers of the solar atmosphere. SPICE will use these spectroheliograms to produce dynamic composition maps of the solar atmosphere to be compared to in-situ measurements of the solar wind composition of the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to study the connectivity between the spacecraft (the Heliosphere) and the Sun. We will discuss the SPICE capabilities for such composition measurements. Title: Erratum: "Modeling the Chromosphere of a Sunspot and the Quiet Sun" (2015, ApJ, 811, 87) Authors: Avrett, E.; Tian, H.; Landi, E.; Curdt, W.; Wuelser, J. -P. Bibcode: 2016ApJ...821...70A Altcode: No abstract at ADS Title: Lyman alpha solar spectral irradiance line profile observations and models Authors: Snow, Martin; Machol, Janet; Quemerais, Eric; Curdt, Werner; Kretschmar, Matthieu; Haberreiter, Margit Bibcode: 2016EGUGA..18.3071S Altcode: Solar lyman alpha solar spectral irradiance measurements are available on a daily basis, but only the 1-nm integrated flux is typically published. The International Space Science Institute (ISSI) in Bern, Switzerland has sponsored a team to make higher spectral resolution data available to the community. Using a combination of SORCE/SOLSTICE and SOHO/SUMER observations plus empirical and semi-empirical modeling, we will produce a dataset of the line profile. Our poster will describe progress towards this goal. Title: The atmosphere of Pluto as observed by New Horizons Authors: Gladstone, G. Randall; Stern, S. Alan; Ennico, Kimberly; Olkin, Catherine B.; Weaver, Harold A.; Young, Leslie A.; Summers, Michael E.; Strobel, Darrell F.; Hinson, David P.; Kammer, Joshua A.; Parker, Alex H.; Steffl, Andrew J.; Linscott, Ivan R.; Parker, Joel Wm.; Cheng, Andrew F.; Slater, David C.; Versteeg, Maarten H.; Greathouse, Thomas K.; Retherford, Kurt D.; Throop, Henry; Cunningham, Nathaniel J.; Woods, William W.; Singer, Kelsi N.; Tsang, Constantine C. C.; Schindhelm, Rebecca; Lisse, Carey M.; Wong, Michael L.; Yung, Yuk L.; Zhu, Xun; Curdt, Werner; Lavvas, Panayotis; Young, Eliot F.; Tyler, G. Leonard; Bagenal, F.; Grundy, W. M.; McKinnon, W. B.; Moore, J. M.; Spencer, J. R.; Andert, T.; Andrews, J.; Banks, M.; Bauer, B.; Bauman, J.; Barnouin, O. S.; Bedini, P.; Beisser, K.; Beyer, R. A.; Bhaskaran, S.; Binzel, R. P.; Birath, E.; Bird, M.; Bogan, D. J.; Bowman, A.; Bray, V. J.; Brozovic, M.; Bryan, C.; Buckley, M. R.; Buie, M. W.; Buratti, B. J.; Bushman, S. S.; Calloway, A.; Carcich, B.; Conard, S.; Conrad, C. A.; Cook, J. C.; Cruikshank, D. P.; Custodio, O. S.; Ore, C. M. Dalle; Deboy, C.; Dischner, Z. J. B.; Dumont, P.; Earle, A. M.; Elliott, H. A.; Ercol, J.; Ernst, C. M.; Finley, T.; Flanigan, S. H.; Fountain, G.; Freeze, M. J.; Green, J. L.; Guo, Y.; Hahn, M.; Hamilton, D. P.; Hamilton, S. A.; Hanley, J.; Harch, A.; Hart, H. M.; Hersman, C. B.; Hill, A.; Hill, M. E.; Holdridge, M. E.; Horanyi, M.; Howard, A. D.; Howett, C. J. A.; Jackman, C.; Jacobson, R. A.; Jennings, D. E.; Kang, H. K.; Kaufmann, D. E.; Kollmann, P.; Krimigis, S. M.; Kusnierkiewicz, D.; Lauer, T. R.; Lee, J. E.; Lindstrom, K. L.; Lunsford, A. W.; Mallder, V. A.; Martin, N.; McComas, D. J.; McNutt, R. L.; Mehoke, D.; Mehoke, T.; Melin, E. D.; Mutchler, M.; Nelson, D.; Nimmo, F.; Nunez, J. I.; Ocampo, A.; Owen, W. M.; Paetzold, M.; Page, B.; Pelletier, F.; Peterson, J.; Pinkine, N.; Piquette, M.; Porter, S. B.; Protopapa, S.; Redfern, J.; Reitsema, H. J.; Reuter, D. C.; Roberts, J. H.; Robbins, S. J.; Rogers, G.; Rose, D.; Runyon, K.; Ryschkewitsch, M. G.; Schenk, P.; Sepan, B.; Showalter, M. R.; Soluri, M.; Stanbridge, D.; Stryk, T.; Szalay, J. R.; Tapley, M.; Taylor, A.; Taylor, H.; Umurhan, O. M.; Verbiscer, A. J.; Versteeg, M. H.; Vincent, M.; Webbert, R.; Weidner, S.; Weigle, G. E.; White, O. L.; Whittenburg, K.; Williams, B. G.; Williams, K.; Williams, S.; Zangari, A. M.; Zirnstein, E. Bibcode: 2016Sci...351.8866G Altcode: 2016arXiv160405356G Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. Whereas the lower atmosphere (at altitudes of less than 200 kilometers) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen (N2) dominates the atmosphere (at altitudes of less than 1800 kilometers or so), whereas methane (CH4), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6) are abundant minor species and likely feed the production of an extensive haze that encompasses Pluto. The cold upper atmosphere shuts off the anticipated enhanced-Jeans, hydrodynamic-like escape of Pluto's atmosphere to space. It is unclear whether the current state of Pluto's atmosphere is representative of its average state - over seasonal or geologic time scales. Title: New Horizons Alice sky Lyman-α at Pluto encounter: Importance for photochemistry Authors: Retherford, K. D.; Gladstone, R.; Stern, S. A.; Weaver, H. A., Jr.; Young, L. A.; Olkin, C.; Cheng, A. F.; Greathouse, T.; Kammer, J.; Linscott, I.; Parker, A. H.; Parker, J. W.; Schindhelm, R.; Singer, K. N.; Steffl, A.; Strobel, D. F.; Summers, M. E.; Tsang, C.; Tyler, G. L.; Versteeg, M.; Woods, W. W.; Ennico Smith, K.; Hinson, D. P.; Pryor, W. R.; Cunningham, N. J.; Curdt, W. Bibcode: 2015AGUFMSM31D2538R Altcode: The third zone of our solar system, including the Pluto system, has a unique illumination environment at UV wavelengths. While direct solar Lyman-α emissions dominate the signal at 121.6 nm at classical solar system distances, the contribution of illumination by Interplanetary Medium (IPM) Lyman-α sky-glow is roughly on par at Pluto (Gladstone et al. 2015). The Pluto-Alice UV imaging spectrograph on New Horizons conducted several dedicated sky scans to measure the IPM Lyman-α both en route to and while at Pluto. These scans provide 6° by 360° great-circle swaths while spinning the spacecraft. Three sets of scans conducted en route are reported in Gladstone et al. (2012). During the Pluto encounter, sets of scans with six such swaths evenly spaced ~30° apart for all-sky coverage were obtained just before closest approach and again just after. These measurements agree well with brightness variations expected for IPM brightnesses peaking in the sunward direction and interspersed with detections of UV bright stars and other sky features. Previous studies estimated contributions of ~2/3rds direct solar Lyα and 1/3rd IPM Lyα. Our early results suggest that these model predictions need revision. These findings have important implications for determining the rates of photochemical reactions within Pluto's atmosphere that are driven by UV photons at 121.6 nm. Similarly, new constraints are provided to the rates of photolysis on Charon's polar winter nightside. These constraints are useful for understanding the volatile transport and long-term stability of the dark red region near Charon's pole discovered by New Horizons. Title: New Horizons Observations of the Atmospheres of Pluto and Charon Authors: Gladstone, G. R.; Stern, S. A.; Weaver, H. A.; Young, L. A.; Ennico, K. A.; Olkin, C. B.; Cheng, A. F.; Greathouse, T. K.; Hinson, D. P.; Kammer, J. A.; Linscott, I. R.; Parker, A. H.; Parker, J. Wm.; Retherford, K. D.; Schindhelm, R.; Singer, K. N.; Steffl, A. J.; Strobel, D. F.; Summers, M. E.; Tsang, C. C. C.; Tyler, G. L.; Versteeg, M. H.; Woods, W. W.; Cunningham, N.; Curdt, W. Bibcode: 2015DPS....4710005G Altcode: Major goals of the New Horizons (NH) mission are to explore and characterize the structure and composition of Pluto’s atmosphere, and to establish whether Charon has a measurable atmosphere of its own. The primary instruments onboard NH which contribute to these goals are the REX instrument, through uplink X-band radio occultations, the Alice instrument, through extreme- and far-ultraviolet solar occultations, and the LORRI panchromatic imager, through high-phase-angle imaging. The associated datasets were obtained following closest approach of NH to Pluto. Pressure and temperature profiles of the lower atmosphere are derived from the REX data, the composition and structure of the extended atmosphere are derived from the Alice data (supported by approach observations of reflected ultraviolet sunlight), and the distribution and properties of Pluto’s hazes are derived from the LORRI data. In this talk an overview of the early atmosphere science results will be presented.This work was supported by NASA's New Horizons project. Title: Pluto's Extended Atmosphere: New Horizons Alice Lyman-α Imaging Authors: Retherford, Kurt D.; Gladstone, G. Randall; Stern, S. Alan; Weaver, Harold A.; Young, Leslie A.; Ennico, Kimberly A.; Olkin, Cathy B.; Cheng, Andy F.; Greathouse, Thomas K.; Hinson, David P.; Kammer, Joshua A.; Linscott, Ivan R.; Parker, Alex H.; Parker, Joel Wm.; Pryor, Wayne R.; Schindhelm, Rebecca; Singer, Kelsi N.; Steffl, Andrew J.; Strobel, Darrell F.; Summers, Michael E.; Tsang, Constantine C. C.; Tyler, G. Len; Versteeg, Maarten H.; Woods, William W.; Cunningham, Nathaniel J.; Curdt, Werner Bibcode: 2015DPS....4710508R Altcode: Pluto's upper atmosphere is expected to extend several planetary radii, proportionally more so than for any planet in our solar system. Atomic hydrogen is readily produced at lower altitudes due to photolysis of methane and transported upward to become an important constituent. The Interplanetary Medium (IPM) provides a natural light source with which to study Pluto's atomic hydrogen atmosphere. While direct solar Lyman-α emissions dominate the signal at 121.6 nm at classical solar system distances, the contribution of diffuse illumination by IPM Lyman-α sky-glow is roughly on par at Pluto (Gladstone et al., Icarus, 2015). Hydrogen atoms in Pluto's upper atmosphere scatter these bright Lyα emission lines, and detailed simulations of the radiative transfer for these photons indicate that Pluto would appear dark against the IPM Lyα background. The Pluto-Alice UV imaging spectrograph on New Horizons conducted several observations of Pluto during the encounter to search for airglow emissions, characterize its UV reflectance spectra, and to measure the radial distribution of IPM Lyα near the disk. Our early results suggest that these model predictions for the darkening of IPM Lyα with decreasing altitude being measureable by Pluto-Alice were correct. We'll report our progress toward extracting H and CH4 density profiles in Pluto's upper atmosphere through comparisons of these data with detailed radiative transfer modeling. These New Horizons findings will have important implications for determining the extent of Pluto's atmosphere and related constraints to high-altitude vertical temperature structure and atmospheric escape.This work was supported by NASA's New Horizons project. Title: Flarelike brightenings of active region loops observed with SUMER Authors: Wang, T. J.; Innes, D. E.; Solanki, S. K.; Curdt, W. Bibcode: 2015arXiv151000337W Altcode: Coronal loops on the east limb of the Sun were observed by SUMER on SOHO for several days. Small flare-like brightenings are detected very frequently in the hot flare line Fe~{\small XIX}. We find that the relatively intense events are in good coincidence with the transient brightenings seen by Yohkoh/SXT. A statistical analysis shows that these brightenings have durations of 5-84 min and extensions along the slit of 2-67 Mm. The integrated energy observed in Fe~{\small XIX} for each event is in the range of $3\times10^{18}-5\times10^{23}$ ergs, and the estimated thermal energy ranges from $10^{26}-10^{29}$ ergs. Application of the statistical method proposed by Parnell \& Jupp (2000) yields a value of 1.5 to 1.8 for the index of a power law relation between the frequency of the events and the radiated energy in Fe~{\small XIX}, and a value of 1.7 to 1.8 for the index of the frequency distribution of the thermal energy in the energy range $>10^{27}$ ergs. We examine the possibility that these small brightenings give a big contribution to heating of the active region corona. Title: Modeling the Chromosphere of a Sunspot and the Quiet Sun Authors: Avrett, E.; Tian, H.; Landi, E.; Curdt, W.; Wülser, J. -P. Bibcode: 2015ApJ...811...87A Altcode: Semiempirical atmospheric modeling attempts to match an observed spectrum by finding the temperature distribution and other physical parameters along the line of sight through the emitting region such that the calculated spectrum agrees with the observed one. In this paper we take the observed spectrum of a sunspot and the quiet Sun in the EUV wavelength range 668-1475 Å from the 2001 SUMER atlas of Curdt et al. to determine models of the two atmospheric regions, extending from the photosphere through the overlying chromosphere into the transition region. We solve the coupled statistical equilibrium and optically thick radiative transfer equations for a set of 32 atoms and ions. The atoms that are part of molecules are treated separately, and are excluded from the atomic abundances and atomic opacities. We compare the Mg ii k line profile observations from the Interface Region Imaging Spectrograph with the profiles calculated from the two models. The calculated profiles for the sunspot are substantially lower than the observed ones, based on the SUMER models. The only way we have found to raise the calculated Mg ii lines to agree with the observations is to introduce illumination of the sunspot from the surrounding active region. Title: Hydrogen Ly-α and Ly-β full Sun line profiles observed with SUMER/SOHO (1996-2009) Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2015A&A...581A..26L Altcode: Context. Accurate hydrogen spectra emitted by the entire solar disc in the Ly-α and Ly-βlines are valuable for deriving the distribution and the behaviour of atomic hydrogen in the heliosphere, for understanding the UV emissions of solar type stars better, and finally for estimating the solar energy input that mainly initiates the chemical processes occurring in the planetary and cometary outer atmospheres.
Aims: In this paper we want to accurately determine the irradiance solar spectral profiles of Ly-α and Ly-β and their evolution through the solar activity cycle 23.
Methods: The SUMER/SOHO spectrometer is a slit spectrometer that is only able to analyse a small part of the solar image. Consequently, we used the scattered light properties of the telescope to obtain average spectra over the solar disc. Then the profile is calibrated using the SOLSTICE/UARS and TIMED/SEE irradiance spectra.
Results: We obtained a set of irradiance Ly-α and Ly-β solar spectra with a 0.002 nm resolution through the solar activity cycle 23. In each line a relation between the integrated profile and the line centre intensity was obtained.Knowing the line irradiance, it is possible to deduce the central line profile intensity, a critical input into the interplanetary and planetary oxygen and hydrogen fluorescent processes.
Conclusions: The observation of H i Ly-α and Ly-β line profiles by SUMER/SOHO during the cycle 23 allows analysis of the evolution of their characteristics and accurate determination of UV radiation input into the solar system.

Profiles are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A26 Title: VizieR Online Data Catalog: Sun hydrogen Lyman irradiance lines profiles (Lemaire+, 2015) Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schuhle, U.; Wilhelm, K. Bibcode: 2015yCat..35810026L Altcode: Set of irradiance Ly-α and Ly-β solar spectra with a 0.002nm resolution through the solar activity cycle 23. The wavelength distance from line center is given every 0.001nm.

(2 data files). Title: Non-LTE modelling of prominence fine structures using hydrogen Lyman-line profiles Authors: Schwartz, P.; Gunár, S.; Curdt, W. Bibcode: 2015A&A...577A..92S Altcode:
Aims: We perform a detailed statistical analysis of the spectral Lyman-line observations of the quiescent prominence observed on May 18, 2005.
Methods: We used a profile-to-profile comparison of the synthetic Lyman spectra obtained by 2D single-thread prominence fine-structure model as a starting point for a full statistical analysis of the observed Lyman spectra. We employed 2D multi-thread fine-structure models with random positions and line-of-sight velocities of each thread to obtain a statistically significant set of synthetic Lyman-line profiles. We used for the first time multi-thread models composed of non-identical threads and viewed at line-of-sight angles different from perpendicular to the magnetic field.
Results: We investigated the plasma properties of the prominence observed with the SoHO/SUMER spectrograph on May 18, 2005 by comparing the histograms of three statistical parameters characterizing the properties of the synthetic and observed line profiles. In this way, the integrated intensity, Lyman decrement ratio, and the ratio of intensity at the central reversal to the average intensity of peaks provided insight into the column mass and the central temperature of the prominence fine structures. Title: Solar and Galactic Cosmic Rays Observed by SOHO Authors: Fleck, Bernhard; Curdt, Werner; Olive, Jean-Philippe; van Overbeek, Ton Bibcode: 2015TESS....131009F Altcode: Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs) have left an imprint on SOHO technical systems. While the solar array efficiency degraded irreversibly down to 75% of its original level over 1 ½ solar cycles, Single Event Upsets (SEUs) in the solid state recorder (SSR) have been reversed by the memory protection mechanism. We compare the daily CRF observed by the Oulu station with the daily SOHO SEU rate and with the degradation curve of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both modulated by the solar cycle and are highly correlated, except for sharp spikes in the SEU rate, caused by isolated SEP events, which also show up as discontinuities in the otherwise slowly decreasing solar ray efficiency. This allows to discriminate between effects with solar and non-solar origin and to compare the relative strength of both. We find that the total number of SSR SEUs with solar origin over the 17 ½ years from January 1996 through June 2013 is of the same order as those generated by cosmic ray hits. 49% of the total solar array degradation during that time can be attributed to proton events, i.e. the effect of a series of short-lived, violent events (SEPs) is comparable to the cycle-integrated damage by cosmic rays. Title: On Extreme-ultraviolet Helium Line Intensity Enhancement Factors on the Sun Authors: Giunta, A. S.; Fludra, A.; Lanzafame, A. C.; O'Mullane, M. G.; Summers, H. P.; Curdt, W. Bibcode: 2015ApJ...803...66G Altcode: Helium lines in the solar EUV spectrum provide useful diagnostics of the solar atmosphere plasma. Helium is one of the few elements that exhibits strong emission lines formed in the lower transition region, and it is the second most abundant element in the Sun. However, the analysis of helium lines is complicated by their optical thickness and the unusual behavior of their intensities, with enhancements by a factor of up to 15 reported in the literature. Detailed study requires spatially and spectrally resolved observations in the EUV range, as well as sophisticated atomic modeling. The present work focuses on the application of the differential emission measure distribution to reproduce the observed fluxes of the He i and He ii lines observed by the Solar and Heliospheric Observatory (SOHO)/Coronal Diagnostic Spectrometer and Hinode/EIS spectrometers, using the latest atomic data. It is found that the comparison between observed and reconstructed intensities for He i resonance lines λλ537.03, 522.21, and 515.62 and the intercombination line λ591.41 does not show a real enhancement. By contrast, He i λ584.33, the first line of the 1{{s}2}{{ }1}S-1s np{{ }1}P resonance series, shows a depletion of a factor ∼2, due to the opacity effect, as supported by non-LTE radiative transfer calculations. For single ionized helium lines 303.78 and 256.32 Å, the enhancement factors obtained are higher and agree with those of previous work. The different behavior of He i and He ii lines suggests a mechanism that affects ionized helium only. Title: The Balmer Lines of He II in the Blue Wing of the Hydrogen Lyman α Line Observed in a Quiescent Prominence Authors: Vial, J. -C.; Eurin, G.; Curdt, W. Bibcode: 2015SoPh..290..381V Altcode: We revisit the prominence observations in the Lyman α line of Curdt et al. (Astron. Astrophys.511, L4, 2010) and focus on the bump in the blue wing of the line, which we identify with He II Balmer lines. We determine the transition candidates, derive an upper limit for the width of the profile and an associated non-thermal velocity close to 0 km s−1, with the assumption that the kinetic temperature is equal to the formation temperature. We compare the total intensity with the corresponding H Lyman α intensity and find a ratio much lower than that measured by Ebadi, Vial, and Ajabshirizadeh (Solar Phys.257, 91, 2009) in other Lyman lines. We confirm this result with observations performed by Schwartz et al. (private communication, 2014), we discuss a possible interpretation, and suggest that this issue needs to be addressed closely in future observations. Title: Solar and Galactic Cosmic Rays Observed by SOHO Authors: Curdt, W.; Fleck, B. Bibcode: 2015CEAB...39..109C Altcode: 2015arXiv150507952C Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs) have left an imprint on SOHO technical systems. While the solar array efficiency degraded irreversibly down to ≈77% of its original level over roughly 1 1/2 solar cycles, Single Event Upsets (SEUs) in the solid state recorder (SSR) have been reversed by the memory protection mechanism. We compare the daily CRF observed by the Oulu station with the daily SOHO SEU rate and with the degradation curve of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both modulated by the solar cycle and are highly correlated, except for sharp spikes in the SEU rate, caused by isolated SEP events, which also show up as discontinuities in the otherwise slowly decreasing solar ray efficiency. This allows to discriminate between effects with solar and non-solar origin and to compare the relative strength of both. We find that during solar cycle 23 (1996 Apr 1 -- 2008 Aug 31) only 6% of the total number of SSR SEUs were caused by SEPs; the remaining 94% were due to galactic cosmic rays. During the maximum period of cycle 23 (2000 Jan 1 -- 2003 Dec 31), the SEP contribution increased to 22%, and during 2001, the year with the highest SEP rate, to 30%. About 40% of the total solar array degradation during the 17 years from Jan 1996 through Feb 2013 can be attributed to proton events, i.e. the effect of a series of short-lived, violent SEP events is comparable to the cycle-integrated damage by cosmic rays. Title: Hot explosions in the cool atmosphere of the Sun Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.; De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V. Bibcode: 2014Sci...346C.315P Altcode: 2014arXiv1410.5842P The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection. Title: Molecular absorption in transition region spectral lines Authors: Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.; Jaeggli, S. Bibcode: 2014A&A...569L...7S Altcode: 2014arXiv1409.1702S
Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra.
Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence.
Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary. The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere.

Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org Title: Scattered Lyman-α radiation of comet 2012/S1 (ISON) observed by SUMER/SOHO Authors: Curdt, W.; Boehnhardt, H.; Vincent, J. -B.; Solanki, S. K.; Schühle, U.; Teriaca, L. Bibcode: 2014A&A...567L...1C Altcode: 2014arXiv1406.4343C During its sungrazing perihelion passage, comet ISON appeared in the field of view of the SUMER spectrometer and allowed unique observations at far-ultraviolet wavelengths with high spatial and temporal resolution. We report results of these observations completed on November 28, 2013, when the comet was only 2.82 Rʘ away from the Sun. Our data show the arrow-shaped dust tail in Ly-α emission trailing behind the predicted position of the nucleus, but offset from the trajectory. We interpret the emission as sunlight that is scattered at μm-sized dust particles. We modeled the dust emission and dynamics to reproduce the appearance of the tail. We were unable to detect any signature of cometary gas or plasma around the expected position of the nucleus and conclude that the outgassing processes must have stopped before the observation started. Moreover, the model we used to reproduce the observed dust tail needs a sharp fall-off of the dust production hours before perihelion transit. We compare the radiances of the disk and the dust tail for an estimate of the dust column density and tail mass. Title: Comet ISON --- from cradle to grave Authors: Boehnhardt, H.; Curdt, W.; Inhester, B.; Lara, L.; Oklay, N.; Podlipnik, B.; Snodgrass, C.; Tubiana, C.; Vincent, J. Bibcode: 2014acm..conf...50B Altcode: Comet ISON came from the Oort Cloud (10,000--100,000 au), the outermost region of the Solar System, where the debris from the formation of giant planets and possible extrasolar comets are stored since the early days of the Sun's existence. The overall chemistry of the comet appears to be normal suggesting a solar origin. During its approach to the Sun, it was active at least since it passed 9.4 au, displaying enhanced activity most likely driven by CO_2 and CO ice sublimation. From about 2.5 au inwards, water-ice sublimation dominated the activity of the km-size nucleus, producing a gas and dust coma of 100,000 km in extension and several million km long plasma and dust tails, most of which were seen overlapping from the Earth. The comet approached the Sun within 0.012 au on 28 Nov.~2013. The fatal disintegration of the nucleus occurred close to the Sun in two steps: About 1.5--0.5 days before perihelion, an extraordinary brightening occurred that may indicate an explosion of the nucleus producing an armada of fragments that continued on the track of the comet with fading activity. The subnuclei exhausted their icy fuel shortly before reaching perihelion and dissolved in a cloud of dust. This cloud and some solid material from the nucleus explosion escaped the Sun and witness the death of the nucleus of comet ISON. Title: Scattered Lyman-alpha radiation of comet 2012/S1 (ISON) observed by SUMER/SOHO Authors: Curdt, W.; Boehnhardt, H.; Germerott, D.; Schuehle, U.; Solanki, S.; Teriaca, L.; Vincent, J. Bibcode: 2014acm..conf..119C Altcode: During its recent perihelion passage, comet ISON came so close to the Sun that it appeared in the field of view (FOV) of the SUMER spectrometer on SOHO and allowed unique observations at far-UV wavelengths with high spatial and temporal resolution. We report results of these observations completed during the comet's encounter with the Sun on November 28.75, 2013. Our data show the dust tail trailing behind the predicted position of the nucleus seen in Lyman-alpha emission as light from the solar disk that is scattered by micron-sized dust particles. The arrow-shaped tail is offset from the trajectory and not aligned with it. We model the dust emission and dynamics to reproduce the appearance of the tail. We could not detect any signature of cometary gas or plasma around the expected position of the nucleus and conclude that the out-gassing processes must have stopped before the comet entered our FOV. Also the model we used to reproduce the observed dust tail needs a sharp fall-off of the dust production hours before perihelion. We compare the radiance of the dust tail to the Lyman-alpha emission of the disk for an estimate of the dust column density. After observing 18 years mostly solar targets, this was the first time that SUMER completed spectroscopic observations of a comet. Title: The SUMER Data in the SOHO Archive Authors: Curdt, W.; Germerott, D.; Wilhelm, K.; Schühle, U.; Teriaca, L.; Innes, D.; Bocchialini, K.; Lemaire, P. Bibcode: 2014SoPh..289.2345C Altcode: 2013arXiv1309.1314C We have released an archive of all observational data of the VUV spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on SOHO that have been acquired until now. The operational phase started with `first light' observations on 27 January 1996 and will end in 2014. Future data will be added to the archive when they become available. The archive consists of a set of raw data (Level 0) and a set of data that are processed and calibrated to the best knowledge we have today (Level 1). This communication describes step by step the data acquisition and processing that has been applied in an automated manner to build the archive. It summarizes the expertise and insights into the scientific use of SUMER spectra that has accumulated over the years. It also indicates possibilities for further enhancement of the data quality. With this article we intend to convey our own understanding of the instrument performance to the scientific community and to introduce the new, standard FITS-format database. Title: Temperature dependence of ultraviolet line parameters in network and internetwork regions of the quiet Sun and coronal holes Authors: Wang, X.; McIntosh, S. W.; Curdt, W.; Tian, H.; Peter, H.; Xia, L. -D. Bibcode: 2013A&A...557A.126W Altcode:
Aims: We study the temperature dependence of the average Doppler shift and the non-thermal line width in network and internetwork regions for both the quiet Sun (QS) and the coronal hole (CH), by using observations of the Solar Ultraviolet Measurements of Emitted Radiation instrument onboard the Solar and Heliospheric Observatory spacecraft.
Methods: We obtain the average Doppler shift and non-thermal line width in the network regions of QS, internetwork regions of QS, network regions of CH, and internetwork regions of CH by applying a single-Gaussian fit to the line profiles averaged in each of the four regions. The formation temperatures of the lines we use cover the range from 104 to 1.2 × 106 K. Two simple scenarios are proposed to explain the temperature dependence of the line parameters in the network regions. In one of the scenarios, the spectral line consists of three components: a rapid, weak upflow generated in the lower atmosphere, a nearly static background, and a slow cooling downflow. In the other scenario, there are just two components, which include a bright core component and a faint wide tail one.
Results: An enhancement of the Doppler shift magnitude and the non-thermal line width in network regions compared to the internetwork regions is reported. We also report that most transition region lines are less redshifted (by 0-8 km s-1) and broader (by 0-5 km s-1) in CH compared to the counterparts of QS. In internetwork regions, the difference in the Doppler shifts between the coronal hole and the QS is slightly smaller, especially for the lines with formation temperatures lower than 2 × 105 K. And the two simple scenarios can reproduce the variation in the line parameters with the temperature very well.
Conclusions: Our results suggest that the physical processes in network and internetwork regions are different and that one needs to separate network and internetwork when discussing dynamics and physical properties of the solar atmosphere. The agreement between the results of the observation and our scenarios suggests that the temperature dependence of Doppler shifts and line widths might be caused by the different relative contributions of the three components at different temperatures. The results may shed new light on our understanding of the complex chromosphere-corona mass cycle. However, the existing observational results do not allow us to distinguish between the two scenarios. At this stage, a high-resolution instrument Interface Region Imaging Spectrograph is highly desirable. Title: European Solar Physics: moving from SOHO to Solar Orbiter and beyond Authors: Solanki, S. K.; Teriaca, L.; Barthol, P.; Curdt, W.; Inhester, B. Bibcode: 2013MmSAI..84..286S Altcode: When ESA and NASA launched the Solar and Heliospheric Observatory (SOHO) to the Sun-Earth L1 point, they also launched European solar physics into a steep upward trajectory. Thanks to the battery of instruments on SOHO our picture of the Sun changed dramatically from that of a sedate, nearly static star into that of a highly structured, dynamic one. Subsequent solar missions have probed higher energy radiation, gazed at the Sun from new vantage points in the ecliptic, analysed the Sun at higher spatial resolution and imaged the whole Sun in many wavelengths at high cadence. Nonetheless, SOHO is still going strong and still delivering unique data. In the meantime European solar physicists are working hard on the next major mission, Solar Orbiter, now being implemented as the M1 mission of ESA's Cosmic Vision program. Solar Orbiter will leave the Earth's orbit and move ever closer to the Sun, reaching a perihelion inside the orbit of Mercury. This will allow it to sample the Sun's dynamic inner heliosphere in situ, while probing the source regions of the ambient solar wind with its remote sensing instruments, a unique combination. Solar Orbiter will also leave the ecliptic and, for the first time, image the Sun's poles. This will bring us closer to finding the missing pieces of the puzzle on how the solar dynamo works. Beyond Solar Orbiter are further exciting prospects, such as the Solar-C mission, or the large European Solar Telescope. Here an overview of solar missions and telescopes and the associated science is given from a European perspective. Title: Explosive Events: Swirling Transition Region Jets Authors: Curdt, W.; Tian, H.; Kamio, S. Bibcode: 2012SoPh..280..417C Altcode: 2012SoPh..tmp...24C; 2012arXiv1201.3199C In this paper, we extend our earlier work to provide additional evidence for an alternative scenario to explain the nature of events called `explosive events'. The bidirected, fast Doppler motion of explosive events observed spectroscopically in the transition region emission is classically interpreted as a pair of bidirectional jets moving upward and downward from a reconnection site. We discuss the problems of this model. In our previous work, we focused basically on the discrepancy of fast Doppler motion without detectable motion in the image plane. We now suggest an alternative scenario for the explosive events, based on our observations of spectral line tilts and bifurcated structure in some events. Both features are indicative of rotational motion in narrow structures. We explain the bifurcation as the result of rotation of hollow cylindrical structures and demonstrate that this kind of sheath model can also be applied to explain the nature of the puzzling `explosive events'. We find that the spectral tilt, the lack of apparent motion, the bifurcation, and a rapidly growing number of direct observations support an alternative scenario of linear, spicular-sized jets with a strong spinning motion. Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. Title: Spectroscopic Observations of Fe XVIII in Solar Active Regions Authors: Teriaca, Luca; Warren, Harry P.; Curdt, Werner Bibcode: 2012ApJ...754L..40T Altcode: 2012arXiv1206.4228T The large uncertainties associated with measuring the amount of high temperature emission in solar active regions (ARs) represents a significant impediment to making progress on the coronal heating problem. Most current observations at temperatures of 3 MK and above are taken with broadband soft X-ray instruments. Such measurements have proven difficult to interpret unambiguously. Here, we present the first spectroscopic observations of the Fe XVIII 974.86 Å emission line in an on-disk AR taken with the SUMER instrument on SOHO. Fe XVIII has a peak formation temperature of 7.1 MK and provides important constraints on the amount of impulsive heating in the corona. Detailed evaluation of the spectra and comparison of the SUMER data with soft X-ray images from the X-Ray Telescope on Hinode confirm that this line is unblended. We also compare the spectroscopic data with observations from the Atmospheric Imaging Assembly (AIA) 94 Å channel on the Solar Dynamics Observatory. The AIA 94 Å channel also contains Fe XVIII, but is blended with emission formed at lower temperatures. We find that it is possible to remove the contaminating blends and form relatively pure Fe XVIII images that are consistent with the spectroscopic observations from SUMER. The observed spectra also contain the Ca XIV 943.63 Å line that, although a factor 2-6 weaker than the Fe XVIII 974.86 Å line, allows us to probe the plasma around 3.5 MK. The observed ratio between the two lines indicates (isothermal approximation) that most of the plasma in the brighter Fe XVIII AR loops is at temperatures between 3.5 and 4 MK. Title: Explosive events - swirling transition region jets Authors: Curdt, Werner; Kamio, Suguru; Tian, Hui; Teriaca, Luca Bibcode: 2012cosp...39..381C Altcode: 2012cosp.meet..381C The bi-directed, fast Doppler motion of explosive events observed spectroscopically in the transition region emission is classically interpreted as a pair of jets moving upward and downward from a reconnection site. We discuss the problems of such a model and provide evidence for an alternative scenario to explain the nature of so-called 'explosive events'. The discrepancy of fast Doppler motion without detectable motion in the image plane is an old, unsolved problem. We now provide the spectral tilt and the jet bifurcation as additional arguments. Both features are indicative of rotational motion in narrow structures. We interpret the bifurcation as the result of rotation of hollow cylindrical structures and demonstrate that such a sheath model can also be applied to explain the nature of the puzzling 'explosive events'. We find that the spectral tilt, the lack of apparent motion, the bifurcation, and a rapidly growing number of direct observations support an alternative scenario of linear, spicular-sized jets with a strong spinning motion. Title: The solar hydrogen Lyman α to Lyman β line ratio Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Woods, T. N. Bibcode: 2012A&A...542L..25L Altcode:
Aims: We investigate the variation in the solar hydrogen Lyman α (Lyα) to Lyman β (Lyβ) line ratio as a function of the solar activity by taking into account new results obtained by SoHO/SUMER and TIMED/SEE.
Methods: We reanalyze data of quiet and active regions previously collected with the LPSP multichannel instrument on OSO8. We then re-examine data obtained on the solar disk with SUMER and compare them with previous data. In a second step, we use the full Sun H i Lyβ profiles to determine the Lyβ contribution to the SEE profiles obtained with a 0.4 nm full width at half-maximum. The variation in the Lyα to Lyβ line ratio is then measured for part of the solar cycle 23 (2002-2008).
Results: We determine the radiance line ratio of the solar H i Lyα to Lyβ line for a quiet Sun area and the relation between the ratio of the Lyα to Lyβ irradiance and the Lyα solar irradiance. Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C. Bibcode: 2012ExA....33..271P Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. Title: Spectroscopic evidence for helicity in explosive events Authors: Curdt, W.; Tian, H. Bibcode: 2011A&A...532L...9C Altcode: 2011arXiv1107.1969C
Aims: We report spectroscopic observations in support of a novel view of transition region explosive events, observations that lend empirical evidence that at least in some cases explosive events may be nothing else but spinning narrow spicule-like structures.
Methods: Our spectra of textbook explosive events with simultaneous Doppler flow of a red and a blue component are extreme cases of high spectroscopic velocities that lack apparent motion, to be expected if interpreted as a pair of collimated, linearly moving jets. The awareness of this conflict led us to the alternative interpretation of redshift and blueshift as a spinning motion of a small plasma volume. In contrast to the bidirectional jet scenario, a small volume of spinning plasma would be fully compatible with the observation of flows without detectable apparent motion. We suspect that these small volumes could be spicule-like structures and try to find evidence for this. We show observations of helical motion in macrospicules and argue that these features - if scaled down to a radius comparable to the slit size of a spectrometer - should have a spectroscopic signature similar to that observed in explosive events, which is admittedly not easily detectable by imagers. Despite of this difficulty, evidence of helicity in spicules has been reported in the literature. This led us to the new insight that the same narrow spinning structures may be the drivers in both cases, structures that imagers observe as spicules and that in spectrometers cross the slit and are seen as explosive events.
Results: We arrive at a concept that supports the idea that explosive events and spicules are different manifestations of the same helicity-driven scenario. In contrast to the conventional view of explosive events as linear bidirectional jets that are triggered by a reconnection event in the transition region, this new interpretation is compatible with the observational results. Consequently, in this case a photospheric or subphotospheric trigger has to be assumed.
Conclusions: We suggest that explosive events/spicules are to be compared to the unwinding of a loaded torsional spring. Title: Continuous upflows and sporadic downflows observed in active regions Authors: Kamio, S.; Peter, H.; Curdt, W.; Solanki, S. K. Bibcode: 2011A&A...532A..96K Altcode: 2011arXiv1107.1993K
Aims: We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops.
Methods: We analyzed images of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at multiple temperatures to detect apparent motions in the coronal loops.
Results: Quasi-periodic brightness fluctuations propagate upwards from the loop footpoint in hot emission at 1 MK, while sporadic downflows are seen in cool emission below 1 MK. The upward motion in hot emission increases just after the cool downflows.
Conclusions: The apparent propagating pattern suggests a hot upflow from the loop footpoints, and is considered to supply hot plasma into the coronal loop, but a wavelike phenomenon cannot be ruled out. Coronal condensation occasionally happens in the coronal loop, and the cool material flows down to the footpoint. Emission from cool plasma could have a significant contribution to hot AIA channels in the event of coronal condensation. Title: Hydrogen Lyα and Lyβ Radiances and Profiles in Polar Colornal Holes Authors: Tian, Hui; Teriaca, Luca; Curdt, Werner; Vial, Jean-Claude Bibcode: 2011shin.confE.166T Altcode: The hydrogen Lyα plays a dominant role in the radiative energy transport in the lower transition region, and is important for the studies of transition-region structure as well as solar wind origin. We investigate the Lyα profiles obtained by the Solar Ultraviolet Measurement of Emitted Radiation spectrograph on the Solar and Heliospheric Observatory spacecraft in coronal holes and the quiet Sun. In a subset of these observations, the Hi Lyβ, Si III, and Ovi lines were also (quasi-)simultaneously recorded. We find that the distances between the two peaks of Lyα profiles are larger in coronal holes than in the quiet Sun, indicating a larger opacity in coronal holes. This difference might result from the different magnetic structures or the different radiation fields in the two regions. Most of the Lyβ profiles in the coronal hole have a stronger blue peak, in contrast to those in quiet-Sun regions while in both regions the Lyα profiles are stronger in the blue peak. Although the asymmetries are likely to be produced by differential flows in the solar atmosphere, their detailed formation processes are still unclear. The radiance ratio between Lyα and Lyβ decreases toward the limb in the coronal hole, which might be due to the different opacity of the two lines. We also find that the radiance distributions of the four lines are set by a combined effect of limb brightening and the different emission level between coronal holes and the quiet Sun. Title: Evolution of microflares associated with bright points in coronal holes and in quiet regions Authors: Kamio, S.; Curdt, W.; Teriaca, L.; Innes, D. E. Bibcode: 2011A&A...529A..21K Altcode: 2010arXiv1009.1957K
Aims: We aim to find similarities and differences between microflares at coronal bright points found in quiet regions and coronal holes, and to study their relationship with large scale flares.
Methods: Coronal bright points in quiet regions and in coronal holes were observed with Hinode/EIS using the same sequence. Microflares associated with bright points are identified from the X-ray lightcurve. The temporal variation of physical properties was traced in the course of microflares.
Results: The lightcurves of microflares indicated an impulsive peak at hot emission followed by an enhancement at cool emission, which is compatible with the cooling model of flare loops. The density was found to increase at the rise of the impulsive peak, supporting chromospheric evaporation models. A notable difference is found in the surroundings of microflares; diffuse coronal jets are produced above microflares in coronal holes while coronal dimmings are formed in quiet regions.
Conclusions: The microflares associated with bright points share common characteristics to active region flares. The difference in the surroundings of microflares are caused by open and closed configurations of the pre-existing magnetic field. Title: The Sunrise Mission Authors: Barthol, P.; Gandorfer, A.; Solanki, S. K.; Schüssler, M.; Chares, B.; Curdt, W.; Deutsch, W.; Feller, A.; Germerott, D.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.; Meller, R.; Müller, R.; Riethmüller, T. L.; Tomasch, G.; Knölker, M.; Lites, B. W.; Card, G.; Elmore, D.; Fox, J.; Lecinski, A.; Nelson, P.; Summers, R.; Watt, A.; Martínez Pillet, V.; Bonet, J. A.; Schmidt, W.; Berkefeld, T.; Title, A. M.; Domingo, V.; Gasent Blesa, J. L.; del Toro Iniesta, J. C.; López Jiménez, A.; Álvarez-Herrero, A.; Sabau-Graziati, L.; Widani, C.; Haberler, P.; Härtel, K.; Kampf, D.; Levin, T.; Pérez Grande, I.; Sanz-Andrés, A.; Schmidt, E. Bibcode: 2011SoPh..268....1B Altcode: 2010arXiv1009.2689B; 2010SoPh..tmp..224B The first science flight of the balloon-borne Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is discussed. Title: The coronal convection Authors: Curdt, W.; Tian, H.; Marsch, E. Bibcode: 2011CEAB...35..187C Altcode: 2011arXiv1101.2365C We study the hydrogen Lyman emission in various solar features -- now including Ly-α observations free from geocoronal absorption -- and investigate statistically the imprint of flows and of the magnetic field on the line profile and radiance distribution. As a new result, we found that in Ly-α rasters locations with higher opacity cluster in the cell interior, while the network has a trend to flatter profiles. Even deeper self reversals and larger peak distances were found in coronal hole spectra. We also compare simultaneous Ly-α and Ly-β profiles. There is an obvious correspondence between asymmetry and redshift for both lines, but, most surprisingly, the asymmetries of Ly-α and Ly-β are opposite. We conclude that in both cases downflows determine the line profile, in case of Ly-α by absorption and in the case of Ly-β by emission. Our results show that the magnetically structured atmosphere plays a dominating role in the line formation and indicate the presence of a persisting downflow at both footpoints of closed loops. We claim that this is the manifestation of a fundamental mass transportation process, which Foukal back in 1978 introduced as the 'coronal convection'. Title: Magnetic and spectroscopic properties of supergranular-scale coronal jets and erupting loops in a polar coronal hole Authors: He, J. -S.; Marsch, E.; Curdt, W.; Tian, H.; Tu, C. -Y.; Xia, L. -D.; Kamio, S. Bibcode: 2010A&A...519A..49H Altcode: Context. Coronal jets and mass ejections associated with erupting loops are two distinct and frequently observed types of transient upflows of plasma in coronal holes (CHs). But the magnetic and spectroscopic properties of these events at the supergranular scale are not well known.
Aims: Here we aim at studying in a polar hole the plasma and field characteristics of coronal jets and erupting loops of a supergranular size, for which we use observations from XRT, EIS and SOT on Hinode as well as EUVI on STEREO.
Methods: The open magnetic field structures related to the coronal jets are obtained by magnetic field extrapolation into the corona from SOT magnetograms. Furthermore, we use the EIS observations to analyze ultraviolet line intensities and Doppler shifts in association with the erupting loops.
Results: We find that the coronal jet plasma is indeed ejected along open field lines, thus confirming the conjecture of jet formation in an open magnetic environment. The magnetic evolution at the jet base is investigated, and the results indicate that the interaction between two flux tubes of opposite magnetic polarities as well as the squeezing of several tubes with identical polarities might be responsible for the jet initiation. We reveal for the first time the spectroscopic signatures of a supergranular-size erupting loop at its early stage, which consists of three steps. The first step is the onset, which is featured by a sudden brightening of one footpoint, as well as by the occurrence of blueshifts along almost its entire path. The second step is the initial expansion of the closed loop, which is estimated to move upward at a speed of about 20 km s-1, as derived from the line-of-sight (LOS) blueshift and the loop enlargement projected onto the plane of the sky. In the third step, the loop's bright footpoint is apparently diminishing its intensity and enhancing its blueshift, which indicates that plasma upflow from the leg is filling the expanding loop volume.
Conclusions: From our results we conclude that in polar CHs, where the steady fast solar wind is known to emanate, there are also at least two possible ways of causing transient plasma outflows at supergranular scale. One is related to coronal jets guided by open field lines, the other to the eruption of closed loops, which is triggered by magnetic reconnection at their footpoints.

3 movies (for Figs. 2-4) are only available in electronic form at http://www.aanda.org Title: Towards a New Formation Flying Solar Coronagraph Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chieze, S.; Zhukov, A. Bibcode: 2010ASPC..424...15L Altcode: We briefly describe an investigation aiming at the development of a giant solar coronagraph instrument onboard of two satellites, separated by about 150 m in formation flight for the detailed observation of the solar coronal plasma. The European Space Agency (ESA) has selected this instrument as the only payload onboard the Proba 3 satellites which will be launched in 2013. The Greek team is developing the command control board of the coronagraph. Title: Hydrogen Lyman Emission through the Solar Cycle Authors: Curdt, W.; Tian, H. Bibcode: 2010ASPC..428...81C Altcode: 2010arXiv1002.3551C We present observations and results of radiance and irradiance studies completed by SOHO/SUMER during the past solar cycle. We find that the cycle variation in Ly-α irradiance as observed by, e.g., UARS/SOLSTICE cannot be explained by quiet Sun radiance data, and conclude that the explanation must be related to differences in the Ly-α radiance of various solar features and changes in their fractional distribution over the solar cycle. Consequently, we studied the emission of the hydrogen Ly-α line in various solar features—for the first time observed by SUMER on disk in full resolution—to investigate the imprint of the magnetic field on line profile and radiance distribution. We also compare quasi-simultaneous Ly-α and Ly-β line profiles. Such high-resolution observations—not hampered by geocoronal absorption—have never been completed before. Title: Solar Transition Region in the Quiet Sun and Active Regions Authors: Tian, H.; Curdt, W.; He, J. -S. Bibcode: 2010aogs...21..277T Altcode: 2009arXiv0912.0345T The solar transition region (TR), in which above the photosphere the temperature increases rapidly and the density drops dramatically, is believed to play an important role in coronal heating and solar wind acceleration. Longlasting upflows are present in the upper TR and interpreted as signatures of mass supply to large coronal loops in the quiet Sun. Coronal bright points (BPs) are local heating phenomena and we found a different Doppler-shift pattern at TR and coronal temperatures in one BP, which might be related to the twisted loop system. The dominant energy loss in the lower TR is the Ly-α emission. It has been found that most Ly-α radiance profiles are stronger in the blue peak, an asymmetry opposite to higher order Lyman lines. This asymmetry is stronger when the downflow in the middle TR is stronger, indicating that the TR flows play an important role in the line formation process. The peak separation of Ly-α is found to be larger in coronal holes than in the quiet Sun, reflecting the different magnetic structures and radiation fields between the two regions. The Lyman line profiles are found to be not reversed in sunspot plume and umbra regions, while they are obviously reversed in the surrounding plage region. At TR temperatures, the densities of the sunspot plume and umbra are a factor of 10 lower than of the plage, indicating that the sunspot plasma emitting at TR temperatures is higher and possibly more extended in height above sunspots than above the plage region. Title: New views on the emission and structure of the solar transition region Authors: Tian, Hui; Marsch, Eckart; Tu, Chuanyi; Curdt, Werner; He, Jiansen Bibcode: 2010PhDT.......178T Altcode: 2010arXiv1004.3017T The Sun is the only star that we can spatially resolve and it can be regarded as a fundamental plasma laboratory of astrophysics. The solar transition region (TR), the layer between the solar chromosphere and corona, plays an important role in solar wind origin and coronal heating. Recent high-resolution observations made by SOHO, TRACE, and Hinode indicate that the TR is highly nonuniform and magnetically structured. Through a combination of spectroscopic observations and magnetic field extrapolations, the TR magnetic structures and plasma properties have been found to be different in coronal holes and in the quiet Sun. In active regions, the TR density and temperature structures also differ in sunspots and the surrounding plage regions. Although the TR is believed to be a dynamic layer, quasi-steady flows lasting from several hours to several days are often present in the quiet Sun, coronal holes, and active regions, indicating some kind of plasma circulation/convection in the TR and corona. The emission of hydrogen Lyman lines, which originates from the lower TR, has also been intensively investigated in the recent past. Observations show clearly that the flows and dynamics in the middle and upper TR can greatly modify the Lyman line profiles. Title: Observations of a rotating macrospicule associated with an X-ray jet Authors: Kamio, S.; Curdt, W.; Teriaca, L.; Inhester, B.; Solanki, S. K. Bibcode: 2010A&A...510L...1K Altcode: 2010arXiv1001.1924K
Aims: We attempt to understand the driving mechanism of a macrospicule and its relationship with a coronal jet.
Methods: We study the dynamics of a macrospicule and an associated coronal jet captured by multi-spacecraft observations. Doppler velocities in both the macrospicule and the coronal jet are determined by EIS and SUMER spectra. Their temporal evolution is studied using X-ray and He II λ304 images.
Results: A blueshift of -120 ± 15 km s-1 is detected on one side of the macrospicule, while a redshift of 50 ± 6 km s-1 is found at the base of the other side. The inclination angle of the macrospicule inferred from a stereoscopic analysis with STEREO suggests that the measured Doppler velocities can be attributed to a rotating motion of the macrospicule rather than a radial flow or an expansion.
Conclusions: The macrospicule is driven by the unfolding motion of a twisted magnetic flux rope, while the associated X-ray jet is a radial outflow. Title: The SUMER Ly-α line profile in quiescent prominences Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U. Bibcode: 2010A&A...511L...4C Altcode: 2010arXiv1002.1197C
Aims: As the result of a novel observing technique, we publish for the first time SoHO-SUMER observations of the true spectral line profile of hydrogen Lyman-α in quiescent prominences. Because SoHO is not in Earth orbit, our high-quality data set is free of geocoronal absorption. We studied the line profile to complement earlier observations of the higher Lyman lines and to substantiate recent model predictions.
Methods: We applied the reduced-aperture observing mode to two prominence targets and did a statistical analysis of the line profiles in both data sets. In particular, we investigated the shape of the profile, the radiance distribution, and the line shape-to-radiance interrelation. We also compared Ly-α data to co-temporal λ 1206 Si iii data.
Results: We find that the average profile of Ly-α has a blue-peak dominance and is reversed more if the line-of-sight is perpendicular to the field lines. The contrast of Ly-α prominence emission rasters is very low, and the radiance distribution differs from the log-normal distribution of the disk. Features in the Si iii line are not always co-spatial with Ly-α emission.
Conclusions: Our empirical results support recent multi-thread models, which predict that asymmetries and depths of the self-reversal depend on the orientation of the prominence axis relative to the line-of-sight. Title: The coronal convection Authors: Curdt, Werner; Tian, Hui; Marsch, Eckart Bibcode: 2010cosp...38.2927C Altcode: 2010cosp.meet.2927C We studied with SUMER the hydrogen Lyman emission in various solar features -now including Ly-α observations -and investigated the imprints that coronal flows and the solar magnetic field have on the line profile and radiance distribution. As a new result, we found that in Ly-α raster maps the locations with higher line opacity (evident by strong self-absorption dips) cluster in the cell interior of the magnetic network, while the lines from the network lanes tend to reveal flatter profiles. Even deeper self reversals and larger peak separations were found in coronal hole spectra. We also compared the quasi-simultaneously obtained Ly-α and Ly-β profiles and found an obvious correspondence between asymmetry and redshift for both lines, but, most surprisingly, the asymmetries of Ly-α and Ly-β are opposite. We conclude that in both cases downflows determine the line profile, in the case of Ly-α by absorption and in the case of Ly-β by emission. Our results, which are further supported by recent Hinode data, show that the magnetic structure of the solar atmosphere plays a dominant role in the line formation, and indicate the prevalence of persistent downflows at both footpoints of closed loops. We suggest all this to be the manifestation of a continuous mass-transportation process, which Foukal back in 1978 introduced as 'coronal convection'. Title: Spectroscopic Diagnostics of Polar Coronal Plumes Authors: Wilhelm, K.; Dwivedi, B. N.; Curdt, W. Bibcode: 2010ASSP...19..454W Altcode: 2010mcia.conf..454W; 2009arXiv0902.4167W Polar coronal plumes seen during solar eclipses can now be studied with space-borne telescopes and spectrometers. We briefly discuss such observations from space with a view to understanding their plasma characteristics. Using these observations, especially from SUMER/SOHO, but also from EUVI/STEREO, we deduce densities, temperatures, and abundance anomalies in plumes and inter-plume regions, and discuss their implications for better understanding of these structures in the Sun's atmosphere. Title: Impusive heating of bright points observed by EIS and SUMER Authors: Kamio, Suguru; Curdt, Werner; Teriaca, Luca; Innes, Davina Bibcode: 2010cosp...38.2838K Altcode: 2010cosp.meet.2838K We studied the temporal variation of bright points (BPs) in the quiet region and in the coronal hole. Time series of X-ray images show significant emission increases in BPs with durations shorter than 10 min. Since these impulsive brightenings are frequently found all over the Sun, study of their mechanism is important for understanding the dynamics in the quiescent corona. Characteristics of light curves of BPs in the transition region and in the corona are similar to those of solar flares, though at a much smaller scale. Fast raster scans with SOHO/SUMER and Hinode/EIS allowed us to obtain light curves in multiple emission lines. At the peak of X-ray flux, a significant emission in Fe XV (2MK), which is normally very weak in BPs, is detected. In addition, diagnostic using the Fe XII line pair indicate density increase in BPs. These results suggest that impulsive heating takes place in the corona, which causes chromospheric evaporation supplying hot plasma into coronal loops. After the X-ray peak, delayed emission increase in He II and O IV is observed, which is interpreted as the cooling of hot plasma. We will discuss the relationship between these small scale flares and jets. Title: ASPIICS / PROBA-3: a formation flying externally-occulted giant coronagraph mission Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A. Bibcode: 2010cosp...38.2858L Altcode: 2010cosp.meet.2858L Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observa-tions of the white light corona inside typically 2-2.5 Rsun. Formation flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs us-ing a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at distances of hundred meters. Such an instrument has just been selected by ESA to fly (by the end of 2013) on its PROBA-3 mission, presently in phase B, to demonstrate formation flying. It will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines (in partic-ular the forbidden line of FeXIV at 530.285 nm) from the coronal base out to 3 Rsun using a Fabry-Perot interferometer. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.05 Rsun from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to try reaching the chromosphere and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload and scientific objectives are detailed. Title: Multi-spacecraft observation of a magnetic cloud Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A. Bibcode: 2010cosp...38.1921D Altcode: 2010cosp.meet.1921D Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observa-tions of the white light corona inside typically 2-2.5 Rsun. Formation flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs us-ing a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at distances of hundred meters. Such an instrument has just been selected by ESA to fly (by the end of 2013) on its PROBA-3 mission, presently in phase B, to demonstrate formation flying. It will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines (in partic-ular the forbidden line of FeXIV at 530.285 nm) from the coronal base out to 3 Rsun using a Fabry-Perot interferometer. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.05 Rsun from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to try reaching the chromosphere and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload and scientific objectives are presented. Title: New views on the emission and structure of the solar transition region Authors: Tian, Hui; Marsch, Eckart; Tu, Chuanyi; Curdt, Werner; He, Jiansen Bibcode: 2010NewAR..54...13T Altcode: The Sun is the only star that we can spatially resolve and it can be regarded as a fundamental plasma laboratory of astrophysics. The solar transition region (TR), the layer between the solar chromosphere and corona, plays an important role in solar wind origin and coronal heating. Recent high-resolution observations made by SOHO, TRACE, and Hinode indicate that the TR is highly nonuniform and magnetically structured. Through a combination of spectroscopic observations and magnetic field extrapolations, the TR magnetic structures and plasma properties have been found to be different in coronal holes and in the quiet Sun. In active regions, the TR density and temperature structures also differ in sunspots and the surrounding plage regions. Although the TR is believed to be a dynamic layer, quasi-steady flows lasting from several hours to several days are often present in the quiet Sun, coronal holes, and active regions, indicating some kind of plasma circulation/convection in the TR and corona. The emission of hydrogen Lyman lines, which originates from the lower TR, has also been intensively investigated in the recent past. Observations show clearly that the flows and dynamics in the middle and upper TR can greatly modify the Lyman line profiles. Title: A new view of solar wind origin near active regions and in polar coronal holes on the basis of Hinode observations Authors: He, Jiansen; Marsch, Eckart; Tu, Chuanyi; Tian, Hui; Guo, Lijia; Curdt, Werner; Xia, Lidong; Kamio, Suguru Bibcode: 2010cosp...38.2938H Altcode: 2010cosp.meet.2938H The possibility of full-range solar observations from Hinode with high temporal and spatial resolution motivated us to revisit the solar wind origin in the solar atmosphere. For the solar wind origin near active regions, we reveal activity in the chromosphere to be responsible for the coronal outflow at the AR edge; meanwhile we also succeeded in finding the related solar wind stream in the heliosphere. Chromospheric spicule-like jets are found to occur intermittently, and to flow in similar direction than the intermittent coronal outflows. EIS observations reveal that there are blue-shifts at the edge of AR in both chromosphere and corona, and that the blue-shift increases with temperature. Therefore, we suggest that the nascent solar wind may probably originate in the chromosphere at the edge of ARs. The connection between the source regions and their respective solar wind streams is established through magnetic field lines, which are extrapolated to reach the solar ecliptic plane at 2.5 Rs. We find that the AR edge may be the source region of an intermediate-speed (400 km/s) solar wind stream. For the solar wind origin in polar coronal holes (CHs), we extend the blue-shift observations from the transition region up to the corona, investigate the magnetic characteristics in association with the polar coronal jets, and study in details the initial phase of meso-scale loop eruption in polar CHs. We find that the blue-shift becomes more and more dominant with increasing temperature from the transition region to the corona. The polar coronal jets are found to be elongated along the extrapolated open field lines, which appear in fanning-out shape. The cancellation between bipolar magnetic fields, or squeezing of monopolar magnetic fields, may be the driver for a jet launch. The meso-scale loop started its eruption with a sudden brightening at one footpoint, then expanded and moved upwardly with a speed of 20 km/s, causing the mass at the footpoint to flow outwardly and to fill in the expanded volume. We suggest that mass confined in the coronal loops may be dynamically released into the outer corona and even heliosphere via magnetic reconnection. References: [1]. He, J.-S., Marsch, E., Tu, C.-Y., Guo, L.-J., Tian, H., Intermittent outflows at the edge of an active region -a possible source of the solar wind. Submitted to AA. [2]. Tian, H., Tu, C.-Y., Marsch, E., He, J.-S., Kamio, S., The nascent fast solar wind observed by the EUV imaging spectrometer on board Hinode, ApJ, 709, L88-L93, 2010. [3]. He, J.-S., Marsch, E., Curdt, W., Tu, C.-Y., Xia, L.-D., Tian, H., Kamio, S., Meso-scale coronal jets and erupting loops guided by magnetic fields in a polar coronal hole region, in preparation. Title: Semiempirical Models of the Solar Atmosphere. III. Set of Non-LTE Models for Far-Ultraviolet/Extreme-Ultraviolet Irradiance Computation Authors: Fontenla, J. M.; Curdt, W.; Haberreiter, M.; Harder, J.; Tian, H. Bibcode: 2009ApJ...707..482F Altcode: Semiempirical atmospheric models of solar surface features as observed at moderate resolution are useful tools for understanding the observed solar spectral irradiance variations. Paper I described a set of models constructed to reproduce the observed radiance spectrum for solar surface features at ~2 arcsec resolution that constitute an average over small-scale features such as granulation. Paper II showed that a revision of previous models of low-chromospheric inter-network regions explains the observed infrared CO lines in addition to the UV and radio continuum from submillimeter to centimetric wavelengths. The present paper (1) shows that the Ca II H and K line wing observations are also explained by the new quiet-Sun-composite model, (2) introduces new low-chromospheric models of magnetic features that follow the ideas in Paper II, (3) introduces new upper chromospheric structures for all quiet-Sun and active-region models, and (4) shows how the new set of models explains EUV/FUV observations of spectral radiance and irradiance. This paper also discusses the chromospheric radiative-loss estimates in each of the magnetic features. The new set of models provides a basis for the spectral irradiance synthesis at EUV/FUV wavelengths based on the features observed on the solar surface. Title: Upflows in Funnel-like Legs of Coronal Magnetic Loops Authors: Tian, Hui; Marsch, Eckart; Curdt, Werner; He, Jiansen Bibcode: 2009ApJ...704..883T Altcode: 2009arXiv0909.0739T The prominent blueshifts of Ne VIII associated with the junctions of the magnetic network in the quiet Sun are still not well understood. By comparing the coronal magnetic-field structures as obtained by a potential-field reconstruction with the conspicuous blueshift patches on the Dopplergram of Ne VIII as observed in an equatorial quiet-Sun region, we find that most of the regions with significant upflow are associated with the funnel-like legs of magnetic loops and cospatial with increments of the line width. These quasi-steady upflows can be regarded as the signatures of mass supply to coronal loops. By using the square root of the line intensity as a proxy for the plasma density, the mass flux of the upflow in each funnel can be estimated. We find that the mass flux is anti-correlated with the funnel's expansion factor as determined from the extrapolated magnetic field. One of the loop systems is associated with a coronal bright point, which was observed by several instruments and exhibited various morphologies in different wavelengths and viewing directions. A remarkable agreement between its magnetic structure and the associated EUV emission pattern was found, suggesting an almost potential-field nature of the coronal magnetic field. We also report the direct detection of a small-scale siphon flow by both STEREO satellites. However, this transient siphon flow occurred in a weak mixed-polarity-field region, which was outside the adjacent magnetic funnel, and thus it is perhaps not related to plasma upflow in the funnel. Based on these observations, we suggest that at upper transition region (TR) temperatures the dominant flows in quiet-Sun coronal loops are long-lasting upflows rather than siphon flows. We also discuss the implications of our results for coronal heating and unresolved magnetic structures. Title: Hydrogen Lyα and Lyβ Radiances and Profiles in Polar Coronal Holes Authors: Tian, Hui; Teriaca, Luca; Curdt, Werner; Vial, Jean-Claude Bibcode: 2009ApJ...703L.152T Altcode: 2009arXiv0909.0735T The hydrogen Lyα plays a dominant role in the radiative energy transport in the lower transition region, and is important for the studies of transition-region structure as well as solar wind origin. We investigate the Lyα profiles obtained by the Solar Ultraviolet Measurement of Emitted Radiation spectrograph on the Solar and Heliospheric Observatory spacecraft in coronal holes and the quiet Sun. In a subset of these observations, the H I Lyβ, Si III, and O VI lines were also (quasi-)simultaneously recorded. We find that the distances between the two peaks of Lyα profiles are larger in coronal holes than in the quiet Sun, indicating a larger opacity in coronal holes. This difference might result from the different magnetic structures or the different radiation fields in the two regions. Most of the Lyβ profiles in the coronal hole have a stronger blue peak, in contrast to those in quiet-Sun regions while in both regions the Lyα profiles are stronger in the blue peak. Although the asymmetries are likely to be produced by differential flows in the solar atmosphere, their detailed formation processes are still unclear. The radiance ratio between Lyα and Lyβ decreases toward the limb in the coronal hole, which might be due to the different opacity of the two lines. We also find that the radiance distributions of the four lines are set by a combined effect of limb brightening and the different emission level between coronal holes and the quiet Sun. Title: Solar transition region above sunspots Authors: Tian, H.; Curdt, W.; Teriaca, L.; Landi, E.; Marsch, E. Bibcode: 2009A&A...505..307T Altcode: 2009arXiv0906.2211T Aims: We study the transition region (TR) properties above sunspots and the surrounding plage regions, by analyzing several sunspot reference spectra obtained by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument in March 1999 and November 2006.
Methods: We compare the SUMER spectra observed in the umbra, penumbra, plage, and sunspot plume regions. The hydrogen Lyman line profiles averaged in each of the four regions are presented. For the sunspot observed in 2006, the electron densities, differential emission measure (DEM), and filling factors of the TR plasma in the four regions are also investigated.
Results: The self-reversals of the hydrogen Lyman line profiles are almost absent in sunspots at different locations (at heliocentric angles of up to 49°) on the solar disk. In the sunspot plume, the Lyman lines are also not reversed, whilst the lower Lyman line profiles observed in the plage region are obviously reversed, a phenomenon found also in the normal quiet Sun. The TR densities of the umbra and plume are similar and one order of magnitude lower than those of the plage and penumbra. The DEM curve of the sunspot plume exhibits a peak centered at log(T / K) ~ 5.45, which exceeds the DEM of other regions by one to two orders of magnitude at these temperatures. We also find that more than 100 lines, which are very weak or not observed anywhere else on the Sun, are well observed by SUMER in the sunspot, especially in the sunspot plume.
Conclusions: We suggest that the TR above sunspots is higher and probably more extended, and that the opacity of the hydrogen lines is much lower above sunspots, compared to the TR above plage regions. Our result indicates that the enhanced TR emission of the sunspot plume is probably caused by a large filling factor. The strongly enhanced emission at TR temperatures and the reduced continuum ensure that many normally weak TR lines are clearly distinctive in the spectra of sunspot plumes.

Tables 5 and 6 are only available in electronic form at http://www.aanda.org Title: Hydrogen Lyman-α and Lyman-β spectral radiance profiles in the quiet Sun Authors: Tian, H.; Curdt, W.; Marsch, E.; Schühle, U. Bibcode: 2009A&A...504..239T Altcode: 2009arXiv0907.1069T Aims: We extend earlier work by studying the line profiles of the hydrogen Lyman-α and Lyman-β lines in the quiet Sun. They were obtained quasi-simultaneously in a raster scan with a size of about 150'' × 120'' near disk center.
Methods: The self-reversal depths of the Ly-α and Ly-β profiles. we are quantified by measuring the maximum spectral radiances of the two horns and the minimum spectral radiance of the central reversal. The information on the asymmetries of the Ly-α and Ly-β profiles is obtained through calculating the 1st and 3rd-order moments of the line profiles. By comparing maps of self-reversal depths and the moments with radiance images of the Lyman lines, photospheric magnetograms, and Dopplergrams of two other optically thin lines, we studied the spatial distribution of the Ly-α and Ly-β profiles with different self-reversal depths, and investigated the relationship between profile asymmetries and flows in the solar atmosphere.
Results: We find that the emissions of the Lyman lines tend to be more strongly absorbed in the internetwork, as compared to those in the network region. Almost all of the Ly-α profiles are self-reversed, while about 17% of the Ly-β profiles are not reversed. The ratio of Ly-α and Ly-β intensities seems to be independent of the magnetic field strength. Most Ly-α profiles are stronger in the blue horn, whereas most Ly-β profiles are stronger in the red horn. However, the opposite asymmetries of Ly-α and Ly-β are not correlated pixel-to-pixel. We also confirm that when larger transition-region downflows are present, the Ly-α and Ly-β profiles are more enhanced in the blue and red horns, respectively. The first-order moment of Ly-β, which reflects the combined effects of the profile asymmetry and motion of the emitting material, strongly correlates with the Doppler shifts of the Si iii and O vi lines, while this correlation is much weaker for Ly-α. Our analysis shows that both Ly-α and Ly-β might be more redshifted if stronger transition-region downflows are present. We also find that the observed average Ly-β profile is redshifted with respect to its rest position. Title: Distribution of jets and magnetic fields in a coronal hole Authors: Kamio, S.; Hara, H.; Watanabe, T.; Curdt, W. Bibcode: 2009A&A...502..345K Altcode: Context: Recent observations of ubiquitous jets in coronal holes suggest that they play an important role in coronal heating and solar wind acceleration.
Aims: The aim of our study is to understand the magnetic connectivity and the formation of jets in coronal holes. The study of jets also helps to understand the magnetic field configuration in the coronal hole.
Methods: A coordinated observation between EIS and SUMER was carried out in a polar coronal hole to investigate both the transition region and the corona. Spectropolarimeter (SP) data allowed us to examine the relationship between the distribution of jets and magnetic fields in the photosphere.
Results: Coronal jets as well as explosive events and cool upflows were identified from EIS and SUMER data. The location of these events are correlated with network fields in the photosphere.
Conclusions: Footpoints of coronal jets are connected to patches of vertical kG fields in the photosphere, which are thought to anchor open fields in the upper corona. Explosive events and cool upflows occur in network regions which harbor low-lying fields in the transition region. Title: Physical Properties of Cooling Plasma in Quiescent Active Region Loops Authors: Landi, E.; Miralles, M. P.; Curdt, W.; Hara, H. Bibcode: 2009ApJ...695..221L Altcode: In the present work, we use SOHO/SUMER, SOHO/UVCS, SOHO/EIT, SOHO/LASCO, STEREO/EUVI, and Hinode/EIS coordinated observations of an active region (AR 10989) at the west limb taken on 2008 April 8 to study the cooling of coronal loops. The cooling plasma is identified using the intensities of SUMER spectral lines emitted at temperatures in the 4.15 <= log T <= 5.45 range. EIS and SUMER spectral observations are used to measure the physical properties of the loops. We found that before cooling took place these loops were filled with coronal hole-like plasma, with temperatures in the 5.6 <= log T <= 5.9 range. SUMER spectra also allowed us to determine the plasma temperature, density, emission measure, element abundances, and dynamic status during the cooling process. The ability of EUVI to observe the emitting region from a different direction allowed us to measure the volume of the emitting region and estimate its emission measure. Comparison with values measured from line intensities provided us with an estimate of the filling factor. UVCS observations of the coronal emission above the active region showed no streamer structure associated with AR 10989 at position angles between 242°and 253fdg EIT, LASCO, and EUVI-A narrowband images and UVCS spectral observations were used to discriminate between different scenarios and monitor the behavior of the active region in time. The present study provides the first detailed measurements of the physical properties of cooling loops, a very important benchmark for theoretical models of loop cooling and condensation. Title: The Ly-α profile and center-to-limb variation of the quiet Sun Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P. Bibcode: 2008A&A...492L...9C Altcode: 2008arXiv0812.1441C Aims: We study the emission of the hydrogen Lyman-α line in the quiet Sun, its center-to-limb variation, and its radiance distribution. We also compare quasi-simultaneous Ly-α and Ly-β line profiles.
Methods: We used the high spectral and spatial resolution of the SUMER spectrometer and completed raster scans at various locations along the disk. For the first time, we used a method to reduce the incoming photon flux to a 20%-level by partly closing the aperture door. We also performed a quasi-simultaneous observation of both Ly-α and Ly-β at the Sun center in sit-and-stare mode. We infer the flow characteristic in the Ly-α map from variations in the calibrated λ 1206 Si iii line centroids.
Results: We present the average profile of Ly-α, its radiance distribution, its center-to-limb behaviour, and the signature of flows on the line profiles. Little center-to-limb variation and no limb brightening are observed in the profiles of the Ly-α line. In contrast to all other lines of the Lyman series, which have a red-horn asymmetry, Ly-α has a robust and - except for dark locations - dominating blue-horn asymmetry. There appears to be a brightness-to-asymmetry relationship. A similar and even clearer trend is observed in the downflow-to-asymmetry relationship. This important result is consistent with predictions from models that include flows. However, the absence of a clear center-to-limb variation in the profiles may be more indicative of an isotropic field than a mainly radial flow.
Conclusions: It appears that the ubiquitous hydrogen behaves in a similar way to a filter that dampens all signatures of the line formation by processes in both the chromosphere and transition region. Title: The redshifted network contrast of transition region emission Authors: Curdt, W.; Tian, H.; Dwivedi, B. N.; Marsch, E. Bibcode: 2008A&A...491L..13C Altcode: 2009arXiv0901.0808C Aims: We study the VUV emission of the quiet Sun and the net redshift of transition region lines in the SUMER spectral range. We aim at establishing a link with atmospheric processes and interpreting the observed downflow as the most evident part of the prevailing global coronal mass transport.
Methods: We rank and arrange all pixels of a monochromatic raster scan by radiance and define equally-sized bins of bright, faint, and medium-bright pixels. Comparing the bright pixels with the faint pixels, we determine the spectrally-resolved network contrast for 19 emission lines. We then compare the contrast centroids of these lines with the position of the line itself. We establish a relationship between the observed redshift of the network contrast with the line formation temperature.
Results: We find that the network contrast is offset in wavelength compared to the emission line itself. This offset, if interpreted as redshift, peaks at middle transition region temperatures and is 10 times higher than the previously reported net redshift of transition region emission lines. We demonstrate that the brighter pixels are more redshifted, causing both a significant shift of the network contrast profile and the well-known net redshift. We show that this effect can be reconstructed from the radiance distribution. This result is compatible with loop models, which assume downflows near both footpoints. Title: SUMER observations of the inverse Evershed effect in the transition region above a sunspot Authors: Teriaca, L.; Curdt, W.; Solanki, S. K. Bibcode: 2008A&A...491L...5T Altcode: 2009arXiv0901.3317T Aims: We analyse SUMER spectral scans of a large sunspot within active region NOAA 10923, obtained on 14-15 November 2006, to determine the morphology and dynamics of the sunspot atmosphere at different heights/temperatures.
Methods: The data analysed here consist of spectroheliograms in the continuum around 142.0 nm and in the Si iv 140.2 nm, O iii 70.3 nm, N iv 76.5 nm, and O iv 79.0 nm spectral lines. Gaussian-fitting of the observed profiles provides line-of-sight velocity and Doppler-width maps.
Results: The data show an asymmetric downflow pattern compatible with the presence of the inverse Evershed flow in a region within roughly twice the penumbral radius at transition-region temperatures up to 0.18 MK. The motions, highly inhomogeneous on small scales, seem to occur in a collar of radially directed filamentary structures, with an average width less than the 1 Mm spatial resolution of SUMER and characterised by different plasma speeds. Assuming that the flows are directed along the field lines, we deduce that such field lines are inclined by 10° to 25° with respect to the solar surface. Title: The redshifted footpoints of coronal loops Authors: Dammasch, I. E.; Curdt, W.; Dwivedi, B. N.; Parenti, S. Bibcode: 2008AnGeo..26.2955D Altcode: The physics of coronal loops holds the key to understanding coronal heating and the flow of mass and energy in the region. However, the energy source, structure maintenance and mass balance in coronal loops are not yet fully understood. Observations of blue- and redshifted emissions have repeatedly been used in the construction of loop models. But observations and interpretations of line shifts have been widely debated. Here we present detailed SUMER observations, which clearly show a steady downflow in both footpoints of coronal loops observed at transition region (TR) and lower corona temperatures. We also show and quantify a correlation existing between this Doppler shift and the spectral radiance. Our results indicate a strong correlation which holds from the chromosphere to the lower corona. We suggest that the downflow in the footpoints may be a common phenomenon on all scales, which could explain, why on a statistical basis bright pixels tend to be more redshifted. We conclude by presenting interpretation of such results and their implications in the light of a viable coronal loop model. The observation of steady downflow in redshifted footpoints seems to be in conflict with impulsive heating. Title: Plasma Flows Guided by Strong Magnetic Fields in the Solar Corona Authors: Marsch, Eckart; Tian, Hui; Sun, Jian; Curdt, Werner; Wiegelmann, Thomas Bibcode: 2008ApJ...685.1262M Altcode: In this study new results are presented regarding the relationships between the coronal magnetic field and the intensities and Doppler shifts of ultraviolet emission lines. This combination of magnetic field and spectroscopic data is used here to study material flows in association with the coronal field. We introduce the term "coronal circulation" to describe this flow, and to indicate that the plasma is not static but flows everywhere in the extended solar atmosphere. The blueshifts and redshifts often seen in transition region and coronal ultraviolet emission lines are interpreted as corresponding to upflows and downflows of the plasma on open (funnels) and closed (loops) coronal magnetic field lines, which tightly confine and strongly lead the flows in the low-beta plasma. Evidence for these processes exists in the ubiquitous redshifts mostly seen at both legs of loops on all scales, and the sporadic blueshifts occurring in strong funnels. Therefore, there is no static magnetically stratified plasma in the corona, since panta rhei, but rather a continuous global plasma circulation, being the natural perpetuation of photospheric convection which ultimately is the driver. Title: Loop Morphology and Flows and their Relation to the Magnetic Field Authors: Teriaca, L.; Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Curdt, W.; Sekii, T. Bibcode: 2008ASPC..397..196T Altcode: In November 2006 we obtained several rasters of a large sunspot and its trailing region using the SUMER spectrometer on SOHO. The observations consist of spectroheliograms in the continuum around 142 nm and in several spectral lines formed between 80000 K and 0.6 MK, covering the temperature range from the chromosphere to the lower corona. The observed profiles provide LOS velocity and Doppler width maps. TRACE images in the EUV passbands and in the 160 nm continuum provide a clear picture of the coronal loops and the chromosphere near their footpoints. The same target was also observed by all the instruments aboard Hinode and, in particular, by the SOT spectro-polarimeter measuring the photospheric magnetic vector. We combined SOT and MDI data (covering a larger FOV) to infer the coronal magnetic field of the active region by a nonlinear force-free field extrapolation. The observed radiance and velocity patterns at the various heights/temperatures throughout the solar atmosphere are compared with the field topology. Title: Velocity Structure of Bright Points in a Coronal Hole Authors: Kamio, S.; Hara, H.; Watanabe, T.; Curdt, W. Bibcode: 2008ASPC..397...35K Altcode: We present the velocity structure of bright points in the corona and in the transition region. This is one of the first results from the coordinated observation with Hinode/EIS and SOHO/SUMER in April 2007. Bright points in the corona are associated with bright patches in the transition region network. The result suggests coronal bright points are rooted in the magnetic field concentration of the network. No clear connection is found between velocities in the corona and the transition region, but observing time difference between EIS and SUMER could be the cause of the dissociation. Title: Modeling the UV/EUV Spectrum with SRPM Authors: Haberreiter, M.; Fontenla, J.; Curdt, W.; Tian, H. Bibcode: 2008ESPM...12.3.12H Altcode: We present a new set of semi-empirical solar atmosphere structures for different features on the solar disk that is consistent with the latest inter- network model by Fontenla et al. (2007), which reproduces the CO lines in the IR as well as the UV and radio continua. The intensity distribution of SUMER observations is used to define a set of solar disk features that accounts for the observed range of upper chromospheric heating. Using these models the UV/EUV (as well as longer wavelengths) radiance spectra are computed with SRPM in full-NLTE using the latest available atomic data and considering 24 elements up to high ionization stages with a total of approximately 14000 atomic levels and approximately 170000 line transitions. The radiance spectra of the new atmosphere structures allow us to study in detail the varying contributions of these features to the solar spectral irradiance. The synthetic spectra are compared with SUMER data and EUV irradiance observations obtained with the EVE rocket-instrument during a recent rocket flight. Title: The line profile and center-to-limb variation of quiet-Sun Lyman-alpha emission Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P. Bibcode: 2008ESPM...12.2.91C Altcode: We study the emission of the hydrogen Lyman-alpha line in the quiet Sun, its center-to-limb variation, and its radiance distribution, which we also compare to the Lyman-beta line. We use the high spectral and spatial resolution of the SUMER spectrometer and take raster scans at various locations on the disk. For the first time, we have used a new method to reduce the incoming photon flux to a 20%-level by partly closing the aperture door. We also performed a quasi-simultaneous observation of both Ly-a and Ly-b at Sun centre in sit-and-stare mode. We deduce the flow characteristic in Ly-a map from variations of the calibrated Si III line centroids. We present the average profile of Ly-a, its radiance distribution, its center-to-limb behaviour, and the signature of flows on the line profiles. Different from all other lines of the Lyman series, which have a red-horn asymmetry, Ly-a has a robust and dominating blue-horn asymmetry. To our knowledge, this result is only predicted by models which include flows. Title: Chromospheric Counterparts of UV Explosive Events Authors: Reardon, K.; Cauzzi, G.; Teriaca, L.; Pitterle, M.; Curdt, W. Bibcode: 2008ESPM...12.2.17R Altcode: We present a study of a unique, multi-wavelength dataset of a quiet sun region with the primary goal of studying explosive events at chromospheric and transition region heights. Several hypotheses have been made about the nature of the explosive events, however the underlying mechanisms remain elusive due to their small spatial and temporal scales. Several theoretical models predict an important role for the chromosphere in the triggering of these events.

To shed light on this issue, we have obtained a comprehensive set of simultaneous high spatial, spectral, and temporal resolution observations on April 18, 2007, combining both ground- and space-based observatories. Most importantly, we carried out coordinated observations with SUMER in the transition region Si IV 140.2 nm line together with high-cadence IBIS imaging spectroscopy of the chromospheric CaII 854.2 nm line. This allows us to examine the chromospheric dynamics and acoustic shocks that underlie the transition region events. We also use SOT/NFI magnetograms to examine the relation of the explosive events to the changes in the magnetic topology. The combined dataset also includes Hinode/EIS rasters and Hinode/XRT images that provide information on the higher-temperature coronal response. Title: Cool and Hot Components of a Coronal Bright Point Authors: Tian, H.; Curdt, W.; Marsch, E.; He, J. -S. Bibcode: 2008ESPM...122.113T Altcode: We performed a systematic study of the Doppler shifts and electron densities measured in an EUV bright point (hereafter BP) observed in more than 10 EUV lines with formation temperatures from log(T=K) = 4.5 to 6.3. Those parts of a BP seen in transition region and coronal lines are defined as its cool and hot components, respectively. We find that the transition from cool to hot occurs at a temperature around log(T=K) = 5.7. The two components of the BP reveal a totally different orientation and Doppler-shift pattern, which might result from a twist of the associated magnetic loop system. The analysis of magnetic-field evolution and topology seems to favour a two-stage heating process, in which magnetic cancelation and separator reconnection are powering, respectively, the cool and hot components of the BP. We also found that the electron densities of both components of the BP are higher than those of the surrounding quiet Sun, and comparable to or smaller than active-region densities. Title: The Redshifted Network Contrast - Signature of Coronal Convectio Authors: Curdt, W.; Tian, H.; Dwivedi, B. N.; Marsch, E. Bibcode: 2008ESPM...12.2.92C Altcode: Observations and interpretations of red- and/or blueshifted emission lines from cosmic objects are crucial to understanding the physical processes at work there. The ubiquituous net redshifts of solar transition region (TR) emission lines are known since the Skylab era. Brekke et al. and Chae et al. independently verified this result by analyzing the high spectral resolution observations from the SUMER/SoHO instrument. Both these groups found similar results for the quantitative dependence of the net redshift on line formation temperatures from 30 000 K to 1 MK. To our knowledge, however, a satisfactory physical explanation of the redshift is still a matter of debate. We present a new method to explain the TR red shift, which is based on the radiance-redshift relationship, and which employs the redshift of the network contrast as compared to the position of the emission line itself. In contrast to the earlier work, our indirect method is unique in several ways namely,

(i) it does not require a good wavelength calibration and thus avoids related problems,

(ii) it is independent of the knowledge of the exact rest wavelength, and

(iii) it intimately relies on the physical processes in the solar atmosphere. Title: Cool and Hot Components of a Coronal Bright Point Authors: Tian, Hui; Curdt, Werner; Marsch, Eckart; He, Jiansen Bibcode: 2008ApJ...681L.121T Altcode: 2009arXiv0906.3005T We performed a systematic study of the Doppler shifts and electron densities measured in an EUV bright point (hereafter BP) observed in more than 10 EUV lines with formation temperatures from log (T/K) = 4.5 to 6.3. Those parts of a BP seen in transition region and coronal lines are defined as its cool and hot components, respectively. We find that the transition from cool to hot occurs at a temperature around log (T/K) = 5.7. The two components of the BP reveal a totally different orientation and Doppler-shift pattern, which might result from a twist of the associated magnetic loop system. The analysis of magnetic field evolution and topology seems to favor a two-stage heating process, in which magnetic cancellation and separator reconnection are powering, respectively, the cool and hot components of the BP. We also found that the electron densities of both components of the BP are higher than those of the surrounding quiet Sun, and comparable to or smaller than active region densities. Title: ``Energy levels and spectral lines of Ne viii'' [Eur. Phys. J. D 39, 173 188 (2006)] Authors: Wilhelm, K.; Curdt, W.; Dammasch, I. E.; Hassler, D. M. Bibcode: 2008EPJD...47..325W Altcode: 2008EPJD..tmp...78W Kramida and Buchet-Poulizac [Eur. Phys. J. D 39, 173 (2006)] provide a comprehensive compilation of Ne VIII energy levels and spectral lines. We are concerned about the data of one line treated in the second paragraph of Section 2, the line at 77.0 nm. This line is very important for solar physics investigations as it is a bright line emitted in the lower corona of the Sun, where mass flux and energy transport determine the properties of the nascent solar wind. Consequently, it has been studied in a number of investigations, of which we want to mention two. The results are published by Peter and Judge [Astrophys. J. 522, 1148 (1999)] and Dammasch et al. [Astron. Astrophys. 346, 285 (1999)]. Both these studies concluded that the rest wavelength of the Ne VIII line in question is 77.0428 nm with standard uncertainties of 0.7 pm and 0.3 pm, respectively. Dammasch et al. discussed, in particular, the uncertainty level of 0.5 pm stated by Bockasten et al. [Proc. Phys. Soc. 81, 522 (1963)]. The conclusion was that it is far too optimistic and not reliable. So, we take issue with the statement of the authors that the Bockasten et al. measurements of this line are the most accurate in the literature. If the Bockasten et al. value (77.0409 nm ± 0.0005 nm) [Proc. Phys. Soc. 81, 522 (1963)] for the rest wavelength of this line were true, it would imply downward movements in the solar corona that are in conflict with the measurements in other lines. Title: Detection of mesogranulation at the upper chromosphere from SOHO/SUMER observations Authors: Kariyappa, R.; Varghese, B. A.; Curdt, W. Bibcode: 2008arXiv0804.3659K Altcode: We have analyzed a time series of spectra in the hydrogen Lyman lines and the Lyman continuum obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the SOlar Heliospheric Observatory (SOHO). The time series of about 2 hours and 22 minutes was obtained on 1999 March 9 in a quiet region near the center of the solar disk. For our analysis, we have selected a Lyman continuum window around 907 A, and the five Lyman lines: Ly5 (937.8 A), Ly7 (926.2 A), Ly9 (920.9 A), Ly11 (918.1 A), and Ly15 (915.3 A). A Fast Fourier analysis has been performed in the spatial domain, all along the slit length used, for all the spectra and for the total duration of the observations. We have detected a significant periodic spatial variations with Fourier transform power peaks around 9-10 arcsec and at 4 arcsec. They correspond to the scale of the mesogranulation structure and the width of the supergranular boundary, respectively. For the first time, this provides evidence for the existence of a meso-scale in the upper chromosphere, of the same size as observed in the photosphere and lower chromosphere by earlier studies. We find from the analysis that there seems to be no signature of any temporal evolution associated with the mesogranules, at least not during our observing period. This result suggests that the life time of mesogranules will be several hours or more, which confirms the earlier findings. In addition, we notice that the size (9-10 arcsec) of the mesocells appears to be the same in all Lyman lines and in the continuum, which are formed at different depths in the chromosphere. Title: Multi-spacecraft observations of polar coronal plumes Authors: Curdt, W.; Wilhelm, K.; Feng, L.; Kamio, S. Bibcode: 2008A&A...481L..61C Altcode: Aims:Coronal plumes, along with their structure and rôle in the acceleration of the fast solar wind, are of considerable importance in understanding the physics of the solar atmosphere, in particular, when contrasted with the adjacent plasma, the so-called interplume regions.
Methods: Observations of coronal plumes in a coronal hole were obtained with the help of spectrographs and imagers on Hinode, SOHO, STEREO, TRACE, and with ground-based instrumentation. The measurements were performed by a large international team in April 2007.
Results: First results of this study from Hinode, SOHO, and STEREO are presented here, at the level of observational facts, leaving the task of detailed analysis to the future. Title: Jets or High-Velocity Flows Revealed in High-Cadence Spectrometer and Imager Co-observations? Authors: Madjarska, M. S.; Doyle, J. G.; Innes, D. E.; Curdt, W. Bibcode: 2007ApJ...670L..57M Altcode: 2007arXiv0710.2199M We report on active region EUV dynamic events observed simultaneously at high cadence with SOHO SUMER and TRACE. Although the features appear in the TRACE Fe IX/X 171 Å images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large-scale magnetic structure, a preexisting loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 104 to 106 K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high-velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km s-1. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 minutes. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events. Title: Log-normal intensity distribution of the quiet-Sun FUV continuum observed by SUMER Authors: Fontenla, J. M.; Curdt, W.; Avrett, E. H.; Harder, J. Bibcode: 2007A&A...468..695F Altcode: We analyse observations of the quiet-Sun far ultraviolet (FUV) continuum at various wavelengths near 1430 Å obtained by the SUMER instrument on SOHO. According to semi-empirical atmospheric models this continuum originates from the layers in the chromosphere where the temperature rises from low values at near-radiative equilibrium to a plateau of about 6000 K. We study raster images and intensity distribution histograms and find that a single log-normal distribution matches these observations very well, and that the spatial structure observed corresponds to a mixture of features at supergranular and smaller scales that probably correspond to granular clusters. Also, a log-normal distribution was found in the literature to correspond to other chromospheric features and we compare here with histograms obtained from a H i Ly-α quiet-Sun image. Because the continuum around 1430 Å is mainly produced by Si i recombination it is expected to respond well to deep chromospheric heating and not be directly affected by velocities. The data suggest that chromospheric heating originates through dissipation of magnetic free-energy fields of small size and magnitude in underlying photospheric intergranular lanes. It has been suggested that such fields can be produced by photospheric dynamos at the intergranular scale and/or by complex fields emerging in a “magnetic carpet”. Such fields are expected to have sufficient free-energy to power the chromospheric heating. Plasma instabilities, such as the Farley-Buneman instability, would allow this free-energy to be dissipated in the chromosphere. Title: The Transition Region Above Sunspots Authors: Curdt, W.; Landi, E. Bibcode: 2007ASPC..370...40C Altcode: We present results from spectroscopic observations of sunspots in the vacuum ultraviolet wavelength range obtained by SUMER on SOHO. The atmospheric conditions above sunspots are very special and remarkably different compared to other parts of the solar atmosphere. The transition region, which is normally a thin layer extends above sunspots very high in altitude and is filled with rather cold, low-density plasma. Sunspot plumes are sites of systematic downflow into a bottom layer, which is coherently oscillating with a 3-minute period. Title: Propagating Waves in the Chromospheric Network Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2007ASPC..368..133G Altcode: Wave modulation of ultraviolet emissions originated in and above quiet chromospheric network is studied. In particular, cross-correlation, wavelet analysis and phase difference analysis of the intensities as well as the Doppler shifts of emission lines of He I 584.33 Å (chromosphere), O V 629.73 Å (transition region) and Mg IX 368.07 Å (corona) are employed to study waves at different heights and their direction of propagation. The results are interpreted as evidence of compressive waves that propagate downward from the transition region to the chromosphere in the observed chromospheric network. Different scenarios regarding the origin and source localization of these waves are discussed. Title: OSIRIS The Scientific Camera System Onboard Rosetta Authors: Keller, H. U.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo, R.; Wenzel, K. -P.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Angulo, M.; Bailey, M. E.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.; Bianchini, G.; Boit, J. -L.; Brown, V.; Burns, J. A.; Büttner, I.; Castro, J. M.; Cremonese, G.; Curdt, W.; Deppo, V. Da; Debei, S.; Cecco, M. De; Dohlen, K.; Fornasier, S.; Fulle, M.; Germerott, D.; Gliem, F.; Guizzo, G. P.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Koschny, D.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Llebaria, A.; López, A.; López-Jimenez, A.; López-Moreno, J.; Meller, R.; Michalik, H.; Michelena, M. D.; Müller, R.; Naletto, G.; Origné, A.; Parzianello, G.; Pertile, M.; Quintana, C.; Ragazzoni, R.; Ramous, P.; Reiche, K. -U.; Reina, M.; Rodríguez, J.; Rousset, G.; Sabau, L.; Sanz, A.; Sivan, J. -P.; Stöckner, K.; Tabero, J.; Telljohann, U.; Thomas, N.; Timon, V.; Tomasch, G.; Wittrock, T.; Zaccariotto, M. Bibcode: 2007SSRv..128..433K Altcode: 2007SSRv..tmp...26K The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. Title: T he Lower Transition Region As Seen In The H I Lyman-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2007ESASP.641E..84T Altcode: The SUMER spectrometer aboard SOHO has been used to acquire several raster images and temporal series of quiet-Sun targets at both disk centre and the limb. Spectra have been recorded simultaneously in the H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal maps of the integrated radiances appear very similar in the two lines, despite the huge difference in optical thickness, a result showing the H I Lyman α to be a good diagnostic of the dynamics and morphology of the lower transition region. Oscillations can be detected and studied at all observed locations. At disk centre, the 3 minute oscillations are sporadically observed in the inter-network but also at locations at the edges of network lanes, while 5 minute oscillations clearly dominate the network. At the limb, evidence of 3 to 5 minute oscillations is found at the base of spicules. Moreover, H I Lyman α spectra shows a high degree of variability, revealing also the signature of explosive events. The combination of high spectral purity images and slit spectra in the H I Lyman α line would therefore be an exceptional new tool to investigate the nature of the solar transition region. This line is therefore of interest for both, a high resolution channel in the EUI instrument and for the EUS spectrometer. Title: T he Lower Transitio n Region As Seen In The H I Lyman-α Line. Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2007ESASP.641E..36T Altcode: The SUMER spectrometer aboard SOHO has been used to acquire several raster images and temporal series of quiet-Sun targets at both disk centre and the limb. Spectra have been recorded simultaneously in the H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal maps of the integrated radiances appear very similar in the two lines, despite the huge difference in optical thickness, a result showing the H I Lyman α to be a good diagnostic of the dynamics and morphology of the lower transition region. Oscillations can be detected and studied at all observed locations. At disk centre, the 3 minute oscillations are sporadically observed in the inter-network but also at locations at the edges of network lanes, while 5 minute oscillations clearly dominate the network. At the limb, evidence of 3 to 5 minute oscillations is found at the base of spicules. Moreover, H I Lyman α spectra shows a high degree of variability, revealing also the signature of explosive events. The combination of high spectral purity images and slit spectra in the H I Lyman α line would therefore be an exceptional new tool to investigate the nature of the solar transition region. This line is therefore of interest for both, a high resolution channel in the EUI instrument and for the EUS spectrometer. Title: T hin Silicon Carbide Coating Of The Primary Mirror Of VUV Imaging Instruments Of Solar Orbiter Authors: Schühle, U.; Uhlig, H.; Curdt, W.; Feigl, T.; Theissen, A.; Teriaca, L. Bibcode: 2007ESASP.641E..83S Altcode: We investigate the thermo-optical and vacuum- ultraviolet properties of thin silicon carbide (SiC) coatings on transparent substrates in view of their use for Solar Orbiter remote sensing VUV instrumentation. We have made experimental studies with thin SiC coatings on quartz plates to evaluate their reflective properties in the VUV spectral range between 58 nm and 123 nm. We discuss the results in relation to the visible and near infrared optical properties of the samples. A thin SiC coating of 10 nm thickness is shown to be a very promising compromise between high VUV reflectivity and low vis/IR absorption. The overall absorption of the solar spectrum by such a mirror is less than 8 %. This will be beneficial for instruments requiring a large aperture due to diffraction and radiometric limitation, in coping with the thermal heat load during the Solar Orbiter mission. As an example, we propose a design of the primary telescope mirror for the Extreme Ultraviolet Spectrometer (EUS). Title: Observations Supporting the Role of Magnetoconvection in Energy Supply to the Quiescent Solar Atmosphere Authors: McIntosh, Scott W.; Davey, Alisdair R.; Hassler, Donald M.; Armstrong, James D.; Curdt, Werner; Wilhelm, Klaus; Lin, Gang Bibcode: 2007ApJ...654..650M Altcode: 2006astro.ph..9503M Identifying the two physical mechanisms behind the production and sustenance of the quiescent solar corona and solar wind poses two of the outstanding problems in solar physics today. We present analysis of spectroscopic observations from the Solar and Heliospheric Observatory that are consistent with a single physical mechanism being responsible for a significant portion of the heat supplied to the lower solar corona and the initial acceleration of the solar wind; the ubiquitous action of magnetoconvection-driven reprocessing and exchange reconnection of the Sun's magnetic field on the supergranular scale. We deduce that while the net magnetic flux on the scale of a supergranule controls the injection rate of mass and energy into the transition region plasma, it is the global magnetic topology of the plasma that dictates whether the released ejecta provides thermal input to the quiet solar corona or becomes a tributary that feeds the solar wind. Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra, L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar, M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti, S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.; Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.; Winter, B.; Zhukov, A. Bibcode: 2007ESASP.641E..33H Altcode: The scientific objectives of Solar Orbiter rely ubiquitously on EUI, its suite of solar atmosphere imaging telescopes. In the configuration discussed here, EUI includes three co-aligned High Resolution Imagers (HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme ultraviolet passbands, dominated by coronal emission. Another HRI is designed for the hydrogen Lyman α radiation in the far UV, imaging the Chromosphere and the lower Transition Region. The current EUI design and some of its development challenges are highlighted. EUI profits from co-rotation phases, solar proximity and departure from the ecliptic. In synergy with the other S.O. payload, EUI probes the dynamics of the solar atmosphere, provides context data for all investigations and helps to link in-situ and remote-sensing observations. In short, it serves all four top-level goals of the mission. For these reasons, the EUI suite is keenly anticipated in the European scientific community and beyond. Title: The Transition Region Above Sunspots Authors: Curdt, W.; Landi, E. Bibcode: 2006ESASP.617E..56C Altcode: 2006soho...17E..56C No abstract at ADS Title: Study of a Small-Scale Eruptive Event Observed by SOHO/SUMER Authors: Tomasz, F.; Régnier, S.; Schwarz, P.; Rybák, J.; Kucera, A.; Heinzel, P.; Curdt, W.; Wöhl Bibcode: 2006ESASP.617E..79T Altcode: 2006soho...17E..79T No abstract at ADS Title: The Dynamic Nature of the Lower Transition Region as Revealed by Spectroscopy of the Hydrogen Lyman-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2006ESASP.617E..77T Altcode: 2006soho...17E..77T No abstract at ADS Title: The Dynamics and Structure of the Solar Atmosphere As Obtained from Combined SUMER/SOHO and TIP2/VTT Observations Authors: Tomasz, F.; Régnier, S.; Schwartz, P.; Rybák, J.; Kucera, A.; Heinzel, P.; Curdt, W.; Wöhl Bibcode: 2006ESASP.617E..78T Altcode: 2006soho...17E..78T No abstract at ADS Title: SOHO/CDS observations of waves above the network Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2006A&A...448.1169G Altcode: We analyze temporal variations in the intensities and the Doppler shifts of He i 584.33 Å (chromosphere), O v 629.73 Å (transition region), and Mg ix 368.07 Å (corona) measured in and above chromospheric network near disk center with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO). There is significant correlation between the He i and O v modulations, with O v intensity leading He i intensity by 27.3 s ± 4.6 s but no significant time shift in the Doppler shift. Cross-correlation between the O v and Mg ix intensities reveals multiple maxima without correlation between their Doppler shifts. Wavelet power analysis gives evidence of intermittent chromospheric and transition-region oscillations with periodicities in the 250-450 s range and of coronal oscillations in the 110-300 s range. Wavelet phase difference analysis shows that the determined time shift between variations of the He i and O v intensities is dominated by waves with about 300 s periodicity. We interpret these results as giving evidence of compressive waves that propagate downward from the transition region to the chromosphere in the particular chromospheric network. We discuss different scenarios regarding origin and source localization of waves, and we speculate on their role in coronal heating above chromospheric network. Title: Flarelike Brightenings of Active Region Loops Observed with SUMER Authors: Wang, T. J.; Innes, D. E.; Solanki, S. K.; Curdt, W. Bibcode: 2005ESASP.600E.105W Altcode: 2005ESPM...11..105W; 2005dysu.confE.105W No abstract at ADS Title: The Dynamics of the Lower Transition Region as Inferred from Spectroscopy of the Hydrogen LYMAN-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2005ESASP.600E.100T Altcode: 2005ESPM...11..100T; 2005dysu.confE.100T No abstract at ADS Title: A new relation between the central spectral solar H I Lyman α irradiance and the line irradiance measured by SUMER/SOHO during the cycle 23 Authors: Emerich, Claude; Lemaire, Philippe; Vial, Jean-Claude; Curdt, Werner; Schühle, Udo; Wilhelm, Klaus Bibcode: 2005Icar..178..429E Altcode: The spectral irradiance at the center of the solar H I Lyman α ( λ=121.5664nm, referred to as Lyα in this paper) line profile is the main excitation source responsible for the atomic hydrogen resonant scattering of cool material in our Solar System. It has therefore to be known with the best possible accuracy in order to model the various Lyα emissions taking place in planetary, cometary, and interplanetary environments. Since the only permanently monitored solar irradiance is the total one (i.e. integrated over the whole Lyα line profile), Vidal-Madjar [1975. Evolution of the solar Lyman alpha flux during four consecutive years. Solar Phys. 40, 69-86] using Orbiting Solar Observatory 5 (OSO-5) satellite Lyα data, established a semi-empirical formula allowing him to deduce the central spectral Lyα irradiance from the total one. This relation has been extensively used for three decades. But, at the low altitude of the OSO-5 orbit, the central part of the solar line profile was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the spectral irradiance at the center of the line was obtained by a complex procedure confronting the observations with simulations of both the geocoronal absorption and the self-reversed shape of the solar Lyα profile. The SUMER spectrometer onboard SOHO positioned well outside the hydrogen geocorona, provided full-Sun Lyα profiles, not affected by such an absorption [Lemaire et al., 1998. Solar H I Lyman α full disk profile obtained with the SUMER/SOHO spectrometer. Astron. Astrophys. 334, 1095-1098; 2002. Variation of the full Sun Hydrogen Lyman α and β profiles with the activity cycle. Proc. SOHO 11 Symposium, ESA SP-508, 219-222; 2004. Variation of the full Sun Hydrogen Lyman profiles through solar cycle 23. COSPAR 2004 Meeting], making it—for the first time—possible to measure the spectral and total Lyα solar irradiances directly and simultaneously. A new relation between these two quantities is derived in an expression that is formally similar to the previous one, but with significantly different parameters. After having discussed the potential causes for such differences, it is suggested that the new relation should replace the old one for any future modeling of the numerous Lyα absorptions and emissions observed in the Solar System. Title: The Structure of the Lower Transition Region as Inferred from the Hydrogen LYMAN-α Line Radiance Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2005ESASP.596E..66T Altcode: 2005ccmf.confE..66T No abstract at ADS Title: A large dust/ice ratio in the nucleus of comet 9P/Tempel 1 Authors: Küppers, Michael; Bertini, Ivano; Fornasier, Sonia; Gutierrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Keller, Horst Uwe; Knollenberg, Jörg; Koschny, Detlef; Kramm, Rainer; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn, M. F.; Angrilli, F.; Bailey, M.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.; Burns, J. A.; Cremonese, G.; Curdt, W.; De Cecco, M.; Debei, S.; Fulle, M.; Gliem, F.; Ip, W. H.; Huhrt, E.; Llebaria, A.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Sabau, L.; Sanz Andres, A.; Sivan, J. P.; Tondello, G.; Wenzel, K. -P. Bibcode: 2005Natur.437..987K Altcode: Comets spend most of their life in a low-temperature environment far from the Sun. They are therefore relatively unprocessed and maintain information about the formation conditions of the planetary system, but the structure and composition of their nuclei are poorly understood. Although in situ and remote measurements have derived the global properties of some cometary nuclei, little is known about their interiors. The Deep Impact mission shot a projectile into comet 9P/Tempel 1 in order to investigate its interior. Here we report the water vapour content (1.5 × 1032 water molecules or 4.5 × 106kg) and the cross-section of the dust (330km2 assuming an albedo of 0.1) created by the impact. The corresponding dust/ice mass ratio is probably larger than one, suggesting that comets are `icy dirtballs' rather than `dirty snowballs' as commonly believed. High dust velocities (between 110ms-1 and 300ms-1) imply acceleration in the comet's coma, probably by water molecules sublimated by solar radiation. We did not find evidence of enhanced activity of 9P/Tempel 1 in the days after the impact, suggesting that in general impacts of meteoroids are not the cause of cometary outbursts. Title: Evidence for In Situ Heating in Active Region Loops Authors: Curdt, W.; Landi, E.; Wang, T. J.; Feldman, U. Bibcode: 2005ESASP.592..475C Altcode: 2005soho...16E..85C; 2005ESASP.592E..85C No abstract at ADS Title: On the nature of the unidentified solar emission near 117 nm Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Hilchenbach, M.; Marsch, E.; Lemaire, P.; Bertaux, J. -L.; Jordan, S. D.; Feldman, U. Bibcode: 2005A&A...439..701W Altcode: Spectral observations of the Sun in the vacuum-ultraviolet wavelength range by SUMER on SOHO led to the discovery of unusual emission features - called humps here - at 116.70 nm and 117.05 nm on either side of the He i 58.43 nm line. This resonance line is seen in the second order of diffraction, whereas the humps are recorded in the first order with the SUMER spectrometer. In its spectra both orders are superimposed. Two less pronounced humps can be detected at 117.27 nm and near 117.85 nm. After rejecting various possibilities of an instrumental cause of the humps, they are studied in different solar regions. Most of the measurements, in particular those related to the limb-brightening characteristics, indicate that the humps are not part of the background continuum. An assembly of spectrally-unresolved atomic or ionic emission lines might be contributing to the hump at 117.05 nm, but no such lines are known near 116.7 nm. It is concluded that we detect genuine radiation, the generation of which is not understood. A two-photon emission process, parametric frequency down conversion, and molecular emissions are briefly considered as causes of the humps, but a final conclusion could not be reached. Title: Initiation of hot coronal loop oscillations: Spectral features Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2005A&A...435..753W Altcode: We explore the excitation of hot loop oscillations observed with the SUMER spectrograph on SOHO by analysing Fe XIX and Fe XXI spectral line profiles in the initial phase of the events. We investigate all 54 Doppler shift oscillations in 27 flare-like events, whose physical parameters have been measured so far. In nearly 50% of the cases, the spectral evolution reveals the presence of two spectral components, one of them almost undisturbed, the other highly shifted. We find that the shifted component reaches maximum Doppler shift (on the order of 100-300 km s-1) and peak intensity almost simultaneously. The velocity amplitude of the shifted component has no correlation with the oscillation amplitudes. These features imply that in these events the initial shifts are not caused by the locally oscillating plasma (or waves), but most likely by a pulse of hot plasma travelling along the loop through the slit position. This interpretation is also supported by several examples showing that standing slow mode waves are set up immediately after the initial line shift pulse (standing slow mode waves are inferred from the 1/4-period phase relationship between the velocity and intensity oscillations). We re-measure the physical parameters of the 54 Doppler oscillations by fitting the time profiles excluding the first peak, and find that the periods are almost unchanged, damping times are shorter by 5%, and amplitudes are smaller by 37% than measured when the first peak is included. We also measure the velocity of the net (background) flow during the oscillations, which is found to be nearly zero. Our result of initial hot flows supports the model of single footpoint (asymmetric) excitation, but contradicts chromospheric evaporation as the trigger. Title: Analysis of Doppler Shifts of Spectral Lines Obtained by the CDS/SOHO Instrument Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2005ASSL..320..203G Altcode: 2005smp..conf..203G No abstract at ADS Title: On the Behaviour of a Blinker in Chromospheric and Transition Region Layers Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2005ASSL..320..207T Altcode: 2005smp..conf..207T No abstract at ADS Title: Variation of the full Sun hydrogen Lyman profiles through solar cycle 23 Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2005AdSpR..35..384L Altcode: The hydrogen Lyman (Lyα, 121.267 nm and Lyβ, 102.572 nm) lines are important contributors to the solar extreme ultra violet (EUV) flux which illuminates the upper Earth’s atmosphere. From high resolution spectral observations performed with the solar ultraviolet measurement of emitted radiations (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO), the detailed profiles of these two lines have been obtained. Some insights into the variation of the shape of the profiles, sampled throughout the present solar cycle 23, are given and discussed. Title: Variability and Dynamics of the Outer Atmospheric Layers in the Quiet Solar Network Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2005HvaOB..29...71G Altcode: A detailed study of the temporal evolution of the chromospheric He I 584.33 Å and the transition region O V 629.73 Å emission line intensities of quiet supergranular network of the Sun near disk centre observed with Coronal Diagnostic Spectrometer (CDS) is presented. A wavelet analysis of the 1729 s (28.8 min) long temporal series was performed in order to derive the duration as well as periods of the chromospheric and the transition region oscillations. The He I line intensities show significant power for periods around 300 s (3.3 mHz), which is relevant only in the second half of the observing sequence (between 800 -- 1700 s). The temporal evolution corresponding to the O V line intensities shows strong power around the period of 400 s (2.5 mHz), which is significant during the whole observing sequence as well as the oscillation of lower power for periods of around 250 s (4.0 mHz), which is present only in the middle of the observing sequence (between 700 -- 1300 s). Title: In-Situ Heating in Active Region Loops Authors: Curdt, W.; Landi, E.; Wang, T.; Feldman, U. Bibcode: 2005HvaOB..29..157C Altcode: We report new observational results and insights in the energy release during transient events on sub-flare level in active region coronal loops. Our work is based on multi-temperature observations obtained high above the limb by the SUMER spectrometer on SOHO. We conclude that the energy is impulsively injected into the loop system from one and only one foot point. This asymmetric injection does not seem to be connected with any bulk flow and there is no indication that the plasma in the loop is replenished or replaced. Therefore the chromospheric evaporation model is not applicable for this type of events. The electron density, Ne, however, increases by up to two orders of magnitude during such events. If no new material is added to the local plasma, then the Ne increase can only be explained by a rapid volume decrease, i.e., by a in-situ pinch effect, compressing and heating the affected plasma. Title: Influence of Transition Region Blinker on the Surrounding Chromospheric and Coronal Plasma Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2005HvaOB..29..197T Altcode: Results of spectral analysis of a blinker observed in the transition region O VI 1037.63 Å line and in the chromospheric Ly β 1025.72 Å line which were acquired using the SUMER spectrometer are presented. Chromospheric and coronal plasma in the vicinity of the blinker are investigated using also TRACE Ly α, UV continuum and Fe IX channels. It was found that initial release of energy was localized in the transition region and plasma has been spreading from transition region as a bi-directional jet. Energy reached chromosphere ∼60 seconds after primary emission in the o6 line. There were detected enhanced emissions for about 25-38% in the chromospheric Lyα and UV continuum. Spatial extent of the blinker response is 6'' along the slit in the Lyα filtergram what is ∼3'' less than extent of the blinker in the o6 line. Maximum extent of the blinker response is 7.5'' in Lyα filtergram. Although, both Lyα and UV continuum reflect physical conditions in chromosphere, their patterns are completely different: pattern of the blinker response is compact in the Lyα and UV continuum shows non-compact structure below the transition region blinker. Coronal plasma was not influenced by the blinker although plasma moving toward observer was detected in the final phase of evolution of the blinker. Title: Observational Evidences for Heating of the Solar Corona by Nanoflares in the Network Derived from the Transition Region Spectral Lines Authors: Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H. Bibcode: 2004ESASP.575..529R Altcode: 2004soho...15..529R No abstract at ADS Title: The SUMER spectral atlas of solar coronal features Authors: Curdt, W.; Landi, E.; Feldman, U. Bibcode: 2004A&A...427.1045C Altcode: We present a spectral atlas of the solar corona in the far-ultraviolet (FUV) and extreme ultraviolet (EUV) wavelength range. The atlas is based on observations obtained between 670 Å and 1609 Å in first order of diffraction and between 465 and 670 Å in second order with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on SOHO (Solar and Heliospheric Observatory). This paper complements the SUMER Spectral Atlas of Solar Disk Features, also published in A&A. The atlas contains off-limb spectra of the corona above a coronal hole, a quiet region, the active corona, and a flare. We provide wavelengths of all detected lines and identification, if available; 311 out of 507 coronal emission lines could be identified or reconfirmed, including several new identifications. Brief descriptions of the data reduction and calibration procedures are given. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.40 (1σ) and the wavelength scale is accurate to typically ≃30 mÅ. The atlas is also available in a machine readable format.

Table \ref{tab3} and Fig. \ref{fig3} are only available in electronic form at http://www.edpsciences.org Title: Dynamics of the Quiet Upper Solar Atmosphere in the Network Authors: Gömöry, P.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H. Bibcode: 2004ESASP.575..400G Altcode: 2004soho...15..400G No abstract at ADS Title: SUNRISE: high-resolution UV/VIS observations of the Sun from the stratosphere Authors: Gandorfer, Achim M.; Solanki, Sami K.; Schüssler, Manfred; Curdt, Werner; Lites, Bruce W.; Martínez Pillet, Valentin; Schmidt, Wolfgang; Title, Alan M. Bibcode: 2004SPIE.5489..732G Altcode: SUNRISE is a balloon-borne solar telescope with an aperture of 1m, working in the UV/VIS optical domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide diffraction-limited images of the photosphere and chromosphere with an unpredecented resolution down to 35km at wavelengths around 220nm. Focal-plane instruments are a spectrograph/polarimeter, a Fabry-Perot filter magnetograph, and a filter imager. The first stratospheric long-duration balloon flight of SUNRISE over Antarctica is planned in winter 2006/2007. SUNRISE is a joint project of the Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofisica de Canarias, La Laguna, Tenerife. In this paper we will present an overview on the mission and give a description of the instrumentation, now, at the beginning of the hardware construction phase. Title: Baseline design of the SUNRISE Telescope Authors: Bittner, Hermann; Erdmann, Matthias; Haberler, Peter; Härtel, Klaus-Ruediger; Barthol, Peter; Curdt, Werner Bibcode: 2004SPIE.5489..927B Altcode: The SUNRISE telescope is part of a balloon-borne instrument for spectro-polarimetric high-resolution observations of the solar atmosphere, to be flown 2007/2008 in the Antarctic summer stratosphere. It is a 1-m UV-VIS Gregory type telescope, operating close to the VIS diffraction limit. The telescope has a steel central frame and a lightweight CFRP trusswork structure with Serrurier properties, providing proper alignment of the optical elements over the varying eleva-tion angle. Mechanisms allow a fine adjustment of the optics. Aberrations caused by residual deformations of the stiff silicon carbide (Cesic) primary mirror are lowered by a dedicated offset in the secondary mirror polish (imprint). The telescope is subjected to the changing heat loads caused by the sun and earth radiation, necessitating measures to provide thermal conditions suitable for high-performance observations. Adequate preliminary solutions for an effective baffling are outlined. Title: Newly Identified Forbidden Transitions within the Ground Configuration of Ions of Very Low Abundance P, Cl, K, and Co Authors: Feldman, U.; Landi, E.; Curdt, W. Bibcode: 2004ApJ...607.1039F Altcode: Forbidden lines from transitions within the ground configuration of highly ionized atoms occupy an important role in diagnosing the properties of astrophysical plasmas. In this paper we report the identification of forbidden lines in the 500-1500 Å range from transitions within the ground configuration of highly ionized ions of the very low abundance phosphorus, chlorine, potassium, and cobalt recorded by SOHO SUMER. For the newly identified lines we provide upper level fractional populations multiplied by relevant spontaneous decay rates. Aided by the newly identified lines, the coronal composition of elements with photospheric abundances of 5×10-7-1×10-8 relative to hydrogen could be established. Title: A New Relation between Central and Total Solar H I Lyman-α Irradiances, as measured by SOHO during Solar Cycle 23 (1996-2003) Authors: Emerich, C.; Lemaire, P.; Vial, J. -C.; Curdt, W.; Schüle, U.; Wilhelm, K. Bibcode: 2004AAS...204.9802E Altcode: 2004BAAS...36..984E The spectral irradiance at the center of the solar H Ly-α line profile is the main excitation source responsible for the atomic hydrogen resonant scattering in cool material. It has therefore to be known with the best possible accuracy to model the H Ly-α emissions taking place in planetary, cometary and interplanetary environments. On the other hand, the only permanently monitored solar irradiance is the total one - either measured by near-Earth satellites, or deduced from its correlation with solar activity indexes. It is the reason why Vidal-Madjar (1975) using OSO-5 satellite H Ly-α data, established a semi-empirical formula allowing to deduce the central H Ly-α irradiance from the integrated one. This relation has been extensively used for three decades. In fact, at the low altitude of the OSO-5 orbit, the observed central part of the solar line profiles was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the solar line center irradiances were not measured directly, but obtained by confronting the measurements with simulations of both the geocoronal absorption and the self-reversed shape of the central solar profile itself.

On the contrary, the SOHO/SUMER spectrometer orbiting well outside the H geocoronal envelope (at the L1 Sun-Earth Lagrange point), provided full Sun H Ly-α profiles, exempt from any central geocoronal absorption (Lemaire et al. (1998, 2002, 2004)). This has made it possible to directly measure the central H Ly-α solar irradiances as a function of the integrated ones, during eight years of Solar Cycle 23. The newly obtained relation confirms the general trend of the previous one, but it is characterized by significantly different coefficients. It will therefore provide new and more accurate inputs for the future modeling of the various Ly-α emissions occurring inside the Solar System. Title: Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum Authors: Lemaire, P.; Gouttebroze, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2004A&A...418..737L Altcode: During the execution of the programme ``Sun as a star'', while the SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and Heliospheric Observatory) slit was collecting the scattered radiation from the telescope mirror far away from the solar disk image, a class X5.3/3b flare erupted on the solar disk, on 25 August 2001. During the first phase of the flare a relative increase of a few percent was detected at the head of the hydrogen Lyman continuum. After correction from the instrumental parameters, the relative signal increase is 70% at the head of the Lyman continuum (910 Å), and 190% in the C II 904 Å multiplet. Accounting for the area of the flare region, the local increase of the radiance of the Lyman continuum and of the C II lines is estimated to be a factor of several thousands. We compare this result with other solar observations and models.

Appendix A is only available in electronic form at http://www.edpsciences.org Title: On Relations among the Calibrated Parameters of the Transition Region Spectral Line Authors: Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H. Bibcode: 2004ESASP.547..311R Altcode: 2004soho...13..311R SUMER/SOHO measurements of the O VI 1031.93 Å emission line (280000 K) in the network and internetwork of the transition region of the quiet solar atmosphere are used for a statistical analysis of the calibrated spectral parameters: the central line intensity (energetic units), the line width (m Å) and the Doppler shift (km/s). A detailed procedure is performed in order to determine the absolute wavelength calibration of the spectra and Doppler shifts using simultaneously observed chromospheric O I 1027.44 Å and 1028.15 Å emission lines (10 000K). The spectral parameters of the O VI line are derived for both single and double Gaussian fitting of the line according to the latest findings on the multi-component nature of the transition region line profiles. Reliability of the absolute wavelength calibration and effects of two classes of the transition region transient events - explosive events and blinkers - are discussed in relation to the overall dependencies of the spectral parameters. Title: On Mutual Relation Among the Outer Atmospheric Layers in Network: SOHO/CDS Study Authors: Gömöry, P.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H. Bibcode: 2004ESASP.547..303G Altcode: 2004soho...13..303G SOHO/CDS measurements of emission in the network of the quiet solar atmosphere near disk center were used to derive mutual relations of emission and dynamics in different temperature regimes in/above supergranular network. Cross-correlation functions of the line intensities and the Doppler shifts of the chromospheric line He I 584.3 Å, the transition region line O V 629.7 Å and the coronal line Mg IX 396.1 Å were calculated in order to study relative variability of different atmospheric layers. Relatively high correlations were found between the intensities and the Doppler shifts of the He I and O V lines with two peaks of the intensity correlation function. The maximum value of the correlation of intensities (CC = 0.86) was reached for the zero time lag and the second maximum (CC = 0.78) was obtained for the time lag -190s (O V precedes He I). Only one sharp peak (CC = 0.55) was detected in the Doppler shift correlation function of these lines for the zero time lag. For the correlation of O V and Mg IX intensities one peak (CC = 0.57) of the correlation function was also discovered for the time lag +150s (Mg IX falls behind O V). In contrast, no correlation was obtained for the Doppler shifts of the O V and Mg IX lines. Summarizing we can assume clear relation in energy transfer and/or mass motion between chromosphere and transition region but no relation was found between corona and the lower parts of the solar atmosphere above the particular network under study. Title: SUMER Observations of Heating and Cooling of Coronal Loops Authors: Curdt, W.; Wang, T. J.; Dwivedi, B. N.; Kliem, B.; Dammasch, I. E. Bibcode: 2004ESASP.547..333C Altcode: 2004soho...13..333C Hot-loop transient events observed by SUMER in hot EUV lines are known to trigger loop oscillations, as reported by Kliem et al. [1] and Wang et al. [2], [3]. Apart from the inference of physical parameters in the solar corona, these observations also carry the signatures of heating and cooling of coronal loops. We present the light curves for various highly-ionized ions which were simultaneously observed during and after the trigger. Even though the majority of SUMER events occur on sub-flare level, it is clear that the heating is impulsive and drives the plasma to a very high temperature of up to 10 MK within minutes. During the cooling phase, however, we find the plasma in gradually decreasing ionization stages which implies that the entire loop system involved in such events is basically in the isothermal state. Such events may also help in our understanding of mass supply and energy transport in the corona. Title: SUMER, UVCS and LASCO Observations of Small-Scale Ejecta Authors: Teriaca, L.; Curdt, W.; Poletto, G. Bibcode: 2004ESASP.547..291T Altcode: 2004soho...13..291T During the fall 2002 SOHO-Sun-Ulysses quadrature, coordinated SUMER/UVCS observations were carried out off the west limb. Data were acquired over six consecutive days in several lines formed in the 2 104 - 106 K temperature range. The center of the SUMER slit was placed around 1.13 R and oriented in the north south direction, while the UVCS slit was set tangent to the solar limb at altitudes ranging between 1.6 and 2.1 R. On 19 and 20 November SUMER observed repeated transient events characterized by a strong increase of the intensity of transition region and Hydrogen Lyman and lines with large line broadenings and line of sight velocities, while little if any variation is seen in lines formed around 106 K. The duration of these events varies between 10-15 minutes up to 1 hour. The SUMER events are associated to streamer-like outflows seen in LASCO images and, in the case of the larger 19 November event, with a small jet travelling at ~400 km/s across the LASCO C2 fiel of view. Title: Overview of Slow Mode Oscillations in Hot Coronal Loops Observed by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E. Bibcode: 2004IAUS..219..712W Altcode: 2003IAUS..219E..70W No abstract at ADS Title: Variation of the full Sun hydrogen Lyman profiles through solar cycle 23 Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2004cosp...35..510L Altcode: 2004cosp.meet..510L The hydrogen Lyman (121.267 nm and 102.572 nm) lines are important contributors to the solar EUV flux which illuminates the upper Earth's atmosphere. From high resolution spectral observations performed with the SUMER FUV-EUV spectrometer on SoHO, the detailed profiles of these two lines have been obtained. Some insights into the variation of the shape of the profiles, sampled throughout the present solar cycle 23, are shown and discussed. Title: SUMER/SOHO and TRACE Study of the Transition Region Blinker Authors: Tomasz, F.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H. Bibcode: 2004ESASP.547..307T Altcode: 2004soho...13..307T The most prominent transient event is presented from an extensive search for the transition region internetwork activity in the quiet solar atmosphere performed by SUMER/SOHO spectrometer and TRACE. SUMER spectra of Ly line (1025.4 Å), two C II lines (1036.3 Å, 1037.0 Å) and O VI line (1037.61 Å) were used for determination of the spatial and temporal evolution of the transient event in the transition region. TRACE images taken in the 1216 Å passband, UV continuum (1700 Å) and Fe IX line (171 Å) were utilized in order to gain information about large-scale coronal structures and small-scale chromospheric variability in the vicinity of the transient event. The main physical and geometrical parameters of the event were derived for the transition region O VI line: the spatial extent of 11 000 km, duration for 9 minutes, intensity enhancement factor of 7 and the Doppler velocities of both signs up to 15 km/s. According to these values the event was identified as a transition region blinker. High deviations of the acquired O VI line profiles from single-Gaussian and some multi-Gaussian profiles reveal dynamics of the event - occurrence of the bidirectional jet which is not typical for blinkers. Besides rapid changes in intensity and in velocity, a rapid increase by a factor of 4.2 was found in the Gaussian width of O VI line as compared to the internetwork. Surrounding chromospheric and coronal structures around the event are discussed on base of the simultaneously taken TRACE images. Title: Observations of oscillations in the transition region above sunspots Authors: Rendtel, J.; Staude, J.; Curdt, W. Bibcode: 2003A&A...410..315R Altcode: Observations during two campaigns of the SUMER spectrograph and the EIT imager onboard SoHO were used to analyse oscillations in bright sunspot plumes. We report variations of both intensity and velocity seen in EUV emission lines originating in the sunspot upper chromosphere and the transition region. The wavelet analysis reveals rapidly changing conditions in the emitting volumes. Generally, oscillations in the 5 min range dominate in the chromosphere, while the transition region lines show oscillations at shorter periods (2 to 3 min). A drift of the oscillation period of the Doppler velocity from 5 min to 2.5 min within about 30 min can be explained by a strongly non-stationary behaviour of the upper chromosphere and transition region, probably related to downstream of material within the plume region. Synchronous EIT observations of the lower corona show no intensity oscillations. This hints either at a strong damping or a downward reflection in the upper transition region or lower corona. Title: The α Cen A and Solar FUV Spectra Authors: Pagano, I.; Linsky, J. L.; Curdt, W.; Valenti, J.; Gagné, M. Bibcode: 2003csss...12..847P Altcode: We present a comparison of the high-resolution FUV spectrum of α Cen A (G2 V) acquired by STIS on HST with the solar FUV spectra acquired by SUMER on SOHO, and by UVSP on SMM, respectively. We compare the line properties of the strongest lines, and discuss the main peculiarities of the FUV emission of both stars. Title: Free-Free Emission in the Far-Ultraviolet Spectral Range: A Resource for Diagnosing Solar and Stellar Flare Plasmas Authors: Feldman, U.; Landi, E.; Doschek, G. A.; Dammasch, I.; Curdt, W. Bibcode: 2003ApJ...593.1226F Altcode: We report the detection of free-free (bremsstrahlung) emission near 1200 Å from a flare at the solar limb observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft. The observations consist of a time series of slit spectra at a fixed pointing that lasted almost 2 hr, during which the observed solar region produced a C8 flare. Using the free-free continuum intensities in conjunction with intensities of high-temperature (106-107 K) emission lines that appear in the same wavelength range, we derive the flare plasma electron density, electron temperature, emission measure, and nonthermal mass motions before, during, and after the flare. We describe a new diagnostic method for determining the temperature of cooling plasmas. Because the free-free radiation is emitted primarily by the interaction of electrons with nuclei of H and He atoms, we are also able to derive the Fe/H, Al/H, and Ca/H abundance ratios from the line intensities of highly ionized Fe, Al, and Ca lines and the intensities of the free-free emission, assuming a He abundance. The present work demonstrates the exceptional plasma diagnostic potential of ultraviolet free-free continuum radiation when coupled with emission-line intensities. We demonstrate that a similar technique could be employed to diagnose plasma properties of stellar flares using a high-resolution spectrometer with a sufficiently large effective collecting area. Title: Hot coronal loop oscillations observed with SUMER: Examples and statistics Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E.; Kliem, B. Bibcode: 2003A&A...406.1105W Altcode: We give an extensive overview of Doppler shift oscillations in hot active region loops obtained with SUMER. The oscillations have been detected in loops sampled 50-100 arcsec off the limb of the Sun in ultraviolet lines, mainly Fe Xix and Fe Xxi, with formation temperature greater than 6 MK. The spectra were recorded along a 300 arcsec slit placed at a fixed position in the corona above the active regions. Oscillations are usually seen along an extended section of the slit and often appear to be from several different portions of the loops (or from different loops). Different portions are sometimes in phase, sometimes out of phase and sometimes show phase shifts along the slit. We measure physical parameters of 54 Doppler shift oscillations in 27 flare-like events and give geometric parameters of the associated hot loops when soft X-ray (SXR) images are available. The oscillations have periods in the range 7-31 min, with decay times 5.7-36.8 min, and show an initial large Doppler shift pulse with peak velocities up to 200 km s-1. The oscillation periods are on average a factor of three longer than the TRACE transverse loop oscillations. The damping times and velocity amplitude are roughly the same, but the derived displacement amplitude is four or five times larger than the transverse oscillation amplitude measured in TRACE images. Unlike TRACE oscillations, only a small fraction of them are triggered by large flares, and they often recur 2-3 times within a couple of hours. All recurring events show initial shifts of the same sign. These data provide the following evidence to support the conclusion that these oscillations are slow magnetoacoustic standing waves in hot loops: (1) the phase speeds derived from observed periods and loop lengths roughly agree with the sound speed; (2) the intensity fluctuation lags the Doppler shifts by 1/4 period; (3) The scaling of the dissipation time of slow waves with period agrees with the observed scaling for 49 cases. They seem to be triggered by micro- or subflares near a footpoint, as revealed in one example with SXR image observations. However other mechanisms cannot as yet be ruled out. Some oscillations showed phase propagation along the slit in one or both directions with apparent speeds in the range of 8-102 km s-1, together with distinctly different intensity and line width distributions along the slit. These features can be explained by the excitation of the oscillation at a footpoint of an inhomogeneous coronal loop, e.g. a loop with fine structure.

Table \ref{osctab} and Appendices A and B are only available in electronic form at http://www.edpsciences.org Title: Overview of Recent Results on Coronal Loop Oscillations Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E. Bibcode: 2003ANS...324...19W Altcode: 2003ANS...324..B18W No abstract at ADS Title: SUNRISE: Balloon-borne High-Resolution Observation of the Sun Authors: Solanki, S. K.; Curdt, W.; Gandorfer, A.; Schüssler, M.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.; Sunrise Team Bibcode: 2003ANS...324..113S Altcode: 2003ANS...324..P20S No abstract at ADS Title: Slow-mode standing waves observed by SUMER in hot coronal loops Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W.; Marsch, E. Bibcode: 2003A&A...402L..17W Altcode: We report the first detection of postflare loop oscillations seen in both Doppler shift and intensity. The observations were recorded in an Fe Xix line by the SUMER spectrometer on SOHO in the corona about 70 min after an M-class flare on the solar limb. The oscillation has a period of about 17 min in both the Doppler velocity and the intensity, but their decay times are different (i.e., 37 min for the velocity and 21 min for the intensity). The fact that the velocity and the intensity oscillations have exactly a 1/4-period phase difference points to the existence of slow-mode standing waves in the oscillating loop. This interpretation is also supported by two other pieces of evidence: (1) the wave period and (2) the amplitude relationship between the intensity and velocity are as expected for a slow-mode standing wave. Title: Nonthermal Mass Motions within the High-Temperature Plasmas above a Complex Solar Active Region Authors: Feldman, U.; Landi, E.; Curdt, W. Bibcode: 2003ApJ...585.1087F Altcode: We report on mass motions in high-temperature plasmas at radial distances of 1.06-1.20 Rsolar corresponding to 3.3×104-1.3×105 km above the west solar limb. The observations were conducted over a 53 hr time period while a complex active region moved across the west solar limb. We found that the nonthermal mass motions in the 2.6×106-6.6×106 K plasmas that were imaged along the slit were in the 20-35 km s-1 velocity range. The magnitude of the nonthermal mass motions was independent of the plasma temperature or its height above the limb. We also found that the emission measure distribution within the 2.6×106-6.6×106 K plasma regimes did not change during most of the observations, an indication that on the average the temperature distribution among the various plasma volumes along the line of sight stayed unchanged. Title: SUNRISE: a balloon-borne telescope for high resolution solar observations in the visible and UV Authors: Solanki, Sami K.; Gandorfer, Achim M.; Schuessler, Manfred; Curdt, W.; Lites, Bruce W.; Martinez-Pillet, Valentin; Schmidt, Wolfgang; Title, Alan M. Bibcode: 2003SPIE.4853..129S Altcode: Sunrise is a light-weight solar telescope with a 1 m aperture for spectro-polarimetric observations of the solar atmosphere. The telescope is planned to be operated during a series of long-duration balloon flights in order to obtain time series of spectra and images at the diffraction-limit and to study the UV spectral region down to ~200 nm, which is not accessible from the ground. The central aim of Sunrise is to understand the structure and dynamics of the magnetic field in the solar atmosphere. Through its interaction with the convective flow field, the magnetic field in the solar photosphere develops intense field concentrations on scales below 100 km, which are crucial for the dynamics and energetics of the whole solar atmosphere. In addition, Sunrise aims to provide information on the structure and dynamics of the solar chromosphere and on the physics of solar irradiance changes. Sunrise is a joint project of the Max-Planck-Institut fuer Aeronomie (MPAe), Katlenburg-Lindau, with the Kiepenheuer-Institut fuer Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofi sica de Canarias, La Laguna, Tenerife. In addition, there are close contacts with associated scientists from a variety of institutes. Title: On the outflow in an equatorial coronal hole Authors: Xia, L. D.; Marsch, E.; Curdt, W. Bibcode: 2003A&A...399L...5X Altcode: We report new observations concerning the source of the fast solar wind by directly comparing Doppler-shift maps of Ne7+ with charts of the photospheric magnetic field in an equatorial coronal hole, which was observed by SUMER/SOHO and NSO/Kitt Peak on November 5, 1999. The relationship between the velocity field, line intensity and magnetic network is discussed. Our data show that there are both dark and bright regions in this coronal hole as seen in the Ne Viii line. The larger blue shifts of the Ne Viii line are associated mainly with the darker region, where the strong magnetic flux with a single polarity is concentrated. Conversely, the smaller blue shifts are measured mainly in the brighter region, with an underlying mixed-polarity magnetic structure. These observational results are in agreement with the model prediction that the fast solar wind is initially accelerated in the coronal funnels, which are regions with globally open coronal fields rooted in the magnetic network. Title: Transition region blinker - spatial and temporal behaviour Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2003HvaOB..27...75T Altcode: From an extensive search for transition region internetwork activity in the quiet Sun atmosphere the most prominent transient event is presented. The basic physical and geometrical parameters of this event are derived from the O VI 1037.61 Å emission spectral line. The spatial extent of 11 000 km, duration for 9 minutes, intensity enhancements factor of 7 and large Doppler velocities of both signs were estimated for the event. According to these values this event was identified as a transition region blinker. Title: Doppler Oscillations of Active Region Loops: Steps towards Coronal Seismology Authors: Curdt, W.; Wang, T. J.; Dammasch, I. E.; Solanki, S. K. Bibcode: 2003HvaOB..27...83C Altcode: Oscillations of coronal loops -- subject of theoretical work for a long time -- can help to determine coronal plasma parameters not otherwise accessible. Therefore, the Doppler oscillations recently observed by the SUMER spectrometer on SOHO are of extreme interest and constitute a significant contribution to the old, but rejuvenated field of coronal seismology. High-velocity oscillation events in hot EUV flare lines are seen almost every time these lines brighten. Such events seem to be a common feature of active region loops. The oscillations always have an impulsive trigger and are strongly damped while they cool down. Lines formed at normal coronal temperatures do not show any signature of these oscillations. Title: Solar observations from space and from the ground Authors: Curdt, W. Bibcode: 2003AN....324..334C Altcode: Recent results from space missions like YOHKOH, SOHO or TRACE as well as ground-based observations clearly indicate that physical processes of most solar phenomena take place on small scales, which are still below the resolution of the instruments employed. There is an urgent need for observations at higher resolution and also for their extension to multi-wavelength regimes. Space-borne as well as ground-based instruments have limitations of the present-day technology, although in a different way. In this communication, an overview of space instruments currently in operation or in the preparation phase is presented and references to more detailed information are given. Title: Hot loop oscillations seen by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2003AN....324..340W Altcode: No abstract at ADS Title: Transition region eruptive event observed with SOHO/CDS in the quiet Sun network Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H. Bibcode: 2003HvaOB..27...67G Altcode: CDS observations of the quiet Sun network in the chromospheric He I 584.33 Å and transition region O V 629.73 Å emission lines over a time period of ∼ 29 min are presented. One eruptive event was detected in this time series of data. The parameters of the network eruptive event are derived and the type of this small-scale activity is identified. The lifetime of the event was ∼ 1 min and it was found only in the transition region emission line. This event had no chromospheric counterpart. All O V spectral profiles of the eruptive event were blueshifted and the maximal Doppler shift was -14.7 km s-1. During an initial phase of the eruptive event, the O V intensity enhancement factor was 2.3. These parameters indicate that the observed event could be a transition region explosive event but measured with the limited resolution of the CDS instrument. Title: Mass Motions and Plasma Properties in the 107 K Flare Solar Corona Authors: Landi, E.; Feldman, U.; Innes, D. E.; Curdt, W. Bibcode: 2003ApJ...582..506L Altcode: In the present work, we analyze Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of a solar limb flare that occurred on 1999 May 9. The analyzed data cover a time span of around 6.4 hr, during which an M-7.6 flare erupted and decayed in the field of view. Two selected regions along the SUMER slit have been considered for quantitative analysis. The main purpose of the present analysis is to measure the mass motions and the nonthermal velocities of the postflare plasmas and their temporal evolution. To achieve this we use lines having formation temperatures in the 2.5×106 to 2×107 K range from which we derive net mass motions and nonthermal velocities and compare them with the properties of the surrounding plasma not affected by the flare activity. To understand the physical conditions of the flaring plasma and of the surrounding material, we derive electron temperature, electron density, and emission measures of the emitting plasma. We find that bulk motions, initially of the order of several hundreds of kilometers per second in both directions, decay within 10 minutes from the flare onset; nonthermal velocities decay to preflare values of around 30 km s-1 in less than 2 hr from the maximum value of around 100 km s-1 at flare onset. The measured electron density does not seem to change during activity, while the flare plasma temperature steadily decays to preflare values. The temperature evolution is consistent with a radiatively cooling plasma, although the uncertainties associated to the measurement of the variation of thermal energy of the flare plasma prevent a definitive conclusion on possible continuous heating of the flaring plasma. Title: Microflaring of a solar bright point Authors: Vilhu, O.; Huovelin, J.; Pohjolainen, S.; Virtanen, J.; Curdt, W. Bibcode: 2002A&A...395..977V Altcode: 2002astro.ph..7274V A 50 x 50 arcsec region near the solar disc center containing a bright point (BP) was observed with the SUMER- spectrograph of the SOHO observatory. The data consist of two hours observation of four far-UV emission lines formed between 2 x 104-6x 105 K, with 2 arcsec spatial, 2.8 min temporal and 4 km s-1 spectral resolution. A striking feature was the strong microflaring of the major persistent BP (with size 8 x 8 arcsec) and the appearance of several short lived transients. The microflaring of each individual 2 x 2 arcsec pixel inside the main BP was coherent, indicating strong interaction of the possible sub arc sec building blocks (magnetic flux tubes). Using the emission measure at 105 K as an indicator of the loop foot point area and magnetic filling factor, we suggest 10 per cent filling factor for the BP observed. This is similar to that on the average surface of a medium-active solar type star. Based on observations with the SUMER-spectrometer on board the SOHO observatory. Title: Doppler oscillations in hot coronal loops Authors: Curdt, W.; Wang, T. J.; Innes, D. E.; Solanki, S. K.; Dammasch, I. E.; Kliem, B.; Ofman, L. Bibcode: 2002ESASP.506..581C Altcode: 2002ESPM...10..581C; 2002svco.conf..581C Recently, a new kind of damped oscillations of hot coronal loops was revealed by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO. Such events seem to be a common feature observed in active region loops, seen very often when these lines brighten. The oscillations always have an impulsive trigger and are strongly damped while they cool down. However, in lines formed at coronal temperatures of ≍2 MK never any signature of these oscillations has been observed. In this study, we present the main properties of Doppler oscillations derived from a statistical study of 17 flare-like events, and a comparison with TRACE transverse loop oscillations. We also discuss the oscillation modes and their damping mechanism. Title: Sunrise: a 1-m balloon borne solar telescope Authors: Solanki, S. K.; Schüssler, M.; Curdt, W.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.; Sunrise Team Bibcode: 2002ESASP.505...27S Altcode: 2002solm.conf...27S; 2002IAUCo.188...27S Sunrise is a light-weight solar telescope with a 1 m aperture for spectro-polarimetric observations of the solar atmosphere. The telescope is planned to be operated during a series of long-duration balloon flights in order to obtain time series of spectra and images at the diffraction-limit and to study the UV spectral region down to ≅200 nm, which is not accessible from the ground. The central aim of Sunrise is to understand the structure and dynamics of the magnetic field in the solar atmosphere. Interacting with the convective flow field, the magnetic field in the solar photosphere develops intense field concentrations on scales below 100 km, which are crucial for the dynamics and energetics of the whole solar atmosphere. In addition, Sunrise aims to provide information on the structure and dynamics of the solar chromosphere and on the physics of solar irradiance changes. Title: Initial features of an X-class flare observed with SUMER and TRACE Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2002ESASP.505..607W Altcode: 2002IAUCo.188..607W; 2002solm.conf..607W A class X1.5 flare started on the solar limb at 00:43 UT on 21 April 2002, which was associated with a CME observed at 01:27 UT by LASCO C2. The coordinated analyses of this flare include TRACE 195 Å images and SUMER spectra in lines of Fe XXI, Fe XII, and C II. We find that: 1) The flare began with a jet seen by TRACE, which was detected by SUMER in the C II line as a strong brightening with blue shifts up to 170 km s-1. At that time only weak emission was detected in Fe XII and Fe XXI. 2) Subsequently, a weak looplike brightening started south of the jet, moving outwards with an average speed of about 150 km s-1. The SUMER spectra responded this moving loop as separatingly brightenings, visible only in the Fe XXI line. The southwards moving component contains red- and blue-shifted emission features and has an apparent speed of ~120 km s-1. The absence of signatures in Fe XII and C II lines indicates that the moving weak loop seen by TRACE corresponds to the emission from very hot plasma, in a blend line in the 195 Å bandpass due to Fe XXIV formed at T > 10 MK. 3) The trigger mechanism of the flare and associated CME can be interpreted in the same way as that proposed by Wang et al. (2002) for an event with similar initial features. Title: Quiet-Sun chromospheric network evolution Authors: Lemaire, Philippe; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002ESASP.505..477L Altcode: 2002solm.conf..477L; 2002IAUCo.188..477L Using the SUMER/SOHO spectrometer we have observed the same quiet-Sun area during several days in a set of eight spectral lines of the transition region. Line intensity maps of the rastered areas are used to separate the interior of the supergranular cells from the network. Then, following the evolution of the supergranular pattern, we measure the variations of intensity and the Doppler shifts at several temperatures of formation of the transition region. We find that the overall flow velocity of the cell interior and the network generally decays within ten hours, which represents a significant part of the supergranular lifetime. Title: Hot loop oscillations seen by SUMER: examples and statistics Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ESASP.505..199W Altcode: 2002solm.conf..199W; 2002IAUCo.188..199W We measure physical parameters of Doppler-shift oscillations in 17 flare-like events. These events have been recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO, along a slit fixed above limb active regions. The selected spectral windows contain emission lines with formation temperatures from ~104 to 107K. The events were only detected in hot flare lines, without any signature in lines formed around 2×106K. Similarly, the Doppler shift oscillations occur in regions coincident with hot soft X-ray loops, but not with EUV loops. The oscillations have periods of 11 - 31 min, with an exponential decay time of 5.5 - 29 min, and show an initial large shift pulse with peak velocities up to 200 km s-1. Several indications suggest that the Doppler oscillations are incompressible coronal loop oscillations, that are usually excited impulsively by weak flare (or microflare) events that also produced a strong emission increase at 5 - 8×106K. Title: Doppler Shift Oscillations of Hot Solar Coronal Plasma Seen by SUMER: A Signature of Loop Oscillations? Authors: Wang, Tongjiang; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ApJ...574L.101W Altcode: We report observations of strongly damped Doppler shift oscillations detected in a flare line, Fe XIX, with the Solar Ultraviolet Measurement of Emitted Radiation spectrometer. Spectra were recorded above an active region at the western limb of the Sun, from lines with formation temperatures ranging from 0.01 to 10 MK. However, the oscillations were seen only in the hot plasma (>6 MK) lines. The Doppler oscillations have periods of 14-18 minutes, with an exponential decay time of 12-19 minutes, and show an initial large blueshift pulse with peak velocities up to 77 km s-1. Several indications suggest that the Doppler oscillations are incompressible coronal loop oscillations that are excited impulsively by a flarelike event that also produced a strong increase in Fe XIX emission. Title: Variation of the full Sun hydrogen Lyman α and β profiles with the activity cycle Authors: Lemaire, Philippe; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002ESASP.508..219L Altcode: 2002soho...11..219L Full Sun hydrogen Lyman α and β profiles obtained through the activity cycle are needed to compare with stars, to understand the hydrogen distribution in the heliosphere and to evaluate the processes in the upper planetary atmospheres. Using the SUMER/SOHO telesocope scattered light properties, we have measured the Lyman α and β profiles at different epochs of the solar activity cycle. Here we report modifications in the intensity and the shape of the profiles. Title: Oscillating hot loops observed by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ESASP.508..465W Altcode: 2002soho...11..465W We report observations of Doppler shift oscillations in hot flare lines emitted from active region loops. The Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO recorded spectra of limb active regions loops in several emission lines with formation temperatures from ~104 to 107K. The events were only detected in the hot flare lines, without any signature in lines formed around 2×106K. There is a large shift pulse of up to 190 km s-1 during the rising phase of the flux which is followed by two or three periods of strongly damped alternating red and blue shift oscillations with periods in the range 12-31 min. Slow mode standing waves match the observed period. However, the initial large Doppler shift pulse suggests that the waves are impulsively generated. Unlike the oscillating loops seen in the TRACE images, these Doppler shift oscillations are sometimes seen without an associated flare. Title: Correlated Dynamics of Hot and Cool Plasmas in the Main Phase of a Solar Flare Authors: Kliem, B.; Dammasch, I. E.; Curdt, W.; Wilhelm, K. Bibcode: 2002ApJ...568L..61K Altcode: We report far-ultraviolet observations of a solar limb flare obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer. At a fixed pointing of the slit above the limb, spectra were simultaneously obtained in several emission lines that covered a wide temperature range from ~104 to ~107 K. The temporal evolution of the spectra revealed, for the first time, a high degree of correlation between the dynamical behavior of hot (T~107 K) and cool (T~104 K) coronal material during the main phase of a flare. We note that the data did not show any indication of the presence of a prominence. Hot and cool plasmas brightened at nearly the same location. Their Doppler shifts, which were opposite to each other, reached peak values simultaneously. Thereafter, the two components showed anticorrelated, rapidly damped, and oscillatory Doppler shifts and a very similar decay of the line widths, but with the cool plasma reaching maximum brightness before the hot plasma. This behavior points to an active role for cool plasma in the dynamics of this flare, different from the usual picture of passive cooling after the impulsive phase. We suggest a model in which the localized cooling of coronal plasma by the thermal instability triggers magnetic reconnection through the resulting enhanced resistivity, the combined processes leading to the correlated dynamics of hot and cool plasmas in a loop-loop interaction geometry. Title: Transition region dynamics from SUMER/SOHO observations: shape of the emission spectral lines Authors: Rybák, J.; Curdt, W.; Kučera, A.; Wöhl, H. Bibcode: 2002ESASP.477..163R Altcode: 2002scsw.conf..163R The quiet sun network/internetwork transition region line profiles of C II 1036.34 Å and O VI 1037.61 Å are outlined emphasizing the temporal/spatial behaviour of their deviations from the Gaussian shape. Systematic deviations of the line profiles from the single-Gaussian shape indicate that transition region emission lines consist of two Gaussian components over almost the whole quiet sun internetwork except their small innermost parts. This finding is in qualitative agreement with the transition region model of Peter (2001). Title: Transition region quiet sun velocity field evolution Authors: Lemaire, P.; Artzner, G.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002AdSpR..30..487L Altcode: The UV/EUV SUMER spectrometer aboard SOHO can record profiles of lines emitted by elements at different stages of ionization corresponding to several temperatures within the transition region temperature range. During the solar cycle minimum in July 1996, we were able to observe the quiet Sun during five consecutive days. From the line positions we have determined the velocity fields and follow their time variations at different temperatures in the transition region. The line intensity maps are used to separate supergranular cells and network and they allow to compare the behaviors of the velocity fields evolution in the two structures. The results are critically analyzed and discussed. Title: Solar Vacuum-ultraviolet Radiometry with SUMER Authors: Wilhelm, K.; Schuhle, U.; Curdt, W.; Dammasch, I. E.; Hollandt, J.; Lemaire, P.; Huber, M. C. E. Bibcode: 2002ISSIR...2..145W Altcode: 2002ESASR...2..145W; 2002rcs..conf..145W Since the beginning of 1996, the space-based telescope and spectrograph SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on the SOlar and Heliospheric Observatory (SOHO) of ESA and NASA has obtained spectra of many features of the quiescent and active Sun with high spectral and spatial resolution. In addition, irradiance and radiance measurements of line and continuum emission have been performed in the wavelength range 46.5 nm to 161.0 nm. The instrument was radiometrically calibrated against the Berlin Electron Storage ring for SYnchrotron radiation (BESSY I), a primary source standard, with the help of a transfer source standard based on a hollow-cathode discharge lamp. A thorough cleanliness programme, specifically aimed at chemical contamination control, resulted in an excellent radiometric stability of the normal-incidence optical system as well as of the detectors. This has been verified under operational conditions by various techniques employed during the SOHO mission, such as line-ratio studies, observations of stars, and comparisons with other instruments. The observations provide vacuum-ultraviolet (VUV) radiometry of the Sun in many emission lines and continua of atoms and ions with relative standard uncertainties of 15 % (detector A) and 20 % (detector B) for the wavelength range 53 nm to 124 nm, with larger uncertainties outside this interval and after the SOHO recovery in 1998. We report on the present state of the SUMER radiometric calibration and provide a full bibliography related to this topic. Title: Correlated Dynamics of Hot and Cool Plasmas in Two Solar Flares Authors: Kliem, B.; Dammasch, I. E.; Curdt, W.; Wilhelm, K. Bibcode: 2002mwoc.conf..271K Altcode: We report far-ultraviolet observations of a solar limb flare by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer. At a fixed pointing of the slit above the limb, spectra were simultaneously obtained in several emission lines that covered a wide temperature range of ≅ 104 -- 107 K. The temporal evolution of the spectra revealed a high degree of correlation between the dynamical behavior of hot (T ~107 K) and cool (T ~104 K) material during the main flare phase. Hot and cool plasma brightened at nearly the same place, with cool plasma reaching maximum brightness before the hot plasma. The opposite line-of-sight velocities reached their peak values simultaneously. A correlated, rapidly damped oscillatory motion followed, while the excess (turbulent) line widths decayed in a similar manner. This behavior points to an active role of cool plasma in the dynamics of this flare, different from the usual picture of passive cooling after the impulsive phase. An interpretation is suggested in terms of magnetic reconnection which is triggered by rapid localized cooling due to the thermal instability in a loop-loop interaction geometry. Title: The SUMER spectral atlas of solar-disk features Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schühle, U.; Lemaire, P. Bibcode: 2001AIPC..598...45C Altcode: 2001sgc..conf...45C A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670 Å and 1609 Å in first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory) [1]. The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI)-contributing in a distinct manner to the average quiet-Sun emission-have their imprint on the BN/CI ratio, which is also shown for the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra, but below 500 Å the responsivity of the normal-incidence optical system is very low. The spectra include emissions from atoms and ions in the temperature range 6 103 K to 2 106 K, i.e., continua and mission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools for studying the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100 Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere it is obvious that our atlas can only be a-hopefully typical-snapshot. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 (1σ), and the wavelength scale is accurate to typically 10 mÅ, which is the level achievable with semi-automatic processing. The SUMER solar-disk spectral atlas will be published in the near future by Curdt et al. [2]. It includes profiles of the average quiet Sun, an equatorial coronal hole, and a sunspot. As an example we show in Fig. 1 the spectral range from 1300 Å to 1342 Å with the prominent O I and C II lines. Resolved emission lines are indicated by a mark, the measured wavelength in angstrom, and the identification, if available. Marks point to line lists available in the literature, where additional information about a specific line can be found [3-7]. New lines or identifications are indicated. Lines observed in first order and in second-order of diffraction are distinguished. Only the three least-significant digits of the wavelength values are given. If available, unidentified lines are characterized by the temperature classification defined in [3] (a: Te<3 105 b: Te~3 105 c: Te~4 105 d: 6 105<Te <9 105 e: Te~1.4 106 f: Te~1.8 106). The vertical axes are scaled to spectral radiance in units of mW sr-1 m-2 Å-1 on the left the radiometric calibration for first order lines is given, on the right for second order lines. Note, that second order lines are always superimposed on a first order background. We have taken care of the type of photocathode (bare or KBr) when applying the radiometric calibration to different sections of the spectrum. Also displayed in green is the BN/CI ratio in an attempt to characterize the quiet-Sun chromospheric network structure. A pre-print of the SUMER spectral atlas and a line list is available at http://www.linmpi.mpg.de/~curdt. . Title: Spectral windows of the solar atmosphere Authors: Curdt, W.; Landi, E. Bibcode: 2001ESASP.493..199C Altcode: 2001sefs.work..199C No abstract at ADS Title: Temporal and spatial variations of the quiet upper chromosphere from SOHO/SUMER observations of hydrogen Lyman lines Authors: Kariyappa, R.; Varghese, B. A.; Curdt, W. Bibcode: 2001A&A...374..691K Altcode: We have analyzed a time series of spectra in the hydrogen Lyman lines and the Lyman continuum obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the SOlar Heliospheric Observatory (SOHO). The time series of about 2 hours and 22 min was obtained on 1999 March 9 in a quiet region near the center of the solar disk. For our analysis, we have selected a Lyman continuum window around 907 Å, and the five Lyman lines: Ly5 (937.8 Å), Ly7 (926.2 Å), Ly9 (920.9 Å), Ly11 (918.1 Å), and Ly15 (915.3 Å). We derived the central intensity of these lines for a large number of locations over the network and inter-network regions. We found from their line-center intensity time series and from the power spectrum analysis that the network and inter-network regions at the upper chromosphere are associated with 5-7 min and 3-min period of intensity oscillations, respectively. Phase difference analysis shows that there is a preponderance of upward-propagating waves in the upper chromosphere. The phase velocity was estimated to be roughly 4-5 km s-1 in the network regions. In addition, a Fast Fourier analysis has been performed in the spatial domain, all along the slit length used, for all the spectra and for the total duration of the observations. We have detected significant periodic spatial variations with Fourier transform power peaks around 9-10 arcsec and at 4 arcsec. They correspond to the scale of mesogranulation structure and the width of the supergranular boundary, respectively. This provides evidence for the existence of a meso-scale in the upper chromosphere, of the same size as observed in the photosphere and lower chromosphere by earlier studies. We notice that the size (9-10 arcsec) of the meso-scale structures appears to be the same in all Lyman lines and in the continuum, which are formed at different depths in the chromosphere. Title: The SUMER spectral atlas of solar-disk features Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schühle, U.; Lemaire, P. Bibcode: 2001A&A...375..591C Altcode: A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670 Å and 1609 Å in the first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on the disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI) - contributing in a distinct manner to the average quiet-Sun emission - have their imprint on the BN/CI ratio, which is also shown for almost the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra. These lines are clearly marked in the atlas. The spectra include emissions from atoms and ions in the temperature range 6*E3 K to 2*E6 K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools to study the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100 Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere, it is obvious that our atlas can only be a - hopefully typical - snapshot. Brief descriptions of the data reduction and calibration procedures are given. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 (1sigma ) and the wavelength scale is accurate to typically 10 mÅ. The atlas is also available in a machine readable form. Table A.1 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/375/591 Title: VizieR Online Data Catalog: SUMER Spectral Atlas of Solar Disk Features (Curdt+, 2001) Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schuhle, U.; Lemaire, P. Bibcode: 2001yCat..33750591C Altcode: List of spectral lines in the wavelength range from 668Å to 1611Å identified in SUMER (Solar Ultraviolet Measurements of Emitted Radiation, spectrograph on the spacecraft SOHO) spectra of the average quiet Sun (QS), a coronal hole (CH) and a sunspot on disk (SS). Spectral lines observed in second order of diffraction which are also given here, extend the lower wavelength limit to below 500Å. For each entry we give the observed wavelengths in angstrom, the identification, the transition, the peak of spectral radiance, Lpeak, in mW/(sr*m2*Å) (incl. background), and a cross-reference to other line lists available in the literature (cf., Sect. 5.1). For second-order lines radiance entries are generally not provided, since the background separation in both orders of diffraction is a non-trivial task, which can not be automated. Only a few radiance values of strong second-order lines with negligible first-order contribution are given, which are marked by an asterisk (*). (1 data file). Title: Chromospheric Dynamics as can be Inferred from SUMER/SOHO Observations Authors: Rybák, J.; Kučera, A.; Curdt, W.; Schühle, U.; Wöhl, H. Bibcode: 2001ASSL..259..247R Altcode: 2001dysu.conf..247R Experience with the SUMER/SOHO observations of the chromospheric dynamics and the reduction of the acquired data is summarized on base of the SOHO Joint Operation Program 78 which is focused on the variability of the chromosphere and the transition region to the corona. Title: Large Doppler Shifts in X-Ray Plasma: An Explosive Start to Coronal Mass Ejection Authors: Innes, D. E.; Curdt, W.; Schwenn, R.; Solanki, S.; Stenborg, G.; McKenzie, D. E. Bibcode: 2001ApJ...549L.249I Altcode: We report observations, taken with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer, of spatially resolved high red and blue Doppler shifts (up to 650 km s-1) from X-ray-emitting plasma in the corona above a flare. The high Doppler shifts are seen minutes after a fast, faint optical front is seen racing through the same part of the corona in images taken with the Mirror Coronagraph for Argentina. The association of the large-scale fast optical emission front with soft X-ray emission and high Doppler shifts suggests plasma heating and acceleration in the wake of a shock. Title: Spectroscopic Signatures of a Flare Observed by SUMER Onboard SOHO Authors: Dammasch, I. E.; Curdt, W.; Kliem, B.; Dwivedi, B. N.; Wilhelm, K. Bibcode: 2001IAUS..203..264D Altcode: On 06 November 1999, SUMER (the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on SOHO) observed a post-flare site above active region NOAA 8758 which was approaching the north-east limb. SUMER recorded a time series taken with a constant slit position and several spectral windows covering a wide temperature range (10 000 - 10 000 000 K), preceded and followed by contextual raster scans. During this operation, a flare of size C4.6 occurred in the observed region, also observed by the GOES 8 X-ray flux monitor, the SOHO/EIT imager and the YOHKOH/SXT instrument. All data sets have been coaligned. The temporal evolution seen in SUMER spectra is presented and compared with the other observations. Title: Spectroscopic features in the EUV emission of a M8 flare observed by SUMER Authors: Curdt, W.; Landi, E.; Feldman, U.; Innes, D.; Dwivedi, B.; Wilhelm, K. Bibcode: 2001IAUS..203..260C Altcode: On May 9, 1999 a flare of size M8 occurred while SUMER obtained a spectral scan above the active region NOAA 8537 at the west limb. We recorded spectra during the pre-flare phase, at flare onset, and during the decay phase. More than 60 flare lines were observed during this event, which include Fe XVIII - Fe XXIII lines that provide evidence of 107 K plasmas. We also recorded lines from He-like ions, such as Ne IX, Na X, Mg XI or Si XIII. Accurate wavelength measurements of such lines are of interest in basic atomic physics studies. Using plasma diagnostic techniques, we investigated the temporal evolution of the electron densities and temperatures during the event. Since the spectra contain lines from many different elements, we were able to determine elemental abundances in the flaring plasma. Title: High-resolution Solar Polarimetry with Sunrise Authors: Schmidt, W.; Solanki, S. K.; Schüssler, M.; Curdt, W.; Lites, B. W.; Title, A. M.; Martinez Pillet, V. Bibcode: 2001AGM....18S1001S Altcode: Sunrise is a 1m balloon-borne solar telescope. It is equipped with a spectrograph polarimeter which combines vector-polarimetry in the visible with diagnostic spectroscopy in the visible and the UV, down to 200 nm. The instrumentation includes a filter-magnetograph and a medium-band filtergraph. The wavelength bands of the latter include the CH-band (430.6 nm) and a UV continuum at 205 nm. Diffraction limited resolution in the UV will be achieved by employing a phase diversity technique. The main telescope is based on a lightweight silicon-carbide mirror, developed within the Solar Lite program. During the long-duration flight at Antarctica, foreseen for late 2005, Sunrise will continuously observe the sun for a period of about ten days, with constant image quality across the full field of view. In-flight alignment of the telescope optics will be controlled by a wavefront sensor. The main goal of Sunrise is to understand the structure and dynamics of the magnetic field in the atmosphere of the sun. To this end, Sunrise will observe small magnetic flux concentrations with dimensions of less than 70 km with high polarimetric accuracy. At the same time, Sunrise will provide diffraction-limited filtergrams of the photosphere and chromosphere with a resolution down to 35 km at a wavelength of 200 nm. Title: Identification of Spectral Lines in the 500-1600 Å Wavelength Range of Highly Ionized Ne, Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni Emitted by Flares (Te>=3×106 K) and Their Potential Use in Plasma Diagnostics Authors: Feldman, U.; Curdt, W.; Landi, E.; Wilhelm, K. Bibcode: 2000ApJ...544..508F Altcode: On 1999 May 9 the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) recorded spectra from a high-temperature region located in the solar corona above the west limb. These spectra contain lines from rather less-abundant elements in solar plasmas. In this paper we present identifications of the high-temperature (Te>=3×106 K) Ne, Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni lines that were detected in the 500-1600 Å spectral range of SUMER. In addition, accurate wavelength measurements have been obtained with uncertainties varying between 0.015 and 0.040 Å (1 σ). Making use of the newly measured wavelengths, we derive energy levels in the ground configuration of a number of highly charged ions. We present intensity ratio calculations of lines in the SUMER range that could be used to measure electron densities in high-temperature solar plasmas. We also provide emissivities for Ca XIII-Ca XV and Fe XVIII-Fe XXIII lines that could be used to determine emission measures and electron temperatures of high-temperature plasmas. We discuss a method for measuring elemental abundance variations in high-temperature solar plasmas using lines presented in the paper. A list of spectral lines spanning the 300-30000 Å wavelength range and their branching ratios that are suitable for efficiency calibration of space-borne spectrographs is provided. Title: Wavelength measurements of heliumlike 1s2s 3S1-1s2p 3P0,2 transitions in Ne8+, Na9+, Mg10+, and Si12+ emitted by solar flare plasmas Authors: Curdt, W.; Landi, E.; Wilhelm, K.; Feldman, U. Bibcode: 2000PhRvA..62b2502C Altcode: With the Solar Ultraviolet Measurements of Emitted Radiation instrument-a high-resolution normal-incidence telescope and spectrometer on board the Solar and Heliospheric Observatory-heliumlike 1s2s 3S1-1s2p 3P0,2 transitions in the highly ionized species Ne8+, Na9+, Mg10+, and Si12+ were observed. The spectral lines were emitted by high-temperature solar flare plasmas. In this paper, we report on wavelength measurements of the He-like lines identified in the recorded spectra. The wavelength uncertainties we obtained from the solar measurements are <=20 mÅ(1σ), and in one case <=30 mÅ. This is comparable to or better than the best determinations so far achieved for these heliumlike 1s2s 3S1-1s2p 3P0,2 transitions with instrumentation in the laboratory. For the Na9+ 3S1-3P2 transition we report what is to our knowledge the first wavelength measurement. The knowledge of the accurate wavelengths can provide important checks on atomic structure calculations. Title: Wavelengths of Forbidden Transitions Arising from Levels Within the Fe+19 2S22P3 Ground Configuration Authors: Kucera, T. A.; Feldman, U.; Widing, K. G.; Curdt, W. Bibcode: 2000ApJ...538..424K Altcode: In this paper we report the identification of all remaining unidentified forbidden lines arising from transitions within levels of the Fe+19 ground configuration. These lines were identified using data from the SOHO/SUMER spectrograph and Skylab. Adjusted wavelength values are also given for some previously observed lines. Forbidden lines that are the result of transitions within levels of the ground configuration of a highly ionized astrophysically abundant element generally have longer wavelengths than resonance lines emitted by the same ion. Many of these forbidden lines are fairly prominent in low-density plasmas and traditionally have been used in determining properties of high-temperature astrophysical plasmas. The identified Fe+19 forbidden lines span the 300-2665 Å wavelength range. Since spontaneous decay rates of forbidden transitions arising from the same upper level are known quite accurately, these lines can be used for calibrating spectrometers over wide wavelength ranges. Title: The EUV Spectrum of Sunspot Plumes Observed by SUMER on SOHO Authors: Curdt, W.; Dwivedi, B. N.; Feldman, U. Bibcode: 2000JApA...21..397C Altcode: No abstract at ADS Title: Newly Discovered Fe XX lines in Flares Observed by SOHO/SUMER and Skylab. Authors: Kucera, T. A.; Feldman, U.; Widing, K. G.; Curdt, W.; Khan, J. I. Bibcode: 2000SPD....31.0264K Altcode: 2000BAAS...32..822K We have used UV spectra from solar flares observed with SOHO/SUMER and Skylab to identify all of the all remaining unidentified forbidden lines arising from transitions within levels of the Fe XX ground configuration. We have also obtained more accurate wavelengths for previously observed lines. Forbidden lines resulting from transitions within levels of the ground configuration of highly ionized elements generally have longer wavelengths than resonance lines emitted by the same ions. Many of these forbidden lines are fairly prominent in low-density plasmas, and have traditionally been used in determining properties of high temperature astrophysical plasmas. The identified Fe XX forbidden lines span the 300-2665 Angstroms wavelength range. Since spontaneous decay rates of forbidden transitions arising from the same upper level are known quite accurately, these lines can be used for calibrating spectrometers over wide wavelength ranges. Title: Solar Irradiances of Ultraviolet Emission Lines Measured During the Minimum of Sunspot Activity in 1996 and 1997 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schuhle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Humbler, M. C. E. Bibcode: 2000PCEC...25..389W Altcode: No abstract at ADS Title: Radiometric Calibration of the Vacuum-Ultraviolet Spectrograph SUMER on the SOHO Spacecraft with the B Detector Authors: Schühle, Udo; Curdt, Werner; Hollandt, Jörg; Feldman, Uri; Lemaire, Philippe; Wilhelm, Klaus Bibcode: 2000ApOpt..39..418S Altcode: The Solar Ultraviolet Measurement of Emitted Radiation (SUMER) vacuum-ultraviolet spectrograph was calibrated in the laboratory before the integration of the instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft in 1995. During the scientific operation of the SOHO it has been possible to track the radiometric calibration of the SUMER spectrograph since March 1996 by a strategy that employs various methods to update the calibration status and improve the coverage of the spectral calibration curve. The results for the A Detector were published previously Appl. Opt. 36, 6416 (1997) . During three years of operation in space, the B detector was used for two and one-half years. We describe the characteristics of the B detector and present results of the tracking and refinement of the spectral calibration curves with it. Observations of the spectra of the stars and Leonis permit an extrapolation of the calibration curves in the range from 125 to 149.0 nm. Using a solar coronal spectrum observed above the solar disk, we can extrapolate the calibration curves by measuring emission line pairs with well-known intensity ratios. The sensitivity ratio of the two photocathode areas can be obtained by registration of many emission lines in the entire spectral range on both KBr-coated and bare parts of the detector s active surface. The results are found to be consistent with the published calibration performed in the laboratory in the wavelength range from 53 to 124 nm. We can extrapolate the calibration outside this range to 147 nm with a relative uncertainty of 30% (1 ) for wavelengths longer than 125 nm and to 46.5 nm with 50% uncertainty for the short-wavelength range below 53 nm. Title: Phase Relations between Chromospheric and Transition Region Oscillations Authors: Krijger, J. M.; Curdt, W.; Heinzel, P.; Schmidt, W. Bibcode: 2000ESASP.463..353K Altcode: 2000sctc.proc..353K No abstract at ADS Title: Solar spectroradiometry with the telescope and spectrograph SUMER on the Solar and Heliospheric Observatory SOHO Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Dammasch, I. E.; Hollandt, J.; Lemaire, P.; Huber, M. C. E. Bibcode: 2000Metro..37..393W Altcode: No abstract at ADS Title: Solar Ultraviolet Irradiance and Radiance Observations by SUMER on SOHO Authors: Dammasch, I. E.; Wilhelm, K.; Curdt, W.; Schühle, U. Bibcode: 1999ESASP.448.1165D Altcode: 1999ESPM....9.1165D; 1999mfsp.conf.1165D No abstract at ADS Title: Simultaneous Observations of Chromospheric and Transition Region Oscillations in HI Lyman Transitions and in Optical Lines Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; Tarbell, T.; von Uexküll, M.; Wilken, V. Bibcode: 1999ESASP.448..177C Altcode: 1999mfsp.conf..177C; 1999ESPM....9..177C No abstract at ADS Title: Chromospheric and Transition Region Dynamics - Reasons and Consequences of the Long-period Instrumental Periodicities of SUMER/SOHO Authors: Rybák, J.; Curdt, W.; Kucera, A.; Schühle, U.; Wöhl, H. Bibcode: 1999ESASP.448..361R Altcode: 1999mfsp.conf..361R; 1999ESPM....9..361R No abstract at ADS Title: Evidence for Non-Maxwellian Electron Energy Distributions in the Solar Transition Region: Si III Line Ratios from SUMER Authors: Pinfield, D. J.; Keenan, F. P.; Mathioudakis, M.; Phillips, K. J. H.; Curdt, W.; Wilhelm, K. Bibcode: 1999ApJ...527.1000P Altcode: Recent calculations of Si III emission-line strengths are compared with SUMER observations from a quiet solar region, a coronal hole, and an active region. Diagnostic line ratios are used to derive Te and Ne for the emitting plasma in each region, and good agreement between theory and observations is found. A major enhancement in the intensity of the 1313 Å emission line is observed, as well as some evidence of a small decrease in the temperature of maximum ionization fraction, as one moves from the coronal hole to the active region. Possible explanations for these effects are discussed, and it is concluded that they may be caused by the presence of nonthermal electrons in the transition region. Title: The solar ultraviolet spectrum from 1200 Å to 1560 Å: a radiometric comparison between SUMER/SOHO and SOLSTICE/UARS Authors: Wilhelm, K.; Woods, T. N.; Schühle, U.; Curdt, W.; Lemaire, P.; Rottman, G. J. Bibcode: 1999A&A...352..321W Altcode: After short descriptions of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer onboard SOHO (the Solar and Heliospheric Observatory) and the SOLSTICE (Solar-Stellar Irradiance Comparison Experiment) spectrometer on UARS (the Upper Atmosphere Research Satellite), a radiometric comparison is carried out of solar irradiance spectra measured by SOLSTICE and spectra derived from SUMER radiance observations of quiet-Sun regions in the wavelength range from 1200 Å to 1560 Å. The emission lines N v (lambda 1238) and C iv (lambda 1548) are considered in detail. For these lines, irradiance data are also available from full-Sun raster scans of SUMER and deviations of less than 15% are found between SOLSTICE and SUMER results - well within the combined uncertainty margins. Title: The Off-Limb Behaviour Of The FIP Effect In The Solar Plasma observed by SUMER on SOHO Authors: Dwivedi, B. N.; Curdt, W.; Wilhelm, K. Bibcode: 1999ESASP.446..293D Altcode: 1999soho....8..293D We present results from a study of EUV off-limb spectra obtained on 1996 August 8 and 9 with the SUMER spectrometer on spacecraft SOHO. With the capabilities of SUMER, we rastered the emitting source from 30'' off the lim outwards, and secured a unique high quality set of high-resolution EUV spectra. Using this observation, we investigate the FIP-effect in the transition region emission in the corona and also its variation as a function of height above the lim. We compare and rediscuss our results with the similar observation taken with SUMER on 1996 June 20 but beginning from 40'' off the limb outwards. The abstrat of this paper is already submitted by Dr W. Curdt : A quiet Sun Spectral Atlas Between 660-1500 A Observed with SUMER on SOHO by Curdt, Brekke, Schuhle, Wilhelm and Dwivedi. Title: Coordinated Observation of a Small Magnetic Region with SUMER and GCT Authors: Wilken, V.; Kneer, F.; Curdt, W. Bibcode: 1999ESASP.446..711W Altcode: 1999soho....8..711W No abstract at ADS Title: The SUMER EUV Atlas in the Spectral Range 670 A - 1498 A Authors: Curdt, W.; Brekke, P.; Schühle, U.; Wilhelm, K.; Dwivedi, B. N. Bibcode: 1999ESASP.446..251C Altcode: 1999soho....8..251C An extreme ultraviolet spectral atlas between 660 and 1600 A (first order) of a quiet Sun, a coronal hole, and a Sun spot region has been derived from observations with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO. More than 1000 emission lines are given with the best available identification. The spectra are radiometrically calibrated. Lines in second order are superimposed on this spectrum. The spectral scans include emissions from atoms and ions in the temperature range from 6 000 to 2000 000 K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This broad wavelength coverage provides an important new diagnostic tool for studying the essential physical parameters throughout the upper solar atmosphere. In particular, the wavelength range shortward of 1100 A as observed by SUMER represents a significant improvement over the spectra produced in the past. A brief description of the data reduction and calibration procedures is given. The absolute intensities are determined with an uncertainty of better than +- 15% in most of the range presented, and the wavelength scale is accurate to better than 0.01 A. The atlas will also be available in machine readable form. Title: Molecular Hydrogen Lines Observed with SUMER in the Spectrum of a Sunspot Authors: Schüehle, U.; Brown, C. M.; Curdt, W.; Feldman, U. Bibcode: 1999ESASP.446..617S Altcode: 1999soho....8..617S No abstract at ADS Title: Coordinated Observation Of A Small Magnetic Region With GCT And SUMER Authors: Wilken, V.; Kneer, F.; Curdt, W. Bibcode: 1999ESASP.446..707W Altcode: 1999soho....8..707W The SUMER instrument and the Gregory-Coude-Telescope (GCT) at the Observatorio del Teide/Tenerife have been used for observations of a small magnetic region in the solar atmosphere. With the GCT 2-dimensional spectro-polarimetry was performed and later analysed by applying the "centre of gravity method" (Semel, 1967) to measure the longitudinal magnetic flux. In this way we obtained seven magnetograms of the target area during the three hours campaign, while SUMER performed every five minutes EUV-scans in two spectral lines. The magnetograms show two cells with diameters of approximately 20000 km and 26000 km. Inside the cells the measured flux within the resolution element of 0.76 arcsec*0.76 arcsec. was ~1*109 Wb (corresponding to 33 Gauss flux density) on average. On the other hand the boundary regions have fluxes up to 1*1010 Wb. SUMER's intensity images of Si II (Chromosphere) and C IV (Transition region) show strong brightenings which very well resemble the magnetic flux pattern in the Photosphere. The intensities of Ne VIII (lower Corona) correlate with the magnetic flux as well, but far less than the former two lines. During the 3h observing run the coarse magnetic structure remains essentially unchanged. However, on scales smaller than 3 arcsec., the temporal intensity fluctuations of the EUV-lines show little similarity, if any. Possibly, at small scales the different EUV-lines originate from different structures which are not excited simultaneously. Title: Chromospheric And Transition Region Dynamics - Reasons and Consequences of the Short Period Instrumental Periodicities of SOHO/SUMER Authors: Rybak, Jan; Curdt, Werner; Kučera, Ales; Schüehle, Udo; Wöehl, Hubertus Bibcode: 1999ESASP.446..579R Altcode: 1999soho....8..579R The instrumentally caused oscillations of the spectral lines intensity and velocity, determined with the SUMER spectrometer onboard SoHO, are presented. On examples of two long-term measurements of O I, C II and O VI lines, it is shown that the reason of this instrumental effect was the insufficient precision of the solar rotation compensation of the spectrometer slit position. In both observational runs the standard rotation compensation procedure, performed on-line by the instrument, was selected for the long-term observations. The minor periodical motion of the slit position on the solar disk was taking place during such observations and this effect produced the regular changes of the measured line intensities and velocities. The significant enhancements of the oscillations amplitudes around the frequency 2.56 mHz and its harmonics were detected in the cases of observations, performed at the disk center. Unfortunately, these frequencies are just in the range of the typical oscillations determined till now in the upper solar atmosphere ! Consequences of this instrumental effect for SUMER measurements of the chromospheric and transition region dynamics are discussed. Procedures how to exclude the effect from the data post-facto as well as how to modify the future SUMER oscillations measurements in order to avoid the effect are proposed Title: Solar Mg X and Fe XII Wavelengths Measured By SUMER Authors: Dammasch, I. E.; Hassler, D. M.; Wilhelm, K.; Curdt, W. Bibcode: 1999ESASP.446..263D Altcode: 1999soho....8..263D Several SUMER studies will be presented that were performed in August/ September 1996 during the "Whole Sun Month" campaign "The large scale structure of the solar minimum corona". The spatial scans with long exposure times cover regions of quiet Sun, polar coronal holes and corona. They are used to determine off-limb the rest wavelengths of coronal lines (Mg X, Fe XII), which are found to differ from earlier literature values. Additionally, we try to determine Doppler velocities on different parts of the disk, which is more complicated, since here the coronal lines are blended with colder lines. Title: Chromospheric Oscillations Observed by SUMER/SOHO Authors: Heinzel, P.; Curdt, W. Bibcode: 1999ASPC..184..201H Altcode: We discuss first observations of the temporal behaviour of the hydrogen Lyman lines made by the SUMER/SOHO spectrometer. Using the Ly 5 line, we show here the global oscillatory pattern of the whole line profile for three representative quiet-Sun structures: cell interior, network boundary, and bright network. Mean power spectra for these structures show several maxima, some of which are quite well correlated with the maxima derived from Ca II K_2V observations. In the cell interior, the power peak is centred between 4.5-5 mHz. No clear evidence of a 3 minute chromospheric mode was found. In the network, we observe a broad range of frequencies, with a maximum between 2-3 mHz. Lyman lines exhibit certain Doppler shifts and asymmetries, but the oscillatory behaviour is mainly due to the intensity variations which are small compared to the line intensity itself (they reach 10-20 % of the mean line intensity). Title: Proton and hydrogen temperatures at the base of the solar polar corona Authors: Marsch, E.; Tu, C. -Y.; Heinzel, P.; Wilhelm, K.; Curdt, W. Bibcode: 1999A&A...347..676M Altcode: The SUMER (Solar Ultraviolet Measurements of Emitted Radiation) Spectrometer on SOHO (Solar and Heliospheric Observatory) has been used to observe the lines of the Lyman series (up to quantum numbers larger than 20) of hydrogen emitted in the solar atmosphere. The line shapes and intensities versus height are obtained near the limb from about -10\arcsec to 70\arcsec. The lines are broad and show the typical self-absorption reversal near the limb, where the emission comes from optically thick material, and change systematically with increasing height. The H i Ly6, Ly7 and Ly9 lines attain a Gaussian shape at heights above the visible limb between about 19\arcsec and 22\arcsec, where the emission comes from an optically thin plasma. The line shapes and intensities can be fitted well by model profiles obtained from multilevel NLTE (Non Local-Thermodynamic-Equilibrium) radiative transfer calculations which allow us, assuming excitation and ionization equilibrium, to derive consistently the temperatures and densities of the hydrogen atoms and, with additional assumptions, of the protons. Temperature values range between 1 10(5) K to 2 10(5) K. We present the systematics of the line shapes as observed in different emission regions and discuss briefly the relevance of these results for the solar wind acceleration and coronal heating. Title: Electron temperature diagnostics for the quiet Sun using SI BT IV lines Authors: Ahmed, S.; Pinfield, D. J.; Mathioudakis, M.; Keenan, F. P.; Phillips, K. J. H.; Curdt, W. Bibcode: 1999A&A...346L..69A Altcode: We compare SUMER observations of six Si riptsize IV emission lines detected at the quiet Sun disk centre with recent theoretical line ratio calculations. Good agreement is found between theory and observation for ratios involving the 1394, 1403 and 818 Ä line intensities. This agreement supports the theoretical prediction that the temperature where Si riptsize IV has its maximum ionisation fraction in ionisation equilibrium is T_max =~ 10(4.8) K, as well as showing that Lyman continuum absorption does not significantly effect line intensities for transitions with wavelengths below 912 Ä. We find that the 815, 1122 and 1128 Ä lines are blended by approximately 30, 55 and 45%, respectively, in the SUMER transitions. Title: The NE BT VIII (lambda 770) resonance line: solar wavelengths determined by SUMER on SOHO Authors: Dammasch, I. E.; Wilhelm, K.; Curdt, W.; Hassler, D. M. Bibcode: 1999A&A...346..285D Altcode: The investigation of the source and acceleration of the solar wind was among the prime scientific goals of SOHO - ESA's and NASA's Solar and Heliospheric Observatory. For the coronal regions closest to the Sun, the bright extreme ultraviolet (EUV) resonance lines of the Ne viii spectrum at 770 { Angstroms} and 780 { Angstroms} with a formation temperature of 630 000 K are promising targets for detecting the initial solar wind outflow. The investigations published up to now using data obtained by SUMER - the Solar Ultraviolet Measurements of Emitted Radiation spectrometer - on SOHO gave conflicting results. They accepted a rest wavelength of 770.409 { Angstroms} for the brighter Ne viii line as reported in the literature. We deduce the solar wavelength of this line for several conditions on the Sun and derive a rest wavelength of (770.428 +/- 0.003) { Angstroms} and outflow speeds in coronal hole regions of ~ 9 km s(-1) . This is in agreement with other recent studies using SUMER data. The rest wavelength determination is based on the assumptions of no average Doppler shift above the solar limb and a comparison with laboratory wavelengths of cool chromospheric lines. Quiet Sun areas exhibit an average blue shift of (1 +/- 1) km s(-1) in this line. Title: Analysis of Extreme-Ultraviolet Off-Limb Spectra Obtained with SUMER/SOHO: Ne VI-Mg VI Emission Lines Authors: Dwivedi, Bhola N.; Curdt, Werner; Wilhelm, Klaus Bibcode: 1999ApJ...517..516D Altcode: We present results from a study of extreme-ultraviolet (EUV) off-limb spectra. These were obtained on 1996 June 20 with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). With the capabilities of SUMER, we rastered the emitting source from 40" off the limb outward, and secured a unique, high-quality set of high-resolution EUV spectra. The scientific objective of this observing sequence was to record Ne VI and Mg VI intercombination/forbidden lines, which provide good possibilities to study the relative element abundance of Ne (high FIP) and Mg (low FIP) in transition-region emission in the corona, and the electron density in the solar atmosphere. While this observing sequence produced excellent spectra of the Ne VI and Mg VI lines, the occurrence of a dynamic event in the corona is an added bonus of the program. We also observed several other bright, as yet unidentified lines. Among these are lines that have been observed for the first time. Using the new data, we have been able to deduce the plasma density and relative element abundance in the source. In addition, improved values of the wavelengths of the Ne VI and Mg VI intercombination/forbidden lines have been obtained. Possible identifications of the bright lines not previously observed, along with their measured intensities, are discussed.

Paper presented at the JD-19/IAU, Kyoto, 1997 August 26-27. Title: Solar Wind Outflow and the Chromospheric Magnetic Network Authors: Hassler, Donald M.; Dammasch, Ingolf E.; Lemaire, Philippe; Brekke, Pal; Curdt, Werner; Mason, Helen E.; Vial, Jean-Claude; Wilhelm, Klaus Bibcode: 1999Sci...283..810H Altcode: No abstract at ADS Title: The New Sun - Probing Solar Plasmas with the SUMER Instrument on SOHO Authors: Curdt, W. Bibcode: 1999PhST...83..104C Altcode: With the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer on SOHO we observe the solar atmosphere with high spectral, spatial, and temporal resolution in the 400 to 1600 Å wavelength range. Selected observational facts are presented. Among these are points concerning the solar EUV spectrum in general, such as line identification and radiometry, and special applications, such as the redshift problem. As an example of plasma diagnostics, a relative abundance measurement as manifestation of the FIP effect is presented. Some of the recent results have not yet appeared in literature. Title: SOHO JOP 078 - variability and properties of the quiet sun supergranular network and internetwork. Authors: Kučera, A.; Curdt, W.; Fludra, A.; Rybák, J.; Wöhl, H. Bibcode: 1999joso.proc..149K Altcode: Study of the variability of the quiet solar atmosphere covering as large as possible range of the temperatures using both the 2D imaging and 1D spectra was the aim of SOHO JOP 78 observations. Supergranular cells were the objects of the authors' main interest. This programme is based on the cooperation of several SOHO instruments (SUMER, CDS, MDI, EIT) and TRACE. Justification of the JOP, cooperation of instruments and specially arranged measurements for the post-facto coalignment of data from different instruments are described in this paper. Title: Coordinated Observation of a Small Magnetic Region with SUMER and GCT Authors: Wilken, V.; Kneer, F.; Curdt, W. Bibcode: 1999AGAb...15...91W Altcode: 1999AGM....15..P08W The SUMER instrument and the Gregory-Coudé-Telescope (GCT) at the Observatorio del Teide/Tenerife have been used for observations of a small magnetic region in the solar atmosphere. The GCT measured the longitudinal magnetic flux, while SUMER performed EUV-scans. The magnetograms show two cells with diameters of approximately 23 000 km. Inside the cells the flux within the resolution element of 0.''76 x 0.''76 was 1 ṡ 10^9 Wb (corresponding to 33 Gauss flux density). The boundary regions have fluxes up to 1 ṡ 1010 Wb. SUMER's intensity images of Si II (Chromosphere) and C IV (Transition Region) show strong brightenings which very well resemble the magnetic flux pattern in the Photosphere. The intensities of Ne VIII (lower Corona) correlate with the magnetic flux far less than the former two lines. On small scales the temporal intensity fluctuations of the EUV lines show only little similarity among each other. Possibly, at small scales the different EUV lines originate from different structures which are not excited simultaneously. Title: Statistical Analysis of EUV and UV Lines Inside and Outside of Solar Coronal Holes Authors: Dammasch, I. E.; Hassler, D. M.; Curdt, W.; Wilhelm, K. Bibcode: 1999SSRv...87..161D Altcode: Two studies performed with SUMER (the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on SOHO) in September 1996 are presented. Spatial scans, a long exposure time and a broad spectral window provide reliable line profiles for various regions of the Sun (off-limb corona, coronal hole, quiet Sun, bright and dark regions on disk) and for different formation temperatures (Si II, 14 000 K; C IV, 100 000 K; Ne VIII, 630 000 K). Line intensity, position and width distributions are presented together with the line positions relative to the wavelength seen above the limb. Title: Signatures of Coronal Hole Spectra Between 660 Å and 1460 Å Measured with SUMER on SOHO Authors: Schühle, U.; Curdt, W.; Wilhelm, K.; Solanki, S. K.; Stucki, K. Bibcode: 1999SSRv...87..299S Altcode: Spectra of the northern polar coronal hole measured with the SUMER spectrometer on SOHO on 25 October 1996 are analyzed. We present spectra taken at locations on the solar disk where part of the spectrometer slit intersects a polar coronal hole region and an area of brighter emission from outside of the coronal hole area. By comparing the line intensities between the parts of the spectrum taken inside the "dark" area of the coronal holes and the brighter regions, we work out the signatures of the specific coronal hole in the chromosphere, transition region and lower corona. We find that emissions of neutral atom lines, of which there are many in the spectrum of SUMER, show no difference between the coronal hole and the bright boundary areas, whereas all ionized species show strong intensity enhancements, including the continuum emissions of carbon and hydrogen. These enhancements are larger than in normal quiet Sun areas. Title: Chromospheric Oscillations Observed by SOHO/SUMER and VTT/GCT on Tenerife Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; von Uexküll, M.; Wilken, V. Bibcode: 1999AGAb...15R..11C Altcode: 1999AGM....15..A12C Previous studies have revealed various oscillations in higher Lyman lines of hydrogen, as observed with SUMER on SOHO (Curdt & Heinzel 1998). The assumption that these periodic phenomena might be related to similar effects observed in optical lines like Ca II K led to the idea of simultaneous observations with the SOHO/SUMER instrument and the VTT/GCT telescopes on Tenerife. First results are presented here for the Lyman series and Lyman continuum. Power spectra in network and internetwork regions have been derived and a preliminary interpretation based on the wave propagation concept is given. In SUMER spectra we found a well-pronounced asymmetry of all Lyman lines, which is related to atmospheric dynamics. The time variation of co-spatial UV and optical data is presented and basic characteristics are discussed. Title: Solar irradiances of UV and EUV lines during the minimum of the sunspot activity in 1996 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schühle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E. Bibcode: 1999AdSpR..24..229W Altcode: Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric preflight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration and on its inflight refinements, the irradiance values at SOHO have been obtained for the lines He i (λ584.33), O v (λ629.74), Ne viii (λ770.41), S v (λ786.47), O iv (λ787.72), S vi (λλ933.39, 944.52), H i Ly ɛ (λ937.80), C iii (λ977.04), N v (λ1238.81), Si i (λ1256.52), and C iv (λ1548.20), and the continuum near 1549 Å. In this contribution, we compare our measurements with other recent irradiance determinations and discuss, in particular, the observations in the C iv line. Title: The O V 1213.9 Angstroms forbidden line in the quiet Sun Authors: Pinfield, D. J.; Mathioudakis, M.; Keenan, F. P.; Phillips, K. J. H.; Curdt, W. Bibcode: 1998A&A...340L..15P Altcode: We present the first unambiguous detection of the O v 1213.9 Angstrom (2s(2) (1) S_0 -> 2s2p (3) P_2) forbidden line in the solar spectrum, using observations obtained with the SUMER instrument on board SOHO. The wavelength separation of the forbidden to the (2s(2) (1) S_0 -> 2s2p (3) P_1) intercombination line at 1218.35 Angstroms is 4.5+/-0.1 Angstroms in excellent agreement with theoretical predictions. The observed line ratio, combined with the latest calculations, allows us to derive an electron density of log {N_e/cm(-3}) = 8.5 +/- 0.15 for the quiet Sun. However, the O v 1213.9 Angstroms line was not detected in the HST spectra of Procyon and we can only place a lower limit of log {N_e/cm(-3}) >= 7.8 to the electron density in this object. Title: Dynamic Behavior of the Upper Solar Atmosphere: Sumer/ Solar and Heliospheric Observatory Observations of Hydrogen Lyman Lines Authors: Curdt, Werner; Heinzel, Petr Bibcode: 1998ApJ...503L..95C Altcode: We present first observations of the temporal evolution of hydrogen Lyman lines, made by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory. A time series of about 33 minutes was obtained on 1997 June 5. The entrance slit has crossed a quiet-Sun region of 115.3" with two internetwork structures (cells) and the bright network regions. A data set of 59 spectra with30 s exposure time was obtained, using the SUMER tracking system to compensate for the solar rotation. For our analysis, we have selected a Lyman continuum window around 907 Å and the three Lyman lines Ly5, Ly9, and Ly15, which are formed at different depths in the upper chromosphere. In the cell interiors, we have detected significant periodic intensity variations with a Fourier transform power peak at 3.3-3.5 minutes, which is consistent with 3 minute internetwork oscillations. They seem to be associated with spatially unresolved ``clusters'' of grains. In the bright network regions, we detect slower oscillations of 6.9-7.6 minutes. These waves seem to propagate upward as we deduce from a phase shift between the three Lyman lines studied. The phase velocity was estimated to be roughly 3 km s-1 in the network. Finally, we discuss the potential usefulness of the hydrogen Lyman lines for diagnostics of the temperature structure of the upper solar atmosphere. Our observations, in particular the fact that we see all Lyman lines in emission all of the time, put certain constraints on the temperature gradients above the region in which numerical simulations do predict a decrease of the mean kinetic temperature. Title: High-Temperature Lines in SUMER Spectra Recorded Above a Bright Solar Active Region Authors: Feldman, U.; Curdt, W.; Doschek, G. A.; Schühle, U.; Wilhelm, K.; Lemaire, P. Bibcode: 1998ApJ...503..467F Altcode: We identify spectral lines emitted by solar abundant elements due primarily to transitions within the 2s22pk and 3s23pk (where k = 1, 5) ground configurations of ions that are formed in ionization equilibrium between 2 × 106 and 8 × 106 K. The transitions were identified in spectra of a bright active region recorded 1997 September 6, by the Solar Ultraviolet Measurements of Emitted Radiation Spectrometer (SUMER) flown on the Solar and Heliospheric Observatory (SOHO). Some of these lines provide useful plasma diagnostic tools for measuring the physical conditions in the solar corona. Title: Ion Temperatures in a Solar Polar Coronal Hole Observed by SUMER on SOHO Authors: Tu, C. -Y.; Marsch, E.; Wilhelm, K.; Curdt, W. Bibcode: 1998ApJ...503..475T Altcode: The temperatures of some highly charged ions in the southern solar polar coronal hole are determined from the widths of the extreme ultraviolet (EUV) lines measured by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO (Solar and Heliospheric Observatory). Radiation from both light ions, such as Ne6+, Ne7+, Mg7+, Mg9+, Si6+, and Si7+, and heavy ions, such as Fe9+, Fe10+, and Fe11+, are recorded in off-limb observations. We refer here to the limb as the height, h0, where the limb brightening of the N IV 765 Å line maximizes. After correction of the measured line widths for instrument contributions, the intrinsic widths of these emission lines are derived. These are produced by thermal motions of the ions and turbulent wave motions of the background plasma. Since the turbulent line broadening should be the same for all the different ions, its upper limit can be determined from the widths of the iron lines, assuming zero iron temperatures. Thus, the range of kinetic temperatures permitted for the light species can be delimited. For example, the average temperature of Ne7+, at heights above the southern limb relative to h0 from 17" to 64", ranges between 1.3 and 5 × 106 K, and the average temperature of Ne6+ ranges between 1 and 4 × 106 K. The interpretation of these measurements does not require knowledge of the ion formation (or electron) temperature. It is also found that the ion thermal speed decreases with increasing mass per charge, while the ion temperature remains roughly constant. In another observation at heights from 167" to 183" above h0, the temperature of the ions increases slightly with increasing mass per charge, while the thermal speed reveals no clear trend. The upper limits of the turbulence amplitude, <δv2>1/2, derived for these two altitude ranges are 33-37 and 44 km s-1, respectively. The implications of these results for the heating of the solar corona and the acceleration of the solar wind are discussed. Title: Ultraviolet Observations of a Dynamic Event in the Solar Corona Authors: Innes, D. E.; Curdt, W.; Dwivedi, B. N.; Wilhelm, K. Bibcode: 1998SoPh..181..103I Altcode: The Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) observations show high Doppler shifts and temporal variations in profiles of ultraviolet lines from low temperature gas in the corona above the active region NOAA 7974. The profiles indicate ≈ 100 km s-1 flows coming from an almost stationary source that appears bright in the lines of N III and Si III. The variations in line-of-sight velocities and intensities suggest small knots of cooling plasma emanating from a small region high in the corona. A few arc sec sunward of the region where the cool flows are seen is an elongated region of enhanced higher temperature, low velocity Ne VI and Mg VI line emission. Title: Solar irradiances and radiances of UV and EUV lines during the minimum of sunspot activity in 1996 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schuehle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E. Bibcode: 1998A&A...334..685W Altcode: Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric pre-flight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration, the irradiance values at SOHO and at 1 AU have been obtained for the lines He i (lambda 584.33 { Angstroms}), O v (lambda 629.74 { Angstroms}), Ne viii (lambda 770.41 { Angstroms}), S v (lambda 786.47 { Angstroms}), O iv (lambda 787.72 { Angstroms}), S vi (lambda lambda 933.39, 944.52 { Angstroms}), H i Ly epsilon (lambda 937.80 { Angstroms}), C iii (lambda 977.04 { Angstroms}), N v (lambda 1238.81 { Angstroms}), Si i (lambda 1256.52 { Angstroms}), and C iv (lambda 1548.20 { Angstroms}). The spatially resolved measurements allowed good estimates to be made of the active region contributions to the irradiance of the quiet Sun. The centre-to-limb radiance variations of these lines have also been obtained from these measurements. For quiet solar conditions, a radiance spectrum was determined for wavelengths from 800 { Angstroms} to 1500 { Angstroms} near the centre of the solar disk. Title: Solar H i Lyman alpha full disk profile obtained with the SUMER/SOHO spectrometer Authors: Lemaire, P.; Emerich, C.; Curdt, W.; Schuehle, U.; Wilhelm, K. Bibcode: 1998A&A...334.1095L Altcode: An uncalibrated solar hydrogen Lyman alpha profile was obtained with the use of the spectrometer on SOHO. The collection of the light scattered by the telescope permitted to average the profile over the full solar disk. The profile taken at the L1 Sun-Earth Lagrangian position is free of the central geocoronal absorption. Then, taking advantage of the absolute flux measured by the SOLSTICE/UARS spectrometer, an absolute line profile intensity is derived, and is compared with previous observations at minimum solar activity. Title: SUMER observations of bi-directional flows in coronal plasmas Authors: Curdt, W.; Innes, D. E.; Wilhelm, K. Bibcode: 1998ESASP.421..123C Altcode: 1998sjcp.conf..123C No abstract at ADS Title: Plasma jets in the solar atmosphere observed in EUV emission lines by SUMER on SOHO Authors: Wilhelm, K.; Innes, E. E.; Curdt, W.; Kliem, B.; Brekke, P. Bibcode: 1998ESASP.421..103W Altcode: 1998sjcp.conf..103W No abstract at ADS Title: The Magnetic Reconnection Explorer (MAGREX) Authors: Schühle, U.; Antionchos, S. K.; Barbee, T. W., Jr.; Bixler, J. V.; Brown, C. M.; Carter, P. H., II; Curdt, W.; Davila, J. M.; Doschek, G.; Feldman, U.; Goldstein, W. H.; Kordas, J.; Lemaire, P.; Mariska, J. T.; Marsch, E.; Moses, J. D.; Seely, J. F.; Wilhelm, K.; Woods, T. N. Bibcode: 1998ESASP.417..289S Altcode: 1998cesh.conf..289S No abstract at ADS Title: Dynamic Behaviour of the Upper Solar Atmosphere: SUMER/SOHO Observations of Hydrogen Lyman Lines Authors: Heinzl, P.; Curdt, W. Bibcode: 1998ESASP.417..321H Altcode: 1998cesh.conf..321H No abstract at ADS Title: OSIRIS-the optical, spectroscopic and infrared remote imaging system for the Rosetta Orbiter Authors: Thomas, N.; Keller, H. U.; Arijs, E.; Barbieri, C.; Grande, M.; Lamy, P.; Rickman, H.; Rodrigo, R.; Wenzel, K. -P.; A'Hearn, M. F.; Angrilli, F.; Bailey, M.; Barucci, M. A.; Bertaux, J. -L.; Brieß, K.; Burns, J. A.; Cremonese, G.; Curdt, W.; Deceuninck, H.; Emery, R.; Festou, M.; Fulle, M.; Ip, W. -H.; Jorda, L.; Korth, A.; Koschny, D.; Kramm, J. -R.; Kührt, E.; Lara, L. M.; Llebaria, A.; Lopez-Moreno, J. J.; Marzari, F.; Moreau, D.; Muller, C.; Murray, C.; Naletto, G.; Nevejans, D.; Ragazzoni, R.; Sabau, L.; Sanz, A.; Sivan, J. -P.; Tondello, G. Bibcode: 1998AdSpR..21.1505T Altcode: The scientific objectives, design, and implementation of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the International Rosetta Mission are described. The instrument comprises two camera systems with a common electronics box. A narrow angle camera will provide high resolution images of the structure and morphology of the nucleus of a comet. A wide angle camera with high straylight rejection and dynamic range will be used to investigate the innermost coma and the emission process at the surface of the comet. An infrared imaging system, which dramatically enhances the scientific return has been included in the narrow angle camera at little extra cost. Title: CESRA Workshop on Coronal Explosive Events Authors: Curdt, W.; Innes, D. E. Bibcode: 1998cee..workE...6C Altcode: Recently, the increasing observational evidence for small-scale transient solar phenomena has intensified the discussion about the mechanism behind these events and their potential relevance for outstanding questions of solar physics. The spectrometers on SOHO - CDS, the Coronal Diagnostic Spectrometer and SUMER, the Solar Ultraviolet Measurements of Emitted Radiation instrument - have returned a wealth of observations of small-scale transient events. Small-scale transient brightenings, mostly in combination with high velocity Doppler flows are occuring continually throughout the quiet Sun (Dere 1991, Innes 1997, Harrison 1997). Similar phenomena have been seen in off limb observations higher in the corona (Curdt 1997). Some of these observations are presented here, and typical parameters and common characteristics in terms of morphology and temporal evolution of the phenomena are described. Many groups suggested that magnetic field cancellations convert magnetic energy into kinetic and thermal plasma energy leading to bursts of high velocity plasma ejected from small sites (e.g. Innes 1998). A joint observation was performed by SUMER and the MDI instrument, the Michelson Doppler Interferometer, which can observe the magnetic field. Both instruments observed the same plasma volume at the same time. The results are presented here. There is clear observational evidence that small-scale transient events are linked to magnetic field variations in support of the flux-cancellation model. Title: Oscillations in Chromosphere and Transition Region Based on SUMER Measurements Authors: Kucera, A.; Curdt, W.; Rybák, J.; Schühle, U.; Wöhl, H. Bibcode: 1998ASPC..155..351K Altcode: 1998sasp.conf..351K No abstract at ADS Title: Solar Radiometry with the Telescope and Vaccum-Ultraviolet Spectrometer Sumer on the Solar and Heliospheric Observatory (SOHO) Authors: Hollandt, J.; Schuhle, U.; Curdt, W.; Dammasch, I. E.; Lamaire, P.; Wihelm, K. Bibcode: 1998Metro..35..671H Altcode: No abstract at ADS Title: The solar disk spectrum between 660 and 1175 Anstroms (first order) obtained by SUMER on SOHO Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle, U.; Lemaire, P. Bibcode: 1997A&AS..126..281C Altcode: SUMER -- Solar Ultraviolet Measurements of Emitted Radiation -- onboard of SOHO -- Solar and Heliospheric Observatory -- obtained its first spectrum on January 25, 1996 near the north polar limb. The range from 660 Angstroms to 1175 Angstroms which has never before been observed with such a good spectral resolution contains a wealth of spectroscopic details. Identification of about 400 lines in this spectral range is given. We list the wavelengths of identified transitions and provide their absolute peak intensities. General spectral features of the most abundant elements H, He, C, N, O, Ne, Mg, Si, S, Ar, and Fe are described. In this spectral range many density- and temperature-sensitive line pairs are found. It is shown in examples how they can be used as diagnostic tools. Table 1 and Fig.nearlimb are also available in digital form at the CDS via anonymous ftp to cdsarc.u-strasbg. fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: The Off-Limb Behaviour of the Solar Transition Region FIP Effect Authors: Laming, J. M.; Feldman, U.; Drake, J. J.; Schuhle, U.; Curdt, W.; Wilhelm, K.; Lemaire, P. Bibcode: 1997AAS...191.7301L Altcode: 1997BAAS...29.1320L We investigate the behaviour of the solar FIP effect (the abundance enhancement of elements with first ionization potential < 10 eV by factor of 3-4 in the corona with respect to photospheric values) with height above the limb in a region of diffuse quiet corona observed by the SUMER instrument on SOHO. Line ratios formed at log T > 5.8 show coronal abundances for all heights. Line ratios formed at lower temperatures are consistent with coronal abundances well off the limb, with the apparent magnitude of the FIP enhancement decreasing by a factor of 1.5 - 2 as one approaches the solar limb. Thus our observations support a spatial variation in the quiet sun transition region FIP effect inferred previously from studies of the full disk solar spectrum (Laming, Drake, & Widing 1995, ApJ, 443, 416 and references therein). This result adds to the probability that emission from the solar disk transition region and corona originates from qualitatively different structures for values of log T {<atop >} 5.8, having different FIP effects. Title: Sonnenradiometrie mit SUMER auf SOHO. Authors: Hollandt, J.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 1997PhyBl..53.1101H Altcode: 1997PhB....53.1101H No abstract at ADS Title: A Coronal Spectrum in the 500--1610 Angstrom Wavelength Range Recorded at a Height of 21,000 Kilometers above the West Solar Limb by the SUMER Instrument on Solar and Heliospheric Observatory Authors: Feldman, U.; Behring, W. E.; Curdt, W.; Schühle, U.; Wilhelm, K.; Lemaire, P.; Moran, T. M. Bibcode: 1997ApJS..113..195F Altcode: We present a solar coronal spectrum recorded by the extreme UV spectrometer SUMER on the Solar and Heliospheric Observatory. The spectrum was taken between 21:28 UT on 1996 June 25 and 02:47 UT on 1996 June 26, at a height of 21,000 km above the west equatorial limb with the slit oriented in the north-south direction. At the time of the observations the Sun was rather quiet, and the west limb appeared ``devoid of any activity.'' The spectrum, which covers the 500-1610 Å wavelength range, originates from plasmas with temperatures ranging between 1.5 × 104 and 1.5 × 106 K. Identification of lines originating from different temperature regimes is facilitated by the appearance of their intensity along the 300" long slit.

Well over 800 lines have been found, many of which were not previously observed. We present the entire spectrum and discuss line identifications. A table of the wavelengths of lines observed, with their identifications and peak intensities, is provided. Although we have identified lines previously detected in laboratory plasmas and a number of new lines not previously observed, over 40% of the SUMER lines remain unidentified. Among the newly detected lines, some have a potential as plasma density diagnostics. Title: Radiometric calibration of SUMER: refinement of the laboratory results under operational conditions on SOHO Authors: Wilhelm, Klaus; Lemaire, Philippe; Feldman, Uri; Hollandt, Jörg; Schühle, Udo; Curdt, Werner Bibcode: 1997ApOpt..36.6416W Altcode: No abstract at ADS Title: Electron Density Diagnostics for the Solar Upper Atmosphere from Spectra Obtained by SUMER/SOHO Authors: Laming, J. M.; Feldman, U.; Schühle, U.; Lemaire, P.; Curdt, W.; Wilhelm, K. Bibcode: 1997ApJ...485..911L Altcode: We evaluate the electron density in various solar regions above the limb observed by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) instrument on SOHO. We find in general good agreement among line ratios from Be-, B-, N-, and Mg-like ions, giving densities of order 108 cm-3. Title: Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths Authors: Seely, J. F.; Feldman, U.; Schühle, U.; Wilhelm, K.; Curdt, W.; Lemaire, P. Bibcode: 1997ApJ...484L..87S Altcode: Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine the contributions of turbulent plasma motion and ion thermal motion to the line widths. The results indicated that the turbulent velocity was approximately 22 km s-1 at 30" above the limb and decreased to less than 10 km s-1 at 109" and 209" above the limb. At 30" above the limb, the ion temperatures of the hotter lines were comparable to the electron temperatures for ionization equilibrium. The ion temperatures of the cooler lines were higher than the ionization equilibrium temperatures; at 109" and 209" above the limb, the ion temperatures were at least a factor of 2.5 higher than the ionization equilibrium temperatures. Title: VizieR Online Data Catalog: Solar disk spectrum (660-1175A) (Curdt+ 1997) Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle, U.; Lemaire, P. Bibcode: 1997yCat..41260281C Altcode: The near-limb quiet-Sun spectrum recorded on January 25, 1996 near the solar North pole is presented in tabular form and in graphical form. Table 1 - the line list - lists all lines found in the spectrum providing absolute peak intensities, measured and literature wavelengths, identification, and classification of the transition. Fig. 4 is a display the composite spectrum. The most prominent lines are labelled. In this figure intensities are given in instrumental units and logarithmic scale. (1 data file). Title: First Results from SOHO on Waves Near the Solar Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.; Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten, R. J. Bibcode: 1997ASPC..118..284S Altcode: 1997fasp.conf..284S We present first results from simultaneous observations with the CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995) for a description of the instruments} onboard SOHO and the VTT at Tenerife. Our aim is to study the wave propagation, shock formation, and transmission properties of the upper chromosphere and transition region. The preliminary results presented here include the variation of velocity power spectra with height, difference in power between internetwork and network regions, and variations in mean flows displayed by different spectral lines. Title: Bright Plumes and Dark Lanes as Observed in MgX 625 Å and NV 1239 Å in the Solar Polar Corona Authors: Marsch, E.; Tu, C. -Y.; Wilhelm, K.; Curdt, W.; Schühle, U.; Dammasch, I. E. Bibcode: 1997ESASP.404..555M Altcode: 1997cswn.conf..555M No abstract at ADS Title: A New Look at the Quiet Sun Network in the Upper Atmosphere During a Minimum of Activity Cycle Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Poland, A.; Falciani, R. Bibcode: 1997ESASP.404..517L Altcode: 1997cswn.conf..517L No abstract at ADS Title: First Results of the SUMER Telescope and Spectrometer on SOHO - I. Spectra and Spectroradiometry Authors: Wilhelm, K.; Lemaire, P.; Curdt, W.; Schühle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Huber, M. C. E.; Vial, J. -C.; Kühne, M.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M.; Feldman, U.; Hollandt, J.; Brekke, P. Bibcode: 1997SoPh..170...75W Altcode: SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 × 106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona. Title: EUV Observations of Bi-Directional Jets in the Solar Corona Authors: Curdt, W.; Dwivedi, B. N.; Innes, D. E. Bibcode: 1997ESASP.404..303C Altcode: 1997cswn.conf..303C No abstract at ADS Title: High resolution solar ultraviolet measurements Authors: Lemaire, P.; Wilhelm, K.; Schühle, U.; Curdt, W.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. -C. Bibcode: 1997AdSpR..20.2249L Altcode: The increase of our understanding of the processes acting in the solar corona and maintaining it is strongly dependent on the quality of the data that are obtained to check theories. The fine structure of the solar atmosphere seen from the photosphere and extending to the hottest parts of the corona requires data with high resolution in all parameter space (angular, spectral and temporal). To constrain the hypotheses that are proposed to describe the solar corona, it is necessary to establish an accurate energy budget taking into account the processes which are acting from the chromosphere to the corona. Some requirements can be established and compared with the data collected so far (or about to be collected) with the present SUMER (Solar Utraviolet Measurements of Emitted Radiations) instrumentation. Title: First Results of the SUMER Telescope and Spectrometer on SOHO - II. Imagery and Data Management Authors: Lemaire, P.; Wilhelm, K.; Curdt, W.; SchÜle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. C.; KÜhne, M.; Huber, M. C. E.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M. Bibcode: 1997SoPh..170..105L Altcode: SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We report on some aspects of the observation programmes that have already led us to a new view of many aspects of the Sun, including quiet Sun, chromospheric and transition region network, coronal hole, polar plume, prominence and active region studies. After an introduction, where we compare the SUMER imaging capabilities to previous experiments in our wavelength range, we describe the results of tests performed in order to characterize and optimize the telescope under operational conditions. We find the spatial resolution to be 1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along the slit. Resolution and sensitivity are adequate to provide details on the structure, physical properties, and evolution of several solar features which we then present. Finally some information is given on the data availability and the data management system. Title: Prominence Observations of the First Joint SUMER- Tenerife Campaign Authors: Curdt, W.; de Boer, C. Bibcode: 1997ASPC..118..303C Altcode: 1997fasp.conf..303C Prominence features above the equatorial limb were obs\-erv\-ed by SUMER in S VI, Ly_epsilon , and other lines. This was complemented by simultaneous H_alpha observations at the German Gregory-Coude telescope at Iza\ na/Tenerife. Additional information about the density and temperature is retrieved from a study on forbidden lines of Ne VI. This data set includes an interesting coronal high velocity event. Title: Building the Spectrum of a G2V Star During a Minimum of Activity Cycle Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Hassler, D. Bibcode: 1997ESASP.404..513L Altcode: 1997cswn.conf..513L No abstract at ADS Title: Analysis of the EUV Spectra Obtained with SUMER/SOHO; - NE VI / MG IV Authors: Dwivedi, B.; Curdt, W.; Wilhelm, K. Bibcode: 1997IAUJD..19E...3D Altcode: The talk will discuss results from a study of EUV off-limb spectra. The spectra were obtained on June 20, 1996, with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on board SOHO. With the capabilities of SUMER, we rastered the emitting source from 40^{''} off the limb and outwards, and secured a unique, high quality set of high resolution EUV spectra. The scientific objective of this observing sequence was to record the Ne VI and Mg VI intercombination lines which provide good possibilities to study the relative high-FIP/low-FIP element abundance Ne/Mg, and electron density in the solar atmosphere. While this observing sequence produced excellent spectra of the Ne VI and Mg VI lines, the presence of several other bright lines, yet unidentified, is an extra bonus of the program. Using the new data, we have been able to deduce the plasma density, emission measure and relative element abundance in the source. In addition, improved values of the wavelengths of the Ne VI and Mg VI intercombination lines have been obtained. Possible identifications of bright, lines which have not previously been observed, will be discussed. Title: Investigation of the Dynamics of Chromosphere and Photosphere from Spectra Obtained by Parallel Observations using SUMER on SOHO and the VTT on Tenerife Authors: Curdt, W.; Kucera, A.; Rybak, J.; Schuhle, U.; Wohl, H. Bibcode: 1997ASPC..118..322C Altcode: 1997fasp.conf..322C This is a preliminary report about parallel observations of chromospheric and photospheric spectra in the ultraviolet and visible spectral regions using SUMER on SOHO and the VTT on Tenerife performed begin of September 1996. The aim is to search for relations of vertical velocity patterns in the upper photosphere and chromosphere in the solar disk center. In addition temporal changes in these parts of the solar atmosphere are investigated. Title: Dynamical Properties of the Chromosphere and Transition Region in the Supergranular Network: What Precision of the Spectral Line Characteristics Can be Reached? Authors: Curdt, W.; Kucera, A.; Rybák, J.; Schühle, U.; Wöhl, H. Bibcode: 1997ESASP.404..307C Altcode: 1997cswn.conf..307C No abstract at ADS Title: Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO Authors: Hollandt, Jörg; Schühle, Udo; Paustian, Wolfgang; Curdt, Werner; Kühne, Michael; Wende, Burkhard; Wilhelm, Klaus Bibcode: 1996ApOpt..35.5125H Altcode: The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard. Title: A Solar EUV Spectral Atlas Observed with SUMER Authors: Brekke, P.; Wilhelm, K.; Lemaire, P.; Curdt, W.; Schuhle, U.; Poland, A.; Kucera, T.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1996AAS...188.3713B Altcode: 1996BAAS...28..879B We present the first solar EUV spectral atlas in the wavelength range 500 -- 1600 { Angstroms}. The spectra were recorded with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) which is part of the ESA/NASA Solar and Heliospheric Observatory (SOHO). The solar spectrum below 1200 { Angstroms} is not very well known. Thus, the present spectral atlas, and SUMER observations in general, represents a new important diagnostic tool to study essential physical parameters of the solar atmosphere. It includes emission from atoms and ions in the temperature range 10(4) to 2 x 10(6) K. Thus, emission lines and continua emitted from the lower chromosphere to the lower corona can be studied. The atlas is also useful as a planning tool for SUMER studies to determine useful dwell times, possible blends, and to select proper data extraction windows. The angular resolution of SUMER is close to 1 arcsec, but the atlas presented here represents an average along part of the 1-arcsec wide slit, typically 30 arcsec. The spectral resolving power of the instrument is lambda /Delta lambda = 17770-38300. For more details about the SUMER instrument we refer to Wilhelm et al. (Solar Physics, 162, 189, 1995). The spectral data in this atlas were obtained with the spectrometer slit positioned at the center of the solar disk with a dwell time of 300 s to bring up weak lines and continua. The full spectral range was put together from a number of exposures each covering approximately 20 { Angstroms} in 1st order on the coated, and therefore most sensitive, part (KrB) of the detector. 1st and 2nd order spectra are superimposed. The spectral atlas is available in a computer readable format together with a IDL program to read and display the data using a widget interface. The atlas and the programs can be obtained via the World Wide Web (http://hydra.mpae.gwdg.de/mpae_projects/SUMER/sumer.html) or by contacting one of the authors. Title: Intercalibration and Co-Registration of the LASCO, UVCS and SUMER instruments on SOHO Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli, M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L. Bibcode: 1996AAS...188.3706M Altcode: 1996BAAS...28..878M Joint observations of equatorial streamers by three SOHO instruments have been used for radiometric intercalibration, co-registration and other spectroscopic comparisons. The results are used to track the stability of the radiometric calibrations of the Ultraviolet Coronagraph Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment at overlapping wavelenghs. Observations of equatorial streamers at heliocentric heights from 1.25 to 1.5 R_⊙ are used for the intercalibrations. The results are compared to pre-launch laboratory calibrations and to observations of stars. The first stellar observation was for 38 AQI. These UV observations are compared to coronal green line (Fe XIV) observations obtained with the Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained in the same time frame. Intercomparisons of spectral line profiles among LASCO, SUMER, and UVCS are also planned. The LASCO research is supported by NASA Grant NDPR S92835D; the UVCS research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland, and SUMER is financially supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution). Title: Transition region studies with the SOHO-SUMER EUV-spectroscope. Authors: Curdt, W.; Wilhelm, K. Bibcode: 1996joso.proc..148C Altcode: No abstract at ADS Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schühle, U.; Lemaire, P.; Gabriel, A.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kühne, M.; Timothy, J. G.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1995SoPh..162..189W Altcode: The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 × 106K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations. Title: Some design and performance features of SUMER: solar ultraviolet measurements of emitted radiation Authors: Wilhelm, Klaus; Curdt, W.; Marsh, E.; Schuehle, Udo H.; Lemaire, Philippe; Gabriel, Alan H.; Vial, J. -C.; Grewing, Michael; Huber, Martin C.; Jordan, S. D.; Poland, Arthur I.; Thomas, Roger J.; Kuehne, Mikhael; Timothy, J. Gethyn; Hassler, Donald M.; Siegmund, Oswald H. Bibcode: 1995SPIE.2517....2W Altcode: The instrument SUMER (solar ultraviolet measurements of emitted radiation) is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 multiplied by 106 K and above. The observations will be performed, on board SOHO (solar and heliospheric observatory) scheduled for launch in November 1995, by a scanning, normal-incidence telescope/spectrometer system in the wavelength range from 500 to 1610 angstrom. Spatial resolution requirements compatible with the pointing stability of SOHO are less than 1000 km corresponding to about 1-arcsec angular resolution. Doppler observations of EUV line shifts and broadenings should permit solar plasma velocity measurements down to 1 km s-1. We report here on some specific features of this instrument related to its pointing as well as its spatial and spectral resolution capabilities. Title: 'SUMER' - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuhne, M.; Lemaire, P.; Marsch, E.; Poland, A. I.; Schuhle, U.; Thomas, R. J.; Timothy, J. G.; Vial, J. -C. Bibcode: 1994scs..conf..619W Altcode: 1994IAUCo.144..619W SUMER is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. The spatial and spectral resolution capabilities of the instrument are considered in some detail, and a new detector concept is introduced. Title: Images of the nucleus of Comet Halley. Volume 1: obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft. Authors: Keller, H. U.; Curdt, W.; Kramm, J. -R.; Thomas, N. Bibcode: 1994inch.book.....K Altcode: Vol. 1 of this atlas is devoted to the images obtained by the Halley Multicolour Camera onboard the Giotto spacecraft. It includes a brief description of the whole project, an account of the image processing and calibration procedures, and a summary of the scientific results to facilitate interpretation of the images. The images are presented in chronological order preceded by a description of the image contents. Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G. Bibcode: 1993BAAS...25.1192W Altcode: No abstract at ADS Title: SUMER: temperatures, densities, and velocities in the outer solar atmosphere. Authors: Lemaire, P.; Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuehne, M.; Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy, J. G.; Vial, J. C. Bibcode: 1992ESASP.348...13L Altcode: 1992cscl.work...13L The SUMER instrumentation, that will be mounted on the SOHO spacecraft, is in development under MPAE leadership. It has some capability to improve the solar angular resolution and the spectral resolution already obtained in the far UV to the extreme UV, corresponding to the temperature range between 104 and a few 106K. The authors give some insights into the SUMER spectrometer that is developed to study the dynamics and to infer temperatures and densities of the low corona and the chromosphere-corona transition zone in using the 50 - 160 nm wavelength range. First, they recall the SUMER scientific goals and the technics used. Then, after a brief description of the instrumentation the expected performances are described. The way the observations can be conducted is emphasized and it is shown how SUMER is operated in coordination with other SOHO instrumentations and in cooperation with ground-based observations. Title: "SUMER" - Solar Ultraviolet Measurements of Emitted Radiation. Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kühne, M.; Lemaire, P.; Marsch, E.; Poland, A. I.; Richter, A. K.; Thomas, R. J.; Timothy, J. G.; Vial, J. C. Bibcode: 1992eocm.rept..225W Altcode: The experiment Solar Ultraviolet Measurements of Emitted Radiation (SUMER) is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. Specifically, SUMER will measure profiles and intensities of extreme ultraviolet (EUV) lines emitted in the solar atmosphere ranging from the upper chromosphere to the lower corona; determine line broadenings, spectral positions and Doppler shifts with high accuracy; provide stigmatic images of selected areas of the Sun in the EUV with high spatial, temporal and spectral resolution and obtain full images of the Sun and the inner corona in selectable EUV lines, corresponding to a temperature range from 104 to more than 1.8×106K. Title: Design Rationale of the Solar Ultraviolet Network / Sun Authors: Dame, L.; Acton, L.; Bruner, M. E.; Connes, P.; Cornwell, T. J.; Curdt, W.; Foing, B. H.; Hammer, R.; Harrison, R.; Heyvaerts, J.; Karabin, M.; Marsch, E.; Martic, M.; Mattic, W.; Muller, R.; Patchett, B.; Roca-Cortes, T.; Rutten, R. J.; Schmidt, W.; Title, A. M.; Tondello, G.; Vial, J. C.; Visser, H. Bibcode: 1992ESOC...39..995D Altcode: 1992hrii.conf..995D No abstract at ADS Title: Development of a thermal control concept for the optical system of the SUMER experiment on SOHO Authors: Curdt, W.; Rathjen, H. Bibcode: 1991secs.conf..785C Altcode: The experiment, Solar Ultraviolet Measurements of Emitted Radiation (SUMER), will observe the solar atmosphere on board the SOHO spaceprobe. The telescope/spectrometer operates in the far UV spectral range with excellent spatial and spectral resolution. The thermal control of SUMER is a delicate task due to extreme thermal requirements and unfavorable boundary conditions. The optical fidelity requires extremely stable mechanical conditions free from dilatation or distortion. Consequently, the operational temperature range is very small and gradients within the structure can not be tolerated. This task is complicated by limitations of heater power and cleanliness requirements dictating the material selection. Internal heat sources (dissipation, absorbed solar flux, and heater power) are small compared to the large surface area. Thus, the long term stability of multilayer insulation performance is an important factor of the thermal design. A detailed thermal mathematical model was established and an exhaustive thermal analysis was performed in several iterations to identify critical areas and to define a reliable thermal design by reducing the uncertainties. Title: Velocity of individual large dust particles ejected from Comet P/Halley Authors: Richter, K.; Curdt, W.; Keller, H. U. Bibcode: 1991A&A...250..548R Altcode: Five discrete events are presented which provide accurate information about the impact locations relative to the comet and lower mass limits of the individual particles. Ejection velocities of about 40 m/s were found for two particles in the 1-mg mass range and of not more than 10 m/s for particles in the 10-mg range for the most probable scenario, where the recorded heavy particles start their trajectories in sunward directed jets during a period around perihelion. The outflow velocities of the 10-mg particles are found to be significantly lower than predicted by gasdynamic calculations. The discrepancy can lead to an alternative interpretation of the observation assuming that the particles found near the nucleus were released from the nucleus a long time ago on a time scale of orbital periods. Similar-size particles were found in long dust trails of short-period comets. This alternative can influence the derivation of the particle size distribution and accumulated mass flux from the observations by the Giotto instruments. Title: The composition and plasma signature of a large dust impact on the Giotto spacecraft Authors: Goldstein, R.; Goldstein, B. E.; Balsiger, H.; Coates, A. J.; Curdt, W.; Keller, H. U.; Neubauer, F. M.; Perry, C.; Zarnecki, J. Bibcode: 1991JGR....9613739G Altcode: At about 14,800 km from the comet Halley nucleus, on the inbound leg, at least six of the sensors onboard the Giotto spacecraft observed an unusual, brief (~30 to 500 ms) event: The ion mass spectrometer data show a brief flow of energetic (up to several hundred electron volts) plasma consisting of protons, water group, and heavier ions. The Johnstone plasma analyzer data show a short burst of plasma, while the dust impact detector system data show an impact event in four of its detectors. The magnetometer signature of the event shows two brief dips in the field. The sudden change in the spacecraft attitude and spin rate observed by the camera at that same time has been interpreted as the result of a large (>=5 mg) dust particle impact on the front bumper shield of the spacecraft. In addition, at about the same time the spacecraft star-tracker suffered damage. Here we give the first report combining direct measurements of the composition and dynamics of a dust impact plasma cloud, the dust particle mass and the location of the impact on the spacecraft. Analysis of the data indicate that the impacting particle was water or ice-bering, possibly loosely compacted, and was composed of one or more of: carbon, nitrogen, and silicon. Title: Large dust particles along the Giotto trajectory Authors: Curdt, W.; Keller, H. U. Bibcode: 1990Icar...86..305C Altcode: Images of Comet Halley taken by the Halley Multicolour Camera (HMC) onboard ESA's Giotto spacecraft provide highly accurate information on the viewing direction. As a part of the spacecraft dynamical system, HMC was very sensitive to attitude variations that occurred during the final approach phase. HMC identified several discrete events that were caused by dust particles in the 1-50 mg range. Together with impacts reported from the Japanese Suisei spacecraft by Uesugi (1986, 20th ESLAB Symp., ESA SP-250 II, 219-222), this is the first independent observation of particles in this mass range. The well-calibrated measurements unequivocally set firm lower limits of the mass of large dust particles. These particles dominate the impact history of the spacecraft and, therefore, the dust mass distribution. The data suggest the existence of a halo of heavy old dust grains surrounding the cometary nucleus. The statistics of the observed impacts are discussed in the context of other dust observations and models. The HMC measurements support models that assume a dust mass distribution dominated by large grains. Title: Dust Production of Comet P/Halley at the Giotto Encounter Authors: Keller, H. U.; Thomas, N.; Curdt, W.; Richter, K. Bibcode: 1990BAAS...22Q1097K Altcode: No abstract at ADS Title: SUMER - Solar ultraviolet measurements of emitted radiation. Authors: Curdt, W.; Wilhelm, K.; Axford, W. I.; Marsch, E.; Richter, A. K.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Timothy, J. G. Bibcode: 1989AGAb....2...14C Altcode: 1989amt..conf...14C No abstract at ADS Title: SUMER: Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, M. C. E.; Lemaire, P.; Marsch, E.; Poland, A. I. Bibcode: 1988sohi.rept...31W Altcode: The SUMER (solar ultraviolet measurements of emitted radiation) experiment is described. It will study flows, turbulent motions, waves, temperatures and densities of the plasma in the upper atmosphere of the Sun. Structures and events associated with solar magnetic activity will be observed on various spatial and temporal scales. This will contribute to the understanding of coronal heating processes and the solar wind expansion. The instrument will take images of the Sun in EUV (extreme ultra violet) light with high resolution in space, wavelength and time. The spatial resolution and spectral resolving power of the instrument are described. Spectral shifts can be determined with subpixel accuracy. The wavelength range extends from 500 to 1600 angstroms. The integration time can be as short as one second. Line profiles, shifts and broadenings are studied. Ratios of temperature and density sensitive EUV emission lines are established. Title: Position of comet P/Halley at the Giotto encounter Authors: Curdt, W.; Wilhelm, K.; Craubner, A.; Krahn, E.; Keller, H. U. Bibcode: 1988A&A...191L...1C Altcode: Images of the Halley Multicolor Camera (HMC) were analyzed to evaluate the fly-by geometry of the Giotto spacecraft past Comet Halley. The position of the comet at closest approach was determined with respect to the spacecraft. Based on the orbit information of Giotto the absolute position of the cometary nucleus could be obtained with very high precision. Title: Collisions with cometary dust recorded by the Giotto HMC camera. Authors: Curdt, W.; Keller, H. U. Bibcode: 1988ESAJ...12..189C Altcode: The authors concentrate on the detailed directional information provided by the Halley Multicolour Camera (HMC) as a result of its excellent resolution and the high attitude stability of the Giotto spacecraft. This information was used to determine the trajectory and to identify attitude excursions caused by discrete dust impacts on the space probe. The events observed by HMC are discussed in the context of observations by spacecraft subsystems and by other experiments. Details of the final approach scenario and the post-encounter status of the camera are revealed. The results imply that the dust mass distribution is dominated by large grains. Title: The Halley multicolour camera Authors: Keller, H. U.; Schmidt, W. K. H.; Wilhelm, K.; Becker, C.; Curdt, W.; Engelhardt, W.; Hartwig, H.; Kramm, J. R.; Meyer, H. J.; Schmidt, R.; Gliem, F.; Krahn, E.; Schmidt, H. P.; Schwarz, G.; Turner, J. J.; Bouyries, P.; Cazes, S.; Angrilli, F.; Bianchini, G.; Fanti, G.; Brunello, P.; Delamere, A.; Reitsema, H.; Jamar, C.; Cucchiaro, A. Bibcode: 1987JPhE...20..807K Altcode: The Halley multicolor camera (HMC) is a high-resolution imaging system on board the ESA Giotto spacecraft to comet Halley. The fast spin of this spacecraft (15 RPM) required a unique and highly specialized design and complex fully autonomous operation. Design criteria and trade-offs and operational aspects are emphasized in this instrument description. Actual performance numbers are given whenever available. The imaging quality is demonstrated by sample images taken from the earth and the comet. Title: Observations by the Halley multicolor camera Authors: Keller, H. U.; Arpigny, C.; Barbieri, C.; Bonnet, R. M.; Cazes, S.; Coradini, M.; Cosmovici, C. B.; Curdt, W.; Delamere, W. A.; Huebner, W. F. Bibcode: 1986ehac....2..347K Altcode: The first image of comet Halley was taken by the multicolor camera (HMC) on 9 March from a distance of 23.6 million km. During the encounter HMC was switched on at 4:12 hr before closest approach CA. It took its first image at 3:06 h before CA. Overall 2043 images were taken in single sensor mode. The inner coma was observed using all 11 filters and polarizers. The transmission curves of the filters (except polarizers) are shown together with the sensitivity of the camera. At 6 min before CA HMC switched to multiple sensor mode taking 4 images almost simultaneously through the clear, blue, and red wideband filters. Only 2% of all data taken could be transmitted in 69 image sets. The last image showing details of the nuclear surface was taken from a slant distance of 1740 km and has a nominal resolution of 39 m per pixel. Title: Observations by the Halley Multicolour Camera Authors: Keller, H. U.; Arpigny, C.; Barbiert, C.; Bonnet, R. M.; Cazes, S.; Cordini, M.; Cosmovici, C. B.; Curdt, W.; Delamere, W. A.; Huebner, W. F.; Hughes, D. W.; Jamar, C.; Kramm, R.; Malaise, D.; Reitsema, H.; Schmidt, H. U.; Schmidt, K.; Schmidt, W. K. H.; Seige, P.; Whipple, F. L.; Wilhelm, K. Bibcode: 1986ESASP.250b.347K Altcode: 1986ehc2.conf..347K The Halley Multicolour Camera (HMC) was the only remote sensing instrument on board the Giotto spacecraft. HMC operated successfully up to the moment when a power surge on the spacecraft impaired operations of several instruments. The very last image frame of HMC was transmitted from about 12 s before closest approach. The first image of comet Halley was taken by HMC on 9 March. The observations of the HMC have consolidated our perception of the nature of comets.