curdt

explanation blue bibcodes open ADS page with paths to full text

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
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.
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.
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.
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 &gt;
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
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.
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.
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.
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
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
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" <A href="/abs/2015ApJ...811...87A">(2015, ApJ, 811, 87)</A>
Authors: Avrett, E.; Tian, H.; Landi, E.; Curdt, W.; Wuelser, J. -P.
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
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.
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.
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.
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
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.
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 \&amp; 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 $&gt;10^{27}$ 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.
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.
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 <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A26">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A26</A>

---------------------------------------------------------
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.
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.
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
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.
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.
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.
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.
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.
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 <A
href="http://www.aanda.org/10.1051/0004-6361/201424432/olm">http://www.aanda.org</A>

---------------------------------------------------------
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.
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.
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.
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.
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.
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.
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.
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
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
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
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.
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.
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.
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.
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
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.
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.
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.
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.
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
<A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
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.
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.
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.
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
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.
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.
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
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.
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
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.
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.
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
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
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.
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
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
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.
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.
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.
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.
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 &lt;= log T &lt;= 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 &lt;= log T &lt;= 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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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&amp;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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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 &gt; 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.
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.
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.
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 (&gt;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.
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.
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.
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.
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.
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.
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.
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.
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&lt;3 105 b: Te~3 105 c:
Te~4 105 d: 6 105&lt;Te
&lt;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.
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.
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: 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.
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.
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.
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.
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.
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.
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&gt;=3×106 K)
and Their Potential Use in Plasma Diagnostics
Authors: Feldman, U.; Curdt, W.; Landi, E.; Wilhelm, K.
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&gt;=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.
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 &lt;=20 mÅ(1σ),
and in one case &lt;=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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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: The SUMER EUV Atlas in the Spectral Range 670 A - 1498 A
Authors: Curdt, W.; Brekke, P.; Schühle, U.; Wilhelm, K.; Dwivedi,
B. N.
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.
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.
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
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.
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.
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.
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.
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.
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
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
1999Sci...283..810H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The New Sun - Probing Solar Plasmas with the SUMER Instrument
on SOHO
Authors: Curdt, W.
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.
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.
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.
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.
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.
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 &amp; 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.
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.
1998A&A...340L..15P Altcode:
We present the first unambiguous detection of the O v 1213.9 Angstrom
(2s(2) (1) S_0 -&gt; 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 -&gt;
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}) &gt;= 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
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.
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.
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, &lt;δv2&gt;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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 &lt; 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 &gt;
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, &amp; 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 {&lt;atop
&gt;} 5.8, having different FIP effects.

---------------------------------------------------------
Title: Sonnenradiometrie mit SUMER auf SOHO.
Authors: Hollandt, J.; Curdt, W.; Schühle, U.; Wilhelm, K.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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: 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.
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.
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.
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.
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.
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.
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 (&gt;=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.
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.
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.
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.
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.
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.
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.
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.
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.
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.