explanation blue bibcodes open ADS page with paths to full text
Author name code: schuehle
ADS astronomy entries on 2022-09-14
=author:"Schuele, U." OR author:"Schuehle, Udo"
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Title: What drives decayless kink oscillations in active region
coronal loops on the Sun?
Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter,
Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David;
Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle,
Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis;
Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel;
Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J.
2022arXiv220904251M Altcode:
We study here the phenomena of decayless kink oscillations in a system
of active region (AR) coronal loops. Using high resolution observations
from two different instruments, namely the Extreme Ultraviolet Imager
(EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly
(AIA) on board the Solar Dynamics Observatory, we follow these AR
loops for an hour each on three consecutive days. Our results show
significantly more resolved decayless waves in the higher-resolution
EUI data compared with the AIA data. Furthermore, the same system of
loops exhibits many of these decayless oscillations on Day-2, while on
Day-3, we detect very few oscillations and on Day-1, we find none at
all. Analysis of photospheric magnetic field data reveals that at most
times, these loops were rooted in sunspots, where supergranular flows
are generally absent. This suggests that supergranular flows, which
are often invoked as drivers of decayless waves, are not necessarily
driving such oscillations in our observations. Similarly, our findings
also cast doubt on other possible drivers of these waves, such as a
transient driver or mode conversion of longitudinal waves near the loop
footpoints. In conclusion, through our analysis we find that none of
the commonly suspected sources proposed to drive decayless oscillations
in active region loops seems to be operating in this event and hence,
the search for that elusive wave driver needs to continue.
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Title: The Lyman-$\alpha$ Emission in a C1.4 Solar Flare Observed
by the Extreme Ultraviolet Imager aboard Solar Orbiter
Authors: Li, Ying; Li, Qiao; Song, De-Chao; Battaglia, Andrea
Francesco; Xiao, Hualin; Krucker, Säm; Schühle, Udo; Li, Hui; Gan,
Weiqun; Ding, M. D.
2022arXiv220806182L Altcode:
The hydrogen Lyman-$\alpha$ (H {\sc i} Ly$\alpha$) emission during solar
flares has rarely been studied in spatially resolved images and its
physical origin has not been fully understood. In this paper, we present
novel Ly$\alpha$ images for a C1.4 solar flare (SOL2021-08-20T22:00)
from the Extreme Ultraviolet Imager aboard Solar Orbiter, together
with multi-waveband and multi-perspective observations from the
Solar Terrestrial Relations Observatory Ahead and the Solar Dynamics
Observatory spacecraft. It is found that the Ly$\alpha$ emission has
a good temporal correlation with the thermal emissions at 1--8 Å and
5--7 keV, indicating that the flaring Ly$\alpha$ is mainly produced by
a thermal process in this small event. However, nonthermal electrons
play a minor role in generating Ly$\alpha$ at flare ribbons during
the rise phase of the flare, as revealed by the hard X-ray imaging and
spectral fitting. Besides originating from flare ribbons, the Ly$\alpha$
emission can come from flare loops, likely caused by plasma heating
and also cooling that happen in different flare phases. It is also
found that the Ly$\alpha$ emission shows fairly similar features with
the He {\sc ii} 304 Å emission in light curve and spatio-temporal
variation along with small differences. These observational results
improve our understanding of the Ly$\alpha$ emission in solar flares
and also provide some insights for investigating the Ly$\alpha$
emission in stellar flares.
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Title: A highly dynamic small-scale jet in a polar coronal hole
Authors: Mandal, Sudip; Chitta, Lakshmi Pradeep; Peter, Hardi;
Solanki, Sami K.; Cuadrado, Regina Aznar; Teriaca, Luca; Schühle,
Udo; Berghmans, David; Auchère, Frédéric
2022A&A...664A..28M Altcode: 2022arXiv220602236M
We present an observational study of the plasma dynamics at the base
of a solar coronal jet, using high resolution extreme ultraviolet
imaging data taken by the Extreme Ultraviolet Imager on board Solar
Orbiter, and by the Atmospheric Imaging Assembly on board Solar
Dynamics Observatory. We observed multiple plasma ejection events
over a period of ∼1 h from a dome-like base that is ca. 4 Mm wide
and is embedded in a polar coronal hole. Within the dome below the
jet spire, multiple plasma blobs with sizes around 1−2 Mm propagate
upwards to the dome apex with speeds of the order of the sound speed
(ca. 120 km s<SUP>−1</SUP>). Upon reaching the apex, some of these
blobs initiate flows with similar speeds towards the other footpoint
of the dome. At the same time, high speed super-sonic outflows
(∼230 km s<SUP>−1</SUP>) are detected along the jet spire. These
outflows as well as the intensity near the dome apex appear to be
repetitive. Furthermore, during its evolution, the jet undergoes
many complex morphological changes, including transitions between
the standard and blowout type eruption. These new observational
results highlight the underlying complexity of the reconnection
process that powers these jets and they also provide insights into
the plasma response when subjected to rapid energy injection. <P
/>Movies associated to Figs. 1, 2, and 4 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243765/olm">https://www.aanda.org</A>
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Title: Linking Small-scale Solar Wind Properties with Large-scale
Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
2022ApJ...935..112T Altcode:
The solar wind measured in situ by Parker Solar Probe in the very
inner heliosphere is studied in combination with the remote-sensing
observation of the coronal source region provided by the METIS
coronagraph aboard Solar Orbiter. The coronal outflows observed near
the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
6.3 R <SUB>⊙</SUB> above the eastern solar limb, can be associated
with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
in two time intervals almost 5 days apart. The two plasma flows
come from two distinct source regions, characterized by different
magnetic field polarity and intensity at the coronal base. It follows
that both the global and local properties of the two streams are
different. Specifically, the solar wind emanating from the stronger
magnetic field region has a lower bulk flux density, as expected,
and is in a state of well-developed Alfvénic turbulence, with low
intermittency. This is interpreted in terms of slab turbulence in the
context of nearly incompressible magnetohydrodynamics. Conversely,
the highly intermittent and poorly developed turbulent behavior of the
solar wind from the weaker magnetic field region is presumably due to
large magnetic deflections most likely attributed to the presence of
switchbacks of interchange reconnection origin.
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Title: The on-ground data reduction and calibration pipeline for
SO/PHI-HRT
Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez,
D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero,
A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero,
L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del
Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama,
J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez,
M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico,
G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.;
Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López
Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.;
Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub,
J.; Strecker, H.; Torralbo, I.; Valori, G.
2022arXiv220814904S Altcode:
The ESA/NASA Solar Orbiter space mission has been successfully launched
in February 2020. Onboard is the Polarimetric and Helioseismic Imager
(SO/PHI), which has two telescopes, a High Resolution Telescope
(HRT) and the Full Disc Telescope (FDT). The instrument is designed
to infer the photospheric magnetic field and line-of-sight velocity
through differential imaging of the polarised light emitted by the
Sun. It calculates the full Stokes vector at 6 wavelength positions
at the Fe I 617.3 nm absorption line. Due to telemetry constraints,
the instrument nominally processes these Stokes profiles onboard,
however when telemetry is available, the raw images are downlinked and
reduced on ground. Here the architecture of the on-ground pipeline
for HRT is presented, which also offers additional corrections not
currently available on board the instrument. The pipeline can reduce
raw images to the full Stokes vector with a polarimetric sensitivity
of $10^{-3}\cdot I_{c}$ or better.
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Title: Coronal Microjets in Quiet-sun Regions Observed with the
Extreme Ultraviolet Imager Onboard Solar Orbiter
Authors: Hou, Zhenyong; He, Jiansen; Berghmans, David; Teriaca, Luca;
Wang, Linghua; Schuehle, Udo; Tian, Hui; Chen, Yajie; Chen, Hechao;
Gao, Yuhang; Bai, Xianyong
2022cosp...44.2536H Altcode:
We report the smallest coronal jets ever observed in the quiet Sun
with recent high resolution observations from the High Resolution
Telescopes (HRI-EUV and HRI-Lyα) of the Extreme Ultraviolet
Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 Å) images,
these microjets usually appear as nearly collimated structures with
brightenings at their footpoints. Their average lifetime, projected
speed, width, and maximum length are 4.6 min, 62 km $s^{-1}$, 1.0 Mm,
and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs
can be identified in some events. A subset of these events also reveal
signatures in the HRI-Lyα (H I Lyα at 1216 Å) images and the extreme
ultraviolet images taken by the Atmospheric Imaging Assembly onboard the
Solar Dynamics Observatory. Our differential emission measure analysis
suggests a multi-thermal nature and an average density of ~1.4x10^9
$cm^{-3}$ for these microjets. Their thermal and kinetic energies were
estimated to be ~3.9x10$^{24}$ erg and ~2.9x10$^{23}$ erg, respectively,
which are of the same order of the released energy predicted by the
nanoflare theory. Most events appear to be located at the edges of
network lanes and magnetic flux concentrations, suggesting that these
coronal microjets are likely generated by magnetic reconnection between
small-scale magnetic loops and the adjacent network field.
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Title: Automatic detection of small-scale EUV brightenings observed
by the Solar Orbiter/EUI
Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.;
Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin,
É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.;
Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti,
S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.;
Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N.
2022A&A...663A.128A Altcode: 2022arXiv220404027A
Context. Accurate detections of frequent small-scale extreme ultraviolet
(EUV) brightenings are essential to the investigation of the physical
processes heating the corona. <BR /> Aims: We detected small-scale
brightenings, termed campfires, using their morphological and
intensity structures as observed in coronal EUV imaging observations
for statistical analysis. <BR /> Methods: We applied a method based
on Zernike moments and a support vector machine (SVM) classifier
to automatically identify and track campfires observed by Solar
Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA). <BR /> Results: This method
detected 8678 campfires (with length scales between 400 km and 4000 km)
from a sequence of 50 High Resolution EUV telescope (HRI<SUB>EUV</SUB>)
174 Å images. From 21 near co-temporal AIA images covering the same
field of view as EUI, we found 1131 campfires, 58% of which were
also detected in HRI<SUB>EUV</SUB> images. In contrast, about 16%
of campfires recognized in HRI<SUB>EUV</SUB> were detected by AIA. We
obtain a campfire birthrate of 2 × 10<SUP>−16</SUP> m<SUP>−2</SUP>
s<SUP>−1</SUP>. About 40% of campfires show a duration longer than 5
s, having been observed in at least two HRI<SUB>EUV</SUB> images. We
find that 27% of campfires were found in coronal bright points and
the remaining 73% have occurred out of coronal bright points. We
detected 23 EUI campfires with a duration greater than 245 s. We found
that about 80% of campfires are formed at supergranular boundaries,
and the features with the highest total intensities are generated at
network junctions and intense H I Lyman-α emission regions observed
by EUI/HRI<SUB>Lya</SUB>. The probability distribution functions for
the total intensity, peak intensity, and projected area of campfires
follow a power law behavior with absolute indices between 2 and 3. This
self-similar behavior is a possible signature of self-organization,
or even self-organized criticality, in the campfire formation
process. <P />Supplementary material (S1-S3) is available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243257/olm">https://www.aanda.org</A>
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Title: The SPICE spectrograph on Solar Orbiter: an introduction and
results from the first Orbits
Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin,
Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera,
Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta,
Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy;
Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina
2022cosp...44.1338A Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument is
the EUV imaging spectrometer on board the Solar Orbiter mission. With
its ability to derive physical properties of the coronal plasma,
SPICE is a key component of the payload to establish the connection
between the source regions and the in-situ measurements of the solar
wind. The spacecraft was successfully launched in February 2020 and
completed its cruise phase in December 2021. During this period,
the remote sensing instruments were mostly operated during limited
periods of time for 'checkout' engineering activities and synoptic
observations. Nonetheless, several of these periods provided enough
opportunities already to obtain new insights on coronal physics. During
the march 2022 perihelion - close to 0.3 AU - SPICE will provide
its highest spatial resolution data so far. Coordinated observations
between the remote sensing and in-situ instruments will provide the
first opportunity to use the full potential of the Solar Orbiter
mission. We will review the instrument characteristics and present
initial results from the cruise phase and first close encounter.
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Title: Observation of Magnetic Switchback in the Solar Corona
Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco;
Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta,
Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman;
Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia;
Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto;
Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania;
Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati,
Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio;
Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère,
Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise;
Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna;
Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo;
Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N.
2022arXiv220603090T Altcode:
Switchbacks are sudden, large radial deflections of the solar wind
magnetic field, widely revealed in interplanetary space by the Parker
Solar Probe. The switchbacks' formation mechanism and sources are still
unresolved, although candidate mechanisms include Alfvénic turbulence,
shear-driven Kelvin-Helmholtz instabilities, interchange reconnection,
and geometrical effects related to the Parker spiral. This Letter
presents observations from the Metis coronagraph onboard Solar Orbiter
of a single large propagating S-shaped vortex, interpreted as first
evidence of a switchback in the solar corona. It originated above
an active region with the related loop system bounded by open-field
regions to the East and West. Observations, modeling, and theory provide
strong arguments in favor of the interchange reconnection origin of
switchbacks. Metis measurements suggest that the initiation of the
switchback may also be an indicator of the origin of slow solar wind.
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Title: The magnetic drivers of campfires seen by the Polarimetric
and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
2022A&A...660A.143K Altcode: 2022arXiv220213859K
Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
(SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
termed campfires, that have been proposed to be brightenings near the
apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
magnetic processes driving these campfires are not understood. <BR
/> Aims: During the cruise phase of SO and at a distance of 0.523
AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
offering the possibility to investigate the surface magnetic field
dynamics underlying campfires at a spatial resolution of about 380
km. <BR /> Methods: We used co-spatial and co-temporal data of the
quiet-Sun network at disc centre acquired with the High Resolution
Imager of SO/EUI at 17.4 nm (HRI<SUB>EUV</SUB>, cadence 2 s) and the
High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
min). Campfires that are within the SO/PHI−SO/EUI common field
of view were isolated and categorised according to the underlying
magnetic activity. <BR /> Results: In 71% of the 38 isolated events,
campfires are confined between bipolar magnetic features, which seem to
exhibit signatures of magnetic flux cancellation. The flux cancellation
occurs either between the two main footpoints, or between one of the
footpoints of the loop housing the campfire and a nearby opposite
polarity patch. In one particularly clear-cut case, we detected the
emergence of a small-scale magnetic loop in the internetwork followed
soon afterwards by a campfire brightening adjacent to the location
of the linear polarisation signal in the photosphere, that is to
say near where the apex of the emerging loop lays. The rest of the
events were observed over small scattered magnetic features, which
could not be identified as magnetic footpoints of the campfire hosting
loops. <BR /> Conclusions: The majority of campfires could be driven
by magnetic reconnection triggered at the footpoints, similar to the
physical processes occurring in the burst-like EUV events discussed
in the literature. About a quarter of all analysed campfires, however,
are not associated to such magnetic activity in the photosphere, which
implies that other heating mechanisms are energising these small-scale
EUV brightenings.
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Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.;
Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.;
Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.;
Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long,
D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca,
L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.;
Jacques, L.; Berghmans, D.
2021A&A...656A..35Z Altcode: 2021arXiv210902169Z
Context. The three-dimensional fine structure of the solar atmosphere
is still not fully understood as most of the available observations
are taken from a single vantage point. <BR /> Aims: The goal of the
paper is to study the three-dimensional distribution of the small-scale
brightening events ("campfires") discovered in the extreme-UV quiet Sun
by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter. <BR />
Methods: We used a first commissioning data set acquired by the EUI's
High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and
we combined it with simultaneous data taken by the Atmospheric Imaging
Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171
Å passband. The two-pixel spatial resolution of the two telescopes
is 400 km and 880 km, respectively, which is sufficient to identify
the campfires in both data sets. The two spacecraft had an angular
separation of around 31.5° (essentially in heliographic longitude),
which allowed for the three-dimensional reconstruction of the campfire
position. These observations represent the first time that stereoscopy
was achieved for brightenings at such a small scale. Manual and
automatic triangulation methods were used to characterize the campfire
data. <BR /> Results: The height of the campfires is located between
1000 km and 5000 km above the photosphere and we find a good agreement
between the manual and automatic methods. The internal structure of
campfires is mostly unresolved by AIA; however, for a particularly
large campfire, we were able to triangulate a few pixels, which are
all in a narrow range between 2500 and 4500 km. <BR /> Conclusions: We
conclude that the low height of EUI campfires suggests that they belong
to the previously unresolved fine structure of the transition region and
low corona of the quiet Sun. They are probably apexes of small-scale
dynamic loops heated internally to coronal temperatures. This work
demonstrates that high-resolution stereoscopy of structures in the
solar atmosphere has become feasible.
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Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot,
Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester,
Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin,
Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith,
Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David;
Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca,
Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre;
Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David
2021AGUFMSH21A..03Z Altcode:
We study the three-dimensional distribution of small-scale brightening
events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun
by the EUI telescope onboard the Solar Orbiter mission. We use one of
the first commissioning data sets acquired by the HRI_EUV telescope of
EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous
SDO/AIA dataset taken in the very similar 171 A passband. The spatial
resolution of the two telescopes is sufficient to identify the campfires
in both datasets. The angular separation between the two spacecraft of
around 31.5 degrees allowed for the three-dimensional reconstruction
of the position of campfires. This is the first time that stereoscopy
was achieved for structures at such a small scale. Manual and automatic
triangulation methods were used. The height of campfires is between 1000
km and 5000 km above the photosphere, and there is a good agreement
between the results of manual and automatic methods. The internal
structure of campfires is mostly not resolved by AIA, but for a large
campfire we could triangulate a few pixels, which are all in a narrow
height range between 2500 and 4500 km. The low height of campfires
suggests that they belong to the previously unresolved fine structure
of the transition region and low corona of the quiet Sun. They are
probably apexes of small-scale dynamic loops internally heated to
coronal temperatures. This work demonstrates that high-resolution
stereoscopy of structures in the solar atmosphere has become possible.
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Title: Propagating brightenings in small loop-like structures in
the quiet-Sun corona: Observations from Solar Orbiter/EUI
Authors: Mandal, Sudip; Peter, Hardi; Chitta, Lakshmi Pradeep;
Solanki, Sami K.; Aznar Cuadrado, Regina; Teriaca, Luca; Schühle,
Udo; Berghmans, David; Auchère, Frédéric
2021A&A...656L..16M Altcode: 2021arXiv211108106M
Brightenings observed in solar extreme-ultraviolet images are generally
interpreted as signatures of micro- or nanoflares occurring in the
transition region or at coronal temperatures. Recent observations
with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have
revealed the smallest of such brightenings (called campfires) in the
quiet-Sun corona. Analyzing EUI 174 Å data obtained at a resolution
of about 400 km on the Sun with a cadence of 5 s on 30 May 2020,
we report here a number of cases in which these campfires exhibit
propagating signatures along their apparently small (3-5 Mm) loop-like
structures. The measured propagation speeds are generally between 25
km s<SUP>−1</SUP> and 60 km s<SUP>−1</SUP>. If the loop plasma is
assumed to be at a million Kelvin, these apparent motions would be
slower than the local sound speed. Furthermore, these brightenings
exhibit nontrivial propagation characteristics such as bifurcation,
merging, reflection, and repeated plasma ejections. We suggest that
these features are manifestations of the internal dynamics of these
small-scale magnetic structures and could provide important insights
into the dynamic response (∼40 s) of the loop plasma to the heating
events and also into the locations of the heating events themselves. <P
/>Movies associated to Figs 2-5, A.1, and B.1 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202142041/olm">https://www.aanda.org</A>
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Title: The first coronal mass ejection observed in both visible-light
and UV H I Ly-α channels of the Metis coronagraph on board Solar
Orbiter
Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini,
F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.;
Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.;
Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki,
A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto,
P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto,
F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.;
Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.;
Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus,
Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar
Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.;
Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter,
H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan,
L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.;
Woch, J.; Zimbardo, G.
2021A&A...656L..14A Altcode:
Context. The Metis coronagraph on board Solar Orbiter offers a new
view of coronal mass ejections (CMEs), observing them for the first
time with simultaneous images acquired with a broad-band filter in
the visible-light interval and with a narrow-band filter around the
H I Ly-α line at 121.567 nm, the so-called Metis UV channel. <BR />
Aims: We show the first Metis observations of a CME, obtained on 16
and 17 January 2021. The event was also observed by the EUI/FSI imager
on board Solar Orbiter, as well as by other space-based coronagraphs,
such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here
with Metis data. <BR /> Methods: Different images are analysed here
to reconstruct the 3D orientation of the expanding CME flux rope using
the graduated cylindrical shell model. This also allows us to identify
the possible location of the source region. Measurements of the CME
kinematics allow us to quantify the expected Doppler dimming in the
Ly-α channel. <BR /> Results: Observations show that most CME features
seen in the visible-light images are also seen in the Ly-α images,
although some features in the latter channel appear more structured
than their visible-light counterparts. We estimated the expansion
velocity of this event to be below 140 km s<SUP>−1</SUP>. Hence,
these observations can be understood by assuming that Doppler dimming
effects do not strongly reduce the Ly-α emission from the CME. These
velocities are comparable with or smaller than the radial velocities
inferred from the same data in a similar coronal structure on the
east side of the Sun. <BR /> Conclusions: The first observations by
Metis of a CME demonstrate the capability of the instrument to provide
valuable and novel information on the structure and dynamics of these
coronal events. Considering also its diagnostics capabilities regarding
the conditions of the ambient corona, Metis promises to significantly
advance our knowledge of such phenomena. <P />Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202142407/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Extreme-UV quiet Sun brightenings observed by the Solar
Orbiter/EUI
Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.;
Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.;
Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.;
Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.;
Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.;
Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.;
Inhester, B.
2021A&A...656L...4B Altcode: 2021arXiv210403382B
Context. The heating of the solar corona by small heating events
requires an increasing number of such events at progressively smaller
scales, with the bulk of the heating occurring at scales that are
currently unresolved. <BR /> Aims: The goal of this work is to study the
smallest brightening events observed in the extreme-UV quiet Sun. <BR />
Methods: We used commissioning data taken by the Extreme Ultraviolet
Imager (EUI) on board the recently launched Solar Orbiter mission. On
30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its
High Resolution EUV telescope (HRI<SUB>EUV</SUB>, 17.4 nm passband)
reached an exceptionally high two-pixel spatial resolution of 400
km. The size and duration of small-scale structures was determined
by the HRI<SUB>EUV</SUB> data, while their height was estimated
from triangulation with simultaneous images from the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory
mission. This is the first stereoscopy of small-scale brightenings
at high resolution. <BR /> Results: We observed small localised
brightenings, also known as `campfires', in a quiet Sun region with
length scales between 400 km and 4000 km and durations between 10 s and
200 s. The smallest and weakest of these HRI<SUB>EUV</SUB> brightenings
have not been previously observed. Simultaneous observations from the
EUI High-resolution Lyman-α telescope (HRI<SUB>Lya</SUB>) do not show
localised brightening events, but the locations of the HRI<SUB>EUV</SUB>
events clearly correspond to the chromospheric network. Comparisons with
simultaneous AIA images shows that most events can also be identified
in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA,
although they appear weaker and blurred. Our differential emission
measure analysis indicated coronal temperatures peaking at log T ≈
6.1 − 6.15. We determined the height for a few of these campfires to
be between 1000 and 5000 km above the photosphere. <BR /> Conclusions:
We find that `campfires' are mostly coronal in nature and rooted in the
magnetic flux concentrations of the chromospheric network. We interpret
these events as a new extension to the flare-microflare-nanoflare
family. Given their low height, the EUI `campfires' could stand as a
new element of the fine structure of the transition region-low corona,
that is, as apexes of small-scale loops that undergo internal heating
all the way up to coronal temperatures.
---------------------------------------------------------
Title: Capturing transient plasma flows and jets in the solar corona
Authors: Chitta, L. P.; Solanki, S. K.; Peter, H.; Aznar Cuadrado,
R.; Teriaca, L.; Schühle, U.; Auchère, F.; Berghmans, D.; Kraaikamp,
E.; Gissot, S.; Verbeeck, C.
2021A&A...656L..13C Altcode: 2021arXiv210915106C
Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma
jets are typical signatures of magnetic reconnection and the associated
impulsive heating of the solar atmospheric plasma. To gain new insights
into the process, high-cadence observations are required to capture
the rapid response of plasma to magnetic reconnection as well as the
highly dynamic evolution of jets. Here, we report the first 2 s cadence
extreme-UV observations recorded by the 174 Å High Resolution Imager of
the Extreme Ultraviolet Imager on board the Solar Orbiter mission. These
observations, covering a quiet-Sun coronal region, reveal the onset
signatures of magnetic reconnection as localized heating events. These
localized sources then exhibit repeated plasma eruptions or jet
activity. Our observations show that this spatial morphological change
from localized sources to jet activity could occur rapidly on timescales
of about 20 s. The jets themselves are intermittent and are produced
from the source region on timescales of about 20 s. In the initial
phases of these events, plasma jets are observed to exhibit speeds,
as inferred from propagating intensity disturbances, in the range of
100 km s<SUP>−1</SUP> to 150 km s<SUP>−1</SUP>. These jets then
propagate to lengths of about 5 Mm. We discuss examples of bidirectional
and unidirectional jet activity observed to have been initiated from
the initially localized bursts in the corona. The transient nature
of coronal bursts and the associated plasma flows or jets along with
their dynamics could provide a benchmark for magnetic reconnection
models of coronal bursts and jets. <P />Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202141683/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Cosmic-ray flux predictions and observations for and with
Metis on board Solar Orbiter
Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi,
M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.;
Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.;
Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.;
De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.;
Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.;
Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.;
Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca,
L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P.
2021A&A...656A..15G Altcode: 2021arXiv210413700G
Context. The Metis coronagraph is one of the remote sensing instruments
hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted
to carry out the first simultaneous imaging of the solar corona in
both visible light (VL) and ultraviolet (UV). High-energy particles
can penetrate spacecraft materials and may limit the performance of
the on-board instruments. A study of the galactic cosmic-ray (GCR)
tracks observed in the first VL images gathered by Metis during the
commissioning phase is presented here. A similar analysis is planned
for the UV channel. <BR /> Aims: We aim to formulate a prediction of
the GCR flux up to hundreds of GeV for the first part of the Solar
Orbiter mission to study the performance of the Metis coronagraph. <BR
/> Methods: The GCR model predictions are compared to observations
gathered on board Solar Orbiter by the High-Energy Telescope in the
range between 10 MeV and 100 MeV in the summer of 2020 as well as with
the previous measurements. Estimated cosmic-ray fluxes above 70 MeV
n<SUP>−1</SUP> have been also parameterized and used for Monte Carlo
simulations aimed at reproducing the cosmic-ray track observations in
the Metis coronagraph VL images. The same parameterizations can also
be used to study the performance of other detectors. <BR /> Results:
By comparing observations of cosmic-ray tracks in the Metis VL images
with FLUKA Monte Carlo simulations of cosmic-ray interactions in
the VL detector, we find that cosmic rays fire only a fraction, on
the order of 10<SUP>−4</SUP>, of the whole image pixel sample. We
also find that the overall efficiency for cosmic-ray identification
in the Metis VL images is approximately equal to the contribution
of Z ≥ 2 GCR particles. A similar study will be carried out during
the whole of the Solar Orbiter's mission duration for the purposes of
instrument diagnostics and to verify whether the Metis data and Monte
Carlo simulations would allow for a long-term monitoring of the GCR
proton flux.
---------------------------------------------------------
Title: First observations from the SPICE EUV spectrometer on Solar
Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
Chitta, L. P.
2021A&A...656A..38F Altcode: 2021arXiv211011252F
<BR /> Aims: We present first science observations taken during the
commissioning activities of the Spectral Imaging of the Coronal
Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
mission. SPICE is a high-resolution imaging spectrometer operating at
extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
the possible types of observations to give prospective users a
better understanding of the science capabilities of SPICE. <BR />
Methods: We have reviewed the data obtained by SPICE between April
and June 2020 and selected representative results obtained with
different slits and a range of exposure times between 5 s and 180
s. Standard instrumental corrections have been applied to the raw
data. <BR /> Results: The paper discusses the first observations
of the Sun on different targets and presents an example of the full
spectra from the quiet Sun, identifying over 40 spectral lines from
neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
magnesium, and iron. These lines cover the temperature range between
20 000 K and 1 million K (10 MK in flares), providing slices of the
Sun's atmosphere in narrow temperature intervals. We provide a list
of count rates for the 23 brightest spectral lines. We show examples
of raster images of the quiet Sun in several strong transition region
lines, where we have found unusually bright, compact structures in the
quiet Sun network, with extreme intensities up to 25 times greater
than the average intensity across the image. The lifetimes of these
structures can exceed 2.5 hours. We identify them as a transition
region signature of coronal bright points and compare their areas and
intensity enhancements. We also show the first above-limb measurements
with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
and O VI lines. We discuss the potential to use abundance diagnostics
methods to study the variability of the elemental composition that can
be compared with in situ measurements to help confirm the magnetic
connection between the spacecraft location and the Sun's surface,
and locate the sources of the solar wind. <BR /> Conclusions: The
SPICE instrument successfully performs measurements of EUV spectra
and raster images that will make vital contributions to the scientific
success of the Solar Orbiter mission.
---------------------------------------------------------
Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
2021A&A...656A..32R Altcode: 2021arXiv210613344R
In this work, we present an investigation of the wind in the solar
corona that has been initiated by observations of the resonantly
scattered ultraviolet emission of the coronal plasma obtained with
UVCS-SOHO, designed to measure the wind outflow speed by applying
Doppler dimming diagnostics. Metis on Solar Orbiter complements the
UVCS spectroscopic observations that were performed during solar
activity cycle 23 by simultaneously imaging the polarized visible
light and the H I Lyman-α corona in order to obtain high spatial and
temporal resolution maps of the outward velocity of the continuously
expanding solar atmosphere. The Metis observations, taken on May 15,
2020, provide the first H I Lyman-α images of the extended corona
and the first instantaneous map of the speed of the coronal plasma
outflows during the minimum of solar activity and allow us to identify
the layer where the slow wind flow is observed. The polarized visible
light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
emissions, obtained with the two Metis channels, were combined in
order to measure the dimming of the UV emission relative to a static
corona. This effect is caused by the outward motion of the coronal
plasma along the direction of incidence of the chromospheric photons
on the coronal neutral hydrogen. The plasma outflow velocity was then
derived as a function of the measured Doppler dimming. The static
corona UV emission was simulated on the basis of the plasma electron
density inferred from the polarized visible light. This study leads
to the identification, in the velocity maps of the solar corona, of
the high-density layer about ±10° wide, centered on the extension
of a quiet equatorial streamer present at the east limb - the coronal
origin of the heliospheric current sheet - where the slowest wind
flows at about 160 ± 18 km s<SUP>−1</SUP> from 4 R<SUB>⊙</SUB>
to 6 R<SUB>⊙</SUB>. Beyond the boundaries of the high-density layer,
the wind velocity rapidly increases, marking the transition between
slow and fast wind in the corona.
---------------------------------------------------------
Title: Exploring the Solar Wind from Its Source on the Corona into
the Inner Heliosphere during the First Solar Orbiter-Parker Solar
Probe Quadrature
Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester;
Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano;
Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.;
Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd
D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.;
Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case,
Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso,
Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry;
Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino,
Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck,
Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro;
Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David
M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto,
Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco,
Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale,
Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini,
Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca,
Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli,
Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano;
Zuppella, Paola
2021ApJ...920L..14T Altcode: 2021arXiv211011031T
This Letter addresses the first Solar Orbiter (SO)-Parker Solar
Probe (PSP) quadrature, occurring on 2021 January 18 to investigate
the evolution of solar wind from the extended corona to the inner
heliosphere. Assuming ballistic propagation, the same plasma volume
observed remotely in the corona at altitudes between 3.5 and 6.3
solar radii above the solar limb with the Metis coronagraph on SO
can be tracked to PSP, orbiting at 0.1 au, thus allowing the local
properties of the solar wind to be linked to the coronal source region
from where it originated. Thanks to the close approach of PSP to the
Sun and the simultaneous Metis observation of the solar corona, the
flow-aligned magnetic field and the bulk kinetic energy flux density
can be empirically inferred along the coronal current sheet with an
unprecedented accuracy, allowing in particular estimation of the Alfvén
radius at 8.7 solar radii during the time of this event. This is thus
the very first study of the same solar wind plasma as it expands from
the sub-Alfvénic solar corona to just above the Alfvén surface.
---------------------------------------------------------
Title: Coronal Microjets in Quiet-Sun Regions Observed with the
Extreme Ultraviolet Imager on Board the Solar Orbiter
Authors: Hou, Zhenyong; Tian, Hui; Berghmans, David; Chen, Hechao;
Teriaca, Luca; Schühle, Udo; Gao, Yuhang; Chen, Yajie; He, Jiansen;
Wang, Linghua; Bai, Xianyong
2021ApJ...918L..20H Altcode: 2021arXiv210808718H
We report the smallest coronal jets ever observed in the quiet Sun with
recent high-resolution observations from the High Resolution Telescopes
(HRI<SUB>EUV</SUB> and HRI<SUB>Lyα</SUB>) of the Extreme Ultraviolet
Imager on board the Solar Orbiter (SO). In the HRI<SUB>EUV</SUB>
(174 Å) images, these microjets usually appear as nearly collimated
structures with brightenings at their footpoints. Their average
lifetime, projected speed, width, and maximum length are 4.6 minutes,
62 km s<SUP>-1</SUP>, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y
shaped structures and moving blobs can be identified in some events. A
subset of these events also reveal signatures in the HRI<SUB>Lyα</SUB>
(H I Lyα at 1216 Å) images and the extreme ultraviolet images
taken by the Atmospheric Imaging Assembly (AIA) on board the Solar
Dynamics Observatory (SDO). Our differential emission-measure (EM)
analysis suggests a multithermal nature and an average density of ~1.4
× 10<SUP>9</SUP> cm<SUP>-3</SUP> for these microjets. Their thermal
and kinetic energies were estimated to be ~3.9 × 10<SUP>24</SUP> erg
and ~2.9 × 10<SUP>23</SUP> erg, respectively, which are of the same
order of the released energy predicted by the nanoflare theory. Most
events appear to be located at the edges of network lanes and magnetic
flux concentrations, suggesting that these coronal microjets are likely
generated by magnetic reconnection between small-scale magnetic loops
and the adjacent network field.
---------------------------------------------------------
Title: Challenges during Metis-Solar Orbiter commissioning phase
Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro;
Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi,
Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel,
Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro;
Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi,
Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina;
Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas;
Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo
Antonio; Zupella, Paola
2021SPIE11852E..5AR Altcode:
Metis is the visible light and UV light imaging coronagraph on board
the ESA-NASA mission Solar Orbiter that has been launched February 10th,
2020, from Cape Canaveral. Scope of the mission is to study the Sun up
close, taking high-resolution images of the Sun's poles for the first
time, and understanding the Sun-Earth connection. Metis coronagraph
will image the solar corona in the linearly polarized broadband visible
radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at
Solar Orbiter perihelion, providing a diagnostics, with unprecedented
temporal coverage and spatial resolution, of the structures and dynamics
of the full corona. Solar Orbiter commissioning phase big challenge was
Covid-19 social distancing phase that affected the way commissioning
of a spacecraft and its payload is typically done. Metis coronagraph
on-board Solar Orbiter had its additional challenges: to wake up and
check the performance of the optical, electrical and thermal subsystems,
most of them unchecked since Metis delivery to spacecraft prime, Airbus,
in May 2017. The roadmap to the fully commissioned coronagraph is here
described throughout the steps from the software functional test,
the switch on of the detectors of the two channels, UV and visible,
to the optimization of the occulting system and the characterization
of the instrumental stray light, one of the most challenging features
in a coronagraph.
---------------------------------------------------------
Title: Calibrating Optical Distortions In The Solar Orbiter Spice
Spectrograph
Authors: Thompson, W.; Schühle, U.; Young, P.
2021AAS...23831302T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
SolarOrbiter is a high-resolution imaging spectrometer operating at
extremeultraviolet (EUV) wavelengths from 70.4-79.0 nm and 97.3-104.9
nm. Asingle-mirror off-axis paraboloid focuses the solar image onto the
entranceslit of the spectrometer section. A Toroidal Variable Line Space
(TVLS)grating images the entrance slit onto a pair of MCP-intensified
APS detectors.Ray-tracing analysis prior to launch showed that the
instrument was subject toa number of small image distortions which
need to be corrected in the finaldata product. We compare the ray
tracing results with measurements made inflight. Co-alignment with
other telescopes on Solar Orbiter will also beexamined.
---------------------------------------------------------
Title: The Extreme ultraviolet imager onboard Solar Orbiter
Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere,
Frederic; Long, David; Schuehle, Udo; Rochus, Pierre
2021cosp...43E.949B Altcode:
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. 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. The EUI consists of three telescopes, the Full Sun Imager
(FSI) and two High Resolution Imagers (HRIs), which are optimised
to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a
coverage from chromosphere up to corona. The EUI instrument design
will be reviewed, and its scientific objectives and plans will be
discussed. Early results of the EUI commissioning will be presented.
---------------------------------------------------------
Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
L.; Thompson, W. T.; Williams, D.
2020AGUFMSH038..09Z Altcode:
Linking solar activity on the surface and in the corona to the inner
heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. Solar
Orbiter's unique combination of remote sensing and in-situ instruments
coupled with observation from other missions such as Parker Solar
Probe will allow us to compare in-situ and remote sensing composition
data. With the addition of modeling, these new results will allow us
to trace back the source of heliospheric plasma. As high telemetry
will not always be available with SPICE, we have developed a method
for measuring relative abundances that is both telemetry efficient
and reliable. Unlike methods based on Differential Emission Measure
(DEM) inversion, the Linear Combination Ratio (LCR) method does not
require a large number of spectral lines. This new method is based
on linear combinations of UV spectral lines. The coefficients of
the combinations are optimized such that the ratio of two linear
combinations of radiances would yield the relative abundance of two
elements. We present some abundance diagnostics tested on different
combinations of spectral lines observable by SPICE.
---------------------------------------------------------
Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
D.; Young, P. R.
2020AGUFMSH038..03P Altcode:
We will present some of the early data of the Spectral Imaging of the
Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
unique features of SPICE is its capability to record a wide range of
wavelengths in the extreme UV with the possibility to record spectral
lines giving access to a continuous plasma temperature range from 10.000
K to well above 1 MK. The data taken so far were for commissioning
purposes and they can be used for a preliminary evaluation of the
science performance of the instrument. Here we will concentrate on
sample spectra covering the whole wavelength region and on the early
raster maps acquired in bright lines in the quiet Sun close to disk
center. Looking at different quiet Sun features we investigate the
thermal structure of the atmosphere and flow structures. For this
we apply fits to the spectral profiles and check the performance in
terms of Doppler shifts and line widths to retrieve the structure of
the network in terms of dynamics. While the amount of data available
so far is limited, we will have a first look on how quiet Sun plasma
responds to heating events. For this, we will compare spectral lines
forming at different temperatures recorded at strictly the same time.
---------------------------------------------------------
Title: Observation of Smallest Ever Detected Brightening Events with
the Solar Orbiter EUI HRI-EUV Imager
Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere,
F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado,
R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
2020AGUFMSH038..01P Altcode:
The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter
acquired its first images in May 2020. The passband of the 17.4 nm
High Resolution Imager (HRI-EUV) is dominated by emission lines of
Fe IX and Fe X, that is the 1 million degree solar corona. The solar
atmosphere at this temperature is dynamic at all scales, down to the
highest spatial resolution available from instruments priori to Solar
Orbiter. During the Commissioning phase, HRI-EUV acquired several high
temporal resolution (a few seconds) sequences at quiet Sun regions at
disk center. The instrument revealed a multitude of brightenings at
the smallest-ever detectable spatial scales which, at that time, was
about 400 km (two pixels). These events appear to be present everywhere
all the time. We present the first results of the analysis of these
sequences with the aim of understanding the role of these small scale
events in the heating of the solar corona.
---------------------------------------------------------
Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
W. T.; Tustain, S.; Williams, D.; Young, P. R.
2020AGUFMSH038..02F Altcode:
SPICE (Spectral Imaging of Coronal Environment) is one of the remote
sensing instruments onboard Solar Orbiter. It is an EUV imaging
spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
bands with exposures as short as 1s. SPICE is the only Solar Orbiter
instrument that can measure EUV spectra from the disk and low corona
of the Sun and record all spectral lines simultaneously. SPICE uses
one of three narrow slits, 2"x11', 4”x11', 6”x11', or a wide slit
30”x14'. The primary mirror can be scanned in a direction perpendicular
to the slit, allowing raster images of up to 16' in size. <P />We
present an overview of the first SPICE data taken on several days
during the instrument commissioning carried out by the RAL Space team
between 2020 April 21 and 2020 June 14. We also include results from
SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
taken between June 16-21<SUP>st</SUP>. We give examples of full spectra
from the quiet Sun near disk centre and provide a list of key spectral
lines emitted in a range of temperatures between 10,000 K and over 1
million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
neon, sulphur and magnesium. We show examples of first raster images
in several strong lines, obtained with different slits and a range
of exposure times between 5s and 180s. We describe the temperature
coverage and density diagnostics, determination of plasma flows, and
discuss possible applications to studies of the elemental abundances
in the corona. We also show the first off-limb measurements with SPICE,
as obtained when the spacecraft pointed at the limb.
---------------------------------------------------------
Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
2020SPIE11444E..0NS Altcode:
Solar-C (EUVST) is the next Japanese solar physics mission to
be developed with significant contributions from US and European
countries. The mission carries an EUV imaging spectrometer with
slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
Telescope) as the mission payload, to take a fundamental step towards
answering how the plasma universe is created and evolves and how the
Sun influences the Earth and other planets in our solar system. In
April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
(Japan Aerospace Exploration Agency) has made the final down-selection
for this mission as the 4th in the series of competitively chosen
M-class mission to be launched with an Epsilon launch vehicle in mid
2020s. NASA (National Aeronautics and Space Administration) has selected
this mission concept for Phase A concept study in September 2019 and
is in the process leading to final selection. For European countries,
the team has (or is in the process of confirming) confirmed endorsement
for hardware contributions to the EUVST from the national agencies. A
recent update to the mission instrumentation is to add a UV spectral
irradiance monitor capability for EUVST calibration and scientific
purpose. This presentation provides the latest status of the mission
with an overall description of the mission concept emphasizing on key
roles of the mission in heliophysics research from mid 2020s.
---------------------------------------------------------
Title: Calibrating optical distortions in the Solar Orbiter SPICE
spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
D.; Sidher, S.
2020AGUFMSH0360029T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
Solar Orbiter is a high-resolution imaging spectrometer operating
at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
image onto the entrance slit of the spectrometer section. A Toroidal
Variable Line Space (TVLS) grating images the entrance slit onto a
pair of MCP-intensified APS detectors. Ray-tracing analysis prior
to launch showed that the instrument was subject to a number of
small image distortions which need to be corrected in the final data
product. We compare the ray tracing results with measurements made in
flight. Co-alignment with other telescopes on Solar Orbiter will also
be examined.
---------------------------------------------------------
Title: First results from the EUI and SPICE observations of Alpha
Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360024B Altcode:
On June 16th 2020 Solar Orbiter made a dedicated observing campaign
where the spacecraft pointed to the solar limb to allow some of the
high resolution instruments to observe the ingress (at the east limb)
and later the egress (west limb) of the occultation of the star Alpha
Leonis by the solar disk. The star was chosen because its luminosity and
early spectral type ensure high and stable flux at wavelengths between
100 and 122 nanometers, a range observed by the High Resolution EUI
Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
of the SPICE spectrograph. Star observations, when feasible, allow
to gather a great deal of information on the instrument performances,
such as the radiometric performance and the instrument optical point
spread function (PSF). <P />We report here the first results from the
above campaign for the two instruments.
---------------------------------------------------------
Title: Solar Orbiter: connecting remote sensing and in situ
measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
Y.; Laker, R.
2020AGUFMSH038..10H Altcode:
A key science goal of the Solar Orbiter mission is to make connections
between phenomena on the Sun and their manifestations in interplanetary
space. To that end, the spacecraft carries a carefully tailored
payload of six remote sensing instruments and four making in situ
measurements. During June 2020, while the spacecraft was around 0.5
AU from the Sun, the remote sensing instruments operated for several
days. While this was primarily an engineering activity, the resulting
observations provided outstanding measurements and represent the ideal
first opportunity to investigate the potential for making connections
between the remote sensing and in situ payloads on Solar Orbiter. <P
/>We present a preliminary analysis of the available remote sensing and
in situ observations, showing how connections can be made, and discuss
the potential for further, more precise mapping to be performed as
the mission progresses.
---------------------------------------------------------
Title: First Images and Initial In-Flight Performance of the Extreme
Ultraviolet Imager On-Board Solar Orbiter.
Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra,
L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.;
Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C.
2020AGUFMSH0360025A Altcode:
The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is
composed of two High Resolution Imagers working at 121.6 (HRI-LYA,
H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one
dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition
region) and 17.4 nm (Fe IX/X, corona). During the commissioning period
following the launch of Solar Orbiter and two and a half months of
outgassing, EUI acquired its first solar images on May 12th, 2020 at
about 0.67 AU. Most of the capabilities of the instrument have been
tested during the following weeks, which revealed excellent overall
performance. HRI-EUV already provided images with an angular resolution
equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide
images of the Sun at Lyman alpha, which have been otherwise relatively
rare, with sub-second cadence capability. FSI will provide context for
connection science but it will also explore regions of the corona never
imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI
uses a complex on-board image processing system including advanced
image compression and event detection algorithms. In particular,
commissioning tests confirm the good performance of the compression,
which is critical given the limited total telemetry volume imposed by
the mission profile. In this paper, we present the main characteristics
of the first images taken in each channel and we provide an initial
assessment of the in-flight performance.
---------------------------------------------------------
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360003T Altcode:
The Solar Orbiter spacecraft carries a powerful set of remote
sensing instruments that allow studying the solar atmosphere with
unprecedented diagnostic capabilities. Many such diagnostics require
the simultaneous usage of more than one instrument. One example of that
is the capability, for the first time, to obtain (near) simultaneous
spatially resolved observations of the emission from the first three
lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
can observe the Lyman beta and gamma lines in its long wavelength
(SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
(FSI-304). Being hydrogen and helium the main components of our star,
these very bright transitions play an important role in the energy
budget of the outer atmosphere via radiative losses and the measurement
of their profiles and radiance ratios is a fundamental constraint to
any comprehensive modelization effort of the upper solar chromosphere
and transition region. Additionally, monitoring their average ratios
can serve as a check out for the relative radiometric performance of
the two instruments throughout the mission. Although the engineering
data acquired so far are far from ideal in terms of time simultaneity
(often only within about 1 h) and line coverage (often only Lyman beta
was acquired by SPICE and not always near simultaneous images from all
three telescopes are available) the analysis we present here still
offers a great opportunity to have a first look at the potential of
this diagnostic from the two instruments. In fact, we have identified
a series of datasets obtained at disk center and at various positions
at the solar limb that allow studying the Lyman alpha to beta radiance
ratio and their relation to He II 30.4 as a function of the position
on the Sun (disk center versus limb and quiet Sun versus coronal holes).
---------------------------------------------------------
Title: Very high-resolution observations of the solar atmosphere
in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard
Solar Orbiter
Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot,
S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.;
Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
2020AGUFMSH0360026A Altcode:
The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of
three telescopes, the Full Sun Imager (FSI) and two High Resolution
Imagers (HRIs). The two HRI telescopes provide images of the base
of the corona, near to the chromosphere, and of the 1 million K
corona. In fact, the HRI-EUV telescope operates around 17.4 nm to
obtain images dominated by emission from lines generated from Fe-IX
and X ions, formed at about 1 MK, while the HRI-LYA telescope provides
narrow band images dominated by the H I Lyman alpha line at 121.6 nm,
formed in the upper chromosphere/lower transition region of the solar
atmosphere around 20,000 K. Thus, the two imagers provide a powerful
diagnostics of the solar structural organization, in terms of loop
hierarchies and connectivity. Here we present an analysis of the first
two near-simultaneous (within 15s) high-resolution images of the solar
quiet atmosphere obtained near disk center by the two high-resolution
telescopes on May 30th 2020, during the commissioning phase of the
mission , when Solar Orbiter was at about 0.56 AU from the Sun.
---------------------------------------------------------
Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
2020A&A...642A...6A Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements. <BR /> Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together. <BR /> Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis. <BR /> Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
---------------------------------------------------------
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.
---------------------------------------------------------
Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
2020A&A...642A..11S Altcode: 2019arXiv190311061S
<BR /> Aims: This paper describes the Polarimetric and Helioseismic
Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
helioseismology instrument to observe the Sun from outside the Sun-Earth
line. It is the key instrument meant to address the top-level science
question: How does the solar dynamo work and drive connections between
the Sun and the heliosphere? SO/PHI will also play an important role
in answering the other top-level science questions of Solar Orbiter,
while hosting the potential of a rich return in further science. <BR
/> Methods: SO/PHI measures the Zeeman effect and the Doppler shift
in the Fe I 617.3 nm spectral line. To this end, the instrument
carries out narrow-band imaging spectro-polarimetry using a tunable
LiNbO<SUB>3</SUB> Fabry-Perot etalon, while the polarisation modulation
is done with liquid crystal variable retarders. The line and the nearby
continuum are sampled at six wavelength points and the data are recorded
by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
are reduced on board, including being inverted under the assumption of
a Milne-Eddington atmosphere, although simpler reduction methods are
also available on board. SO/PHI is composed of two telescopes; one,
the Full Disc Telescope, covers the full solar disc at all phases of
the orbit, while the other, the High Resolution Telescope, can resolve
structures as small as 200 km on the Sun at closest perihelion. The high
heat load generated through proximity to the Sun is greatly reduced by
the multilayer-coated entrance windows to the two telescopes that allow
less than 4% of the total sunlight to enter the instrument, most of
it in a narrow wavelength band around the chosen spectral line. <BR />
Results: SO/PHI was designed and built by a consortium having partners
in Germany, Spain, and France. The flight model was delivered to
Airbus Defence and Space, Stevenage, and successfully integrated into
the Solar Orbiter spacecraft. A number of innovations were introduced
compared with earlier space-based spectropolarimeters, thus allowing
SO/PHI to fit into the tight mass, volume, power and telemetry budgets
provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
challenges posed by the mission's highly elliptical orbit.
---------------------------------------------------------
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
<BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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 mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
2020A&A...642A...1M Altcode: 2020arXiv200900861M
<BR /> Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
2015-2025 programme and a mission of international collaboration between
ESA and NASA, will explore the Sun and heliosphere from close up and
out of the ecliptic plane. It was launched on 10 February 2020 04:03
UTC from Cape Canaveral and aims to address key questions of solar and
heliospheric physics pertaining to how the Sun creates and controls
the Heliosphere, and why solar activity changes with time. To answer
these, the mission carries six remote-sensing instruments to observe
the Sun and the solar corona, and four in-situ instruments to measure
the solar wind, energetic particles, and electromagnetic fields. In
this paper, we describe the science objectives of the mission, and how
these will be addressed by the joint observations of the instruments
onboard. <BR /> Methods: The paper first summarises the mission-level
science objectives, followed by an overview of the spacecraft and
payload. We report the observables and performance figures of each
instrument, as well as the trajectory design. This is followed by a
summary of the science operations concept. The paper concludes with a
more detailed description of the science objectives. <BR /> Results:
Solar Orbiter will combine in-situ measurements in the heliosphere
with high-resolution remote-sensing observations of the Sun to address
fundamental questions of solar and heliospheric physics. The performance
of the Solar Orbiter payload meets the requirements derived from the
mission's science objectives. Its science return will be augmented
further by coordinated observations with other space missions and
ground-based observatories. <P />ARRAY(0x207ce98)
---------------------------------------------------------
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. <BR /> 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. <BR />
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. <BR /> 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. <BR /> 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: Metis: the Solar Orbiter visible light and ultraviolet
coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
María; Amoruso, Mauro; Centonze, Vito
2020A&A...642A..10A Altcode: 2019arXiv191108462A
<BR /> Aims: Metis is the first solar coronagraph designed for a
space mission and is capable of performing simultaneous imaging of the
off-limb solar corona in both visible and UV light. The observations
obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
will enable us to diagnose, with unprecedented temporal coverage and
spatial resolution, the structures and dynamics of the full corona
in a square field of view (FoV) of ±2.9° in width, with an inner
circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
R<SUB>⊙</SUB> to about 9 R<SUB>⊙</SUB>, owing to the eccentricity
of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
mission profile, Metis will be able to observe the solar corona
from a close (0.28 AU, at the closest perihelion) vantage point,
achieving increasing out-of-ecliptic views with the increase of the
orbit inclination over time. Moreover, observations near perihelion,
during the phase of lower rotational velocity of the solar surface
relative to the spacecraft, allow longer-term studies of the off-limb
coronal features, thus finally disentangling their intrinsic evolution
from effects due to solar rotation. <BR /> Methods: Thanks to a novel
occultation design and a combination of a UV interference coating of
the mirrors and a spectral bandpass filter, Metis images the solar
corona simultaneously in the visible light band, between 580 and 640
nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
channel also includes a broadband polarimeter able to observe the
linearly polarised component of the K corona. The coronal images in
both the UV H I Lyman-α and polarised visible light are obtained at
high spatial resolution with a spatial scale down to about 2000 km
and 15 000 km at perihelion, in the cases of the visible and UV light,
respectively. A temporal resolution down to 1 s can be achieved when
observing coronal fluctuations in visible light. <BR /> Results: The
Metis measurements, obtained from different latitudes, will allow for
complete characterisation of the main physical parameters and dynamics
of the electron and neutral hydrogen/proton plasma components of the
corona in the region where the solar wind undergoes the acceleration
process and where the onset and initial propagation of coronal mass
ejections (CMEs) take place. The near-Sun multi-wavelength coronal
imaging performed with Metis, combined with the unique opportunities
offered by the Solar Orbiter mission, can effectively address crucial
issues of solar physics such as: the origin and heating/acceleration
of the fast and slow solar wind streams; the origin, acceleration,
and transport of the solar energetic particles; and the transient
ejection of coronal mass and its evolution in the inner heliosphere,
thus significantly improving our understanding of the region connecting
the Sun to the heliosphere and of the processes generating and driving
the solar wind and coronal mass ejections. <BR /> Conclusions: This
paper presents the scientific objectives and requirements, the overall
optical design of the Metis instrument, the thermo-mechanical design,
and the processing and power unit; reports on the results of the
campaigns dedicated to integration, alignment, and tests, and to
the characterisation of the instrument performance; describes the
operation concept, data handling, and software tools; and, finally,
the diagnostic techniques to be applied to the data, as well as a brief
description of the expected scientific products. The performance of the
instrument measured during calibrations ensures that the scientific
objectives of Metis can be pursued with success. <P />Metis website:
<A href="http://metis.oato.inaf.it">http://metis.oato.inaf.it</A>
---------------------------------------------------------
Title: Optical design of the multi-wavelength imaging coronagraph
Metis for the solar orbiter mission
Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.;
Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro,
D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.;
Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.;
Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle,
U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki,
A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero,
A.; Castronuovo, M.
2020ExA....49..239F Altcode: 2020ExA...tmp...14F
This paper describes the innovative optical design of the Metis
coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a
multi-wavelength, externally occulted telescope for the imaging
of the solar corona in both the visible and ultraviolet wavelength
ranges. Metis adopts a novel occultation scheme for the solar disk,
that we named "inverse external occulter", for reducing the extremely
high thermal load on the instrument at the spacecraft perihelion. The
core of the Metis optical design is an aplanatic Gregorian telescope
common to both the visible and ultraviolet channels. A suitable
dichroic beam-splitter, optimized for transmitting a narrow-band in
the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband
in the visible (580-640 nm) spectral range, is used to separate the
two optical paths. Along the visible light optical path, a liquid
crystal electro-optical modulator, used for the first time in space,
allows making polarimetric measurements.
---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz,
W. K.; Schühle, U.
2019AGUFMSH21D3291R Altcode:
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. <P />EUI aims at improving our
understanding of the structure and dynamics of the solar atmosphere. EUI
will take images of the solar atmosphere, globally as well as at high
resolution, and from high solar latitude perspectives. <P />EUI consists
of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm
and 30.4 nm to provide a coverage from chromosphere up to corona. EUI
is designed to cope with the strong constraints that Solar Orbiter has
as a deep space mission. Limited telemetry availability is compensated
by state-of-the-art image compression, on board image processing and
event selection. The imposed power limitations and potentially harsh
radiation environment lead to the usage of novel CMOS sensors. As
the unobstructed field of view of the telescopes needs to protrude
through the spacecraft heat shield, the apertures were kept as small as
possible. This lead to a systematic effort to optimize the throughput
of every optical element and the reduction of noise levels in the
sensor. <P />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 on board software,
the intended operations, the ground software and the foreseen data
products. <P />EUI will bring unique science opportunities thanks to its
specific design, its viewpoint and thanks to the planned synergies with
the other Solar Orbiter instruments. We highlight in particular 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: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
2019SPIE11118E..07S Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
---------------------------------------------------------
Title: Optical alignment of the Solar Orbiter EUI flight instrument
Authors: Mazzoli, A.; Halain, J. -P.; Auchère, F.; Barbay, J.;
Meining, S.; Philippon, A.; Morinaud, G.; Roose, S.; Hellin, M. -L.;
Jacques, L.; Schühle, U.; Dumesnil, C.; Mercier, R.; Renotte, E.;
Rochus, P.
2019SPIE11180E..1OM Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet
(17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It
is composed of three channels, each one containing a telescope. Two
of these channels are high resolution imagers (HRI) at respectively
17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly ), each one composed of two
off-axis aspherical mirrors. The third channel is a full sun imager
(FSI) composed of one single off-axis aspherical mirror and working
at 17.1 nm and 30.4 nm alternatively. This paper presents the optical
alignment of each telescope. The alignment process involved a set of
Optical Ground Support Equipment (OGSE) such as theodolites, laser
tracker, visible-light interferometer as well as a 3D Coordinates
Measuring Machine (CMM). The mirrors orientation have been measured
with respect to reference alignment cubes using theodolites. Their
positions with respect to reference pins on the instrument optical
bench have been measured using the 3D CMM. The mirrors orientations and
positions have been adjusted by shimming of the mirrors mount during
the alignment process. After this mechanical alignment, the quality
of the wavefront has been checked by interferometric measurements,
in an iterative process with the orientation and position adjustment
to achieve the required image quality.
---------------------------------------------------------
Title: Optical performance of the Metis coronagraph on the Solar
Orbiter ESA mission
Authors: Frassetto, Fabio; Da Deppo, Vania; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Giana; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone,
Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio;
Teriaca, Luca; Schühle, Udo; Heerlein, Klaus; Uslenghi, Michela
2019SPIE11180E..6YF Altcode:
The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is
expected to provide new insights into the solar dynamics. In detail,
it is designed to address three main questions: the energy deposition
mechanism at the poles (where the fast wind is originated), the
source of the slow wind at lower altitude, and how the global corona
evolves, in particular in relation to the huge plasma ejections that
occasionally are produced. To obtain the required optical performance,
not only the Metis optical design has been highly optimized, but the
alignment procedure has also been subjected to an accurate evaluation
in order to fulfill the integration specifications. The telescope
assembling sequence has been constructed considering all the subsystems
manufacturing, alignment and integration tolerances. The performance
verification activity is an important milestone in the instrument
characterization and the obtained results will assure the fulfillment
of the science requirements for its operation in space. The entire
alignment and verification phase has been performed by the Metis team in
collaboration with Thales Alenia Space Torino and took place in ALTEC
(Turin) at the Optical Payload System Facility using the Space Optics
Calibration Chamber infrastructure, a vacuum chamber especially built
and tested for the alignment and calibration of the Metis coronagraph,
and suitable for tests of future payloads. The goal of the alignment,
integration, verification and calibration processes is to measure
the parameters of the telescope, and the characteristics of the two
Metis channels: visible and ultraviolet. They work in parallel thanks
to the peculiar optical layout. The focusing and alignment performance
of the two channels must be well understood, and the results need to be
easily compared to the requirements. For this, a dedicated illumination
method, with both channels fed by the same source, has been developed;
and a procedure to perform a simultaneous through focus analysis has
been adopted. In this paper the final optical performance achieved by
Metis is reported and commented.
---------------------------------------------------------
Title: Stray light calibration for the Solar Orbiter/Metis solar
coronagraph
Authors: Landini, F.; Romoli, M.; Fineschi, S.; Casini, C.; Baccani,
C.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro,
D.; Andretta, V.; Castronuovo, M.; Casti, M.; Capobianco, G.; Massone,
G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Pancrazzi, M.; Teriaca,
L.; Schuehle, U.; Heerlein, K.; Uslenghi, M.
2019SPIE11180E..2IL Altcode:
The Solar Orbiter/Metis visible and UV solar coronagraph redefines
the concept of external occultation in solar coronagraphy. Classical
externally occulted coronagraphs are characterized by an occulter in
front of the telescope entrance aperture. Solar Orbiter will approach
the Sun down to 0.28 AU: in order to reduce the thermal load, the
Metis design switches the positions of the entrance aperture and the
external occulter thus achieving what is called the inverted external
occultation. The inverted external occulter (IEO) consists of a circular
aperture on the Solar Orbiter thermal shield that acts as coronagraph
entrance pupil. A spherical mirror, located 800 mm behind the IEO, back
rejects the disklight through the IEO itself. To pursue the goal of
maximizing the reduction of the stray light level on the focal plane,
an optimization of the IEO shape was implemented. The stray light
calibration was performed in a clean environment in front of the OPSys
solar disk divergence simulator (at ALTEC, in Torino, Italy), which is
able to emulate different heliocentric distances. Ground calibrations
were a unique opportunity to map the Metis stray light level thanks to
a pure solar disk simulator without the solar corona. The stray light
calibration was limited to the visible light case, being the most
stringent. This work is focused on the description of the laboratory
facility that was used to perform the stray light calibration and on
the calibration results.
---------------------------------------------------------
Title: The EUI instrument onboard Solar Orbiter: the EUV corona
imaged differently
Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric;
Harra, Louise; Schmutz, Werner; Schühle, Udo
2018csc..confE..73B Altcode:
The ESA Solar Orbiter mission is designed to determine how the Sun
creates and controls the heliosphere. The spacecraft will bring
a combination of in situ and remote sensing instruments out of the
ecliptic (>30°) and close to the sun (0.3 solar-radii). The launch
of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme
Ultraviolet Imager is part of the remote-sensing package of Solar
Orbiter, to be operating during 3 ten-day periods of each orbit around
the Sun, which last roughly half a year. These 3 periods will correspond
to perihelion and maximal solar latitude north and south. The Extreme
Ultraviolet Imager is itself a suite of three UV and EUV telescopes
that observe the solar atmosphere both globally as well as at very
high resolution. The two high-resolution imagers (HRIs) will image the
solar atmosphere in the chromospheric Lyman alpha line and the coronal
17nm pass band with a resolution of 0.5 arcsec. From perihelion, this
will correspond to a pixel footprint on the solar disc of (110km)^2
. The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV
passbands, will provide a global view of the solar atmosphere and is
therefore an essential building block for the "connection science"
of the Solar Orbiter mission. The FSI field of view is large enough
(228arcmin) that, even at perihelion and at maximal off-points by Solar
Orbiter, the full solar disk remains in the field of view. This large
FOV and the FSI's high sensitivity will allow to image the "transition
corona" where the topology of streamers and pseudo-streamers fades in
the solar wind. Furthermore, FSI will be the first to image all this
from out of the ecliptic. In this talk we will give an overview of the
EUI instrument. We will focus on the novel aspects of EUI that will
allow it to image beyond what previous EUV imagers could show us: EUV
imaging from the highest solar latitude, with the widest field-of-view
and at highest spatial resolution.
---------------------------------------------------------
Title: Broadband EUV/FUV mirror coatings for a solar spectrograph
mission
Authors: Teriaca, Luca; Feigl, Torsten; Schühle, Udo
2018SPIE10699E..2YT Altcode:
As it is rich in spectral lines emitted by plasma between 10000 K
and 20 MK, the vacuum ultraviolet (VUV - 17 to 200 nm) solar spectrum
is extremely valuable for instruments that study the physics of the
solar atmosphere. We present multilayer coatings with simultaneous
broadband reflectance in the two spectral ranges of 16.9 nm to 21.5 nm
and 46.3 nm to 127.5 nm. The coatings are based on Mo/Si multilayers
with a thin capping layer of boron carbide (B<SUB>4</SUB>C). Samples
were produced and their reflectance measured. Their performance in
terms of resistance to high temperatures and low micro-roughness was
also assessed by measurement. Our study shows that a coating with the
characteristics required by next generation spectrometers for studies
of the solar atmosphere is feasible.
---------------------------------------------------------
Title: The solar orbiter Metis and EUI intensified CMOS-APS detectors:
concept, main characteristics, and performance
Authors: Schühle, Udo; Teriaca, Luca; Aznar Cuadrado, Regina;
Heerlein, Klaus; Uslenghi, Michela; Werner, Stephan
2018SPIE10699E..34S Altcode:
Two instruments aboard the Solar Orbiter mission, the Extreme
Ultraviolet Imager and the Metis coronagraph, are using cameras of
similar design to obtain images in the Lyman alpha line of hydrogen
at 121.6 nm. Each of these cameras is based on an APS sensor used
as readout of a single microchannel plate intensifier unit whose
output current is converted into visible light photons through a
phosphor screen. Before integration on the respective instruments, both
detector's flight models have been characterized and calibrated. In this
paper, we describe the two camera systems, the results of qualification
tests, and report their performance characteristics.
---------------------------------------------------------
Title: The EUI flight instrument of Solar Orbiter: from optical
alignment to end-to-end calibration
Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.;
Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado,
R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.;
Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin,
M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli,
A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.;
Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P.
2018SPIE10699E..0HH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral
ranges. The development of the EUI instrument has been successfully
completed with the optical alignment of its three channels' telescope,
the thermal and mechanical environmental verification, the electrical
and software validations, and an end-toend on-ground calibration of
the two-units' flight instrument at the operating wavelengths. The
instrument has been delivered and installed on the Solar Orbiter
spacecraft, which is now undergoing all preparatory activities before
launch.
---------------------------------------------------------
Title: In-flight performance of the solar UV radiometer LYRA/PROBA-2
Authors: Stockman, Y.; BenMoussa, A.; Dammasch, I.; Defise, J. -M.;
Dominique, M.; Halain, J. -P.; Hochedez, J. -F.; Koller, S.; Schmutz,
W.; Schühle, U.
2017SPIE10565E..0AS Altcode:
LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload
(Fig. 1). The PROBA-2 [1] mission has been launched on 02 November
2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude
of 725 km. Its nominal operation duration is two years with possible
extension of 2 years. PROBA-2 is a small satellite developed under
an ESA General Support Technology Program (GSTP) contract to perform
an in-flight demonstration of new space technologies and support a
scientific mission for a set of selected instruments [2]. PROBA-2 host
17 technological demonstrators and 4 scientific instruments. The mission
is tracked by the ESA Redu Mission Operation Center. One of the four
scientific instruments is LYRA that monitors the solar irradiance at a
high cadence (> 20 Hz) in four soft X-Ray to VUV large passbands: the
"Lyman-Alpha" channel, the "Herzberg" continuum range, the "Aluminium"
and "Zirconium" filter channels. The radiometric calibration is
traceable to synchrotron source standards [3]. LYRA benefits from wide
bandgap detectors based on diamond. It is the first space assessment
of these revolutionary UV detectors for astrophysics. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
the strong solar visible light) and, therefore, visible light blocking
filters become superfluous. To correlate the data of this new detector
technology, silicon detectors with well known characteristics are also
embarked. Due to the strict allocated mass and power budget (5 kg, 5W),
and poor priority to the payload needs on such platform, an optimization
and a robustness of the instrument was necessary. The first switch-on
occured on 16 November 2009. Since then the instrument performances
have been monitored and analyzed during the commissioning period. This
paper presents the first-light and preliminary performance analysis.
---------------------------------------------------------
Title: LYRA, solar uv radiometer on the technology demonstration
platform PROBA-2
Authors: Stockman, Y.; Hochedez, J. -F.; Schmutz, W.; BenMoussa, A.;
Defise, J. -M.; Denis, F.; D'Olieslaeger, M.; Dominique, M.; Haenen,
K.; Halain, J. -P.; Koller, S.; Koizumi, S.; Mortet, V.; Rochus, P.;
Schühle, U.; Soltani, A.; Theissen, A.
2017SPIE10567E..3KS Altcode:
LYRA is a solar radiometer part of the PROBA 2 micro satellite
payload. LYRA will monitor the solar irradiance in four soft X-Ray -
VUV passbands. They have been chosen for their relevance to Solar
Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/
Herzberg continuum range, 3/ Aluminium filter channel (including
He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric
calibration is traceable to synchrotron source standards. The
stability will be monitored by on-board calibration sources (LEDs),
which allow us to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first
space assessment of revolutionary UV detectors. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
visible light) and therefore, make dispensable visible light blocking
filters. To correlate the data of this new detector technology, well
known technology, such as Si detectors are also embarked. The SWAP
EUV imaging telescope will operate next to LYRA on PROBA-2. Together,
they will provide a high performance solar monitor for operational
space weather nowcasting and research. LYRA demonstrates technologies
important for future missions such as the ESA Solar Orbiter.
---------------------------------------------------------
Title: Characterization of the UV detector of Solar Orbiter/Metis
Authors: Uslenghi, Michela; Schühle, Udo H.; Teriaca, Luca; Heerlein,
Klaus; Werner, Stephan
2017SPIE10397E..1KU Altcode:
Metis, one of the instruments of the ESA mission Solar Orbiter (to be
launched in February 2019), is a coronograph able to perform broadband
polarization imaging in the visible range (580-640 nm), and narrow
band imaging in UV (HI Lyman-α 121.6 nm) . The detector of the UV
channel is an intensified camera, based on a Star-1000 rad-hard CMOS
APS coupled via a 2:1 fiber optic taper to a single stage Microchannel
Plate intensifier, sealed with an entrance MgF<SUB>2</SUB> window
and provided with an opaque KBr photocathode. Before integration
in the instrument, the UVDA (UV Detector Assembly) Flight Model
has been characterized at the MPS laboratory and calibrated in the
UV range using the detector calibration beamline of the Metrology
Light Source synchrotron of the Physikalisch-Technische Bundesanstalt
(PTB). Linearity, spectral calibration, and response uniformity at 121.6
nm have been measured. Preliminary results are reported in this paper.
---------------------------------------------------------
Title: The VUV instrument SPICE for Solar Orbiter: performance
ground testing
Authors: Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.;
Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi,
Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy;
Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej;
Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.;
Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy;
Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred;
Munro, Grant J.; Holmes, William; Doyle, Peter
2017SPIE10397E..08C Altcode:
SPICE is an imaging spectrometer operating at vacuum ultraviolet
(VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a
facility instrument on the Solar Orbiter mission, which carries
10 science instruments in all, to make observations of the Sun's
atmosphere and heliosphere, at close proximity to the Sun, i.e to
0.28 A.U. at perihelion. SPICE's role is to make VUV measurements
of plasma in the solar atmosphere. SPICE is designed to achieve
spectral imaging at spectral resolution >1500, spatial resolution
of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many
strong constraints on the instrument design imposed by the mission
requirements prevent the imaging performance from exceeding those of
previous instruments, but by being closer to the sun there is a gain in
spatial resolution. The price which is paid is the harsher environment,
particularly thermal. This leads to some novel features in the design,
which needed to be proven by ground test programs. These include a
dichroic solar-transmitting primary mirror to dump the solar heat, a
high in-flight temperature (60deg.C) and gradients in the optics box,
and a bespoke variable-line-spacing grating to minimise the number of
reflective components used. The tests culminate in the systemlevel test
of VUV imaging performance and pointing stability. We will describe how
our dedicated facility with heritage from previous solar instruments,
is used to make these tests, and show the results, firstly on the
Engineering Model of the optics unit, and more recently on the Flight
Model. For the keywords, select up to 8 key terms for a search on your
manuscript's subject.
---------------------------------------------------------
Title: The qualification campaign of the EUI instrument of Solar
Orbiter
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle,
U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Verbeeck, C.; Smith, P.
2016SPIE.9905E..2XH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument is one of the ten
scientific instruments on board the Solar Orbiter mission to be launched
in October 2018. It will provide full-sun and high-resolution images of
the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in
the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument
design has been completed with the Assembly, Integration and Test
(AIT) of the instrument two-units Qualification Model (QM). Optical,
electrical, electro-magnetic compatibility, thermal and mechanical
environmental verifications were conducted and are summarized here. The
integration and test procedures for the Flight Model (FM) instrument
and sub-systems were also verified. Following the Qualification Review,
the flight instrument activities were started with the assembly of
the flight units. The mechanical and thermal acceptance tests and an
end-to-end final calibration in the (E)UV will then be conducted before
delivery for integration on the Solar Orbiter Spacecraft by end of 2016.
---------------------------------------------------------
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: 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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. <P
/>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: The extreme ultraviolet imager of solar orbiter: optical
design and alignment scheme
Authors: Halain, J. -P.; Mazzoli, A.; Meining, S.; Rochus, P.; Renotte,
E.; Auchère, F.; Schühle, U.; Delmotte, F.; Dumesnil, C.; Philippon,
A.; Mercier, R.; Hermans, A.
2015SPIE.9604E..0HH Altcode:
The Extreme Ultraviolet Imager (EUI) is one of the remote sensing
instruments on-board the Solar Orbiter mission. It will provide
dual-band full-Sun images of the solar corona in the extreme ultraviolet
(17.1 nm and 30.4 nm), and high resolution images of the solar disk in
both extreme ultraviolet (17.1 nm) and vacuum ultraviolet (Lyman-alpha
121.6 nm). The EUI optical design takes heritage of previous similar
instruments. The Full Sun Imager (FSI) channel is a single mirror
Herschel design telescope. The two High Resolution Imager (HRI)
channels are based on a two-mirror optical refractive scheme, one
Ritchey-Chretien and one Gregory optical design for the EUV and the
Lyman-alpha channels, respectively. The spectral performances of the
EUI channels are obtained thanks to dedicated mirror multilayer coatings
and specific band-pass filters. The FSI channel uses a dual-band mirror
coating combined with aluminum and zirconium band-pass filters. The HRI
channels use optimized band-pass selection mirror coatings combined
with aluminum band-pass filters and narrow band interference filters
for Lyman-alpha. The optical performances result from accurate mirror
manufacturing tolerances and from a two-step alignment procedure. The
primary mirrors are first co-aligned. The HRI secondary mirrors
and focal planes positions are then adjusted to have an optimum
interferometric cavity in each of these two channels. For that purpose
a dedicated alignment test setup has been prepared, composed of a dummy
focal plane assembly representing the detector position. Before the
alignment on the flight optical bench, the overall alignment method
has been validated on the Structural and Thermal Model, on a dummy
bench using flight spare optics, then on the Qualification Model to
be used for the system verification test and qualifications.
---------------------------------------------------------
Title: The extreme UV imager telescope on-board the Solar Orbiter
mission: overview of phase C and D
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz,
W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo,
M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C.
2015SPIE.9604E..0GH Altcode:
The Solar Orbiter mission is composed of ten scientific instruments
dedicated to the observation of the Sun's atmosphere and its
heliosphere, taking advantage of an out-of ecliptic orbit and at
perihelion reaching a proximity close to 0.28 A.U. On board Solar
Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun
image sequences of the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm), and high-resolution image sequences of the solar disk
in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet
(121.6 nm). The EUI concept uses heritage from previous similar extreme
ultraviolet instrument. Additional constraints from the specific orbit
(thermal and radiation environment, limited telemetry download) however
required dedicated technologies to achieve the scientific objectives
of the mission. The development phase C of the instrument and its
sub-systems has been successfully completed, including thermomechanical
and electrical design validations with the Structural Thermal Model
(STM) and the Engineering Model (EM). The instrument STM and EM units
have been integrated on the respective spacecraft models and will
undergo the system level tests. In parallel, the Phase D has been
started with the sub-system qualifications and the flight parts
manufacturing. The next steps of the EUI development will be the
instrument Qualification Model (QM) integration and qualification
tests. The Flight Model (FM) instrument activities will then follow
with the acceptance tests and calibration campaigns.
---------------------------------------------------------
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. <P />(2 data files).
---------------------------------------------------------
Title: Degradation assessment of LYRA after 5 years on orbit -
Technology Demonstration -
Authors: BenMoussa, A.; Giordanengo, B.; Gissot, S.; Dammasch, I. E.;
Dominique, M.; Hochedez, J. -F.; Soltani, A.; Bourzgui, N.; Saito,
T.; Schühle, U.; Gottwald, A.; Kroth, U.; Jones, A. R.
2015ExA....39...29B Altcode: 2015ExA...tmp....1B
We present a long-term assessment of the radiometric calibration and
degradation of the Large Yield Radiometer (LYRA), which has been on
orbit since 2009. LYRA is an ultraviolet (UV) solar radiometer and is
the first space experiment using aboard a pioneering diamond detector
technology. We show that LYRA has degraded after the commissioning phase
but is still exploitable scientifically after almost 5 years on orbit
thanks to its redundancy design and calibration strategy correcting for
instrument degradation. We focus on the inflight detector's calibration
and show that diamond photodetectors have not degraded while silicon
reference photodiodes that are even less exposed to the Sun show an
increase of their dark current and a decrease of their photoresponse.
---------------------------------------------------------
Title: The extreme UV imager of solar orbiter: from detailed design
to flight model
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.;
Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.;
Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith,
P.; Winter, B.
2014SPIE.9144E..08H Altcode:
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. After the breadboarding and prototyping activities that
focused on key technologies, the EUI project has completed the design
phase and has started the final manufacturing of the instrument and its
validation. The EUI instrument has successfully passed its Critical
Design Review (CDR). The process validated the detailed design of
the Optical Bench unit and of its sub-units (entrance baffles, doors,
mirrors, camera, and filter wheel mechanisms), and of the Electronic
Box unit. In the same timeframe, the Structural and Thermal Model
(STM) test campaign of the two units have been achieved, and allowed
to correlate the associated mathematical models. The lessons learned
from STM and the detailed design served as input to release the
manufacturing of the Qualification Model (QM) and of the Flight Model
(FM). The QM will serve to qualify the instrument units and sub-units,
in advance of the FM acceptance tests and final on-ground calibration.
---------------------------------------------------------
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 R<SUB>ʘ</SUB>
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: 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: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
2013SoPh..288..389B Altcode: 2013arXiv1304.5488B
We present the lessons learned about the degradation observed in
several space solar missions, based on contributions at the Workshop
about On-Orbit Degradation of Solar and Space Weather Instruments
that took place at the Solar Terrestrial Centre of Excellence (Royal
Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
workshop was to open discussions related to the degradation observed
in Sun-observing instruments exposed to the effects of the space
environment. This article summarizes the various lessons learned
and offers recommendations to reduce or correct expected degradation
with the goal of increasing the useful lifespan of future and ongoing
space missions.
---------------------------------------------------------
Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
Zender, J.
2013SoPh..286...43S Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
The Sun Watcher with Active Pixels and Image Processing (SWAP) is
an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
(PROBA2) mission launched on 2 November 2009. SWAP has a spectral
bandpass centered on 17.4 nm and provides images of the low solar
corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
an imaging cadence of about two minutes. SWAP is designed to monitor
all space-weather-relevant events and features in the low solar
corona. Given the limited resources of the PROBA2 microsatellite,
the SWAP telescope is designed with various innovative technologies,
including an off-axis optical design and a CMOS-APS detector. This
article provides reference documentation for users of the SWAP image
data.
---------------------------------------------------------
Title: Status of RAISE, the Rapid Acquisition Imaging Spectrograph
Experiment
Authors: Laurent, Glenn T.; Hassler, D. M.; DeForest, C.; Ayres,
T. R.; Davis, M.; De Pontieu, B.; Schuehle, U.; Warren, H.
2013SPD....44..145L Altcode:
The Rapid Acquisition Imaging Spectrograph Experiment (RAISE) sounding
rocket payload is a high speed scanning-slit imaging spectrograph
designed to observe the dynamics and heating of the solar chromosphere
and corona on time scales as short as 100 ms, with 1 arcsec spatial
resolution and a velocity sensitivity of 1-2 km/s. The instrument is
based on a new class of UV/EUV imaging spectrometers that use only
two reflections to provide quasi-stigmatic performance simultaneously
over multiple wavelengths and spatial fields. The design uses an
off-axis parabolic telescope mirror to form a real image of the sun
on the spectrometer entrance aperture. A slit then selects a portion
of the solar image, passing its light onto a near-normal incidence
toroidal grating, which re-images the spectrally dispersed radiation
onto two array detectors. Two full spectral passbands over the same
one-dimensional spatial field are recorded simultaneously with no
scanning of the detectors or grating. The two different spectral
bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two
intensified Active Pixel Sensor (APS) detectors whose focal planes are
individually adjusted for optimized performance. The telescope and
grating are coated with B4C to enhance short wavelength (2nd order)
reflectance, enabling the instrument to record the brightest lines
between 602-622Å and 761-780Å at the same time. RAISE reads out the
full field of both detectors at 5-10 Hz, allowing us to record over
1,500 complete spectral observations in a single 5-minute rocket flight,
opening up a new domain of high time resolution spectral imaging and
spectroscopy. We present an overview of the project, a summary of the
maiden flight results, and an update on instrument status.Abstract
(2,250 Maximum Characters): The Rapid Acquisition Imaging Spectrograph
Experiment (RAISE) sounding rocket payload is a high speed scanning-slit
imaging spectrograph designed to observe the dynamics and heating of the
solar chromosphere and corona on time scales as short as 100 ms, with 1
arcsec spatial resolution and a velocity sensitivity of 1-2 km/s. The
instrument is based on a new class of UV/EUV imaging spectrometers
that use only two reflections to provide quasi-stigmatic performance
simultaneously over multiple wavelengths and spatial fields. The design
uses an off-axis parabolic telescope mirror to form a real image of
the sun on the spectrometer entrance aperture. A slit then selects
a portion of the solar image, passing its light onto a near-normal
incidence toroidal grating, which re-images the spectrally dispersed
radiation onto two array detectors. Two full spectral passbands over
the same one-dimensional spatial field are recorded simultaneously with
no scanning of the detectors or grating. The two different spectral
bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two
intensified Active Pixel Sensor (APS) detectors whose focal planes are
individually adjusted for optimized performance. The telescope and
grating are coated with B4C to enhance short wavelength (2nd order)
reflectance, enabling the instrument to record the brightest lines
between 602-622Å and 761-780Å at the same time. RAISE reads out the
full field of both detectors at 5-10 Hz, allowing us to record over
1,500 complete spectral observations in a single 5-minute rocket flight,
opening up a new domain of high time resolution spectral imaging and
spectroscopy. We present an overview of the project, a summary of the
maiden flight results, and an update on instrument status.
---------------------------------------------------------
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<SUP> - 1</SUP> or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
---------------------------------------------------------
Title: Multi Element Telescope for Imaging and Spectroscopy (METIS)
coronagraph for the Solar Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero;
Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi,
Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro;
Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco,
Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania;
D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel,
Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe;
Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo,
Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
2012SPIE.8443E..09A Altcode:
METIS, the “Multi Element Telescope for Imaging and Spectroscopy”,
is a coronagraph selected by the European Space Agency to be part of
the payload of the Solar Orbiter mission to be launched in 2017. The
unique profile of this mission will allow 1) a close approach to the
Sun (up to 0.28 A.U.) thus leading to a significant improvement in
spatial resolution; 2) quasi co-rotation with the Sun, resulting in
observations that nearly freeze for several days the large-scale outer
corona in the plane of the sky and 3) unprecedented out-of-ecliptic
view of the solar corona. This paper describes the experiment concept
and the observational tools required to achieve the science drivers
of METIS. METIS will be capable of obtaining for the first time: •
simultaneous imaging of the full corona in polarized visible-light
(590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); •
monochromatic imaging of the full corona in the extreme ultraviolet
He II Lyman α (30.4 nm); • spectrographic observations of the HI
and He II Ly α in corona. These measurements will allow a complete
characterization of the three most important plasma components of
the corona and the solar wind, that is, electrons, hydrogen, and
helium. This presentation gives an overview of the METIS imaging and
spectroscopic observational capabilities to carry out such measurements.
---------------------------------------------------------
Title: A prototype of the UV detector for METIS on Solar Orbiter
Authors: Uslenghi, M.; Incorvaia, S.; Fiorini, M.; Schühle, U. H.;
Teriaca, L.; Wilkinson, E.; Siegmund, O. H.; Antonucci, E.; Fineschi,
S.; Naletto, G.; Nicolini, G.; Nicolosi, G.; Romoli, M.; Focardi, M.
2012SPIE.8443E..3IU Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) is one of
the instruments included in the science payload of the ESA mission Solar
Orbiter: a coronograph able to perform broadband polarization imaging
in the visible range, and narrow band imaging in UV (HI Lyman-α)
and EUV (HeII Lyman-α). In addition, it will acquire spectra of the
solar corona simultaneously to UV/EUV imaging. It will be equipped
with two detectors: a hybrid APS dedicated to the visible channel and
an Intensified APS for the UV/EUV channel. The spectroscopic channel
will share the same detector as the UV/EUV corona imaging, with the
spectrum imaged on a portion of the detector not used by the corona
image. We present the development of the UV/EUV detector consisting
of a CMOS APS imaging device to be coupled with a microchannel plate
intensifier. Other than constraints related to the harsh environment
(radiation, temperature, visible stray-light), the METIS UV detector has
the additional challenge of managing different count rates associated
with the three different kind of measurements (UV imaging, EUV imaging
and spectroscopy). The required dynamic range is further extended
since observations will be planned at different distances from the
Sun, varying image scale over a fixed vignetting function. We will
present the architecture of this UV detector, describing the prototype
developed in order to optimize the performance on the overall dynamic
range required by METIS.
---------------------------------------------------------
Title: METIS: a novel coronagraph design for the Solar Orbiter mission
Authors: Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero;
Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Abbo, Lucia;
Andretta, Vincenzo; Bemporad, Alessandro; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.;
Moses, J. Dan; Nicolosi, Piergiorgio; Pancrazzi, Maurizio; Pelizzo,
Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
2012SPIE.8443E..3HF Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS,
the “Multi Element Telescope for Imaging and Spectroscopy”,
is a coronagraph selected by the European Space Agency to be part
of the payload of the Solar Orbiter mission to be launched in
2017. The mission profile will bring the Solar Orbiter spacecraft
as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic
providing a unique platform for helio-synchronous observations of
the Sun and its polar regions. METIS coronagraph is designed for
multi-wavelength imaging and spectroscopy of the solar corona. This
presentation gives an overview of the innovative design elements of
the METIS coronagraph. These elements include: i) multi-wavelength,
reflecting Gregorian-telescope; ii) multilayer coating optimized for
the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer
for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii)
inverse external-occulter scheme for reduced thermal load at spacecraft
peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror
to feed a 1<SUP>st</SUP> and 4<SUP>th</SUP>-order spherical varied
line-spaced (SVLS) grating placed on a section of the secondary mirror;
v) liquid crystals electro-optic polarimeter for observations of the
visible-light K-corona. The expected performances are also presented.
---------------------------------------------------------
Title: The EUI instrument on board the Solar Orbiter mission: from
breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
2012SPIE.8443E..07H Altcode:
The Solar Orbiter mission will explore the connection between the Sun
and its heliosphere, taking advantage of an orbit approaching the Sun at
0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. To achieve the required scientific performances under the
challenging constraints of the Solar Orbiter mission it was required
to further develop existing technologies. As part of this development,
and of its maturation of technology readiness, a set of breadboard and
prototypes of critical subsystems have thus been realized to improve
the overall instrument design. The EUI instrument architecture, its
major components and sub-systems are described with their driving
constraints and the expected performances based on the breadboard and
prototype results. The instrument verification and qualification plan
will also be discussed. We present the thermal and mechanical model
validation, the instrument test campaign with the structural-thermal
model (STM), followed by the other instrument models in advance of
the flight instrument manufacturing and AIT campaign.
---------------------------------------------------------
Title: CMOS sensor and camera for the PHI instrument on board Solar
Orbiter: evaluation of the radiation tolerance
Authors: Piqueras, J.; Heerlein, K.; Werner, S.; Enge, R.; Schühle,
U.; Woch, J.; De Ridder, T.; Meynants, G.; Wolfs, B.; Lepage, G.;
Diels, W.
2012SPIE.8453E..14P Altcode:
The ESA/NASA Solar Orbiter mission, to be launched in 2017, will
explore the Sun at a much closer distance than any previous solar
observatory. On board the spacecraft, a high-resolution magnetograph
(PHI) will provide two-dimensional measurements of the photospheric
vector magnetic field and line-of-sight velocity. The environmental
conditions encountered during the mission, together with the
stringent performance requirements of the instrument, define the
set of specifications for the camera system. A custom designed
CMOS sensor (with 2048×2050 pixels) has been developed to fulfill
the aimed radiation hardness and performance. This sensor must
demonstrate a cadence above 10 fps with a full-well capacity higher
than 10<SUP>5</SUP> electrons in a 10-μm pixel pitch. We report the
characterization and qualification tests. The radiation test campaign
has been completed up to a TID of 150 krad(Si), proton fluence up to
4 × 10<SUP>11</SUP> at 10 MeV and 2 × 10<SUP>11</SUP> at 20 MeV, and
with heavy ions to check for latch-up and SEFI failures. In parallel,
a radiation tolerant camera electronic readout system has been built
to control the sensor and readout images, digitize the data, and
communicate with the data handling system of the PHI instrument. In
addition, we present the main issues related to the camera design and
future perspectives.
---------------------------------------------------------
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:
<BR /> 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. <BR /> 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). <BR /> 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: LEMUR (Large European Module for solar Ultraviolet Research):
a VUV imaging spectrograph for the JAXA Solar-C Mission
Authors: Korendyke, Clarence M.; Teriaca, Luca; Doschek, George A.;
Harra, Louise K.; Schühle, Udo H.; Shimizu, Toshifumi
2011SPIE.8148E..0IK Altcode: 2011SPIE.8148E..17K
LEMUR is a VUV imaging spectrograph with 0.28" resolution. Incident
solar radiation is imaged onto the spectrograph slit by a single
mirror telescope consisting of a 30-cm steerable f/12 off-axis
paraboloid mirror. The spectrograph slit is imaged and dispersed by
a highly corrected grating that focuses the solar spectrum over the
detectors. The mirror is coated with a suitable multilayer with B4C
top-coating providing a reflectance peak around 18.5 nm besides the
usual B4C range above 500Å. The grating is formed by two halves, one
optimized for performances around 185Å and the other above 500Å. Three
intensified CCD cameras will record spectra above 50 nm while a large
format CCD array with an aluminum filter will be used around 185Å.
---------------------------------------------------------
Title: The Lyman-alpha telescope of the extreme ultraviolet imager
on Solar Orbiter
Authors: Schühle, Udo; Halain, Jean-Philippe; Meining, Stefan;
Teriaca, Luca
2011SPIE.8148E..0KS Altcode: 2011SPIE.8148E..19S
On the Solar Orbiter mission, the Extreme Ultraviolet Imager (EUI)
set of filtergraph-telescopes consists of two highresolution imagers
(HRI) and one dual-band full Sun imager (FSI) that will provide images
of the solar atmosphere in the extreme ultraviolet and in the Lyman-α
line of hydrogen at 121.6 nm. The Lyman-α HRI, in particular, will
provide imaging of the upper chromospheres/lower transition region of
the Sun at unprecedented high cadence and at an angular resolution of 1"
(corresponding to a spatial resolution of 200 km at perihelion). For
vacuum-ultraviolet imaging of the Sun the main requirements for the
instrumentation are high resolution, high cadence, and large dynamic
range. We present here the novel solutions of the instrument design
and show in detail the predicted performance of this telescope. We
describe in detail how the high throughput and spectral purity at 121.6
nm is achieved. The technical solutions include multilayer coatings
of the telescope mirrors for high reflectance at 121.6 nm, combined
with interference filters and a multichannel-plate intensified CMOS
active pixel camera. We make use of the design flexibilities of this
camera to optimize the dynamic range in the focal plane.
---------------------------------------------------------
Title: The technical challenges of the Solar-Orbiter EUI instrument
Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry;
Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric;
Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence;
Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François;
Ben Moussa, Ali
2010SPIE.7732E..0RH Altcode: 2010SPIE.7732E..20H
The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of
a suite of two high-resolution imagers (HRI) and one dual-band full
Sun imager (FSI) that will provide EUV and Lyman-α images of the
solar atmospheric layers above the photosphere. The EUI instrument is
based on a set of challenging new technologies allowing to reach the
scientific objectives and to cope with the hard space environment of
the Solar Orbiter mission. The mechanical concept of the EUI instrument
is based on a common structure supporting the HRI and FSI channels,
and a separated electronic box. A heat rejection baffle system is
used to reduce the Sun heat load and provide a first protection level
against the solar disk straylight. The spectral bands are selected by
thin filters and multilayer mirror coatings. The detectors are 10μm
pitch back illuminated CMOS Active Pixel Sensors (APS), best suited
for the EUI science requirements and radiation hardness. This paper
presents the EUI instrument concept and its major sub-systems. The
current developments of the instrument technologies are also summarized.
---------------------------------------------------------
Title: First light of SWAP on-board PROBA2
Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc;
Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre;
Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo
2010SPIE.7732E..0PH Altcode: 2010SPIE.7732E..18H
The SWAP telescope (Sun Watcher using Active Pixel System detector
and Image Processing) is an instrument launched on 2nd November 2009
on-board the ESA PROBA2 technological mission. SWAP is a space weather
sentinel from a low Earth orbit, providing images at 174 nm of the
solar corona. The instrument concept has been adapted to the PROBA2
mini-satellite requirements (compactness, low power electronics and
a-thermal opto-mechanical system). It also takes advantage of the
platform pointing agility, on-board processor, Packetwire interface
and autonomous operations. The key component of SWAP is a radiation
resistant CMOS-APS detector combined with onboard compression and
data prioritization. SWAP has been developed and qualified at the
Centre Spatial de Liège (CSL) and calibrated at the PTBBessy
facility. After launch, SWAP has provided its first images on 14th
November 2009 and started its nominal, scientific phase in February
2010, after 3 months of platform and payload commissioning. This
paper summarizes the latest SWAP developments and qualifications,
and presents the first light results.
---------------------------------------------------------
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
<BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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: Solar-blind UV detectors based on wide band gap semiconductors
Authors: Schuhle, Udo; Hochedez, Jean-Francois
2010ISSIR...9..429S Altcode:
Solid-state photon detectors based on semiconductors other than
silicon are not yet considered mature technology but their current
development opens new possibilities, also for space observations. Such
devices are especially attractive for ultraviolet radiation detection,
as semiconductor materials with band gaps larger than that of silicon
can be produced and used as "visible-blind" or "solar-blind" detectors
that are not affected by daylight. Here we evaluate the advantages
of such detectors compared to silicon-based devices and report on the
semiconductor detectors that have been fabricated in recent years with
materials having large band-gap energies. We describe the most common
pixel designs and characterize their general properties.
---------------------------------------------------------
Title: The Structure and Dynamics of the Upper Chromosphere and Lower
Transition Region as Revealed by the Subarcsecond VAULT Observations
Authors: Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.;
Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.;
Nestoras, I.
2010SoPh..261...53V Altcode: 2009arXiv0912.2272V
The Very high Angular resolution ULtraviolet Telescope (VAULT) is a
sounding rocket payload built to study the crucial interface between
the solar chromosphere and the corona by observing the strongest line
in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT
succeeded in obtaining the first ever subarcsecond ( 0.5\hbox{$^”$}
) images of this region with high sensitivity and cadence. Detailed
analyses of those observations contributed significantly to new
ideas about the nature of the transition region. Here, we present
a broad overview of the Ly α atmosphere as revealed by the VAULT
observations and bring together past results and new analyses from the
second VAULT flight to create a synthesis of our current knowledge
of the high-resolution Ly α Sun. We hope that this work will serve
as a good reference for the design of upcoming Ly α telescopes and
observing plans.
---------------------------------------------------------
Title: Intensified solid state sensor cameras: ICCD and IAPS
Authors: Schuhle, Udo
2010ISSIR...9..419S Altcode:
We describe the general design of intensified charge coupled devices
and intensified active pixel sensors: cameras using microchannel plate
intensifiers in combination with imaging arrays, like CCDs or CMOS-APS
sensors. Several design options are compared and the capabilities and
shortcomings of these devices will be highlighted and discussed. We
describe, in particular, the properties of the intensifiers, phosphor
anodes, and coupling schemes. The coupling between the intensifier
and the image sensor is a special technological step that adds to this
type of camera a great amount of flexibility and design options.
---------------------------------------------------------
Title: Pre-flight calibration of LYRA, the solar VUV radiometer on
board PROBA2
Authors: Benmoussa, A.; Dammasch, I. E.; Hochedez, J. -F.; Schühle,
U.; Koller, S.; Stockman, Y.; Scholze, F.; Richter, M.; Kroth, U.;
Laubis, C.; Dominique, M.; Kretzschmar, M.; Mekaoui, S.; Gissot, S.;
Theissen, A.; Giordanengo, B.; Bolsee, D.; Hermans, C.; Gillotay,
D.; Defise, J. -M.; Schmutz, W.
2009A&A...508.1085B Altcode:
Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet
(VUV) solar radiometer, planned to be launched in November 2009 on
the European Space Agency PROBA2, the Project for On-Board Autonomy
spacecraft.<BR /> Methods: The instrument was radiometrically
calibrated in the radiometry laboratory of the Physikalisch-Technische
Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton
radiation (BESSY II). The calibration was done using monochromatized
synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines
using reference detectors calibrated with the help of an electrical
substitution radiometer as the primary detector standard.<BR /> Results:
A total relative uncertainty of the radiometric calibration of the LYRA
instrument between 1% and 11% was achieved. LYRA will provide irradiance
data of the Sun in four UV passbands and with high temporal resolution
down to 10 ms. The present state of the LYRA pre-flight calibration
is presented as well as the expected instrument performance.<BR />
---------------------------------------------------------
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. <BR />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. <BR />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: 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. <BR
/>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. <BR />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. <BR />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: SWAP onboard PROBA2: An Innovative EUV Imager Designed for
Space Weather
Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.;
Schuehle, U.
2008ESPM...122.116D Altcode:
PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite
that is being prepared for launch in 2009. Its primary goal is the
demonstration of new technologies in the space environment. Furthermore,
the satellite carries an ambitious suite of both in-situ and
remote sensing instruments for monitoring space weather, despite
the modest onboard resources. Both the spacecraft and the remote
sensing instruments are mainly developed within Belgium. <P />One of
the main instruments, SWAP (Sun Watcher with APS detectors and image
Processing), is a compact EUV imager. It carries the first APS detector
with an EUV sensitive scintillator coating to be flown in orbit. In
addition to the new detector, the PROBA2/SWAP design is innovative
in the sense that the instrument will make heavy use of on-board data
processing and autonomous operations. These will range from automatic
off-pointing and tracking of appropriate solar events, to pre-downlink
data prioritisation, and feature and event recognition procedures. <P
/>We discuss the first results of the SWAP pre-flight calibration and
the strengths and weaknesses of the instrument [2]. With a narrow
spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an
image cadence of 1 min, its design is ideal for monitoring most CME
associated phenomena on the solar disk and close to the limb. <P />[1]
Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689,
66890S <P />[2] De Groof A., Berghmans D., Nicula B., et al. 2008,
Solar Phys. 249, 147-163
---------------------------------------------------------
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: CMOS-APS Detectors for Solar Physics: Lessons Learned during
the SWAP Preflight Calibration
Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.;
Defise, J. -M.; Thibert, T.; Schühle, U.
2008SoPh..249..147D Altcode: 2008SoPh..tmp...62D
CMOS-APS imaging detectors open new opportunities for remote sensing
in solar physics beyond what classical CCDs can provide, offering
far less power consumption, simpler electronics, better radiation
hardness, and the possibility of avoiding a mechanical shutter. The
SWAP telescope onboard the PROBA2 technology demonstration satellite
of the European Space Agency will be the first actual implementation
of a CMOS-APS detector for solar physics in orbit. One of the goals
of the SWAP project is precisely to acquire experience with the
CMOS-APS technology in a real-live space science context. Such a
precursor mission is essential in the preparation of missions such as
Solar Orbiter where the extra CMOS-APS functionalities will be hard
requirements. The current paper concentrates on specific CMOS-APS
issues that were identified during the SWAP preflight calibration
measurements. We will discuss the different readout possibilities that
the CMOS-APS detector of SWAP provides and their associated pros and
cons. In particular we describe the "image lag" effect, which results in
a contamination of each image with a remnant of the previous image. We
have characterised this effect for the specific SWAP implementation
and we conclude with a strategy on how to successfully circumvent the
problem and actually take benefit of it for solar monitoring.
---------------------------------------------------------
Title: Search for photospheric footpoints of quiet Sun transition
region loops
Authors: Sánchez Almeida, J.; Teriaca, L.; Sütterlin, P.; Spadaro,
D.; Schühle, U.; Rutten, R. J.
2007A&A...475.1101S Altcode: 2007arXiv0709.3451S
Context: The footpoints of quiet Sun Transition Region (TR) loops
do not seem to coincide with the photospheric magnetic structures
appearing in traditional low-sensitivity magnetograms. <BR />Aims: We
look for the so-far unidentified photospheric footpoints of TR loops
using G-band bright points (BPs) as proxies for photospheric magnetic
field concentrations. <BR />Methods: We compare TR measurements with
SoHO/SUMER and photospheric magnetic field observations obtained with
the Dutch Open Telescope. <BR />Results: Photospheric BPs are associated
with bright TR structures, but they seem to avoid the brightest parts
of the structure. BPs appear in regions that are globally redshifted,
but they avoid extreme velocities. TR explosive events are not clearly
associated with BPs. <BR />Conclusions: The observations are not
inconsistent with the BPs being footpoints of TR loops, although we
have not succeeded to uniquely identify particular BPs with specific
TR loops.
---------------------------------------------------------
Title: SWAP: a novel EUV telescope for space weather
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans,
David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat,
Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez,
Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank
2007SPIE.6689E..0SD Altcode: 2007SPIE.6689E..24D
The SWAP telescope (Sun Watcher using Active Pixel System detector and
Image Processing) is being developed to be part of the PROBA2 payload,
an ESA technological mission to be launched in early 2008. SWAP
is directly derived from the concept of the EIT telescope that we
developed in the '90s for the SOHO mission. Several major innovations
have been introduced in the design of the instrument in order to
be compliant with the requirements of the PROBA2 mini-satellite:
compactness with a new of-axis optical design, radiation resistance
with a new CMOS-APS detector, a very low power electronics, an athermal
opto-mechanical system, optimized onboard compression schemes combined
with prioritization of collected data, autonomy with automatic
triggering of observation and off-pointing procedures in case of
Solar event occurrence, ... All these new features result from the low
resource requirements (power, mass, telemetry) of the mini-satellite,
but also take advantage of the specificities of a modern technological
platform, such as quick pointing agility, new powerful on-board
processor, Packetwire interface and autonomous operations. These
new enhancements will greatly improve the operations of SWAP as
a space weather sentinel from a low Earth orbit while the downlink
capabilities are limited. This paper summarizes the conceptual design,
the development and the qualification of the instrument, the autonomous
operations and the expected performances for science exploitation.
---------------------------------------------------------
Title: Multi-wavelength Analysis of a Quiet Solar Region
Authors: Tsiropoula, G.; Tziotziou, K.; Giannikakis, J.; Young, P.;
Schühle, U.; Heinzel, P.
2007ASPC..368..171T Altcode: 2007arXiv0704.1592T
We present observations of a solar quiet region obtained by the
ground-based Dutch Open Telescope (DOT), and by instruments on the
spacecraft SOHO and TRACE. The observations were obtained during a
coordinated observing campaign on October 2005. The aim of this work
is to present the rich diversity of fine-scale structures that are
found at the network boundaries and their appearance in different
instruments and different spectral lines that span the photosphere
to the corona. Detailed studies of these structures are crucial to
understanding their dynamics in different solar layers, as well as
the role such structures play in the mass balance and heating of the
solar atmosphere.
---------------------------------------------------------
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: 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: Instrumental Approaches To Achieve The Measurements Required
For Exploring The Energetics, Dynamics A nd Fine-Scale Structure Of
The Sun's Magnetized Atmosphere
Authors: Schühle, U.
2007ESASP.641E..17S Altcode:
An overview is given about the technical implementation of the remote
sensing instrumentation of the Solar Orbiter mission. We will discuss
the "science implementation" related to the specific scientific goal
"Explore the energetics, dynamics and fine-scale structure of the
Sun's magnetized atmosphere". The technical approaches to implement the
observational scenarios outlined in the Science Requirements Document
(SRD) are reviewed. Some technical design options proposed for the
remote sensing instruments will be shown in detail and some open
technical issues are highlighted in regard to answering the question
"How do we achieve this goal?".
---------------------------------------------------------
Title: Optical Design Of The Extreme Ultraviolet Spectrometer (EUS)
On Board Solar Orbiter
Authors: Middleton, K.; Da Deppo, V.; Poletto, L.; Schühle, U.;
Thomas, R. J.; Young, P. R.
2007ESASP.641E..48M Altcode:
We present optical designs for the Extreme Ultraviolet Imaging
Spectrometer (EUS) proposed for Solar Orbiter. We summarise the
scientific requirements for EUS and show how they translate into an
instrument specification and optical design. Two design options are
presented: one utilising a normal incidence telescope and one utilising
a grazing incidence telescope. Both options use the same design of
spectrometer, which incorporates a Toroidal Varied Line-Space (TVLS)
grating, allowing high quality imaging at relatively large spectrometer
magnifications. This results in a very compact yet high performance
design. We give estimates of the instrument's optical performance and
throughput and discuss briefly some heat management strategies.
---------------------------------------------------------
Title: LYRA - a solar UV radiometer using diamond detectors
Authors: Theissen, A.; Benmoussa, A.; Schühle, U.; Hochedez, J. -F.;
Schmutz, W.
2007msfa.conf...27T Altcode:
LYRA, the Lyman-α radiometer, is a highcadence (100 Hz) solar
VUV radiometer which will measure diskintegrated irradiances in 4
wavelength channels. Special emphasis is given on novel detectors based
on diamond which will be tested for the first time in space. Two kinds
of detectors are employed: MSM and PiNtype detectors. Their particular
advantage compared to silicon detectors lies in their solar blindness
with a UV/visible reduction ratio of at least four orders of magnitude,
which simplifies the design of UV instruments.
---------------------------------------------------------
Title: S pace Qualification Of A Thin Wafer Lithium Niobate Etalon
For The Visible Light Imager And Magnetograph (Vim)
Authors: Schühle, U.; Mathew, S. K.; Wedemeier, M.; Hartwig, H.;
Ballesteros, E.; Martinez Pillet, V.; Solanki, S. K.
2007ESASP.641E..82S Altcode:
For the Visible Light Imager and Magnetograph (VIM) a high-resolution
filtergraph is under design. The system takes advantage of a lithium
niobate (LiNbO3) crystal which can be used as a scanning filter using
high voltage for tuning. We have undertaken first studies to qualify
a lithium niobate wafer of 70 mm aperture size for deployment and use
in space. We show the results of the mechanical mounting and vibration
and thermal cycling tests as well as stability tests under fast voltage
tuning in vacuum. Although these tests have all been very successful,
further environmental testing is necessary to fully space-qualify the
filter for the Solar Orbiter mission.
---------------------------------------------------------
Title: Solar Coronal Magnetic Field Mapper
Authors: Solanki, S. K.; Raouafi, N. -E.; Gandorfer, A.; Schühle,
U.; Lagg, A.
2006ESASP.617E.160S Altcode: 2006soho...17E.160S
No abstract at ADS
---------------------------------------------------------
Title: Hα Chromospheric Mottles and their UV/EUV Counterparts Seen
by SOHO/Sumer
Authors: Tziotziou, K.; Heinzel, P.; Tsiropoula, G.; Schühle, U.
2006ESASP.617E.112T Altcode: 2006soho...17E.112T
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: Prominence Parameters Derived from Hydrogen Lyman-α Spectral
Profiles Measured by SOHO/SUMER
Authors: Gunár, S.; Teriaca, L.; Heinzel, P.; Schühle, U.
2006ESASP.617E..63G Altcode: 2006soho...17E..63G
No abstract at ADS
---------------------------------------------------------
Title: LYRA, a solar UV radiometer on Proba2
Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.;
Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.;
Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.;
Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar,
M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.;
Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.;
Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen,
R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P.
2006AdSpR..37..303H Altcode:
LYRA is the solar UV radiometer that will embark in 2006 onboard
Proba2, a technologically oriented ESA micro-mission. LYRA is
designed and manufactured by a Belgian Swiss German consortium (ROB,
PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international
collaborations. It will monitor the solar irradiance in four UV
passbands. They have been chosen for their relevance to Solar Physics,
Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel,
(2) the 200 220 nm Herzberg continuum range, (3) the Aluminium
filter channel (17 70 nm) including He II at 30.4 nm and (4) the
Zirconium filter channel (1 20 nm). The radiometric calibration will
be traceable to synchrotron source standards (PTB and NIST). The
stability will be monitored by onboard calibration sources (LEDs),
which allow to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first space
assessment of a pioneering UV detectors program. Diamond sensors make
the instruments radiation-hard and solar-blind: their high bandgap
energy makes them insensitive to visible light and, therefore, make
dispensable visible light blocking filters, which seriously attenuate
the desired ultraviolet signal. Their elimination augments the effective
area and hence the signal-to-noise, therefore increasing the precision
and the cadence. The SWAP EUV imaging telescope will operate next to
LYRA on Proba2. Together, they will establish a high performance solar
monitor for operational space weather nowcasting and research. LYRA
demonstrates technologies important for future missions such as the
ESA Solar Orbiter.
---------------------------------------------------------
Title: SWAP onboard PROBA 2, a new EUV imager for solar monitoring
Authors: Berghmans, D.; Hochedez, J. F.; Defise, J. M.; Lecat, J. H.;
Nicula, B.; Slemzin, V.; Lawrence, G.; Katsyiannis, A. C.; van der
Linden, R.; Zhukov, A.; Clette, F.; Rochus, P.; Mazy, E.; Thibert,
T.; Nicolosi, P.; Pelizzo, M. -G.; Schühle, U.
2006AdSpR..38.1807B Altcode:
SWAP (Sun Watcher using Active Pixel system detector and image
processing) is a solar imager in the extreme ultraviolet (EUV)
that has been selected to fly in 2007 on the PROBA 2 technological
platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien
telescope equipped with an EUV enhanced active pixel sensor detector
(coated APS). This type of detector has advantages that promise to
be very profitable for solar EUV imaging. SWAP will provide solar
coronal images at a 1-min cadence in a bandpass centered on 17.5
nm. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or EIT-waves, associated with the
early phase of coronal mass ejections. Image processing software will
be developed that automatically detects these phenomena and sends out
space weather warnings. Together with its sister instrument LYRA, also
onboard PROBA 2, SWAP will serve as a high performance solar monitoring
tool to be used in operational space weather forecasting. The SWAP
data will complement the solar observations provided by instruments
like SOHO-EIT, and STEREO-SECCHI.
---------------------------------------------------------
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: 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: 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: SWAP: Sun watcher with a new EUV telescope on a technology
demonstration platform
Authors: Defise, Jean-Marc; Lecat, Jean-Hervé; Mazy, Emmanuel;
Rochus, Pierre; Rossi, Laurence; Thibert, Tanguy; Gillis, Jean-Marie;
Berghmans, David; Hochedez, Jean-François; Schühle, Udo
2004ESASP.554..257D Altcode: 2004icso.conf..257D
SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) is an instrument that has been selected to fly on the
PROBA-2 technology demonstration platform, a program of the European
Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis
degraded Ritchey Chretien telescope that will image the EUV solar
corona at 19.5 nm on a specifically fabricated extreme ultraviolet
(EUV) sensitivity enhanced CMOS APS detector. The optical design and
the optical coatings are derived from the Extreme Ultraviolet Imaging
Telescope (EIT) operating on-board SOHO since 1995. It has been adapted
for a single wavelength telescope with off-axis optics. It allows to
use smaller optics and filters, with simple internal baffles avoiding
external protruding parts. The superpolished optics will receive a
multilayer coating that provides spectral selection centred on 19.5
nm and EUV reflectivity in normal incidence. This compact design is
specifically adapted for accommodation on PROBA-2, where mass and
envelope requirements are very stringent The SWAP PROBA-2 program will
be an opportunity to demonstrate this new optical concept, while it
will also validate space remote sensing with APS detectors, as well as
on-board image processing capabilities. On the science outcomes, SWAP
will provide solar corona images in the Fe XII line on a baselined 2-min
cadence. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or 'EIT-waves', associated with the
early phase of coronal mass ejections. The SWAP data will complement
the observations provided by SOHO-EIT, and STEREO-SECCHI.
---------------------------------------------------------
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. <P />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. <P />Appendix A is
only available in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: Development of imaging arrays for solar UV observations based
on wide band gap materials
Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis;
Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul;
Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock,
Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex,
Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos;
Omnes, Franck; John, Joachim; Van Hoof, Chris
2004SPIE.5171..231S Altcode:
Solar ultraviolet imaging instruments in space pose most demanding
requirements on their detectors in terms of dynamic range, low noise,
high speed, and high resolution. Yet UV detectors used on missions
presently in space have major drawbacks limiting their performance
and stability. In view of future solar space missions we have started
the development of new imaging array devices based on wide band gap
materials (WBGM), for which the expected benefits of the new sensors -
primarily visible blindness and radiation hardness - will be highly
valuable. Within this initiative, called "Blind to Optical Light
Detectors (BOLD)", we have investigated devices made of AlGa-nitrides
and diamond. We present results of the responsivity measurements
extending from the visible down to extreme UV wavelengths. We discuss
the possible benefits of these new devices and point out ways to build
new imaging arrays for future space missions.
---------------------------------------------------------
Title: SWAP: Sun watcher using APS detector on-board PROBA-2, a new
EUV off-axis telescope on a technology demonstration platform
Authors: Defise, Jean-Marc; Berghmans, David; Hochedez, Jean-Francois
E.; Lecat, Jean-Herve M.; Mazy, Emmanuel; Rochus, Pierre L.; Thibert,
Tanguy; Nicolosi, Piergiorgio; Pelizzo, Maria G.; Schuehle, Udo H.;
Van der Linden, Ronald A. M.; Zhukov, Andrei N.
2004SPIE.5171..143D Altcode:
SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) is an instrument that has been selected to fly on the
PROBA-II technology demonstration platform, a program of the European
Space Agency (ESA) to be launched in 2006. This paper presents the
instrument concept and its scientific goals. SWAP uses an off-axis
Ritchey Chretien telescope that will image the EUV solar corona at 19.5
nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity
enhanced CMOS APS detector. This type of detector has advantages that
promise to be very profitable for solar EUV imaging. The SWAP design
is built on a similar concept as the MAGRITTE instrument suite for
the NASA Solar Dynamics Observatory (SDO) mission to be launched in
2007. The optics have been adapted to the detector size. The SWAP
PROBA-2 program will be an opportunity to demonstrate and validate
the optical concept of MAGRITTE, while it will also validate space
remote sensing with APS detectors. On the science outcomes, SWAP will
provide solar corona images in the Fe XII line on a baselined 1-min
cadence. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or 'EIT-waves", associated with the
early phase of coronal mass ejections. Image recognition software will
be developed that automatically detects these phenomena and sends out
space weather warnings. Different modules of this software will run
both on the ground system as well as on the onboard computer of PROBA
II. The SWAP data will complement the observations provided by SOHO-EIT,
and STEREO-SECCHI.
---------------------------------------------------------
Title: MAGRITTE: an instrument suite for the solar atmospheric
imaging assembly (AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, Pierre L.; Defise, Jean-Marc; Halain, Jean-Philippe;
Jamar, Claude A. J.; Mazy, Emmanuel; Rossi, Laurence; Thibert,
Tanguy; Clette, Frederic; Cugnon, Pierre; Berghmans, David; Hochedez,
Jean-Francois E.; Delaboudiniere, Jean-Pierre; Auchere, Frederic;
Mercier, Raymond; Ravet, Marie-Francoise; Delmotte, Franck; Idir,
Mourad; Schuehle, Udo H.; Bothmer, Volker; Fineschi, Silvano; Howard,
Russell A.; Moses, John D.; Newmark, Jeffrey S.
2004SPIE.5171...53R Altcode:
The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics
Observatory will characterize the dynamical evolution of the solar
plasma from the chromosphere to the corona, and will follow the
connection of plasma dynamics with magnetic activity throughout the
solar atmosphere. The AIA consists of 7 high-resolution imaging
telescopes in the following spectral bandpasses: 1215Å. Ly-a,
304 Å He II, 629 Å OV, 465 Å Ne VII, 195 Å Fe XII (includes Fe
XXIV), 284 Å Fe XV, and 335 Å Fe XVI. The telescopes are grouped
by instrumental approach: the MAGRITTE Filtergraphs (R. MAGRITTE,
famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
channels with bandpasses ranging from 195 to 1216 Å, and the SPECTRE
Spectroheliograph with one soft-EUV channel at OV 629 Å. They will be
simultaneously operated with a 10-second imaging cadence. These two
instruments, the electronic boxes and two redundant Guide Telescopes
(GT) constitute the AIA suite. They will be mounted and coaligned on a
dedicated common optical bench. The GTs will provide pointing jitter
information to the whole SHARPP assembly. This paper presents the
selected technologies, the different challenges, the trade-offs to be
made in phase A, and the model philosophy. From a scientific viewpoint,
the unique combination high temporal and spatial resolutions with the
simultaneous multi-channel capability will allow MAGRITTE / SPECTRE
to explore new domains in the dynamics of the solar atmosphere, in
particular the fast small-scale phenomena. We show how the spectral
channels of the different instruments were derived to fulfill the
AIA scientific objectives, and we outline how this imager array will
address key science issues, like the transition region and coronal waves
or flare precursors, in coordination with other SDO experiments. We
finally describe the real-time solar monitoring products that will be
made available for space-weather forecasting applications.
---------------------------------------------------------
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: Calibration of space instrumentation with synchrotron radiation
Authors: Richter, M.; Gottwald, A.; Scholze, F.; Schühle, U.; Ulm, G.
2004cosp...35.1938R Altcode: 2004cosp.meet.1938R
The Physikalisch-Technische Bundesanstalt (PTB) is Germany's national
metrology institute providing scientific and technical services. For
more than 20 years, PTB has used synchrotron radiation at the electron
storage rings BESSY I and BESSY II for photon metrology in the
spectral range from UV radiation to X-rays, e.g. for the calibration
of radiation sources, detectors, and spectrometers as well as for
the characterization of optical components. Most of the measurements
are based on two different primary standards, electron storage
rings as primary radiation source standards and cryogenic electrical
substitution radiometers as primary detector standards. Many activities
are related to radiometric calibrations of space-based instruments for
extraterrestrial, solar, and astronomical missions. Outstanding examples
have been the calibration of the SUMER and CDS spectrographs of the
SOHO mission, X-ray detector calibrations for the X-ray observatories
Chandra and XMM-Newton, and the calibration of Lyman-alpha detectors
for the NASA satellites TWINS. This contribution presents examples from
recent work, in particular within the framework of the ESA projects
PROBA 2 and Solar Orbiter.
---------------------------------------------------------
Title: Solar-Blind Diamond Detectors for Lyra, the Solar VUV
Radiometer on Board Proba II
Authors: Benmoussa, A.; Hochedez, J. -F.; Schmutz, W. K.; Schühle,
U.; Nesládek, M.; Stockman, Y.; Kroth, U.; Richter, M.; Theissen,
A.; Remes, Z.; Haenen, K.; Mortet, V.; Koller, S.; Halain, J. P.;
Petersen, R.; Dominique, M.; D'Olieslaeger, M.
2003ExA....16..141B Altcode:
Fabrication, packaging and experimental results on the calibration
of metal-semiconductor-metal (MSM) photodetectors made on diamond
are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use
diamond detectors for the first time in space for a solar physics
instrument. A set of measurement campaigns was designed to obtain the
XUV-to-VIS responsivity of the devices and other characterizations. The
measurements of responsivity in EUV and VUV spectral ranges (40 240
nm) have been carried out by the Physkalisch-Technische Bundesanstalt
(PTB) in Germany at the electron storage ring BESSY II. The longer
wavelength range from 210 to 1127 nm was measured with monochromatic
light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a
photoresponse which lie in the 35 65 mA/W range at 200 nm (corresponding
to an external quantum efficiency of 20 40%) and indicate a visible
rejection ratio (200 500 nm) higher than four orders of magnitude.
---------------------------------------------------------
Title: Cleanliness and calibration stability of UV instruments on SOHO
Authors: Schuehle, Udo H.
2003SPIE.4853...88S Altcode:
Optical instruments for solar observations from space have in the past
suffered from degradation of responsivity caused by contamination from
various materials used in spacecraft and instrument construction. This
was particularly detrimental in the ultraviolet range of the spectrum
where the solar irradiance is weak, compared to the visible, yet strong
enough to cause polymerization of organic contaminants on optical
surfaces that are continuously exposed. The Solar and Heliospheric
Observatory (SOHO) mission could largely avoid such effects. Material
selection and special design features of instruments and spacecraft
contributed mostly to this success. The various kinds of remote sensing
instruments on SOHO have achieved a stability of their responsivity
through special cleanliness requirements. This contribution will
highlight those design aspects which are generally useful for future
solar missions. Analysis of instrument responsivity data shows that
under these circumstances the stability was actually not limited
by contamination but by the instabilities inherent to the present
detector technology.
---------------------------------------------------------
Title: Intercalibration of SUMER and CDS on SOHO. III. SUMER and
CDS-GIS
Authors: Pauluhn, Anuschka; Lang, Jim; Breeveld, Eddie R.; Solanki,
Sami K.; Schühle, Udo
2003ApOpt..42..657P Altcode:
Simultaneous observation of the same solar sources with different
instruments is one way to test prelaunch radiometric calibrations and
to detect changes in responsivity with time of extreme-ultraviolet
instruments in space. Here we present the results of intercalibration
of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
spectrometer (detectors A and B) and the GIS (Grazing Incidence
Spectrometer), one of two spectrometers that compose the CDS (Coronal
Diagnostic Spectrometer) on the Solar and Heliospheric Observatory
(SOHO). The two instruments observed simultaneously radiances of
emission lines at or near the center of the solar disk. The emission
line chosen for intercomparison was Ne viii at 770 Å. However,
such an intercomparison of the SUMER and CDS-GIS measurements means
comparing two data sets with large differences in resolution and field
of view. The latter difference, especially, introduces differences
in the measured intensities caused by the solar variability that is
relatively strong in the 770- Å line. Using a statistical approach to
overcome this problem, we found that the ratio of the GIS to the SUMER
average radiances amounted to 2.6 +/- 0.9 before the SOHO ’s loss of
attitude and to 2.1 +/- 0.7 afterward. These findings confirm earlier
estimates of the GIS ’s responsivity being too low, and an update
of the GIS calibration is recommended. Despite the large differences
in resolution and field of view of the two instruments, the shapes of
their normalized and rescaled histograms of the radiances agree well
and therefore represent characteristic features of the Ne viii line.
---------------------------------------------------------
Title: New UV detectors for solar observations
Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.;
Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.;
Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.;
Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider,
Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.;
Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock,
Anthony J.; Van Hoof, Chris A.
2003SPIE.4853..419H Altcode:
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide bandgap
materials (in particular diamond and Al-Ga-nitrides). The investigation
is proposed in view of the Solar Orbiter (S.O.) UV instruments, for
which the expected benefits of the new sensors -primarily visible
blindness and radiation hardness- will be highly valuable. Despite
various advances in the technology of imaging detectors over the last
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations inherent to their actual material
and technology. Yet, the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will be decisive for
the forthcoming solar space missions. The advent of imagers based on
wide-bandgap materials will permit new observations and, by simplifying
their design, cheaper instruments. As for the Solar Orbiter, the
aspiration for wide-bandgap material (WBGM) based UV detectors is still
more sensible because the spacecraft will approach the Sun where the
heat and the radiation fluxes are high. We describe the motivations,
and present the program to achieve revolutionary flight cameras within
the Solar Orbiter schedule as well as relevant UV measurements.
---------------------------------------------------------
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: Preface (SOLMAG 2002)
Authors: Tsiropoula, Georgia; Schühle, Udo
2002ESASP.505D..13T Altcode: 2002IAUCo.188D..13T; 2002solm.confD..13T
No abstract at ADS
---------------------------------------------------------
Title: Intercalibration of CDS and SUMER
Authors: Pauluhn, A.; Lang, J.; Schühle, U.; Solanki, S. K.; Wilhelm,
K.; Pike, C. D.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber,
M. C. E.
2002ESASP.508..223P Altcode: 2002soho...11..223P
The outcome of the Joint Observing Programme (JOP) Intercal-01, which
is the intercalibration of the SUMER (Solar Ultraviolet Measurements
of Emitted Radiation) instrument (detectors A and B) and the two CDS
(Coronal Diagnostic Spectrometer) instruments, the Normal Incidence
Spectrometer (NIS) and the Grazing Incidence Spectrometer (GIS),
is presented. Recent calibration updates of both instruments have
been employed, and the results indicate a very good correlation and
agreement of the measured radiances within the individual uncertainties.
---------------------------------------------------------
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: 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: The Solar Orbiter Mission and Design Recommendations
Authors: Schuhle, U.; Thomas, R.; Hochedez, J. -F.
2002ISSIR...2..361S Altcode: 2002ESASR...2..361S; 2002rcs..conf..361S
A short overview is given of the Solar Orbiter mission. First, the key
scientific aims of the mission are briefly described. As the mission
profile has consequences on the design of the payload instruments
and their calibration, the mission design is described. Possible
implications and problems for the cleanliness and the calibration
stability of the instruments are outlined. Some solutions are discussed.
---------------------------------------------------------
Title: Intercalibration of CDS and SUMER
Authors: Pauluhn, A.; Lang, J.; Schuhle, U.; Solanki, S. K.; Wilhelm,
K.; Thompson, W. T.; Pike, C. D.; Ruedi, I.; Hollandt, J.; Huber,
M. C. E.
2002ISSIR...2..235P Altcode: 2002rcs..conf..235P; 2002ESASR...2..235P
Simultaneous observations of the same solar features with different
instruments provide a way to compare radiometric calibrations and
detect changes in responsivity with time of EUV instruments in space
within the combined uncertainties of the individual instruments. Here
we present the intercalibration of the SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) instrument (detectors A and B) and
the two CDS (Coronal Diagnostic Spectrometer) instruments, the Normal
Incidence Spectrometer (NIS) and the Grazing Incidence Spectrometer
(GIS) on the Solar and Heliospheric Observatory (SOHO). This work
describes the results of the Joint Observing Programme Intercal 01
and presents quiet-Sun comparisons from March 1996 up to February
2001, which represents the complete set of all available Intercal
01 measurements. Recent calibration updates of both instruments are
employed, and the results indicate a very good correlation and agreement
of the measured radiances within the combined uncertainties.
---------------------------------------------------------
Title: Properties of ultraviolet lines observed with the Coronal
Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Pike, C. D.; Schühle, U.;
Rüedi, I.; Pauluhn, A.; Brković, A.
2002A&A...381..653S Altcode:
We present an analysis of 14 ultraviolet emission lines belonging to
different atoms and ions observed inside polar coronal holes and in
the normal quiet Sun. The observations were made with the Coronal
Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric
Observatory (SOHO). This study extends previous investigations made
with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
spectrometer to higher temperatures. We compare line intensities,
shifts and widths in coronal holes with the corresponding values
obtained in the quiet Sun. While all lines formed at temperatures above
7 x 10<SUP>5</SUP> K show clearly the presence of the hole in their
intensities, differences in line width are more subtle, with cooler
lines being broader in coronal holes, while hotter lines tend to be
narrower. According to the present data all lines are blueshifted inside
the coronal hole compared to the normal quiet Sun. Almost all the lines
formed between 80 000 K and 600 000 K (i.e. transition-region lines)
show a correlation between blueshifts and brightness within coronal
holes. This is in agreement with the conclusion reached by Hassler et
al. (\cite{Hassler1999}) that the fast solar wind emanates from the
network and supports our previous study (Stucki et al. 2000b). For
coronal lines, this trend seems to be reversed.
---------------------------------------------------------
Title: New UV Detector Concepts
Authors: Hochedez, J. -F.; Schuhle, U.; Lemaire, P.
2002ISSIR...2..371H Altcode: 2002rcs..conf..371H; 2002ESASR...2..371H
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide-bandgap
semiconductor materials (in particular diamond and Al-Ganitrides). This
investigation is proposed in view of the Solar Orbiter UV instruments,
for which the expected benefits of the new sensors, visible blindness
and radiation hardness, will be highly valuable. Despite various
advances in the technology of imaging detectors over the last few
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations which are inherent to their actual material
and technology. Yet the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will all be decisive for
forthcoming solar space missions. The advent of imagers made of large
wide-bandgap semiconductors would surmount many present weaknesses. This
would open up new scientific prospects and, by simplifying their design,
would even make the instruments cheaper. As for the Solar Orbiter,
the aspiration for wide-bandgap semiconductor-based UV detectors is
still more desirable because the spacecraft will approach the Sun
where heat and radiation fluxes are high. We describe the motivations
leading to such new developments, and present a programme to achieve
revolutionary flight cameras within the Solar Orbiter schedule.
---------------------------------------------------------
Title: Intercalibration of SUMER and CDS on SOHO. II. SUMER detectors
A and B and CDS NIS
Authors: Pauluhn, Anuschka; Rüedi, Isabelle; Solanki, Sami K.;
Schühle, Udo; Wilhelm, Klaus; Lang, Jim; Thompson, William T.;
Hollandt, Jörg
2001ApOpt..40.6292P Altcode:
Results of an intercalibration between the extreme-ultraviolet
spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar
Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar
and Heliospheric Observatory (SOHO) are reported. The results of the
joint observing program Intercal_01 are described, and intercalibration
results up to July 2000 of both SUMER detectors A and B and of the
CDS Normal Incidence Spectrometer (NIS) are presented. The instruments
simultaneously observed radiance of emission lines at the center of the
Sun, and three lines have been chosen for intercomparison: He I 584 Å,
Mg X 609 Å, and Mg X 624 Å. Initially the same area was observed by
both instruments, but, after restrictions were imposed by the scanning
mechanism of SUMER in November 1996, the instruments viewed areas of
different sizes. Nevertheless, the temporal correlation between the
two instruments remained good through June 1998, when contact with
the SOHO spacecraft was lost. Until then the CDS instrument measured
(33+/-5)% and (38+/-7)% (+/-1σ) higher intensity than SUMER in the
Hz I 584-Å line on average for detectors A and B, respectively. Data
from SUMER detector B agreed well for Mg X 609 Å and Mg X 624 Å
with the CDS intensities, showing offsets of (2+/-10)% and (9+/-15)%,
much less than the data of detector A with offsets of (7+/-8)% and
(16+/-7)% for the two lines, respectively, relative to CDS. Finally,
the intercalibration measurements after the loss and recovery of the
SOHO spacecraft are analyzed. The data for observations from November
1998 to July 2000 are compared, and it is shown that, although the
responses of the instruments have changed, the CDS and the SUMER still
perform well, and their temporal correlation is good.
---------------------------------------------------------
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 10<SUP>3</SUP> K to 2 10<SUP>6</SUP> 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:
T<SUB>e</SUB><3 10<SUP>5</SUP> b: T<SUB>e</SUB>~3 10<SUP>5</SUP> c:
T<SUB>e</SUB>~4 10<SUP>5</SUP> d: 6 10<SUP>5</SUP><T<SUB>e</SUB>
<9 10<SUP>5</SUP> e: T<SUB>e</SUB>~1.4 10<SUP>6</SUP> f:
T<SUB>e</SUB>~1.8 10<SUP>6</SUP>). The vertical axes are scaled
to spectral radiance in units of mW sr<SUP>-1</SUP> m<SUP>-2</SUP>
Å<SUP>-1</SUP> 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: Wide bandgap EUV and VUV imagers for the Solar Orbiter
Authors: Hochedez, Jean-François; Lemaire, Philippe; Pace, Emanuele;
Schühle, Udo; Verwichte, Erwin
2001ESASP.493..245H Altcode: 2001sefs.work..245H
No abstract at ADS
---------------------------------------------------------
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.
2001A&A...375..591C Altcode:
A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of
the Sun between 670 Å and 1609 Å in the first order of diffraction
has been derived from observations obtained with the SUMER (Solar
Ultraviolet Measurements of Emitted Radiation) spectrograph on the
spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains
spectra of the average quiet Sun, a coronal hole and a sunspot on the
disk. Different physical parameters prevalent in the bright network (BN)
and in the cell interior (CI) - contributing in a distinct manner to
the average quiet-Sun emission - have their imprint on the BN/CI ratio,
which is also shown for almost the entire spectral range. With a few
exceptions, all major lines are given with their identifications and
wavelengths. Lines that appear in second order are superimposed on the
first order spectra. These lines are clearly marked in the atlas. The
spectra include emissions from atoms and ions in the temperature range
6*E<SUP>3</SUP> K to 2*E<SUP>6</SUP> K, i.e., continua and emission
lines emitted from the lower chromosphere to the corona. This spectral
atlas, with its broad wavelength coverage, provides a rich source of new
diagnostic tools to study the physical parameters in the chromosphere,
the transition region and the corona. In particular, the wavelength
range below 1100 Å as observed by SUMER represents a significant
improvement over the spectra produced in the past. In view of the
manifold appearance and temporal variation of the solar atmosphere,
it is obvious that our atlas can only be a - hopefully typical -
snapshot. Brief descriptions of the data reduction and calibration
procedures are given. The spectral radiances are determined with a
relative uncertainty of 0.15 to 0.30 (1sigma ) and the wavelength
scale is accurate to typically 10 mÅ. The atlas is also available
in a machine readable form. Table A.1 is only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/591
---------------------------------------------------------
Title: VizieR Online Data Catalog: SUMER Spectral Atlas of Solar
Disk Features (Curdt+, 2001)
Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi,
B. N.; Schuhle, U.; Lemaire, P.
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, L<SUP>peak</SUP>, in
mW/(sr*m<SUP>2</SUP>*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: Comparison of quiet-Sun radiances measured by CDS and SUMER
on SOHO
Authors: Pauluhn, A.; Solanki, S. K.; Schühle, U.; Wilhelm, K.;
Lang, J.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber, M. C. E.
2001SSRv...97...63P Altcode:
Since the beginning of the SOHO (Solar and Heliospheric Observatory)
mission an intercalibration programme was carried out which included
simultaneous observations of the EUV instruments CDS (Coronal Diagnostic
Spectrometer) and SUMER (Solar Ultraviolet Measurements of Emitted
Radiation) of common targets on the quiet Sun. The observations in the
chromospheric line of He i (584 Å) and the two coronal lines of Mg x
(609 Å and 624 Å) thus cover the long period of 4 years and provide a
data set highly suitable not only for instrumental comparison but also
for studies of the quiet Sun's long term variability. Up to the SOHO
accident, both instruments show a very good temporal correlation and
stability. Even after the loss and recovery of the spacecraft, when
the instruments had been exposed to extreme temperature conditions,
the performance of the CDS and SUMER instruments is still good, as is
the temporal correlation. However, the ratio between the efficiencies
of the two instruments, which remained constant with time until the
SOHO accident seems to have changed afterwards. In the coronal lines
both instruments show an increase of average radiances towards the
solar maximum.
---------------------------------------------------------
Title: Statistical Features of the Quiet Sun in EUV
Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.;
Schühle, U.
2001IAUS..203..416P Altcode:
The frequency distribution of the extreme ultraviolet (EUV) intensities
in the quiet Sun has in the past usually been modelled using two
Gaussians. Here we test this and other distribution functions against
observed distributions with exceptional statistics. The data were
obtained in a number of spectral lines observed with two extreme
ultraviolet spectrometers, CDS (Coronal Diagnostic Spectrometer)
and SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on
board the Solar and Heliospheric Observatory (SOHO). We show that the
frequency distribution of the radiance is best modelled by a lognormal
distribution or by a sum of a lognormal and a Gaussian. The fact that
the radiance distribution of the quiet Sun including the network and
the intranetwork is better reproduced by a single lognormal distribution
function than by two Gaussians suggests that the same heating processes
are acting in both types of features. The shape of the distribution
function shows a clear temperature dependence.
---------------------------------------------------------
Title: Properties of Solar Polar Coronal Hole Plasmas Observed above
the Limb
Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Schühle, U.;
Wilhelm, K.
2001ApJ...546..559D Altcode:
We determine the line-of-sight emission measure distribution and
nonthermal motions as a function of height above the limb in the
north and south polar coronal holes. These quantities are derived from
extreme-ultraviolet (EUV) spectra obtained from the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) spectrometer on the Solar
and Heliospheric Observatory (SOHO) spacecraft. The SUMER slit was
oriented along the north-south direction for all the observations,
and the spatial resolution is about 1". The spectra were obtained
from a number of different types of observations in 1996. We select
a group of emission lines for analysis for which, under the usual
assumption of ionization equilibrium, the maximum emissivities span
the temperature range from about 3×10<SUP>5</SUP> K up to about
1.1×10<SUP>6</SUP> K. We compare our results with recently published
similar observations of a west limb quiet-Sun streamer region, with
other coronal hole results based on SUMER spectra, and with earlier
observations of the quiet Sun and coronal holes obtained from Skylab
and rocket spectra. We find that the electron temperature in the polar
holes increases with height above the limb, that the emission measure
distribution of plasma located at line-of-sight heights less than
about 60" peaks at a temperature of about 9×10<SUP>5</SUP> K, and that
nonthermal motions sometimes, but not always, increase slightly with
height above the limb. When observed, these increases level off above
the limb at about 120". We speculate that the increases with height
above the limb may be a manifestation of the fast solar wind. They
may also be due to the reduction in transition region structures with
increasing limb height. We also discuss wave heating as a cause of
the line width increases.
---------------------------------------------------------
Title: Radiance of Solar Spectral Lines observed with CDS and SUMER
on SOHO (CD-ROM Directory: contribs/pauluhn)
Authors: Pauluhn, A.; Schühle, U.; Solanki, S. K.; Rüedi, I.; Lang,
J.; Pike, C. D.; Thompson, W. T.; Huber, M. C. E.
2001ASPC..223..721P Altcode: 2001csss...11..721P
No abstract at ADS
---------------------------------------------------------
Title: Comparison of far-ultraviolet emission lines formed in coronal
holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I.; Wilhelm,
K.; Stenflo, J. O.; Brković, A.; Huber, M. C. E.
2000A&A...363.1145S Altcode:
We present an analysis of 26 far-ultraviolet emission lines belonging
to 19 atoms and ions observed on both sides of the boundary of polar
coronal holes as well as other quiet Sun areas along the limb. The
observations were made with the SUMER instrument (Solar Ultraviolet
Measurements of Emitted Radiation) onboard the Solar and Heliospheric
Observatory (SOHO). We compare line intensities, shifts and widths
in coronal holes with the corresponding values obtained in the quiet
Sun. We find that with increasing formation temperature, spectral
lines show on average an increasingly stronger blueshift in coronal
holes relative to the quiet Sun at equal heliospheric angle, with the
coolest lines in our sample (formation temperature ~ 10<SUP>4</SUP>
K) indicating a small relative redshift. With respect to the rest
wavelength, however, only lines formed above 5 * 10<SUP>5</SUP> K
show blueshifts in coronal holes, which is not very different from
the quiet Sun. The width of the lines is generally larger (by a few
kilometers per second) inside the coronal hole. Intensity measurements
clearly show the presence of the coronal hole in Ne VIII lines as well
as in Fe XII, and provide evidence for a slightly enhanced emission
in polar coronal holes for lines formed below 10<SUP>5</SUP> K. This
last result is, however, less certain than the rest due to relatively
poor statistics. Intensity histograms also exhibit distinct differences
between coronal hole and quiet-Sun data. For cooler chromospheric lines,
such as Ni II, the coronal holes display a greater spread in intensities
than the quiet Sun. Transition-region lines, e.g. O IV, do not reveal
such differences, while Ne VIII shows characteristics of a coronal line
with lower average intensity and lower intensity spread inside holes.
---------------------------------------------------------
Title: Statistics of quiet Sun extreme ultraviolet intensities
Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.;
Schühle, U.
2000A&A...362..737P Altcode:
The frequency distribution of the extreme ultraviolet (EUV) emission
line intensities in the quiet Sun has in the past often been modelled
using two Gaussians. This gives adequate fits to observed distributions
of average statistical significance. In this paper we test this
and other distribution functions against observed distributions with
exceptional statistical significance. The data were obtained in a number
of spectral lines observed with two extreme ultraviolet spectrometers
on board the Solar and Heliospheric Observatory (SOHO). In this way,
the influence of spatial resolution and other instrument-specific
parameters can be identified. The observations span a period of
more than two years and provide a very large data set of radiance
measurements of the quiet Sun at or near solar disk centre. We show
that the frequency distribution of the radiance is best modelled by
a lognormal distribution. The fact that the radiance distribution of
the quiet Sun including the network and the intranetwork is better
reproduced by a single lognormal distribution function than by two
Gaussians suggests that the same heating processes are acting in both
types of features. The parameters of the lognormal fit show a clear
temperature dependence, with the transition region lines exhibiting the
largest skewness of the distribution and the chromospheric intensity
distributions being the most symmetric.
---------------------------------------------------------
Title: On the relationship between shift and intensity of ultraviolet
lines in coronal holes and the quiet Sun
Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I.
2000A&A...362L..49S Altcode:
We study the relationship between wavelength shifts and intensities
of chromospheric, transition-region and coronal ultraviolet emission
lines in polar coronal holes and in the normal quiet Sun using SUMER
data. Within coronal holes almost all the lines showing the network
and formed above 30 000 K show a correlation between blueshifts
and brightness. This extends and supports the conclusion reached
by Hassler et al. (1999) that the fast solar wind emanates from the
network. In the normal quiet Sun, however, we find that only lines
formed above 2-3 * 10<SUP>5</SUP> K show such a trend, the cooler
lines being more redshifted in the network. This suggests that either
there is a fundamental difference in the initial acceleration of
the solar wind in coronal holes and the normal quiet Sun, or that
the wavelength-shift versus brightness relationship in the quiet Sun
stems from other processes or structures (loops) than in coronal holes
(open field lines).
---------------------------------------------------------
Title: Radiance variations of the quiet Sun at far-ultraviolet
wavelengths
Authors: Schühle, U.; Wilhelm, K.; Hollandt, J.; Lemaire, P.;
Pauluhn, A.
2000A&A...354L..71S Altcode:
We have measured the radiance of quiet-Sun areas at the centre of the
solar disk using the vacuum-ultraviolet telescope-spectrograph SUMER
(Solar Ultraviolet Measurements of Emitted Radiation) on the Solar and
Heliospheric Observatory (SOHO). The radiances of selected emission
lines have been measured from March 1996 to the present. The lines that
have been observed regularly since the beginning of the SOHO mission
are He i 584 Å, Mg x 609 Å and 624 Å, Ne viii 770 Å, N v 1238 Å,
and the H i Lyman continuum at 880 Å. We investigate the variability
of these emission lines during the solar minimum and the ascending
phase of the present solar activity cycle. The transition region and
coronal lines show an increasing trend of up to 100% since the sunspot
minimum. The results are important for models of solar VUV variability
on the basis of radiance contrast ratios of solar disk regions. Our
spatially resolved images allow a separation of the network and cell
areas of the quiet-Sun. Both regimes show similar variations.
---------------------------------------------------------
Title: Mid-term Radiance Variation of Far-Ultraviolet Emission Lines
from Quiet-Sun Areas
Authors: Schühle, U.; Hollandt, Jorg; Pauluhn, Anuschka; Wilhelm,
Klaus
2000ESASP.463..427S Altcode: 2000sctc.proc..427S
No abstract at ADS
---------------------------------------------------------
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: Comparison of Transient Network Brightenings and Explosive
Events in the Solar Transition Region
Authors: Chae, Jongchul; Wang, Haimin; Goode, Philip R.; Fludra,
Andrzej; Schühle, Udo
2000ApJ...528L.119C Altcode:
The relation between transient network brightenings, known as blinkers,
and explosive events is examined based on coordinated quiet Sun
observations in the transition region line O V λ630 recorded by
the Coronal Diagnostic Spectrometer (CDS), in the transition region
line Si IV λ1402 recorded by the Solar Ultraviolet Measurements of
Emitted Radiation (SUMER) instrument, and in photospheric magnetograms
taken by the Big Bear Solar Observatory videomagnetograph. From these
observations, we find that (1) explosive events, which are traditionally
defined as features with very broad UV line profiles, tend to keep
away from the centers of network brightenings and are mostly located
at the edges of such brightenings, (2) CDS blinkers consist of many
small-scale, short-lived SUMER “unit brightening events” with a
size of a few arcseconds and a lifetime of a few minutes, and most
importantly (3) each SUMER unit brightening event is characterized by
a UV line profile that is not as broad as those of explosive events,
but still has significantly enhanced wings. Our results imply that,
like explosive events, individual unit brightening events involve high
velocities, and, hence, blinkers may have the same physical origin
as explosive events. It is likely that transient network brightenings
and explosive events are both due to magnetic reconnection--but with
different magnetic geometries.
---------------------------------------------------------
Title: Radiance Variations of Vacuum-Ultraviolet Emission Lines of
the Quiet Sun Observed with SUMER on SOHO
Authors: Schuhle, U.; Pauluhn, A.; Hollandt, J.; Lemaire, P.;
Wilhelm, K.
2000PCEC...25..429S Altcode:
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: Dynamics of Chromiospheric and Transition Region Lines Observed
with SOHO/SUMER and the GCT/Tenerife
Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing,
B. H.; Wilhelm, K.
2000AdSpR..25.1731M Altcode:
High-resolution spectroscopic observations of the quiet Sun have been
carried out in September 1996 at the German Gregory Coudé Telescope
(GCT) in Tenerife and in May 1997 with the SUMER instrument onboard
SOHO. Time sequences of spectra in the visible and near infrared
as well as in the ultraviolet have been taken, covering a range of
heights from the solar photosphere up into the transition region. In
this contribution we present the dynamical behaviour observed at the
various heights in the solar atmosphere
---------------------------------------------------------
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: 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: 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: Relationship between Line Shift and Intensity Inside Coronal
Holes
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Schüehle, U.
1999ESASP.446..633S Altcode: 1999soho....8..633S
We analyse SUMER spectra of a group of lines belonging to chromospheric,
transition region and coronal ions obtained on both sides of the
boundary of polar coronal holes as well as at other locations along the
limb. We study the relationship between line shifts and intensities in
coronal holes and compare to values obtained in the quiet Sun. We find
that within coronal holes, a trend can be detected in some transition
region lines, like O V and N V, in the sense that the lines are more
strongly blueshifted in brighter regions. This is in agreement with
the conclusion reached by Hassler et al. (1999, Science 283, 810-813)
that the fast solar wind emanates from the network. Furthermore,
a correlation of line shifts of ions formed at higher temperatures
(Ne VIII, Fe XII) with intensities of lines showing network structures
(Si I, N III) is presented.
---------------------------------------------------------
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: 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: Coordinated observations between SOHO/SUMER and ground during
the 1998 total eclipse: Non-thermal line broadenings and electron
densities in a polar coronal hole
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
S.; Schühle, U.
1999AIPC..471..285P Altcode: 1999sowi.conf..285P
Alfvén waves represent one of the most prominent ways of heating the
solar corona and accelerating the solar wind. One of their signatures
is to broaden the spectral lines in excess of their thermal width. Here
we aim to combine observations of non-thermal broadenings measured
by SUMER in OVI (1037.6 Å) line and electronic densities derived
from white-light observations during the 1998 total eclipse. After
checking the validity of the frequently-used assumption of equal ion
and electron temperatures, we compute the variation of the non-thermal
velocity as a function of height in an interplume region within the
south polar coronal hole.
---------------------------------------------------------
Title: Properties of Quiet-Sun Coronal Plasmas at Distances of
1.03<=R<SUB>solar</SUB><=1.50 along the Solar Equatorial Plane
Authors: Feldman, U.; Doschek, G. A.; Schühle, U.; Wilhelm, K.
1999ApJ...518..500F Altcode:
We determine the physical properties, i.e., electron temperature,
density, line-of-sight emission measure, and element-abundance variation
with height, in the Sun's equatorial west limb streamer region from
extreme-ultraviolet (EUV) spectra recorded by the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and
Heliospheric Observatory (SOHO) spacecraft. The spectra were recorded
on 1996 November 21-22 during a special “roll” maneuver in which
the SUMER slit was oriented in the east-west direction. Because the
SUMER spectrometer is stigmatic along the slit length, the spectra are
spatially resolved in the east-west direction. The spectra we discuss
cover an effective distance range outside the west limb from 1.03 to
1.50 solar radii (R<SUB>solar</SUB>) the maximum spatial resolution is
1<SUP>”</SUP>. We select a group of emission lines for analysis that
under the usual ionization equilibrium assumption span the temperature
range from 3×10<SUP>5</SUP> up to 2×10<SUP>6</SUP> K. However,
we note that above the limb a major fraction of a line intensity may
arise at a temperature that is far from the temperature of maximum
emitting efficiency in ionization equilibrium. In this paper we assume
ionization equilibrium in deriving plasma parameters. Readers can redo
our analysis without this assumption if desired, because the line
intensities we present in this paper are simply the measured photon
production rates in the lines. Assuming ionization equilibrium, we
determine the electron temperature, electron density, line-of-sight
emission measure, and abundance variation with height above the limb
from the line intensities and line intensity ratios. The spatial
resolution has allowed us to detect an apparent element-abundance
variation as a function of height above the west limb that is strong
evidence for gravitational settling of “heavy” elements.
---------------------------------------------------------
Title: Coronal Hole Properties Observed with SUMER
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.;
Brković , A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E.
1999SSRv...87..315S Altcode:
We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained
on both sides of the boundary of polar coronal holes as well as at
other locations along the limb. We compare line intensities, shifts
and widths in coronal holes with values obtained in the quiet Sun. We
find that with increasing formation temperature, spectral lines show
an increasingly stronger blueshift in coronal holes relative to the
quiet Sun at an equal heliospheric angle. The width of the lines is
generally larger (by a few km/s) inside the coronal hole. Intensity
measurements show the presence of the coronal hole in Ne VIII lines
as well as in Fe XII, with evidence for a slightly enhanced emission
in polar coronal holes for lines formed below 10<SUP>5</SUP> K.
---------------------------------------------------------
Title: Coronal Holes Versus Normal Quiet Sun Observed with SUMER
Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.;
Brković, A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E.
1999Ap&SS.264...53S Altcode: 1998Ap&SS.264...53S
We present a preliminary analysis of spectral lines obtained with the
SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation)
onboard the Solar and Heliospheric Observatory (SOHO), as observed
during three observing campaigns. From the 70 observed spectral lines,
we selected 12, representing 9 ions or atoms, in order to analyse line
intensities, shifts and widths in polar coronal holes as well as in the
normal quiet Sun. We find that coronal lines show a distinct blueshift
in coronal holes relative to the quiet Sun at equal heliospheric
angle, while there is no evidence for such a shift for lines formed at
temperatures below 10^5 K. The widths of lines formed at temperatures
above 3 - 10^4 K are slightly increased inside the coronal hole,
but unaffected for lower temperatures. Intensity measurements clearly
show the center-to-limb variation, as well as an intensity diminution
inside the coronal hole for lines formed above approximately 10^5 K.
---------------------------------------------------------
Title: Outflow Velocities at the Base of a Polar Coronal Hole During
the 1998 Total Eclipse
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
S.; Schühle, U.
1999SSRv...87..291P Altcode:
Polar coronal holes represent the most convincing site from which the
high-speed solar wind originates. Here we report high-accuracy Doppler
shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO
inside an interplume region within the south polar coronal hole. We
infer limits on the outflow velocity and draw hints about the flow
geometry.
---------------------------------------------------------
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: 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 Electron Pressure in the Solar Lower Transition Region
Determined from O V and Si III Density-sensitive Line Ratios
Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Warren, H. P.;
Schüle, U.; Wilhelm, K.
1998ApJ...507..991D Altcode:
We determine the electron density at the temperatures of formation
of O<SUP>+4</SUP> and Si<SUP>+2</SUP> ions, which are about 2.5 ×
10<SUP>5</SUP> and 3.2 × 10<SUP>4</SUP> K in ionization equilibrium,
respectively. These temperatures occur in the lower transition
region of the Sun's atmosphere and allow a test of the often invoked
assumption of constant pressure in quiet-Sun models. The O<SUP>+4</SUP>
density is determined from a density-sensitive spectroscopic O V
line ratio involving 2s2p<SUP>3</SUP>P-2p<SUP>2</SUP><SUP>3</SUP>P
transitions that fall near 760 Å. The Si<SUP>+2</SUP> density is
determined from a density-sensitive Si III line ratio within the
3s3p<SUP>3</SUP>P-3p<SUP>2</SUP><SUP>3</SUP>P multiplet near 1300
Å. There are few available line ratio techniques for determining
the density and hence electron pressure in the quiet-Sun and coronal
hole transition regions using lines emitted by the same ion, and
determining these quantities is the principal motivation for this
work. The spectra used in our analysis were obtained from the Solar
Ultraviolet Measurements of Emitted Radiation (SUMER) experiment on the
Solar and Heliospheric Observatory (SOHO). We determine the electron
density and pressure in typical quiet-Sun/coronal hole regions, and
densities in active region brightenings and in an explosive event. Our
O V and Si III results indicate that constant pressure is valid or
nearly valid in quiet-Sun lower transition regions, although there
are complications arising from the weakness of a key Si III line in
the quiet-Sun disk spectra. We also discuss our results in light of
other density measurements and theories regarding the structure and
heating of the transition region.
---------------------------------------------------------
Title: Coronal Composition above the Solar Equator and the North Pole
as Determined from Spectra Acquired by the SUMER Instrument on SOHO
Authors: Feldman, U.; Schühle, U.; Widing, K. G.; Laming, J. M.
1998ApJ...505..999F Altcode:
Using spectra obtained by the SUMER instrument on the Solar and
Heliospheric Observatory (SOHO) we have determined the composition of
the bulk of the coronal plasma in the vicinity of the solar surface
over a polar coronal hole and an equatorial region. Our measurements
show that although low first ionization potential (FIP) elements are
enriched by about a factor of 4 in the corona above the quiet equatorial
region, little or no enrichment exists above the north polar coronal
hole. These observations are in good agreement with the Ulysses in
situ observations in both fast speed and slow speed winds.
---------------------------------------------------------
Title: SUMER Measurements of Nonthermal Motions: Constraints on
Coronal Heating Mechanisms
Authors: Chae, Jongchul; Schühle, Udo; Lemaire, Philippe
1998ApJ...505..957C Altcode:
We have determined nonthermal velocities in the quiet Sun at
temperatures between 10<SUP>4</SUP> K and 2 × 10<SUP>6</SUP> K by
measuring the widths of a number of EUV and far-ultraviolet (FUV)
lines taken with SUMER on board the SOHO spacecraft. The broadenings
owing to the SUMER instrument and the finite opacity in each line
have been carefully examined. The nonthermal velocity at temperatures
below 2 × 10<SUP>4</SUP> K is smaller than 10 km s<SUP>-1</SUP>. The
velocity increases with temperature, reaches a peak value of 30
km s<SUP>-1</SUP> around 3 × 10<SUP>5</SUP> K, and then decreases
with the temperature. The coronal nonthermal velocity is about 20 km
s<SUP>-1</SUP>. There exists a strong correlation between intensity
and nonthermal velocity at temperatures 2 × 10<SUP>4</SUP>-1 ×
10<SUP>5</SUP> K. The correlation at higher temperatures weakens as
temperature increases. Furthermore, there is a spatial correlation
between the nonthermal velocities inferred from a set of any two lines
with temperatures below 2 × 10<SUP>5</SUP> K. Neither significant
center-to-limb variation nor meaningful dependence on the integration
time was found from the measured nonthermal velocities. We have
discovered the existence of high-velocity components in the observed
S VI λ933.4 line profiles. The average nonthermal velocity and
intensity fraction of this S VI line high-velocity component are found
to be 55 km s<SUP>-1</SUP> and 0.25, respectively. <P />Observational
characteristics of nonthermal motions carry some problems that should be
solved when interpreting observed nonthermal motions in terms of either
unresolved loop flows or Alfvén waves. The isotropic and very small
scale nature of the observed nonthermal motions appears to be suited to
the MHD turbulence interpretation of nonthermal motions. The turbulent
heating rates inferred from the measured nonthermal motions can account
for the radiative loss throughout the transition region and corona if
the nonthermal motions are truly turbulent motions whose mechanical
energy is injected at a scale of 1000 km (Kolmogorov-type turbulence)
or 15 km (Kraichnan-type turbulence). The existence of high-velocity
components at temperatures 6 × 10<SUP>4</SUP>-2 × 10<SUP>5</SUP>
K appears as observational evidence supporting nanoflare heating at
these temperatures.
---------------------------------------------------------
Title: Chromospheric Upflow Events Associated with Transition Region
Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
R.; Schühle, Udo
1998ApJ...504L.123C Altcode:
Transition region explosive events are considered to be a manifestation
of small-scale magnetic reconnection ubiquitously occurring--even in
the quiet Sun. In this paper, we report a close association between
transition region explosive events and chromospheric upflow events seen
in Hα. From a comparison of the Big Bear Solar Observatory (BBSO)
Hα spectrograph data and the Solar and Heliospheric Observatory
(SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
data, we found a succession of chromospheric upflow events at sites
where repeated explosive events occurred. Individual chromospheric
events appear as compact dark features that are best visible in
Hα-0.5 Å and that have a size of 2"-3" and a lifetime of 1-2
minutes. They are characterized by an upward motion of 15-30 km
s<SUP>-1</SUP>, a temperature of 10<SUP>4</SUP> K, a mass density
of 1×10<SUP>-13</SUP> g, and a nonthermal velocity less than 10
km s<SUP>-1</SUP>. Unlike spicules, which display descending motion
following their ascending phase, these upflow events are not followed
by noticeable redshifts. “Hα jets” at -1.0 Å studied by Wang et
al. appear to be a special case of this kind of chromospheric upflow
event. The physical characteristics of chromospheric upflow events and
their close association with transition region explosive events suggest
that chromospheric upflow events may be the manifestation of cool plasma
material flowing into magnetically diffusive regions, while explosive
events represent hot plasma material flowing out of the same regions.
---------------------------------------------------------
Title: The Si/Ne Abundance Ratio in Polar Coronal Hole and Quiet-Sun
Coronal Regions
Authors: Doschek, G. A.; Laming, J. M.; Feldman, U.; Wilhelm, K.;
Lemaire, P.; Schühle, U.; Hassler, D. M.
1998ApJ...504..573D Altcode:
Using spectra obtained from the Solar Ultraviolet Measurements
of Emitted Radiation (SUMER) spectrometer flown on the Solar and
Heliospheric Observatory (SOHO) spacecraft, we determine the Si/Ne
abundance ratio in diffuse, interplume polar coronal hole regions,
as well as the ratio relative to quiet-Sun coronal regions. Ne has
the second highest first ionization potential (FIP) of solar abundant
elements, and Si is a low-FIP element. Thus the Si/Ne ratio is a
sensitive indicator of abundance variations due to the FIP effect. We
develop new spectroscopic diagnostics for the determination of the
Si/Ne abundance ratio. Assuming ionization equilibrium, we find that
the Si/Ne abundance ratio in interplume polar coronal hole regions is
about a factor of 2 greater than the photospheric value and is close
to or the same as in coronal quiet-Sun regions. This result pertains
to the electron temperature range 5-8 × 10<SUP>5</SUP> K. However,
the combined atomic physics, instrumental, and statistical uncertainty
in this result is about a factor of 2, and therefore this observed
enhancement is consistent with no enhancement in the polar hole
abundances. Nevertheless, our results follow the same trend, i.e., a
greater than photospheric abundance ratio of low-FIP elements in the
corona relative to high-FIP elements, as found from other abundance
measurements in the corona that involve different atomic physics and
different instruments. Therefore we feel that our results reflect
an actual abundance enhancement, despite being within an uncertainty
level bar that encompasses photospheric abundances. We also examine
the Ne/Mg abundance ratio over a 24.5 hr observation and find no
significant abundance variations. (Mg is a low-FIP element.) Thus,
no large transient abundance variations appear to occur on timescales
shorter than about a day, although this result is based on only
one observation. From lines of Mg VII, Mg VIII, Mg IX, and Mg X we
find that the electron temperature along the line of sight increases
with height above the limb over the polar coronal holes, as has been
previously reported. We determine the emission measure distribution as
a function of height from Mg VII, Mg VIII, and Mg X lines. We determine
average temperatures along the line of sight over the polar holes from
Ne VIII/Ne VII, Mg VIII/Mg VII, and Si VIII/Si VII line ratios. We also
discuss the temperature properties of the coronal hole and quiet-Sun
regions using forbidden lines of Fe X and Fe XI. We comment on the
possibility that ionization equilibrium is not valid in polar coronal
hole regions, a possible scenario in light of recent observations that
show outflows in coronal holes beginning at about the temperature of
formation of Ne VIII.
---------------------------------------------------------
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 2s<SUP>2</SUP>2p<SUP>k</SUP> and
3s<SUP>2</SUP>3p<SUP>k</SUP> (where k = 1, 5) ground configurations
of ions that are formed in ionization equilibrium between 2 ×
10<SUP>6</SUP> and 8 × 10<SUP>6</SUP> 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: Evidence in Support of the “Nanoflare” Picture of Coronal
Heating from SUMER Data
Authors: Judge, P. G.; Hansteen, V.; Wikstøl, Ø.; Wilhelm, K.;
Schühle, U.; Moran, T.
1998ApJ...502..981J Altcode:
We study high signal-to-noise profiles of O IV emission lines obtained
using the SUMER instrument on SOHO. Data for the quiet Sun obtained
close to the disk center and at the solar limb were acquired. After
careful data processing in which disk data were analyzed differentially
against limb data, we find a systematic correlation between a
density-sensitive emission-line ratio and Doppler shift across the
same emission-line profiles. While unidentified blended lines cannot be
completely discounted, the data suggest that the effects of such blends
are small. Based on theoretical results in an earlier paper, we argue
that if wave motions are responsible for the observed behavior, then
the data reveal evidence for compressive waves propagating downward
from the corona to the chromosphere. This analysis naturally lends
support to the dominance of the “nanoflare” mechanism for coronal
heating over other theories that invoke upward wave propagation,
but other mechanisms capable of generating downward-propagating waves
cannot be discounted. If, instead, steady flows are the cause of the
observed behavior, such as return flows from spicules, then they must
be such that the density is higher in the downflowing plasma. While
these particular data do not allow us to discriminate between waves
or steady flows, additional data from SOHO should be able to address
this problem. This work required and achieved very accurate wavelength
calibrations (better than 1/5 of a pixel on the detectors), taking
SUMER close to its observational capabilities. We therefore present
the elements of the analysis and calibration of SUMER data that may
be of interest to other users.
---------------------------------------------------------
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 L<SUB>1</SUB> 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: Photospheric Magnetic Field Changes Associated with Transition
Region Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
R.; Schühle, Udo
1998ApJ...497L.109C Altcode:
From a comparison of the Solar and Heliospheric Observatory SUMER
spectral data and a time series of Big Bear Solar Observatory
magnetograms, we present observational clues to the physical origin of
transition region explosive events. First, explosive events rarely occur
in the interior of strong magnetic flux concentrations but rather are
preferentially found in regions with weak and mixed polarity fluxes that
display magnetic neutral lines. Second, the majority of explosive events
happen during the “cancellation” of photospheric magnetic flux. Third,
there is a strong tendency for explosive events to occur repeatedly, as
bursts, while local photospheric magnetic flux continuously decreases
because of cancellation. These results strongly support the idea that
transition region explosive events are a manifestation of magnetic
reconnection occurring in the quiet Sun. Furthermore, one may infer from
the third result that the explosive events represent repetitive fast
magnetic reconnections in the transition region, which are initiated
by slow magnetic reconnections occurring beneath.
---------------------------------------------------------
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: 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: VLA-SOHO Observations of Evolving Coronal Structures on the Sun
Authors: Willson, R. F.; Lang, K. R.; Thompson, B.; Schuehle, U.;
Zarro, D. M.
1998ASPC..154..727W Altcode: 1998csss...10..727W
Very Large Array (VLA) observations at 3.5, 6.2, and 91.6 cm wavelength
have been combined with EUV spectroheliograms from the Solar and
Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS)
and Extreme Ultraviolet Telescope (EIT) to study evolving sources in the
transition region and corona above a solar active region. In some cases,
transient events, lasting minutes to tens of minutes, were observed
at both radio and EUV wavelengths, while other events were detected
in only one spectral domain. The combined data sets suggest that the
EUV-associated microwave sources are produced by thermal gyroresonance
or nonthermal gyrosynchrotron radiation, primarily in regions of high
magnetic field strength near sunspots. Observations at 91.6 cm also
show the sudden appearance of a low-lying, nonthermal source in the
low corona around the time that cool, outwardly-propagating plasma
was detected by the SOHO/EIT.
---------------------------------------------------------
Title: Observations of the solar atmosphere from the Solar and
Heliospheric Observatory (SOHO).
Authors: Schühle, U.
1997JXST....7..249S Altcode:
The Solar and Heliospheric Observatory (SOHO) spacecraft was launched
on December 2, 1995, into a halo orbit around the first Lagrangian
Point L1 between Sun and Earth, carrying into space a payload of twelve
Sun observing instruments. Among them is a set of four complementary
telescope/spectrometers to study phenomena and dynamics of the Sun's
atmosphere in the far or extreme ultraviolet: The Extreme-Ultraviolet
Imaging Telescope (EIT), the Coronal Diagnostic Spectrometer (CDS),
the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), and
the Ultraviolet Coronagraph Spectrometer (UVCS). The spectral coverage
of these instruments, which extents from 151 to 1610 Å, allows remote
sensing investigations of the solar atmosphere by means of spectroscopic
and imaging techniques with a spatial resolution down to 1 arcsec. Each
one of these instruments by itself is a technological achievement
making use of normal incidence, grazing incidence, or multilayer optical
techniques to cover the appropriate spectral ranges for each scientific
objective. Many of the plasma diagnostic studies have been carried
out during the first months of the mission, and this contribution will
give an overview of the capabilities of each instrument and the types
of observations being made by individual and joint operations.
---------------------------------------------------------
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 < 10 eV by
factor of 3-4 in the corona with respect to photospheric values) with
height above the limb in a region of diffuse quiet corona observed
by the SUMER instrument on SOHO. Line ratios formed at log T >
5.8 show coronal abundances for all heights. Line ratios formed at
lower temperatures are consistent with coronal abundances well off the
limb, with the apparent magnitude of the FIP enhancement decreasing
by a factor of 1.5 - 2 as one approaches the solar limb. Thus our
observations support a spatial variation in the quiet sun transition
region FIP effect inferred previously from studies of the full disk
solar spectrum (Laming, Drake, & Widing 1995, ApJ, 443, 416
and references therein). This result adds to the probability that
emission from the solar disk transition region and corona originates
from qualitatively different structures for values of log T {<atop
>} 5.8, having different FIP effects.
---------------------------------------------------------
Title: Sonnenradiometrie mit SUMER auf SOHO.
Authors: Hollandt, J.; Curdt, W.; Schühle, U.; Wilhelm, K.
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 × 10<SUP>4</SUP> and 1.5 × 10<SUP>6</SUP>
K. Identification of lines originating from different temperature
regimes is facilitated by the appearance of their intensity along the
300" long slit. <P />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: Observations of Polar Plumes with the SUMER Instrument on SOHO
Authors: Hassler, D. M.; Wilhelm, K.; Lemaire, P.; Schühle, U.
1997SoPh..175..375H Altcode:
We present new observations of O vi 1032 Å line profiles in polar
plumes, and inter-plume regions, on the disk and above the limb in
the north coronal hole obtained with the SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) instrument on the SOHO (Solar and
Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min
spectroheliogram was scanned above the north polar coronal hole with
the entrance slit extending from 1.03 to 1.33 solar radii with 1.5 arc
sec spatial resolution and ≈ 0.044 Å per pixel spectral resolution
in the wavelength range 1020-1040 Å. Detailed plume structure in
O vi 1032 Å can be seen extending beyond 1.3 solar radii, with
intensities in the plume regions 10-50% brighter, but line widths
10-15% narrower, than the inter-plume regions. Possible explanations
for this observed anti-correlation between line width and intensity
in the plume and inter-plume regions are discussed. We conclude that
the source of the high-speed solar wind may not be polar plumes, but
the inter-plume lanes associated with open magnetic field regions of
the chromospheric network.
---------------------------------------------------------
Title: Laboratory Identification of Temperature Diagnostic Si VII and
S IX Lines Present in the Solar Coronal Spectra Measured by SUMER/SOHO
Authors: Kink, I.; Jupén, C.; Engström, L.; Feldman, U.; Laming,
J. M.; Schühle, U.
1997ApJ...487..956K Altcode:
The solar coronal spectrum between 500 and 1610 Å and at a
height of 21,000 km above the west equatorial limb has recently
been recorded by the SUMER instrument on SOHO. Using laboratory
spectra obtained with the beam-foil technique, we report
the identification of 32 lines observed in this spectrum as
2s<SUP>2</SUP>2p<SUP>3</SUP>3s-2s<SUP>2</SUP>2p<SUP>3</SUP>3p and
2s<SUP>2</SUP>2p<SUP>3</SUP>3p-2s<SUP>2</SUP>2p<SUP>3</SUP>3d
transitions in Si VII and S IX. Theoretical gA-values
and branching ratios for the observed lines, obtained from
semiempirical configuration interaction calculations, are also
presented. Intensity ratios between the 2s<SUP>2</SUP>2p<SUP>4</SUP>
<SUP>3</SUP>P<SUB>1</SUB>-2s<SUP>2</SUP>2p<SUP>4</SUP>
<SUP>1</SUP>S<SUB>0</SUB> forbidden transition and transition from
the newly identified high-excitation lines that appear in the same
wavelength range are temperature sensitive. Calculations of the
intensity ratios between the forbidden line and the high-excitation
lines for three temperatures are presented. A comparison between the
calculations and some of the SUMER observations is provided.
---------------------------------------------------------
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 10<SUP>8</SUP> cm<SUP>-3</SUP>.
---------------------------------------------------------
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<SUP>-1</SUP> at 30"
above the limb and decreased to less than 10 km s<SUP>-1</SUP> 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: Electron Densities in the Solar Polar Coronal Holes from
Density-Sensitive Line Ratios of Si VIII and S X
Authors: Doschek, G. A.; Warren, H. P.; Laming, J. M.; Mariska, J. T.;
Wilhelm, K.; Lemaire, P.; Schühle, U.; Moran, T. G.
1997ApJ...482L.109D Altcode:
We derive electron densities as a function of height in the north and
south polar coronal holes from a forbidden spectral line ratio of Si
VIII. Si VIII is produced at about 8 × 10<SUP>5</SUP> K in ionization
equilibrium. We also derive densities from a similar line ratio of S X
(1.3 × 10<SUP>6</SUP> K). The spectra were obtained with the Solar
Ultraviolet Measurements of Emitted Radiation spectrometer flown on
the Solar and Heliospheric Observatory spacecraft. In addition to the
primary mechanism of electron impact excitation, the derivation of
theoretical level populations for Si VIII and S X includes both proton
and resonance capture excitation. We compare the coronal hole results
to quiet-Sun coronal measurements obtained outside the east and west
limbs. We find for distances of a few arcseconds outside the solar
limb that the average line-of-sight electron densities in the coronal
holes are about a factor of 2 lower than in quiet-Sun regions. The
decrease of density with height is exponential in the polar holes. We
also confirm the result known from a variety of earlier observations
that the temperature of most of the plasma in coronal holes does not
exceed about 10<SUP>6</SUP> K.
---------------------------------------------------------
Title: Translimb Spectroscopy with SOHO/SUMER
Authors: Ayres, T. R.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Ruedi,
I.; Solanki, S.
1997SPD....28.0104A Altcode: 1997BAAS...29..879A
We have used SUMER to obtain deep exposures of the 1300--1400 Angstroms
spectrum, at the extreme limb and off-limb. Previous “translimb”
studies in the thermal infrared had revealed remarkable extensions
of cold material (T ~ 3000 K)---traced by carbon monoxide emission
lines---into the heart of the hot chromosphere. A main objective of
our program was to search for corresponding far-UV signatures of the
“thermally-bifurcated” low chromosphere; for example, radiatively
fluoresced emissions of the CO A--X 4th-positive system (collisional
excitation would be negligible in cold gas). We conducted two separate
observing programs with SUMER. Both made use of the 1(”) -diameter
circular aperture, translated across the limb in the minimum motor
step increments of 0.(”) 375, along the central meridian in the
Northern polar coronal hole. The first program executed for nine hours
beginning 19UT 25 Oct 1996. The full wavelength range was 1340--1400
Angstroms. It was recorded in two overlapping segments, placing key
regions of the spectrum alternately on the KBr and bare parts of
the detector, to help isolate 2nd-order features. Each segment was
integrated for 500 s, and 32 pairs were obtained to span a 12(”)
swath centered on the optical limb. The second program was conducted
00--09UT 01 Dec 1996. It consisted of a single wavelength setting
(1300--1340 Angstroms) with exposure time 500 s, but twice the spatial
coverage of the earlier series: 64 steps, for a total displacement
of 24(”) . The strong chromospheric resonance lines of atomic oxygen
(1302--1305 Angstroms) and ionized carbon (1334--1335 Angstroms) were
observed on the bare part of the MCP camera. We report our progress
in cataloging the rich, diverse translimb emission spectrum; and our
efforts to deduce fundamental properties of the thermally heterogeneous
chromosphere. [-3mm] SOHO is a project of international cooperation;
the participation of TRA was supported by NASA grant NAG5-3226.
---------------------------------------------------------
Title: New Insights into the Physical Mechanisms of Polar Plumes
with Observations from the SUMER Instrument on SOHO
Authors: Hassler, Donald M.; Wilhelm, Klaus; Lemaire, Philippe;
Schuehle, Udo
1997SPD....28.0802H Altcode: 1997BAAS...29..912H
SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
line profiles above the limb in coronal holes are important for
constraining thermodynamic models governing the outflow of the solar
wind. Observational constraints in terms of thermal and nonthermal
velocities, and upper limits on wave velocity amplitudes can be directly
compared with in-situ observations. We present new observations of
line profiles in polar plumes, and inter-plume regions, above the
limb in coronal holes obtained with the SUMER instrument on the SOHO
spacecraft. Detailed structure can be seen extending beyond 1.5 solar
radii (out to the edge of the SUMER field-of-view), with intensities in
the plume regions roughly 10-50% brighter than the inter-plume regions,
but line widths in the plumes roughly 10% narrower than the inter-plume
regions. Possible explanations for this observed anti-correlation
between line width and intensity, and the correspondence with observed
in-situ solar wind signatures will be discussed.
---------------------------------------------------------
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: Determination of the Formation Temperature of Si IV in the
Solar Transition Region
Authors: Doschek, G. A.; Mariska, J. T.; Warren, H. P.; Wilhelm, K.;
Lemaire, P.; Kucera, T.; Schühle, U.
1997ApJ...477L.119D Altcode:
Using spectra obtained with the Solar Ultraviolet Measurements
of Emitted Radiation (SUMER) spectrometer flown on the Solar and
Heliospheric Observatory spacecraft, we deduce the temperature
of formation of the Si IV ion in the solar transition region
from the Si IV ultraviolet spectral line intensity ratio, 3p
<SUP>2</SUP>P<SUB>3/2</SUB>-3d <SUP>2</SUP>D<SUB>3/2,5/2</SUB>/3s
<SUP>2</SUP>S<SUB>1/2</SUB>-3p <SUP>2</SUP>P<SUB>1/2</SUB>,
and compare the result to the temperature predicted under the
assumption of ionization equilibrium. The wavelengths are as
follows: <SUP>2</SUP>D<SUB>3/2,5/2</SUB>, 1128.325, 1128.340 Å
<SUP>2</SUP>P<SUB>1/2</SUB>, 1402.770 Å. Ratios are derived for
typical features of the quiet Sun, such as cell center and network,
and are systematically higher than those predicted at the 6.3 ×
10<SUP>4</SUP> K ionization equilibrium temperature of formation
of Si IV. For most solar features the ratios imply a temperature
of formation of about 8.5 × 10<SUP>4</SUP> K. The ratios for the
faintest features imply a temperature of formation of up to 1.6 ×
10<SUP>5</SUP> K. It is not clear, however, that all the discrepancies
between the measured and theoretical ratios are due to a temperature
effect. Accurate temperature measurements are important since a large
discrepancy from ionization equilibrium has significant implications
for the physics of the transition region, such as the possible presence
of nonthermal electrons.
---------------------------------------------------------
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: SUMER Observations Detecting Downward Propagating Waves in
the Solar Transition Region
Authors: Wiskstøl, Ø.; Judge, P. G.; Hansteen, V.; Wilhelm, K.;
Schühle, U.; Moran, T.
1997ESASP.404..731W Altcode: 1997cswn.conf..731W
No abstract at ADS
---------------------------------------------------------
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 × 10<SUP>6</SUP> 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: SOHO observations of the north polar solar wind
Authors: Peres, G.; Ciaravella, A.; Betta, R.; Orlando, S.; Reale,
F.; Kohl, J.; Noci, G.; Fineschi, S.; Romoli, M.; Brekke, P.; Fludra,
A.; Gurman, J. B.; Lemaire, P.; Schuhle, U.
1997ESASP.404..587P Altcode: 1997cswn.conf..587P
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: 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: 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: 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 10<SUP>4</SUP> to 2 × 10<SUP>6</SUP>K 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 10<SUP>4</SUP> to 2 multiplied by 10<SUP>6</SUP>
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<SUP>-1</SUP>. We report
here on some specific features of this instrument related to its
pointing as well as its spatial and spectral resolution capabilities.
---------------------------------------------------------
Title: Solar Ultraviolet Measurements of Ultraviolet Radiation
(SUMER) instrument on SOHO: design, performance predictions, and
calibration aspects
Authors: Schuehle, Udo H.
1994SPIE.2283...47S Altcode:
The solar EUV spectrometer SUMER will operate in the wavelength
range 500 angstrom to 1600 angstrom on the SOHO spacecraft. It will
allow measurements of profiles, Doppler shifts, and intensities of
solar extreme ultraviolet lines. Various mechanisms for pointing and
focusing of the optical components contribute to the versatility of the
instrument. The normal incidence optical design of the telescope and
the spectrometer puts very stringent constraints on the cleanliness of
the instrument and the mechanical design. The calibration techniques
used, including imaging tests in the EUV, wavelength, and radiometric
calibrations are outlined, and performance predictions are given.
---------------------------------------------------------
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: SUMER - Solar Ultraviolet Measurements of Emitted Radiation
Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel,
A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.;
Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G.
1993BAAS...25.1192W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Cleanliness Control Program for SUMER/SOHO
Authors: Schühle, U.
1993uxrs.conf..373S Altcode:
No abstract at ADS
