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Author name code: teriaca
ADS astronomy entries on 2022-09-14
author:"Teriaca, Luca"
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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: Coronal mass ejection followed by a prominence eruption and
a plasma blob as observed by Solar Orbiter
Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro,
D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu,
D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel,
P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse,
G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli,
M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L.
2022A&A...665A...7B Altcode: 2022arXiv220210294B
Context. On 2021 February 12, two subsequent eruptions occurred above
the western limb of the Sun, as seen along the Sun-Earth line. The
first event was a typical slow coronal mass ejection (CME), followed
∼7 h later by a smaller and collimated prominence eruption,
originating south of the CME, followed by a plasma blob. These
events were observed not only by the SOHO and STEREO-A missions,
but also by the suite of remote-sensing instruments on board Solar
Orbiter. <BR /> Aims: We show how data acquired by the Full Sun
Imager (FSI), the Metis coronagraph, and the Heliospheric Imager
(HI) from the Solar Orbiter perspective can be combined to study
the eruptions and different source regions. Moreover, we show how
Metis data can be analyzed to provide new information about solar
eruptions. <BR /> Methods: Different 3D reconstruction methods were
applied to the data acquired by different spacecraft, including
remote-sensing instruments on board Solar Orbiter. Images acquired
by the two Metis channels in the visible light (VL) and H I Ly-α
line (UV) were combined to derive physical information about the
expanding plasma. The polarization ratio technique was also applied
for the first time to Metis images acquired in the VL channel. <BR
/> Results: The two eruptions were followed in 3D from their source
region to their expansion in the intermediate corona. By combining
VL and UV Metis data, the formation of a post-CME current sheet (CS)
was followed for the first time in the intermediate corona. The
plasma temperature gradient across a post-CME blob propagating
along the CS was also measured for the first time. Application
of the polarization ratio technique to Metis data shows that by
combining four different polarization measurements, the errors are
reduced by ∼5 − 7%. This constrains the 3D plasma distribution
better. <P />Movies associated to Figs. 4-7 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243162/olm">https://www.aanda.org</A>
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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: 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: UV coronagraphic observations of an erupting prominence in
the H I Ly-alpha line by Metis on-board Solar Orbiter
Authors: Russano, Giuliana; Teriaca, Luca; Andretta, Vincenzo; Sasso,
Clementina; de Leo, Yara; Uslenghi, Michela
2022cosp...44.2412R Altcode:
We show an erupting prominence event occurred on October 25, 2021 above
the South-Est limb of the Sun, observed by the Solar Orbiter (SolO)
Metis coronagraph UV channel, a narrow-band filter around the H I Ly
$\alpha$ line at 121.567 nm. The event, associated to a Coronal Mass
Ejection (CME), was visible also in the Metis visible light channel
and was also observed by other coronagraphs in orbit around the Sun,
like STEREO-A SECCHI COR1 and COR2 and SOHO/LASCO-C2. The observed CME
had a projected speed on the order of ∼ 220 km s‑1, as provided
by the CACTUS catalog. The event first appears in the STEREO-A EUVI
304 Å images as a typical limb prominence starting at 06:15 UT,
then it crossed the fields-of-view (FOVs) of STEREO-A SECCHI COR1
and SOHO/LASCO-C2 (respectively at 8:00 UT and 9:00 UT), until it
shows up in the Metis FOV at 14:00 UT where the prominence eruption
can be followed as far as ~ 10.2 solar radii. From the Solar Orbiter
perspective (very similar to that of SOHO and SDO since the separation
angle SolO-Sun-Earth was 5 deg), the source region of the eruption
was located just behind the Est limb, as suggested by STEREO-A EUVI
304 Å images (the separation angle STEREO-A-Sun-Earth was ~38 deg),
and by the fact that no significant associated signature is seen in
the AIA/SDO coronal imagers. This presentation will summarize the
ongoing analysis to derive geometrical and physical parameters of the
prominence as well as the expanding plasma magnetic field profiles of
this interesting event.
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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.
---------------------------------------------------------
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>
---------------------------------------------------------
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: Multipoint remote and in situ observations of interplanetary
coronal mass ejection structures during 2011 and associated
geomagnetic storms
Authors: Mishra, Wageesh; Dave, Kunjal; Srivastava, Nandita; Teriaca,
Luca
2021MNRAS.506.1186M Altcode:
We present multipoint remote and in situ observations of interplanetary
coronal mass ejection (ICME) structures during the year 2011. The
selected ICMEs arrived at Earth on 2011 March 11 and 2011 August 6,
and led to geomagnetic storms. Around the launch of these CMEs from
the Sun, the coronagraphs onboard STEREO-Aand-B and SOHO enabled the
CMEs to be imaged from three longitudinally separated viewpoints. We
attempt to identify the in situ plasma and magnetic parameters of
the ICME structures at multiple locations, for example at both STEREO
spacecraft and also at the ACE/Wind spacecraft near the first Sun-Earth
Lagrangian point (L1), to investigate the global configuration,
interplanetary propagation, arrival times and geomagnetic response of
the ICMEs. The near-Earth identified ICMEs of March 11 and August 6
formed as a result of the interaction of two successive CMEs observed
in the inner corona on March 7 (for the March 11 ICME) and on August
3-4 (for the August 6 ICME). Our study suggests that the structures
associated with interacting CMEs, possibly as a result of deflection or
large sizes, may reach to even larger longitudinally separated locations
in the heliosphere. Our multipoint in situ analysis shows that the
characteristics of the same shock, propagating in a pre-conditioned
medium, may be different at different longitudinal locations in the
heliosphere. Similarly, multiple cuts through the same ejecta/complex
ejecta, formed as a result of CME-CME interaction, are found to have
inhomogeneous properties. The study highlights the difficulties in
connecting the local observations of an ICME from a single in situ
spacecraft to its global structures.
---------------------------------------------------------
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: Magnetic imaging of the outer solar atmosphere (MImOSA)
Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
2021ExA...tmp...95P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability of
planets orbiting these host stars. Although the magnetic field at the
surface of the Sun is reasonably well characterised by observations,
the information on the magnetic field in the higher atmospheric layers
is mainly indirect. This lack of information hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution
and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is
designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter
based on a 30 cm telescope that combines high throughput in the
extreme UV with polarimetry to connect the magnetic measurements
of the other two instruments. Placed in a near-Earth orbit, the data
downlink would be maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-based
observatories. This mission to measure the magnetic field will finally
unlock the driver of the dynamics in the outer solar atmosphere and
thereby will greatly advance our understanding of the Sun and the
heliosphere.
---------------------------------------------------------
Title: In-flight optical performance assessment for the Metis solar
coronagraph
Authors: Da Deppo, Vania; Chioetto, Paolo; Andretta, Vincenzo; Casini,
Chiara; Frassetto, Fabio; Slemer, Alessandra; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Heinzel, Petr; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca;
Bemporad, Alessandro; Casti, Marta; Fabi, Michele; Grimani, Catia;
Heerlein, Klaus; Jerse, Giovanna; Landini, Federico; Liberatore,
Alessandro; Magli, Enrico; Melich, Radek; Pancrazzi, Maurizio; Pelizzo,
Maria-G.; Romano, Paolo; Sasso, Clementina; Straus, Thomas; Susino,
Roberto; Uslenghi, Michela; Volpicelli, Cosimo Antonio
2021SPIE11852E..10D Altcode:
Metis is a multi-wavelength coronagraph onboard the European Space
Agency (ESA) Solar Orbiter mission. The instrument features an
innovative instrument design conceived for simultaneously imaging the
Sun's corona in the visible and ultraviolet range. The Metis visible
channel employs broad-band, polarized imaging of the visible K-corona,
while the UV one uses narrow-band imaging at the HI Ly , i.e. 121.6
nm. During the commissioning different acquisitions and activities,
performed with both the Metis channels, have been carried out with the
aim to check the functioning and the performance of the instrument. In
particular, specific observations of stars have been devised to assess
the optical alignment of the telescope and to derive the instrument
optical parameters such as focal length, PSF and possibly check the
optical distortion and the vignetting function. In this paper, the
preliminary results obtained for the PSF of both channels and the
determination of the scale for the visible channel will be described
and discussed. The in-flight obtained data will be compared to those
obtained on-ground during the calibration campaign.
---------------------------------------------------------
Title: On-ground flat-field calibration of the Metis coronagraph
onboard the Solar Orbiter ESA mission
Authors: Casini, C.; Da Deppo, V.; Zuppella, P.; Chioetto, P.; Slemer,
A.; Frassetto, F.; Romoli, M.; Landini, F.; Pancrazzi, M.; Andretta,
V.; De Leo, Y.; Bemporad, A.; Fabi, M.; Fineschi, S.; Frassati, F.;
Grimani, C.; Jerse, G.; Heerlein, K.; Liberatore, A.; Magli, E.;
Naletto, G.; Nicolini, G.; Pelizzo, M. G.; Romano, P.; Sasso, C.;
Spadaro, D.; Stangalini, M.; Straus, T.; Susino, R.; Teriaca, L.;
Uslenghi, M.; Casti, M.; Heinzel, P.; Volpicelli, A.
2021SPIE11852E..5BC Altcode:
Solar Orbiter, launched on February 9<SUP>th</SUP> 2020, is an
ESA/NASA mission conceived to study the Sun. This work presents
the embedded Metis coronagraph and its on-ground calibration in the
580-640 nm wavelength range using a flat field panel. It provides
a uniform illumination to evaluate the response of each pixel of
the detector; and to characterize the Field of View (FoV) of the
coronagraph. Different images with different exposure times were
acquired during the on-ground calibration campaign. They were analyzed
to verify the linearity response of the instrument and the requirements
for the FoV: the maximum area of the sky that Metis can acquire.
---------------------------------------------------------
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: In-flight calibration of Metis coronagraph on board of
Solar Orbiter
Authors: Liberatore, A.; Fineschi, S.; Casti, M.; Capobianco, G.;
Romoli, M.; Andretta, V.; Bemporad, A.; Da Deppo, V.; De Leo, Y.; Fabi,
M.; Frassetto, F.; Grimani, C.; Heerlein, K.; Heinzel, P.; Jerse,
G.; Landini, F.; Magli, E.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Slemer, A.; Spadaro, D.;
Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Volpicelli, C. A.;
Zuppella, P.
2021SPIE11852E..48L Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched at the begin of 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun
from a very close distance and increasing the latitude with respect
to the ecliptic plane. In particular, Metis is aimed at the overall
characterization and study of the solar corona and solar wind. Metis
instrument acquires images of the solar corona in two different
wavelengths simultaneously; ultraviolet (UV) and visible-light (VL). The
VL channel includes a polarimeter with an electro-optically modulating
Liquid Crystal Variable Retarder (LCVR) to measure the linearly
polarized brighness pB) of the K-corona. This paper presents part of
the in-flight calibration results for both wavelength channels together
with a comparison with on-ground calibrations. The orientation of the
K-corona linear polarization was used for the in-flight calibration
of the Metis polarimeter. This paper describes the correction of the
on-ground VL vignetting function after the in-flight adjustment of
the internal occulter. The same vignetting function was adaptated to
the UV channel.
---------------------------------------------------------
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, Luca
2021EGUGA..2314801T 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 (HRILYA) 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: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA):
Unlocking the driver of the dynamics in the upper solar atmosphere
Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J.
2021arXiv210101566P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability
of planets orbiting these host stars. The lack of information on the
magnetic field in the higher atmospheric layers hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution and high
sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to
measure the large-scale magnetic field in the corona with an aperture
of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with
polarimetry to connect the magnetic measurements of the other two
instruments. This mission to measure the magnetic field will unlock
the driver of the dynamics in the outer solar atmosphere and thereby
greatly advance our understanding of the Sun and the heliosphere.
---------------------------------------------------------
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: Current Status of the Solar-C_EUVST Mission
Authors: Imada, S.; Shimizu, T.; Kawate, T.; Toriumi, S.; Katsukawa,
Y.; Kubo, M.; Hara, H.; Suematsu, Y.; Ichimoto, K.; Watanabe, T.;
Watanabe, K.; Yokoyama, T.; Warren, H.; Long, D.; Harra, L. K.;
Teriaca, L.
2020AGUFMSH056..05I Altcode:
Solar-C_EUVST (EUV High-Throughput Spectroscopic Telescope) is designed
to comprehensively understand the energy and mass transfer from the
solar surface to the solar corona and interplanetary space, and to
investigate the elementary processes that take place universally
in cosmic plasmas. As 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, the proposed mission
is designed to comprehensively understand how mass and energy are
transferred throughout the solar atmosphere. Understanding the solar
atmosphere, which connects to the heliosphere via radiation, the solar
wind and coronal mass ejections, and energetic particles is pivotal
for establishing the conditions for life and habitability in the solar
system. <P />The two primary science objectives for Solar-C_EUVST are :
I) Understand how fundamental processes lead to the formation of the
solar atmosphere and the solar wind, II) Understand how the solar
atmosphere becomes unstable, releasing the energy that drives solar
flares and eruptions. Solar-C_EUVST will, A) seamlessly observe all
the temperature regimes of the solar atmosphere from the chromosphere
to the corona at the same time, B) resolve elemental structures of the
solar atmosphere with high spatial resolution and cadence to track their
evolution, and C) obtain spectroscopic information on the dynamics of
elementary processes taking place in the solar atmosphere. <P />In this
talk, we will first discuss the science target of the Solar-C_EUVST,
and then discuss the current status of the Solar-C_EUVST mission.
---------------------------------------------------------
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: A sensitivity analysis of the updated optical design for
EUVST on the Solar-C mission
Authors: Kawate, Tomoko; Tsuzuki, Toshihiro; Shimizu, Toshifumi;
Imada, Shinsuke; Katsukawa, Yukio; Hara, Hirohisa; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Hattori, Tomoya; Narasaki, Shota; Warren, Harry P.;
Teriaca, Luca; Korendyke, Clarence M.; Brown, Charles M.; Auchere,
Frederic
2020SPIE11444E..3JK Altcode:
The EUV high-throughput spectroscopic telescope (EUVST) onboard the
Solar-C mission has the high spatial (0.4”) resolution over a wide
wavelength range in the vacuum ultraviolet. To achieve high spatial
resolution under a design constraint given by the JAXA Epsilon launch
vehicle, we further update the optical design to secure margins
needed to realize 0.4” spatial resolution over a field of view of
100”×100”. To estimate the error budgets of spatial and spectral
resolutions due to installation and fabrication errors, we perform a
sensitivity analysis for the position and orientation of each optical
element and for the grating parameters by ray tracing with the Zemax
software. We obtain point spread functions (PSF) for rays from 9
fields and at 9 wavelengths on each detector by changing each parameter
slightly. A full width at half maximum (FWHM) of the PSF is derived at
each field and wavelength position as a function of the perturbation
of each optical parameter. Assuming a mount system of each optical
element and an error of each optical parameter, we estimate spatial
and spectral resolutions by taking installation and fabrication errors
into account. The results of the sensitivity analysis suggest that
budgets of the total of optical design and the assembly errors account
for 15% and 5.8% of our budgets of the spatial resolution in the long
wavelength and short wavelength bands, respectively. On the other hand,
the grating fabrication errors give a large degradation of spatial and
spectral resolutions, and investigations of compensators are needed
to relax the fabrication tolerance of the grating surface parameters.
---------------------------------------------------------
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: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
2020A&A...642A...2R Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk. <BR /> Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies. <BR /> Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter. <BR /> Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission. <BR /> Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.
---------------------------------------------------------
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 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: Probing the thermodynamic state of a Coronal Mass Ejection
(CME) up to 1 AU
Authors: Mishra, Wageesh; Wang, Yuming; Teriaca, Luca; Zhang, Jie;
Chi, Yutian
2020FrASS...7....1M Altcode:
Several earlier studies have attempted to estimate some of the
thermodynamic properties of Coronal Mass Ejections (CMEs) either
very close to the Sun or at 1 AU. In the present study, we attempt
to extrapolate the internal thermodynamic properties of 2010 April
3 flux rope CME from near the Sun to 1 AU. For this purpose, we use
the flux rope internal state (FRIS) model which is constrained by
the kinematics of the CME. The kinematics of the CME is estimated
using the STEREO/COR and HI observations in combination with drag
based model (DBM) of CME propagation. Using the FRIS model, we focus
on estimating the polytropic index of the CME plasma, heating/cooling
rate, entropy changing rate, Lorentz force and thermal pressure force
acting inside the CME. Our study finds that the polytropic index of
the selected CME ranges between 1.7 to 1.9. This implies that the CME
is in the heat-releasing state (i.e., entropy loss) throughout its
journey from the Sun to Earth. The hindering role of Lorentz force and
contributing role of thermal pressure force in governing the expansion
of the CME is also identified. On comparing the estimated properties
of the CME flux rope from the FRIS model with the in situ observations
of the CME taken at 1 AU, we find relevant discrepancies between the
results predicted by the model and the observations. We outline the
approximations made in our study of probing the internal state of the
CME during its heliospheric evolution and discuss the possible causes
of the observed discrepancies.
---------------------------------------------------------
Title: The SPICE (Spectral Imaging of the Coronal Environment)
Ultraviolet Imaging Spectrograph Investigation
Authors: Hassler, D.; Auchere, F.; Carlsson, M.; Fludra, A.; Giunta,
A. S.; Mueller, D.; Peter, H.; Parenti, S.; Teriaca, L.; Fredvik, T.
2019AGUFMSH24A..02H Altcode:
One of the primary objectives of the Solar Orbiter mission is to link
remote sensing observations of the solar surface structures with in-situ
observations of solar wind streams. The SPICE (Spectral Imaging of the
Coronal Environment) instrument will characterize the plasma properties
of regions near the Sun to directly compare with in-situ measurements
from both Solar Orbiter & Parker Solar Probe. Specifically, SPICE
will map outflow velocities of surface features to solar wind structures
with similar composition (FIP, M/q) measured in-situ by the SWA/HIS
instrument on Solar Orbiter. These observations will help discriminate
models of solar wind origin by matching composition signatures in
solar wind streams to surface feature composition, and discriminate
physical processes that inject material from closed structures into
solar wind streams. <P />This presentation will provide an overview of
the SPICE investigation, including science & measurement objective,
instrument design, capabilities and performance as measured during
calibration prior to delivery to the Solar Orbiter spacecraft. The
presentation will also provide a description of the operations concept
and data processing during the mission.
---------------------------------------------------------
Title: Concept study of Solar-C_EUVST optical design
Authors: Kawate, Tomoko; Shimizu, Toshifumi; Imada, Shinsuke; Tsuzuki,
Toshihiro; Katsukawa, Yukio; Hara, Hirohisa; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Warren, Harry; Teriaca, Luca; Korendyke, Clarence
M.; Brown, Charles
2019SPIE11118E..1NK Altcode:
The main characteristics of Solar-C_EUVST are the high temporal and
high spatial resolutions over a wide temperature coverage. In order
to realize the instrument for meeting these scientific requirements
under size constraints given by the JAXA Epsilon vehicle, we examined
four-dimensional optical parameter space of possible solutions of
geometrical optical parameters such as mirror diameter, focal length,
grating magnification, and so on. As a result, we have identified
the solution space that meets the EUVST science objectives and rocket
envelope requirements. A single solution was selected and used to define
the initial optical parameters for the concept study of the baseline
architecture for defining the mission concept. For this solution, we
optimized the grating and geometrical parameters by ray tracing of the
Zemax software. Consequently, we found an optics system that fulfills
the requirement for a 0.4" angular resolution over a field of view of
100" (including margins) covering spectral ranges of 170-215, 463-542,
557-637, 690-850, 925-1085, and 1115-1275 A. This design achieves an
effective area 10 times larger than the Extreme-ultraviolet Imaging
Spectrometer onboard the Hinode satellite, and will provide seamless
observations of 4.2-7.2 log(K) plasmas for the first time. Tolerance
analyses were performed based on the optical design, and the moving
range and step resolution of focus mechanisms were identified. In
the presentation, we describe the derivation of the solution space,
optimization of the optical parameters, and show the results of ray
tracing and tolerance analyses.
---------------------------------------------------------
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 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: Alignment procedure for the Gregorian telescope of the Metis
coronagraph for the Solar Orbiter ESA mission
Authors: Da Deppo, Vania; Mottini, Sergio; Naletto, Giampiero;
Frassetto, Fabio; Zuppella, Paola; Sertsu, Mewael G.; Romoli, Marco;
Fineschi, Silvano; Antonucci, Ester; Nicolini, Gianalfredo; Nicolosi,
Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Castronuovo, Marco;
Casti, Marta; Capobianco, Gerardo; Massone, Giuseppe; Susino, Roberto;
Landini, Federico; Pancrazzi, Maurizio; Casini, Chiara; Teriaca,
Luca; Uslenghi, Michela
2019SPIE11180E..76D Altcode:
Metis is a solar coronagraph mounted on-board the Solar Orbiter ESA
spacecraft. Solar Orbiter is scheduled for launch in February 2020
and it is dedicated to study the solar and heliospheric physics from a
privileged close and inclined orbit around the Sun. Perihelion passages
with a minimum distance of 0.28 AU are foreseen. Metis features two
channels to image the solar corona in two different spectral bands:
in the HI Lyman at 121.6 nm, and in the polarized visible light band
(580 - 640 nm). Metis is a solar coronagraph adopting an "inverted
occulted" configuration. The inverted external occulter (IEO) is a
circular aperture followed by a spherical mirror which back rejects
the disk light. The reflected disk light exits the instrument through
the IEO aperture itself, while the passing coronal light is collected
by the Metis telescope. Common to both channels, the Gregorian on-axis
telescope is centrally occulted and both the primary and the secondary
mirror have annular shape. Classic alignment methods adopted for on-axis
telescope cannot be used, since the on-axis field is not available. A
novel and ad hoc alignment set-up has been developed for the telescope
alignment. An auxiliary visible optical ground support equipment source
has been conceived for the telescope alignment. It is made up by four
collimated beams inclined and dimensioned to illuminate different
sections of the annular primary mirror without being vignetted by
other optical or mechanical elements of the instrument.
---------------------------------------------------------
Title: Metis/Solar Orbiter polarimetric visible light channel
calibration
Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Romoli, M.;
Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.;
Andretta, V.; Castronuovo, M.; Massone, G.; Susino, R.; Da Deppo, V.;
Frassetto, F.; Landini, F.; Pancrazzi, M.; Teriaca, L.; Uslenghi, M.
2019SPIE11180E..3CC Altcode:
Metis is the solar coronagraph of the ESA mission Solar Orbiter. For
the first time, Metis will acquire simultaneous images of the solar
corona in linearly polarized, broadband visible light (580-640 nm) and
in the narrow-band HI Ly-α line (121.6 nm). The visible light path
includes a polarimeter, designed to observe and analyse the K-corona
linearly polarized by Thomson scattering. The polarimeter comprises a
liquid crystal Polarization Modulation Package (PMP) together with a
quarter-wave retarder and a linear polarizer. The Metis PMP consists of
two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with
their fast axis parallel with respect to each other and a pre-tilted
angle of the molecules in opposite direction. This configuration results
in an instrumental wide field of view (+/-7°). The LCVRs provide an
electro-optical modulation of the input polarized light by applying an
electric field to the liquid crystal molecules inside the cells. A given
optical retardance can be induced in the LCVRs by selecting a suitable
voltage value. This paper reports the polarimetric characterization of
the Visible-light channel for the Metis/Solar Orbiter coronagraph. The
retardance-to-voltage calibration of the electro-optical polarimeter was
characterized over the entire field of view of the coronagraph yielding
a complete "polarimetric flat-field" of the Metis Visible-light channel.
---------------------------------------------------------
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: 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: METIS, the Multi Element Telescope for Imaging and
Spectroscopy: an instrument proposed for the solar orbiter mission
Authors: Antonucci, E.; Andretta, V.; Cesare, S.; Ciaravella, A.;
Doschek, G.; Fineschi, S.; Giordano, S.; Lamy, P.; Moses, D.; Naletto,
G.; Newmark, J.; Poletto, L.; Romoli, M.; Solanki, S.; Spadaro, D.;
Teriaca, L.; Zangrilli, L.
2017SPIE10566E..0LA Altcode:
METIS, the Multi Element Telescope for Imaging and Spectroscopy,
is an instrument proposed to the European Space Agency to be part of
the payload of the Solar Orbiter mission. The instrument design has
been conceived for performing extreme ultraviolet (EUV) spectroscopy
both on the solar disk and off-limb, and near-Sun coronagraphy
and spectroscopy. The proposed instrument suite consists of three
different interconnected elements, COR, EUS and SOCS, sharing the
same optical bench, electronics, and S/C heat shield aperture. COR is
a visible-EUV multiband coronagraph based on a classical externally
occulted design. EUS is the component of the METIS EUV disk spectrometer
which includes the telescope and all the related mechanisms. Finally,
SOCS is the METIS spectroscopic component including the dispersive
system and the detectors. The capability of inserting a small telescope
collecting coronal light has been added to perform also EUV coronal
spectroscopy. METIS can simultaneously image the visible and ultraviolet
emission of the solar corona and diagnose, with unprecedented temporal
coverage and space resolution the structure and dynamics of the full
corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙,
measured from Sun centre) at minimum (maximum) perihelion during the
nominal mission. It can also perform spectroscopic observations of the
solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region,
and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125
nm spectral band.
---------------------------------------------------------
Title: METIS: the visible and UV coronagraph for solar orbiter
Authors: Romoli, M.; Landini, F.; Antonucci, E.; Andretta, V.;
Berlicki, A.; Fineschi, S.; Moses, J. D.; Naletto, G.; Nicolosi, P.;
Nicolini, G.; Spadaro, D.; Teriaca, L.; Baccani, C.; Focardi, M.;
Pancrazzi, M.; Pucci, S.; Abbo, L.; Bemporad, A.; Capobianco, G.;
Massone, G.; Telloni, D.; Magli, E.; Da Deppo, V.; Frassetto, F.;
Pelizzo, M. G.; Poletto, L.; Uslenghi, M.; Vives, S.; Malvezzi, M.
2017SPIE10563E..1MR Altcode:
METIS coronagraph is designed to observe the solar corona with an
annular field of view from 1.5 to 2.9 degrees in the visible broadband
(580-640 nm) and in the UV HI Lyman-alpha, during the Sun close
approaching and high latitude tilting orbit of Solar Orbiter. The
big challenge for a coronagraph is the stray light rejection. In
this paper after a description of the present METIS optical design,
the stray light rejection design is presented in detail together with
METIS off-pointing strategies throughout the mission. Data shown in this
paper derive from the optimization of the optical design performed with
Zemax ray tracing and from laboratory breadboards of the occultation
system and of the polarimeter.
---------------------------------------------------------
Title: Spectroscopy of Very Hot Plasma in Non-flaring Parts of a
Solar Limb Active Region: Spatial and Temporal Properties
Authors: Parenti, Susanna; del Zanna, Giulio; Petralia, Antonino;
Reale, Fabio; Teriaca, Luca; Testa, Paola; Mason, Helen E.
2017ApJ...846...25P Altcode: 2017arXiv170708445P
In this work we investigate the thermal structure of an off-limb
active region (AR) in various non-flaring areas, as it provides key
information on the way these structures are heated. In particular,
we concentrate on the very hot component (> 3 {MK}) as it is a
crucial element to distinguish between different heating mechanisms. We
present an analysis using Fe and Ca emission lines from both the
Solar Ultraviolet Measurement of Emitted Radiation (SUMER) on board
the Solar and Heliospheric Observatory (SOHO) and the EUV Imaging
Spectrometer (EIS) on board Hinode. A data set covering all ionization
stages from Fe x to Fe xix has been used for the thermal analysis
(both differential emission measure and emission measure, EM). Ca
xiv is used for the SUMER-EIS radiometric cross calibration. We show
that the very hot plasma is present and persistent almost everywhere
in the core of the limb AR. The off-limb AR is clearly structured in
Fe xviii. Almost everywhere, the EM analysis reveals plasma at 10 MK
(visible in Fe xix emission), which is down to 0.1% of EM of the main
3 {MK} plasma. We estimate the power-law index of the hot tail of
the EM to be between -8.5 and -4.4. However, the question about the
possible existence of a small minor peak at around 10 {MK} remains
open. The absence in some part of the AR of the Fe xix and Fe xxiii
lines (which fall into our spectral range) enables us to determine
an upper limit on the EM at these temperatures. Our results include
a new Ca xiv 943.59 Å atomic model.
---------------------------------------------------------
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 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: Propagating disturbances along fan-like coronal loops in an
active region
Authors: Mandal, Sudip; Samanta, Tanmoy; Banerjee, Dipankar; Krishna
Prasad, S.; Teriaca, Luca
2015RAA....15.1832M Altcode: 2015arXiv150504710M
Propagating disturbances are often observed in active region
fan-like coronal loops. They were thought to be due to slow
mode magnetohydrodynamic waves based on some of the observed
properties. However, recent studies involving spectroscopy indicate
that they could be due to high speed quasi-periodic upflows which are
difficult to distinguish from upward propagating slow waves. In this
context, we have studied a fan loop structure in the active region AR
11465 using simultaneous spectroscopic and imaging observations from the
Extreme Ultraviolet Imaging Spectrometer onboard Hinode and Atmospheric
Imaging Assembly onboard Solar Dynamics Observatory. Analysis of the
data shows significant oscillations at different locations. We explore
the variations in different line parameters to determine whether the
waves or flows could cause these oscillations to improve the current
understanding of the nature of these disturbances.
---------------------------------------------------------
Title: Solar extreme ultraviolet variability of the quiet Sun
Authors: Shakeri, F.; Teriaca, L.; Solanki, S. K.
2015A&A...581A..51S Altcode: 2015arXiv150705786S
The last solar minimum has been unusually quiet compared to the previous
minima (since space-based radiometric measurements are available). The
Sun's magnetic flux was substantially lower during this minimum. Some
studies also show that the total solar irradiance during the minimum
after cycle 23 may have dropped below the values known from the two
minima prior to that. For chromospheric and coronal radiation, the
situation is less clear-cut. The Sun's 10.7 cm flux shows a decrease of
~4% during the solar minimum in 2008 compared to the previous minimum,
but Ca ii K does not. Here we consider additional wavelengths in
the extreme ultraviolet (EUV), specifically transitions of He i at
584.3 Å and O v at 629.7 Å, of which the CDS spectrometer aboard
SOHO has been taking regular scans along the solar central meridian
since 1996. We analysed this unique dataset to verify if and how the
radiance distribution undergoes measurable variations between cycle
minima. To achieve this aim we determined the radiance distribution
of quiet areas around the Sun centre. Concentrating on the last two
solar minima, we found out that there is very little variation in the
radiance distribution of the chromospheric spectral line He i between
these minima. The same analysis shows a modest, although significant,
4% variation in the radiance distribution of the TR spectral line O
v. These results are comparable to those obtained by earlier studies
employing other spectral features, and they confirm that chromospheric
indices display a small variation, whereas in the transition region
a more significant reduction of the brighter features is visible.
---------------------------------------------------------
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: In-flight UV and polarized-VL radiometric calibrations of
the solar orbiter/METIS imaging coronagraph
Authors: Focardi, M.; Capobianco, G.; Andretta, V.; Sasso, C.; Romoli,
M.; Landini, F.; Fineschi, S.; Pancrazzi, M.; Bemporad, A.; Nicolini,
G.; Pucci, S.; Uslenghi, M.; Naletto, G.; Nicolosi, P.; Spadaro, D.;
Teriaca, L.; SchuÌhle, U. H.; Antonucci, E.
2014SPIE.9144E..09F Altcode:
METIS is an innovative inverted occulted solar coronagraph capable of
obtaining for the first time simultaneous imaging of the full corona
in linearly polarized visible-light (580-640 nm) and narrow-band
(+/- 10 nm) ultraviolet H I Ly-α (121.6 nm). It has been selected to
fly aboard the Solar Orbiter<SUP>1</SUP> spacecraft, whose launch is
foreseen in July 2017. Thanks to its own capabilities and exploiting
the peculiar opportunities offered by the Solar Orbiter planned orbit,
METIS will address some of the still open issues in understanding the
physical processes in the corona and inner heliosphere. The Solar
Orbiter Nominal Mission Phase (NMP) will be characterized by three
scientific observing windows per orbit and METIS will perform at least
one in-flight calibration per observing window. The two imaging channels
of METIS will be calibrated on ground and periodically checked, verified
and re-calibrated in-flight. In particular, radiometric calibration
images will be needed to determine the absolute brightness of the solar
corona. For UV radiometric calibration a set of targets is represented
by continuum-emitting early type bright stars (e.g. A and B spectral
types) whose photospheres produce a bright far-ultraviolet continuum
spectrum stable over long timescales. These stars represent an important
reference standard not only for METIS in-flight calibrations but
also for other Solar Orbiter instruments and they will be crucial for
instruments cross-calibrations as well. For VL radiometric calibration,
a set of linearly polarized stars will be used. These targets shall
have a minimum degree of linear polarization (DoLP > 5%) and a
detectable magnitude, compatible with the instrument integration times
constrained by the desired S/N ratio and the characteristics of the
spacecraft orbit dynamics.
---------------------------------------------------------
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: Hardware and software architecture on board solar
orbiter/METIS: an update
Authors: Pancrazzi, M.; Focardi, M.; Nicolini, G.; Andretta, V.;
Uslenghi, M.; Magli, E.; Ricci, M.; Bemporad, A.; Spadaro, D.; Landini,
F.; Romoli, M.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolosi,
P.; Teriaca, L.
2014SPIE.9144E..3FP Altcode:
METIS, is one of the ten instruments selected to be part of the Solar
Orbiter payload; it is a coronagraph that will investigate the inner
part of the heliosphere performing imaging in the visible band and in
the hydrogen Lyman α line @ 121.6 nm. METIS has recently undergone
throughout a revision to simplify the instrument design. This paper
will provide an overview of the updated hardware and software design of
the coronagraph as presented at the Instrument Delta-Preliminary Design
Review occurred in April 2014. The current configuration foresees two
detectors, an Intensified APS for the UV channel and an APS for the
visible light equipped with a Liquid Crystal Variable Retarder (LCVR)
plate to perform broadband visible polarimetry. Each detector has a
proximity electronics generating the control and readout signals for
the sensor but the operations of the two devices are in charge of a
centralized unit, the METIS Processing and Power Unit (MPPU). The MPPU
operates the remaining electrical subsystems supplying them with power
and providing on board storage and processing capabilities. Its design
foresees the redundancy of the most critical parts, thus mitigating the
effects of possible failures of the electronics subsystems. The central
monitoring unit is also in charge of providing the communication with
the S/C, handling the telemetry and telecommand exchange with the
platform. The data acquired by the detectors shall undergo through
a preliminary on-board processing to maximize the scientific return
and to provide the necessary information to validate the results on
ground. Operations as images summing, compression and cosmic rays
monitoring and removal will be fundamental not only to mitigate the
effects of the main sources of noise on the acquired data, but also to
maximize the data volume to be transferred to the spacecraft in order to
fully exploit the limited bandwidth telemetry downlink. Finally, being
Solar Orbiter a deep-space mission, some METIS procedures have been
designed to provide the instrument an efficient autonomous behavior
in case of an immediate reaction is required as for the arising of
transient events or the occurrence of safety hazards conditions.
---------------------------------------------------------
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: Characteristics of polar coronal hole jets
Authors: Chandrashekhar, K.; Bemporad, A.; Banerjee, D.; Gupta, G. R.;
Teriaca, L.
2014A&A...561A.104C Altcode: 2013arXiv1310.8106C
Context. High spatial- and temporal-resolution images of coronal hole
regions show a dynamical environment where mass flows and jets are
frequently observed. These jets are believed to be important for the
coronal heating and the acceleration of the fast solar wind. <BR />
Aims: We studied the dynamics of two jets seen in a polar coronal hole
with a combination of imaging from EIS and XRT onboard Hinode. We
observed drift motions related to the evolution and formation of
these small-scale jets, which we tried to model as well. <BR />
Methods: Stack plots were used to find the drift and flow speeds
of the jets. A toymodel was developed by assuming that the observed
jet is generated by a sequence of single reconnection events where
single unresolved blobs of plasma are ejected along open field lines,
then expand and fall back along the same path, following a simple
ballistic motion. <BR /> Results: We found observational evidence that
supports the idea that polar jets are very likely produced by multiple
small-scale reconnections occurring at different times in different
locations. These eject plasma blobs that flow up and down with a motion
very similar to a simple ballistic motion. The associated drift speed of
the first jet is estimated to be ≈27 km s<SUP>-1</SUP>. The average
outward speed of the first jet is ≈171 km s<SUP>-1</SUP>, well below
the escape speed, hence if simple ballistic motion is considered, the
plasma will not escape the Sun. The second jet was observed in the south
polar coronal hole with three XRT filters, namely, C<SUB>-</SUB>poly,
Al<SUB>-</SUB>poly, and Al<SUB>-</SUB>mesh filters. Many small-scale
(≈3″-5″) fast (≈200-300 km s<SUP>-1</SUP>) ejections of
plasma were observed on the same day; they propagated outwards. We
observed that the stronger jet drifted at all altitudes along the
jet with the same drift speed of ≃7 km s<SUP>-1</SUP>. We also
observed that the bright point associated with the first jet is a
part of sigmoid structure. The time of appearance of the sigmoid
and that of the ejection of plasma from the bright point suggest
that the sigmoid is the progenitor of the jet. <BR /> Conclusions:
The enhancement in the light curves of low-temperature EIS lines in
the later phase of the jet lifetime and the shape of the jet's stack
plots suggests that the jet material falls back, and most likely cools
down. To further support this conclusion, the observed drifts were
interpreted within a scenario where reconnection progressively shifts
along a magnetic structure, leading to the sequential appearance of
jets of about the same size and physical characteristics. On this
basis, we also propose a simple qualitative model that mimics the
observations. <P />Movies 1-3 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201321213/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Quiet Sun Explosive Events: Jets, Splashes, and Eruptions
Authors: Innes, D. E.; Teriaca, L.
2013SoPh..282..453I Altcode: 2012arXiv1210.7667I
Explosive events appear as broad non-Gaussian wings in the line
profiles of small transition-region phenomena. Images from the Solar
Dynamics Observatory (SDO) give a first view of the plasma dynamics
at the sites of explosive events seen simultaneously in O VI spectra
of a region of quiet Sun, taken with the ultraviolet spectrometer
Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard
the Solar and Heliospheric Observatory (SOHO). Distinct event
bursts were seen either at the junction of supergranular network
cells or near emerging flux. Three are described in the context of
their surrounding transition region (304 Å) and coronal (171 Å)
activity. One showed plasma ejections from an isolated pair of sites,
with a time lag of 50 seconds between events. At the site where the
later explosive event was seen, the extreme ultraviolet (EUV) images
show a hot core surrounded by a small, expanding ring of chromospheric
emission, which we interpret as a "splash." The second explosive-event
burst was related to flux cancellation, inferred from Helioseismic and
Magnetic Imager (HMI) magnetograms, and a coronal dimming surrounded
by a ring of bright EUV emission with explosive events at positions
where the spectrometer slit crossed the bright ring. The third series
of events occurred at the base of a slow, small coronal mass ejection
(mini-CME). All events studied here imply jet-like flows probably
triggered by magnetic reconnection at supergranular junctions. Events
come from sites close to the footpoints of jets seen in Atmospheric
Imaging Assembly (AIA) images, and possibly from the landing site of
high-velocity flows. They are not caused by rapid rotation in spicules.
---------------------------------------------------------
Title: European Solar Physics: moving from SOHO to Solar Orbiter
and beyond
Authors: Solanki, S. K.; Teriaca, L.; Barthol, P.; Curdt, W.;
Inhester, B.
2013MmSAI..84..286S Altcode:
When ESA and NASA launched the Solar and Heliospheric Observatory (SOHO)
to the Sun-Earth L1 point, they also launched European solar physics
into a steep upward trajectory. Thanks to the battery of instruments
on SOHO our picture of the Sun changed dramatically from that of a
sedate, nearly static star into that of a highly structured, dynamic
one. Subsequent solar missions have probed higher energy radiation,
gazed at the Sun from new vantage points in the ecliptic, analysed
the Sun at higher spatial resolution and imaged the whole Sun in many
wavelengths at high cadence. Nonetheless, SOHO is still going strong and
still delivering unique data. In the meantime European solar physicists
are working hard on the next major mission, Solar Orbiter, now being
implemented as the M1 mission of ESA's Cosmic Vision program. Solar
Orbiter will leave the Earth's orbit and move ever closer to the Sun,
reaching a perihelion inside the orbit of Mercury. This will allow it
to sample the Sun's dynamic inner heliosphere in situ, while probing
the source regions of the ambient solar wind with its remote sensing
instruments, a unique combination. Solar Orbiter will also leave the
ecliptic and, for the first time, image the Sun's poles. This will
bring us closer to finding the missing pieces of the puzzle on how
the solar dynamo works. Beyond Solar Orbiter are further exciting
prospects, such as the Solar-C mission, or the large European Solar
Telescope. Here an overview of solar missions and telescopes and the
associated science is given from a European perspective.
---------------------------------------------------------
Title: Doppler shift of hot coronal lines in a moss area of an
active region
Authors: Dadashi, N.; Teriaca, L.; Tripathi, D.; Solanki, S. K.;
Wiegelmann, T.
2012A&A...548A.115D Altcode: 2012arXiv1211.5473D
The moss is the area at the footpoint of the hot (3 to 5 MK) loops
forming the core of the active region where emission is believed to
result from the heat flux conducted down to the transition region from
the hot loops. Studying the variation of Doppler shift as a function
of line formation temperatures over the moss area can give clues
on the heating mechanism in the hot loops in the core of the active
regions. We investigate the absolute Doppler shift of lines formed
at temperatures between 1 MK and 2 MK in a moss area within active
region NOAA 11243 using a novel technique that allows determining the
absolute Doppler shift of EUV lines by combining observations from
the SUMER and EIS spectrometers. The inner (brighter and denser) part
of the moss area shows roughly constant blue shift (upward motions)
of 5 km s<SUP>-1</SUP> in the temperature range of 1 MK to 1.6 MK. For
hotter lines the blue shift decreases and reaches 1 km s<SUP>-1</SUP>
for Fe xv 284 Å (~2 MK). The measurements are discussed in relation
to models of the heating of hot loops. The results for the hot coronal
lines seem to support the quasi-steady heating models for nonsymmetric
hot loops in the core of active regions.
---------------------------------------------------------
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: Spectroscopic observations of propagating disturbances in a
polar coronal hole: evidence of slow magneto-acoustic waves
Authors: Gupta, G. R.; Teriaca, L.; Marsch, E.; Solanki, S. K.;
Banerjee, D.
2012A&A...546A..93G Altcode: 2012arXiv1209.3524G
<BR /> Aims: We focus on detecting and studying quasi-periodic
propagating features that have been interpreted in terms of both slow
magneto-acoustic waves and of high-speed upflows. <BR /> Methods:
We analyzed long-duration spectroscopic observations of the on-disk
part of the south polar coronal hole taken on 1997 February 25 by
the SUMER spectrometer onboard SOHO. We calibrated the velocity
with respect to the off-limb region and obtained time-distance maps
in intensity, Doppler velocity, and line width. We also performed a
cross-correlation analysis on different time series curves at different
latitudes. We studied average spectral line profiles at the roots
of propagating disturbances and along the propagating ridges, and
performed a red-blue asymmetry analysis. <BR /> Results: We clearly
find propagating disturbances in intensity and Doppler velocity with
a projected propagation speed of about 60 ± 4.8 km s<SUP>-1</SUP>
and a periodicity of ≈14.5 min. To our knowledge, this is the first
simultaneous detection of propagating disturbances in intensity as
well as in Doppler velocity in a coronal hole. During the propagation,
an intensity enhancement is associated with a blueshifted Doppler
velocity. These disturbances are clearly seen in intensity also
at higher latitudes (i.e., closer to the limb), while disturbances
in Doppler velocity become faint there. The spectral line profiles
averaged along the propagating ridges are found to be symmetric, to
be well fitted by a single Gaussian, and have no noticeable red-blue
asymmetry. <BR /> Conclusions: Based on our analysis, we interpret
these disturbances in terms of propagating slow magneto-acoustic waves.
---------------------------------------------------------
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: Spectroscopic Observations of Fe XVIII in Solar Active Regions
Authors: Teriaca, Luca; Warren, Harry P.; Curdt, Werner
2012ApJ...754L..40T Altcode: 2012arXiv1206.4228T
The large uncertainties associated with measuring the amount of
high temperature emission in solar active regions (ARs) represents
a significant impediment to making progress on the coronal heating
problem. Most current observations at temperatures of 3 MK and above
are taken with broadband soft X-ray instruments. Such measurements
have proven difficult to interpret unambiguously. Here, we present the
first spectroscopic observations of the Fe XVIII 974.86 Å emission
line in an on-disk AR taken with the SUMER instrument on SOHO. Fe
XVIII has a peak formation temperature of 7.1 MK and provides important
constraints on the amount of impulsive heating in the corona. Detailed
evaluation of the spectra and comparison of the SUMER data with soft
X-ray images from the X-Ray Telescope on Hinode confirm that this line
is unblended. We also compare the spectroscopic data with observations
from the Atmospheric Imaging Assembly (AIA) 94 Å channel on the Solar
Dynamics Observatory. The AIA 94 Å channel also contains Fe XVIII, but
is blended with emission formed at lower temperatures. We find that it
is possible to remove the contaminating blends and form relatively pure
Fe XVIII images that are consistent with the spectroscopic observations
from SUMER. The observed spectra also contain the Ca XIV 943.63 Å
line that, although a factor 2-6 weaker than the Fe XVIII 974.86 Å
line, allows us to probe the plasma around 3.5 MK. The observed ratio
between the two lines indicates (isothermal approximation) that most
of the plasma in the brighter Fe XVIII AR loops is at temperatures
between 3.5 and 4 MK.
---------------------------------------------------------
Title: Multi wavelength Study of Polar X-ray Jets using Hinode and SDO
Authors: Chandrashekhar, K.; Gupta, Girjesh R.; Banerjee, Dipankar;
Teriaca, Luca
2012cosp...39..310C Altcode: 2012cosp.meet..310C
High spatial and temporal resolution images of the solar transition
region in quiet and coronal hole regions show a dynamical environment
where mass flows and jets are commonly observed. We study a
polar jet with a combination of imaging from EIS and XRT on board
Hinode. We measure jet parameters, e.g. length, width, life time,
outward speed. The bright point associated with the jet is part
of a sigmoidal structure. The time of appearance of the sigmoid and
ejection of plasma from the bright point suggests that the sigmoid is a
progenitor of the jet. Before and after the main jet event, we observe
small collimated plasma flows from the bright point to the footpoint
of the jet. These observations suggest that repetitive reconnection
between emerging flux and the ambient open field in the coronal hole
causes the polar jets. Average outward speed of the jet is 160 km/s,
well below the escape speed. The enhancement in the light curves of
low temperature EIS lines after the occurrence of the jet suggests
that the jet material is falling back. To supplement these results
we studied two polar coronal jets observed by AIA and HMI on board
SDO. These jets have speeds around 200 to 300 km/s. The temperature
response and the associated magnetic flux changes are studied using
the multiple channels of AIA and HMI. The light curves as recorded
with different AIA channels are compared with magnetic flux evolution
as recorded by HMI. We will show that in spite of the better time and
spatial resolution of AIA, the overlapping temperature response of
AIA channels causes difficulty in proper diagnosis.
---------------------------------------------------------
Title: Spectroscopic Observations of Propagating Disturbances in
Polar Coronal Hole
Authors: Gupta, Girjesh R.; Marsch, Eckart; Solanki, Sami K.; Banerjee,
Dipankar; Teriaca, Luca
2012cosp...39..689G Altcode: 2012cosp.meet..689G
We focus on long duration spectroscopic observations of the south
polar coronal hole taken on 1997 February 25 by the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) spectrometer aboard SOHO. We
analyze the data in the on-disk part of the coronal hole to find any
signature of propagating waves or high speed up-flows. We find the
clear presence of propagating disturbances in intensity and Doppler
velocity with a projected propagation speed of about 60~km~s^{-1} and
a periodicity of ≈14.5~min. During the propagation, the intensity
enhancement is associated with a blue-shifted Doppler velocity. These
disturbances are clearly seen in intensity at higher latitudes
(i.e. closer to the limb), whereas disturbances in Doppler velocity
becomes faint there. We study average spectral line profiles at the
roots of these disturbances and along the propagating ridge. Based on
our analysis, we interpret these disturbances in terms of propagating
slow magneto-acoustic waves.
---------------------------------------------------------
Title: Explosive events - swirling transition region jets
Authors: Curdt, Werner; Kamio, Suguru; Tian, Hui; Teriaca, Luca
2012cosp...39..381C Altcode: 2012cosp.meet..381C
The bi-directed, fast Doppler motion of explosive events observed
spectroscopically in the transition region emission is classically
interpreted as a pair of jets moving upward and downward from a
reconnection site. We discuss the problems of such a model and provide
evidence for an alternative scenario to explain the nature of so-called
'explosive events'. The discrepancy of fast Doppler motion without
detectable motion in the image plane is an old, unsolved problem. We
now provide the spectral tilt and the jet bifurcation as additional
arguments. Both features are indicative of rotational motion in narrow
structures. We interpret the bifurcation as the result of rotation of
hollow cylindrical structures and demonstrate that such a sheath model
can also be applied to explain the nature of the puzzling 'explosive
events'. We find that the spectral tilt, the lack of apparent motion,
the bifurcation, and a rapidly growing number of direct observations
support an alternative scenario of linear, spicular-sized jets with
a strong spinning motion.
---------------------------------------------------------
Title: 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: The quiet Sun average Doppler shift of coronal lines up to 2 MK
Authors: Dadashi, N.; Teriaca, L.; Solanki, S. K.
2011A&A...534A..90D Altcode: 2011arXiv1109.4493D
Context. The average Doppler shift shown by spectral lines formed
from the chromosphere to the corona reveals important information
on the mass and energy balance of the solar atmosphere, providing
an important observational constraint to any models of the solar
corona. Previous spectroscopic observations of vacuum ultra-violet
(VUV) lines have revealed a persistent average wavelength shift of
lines formed at temperatures up to 1 MK. At higher temperatures,
the behaviour is still essentially unknown. <BR /> Aims: Here we
analyse combined SUMER (Solar Ultraviolet Measurements of Emitted
Radiation)/SoHO (Solar and Heliospheric Observatory) and EIS (EUV
Imaging Spectrometer)/Hinode observations of the quiet Sun around
disk centre to determine, for the first time, the average Doppler
shift of several spectral lines formed between 1 and 2 MK, where the
largest part of the quiet coronal emission is formed. <BR /> Methods:
The measurements are based on a novel technique applied to EIS spectra
to measure the difference in Doppler shift between lines formed at
different temperatures. Simultaneous wavelength-calibrated SUMER spectra
allow establishing the absolute value at the reference temperature of
T ≈ 1 MK. <BR /> Results: The average line shifts at 1 MK < T <
1.8 MK are modestly, but clearly bluer than those observed at 1 MK. By
accepting an average blue shift of about (-1.8 ± 0.6) km s<SUP>-1</SUP>
at 1 MK (as provided by SUMER measurements), this translates into a
maximum Doppler shift of (-4.4 ± 2.2) km s<SUP>-1</SUP> around 1.8
MK. The measured value appears to decrease to about (-1.3 ± 2.6) km
s<SUP>-1</SUP> at the Fe xv formation temperature of 2.1 MK. <BR />
Conclusions: The measured average Doppler shift between 0.01 and 2.1
MK, for which we provide a parametrisation, appears to be qualitatively
and roughly quantitatively consistent with what foreseen by 3D coronal
models where heating is produced by dissipation of currents induced
by photospheric motions and by reconnection with emerging magnetic flux.
---------------------------------------------------------
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: Hydrogen Lyα and Lyβ Radiances and Profiles in Polar
Colornal Holes
Authors: Tian, Hui; Teriaca, Luca; Curdt, Werner; Vial, Jean-Claude
2011shin.confE.166T Altcode:
The hydrogen Lyα plays a dominant role in the radiative energy
transport in the lower transition region, and is important for
the studies of transition-region structure as well as solar wind
origin. We investigate the Lyα profiles obtained by the Solar
Ultraviolet Measurement of Emitted Radiation spectrograph on the
Solar and Heliospheric Observatory spacecraft in coronal holes and
the quiet Sun. In a subset of these observations, the Hi Lyβ, Si III,
and Ovi lines were also (quasi-)simultaneously recorded. We find that
the distances between the two peaks of Lyα profiles are larger in
coronal holes than in the quiet Sun, indicating a larger opacity in
coronal holes. This difference might result from the different magnetic
structures or the different radiation fields in the two regions. Most
of the Lyβ profiles in the coronal hole have a stronger blue peak,
in contrast to those in quiet-Sun regions while in both regions the
Lyα profiles are stronger in the blue peak. Although the asymmetries
are likely to be produced by differential flows in the solar atmosphere,
their detailed formation processes are still unclear. The radiance ratio
between Lyα and Lyβ decreases toward the limb in the coronal hole,
which might be due to the different opacity of the two lines. We also
find that the radiance distributions of the four lines are set by a
combined effect of limb brightening and the different emission level
between coronal holes and the quiet Sun.
---------------------------------------------------------
Title: Propagating MHD Waves in Coronal Holes
Authors: Banerjee, D.; Gupta, G. R.; Teriaca, L.
2011SSRv..158..267B Altcode: 2010SSRv..tmp..180B; 2010arXiv1009.2980B
Coronal holes are the coolest and darkest regions of the upper solar
atmosphere, as observed both on the solar disk and above the solar
limb. Coronal holes are associated with rapidly expanding open magnetic
fields and the acceleration of the high-speed solar wind. During
the years of the solar minima, coronal holes are generally confined
to the Sun's polar regions, while at solar maxima they can also be
found at lower latitudes. Waves, observed via remote sensing and
detected in-situ in the wind streams, are most likely responsible
for the wind and several theoretical models describe the role of MHD
waves in the acceleration of the fast solar wind. This paper reviews
the observational evidences of detection of propagating waves in
these regions. The characteristics of the waves, like periodicities,
amplitude, speed provide input parameters and also act as constraints
on theoretical models of coronal heating and solar wind acceleration.
---------------------------------------------------------
Title: Morphology, dynamics and plasma parameters of plumes and
inter-plume regions in solar coronal holes
Authors: Wilhelm, K.; Abbo, L.; Auchère, F.; Barbey, N.; Feng, L.;
Gabriel, A. H.; Giordano, S.; Imada, S.; Llebaria, A.; Matthaeus,
W. H.; Poletto, G.; Raouafi, N. -E.; Suess, S. T.; Teriaca, L.; Wang,
Y. -M.
2011A&ARv..19...35W Altcode: 2011arXiv1103.4481W
Coronal plumes, which extend from solar coronal holes (CH) into the high
corona and—possibly—into the solar wind (SW), can now continuously
be studied with modern telescopes and spectrometers on spacecraft,
in addition to investigations from the ground, in particular, during
total eclipses. Despite the large amount of data available on these
prominent features and related phenomena, many questions remained
unanswered as to their generation and relative contributions to
the high-speed streams emanating from CHs. An understanding of the
processes of plume formation and evolution requires a better knowledge
of the physical conditions at the base of CHs, in plumes and in the
surrounding inter-plume regions. More specifically, information is
needed on the magnetic field configuration, the electron densities
and temperatures, effective ion temperatures, non-thermal motions,
plume cross sections relative to the size of a CH, the plasma bulk
speeds, as well as any plume signatures in the SW. In spring 2007, the
authors proposed a study on `Structure and dynamics of coronal plumes
and inter-plume regions in solar coronal holes' to the International
Space Science Institute (ISSI) in Bern to clarify some of these aspects
by considering relevant observations and the extensive literature. This
review summarizes the results and conclusions of the study. Stereoscopic
observations allowed us to include three-dimensional reconstructions
of plumes. Multi-instrument investigations carried out during several
campaigns led to progress in some areas, such as plasma densities,
temperatures, plume structure and the relation to other solar phenomena,
but not all questions could be answered concerning the details of
plume generation process(es) and interaction with the SW.
---------------------------------------------------------
Title: Evolution of microflares associated with bright points in
coronal holes and in quiet regions
Authors: Kamio, S.; Curdt, W.; Teriaca, L.; Innes, D. E.
2011A&A...529A..21K Altcode: 2010arXiv1009.1957K
<BR /> Aims: We aim to find similarities and differences between
microflares at coronal bright points found in quiet regions and
coronal holes, and to study their relationship with large scale
flares. <BR /> Methods: Coronal bright points in quiet regions
and in coronal holes were observed with Hinode/EIS using the same
sequence. Microflares associated with bright points are identified from
the X-ray lightcurve. The temporal variation of physical properties was
traced in the course of microflares. <BR /> Results: The lightcurves
of microflares indicated an impulsive peak at hot emission followed by
an enhancement at cool emission, which is compatible with the cooling
model of flare loops. The density was found to increase at the rise of
the impulsive peak, supporting chromospheric evaporation models. A
notable difference is found in the surroundings of microflares;
diffuse coronal jets are produced above microflares in coronal
holes while coronal dimmings are formed in quiet regions. <BR />
Conclusions: The microflares associated with bright points share
common characteristics to active region flares. The difference in the
surroundings of microflares are caused by open and closed configurations
of the pre-existing magnetic field.
---------------------------------------------------------
Title: Accelerating Waves in Polar Coronal Holes as Seen by EIS
and SUMER
Authors: Gupta, G. R.; Banerjee, D.; Teriaca, L.; Imada, S.;
Solanki, S.
2010ApJ...718...11G Altcode: 2010arXiv1005.3453G
We present EIS/Hinode and SUMER/SOHO observations of propagating
disturbances detected in coronal lines in inter-plume and plume
regions of a polar coronal hole. The observation was carried out on
2007 November 13 as part of the JOP196/HOP045 program. The SUMER
spectroscopic observation gives information about fluctuations in
radiance and on both resolved (Doppler shift) and unresolved (Doppler
width) line-of-sight velocities, whereas EIS 40” wide slot images
detect fluctuations only in radiance but maximize the probability
of overlapping field of view between the two instruments. From
distance-time radiance maps, we detect the presence of propagating
waves in a polar inter-plume region with a period of 15-20 minutes
and a propagation speed increasing from 130 ± 14 km s<SUP>-1</SUP>
just above the limb to 330 ± 140 km s<SUP>-1</SUP> around 160” above
the limb. These waves can be traced to originate from a bright region
of the on-disk part of the coronal hole where the propagation speed
is in the range of 25 ± 1.3 to 38 ± 4.5 km s<SUP>-1</SUP>, with the
same periodicity. These on-disk bright regions can be visualized as the
base of the coronal funnels. The adjacent plume region also shows the
presence of propagating disturbances with the same range of periodicity
but with propagation speeds in the range of 135 ± 18 to 165 ± 43 km
s<SUP>-1</SUP> only. A comparison between the distance-time radiance
map of the two regions indicates that the waves within the plumes are
not observable (may be getting dissipated) far off-limb, whereas this
is not the case in the inter-plume region. A correlation analysis was
also performed to find out the time delay between the oscillations at
several heights in the off-limb region, finding results consistent with
those from the analysis of the distance-time maps. To our knowledge,
this result provides first spectroscopic evidence of the acceleration of
propagating disturbances in the polar region close to the Sun (within
1.2 R/R <SUB>sun</SUB>), which provides clues to the understanding of
the origin of these waves. We suggest that the waves are likely either
Alfvénic or fast magnetoacoustic in the inter-plume region and slow
magnetoacoustic in the plume region. This may lead to the conclusion
that inter-plumes are a preferred channel for the acceleration of the
fast solar wind.
---------------------------------------------------------
Title: Observations of a rotating macrospicule associated with an
X-ray jet
Authors: Kamio, S.; Curdt, W.; Teriaca, L.; Inhester, B.; Solanki,
S. K.
2010A&A...510L...1K Altcode: 2010arXiv1001.1924K
<BR /> Aims: We attempt to understand the driving mechanism of a
macrospicule and its relationship with a coronal jet. <BR /> Methods:
We study the dynamics of a macrospicule and an associated coronal jet
captured by multi-spacecraft observations. Doppler velocities in both
the macrospicule and the coronal jet are determined by EIS and SUMER
spectra. Their temporal evolution is studied using X-ray and He II λ304
images. <BR /> Results: A blueshift of -120 ± 15 km s<SUP>-1</SUP>
is detected on one side of the macrospicule, while a redshift of 50
± 6 km s<SUP>-1</SUP> is found at the base of the other side. The
inclination angle of the macrospicule inferred from a stereoscopic
analysis with STEREO suggests that the measured Doppler velocities can
be attributed to a rotating motion of the macrospicule rather than
a radial flow or an expansion. <BR /> Conclusions: The macrospicule
is driven by the unfolding motion of a twisted magnetic flux rope,
while the associated X-ray jet is a radial outflow.
---------------------------------------------------------
Title: The SUMER Ly-α line profile in quiescent prominences
Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.
2010A&A...511L...4C Altcode: 2010arXiv1002.1197C
<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: 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: Accelerating disturbances in polar plume and inter-plume
Authors: Gupta, Girjesh R.; Banerjee, Dipankar; Teriaca, Luca; Imada,
Shinsuke; Solanki, Sami
2010cosp...38.2937G Altcode: 2010cosp.meet.2937G
We present EIS/Hinode & SUMER/SoHO joint observations allowing the
first spectroscopic detection of accelerating disturbances as recorded
with coronal lines in inter-plume and plume regions of a polar coronal
hole. From time-distance radiance maps, we detect the presence of
propagating disturbances in a polar inter-plume region with a period
of 15 to 20 min and a propagation speed increasing from 130±14 km/s
just above the limb, to 330±140 km/s around 160" above the limb. These
disturbances can also be traced to originate from a bright region of
the on-disk part of the coronal hole where the propagation speed was
found to be in the range of 25±1.3 to 38±4.5 km/s, with the same
periodicity. These on-disk bright regions can be vi-sualized as the
base of the coronal funnels. The adjacent plume region also shows the
presence of propagating disturbance with the same range of period but
with propagation speeds in the range of 135±18 to 165±43 km/s only. A
comparison between the time-distance radiance map of both regions,
indicate that the disturbances within the plumes are not observable (may
be getting dissipated) far off-limb whereas this is not the case in the
inter-plume region. Conclu-sions drawn from these observations in terms
of accelerating waves or high speed jets/upflows will be discussed.
---------------------------------------------------------
Title: Impusive heating of bright points observed by EIS and SUMER
Authors: Kamio, Suguru; Curdt, Werner; Teriaca, Luca; Innes, Davina
2010cosp...38.2838K Altcode: 2010cosp.meet.2838K
We studied the temporal variation of bright points (BPs) in the quiet
region and in the coronal hole. Time series of X-ray images show
significant emission increases in BPs with durations shorter than 10
min. Since these impulsive brightenings are frequently found all over
the Sun, study of their mechanism is important for understanding the
dynamics in the quiescent corona. Characteristics of light curves of
BPs in the transition region and in the corona are similar to those of
solar flares, though at a much smaller scale. Fast raster scans with
SOHO/SUMER and Hinode/EIS allowed us to obtain light curves in multiple
emission lines. At the peak of X-ray flux, a significant emission in Fe
XV (2MK), which is normally very weak in BPs, is detected. In addition,
diagnostic using the Fe XII line pair indicate density increase in
BPs. These results suggest that impulsive heating takes place in the
corona, which causes chromospheric evaporation supplying hot plasma
into coronal loops. After the X-ray peak, delayed emission increase
in He II and O IV is observed, which is interpreted as the cooling
of hot plasma. We will discuss the relationship between these small
scale flares and jets.
---------------------------------------------------------
Title: Results from the Past Hinode/SUMER Campaigns
Authors: Teriaca, L.
2009ASPC..415..309T Altcode:
The SUMER VUV spectrometer aboard SOHO currently observes spectral
lines and continua in the 67 nm to 150 nm range. This emission
mostly samples the solar atmosphere from the chromosphere to the
lower corona (≤ 1 MK), through the transition region. As such,
this instrument is an ideal complement to the Hinode instruments,
helping coupling the observations of the photospheric magnetic field
and of the photospheric and chromospheric emission performed by SOT
with the images and spectra of the hot corona (≥ 1 MK) obtained by
XRT and EIS. Since the launch of Hinode in the fall of 2006, there
have been six SUMER campaigns during which combined observations were
obtained. Of these, three are full bilateral joint campaigns, the last
of which was run at the end of September 2008. Here I report on some
of the scientific results derived from these campaigns.
---------------------------------------------------------
Title: Multi-Instrument Campaigns to Observe the Off-Limb Corona
Authors: Del Zanna, G.; Andretta, V.; Poletto, G.; Teriaca, L.; Ko,
Y. -K.; Mason, H. E.; Vourdilas, A.; Bemporad, A.; Magri, M.
2009ASPC..415..315D Altcode:
We briefly describe two multi-instrument campaigns we coordinated to
observe the off-limb corona in 2007, with some preliminary results. The
first one (Hinode HOP 7) was a SOHO/Hinode/TRACE/STEREO/Ulysses
week-long campaign during the SOHO-Ulysses quadrature in 2007 May. We
could not achieve all of our goals, however we were very fortunate in
that the “Del Zanna” active region appeared on the Sun at the right
longitude, and that a filament eruption and a CME were observed. Of
particular significance is the finding of large (100 km s<SUP>-1</SUP>)
non-thermal broadenings in all coronal lines observed by Hinode/EIS
in the region where the filament was erupting. The second campaign
(Hinode HOP 44) involved SOHO (CDS, SUMER, UVCS), Hinode, and TRACE to
measure the physical parameters of plume/interplume regions in the polar
coronal holes from the low corona to 1.7 solar radii, on 30/10-4/11. We
obtained a good set of observations, however various instrumental
constraints and the lack of fully developed plumes limited our goals.
---------------------------------------------------------
Title: Hydrogen Lyα and Lyβ Radiances and Profiles in Polar
Coronal Holes
Authors: Tian, Hui; Teriaca, Luca; Curdt, Werner; Vial, Jean-Claude
2009ApJ...703L.152T Altcode: 2009arXiv0909.0735T
The hydrogen Lyα plays a dominant role in the radiative energy
transport in the lower transition region, and is important for
the studies of transition-region structure as well as solar wind
origin. We investigate the Lyα profiles obtained by the Solar
Ultraviolet Measurement of Emitted Radiation spectrograph on the
Solar and Heliospheric Observatory spacecraft in coronal holes and the
quiet Sun. In a subset of these observations, the H I Lyβ, Si III,
and O VI lines were also (quasi-)simultaneously recorded. We find
that the distances between the two peaks of Lyα profiles are larger
in coronal holes than in the quiet Sun, indicating a larger opacity in
coronal holes. This difference might result from the different magnetic
structures or the different radiation fields in the two regions. Most
of the Lyβ profiles in the coronal hole have a stronger blue peak,
in contrast to those in quiet-Sun regions while in both regions the
Lyα profiles are stronger in the blue peak. Although the asymmetries
are likely to be produced by differential flows in the solar atmosphere,
their detailed formation processes are still unclear. The radiance ratio
between Lyα and Lyβ decreases toward the limb in the coronal hole,
which might be due to the different opacity of the two lines. We also
find that the radiance distributions of the four lines are set by a
combined effect of limb brightening and the different emission level
between coronal holes and the quiet Sun.
---------------------------------------------------------
Title: Solar transition region above sunspots
Authors: Tian, H.; Curdt, W.; Teriaca, L.; Landi, E.; Marsch, E.
2009A&A...505..307T Altcode: 2009arXiv0906.2211T
Aims: We study the transition region (TR) properties above sunspots and
the surrounding plage regions, by analyzing several sunspot reference
spectra obtained by the SUMER (Solar Ultraviolet Measurements of Emitted
Radiation) instrument in March 1999 and November 2006. <BR />Methods:
We compare the SUMER spectra observed in the umbra, penumbra, plage,
and sunspot plume regions. The hydrogen Lyman line profiles averaged
in each of the four regions are presented. For the sunspot observed
in 2006, the electron densities, differential emission measure (DEM),
and filling factors of the TR plasma in the four regions are also
investigated. <BR />Results: The self-reversals of the hydrogen Lyman
line profiles are almost absent in sunspots at different locations (at
heliocentric angles of up to 49°) on the solar disk. In the sunspot
plume, the Lyman lines are also not reversed, whilst the lower Lyman
line profiles observed in the plage region are obviously reversed, a
phenomenon found also in the normal quiet Sun. The TR densities of the
umbra and plume are similar and one order of magnitude lower than those
of the plage and penumbra. The DEM curve of the sunspot plume exhibits
a peak centered at log(T / K) ~ 5.45, which exceeds the DEM of other
regions by one to two orders of magnitude at these temperatures. We
also find that more than 100 lines, which are very weak or not observed
anywhere else on the Sun, are well observed by SUMER in the sunspot,
especially in the sunspot plume. <BR />Conclusions: We suggest that the
TR above sunspots is higher and probably more extended, and that the
opacity of the hydrogen lines is much lower above sunspots, compared to
the TR above plage regions. Our result indicates that the enhanced TR
emission of the sunspot plume is probably caused by a large filling
factor. The strongly enhanced emission at TR temperatures and the
reduced continuum ensure that many normally weak TR lines are clearly
distinctive in the spectra of sunspot plumes. <P />Tables 5 and 6 are
only available in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Propagating waves in polar coronal holes as seen by SUMER
& EIS
Authors: Banerjee, D.; Teriaca, L.; Gupta, G. R.; Imada, S.; Stenborg,
G.; Solanki, S. K.
2009A&A...499L..29B Altcode: 2009arXiv0905.1013B
Context: To study the dynamics of coronal holes and the role of waves in
the acceleration of the solar wind, spectral observations were performed
over polar coronal hole regions with the SUMER spectrometer on SoHO and
the EIS spectrometer on Hinode. <BR />Aims: Using these observations,
we aim to detect the presence of propagating waves in the corona and
to study their properties. <BR />Methods: The observations analysed
here consist of SUMER spectra of the Ne viii 770 Å line (T = 0.6 MK)
and EIS slot images in the Fe xii 195 Å line (T = 1.3 MK). Using the
wavelet technique, we study line radiance oscillations at different
heights from the limb in the polar coronal hole regions. <BR />Results:
We detect the presence of long period oscillations with periods of 10
to 30 min in polar coronal holes. The oscillations have an amplitude
of a few percent in radiance and are not detectable in line-of-sight
velocity. From the time distance maps we find evidence for propagating
velocities from 75 km s<SUP>-1</SUP> (Ne viii) to 125 km s<SUP>-1</SUP>
(Fe xii). These velocities are subsonic and roughly in the same ratio
as the respective sound speeds. <BR />Conclusions: We interpret the
observed propagating oscillations in terms of slow magneto-acoustic
waves. These waves can be important for the acceleration of the fast
solar wind.
---------------------------------------------------------
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: SUMER observations of the inverse Evershed effect in the
transition region above a sunspot
Authors: Teriaca, L.; Curdt, W.; Solanki, S. K.
2008A&A...491L...5T Altcode: 2009arXiv0901.3317T
Aims: We analyse SUMER spectral scans of a large sunspot within active
region NOAA 10923, obtained on 14-15 November 2006, to determine
the morphology and dynamics of the sunspot atmosphere at different
heights/temperatures. <BR />Methods: The data analysed here consist
of spectroheliograms in the continuum around 142.0 nm and in the Si
iv 140.2 nm, O iii 70.3 nm, N iv 76.5 nm, and O iv 79.0 nm spectral
lines. Gaussian-fitting of the observed profiles provides line-of-sight
velocity and Doppler-width maps. <BR />Results: The data show an
asymmetric downflow pattern compatible with the presence of the inverse
Evershed flow in a region within roughly twice the penumbral radius
at transition-region temperatures up to 0.18 MK. The motions, highly
inhomogeneous on small scales, seem to occur in a collar of radially
directed filamentary structures, with an average width less than the 1
Mm spatial resolution of SUMER and characterised by different plasma
speeds. Assuming that the flows are directed along the field lines,
we deduce that such field lines are inclined by 10° to 25° with
respect to the solar surface.
---------------------------------------------------------
Title: Loop Morphology and Flows and their Relation to the Magnetic
Field
Authors: Teriaca, L.; Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Curdt,
W.; Sekii, T.
2008ASPC..397..196T Altcode:
In November 2006 we obtained several rasters of a large sunspot
and its trailing region using the SUMER spectrometer on SOHO. The
observations consist of spectroheliograms in the continuum around
142 nm and in several spectral lines formed between 80000 K and
0.6 MK, covering the temperature range from the chromosphere to
the lower corona. The observed profiles provide LOS velocity and
Doppler width maps. TRACE images in the EUV passbands and in the 160
nm continuum provide a clear picture of the coronal loops and the
chromosphere near their footpoints. The same target was also observed
by all the instruments aboard Hinode and, in particular, by the SOT
spectro-polarimeter measuring the photospheric magnetic vector. We
combined SOT and MDI data (covering a larger FOV) to infer the coronal
magnetic field of the active region by a nonlinear force-free field
extrapolation. The observed radiance and velocity patterns at the
various heights/temperatures throughout the solar atmosphere are
compared with the field topology.
---------------------------------------------------------
Title: The line profile and center-to-limb variation of quiet-Sun
Lyman-alpha emission
Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P.
2008ESPM...12.2.91C Altcode:
We study the emission of the hydrogen Lyman-alpha line in the quiet
Sun, its center-to-limb variation, and its radiance distribution, which
we also compare to the Lyman-beta line. We use the high spectral and
spatial resolution of the SUMER spectrometer and take raster scans at
various locations on the disk. For the first time, we have used a new
method to reduce the incoming photon flux to a 20%-level by partly
closing the aperture door. We also performed a quasi-simultaneous
observation of both Ly-a and Ly-b at Sun centre in sit-and-stare
mode. We deduce the flow characteristic in Ly-a map from variations of
the calibrated Si III line centroids. We present the average profile
of Ly-a, its radiance distribution, its center-to-limb behaviour,
and the signature of flows on the line profiles. Different from all
other lines of the Lyman series, which have a red-horn asymmetry, Ly-a
has a robust and dominating blue-horn asymmetry. To our knowledge,
this result is only predicted by models which include flows.
---------------------------------------------------------
Title: Chromospheric Counterparts of UV Explosive Events
Authors: Reardon, K.; Cauzzi, G.; Teriaca, L.; Pitterle, M.; Curdt, W.
2008ESPM...12.2.17R Altcode:
We present a study of a unique, multi-wavelength dataset of a quiet
sun region with the primary goal of studying explosive events at
chromospheric and transition region heights. Several hypotheses
have been made about the nature of the explosive events, however the
underlying mechanisms remain elusive due to their small spatial and
temporal scales. Several theoretical models predict an important
role for the chromosphere in the triggering of these events. <P
/>To shed light on this issue, we have obtained a comprehensive
set of simultaneous high spatial, spectral, and temporal resolution
observations on April 18, 2007, combining both ground- and space-based
observatories. Most importantly, we carried out coordinated observations
with SUMER in the transition region Si IV 140.2 nm line together
with high-cadence IBIS imaging spectroscopy of the chromospheric CaII
854.2 nm line. This allows us to examine the chromospheric dynamics
and acoustic shocks that underlie the transition region events. We
also use SOT/NFI magnetograms to examine the relation of the explosive
events to the changes in the magnetic topology. The combined dataset
also includes Hinode/EIS rasters and Hinode/XRT images that provide
information on the higher-temperature coronal response.
---------------------------------------------------------
Title: Helium Line Formation and Abundance during a C-Class Flare
Authors: Andretta, Vincenzo; Mauas, Pablo J. D.; Falchi, Ambretta;
Teriaca, Luca
2008ApJ...681..650A Altcode: 2008arXiv0803.0418A
During a coordinated campaign that took place in 2001 May, a C-class
flare was observed both with SOHO instruments and with the Dunn Solar
Telescope of the National Solar Observatory at Sacramento Peak. In
two previous papers we described the observations and discussed some
dynamical aspects of the earlier phases of the flare, as well as the
helium line formation in the active region prior to the event. Here we
extend the analysis of the helium line formation to the later phases
of the flare in two different locations of the flaring area. We have
devised a new technique, exploiting all available information from
various SOHO instruments, to determine the spectral distribution of
the photoionizing EUV radiation produced by the corona overlying the
two target regions. In order to find semiempirical models matching
all of our observables, we analyzed the effect on the calculated
helium spectrum, both of A<SUB>He</SUB> (the He abundance) and of
the uncertainties in the incident EUV radiation (level and spectral
distribution). We found that the abundance has in most cases (but not
in all) a larger effect than the coronal back-radiation. The result
of our analysis is that, considering the error of the measured lines
and adopting our best estimate for the coronal EUV illumination, the
value A<SUB>He</SUB> = 0.075 +/- 0.010 in the chromosphere (for T >
6300 K) and transition region yields reasonably good matches for all
the observed lines. This value is marginally consistent with the most
commonly accepted photospheric value, A<SUB>He</SUB> = 0.085.
---------------------------------------------------------
Title: Analysis of the Fe X and Fe XIV line width in the solar corona
using LASCO-C1 spectral data
Authors: Mierla, M.; Schwenn, R.; Teriaca, L.; Stenborg, G.;
Podlipnik, B.
2008A&A...480..509M Altcode: 2009arXiv0903.0496M
Aims:The purpose of this paper is to analyze the variation in
the line width with height in the inner corona (region above 1.1
R<SUB>⊙</SUB>), by using the spectral data from LASCO-C1 aboard
SOHO. We used data acquired at activity minimum (August-October 1996)
and during the ascending phase of the solar cycle (March 1998). <BR
/>Methods: Series of images acquired at different wavelengths across
the Fe X 637.6 nm (red) and Fe XIV 530.3 nm (green) coronal lines
by LASCO-C1 allowed us to build radiance and width maps of the
off-limb solar corona. <BR />Results: In 1996, the line width of Fe
XIV was roughly constant or increased with height up to around 1.3
R<SUB>⊙</SUB> and then it decreased. The Fe X line width increased
with height up to the point where the spectra were too noisy to allow
line width measurements (around 1.3 R<SUB>⊙</SUB>). Fe X showed
higher effective temperatures as compared with Fe XIV. In 1998 the
line width of Fe XIV was roughly constant with height above the limb
(no Fe X data available).
---------------------------------------------------------
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: Study of a Solar Streamer on March 1998 using LASCO-C1
Spectral Data
Authors: Mierla, M.; Schwenn, R.; Teriaca, L.; Stenborg, G.;
Podlipnik, B.
2007AIPC..895...75M Altcode:
The slow solar wind is supposed to originate from coronal regions
associated with streamers. It is not clear yet how the closed magnetic
field structures of streamers are opening up in order to release
the plasma. An analysis of this subject, particularly of a streamer
on March 1998, is done using LASCO-C1 spectral data. LASCO-C1 is
an internally occulted coronagraph on the SOHO spacecraft. It has
a tunable Fabry-Perot interferometer which allows taking spectral
scans of selected coronal emission lines. From measured line profiles
we deduced physical quantities like temperature and flow velocities
along the line of sight. This way, we obtained information on the flow
pattern in the low corona.
---------------------------------------------------------
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: The dynamics of the minimum solar corona during the period
August October 1996
Authors: Mierla, M.; Schwenn, R.; Teriaca, L.; Stenborg, G.;
Podlipnik, B.
2007AdSpR..40.1049M Altcode:
The paper presents the dynamics of the solar corona at the minimum
phase of the solar cycle (period August-October 1996), as inferred
from LASCO-C1 spectral data. LASCO-C1 is an internally occulted
coronagraph aboard the SOHO spacecraft. It has a tunable Fabry-Pérot
interferometer which allows taking spectral scans of selected coronal
emission lines. From measured line profiles we deduced physical
quantities such as temperature and flow velocities along the line of
sight. This way, we obtained information on the flow pattern in the
low corona (1.1-1.6 solar radii).
---------------------------------------------------------
Title: LASCO-C1 Spectral Analysis of Flows in the Inner Corona
Authors: Mierla, Marilena; Schwenn, Rainer; Teriaca, Luca; Stenborg,
Guillermo; Podlipnik, Borut
2007RoAJ...17..167M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Evaporation Regime in a Confined Flare
Authors: Falchi, A.; Teriaca, L.; Maltagliati, L.
2006SoPh..239..193F Altcode: 2006SoPh..tmp...87F
We studied the evolution of a small eruptive flare (GOES class C1)
from its onset phase using multi-wavelength observations that sample
the flare atmosphere from the chromosphere to the corona. The main
instruments involved were the Coronal Diagnostic Spectrometer (CDS)
aboard SOHO and facilities at the Dunn Solar Tower of the National
Solar Observatory/Sacramento Peak. Transition Region and Coronal
Explorer (TRACE) together with Ramaty High-Energy Spectroscopic Imager
(RHESSI) also provided images and spectra for this flare. Hα and TRACE
images display two loop systems that outline the pre-reconnection and
post-reconnection magnetic field lines and their topological changes
revealing that we are dealing with an eruptive confined flare. RHESSI
data do not record any detectable emission at energies ≥25 keV, and
the observed count spectrum can be well fitted with a thermal plus a
non-thermal model of the photon spectrum. A non-thermal electron flux
F ≈ 5 × 10<SUP>10</SUP> erg cm<SUP>−2</SUP> s<SUP>−1</SUP>
is determined. The reconstructed images show a very compact source
whose peak emission moves along the photospheric magnetic inversion
line during the flare. This is probably related to the motion of the
reconnection site, hinting at an arcade of small loops that brightens
successively. The analysis of the chromospheric spectra (Ca II K, He I
D<SUB>3</SUB> and Hγ, acquired with a four-second temporal cadence)
shows the presence of a downward velocity (between 10 and 20 km
s<SUP>−1</SUP>) in a small region intersected by the spectrograph
slit. The region is included in an area that, at the time of the
maximum X-ray emission, shows upward motions at transition region
(TR) and coronal levels. For the He I 58.4 and O V 62.97 lines,
we determine a velocity of ≈−40 km s<SUP>−1</SUP> while for
the Fe XIX 59.22 line a velocity of ≈−80 km s<SUP>−1</SUP> is
determined with a two-component fitting. The observations are discussed
in the framework of available hydrodynamic simulations and they are
consistent with the scenario outlined by Fisher (1989). No explosive
evaporation is expected for a non-thermal electron beam of the observed
characteristics, and no gentle evaporation is allowed without upward
chromospheric motion. It is suggested that the energy of non-thermal
electrons can be dissipated to heat the high-density plasma, where
possibly the reconnection occurs. The consequent conductive flux drives
the evaporation process in a regime that we can call sub-explosive.
---------------------------------------------------------
Title: Dynamics and evolution of an eruptive flare
Authors: Teriaca, L.; Falchi, A.; Falciani, R.; Cauzzi, G.;
Maltagliati, L.
2006A&A...455.1123T Altcode: 2009arXiv0903.0232T
Aims.We study the dynamics and the evolution of a C2.3 two-ribbon
flare, developed on 2002 August 11, during the impulsive phase
as well as during the long gradual phase. To this end we obtained
multiwavelength observations using the CDS spectrometer aboard SOHO,
facilities at the National Solar Observatory/Sacramento Peak, and the
TRACE and RHESSI spacecrafts.<BR /> Methods: .CDS spectroheliograms
in the Fe xix, Fe xvi, O v and He i lines allow us to determine the
velocity field at different heights/temperatures during the flare
and to compare them with the chromospheric velocity fields deduced
from Hα image differences. TRACE images in the 17.1 nm band greatly
help in determining the morphology and the evolution of the flaring
structures.<BR /> Results: .During the impulsive phase a strong
blue-shifted Fe xix component (-200 km s<SUP>-1</SUP>) is observed at
the footpoints of the flaring loop system, together with a red-shifted
emission of O v and He i lines (20 km s<SUP>-1</SUP>). In one footpoint
simultaneous Hα data are also available and we find, at the same time
and location, downflows with an inferred velocity between 4 and 10 km
s<SUP>-1</SUP>. We also verify that the "instantaneous" momenta of the
oppositely directed flows detected in Fe xix and Hα are equal within
one order of magnitude. These signatures are in general agreement with
the scenario of explosive chromospheric evaporation. Combining RHESSI
and CDS data after the coronal upflows have ceased, we prove that,
independently from the filling factor, an essential contribution to
the density of the post-flare loop system is supplied from evaporated
chromospheric material. Finally, we consider the cooling of this loop
system, that becomes successively visible in progressively colder
signatures during the gradual phase. We show that the observed cooling
behaviour can be obtained assuming a coronal filling factor of ≈0.2
to 0.5.<BR />
---------------------------------------------------------
Title: Helium Line Formation During the Decay Phase of a Small
Two-Ribbon Flare
Authors: Andretta, V.; Mauas, P. J. D.; Falchi, A.; Teriaca, L.
2006ESASP.617E.151A Altcode: 2006soho...17E.151A
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: Rhessi Images and Spectra of Two Small Flares
Authors: Maltagliati, L.; Falchi, A.; Teriaca, L.
2006SoPh..235..125M Altcode: 2005astro.ph..8490M
We studied the evolution of two small flares (GOES class C2 and C1)
that developed in the same active region with different morphological
characteristics: one is extended and the other is compact. We analyzed
the accuracy and the consistency of different algorithms implemented
in Reuven Ramaty High-Energy Spectroscopic Imager (RHESSI) software to
reconstruct the image of the emitting sources, for energies between 3
and 12 keV. We found that all tested algorithms give consistent results
for the peak position, while the other parameters can differ at most by
a factor 2. Pixon and Forward-fit generally converge to similar results
but Pixon is more reliable for reconstructing a complex source. We
investigated the spectral characteristics of the two flares during their
evolution in the 3-25 keV energy band. We found that a single thermal
model of the photon spectrum is inadequate to fit the observations and
we needed to add either a non-thermal model or a hot thermal one. The
non-thermal and the double thermal fits are comparable. If we assume
a non-thermal model, the non-thermal energy is always higher than the
thermal one. Only during the very final decay phase a single thermal
model fits the observed spectrum fairly well.
---------------------------------------------------------
Title: LASCO-C1 Spectral Data Analysis of the Slow Solar Wind
Authors: Mierla, M.; Schwenn, R.; Teriaca, L.; Podlipnik, B.;
Stenborg, G.
2005ESASP.600E..45M Altcode: 2005dysu.confE..45M; 2005ESPM...11...45M
No abstract at ADS
---------------------------------------------------------
Title: The Dynamics of the Lower Transition Region as Inferred from
Spectroscopy of the Hydrogen LYMAN-α Line
Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.;
Marsch, E.
2005ESASP.600E.100T Altcode: 2005ESPM...11..100T; 2005dysu.confE.100T
No abstract at ADS
---------------------------------------------------------
Title: 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: The widths of vacuum-ultraviolet spectral lines in the
equatorial solar corona observed with CDS and SUMER
Authors: Wilhelm, K.; Fludra, A.; Teriaca, L.; Harrison, R. A.;
Dwivedi, B. N.; Pike, C. D.
2005A&A...435..733W Altcode:
Observations of the solar equatorial corona between heights of 36 Mm and
184 Mm above the limb obtained by the SOHO spectrometers CDS and SUMER
in December 2003 are presented and discussed with special emphasis on
the widths of the spectral lines Mg x at 62.50 nm, Al xi at 55.00 nm
and 56.82 nm, Ca x at 55.78 nm, and Si xi at 58.09 nm. SUMER observed,
in addition, the lines Mg x 60.98 nm, Ca x 57.40 nm, Fe xii 124.20 nm,
Fe xvii 115.31 nm, and Ca xiii 113.37 nm. The Si xii 52.11 nm line
was only observed by CDS. A different behaviour of the line width
of Mg x 62.50 nm as a function of height above the limb had been
found in studies carried out independently with both instruments at
different times. It is the aim of this joint investigation to (a)
study instrumental effects on line-width results; and (b) provide a
thorough analysis of line profiles with altitude for the new campaign.
---------------------------------------------------------
Title: Helium line formation in a solar active region
Authors: Mauas, P. J. D.; Andretta, V.; Falchi, A.; Falciani, R.;
Teriaca, L.; Cauzzi, G.
2005ESASP.560..811M Altcode: 2005csss...13..811M
No abstract at ADS
---------------------------------------------------------
Title: Helium Line Formation and Abundance in a Solar Active Region
Authors: Mauas, P. J. D.; Andretta, V.; Falchi, A.; Falciani, R.;
Teriaca, L.; Cauzzi, G.
2005ApJ...619..604M Altcode: 2004astro.ph.12058M
An observing campaign (SOHO JOP 139), coordinated between ground-based
and Solar and Heliospheric Observatory (SOHO) instruments, has been
planned to obtain simultaneous spectroheliograms of the same active
region in several spectral lines. The chromospheric lines Ca II K,
Hα, and Na I D, as well as He I 10830, 5876, 584, and He II 304 Å
lines have been observed. The EUV radiation in the range λ<500
Å and in the range 260<λ<340 Å has also been measured at
the same time. These simultaneous observations allow us to build
semiempirical models of the chromosphere and low transition region of
an active region, taking into account the estimated total number of
photoionizing photons impinging on the target active region and their
spectral distribution. We obtained a model that matches very well all
the observed line profiles, using a standard value for the He abundance
([He]=0.1) and a modified distribution of microturbulence. For this
model we study the influence of the coronal radiation on the computed
helium lines. We find that, even in an active region, the incident
coronal radiation has a limited effect on the UV He lines, while it
is of fundamental importance for the D3 and 10830 Å lines. Finally,
we build two more models, assuming values of He abundance [He]=0.07 and
1.5, only in the region where temperatures are >1×10<SUP>4</SUP>
K. This region, between the chromosphere and transition region, has been
indicated as a good candidate for processes that might be responsible
for strong variations of [He]. The set of our observables can still be
well reproduced in both cases, changing the atmospheric structure mainly
in the low transition region. This implies that, to choose between
different values of [He], it is necessary to constrain the transition
region with different observables, independent of the He lines.
---------------------------------------------------------
Title: Dynamics of the Solar Corona Using LASCO-C1 Spectral Data
Authors: Mierla, Marilena; Schwenn, Rainer; Teriaca, Luca; Stenborg,
Guillermo; Podlipnik, Borut
2005RoAJ...15..137M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Using LASCO-C1 spectroscopy for coronal diagnostics
Authors: Mierla, M.; Schwenn, R.; Teriaca, L.; Stenborg, G.;
Podlipnik, B.
2005AdSpR..35.2199M Altcode:
The LASCO-C1 telescope was designed to perform spectral analysis of
coronal structures by means of a tunable Fabry-Pérot interferometer
acquiring images at different wavelengths. Results from spectral
scans of the Fe XIV 5303 Å green coronal emission line are
presented. Physical quantities like the ion temperature (line widths),
and the flow velocity along the line of sight (Doppler shifts) are
obtained over the entire corona.
---------------------------------------------------------
Title: Overview of AN Eruptive Flare: from Chromospheric Evaporation
to Cooling of Hot Flaring Loops
Authors: Teriaca, L.; Maltagliati, L.; Falchi, A.; Falciani, R.;
Cauzzi, G.
2004ESASP.575..265T Altcode: 2004soho...15..265T
No abstract at ADS
---------------------------------------------------------
Title: Transition region small-scale dynamics as seen by SUMER on SOHO
Authors: Teriaca, L.; Banerjee, D.; Falchi, A.; Doyle, J. G.;
Madjarska, M. S.
2004A&A...427.1065T Altcode:
High spectral, spatial and temporal resolution UV observations
of the quiet Sun transition region show a highly structured and
dynamical environment where transient supersonic flows are commonly
observed. Strongly non-Gaussian line profiles are the spectral
signatures of these flows and are known in the literature as explosive
events. In this paper we present a high spatial resolution (≈ 1”)
spectroheliogram of a 273”× 291” area of the quiet Sun acquired with
SUMER/SOHO in the O VI spectral line at λ103.193 nm. The extremely high
quality of these observations allows us to identify tens of explosive
events from which we estimate an average size of 1800 km and a birthrate
of 2500 s<SUP>-1</SUP> over the entire Sun. Estimates of the kinetic and
enthalpy fluxes associated with these events show that explosive events
are not important as far as solar coronal heating is concerned. The
relationship with the underlying photospheric magnetic field is also
studied, revealing that explosive events generally occur in regions
with weak (and, very likely, mixed polarity) magnetic flux. By studying
the structure of upward and downward flows exceeding those associated
to average quiet Sun profiles, we find a clear correlation between
the “excess” flows and the magnetic network. However, although
explosive events are always associated with flow patterns often
covering areas larger than the explosive event itself, the contrary is
not true. In particular, almost all flows associated with the stronger
concentrations of photospheric magnetic flux do not show non-Gaussian
line profiles. In some cases, non-Gaussian line profiles are associated
with supersonic flows in small magnetic loops. The case of a small
loop showing a supersonic siphon-like flow of ≈130 km s<SUP>-1</SUP>
is studied in detail. This is, to our knowledge, the first detection
of a supersonic siphon-like flow in a quiet Sun loop. In other cases,
the flow patterns associated with explosive events may suggest a
relation with UV spicules.
---------------------------------------------------------
Title: On the widths of the Mg X lines near 60 nm in the corona
Authors: Wilhelm, K.; Dwivedi, B. N.; Teriaca, L.
2004A&A...415.1133W Altcode:
We examine the line widths of both components of the Mg X 2s
<SUP>2</SUP>S<SUB>1/2</SUB>-2p <SUP>2</SUP>P<SUB>1/2,3/2</SUB>
doublet at 60.98 nm and 62.50 nm in the low corona of the quiet Sun,
and find that the Doppler width (i.e. half 1/e width) broadens from
Δ λ<SUB>D</SUB> ≈ 8.2 pm to ≈9.5 pm (with an estimated relative
standard uncertainty of 4%) between the limb and 220 Mm above the
limb in the equatorial corona. In a polar coronal hole, the Doppler
width increases from 10.8 pm near 30 Mm to 11.4 pm at around 80
Mm. The analysis does not provide any evidence for a narrowing of
the emission-line profiles as a function of the distance from the
solar limb.
---------------------------------------------------------
Title: SUMER, UVCS and LASCO Observations of Small-Scale Ejecta
Authors: Teriaca, L.; Curdt, W.; Poletto, G.
2004ESASP.547..291T Altcode: 2004soho...13..291T
During the fall 2002 SOHO-Sun-Ulysses quadrature, coordinated SUMER/UVCS
observations were carried out off the west limb. Data were acquired
over six consecutive days in several lines formed in the 2 104 - 106
K temperature range. The center of the SUMER slit was placed around
1.13 R and oriented in the north south direction, while the UVCS slit
was set tangent to the solar limb at altitudes ranging between 1.6 and
2.1 R. On 19 and 20 November SUMER observed repeated transient events
characterized by a strong increase of the intensity of transition region
and Hydrogen Lyman and lines with large line broadenings and line of
sight velocities, while little if any variation is seen in lines formed
around 106 K. The duration of these events varies between 10-15 minutes
up to 1 hour. The SUMER events are associated to streamer-like outflows
seen in LASCO images and, in the case of the larger 19 November event,
with a small jet travelling at ~400 km/s across the LASCO C2 fiel
of view.
---------------------------------------------------------
Title: Dynamic properties of the solar corona: SOHO/LASCO observations
Authors: Mierla, M.; Schwenn, R.; Stenborg, G.; Teriaca, L.;
Podlipnik, B.
2004cosp...35.2275M Altcode: 2004cosp.meet.2275M
With the launch of the SOHO spacecraft in December 1995, the quality of
corona observations has improved significantly. The LASCO instruments
with their field of view now extending from 1.1 Rs (C1) to 30 Rs (C3)
offer sufficient sensitivity to make an almost continuous outflow in
the streamer belt visible. We report on two different approaches to
study the plasma motion, both in the plane of the sky and along the
line of sight. 1. By means of a multi-resolution image processing
technique based on wavelet packets the boundaries and the internal
details of originally faint and diffuse structures are enhanced. This
approach allows unambiguous image interpretation and provides a means
for the quantification of stationary and dynamic coronal structures
required for conducting morphological studies. 2. The LASCO/C1 telescope
was designed to perform spectral analysis on coronal structures. The
tunable Fabry-Perot interferometer allows to obtain images at different
wavelengths. Results from spectral scans of the coronal green and
red emission lines are presented. From the line profiles physical
quantities like temperatures (from line widths), and flow velocities
(from Doppler shifts) along the line of sight are deduced.
---------------------------------------------------------
Title: Line Shift Variations in Solar Transition Region Lines
Authors: Doyle, J. G.; Madjarska, M.; Giamikakis, J.; Teriaca, L.;
Roussev, I.
2003csss...12..619D Altcode:
Two high time cadence datasets, taken in C III 977Å and O VI 1032Å
were analysed in an effort to establish the extent of the variability
in the Doppler-shift of typical mid-transition region lines. In C
III, the shortest time-scale variability seems to occur in the network
boundary regions where the line-shift can vary by 7-8 km s<SUP>-1</SUP>
in less than 1 min. The internetwork region also shows variability
although this tends to be longer lived, ∼2-3 mins. The average C III
line-shift in all regions is for a red-shift of ∼ 8 km s<SUP>-1</SUP>
in very good agreement with that derived by others. Furthermore, there
does not seem to be any obvious difference in the average line-shift
in network and internetwork regions. On a few rare occasions, the C
III line was blue-shifted. The O VI line was also red-shifted with the
network region showing evidence for a periodicity. These observations
were compared to model line profiles based on the response of a 2D MHD
environment representing the solar transition region to micro-scale
energy depositions. A variety of temperatures at which the energy
deposition takes place as well as the amount of energy deposited
was examined.
---------------------------------------------------------
Title: Solar wind acceleration in low density regions
Authors: Teriaca, L.; Poletto, G.; Romoli, M.; Biesecker, D.
2003AIPC..679..327T Altcode:
High speed solar wind is known to originate in polar coronal holes
which, however, are made up of two components: bright, high density
regions known as plumes, and dark, weakly emitting low density regions
known as interplumes. Recent space observations have shown that the
width of UV lines is larger in interplume regions [see e.g. 1, 2]
while observations of the ratio of the O VI doublet lines at 1032 and
1037 Å, at the altitude of 1.7 solar radii, suggest higher outflows in
interplume regions than in plumes [3]. These results seem to locate the
source of the fast solar wind in the interplume regions. The present
work aims at identifying the outflow speed vs. altitude profile of
the O VI ions, at heights up to 2 solar radii, both in plumes and
interplume regions. To this end, we examined SUMER and UVCS data taken
in the North polar coronal hole on June 3, 1996 over the altitude
range between 1 and 2 solar radii. A Doppler dimming analysis applied
to our data allows us to determine the outflow speed in interplume
regions throughout the range covered by the observations. Our results
favor interplumes as sources of fast wind. However, models mimicking
observations in plume regions will also be discussed.
---------------------------------------------------------
Title: The Nascent Solar Wind: Origin and Acceleration
Authors: Teriaca, Luca; Poletto, Giannina; Romoli, Marco; Biesecker,
Doug A.
2003ApJ...588..566T Altcode:
High-speed solar wind is known to originate in polar coronal holes,
which, however, are made up of two components: bright, high-density
regions known as “plumes” and dark, weakly emitting low-density
regions known as “interplumes.” Recent space observations have
shown that the width of UV lines is larger in interplume regions, while
observations of the ratio of the O VI doublet lines at 1032 and 1037 Å,
at 1.7 solar radii, suggest higher outflows in interplume regions than
in plumes at that altitude. These results favor interplume regions as
sources of the fast solar wind. The present work aims at investigating
the outflow speed versus altitude properties of the O VI and H I
ions, at heights below 2 solar radii, in both plumes and interplume
regions. To this end, we examined Solar Ultraviolet Measurement of
Emitted Radiation (SUMER) and Ultraviolet Coronagraph Spectrometer
(UVCS) observations of a north polar coronal hole taken on 1996 June
3, over the altitude range between 1 and 2 solar radii, and through
a Doppler dimming analysis of our data, we show that interplume
areas may be really identified as sources of fast wind streams. The
behavior of plumes, on the contrary, can be interpreted in terms of
static structures embedded in the interplume ambient. We conclude by
comparing our results with the predictions of theoretical models of
the solar wind and giving an empirical estimate of the heating rate,
per particle, for H I and O VI ions in interplume regions at 1.75 and
2.0 solar radii.
---------------------------------------------------------
Title: Solar and Heliospheric Observatory/Coronal Diagnostic
Spectrograph and Ground-based Observations of a Two-Ribbon Flare:
Spatially Resolved Signatures of Chromospheric Evaporation
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
2003ApJ...588..596T Altcode:
During a coordinated observing campaign (Solar and Heliospheric
Observatory, SOHO JOP 139), we obtained simultaneous spectroheliograms
of a solar active region in several spectral lines, sampling levels
from the chromosphere to the corona. Ground-based spectroheliograms
were acquired at the Dunn Solar Tower of the National Solar
Observatory/Sacramento Peak in four chromospheric lines, while the
coronal diagnostic spectrograph on board SOHO was used to obtain
rasters of the active region in transition region (TR) and coronal
lines. Such a complete data set allowed us to compare the development
of intensity and velocity fields during a small two-ribbon flare
in the whole atmosphere. In particular, we obtained for the first
time quasi-simultaneous and spatially resolved observations of
velocity fields during the impulsive phase of a flare, in both the
chromosphere and upper atmosphere. In this phase, strong downflows
(up to 40 km s<SUP>-1</SUP>) following the shape of the developing
ribbons are measured at chromospheric levels, while strong upward
motions are instead measured in TR (up to -100 km s<SUP>-1</SUP>)
and coronal lines (-160 km s<SUP>-1</SUP>). The spatial pattern of
these velocities have a common area about 10" wide. This is the first
time that opposite-directed flows at different atmospheric levels
are observed in the same spatial location during a flare. These
signatures are highly suggestive of the chromospheric evaporation
scenario predicted in theoretical models of flares.
---------------------------------------------------------
Title: An EUV Bright Point as seen by SUMER, CDS, MDI and EIT
on-board SoHO
Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L.; Banerjee, D.
2003A&A...398..775M Altcode:
This paper presents the formation, evolution and decay of a coronal
bright point via a spectroscopic analysis of its transition region
counterpart and the evolution of the underlying magnetic bipole during
3 days of almost continuous observations. The data were obtained with
various instruments on-board SoHO, including the SUMER spectrograph
in the transition region line S VI 933.40 Å, CDS in the He I 584.33,
O V 629.73 and Mg IX 368.06 Å lines, plus MDI and EIT. The existence
of the coronal feature is strongly correlated with the evolution of
the underlying bipolar region. The lifetime of the bright point from
the moment when it was first visible in the EIT images until its
complete disappearance was ~ 18 hrs. Furthermore, the bright point
only became visible at coronal temperatures when the two converging
opposite magnetic polarities were ~ 7000 km apart. As far as the
temporal coverage of the data permits, we found that the bright point
disappeared at coronal temperatures after a full cancellation of one of
the magnetic polarities. The spectroscopic analysis reveals the presence
of small-scale ( ~ 6 arcsec) transient brightenings within the bright
point with a periodicity of ~ 6 min. The Doppler shift in the bright
point was found to be in the range of -10 to 10 km ; s<SUP>-1</SUP>
although it is dominated by a red-shifted emission which is associated
with regions characterized by stronger “quiet” Sun photospheric
magnetic flux. Small-scale brightenings within the bright point show
velocity variations in the range 3-6 km ; s<SUP>-1</SUP>. In general
the bright point has a radiance ~ 4 times higher than that of the
network. No relation was found between the bright point and the UV
explosive event phenomena.
---------------------------------------------------------
Title: Interplume as source of the fast solar wind
Authors: Teriaca, L.; Poletto, G.; Romoli, M.; Biesecker, D. A.
2003MmSAI..74..713T Altcode:
High speed solar wind is known to originate in polar coronal holes
which, however, are made up of two components: bright, high density
regions known as plumes and dark, weakly emitting low density
regions known as interplumes. Recent space observations have shown
that the width of UV lines is larger in interplume regions. Moreover,
observations of the ratio of the O VI doublet lines at 1032 and 1037 Å,
at 1.7 R<SUB>sun</SUB>, suggest higher outflows in interplume regions
than in plumes at that altitude. In this work we examine SUMER and
UVCS observations of a north polar coronal hole taken on 1996 June 3,
over the altitude range between 1 and 2 R<SUB>sun</SUB> and, through
a Doppler dimming analysis of our data, we show that interplume areas
may be really identified as sources of fast wind streams. The behavior
of plumes, on the contrary, can be interpreted in terms of static
structures embedded in the interplume ambient. We conclude comparing our
results with the predictions of theoretical models of the solar wind.
---------------------------------------------------------
Title: Spatially resolved signatures of chromospheric evaporation
during a small two-ribbon flare
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
2003MmSAI..74..635T Altcode:
Ground based spectroheliograms of a solar active region were acquired
in four chromospheric lines simultaneously with rasters in transition
region (TR) and coronal lines obtained with the Coronal Diagnostic
Spectrograph (CDS) aboard SOHO. Such a complete dataset allows us to
study the development of intensity and velocity fields during a small
two-ribbon flare in the whole atmosphere. In particular, we obtain for
the first time quasi-simultaneous and spatially resolved observations
of velocity fields during the impulsive phase of a flare, both in
chromosphere and upper atmosphere. In this phase, strong downflows
(up to 40 km s<SUP>-1</SUP>) following the shape of the developing
ribbons are measured at chromospheric levels, while strong upward
motions are measured in TR (up to -100 km s<SUP>-1</SUP>) and coronal
lines (-160 km s<SUP>-1</SUP>). The spatial pattern of these velocities
have a common area about 10 arcsec wide. This is the first time that
opposite directed flows at different atmospheric levels are observed
in the same spatial location during a flare. These signatures are
highly suggestive of the chromospheric evaporation scenario predicted
in theoretical models of flares.
---------------------------------------------------------
Title: Behaviour of Hydrogen Lyman lines in a prominence region from
SUMER and CDS
Authors: Aznar Cuadrado, R.; Andretta, V.; Teriaca, L.; Kucera, T. A.
2003MmSAI..74..611A Altcode:
We present observations of a prominence, taken on 1998 February 20 in
the framework of SOHO Joint Observing Program no. 63. The instruments
involved were SUMER and the NIS Spectrograph of CDS. The SUMER spectral
range includes the hydrogen Lyman series - starting from Ly-epsilon -
down to the head of the Lyman continuum, while CDS observed a number of
lines from T ~ 10<SUP>4</SUP> K to T ~ 2x 10<SUP>6</SUP> K. For these
observations, we were able to obtain a satisfactory determination of
the pointing of the SUMER slit relative to CDS. We thus examined - and
compared with information from CDS spectra - the main characteristics of
the hydrogen Lyman series lines and of other strong lines in the SUMER
spectral interval. We also studied the properties (depth, asymmetry)
of the central reversal present in several or all of the Lyman lines
in some regions of the prominence.
---------------------------------------------------------
Title: Chromospheric and Transition region He lines during a flare
Authors: Falchi, A.; Mauas, P. J. D.; Andretta, V.; Teriaca, L.;
Cauzzi, G.; Falciani, R.; Smaldone, L. A.
2003MmSAI..74..639F Altcode:
An observing campaign (SOHO JOP 139), coordinated between ground
based and SOHO instruments, has been planned to obtain simultaneous
spectroheliograms of the same area in several spectral lines. The
chromospheric lines Ca II K, Hα and Na I D as well as He I 10830,
5876, 584 and 304 Ålines have been observed. These observations allow
us to build semi-empirical models of the atmosphere before and during
a small flare. With these models, constructed to match the observed
line profiles, we can test the He abundance value.
---------------------------------------------------------
Title: Transition region small-scale dynamics: UV explosive events
Authors: Teriaca, L.; Falchi, A.; Doyle, J. G.; Madjarska, M. S.;
Banerjee, D.
2002ESASP.506..777T Altcode: 2002ESPM...10..777T; 2002svco.conf..777T
High spectral, spatial and temporal resolution UV observations of the
quiet Sun transition region show a highly structured and dynamical
environment where transient events such as brightenings, blinkers
and explosive events occur continuously. In particular explosive
events are characterized by strongly non-Gaussian line profiles
witnessing velocities up to 200 km s<SUP>-1</SUP>. The high kinetic
and enthalpy fluxes associated with these events could be important
in the energy balance of the transition region and, perhaps, of the
whole corona. In this paper we present a high spatial resolution (~1")
spectroheliogram of a 270×290 arcsec<SUP>2</SUP> wide area of the
quiet Sun acquired with SUMER/SoHO in the O VI 1032 spectral line. The
extremely high quality of these observations allows us to identify
tens of explosive events and to study their relationship with the
underlying photospheric magnetic field. Moreover, the behaviour of lines
emitted by plasma at chromospheric (2×10<SUP>4</SUP>K) and coronal
(10<SUP>6</SUP>K) temperatures during transition region explosive
events is investigated. We conclude that those events do not contribute
significantly to the energy balance of the corona and seems typical
of structure not obviously connected to the T≥10<SUP>6</SUP>K corona.
---------------------------------------------------------
Title: SUMER observations of hydrogen Lyman series and continuum in
a prominence
Authors: Andretta, Vincenzo; Aznar Cuadrado, Regina; Kucera, Therese
A.; Teriaca, Luca
2002ESASP.506..419A Altcode: 2002svco.conf..419A; 2002ESPM...10..419A
We present observations of a prominence, taken on February 20, 1998 in
the framework of SOHO Joint Observing Program no. 63. The instruments
involved were SUMER and the Normal Incidence Spectrograph (NIS) of
CDS. The SUMER spectral range includes the hydrogen Lyman series
- starting from Ly-ɛ - down to the head of the Lyman continuum,
while CDS observed a number of lines from T ~ 10<SUP>4</SUP>K to T ~
2×10<SUP>6</SUP>K. For these observations, we were able to obtain a
satisfactory determination of the pointing of the SUMER slit relative to
CDS. We thus examined - and compared with information from CDS spectra
- the main characteristics of the hydrogen Lyman series lines and of
other strong lines in the SUMER spectral interval. We also studied
the properties (depth, asymmetry) of the central reversal present in
several or all of the Lyman lines in some regions of the prominence.
---------------------------------------------------------
Title: Temporal variability in the Doppler-shift of solar transition
region lines
Authors: Doyle, J. G.; Madjarska, M. S.; Roussev, I.; Teriaca, L.;
Giannikakis, J.
2002A&A...396..255D Altcode:
High cadence datasets taken in C III 977 Å, O VI 1032 Å and Ne
VIII 720 Å were analysed in an effort to establish the extent
of the variability in the Doppler-shift of typical mid-transition
region lines. The shortest time-scale variability seems to occur
in the network boundary regions where the line-shift can vary by
7-8 km s<SUP>-1</SUP> in less than 1 min. The internetwork region
also shows variability although this tends to be longer lived, ~
2-3 min. The average line-shift in C III is a red-shift which ranges
from ~ 2 km s<SUP>-1</SUP> to ~ 20 km s<SUP>-1</SUP> with an average
value for all regions selected being around 10 km s<SUP>-1</SUP>
in very good agreement with that derived by others. The red-shift
values indicate a clear difference between network and internetwork
regions, with the largest red-shift being present at the network
boundary. For O VI, this gives an average red-shift ranging from 5 to
10 km s<SUP>-1</SUP>. For Ne VIII, there is a 13 km s<SUP>-1</SUP>
difference between internetwork and bright network plasma with the
bright network being more red-shifted. This could imply that the
bright network regions are dominated by spicule down-flow.\ In the
second part we present results from 2-dimensional (2D) dissipative
magnetohydrodynamic (MHD) simulations of the response of the solar
transition region to micro-scale energy depositions. A variety of
temperatures at which the energy deposition takes place as well as the
amount of energy deposited are examined. This work is a continuation
of previous related simulations where small-scale energy depositions
were modelled in 1D hydrodynamics. The observable consequences of
such transient events are then computed for three transition region
lines, namely C IV 1548 Å, O VI 1032 Å, and Ne VIII 770 Å, under
the consideration of non-equilibrium ionization.
---------------------------------------------------------
Title: Chromospheric evaporation in a two-ribbon flare
Authors: Cauzzi, G.; Falchi, A.; Teriaca, L.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
2002ESASP.506..561C Altcode: 2002ESPM...10..561C; 2002svco.conf..561C
We present simultaneous, spatially and temporally resolved
chromospheric, transition region and coronal observations of a small
eruptive flare studied throughout its whole development. We show
that strong and co-spatial plasma motions, oppositely directed in the
chromosphere (downflows) and in upper atmospheric layers (upflows),
develop at the onset of the flare. For the first time, we prove that
such oppositely directed flows originate from the same flaring kernels
in different atmospheric layers. Using realistic values for the plasma
parameters in the flaring loop, we also estimate a balance between
the upward and downward momenta. Our observations confirm in a very
convincing way the scenario of chromospheric evaporation predicted in
theoretical models of flares.
---------------------------------------------------------
Title: Transition region explosive events: Do they have a coronal
counterpart?
Authors: Teriaca, L.; Madjarska, M. S.; Doyle, J. G.
2002A&A...392..309T Altcode:
EUV explosive events are a prominent class of phenomena characterizing
the solar transition region. Their correct location in the wider
frame-work of the outer solar atmosphere can provide important insight
on the nature of the transition region itself and its relationship
with the hotter corona and the cooler chromosphere. In this paper
we present new high-cadence SUMER observations of the “quiet”
Sun obtained simultaneously in the mid-transition region N V 1238.8
Å line (1.8x 10<SUP>5</SUP> K) and in the coronal Mg X 625 Å line
(1.1x 10<SUP>6</SUP> K). These observations are aimed at providing
information on the behaviour of the coronal plasma during EUV
transition region explosive events detected in N V 1238.8 Å. None of
the events observed in N V shows any detectable signature in the Mg
X line profile or in its integrated intensity. The analysis of 1996
observations obtained simultaneously in N V 1238.8 Å and S II 1253.8
Å (3.5x 10<SUP>4</SUP> K) shows, instead, a weak but clear presence
of enhanced wings in the S II line profile during a series of events
observed in N V. These results suggest that EUV explosive events are
not directly relevant in heating the corona and are characteristic of
structures not obviously connected with the upper corona. The evidence
of a chromospheric response suggests that, contrary to some previous
suggestions, explosive events have a chromospheric origin.
---------------------------------------------------------
Title: Combined space and ground based observations of a C-1 flare
Authors: Teriaca, L.; Falchi, A.; Cauzzi, G.; Falciani, R.; Smaldone,
L. A.; Andretta, V.
2002ESASP.508..457T Altcode: 2002soho...11..457T
We present temporally and spatially resolved space and ground based
observations of a C1 flare. Ground based spectroheliograms were acquired
at the Dunn Solar Tower of NSO/Sacramento Peak in several chromospheric
lines. Simultaneously, the Coronal Diagnostic Spectrograph (CDS)
aboard SoHO was used to obtrain rasters of the same active region
in transiton region (TR) and coronal lines. This unique dataset
provides us, for the first time, with spatially resolved observations
of velocity fields during the impulsive phase of the flare, from the
chromosphere up to the TR and the corona. At the time of the emission
peak, a large area of the flaring kernel observed in TR lines is
characterized by upward velocities. A ~6"×6" kernel displays upflows
velocity above 80 km s<SUP>-1</SUP>. In this same area we found, in
data obtained about 3 minutes later, chromospheric downflows of 10 -
20 km s<SUP>-1</SUP>. This is the first time that opposite directed
flows at different atmospheric levels are observed in the same spatial
location during a flare.
---------------------------------------------------------
Title: The fall 2001 polar SOHO-Ulysses quadrature campaign:
preliminary results
Authors: Aznar Cuadrado, R.; Poletto, G.; Teriaca, L.; Suess, S. T.
2002ESASP.508..481A Altcode: 2002soho...11..481A
We present here UVCS observations of a polar coronal hole,
acquired during the October/November 2001 SOHO-Sun-Ulysses
quadrature. SOHO-Ulysses quadratures occur when the SOHO-Sun-Ulysses
included angle is 90° and offer the unique opportunity of comparing
the properties of plasma parcels, observed by SOHO in the corona,
with properties of the same parcels, measured in situ, in due time,
by Ulysses. The October/November 2001 quadrature occurred at a time
when Ulysses was at ≍2.2 A.U., at a northern heliographic latitude
of ≍80°, off the West limb of the Sun. Observations were taken from
October 29 to November 12, 2001, with a ≍3 days data gap, after the
eruption of CMEs and the emission of highly energetic particles, on 3-4
November. The UVCS slit was set normal to the solar radius, with the
radial to Ulysses going through its zero position. At the time of the
campaign, the radial to Ulysses crossed a polar coronal hole. Although
its shape was changing, Ulysses was permanently located in a high speed
region where CMEs signature can be recognized. Observations in hydrogen
Lyman-α and in the 1032 and 1037 Å O VI doublet lines have been made
at 1.6 and 2 R<SUB>solar</SUB>. Line intensities are compared with
intensities typically found, at the same altitudes, in polar coronal
holes at minimum solar activity and in equatorial holes. The temporal
profile of the O VI doublet line ratio and of the O VI line widths,
at the position where the radial to Ulysses traverses the solar corona,
are shown and a tentative interpreation of the data is outlined.
---------------------------------------------------------
Title: Dynamics and Diagnostics of Explosive Events and Blinkers
Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L.
2002mwoc.conf...69M Altcode:
The knowledge of the main physical parameters of UV explosive events
and blinkers, such as density and temperature, is of great importance
for the better understanding of the true nature of these transient
events. In this context, density and temperature diagnostics based on
lines belonging to O iv 1400Å and O iii multiplets is presented for
both kind of events. The dynamics of the solar transient phenomena
is revealed through their temporal and spatial evolution as observed
in spectral lines covering a wide temperature range. The results
are obtained using SUMER, CDS, MDI and EIT aboard SoHO, TRACE and
Big Bear Solar Observatory observations and are aimed to give more
information about the main properties of these phenomena. The events
are also studied in connection with the evolution of the underlying
magnetic field, searching for observational evidences of their further
propagation higher in the solar corona.
---------------------------------------------------------
Title: Radial velocities and orbital solution of the active binary
star FG Ursae Majoris
Authors: Marino, G.; Catalano, S.; Frasca, A.; Marilli, E.; Teriaca, L.
2002IBVS.5227....1M Altcode:
The orbital parameters of the single-lined active binary FG UMa
are derived, for the first time, by analyzing medium-resolution
spectra collected at Catania Astrophysical Observatory from 1997 till
2000. Radial velocities were measured by using the cross correlation
technique.
---------------------------------------------------------
Title: Oxygen abundance in polar coronal holes
Authors: Teriaca, L.; Poletto, G.; Falchi, A.; Doyle, J. G.
2001AIPC..598...65T Altcode: 2001sgc..conf...65T
Fast solar wind is known to emanate from polar coronal holes. However,
only recently attention has been given to the problem of where,
within coronal holes, fast wind originates. Information on whether the
fast solar wind originates from plumes or interplume regions may be
obtained by comparing the elemental abundances in these regions with
those characterizing the fast wind. Here we present a first attempt
to determine the oxygen abundance in the interplume regions by using
spectra taken at times of minimum in the solar cycle (when it is
easier to identify these structures) by the SUMER spectrograph aboard
SoHO. To this end, we analyze spectra taken in 1996 in polar regions,
at altitudes ranging between 1.05 and 1.3 R<SUB>solar</SUB>, finding a
value >=8.5 for the oxygen abundance in the interplume regions. From
the analysis of the O VI 1032 to 1037 line intensity ratio we also find
no evidence of outflow velocities below 1.2 solar radii in interplume
regions, while there are indications that outflow motions start to be
significant above 1.5 solar radii. The method used and the assumptions
made are discussed in light of the derived values. Our values are
compared with previous determinations in the corona and solar wind. .
---------------------------------------------------------
Title: Measuring Solar Abundances
Authors: von Steiger, R.; Vial, J. -C.; Bochsler, P.; Chaussidon, M.;
Cohen, C. M. S.; Fleck, B.; Heber, V. S.; Holweger, H.; Issautier, K.;
Lazarus, A. J.; Ogilvie, K. W.; Paquette, J. A.; Reisenfeld, D. B.;
Teriaca, L.; Wilhelm, K.; Yusainee, S.; Laming, J. M.; Wiens, R. C.
2001AIPC..598...13V Altcode: 2001sgc..conf...13V
This is the rapporteur paper of Working Group 2 on Measuring Solar
Abundances. The working group presented and discussed the different
observations and methods for obtaining the elemental and isotopic
composition of the Sun, and critically reviewed their results and
the accuracies thereof. Furthermore, a few important yet unanswered
questions were identified, and the potential of future missions to
provide answers was assessed. .
---------------------------------------------------------
Title: Coronal and solar wind elemental abundances
Authors: Raymond, J. C.; Mazur, J. E.; Allegrini, F.; Antonucci, E.;
Del Zanna, G.; Giordano, S.; Ho, G.; Ko, Y. -K.; Landi, E.; Lazarus,
A.; Parenti, S.; Poletto, G.; Reinard, A.; Rodriguez-Pacheco, J.;
Teriaca, L.; Wurz, P.; Zangrilli, L.
2001AIPC..598...49R Altcode: 2001sgc..conf...49R
Coronal elemental abundances, as compared with abundances in the solar
wind and solar energetic particles, provide the means for connecting
solar wind gas with its coronal source. Comparison of coronal abundances
with photospheric values shows fractionation with the ionization
potential of the atom, providing important, though not yet fully
understood, information about the exchange of material between corona
and chromosphere. Fractionation due to gravitational settling provides
clues about flows within the corona. In this paper, we discuss the
uncertainties of abundance determinations with spectroscopic techniques
and in situ measurements, we survey the ranges of abundance variations
in both the corona and solar wind, and we discuss the progress in
correlating solar wind features with their coronal sources. .
---------------------------------------------------------
Title: Electron density variations during ultraviolet transient events
Authors: Teriaca, L.; Madjarska, M. S.; Doyle, J. G.
2001SoPh..200...91T Altcode:
% High-resolution temporal observations performed with the SUMER
spectrometer on SOHO provide an opportunity to investigate the electron
density variations in the `quiet-Sun' solar transition region due to
UV transient events. Two datasets obtained in the density sensitive
lines belonging to the O iv 1400 Å multiplet were searched for such
events, leading to the identification of two explosive events, on 10
July 1996 and 31 May 1997. In both cases, the O iv 1401.16/1404.81
density-sensitive line intensity ratio shows a clear variation,
corresponding to enhancements in the electron density by factors of
∼3. This is fully consistent with recent 2.5D MHD simulations. The
10 July 1996 dataset also provided us with the opportunity to monitor
the behavior of the electron density through an UV blinker. Despite
an increase of a factor of two in the line intensities, no variation
of the electron density was found. This suggests that the intensity
enhancement is due to an increase in the filling factor.
---------------------------------------------------------
Title: Numerical Modeling of the Transition Region Dynamics
Authors: Teriaca, L.; Doyle, J. G.
2001ASSL..259..307T Altcode: 2001dysu.conf..307T
We explore the idea that the occurrence of nano-flares in a magnetic
loop around the O VI formation temperature could explain the observed
red-shift of mid-low transition region lines as well as the blue-shift
observed in low coronal lines (T > 6 times 10<SUP>5</SUP>
K). Observations are compared to numerical simulations of the
response of the solar atmosphere to an energy perturbation of 4 times
10<SUP>24</SUP> ergs representing an energy release during magnetic
reconnection in a 1-D semi-circular flux tube. The temporal evolution
of the thermodynamic state of the loop is finally converted into C
III 977, C IV 1548, O V 630, O VI 1032, Ne VII 465 and Ne VIII 770
line profiles in non-equilibrium ionization. Performing an integration
over the entire period of simulation, redshifts of 8.5, 6.1 and 1.7 km
s<SUP>-1</SUP>, are found in C III, C IV, and O V while blue-shifts
of -1.8, -3.9 and -10.7 km s<SUP>-1</SUP> were derived for O VI,
Ne VII and Ne VIII respectively, in good agreement with observations.
---------------------------------------------------------
Title: Electron Density Enhancement During an UV Explosive Event
Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L.
2001IAUS..203..407M Altcode:
High resolution temporal observations performed with the SUMER
spectrometer on SOHO provide us the opportunity to investigate the
electron density variations in the solar mid transition region due
to explosive event-like phenomena. The O IV 1401.16/1404.81 density
sensitive line intensity ratio shows a clear increase during a strong
explosive event, corresponding to an electron density enhancement of
a factor of ~ 3.5 respect to pre-event values. This is consistent
with recent MHD simulations (2.5 D) carried out by Karpen et
al. (1998). Karpen J. T., Antiochos S. K., DeVore C. R. and Golub L.,
1998, ApJ 495, 491.
---------------------------------------------------------
Title: Structure and dynamics of the solar outer atmosphere as
inferred from EUV observations
Authors: Teriaca, Luca Nunzio
2001PhDT.........2T Altcode:
EUV observations obtained with the SUMER/SOHO are analysed,
obtaining information about the density, temperature and velocity
fields characterizing the solar plasma. We measure the amount of line
shift and width as a function of temperature for several transition
region lines, on both quiet Sun and, an active region. A reversal from
redshift to blueshift happens at temperatures above 5 10<SUP> 5</SUP>
K. We explore the idea that the occurrence of nano-flares in a magnetic
loop could explain the observed line shift behaviour. Observations
are compared to numerical simulations of the response of the solar
atmosphere to an energy perturbation. The temporal evolution of
the thermodynamic state of the loop model is converted into line
profiles in non-equilibrium ionization, finding good agreement with
observations. The center-to-limb variation of the non-thermal velocity
is particularly important in discriminating the heating mechanism. Full
disk images in He I, C IV and Ne VIII are, hence, used to investigate
whether there exists a center-to-limb variation in the line width,
finding that the unresolved mass motions in the solar atmosphere
are prevalently isotropic. The effects of energetic phenomena on the
solar plasma have also been studied through high-resolution temporal
observations of the electron density behaviour during UV transient
events, finding enhancements of a factor of ~3 associated with explosive
events. We also provide electron density measurements in network and
internetwork regions and during an UV blinker. The measurement of
line widths can provide information concerning velocity fluctuations
associated with MHD waves in the corona. The velocity fields in plume
and inter-plume regions were investigated in detail, showing that the
darker inter-plume lanes (believed to be the locations where the fast
solar wind originates) are characterized by broader line profiles. The
variation of the line width and electron density as a function of height
above two coronal holes was, hence, obtained in the inter-plume. We
find that the non-thermal velocity is inversely proportional to the
quadratic root of the electron density, in excellent agreement with
that predicted for undamped radially propagating Alfvén waves. We
show that the energy flux associated with these hydromagnetic waves
is sufficient to drive the high speed solar wind streams.
---------------------------------------------------------
Title: SUMER Observations of the Solar Transition Region: Spatial
and Temporal Behaviour
Authors: Teriaca, L.; Doyle, J. G.; Banerjee, D.
2001IAUS..203..425T Altcode:
In this paper we examine the spatial and temporal behaviour of the quiet
Sun transition region using high resolution SUMER observations in O VI
1032. The observations are devoted to the study of the variability in
the transition region and consists of four raster scans of the same
area followed by a long series of spectra taken in the same position
with high temporal cadence. A detailed study of the raster images
allows us to differentiate the network and internetwork through
Doppler shift and line width measurements. We have also identified
several explosive-events like phenomena toghether with an UV bright
point. We also show evidence for a possible formation of a shock front
after one partcular bright point appearence. The oscillatory nature
of the transition region is finally investigated using the wavelet
analysis and particular attention has been paid to the effect due to
the occurrence of explosive events.
---------------------------------------------------------
Title: The magnetic activity cycle of II Pegasi: results from
twenty-five years of wide-band photometry
Authors: Rodonò, M.; Messina, S.; Lanza, A. F.; Cutispoto, G.;
Teriaca, L.
2000A&A...358..624R Altcode:
We present an analysis of a sequence of light curves of the RS CVn-type
binary II Pegasi extending from 1974 to 1998. The distribution of
the spotted area versus longitude is derived by Maximum Entropy
and Tikhonov regularized maps, assuming a constant spot temperature
(Lanza et al. 1998a). The spot pattern on the active K2 IV star can
be subdivided into a component uniformly distributed in longitude and
a second unevenly distributed component, which is responsible for the
observed photometric modulation. The uniformly distributed component
appears to be possibly modulated with an activity cycle of ~ 13.5
yr. The unevenly distributed component is mainly concentrated around
three major active longitudes. The spot activity appears practically
permanent at one longitude, but the spot area changes with a cycle of
~ 9.5 yr. On the contrary, the spot activity is discontinuous at the
other two longitudes, and it switches back and forth between them with
a cycle of ~ 6.8 yr. However, before each switching is completed, a
transition phase of ~ 1.05 yr, during which both longitudes are active,
occurs. After this transient phase, spot activity remains localized at
one of the two longitudes for ~ 4.7 yr untill another switching event
occurs, which re-establishes spot activity at the other longitude. The
longitude separation between the permanent and the switching active
longitudes is closest during the switching phases and it varies along
the ~ 6.8 yr cycle. Different time scales characterize the activity at
the permanent longitude and at the switching longitudes: a period of ~
9.5 yr is related to the activity cycle at the permanent longitude, and
a period of ~ 4.3 yr characterizes the spot life time at the switching
longitudes in between switching events. The photometric period of the
active star changes from season to season with a relative amplitude
of 1.5% and a period of ~ 4.7 yr. Such a variation of the photometric
period may be likely associated with the phase shift of the light curves
produced by the switching of spot activity from one active longitude to
the other. The permanently active longitude shows a steady migration
towards decreasing orbital phases, with an oscillating migration rate
along the 9.5 yr cycle period and nearly in phase with the variation of
its spotted area. The amplitude of the differential rotation derived
from such a behaviour is of the order of ~ 0.023%, about one order
of magnitude smaller than estimated by Henry et al. (1995). The other
two active longitudes migrates also towards decreasing orbital phase,
but at a discontinuous rate. There appears to be no correlation between
the location of the active longitudes with respect to the line joining
the two components of the system and their activity level.
---------------------------------------------------------
Title: Polar Plumes and Inter-plume regions as observed by SUMER
on SOHO
Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Lemaire, P.
2000SoPh..194...43B Altcode:
We present observations of O vi 1032 Å line profiles obtained
with the SUMER instrument on SOHO extending from the solar
disk to 1.5 R<SUB>⊙</SUB> above the limb in the north polar
coronal hole. Variations of the intensity and linewidth in the
polar plume and inter-plume regions are investigated. We find an
anti-correlation between the intensity and the linewidth in the plume
and inter-plume regions with detailed plume structures been seen out
to 1.5 R<SUB>⊙</SUB>. Possible implications regarding the magnetic
topologies of these two regions and related heating mechanisms are
discussed. The O vi linewidth measurements are combined with UVCS output
to provide an overview of its variations with height extending up to
3.5 R<SUB>⊙</SUB>. We find a linear increase of the linewidth from
1 to 1.2 R<SUB>⊙</SUB>, then a plateau followed by a sharp increase
around 1.5 R<SUB>⊙</SUB>.
---------------------------------------------------------
Title: Solar transition region line broadening: Limb to limb
measurements
Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D.
2000A&A...356..335D Altcode:
Full disk images from SUMER/SoHO taken in He I, C IV and Ne VIII are
used to investigate whether there exists a center-to-limb variation
in the line width. Both C IV and He I show such a variation but the
higher temperature Ne VIII line is relatively constant. For C IV,
this corresponds to ~ 3 km s<SUP>-1</SUP> difference while He I
is significantly larger particularly at the limb. This work may
suggest that the non-thermal motions are slightly non-isotropic in
the transition region and upper chromosphere, with the horizontal
unresolved motions exceeding those in the vertical plane however a more
probable explanation is that the lines are broadened due to opacity
effects. The more slower variation in the C IV 1548 Ä line width could
be explained by increasing the opacity from zero at disk center to ~ 1
at the limb. For He I the opacity is significantly grater than unity at
the limb. This therefore implying all mass motions in the chromosphere,
transition region and corona are isotropic.
---------------------------------------------------------
Title: New Insight in Transition Region Dynamics as Derived from
SUMER Observations and Numerical Modelling
Authors: Teriaca, L.; Doyle, J. G.; Erdélyi, R.; Sarro, L. M.;
Banerjee, D.
1999ESASP.448..379T Altcode: 1999ESPM....9..379T; 1999mfsp.conf..379T
No abstract at ADS
---------------------------------------------------------
Title: New insight into transition region dynamics via SUMER
observations and numerical modelling
Authors: Teriaca, L.; Doyle, J. G.; Erdélyi, R.; Sarro, L. M.
1999A&A...352L..99T Altcode:
We explore the idea that the occurrence of nano-flares in a magnetic
loop around the O vi formation temperature could explain the
observed red-shift of mid-low transition region lines as well as the
blue-shift observed in low coronal lines (T > 6x 10<SUP>5\</SUP>
K). Observations are compared to numerical simulations of the response
of the solar atmosphere to an energy perturbation of 4x 10<SUP>24</SUP>
ergs representing an energy release during magnetic reconnection
in a 1-D semi-circular flux tube. The temporal evolution of the
thermodynamic state of the loop is converted into C iv 1548, O vi 1032
and Ne viii 770 line profiles in non-equilibrium ionization. Performing
an integration over the entire period of simulations, a redshift of ~
6\ km\ s<SUP>-1</SUP> is found in C iv, while a blue-shift of ~ 2\ km\
s<SUP>-1</SUP> and ~ 10\ km\ s<SUP>-1</SUP> were derived for O vi and
Ne viii, respectively, in reasonable agreement with observations.
---------------------------------------------------------
Title: SUMER Observations of Line Shifts in the Quiet Sun and in an
Active Region
Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G.; Erdély, R.
1999ESASP.446..645T Altcode: 1999soho....8..645T
The UV spectral lines formed at transition region temperatures in the
solar atmosphere, shows a prevailing redshifted emission. Using the
Solar Ultraviolet Measurements of Emitted Radiation spectrometer
flown on the Solar and Heliospheric Observatory spacecraft, we
measure the amount of line shift as a function of the temperature
for several spectral lines formed in the range between 10<SUP>4</SUP>
and 10<SUP>6</SUP> K. We analyze spectrograms relative to the quiet
Sun and to the active region NOAA 7946. The velocities derived are
increasing from a redshift of ~ 0 km/s at ~ 20000 K to 10 km/s
at 1.9x10<SUP>5</SUP> K for the quiet Sun, and to ~ 15 km/s at
10<SUP>5</SUP> K for the active region. At higher temperature an
opposite behaviour is observed. In the quiet Sun a blueshift of ~ -2
km/s is observed at the Ne viii formation temperature (6x10<SUP>5</SUP>
K), while in the active region, a blue-shifted value around -8 km/s is
observed for the same spectral line. By 10<SUP>6</SUP> K the blueshift
is ~ -10 km/s in the active region as measured by Fe xii 1242.
---------------------------------------------------------
Title: Coronal Hole Diagnostics out to 8 solar radii
Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D.; Fludra, A.
1999ESASP.446..281D Altcode: 1999soho....8..281D
The line width measurements (from Si VIII) and N<SUB>e</SUB> estimates
(from Si VIII and Si IX) based on SUMER and CDS observations are
combined with LASCO and UVCS output to provide an overview of its
variations with height above a polar coronal hole. From the combined
dataset we find a radial dependence of the electron density, in the
range 1-2 solar radii as r-8, from 2 to 4 solar radii as r-4 and then
as r-2. Combining the Si VIII half width at 1/e of the peak intensity
with the UVCS O VI half width, we find a small increase of the half
width from 1 to 1.2 solar radii, then a plateau until 1.5 solar radii,
thereafter a sharp increase until 2 solar radii, finally a more gradual
increase reaching 550 km/s at 3.5 solar radii. Our data suggests that
the MHD waves responsible for the excess line broadening tends to
become non-linear as it reaches 1.2 solar radii.
---------------------------------------------------------
Title: SUMER observations of Doppler shift in the quiet Sun and in
an active region
Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G.
1999A&A...349..636T Altcode:
The UV spectral lines formed at transition region temperatures in the
solar atmosphere, show a prevailing redshifted emission. Using the Solar
Ultraviolet Measurements of Emitted Radiation spectrometer flown on the
Solar and Heliospheric Observatory spacecraft, we measure the amount
of line shift as a function of the temperature for several spectral
lines formed in the range between 10(4) and 10(6) \ K. We analyze
spectrograms relative to the quiet Sun and to the active region NOAA\
7946. The velocities derived are increasing from a redshift of ~ \
0 \ km ; s(-1) at ~ 20000\ K to 10\ km ; s(-1) at 1.9\ 10(5) \ K for
the quiet Sun, and to ~ 15 \ km ; s(-1) at 10(5) \ K for the active
region. At higher temperature an opposite behaviour is observed. In
the quiet Sun a blueshift of ~ \ -2 \ km ; s(-1) is observed at the
Ne viii formation temperature (6.3\ 10(5) \ K), while in the active
region, a blue-shifted value around -8\ km ; s(-1) is observed for
the same spectral line. The finding of blueshift in Ne viii is due to
the adoption of a new rest wavelength of 770.428 Ä. By 10(6) \ K the
blueshift is ~ \ -10 \ km ; s(-1) in the active region as measured by
Fe xii 1242.
---------------------------------------------------------
Title: Coronal hole diagnostics out to 8R<SUB>sun</SUB>
Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D.
1999A&A...349..956D Altcode:
The Si viii line width measurements and N_e estimates based on SUMER
observations are combined with LASCO and UVCS output to provide an
overview of its variations with height above a polar coronal hole. From
the combined dataset we find a radial dependence of the electron
density, in the range 1-2 R<SUB>sun</SUB> as r(-8) , from 2 to 4
R<SUB>sun</SUB> as r(-4) and then as r(-2) . Combining the Si viii half
width at 1/e of the peak intensity with the UVCS O vi half width, we
find a small increase of the half width from 1 to 1.2 R<SUB>sun</SUB>,
then a plateau until 1.5 R<SUB>sun</SUB>, thereafter a sharp increase
until 2 R<SUB>sun</SUB>, finally a more gradual increase reaching 550
km s(-1) at 3.5 R<SUB>sun</SUB>. Our data suggests that the MHD waves
responsible for the excess line broadening tends to become non-linear
as it reaches 1.2 R<SUB>sun</SUB>.
---------------------------------------------------------
Title: Alfvén waves in the solar polar coronal holes
Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Wilhelm, K.
1999AIPC..471..289B Altcode: 1999sowi.conf..289B
We study the variation of the line width and electron density as a
function of height above two coronal holes from forbidden spectral
lines of Si VIII. The spectra were obtained with the Solar Ultraviolet
Measurements of Emitted Radiation spectrometer flown on the Solar and
Heliospheric Observatory spacecraft. The observations concentrate on the
dark regions outside the plumes, which are believed to be the location,
where the fast solar wind originates. The line width data show that
the non-thermal line-of-sight velocity increases from 20 km s-1 at
27 arc sec above the limb to 37 km s-1 some 370 arc sec (i.e. ~1.38
R<SUB>solar</SUB>) above the limb. The electron density shows a
decrease from 3.5 10<SUP>8</SUP> cm<SUP>-3</SUP> to 1.6 10<SUP>7</SUP>
cm<SUP>-3</SUP> over the same distance. This data implies that the
non-thermal velocity is inversely proportional to the quadratic root of
the electron density in the range 1-1.2 R<SUB>solar</SUB>, in excellent
agreement with that predicted for undamped radially propagating Alfvén
waves. Beyond 1.2 R<SUB>solar</SUB> our data suggests an effective
breakdown of linear theory for the propagation of Alfvén waves.
---------------------------------------------------------
Title: Line Width Variations above a Coronal Hole: Implications
for Heating
Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D.
1999ASPC..158..366D Altcode: 1999ssa..conf..366D
No abstract at ADS
---------------------------------------------------------
Title: SUMER Observations of Doppler Shifts in the Quiet Sun and an
Active Region
Authors: Teriaca, L.; Doyle, J. G.; Banerjee, D.
1999ASPC..158..362T Altcode: 1999ssa..conf..362T
No abstract at ADS
---------------------------------------------------------
Title: Light Curve Variation and Flare Eruption in the Sun and Stars
Authors: Teriaca, L.; Catalano, S.
1999ASPC..158..243T Altcode: 1999ssa..conf..243T
No abstract at ADS
---------------------------------------------------------
Title: Broadening of SI VIII lines observed in the solar polar
coronal holes
Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Wilhelm, K.
1998A&A...339..208B Altcode:
We study the variation of the line width and electron density as a
function of height above two coronal holes from forbidden spectral
lines of Si viii. The spectra were obtained with the Solar Ultraviolet
Measurements of Emitted Radiation spectrometer flown on the Solar and
Heliospheric Observatory spacecraft. The observations concentrate on the
dark regions outside the plumes, which are believed to be the locations,
where the fast solar wind originates. The line width data show that
the non-thermal line-of-sight velocity increases from 27 {km s}(-1) at
27 arc sec above the limb to 46 {km s}(-1) some 250 arc sec ({i.e. } ~
180,000 km) above the limb. The electron density shows a decrease from
1.1 10(8) {cm}(-3) to 1.6 10(7) {cm}(-3) over the same distance. This
data implies that the non-thermal velocity is inversely proportional
to the quadratic root of the electron density, in excellent agreement
with that predicted for undamped radially propagating Alfven waves. We
show that the energy flux associated with these hydromagnetic waves
is sufficient to drive the high speed solar wind streams.
---------------------------------------------------------
Title: Line Width Variations in the Solar Polar Coronal Holes
Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G.
1998ESASP.417..329T Altcode: 1998cesh.conf..329T
No abstract at ADS
---------------------------------------------------------
Title: Stellar Flare and Light Curve Variations in Active Binary
Systems
Authors: Teriaca, L.
1997PhDT........20T Altcode:
No abstract at ADS
