explanation blue bibcodes open ADS page with paths to full text
Author name code: fineschi
ADS astronomy entries on 2022-09-14
author:"Fineschi, Silvano"
---------------------------------------------------------
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>
---------------------------------------------------------
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.
---------------------------------------------------------
Title: Science with the ASPIICS coronagraph onboard PROBA-3
Authors: Gunár, Stanislav; Fineschi, Silvano; Inhester, Bernd;
Zhukov, Andrei; Mierla, Marilena; Tsinganos, Kanaris; Lamy, Philippe;
Rudawy, Pawel
2022cosp...44.1326G Altcode:
The giant distributed coronagraph ASPIICS onboard the formation-flying
mission PROBA-3 of ESA will investigate hitherto practically
unexplored inner depths of the solar corona. This region lies above
the reach of disk imagers such as SDO and below the inner limit of
other coronagraphs. Although difficult to observe, the inner corona
is a place of great interest. This is where the fast solar wind gets
accelerated to supersonic velocities and where CMEs also reach their
maximum accelerations. It is also the place where the transition between
the regions of the closed and open magnetic field often happens and
the slow solar wind originates. Thanks to its field of view (2048 x
2048 pixels) reaching from 1.098 to 3 Rsun, good spatial resolution
(2.8 arcsec per pixel) and minimized straylight, ASPIICS will be able
to follow the connectivity of magnetic structures in corona down to the
solar surface. When coupled with regular (every week) long duration
(up to 6 hours) observations, it will allow us to comprehensively
compare and validate the MHD models of the large-scale coronal magnetic
field configuration and its evolution. The inner field-of-view limit
reaching very close to the solar surface will also enable us to study
the onset and early evolution of CMEs or to follow erupting prominences
beyond the reaches of the disk imagers. Thanks to the high cadence
(up to 2 seconds) we can start to investigate the manifestation of
small-scale solar dynamic processes within the inner corona. Moreover,
together with the DARA instrument measuring the total solar irradiance
onboard the occulting spacecraft of PROBA-3, ASPIICS will help us to
understand the partition of the magnetic free energy into the radiative
energy and the kinetic energy during solar eruptions. The pursuit of
these science goals will happen in coordination with Solar Orbiter,
Parker Solar Probe, Aditya-L1, and ASO-S. The synergies stemming from
these collaborations are promising to lead us into a golden age of
space coronagraphy.
---------------------------------------------------------
Title: The observed large scale equatorial UV corona: new perspectives
with 'recent', 'future' and 'old' data
Authors: Abbo, Lucia; Fineschi, Silvano; Parenti, Susanna; Romoli,
Marco; Pancrazzi, Maurizio; Andretta, Vincenzo; Auchère, Frédéric;
Susino, Roberto; Spadaro, Daniele; Nicolini, Gianalfredo; Giordano,
Silvio; Zangrilli, Luca
2022cosp...44.1327A Altcode:
In order to understand the sources and the physical mechanisms for the
propagation of the Slow Solar Wind (SSW), it is essential to analyze
solar data in the region which shapes the large scale structure in
corona where the SSW is accelerated, such as streamers and boundaries
coronal hole/streamer. The focus of this work is to trace the channels
where the SSW escapes from the solar disk up to 5 solar radii in
corona. We give an overview on how Solar Orbiter observations (remote
sensing and in-situ) together with other space missions (i.e. SPP and
PROBA-3) can give a major contribution to the study of the evolution
of the streamer belt and global corona, of the role of the coronal
magnetic field topology in controlling the solar wind dynamics and
abundance, and of abundance anomalies in streamers and in boundaries
CH/streamer. In particular, we study how to trace back some equatorial
features from the extended corona to the disk. We analyse recent Metis
observations in corona together with the Extreme Ultraviolet Imager
(EUI) observations on disk and corona (by using the occulter). We also
present results from SOHO observations in 1996-1997 (solar minimum),
during which was observed a stable equatorial streamer belt with a
typical dipole magnetic structure. We have analyzed data by UVCS,
SUMER, CDS to trace large scale features and also sub-structures at
very high spatial resolution from the disk up to 3 solar radii. This
comparison and overlapping is still unique in solar physics and it can
improve our knowledge about the origin, acceleration and propagation
of the solar wind.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: Sky Brightness Evaluation at Concordia Station, Dome C,
Antarctica, for Ground-Based Observations of the Solar Corona
Authors: Liberatore, Alessandro; Capobianco, Gerardo; Fineschi,
Silvano; Massone, Giuseppe; Zangrilli, Luca; Susino, Roberto; Nicolini,
Gianalfredo
2022SoPh..297...29L Altcode: 2022arXiv220100660L
The evaluation of sky characteristics plays a fundamental role for
many astrophysical experiments and ground-based observations. In solar
physics, the main requirement for such observations is a very low
sky brightness value, less than 10<SUP>−6</SUP> of the solar disk
brightness (B<SUB>⊙</SUB>). Few places match such a requirement
for ground-based, out-of-eclipse coronagraphic measurements. One of
these places is, for instance, the Mauna Loa Observatory (≈3400 m
a.s.l.). Another candidate coronagraphic site is the Dome C plateau
in Antarctica. In this article, we show the first results of the sky
brightness measurements at Dome C with the Extreme Solar Coronagraphy
Antarctic Program Experiment (ESCAPE) at the Italian-French Concordia
Station, on Dome C, Antarctica (≈3300 m a.s.l.) during the 34th and
35th summer Campaigns of the Italian Piano Nazionale Ricerche Antartiche
(PNRA). The sky brightness measurements were carried out with the
internally occulted Antarctic coronagraph AntarctiCor. In optimal
atmospheric conditions the sky brightness of Dome C has reached values
of the order of 1.0 - 0.7 ×10<SUP>−6</SUP>B<SUB>⊙</SUB>.
---------------------------------------------------------
Title: Scattering Polarization Diagnostic of the UV Corona
Authors: Casini, R.; Gibson, S.; Newmark, J.; Fineschi, S.; Gilbert, H.
2022heli.conf.4053C Altcode:
A largely unexplored diagnostic of the coronal magnetic field vector
is offered by the linear polarization signature of the Hanle effect
of far ultraviolet (FUV) resonance lines.
---------------------------------------------------------
Title: The COronal Magnetism Observatory (COMO)
Authors: Casini, Roberto; Newmark, Jeffrey; Fineschi, Silvano;
Burkepile, Joan; Gibson, Sarah; Gilbert, Holly; Raouafi, Nour
2021AGUFMSH15G2092C Altcode:
Structuring of solar coronal plasma by the magnetic field is the
key to understanding the fundamental physical processes of energy
dissipation in the corona. The coronal magnetic field is crucial to
understanding coronal dynamics and space weather. We present the
COronal Magnetism Observatory (COMO), a new polarimetric imaging
solar coronagraph for the FUV (H Ly-alpha), to be deployed to the
International Space Station. COMO will provide the first global maps
of the magnetic field and solar wind properties from 1.1 to 3 Rsun.The
instrument will measure the linearly polarized scattered light from
the low through the middle corona with a spatial sampling of 2.8
arcsec/pixel. The science mission relies on a variety of different
polarization diagnostic methods (unsaturated Hanle effect, Doppler
dimming) to infer information on the magnetic state of the active
low corona, and the solar wind velocity/acceleration in the middle
corona. The instrument design is an adaptation of the internally
occulted coronagraph for the Sounding-rocket Coronagraphic Experiment
(SCORE), successfully flown in 2009 as part of the NASA HERSCHEL
experiment, and the dual-beam polarimeter adopts a newly developed,
highly stable, Al-MgF2 multilayer coating for the polarization analyzer.
---------------------------------------------------------
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: Study of two interacting interplanetary coronal mass
ejections encountered by Solar Orbiter during its first perihelion
passage. Observations and modeling
Authors: Telloni, D.; Scolini, C.; Möstl, C.; Zank, G. P.;
Zhao, L. -L.; Weiss, A. J.; Reiss, M. A.; Laker, R.; Perrone, D.;
Khotyaintsev, Y.; Steinvall, K.; Sorriso-Valvo, L.; Horbury, T. S.;
Wimmer-Schweingruber, R. F.; Bruno, R.; D'Amicis, R.; De Marco,
R.; Jagarlamudi, V. K.; Carbone, F.; Marino, R.; Stangalini, M.;
Nakanotani, M.; Adhikari, L.; Liang, H.; Woodham, L. D.; Davies, E. E.;
Hietala, H.; Perri, S.; Gómez-Herrero, R.; Rodríguez-Pacheco, J.;
Antonucci, E.; Romoli, M.; Fineschi, S.; Maksimovic, M.; Souček,
J.; Chust, T.; Kretzschmar, M.; Vecchio, A.; Müller, D.; Zouganelis,
I.; Winslow, R. M.; Giordano, S.; Mancuso, S.; Susino, R.; Ivanovski,
S. L.; Messerotti, M.; O'Brien, H.; Evans, V.; Angelini, V.
2021A&A...656A...5T Altcode:
Context. Solar Orbiter, the new-generation mission dedicated to solar
and heliospheric exploration, was successfully launched on February
10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion
passage in June 2020, two successive interplanetary coronal mass
ejections (ICMEs), propagating along the heliospheric current sheet
(HCS), impacted the spacecraft. <BR /> Aims: This paper addresses the
investigation of the ICMEs encountered by Solar Orbiter on June 7−8,
2020, from both an observational and a modeling perspective. The aim is
to provide a full description of those events, their mutual interaction,
and their coupling with the ambient solar wind and the HCS. <BR />
Methods: Data acquired by the MAG magnetometer, the Energetic Particle
Detector suite, and the Radio and Plasma Waves instrument are used to
provide information on the ICMEs' magnetic topology configuration,
their magnetic connectivity to the Sun, and insights into the
heliospheric plasma environment where they travel, respectively. On
the modeling side, the Heliospheric Upwind eXtrapolation model, the
3D COronal Rope Ejection technique, and the EUropean Heliospheric
FORecasting Information Asset (EUHFORIA) tool are used to complement
Solar Orbiter observations of the ambient solar wind and ICMEs,
and to simulate the evolution and interaction of the ejecta in the
inner heliosphere, respectively. <BR /> Results: Both data analysis
and numerical simulations indicate that the passage of two distinct,
dynamically and magnetically interacting (via magnetic reconnection
processes) ICMEs at Solar Orbiter is a possible scenario, supported by
the numerous similarities between EUHFORIA time series at Solar Orbiter
and Solar Orbiter data. <BR /> Conclusions: The combination of in situ
measurements and numerical simulations (together with remote sensing
observations of the corona and inner heliosphere) will significantly
lead to a deeper understanding of the physical processes occurring
during the CME-CME interaction. <P />Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140648/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 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: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
---------------------------------------------------------
Title: Laboratory testbed for the calibration and the validation of
the shadow position sensor subsystem of the PROBA3 ESA mission
Authors: Loreggia, Davide; Zangrilli, Luca; Capobianco, Gerardo;
Massone, Giuseppe; Belluso, Massimiliano; Fineschi, Silvano; Amadori,
Francesco; Noce, Vladimiro; Bemporad, Alessandro; Casti, Marta;
Nicolini, Gianalfredo; Landini, Federico; Pancrazzi, Maurizio;
Romoli, Marco
2021SPIE11852E..6QL Altcode:
The PROBA3 mission of the European Space Agency is the first formation
flying (FF) mission that will be flown in high elliptic geocentric
orbit aiming at verifying and validating different metrology control
systems and algorithms in order to realize and maintain the formation
of two independent spacecraft, in total autonomy. The final target
accuracy for the relative and absolute alignment of the two satellites
is of about 2mm over an inter satellite distance of 144.3m. During
the FF, the two spacecraft will realize a giant coronagraph with
the external occulter on one payload and the telescope on the other
one. The Sun Corona observation will be the scientific tool for the
FF validation. Between the different metrology systems that will be
tested, the Shadow Position Sensor (SPS) is the most challenging one,
aiming at returning the relative and absolute position of the formation
with the finest accuracy: 0.5mm out of the guidance and navigation and
control loop and 2mm within the loop. The mission program is now in the
Phase D with the realization and the testing of the flight model. Due to
the high expected performance, a fine calibration of the SPS subsystem
is mandatory. In this paper, we discuss the radiometric and spectral
calibration plan, the algorithm validation procedure, and the laboratory
test-bed realized to reproduce the in-flight observation conditions
of the SPS by using a set of calibrated LED and a mechanical set-up
equivalent to the SPS system. Preliminary results are also reviewed.
---------------------------------------------------------
Title: PolarCam micropolarizer cameras characterization and usage
Authors: Liberatore, A.; Fineschi, S.; Capobianco, G.; Massone, G.;
Zangrilli, L.; Nicolini, G.; Susino, R.
2021SPIE11852E..0WL Altcode:
Several experiments need to acquire images with different linear
polarisation. Acquisition of successive images through a rotating
polarising elements give the possibility to achieve this goal. However,
the subsequent acquisition of these images implies a temporal modulation
and a rotation mechanism (with a consequent consumption of space,
power, etc. . . ). The PolarCam©, a camera where an array of linear
micropolarizers with orientation are matching the sensor's pixels, tries
to solve these problems. In the present manuscript the features of this
camera and the main aspects of its calibration are shown. Finally, an
example of its application is presented. In particular, our application
of this camera is for the Antarctica solar Coronagraph -AntarctiCor-
for the "Extreme Solar Coronagraphy Antarctic Program Experiment"
-ESCAPE- that used this technology for a ground-based polarimetric
study of the solar K-corona from the Italian-French Concordia Base
(Dome C - Antarctica).
---------------------------------------------------------
Title: Metrology on-board PROBA-3: The shadow position sensors
subsystem
Authors: Noce, Vladimiro; Loreggia, Davide; Capobianco, Gerardo;
Fineschi, Silvano; Bemporad, Alessandro; Casti, Marta; Buckley, Steven;
Romoli, Marco; Focardi, Mauro; Belluso, Massimiliano; Thizy, Cédric;
Hermans, Aline; Galano, Damien; Versluys, Jorg
2021AdSpR..67.3807N Altcode:
PROBA-3 is an ESA mission aimed at the demonstration of formation flying
performance of two satellites that will form a giant coronagraph in
space. The first spacecraft will host a telescope imaging the solar
corona in visible light, while the second, the external occulter,
will produce an artificial eclipse. This instrument is named ASPIICS
(Association of Spacecraft for Polarimetric and Imaging Investigation of
the Corona of the Sun). To accomplish the payload's scientific tasks,
PROBA-3 will ensure sub-millimeter reciprocal positioning of its two
satellites using closed-loop on-board metrology. Several metrology
systems will be used and the Shadow Position Sensor (SPS) subsystem
senses the penumbra around the instrument aperture and returns the
3-D displacement of the coronagraph satellite, with respect to its
nominal position, by running a dedicated algorithm. In this paper,
we describe how the SPS works and the choices made to accomplish the
mission objectives.
---------------------------------------------------------
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: PROBA-3 mission and the Shadow Position Sensors: Metrology
measurement concept and budget
Authors: Loreggia, Davide; Fineschi, Silvano; Capobianco,
Gerardo; Bemporad, Alessandro; Casti, Marta; Landini, Federico;
Nicolini, Gianalfredo; Zangrilli, Luca; Massone, Giuseppe; Noce,
Vladimiro; Romoli, Marco; Terenzi, Luca; Morgante, Gianluca; Belluso,
Massimiliano; Thizy, Cedric; Galy, Camille; Hermans, Aline; Franco,
Pierre; Pirard, Ariane; Rossi, Laurence; Buckley, Steve; Spillane,
Raymond; O'Shea, Martin; Galano, Damien; Versluys, Jorg; Hernan, Ken;
Accatino, Luciano
2021AdSpR..67.3793L Altcode:
PROBA-3 is a space mission of the European Space Agency that will test,
and validate metrology and control systems for autonomous formation
flying of two independent satellites. PROBA-3 will operate in a High
Elliptic Orbit and when approaching the apogee at 6·10<SUP>4</SUP> Km,
the two spacecraft will align to realize a giant externally occulted
coronagraph named ASPIICS, with the telescope on one satellite and
the external occulter on the other one, at inter-satellite distance
of 144.3 m. The formation will be maintained over 6 hrs across the
apogee transit and during this time different validation operations
will be performed to confirm the effectiveness of the formation flying
metrology concept, the metrology control systems and algorithms, and
the spacecraft manoeuvring. The observation of the Sun's Corona in the
field of view [1.08;3.0]R<SUB>Sun</SUB> will represent the scientific
tool to confirm the formation flying alignment. In this paper, we review
the mission concept and we describe the Shadow Position Sensors (SPS),
one of the metrological systems designed to provide high accuracy
(sub-millimetre level) absolute and relative alignment measurement
of the formation flying. The metrology algorithm developed to convert
the SPS measurements in lateral and longitudinal movement estimation
is also described and the measurement budget summarized.
---------------------------------------------------------
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: Formation flying performances simulator for the shadow position
sensors of the ESA PROBA-3 mission
Authors: Capobianco, Gerardo; Amadori, Francesco; Fineschi, Silvano;
Bemporad, Alessandro; Casti, Marta; Loreggia, Davide; Noce, Vladimiro;
Pancrazzi, Maurizio; Landini, Federico; Thizy, Cedric; Rougeot,
Raphael; Galano, Damien; Versluys, Jorg
2021SPIE11852E..6PC Altcode:
PROBA-3 (PRoject for OnBoard Autonomy) is an ESA mission to be launched
on beginning of 2023 where a spacecraft is used as an external occulter
(OSC-Occulter Spacecraft), to create an artificial solar eclipse as
observed by a second spacecraft, the coronagraph (CSC-Coronagraph
Spacecraft). The two spacecrafts (SCs) will orbit around the Earth,
with a highly elliptic orbit (HEO), with the perigee at 600 km, the
apogee at about 60530 km and an eccentricity of ≍ 0.81. The orbital
period is of 19.7 hours and the precise formation flight (within 1
mm) will be maintained for about 6 hours over the apogee, in order
to guarantee the observation of the solar corona with the required
spatial resolution. The relative alignment of the two spacecrafts is
obtained by combining information from several subsystems. One of
the most accurate subsystems is the Shadow Position Sensors (SPS),
composed of eight photo-multipliers installed around the entrance
pupil of the CSC. The SPS will monitor the penumbra generated by the
occulter spacecraft, whose intensity will change according to the
relative position of the two satellites. A dedicated algorithm has
been developed to retrieve the displacement of the spacecrafts from
the measurements of the SPS. Several tests are required in order to
evaluate the robustness of the algorithm and its performances/results
for different possible configurations. A software simulator has been
developed for this purpose. The simulator includes the possibility
to generate synthetic 2-D penumbra profile maps or analyze measured
profiles and run different versions of the retrieving algorithms,
including the "on-board" version. In order to import the "as-built"
algorithms, the software is coded using Matlab. The main aspects of the
simulator, such as the results of the simulations, with the inclusion
of some specific case studies, will be reported and discussed in
this paper.
---------------------------------------------------------
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: First-light Science Observations of the Metis Solar Coronagraph
Authors: Fineschi, S.; Romoli, M.; Andretta, V.; Bemporad, A.;
Capobianco, G.; Casti, M.; Da Deppo, V.; De Leo, Y.; Fabi, M.;
Frassetto, F.
2021SPIE11852E..11F Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched in February 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun from
as close as 0.28 AU and from ecliptic latitudes as high as 30?. Metis,
in particular, is aimed at the study and the overall characterization
of the solar corona and solar wind. This instrument is an innovative
inverted-occultation coronagraph that will image the solar corona for
the first time simultaneously in two different wavelength band-passes:
in the linearly-polarized visible-light (VL), between 580 and 640 nm,
and in the ultraviolet (UV) Lyman-a line of hydrogen, HI at 121.6 nm
by combining in the same telescope UV interference mirror coatings
(Al/MgF2) and spectral bandpass filters. The visible channel includes
a broad-band polarimeter to observe the linearly polarized component of
the K corona. These measurements will allow a complete characterization
of the physical parameters, such as density and outflow speed, of
the two major plasma components of the corona and the solar wind:
electrons (protons) and hydrogen. After a period of commissioning, by
the summer of 2020, Metis will have performed the First-light Science
Observations during the "Remote-Sensing Check-out Window" (RSCW) that
is a telemetry contact period, specifically allocated before entering
the operational phase at the end of 2021. This presentation will report
the first-light science observations of Metis represented by the UV
and polarized VL images of the corona. The calibration results from
the commissioning will be used for the correction of the instrumental
effects. The resulting first-light maps of the coronal electron and
hydrogen distributions will be presented.
---------------------------------------------------------
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: Simulating the Solar Minimum Corona in UV Wavelengths with
Forward Modeling II. Doppler Dimming and Microscopic Anisotropy Effect
Authors: Zhao, Jie; Gibson, Sarah E.; Fineschi, Silvano; Susino,
Roberto; Casini, Roberto; Cranmer, Steven R.; Ofman, Leon; Li, Hui
2021ApJ...912..141Z Altcode:
In ultraviolet (UV) spectropolarimetric observations of the solar
corona, the existence of a magnetic field, solar wind velocity, and
temperature anisotropies modify the linear polarization associated with
resonant scattering. Unlike previous empirical models or global models,
which present blended results of the above physical effects, in this
work, we forward-model expected signals in the H I Lyα line (121.6 nm)
by adopting an analytic model that can be adjusted to test the roles
of different effects separately. We find that the impact of all three
effects is most evident in the rotation of the linear polarization
direction. In particular, (1) for magnetic fields between ∼10 and
∼100 G, the Hanle effect modifies the linear polarization at low
coronal heights, rotating the linear polarization direction clockwise
(counterclockwise) when the angle between the magnetic field and the
local vertical is greater (less) than the van Vleck angle, which is
consistent with the result of Zhao et al.; (2) solar wind velocity,
which increases with height, has a significant effect through the
Doppler dimming effect at higher coronal heights, rotating the linear
polarization direction in an opposite fashion to the Hanle effect;
and (3) kinetic temperature anisotropies are most significant at
lower heights in open nonradial magnetic field regions, producing
tilt opposite to isotropic Doppler dimming. The fact that the three
effects operate differently in distinct spatial regimes opens up the
possibility for using linear polarization measurements in UV lines to
diagnose these important physical characteristics of the solar corona.
---------------------------------------------------------
Title: The Coronal Magnetograph (CorMag): Deriving the Coronal
Magnetic Field Topology from Antarctica and the Stratosphere.
Authors: Fineschi, Silvano; Loreggia, Davide; Susino, Roberto;
Landini, Federico; Romoli, Marco; Capobianco, Gerardo; Zangrilli,
Luca; Liberatore, Alessandro; Pancrazzi, Maurizio
2021cosp...43E1806F Altcode:
The Coronal Magnetograph - CorMag - experiment aims at studying the
magnetic field topology of the solar corona. The direction of the
coronal magnetic field vector would be derived from narrow-wavelength
bandpass observations of the linearly polarized FeXIV line-emission
(530.3 nm), interpreted through the "saturated" Hanle effect. CorMag
is an internally-occulted coronagraph whose design was derived from the
externally-occulted, formation-flying ASPIICS coronagraph of the PROBA-3
ESA solar mission. Preliminary tests of CorMag were carried out during
two campaigns in Antarctica at the Concordia Italian-French Station in
2018/2019 and 2019/2020. This presentation reports the results of those
tests. CorMag has been selected for a stratospheric balloon flight
is 2021 and the configuration for this mission will be illustrated,
together with the expected polarization sensitivity. This mission is a
demonstrator for future space-based coronagraphs with the capability
of visible-light and infrared polarization measurements for coronal
magnetic field diagnostics.
---------------------------------------------------------
Title: SWELTO -- Space WEather Laboratory in Turin Observatory
Authors: Bemporad, A.; Abbo, L.; Barghini, D.; Benna, C.; Biondo,
R.; Bonino, D.; Capobianco, G.; Carella, F.; Cora, A.; Fineschi, S.;
Frassati, F.; Gardiol, D.; Giordano, S.; Liberatore, A.; Mancuso, S.;
Mignone, A.; Rasetti, S.; Reale, F.; Riva, A.; Salvati, F.; Susino,
R.; Volpicelli, A.; Zangrilli, L.
2021arXiv210107037B Altcode:
SWELTO -- Space WEather Laboratory in Turin Observatory is a
conceptual framework where new ideas for the analysis of space-based
and ground-based data are developed and tested. The input data are
(but not limited to) remote sensing observations (EUV images of the
solar disk, Visible Light coronagraphic images, radio dynamic spectra,
etc...), in situ plasma measurements (interplanetary plasma density,
velocity, magnetic field, etc...), as well as measurements acquired
by local sensors and detectors (radio antenna, fluxgate magnetometer,
full-sky cameras, located in OATo). The output products are automatic
identification, tracking, and monitoring of solar stationary and dynamic
features near the Sun (coronal holes, active regions, coronal mass
ejections, etc...), and in the interplanetary medium (shocks, plasmoids,
corotating interaction regions, etc...), as well as reconstructions of
the interplanetary medium where solar disturbances may propagate from
the Sun to the Earth and beyond. These are based both on empirical
models and numerical MHD simulations. The aim of SWELTO is not only
to test new data analysis methods for future application for Space
Weather monitoring and prediction purposes, but also to procure,
test and deploy new ground-based instrumentation to monitor the
ionospheric and geomagnetic responses to solar activity. Moreover,
people involved in SWELTO are active in outreach to disseminate the
topics related with Space Weather to students and the general public.
---------------------------------------------------------
Title: The MDOR/PDOR on-line module for MISO, the planning software
of Solar Orbiter instruments
Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio;
Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso,
Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola;
Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche,
Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère,
Frédéric; Romoli, Marco
2020SPIE11452E..0SV Altcode:
Solar Orbiter is a solar mission that will approach the Sun down to a
minimum perihelion of 0.28 AU and will increase its orbit inclination
with respect to the ecliptic up to a maximum angle of 34 deg. For
imagers aboard Solar Orbiter there will be three 10-days remote sensing
windows per orbit. Observations shall be carefully planned at least 6
months in advance. The Multi Instrument Sequence Organizer (MISO) is
a web based platform developed by the SPICE group and made available
to support Solar Orbiter instruments teams in planning observations
by assembling Mission Database sequences. Metis is the UV and visible
light coronagraph aboard Solar Orbiter. Metis is a complex instrument
characterized by a rich variety of observing modes, which required a
careful commissioning activity and will need support for potential
maintenance operations throughout the mission. In order to support
commissioning and maintenance activities, the Metis team developed
a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct
Operation Request) module integrated in MISO and made available to all
Solar Orbiter instruments. An effort was made in order to interpret
the coding philosophy of the main project and to make the additional
module as homogeneous as possible both to the web interface and to the
algorithm logic, while integrating characteristics which are peculiar
to PDORs and MDORs. An user friendly web based interface allows the
operator to build the operation request and to successively modify or
integrate it with further or alternative information. In the present
work we describe the PDOR/MDOR module for MISO by addressing its logic
and main characteristics.
---------------------------------------------------------
Title: A Journey of Exploration to the Polar Regions of a Star:
Probing the Solar Poles and the Heliosphere from High Helio-Latitude
Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.;
Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.;
Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi,
S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.;
Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.;
Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli,
M.; Sekii, T.; Spadaro, D.; Veronig, A.
2020AGUFMSH0110005F Altcode:
A mission to view the solar poles from high helio-latitudes (above
60°) will build on the experience of Solar Orbiter as well as a long
heritage of successful solar missions and instrumentation (e.g. SOHO,
STEREO, Hinode, SDO), but will focus for the first time on the solar
poles, enabling scientific investigations that cannot be done by
any other mission. One of the major mysteries of the Sun is the solar
cycle. The activity cycle of the Sun drives the structure and behaviour
of the heliosphere and is, of course, the driver of space weather. In
addition, solar activity and variability provides fluctuating input
into the Earth climate models, and these same physical processes
are applicable to stellar systems hosting exoplanets. One of the
main obstructions to understanding the solar cycle, and hence all
solar activity, is our current lack of understanding of the polar
regions. We describe a mission concept that aims to address this
fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
---------------------------------------------------------
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: 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: On the Possibility of Detecting Helium D3 Line Polarization
with Metis
Authors: Heinzel, Petr; Štěpán, Jiři; Bemporad, Alessandro;
Fineschi, Silvano; Jejčič, Sonja; Labrosse, Nicolas; Susino, Roberto
2020ApJ...900....8H Altcode: 2020arXiv200708940H
Metis, the space coronagraph on board the Solar Orbiter, offers us
new capabilities for studying eruptive prominences and coronal mass
ejections (CMEs). Its two spectral channels, hydrogen Lα and visible
light (VL), will provide for the first time coaligned and cotemporal
images to study dynamics and plasma properties of CMEs. Moreover,
with the VL channel (580-640 nm) we find an exciting possibility
to detect the helium D<SUB>3</SUB> line (587.73 nm) and its linear
polarization. The aim of this study is to predict the diagnostic
potential of this line regarding the CME thermal and magnetic
structure. For a grid of models we first compute the intensity of the
D<SUB>3</SUB> line together with VL continuum intensity due to Thomson
scattering on core electrons. We show that the Metis VL channel will
detect a mixture of both, with predominance of the helium emission at
intermediate temperatures between 30 and 50,000 K. Then we use the
code HAZEL to compute the degree of linear polarization detectable
in the VL channel. This is a mixture of D<SUB>3</SUB> scattering
polarization and continuum polarization. The former one is lowered in
the presence of a magnetic field and the polarization axis is rotated
(Hanle effect). Metis has the capability of measuring Q/I and U/I
polarization degrees and we show their dependence on temperature and
magnetic field. At T = 30,000 K we find a significant lowering of
Q/I which is due to strongly enhanced D<SUB>3</SUB> line emission,
while depolarization at 10 G amounts roughly to 10%.
---------------------------------------------------------
Title: Optical design of the multi-wavelength imaging coronagraph
Metis for the solar orbiter mission
Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.;
Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro,
D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.;
Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.;
Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle,
U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki,
A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero,
A.; Castronuovo, M.
2020ExA....49..239F Altcode: 2020ExA...tmp...14F
This paper describes the innovative optical design of the Metis
coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a
multi-wavelength, externally occulted telescope for the imaging
of the solar corona in both the visible and ultraviolet wavelength
ranges. Metis adopts a novel occultation scheme for the solar disk,
that we named "inverse external occulter", for reducing the extremely
high thermal load on the instrument at the spacecraft perihelion. The
core of the Metis optical design is an aplanatic Gregorian telescope
common to both the visible and ultraviolet channels. A suitable
dichroic beam-splitter, optimized for transmitting a narrow-band in
the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband
in the visible (580-640 nm) spectral range, is used to separate the
two optical paths. Along the visible light optical path, a liquid
crystal electro-optical modulator, used for the first time in space,
allows making polarimetric measurements.
---------------------------------------------------------
Title: The Solaris Solar Polar Mission
Authors: Hassler, Donald M.; Newmark, Jeff; Gibson, Sarah; Harra,
Louise; Appourchaux, Thierry; Auchere, Frederic; Berghmans, David;
Colaninno, Robin; Fineschi, Silvano; Gizon, Laurent; Gosain, Sanjay;
Hoeksema, Todd; Kintziger, Christian; Linker, John; Rochus, Pierre;
Schou, Jesper; Viall, Nicholeen; West, Matt; Woods, Tom; Wuelser,
Jean-Pierre
2020EGUGA..2217703H Altcode:
The solar poles are one of the last unexplored regions of the solar
system. Although Ulysses flew over the poles in the 1990s, it did
not have remote sensing instruments onboard to probe the Sun's polar
magnetic field or surface/sub-surface flows.We will discuss Solaris,
a proposed Solar Polar MIDEX mission to revolutionize our understanding
of the Sun by addressing fundamental questions that can only be answered
from a polar vantage point. Solaris uses a Jupiter gravity assist to
escape the ecliptic plane and fly over both poles of the Sun to >75
deg. inclination, obtaining the first high-latitude, multi-month-long,
continuous remote-sensing solar observations. Solaris will address key
outstanding, breakthrough problems in solar physics and fill holes in
our scientific understanding that will not be addressed by current
missions.With focused science and a simple, elegant mission design,
Solaris will also provide enabling observations for space weather
research (e.g. polar view of CMEs), and stimulate future research
through new unanticipated discoveries.
---------------------------------------------------------
Title: Global helium abundance measurements in the solar corona
Authors: Moses, John D.; Antonucci, Ester; Newmark, Jeffrey; Auchère,
Frédéric; Fineschi, Silvano; Romoli, Marco; Telloni, Daniele;
Massone, Giuseppe; Zangrilli, Luca; Focardi, Mauro; Landini, Federico;
Pancrazzi, Maurizio; Rossi, Guglielmo; Malvezzi, Andrea M.; Wang,
Dennis; Leclec'h, Jean-Christophe; Moalic, Jean-Pierre; Rouesnel,
Frédéric; Abbo, Lucia; Canou, Aurélien; Barbey, Nicolas; Guennou,
Chloé; Laming, John M.; Lemen, James; Wuelser, Jean-Pierre; Kohl,
John L.; Gardner, Lawrence D.
2020NatAs...4.1134M Altcode: 2020NatAs.tmp..152M
Solar abundances have been historically assumed to be representative
of cosmic abundances. However, our knowledge of the solar abundance
of helium, the second most abundant element, relies mainly on
models<SUP>1</SUP> and indirect measurements through helioseismic
observations<SUP>2</SUP>, because actual measurements of helium in the
solar atmosphere are very scarce. Helium cannot be directly measured
in the photosphere because of its high first ionization potential,
and measurements of its abundance in the inner corona have been
sporadic<SUP>3,4</SUP>. In this Letter, we present simultaneous global
images of the helium (out to a heliocentric distance of 3R<SUB>⊙</SUB>
(solar radii)) and hydrogen emission in the solar corona during
the minimum of solar activity of cycle 23 and directly derive the
helium abundance in the streamer region and surrounding corona
(out to 2.2R<SUB>⊙</SUB>). The morphology of the He<SUP>+</SUP>
corona is markedly different from that of the H corona, owing to
significant spatial variations in helium abundance. The observations
show that the helium abundance is shaped according to and modulated
by the structure of the large-scale coronal magnetic field and that
helium is almost completely depleted in the equatorial regions during
the quiet Sun. This measurement provides a trace back to the coronal
source of the anomalously slow solar wind observed in the heliosphere
at the Sun-Earth Lagrangian point L1 in 2009, during the exceptionally
long-lasting minimum of solar activity cycle 23.
---------------------------------------------------------
Title: Metis: Coronagraph Performance & Coordinated Observations
Authors: Fineschi, S.
2019AGUFMSH21D3293F Altcode:
Metis coronagraph is one of the remote-sensing instruments of Solar
Orbiter and is aimed at the study and overall characterization of the
solar corona. Metis is an innovative inverted-occultation coronagraph
that will image the solar corona in two different wavelengths: in
the visible light, between 580 and 640 nm, and in the ultraviolet
(UV) Lyman-α line of hydrogen, HI at 121.6 nm by combining in the
same telescope UV interference mirror coatings (Al/MgF2) and spectral
bandpass filters. The visible channel includes a broad-band polarimeter
to observe the linearly polarized component of the K corona. These
measurements will allow a complete characterization of the two major
plasma components of the corona and the solar wind: electrons (protons)
and hydrogen. <P />This presentation will give an overview of the
Metis performance as determined by the ground calibrations. The ground
calibrations in visible-light comprised: i) stray-light rejection, ii)
imaging (PSF), iii) vignetting, iv) radiometric and v) polarimetric
performances. In the UV, Metis was tested for the vi) imaging and the
vii) radiometric performances. The stray-light rejection was measured
with a sensitivity down to less than one-billionth of the light level
of the visible-light source developed to simulate the illuminating Sun
at different distances from the Solar Orbiter spacecraft. <P />This
presentation will report the main results of these tests showing
that the Metis performance matches the scientific requirements. <P
/>Metis observations of the solar corona from the unique vantage
points of the Solar Orbiter mission, in conjunction with coordinated
coronal observations from simultaneous space missions dedicated to
the heliophysics, will provide a multi-point-of-view, multi-messenger
perspective of the solar corona. This presentation will describe the
opportunities and plans of coordinated observations of Metis with
the coronagraphs of other space missions (e.g., SOHO, STEREO, PSP,
PROBA-3, Aditya).
---------------------------------------------------------
Title: Detection of Coronal Mass Ejections at L1 and Forecast of
Their Geoeffectiveness
Authors: Telloni, Daniele; Antonucci, Ester; Bemporad, Alessandro;
Bianchi, Tiziano; Bruno, Roberto; Fineschi, Silvano; Magli, Enrico;
Nicolini, Gianalfredo; Susino, Roberto
2019ApJ...885..120T Altcode:
A novel tool aimed to detect solar coronal mass ejections (CMEs)
at the Lagrangian point L1 and to forecast their geoeffectiveness
is presented in this paper. This approach is based on the analysis
of in situ magnetic field and plasma measurements to compute some
important magnetohydrodynamic quantities of the solar wind (the total
pressure, the magnetic helicity, and the magnetic and kinetic energy),
which are used to identify the CME events, that is their arrival and
transit times, and to assess their likelihood for impacting the Earths
magnetosphere. The method is essentially based on the comparison of
the topological properties of the CME magnetic field configuration and
of the CME energetic budget with those of the quasi-steady ambient
solar wind. The algorithm performances are estimated by testing the
tool on solar wind data collected in situ by the Wind spacecraft from
2005 to 2016. In the scanned 12 yr time interval, it results that
(i) the procedure efficiency is of 86% for the weakest magnetospheric
disturbances, increasing with the level of the geomagnetic storming,
up to 100% for the most intense geomagnetic events, (ii) zero false
positive predictions are produced by the algorithm, and (iii) the
mean delay between the potentially geoeffective CME detection and
the geomagnetic storm onset if of 4 hr, with a 98% 2-8 hr confidence
interval. Hence, this new technique appears to be very promising in
forecasting space weather phenomena associated to CMEs.
---------------------------------------------------------
Title: Distributed framework for Space Weather forecasts
Authors: Fabio Mulone, Angelo; Casti, Marta; Susino, Roberto; Messineo,
Rosario; Antonucci, Ester; Chiesura, Gabriele; Telloni, Daniele;
De March, Ruben; Magli, Enrico; Bemporad, Alessandro; Nicolini,
Gianalfredo; Fineschi, Silvano; Solitro, Filomena; Martino, Michele
2019EPSC...13.1997F Altcode:
HDS (Heliospheric Data System) is a system designed and implemented to
provide space weather services. The main system goal is to reduce the
time between the space weather services definition and their activation
in operating environment. It is capable to manage and process near-real
time data. Tens of different data sources, related to past and current
missions, have been integrated. Data managed by the system have been
described using standard data models. Big data technologies have
been exploited to deal with the challenges of big data management
and processing. The first version of the system provided medium and
short-term forecast of geo-effective space weather events like the
coronal mass ejections (CMEs).
---------------------------------------------------------
Title: Simulating the Solar Corona in the Forbidden and Permitted
Lines with Forward Modeling. I. Saturated and Unsaturated Hanle
Regimes
Authors: Zhao, Jie; Gibson, Sarah E.; Fineschi, Silvano; Susino,
Roberto; Casini, Roberto; Li, Hui; Gan, Weiqun
2019ApJ...883...55Z Altcode:
The magnetic field in the corona is important for understanding solar
activity. Linear polarization measurements in forbidden lines in the
visible/IR provide information about coronal magnetic direction and
topology. However, these measurements do not provide a constraint on
coronal magnetic field strength. The unsaturated, or critical regime
of the magnetic Hanle effect is potentially observable in permitted
lines for example in the UV, and would provide an important new
constraint on the coronal magnetic field. In this paper we present
the first side-by-side comparison of forbidden versus permitted linear
polarization signatures, examining the transition from the unsaturated
to the saturated regime. In addition, we use an analytic 3D flux rope
model to demonstrate the Hanle effect for the line-of-sight versus
plane-of-sky (POS) components of the magnetic field. As expected, the
linear polarization in the unsaturated regime will vary monotonically
with increasing magnetic field strength for regions where the magnetic
field is along the observer’s line of sight. The POS component of
the field produces a linear polarization signature that varies with
both the field strength and direction in the unsaturated regime. Once
the magnetic field is strong enough that the effect is saturated, the
resulting linear polarization signal is essentially the same for the
forbidden and permitted lines. We consider how such observations might
be used together in the future to diagnose the coronal magnetic field.
---------------------------------------------------------
Title: Comparing extrapolations of the coronal magnetic field
structure at 2.5 R<SUB>⊙</SUB> with multi-viewpoint coronagraphic
observations
Authors: Sasso, C.; Pinto, R. F.; Andretta, V.; Howard, R. A.;
Vourlidas, A.; Bemporad, A.; Dolei, S.; Spadaro, D.; Susino, R.;
Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Frassetto, F.;
Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.;
Romoli, M.; Telloni, D.; Ventura, R.
2019A&A...627A...9S Altcode: 2019arXiv190509005S
The magnetic field shapes the structure of the solar corona, but we
still know little about the interrelationships between the coronal
magnetic field configurations and the resulting quasi-stationary
structures observed in coronagraphic images (such as streamers,
plumes, and coronal holes). One way to obtain information on the
large-scale structure of the coronal magnetic field is to extrapolate
it from photospheric data and compare the results with coronagraphic
images. Our aim is to verify whether this comparison can be a fast
method to systematically determine the reliability of the many methods
that are available for modeling the coronal magnetic field. Coronal
fields are usually extrapolated from photospheric measurements that
are typically obtained in a region close to the central meridian on
the solar disk and are then compared with coronagraphic images at the
limbs, acquired at least seven days before or after to account for solar
rotation. This implicitly assumes that no significant changes occurred
in the corona during that period. In this work, we combine images from
three coronagraphs (SOHO/LASCO-C2 and the two STEREO/SECCHI-COR1) that
observe the Sun from different viewing angles to build Carrington maps
that cover the entire corona to reduce the effect of temporal evolution
to about five days. We then compare the position of the observed
streamers in these Carrington maps with that of the neutral lines
obtained from four different magnetic field extrapolations to evaluate
the performances of the latter in the solar corona. Our results show
that the location of coronal streamers can provide important indications
to distinguish between different magnetic field extrapolations.
---------------------------------------------------------
Title: OPSys: optical payload systems facility for space
instrumentation integration and calibration
Authors: Capobianco, Gerardo; Fineschi, Silvano; Massone, Giuseppe;
Landini, Federico; Casti, Marta; Bellomo, Alessandro; Deffacis,
Maurizio; Romoli, Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto,
Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele
2019SPIE11180E..7MC Altcode:
The Optical Payload System (OPSys) is an INAF (italian National
Institute for Astrophysics) facility hosted by Aerospace Logistics
Technology Engineering Company (ALTEC SpA) in Turin, Italy. The facility
is composed by three clean rooms having different cleanliness levels,
a thermo-vacuum chamber (SPOCC, Space Optics calibration Chamber)
with a motorized optical bench and several light sources covering the
range from the extreme ultraviolet to the red light wavelengths. The
SPOCC has been designed having in mind the very stringent requirements
of the calibration of solar coronagraphs and the suppression of
the stray-light. The facility and the optical performances will be
described here. The calibration campaign performed on Metis space
coronagraph will be reported as a case study.
---------------------------------------------------------
Title: Straylight analysis on ASPIICS, PROBA-3 coronagraph
Authors: Galy, C.; Thizy, C.; Stockman, Y.; Galano, D.; Rougeot,
R.; Melich, R.; Shestov, S.; Landini, F.; Zukhov, A.; Kirschner, V.;
Horodyska, P.; Fineschi, S.
2019SPIE11180E..2HG Altcode:
PROBA-3 is a mission devoted to the in-orbit demonstration (IOD)
of precise formation flying (F²) techniques and technologies for
future ESA missions. The mission includes two spacecraft. One of
them will act as an external occulter for scientific observations
of the solar corona from the other spacecraft, which will hold the
ASPIICS coronagraph instrument, under CSL responsibility. The ASPIICS
instrument on PROBA-3 looks at the solar corona through a refractive
telescope, able to select 3 different spectral bands: Fe XIV line @
530.4nm, He I D3 line @587.7nm, and the white-light spectral band
[540;570nm]. The external occulter being located at 150 meters from
the instrument entrance, will allow ASPIICS to observe the corona
really close to the solar limb, probably closer than any internally
or externally occulted coronagraph ever observed. This paper will
present the straylight model and analyses carried out by CSL. A first
specificity of the analysis is that the scene on the useful Field of
View (FOV) is the solar corona which has a brightness dynamic range as
high as 10<SUP>3</SUP> between the close corona, close to 1 solar radius
(Rsun), and the "distant" corona around 3RSun. The specifications are
very stringent for this type of instrument. A consensus was found
and will be presented regarding the expected straylight within the
FOV. It will also be shown that to achieve realistic estimations it
is required to take into account the exact location of the created
straylight as well as the entrance field. The second specificity that
had to be analyzed is that the diffraction from the solar disk by the
external occulter enters the instrument un-obstructed until the internal
occulter, and with a brightness 100 times higher than the close corona
( 1RSun) brightness. The simulation of this diffraction as well as its
propagation inside the ASPIICS telescope creating additional straylight,
had to be carefully established in order to give realistic results of
its impact on the performances while being actually possible to compute.
---------------------------------------------------------
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: PROBA-3 formation-flying metrology: algorithms for the shadow
position sensor system
Authors: Casti, M.; Bemporad, A.; Fineschi, S.; Capobianco, G.;
Loreggia, D.; Noce, V.; Landini, F.; Thizy, C.; Galano, D.; Rougeot, R.
2019SPIE11180E..82C Altcode:
PROBA-3 ESA's mission aims at demonstrating the possibility and the
capacity to carry out a space mission in which two spacecrafts fly in
formation and maintain a fixed configuration. In particular, these
two satellites - the Coronagraph Spacecraft (CSC) and the Occulter
Spacecraft (OSC) - will form a 150-meters externally occulted
coronagraph for the purpose of observing the faint solar corona,
close to the solar limb - i.e. 1.05 solar radii from the Sun's center
(R<SUB>Θ</SUB>). The first satellite will host the ASPIICS (Association
de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne
Solaire) coronagraph as primary payload. These features give to the
PROBA-3 mission the characteristics of both, a technological and a
scientific mission. Several metrology systems have been implemented
in order to keep the formation-flying configuration. Among them,
the Shadow Position Sensors (SPSs) assembly. The SPSs are designed
to verify the sun-pointing alignment between the Coronagraph
pupil entrance centre and the umbra cone generated by the Occulter
Disk. The accurate alignment between the spacecrafts is required for
observations of the solar corona as much close to the limb as 1.05
R<SUB>Θ</SUB>.The metrological system based on the SPSs is composed
of two sets of four micro arrays of Silicon Photomultipliers (SiPMs)
located on the coronagraph pupil plane and acquiring data related
to the intensity of the penumbra illumination level to retrieve the
spacecrafts relative position. We developed and tested a dedicated
algorithm for retrieving the satellites position with respect to the
Sun. Starting from the measurements of the penumbra profile in four
different spots and applying a suitable logic, the algorithm evaluates
the spacecraft tri-dimensional relative position. In particular, during
the observational phase, when the two satellites will be at 150 meters
of distance, the algorithm will compute the relative position around
the ideal aligned position with an accuracy of 500μm within the lateral
plane and 500 mm for the longitudinal measurement. This work describes
the formation flying algorithm based on the SPS measurements. In
particular, the implementation logic and the formulae are described
together with the results of the algorithm testing.
---------------------------------------------------------
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: Polarimetric performance of a polarization modulator based
on liquid crystal variable retarders for wide acceptance angles
Authors: Parejo, Pilar García.; Álvarez-Herrero, Alberto; Capobianco,
Gerardo; Fineschi, Silvano
2019JATIS...5c4002P Altcode:
Liquid crystal variable retarders (LCVRs) will be used in the
polarization modulation packages (PMPs) of the instruments SO/PHI
(Polarimetric and Helioseismic Imager) and METIS/COR (Multielement
Telescope for Imaging and Spectroscopy, Coronagraph) of the Solar
Orbiter Mission of the European Space Agency (ESA). Optical retarders
are dependent on the angle of incidence (AOI). Since the optical
retardances during the polarization modulations are optimized for a
particular AOI, other angles increase the polarimetric measurement
error. Coronagraphs, such as METIS, are characterized by having wide
field-of-view (FoV), which involves large incidence angles through
the entire instrument. METIS PMP will work with collimated beams and
an AOI up to ±7.0 deg. For this reason, a double LCVR configuration
with molecular tilts in opposite directions was selected for METIS PMP,
which provides lower angular dependence. The polarimetric performance of
the METIS PMP flight model was measured at different AOIs and compared
to a single LCVR PMP. The results shown in this paper demonstrate
that the functional concept used in METIS guarantees the polarimetric
performances at the wide FoV expected in METIS coronagraph. Moreover,
a detailed theoretical model is showed and compared to the experimental
data, finding successful agreement, which can be very helpful for the
design of instruments characterized by wide FoV.
---------------------------------------------------------
Title: Effect of the non-uniform solar chromospheric Lyα radiation
on determining the coronal H I outflow velocity
Authors: Dolei, S.; Spadaro, D.; Ventura, R.; Bemporad, A.; Andretta,
V.; Sasso, C.; Susino, R.; Antonucci, E.; Da Deppo, V.; Fineschi,
S.; Frassetto, F.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Romoli, M.
2019A&A...627A..18D Altcode:
We derived maps of the solar wind outflow velocity of coronal
neutral hydrogen atoms at solar minimum in the altitude range
1.5-4.0 R<SUB>⊙</SUB>. We applied the Doppler dimming technique to
coronagraphic observations in the UV H I Lyα line at 121.6 nm. The
technique exploits the intensity reduction in the coronal line with
increasing velocities of the outflowing plasma to determine the
solar wind velocity by iterative modelling. The Lyα line intensity
is sensitive to the wind outflow velocity and also depends on the
physical properties of coronal particles and underlying chromospheric
emission. Measurements of irradiance by the chromospheric Lyα
radiation in the corona are required for a rigorous application of
the Doppler dimming technique, but they are not provided by past
and current instrumentations. A correlation function between the H
I 121.6 nm and He II 30.4 nm line intensities was used to construct
Carrington rotation maps of the non-uniform solar chromospheric Lyα
radiation and thus to compute the Lyα line irradiance throughout
the outer corona. Approximations concerning the temperature of
the scattering H I atoms and exciting solar disc radiation were
also adopted to significantly reduce the computational time and
obtain a faster procedure for a quick-look data analysis of future
coronagraphic observations. The effect of the chromospheric Lyα
brightness distribution on the resulting H I outflow velocities
was quantified. In particular, we found that the usual uniform-disc
approximation systematically leads to an overestimated velocity in
the polar and mid-latitude coronal regions up to a maximum of about
50-60 km s<SUP>-1</SUP> closer to the Sun. This difference decreases at
higher altitudes, where an increasingly larger chromospheric portion,
including both brighter and darker disc features, contributes to
illuminate the solar corona, and the non-uniform radiation condition
progressively approaches the uniform-disc approximation.
---------------------------------------------------------
Title: Spectropolarimetric diagnostics of coronal magnetic field
from UV and visible/IR during solar minimum
Authors: Zhao, Jie; Gibson, Sarah; Fineschi, Silvano; Susino, Roberto
2019AAS...23430212Z Altcode:
The invisible magnetic field in the corona plays an important role
for solar activity, hence measuring the coronal magnetic field
is highly desired. The linear polarization measurements in the
saturated Hanle regime of visible/IR are already obtained by the CoMP
telescope providing information about coronal magnetic direction
and topology. Other observations such as linear polarization in
UV unsaturated Hanle measurements provide important complementary
information about the strength of 3D coronal field. Until such
observations are available, we turn to the FORWARD model (Gibson et
al. 2016) to explore how these polarization data might be used together
to interpret the coronal magnetic field. As a physical state to input
into FORWARD, the analytic magnetic model in this work is adopted
from Gibson et al.(1996), which is an axisymmetric model and gives
a potential field with an exception at the boundary of the helmet
streamer where current sheets are added between the open and closed
fields. The plasma model is adopted from Sittler&Guhathakurta
(1999) and Vásquez et al. (2003), which is consistent with
multi-observations. Given this model input of a 3D distribution of
magnetic field and plasma for solar minimum, we obtain simulated
polarization results in UV and visible/IR wavelengths. This allows us
to consider how such observations might be used together in future to
diagnose the coronal magnetic field.
---------------------------------------------------------
Title: AntarctiCor: Solar Coronagraph in Antarctica for the ESCAPE
Project
Authors: Fineschi, S.; Capobianco, G.; Massone, G.; Susino, R.;
Zangrilli, L.; Bemporad, A.; Liberatore, A.; Landini, F.; Romoli,
M.; Damé, L.; Christille, J. M.; Sandri, P.; Marmonti, M.; Galy, C.
2019NCimC..42...26F Altcode:
The Antarctica solar coronagraph - AntarctiCor- for the "Extreme
Solar Coronagraphy Antarctic Program Experiment" -ESCAPE- comprises
an internally-occulted coronagraph based on the externally-occulted
ASPIICS coronagraph for the ESA formation-flying PROBA-3 mission. This
paper describes the AntarctiCor design for ground-based observations
from the DomeC Antarctica plateau of the polarized broad-band (591 nm
± 5 nm) K-corona and of the narrow-band (FWHM = 0.5 nm), polarized
emission of the coronal green-line at 530.3 nm. The science goal of
these observations is to map the topology and dynamics of the coronal
magnetic field, addressing coronal heating and space weather questions.
---------------------------------------------------------
Title: Metrology on-board PROBA-3: The Shadow Position Sensor (SPS)
subsystem
Authors: Noce, V.; Romoli, M.; Focardi, M.; Fineschi, S.; Loreggia,
D.; Casti, M.; Landini, F.; Baccani, C.; Bemporad, A.; Belluso, M.;
Capobianco, G.; Thizy, C.; Denis, F.; Buckley, S.
2019NCimC..42...27N Altcode:
PROBA-3 is an ESA Mission whose aim is to demonstrate the in-orbit
Formation Flying and attitude control capabilities of its two satellites
by means of closed-loop, on-board metrology. The two small spacecraft
will form a giant externally occulted coronagraph that will observe in
visible polarized light the inner part of the solar corona. The SPS
subsystem is composed of eight sensors that will measure, with the
required sensitivity and dynamic range, the penumbra light intensity
around the coronagraph instrument entrance pupil.
---------------------------------------------------------
Title: The Heliospheric Space Weather Center: A novel space weather
service
Authors: Casti, M.; Mulone, A. F.; Susino, R.; Chiesura, G.;
Telloni, D.; De March, R.; Antonucci, E.; Messineo, R.; Bemporad,
A.; Solitro, F.; Fineschi, S.; Magli, E.; Nicolini, G.; Caronte, ,
F.; Messerotti, M.
2019NCimC..42...48C Altcode:
The Heliospheric Space Weather Center project is the result of the
synergy between the Aerospace Logistics Technology Engineering Company
(ALTEC S.p.A.) and the INAF-Astrophysical Observatory of Torino,
both located in Turin, Italy. The main goal of this project is to
provide space weather medium and short-term forecast, by combining
remote-sensing and in situ open data with novel data analysis
technologies, giving to scientists the possibility of designing,
implementing, and validating space-weather algorithms using extensive
data sets.
---------------------------------------------------------
Title: Wide field of view liquid crystals-based modulator for the
polarimeter of the Metis/Solar Orbiter
Authors: Capobianco, Gerardo; Casti, Marta; Fineschi, Silvano;
Massone, Giuseppe; Sertsu, Mewael G.; Landini, Federico; Romoli,
Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Alvarez Herrero, Alberto;
Garcia Parejo, Pilar; Marmonti, Matteo
2018SPIE10698E..30C Altcode:
Metis is an inverted occulted coronagraph on-board the ESA/Solar
Orbiter mission. The visible light path of the instrument will observe
the "white" light (580-640 nm) linearly-polarized emission from the
solar corona. The coronal polarized brightness allows retrieval of
physical parameters such as the electron density and temperature of
the K-corona. The Metis polarimeter comprises a quarter-wave retarder,
the liquid crystal polarization modulation package (PMP) and a linear
polarizer working as polarization analyser. The PMP consists of two
Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with
the fast axes parallels one to each other and a pre-tilted angle of the
molecules in opposite direction, in order to maximize the homogeneity of
the retardance across instrumental wide field of view: +/-7 deg. This
presentation reports the characterization of the PMP breadboard
(BB), fully representative of the optical/polarimetric performances
of the flight model. This characterization consisted in determining
the performances of the device in terms of retardance as function of
the applied voltage at different temperatures, angle of incidence and
the variation of the retardance as a function of the wavelength. The
calibrations were performed by measuring the complete Mueller matrix
of the PMP-BB. The experimental results have been compared with the
parameters of the theoretical model (e.g., depolarization, effective
retardance, cells misalignment).
---------------------------------------------------------
Title: Space Weather Services from Integration of Remote Sensing
and In Situ Data from several Solar Space Missions
Authors: Bemporad, Alessandro; Fineschi, Silvano; Telloni, Daniele;
Antonucci, Ester; Susino, Roberto; Nicolini, Gianalfredo; Casti,
Marta; Messineo, Rosario; Fabio Mulone, Angelo; Filippi, Fabio;
Solitro, Filomena; Ciampolini, Armando; Martino, Michele; Magli,
Enrico; Volpicelli, Antonio; Bjorklund, Tomas
2018cosp...42E.268B Altcode:
The Heliospheric Data Centre project for Space Weather medium-term and
short-term forecast combines remote sensing and in situ open-access data
relative to the Sun, the Heliosphere and the Earth's magnetosphere. This
is done with the novel big data technologies, to provide scientists
with the possibility to design, implement and validate Space Weather
algorithms on extensive datasets.The Heliospheric Data Centre is
a joint effort between ALTEC and INAF-OATo, both located in Turin,
Italy. The project has two main objectives:1. Consolidate and evolve
the Heliospheric Data Centre, initially set up with the SOHO data
coming from the ESA approved SOLAR (SOho Long-term ARchive) archive,
in order to manage additional solar archives storing solar coronal and
heliospheric data coming from ESA and NASA space programs.2. Develop
a Heliospheric Space Weather Centre to forecast the impacts of solar
disturbances on the Heliosphere and the Earth's magnetosphere.
---------------------------------------------------------
Title: Magnetic field measurements in the solar corona: facing the
challenge with ground and space based observations
Authors: Bemporad, Alessandro; Fineschi, Silvano; Mancuso, Salvatore;
Gibson, Sarah; Susino, Roberto; Massone, . Giuseppe; Capobianco,
Gerardo; Frassati, Federica
2018cosp...42E.265B Altcode:
Actual limitations in understanding physical processes occurring
in the solar atmosphere are related with our poor capabilities in
measuring magnetic fields in its layers. The knowledge of magnetic
fields in the solar corona is crucial to understand the origin of solar
flares and Coronal Mass Ejections, waves, coronal heating and solar
wind acceleration. For these reasons many different techniques have
been proposed to provide these measurements by analysing the emission
related with many different physical phenomena (e.g.: radio observations
of gyrosynchrotron and free-free emission, infrared observations of
Zeeman effect, visible and infrared obervations of the Hanle effect,
UV-EUV observations of CME-driven shock waves, etc..). In order
to provide a continuous monitoring of coronal fields, new ground-
and space-based instrumentations are currently under development, as
well as new techniques to infer the real fields from the line-of-sight
integrated coronal emission. At the same time, the forward modelling of
the expected emission starting from different possible coronal field
configurations is being developed, allowing the definition of the
required properties for future instrumentation and the verification
of the data analysis results.
---------------------------------------------------------
Title: Early detection and propagation forecast of CMEs from
coronagraphic images
Authors: Bemporad, Alessandro; Fineschi, Silvano; Mancuso, Salvatore;
Giordano, Silvio; Susino, Roberto; Zangrilli, Luca
2018cosp...42E.269B Altcode:
In order to forecast the arrival times of Coronal Mass Ejections (CMEs)
at 1 AU for Space Weather purposes, many different pipelines and tools
are actually under development by different groups. The solar physics
group in Turin Observatory is currently developing new routines to
derive from the analysis of remote sensing data different information
needed for CME forecasting. These include the determination of ambient
Parker spiral conditions, the early detection of CMEs from coronagraphic
images, and their propagation in the interplanetary medium taking into
account magnetic drag forces. First results on thse activities will
be reviewd here.
---------------------------------------------------------
Title: Linear Line-Polarimetry: probing the magnetic field mechanisms
of energy deposition in corona.
Authors: Fineschi, Silvano; Gibson, Sarah; Susino, Roberto; Zhao, Jie
2018cosp...42E1073F Altcode:
Optically-thin, UV spectral lines in corona are linearly polarized by
resonance scattering of chromospheric line-emissions off coronal ions.In
the presence of coronal magnetic fields, the resontantly-scattered
line-polarization is modified by the Hanle effect. Spectro-polarimetric
UV observations from space of these line-emissions, interpreted in
terms of the Hanle effects, are a powerful tool for the diagnostics of
magnetic fields in the solar chromosphere/corona.Through the anisotropic
Doppler-dimmng effect, the linear polarization of optically thin
spectral lines is sensitive to anisotropic ion-velocity distributions
that can be induced by the ion-cyclotron resonance between plasmas and
MHD waves in corona. This effect is believed to influence some heavy
ions in the solar corona. Thus, coronal polarimetry of resonantly
scattered UV spectral lines can also serve as a powerful tool for
probing the magnetic field mechanism(s) of energy deposition in
corona.This presentation reports the parameter study carried out
by forward modeling of the linear polarization of the coronal UV
spectral lines HI Lyman-α, 121.6 nm, and OVI, 103.2 nm. The study was
based on the FORWARD numerical code developed by the High Altitude
Observatory. The study used FORWARD to reproduce synthetic linear
line-polarization maps for different MHD models of the corona.The
results from the parameters study indicate that the Hanle effect
diagnostics is most effective within a few tens of solar radii from
the solar limb in closed-field, active regions where the strength
the coronal magnetic field is within the Hanle effect sensitivity for
the HI Lyman-α and OVI lines (i.e., 2-60 gauss). On the other hand,
the effect of anisotropic velocity field distributions of scattering
ions on the line-polarization emitted by resonance scattering is most
effective in open-filed regions of non-radial solar wind, such as the
interface coronal holes-streamers.
---------------------------------------------------------
Title: Straylight analysis for the externally occulted Lyot solar
coronagraph ASPIICS
Authors: Rougeot, Raphaël.; Aime, Claude; Baccani, Cristian; Fineschi,
Silvano; Flamary, Rémi; Galano, Damien; Galy, Camille; Kirschner,
Volker; Landini, Federico; Romoli, Marco; Shestov, Sergei; Thizy,
Cédric; Versluys, Jorg; Zhukov, Andrei
2018SPIE10698E..2TR Altcode:
The ESA formation Flying mission Proba-3 will y the giant solar
coronagraph ASPIICS. The instrument is composed of a 1.4 meter diameter
external occulting disc mounted on the Occulter Spacecraft and a
Lyot-style solar coronagraph of 50mm diameter aperture carried by the
Coronagraph Spacecraft positioned 144 meters behind. The system will
observe the inner corona of the Sun, as close as 1.1 solar radius. For
a solar coronagraph, the most critical source of straylight is the
residual diffracted sunlight, which drives the scientific performance
of the observation. This is especially the case for ASPIICS because
of its reduced field-of-view close to the solar limb. The light from
the Sun is first diffracted by the edge of the external occulter, and
then propagates and scatters inside the instrument. There is a crucial
need to estimate both intensity and distribution of the diffraction on
the focal plane. Because of the very large size of the coronagraph, one
cannot rely on representative full scale test campaign. Moreover, usual
optics software package are not designed to perform such diffraction
computation, with the required accuracy. Therefore, dedicated approaches
have been developed in the frame of ASPIICS. First, novel numerical
models compute the diffraction profile on the entrance pupil plane and
instrument detector plane (Landini et al., Rougeot et al.), assuming
perfect optics in the sense of multi-reflection and scattering. Results
are confronted to experimental measurements of diffraction. The paper
reports the results of the different approaches.
---------------------------------------------------------
Title: Development of ASPIICS: a coronagraph based on Proba-3
formation flying mission
Authors: Galano, Damien; Bemporad, Alessandro; Buckley, Steve; Cernica,
Ileana; Dániel, Vladimír.; Denis, François; de Vos, Lieve; Fineschi,
Silvano; Galy, Camille; Graczyk, Rafal; Horodyska, Petra; Jacob,
Jérôme; Jansen, Richard; Kranitis, Nektarios; Kurowski, Michal;
Ladno, Michal; Ledent, Philippe; Loreggia, Davide; Melich, Radek;
Mollet, Dominique; Mosdorf, Michal; Paschalis, Antonios; Peresty,
Radek; Purica, Munizer; Radzik, Bartlomiej; Rataj, Miroslaw; Rougeot,
Raphaël.; Salvador, Lucas; Thizy, Cédric; Versluys, Jorg; Walczak,
Tomasz; Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei
2018SPIE10698E..2YG Altcode:
This paper presents the recent achievements in the development
of ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun), a solar coronagraph that is the
primary payload of ESA's formation flying in-orbit demonstration mission
PROBA-3. The PROBA-3 Coronagraph System is designed as a classical
externally occulted Lyot coronagraph but it takes advantage of the
opportunity to place the 1.4 meter wide external occulter on a companion
spacecraft, about 150m apart, to perform high resolution imaging of the
inner corona of the Sun as close as 1.1 solar radii. Besides providing
scientific data, ASPIICS is also equipped with sensors for providing
relevant navigation data to the Formation Flying GNC system. This paper
is reviewing the recent development status of the ASPIICS instrument
as it passed CDR, following detailed design of all the sub-systems
and testing of STM and various Breadboard models.
---------------------------------------------------------
Title: Calibration of the liquid crystal visible-light polarimeter
for the Metis/Solar Orbiter coronagraph
Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Landini, F.; Romoli,
M.; Antonucci, E.; Andretta, V.; Naletto, G.; Nicolini, G.; Spadaro,
D.; Alvarez-Herrero, A.; Garcia-Parejo, P.; Marmonti, M.
2018SPIE10698E..31C Altcode:
Metis is the solar coronagraph selected for the payload of the ESA
Solar Orbiter mission. Metis will acquire simultaneous imaging in
linearly polarized, broadband visible light (580-640 nm) and in the
narrow-band HI Ly-α line (121.6 nm). The METIS 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. 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 presentation will report the polarimetric
characterization of the Flight Model of the Metis polarimeter and the
voltage-to-retardance calibration.
---------------------------------------------------------
Title: Simulating the solar minimum corona in UV and visible/IR
wavelengths with forward modeling
Authors: Zhao, Jie; Fineschi, Silvano; Gibson, Sarah; Susino, Roberto
2018cosp...42E3853Z Altcode:
The magnetic field in the corona is important for understanding
solar activity, but is difficult to measure due to the tenuous
plasma. Therefore many alternative methods have been adopted to get
the 3D magnetic field in the corona, such as extrapolation methods
relying on the photospheric magnetograms. Such extrapolations make
problematic assumptions about the force-free nature of the photosphere,
and are highly sensitive to uncertainties in the photosphere magnetic
measurements. Measuring the coronal magnetic field directly is thus
to be desired, and linear polarization measurements in the visible/IR
are already obtained by the CoMP telescope providing information about
coronal magnetic direction and topology. However other observations
such as circlar polarization in the visible/IR and UV unsaturated Hanle
measurements are needed to better observe the 3D coronal field. Until
such observations are available, we turn to the FORWARD model (Gibson et
al. 2016) which simulates all of these polarization data. As a physical
state to input into FORWARD, the analytic magnetic model in this work
is adopted from Gibson et al.(1996), which gives a potential field
with an exception at the boundary of the helmet streamer where current
sheets are added between the open and closed fields. This analytic
model has the benifit of matching white light and also photospheric
magnetic flux observations at solar minimum. Given this model input
of a 3D distribution of magnetic field and plasma, we obtain simulated
polarization results in UV and visible/IR wavelengths. This allows us
to consider how such observations might be used together in future to
diagnose the coronal magnetic field.
---------------------------------------------------------
Title: Coatings for improved far-UV astrophysics observations
Authors: Honrado-Benitez, Carlos; Fineschi, Silvano; Malvezzi,
A. Marco; Giglia, Angelo; Massone, . Giuseppe; Capobianco, Gerardo;
Larruquert, Juan; Nannarone, Stefano; Gutiérrez-Luna, Nuria; De Lis,
Tomás; Espinosa-Yáñez, Lucía; Perea-Abarca, Belen; Rodríguez-de
Marcos, Luis; Chavero-Royan, Jose
2018cosp...42E1484H Altcode:
Knowledge of temperature, densities, and chemical abundances of hot
plasmas that exist in stars including the Sun, in the interstellar and
intergalactic medium, and in active galactic nuclei can be optimally
determined through observations in key diagnostic spectral lines, many
of which are in the far ultraviolet range (FUV, 100-200 nm), such as the
Lyman series of atomic Hydrogen and Deuterium, and the Lyman bands of
their molecules, along with lines of OI and OVI, CIV, etc. For habitable
exoplanet search, the FUV spectrum of M stars is a useful diagnostic
tool of biologically generated gases in planet atmospheres. Measuring
the magnetic field in the different layers of the Sun's atmosphere can
be optimally performed by means of polarimetry in the FUV and in the
UV. The development of more efficient FUV coatings is key to advance
in many fields of astrophysics and solar physics. With this goal,
GOLD (Spanish acronym of Thin Film Optics Group) has been devoting a
long effort to develop high-performance coatings to address specific
targets.In this poster, GOLD's capacity to develop and measure FUV
coatings will be summarized. A 75-cm diameter chamber in an ISO-6 clean
room is used to prepare FUV coatings satisfying space requirements. The
main deposition technique is evaporation and ion-beam-sputtering is
also available. Coating performance is conveniently measured with
an in-house reflectometer covering the 40-190 nm spectral range.The
presentation will display the performance of FUV coatings that can be
prepared at GOLD: 1) Transmittance filters peaked at λ ≥ 120 nm with
a strong peak-to-visible rejection 2) Broadband mirrors with enhanced
FUV reflectance 3) Narrowband mirrors tuned at FUV wavelengths as
short as H Lyman β (102.6 nm) 4) Polarizers at H Lyman α (121.6 nm)
and other FUV and UV spectral lines
---------------------------------------------------------
Title: Mapping the solar wind HI outflow velocity in the inner
heliosphere by coronagraphic ultraviolet and visible-light
observations
Authors: Dolei, S.; Susino, R.; Sasso, C.; Bemporad, A.; Andretta,
V.; Spadaro, D.; Ventura, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.;
Fineschi, S.; Focardi, M.; Frassetto, F.; Giordano, S.; Landini, F.;
Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.;
Telloni, D.
2018A&A...612A..84D Altcode:
We investigated the capability of mapping the solar wind outflow
velocity of neutral hydrogen atoms by using synergistic visible-light
and ultraviolet observations. We used polarised brightness images
acquired by the LASCO/SOHO and Mk3/MLSO coronagraphs, and synoptic Lyα
line observations of the UVCS/SOHO spectrometer to obtain daily maps
of solar wind H I outflow velocity between 1.5 and 4.0 R<SUB>⊙</SUB>
on the SOHO plane of the sky during a complete solar rotation (from
1997 June 1 to 1997 June 28). The 28-days data sequence allows us to
construct coronal off-limb Carrington maps of the resulting velocities
at different heliocentric distances to investigate the space and time
evolution of the outflowing solar plasma. In addition, we performed
a parameter space exploration in order to study the dependence of the
derived outflow velocities on the physical quantities characterising
the Lyα emitting process in the corona. Our results are important
in anticipation of the future science with the Metis instrument,
selected to be part of the Solar Orbiter scientific payload. It was
conceived to carry out near-sun coronagraphy, performing for the first
time simultaneous imaging in polarised visible-light and ultraviolet
H I Lyα line, so providing an unprecedented view of the solar wind
acceleration region in the inner corona. <P />The movie (see Sect. 4.2)
is available at https://www.aanda.org
---------------------------------------------------------
Title: Visibility of Prominences Using the He I D<SUB>3</SUB> Line
Filter on the PROBA-3/ASPIICS Coronagraph
Authors: Jejčič, S.; Heinzel, P.; Labrosse, N.; Zhukov, A. N.;
Bemporad, A.; Fineschi, S.; Gunár, S.
2018SoPh..293...33J Altcode: 2018arXiv180700155J
We determine the optimal width and shape of the narrow-band filter
centered on the He I D<SUB>3</SUB> line for prominence and coronal
mass ejection (CME) observations with the ASPIICS (Association of
Spacecraft for Polarimetric and Imaging Investigation of the Corona of
the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy)
satellite, to be launched in 2020. We analyze He I D<SUB>3</SUB> line
intensities for three representative non-local thermal equilibrium
prominence models at temperatures 8, 30, and 100 kK computed with a
radiative transfer code and the prominence visible-light (VL) emission
due to Thomson scattering on the prominence electrons. We compute
various useful relations at prominence line-of-sight velocities of 0,
100, and 300 km s<SUP>−1</SUP> for 20 Å wide flat filter and three
Gaussian filters with a full-width at half-maximum (FWHM) equal to 5,
10, and 20 Å to show the relative brightness contribution of the He I
D<SUB>3</SUB> line and the prominence VL to the visibility in a given
narrow-band filter. We also discuss possible signal contamination by Na
I D<SUB>1</SUB> and D<SUB>2</SUB> lines, which otherwise may be useful
to detect comets. Our results mainly show that i) an optimal narrow-band
filter should be flat or somewhere between flat and Gaussian with an
FWHM of 20 Å in order to detect fast-moving prominence structures,
ii) the maximum emission in the He I D<SUB>3</SUB> line is at 30 kK
and the minimal at 100 kK, and iii) the ratio of emission in the He I
D<SUB>3</SUB> line to the VL emission can provide a useful diagnostic
for the temperature of prominence structures. This ratio is up to 10
for hot prominence structures, up to 100 for cool structures, and up
to 1000 for warm structures.
---------------------------------------------------------
Title: Comprehensive Analysis of the Geoeffective Solar Event
of 21 June 2015: Effects on the Magnetosphere, Plasmasphere, and
Ionosphere Systems
Authors: Piersanti, Mirko; Alberti, Tommaso; Bemporad, Alessandro;
Berrilli, Francesco; Bruno, Roberto; Capparelli, Vincenzo; Carbone,
Vincenzo; Cesaroni, Claudio; Consolini, Giuseppe; Cristaldi, Alice;
Del Corpo, Alfredo; Del Moro, Dario; Di Matteo, Simone; Ermolli,
Ilaria; Fineschi, Silvano; Giannattasio, Fabio; Giorgi, Fabrizio;
Giovannelli, Luca; Guglielmino, Salvatore Luigi; Laurenza, Monica;
Lepreti, Fabio; Marcucci, Maria Federica; Martucci, Matteo; Mergè,
Matteo; Pezzopane, Michael; Pietropaolo, Ermanno; Romano, Paolo;
Sparvoli, Roberta; Spogli, Luca; Stangalini, Marco; Vecchio, Antonio;
Vellante, Massimo; Villante, Umberto; Zuccarello, Francesca; Heilig,
Balázs; Reda, Jan; Lichtenberger, János
2017SoPh..292..169P Altcode:
A full-halo coronal mass ejection (CME) left the Sun on 21 June 2015
from active region (AR) NOAA 12371. It encountered Earth on 22 June
2015 and generated a strong geomagnetic storm whose minimum Dst value
was −204 nT. The CME was associated with an M2-class flare observed
at 01:42 UT, located near disk center (N12 E16). Using satellite data
from solar, heliospheric, and magnetospheric missions and ground-based
instruments, we performed a comprehensive Sun-to-Earth analysis. In
particular, we analyzed the active region evolution using ground-based
and satellite instruments (Big Bear Solar Observatory (BBSO), Interface
Region Imaging Spectrograph (IRIS), Hinode, Atmospheric Imaging Assembly
(AIA) onboard the Solar Dynamics Observatory (SDO), Reuven Ramaty High
Energy Solar Spectroscopic Imager (RHESSI), covering Hα , EUV, UV, and
X-ray data); the AR magnetograms, using data from SDO/Helioseismic and
Magnetic Imager (HMI); the high-energy particle data, using the Payload
for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA)
instrument; and the Rome neutron monitor measurements to assess the
effects of the interplanetary perturbation on cosmic-ray intensity. We
also evaluated the 1 - 8 Å soft X-ray data and the ∼1 MHz type III
radio burst time-integrated intensity (or fluence) of the flare in order
to predict the associated solar energetic particle (SEP) event using
the model developed by Laurenza et al. (Space Weather7(4), 2009). In
addition, using ground-based observations from lower to higher latitudes
(International Real-time Magnetic Observatory Network (INTERMAGNET) and
European Quasi-Meridional Magnetometer Array (EMMA)), we reconstructed
the ionospheric current system associated with the geomagnetic
sudden impulse (SI). Furthermore, Super Dual Auroral Radar Network
(SuperDARN) measurements were used to image the global ionospheric
polar convection during the SI and during the principal phases of
the geomagnetic storm. In addition, to investigate the influence of
the disturbed electric field on the low-latitude ionosphere induced
by geomagnetic storms, we focused on the morphology of the crests
of the equatorial ionospheric anomaly by the simultaneous use of the
Global Navigation Satellite System (GNSS) receivers, ionosondes, and
Langmuir probes onboard the Swarm constellation satellites. Moreover,
we investigated the dynamics of the plasmasphere during the different
phases of the geomagnetic storm by examining the time evolution of
the radial profiles of the equatorial plasma mass density derived from
field line resonances detected at the EMMA network (1.5 <L <6.5
). Finally, we present the general features of the geomagnetic response
to the CME by applying innovative data analysis tools that allow us
to investigate the time variation of ground-based observations of the
Earth's magnetic field during the associated geomagnetic storm.
---------------------------------------------------------
Title: ASPIICS: a giant, white light and emission line coronagraph
for the ESA proba-3 formation flight mission
Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.;
Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin,
S.; Schmutz, W.; Tsinganos, K.; Zhukov, A.
2017SPIE10565E..0TL Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observations of the white light corona inside typically 2-2.5
solar radii (Rsun). Formation flying offers and elegant solution to
these limitations and allows conceiving giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at a distance of hundred meters [1, 2]. Such
an instrument ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) has been selected
by the European Space Agency (ESA) to fly on its PROBA-3 mission
of formation flying demonstration which is presently in phase B
(Fig. 1). The classical design of an externally-occulted coronagraph is
adapted to the formation flying configuration allowing the detection
of the very inner corona as close as 0.04 solar radii from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules
[3]. ASPIICS will perform (i) high spatial resolution imaging of the
continuum K+F corona in photometric and polarimetric modes, (ii) high
spatial resolution imaging of the E-corona in two coronal emission lines
(CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry
of the Fe XIV emission line. ASPIICS will address the question of the
coronal heating and the role of waves by characterizing propagating
fluctuations (waves and turbulence) in the solar wind acceleration
region and by looking for oscillations in the intensity and Doppler
shift of spectral lines. The combined imaging and spectral diagnostics
capabilities available with ASPIICS will allow mapping the velocity
field of the corona both in the sky plane (directly on the images)
and along the line-of-sight by measuring the Doppler shifts of
emission lines in an effort to determine how the different components
of the solar wind, slow and fast are accelerated. With a possible
launch in 2014, ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high-resolution imaging and spectroscopy,
CMEs will be thoroughly characterized.
---------------------------------------------------------
Title: The optimization of the inverted occulter of the solar
orbiter/METIS coronagraph/spectrometer
Authors: Landini, F.; Vives, S.; Romoli, M.; Guillon, C.; Pancrazzi,
M.; Escolle, C.; Focardi, M.; Fineschi, S.; Antonucci, E.; Nicolini,
G.; Naletto, G.; Nicolosi, P.; Spadaro, D.
2017SPIE10564E..0FL Altcode:
The coronagraph/spectrometer METIS (Multi Element Telescope for Imaging
and Spectroscopy), selected to fly aboard the Solar Orbiter ESA/NASA
mission, is conceived to perform imaging (in visible, UV and EUV)
and spectroscopy (in EUV) of the solar corona. It is an integrated
instrument suite located on a single optical bench and sharing a
unique aperture on the satellite heat shield. As every coronagraph,
METIS is highly demanding in terms of stray light suppression. In
order to meet the strict thermal requirements of Solar Orbiter, METIS
optical design has been optimized by moving the entrance pupil at the
level of the external occulter on the S/C thermal shield, thus reducing
the size of the external aperture. The scheme is based on an inverted
external-occulter (IEO). The IEO consists of a circular aperture on
the Solar Orbiter thermal shield. A spherical mirror rejects back the
disk-light through the IEO. The experience built on all the previous
space coronagraphs forces designers to dedicate a particular attention
to the occulter optimization. Two breadboards were manufactured to
perform occulter optimization measurements: BOA (Breadboard of the
Occulting Assembly) and ANACONDA (AN Alternative COnfiguration for the
Occulting Native Design Assembly). A preliminary measurement campaign
has been carried on at the Laboratoire d'Astrophysique de Marseille. In
this paper we describe BOA and ANACONDA designs, the laboratory set-up
and the preliminary results.
---------------------------------------------------------
Title: Preliminary error budget analysis of the coronagraphic
instrument metis for the solar orbiter ESA mission
Authors: Da Deppo, Vania; Poletto, Luca; Crescenzio, Giuseppe;
Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero
2017SPIE10564E..3BD Altcode:
METIS, the Multi Element Telescope for Imaging and Spectroscopy, is
the solar coronagraph foreseen for the ESA Solar Orbiter mission. METIS
is conceived to image the solar corona from a near-Sun orbit in three
different spectral bands: in the HeII EUV narrow band at 30.4 nm, in
the HI UV narrow band at 121.6 nm, and in the polarized visible light
band (590 - 650 nm). It also incorporates the capability of multi-slit
spectroscopy of the corona in the UV/EUV range at different heliocentric
heights. METIS is an externally occulted coronagraph which adopts an
"inverted occulted" configuration. The Inverted external occulter
(IEO) is a small circular aperture at the METIS entrance; the Sun-disk
light is rejected by a spherical mirror M0 through the same aperture,
while the coronal light is collected by two annular mirrors M1-M2
realizing a Gregorian telescope. To allocate the spectroscopic part,
one portion of the M2 is covered by a grating (i.e. approximately 1/8
of the solar corona will not be imaged). This paper presents the error
budget analysis for this new concept coronagraph configuration, which
incorporates 3 different sub-channels: UV and EUV imaging sub-channel,
in which the UV and EUV light paths have in common the detector and
all of the optical elements but a filter, the polarimetric visible
light sub-channel which, after the telescope optics, has a dedicated
relay optics and a polarizing unit, and the spectroscopic sub-channel,
which shares the filters and the detector with the UV-EUV imaging one,
but includes a grating instead of the secondary mirror. The tolerance
analysis of such an instrument is quite complex: in fact not only
the optical performance for the 3 sub-channels has to be maintained
simultaneously, but also the positions of M0 and of the occulters
(IEO, internal occulter and Lyot stop), which guarantee the optimal
disk light suppression, have to be taken into account as tolerancing
parameters. In the aim of assuring the scientific requirements are
optimally fulfilled for all the sub-channels, the preliminary results
of manufacturing, alignment and stability tolerance analysis for the
whole instrument will be described and discussed.
---------------------------------------------------------
Title: Evaluation of the stray light from the diffraction of METIS
coronagraph external occulter
Authors: Romoli, M.; Landini, F.; Moses, D.; Fineschi, S.; Pancrazzi,
M.; Focardi, M.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi,
P.; Spadaro, D.
2017SPIE10564E..37R Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy) is an
externally occulted coronagraph part of the Solar Orbiter payload. METIS
innovative occulting system, called inverted externally occulter (IEO),
consists of a circular aperture, IEO, that acts also as the entrance
pupil of the instrument, and a solar disk rejection mirror (M0),
placed at the bottom end of the coronagraph boom. M0 reflects back
through IEO the solar disk radiation, letting the coronal radiation
enter the coronagraph telescope. Light diffracted by IEO enters the
telescope and has to be minimized with a proper shape of the IEO
edge. The paper describes the theoretical results of the diffraction
analysis extended to the scattered light by the primary mirror of the
telescope onto the primary focal plane. A summary of the entire stray
light reduction capabilities of METIS is also given.
---------------------------------------------------------
Title: Internal checkup illumination sources for METIS coronagraph
on solar orbiter
Authors: Frassetto, F.; Poletto, L.; Fineschi, S.; De Santi, C.;
Meneghini, M.; Meneghesso, G.; Antonucci, E.; Naletto, G.; Romoli,
M.; Spadaro, D.; Nicolini, G.
2017SPIE10563E..5JF Altcode:
METIS is one of the remote sensing instrument on the Solar Orbiter
mission. It will acquire coronal images from distances from the Sun
as close as 0.28 AU. The mission innovations rely not only in the
spacecraft orbit; METIS introduces many technical breakthroughs in the
optical layout and in many other areas, mainly the inverted external
occulter and the visible light (VL) polarimeter.
---------------------------------------------------------
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: Multilayer coatings for multiband spectral observations
Authors: Zuccon, S.; Garoli, D.; Pelizzo, M. G.; Nicolosi, P.;
Fineschi, S.; Windt, D.
2017SPIE10567E..3JZ Altcode:
Extreme UltraViolet instrumentation often requires the use of multilayer
coated optics. Such coatings have a limited working bandwidth, and
therefore are optimized to perform in correspondence of specific EUV
spectral lines. Nevertheless, contemporary observations of the same
target in other spectral region would strongly improve scientific
knowledge. In this work we present a study on multilayers optimized to
achieve high efficiency also in other spectral bands. These coatings
would allow the realization of very compact instruments, such as UVCI
on board of the Solar Orbiter.
---------------------------------------------------------
Title: METIS-ESA solar orbiter mission internal straylight analysis
Authors: Verroi, E.; Da Deppo, V.; Naletto, G.; Fineschi, S.;
Antonucci, E.
2017SPIE10563E..1NV Altcode:
METIS is the Multi Element Telescope for Imaging and Spectroscopy
for the ESA Solar Orbiter. Its target is the solar corona from a
near-Sun orbit in two different spectral bands: the HI UV narrow
band at 121.6 nm, and the VL visible light band. METIS adopts a novel
inverted externally occulted configuration, where the disk light is
shielded by an annular occulter, and an annular aspherical mirror M1
collects the signal coming from the corona. After M1 the coronal light
passes through an internal occulter and is then reflected by a second
annular mirror M2 toward a narrow filter for the 121.6 nm HI line
selection. The visible light reflected by the filter is used to feed
a visible light (580 - 640 nm) polarimetric channel. The photospheric
light passing through the entrance aperture is back-rejected by a
spherical rejection mirror. Since the coronal light is enormously
fainter than the photospheric one, a very tough suppression is needed
for the internal stray light, in particular the requirement for the
stray light suppression is more stringent in the VL than in the UV,
because the emission of the corona with respect to the disk emission
is different in the two cases, and the requirements are a suppression
of at least 10<SUP>-9</SUP> times for the VL and a suppression of at
least 10<SUP>-7</SUP> times for the UV channel. This paper presents the
stray light analysis for this new coronographic configuration. The
complexity of the optomechanical design of METIS, combined with
the faintness of the coronal light with respect to the solar disk
noise, make a standard ray tracing approach not feasible because it
is not sufficient to stop at the first generation of scattered rays
in order to check the requirements. Also scattered rays down to the
fourth generation must be treated as sources of new scattering light,
to analyze the required level of accuracy. If used in a standard ray
tracing scattering analysis, this approach is absolutely beyond the
computational capabilities today available; therefore we opted for a
scattering ray generation with a Montecarlo method in which after a
father ray hits a surface, only one ray is generated, randomly selected
according to the distribution of the transmitted energy. These rays
bring with them all the energy that is otherwise distributed between
all the rays of second generation, making the model more realistic and
avoiding loss of energy due to the rays sampling. The stray light has
been studied in function of the mechanical roughness of the surfaces
and the obtained results indicate an instrument stray light blocking
performance well within the requirements in both channels.
---------------------------------------------------------
Title: Constraining the pass-band of future space-based coronagraphs
for observations of solar eruptions in the FeXIV 530.3 nm "green line"
Authors: Bemporad, Alessandro; Pagano, Paolo; Giordano, Silvio;
Fineschi, Silvano
2017ExA....44...83B Altcode: 2017ExA...tmp...28B
Observations of the solar corona in the FeXIV 530.3 nm "green line"
have been very important in the past, and are planned for future
coronagraphs on-board forthcoming space missions such as PROBA-3
and Aditya. For these instruments, a very important parameter to be
optimized is the spectral width of the band-pass filter to be centred
over the "green line". Focusing on solar eruptions, motions occurring
along the line of sight will Doppler shift the line profiles producing
an emission that will partially fall out of the narrower pass-band,
while broader pass-band will provide observations with reduced
spectral purity. To address these issues, we performed numerical
(MHD) simulation of CME emission in the "green line" and produced
synthetic images assuming 4 different widths of the pass-band (Δλ =
20 Å, 10 Å, 5 Å, and 2 Å). It turns out that, as expected, during
solar eruptions a significant fraction of "green line" emission will
be lost using narrower filters; on the other hand these images will
have a higher spectral purity and will contain emission coming from
parcels of plasma expanding only along the plane of the sky. This
will provide a better definition of single filamentary features and
will help isolating single slices of plasma through the eruption, thus
reducing the problem of superposition of different features along the
line of sight and helping physical interpretation of limb events. For
these reasons, we suggest to use narrower band passes (Δλ ≤ 2 Å)
for the observations of solar eruptions with future coronagraphs.
---------------------------------------------------------
Title: An improved version of the Shadow Position Sensor readout
electronics on-board the ESA PROBA-3 Mission
Authors: Noce, V.; Focardi, M.; Buckley, S.; Bemporad, A.; Fineschi,
S.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco, G.; Loreggia,
D.; Casti, M.; Romoli, M.; Accatino, L.; Thizy, C.; Denis, F.;
Ledent, P.
2017SPIE10397E..1BN Altcode:
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA)
composed by two satellites flying in formation and aimed at achieving
unprecedented performance in terms of relative positioning. The mission
purpose is, in first place, technological: the repeated formation
break and acquisition during each orbit (every about twenty hours)
will be useful to demonstrate the efficacy of the closed-loop control
system in keeping the formation-flying (FF) and attitude (i.e. the
alignment with respect to the Sun) of the system. From the scientific
side, instead, the two spacecraft will create a giant instrument
about 150 m long: an externally occulted coronagraph named ASPIICS
(Association of Spacecraft for Polarimetric and Imaging Investigation of
the Corona of the Sun) dedicated to the study of the inner part of the
visible solar corona. The two satellites composing the mission are: the
Coronagraph Spacecraft (CSC), hosting the Coronagraph Instrument (CI),
and the disk-shaped (1.4 m diameter) Occulter Spacecraft (OSC). The
PROBA-3 GNC (Guidance, Navigation and Control) system will employ
several metrological subsystems to keep and retain the desired relative
position and the absolute attitude (i.e. with respect to the Sun) of
the aligned spacecraft, when in observational mode. The SPS subsystem
[5] is one of these metrological instruments. It is composed of eight
silicon photomultipliers (SiPMs), sensors operated in photovoltaic mode
[6] that will sense the penumbra light around the Instrument's pupil so
to detect any FF displacement from the nominal position. In proximity
of the CDR (Critical Design Review) phase, we describe in the present
paper the changes occurred to design in the last year in consequence
of the tests performed on the SPS Breadboard (Evaluation Board, EB)
and the SPS Development Model (DM) and that will finally lead to the
realization of the flight version of the SPS system.
---------------------------------------------------------
Title: Test plan for the PROBA3/ASPIICS scaled model measurement
campaign
Authors: Landini, Federico; Baccani, Cristian; Vives, Sébastien;
Fineschi, Silvano; Romoli, Marco; Capobianco, Gerardo; Massone,
Giuseppe; Casti, Marta; Bemporad, Alessandro; Focardi, Mauro;
Pancrazzi, Maurizio; Loreggia, Davide; Noce, Vladimiro; Corso, Alain
Jody; Thizy, Cédric; Renotte, Etienne; Marquet, Benoît
2017SPIE10397E..1CL Altcode:
PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun) is the first formation flight
solar coronagraph, scheduled by ESA for a launch and currently in phase
C/D. It is constituted by two spacecraft (one hosting the occulter,
diameter 142 cm, and one with the telescope) separated by 144 m, kept
in strict alignment by means of complex active and metrology custom
systems. The stray light analysis, which is always one the most critical
work packages for a solar coronagraph, has been only theoretically
investigated so far due to the difficulty of replicating the actual
size system in a clean laboratory environment. The light diffracted
by the external occulter is the worst offender for the stray light
level on the instrument focal plane, thus there is strong interest for
scaling at least the occultation system of the coronagraph and test it
in front of a solar simulator in order to experimentally validate the
expected theoretical performance. The theory for scaling the occulter,
the occulter-pupil distance and the source dimension has been developed
and a scaled model is being manufactured. A test campaign is going to be
conducted at the OPSys facility in Torino in front of a solar simulator
(conveniently scaled). This work accounts for the description of the
scaled model laboratory set-up and of the test plan.
---------------------------------------------------------
Title: Optical measurements of the mirrors and of the interferential
filter of the Metis coronagraph on Solar Orbiter
Authors: Sandri, P.; Sarra, P.; Radaelli, P.; Morea, D.; Melich,
R.; Berlicki, A.; Antonucci, E.; Castronuovo, M. M.; Fineschi, S.;
Naletto, G.; Nicolini, G.; Romoli, M.
2017SPIE10397E..16S Altcode:
The paper describes the wavefront error measurements of the concave
ellipsoidal mirrors M1 and M2, of the concave spherical mirror M0 and
of the flat interferential filter IF of the Metis coronagraph. Metis is
an inverted occultation coronagraph on board of the ESA Solar Orbiter
mission providing a broad-band imaging of the full corona in linearly
polarized visible-light (580 - 640 nm) and a narrow-band imaging of
the full corona in the ultraviolet Lyman α (121.6 nm). Metis will
observe the solar outer atmosphere from a close distance to the Sun
as 0.28 A.U. and from up to 35deg out-of-ecliptic. The measurements of
wavefront error of the mirrors and of the interferential filter of Metis
have been performed in a ISO5 clean room both at component level and at
assembly level minimizing, during the integration, the stress introduced
by the mechanical hardware. The wavefront error measurements have been
performed with a digital interferometer for mirrors M0, M1 and M2 and
with a Shack-Hartmann wavefront sensor for the interferential filter.
---------------------------------------------------------
Title: Polarizers tuned at key far-UV spectral lines for space
instrumentation
Authors: Larruquert, Juan I.; Malvezzi, A. Marco; Rodríguez-de Marcos,
Luis; Giglia, Angelo; Gutiérrez-Luna, Nuria; Espinosa-Yáñez,
Lucía.; Honrado-Benítez, Carlos; Aznárez, José A.; Massone,
Giuseppe; Capobianco, Gerardo; Fineschi, Silvano; Nannarone, Stefano
2017SPIE10235E..0KL Altcode:
Polarimetry is a valuable technique to help us understand the
role played by the magnetic field of the coronal plasma in the
energy transfer processes from the inner parts of the Sun to the
outer space. Polarimetry in the far ultraviolet (FUV: 100-200 nm),
which must be performed from space due to absorption in terrestrial
atmosphere, supplies fundamental data of processes that are
governed by the Doppler and Hanle effects on resonantly scattered
line-emission. To observe these processes there are various key
spectral lines in the FUV, from which H I Lyman α (121.6 nm) is
the strongest one. Hence some solar physics missions that have been
proposed or are under development plan to perform polarimetry at 121.6
nm, like the suborbital missions CLASP I (2015) and CLASP II (2018),
and the proposed solar missions SolmeX and COMPASS and stellar mission
Arago. Therefore, the development of efficient FUV linear polarizers
may benefit these and other possible future missions. C IV (155 nm)
and Mg II (280 nm) are other spectral lines relevant for studies of
solar and stellar magnetized atmospheres. High performance polarizers
can be obtained with optimized coatings. Interference coatings can
tune polarizers at the spectral line(s) of interest for solar and
stellar physics. Polarizing beamsplitters consist in polarizers that
separate one polarization component by reflection and the other by
transmission, which enables observing the two polarization components
simultaneously with a single polarizer. They involve the benefit of a
higher efficiency in collection of polarization data due to the use
of a single polarizer for the two polarization components and they
may also facilitate a simplified design for a space polarimeter. We
present results on polarizing beamsplitters tuned either at 121.6 nm
or at the pair of 155 and 280 nm spectral lines.
---------------------------------------------------------
Title: Preliminary evaluation of the diffraction behind the PROBA
3/ASPIICS optimized occulter
Authors: Baccani, Cristian; Landini, Federico; Romoli, Marco; Taccola,
Matteo; Schweitzer, Hagen; Fineschi, Silvano; Bemporad, Alessandro;
Loreggia, Davide; Capobianco, Gerardo; Pancrazzi, Maurizio; Focardi,
Mauro; Noce, Vladimiro; Thizy, Cédric; Servaye, Jean-Sébastien;
Renotte, Etienne
2016SPIE.9904E..50B Altcode:
PROBA-3 is a technological mission of the European Space Agency
(ESA), devoted to the in-orbit demon- stration of formation flying
(FF) techniques and technologies. ASPIICS is an externally occulted
coronagraph approved by ESA as payload in the framework of the PROBA-3
mission and is currently in its C/D phase. FF offers a solution to
investigate the solar corona close the solar limb using a two-component
space system: the external occulter on one spacecraft and the optical
instrument on the other, separated by a large distance and kept in
strict alignment. ASPIICS is characterized by an inter-satellite
distance of ∼144 m and an external occulter diameter of 1.42 m. The
stray light due to the diffraction by the external occulter edge is
always the most critical offender to a coronagraph performance: the
designer work is focused on reducing the stray light and carefully
evaluating the residuals. In order to match this goal, external
occulters are usually characterized by an optimized shape along the
optical axis. Part of the stray light evaluation process is based on the
diffraction calculation with the optimized occulter and with the whole
solar disk as a source. We used the field tracing software VirtualLabTM
Fusion by Wyrowski Photonics [1] to simulate the diffraction. As a
first approach and in order to evaluate the software, we simulated
linear occulters, through as portions of the flight occulter, in order
to make a direct comparison with the Phase-A measurements [2].
---------------------------------------------------------
Title: Characterization of the ASPIICS/OPSE metrology sub-system
and PSF centroiding procedure
Authors: Loreggia, D.; Fineschi, S.; Capobianco, G.; Bemporad,
A.; Focardi, M.; Landini, F.; Massone, G.; Casti, M.; Nicolini, G.;
Pancrazi, M.; Romoli, M.; Noce, V.; Baccani, C.; Cernica, I.; Purica,
M.; Nisulescu, M.; Thizy, C.; Servaye, J. S.; Renotte, E.
2016SPIE.9904E..5OL Altcode:
years have raised increasing interest. Many applications of astronomical
observation techniques, as coronography and interferometry get great
benefit when moved in space and the employment of diluted systems
represents a milestone to step-over in astronomical research. In
this work, we present the Optical Position Sensors Emitter (OPSE)
metrological sub-system on-board of the PROBA3. PROBA3 is an ESA
technology mission that will test in-orbit many metrology techniques for
the maintenance of a Formation Flying with two satellites, in this case
an occulter and a main satellite housing a coronagraph named ASPIICS,
kept at an average inter-distance of 144m. The scientific task is the
observation of the Sun's Corona at high spatial and temporal resolution
down to 1.08R⊙. The OPSE will monitor the relative position of the two
satellites and consists of 3 emitters positioned on the rear surface
of the occulter, that will be observed by the coronagraph itself. A
Centre of Gravity (CoG) algorithm is used to monitor the emitter's PSF
at the focal plane of the Coronagraph retrieving the Occulter position
with respect to the main spacecraft. The 3σ location target accuracy
is 300μm for lateral movement and 21cm for longitudinal movements. A
description of the characterization tests on the OPSE LED sources,
and of the design for a laboratory set-up for on ground testing is
given with a preliminary assessment of the performances expected from
the OPSE images centroiding algorithm.
---------------------------------------------------------
Title: The satellite formation flying in lab: PROBA-3/ASPIICS
metrology subsystems test-bed
Authors: Capobianco, G.; Loreggia, D.; Fineschi, S.; Focardi, M.;
Bemporad, A.; Casti, M.; Noce, V.; Landini, F.; Baccani, C.; Pancrazzi,
M.; Romoli, M.; Massone, G.; Nicolini, G.; Buckley, S.; O'Neill, K.;
Cernica, I.; Purica, M.; Budianu, E.; Thizy, C.; Servaye, J. -S.;
Mechmech, I.; Renotte, Etienne
2016SPIE.9904E..6EC Altcode:
Formation flying is one of the most promising techniques for the
future of astronomy and astrophysics from the space. The capabilities
of the rockets strongly affect the dimensions and the weights of
telescopes and instrumentation to be launched. Telescopes composed by
several smallest satellites in formation flying, could be the key for
build big space telescopes. With this aim, the ESA PROBA-3 mission
will demonstrate the capabilities of this technology, maintaining
two satellites aligned within 1 mm (longitudinal) when the nominal
distance between the two is of around 144m. The scientific objective
of the mission is the observation of the solar corona down to 1.08
solar radii. The Coronagraph Spacecraft (CSC) will observe the Sun,
when the second spacecraft, the Occulter Spacecraft (OSC) will work
as an external occulter, eclipsing to the CSC the sun disk. The
finest metrology sub-systems, the Shadow Position Sensors (SPS) and
the Occulter Position Sensor Emitters (OPSE) identifying respectively
the CSC-Sun axis and the formation flying (i.e., CSC-OSC) axis will be
considered here. In particular, this paper is dedicated to the test-bed
for the characterization, the performance analysis and the algorithms
capabilities analysis of the both the metrology subsystems. The
test-bed is able to simulate the different flight conditions of the two
spacecraft and will give the opportunity to check the response of the
subsystems in the conditions as close as possible to the flight ones.
---------------------------------------------------------
Title: Future space missions and ground observatory for measurements
of coronal magnetic fields
Authors: Fineschi, Silvano; Gibson, Sarah; Bemporad, Alessandro;
Zhukov, Andrei; Damé, Luc; Susino, Roberto; Larruquert, Juan
2016cosp...41E.602F Altcode:
This presentation gives an overview of the near-future perspectives for
probing coronal magnetism from space missions (i.e., SCORE and ASPIICS)
and ground-based observatory (ESCAPE). Spectro-polarimetric imaging of
coronal emission-lines in the visible-light wavelength-band provides an
important diagnostics tool of the coronal magnetism. The interpretation
in terms of Hanle and Zeeman effect of the line-polarization
in forbidden emission-lines yields information on the direction
and strength of the coronal magnetic field. As study case, this
presentation will describe the Torino Coronal Magnetograph (CorMag)
for the spectro-polarimetric observation of the FeXIV, 530.3 nm,
forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC)
Lyot filter and a LC linear polarimeter. The CorMag filter is part
of the ESCAPE experiment to be based at the French-Italian Concordia
base in Antarctica. The linear polarization by resonance scattering
of coronal permitted line-emission in the ultraviolet (UV)can be
modified by magnetic fields through the Hanle effect. Space-based
UV spectro-polarimeters would provide an additional tool for the
disgnostics of coronal magnetism. As a case study of space-borne UV
spectro-polarimeters, this presentation will describe the future upgrade
of the Sounding-rocket Coronagraphic Experiment (SCORE) to include new
generation, high-efficiency UV polarizer with the capability of imaging
polarimetry of the HI Lyman-α, 121.6 nm. SCORE is a multi-wavelength
imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and
visible-light broad-band emission of the polarized K-corona. SCORE
has flown successfully in 2009. The second lauch is scheduled in
2016. Proba-3 is the other future solar mission that would provide
the opportunity of diagnosing the coronal magnetic field. Proba-3 is
the first precision formation-flying mission to launched in 2019). A
pair of satellites will fly together maintaining a fixed configuration
as a 'large rigid structure' in space. The paired satellites will
together form a 150-m long solar coronagraph (ASPIICS) to study the
Sun's faint corona closer to the solar limb than has ever before been
achieved. High-resolution imaging in polarized visible-light of shock
waves generated by Coronal Mass Ejections would provide a diagnostics
of the magnetic field in the pre-shock ambient corona.
---------------------------------------------------------
Title: Recent achievements on ASPIICS, an externally occulted
coronagraph for PROBA-3
Authors: Renotte, Etienne; Buckley, Steve; Cernica, Ileana;
Denis, François; Desselle, Richard; De Vos, Lieve; Fineschi,
Silvano; Fleury-Frenette, Karl; Galano, Damien; Galy, Camille;
Gillis, Jean-Marie; Graas, Estelle; Graczyk, Rafal; Horodyska, Petra;
Kranitis, Nektarios; Kurowski, Michal; Ladno, Michal; Liebecq, Sylvie;
Loreggia, Davide; Mechmech, Idriss; Melich, Radek; Mollet, Dominique;
Mosdorf, Michał; Mroczkowski, Mateusz; O'Neill, Kevin; Patočka,
Karel; Paschalis, Antonis; Peresty, Radek; Radzik, Bartlomiej; Rataj,
Miroslaw; Salvador, Lucas; Servaye, Jean-Sébastien; Stockman, Yvan;
Thizy, Cédric; Walczak, Tomasz; Zarzycka, Alicja; Zhukov, Andrei
2016SPIE.9904E..3DR Altcode:
This paper presents the current status of ASPIICS, a solar
coronagraph that is the primary payload of ESA's formation flying
in-orbit demonstration mission PROBA-3. The "sonic region" of the
Sun corona remains extremely difficult to observe with spatial
resolution and sensitivity sufficient to understand the fine scale
phenomena that govern the quiescent solar corona, as well as phenomena
that lead to coronal mass ejections (CMEs), which influence space
weather. Improvement on this front requires eclipse-like conditions
over long observation times. The space-borne coronagraphs flown so
far provided a continuous coverage of the external parts of the
corona but their over-occulting system did not permit to analyse
the part of the white-light corona where the main coronal mass is
concentrated. The PROBA-3 Coronagraph System, also known as ASPIICS
(Association of Spacecraft for Polarimetric and Imaging Investigation of
the Corona of the Sun) is designed as a classical externally occulted
Lyot coronagraph but it takes advantage of the opportunity to place
the external occulter on a companion spacecraft, about 150m apart,
to perform high resolution imaging of the inner corona of the Sun as
close as ~1.1 solar radii. The images will be tiled and compressed on
board in an FPGA before being down-linked to ground for scientific
analyses. ASPIICS is built by a large European consortium including
about 20 partners from 7 countries under the auspices of the European
Space Agency. This paper is reviewing the recent development status
of the ASPIICS instrument as it is approaching CDR.
---------------------------------------------------------
Title: Advances in far-ultraviolet reflective and transmissive
coatings for space applications
Authors: Rodríguez-de Marcos, Luis; Aznárez, José A.; Méndez,
José A.; Larruquert, Juan I.; Vidal-Dasilva, M.; Malvezzi, A. Marco;
Giglia, Angelo; Capobianco, Gerardo; Massone, Giuseppe; Fineschi,
Silvano; Nannarone, Stefano
2016SPIE.9912E..2ER Altcode:
Exploitation of far ultraviolet (FUV, 100-200 nm) observations extends
to most areas of modern astronomy, from detailed observations of
Solar System objects, the interstellar medium, exoplanets, stars and
galaxies, to studies of crucial cosmological relevance. Despite several
developments in recent decades, yet many observations are not possible
due to technical limitations, of which one of the most important is
the lack of optical coatings with high throughput. Development and
optimization of such efficient FUV coatings have been identified
in several roadmap reports as a key goal for future missions. The
success of this development will ultimately improve the performance of
nowadays feasible optical instruments and will enable new scientific
imaging capabilities. GOLD's research is devoted to developing novel
coatings with enhanced performance for space optics. Several deposition
systems are available for the deposition of multilayer coatings. A
deposition system was developed to deposit FUV coatings to satisfy
space requirements. It consists of a 75-cm-diameter deposition chamber
pumped with a cryo-pump and placed in an ISO-6 clean room. This chamber
is available for deposition by evaporation of top-requirement coatings
such as Al/ MgF<SUB>2</SUB> mirrors or (Al/MgF<SUB>2</SUB>)<SUB>n</SUB>
multilayer coatings for transmittance filters. A plan to add an
Ion-Beam-Sputtering system in this chamber is under way. In this and
other chambers at GOLD the following FUV coatings can be prepared:
Transmittance filters based on (Al/MgF<SUB>2</SUB>)<SUB>n</SUB>
multilayer coatings. These filters can be designed to have a peak at
the FUV spectral line or band of interest and a high peak-to-visible
transmittance ratio. Filters can be designed with a peak transmittance
at a wavelength as short as 120 nm and with a transmittance in the
visible smaller than 10<SUP>-5</SUP>. Narrowband reflective coatings
peaked close to H Lyman β (102.6 nm) with a reflectance at H Lyman α
(121.6 nm) two orders of magnitude below the one at 102.6 nm. Other
potential spectral lines at which these coatings could be peaked
are the OVI doublet (103.2, 103.8 nm). Narrowband reflective mirrors
based on (MgF<SUB>2</SUB>/LaF<SUB>3</SUB>)<SUB>n</SUB> multilayers
peaked at a wavelength as short as 120 nm. Target wavelengths include
lines of high interest for space observations, such as H Lyman α
(121.6 nm), OI (130.4 and 135.6 nm), CIV (154.8, 155.1 nm), among
others. Coating-based linear polarizers tuned at H Lyman α (121.6 nm)
both based on reflectance or on transmittance. Reflective polarizers
present a high efficiency. Transmissive polarizers have a more modest
peak performance compared to reflective polarizers; however, they
involve spectral filtering properties to reject the long FUV and even
more the near UV to the IR, which turn them competitive compared to
reflective polarizers. In this communication we present a summary of
our research on the above FUV coatings developed at GOLD.
---------------------------------------------------------
Title: The shadow position sensors (SPS) formation flying metrology
subsystem for the ESA PROBA-3 mission: present status and future
developments
Authors: Focardi, M.; Noce, V.; Buckley, S.; O'Neill, K.; Bemporad,
A.; Fineschi, S.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco,
G.; Loreggia, D.; Casti, M.; Romoli, M.; Massone, G.; Nicolini, G.;
Accatino, L.; Thizy, C.; Servaye, J. S.; Mechmech, I.; Renotte, E.
2016SPIE.9904E..4ZF Altcode:
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed
of two formation-flying satellites, planned for their joint launch
by the end of 2018. Its main purposes have a dual nature: scientific
and technological. In particular, it is designed to observe and study
the inner part of the visible solar corona, thanks to a dedicated
coronagraph called ASPIICS (Association of Spacecraft for Polarimetric
and Imaging Investigation of the Corona of the Sun), and to demonstrate
the in-orbit formation flying (FF) and attitude control capability of
its two satellites. The Coronagraph payload on-board PROBA-3 consists
of the following parts: the Coronagraph Instrument (CI) with the Shadow
Position Sensor (SPS) on the Coronagraph Spacecraft (CSC), the Occulter
Position Sensor (OPSE) [3] [4] and the External Occulting (EO) disk
on the Occulter Spacecraft (OSC). The SPS subsystem [5] is one of the
main metrological devices of the Mission, adopted to control and to
maintain the relative (i.e. between the two satellites) and absolute
(i.e. with respect to the Sun) FF attitude. It is composed of eight
micro arrays of silicon photomultipliers (SiPMs) [6] that shall be
able to measure, with the required sensitivity and dynamic range as
asked by ESA, the penumbral light intensity on the Coronagraph entrance
pupil. With the present paper we describe the testing activities on the
SPS breadboard (BB) and Development Model (DM) as well as the present
status and future developments of this PROBA-3 metrological subsystem.
---------------------------------------------------------
Title: Diagnostics of Coronal Magnetic Fields Through the Hanle
Effect in UV and IR Lines
Authors: Raouafi, Nour E.; Riley, Pete; Gibson, Sarah; Fineschi,
Silvano; Solanki, Sami K.
2016FrASS...3...20R Altcode: 2016arXiv160608493R
The plasma thermodynamics in the solar upper atmosphere, particularly in
the corona, are dominated by the magnetic field, which controls the flow
and dissipation of energy. The relative lack of knowledge of the coronal
vector magnetic field is a major handicap for progress in coronal
physics. This makes the development of measurement methods of coronal
magnetic fields a high priority in solar physics. The Hanle effect in
the UV and IR spectral lines is a largely unexplored diagnostic. We
use magnetohydrodynamic (MHD) simulations to study the magnitude of the
signal to be expected for typical coronal magnetic fields for selected
spectral lines in the UV and IR wavelength ranges, namely the HI Ly-α
and the He I 10830 Å lines. We show that the selected lines are useful
for reliable diagnosis of coronal magnetic fields. The results show
that the combination of polarization measurements of spectral lines
with different sensitivities to the Hanle effect may be most appropriate
for deducing coronal magnetic properties from future observations.
---------------------------------------------------------
Title: Measuring coronal magnetic fields with remote sensing
observations of shock waves
Authors: Bemporad, Alessandro; Susino, Roberto; Frassati, Federica;
Fineschi, Silvano
2016FrASS...3...17B Altcode: 2016arXiv160805536B
Recent works demonstrated that remote sensing observations of shock
waves propagating into the corona and associated with major solar
eruptions can be used to derive the strength of coronal magnetic
fields met by the shock over a very large interval of heliocentric
distances and latitudes. This opinion article will summarize most
recent results obtained on this topic and will discuss the weaknesses
and strengths of these techniques to open a constructive discussion
with the scientific community.
---------------------------------------------------------
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Yuan-Kuen; Moses, John; Laming, John; Strachan, Leonard;
Tun Beltran, Samuel; Tomczyk, Steven; Gibson, Sarah; Auchere, Frederic;
Casini, Roberto; Fineschi, Silvano; Knoelker, Michael; Korendyke,
Clarence; McIntosh, Scott; Romoli, Marco; Rybak, Jan; Socker, Dennis;
Vourlidas, Angelos; Wu, Qian
2016FrASS...3....1K Altcode:
Comprehensive measurements of magnetic fields in the solar corona have
a long history as an important scientific goal. Besides being crucial
to understanding coronal structures and the Sun’s generation of space
weather, direct measurements of their strength and direction are also
crucial steps in understanding observed wave motions. In this regard,
the remote sensing instrumentation used to make coronal magnetic field
measurements is well suited to measuring the Doppler signature of waves
in the solar structures. In this paper, we describe the design and
scientific values of the Waves and Magnetism in the Solar Atmosphere
(WAMIS) investigation. WAMIS, taking advantage of greatly improved
infrared filters and detectors, forward models, advanced diagnostic
tools and inversion codes, is a long-duration high-altitude balloon
payload designed to obtain a breakthrough in the measurement of
coronal magnetic fields and in advancing the understanding of the
interaction of these fields with space plasmas. It consists of a 20 cm
aperture coronagraph with a visible-IR spectro-polarimeter focal plane
assembly. The balloon altitude would provide minimum sky background and
atmospheric scattering at the wavelengths in which these observations
are made. It would also enable continuous measurements of the strength
and direction of coronal magnetic fields without interruptions from
the day-night cycle and weather. These measurements will be made
over a large field-of-view allowing one to distinguish the magnetic
signatures of different coronal structures, and at the spatial and
temporal resolutions required to address outstanding problems in
coronal physics. Additionally, WAMIS could obtain near simultaneous
observations of the electron scattered K-corona for context and to
obtain the electron density. These comprehensive observations are not
provided by any current single ground-based or space observatory. The
fundamental advancements achieved by the near-space observations of
WAMIS on coronal field would point the way for future ground based
and orbital instrumentation.
---------------------------------------------------------
Title: Towards a Data-Optimized Coronal Magnetic Field Model (DOC-FM):
Synthetic Test Beds and Multiwavelength Forward Modeling
Authors: Gibson, S. E.; Dalmasse, K.; Fan, Y.; Fineschi, S.; MacKay,
D.; Rempel, M.; White, S. M.
2015AGUFMSH54B..04G Altcode:
Understanding the physical state of the solar corona is key to
deciphering the origins of space weather as well as to realistically
representing the environment to be navigated by missions such as
Solar Orbiter and Solar Probe Plus. However, inverting solar coronal
observations to reconstruct this physical state -- and in particular
the three-dimensional coronal magnetic field - is complicated by
limited lines of sight and by projection effects. On the other hand,
the sensitivity of multiwavelength observations to different physical
mechanisms implies a potential for simultaneous probing of different
parts of the coronal plasma. In order to study this complementarity, and
to ultimately establish an optimal set of observations for constraining
the three-dimensional coronal magnetic field, we are developing a suite
of representative simulations to act as diagnostic test beds. We will
present three such test beds: a coronal active region, a quiescent
prominence, and a global corona. Each fully define the physical state
of density, temperature, and vector magnetic field in three dimensions
throughout the simulation domain. From these test beds, and using the
FORWARD SolarSoft IDL codes, we will create a broad range of synthetic
data. Radio observables will include intensity and circular polarization
(including gyroresonance effects) and Faraday rotation for a range of
frequencies. Infrared and visible forbidden line diagnostics of Zeeman
and saturated Hanle effects will yield full Stokes vector (I, Q, U,
V) synthetic data, and UV permitted line Hanle diagnostics will yield
intensity and linear polarization. In addition, we will synthesize
UV and SXR imager data, UV/EUV spectrometric data, and white light
brightness and polarized brightness. All of these synthetic data,
along with the "ground truth" physical state of the simulations from
which they are derived, will be made available to the community for
the purpose of testing coronal inversion techniques.
---------------------------------------------------------
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Strachan, L.; Ko, Y. -K.; Moses, J. D.; Laming, J. M.;
Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S.; Knoelker, M.;
Korendyke, C.; Mcintosh, S.; Romoli, M.; Rybak, J.; Socker, D.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
2015IAUS..305..121S Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exist only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure, solar
activity, and the role of MHD waves in heating and accelerating the
solar wind. Fortunately, the remote sensing instrumentation used to make
magnetic field measurements is also well suited to measure the Doppler
signature of waves in the solar structures. We present here a mission
concept for the Waves And Magnetism In the Solar Atmosphere (WAMIS)
experiment which is proposed for a NASA long-duration balloon flight.
---------------------------------------------------------
Title: Recurrent flares in active region NOAA 11283
Authors: Romano, P.; Zuccarello, F.; Guglielmino, S. L.; Berrilli, F.;
Bruno, R.; Carbone, V.; Consolini, G.; de Lauretis, M.; Del Moro, D.;
Elmhamdi, A.; Ermolli, I.; Fineschi, S.; Francia, P.; Kordi, A. S.;
Landi Degl'Innocenti, E.; Laurenza, M.; Lepreti, F.; Marcucci, M. F.;
Pallocchia, G.; Pietropaolo, E.; Romoli, M.; Vecchio, A.; Vellante,
M.; Villante, U.
2015A&A...582A..55R Altcode:
Context. Flares and coronal mass ejections (CMEs) are solar phenomena
that are not yet fully understood. Several investigations have
been performed to single out their related physical parameters that
can be used as indices of the magnetic complexity leading to their
occurrence. <BR /> Aims: In order to shed light on the occurrence of
recurrent flares and subsequent associated CMEs, we studied the active
region NOAA 11283 where recurrent M and X GOES-class flares and CMEs
occurred. <BR /> Methods: We use vector magnetograms taken by HMI/SDO
to calculate the horizontal velocity fields of the photospheric
magnetic structures, the shear and the dip angles of the magnetic
field, the magnetic helicity flux distribution, and the Poynting
fluxes across the photosphere due to the emergence and the shearing
of the magnetic field. <BR /> Results: Although we do not observe
consistent emerging magnetic flux through the photosphere during the
observation time interval, we detected a monotonic increase of the
magnetic helicity accumulated in the corona. We found that both the
shear and the dip angles have high values along the main polarity
inversion line (PIL) before and after all the events. We also note
that before the main flare of X2.1 GOES class, the shearing motions
seem to inject a more significant energy than the energy injected
by the emergence of the magnetic field. <BR /> Conclusions: We
conclude that the very long duration (about 4 days) of the horizontal
displacement of the main photospheric magnetic structures along the
PIL has a primary role in the energy release during the recurrent
flares. This peculiar horizontal velocity field also contributes to
the monotonic injection of magnetic helicity into the corona. This
process, coupled with the high shear and dip angles along the main
PIL, appears to be responsible for the consecutive events of loss
of equilibrium leading to the recurrent flares and CMEs. <P />A
movie associated to Fig. 4 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525887/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: The Shadow Positioning Sensors (SPS) for formation flying
metrology on-board the ESA-PROBA3 mission
Authors: Bemporad, A.; Baccani, C.; Capobianco, G.; Fineschi, S.;
Focardi, M.; Landini, F.; Loreggia, D.; Massone, G.; Nicolini, G.;
Noce, V.; Pancrazzi, M.; Romoli, M.; Buckley, S.; O'Neill, K.; Renotte,
E.; Servaye, J. S.; Thizy, C.
2015SPIE.9604E..0CB Altcode:
PROBA3 is an ESA technology mission devoted to in-orbit demonstration
of the formation flight (FF) technique, with two satellites kept at an
average inter-distance by about 144 m. The ASPIIC instrument on-board
PROBA3 will be the first ever space-based coronagraph working on
one satellite and having the external occulter located on the second
satellite, thus allowing observations of the inner solar corona with
unprecedented reduction of stray light. During the observational
periods, the FF configuration will be maintained with very high
precision and two different techniques will be implemented: the use of
Shadow Positioning Sensors (SPS) located on the Coronagraph Spacecraft
(diodes measuring the penumbral light intensity on the entrance pupil
plane) and the use of Occulter Position Sensor LEDs (OPSE) located
on the back side of the Occulter Spacecraft. This paper will review
the main instrumental requirements on the SPS needed to determine the
3-dimensional relative positioning of the two PROBA3 satellites with
high precision.
---------------------------------------------------------
Title: Design and modelisation of ASPIICS optics
Authors: Galy, C.; Fineschi, S.; Galano, D.; Howard, R. A.; Kintziger,
C.; Kirschner, V.; Koutchmy, S.; Lamy, P.; Mazzoli, A.; Melich, R.;
Mestreau-Garreau, A.; Renotte, E.; Servaye, J. S.; Stockman, Y.;
Thizy, C.; Zhukov, A.
2015SPIE.9604E..0BG Altcode:
In the framework of development of ASPIICS (Association of Spacecraft
for Polarimetric and Imaging Investigation of the Corona of the Sun),
the Centre Spatial de Liege is responsible of the optical design of
the coronagraph and the optics will be manufactured by TOPTEC. The
particularity of this coronagraph is to have an external occulter
located 150 m ahead of the first imaging lens. This external occulter
is re-imaged on an internal occulter which function is - as in a
classical externally occulted Lyot coronagraph - to block the sun
light diffracted by the external occulter and to reduce the straylight
on the detector. The selection of this configuration is driven by the
requirement to observe the corona as close as possible to the solar limb
(i.e. 1 R<SUB>Sun</SUB>) without imaging the limb itself. A requirement
of 1.08 R<SUB>Sun</SUB> is specified at optical design level to grant
1.2 R<SUB>sun</SUB> at instrument level. The coronograph instrument is
designed to have a field of view of 1.6° x 1.6° with a resolution of
less than 6 arcsec. Its performances are limited by diffraction in a
530 - 590 nm wavelength range. This paper presents the optical design
and demonstrates that by design the requirements are fulfilled within
the misalignment, manufacturing and thermo-elastic error contributions.
---------------------------------------------------------
Title: OPSE metrology system onboard of the PROBA3 mission of ESA
Authors: Loreggia, D.; Bemporad, A.; Capobianco, G.; Fineschi, S.;
Focardi, M.; Landini, F.; Massone, G.; Nicolini, G.; Pancrazzi, M.;
Romoli, M.; Cernica, I.; Purica, M.; Budianu, E.; Thizy, C.; Renotte,
E.; Servaye, J. S.
2015SPIE.9604E..0FL Altcode:
In recent years, ESA has assessed several mission involving formation
flying (FF). The great interest in this topics is mainly driven by the
need for moving from ground to space the location of next generation
astronomical telescopes overcoming most of the critical problems,
as example the construction of huge baselines for interferometry. In
this scenario, metrology systems play a critical role. PROBA3 is
an ESA technology mission devoted to in-orbit demonstration of the
FF technique, with two satellites, an occulter and a main satellite
housing a coronagraph named ASPIICS, kept at an average inter-distance
by about 144m, with micron scale accuracy. The guiding proposal is
to test several metrology solution for spacecraft alignment, with the
important scientific return of having observation of Corona at never
reached before angular field. The Shadow Position Sensors (SPS), and the
Optical Position Emitters Sensors (OPSE) are two of the systems used
for FF fine tracking. The SPS are finalized to monitor the position
of the two spacecraft with respect to the Sun and are discussed in
dedicated papers presented in this conference. The OPSE will monitor
the relative position of the two satellites and consists of 3 emitters
positioned on the rear surface of the occulter, that will be observed
by the coronagraph itself. By following the evolution of the emitters
images at the focal plane the alignment of the two spacecrafts is
retrieved via dedicated centroiding algoritm. We present an overview
of the OPSE system and of the centroiding approach.
---------------------------------------------------------
Title: Design status of ASPIICS, an externally occulted coronagraph
for PROBA-3
Authors: Renotte, Etienne; Alia, Andres; Bemporad, Alessandro;
Bernier, Joseph; Bramanti, Cristina; Buckley, Steve; Capobianco,
Gerardo; Cernica, Ileana; Dániel, Vladimir; Darakchiev, Radoslav;
Darmetko, Marcin; Debaize, Arnaud; Denis, François; Desselle,
Richard; de Vos, Lieve; Dinescu, Adrian; Fineschi, Silvano;
Fleury-Frenette, Karl; Focardi, Mauro; Fumel, Aurélie; Galano,
Damien; Galy, Camille; Gillis, Jean-Marie; Górski, Tomasz; Graas,
Estelle; Graczyk, Rafał; Grochowski, Konrad; Halain, Jean-Philippe
A.; Hermans, Aline; Howard, Russ; Jackson, Carl; Janssen, Emmanuel;
Kasprzyk, Hubert; Kosiec, Jacek; Koutchmy, Serge; Kovačičinová,
Jana; Kranitis, Nektarios; Kurowski, Michał; Ładno, Michał; Lamy,
Philippe; Landini, Federico; Lapáček, Radek; Lédl, Vít.; Liebecq,
Sylvie; Loreggia, Davide; McGarvey, Brian; Massone, Giuseppe; Melich,
Radek; Mestreau-Garreau, Agnes; Mollet, Dominique; Mosdorf, Łukasz;
Mosdorf, Michał; Mroczkowski, Mateusz; Muller, Raluca; Nicolini,
Gianalfredo; Nicula, Bogdan; O'Neill, Kevin; Orleański, Piotr;
Palau, Marie-Catherine; Pancrazzi, Maurizio; Paschalis, Antonios;
Patočka, Karel; Peresty, Radek; Popescu, Irina; Psota, Pavel; Rataj,
Miroslaw; Rautakoski, Jan; Romoli, Marco; Rybecký, Roman; Salvador,
Lucas; Servaye, Jean-Sébastien; Solomon, Cornel; Stockman, Yvan;
Swat, Arkadiusz; Thizy, Cédric; Thomé, Michel; Tsinganos, Kanaris;
Van der Meulen, Jim; Van Vooren, Nico; Vit, Tomáš; Walczak, Tomasz;
Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei
2015SPIE.9604E..0AR Altcode:
The "sonic region" of the Sun corona remains extremely difficult to
observe with spatial resolution and sensitivity sufficient to understand
the fine scale phenomena that govern the quiescent solar corona,
as well as phenomena that lead to coronal mass ejections (CMEs),
which influence space weather. Improvement on this front requires
eclipse-like conditions over long observation times. The space-borne
coronagraphs flown so far provided a continuous coverage of the external
parts of the corona but their over-occulting system did not permit to
analyse the part of the white-light corona where the main coronal mass
is concentrated. The proposed PROBA-3 Coronagraph System, also known
as ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun), with its novel design, will
be the first space coronagraph to cover the range of radial distances
between ~1.08 and 3 solar radii where the magnetic field plays a crucial
role in the coronal dynamics, thus providing continuous observational
conditions very close to those during a total solar eclipse. PROBA-3
is first a mission devoted to the in-orbit demonstration of precise
formation flying techniques and technologies for future European
missions, which will fly ASPIICS as primary payload. The instrument
is distributed over two satellites flying in formation (approx. 150m
apart) to form a giant coronagraph capable of producing a nearly perfect
eclipse allowing observing the sun corona closer to the rim than ever
before. The coronagraph instrument is developed by a large European
consortium including about 20 partners from 7 countries under the
auspices of the European Space Agency. This paper is reviewing the
recent improvements and design updates of the ASPIICS instrument as
it is stepping into the detailed design phase.
---------------------------------------------------------
Title: Formation flying metrology for the ESA-PROBA3 mission:
the Shadow Position Sensors (SPS) silicon photomultipliers (SiPMs)
readout electronics
Authors: Focardi, M.; Bemporad, A.; Buckley, S.; O'Neill, K.; Fineschi,
S.; Noce, V.; Pancrazzi, M.; Landini, F.; Baccani, C.; Capobianco,
G.; Romoli, M.; Loreggia, D.; Nicolini, G.; Massone, G.; Thizy, C.;
Servaye, J. S.; Renotte, E.
2015SPIE.9604E..0DF Altcode:
The European Space Agency (ESA) is planning to launch in 2018 the PROBA3
Mission, designed to demonstrate the inorbit formation flying (FF)
attitude capability of its two satellites and to observe the inner part
of the visible solar corona as the main scientific objective. The solar
corona will be observed thanks to the presence on the first satellite,
facing the Sun, of an external occulter producing an artificial eclipse
of the Sun disk. The second satellite will carry on the coronagraph
telescope and the digital camera system in order to perform imaging
of the inner part of the corona in visible polarized light, from
1.08 R<SUB>⦿</SUB> up to about 3 R<SUB>⦿</SUB>. One of the main
metrological subsystems used to control and to maintain the relative
(i.e. between the two satellites) and absolute (i.e. with respect to
the Sun) FF attitude is the Shadow Position Sensor (SPS) assembly. It
is composed of eight micro arrays of silicon photomultipliers (SiPMs)
able to measure with the required sensitivity and dynamic range the
penumbral light intensity on the Coronagraph entrance pupil. In the
following of the present paper we describe the overall SPS subsystem
and its readout electronics with respect to the capability to satisfy
the mission requirements, from the light conversion process on board the
silicon-based SPS devices up to the digital signal readout and sampling.
---------------------------------------------------------
Title: Significance of the occulter diffraction for the PROBA3/ASPIICS
formation flight metrology
Authors: Landini, Federico; Bemporad, Alessandro; Focardi, Mauro;
Fineschi, Silvano; Romoli, Marco; Pancrazzi, Maurizio; Baccani,
Cristian; Capobianco, Gerardo; Loreggia, Davide; Nicolini,
Gianalfredo; Massone, Giuseppe; Noce, Vladimiro; Thizy, Cédric;
Servaye, Jean-Sébastien; Renotte, Etienne
2015SPIE.9604E..0EL Altcode:
PROBA-3/ASPIICS is a formation flying coronagraph selected by ESA and
currently in its C/D phase. It is constituted by two spacecrafts (OSC,
Occulter SpaceCraft, carrying the occulter, diameter 142 cm, and CSC,
Coronagraph SpaceCraft, with the telescope) separated by ~144 m, kept
in strict alignment by means of an active custom system. The alignment
active system most critical components are the Shadow Positioning
Sensors (SPS), a series of Si-PM (Silicon Photomultiplier) measuring
the penumbra generated by the occulter. The arrangement of the SPSs
around the telescope entrance aperture is defined as a trade-off between
mechanical constraints and maximum sensitivity to misalignments. The
signal detected by the SPSs can be approximately simulated with a
geometrical analysis based on the variation of the penumbra generated
by the external occulter. The stray light generated by the diffraction
from the external occulter may affect the SPSs signal. It is mandatory
to carefully evaluate its level in order to refine the active alignment
adjustment algorithm. This work is dedicated to the description of the
preliminary investigation performed in order to evaluate the impact
of the diffraction on the SPSs signal.
---------------------------------------------------------
Title: Stray-light analyses of the METIS coronagraph on Solar Orbiter
Authors: Fineschi, S.; Sandri, P.; Landini, F.; Romoli, M.; DaDeppo,
V.; Frassetto, F.; Verroi, E.; Naletto, G.; Morea, D.; Antonucci,
E.; Spadaro, D.; Andretta, V.
2015SPIE.9604E..0KF Altcode:
The METIS coronagraph on board the Solar Orbiter mission will have the
unique opportunity of observing the solar outer atmosphere as close
to the Sun as 0.28 A.U., and from up to 35° out-of-ecliptic. The
telescope design of the METIS coronagraph includes two optical paths:
i) broad-band imaging of the full corona in linearly polarized
visible-light (VL: 580-640 nm), ii) narrow-band imaging of the full
corona in the ultraviolet (UV) Lyman α (121.6 nm). This paper describes
the stray-light analyses performed on the UV and VL channels of the
METIS Telescope with the nonsequential modality of Zemax OpticStudio. A
detailed opto-mechanical model of the METIS Telescope is simulated
by placing the CAD parts of all the sub-assemblies at the nominal
position. Each surface, mechanical and optical, is provided with a
modelled coating and BSDF reproducing the optical and the diffusing
properties. The geometric model allows for the verification of the
correct functioning of the blocking elements inside the telescope
and for an evaluation of the stray-light level due to surface
roughness. The diffraction off the inner edge of the IEO on the plane
of the IO is modelled separately from the contributor of the surface
micro-roughness. The contributors due to particle contamination and
cosmetic defects are also analysed. The results obtained are merged
together and compared to the requirements of stray-light. The results
of this analysis together with those from two different analyses based
on a Montecarlo ray-trace and a semi-analytical model are consistent
with each other and indicate that the METIS design meets the stray-light
level requirements
---------------------------------------------------------
Title: Illumination system in visible light with variable
solar-divergence for the solar orbiter METIS coronagraph
Authors: Tordi, M.; Bartolozzi, M.; Fineschi, S.; Capobianco, G.;
Massone, G.; Cesare, S.
2015SPIE.9604E..0VT Altcode:
The measurement of the stray-rejection capabilities of METIS is part
of the acceptance package of the instrument. The Illumination System
in Visible Light (ISVL) has been developed to allow the stray-light
rejection measurement down to 1x10<SUP>-9</SUP> and under different
operating conditions. The main characteristics of ISVL are outlined
and discussed; the activities for the integration and verification
of ISVL included the absolute radiometric characterization of the
facility, including radiance measurement and radiance spatial and
angular distribution. The procedures used to measure the performances
of the facility are discussed and the obtained results illustrated.
---------------------------------------------------------
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Y. K.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson,
S. E.; Knoelker, M.; Korendyke, C.; Laming, J. M.; Mcintosh, S. W.;
Moses, J. D.; Romoli, M.; Rybak, J.; Socker, D. G.; Strachan, L.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
2014AGUFMSH53B4221K Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exists only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure,
solar activity and the role of MHD waves in heating and accelerating
the solar wind. Fortunately, the remote sensing instrumentation used
to make magnetic field measurements is also well suited for measuring
the Doppler signature of waves in the solar structures. With this
in mind, we are proposing the WAMIS (Waves and Magnetism in the
Solar Atmosphere) investigation. WAMIS will take advantage of greatly
improved infrared (IR) detectors, forward models, advanced diagnostic
tools and inversion codes to obtain a breakthrough in the measurement
of coronal magnetic fields and in the understanding of the interaction
of these fields with space plasmas. This will be achieved with a high
altitude balloon borne payload consisting of a coronagraph with an IR
spectro-polarimeter focal plane assembly. The balloon platform provides
minimum atmospheric absorption and scattering at the IR wavelengths in
which these observations are made. Additionally, a NASA long duration
balloon flight mission from the Antarctic can achieve continuous
observations over most of a solar rotation, covering all of the key
time scales for the evolution of coronal magnetic fields. With these
improvements in key technologies along with experience gained from
current ground-based instrumentation, WAMIS will provide a low-cost
mission with a high technology readiness leve.
---------------------------------------------------------
Title: ASPIICS: an externally occulted coronagraph for PROBA-3:
Design evolution
Authors: Renotte, Etienne; Baston, Elena Carmen; Bemporad,
Alessandro; Capobianco, Gerardo; Cernica, Ileana; Darakchiev,
Radoslav; Denis, François; Desselle, Richard; De Vos, Lieve;
Fineschi, Silvano; Focardi, Mauro; Górski, Tomasz; Graczyk, Rafał;
Halain, Jean-Philippe; Hermans, Aline; Jackson, Carl; Kintziger,
Christian; Kosiec, Jacek; Kranitis, Nektarios; Landini, Federico;
Lédl, Vít.; Massone, Giuseppe; Mazzoli, Alexandra; Melich, Radek;
Mollet, Dominique; Mosdorf, Michał; Nicolini, Gianalfredo; Nicula,
Bogdan; Orleański, Piotr; Palau, Marie-Catherine; Pancrazzi, Maurizio;
Paschalis, Antonis; Peresty, Radek; Plesseria, Jean-Yves; Rataj,
Miroslaw; Romoli, Marco; Thizy, Cédric; Thomé, Michel; Tsinganos,
Kanaris; Wodnicki, Ryszard; Walczak, Tomasz; Zhukov, Andrei
2014SPIE.9143E..2MR Altcode:
PROBA-3 is a mission devoted to the in-orbit demonstration of
precise formation flying techniques and technologies for future ESA
missions. PROBA-3 will fly ASPIICS (Association de Satellites pour
l'Imagerie et l'Interferométrie de la Couronne Solaire) as primary
payload, which makes use of the formation flying technique to form a
giant coronagraph capable of producing a nearly perfect eclipse allowing
to observe the sun corona closer to the rim than ever before. The
coronagraph is distributed over two satellites flying in formation
(approx. 150m apart). The so called Coronagraph Satellite carries the
camera and the so called Occulter Satellite carries the sun occulter
disc. This paper is reviewing the design and evolution of the ASPIICS
instrument as at the beginning of Phase C/D.
---------------------------------------------------------
Title: Polarimetric calibrations and astronomical polarimetry in
the V-band with Solar Orbiter/METIS instrument
Authors: Capobianco, Gerardo; Fineschi, Silvano; Focardi, Mauro;
Andretta, Vincenzo; Massone, Giuseppe; Bemporad, Alessandro; Romoli,
Marco; Antonucci, Ester; Naletto, Giampiero; Nicolini, Gianalfredo;
Nicolosi, Piergiorgio; Spadaro, Daniele
2014SPIE.9143E..4VC Altcode:
METIS is one of the remote sensing instruments on board the ESA-
Solar Orbiter mission, that will be launched in July 2017. The Visible
Light Channel (VLC) of the instrument is composed by an achromatic
LC-based polarimeter for the study of the linearly polarized solar
K-corona in the 580-640 nm bandpass. The laboratory calibrations with
spectropolarimetric techniques and the in-flight calibrations of this
channel, using some well knows linearly polarized stars in the FoV
of the instrument with a degree of linear polarization DOLP > 10%
are here discussed. The selection of the stars and the use of other
astronomical targets (i.e. planets, comets,…) and the opportunity
of measurements of the degree of linear polarization in the visible
bandpass of some astronomical objects (i.e. Earth, comets,…) are
also objects of this paper.
---------------------------------------------------------
Title: On-board CME detection algorithm for the Solar Orbiter-METIS
coronagraph
Authors: Bemporad, A.; Andretta, V.; Pancrazzi, M.; Focardi, M.;
Straus, T.; Sasso, C.; Spadaro, D.; Uslenghi, M.; Antonucci, E.;
Fineschi, S.; Abbo, L.; Nicolini, G.; Landini, F.; Romoli, M.; Naletto,
G.; Nicolosi, P.
2014SPIE.9152E..0KB Altcode:
The METIS coronagraph is one of the instruments part of the payload of
the ESA - Solar Orbiter mission to be launched in 2017. The spacecraft
will operate much like a planetary encounter mission, with the main
scientific activity taking place with the remote-sensing instruments
during three 10-days intervals per orbit: optimization of the different
instrument observing modes will be crucial. One of the key scientific
targets of METIS will be the study of transient ejections of mass
through the solar corona (Coronal Mass Ejections - CMEs) and their
heliospheric evolution. METIS will provide for the first time imaging of
CMEs in two different wavelengths: VL (visible light 580- 640 nm) and UV
(Lyman-α line of HI at 121.6 nm). The detection of transient phenomena
shall be managed directly by the METIS Processing and Power Unit (MPPU)
by means of both external triggers ("flags") coming from other Solar
Orbiter instruments, and internal "flags" produced directly by the METIS
on-board software. METIS on-board algorithm for the automatic detection
of CMEs will be based on running differences between consecutive images
re-binned to very low resolution and thresholded for significant changes
over a minimum value. Given the small relative variation of white light
intensity during CMEs, the algorithm will take advantage of VL images
acquired with different polarization angles to maximize the detection
capability: possible false detections should be automatically managed
by the algorithm. The algorithm will be able to provide the CME first
detection time, latitudinal direction of propagation on the plane
of the sky (within 45 degrees), a binary flag indicating whether a
"halo CME" has been detected.
---------------------------------------------------------
Title: Coating and surface finishing definition for the Solar
Orbiter/METIS inverted external occulter
Authors: Landini, Federico; Romoli, Marco; Vives, Sebastien; Baccani,
Cristian; Escolle, Clement; Pancrazzi, Maurizio; Focardi, Mauro;
Da Deppo, Vania; Moses, John D.; Fineschi, Silvano
2014SPIE.9151E..5HL Altcode:
The METIS coronagraph aboard the Solar Orbiter mission will undergo
extreme environmental conditions (e.g., a thermal excursion of about
350 degrees throughout the various mission phases), due to the peculiar
spacecraft trajectory that will reach a perihelion of 0.28 AUs. METIS
is characterized by an innovative design for the occultation system
that allows to halve the thermal load inside the instrument while
guaranteeing the stray light reduction that is required for a solar
coronagraph. The Inverted External Occulter (IEO) concept revolutionizes
the classical scheme, by exchanging the usual positions of the entrance
aperture (that is now the outermost element of the instrument facing
the Sun) with the actual occulter (that is a spherical mirror inside
the coronagraph boom). The chosen material for the IEO manufacturing
is Titanium, as a trade o_ between light weight, strength and low
thermal expansion coefficient. A 2 years long test campaign has
been run to define the IEO geometry, and its results are addressed
in previous dedicated papers. This work describes the results of a
further campaign aimed at defining the IEO surface and edge finishing,
the support flange geometry and the Titanium coating. Various edge
finishing were installed on a prototype of the instrument occulting
system and their performance in stray light reduction were compared. The
support flange geometry was designed in order to reduce the overall
weight, to control the thermal load and to accentuate its stray light
suppression performance. The coating is a particularly delicate issue. A
black coating is necessary in order to assess the stray light issues,
typically critical for visible coronagraphs. Black coating of Titanium
is not a standard process, thus several space qualified black coatings
were experimented on Titanium and characterized. The impact of the IEO
coatings was evaluated, the reflectivity and the BRDFs were measured
and are addressed in the paper.
---------------------------------------------------------
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: 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: On-board detection and removal of cosmic ray and solar
energetic particle signatures for the Solar Orbiter-METIS coronagraph
Authors: Andretta, V.; Bemporad, A.; Focardi, M.; Grimani, C.;
Landini, F.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Straus, T.;
Uslenghi, M. C.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolini,
G.; Nicolosi, P.; Romoli, M.
2014SPIE.9152E..2QA Altcode:
METIS is part of the science payload of Solar Orbiter. It is a
coronagraph designed to obtain images of the outer solar corona both in
the visible 580-640 nm band and in the UV, in a narrow band centered
around the hydrogen Lyman-α line. We describe the main features of
the procedures to remove signatures due to cosmic rays (CRs) and to
solar energetic particles (SEPs) comparing them with alternatives in
other contexts and in other solar coronagraphic missions. Our analysis
starts from a realistic assessment of the radiation environment where
the instrument is expected to operate, which is characteristic of the
interplanetary space of the inner solar system, but quite unusual for
most solar missions.
---------------------------------------------------------
Title: NEOCE: a new external occulting coronagraph experiment for
ultimate observations of the chromosphere, corona and interface
Authors: Damé, Luc; Fineschi, Silvano; Kuzin, Sergey; Von
Fay-Siebenburgen, Erdélyi Robert
2014cosp...40E.617D Altcode:
Several ground facilities and space missions are currently dedicated
to the study of the Sun at high resolution and of the solar corona
in particular. However, and despite significant progress with the
advent of space missions and UV, EUV and XUV direct observations
of the hot chromosphere and million-degrees coronal plasma, much is
yet to be achieved in the understanding of these high temperatures,
fine dynamic dissipative structures and of the coronal heating in
general. Recent missions have shown the definite role of a wide
range of waves and of the magnetic field deep in the inner corona,
at the chromosphere-corona interface, where dramatic and physically
fundamental changes occur. The dynamics of the chromosphere and corona
is controlled and governed by the emerging magnetic field. Accordingly,
the direct measurement of the chromospheric and coronal magnetic fields
is of prime importance. The solar corona consists of many localised
loop-like structures or threads with the plasmas brightening and
fading independently. The plasma evolution in each thread is believed
to be related to the formation of filaments, each one being dynamic,
in a non-equilibrium state. The mechanism sustaining this dynamics,
oscillations or waves (Alfvén or other magneto-plasma waves),
requires both very high-cadence, multi-spectral observations, and high
resolution and coronal magnetometry. This is foreseen in the future
Space Mission NEOCE (New External Occulting Coronagraph Experiment),
the ultimate new generation high-resolution coronagraphic heliospheric
mission, to be proposed for ESA M4. NEOCE, an evolution of the HiRISE
mission, is ideally placed at the L5 Lagrangian point (for a better
follow-up of CMEs), and provides FUV imaging and spectro-imaging,
EUV and XUV imaging and spectroscopy, and ultimate coronagraphy by
a remote external occulter (two satellites in formation flying 375 m
apart minimizing scattered light) allowing to characterize temperature,
densities and velocities up to the solar upper chromosphere, transition
zone and inner corona with, in particular, 2D very high resolution
multi-spectral imaging-spectroscopy and direct coronal magnetic field
measurement: a unique set of tools to understand the structuration and
onset of coronal heating. We give a detailed account of the proposed
mission profile, and its major scientific objectives and model payload
(in particular of the SuperASPIICS package of visible, NIR and UV,
Lyman-Alpha and OVI, coronagraphs).
---------------------------------------------------------
Title: HeMISE (Helio-Magnetism Investigation from the Sun to Earth):
a twin spacecraft mission at the Sun-Earth Lagrangian points L4 and L5
Authors: Bemporad, Alessandro; Fineschi, Silvano; Focardi, Mauro;
Landini, Federico; Romoli, Marco; Pancrazzi, Maurizio
2014cosp...40E.275B Altcode:
The Sun-Earth environment is a much more dynamic and eventful system
than the common-life experience of looking at the sky can suggest and
severe disturbances on the Earth magnetic field called geomagnetic
storms often occur. These sudden disturbances can adversely affect
the health of humans in space and in high altitude commercial
flights. Further advancing in our forecasting capabilities of these
storms will necessary requires a much deeper understanding of the
origin on the Sun and propagation in the interplanetary medium of
these disturbances. This means that we need a better understanding
of how magnetic fields are generated in the solar interior, how
their emergence through the photosphere, their storage and release
in the lower corona, and the final connection with our planet: a
mission specifically dedicated to this objective is needed. So far
measurements of the solar magnetic field are mostly restricted to the
low layers of the solar atmosphere. Extrapolation techniques underlying
numerous assumptions are used to estimate the magnetic field in the
transition region from the chromospheres to the corona and in the corona
itself. More recently, ground-based spectropolarimetry has proven to
be very useful to provide information of the coronal magnetic fields on
the plane of the sky, but there are no spacecraft providing at the same
time measurement of photospheric fields responsible for the coronal
configuration. The solution will be offered by a multi-spacecraft
mission designed to study at the same time photospheric and coronal
magnetic fields and the interplanetary evolution of generated solar
transients propagating along the Sun-Earth line. The HeMISE mission
will investigate the emission and its polarization from the extreme
ultraviolet to the white light wavelengths regimes. This will be done
by 2 twin spacecraft, carrying remote sensing and in situ instruments,
located in stable orbits around L4 and L5 Lagrangian points. Twin
spacecraft with photospheric and coronal magnetometers will open the
possibility for stereoscopic global helioseismology and will allow
for the first time to combine photospheric fields measured by one
spacecraft with coronal fields measured by the second spacrecraft
in quasi-quadrature, thus providing for the first time a continuous
coverage of solar magnetic fields through the solar atmosphere. The
main concepts of this mission will be illustrated here.
---------------------------------------------------------
Title: SCORE - Sounding-rocket Coronagraphic Experiment
Authors: Fineschi, Silvano; Moses, Dan; Romoli, Marco
2014cosp...40E.869F Altcode:
The Sounding-rocket Coronagraphic Experiment - SCORE - is a The
Sounding-rocket Coronagraphic Experiment - SCORE - is a coronagraph for
multi-wavelength imaging of the coronal Lyman-alpha lines, HeII 30.4 nm
and HI 121.6 nm, and for the broad.band visible-light emission of the
polarized K-corona. SCORE has flown successfully in 2009 acquiring the
first images of the HeII line-emission from the extended corona. The
simultaneous observation of the coronal Lyman-alpha HI 121.6 nm,
has allowed the first determination of the absolute helium abundance
in the extended corona. This presentation will describe the lesson
learned from the first flight and will illustrate the preparations
and the science perspectives for the second re-flight approved by
NASA and scheduled for 2016. The SCORE optical design is flexible
enough to be able to accommodate different experimental configurations
with minor modifications. This presentation will describe one of such
configurations that could include a polarimeter for the observation the
expected Hanle effect in the coronal Lyman-alpha HI line. The linear
polarization by resonance scattering of coronal permitted line-emission
in the ultraviolet (UV) can be modified by magnetic fields through the
Hanle effect. Thus, space-based UV spectro-polarimetry would provide
an additional new tool for the diagnostics of coronal magnetism.
---------------------------------------------------------
Title: MASC: Magnetic Activity of the Solar Corona
Authors: Auchere, Frederic; Fineschi, Silvano; Gan, Weiqun; Peter,
Hardi; Vial, Jean-Claude; Zhukov, Andrei; Parenti, Susanna; Li, Hui;
Romoli, Marco
2014cosp...40E.149A Altcode:
We present MASC, an innovative payload designed to explore the magnetic
activity of the solar corona. It is composed of three complementary
instruments: a Hard-X-ray spectrometer, a UV / EUV imager, and a Visible
Light / UV polarimetric coronagraph able to measure the coronal magnetic
field. The solar corona is structured in magnetically closed and
open structures from which slow and fast solar winds are respectively
released. In spite of much progress brought by two decades of almost
uninterrupted observations from several space missions, the sources and
acceleration mechanisms of both types are still not understood. This
continuous expansion of the solar atmosphere is disturbed by sporadic
but frequent and violent events. Coronal mass ejections (CMEs) are
large-scale massive eruptions of magnetic structures out of the corona,
while solar flares trace the sudden heating of coronal plasma and the
acceleration of electrons and ions to high, sometimes relativistic,
energies. Both phenomena are most probably driven by instabilities
of the magnetic field in the corona. The relations between flares
and CMEs are still not understood in terms of initiation and energy
partition between large-scale motions, small-scale heating and
particle acceleration. The initiation is probably related to magnetic
reconnection which itself results magnetic topological changes due to
e.g. flux emergence, footpoints motions, etc. Acceleration and heating
are also strongly coupled since the atmospheric heating is thought to
result from the impact of accelerated particles. The measurement of
both physical processes and their outputs is consequently of major
importance. However, despite its fundamental importance as a driver
for the physics of the Sun and of the heliosphere, the magnetic field
of our star’s outer atmosphere remains poorly understood. This
is due in large part to the fact that the magnetic field is a very
difficult quantity to measure. Our knowledge of its strength and
orientation is primarily based on extrapolations from photospheric
observations, not from direct measurements. These extrapolations
require strong assumptions on critical but unobserved quantities and
thus fail to accurately reproduce the complex topologies inferred
from remote-sensing observations of coronal structures in white
light, EUV, and X-rays. Direct measurements of the coronal magnetic
field are also clearly identified by the international heliophysics
community as a key element susceptible to lead to major breakthroughs
in the understanding of our star. MASC is thus designed to answer
the following top-level scientific questions: 1. What is the global
magnetic field configuration in the corona? 2. What is the role of
the magnetic field in the triggering of flares and CMEs? 3. What is
the role of the magnetic field in the acceleration mechanisms of the
solar winds? 4. What is the energy spectrum and in particular what are
the highest energies to which charged particles can be accelerated in
the solar corona? MASC will address these fundamental questions with
a suite of instruments composed of an X-ray spectrometer, a UV / EUV
imager, and a coronagraph working in the visible and at Lyman alpha. The
spectrometer will provide information on the energetics of solar flares,
in particular at very high energies of accelerated particles. The
UV / EUV imager will provide constraints on the temperature of the
flaring and non-flaring corona. The coronagraph will provide the number
density of free electrons in the corona, maps of the outflow velocity
of neutral hydrogen, and measurements of the coronal magnetic field,
via the Hanle effect. These measurements will be performed at all
steps of the flare-CME processes, thus providing a detailed picture
of the solar coronal dynamics in the quiet and eruptive periods.
---------------------------------------------------------
Title: Occultation systems in space-borne telescopes dedicated to
the observation of the solar corona
Authors: Landini, Federico; Fineschi, Silvano; Moses, Daniel;
Romoli, Marco
2014cosp...40E1747L Altcode:
The observation of the solar corona in white light is a challenging task
because of the poor contrast of the signal (i.e., the solar corona)
to the stray light noise. The main task a coronagraph or heliospheric
imager designer shall face is the reduction of the stray light. This
is particularly important in space-borne instruments with an external
occultation. A large part of the field literature is dedicated to
the optimization of the occulting system in order to reduce the
total amount of stray light on the instrument focal plane. From the
pioneering work of Newkirk and Bohlin in 1965, several solutions have
been elaborated in optimizing the occulters shape. Despite a series of
classical optimizing shapes has been employed in many solar missions,
each optimization shall fit the constraint of the instrument design and
of the mission characteristics. Forthcoming solar space missions such
as ASPIICS on PROBA3 (formation flight) and Solar Orbiter (approaching
the Sun with a perihelion of 0.28 AU) will introduce considerable
technological innovations and their characteristics impose demanding
efforts on the scientific payloads in order to be compliant with
the constraints. This work reviews the most effective occultation
systems that have been employed by past coronagraphs, spectrographs
and heliospheric imagers. Moreover, it illustrates the innovative
solutions that are going to be adopted by the missions to come.
---------------------------------------------------------
Title: Space- and Ground-based Coronal Spectro-Polarimetry
Authors: Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan;
Capobianco, Gerardo
2014cosp...40E.868F Altcode:
This presentation gives an overview of the near-future perspectives of
ultraviolet and visible-light spectro-polarimetric instrumentation
for probing coronal magnetism from space-based and ground-based
observatories. Spectro-polarimetric imaging of coronal emission-lines
in the visible-light wavelength-band provides an important diagnostics
tool of the coronal magnetism. The interpretation in terms of Hanle and
Zeeman effect of the line-polarization in forbidden emission-lines
yields information on the direction and strength of the coronal
magnetic field. As study case, this presentation will describe the
Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric
observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag
- consisting of a Liquid Crystal (LC) Lyot filter and a LC linear
polarimeter - has been recently installed on the Lomnicky Peak
Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag
will be presented. The linear polarization by resonance scattering
of coronal permitted line-emission in the ultraviolet (UV)can be
modified by magnetic fields through the Hanle effect. Space-based
UV spectro-polarimeters would provide an additional tool for the
disgnostics of coronal magnetism. As a case study of space-borne
UV spectro-polarimeters, this presentation will describe the future
upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to
include the capability of imaging polarimetry of the HI Lyman-alpha,
121.6 nm. SCORE is a multi-wavelength imager for the emission-lines,
HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission
of the polarized K-corona. SCORE has flown successfully in 2009. This
presentation will describe how in future re-flights SCORE could observe
the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.
---------------------------------------------------------
Title: Formation Flying Instrumentation for Remote Sensing of the
Solar Corona
Authors: Moses, Daniel; Fineschi, Silvano
2014cosp...40E2183M Altcode:
The Sun is the closest and most luminous astrophysical object, yet
observational advances in many aspects of solar physics are limited by
photometric/spatial/temporal/spectral/polarimetric resolution. Increased
aperture and longer optical throws are essential build on the advances
achieved in the SOHO, STEREO, Hinode and SDO missions. However, in the
case of space-based investigations, simply enlarging prior instrument
designs quickly leads to a payload mass greatly exceeding the current
launch options. By separating an otherwise large instrument into two
or more smaller, separate spacecraft flying in precise formation, one
can dramatically reduce launch mass - although at the cost of more
sophisticated spacecraft systems. This presentation will review the
current formation flying state of the art and explore possibilities for
future application of this technology to remote sensing investigations
of the solar corona
---------------------------------------------------------
Title: Solar-Sail CubeSats for Space Weather Monitoring from
Earth-Sun L-points
Authors: Fineschi, Silvano; Bemporad, Alessandro; Landini, Federico;
Vola, Nicole; Circi, Christian; Viscio, Maria Antonietta; Fumenti,
Federico
2014cosp...40E.870F Altcode:
This presentation describes the possibilities for space weather
monitoring that solar-sail CubeSats would enable from the Sun-Earth
L-points. The mission proposed consists of a 6U CubeSats system with
solar-sail propulsion to reach and orbit the L4 and L5 Earth-Sun
Lagragian points. The payload would include compact "in-situ"
instrumentation (e.g., radiation dosimeters) and a miniature
visible-light, wide-angle coronagraph (WACor). The WACor observations
of Coronal Mass Ejections (CMEs) travelling along the the Earth-Sun
interplanetary space would allow early warning of geo-effective solar
storms. This presentation will illustrate the mission profile and
the solar-sail orbit at the L-points, and will describe the expected
performances of the miniature WACor in detecting fast (>1000 km/s),
Earth-directed CMEs.
---------------------------------------------------------
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: Preliminary internal straylight analysis of the METIS
instrument for the Solar Orbiter ESA mission
Authors: Verroi, Enrico; Da Deppo, Vania; Naletto, Giampiero; Fineschi,
Silvano; Antonucci, Ester
2012SPIE.8442E..4NV Altcode:
METIS, the multi element telescope for imaging and spectroscopy, is
a solar coronagraph foreseen for the Solar Orbiter mission. METIS is
conceived to observe the solar corona from a near-sun orbit in three
different spectral bands: in the HeII EUV narrow band at 30.4 nm,
in the HI UV narrow band at 121.6 nm, and in the visible light band
(500 - 650 nm). The visible light from the corona is ten million times
fainter than the light emitted by the solar disk, so a very stringent
light suppression design is needed for the visible channel. METIS
adopts an “inverted occulted” configuration, where the disk light is
shielded by an annular shape occulter, after which an annular aspherical
mirror M1 collects the signal coming from the corona. The disk light
heading through M1 is back-rejected by a suitable spherical mirror
M0. This paper presents the stray light analysis for this new-concept
configuration, performed with a ray tracing simulation, to insure the
opto-mechanical design grants a stray light level below the limit of
10<SUP>-9</SUP> times the coronal signal intensity. A model of the
optics and of the mechanical parts of the telescope has been realized
with ASAP (Breault Research TM); by means of a Montecarlo ray tracing,
the effect of stray light on VIS and UV&#69UV channels has been
simulated.
---------------------------------------------------------
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: Optimization of the occulter for the Solar Orbiter/METIS
coronagraph
Authors: Landini, Federico; Vivès, Sébastien; Romoli, Marco; Guillon,
Christophe; Pancrazzi, Maurizio; Escolle, Clement; Focardi, Mauro;
Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Nicolini,
Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele
2012SPIE.8442E..27L Altcode:
METIS (Multi Element Telescope for Imaging and Spectroscopy
investigation), selected to fly aboard the Solar Orbiter ESA/NASA
mission, is conceived to perform imaging (in visible, UV and EUV) and
spectroscopy (in EUV) of the solar corona, by means of an integrated
instrument suite located on a single optical bench and sharing the
same aperture on the satellite heat shield. As every coronagraph, METIS
is highly demanding in terms of stray light suppression. Coronagraphs
history teaches that a particular attention must be dedicated to the
occulter optimization. The METIS occulting system is of particular
interest due to its innovative concept. In order to meet the strict
thermal requirements of Solar Orbiter, METIS optical design has been
optimized by moving the entrance pupil at the level of the external
occulter on the S/C thermal shield, thus reducing the size of the
external aperture. The scheme is based on an inverted external-occulter
(IEO). The IEO consists of a circular aperture on the Solar Orbiter
thermal shield. A spherical mirror rejects back the disk-light
through the IEO. A breadboard of the occulting assembly (BOA) has
been manufactured in order to perform stray light tests in front of
two solar simulators (in Marseille, France and in Torino, Italy). A
first measurement campaign has been carried on at the Laboratoire
d'Astrophysique de Marseille. In this paper we describe the BOA design,
the laboratory set-up and the preliminary results.
---------------------------------------------------------
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: Analysis of optical efficiency of METIS coronagraph telescope
on board of the Solar Orbiter mission
Authors: Polito, V.; Corso, A. J.; Zuppella, P.; Nicolosi, P.;
Fineschi, S.; Antonucci, E.; Windt, D. L.; Pelizzo, M. G.
2012SPIE.8443E..3GP Altcode:
The Multi Element Telescope for Imaging and Spectroscopy (METIS)
coronagraph is an instrument belonging to the SOLar Orbiter(SOLO)
mission payload which will perform the imaging of the solar corona
in three different spectral ranges: 30.4 nm (He-II Lyman-α line),
121.6 nm (H-I Lyman- α line) and visible spectral range (500-650
nm). Optical coatings with high reflectance performances at the
interested wavelengths are required to collect enough light at the
detector level. Different multilayer structures based on Si/Mo couples
with appropriate capping layers have been already designed and tested to
achieve this purpose. A model has been developed in order to estimate
the efficiency's performances of the instrument on the whole field of
view (FoV) by considering the ray paths. The results shown have been
obtained taking into account of the experimental results on multilayers
structures previously tested and the optical design of the instrument.
---------------------------------------------------------
Title: Electro-optical polarimeters for ground-based and space-based
observations of the solar K-corona
Authors: Capobianco, G.; Fineschi, S.; Massone, G.; Balboni, E.;
Malvezzi, A. M.; Crescenzio, G.; Zangrilli, L.; Calcidese, P.;
Antonucci, E.; Patrini, M.
2012SPIE.8450E..40C Altcode:
Polarimeters based on electro-optically tunable liquid crystals
(LC) represent a new technology in the field of observational
astrophysics. LC-based polarimeters are good candidates for replacing
mechanically rotating polarimeters in most ground-based and space-based
applications. During the 2006 total solar eclipse, we measured the
visible-light polarized brightness (pB) of the solar K-corona with
a LC-based polarimeter and imager (E-KPol). In this presentation,
we describe the results obtained with the E-KPol, and we evaluate its
performances in view of using a similar device for the pB imaging of
the K-corona from space-based coronagraphs. Specifically, a broad-band
LC polarimeter is planned for the METIS (Multi Element Telescope for
Imaging and Spectroscopy) coronagraph for the Solar Orbiter mission to
be launched in 2017. The METIS science driver of deriving the coronal
electron density from pB images requires an accuracy of better than 1%
in the measurement of linear polarization. We present the implications
of this requirement on the METIS design to minimize the instrumental
polarization of the broad-band visible-light (590-650 nm) polarimeter
and of the other optics in the METIS visible-light path. Finally, we
report preliminary ellipsometric measurements of the optical components
of the METIS visible-light path.
---------------------------------------------------------
Title: The processing and power unit of the METIS coronagraph aboard
the Solar Orbiter space mission
Authors: Focardi, M.; Pancrazzi, M.; Uslenghi, M.; Nicolini, G.;
Magli, E.; Landini, F.; Romoli, M.; Antonucci, E.; Fineschi, S.;
Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Gennaro, C.;
Zoppo, G. P.; Stevoli, A.; Battistelli, E.; Rusconi, A.
2012SPIE.8442E..4IF Altcode:
The Multi Element Telescope for Imaging and Spectroscopy (METIS) is the
coronagraph selected for the Solar Orbiter payload, adopted in October
2011 by ESA for the following Implementation Phase. The instrument
design has been conceived by a team composed by several research
institutes with the aim to perform both VIS and EUV narrow-band
imaging and spectroscopy of the solar corona. METIS, owing to its
multi-wavelength capability, will address some of the major open issues
in understanding the physical processes in the corona and the solar
wind origin and properties, exploiting the unique opportunities offered
by the SO mission profile. The METIS Processing and Power Unit (MPPU)
is the Instrument's power supply and on-board data handling modular
electronics, designed to address all the scientific requirements of
the METIS Coronagraph. MPPU manages data and command flows, the timing
and power distribution networks and its architecture reflects several
trade-off solutions with respect to the allocated resources in order
to reduce any possible electronics single-point failure. This paper
reports on the selected HW and SW architectures adopted after the
Preliminary Design Review (PDR), performed by ESA in early 2012.
---------------------------------------------------------
Title: MESSI: the METIS instrument software simulator
Authors: Nicolini, G.; Andretta, V.; Abbo, L.; Antonucci, E.; Bemporad,
A.; Capobianco, G.; Crescenzio, G.; Fineschi, S.; Focardi, M.; Magli,
E.; Naletto, G.; Nicolosi, G.; Pancrazzi, M.; Ricci, M.; Romoli, M.;
Uslenghi, M.; Volpicelli, A.
2012SPIE.8449E..1LN Altcode:
Instrument software simulators are becoming essential both for
supporting the instrument design and for planning the future
operations. In this paper we present the Software Simulator developed
for the METIS coronagraph, an instrument of the Solar Orbiter ESA
mission. We describe its architecture and the modules it is composed
of, and how they interchange data to simulate the whole acquisition
chain from the photons entering the front window to the stream
of telemetry? data received and analysed on ground. Each software
module simulates an instrument subsystem by combining theoretical
models and measured subsystem properties. A web-based application
handles the remote user interfaces of the Institutions of the METIS
Consortium, allowing users from various sites to overview and interact
with the data flow, making possible for instance input and output at
intermediate nodes. Description of the modes of use of the simulator,
both present and future, are given with examples of results. These
include not only design-aid tasks, as the evaluation and the tuning
of the image compression algorithms, but also those tasks aimed to
plan the in-flight observing sequences, based on the capability of
the simulator of performing end to end simulations of science cases.
---------------------------------------------------------
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: Imaging polarimetry with the METIS coronagraph of the Solar
Orbiter mission
Authors: Crescenzio, Giuseppe; Fineschi, Silvano; Capobianco, Gerardo;
Nicolini, Gianalfredo; Massone, Giuseppe; Malvezzi, Marco A.; Landini,
Federico; Romoli, Marco; Antonucci, Ester
2012SPIE.8443E..3JC Altcode:
METIS, the "Multi Element Telescope for Imaging and Spectroscopy", is a
coronagraph of the Solar Orbiter mission to be launched in 2017. The
METIS coronagraph includes three optical paths for i) broad-band
imaging of the full corona in polarized visible-light (590-650 nm);
ii) narrow-band coronal imaging in the UV HI Ly α (121.6 nm) and
extreme-UV He II Ly α (30.4 nm), and iii) spectroscopic observations
of the HI and He II Ly α. This presentation describes the optical
design of the METIS visible-light path for imaging polarimetry of the
K-corona. The achromatic polarimeter's requirements on polarization
sensitivity, achromatic response and instrumental polarization control
are described. The expected performances of the visible-light path
are also presented.
---------------------------------------------------------
Title: ESCAPE : a first step to high resolution solar coronagraphy
in Antarctica
Authors: Damé, L.; Abe, L.; Faurobert, M.; Fineschi, S.; Kuzin, S.;
Lamy, P.; Meftah, M.; Vives, S.
2012EAS....55..359D Altcode:
The Dome C high plateau is unique for coronagraphic observations: sky
brightness is reduced, water vapour is low, seeing is excellent and
continuity of observations on several weeks is possible. ESCAPE (the
Extreme Solar Coronagraphy Antarctic Program Experiment) will perform
2-dimensional spectroscopy of the forbidden line of FeXIV at 530.285 nm:
precise line profile analysis will allow the diagnostic of the nature
of waves by simultaneous measurements of velocities and intensities in
the corona. ESCAPE is proposed to Institut Paul-Emile Victor (IPEV)
for a campaign in 2012-2013 at Dome C/Concordia since all subsystems
are available in particular thanks to an ESA STARTIGER 2010 R&D
"Toward a New Generation of Formation Flying Coronagraph". Using
state-of-the-art technologies developed for Space missions (a
Three Mirrors Anastigmat telescope, the TMA, a 4 stages Liquid
Crystal Tunable-filter Polarimeter, the LCTP) allows us to propose
an automated Coronal Green Line full-field Polarimeter for unique
observations (waves nature and intensity to address coronal heating)
with the best possible performances on Earth and for preparing and
testing the technologies for the next steps in Space. No other site
would allow such coronagraphic performances (the sky brightness is a
factor 2 to 4 better than in Hawaï) and with high spatial resolution
(better than an arcsec is possible).
---------------------------------------------------------
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 solar orbiter METIS coronagraph data signal processing
chain
Authors: Pancrazzi, M.; Focardi, M.; Uslenghi, M.; Nicolini, G.;
Magli, E.; Landini, F.; Romoli, M.; Bemporad, A.; Antonucci, E.;
Fineschi, S.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.
2011SPIE.8167E..2CP Altcode: 2011SPIE.8167E..66P
METIS, the Multi Element Telescope for Imaging and Spectroscopy,
is one of the instruments selected in 2009 by ESA to be part of the
payload of the Solar Orbiter mission. The instrument design has been
conceived to perform both multiband imaging and UV spectroscopy of
the solar corona. The two sensors of the detecting system will produce
images in visible light and in two narrow UV bands, at 121.6 and 30.4
nm. The instrument is constituted by several subunits that have to be
properly controlled and synchronized in order to provide the expected
performances. Moreover, the large amount of data collected by METIS has
to be processed by the on board electronics to reduce the data volume
to be delivered to ground by telemetry. These functionalities will be
realized by a dedicated electronics, the Main Power and Processing Unit
(MPPU). This paper will provide an overview of the METIS data handling
system and the expected on board data processing.
---------------------------------------------------------
Title: Liquid crystals Lyot filter for solar coronagraphy
Authors: Fineschi, S.; Capobianco, G.; Massone, G.; Baur, T.; Bemporad,
A.; Abbo, L.; Zangrilli, L.; Dadeppo, V.
2011SPIE.8148E..08F Altcode: 2011SPIE.8148E...7F
The "Association de Satellites Pour l'Imagerie et l'Interférométrie
de la Couronne Solaire", ASPIICS, is a solar coronagraph to be flown on
the PROBA 3 Technology mission of the European Space Agency. ASPIICS
heralds the next generation of coronagraphs for solar research,
exploiting formation flying to gain access to the inner corona under
eclipse-like conditions in space. The science goal is high spatial
resolution imaging and two-dimensional spectrophotometry of the Fe
XIV, 530.3 nm, emission line. This work describes a liquid crystal
Lyot tunable-filter and polarimeter (LCTP) that can implement this
goal. The LCTP is a bandpass filter with a full width at half maximum
of 0.15 nm at a wavelength of 530.3 nm. The center wavelength of the
bandpass is tunable in 0.01 nm steps from 528.64 nm to 533.38 nm. It
is a four stage Lyot filter with all four stages wide-fielded. The
free spectral range between neighboring transmission bands of the
filter is 2.7 nm. The wavelength tuning is non-mechanical using
nematic liquid crystal variable retarders (LCVR's). A separate LCVR
of the Senarmont design, in tandem with the filter, is used for the
polarimetric measurements. A prototype of the LCTP has been built and
its measured performances are presented here.
---------------------------------------------------------
Title: Space-qualified liquid-crystal variable retarders for
wide-field-of-view coronagraphs
Authors: Uribe-Patarroyo, N.; Alvarez-Herrero, A.; García Parejo,
P.; Vargas, J.; Heredero, R. L.; Restrepo, R.; Martínez Pillet, V.;
del Toro Iniesta, J. C.; López, A.; Fineschi, S.; Capobianco, G.;
Georges, M.; López, M.; Boer, G.; Manolis, I.
2011SPIE.8148E..10U Altcode: 2011SPIE.8148E..31U
Liquid-crystal variable retarders (LCVRs) are an emergent technology
for space-based polarimeters, following its success as polarization
modulators in ground-based polarimeters and ellipsometers. Wide-field
double nematic LCVRs address the high angular sensitivity of nematic
LCVRs at some voltage regimes. We present a work in which wide-field
LCVRs were designed and built, which are suitable for wide-field-of-view
instruments such as polarimetric coronagraphs. A detailed model of
their angular acceptance was made, and we validated this technology
for space environmental conditions, including a campaign studying the
effects of gamma, proton irradiation, vibration and shock, thermo-vacuum
and ultraviolet radiation.
---------------------------------------------------------
Title: OPSys: optical payload systems facility for testing space
coronagraphs
Authors: Fineschi, S.; Crescenzio, G.; Massone, G.; Capobianco, G.;
Zangrilli, L.; Antonucci, E.; Anselmi, F.
2011SPIE.8148E..0WF Altcode: 2011SPIE.8148E..28F
The Turin Astronomical Observatory, Italy, has implemented in ALTEC,
Turin, a new Optical Payload Systems (OPSys) facility for testing of
contamination sensitive optical space flight instrumentation. The
facility is specially tailored for tests on solar instruments like
coronagraphs. OPSys comprises an ISO 7 clean room for instrument
assembly and a relatively large (4.4 m<SUP>3</SUP>) optical test
and calibration vacuum chamber: the Space Optics Calibration Chamber
(SPOCC). SPOCC consists of a test section with a vacuum-compatible
motorized optical bench, and of a pipeline section with a sun simulator
at the opposite end of the optical bench hosting the instrumentation
under tests. The solar simulator is an off-axis parabolic mirror
collimating the light from the source with the solar angular
divergence. After vacuum conditioning, the chamber will operate at
an ultimate pressure of 10<SUP>-6</SUP> mbar. This work describes
the SPOCC's vacuum system and optical design, and the post-flight
stray-light tests to be carried out on the Sounding-rocket Experiment
(SCORE). This sub-orbital solar coronagraph is the prototype of the
METIS coronagraph for the ESA Solar Orbital mission whose closest
perihelion is one-third of the Sun-Earth distance. The plans are
outlined for testing METIS in the SPOCC simulating the observing
conditions from the Solar Orbiter perihelion.
---------------------------------------------------------
Title: The coronal suprathermal particle explorer (C-SPEX)
Authors: Moses, J. Daniel; Brown, Charles; Doschek, George; Ko,
Yuan-Kuen; Korendyke, Clarence; Laming, J. Martin; Socker, Dennis;
Tylka, Allen; McMullin, Donald; Ng, Chee; Wassom, Steven; Lee, Martin;
Auchère, Frédéric; Fineschi, Silvano; Carter, Tim
2011SPIE.8148E..0JM Altcode: 2011SPIE.8148E..18M
The primary science objective of the Coronal Suprathermal Particle
Explorer (C-SPEX) is to investigate the spatial and temporal
variations of coronal suprathermal particle populations that are
seeds for acceleration to solar energetic particles (SEPs). It is
understood that such seed particle populations vary with coronal
structures and can change responding to solar flare and coronal mass
ejection (CME) events. Models have shown that higher densities of
suprathermal protons can result in higher rates of acceleration to
high energies. Understanding the variations in the suprathermal seed
particle population is thus crucial for understanding the variations
in SEPs. However, direct measurements are still lacking. C-SPEX
will measure the variation in the suprathermal protons across
various coronal magnetic structures, before/after the passage of CME
shocks, in the post-CME current sheets, and before/after major solar
flares. Understanding the causes for variation in the suprathermal
seed particle population and its effect on the variation in SEPs
will also help build the predictive capability of SEPs that reach
Earth. The CSPEX measurements will be obtained from instrumentation
on the International Space Station (ISS) employing well-established
UV coronal spectroscopy techniques.
---------------------------------------------------------
Title: SiC/Mg multilayer coatings for SCORE coronagraph: long term
stability analysis
Authors: Pelizzo, Maria Guglielmina; Fineschi, Silvano; Zuppella,
Paola; Corso, Alain Jody; Windt, David L.; Nicolosi, Piergiorgio
2011SPIE.8148E..0MP Altcode: 2011SPIE.8148E..20P
SiC/Mg multilayers have been used as coatings of the Sounding-rocket
CORonagraphic Experiment (SCORE) telescope mirrors launched during the
NASA HERSCHEL program. This materials couple has been largely studied
by researchers since it provides higher performances than a standard
Mo/Si multilayer; the SCORE mirrors show in fact a peak reflectance of
around 40% at HeII 30.4 nm. Nevertheless, long term stability of this
coating is an open problem. A study on the aging and stability of this
multilayer has been carried on. SiC/Mg multilayer samples characterized
by different structural parameters have been deposited. They have
been measured just after deposition and four years later to verify
degradation based on natural aging. Experimental results and analysis
are presented.
---------------------------------------------------------
Title: Solar Physics and Space Weather Instrumentation IV
Authors: Fineschi, Silvano; Fennelly, Judy
2011SPIE.8148E....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectropolarimetric forward modelling of the lines of the
Lyman-series using a self-consistent, global, solar coronal model
Authors: Khan, A.; Belluzzi, L.; Landi Degl'Innocenti, E.; Fineschi,
S.; Romoli, M.
2011A&A...529A..12K Altcode:
Context. The presence and importance of the coronal magnetic field
is illustrated by a wide range of phenomena, such as the abnormally
high temperatures of the coronal plasma, the existence of a slow and
fast solar wind, the triggering of explosive events such as flares
and CMEs. <BR /> Aims: We investigate the possibility of using the
Hanle effect to diagnose the coronal magnetic field by analysing
its influence on the linear polarisation, i.e. the rotation of
the plane of polarisation and depolarisation. <BR /> Methods: We
analyse the polarisation characteristics of the first three lines
of the hydrogen Lyman-series using an axisymmetric, self-consistent,
minimum-corona MHD model with relatively low values of the magnetic
field (a few Gauss). <BR /> Results: We find that the Hanle effect
in the above-mentioned lines indeed seems to be a valuable tool for
analysing the coronal magnetic field. However, great care must be
taken when analysing the spectropolarimetry of the Lα line, given
that a non-radial solar wind and active regions on the solar disk
can mimic the effects of the magnetic field, and, in some cases, even
mask them. Similar drawbacks are not found for the Lβ and Lγ lines
because they are more sensitive to the magnetic field. We also briefly
consider the instrumental requirements needed to perform polarimetric
observations for diagnosing the coronal magnetic fields. <BR />
Conclusions: The combined analysis of the three aforementioned lines
could provide an important step towards better constrainting the value
of solar coronal magnetic fields.
---------------------------------------------------------
Title: The Coronal Suprathermal Particle Explorer (C-SPEX)
Authors: Moses, John Daniel; Brown, C. M.; Doschek, G. A.; -. Ko,
Y.; Korendyke, C. M.; Laming, J. M.; Rakowski, C. E.; Socker, D. G.;
Tylka, A.; Ng, C. K.; Wassom, S. R.; McMullin, D. R.; Lee, M. A.;
Auchere, F.; Fineschi, S.
2011SPD....42.1519M Altcode: 2011BAAS..43S.1519M
The primary science objective of the Coronal Suprathermal Particle
Explorer (C-SPEX) is to investigate the spatial and temporal
variations of coronal suprathermal particle populations that are
seeds for acceleration to solar energetic particles (SEPs). It is
understood that such seed particle populations vary with coronal
structures and can change responding to solar flare and coronal mass
ejection (CME) events. Models have shown that higher densities of
suprathermal protons can result in higher rates of acceleration to
high energies. Understanding the variations in the suprathermal seed
particle population is thus crucial for understanding the variations
in SEPs. However, direct measurements are still lacking. <P />C-SPEX
will measure the variation in the suprathermal protons across various
coronal magnetic structures, before/after the passage of CME shocks, in
the post-CME current sheets, and before/after major solar flares. The
measurements will not only constrain models of SEP acceleration but
also constrain models of the production of suprathermal particles from
processes such as magnetic reconnection at the Sun. Understanding the
causes for variation in the suprathermal seed particle population and
its effect on the variation in SEPs will also help build the predictive
capability of SEPs that reach Earth. <P />The C-SPEX measurements will
be obtained from instrumentation on the International Space Station
(ISS) employing well-established UV coronal spectroscopy techniques. The
unique aspect of C-SPEX is a >100-fold increase of light gathering
power over any previous UV coronal spectrometer. It is demonstrated
C-SPEX will thus overcome the limitations in signal to noise that have
thwarted prior attempts to observe suprathermals in the corona. <P />The
present lack of a means to predict the variability of SEP intensities
and the likelihood C-SPEX will help develop such predictions makes the
proposed investigation directly relevant to each of the three strategic
objectives of the NASA Heliophysics Research Strategic Objectives.
---------------------------------------------------------
Title: Towards a New Formation Flying Solar Coronagraph
Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos,
K.; Turck-Chieze, S.; Zhukov, A.
2010ASPC..424...15L Altcode:
We briefly describe an investigation aiming at the development of a
giant solar coronagraph instrument onboard of two satellites, separated
by about 150 m in formation flight for the detailed observation of the
solar coronal plasma. The European Space Agency (ESA) has selected this
instrument as the only payload onboard the Proba 3 satellites which
will be launched in 2013. The Greek team is developing the command
control board of the coronagraph.
---------------------------------------------------------
Title: HERSCHEL Sounding Rocket Mission Observations of the Helium
Corona
Authors: Newmark, Jeffrey; Moses, J.; Antonucci, E.; Fineschi, S.;
Abbo, L.; Telloni, D.; Auchere, F.; Barbey, N.; Romoli, M.
2010AAS...21640721N Altcode:
The HERSCHEL (Helium Resonant Scattering in the Corona and Heliosphere)
investigation successfully obtained unprecedented images of the helium
and hydrogen components of the solar corona out to 3 solar radii
during a suborbital flight on 14 September 2009. Preliminary analysis
of these observations indicates the spatial distribution of the helium
abundance and outflow velocity provides powerful diagnostics for the
source and dynamics of the slow solar wind during the time of solar
minimum activity. An analysis of co-temporal STEREO EUVI data to derive
the temperature of low coronal structures associated with the regions
of enhanced helium abundance observed by HERSCHEL provides evidence the
relative first ionization potential (FIP) of helium and hydrogen may
play an important role in the observed abundance distribution. <P />NRL
was supported by the Office of Naval Research and NASA under NDPRS6598G.
---------------------------------------------------------
Title: Gamma astrometric measurement experiment -science and
implementation
Authors: Gai, Mario; Vecchiato, Alberto; Lattanzi, Mario G.; Ligori,
Sebastiano; Loreggia, Davide; Fineschi, Silvano
2010cosp...38.3824G Altcode: 2010cosp.meet.3824G
GAME (Gamma Astrometric Measurement Experiment) is a mission concept
taking advantage of astronomical techniques for high precision
measurements of interest to Fundamental Physics, and in particular
the γ parameter of the Parameterized Post-Newtonian formulation of
gravi-tation theories modifying the General Relativity. A space based
telescope, looking close to the Solar limb thanks to coronagraphic
techniques, may implement astrometric measurements sim-ilar to those
performed in the solar eclipse of 1919, when Dyson, Eddington and
collaborators measured for the first time the gravitational bending of
light. Simulations show that the final accuracy of GAME can reach the
10-7 level. GAME will be a decisive experiment for the understanding of
gravity physics, cosmology and the Universe evolution. The observations
leading to Dark Matter (e.g. galaxy rotation curves) and Dark Energy
(accelerated expansion of the Universe) might be explained with a
modified version of General Relativity, e.g. in which the curvature
invariant R is no longer constant as in Einstein's equations, i.e. the
f (R) gravity theories. A 10-7 level determination of γ will provide
stringent constraints on acceptable theories. Also, high precision
astrometry makes accessible other appealing measurements, e.g. the
light deflection induced by the quadrupole moment of giant planets,
like Jupiter or Saturn, and, by high precision determination of the
orbits of Mercury and high elongation asteroids, the PPN parameter
β. GAME may also carry out measurements on selected astrophysical
targets, e.g. nearby, bright stars known to host companions with
minimum masses in the planetary/brown dwarf regime, and orbital
radii in the 3-7 AU range, which are observed by no other present or
planned campaigns. GAME, also thanks to high-cadence, high-precision
photometry on transit-ing exoplanet systems, will thus improve on
our understanding of the actual mass distribution and multiplicity of
sub-stellar companions. The GAME measurement principle is based on the
differential astrometric signature on the stellar positions. Calibration
is implemented by observation of stellar fields affected by neg-ligible
deflection. The instrument concept is based on a dual field, multiple
aperture Fizeau interferometer, observing simultaneously sky regions
close to the Solar limb. Coronagraphic solutions are embedded in
the astrometric telescope design, to achieve a rejection factor of
the Sun disk and stray light of ∼ 10-9 . An array of apertures
implemented by pupil masking on an underlying telescope with primary
diameter below one meter, with long focal length, fulfills the mission
specifications by providing individual photo-center precision better
than 1 milli-arcsecond for source magnitude 15 or brighter.
---------------------------------------------------------
Title: ASPIICS / PROBA-3: a formation flying externally-occulted
giant coronagraph mission
Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz,
W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.2858L Altcode: 2010cosp.meet.2858L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are detailed.
---------------------------------------------------------
Title: Multi-spacecraft observation of a magnetic cloud
Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de
Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt,
W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.;
Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.1921D Altcode: 2010cosp.meet.1921D
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are presented.
---------------------------------------------------------
Title: SCORE CCD visible camera calibration for the HERSCHEL
suborbital mission
Authors: Pancrazzi, M.; Focardi, M.; Landini, F.; Romoli, M.; Fineschi,
S.; Gherardi, A.; Massone, G.; Pace, E.; Paganini, D.; Rossi, G.
2009SPIE.7438E..0JP Altcode: 2009SPIE.7438E..15P
HERSCHEL is a suborbital mission which will observe the solar
corona in the UV and visible light by means of two coronagraphs
and an EUV imager. One of the two coronagraphs is SCORE (Sounding
CORonagraphic Experiment), developed mainly by some Italian scientific
institutions. SCORE performs imaging of the extended corona from 1.4
to 4 solar radii in the broadband visible and in the UV lines HI 121.6
nm and HeII 30.4 nm. The CCD visible camera (VLD) of SCORE has been
designed, built and characterized at the XUVLab of the University of
Florence. In this paper we will describe the VLD calibration and testing
performed before launch in order to evaluate the performances of SCORE.
---------------------------------------------------------
Title: The Gamma Astrometric Measurement Experiment (GAME)
Authors: Gai, Mario; Vecchiato, Alberto; Ligori, Sebastiano; Fineschi,
Silvano; Lattanzi, Mario G.
2009SPIE.7438E..0TG Altcode: 2009SPIE.7438E..20G
The GAME mission concept is aimed at very precise measurement of the
gravitational deflection of light by the Sun, by an optimized telescope
in the visible and launched in orbit on a small class satellite. The
targeted precision on the γ parameter of the Parametrized
Post-Newtonian formulation of General Relativity is 10<SUP>-6</SUP> or
better, i.e. one to two orders of magnitude better than the best current
results. Such precision is suitable to detect possible deviations from
unity value, associated to generalized Einstein models for gravitation,
with potentially huge impacts on the cosmological distribution of
dark matter and dark energy. The measurement principle is based on
differential astrometric signature on the stellar positions, i.e. on
the spatial component of the effect rather than the temporal component
as in recent experiments using radio link delay timing. Exploiting the
observation strategy, it is also possible to target other interesting
scientific goals both in the realm of General Relativity and in the
observations of extrasolar systems. The instrument is a dual field,
multiple aperture Fizeau interferometer, observing simultaneously two
regions close to the Solar limb. The diluted optics approach is selected
for efficient rejection of the solar radiation, while retaining an
acceptable angular resolution on the science targets. We describe the
science motivation, the proposed mission profile, the payload concept
and the expected performance from recent results.
---------------------------------------------------------
Title: Solar Physics and Space Weather Instrumentation III
Authors: Fineschi, Silvano; Fennelly, Judy A.
2009SPIE.7438E....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Calibration of the EKPol K-corona imaging polarimeter
Authors: Zangrilli, Luca; Fineschi, Silvano; Capobianco, Gerardo
2009SPIE.7438E..0WZ Altcode: 2009SPIE.7438E..23Z
The Dual Rotating Retarder Polarimeter technique has been used for
the calibration of the EKPol polarimeter, which is a K-corona imaging
instrument based on a Liquid Crystal Variable Retarder (LCVR), and
designed to measure the linear polarized radiation coming from the
solar corona during total solar eclipses. We put a major emphasis on
the EKPol properties at different wavelengths and temperature. In
particular, the chromatic dependence of the LCVR rotation prevents
from using large band observations, owing to the loss of contrast in
the measured modulation curves. This study is also intended as a basis
for the design of achromatic LCVRs.
---------------------------------------------------------
Title: POLAR investigation of the Sun—POLARIS
Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.;
Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.;
Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler,
D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy,
N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt,
R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.;
Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.;
Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T.
2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A
The POLAR Investigation of the Sun (POLARIS) mission uses a combination
of a gravity assist and solar sail propulsion to place a spacecraft
in a 0.48 AU circular orbit around the Sun with an inclination of 75°
with respect to solar equator. This challenging orbit is made possible
by the challenging development of solar sail propulsion. This first
extended view of the high-latitude regions of the Sun will enable
crucial observations not possible from the ecliptic viewpoint or from
Solar Orbiter. While Solar Orbiter would give the first glimpse of
the high latitude magnetic field and flows to probe the solar dynamo,
it does not have sufficient viewing of the polar regions to achieve
POLARIS’s primary objective: determining the relation between the
magnetism and dynamics of the Sun’s polar regions and the solar cycle.
---------------------------------------------------------
Title: In situ spectroscopy of the solar corona
Authors: Morgan, H.; Fineschi, S.; Habbal, S. R.; Li, B.
2008A&A...482..981M Altcode:
Context: Future spacecraft missions, such as the proposed Solar Probe
mission, will venture close to the Sun, allowing spectrometers measuring
emission from heavy ions or neutrals in the solar wind to have radial
lines of sight (LOS) pointing away from the Sun, or indeed in any
direction other than sunwards. <BR />Aims: We show that a radial LOS
gives excellent solar wind diagnostics, with tight constraints on ion
density, outflow velocity, and effective temperature parallel to the
coronal magnetic field. In addition, we present the concept that a
spectrometer onboard a spacecraft reaching the solar corona can yield
measurements somewhat similar to an in situ sampling instrument, in
that the 3D velocity distribution and density of the emitting ions
can be measured. <BR />Methods: The well-studied O VI doublet at
1031.96 and 1037.6 Å and the H Ly-α line at 1215.67 Å are chosen
as examples. Solar wind parameters obtained from a 2D three-fluid
magnetohydrodynamic (MHD) model, and formulations for collisional and
radiative emission along a radial LOS, are used to calculate spectral
line profiles for these lines at various heights within a streamer
and coronal hole. <BR />Results: For O VI, the collisional line
profiles directly measure the ion velocity distribution in the radial
direction, with the general Doppler shift of the profiles related
to the bulk ion outflow velocity and the width of the line related
to the effective ion temperature parallel to the magnetic field. An
obvious skew in the collisional profiles is seen in regions with a
high gradient in outflow velocity and/or temperature. The resonant (or
radiative) line profiles behave very differently from those currently
observed in 90° scattering. They are more closely related to the
profile and distribution of the exciting chromospheric spectrum: the
lines are narrow and are centered at wavelengths mirrored around the
rest wavelength of the ion emission, allowing easy separation of the
collisional and radiative components. Despite the Ly-α line being much
more intense than the O VI lines, the large width and high intensity
of the Ly-α radiative component in comparison to the collisional
component is such that these two components cannot be separated. The
Ly-α line is therefore less suitable for solar wind diagnostics. <BR
/>Conclusions: The prospect of coronal in situ spectral observations,
combined with simultaneous in situ sampling measurements of the solar
wind and magnetic field will give unsurpassed constraints on models
of solar wind heating and acceleration.
---------------------------------------------------------
Title: Investigation of the solar wind outflows and joint observations
during the total solar eclipse of March 29, 2006
Authors: Abbo, Lucia; Zangrilli, Luca; Antonucci, Ester; Fineschi,
Silvano; Kohl, John; Giordano, Silvio; Massone, Giuseppe; Capobianco,
Gerardo; Calcidese, Paolo; Porcu, Francesco
2008cosp...37....7A Altcode: 2008cosp.meet....7A
During the total solar eclipse of 29 March 2006, SOHO observations of
JOP158 were coordinated with ground based instruments. In particular,
the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO has
observed the south coronal hole in the OVI doublet emission in order
to probe the role of plume and interplume regions in the dynamics of
the fast solar wind. From the analysis of the polarized K-solar corona
measurements obtained with the EKPol polarimeter from the site of c
(desert of Sahara, Lybia), we estimate the coronal electron density
radial profiles and perform a Doppler dimming analysis of the OVI
doublet line intensities to measure the outflow velocity.
---------------------------------------------------------
Title: Space Coronagraphy: Future Prospects from the Solar Orbiter
and Probe Missions
Authors: Fineschi, Silvano
2008cosp...37..884F Altcode: 2008cosp.meet..884F
The ESA Solar Orbiter and NASA Solar Probe missions proposed for
flying in the next decade will provide unique platforms for space
coronagraphy. I will review the possibilities offered by these two
solar missions to the study of the physics of the corona. The payload
of the Solar Orbiter is currently being selected and it will include
a coronagraph. I will describe the unique observations that such an
instrument would be able to carry out from the Orbiter. This spacecraft
will offer a close-up (0.25 AU), out-of-the-ecliptic and co-rotating
view of the Sun. The Solar Probe's trajectory would take the spacecraft
through the innermost coronal layers. This would offer the unique
opportunity for backward looking observations through the corona. I
will review the exciting new science that this viewpoint would enable.
---------------------------------------------------------
Title: Solar Physics and Space Weather Instrumentation II
Authors: Fineschi, Silvano; Viereck, Rodney A.
2007SPIE.6689E....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Numerical simulations of coronal hole-associated neutral
solar wind as expected at the Solar Orbiter position
Authors: D'Amicis, R.; Orsini, S.; Antonucci, E.; di Lellis, A. M.;
Hilchenbach, M.; Telloni, D.; Mura, A.; Milillo, A.; Fineschi, S.;
Bruno, R.
2007JGRA..112.6110D Altcode: 2007JGRA..11206110D
Neutral hydrogen is indicative of the behavior of the main solar wind
component formed by protons out to at least 5 R<SUB>⊙</SUB>. In
fact, beyond this distance, the characteristic time for charge
exchange between hydrogen atoms and protons becomes larger than the
coronal expansion timescale, causing the neutrals to decouple from
the charged solar wind. The mean free path of the neutral component
rapidly increases with the radial distance so that neutrals generated
at heliocentric distances ≥24 R<SUB>⊙</SUB> fly unperturbed and
eventually are detected by Solar Orbiter (perihelion at approximately
48 R<SUB>⊙</SUB>), since their mean free path is long enough to
let neutrals reach the neutral solar wind detector. However, the
computation of the differential flux shows that the bulk of the flux
detected at the Solar Orbiter vantage point mainly comes from about 9
R<SUB>⊙</SUB>. Neutrals retain information on the three-dimensional
distribution of hydrogen at the level where they are generated as the
proton velocity distribution is frozen within the generated neutrals
and transferred up to the Solar Orbiter position. In the present study,
we report our preliminary results from our simulation of the neutral
solar wind distribution as predicted at the Solar Orbiter position and
considering the evolution of a coronal hole-emerging solar wind whose
major parameters are estimated by the Solar and Heliospheric Observatory
(SOHO) Ultraviolet Coronagraph Spectrometer (UVCS) experiment. The
synergy between corona remote sensing and in situ neutral particle
observations will enable us to infer the degree of anisotropy, if any,
in the neutral and charged coronal hydrogen close to the Sun.
---------------------------------------------------------
Title: La missione SOHO
Authors: Fineschi, S.
2007AsUAI...2...25F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Viewing Structure In Coronal Images
Authors: Morgan, H.; Habbal, S. R.; Fineschi, S.
2007ESASP.641E..15M Altcode:
New image processing techniques, applied to white-light, pB , UV
or EUV observations, reveal the fine-scale detail of the corona
whilst accurately depicting the large-scale structure. The images
produced by the techniques give new insights into the structure of
streamers, are useful to unravel the complex topology of the solar
maximum corona, and can help make connections between coronal and
solar disk features. CMEs are seen in striking de- tail out to ∼18R
. The quality of imaging produced by missions such as Solar Orbiter
have a strong influence on the impact of that mission, and the solar
remote sensing instrumentation, in particular the EUV imager and coro-
nagraph, can maximize their scientific effectiveness by employing the
new processing techniques.
---------------------------------------------------------
Title: Observing The He II Off-Limb Corona From Solar Orbiter
Authors: Giordano, S.; Fineschi, S.; Ofman, L.; Mancuso, S.; Abbo, L.
2007ESASP.641E..31G Altcode:
The SOLar Orbiter, SOLO, represents a unique platform for off-limb
solar corona observations, because of the near-Sun, helio-synchronous
and out-of-ecliptic perspective. We discuss as the simultaneous
monochromatic imaging of the UltraViolet spectral lines emitted by
the neutral hydrogen (HI) and singly ionized helium ions (HeII) in
solar corona in addition to the visible light imaging allows to use
the Doppler dimming diagnostics to derive velocity maps of the full
corona and the maps of the abundance of helium relative to hydrogen. We
compute the expected HeII 303. 78 A, HI Lyα 1215. 56 A and Visible
Light emissivity for a coronal model derived from a MHD computation of
the coronal physical parameters, such as electron and ions density,
kinetic temperatures and outflow velocity in the region from 1. 2
to 5. 0 solar radii. The UV lines are Doppler dimmed in presence of
outflows, moreover we take into account the possibility of pumping
effect on the He II line due to nearby Si XI 303. 32 A spectral line
which can excited the He II line for plasma speeds around 450 km/s. We
study as the helium coronal diagnostics from the out-of-ecliptic and
helio-synchronous observations can moreover address the understanding
of the processes leading to the elemental composition of the coronal
streamers and hole boundaries, as example to establish roles of
gravitational settling and Coulomb drag.
---------------------------------------------------------
Title: Numerical Simulations Of The Neutral Solar Wind Distribution
As Expected At The Solar Orbiter Position
Authors: D'Amicis, R. D.; Orsini, S.; Antonucci, E.; Hilchenbach, M.;
Di Lellis, A. M.; Telloni, D.; Fineschi, S.; Milillo, A.; Bruno, R.;
Mura, A.; De Angelis, E.
2007ESASP.641E..10D Altcode:
Neutral hydrogen is indicative of the behavior of the main solar wind
component formed by protons out to at least 5 solar radii. In fact,
beyond this distance the characteristic time for charge exchange
between hydrogen atoms and protons becomes shorter than the coronal
expansion time scale causing the neutrals to decouple from the
charged solar wind. However they retain information on the three-
dimensional coronal distribution of hydrogen at the distance where they
are generated. Considering the great importance of neutral solar wind
(NSW) measurements to understand the evolution of the main solar wind
component after decoupling from the neutrals, a NSW detector is at the
moment one of the High Priority Augmentation instruments of the Solar
Orbiter mission. In the present study, we report our preliminary results
concerning the simulation of the NSW distribution as expected at the
Solar Orbiter position. We consider the evolution of a coronal-hole
emerging solar wind whose major parameters are estimated by the
SOHO UVCS experiment. The synergy between in- itu and remote sensing
measurements will enable us to infer the degree of anisotropy, if any,
in the neutral and charged coronal hydrogen close to the Sun.
---------------------------------------------------------
Title: T he HERSCHEL/SCORE Visible And UV Coronagraph
Authors: Romoli, M.; Capobianco, G.; Da Deppo, V.; Fineschi, S.;
Focardi1, M.; Gherardi1, A.; Landini1, F.; Malvezzi, M. A.; Naletto,
G.; Nicolosi, P.; Pace, E.; Pancrazzi, M.; Pelizzo, M. G.; Rossi,
G.; Zangrilli, L.; Antonucci, E.
2007ESASP.641E..79R Altcode:
The Herschel (HElium Resonant Scattering in the Corona and HELiosphere)
experiment, approved by NASA in 2003 within the Living With a Star
program, to be flown on a sounding rocket, is designed to investigate
the helium coronal abundance and the solar wind acceleration region
by obtaining the first simultaneous observations of the electron,
proton and helium solar corona. The HER- SCHEL payload consists of
several instruments that image the solar corona in the EUV and in the
visible from the disk to the extended corona. SCORE (Solar CORono-
graph Experiment) is a coronagraph that has the capabil- ity of
imaging the solar corona from 1.4 to 3.5 solar radii in the EUV lines
of HI 121.6 nm and HeII 30.4 nm and in the visible broadband polarized
brightness. The SCORE coronagraph consists of an externally occulted
reflecting telescope in off-axis gregorian configuration with a novel
design in the stray light rejection. The use of multilayer mirrors
in normal incidence makes possible the observa- tions in all three
wavelength bands with the same telescope. HERSCHEL/SCORE aims also at
testing in space the performances of this design and establishing a
proof- of-principle for the Ultraviolet Coronagraph of Solar Orbiter.
---------------------------------------------------------
Title: Progress Toward Measurements of Suprathermal Tails in Coronal
Proton Velocity Distributions
Authors: Kohl, J. L.; Panazyuk, A. V.; Cranmer, S. R.; Fineschi, S.;
Gardner, L. D.; Phillips, D. H.; Raymond, J. C.; Uzzo, M.
2006ESASP.617E..25K Altcode: 2006soho...17E..25K
No abstract at ADS
---------------------------------------------------------
Title: Prospects of Coronal Spectro-Imaging from Solar Orbiter
and Probe
Authors: Fineschi, S.
2006cosp...36.3347F Altcode: 2006cosp.meet.3347F
Solar Orbiter and Solar Probe are future missions of the International
Living With a Star ILWS initiative They will fly through the corona
with unprecedented proximity to the Sun and will provinde unique
platforms for coronal studies Instrument concepts will be reviewed
for imaging spectroscopy of ultraviolet UV coronal lines in the 30-120
nm wavelength range These concepts will exploit the unique observing
standpoint provided by these ILWS missions The science objective
of these remote-sensing instruments is the measurement of physical
parameters of the solar wind i e outflow speed velocity distributions
density and the correlation with in situ measurements The instrument
concepts are based on Toroidal Varied Line-Space TVLS gratings with
multiple slits at the entrance aperture of the spectrograph For
a given spectral line the complete two-dimensional imaging of the
corona is obtained by interpolating the slit images along the spectral
dispersion direction A prototype of this UV spectro-imager concept
for the Solar Orbiter will be tested with the Italian Sounding-rocket
CORonal Experiment SCORE on a NASA sounding-rocket payload The Solar
Probe will provide the unique possibility of observing UV coronal
line-emission from inside-out that is along the radial direction of the
solar wind outflow and away from the sun The collisional and resonantly
scattered components of the line-emissions when observed radially are
spectroscopically separated This allows a direct measure of the wind
s outflow speed from the Doppler shift of the
---------------------------------------------------------
Title: EKPol: Liquid Crystal Polarimeter for Eclipse Observations
of the K-Corona
Authors: Zangrilli, L.; Fineschi, S.; Massone, G.; Capobianco, G.;
Porcu, F.; Calcidese, P.
2006spse.conf...37Z Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Initial Attempt to Measure Suprathermal Tails in Coronal
Proton Velocity Distributions
Authors: Kohl, J. L.; Cranmer, S. R.; Fineschi, S.; Gardner, L. D.;
Panasyuk, A. V.; Raymond, J. C.; Uzzo, M.
2005AGUFMSH44A..05K Altcode:
Test observations made with the Ultraviolet Coronagraph Spectrometer
(UVCS) on SOHO in August 2005 are being used to make an initial
assessment of the possibility of measuring suprathermal tails in the
proton velocity distribution functions. Any successful theory of solar
energetic particle (SEP) production by CME shocks must account for the
large observed variations in SEP spectral characteristics and elemental
abundances. Some have proposed that this variability arises from an
inherently variable population of suprathermal seed particles (e.g.,
Mason et al. 2005): some that exist all the time in the solar wind
(with varying properties depending on wind speed) and some that are
associated with prior flares and CME shocks (e.g., Kahler 2004; Tylka
et al. 2005). As yet, though, the suprathermal particle population in
the solar corona has never been measured. The seed particle number
density predicted for typical gradual SEP events is about 0.002 -
0.01 times the thermal population (e.g., Lee 2005), and should, in at
least some cases, correspond to a measurable enhancement in the wing
of the H I Ly-alpha profile. In August 2005, the Ly-alpha channel of
UVCS was recommissioned and used to observe HI Ly-alpha line profiles
at 2.0 solar radii in coronal holes, helmet streamers, above active
regions and after a CME. The holographically ruled diffraction grating
provides the low stray light level needed to observe the tail of the
line profile out to about 0.5 nm from line center. New observations
as well as measurements from the original UVCS laboratory calibration
and in flight measurements from earlier in the mission are being
used to characterize the instrument response to monochromatic light
so such instrument effects can be removed. Initial results will be
reported. This work is supported by NASA Grant NNG05GG38G to the
Smithsonian Astrophysical Observatory Kahler, S. W. 2004, ApJ, 603,
330. Lee, M. A. 2005, ApJ Supp., 158, 38. Mason, G., Desai, M.,
Mazur, J., & Dwyer, J. 2005, COSPAR 35th Scientific Assemly,
p. 1596. Tylka, A. J., et al. 2005, ApJ, 625, 474.
---------------------------------------------------------
Title: KPol: liquid crystal polarimeter for K-corona observations
from the SCORE coronagraph
Authors: Fineschi, Silvano; Zangrilli, Luca; Rossi, Guglielmo; Gori,
Luca; Romoli, Marco; Corti, Gianni; Capobianco, Gerardo; Antonucci,
Ester; Pace, Emanuele
2005SPIE.5901..389F Altcode:
We describe the design and first calibration tests of an imaging
polarimeter based on Liquid Crystal Variable Retarders (LCVRs),
for the study of the solar K-corona. This K-polarimeter (KPol) is
part of the visible light path of the UltraViolet and Visible-light
Coronal Imager (UVCI) of the Sounding-rocket Coronagraphic Experiment
(SCORE). SCORE/UVCI is an externally occulted, off-axis Gregorian
telescope, optimized for the narrow-band (i.e., λ/▵λ ~10) imaging
of the HeII, λ 30.4 nm and HI λ 121.6 nm coronal emission. We
present some preliminary results of the application of LCVR plates
to measurements of linear polarized radiation. LCVR plates replace
mechanically rotating retarders with electro-optical devices, without
no moving parts. LCVR are variable waveplates, in which the change of
the retardance is induced by a variable applied voltage. The retardance
of a LCVR is a function of the wavelength. KPol observations of the
visible coronal continuum of the Sun (K-corona) will be made over the
450-600 nm wavelength band. We have studied the LCVR's properties in
this bandpass. We tested a LCVR plate assembled in a linear polarization
rotator configuration to measure the polarization plane rotation of
input radiation as a function of wavelength. We estimated the LCVR's
chromatic response in the KPol wavelength bandpass. The preliminary
results show reasonable achromatic behaviour at high regimes of the
driving voltage, V<SUB>d</SUB> (i.e., V<SUB>d</SUB>>3 volt).
---------------------------------------------------------
Title: Solar Physics and Space Weather Instrumentation
Authors: Fineschi, Silvano; Viereck, Rodney A.
2005SPIE.5901.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectro-imaging of the extreme-UV solar corona
Authors: Fineschi, Silvano; Moses, J. Dan; Thomas, Roger J.
2005SPIE.5901..289F Altcode:
This paper describes an instrument concept for imaging spectroscopy
of ultraviolet (UV) line emission from the solar corona, in the
(30-120) nm wavelength range. The optical design for this Ultraviolet
Spectro-Coronagraph (UVSC) instrument concept is an externally occulted,
off-axis Gregorian telescope where the secondary mirror is a Toroidal
Varied Line-Space (TVLS) grating. A field stop with multiple slits is
at the prime focus of the telescope's mirror. This multi-slit field
stop is the entrance aperture for the spectrograph. The slits select
a number of strips in the field-of-view (FOV) with enough separation
to minimize the spectral overlap of the UV lines dispersed by the TVLS
grating. The complete two-dimensional imaging of the FOV is obtained
by interpolating the slit images along the spectral dispersion
direction. This paper discusses the use of an UVSC instrument on
HERSCHEL, a NASA sounding-rocket payload. HERSCHEL includes the
Sounding-rocket CORonal Experiment (SCORE) that currently comprises
a UV Coronagraphic Imager (UVCI) for narrow-band (i.e., λ/Δλ≈10)
imaging of the HeII, 30.38 nm, line. Adding a spectroscopic capability
(i.e., λ/Δλ ≈ 0.3-1 × 10<SUP>4</SUP>) to the UVCI would enhance
the HERSCHEL's science. This paper presents the ray-tracing results
of the expected spectral and spatial performances of a UVSC/SCORE
optimised for the HeII, 30.38 nm, line.
---------------------------------------------------------
Title: Space applications of Si/B<SUB>4</SUB>C multilayer coatings at
extreme ultra-violet region; comparison with standard Mo/Si coatings
Authors: Frassetto, F.; Garoli, D.; Monaco, G.; Nicolosi, P.;
Pascolini, M.; Pelizzo, M. G.; Mattarello, V.; Patelli, A.; Rigato,
V.; Giglia, A.; Nannarone, S.; Antonucci, E.; Fineschi, S.; Romoli, M.
2005SPIE.5901..161F Altcode:
In the extreme ultra-violet region, multilayer coatings are the only
technique to obtain high reflectivity in normal incidence optical
configurations. The interference process which regulates periodic
multilayers behavior offers narrow-band spectral filtering without the
use of additional filters, fact that makes these coatings particularly
suitable for lines emission observations. Despite the large amount of
possible materials combinations, Mo/Si multilayers are the standard
choice for space research on plasma physics in the 13 - 30 nm spectral
region. In this work Si/B<SUB>4</SUB>C is presented as an alternative
material couple for the 30.4 nm selection. Attractive features are the
better spectral purity and the second order reflectivity reduction. A
possible application to the Sounding CORonagraph Experiment is
described as an example. B<SUB>4</SUB>C thin films have been used to
characterize this material in terms of optical constants in the 40 nm -
150 nm spectral region where, currently, only few data are available.
---------------------------------------------------------
Title: Ultraviolet spectroscopy of solar energetic particle source
regions
Authors: Kohl, J. L.; Cranmer, S.; Esser, R.; Gardner, L. D.; Fineschi,
S.; Lin, J.; Panasyuk, A.; Raymond, J. C.; Strachan, L.
2005SPIE.5901..262K Altcode:
A problem of fundamental importance for future space travel to the
Moon and Mars is the determination and prediction of the radiation
environment generated by the Sun. The sources of solar energetic
particles (SEP) and the physical processes associated with their
acceleration and propagation are not well understood. Ultraviolet
coronagraphic spectroscopy uniquely has the capabilities for determining
the detailed plasma properties of the likely source regions of such
particles. This information can be used to develop empirical models
of the source regions for specific events, and it can provide the key
information needed to identify and understand the physical processes
that produce SEP hazards. UVCS/SOHO observations have provided the first
detailed diagnostics of the plasma parameters of coronal mass ejections
(CMEs) in the extended corona. These observations have provided new
insights into the roles of shock waves, reconnection and magnetic
helicity in CME eruptions. Next generation ultraviolet coronagraph
spectrometers could provide additional diagnostic capabilities. This
paper summarizes past observations, and discusses the diagnostic
potential of advanced ultraviolet coronagraphic spectroscopy for
characterizing two possible sites of SEP production: CME shocks and
reconnection current sheets.
---------------------------------------------------------
Title: Solar Probe's Inside-Out UV Spectrography of the Solar Wind
Authors: Fineschi, S.; Habbal, S. R.; Morgan, H.
2005AGUSMSH41A..05F Altcode:
The Solar Probe will fly through the corona, as close as 3 solar radii
from the photosphere at perihelion. This will provide the unique and
first-ever possibility of remote-sensing observations of ultraviolet
(UV) coronal line-emission from inside-out, that is, along the radial
direction of the solar wind outflow, and away from the Sun. Past UV
spectrographic observations of the corona have been possible only from
a sideways perspective (e.g., UVCS/SOHO). The expected UV spectra of the
OVI doublet, 103.2/103.4 nm, Lyman-alpha HI, 121.6 nm, and HeII, 304 nm,
lines from the Probe's new radial perspective will be presented. The
collisional and resonantly scattered components of the line-emission
when observed radially are spectroscopically separated. This allows a
direct measure of the solar wind outflow speed from the Doppler shift
of the collisional component. The line profiles and intensities of both
components yield information on the unresolved velocity distribution of
ions along the radial direction. This is the predominant direction of
the coronal magnetic field. In the past, sideways, UV spectroscopic
observations of line-emission have yielded information on the
unresolved ion velocity distribution perpendicular to the magnetic
field. Therefore, radial UV spectroscopic observations from Solar
Probe will offer a unique opportunity of investigating the anisotropy
of the unresolved coronal ion velocity distribution for the first time.
---------------------------------------------------------
Title: HERSCHEL Suborbital Program: 3-D Applications for the STEREO
Mission
Authors: Moses, J. D.; Newmark, J.; McMullin, D.; Antonucci, E.;
Fineschi, S.; Gardiol, D.; Zangrilli, L.; Romoli, M.; Pace, E.; Gori,
L.; Landini, F.; Gherardi, A.; da Deppo, V.; Naletto, G.; Nicolosi, P.;
Pelizzo, M.; Malvezzi, M.; Auchere, F.; Delaboudiniere, J.; Howard, R.
2004AGUFMSH23A..08M Altcode:
The HERSCHEL (HElium Resonance Scatter in the Corona and HELiosphere)
Suborbital Program is an international collaborative program between
a consortium of Italian Universities & Observatories led by
Dr. E. Antonucci (and funded by the Italian Space Agency, ASI), the
French IAS (funded in part by CNES) and the Solar Physics Branch of
NRL (by NASA SEC and the Office of Naval Research). HERSCHEL will:
investigate the slow and fast solar wind, determine the helium
distribution and abundance in the corona, and test solar wind
acceleration models; by obtaining simultaneous observations of
the electron, proton and helium solar coronae. HERSCHEL will also
establish proof-of-principle for the Ultra-Violet Coronagraph, which
is in the ESA Solar Orbiter Mission baseline. The HERSCHEL launch date
has been linked to the STEREO launch date to allow coordinated science
between the two missions. One aspect of this scientific coordination is
establishing the 3-D structure of the inner corona. HERSCHEL provides
a third viewpoint for the inner corona covered by the A&B STEREO
SECCHI COR-1. HERSCHEL is the only scheduled, space-based asset that
could provide this third viewpoint for the critical inner corona viewed
by STEREO COR-1 (although lower resolution, ground-based cononagraphs
will make a contribution). A third viewpoint dramatically increases
one's ability to establish the 3-D structure of an optically thin object
(e.g. the metric in Fig. 7 of Davila 1994, ApJ 423, 871). HERSCHEL will
provide at least a snapshot of that viewpoint, plus a wide range of
additional information on the H and He composition of the inner corona.
---------------------------------------------------------
Title: Solar ultraviolet spectro-coronagraph with toroidal varied
line-space (TVLS) grating
Authors: Fineschi, Silvano; Korendyke, Clarence M.; Moses, J. Dan;
Thomas, Roger J.
2004SPIE.5487.1165F Altcode:
This paper describes an instrument for imaging spectroscopy
of ultraviolet (UV) line emission from the solar corona, in the
0.3-1.2x102 nm wavelength range. The optical design for this Ultraviolet
Spectro-Coronagraph (UVSC) is an externally occulted, off-axis Gregorian
telescope where the secondary mirror is a Toroidal Varied Line-Space
(TVLS) grating. A field stop with multiple slits is at the prime focus
of the telescope"s mirror. This multi-slit field stop is the entrance
aperture for the spectrograph. The slits select a number of strips in
the field-of-view (FOV) with enough separation to minimize the spectral
overlap of the UV lines dispersed by the TVLS grating. This type of
gratings allows for a much larger stigmatic FOV (i.e., 3° x 4°)
in both the spatial and spectral direction than that of the Toroidal
Uniform Line-Space (TULS) gratings. The complete imaging of the FOV is
obtained by interpolating the slit images along the spectral dispersion
direction. As an example, this paper discusses the possible use of a
UVSC instrument on HERSCHEL, a NASA sounding-rocket payload, and on
Solar Orbiter (SOLO), an ESA mission. HERSCHEL includes the Sounding
CORona Experiment (SCORE) that comprises a UV Coronagraphic Imager
(UVCI) for narrow-band (i.e., λ/Δλ≈10) imaging of the HeII, 30.4
nm, line. How a spectroscopic capability (i.e., λ/▵λ ≈0.3-1 x
10<SUP>4</SUP>) would enhance the HERSCHEL science is discussed. The
SOLO mission is planned for launch in 2013. Its orbital profile will
bring the spacecraft as close to the Sun as 0.22 A.U. Also SOLO would
represent an ideal and unique platform for a compact UVSC instrument
(i.e., ≈ 1-m length) capable of obtaining simultaneous imaging and
spectroscopy of the UV corona. The expected optical performances are
presented for a UVSC/SOLO optimised for the OVI doublet, 103.2/103.7 nm.
---------------------------------------------------------
Title: SPECTRE: a spectro-heliograph for the transition region
Authors: Naletto, G.; Antonucci, E.; Fineschi, S.; da Deppo, V.;
Nicolosi, P.; Romoli, M.; Zangrilli, L.; Gardiol, D.; Loreggia, D.;
Malvezzi, M.; Howard, R.; Moses, D.
2004ESASP.554..251N Altcode: 2004icso.conf..251N
The SPECtro-heliograph for the Transition REgion (SPECTRE) experiment
is one of the instruments of the Solar Heliospheric Activity Research
and Prediction Program (SHARPP) suite initially foreseen aboard the
NASA mission Solar Dynamics Observa-tory (SDO) of the International
Living With a Star (ILWS) program. The scientific objective of the
SPECTRE experiment was to characterize the rapid evolution of plasma in
the transition region of the solar atmosphere, producing full-disk 1.2
arcsec-resolution images of the solar atmosphere at the very critical
63 nm OV spectral line, characterizing a solar plasma temperature of
about 250,000K. Unfortunately, NASA very recently and unexpectedly,
during the instrument Phase A study, decided not to proceed with the
realization of SHARPP. The authors of this paper think that all the
work done so far in the definition of SPECTRE should not be lost. So,
they have decided to summarize in this paper the main characteristics
of this instrument and the results of the analysis so far performed:
the hope is that in a next future this work can be used again for
realizing an instrument having similar characteristics.
---------------------------------------------------------
Title: CCD camera for ground- and space-based solar corona
observations
Authors: Gherardi, Alessandro; Gori, Luca; Focardi, Mauro; Pace,
Emanuele; Romoli, Marco; Fineschi, Silvano; Zangrilli, Luca; Gardiol,
Daniele; Antonucci, Ester
2004SPIE.5171..247G Altcode:
A new concept CCD camera is currently under development at the XUVLab
of the Department of Astronomy and Space Science of the University
of Florence. This CCD camera is the proposed detector for the space-
and ground-based solar corona observations. This camera will be the
detector for the polarimetric channels of the UVC coronagraph of
the HERSCHEL rocket mission to observe the solar corona in an optical
broadband. The ground-based application consists in a UVC prototype for
coronagraphic measurements from Earth in the visible range. Within this
project, a CCD camera with innovative features has been produced: the
camera controller allows the fine tuning of all the parameters related
to charge transfer and CCD readout, i.e., the use of virtually any CCD
sensor, and it implements the new concept of high level of versatility,
easy management, TCP/IP remote control and display.
---------------------------------------------------------
Title: Telescopes and Instrumentation for Solar Astrophysics
Authors: Fineschi, Silvano; Gummin, Mark A.
2004SPIE.5171.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: MAGRITTE: an instrument suite for the solar atmospheric
imaging assembly (AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, Pierre L.; Defise, Jean-Marc; Halain, Jean-Philippe;
Jamar, Claude A. J.; Mazy, Emmanuel; Rossi, Laurence; Thibert,
Tanguy; Clette, Frederic; Cugnon, Pierre; Berghmans, David; Hochedez,
Jean-Francois E.; Delaboudiniere, Jean-Pierre; Auchere, Frederic;
Mercier, Raymond; Ravet, Marie-Francoise; Delmotte, Franck; Idir,
Mourad; Schuehle, Udo H.; Bothmer, Volker; Fineschi, Silvano; Howard,
Russell A.; Moses, John D.; Newmark, Jeffrey S.
2004SPIE.5171...53R Altcode:
The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics
Observatory will characterize the dynamical evolution of the solar
plasma from the chromosphere to the corona, and will follow the
connection of plasma dynamics with magnetic activity throughout the
solar atmosphere. The AIA consists of 7 high-resolution imaging
telescopes in the following spectral bandpasses: 1215Å. Ly-a,
304 Å He II, 629 Å OV, 465 Å Ne VII, 195 Å Fe XII (includes Fe
XXIV), 284 Å Fe XV, and 335 Å Fe XVI. The telescopes are grouped
by instrumental approach: the MAGRITTE Filtergraphs (R. MAGRITTE,
famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
channels with bandpasses ranging from 195 to 1216 Å, and the SPECTRE
Spectroheliograph with one soft-EUV channel at OV 629 Å. They will be
simultaneously operated with a 10-second imaging cadence. These two
instruments, the electronic boxes and two redundant Guide Telescopes
(GT) constitute the AIA suite. They will be mounted and coaligned on a
dedicated common optical bench. The GTs will provide pointing jitter
information to the whole SHARPP assembly. This paper presents the
selected technologies, the different challenges, the trade-offs to be
made in phase A, and the model philosophy. From a scientific viewpoint,
the unique combination high temporal and spatial resolutions with the
simultaneous multi-channel capability will allow MAGRITTE / SPECTRE
to explore new domains in the dynamics of the solar atmosphere, in
particular the fast small-scale phenomena. We show how the spectral
channels of the different instruments were derived to fulfill the
AIA scientific objectives, and we outline how this imager array will
address key science issues, like the transition region and coronal waves
or flare precursors, in coordination with other SDO experiments. We
finally describe the real-time solar monitoring products that will be
made available for space-weather forecasting applications.
---------------------------------------------------------
Title: A white light coronagraph for the SDO mission
Authors: Frassetto, F.; Naletto, G.; Nicolosi, P.; Antonucci, E.;
Fineschi, S.
2004cosp...35.4390F Altcode: 2004cosp.meet.4390F
The Solar Dynamic Observatory is the first mission planned within the
International Living with a Star ESA/NASA program. We have proposed for
this mission a standard heritage visible light coronagraph, and here
we describe this instrument. The main features of this coronagraph,
whose design is based on the classical externally occulted Lyot optical
configuration, are a field of view ranging from 2 and 15 solar radii,
an angular resolution of 14 arcsec (per pixel), a spectral bandpass
from 650 nm to 750 nm, and an instrument speed of about f/6. With
this instrument will be possible to study the evolutions of typical
solar phenomena like coronal mass ejections with a improved temporal
resolution and angular coverage.
---------------------------------------------------------
Title: The HElium Resonance Scattering in the Corona and HELiosphere
(HERSCHEL)
Authors: Fineschi, S.; Herschel Team
2004cosp...35.4567F Altcode: 2004cosp.meet.4567F
The HERSCHEL (HElium Resonance Scattering in the Corona and Heliosphere)
sounding-rocket payload has been selected in 2003 in the Living with
a Star (LWS) Targeted Research and Technology program. The HERSCHEL
experiment is designed to investigate the helium coronal abundance and
solar wind acceleration by obtaining simultaneous observations of the
electron, proton and helium solar coronae. The HERSCHEL instrument
package consists of the Extreme Ultraviolet Imaging Telescope (EIT)
for on-disk coronal observations and the Ultraviolet and Visible-light
Coronagraphic Imager (UVCI) for off-limb observations of the corona. The
UVCI is an externally occulted, reflecting coronagraph with an
off-axis Gregorian telescope. UVCI will be able to take coronal
images at heliocentric heights comprised between 1.2 to 3.5 solar
radii of a) K-corona polarized brightness (pB); b) H I Lyman-a, 121.6
nm, line-emission; c) He II Lyman-a, 30.4 nm, line. Synthetic images
obtained from coronal models and the expected instrument response will
be presented. The key element in the UVCI instrument concept is that
the mirrors with multilayer coatings optimized for 30.4 nm still have
good reflectivity at 121.6 nm and in the visible. The optical design
concept for the UVCI instrument will be discussed, together with its
expected optical and throughput performances.
---------------------------------------------------------
Title: The Ultraviolet and Visible-light Coronagraph of the HERSCHEL
experiment
Authors: Romoli, M.; Antonucci, E.; Fineschi, S.; Gardiol, D.;
Zangrilli, L.; Malvezzi, M. A.; Pace, E.; Gori, L.; Landini, F.;
Gherardi, A.; da Deppo, V.; Naletto, G.; Nicolosi, P.; Pelizzo, M. G.;
Moses, J. D.; Newmark, J.; Howard, R.; Auchere, F.; Delaboudinière,
J. P.
2003AIPC..679..846R Altcode:
The Herschel (HElium Resonant Scattering in the Corona and HELiosphere)
experiment, to be flown on a sounding rocket, will investigate the
helium coronal abundance and the solar wind acceleration from a
range of solar source structures by obtaining the first simultaneous
observations of the electron, proton and helium solar corona. The
HERSCHEL payload consists of the EUV Imaging Telescope (EIT), that
resembles the SOHO/EIT instrument, and the Ultraviolet and Visible
Coronagraph (UVC).UVC is an imaging coronagraph that will image
the solar corona from 1.4 to 4 solar radii in the EUV lines of HI
121.6 nm and the HeII 30.4 nm and in the visible broadband polarized
brightness. The UVC coronagraph is externally occulted with a novel
design as far as the stray light rejection is concerned. Therefore,
HERSCHEL will also establish proof-of-principle for the Ultraviolet
Coronagraph, which is in the ESA Solar Orbiter Mission baseline.The
scientific objectives of the experiment will be discussed, togetherwith
a description of the UVC coronagraph.
---------------------------------------------------------
Title: Simulation of Coronal Hole-Associated Neutral Solar Wind as
Expected at the Solar Orbiter Position
Authors: D'Amicis, R.; Hilchenbach, M.; Orsini, S.; Antonucci, E.;
Bruno, R.; Milillo, A.; Fineschi, S.; di Lellis, A. M.; Massetti, S.
2003EAEJA....10167D Altcode:
Neutral atoms are closely coupled to the emerging solar wind plasma
in the solar corona. After escaping from this region, where the solar
wind plasma experiences several acceleration processes, beyond 3
solar radii the neutral atoms become more and more decoupled from the
plasma. Therefore, the neutral atoms may be considered as an in-situ
trace particle population flowing within the solar wind plasma,
since they allow the information of the acceleration regions to be
reconstructed by remote detection from any vantage point. Hence,
the actual neutral solar wind (NSW) detection allows estimates of
the emerging solar wind density, bulk velocity, temperature, and
anisotropy. In the present study, we simulate the NSW distribution
as expected at the Solar Orbiter position, considering the major
parameters of a coronal-hole emerging solar wind as estimated by the
SOHO UVCS experiment.
---------------------------------------------------------
Title: Advanced spectroscopic and coronographic explorer: science
payload design concept
Authors: Gardner, Larry D.; Kohl, John L.; Daigneau, Peter S.; Smith,
Peter L.; Strachan, Leonard, Jr.; Howard, Russell A.; Socker, Dennis
G.; Davila, Joseph M.; Noci, Giancarlo C.; Romoli, Marco; Fineschi,
Silvano
2003SPIE.4843....1G Altcode:
The Advanced Spectroscopic and Coronagraphic Explorer (ASCE) was
proposed in 2001 to NASA's Medium-Class Explorer (MIDEX) program
by the Smithsonian Astrophysical Observatory in collaboration with
the Naval Research Laboratory, Goddard Space Flight Center and the
Italian Space Agency. It is one of four missions selected for Phase A
study in 2002. ASCE is composed of three instrument units: an Advanced
Ultraviolet Coronagraph Spectrometer (AUVCS), an Advanced Large Aperture
visible light Spectroscopic Coronagraph (ALASCO), and an Advanced Solar
Disk Spectrometer (ASDS). ASCE makes use of a 13 m long boom that is
extended on orbit and positions the external occulters of AUVCS and
ALASCO nearly 15 m in front of their respective telescope mirrors. The
optical design concepts for the instruments will be discussed.
---------------------------------------------------------
Title: Polarimetry in Astronomy
Authors: Fineschi, Silvano
2003SPIE.4843.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet and Visible-light Coronagraphic Imager (UVCI)
Authors: Fineschi, Silvano; Antonucci, Ester; Romoli, Marco; Gardiol,
Daniele; Naletto, Giampiero; Giordano, Silvio; Malvezzi, Marco;
Da Deppo, Vania; Zangrilli, Luca; Noci, Giancarlo
2003SPIE.4853..162F Altcode:
The HERSCHEL (HElium Resonance Scattering in the Corona and HELiosphere)
Sun-Earth Sub-Orbital Program is a proposed sounding-rocket payload
designed to investigate helium coronal abundance and solar wind
acceleration from a range of solar source structures by obtaining
simultaneous observations of the electron, proton and helium solar
coronae. HERSCHEL will provide the first measurements of the coronal
helium abundance in source regions of the solar wind, thus bringing
key elements to our understanding of the Sun-Earth connections. The
HERSCHEL instrument package consists of the Extreme Ultraviolet Imaging
Telescope (EIT) for on-disk coronal observations and the Ultraviolet and
Visible-light Coronagraphic Imager (UVCI) for off-limb observations of
the corona. The UVCI is an externally occulted, reflecting coronagraph
with an off-axis Gregorian telescope. UVCI will be able to take coronal
images at heliocentric heights comprised between 1.2 to 3.5 solar radii
of a) K-corona polarized brightness (pB); b) H I Lyman-α, 121.6 nm,
line-emission; c) He II Lyman-α, 30.4 nm, line. The key element in the
UVCI instrument concept is that the mirrors with multilayer coatings
optimized for 30.4 nm still have good reflectivity at 121.6 nm and
in the visible. The optical design concept for the UVCI instrument
will be discussed, together with its expected optical and throughput
performances.
---------------------------------------------------------
Title: Imaging Stokes polarimeter based on liquid crystals for the
study of the K-solar corona
Authors: Zangrilli, L.; Fineschi, S.; Loreggia, D.; Gardiol, D.;
Antonucci, E.; Cora, A.
2003MmSAI..74..528Z Altcode:
We describe the project of an imaging Stokes polarimeter based on
liquid crystals, for the study of the K-solar corona. Liquid crystals
retarders are electrically variable waveplates. The change of the
retardance, induced by a variable applied voltage, is a function of
the wavelength. As observations of the visible coronal continuum are
usually made over the band 450-600 nm, we are interested in studying
the properties of these retarders as a function of the wavelength. This
polarimeter is thought to be implemented on ground-based and space-borne
coronagraphs.
---------------------------------------------------------
Title: Solar and Stellar Polarimetry with Liquid Crystal Retarders
Authors: Zangrilli, L.; Loreggia, D.; Gardiol, D.; Fineschi, S.
2003MmSAI..74..807Z Altcode:
We present some preliminary result of a study for the application
of Liquid Crystals Variable Retarder (LCVR) plates in achromatic
imaging Stokes polarimeters. The use of LCVR plates allows to
replace mechanically rotating retarders of a polarimeter with
electrically controlled devices, without having moving parts. Broad
band instruments in the visible spectrum are required when observing
photon flux limited astronomical sources. These observations are
favoured by using polarimeters achromatic over a consistent portion
of the visible band. We propose to develope an achromatic polarimeter
based on electro-optically modulating liquid crystals for ground and
space-based instrumentation.
---------------------------------------------------------
Title: UVCI for HERSCHEL: instrument description and activity
status report
Authors: Gardiol, D.; Romoli, M.; Landini, F.; Naletto, G.; Da Deppo,
V.; Malvezzi, M.; Apollonio, P.; Duchini, G.; Rusconi, E.; Santori,
A.; Antonucci, E.; Fineschi, S.; Loreggia, D.; Zangrilli, L.; Gori,
L.; Nicolosi, P.; Pelizzo, M. G.
2003MmSAI..74..839G Altcode:
The Ultraviolet and Visible light Coronagraphic Imager (UVCI) is an
imaging coronagraph that will take pictures of the solar corona from 1.4
up to 3.5 solar radii at three different wavelengths, HI Ly-alpha 121.6
nm, HeII Ly-alpha 30.4 nm, and broadband visible polarized light. It
is part of the HERSCHEL experiment (HElium Resonant Scattering in the
Corona and HELiosphere) and it will fly on a sounding rocket. The
instrument optical design consists of two twin off-axis Gregorian
externally occulted telescopes, with multilayer-coated optics optimised
respectively for the HI and HeII lines.\ We describe the instrument
structure design and the associated optical tolerances analysis. The
structure is conceived to attain high stiffness with the lowest possible
weight. Tolerances on the positioning of the optical elements, for
alignment purpose, have been evaluated through a geometrical approach
and ray-tracing method.
---------------------------------------------------------
Title: The ASCE EUV Polarimeter
Authors: Romoli, M.; Fineschi, S.; Uslenghi, M.; Corti, G.; Pace,
E.; Ciaravella, A.; Tondello, G.; Noci, G.; Gardner, L. D.; Kohl, J. L.
2003MmSAI..74..835R Altcode:
The SOHO mission has achieved important results in the physics of
solar wind and coronal mass ejection acceleration, but most of the
processes that drive this acceleration have not yet been explained. The
Advanced Spectroscopic and Coronagraphic Explorer (ASCE) mission will
carry on-board spectroscopic and polarimetric instrumentation of new
generation that is designed to address the fundamental questions on this
processes. Following a brief description of ASCE scientific objectives
and instrumentation, the EUV polarimetric channel is described. The
EUV Polarimeter (EUVP) is designed to measure for the first time the
magnetic field vector in the extended corona through the Hanle effect,
and the anisotropy of the ion velocity. The EUVP represents the
contribution of the Italian solar physics community to the ASCE mission.
---------------------------------------------------------
Title: MAGRITTE / SPECTRE : the Solar Atmospheric Imaging Assembly
(AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, P.; Defise, J. M.; Halain, J. P.; Mazy, E.; Jamar, C.;
Clette, F.; Cugnon, P.; Berghmans, D.; Hochedez, J. F.; Delaboudiniere,
J. P.; Artzner, G.; Auchere, F.; Mercier, R.; Ravet, M. F.; Delmotte,
M.; Idir, M.; Fineschi, S.; Antonucci, E.; Harrison, R. A.; Howard,
R. A.; Moses, J. D.; Newmark, J. S.
2002AGUFMSH21C..05R Altcode:
The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar
Dynamics Observatory will characterize the dynamical evolution of
the solar plasma from the chromosphere to the corona, and will follow
the connection of plasma dynamics with magnetic activity throughout
the solar atmosphere. The AIA consists of 7 high resolution imaging
telescopes in the following spectral bandpasses: 1215 \x8F Ly-a, 304
\x8F He II, 629 \x8F OV, 465 \x8F Ne VII, 195 \x8F Fe XII (includes Fe
XXIV), 284 \x8F Fe XV, and 335 \x8F Fe XVI. The telescopes are grouped
by instrumental approach: the Magritte Filtergraphs (R. Magritte,
famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
channels with bandpasses ranging from 195 to 1216 \x8F, and the SPECTRE
Spectroheliograph with one soft-EUV channel at OV 629 \x8F. They will
be simultaneously operated with a 10-second imaging cadence. These two
instruments, the electronic boxes and two redundant Guide Telescopes
(GT) constitute the AIA suite. They will be mounted and coaligned on a
dedicated common optical bench. The GTs will provide pointing jitter
information to the whole SHARPP assembly. This poster presents the
selected technologies, the different challenges, the trade-offs to be
made in phase A, and the model philosophy. From a scientific viewpoint,
the unique combination high temporal and spatial resolutions with the
simultaneous multi-channel capability will allow Magritte/SPECTRE
to explore new domains in the dynamics of the solar atmosphere, in
particular the fast small-scale phenomena. We show how the spectral
channels of the different instruments were derived to fulfill the
AIA scientific objectives, and we outline how this imager array will
address key science issues, like the transition region and coronal waves
or flare precursors, in coordination with other SDO experiments. We
finally describe the real-time solar monitoring products that will be
made available for space-weather forecasting applications.
---------------------------------------------------------
Title: Solar and Heliospheric Observatory Ultraviolet Coronagraph
Spectrometer and Yohkoh Soft X-Ray Telescope Observations of the
High-Temperature Corona above an Active Region Complex
Authors: Ko, Yuan-Kuen; Raymond, John C.; Li, Jing; Ciaravella,
Angela; Michels, Joseph; Fineschi, Silvano; Wu, Rai
2002ApJ...578..979K Altcode:
We present the results of Solar and Heliospheric Observatory Ultraviolet
Coronagraph Spectrometer (SOHO/UVCS) and Yohkoh Soft X-Ray Telescope
(SXT) observations above an active region complex (AR 8194, 8195,
and 8198) at the southeast limb on 1998 April 6-7. This active
region complex appears to be the base of a small streamer seen by
the Large Angle and Spectrometric Coronagraph Experiment (LASCO/C2)
at the southeast limb. The UVCS was offset-pointed to observe low
in the corona from 1.22 up to 1.6 R<SUB>solar</SUB> with normal
pointing. High-temperature lines such as [Fe XVIII] λ974 and Ne
IX λ1248 were present in this region, implying that the electron
temperature is higher than that in the quiet-Sun corona. This region
of the corona is also seen as particularly bright in the Yohkoh/SXT,
SOHO EUV Imaging Telescope high-temperature filter (Fe XV λ284)
and SOHO/LASCO C1. The electron temperature analysis indicates a
two-temperature structure, one of ~1.5×10<SUP>6</SUP> K, which is
similar to that observed in quiet-Sun streamers, and the other at
a high temperature of ~3.0×10<SUP>6</SUP> K. This two-temperature
region likely corresponds to two distinct coronal regions overlapping
in the line of sight. We compare the electron temperature and emission
measure results from the SOHO/UVCS data with those from the Yohkoh/SXT
data. The absolute elemental abundances show a general first ionization
potential effect and decrease with height for all the elements. This is
consistent with the effect of gravitational settling, which, however,
cannot totally account for the observed elemental abundances. Other
mechanisms that are likely to affect the coronal elemental abundance
are discussed.
---------------------------------------------------------
Title: Elemental Abundances and Post-Coronal Mass Ejection Current
Sheet in a Very Hot Active Region
Authors: Ciaravella, A.; Raymond, J. C.; Li, J.; Reiser, P.; Gardner,
L. D.; Ko, Y. -K.; Fineschi, S.
2002ApJ...575.1116C Altcode:
A peculiar young active region was observed in 1998 March with the
Ultraviolet Coronagraph Spectrometer (UVCS) over the southwest limb. The
spectra showed strong emission in the λ974 line of fluorine-like
iron, [Fe XVIII], which is brightest at an electron temperature of
10<SUP>6.8</SUP> K, and lines of Ne IX, [Ca XIV], [Ca XV], Fe XVII, [Ni
XIV], and [Ni XV]. It is the only active region so far observed to show
such high temperatures 0.5 R<SUB>solar</SUB> above the solar limb. We
derive the emission measure and estimate elemental abundances. The
active region produced a number of coronal mass ejections (CMEs). After
one CME on March 23, a bright post-CME arcade was seen in EIT and
Yohkoh/SXT images. Between the arcade and the CME core, UVCS detected
a very narrow, very hot feature, most prominently in the [Fe XVIII]
line. This feature seems to be the reconnection current sheet predicted
by flux rope models of CMEs. Its thickness, luminosity, and duration
seem to be consistent with the expectations of the flux rope models
for CME. The elemental abundances in the bright feature are enhanced
by a factor of 2 compared to those in the surrounding active region,
i.e., a first ionization potential enhancement of 7-8 compared to the
usual factor of 3-4.
---------------------------------------------------------
Title: HElium Resonance Scattering in the Corona and HELiosphere
(HERSCHEL)
Authors: Moses, J. D.; Newmark, J.; Howard, R.; Auchere, F.; Antonucci,
E.; Fineschi, S.; Romoli, M.
2002AGUSMSH21B..03M Altcode:
The proposed HERSCHEL (HElium Resonance Scattering in the Corona and
HELiosphere) program will investigate coronal heating and solar wind
acceleration from a range of solar source structures by obtaining
simultaneous observations of the electron, proton and helium solar
coronae. The HERSCHEL will establish proof-of-principle for the
Ultra-Violet Coronagraph (UVC), which is in the ESA Solar Orbiter
Mission baseline. The NRL Solar Physics Branch is joining with the
Italian UVC Consortium to address the objectives of the International
Living With a Star program with this combination of NASA suborbital
program and ESA Solar Orbiter flight opportunities. Indeed, while
the Solar Orbiter flight is still many years away, the 3 year program
being proposed here is essential in order to prove the validity of this
exciting new concept before the Solar Orbiter instrument selection is
finalized. This proposal aims to develop instrumentation that for the
first time will directly image and characterize on a global coronal
scale the two must abundant elements, hydrogen and helium. This will
directly address three outstanding questions in the Sun-Earth Connection
theme: 1) Origin of the slow solar wind, 2) Acceleration mechanisms of
the fast solar wind, and 3) Variation of Helium abundance in coronal
structures. Additionally, by establishing proof of concept for the
UVC on Solar Orbiter, this will facilitate future investigations
of CME's kinematics, and solar cycle evolution of the electron,
proton, and helium coronae. Lastly, this mission fits the goals of
the International Living With a Star (ILWS) program. This work has
been supported by the Office of Naval Research.
---------------------------------------------------------
Title: The Helium Focusing Cone of the Local Interstellar Medium
Close to the Sun
Authors: Michels, J. G.; Raymond, J. C.; Bertaux, J. L.; Quémerais,
E.; Lallement, R.; Ko, Y. -K.; Spadaro, D.; Gardner, L. D.; Giordano,
S.; O'Neal, R.; Fineschi, S.; Kohl, J. L.; Benna, C.; Ciaravella,
A.; Romoli, M.; Judge, D.
2002ApJ...568..385M Altcode:
The Solar and Heliospheric Observatory (SOHO) Ultraviolet Coronagraph
Spectrometer is used to observe the interplanetary He focusing cone
within 1 AU. Taken over 2 yr and from differing orbit positions, the
series of observations includes measurements of He I 584 Å and Lyβ
intensities. The cone itself is spatially well defined, and the He I
intensity within the cone was ~45 R in 1996 December, compared with
~1 R for lines of sight outward from 1 AU. Between 1996 December and
1998 June, the focusing cone dimmed by a factor of 3.3 as the level of
solar activity rose. This is the first time that interstellar helium
is observed so near the Sun. Measured intensities are compared to a
detailed temperature and density model of interstellar helium in the
solar system. The model includes EUV ionization but does not include
ionization by electron impact from solar wind electrons. There are
several features in the data model comparison that we attribute to
the absence of electron impact ionization in the model. The absolute
maximum intensity of 45 R first measured in 1996 December calls for
an ionization 45% more intense than the EUV photoionization alone as
measured by the Solar EUV Monitor/Charge, Element, and Isotope Analysis
System (SEM/CELIAS) on SOHO. Important day-to-day variations of the
intensity are observed, as well as a general decrease as the solar
activity rises (both absolute and divided by a model with a constant
ionization). This general decrease is even larger than predicted by a
model run with the SEM/CELIAS photoionization rate alone, in spite of a
factor of 1.5 increase of this rate from 1996 December to 1998 June. At
this time, an additional ionization rate of 0.56×10<SUP>-7</SUP>
s<SUP>-1</SUP> (compared with 1.00×10<SUP>-7</SUP> s<SUP>-1</SUP> from
solar EUV) is required to fit the measured low intensity. We attribute
this additional rate to solar wind electron impact ionization of the
atoms. This shows that the helium intensity pattern is a very sensitive
indicator of the electron density and temperature near the Sun.
---------------------------------------------------------
Title: A High Temperature Corona above an Active Region Complex
Authors: Ko, Y. -K.; Raymond, J. C.; Li, J.; Ciaravella, A.; Michels,
J.; Fineschi, S.; Wu, R.
2002mwoc.conf...73K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: In-flight Calibration of the UVCS White Light Channel
Authors: Romoli, M.; Frazin, R. A.; Kohl, J. L.; Gardner, L. D.;
Cranmer, S. R.; Reardon, K.; Fineschi, S.
2002ISSIR...2..181R Altcode: 2002ESASR...2..181R; 2002rcs..conf..181R
The UVCS White Light Channel (WLC) is designed to measure the linearly
polarized radiance (pB) of the corona, in the wavelength band from 450
nm to 600 nm, in order to derive one of the fundamental parameters of
the solar corona: the electron density. This paper gives a thorough
description of the in-flight radiometric calibration of the WLC, which
uses the star α Leo and the planet Jupiter as transfer standards
and is based on calibrations of ground-based instruments. The
method for computing the polarized radiance from the measurements
is also described, together with the stray light and polarization
characterizations obtained from dedicated, in-flight measurements.
---------------------------------------------------------
Title: UV Radiometric Calibration of UVCS
Authors: Gardner, L. D.; Smith, P. L.; Kohl, J. L.; Atkins, N.;
Ciaravella, A.; Miralles, M. P.; Panasyuk, A.; Raymond, J. C.;
Strachan, L., Jr.; Suleiman, R. M.; Romoli, M.; Fineschi, S.
2002ISSIR...2..161G Altcode: 2002ESASR...2..161G; 2002rcs..conf..161G
The Ultraviolet Coronagraph Spectrometer (UVCS) was characterized
and radiometrically calibrated in the laboratory as a system at the
Harvard-Smithsonian Center for Astrophysics in June of 1995. Component
level calibrations of optical components and detectors were also
performed. After launch, an in-flight calibration activity was carried
out that extended the laboratory calibration, compared UVCS measurements
of stars to those of other instruments and monitored the radiometric
stability of UVCS through repeated measurements of stars that are
believed to have nearly constant ultraviolet irradiance. In-flight
measurements have, in general, confirmed the laboratory radiometric
calibration. Comparisons to Spartan 201 observations of the same coronal
structures agree within 10 %. The system responsivity, although it has
changed somewhat during the six years of operation, is well behaved
and characterizable. This paper describes the UVCS calibration and
its results.
---------------------------------------------------------
Title: Spectropolarimetric measurements of the extreme-ultraviolet
emission from helium following e-, H+, H2+, and H3+ charged particle
impact
Authors: Merabet, Hocine; Bruch, Reinhard F.; Hanni, Jonathan; Godunov,
Alexander; McGuire, James; Bray, Igor; Fursa, D. V.; Bartchat, Klaus;
Tseng, Hsiang-Chi; Lin, Chii-Dong; Fineschi, Silvano
2001SPIE.4498..207M Altcode:
We present here comprehensive experimental data corresponding
to helium extreme ultraviolet emission (EUV) for the 300-600A
wavelength range in e<SUP>-</SUP> + He, H<SUP>+</SUP> + He, and
Hn<SUB>n</SUB><SUP>+</SUP> + He (n=2-3) collisions with impact
velocities ranging from 1.4 to 6.9 a.u. The degree of linear
polarization associated with HeI (1snp) <SUP>1</SUP>P<SUP>o</SUP>
-> (1s<SUP>2</SUP>) <SUP>1</SUP>S decays for n-2-5 ((lambda)
=510 to 584A) and HeII (2p) <SUP>2</SUP>P<SUP>o</SUP> -> (1s)
<SUP>2</SUP>S transitions ((lambda) =304A), have been measured at
intermediate and higher energies. These measurements have been conducted
using a compact lightweight molybdenum/silicon multilayer mirror (MLM)
spetropolarimeter. These experimental results are compared with our most
advanced theoretical calculations using the close coupling method and
several many body perturbation approaches. In this study, the degree of
linear polarization will be discussed as a function of the projectile
charge to elucidate few body excitation and ionization-excitation
processes. Specifically, more sophisticated calculations including
second Born approximation with full off-energy terms for the HeII (2p)
<SUP>2</SUP>P<SUP>o</SUP> sublevels have been used. The excellent
agreement with our HeII Lyman-(alpha) data clearly demonstrates
that off-energy terms in two-electron atomic interaction have very
prominent effects. Our comprehensive experimental and theoretical
database is also of great importance for the understanding of solar
physics phenomena. Such results can be used as a new diagnostic tool
for clarifying the role of electron and proton beams in solar flares.
---------------------------------------------------------
Title: Stray light evaluation of the Ultraviolet and Visible-light
Coronagraph Imager (UVCI) rocket prototype
Authors: Romoli, Marco; Landini, Federico; Fineschi, Silvano; Gardiol,
Daniele; Naletto, Giampiero; Malvezzi, Marco; Tondello, Giuseppe;
Noci, Giancarlo C.; Antonucci, Ester
2001SPIE.4498...27R Altcode:
The Ultraviolet and Visible-light Coronagraph Imager (UVCI) proposed
for the European Space Agency (ESA) Solar Orbiter mission, is designed
to image the visible and the ultraviolet coronal emissions, in order to
diagnose the solar corona. The UVCI is an externally occulted reflection
coronagraph that obtains monochromatic images in the neutral hydrogen
HI 121.6 nm and in the single ionized helium HeII 30.4 nm lines, and
measures the polarized brightness (pB) of the K-corona in broadband
visible light. One of the most stringent requirements in the design
of a coronagraph is the stray light rejection. The stray light is
produced by solar disk radiation which is several order of magnitude
brighter than the coronal radiation in both visible and UV. The solar
disk radiation enters the instrument through the external aperture and
stray light is produced by diffraction off the edges of the apertures
and of the optical components, non-specular reflections off the mirror
surfaces, and scattering off the mechanical structure. In this paper,
the features in the optical design that contribute to the stray light
reduction are described, and an analysis of all possible stray light
contributions is performed on the optical configuration of the UVCI
sounding rocket prototype (UVC-SR). From this analysis, a stray light
model has been developed and its results are compared with the minimum
measurable signal expected from the solar corona.
---------------------------------------------------------
Title: UV/EUV and Visible Space Instrumentation for Astronomy and
Solar Physics
Authors: Siegmund, Oswald H.; Fineschi, Silvano; Gummin, Mark A.
2001SPIE.4498.....S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Advanced Spectroscopic and Coronagraphic Explorer Mission
Authors: Kohl, J. L.; Howard, R.; Davila, J.; Noci, G.; Esser, R.;
Ciaravella, A.; Cranmer, S.; Fineschi, S.; Gardner, L.; Raymond, J.;
Romoli, M.; Smith, P.; Socker, D.; Strachan, L.; Van Ballegooijen, A.
2001AGUFMSH31B0711K Altcode:
SOHO has provided profound insights into the physics of solar wind
acceleration and coronal mass ejections. Although significant
progress has been made, most of the dominant physical processes
controlling these phenomena are still not identified. The Advanced
Spectroscopic and Coronagraphic Explorer Mission provides next
generation spectroscopic and polarimetric instrumentation aimed at
identifying these processes. The launch is planned for March 2007 with
mission operations and data analysis continuing for 5 years. The data
will be unrestricted and available to the community. The envisioned
program includes a Guest Investigator Program with an average of 15
grants to be awarded in response to proposals submitted during the
first year of the mission. Information about the proposed scientific
goals and instrumentation will be presented.
---------------------------------------------------------
Title: Extended UV corona imaging from the Solar Orbiter: the
Ultraviolet and Visible-light Coronagraph (UVC)
Authors: Fineschi, Silvano; Antonucci, Ester; Gardiol, Daniele; da
Deppo, Vania; Naletto, Giampiero; Romoli, Marco; Cacciani, Alessandro;
Malvezzi, Marco
2001ESASP.493..217F Altcode: 2001sefs.work..217F
No abstract at ADS
---------------------------------------------------------
Title: Space-based Instrumentation for Magnetic Field Studies of
Solar and Stellar Atmospheres
Authors: Fineschi, S.
2001ASPC..248..597F Altcode: 2001mfah.conf..597F
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet and visible-light coronagraph for the Solar
Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Gardiol, Daniele; Noci,
Giancarlo C.; Romoli, Marco; Naletto, Giampiero; Tondello, Giuseppe;
Zattarin, Marco; Malvezzi, Andrea M.; Cesare, Stefano
2000SPIE.4139..378A Altcode:
The Ultraviolet and Visible-light Coronagraph (UVC) is one of the
solar remote-sensing instruments proposed for the model payload of the
Solar Orbiter mission. The Solar Orbiter is one of the two 'Flexible'
missions selected in September 2000 by the European Space Agency (ESA)
for the definition study phase. A novel orbital design takes the orbiter
as close as 0.21 astronomical units (AU) to the Sun, with heliographic
latitudes as high as 38 degrees for observations of the solar polar
regions at very high spatial resolution. From this vantage point,
the UVC can, at the same time, image the visible and ultraviolet
coronal emissions and diagnose, with unprecedented temporal and
spatial resolution (down to 1200 km) the full solar corona. The UVC's
optical design, presented here, consists of an externally occulted,
off-axis Gregorian with multilayer-coated optics. The UVC can obtain
monochromatic images in the neutral hydrogen HI Lyman (alpha) , (lambda)
121.6 nm, and single-ionized helium HEII Lyman (alpha) , (lambda) 30.4
nm, lines and measure the polarized brightness (pB) of the visible
K-corona. The ultraviolet Lyman (alpha) lines are separated with two
multilayer coatings mirror and an extreme-ultraviolet transmission
filter. The mirrors' coating optimized for 30.4 nm still has a good
reflectivity at 121.6 nm and visible. The optical performances,
resulting from ray-tracing calculations, are presented here, along
with the expected system response to the coronal signal.
---------------------------------------------------------
Title: Instrumentation for UV/EUV Astronomy and Solar Missions
Authors: Fineschi, Silvano; Korendyke, Clarence M.; Siegmund, Oswald
H.; Woodgate, Bruce E.
2000SPIE.4139.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Efficiency variations of UVCS/SOHO based on laboratory
measurements of replica gratings
Authors: Gardner, Larry D.; Atkins, Nigel; Fineschi, Silvano; Smith,
Peter L.; Kohl, John L.; Maccari, L.; Romoli, Marco
2000SPIE.4139..362G Altcode:
We have carried out measurements of efficiency as functions of position
across the surfaces of replica grating made from the same masters
as the UVCS/SOHO flight units. Variations in first order efficiency
which significantly affect the interpretation of UVCS data are found
along the direction perpendicular to the grooves. Variations are also
found along the direction parallel to the grooves, but these do not
seriously affect UVCS data interpretation. The measurements and their
application to the radiometric calibration of UVCS/SOHO are discussed.
---------------------------------------------------------
Title: Temperature, density and magnetic field structure of the
corona during the total eclipse of 1999 August 11
Authors: Habbal, S. R.; Johnson, J.; Nisenson, P.; Woo, R.; Fineschi,
S.; Esser, R.; Wood, C. H.; Hale, J.; Forman, M. A.; Johnson, J. A.;
Jabbour, J.
2000SPD....31.0235H Altcode: 2000BAAS...32..817H
The goal of the eclipse expedition of the Harvard-Smithsonian Center
for Astrophysics on 1999 August 11 to Ayn Diwar in Syria was to explore
the temperature, density and magnetic structure of the corona through
simultaneous imaging in the Fe X 6374, XIV 5303 and XI 7892 Angstroms
lines, the Hα 6563 Angstroms line, and the polarized brightness or
white light. Polarization measurements were made in the Fe XIV 5303
Angstroms and Hα 6563 Angstroms lines to yield the direction of the
coronal magnetic field. Inferences of the temperature distribution
were made from the three iron lines, while density profiles were
derived from the polarized brightness measurements. Supporting
space based observations were acquired with LASCO and UVCS on
SOHO. The comprehensive diagnostic resulting from the analysis of the
observations of the close-to-spherically symmetric corona of 1999
August 11 approaching solar maximum will be presented. Funding for
this research was provided by NSF grant ATM 9521733 to the Smithsonian
Astrophysical Observatory. We acknowledge the generous hospitality
and support bestowed upon the team by the Syrian Ministry of Higher
Education to conduct the experiment in Syria. The digitization of
the photographic film was made with the help of Dr. J. Thornton and
S. Sarafian from the Image Science Laboratory at Polaroid Corporation.
---------------------------------------------------------
Title: Polarimetry of the UV solar corona with ASCE
Authors: Fineschi, Silvano; Gardner, Larry D.; Kohl, John L.; Romoli,
Marco; Pace, Emanuele; Corti, Gianni; Noci, Giancarlo C.
1999SPIE.3764..147F Altcode:
The Advanced Solar Coronal Explorer (ASCE) is a mid-explorer (MidEx)
mission selected, together with other five, for the a Phase A Concept
Study in the 1999 round of MidEX proposal. ASCE's spacecraft bus is
a SPARTAN 400 reusable carrier deployed in low Earth orbit by the
Space Shuttle. ASCE's payload comprises two instrument modules,
the Spectroscopic and Polarimetric Coronagraph (SPC) and the
Extreme Ultraviolet Imager (EUVI). The scientific objective of the
mission is the investigation, through spectroscopic and polarimetric
techniques, of the physics of the coronal heating and of the solar
wind acceleration. A critical physical parameter of the corona is the
magnetic field. Polarimetric measurements of UV coronal radiation
and their interpretation through the Hanle effect can be used for
coronal magnetic field diagnostics. One of the SPC spectrometers,
the Spectroscopy/Polarimetry channel (SPCH), includes a reflecting
Brewster-angle polarimeter for measurements of the linear polarization
of the HI Lyman series lines (i.e., Ly-(alpha) , -(beta) , and (gamma)
) and of the O VI 1032 Angstrom line. In this paper, the optical design
of the SPCH polarimeter is described. A relevant element of this design
is the external occulter (EXO) that is supported on a boom, which is
extended 10 m beyond the instrument aperture, once the instrument is in
station. The analysis of the stray- light reduction provided by this
occulting system is described in this paper. The principal source of
stray light is solar disk light that is diffracted from the edge of the
EXO and scattered from the telescope mirror. The analysis shows that the
stray-light is less than 10<SUP>-2</SUP> the coronal signal. This level
of stray-light rejection minimizes the polarized stray light that may
be introduced by the EXO's straight edge. The most appropriate material
for the polarizer has been found to be CaF<SUB>2</SUB>. The material
selection criteria are described. Finally, the paper illustrates with
an example that if the linear polarization can be measured better than
1%, then the instrumental sensitivity to magnetic fields may reach a
few gauss (greater than 2 gauss), in coronal active regions.
---------------------------------------------------------
Title: Coronal Magnetic Field Diagnostics with UV Spectropolarimetry
Authors: Fineschi, S.; van Ballegoijen, A.; Kohl, J. L.
1999ESASP.446..317F Altcode: 1999soho....8..317F
No abstract at ADS
---------------------------------------------------------
Title: UVCS/SOHO observations of coronal streamers
Authors: Frazin, R. A.; Modigliani, A.; Ciaravella, A.; Dennis, E.;
Fineschi, S.; Gardner, L. D.; Michels, J.; O'Neal, R.; Raymond, J. C.;
Wu, C. -R.; Noci, G.; Kohl, J. L.
1999AIPC..471..235F Altcode: 1999sowi.conf..235F
We used the Ultraviolet Coronagraph Spectrometer (UVCS) on the
Solar and Heliospheric Observatory (SOHO) to obtain line profiles
in mid-latitude coronal streamers between 1.3 R<SUB>solar</SUB> and
5.5 R<SUB>solar</SUB> during a period of moderate solar activity. We
present a summary of the preliminary results. These results clearly
indicate that the mid-latitude streamers observed during this time
period have very different spectral properties than the equatorial
streamers observed near solar minimum.
---------------------------------------------------------
Title: Comparison of outflow velocity determinations with UVCS and
LASCO for the coronal mass ejection of 13-14 August 1997
Authors: Strachan, L.; Ciaravella, A.; Raymond, J. C.; Fineschi, S.;
O'Neal, R.; Kohl, J. L.; Modigliani, A.; Noci, G.; Andrews, M. D.
1999AIPC..471..637S Altcode: 1999sowi.conf..637S
The Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO observed
a Coronal Mass Ejection (CME) on 13-14 August 1997. The event was
observed simultaneously with the LASCO white light coronagraphs. This
paper describes the results from a comparison of outflow velocities
determined from UVCS Doppler dimming studies with the velocities
determined by examining the proper motions of the CME as measured by
LASCO. In addition, estimates for line of sight velocities, densities
and kinetic temperatures are discussed.
---------------------------------------------------------
Title: An Empirical Model of a Polar Coronal Hole at Solar Minimum
Authors: Cranmer, S. R.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Strachan, L.; Panasyuk, A. V.;
Gardner, L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond,
J. C.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.;
Ciaravella, A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.;
Martin, R.; Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal,
R. H.; Pernechele, C.; Poletto, G.; Smith, P. L.; Suleiman, R. M.
1999ApJ...511..481C Altcode:
We present a comprehensive and self-consistent empirical model
for several plasma parameters in the extended solar corona above
a polar coronal hole. The model is derived from observations
with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO)
during the period between 1996 November and 1997 April. We compare
observations of H I Lyα and O VI λλ1032, 1037 emission lines
with detailed three-dimensional models of the plasma parameters and
iterate for optimal consistency between measured and synthesized
observable quantities. Empirical constraints are obtained for
the radial and latitudinal distribution of density for electrons,
H<SUP>0</SUP>, and O<SUP>5+</SUP>, as well as the outflow velocity
and unresolved anisotropic most probable speeds for H<SUP>0</SUP> and
O<SUP>5+</SUP>. The electron density measured by UVCS/SOHO is consistent
with previous solar minimum determinations of the white-light coronal
structure; we also perform a statistical analysis of the distribution
of polar plumes using a long time series. From the emission lines we
find that the unexpectedly large line widths of H<SUP>0</SUP> atoms
and O<SUP>5+</SUP> ions at most heights are the result of anisotropic
velocity distributions. These distributions are not consistent with
purely thermal motions or the expected motions from a combination of
thermal and transverse wave velocities. Above 2 R<SUB>solar</SUB>,
the observed transverse most probable speeds for O<SUP>5+</SUP> are
significantly larger than the corresponding motions for H<SUP>0</SUP>,
and the outflow velocities of O<SUP>5+</SUP> are also significantly
larger than the corresponding velocities of H<SUP>0</SUP>. Also, the
latitudinal dependence of intensity constrains the geometry of the
wind velocity vectors, and superradial expansion is more consistent
with observations than radial flow. We discuss the constraints and
implications on various theoretical models of coronal heating and
acceleration.
---------------------------------------------------------
Title: EUV Spectral Line Profiles in Polar Coronal Holes from 1.3
to 3.0 R<SUB>solar</SUB>
Authors: Kohl, J. L.; Esser, R.; Cranmer, S. R.; Fineschi, S.; Gardner,
L. D.; Panasyuk, A. V.; Strachan, L.; Suleiman, R. M.; Frazin, R. A.;
Noci, G.
1999ApJ...510L..59K Altcode:
Spectral line profiles have been measured for H I λ1216, O VI λλ1032,
1037, and Mg X λ625 in a polar coronal hole observed during 1997
September 15-29, at projected heliographic heights ρ between 1.34
and 2.0 R<SUB>solar</SUB>. Observations of H I λ1216 and the O
VI doublet from 1997 January for ρ=1.5-3.0 R<SUB>solar</SUB> are
provided for comparison. The O VI lines are well fit to a narrow and
broad component which appear to be associated with regions of higher
and lower spectral radiance, respectively. The narrow components
dominate at low heights and become a small fraction of the lines at
higher heights. Mg X λ625 is observed to have a narrow component at
ρ=1.34 R<SUB>solar</SUB> which accounts for only a small fraction of
the observed spectral radiance. In the case of the broad components,
the values of v<SUB>1/e</SUB> for O VI are only slightly larger than
those for H I at ρ=1.34 R<SUB>solar</SUB> but are significantly
larger at ρ=1.5 R<SUB>solar</SUB> and much larger for ρ>1.75
R<SUB>solar</SUB>. In contrast, the Mg X values are less than those
of H I up to 1.75 and then increase rapidly up to at least ρ=2.0
R<SUB>solar</SUB> but never reach the values of O VI.
---------------------------------------------------------
Title: Plasma Properties in Coronal Holes Derived from Measurements
of Minor Ion Spectral Lines and Polarized White Light Intensity
Authors: Esser, Ruth; Fineschi, Silvano; Dobrzycka, Danuta; Habbal,
Shadia R.; Edgar, Richard J.; Raymond, John C.; Kohl, John L.;
Guhathakurta, Madhulika
1999ApJ...510L..63E Altcode:
Recent observations of the Lyα λ1216, Mg X λ625, and O VI λ1038
spectral lines carried out with the Ultraviolet Coronagraph Spectrometer
(UVCS) on board SOHO at distances in the range 1.35-2.1 R<SUB>S</SUB> in
the northern coronal hole are used to place limits on the turbulent wave
motions of the background plasma and the thermal motions of the protons
and Mg<SUP>+9</SUP> and O<SUP>+5</SUP> ions. Limits on the turbulent
wave motion are estimated from the measured line widths and electron
densities derived from white light coronagraph observations, assuming
WKB approximation at radial distances covered by the observations. It
is shown that the contribution of the turbulent wave motion to the
widths of the measured spectral lines is small compared to thermal
broadening. The observations show that the proton temperature slowly
increases between 1.35 and 2.7 R<SUB>S</SUB> and does not exceed
3×10<SUP>6</SUP> K in that region. The temperature of the minor ions
exceeds the proton temperature at all distances, but the temperatures
are neither mass proportional nor mass-to -charge proportional. It is
shown, for the first time, that collision times between protons and
minor ions are small compared to the solar wind expansion times in
the inner corona. At 1.35 R<SUB>S</SUB> the expansion time exceeds
the proton Mg<SUP>+9</SUP> collision time by more than an order of
magnitude. Nevertheless, the temperature of the Mg ions is significantly
larger than the proton temperature, which indicates that the heating
mechanism has to act on timescales faster than minutes. When the
expansion time starts to exceed the collision times a rapid increase
of the O<SUP>+5</SUP> ion spectral line width is seen. This indicates
that the heavier and hotter ions lose energy to the protons as long as
collision frequencies are high, and that the ion spectral line width
increases rapidly as soon as this energy loss stops.
---------------------------------------------------------
Title: UVCS/SOHO Ion Kinetics in Coronal Streamers
Authors: Frazin, R. A.; Ciaravella, A.; Dennis, E.; Fineschi, S.;
Gardner, L. D.; Michels, J.; O'Neal, R.; Raymond, J. C.; Wu, C. -R.;
Kohl, J. L.; Modigliani, A.; Noci, G.
1999SSRv...87..189F Altcode:
We made streamer observations with the Ultraviolet Coronagraph
Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO)
during the early part of 1998, which was a time of moderate solar
activity. We present an empirical study of coronal ion kinetics using
the line profiles from these observations. Our first and most striking
result is that the mid-latitude (ML) streamers have much narrower
O VI 1032 Å line profiles than the solar minimum equatorial (SME)
streamers. Our second result is that the line profiles from a small
collection of ions in ML streamers do not seem to be consistent with
the ions having a single temperature and turbulent velocity. We discuss
several interpretations, including line of sight (LOS) effects. This
work is supported by the National Aeronautics and Space Administration
under grant NAG-3192 to the Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: Ly-α Observation of a Coronal Streamer with UVCS/SOHO
Authors: Maccari, L.; Noci, G.; Modigliani, A.; Romoli, M.; Fineschi,
S.; Kohl, J. L.
1999SSRv...87..265M Altcode:
In this paper we discuss some characteristics of an equatorial streamer
observed by UVCS in July 1997. We determine the height distribution
of the Ly-α total intensity and of its width. We focus our attention,
in particular, on the time variability of these parameters.
---------------------------------------------------------
Title: UVCS/SOHO Observations of Spectral Line Profiles in Polar
Coronal Holes
Authors: Kohl, J. L.; Fineschi, S.; Esser, R.; Ciaravella, A.; Cranmer,
S. R.; Gardner, L. D.; Suleiman, R.; Noci, G.; Modigliani, A.
1999SSRv...87..233K Altcode:
Ultraviolet emission line profiles have been measured on 15-29 September
1997 for H I 1216 Å, O VI 1032, 1037 Å and Mg X 625 Å in a polar
coronal hole, at heliographic heights ϱ (in solar radii) between 1.34
and 2.0. Observations of H I 1216 Å and the O VI doublet from January
1997 for ϱ = 1.5 to 3.0 are provided for comparison. Mg X 625 Å is
observed to have a narrow component at ϱ = 1.34 which accounts for
only a small fraction of the observed spectral radiance, and a broad
component that exists at all observed heights. The widths of O VI broad
components are only slightly larger than those for H I at ϱ = 1.34,
but are significantly larger at ϱ = 1.5 and much larger for ϱ >
1.75. In contrast, the Mg X values are less than those of H I up to
1.75 and then increase rapidly up to at least ϱ = 2.0, but never
reach the values of O VI.
---------------------------------------------------------
Title: Ultraviolet and X-ray detection, spectroscopy, and polarimetry
III : 19-20 July 1999, Denver, Colorado
Authors: Fineschi, Silvano; Woodgate, Bruce E.; Kimble, Randy A.
1999SPIE.3764.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: X-Ray and Ultraviolet Spectroscopy and Polarimetry II
Authors: Fineschi, Silvano
1998SPIE.3443.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: White-light stray light test of the SOHO UVCS
Authors: Leviton, Douglas B.; Gardner, Larry D.; Fineschi, Silvano;
Jhabvala, Murzy D.; Kohl, John L.; Romoli, Marco; Noci, Giancarlo C.
1998SPIE.3443...50L Altcode:
During the late stages of integration at MATRA-Marconi in Toulouse,
France of the Ultraviolet Coronagraph Spectrometer (UVCS) for the joint
NASA/ESA (European Space Agency) Solar and Heliospheric Observatory
(SOHO), project management for the International Solar and Terrestrial
Physics Project (ISTP) at Goddard Space Flight Center (GSFC) became
concerned that the instrument's elaborate stray light rejection system
had not been tested and might possibly be misaligned such that the
instrument could not deliver promised scientific returns. A white light
stray light test, which would place an upper bound on UVCS's stray
light rejection capability, was commissioned, conceived, and carried
out. This upper bound value would be indicative of the weakest coronal
features the spectrometer would be capable of discerning. The test was
rapidly developed at GSFC, in parallel with spacecraft integration,
in coordination with science team members from Harvard- Smithsonian
Center for Astrophysics (CFA) and was carried out at MATRA in late
February 1995. The outcome of this test helped justify later impact
to integration schedule to conduct similar much needed testing with
visible and far ultraviolet light at CFA in a facility specifically
designed to perform such tests.
---------------------------------------------------------
Title: Grating stray light analysis and control in the UVCS/SOHO
Authors: Fineschi, Silvano; Gardner, Larry D.; Kohl, John L.; Romoli,
Marco; Noci, Giancarlo C.
1998SPIE.3443...67F Altcode:
The Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and
Heliospheric (SOHO) mission has been developed for spectroscopic
and polarimetric determinations of temperatures, densities and
flow velocities in the extended solar corona. The instrument
consists of a visible light (VL) polarimeter, and two ultraviolet
(UV) spectrometers, optimized for the H I Lyman (alpha) (Ly-(alpha)
) line ((lambda) 1216 angstrom) and for the O VI doublet ((lambda)
(lambda) 1032/1037 angstrom). The stray-light profile of the Ly-(alpha)
holographic grating has been measured, in a laboratory set-up, in
both the spatial and spectral directions. The observed profile has
been found to be a combination of two components: the scattering
from the grating surface, and the Fraunhofer diffraction due to the
vignetting of the grating. An analytical expression for the scattering
component of the grating point spread function (PSF) has been derived
from a simple model of the grating surface roughness. The stray-light
profile generated by the analytical expression of the grating PSF gives
a good fit of stray-light profile measured in the laboratory. This
instrument function has been used in the analysis of in-flight UVCS
observations of the profile of electron scattered Ly- (alpha) from the
solar corona. These observations have resulted, for the first time,
in the most direct measurement of the coronal electron temperature.
---------------------------------------------------------
Title: Solar Wind at 6.8 Solar Radii from UVCS Observation of Comet
C/1996Y1
Authors: Raymond, John C.; Fineschi, S.; Smith, P. L.; Gardner, L.;
O'Neal, R.; Ciaravella, A.; Kohl, J. L.; Marsden, B.; Williams, G. V.;
Benna, C.; Giordano, S.; Noci, G.; Jewitt, D.
1998ApJ...508..410R Altcode:
The comet C/1996Y1, a member of the Kreutz family of Sun-grazing comets,
was observed with the Ultraviolet Coronagraph Spectrometer (UVCS)
aboard the Solar and Heliospheric Observatory (SOHO) satellite. The
Lyα line profile and spatial distribution are interpreted in terms
of the theory of bow shocks driven by mass-loading. At the time of
the observation, the comet was 6.8 R<SUB>⊙</SUB> from the Sun in
a region of high-speed wind, a region difficult to observe directly
with the SOHO instruments but an important region for testing models
of solar wind acceleration and heating. We find a solar wind speed
below 640 km s<SUP>-1</SUP> and a constraint on the combination of
solar wind speed and proton temperature. The total energy per proton at
6.8 R<SUB>⊙</SUB> is 50%-75% of the energy at 1 AU, indicating that
significant heating occurs at larger radii. The centroid and width
of the Lyα line generally confirm the predictions of models of the
cometary bow shock driven by mass-loading as cometary molecules are
ionized and swept up in the solar wind. We estimate an outgassing rate
of 20 kg s<SUP>-1</SUP>, which implies an active area of the nucleus
only about 6.7 m in diameter at 6.8 R<SUB>⊙</SUB>. This is likely
to be the size of the nucleus, because any inert mantle would have
probably been blown off during the approach to the Sun.
---------------------------------------------------------
Title: UVCS/SOHO Empirical Determinations of Anisotropic Velocity
Distributions in the Solar Corona
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Cranmer, S. R.; Strachan, L.; Panasyuk, A. V.; Gardner,
L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond, J. C.;
Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.; Ciaravella,
A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.; Martin, R.;
Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal, R. H.; Pernechele,
C.; Poletto, G.; Smith, P. L.; Suleiman, R. M.
1998ApJ...501L.127K Altcode:
We present a self-consistent empirical model for several plasma
parameters of a polar coronal hole near solar minimum, derived from
observations with the Solar and Heliospheric Observatory Ultraviolet
Coronagraph Spectrometer. The model describes the radial distribution of
density for electrons, H<SUP>0</SUP>, and O<SUP>5+</SUP> and the outflow
velocity and unresolved most probable velocities for H<SUP>0</SUP>
and O<SUP>5+</SUP> during the period between 1996 November and 1997
April. In this Letter, we compare observations of H I Lyα and O
VI λλ1032, 1037 emission lines with spatial models of the plasma
parameters, and we iterate for optimal consistency between measured and
synthesized observable quantities. The unexpectedly large line widths
of H<SUP>0</SUP> atoms and O<SUP>5+</SUP> ions at most radii are the
result of anisotropic velocity distributions, which are not consistent
with purely thermal motions or the expected motions from a combination
of thermal and transverse wave velocities. Above 2 R<SUB>solar</SUB>,
the observed transverse, most probable speeds for O<SUP>5+</SUP> are
significantly larger than the corresponding motions for H<SUP>0</SUP>,
and the outflow velocities of O<SUP>5+</SUP> are also significantly
larger than the corresponding velocities of H<SUP>0</SUP>. We discuss
the constraints and implications on various theoretical models of
coronal heating and acceleration.
---------------------------------------------------------
Title: The white light polarimeter of SOHO/UVCS
Authors: Romoli, M.; Benna, C.; Fineschi, S.; Gardner, L. D.; Kohl,
J. L.; Noci, G.
1998MmSAI..69..703R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet Spectroscopy of a Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli,
M.; Benna, C.; Gardner, L.; Giordano, S.; Michels, J.; O'Neal, R.;
Antonucci, E.; Kohl, J.; Noci, G.
1998ASPC..150..370C Altcode: 1998npsp.conf..370C; 1998IAUCo.167..370C
No abstract at ADS
---------------------------------------------------------
Title: Velocity Fields in the Solar Corona during Mass Ejections as
Observed with UVCS-SOHO
Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Giordano, S.; Spadaro, D.;
Ciaravella, A.; Raymond, C. J.; Naletto, G.; Fineschi, S.; Romoli, M.;
Siegmund, O. H. W.; Benna, C.; Michels, J.; Modigliani, A.; Panasyuk,
A.; Pernechele, C.; Smith, P. L.; Strachan, L.; Ventura, R.
1997ApJ...490L.183A Altcode:
This Letter presents the observations of the first two coronal mass
ejections (CMEs) obtained with the Ultraviolet Coronagraph Spectrometer
of SOHO. Both CMEs were observed at high spectral resolution in the
ultraviolet domain. The first event on 1996 June 6-7 was observed in H I
Lyα λ1216 and Lyβ λ1026, O VI λλ1032 and 1037, Si XII λλ499 and
521 and imaged within 1.5 and 5 R<SUB>solar</SUB>. The second event on
1996 December 23 was observed in several H I lines and cool lines such
as C III λ977, N III λλ990-992, and O V λ630. The analysis of line
profiles has allowed us to determine the line-of-sight velocities of the
extended corona during a mass ejection. In particular there is evidence
for mass motions consistent with untwisting magnetic fields around an
erupted flux tube in one of the events and line of sight velocities of
200 km s<SUP>-1</SUP> in the early phase of the second event presumably
related to the expansion of the leading arch of the transient.
---------------------------------------------------------
Title: Solar Wind Acceleration in the Solar Corona
Authors: Giordano, S.; Antonucci, E.; Benna, C.; Kohl, J. L.; Noci,
G.; Michels, J.; Fineschi, S.
1997ESASP.415..327G Altcode: 1997cpsh.conf..327G
No abstract at ADS
---------------------------------------------------------
Title: Determination of 3D Coronal Structures from UVCS/SOHO Synoptic
Observations
Authors: Strachan, L.; Panasyuk, A. V.; Fineschi, S.; Gardner, L. D.;
Raymond, J. C.; ANtonucci, E.; Giordano, S.; Romoli, M.; Noci, G.;
Kohl, J. L.
1997ESASP.415..539S Altcode: 1997cpsh.conf..539S
No abstract at ADS
---------------------------------------------------------
Title: A User's Guide to UVCS/SOHO
Authors: Kohl, J. L.; Noci, G.; Cranmer, S. R.; Fineschi, S.; Gardner,
L. D.; Halas, C. D.; Smith, P. L.; Strachan, L.; Suleiman, R. M.
1997AAS...191.7309K Altcode: 1997BAAS...29Q1322K
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is currently
being used to observe the extended solar corona between 1 and 10
heliocentric radii. In its first two years of operation, UVCS/SOHO
has made spectroscopic measurements leading to the determination of
densities, velocities, temperatures, and elemental abundances in coronal
holes, equatorial streamers, and coronal mass ejections. Observations
of selected non-solar targets, such as near-ecliptic stars, planets,
comets, and interplanetary hydrogen and helium, have also produced
interesting astronomical results. This poster presents a brief
review of the UVCS/SOHO spectroscopic and polarimetric diagnostic
capabilities, highlighted by pertinent observational data. Most
importantly, we summarize the procedures that have been designed
to allow UVCS/SOHO data to be used by a wide array of researchers,
and invite participation in this unique investigation. Scientists
interested in UVCS/SOHO observations are encouraged to fill
out the “Get Involved” questionnaire located on the WWW at:
http://cfa-www.harvard.edu/uvcs/ This work is supported by the National
Aeronautics and Space Administration under grant NAG5-3192 to the
Smithsonian Astrophysical Observatory, by Agenzia Spaziale Italiana,
and by Swiss funding agencies.
---------------------------------------------------------
Title: Ultraviolet Observations of Coronal Mass Ejections
Authors: Ciaravella, A.; Raymond, J. C.; Benna, C.; Fineschi, S.;
Gardner, L. D.; Giordano, S.; O'Neal, R. H.; Reale, F.; Romoli, M.;
Michels, J.; Antonucci, E.; Kohl, J. L.; Noci, G.
1997ESASP.415..543C Altcode: 1997cpsh.conf..543C
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet Coronagraph Spectrometer Observation of the 1996
December 23 Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli,
M.; Benna, C.; Gardner, L.; Giordano, S.; Michels, J.; O'Neal, R.;
Antonucci, E.; Kohl, J.; Noci, G.
1997ApJ...491L..59C Altcode:
The Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar
and Heliospheric Observatory (SOHO) observed a spectacular coronal
mass ejection (CME) caused by a prominence eruption on 1996 December
23. The evolution of the ejected prominence material was followed for
1 hr and 50 minutes. The observation consists of a series of 5 minute
exposures, at a fixed heliocentric distance of 1.5 R<SUB>solar</SUB>
in several spectral ranges. The Lyman lines of hydrogen brighten
more than 2 orders of magnitude during the CME. The C III 977.02 Å
line is very bright, and many other low-temperature lines have been
detected. Line intensities and profiles provide important diagnostics
for the physical and dynamical parameters of the ejected plasma. Lines
widths show nonthermal line broadening due to a plasma expansion with
velocity larger than 50 km s<SUP>-1</SUP>. The Lyα inside the CME
region shows red and blue shifts, up to 0.2 Å (50 km s<SUP>-1</SUP>)
and 0.8 Å (200 km s<SUP>-1</SUP>), respectively. A preliminary estimate
shows a flat emission measure distribution 3 or 4 orders of magnitude
smaller than typical prominence emission measures. Essentially the same
structure in space and velocity is seen in the Lyman lines, in C III
(10<SUP>5</SUP> K) and in O VI (3×10<SUP>5</SUP> K).
---------------------------------------------------------
Title: Origins of the Slow and the Ubiquitous Fast Solar Wind
Authors: Habbal, S. R.; Woo, R.; Fineschi, S.; O'Neal, R.; Kohl, J.;
Noci, G.; Korendyke, C.
1997ApJ...489L.103H Altcode: 1997astro.ph..9021H
We present in this Letter the first coordinated radio occultation
measurements and ultraviolet observations of the inner corona below
5.5R<SUB>s</SUB>, obtained during the Galileo solar conjunction in
1997 January, to establish the origin of the slow solar wind. Limits
on the flow speed are derived from the Doppler dimming of the
resonantly scattered component of the oxygen 1032 and 1037.6 Å
lines as measured with the ultraviolet coronagraph spectrometer
(UVCS) on the Solar and Heliospheric Observatory (SOHO). White light
images of the corona from the large-angle spectroscopic coronagraph
(LASCO) on SOHO taken simultaneously are used to place the Doppler
radio scintillation and ultraviolet measurements in the context of
coronal structures. These combined observations provide the first
direct confirmation of the view recently proposed by Woo & Martin
that the slow solar wind is associated with the axes, also known as
stalks, of streamers. Furthermore, the ultraviolet observations also
show how the fast solar wind is ubiquitous in the inner corona and
that a velocity shear between the fast and slow solar wind develops
along the streamer stalks.
---------------------------------------------------------
Title: Composition of Coronal Streamers from the SOHO Ultraviolet
Coronagraph Spectrometer
Authors: Raymond, J. C.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi,
S.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella,
A.; Cranmer, S.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.;
Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, Peter L.; Suleiman, R. M.; Strachan, L.
1997SoPh..175..645R Altcode:
The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers
the 940-1350 Å range as well as the 470-630 Å range in second
order. It has detected coronal emission lines of H, N, O, Mg, Al, Si,
S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance
scattering of emission lines from the solar disk dominates the
intensities of a few lines, but electron collisional excitation produces
most of the lines observed. Resonance, intercombination and forbidden
lines are seen, and their relative line intensities are diagnostics
for the ionization state and elemental abundances of the coronal gas.
---------------------------------------------------------
Title: First Results from the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Strachan, L.; Fineschi, S.;
Raymond, J. C.; Romoli, M.; Spadaro, D.; Panasyuk, A.; Siegmund,
O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, S. R.; Giordano, S.;
Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.;
Pernechele, C.; Poletto, G.; Smith, P. L.
1997SoPh..175..613K Altcode:
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being
used to observe the extended solar corona from 1.25 to 10 R⊙ from
Sun center. Initial observations of polar coronal holes and equatorial
streamers are described. The observations include measurements of
spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å,
Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx
610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been
observed. Preliminary results for derived H<SUP>0</SUP>, O<SUP>5+</SUP>,
Mg<SUB>9+</SUB>, and Fe<SUP>11+</SUP> velocity distributions and initial
indications of outflow velocities for O<SUP>5+</SUP> are described. In
streamers, the H<SUP>0</SUP> velocity distribution along the line of
sight (specified by the value at e<SUP>-1</SUP>, along the line of
sight) decreases from a maximum value of about 180 km s<SUP>-1</SUP>
at 2 R⊙ to about 140 km s<SUP>-1</SUP> at 8 R⊙. The value for
O<SUP>5+</SUP> increases with height reaching a value of 150 km
s<SUP>-1</SUP> at 4.7 R⊙. In polar coronal holes, the O<SUP>5+</SUP>
velocity at e<SUP>-1</SUP> is about equal to that of H<SUP>0</SUP>
at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O<SUP>5+</SUP>
in both streamers and coronal holes were found to have anisotropic
velocity distributions with the smaller values in the radial direction.
---------------------------------------------------------
Title: Empirical Models of the Extended Solar Corona
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Ciaravella, A.;
Cranmer, S.; Dobrzycka, D.; Fineschi, S.; Gardner, L. D.; Huber,
M. C. E.; Panasyuk, A.; Raymond, J. C.; Strachan, L.
1997SPD....28.0303K Altcode: 1997BAAS...29..907K
Ultraviolet spectroscopy is being used to produce self consistent
empirical models of polar coronal holes and equatorial streamers in the
extended solar corona. The models are intended to provide experimental
values for many of the primary plasma parameters of the extended corona,
which can then be used to constrain theoretical coronal and solar
wind models. The empirical models are based on synoptic observations
and other measurements of spectral line profiles and intensities of
H I Lyalpha , O VI 1032 Angstroms and 1037 Angstroms, Fe XII 1242
Angstroms, Mg X 625 Angstroms and several others. Information about
velocity distributions, outflow velocities, densities and elemental
abundances as derived from the observations are specified in the
models. The models used to specify the empirically derived parameters
include a description of well established theoretical processes such
as those controlling ionization balance, collisional excitation,
and resonant scattering. They do not include any descriptions of
less well established processes such as heating functions, transverse
wave motions or direct momentum deposition by waves. The intent is to
provide, to the maximum extent possible, empirical descriptions that
can be used, together with theoretical models, to help identify the
dominant physical processes responsible for coronal heating, solar wind
acceleration and the chemical composition of the solar wind. This work
is supported by NASA Grant NAG5-3192 to the Smithsonian Astrophysical
Observatory, the Italian Space Agency and Swiss funding sources.
---------------------------------------------------------
Title: UVCS/SOHO Synoptic Observations of the Extended Corona during
the Whole Sun Month Campaign
Authors: Strachan, L.; Fineschi, S.; Gardner, L. D.; Panasyuk, A. V.;
Kohl, J. L.; Antonucci, E.; Giordano, S.; Romoli, M.
1997SPD....28.0122S Altcode: 1997BAAS...29..883S
Daily synoptic observations were made with UVCS/SOHO during the Whole
Sun Month (10 August to 8 September 1996) in order to characterize
the large-scale spatial distributions of plasma parameters in the
solar corona from 1.5 to 3 solar radii. We use observed line profiles
and intensities of H I Lyman alpha and O VI 1032/1037 Angstroms,
and white light polarized brightness measurements to derive physical
properties of the plasma in the solar wind acceleration region. Line of
sight velocity distributions and bulk outflow velocities for neutral
hydrogen and for O({5) +}, and electron densities can be derived from
these measurements. We show some results from the on-going effort and
present some of these data as synoptic maps. The ultimate goal of this
work is to produce a data set that can be used in developing empirical
models that describe the solar minimum conditions of the extended
corona. This work is supported by NASA under Grant NAG5-3192 to the
Smithsonian Astrophysical Observatory, by the Italian Space Agency,
and by Swiss funding sources.
---------------------------------------------------------
Title: Ultraviolet Spectroscopy of Coronal Mass Ejection
Authors: Ciaravella, A.; Raymond, J. C.; Fineschi, S.; Romoli, M.;
Antonucci, E.
1997SPD....28.0121C Altcode: 1997BAAS...29..883C
The Ultraviolet Coronagraph Spectrometer (UVCS) observed a spectacular
coronal mass ejection (CME) on December 23 1996, caused by a prominence
eruption. The evolution of the ejected plasma was followed for about 2h
in both ultraviolet and visible light channels. The observation consists
of a series of 5 minutes exposures, at heliocentric distance of 1.5
R_sun. Excursions of more than two orders of magnitude are detected in
the Lyalpha (1216 Angstroms/), Lybeta (1026 Angstroms/), Lygamma (972
Angstroms/) and Lydelta (949 Angstroms/) lines of hydrogen. The C III
(977 A) is very bright during the CME evolution, but many other more
weak low temperature lines, like N III (991 Angstroms/, 991 Angstroms/),
N II (1085 Angstroms/), N V (1242 Angstroms/), have been detected. Line
intensities and profiles have been measured providing important
diagnostics for a very detailed study of physical and dynamical
parameters of CME. Lines widths show non-thermal line broadening due
to an expansion of plasma with velocity larger than 50 km/sec. The
Lyalpha spatial pattern of the line shift appears very structured with
red and blue shifts, along the line of sight, up to 0.2 Angstroms/
( 50km/sec) and 1 Angstroms ( 200 km/sec) respectively. The data also
provide the emission measure in the LogT range 4.0 - 5.5. A variation
of one order of magnitude has been observed in the polarized brightness.
---------------------------------------------------------
Title: Absolute Elemental Abundances in Streamers
Authors: Raymond, J. C.; Kohl, J.; Suleiman, R.; Ciaravella, A.;
Fineschi, S.; Gardner, L.; Panasyuk, A.; Strachan, L.; Noci, G.;
Antonucci, E.; Nicolosi, P.; Naletto, G.; Giordano, S.; Benna, C.
1997SPD....28.0114R Altcode: 1997BAAS...29..881R
The UVCS instrument aboard the SOHO satellite has measured the
intensities of emission lines of H, N, O, Mg, Al, S, Ar, Ca ,Fe and Ni
at 1.5 solar radii in a quiescent equatorial helmet streamer and in an
active region streamer. The First Ionization Potential (FIP) effect is
clearly seen. Low FIP elements show nearly photospheric abundances above
the active region and along the edges of the equatorial streamer, while
high FIP elements are depleted by a factor of 2-3. Near the center of
the streamer, presumably the closed field region, the low-FIP elements
are at about 1/3 photospheric abundances, and the high FIP elements
are near 1/10 their photospheric values.
---------------------------------------------------------
Title: Optical performances of the Ultraviolet Coronagraph
Spectrometer of the Solar Heliospheric Observatory
Authors: Pernechele, Claudio; Naletto, Giampiero; Nicolosi,
Piergiorgio; Tondello, Giuseppe; Fineschi, Silvano; Romoli, Marco;
Noci, Giancarlo; Spadaro, Daniele; Kohl, John L.
1997ApOpt..36..813P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Plume and interplume regions and solar wind acceleration in
polar coronal holes between 1.5 and 3.5 R
Authors: Giordano, S.; Antonucci, E.; Benna, C.; Romoli, M.; Noci,
G.; Kohl, J. L.; Fineschi, S.; Michels, J.; Naletto, G.
1997ESASP.404..413G Altcode: 1997cswn.conf..413G
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet spectroscopy of a coronal mass ejection with UVCS
Authors: Ciaravella, A.; Raymond, J.; Fineschi, S.; Romoli, M.; Benna,
C.; Gardner, L.; Giordano, S.; O'Neal, R.; Michels, J.; Antonucci,
E.; Noci, G.; Kohl, J.
1997ESASP.404..279C Altcode: 1997cswn.conf..279C
No abstract at ADS
---------------------------------------------------------
Title: Intercomparison between UVCS/WLC and LASCO/C2 measured
polarized brightness
Authors: Romoli, M.; Biesecker, D.; Benna, C.; Fineschi, S.; Lamy,
P. L.; Llebaria, A.; Kohl, J. L.; Noci, G.
1997ESASP.404..637R Altcode: 1997cswn.conf..637R
No abstract at ADS
---------------------------------------------------------
Title: Signature of open magnetic field lines in the extended solar
corona and of solar wind acceleration
Authors: Antonucci, E.; Giordano, S.; Benna, C.; Kohl, J. L.; Noci,
G.; Michels, J.; Fineschi, S.
1997ESASP.404..175A Altcode: 1997cswn.conf..175A
No abstract at ADS
---------------------------------------------------------
Title: KCorona polarized brightness and electron density measurement
with the visible light polarimeter of UVCS
Authors: Romoli, M.; Benna, C.; Cranmer, S.; Fineschi, S.; Gardner,
L. D.; Strachan, L.; Kohl, J. L.; Noci, G.
1997ESASP.404..633R Altcode: 1997cswn.conf..633R
No abstract at ADS
---------------------------------------------------------
Title: UVCS/SOHO empirical models of solar coronal holes
Authors: Cranmer, S. R.; Kohl, J. L.; Noci, G.; Strachan, L.;
Panasyuk, A. V.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond,
J. C.; Suleiman, R. M.; O'Neal, R. H.
1997ESASP.404..295C Altcode: 1997cswn.conf..295C
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic observations of the extended corona during the
SOHO whole sun month
Authors: Strachan, L.; Raymond, J. C.; Panasyuk, A. V.; Fineschi,
S.; Gardner, L. D.; Antonucci, E.; Giordano, S.; Romoli, M.; Noci,
G.; Kohl, J. L.
1997ESASP.404..691S Altcode: 1997cswn.conf..691S
No abstract at ADS
---------------------------------------------------------
Title: Measurements of H I and O VI velocity distributions in the
extended solar corona with UVCS/SOHO and UVCS/Spartan 201
Authors: Kohl, J. H.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi, S.; Raymond, J. C.;
Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella,
A.; Cranmer, S. R.; Giordano, S.; Karovska, M.; Martin, R.; Michels,
J.; Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, P. L.; Strachan, L.
1997AdSpR..20....3K Altcode:
The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric
Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on
the Spartan 201 satellite, UVCS/Spartan, have been used to measure
H I 1215.67 A˚ line profiles in polar coronal holes of the Sun at
projected heliocentric heights between 1.5 and 3.0 R_solar. UVCS/SOHO
also measured line profiles for H I 1025.72 A˚, O VI 1032/1037 A˚,
and Mg X 625 A˚. The reported UVCS/SOHO observations were made between
5 April and 21 June 1996 and the UVCS/Spartan observations were made
between 11 and 12 April 1993. Both sets of measurements indicate that a
significant fraction of the protons along the line of sight in coronal
holes have velocities larger than those for a Maxwellian velocity
distribution at the expected electron temperature. Most probable
speeds for O^5+ velocity distributions along the lines of sight are
smaller than those of H^0 at 1.5 R_solar, are comparable at about 1.7
R_solar and become significantly larger than the H^0 velocities above
2 R_solar. There is a tendency for the O^5+ line of sight velocity
distribution in concentrations of polar plumes to be more narrow than
those in regions away from such concentrations. UVCS/SOHO has identified
31 spectral lines in the extended solar corona.
---------------------------------------------------------
Title: First Results from UVCS: Dynamics of the Extended Corona
Authors: Antonucci, E.; Noci, G.; Kohl, J. L.; Tondello, G.; Huber,
M. C. E.; Giordano, S.; Benna, C.; Ciaravella, A.; Fineschi, S.;
Gardner, L. D.; Martin, R.; Michels, J.; Naletto, G.; Nicolosi, P.;
Panasyuk, A.; Raymond, C. J.; Romoli, M.; Spadaro, D.; Strachan, L.;
van Ballegooijen, A.
1997ASPC..118..273A Altcode: 1997fasp.conf..273A
The Ultraviolet Coronagraph Spectrometer (UVCS) started to observe
the Sun at the end of January 1996. Here we present a selection of
results obtained with the UVCS in the first months of operation. UV
spectral line profiles in coronal holes, and in general in regions
with open magnetic field lines, are much broader than in closed
field line regions; that is, line-of-sight velocities are much
larger in open field lines . Polar plumes have narrower profiles
than interplume regions. The O VI ratio diagnostics indicates that in
polar coronal holes the outflow velocity is progressively increasing
with heliodistance and exceeds 100 km/sec near 2--2.5 solar radii. A
coronal mass ejection observation has revealed line--of--sight plasma
motions of 100 km/sec and a complex dynamics.
---------------------------------------------------------
Title: SOHO observations of the north polar solar wind
Authors: Peres, G.; Ciaravella, A.; Betta, R.; Orlando, S.; Reale,
F.; Kohl, J.; Noci, G.; Fineschi, S.; Romoli, M.; Brekke, P.; Fludra,
A.; Gurman, J. B.; Lemaire, P.; Schuhle, U.
1997ESASP.404..587P Altcode: 1997cswn.conf..587P
No abstract at ADS
---------------------------------------------------------
Title: First results from UVCS/SOHO
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.;
Raymond, J. C.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.;
Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Panasyuk,
A.; Pernechele, C.; Poletto, G.; Smith, P. L.; Strachan, L.
1997AdSpR..20.2219N Altcode:
We present here the first results obtained by the Ultraviolet
Coronagraph Spectrometer (UVCS) operating on board the SOHO
satellite. The UVCS started to observe the extended corona at the end
of January 1996; it routinely obtains coronal spectra in the 1145 A˚ -
1287 A˚, 984 A˚ - 1080 A˚ ranges, and intensity data in the visible
continuum. Through the composition of slit images it also produces
monocromatic images of the extended corona. The performance of the
instrument is excellent and the data obtained up to now are of great
interest. We briefly describe preliminary results concerning polar
coronal holes, streamers and a coronal mass ejection, in particular: the
very large r.m.s. velocities of ions in polar holes (hundreds km/sec
for OVI and MgX); the puzzling difference between the HI Ly-alpha
image and that in the OVI resonance doublet, for most streamers; the
different signatures of the core and external layers of the streamers
in the width of the ion lines and in the OVI doublet ratio, indicating
larger line-of-sight (l.o.s.) and outflow velocities in the latter.
---------------------------------------------------------
Title: The quiescent corona and slow solar wind
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Fineschi, S.; Gardner, L. D.; Korendyke, C. M.; Nicolosi,
P.; Romoli, M.; Spadaro, D.; Maccari, L.; Raymond, J. C.; Siegmund,
O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.;
Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto,
G.; Smith, P. L.; Strachan, L.
1997ESASP.404...75N Altcode: 1997cswn.conf...75N; 1997soho....5...75N
No abstract at ADS
---------------------------------------------------------
Title: Stray light, radiometric, and spectral characterization of
UVCS/SOHO: laboratory calibration and flight performance
Authors: Gardner, Larry D.; Kohl, J. L.; Daigneau, P. S.; Dennis,
E. F.; Fineschi, Silvano; Michels, J.; Nystrom, George U.;
Panasyuk, Alexander; Raymond, John C.; Reisenfeld, D. J.; Smith,
Peter L.; Strachan, Leonard; Suleiman, R.; Noci, G. C.; Romoli, Marco;
Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.; Benna,
C.; Giordano, S.; Tondello, Giuseppe; Nicolosi, Piergiorgio; Naletto,
Giampiero; Pernechele, Claudio; Spadaro, D.; Siegmund, Oswald H.;
Allegra, A.; Carosso, Paolo A.; Jhabvala, Murzy D.
1996SPIE.2831....2G Altcode:
The Ultraviolet Coronagraph Spectrometer is one of the instruments
on board the Solar and Heliospheric Observatory spacecraft, which
was launched in December, 1995. The instrument is designed to make
ultraviolet spectrometric measurements and visible polarimetric
measurements of the extended solar corona. Prior to launch laboratory
measurements were carried out to determine system level values for
many of the key performance parameters. Further measurements on
instrument performance have been carried out since launch. Presented
are descriptions of measurement techniques and representative results.
---------------------------------------------------------
Title: Coordinated SOHO Observations of Polar Plumes
Authors: Deforest, C. E.; Scherrer, P. H.; Tarbell, T.; Harrison,
R. A.; Fludra, A.; Delaboudiniere, J. P.; Gurman, J. B.; Wilhelm,
K.; Lemaire, P.; Hassler, D. M.; Kohl, J. L.; Noci, G.; Fineschi,
S.; Brueckner, G. E.; Howard, R. A.; Cyr, O. C. St.
1996AAS...188.4909D Altcode: 1996BAAS...28R.898D
On 7 and 8 March 1996, SOHO instruments engaged in their first
joint science operation, a 12-hr observation of polar plumes
over the South polar coronal hole. The observing mini-campaign
included observations from SOHO, other spacecraft, and ground-based
observatories. Contributing SOHO instruments -- in order of altitude,
MDI, CDS, SUMER, EIT, UVCS, and LASCO -- made overlapping, simultaneous
observations of plume structures from the photosphere out to the
LASCO C3 limit of 32 solar radii. MDI provided line-of-sight surface
magnetograms with a one-min cadence and 0.6 arcsec resolution;
CDS, SUMER, and EIT supplied temperature-sensitive images of the
lower corona with varying cadences and resolutions; UVCS measured
fluctuations in Ly B intensity across the coronal hole with a one-min
cadence at 1.4 R0; and LASCO imaged the entire corona out to 30 R0 in
various visible passbands. Plume footpoints in the lower corona are
observed by EIT and CDS to vary by a factor of two in EUV brightness
with a timescale of tens of minutes, while the structures above are
(as as been previously observed) quiescent on at least a ten-hr time
scale. We present preliminary results of cross-instrument analysis
of the observed plumes, and suggest how this and similar future data
sets can be used to constrain quiet-sun wind acceleration and coronal
heating models for the coronal hole. This research is supported by
the SOI-MDI NASA contract NAG5-3077 at Stanford University. SOHO is
project of international cooperation between NASA and ESA.
---------------------------------------------------------
Title: In-Flight Performance of the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Gardner, L. D.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Ciaravella, A.; Fineschi, S.; Giordano,
S.; Moran, T.; Naletto, G.; Nicolosi, P.; Romoli, M.; Strachan,
L.; Benna, C.; Pernechele, C.; Raymond, J. C.; Siegmund, O. H. W.;
Spadaro, D.; Smith, P. L.
1996AAS...188.3705G Altcode: 1996BAAS...28..878G
The in-flight performance of the SOHO Ultraviolet Coronagraph
Spectrometer (UVCS/SOHO) is consistent with the pre-launch
characterization and meets all planned observational
requirements. Measurements of the key UVCS/SOHO performance
characteristics have been performed. This paper describes the
measurement techniques and the results. In-flight values for the
spectral and spatial resolutions, wavelength scales, the flat
fields, the geometric distortions, radiometric calibrations,
and stray light levels for the two ultraviolet channels have been
determined. Comparisons will be made to pre-flight measurements at both
the component level and system level. This work is supported by NASA
under contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland.
---------------------------------------------------------
Title: Spectroscopic Diagnostic Techniques with the SOHO Ultraviolet
Coronagraph Spectrometer
Authors: Romoli, M.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello,
G.; Huber, M. C. E.; Fineschi, S.; Karovska, M.; Moran, T.; Strachan,
L.; Ciaravella, A.; Benna, C.; Gardner, L. D.; Giordano, S.; Naletto,
G.; Nicolosi, P.; Raymond, J. C.; Siegmund, O. H. W.; Spadaro, D.;
Smith, P. L.
1996AAS...188.3703R Altcode: 1996BAAS...28R.877R
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) uses
spectroscopic diagnostic techniques and polarimetry to determine
velocity distributions, temperatures, outflow velocities and densities
of protons, electrons, and several minor ions in the extended solar
corona. This paper describes the initial use of these techniques with
UVCS/SOHO. Velocity distributions are derived from the observed spectral
line profiles. In some cases, grating scans are used to improve the
spectral resolution. The Doppler dimming method is used to determine
radial outflow velocities and spectral line shifts are used for line of
sight velocity measurements. The electron densities are derived from
visible polarized radiance measurements. The status of attempts to
derive electron temperatures from observations of electron scattered
HI Lyman-alpha will be presented. This research is supported by NASA
Contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland.
---------------------------------------------------------
Title: Ultraviolet Imaging of the Extended Solar Corona with the
SOHO Ultraviolet Coronagraph Spectrometer
Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Strachan, L.; Giordano, S.; Panasyuk, A.; Benna, C.;
Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi,
P.; Raymond, J. C.; Romoli, M.; Siegmund, O. H. W.; Spadaro, D.;
Smith, P. L.
1996AAS...188.3701N Altcode: 1996BAAS...28..877N
Spectroscopic observations of the extended solar corona with the SOHO
Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) can be used to produce
images of the extended solar corona in several ultraviolet spectral
lines. The images are produced by scanning coronal images across the
spectrometer entrance slits. The slits intercept a 40 arcminute slice of
the corona parallel to the limb tangent. Telescope mirror motions can
be used to scan from about 1.25 to 10 R_⊙. The instrument is rolled
about its Sun-center axis to obtain images of the full corona. The
spatial resolution depends on the selected slit width and the combined
resolution of the spectrometer and XDL detectors. It is limited by
diffraction for observations near the Sun where only a narrow strip of
the telescope mirror is unvignetted by the external occulter. Images
of equatorial streamers in HI Lyman-alpha and beta, and in O VI 103.2
nm will be presented. Ultraviolet images of polar plumes will also be
provided. In some cases, interpolation techniques are used to fill-in
gaps in the raster pattern. This research is supported by NASA Contract
NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian
Space Agency and by Switzerland.
---------------------------------------------------------
Title: Coordinated SOHO Observations of Polar Plumes: Ultraviolet
Spectroscopy with UVCS
Authors: Fineschi, S.; Kohl, J. L.; Noci, G.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Giordano, S.; Romoli,
M.; Benna, C.; Ciaravella, A.; Naletto, G.; Nicolosi, P.; Raymond,
J. C.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.
1996AAS...188.3704F Altcode: 1996BAAS...28..877F
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) observed polar
plumes at the south polar coronal hole on 7 March 1996. Observations
were made in H I Ly-alpha, Ly-beta and O VI 103.2 and 103.7
nm. Heliocentric heights from 1.5 to 3.2 R_⊙ were observed. In
addition, HI Ly-alpha observations with 60 sec time resolution were
obtained at a heliocentric height of 1.6 solar radii. The polar plumes
are clearly distinguishable in both H I Ly-alpha and O VI. These
measurements were made in coordination with time resolved magnetograms
by the Michelson Doppler Imager (MDI) and time resolved XUV images
by the Extreme-Ultraviolet Imaging Telescope (EIT). This work is
supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical
Observatory, by the Italian Space Agency and by Switzerland.
---------------------------------------------------------
Title: First Results from the SOHO Ultraviolet Coronagraph
Spectrometer
Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber,
M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.;
Giordano, S.; Karovska, M.; Michels, J.; Naletto, G.; Nicolosi, P.;
Poletto, G.; Pernechele, C.; Raymond, J. C.; Romoli, M.; Siegmund,
O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.
1996AAS...188.4906K Altcode: 1996BAAS...28R.897K
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used
to observe the extended solar corona from 1.25 to 10 R_⊙ from Sun
center. Initial observations of polar coronal holes, polar plumes,
equatorial streamers and the diffuse mid-latitude corona will be
presented. The observations include measurements of spectral line
profiles for HI Lyman alpha and beta, and O VI 103.2 and 103.7
nm. Line intensities for Mg X 61.0 nm, Si XII 49.9 and 52.0 nm,
S X 119.6 nm, Fe XII 124.2 nm and several other minor ions have been
observed. Observations with moderate time resolution (about 1 minute) at
one strip of the corona will also be presented. Preliminary results for
derived proton and O VI velocity distributions and initial indications
of outflow velocities for protons, and O VI will be discussed as
well as preliminary results for other spectroscopic diagnostics
techniques. This research is supported by NASA Contract NAS5-31250 to
the Smithsonian Astrophysical Observatory, by the Italian Space Agency
and by Switzerland.
---------------------------------------------------------
Title: Coronal Emission Lines with UVCS
Authors: Raymond, J. C.; Noci, G.; Kohl, J. L.; Antonucci, E.;
Tondello, G.; Huber, M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.;
Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Romoli, M.;
Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.; Martin, R.
1996AAS...188.3702R Altcode: 1996BAAS...28Q.877R
The Ultraviolet Coronagraph Spectrometer aboard the SOHO satellite has
observed the extended solar corona in H I Lyalpha and O VI lines for
coronal diagnostics, but other, fainter, lines are also present. We
discuss a spectral atlas obtained from emission in equatorial streamers
and above solar active regions, pointing out lines which are especially
useful for determining the elemental abundances, ionization state,
and density of the emitting plasma. This work is supported by NASA
under contract NAS5-31250 to the Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: Intercalibration and Co-Registration of the LASCO, UVCS and
SUMER instruments on SOHO
Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello,
G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle,
U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli,
M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano,
S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith,
P. L.; Strachan, L.
1996AAS...188.3706M Altcode: 1996BAAS...28..878M
Joint observations of equatorial streamers by three SOHO instruments
have been used for radiometric intercalibration, co-registration and
other spectroscopic comparisons. The results are used to track the
stability of the radiometric calibrations of the Ultraviolet Coronagraph
Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) experiment at overlapping wavelenghs. Observations
of equatorial streamers at heliocentric heights from 1.25 to 1.5
R_⊙ are used for the intercalibrations. The results are compared to
pre-launch laboratory calibrations and to observations of stars. The
first stellar observation was for 38 AQI. These UV observations are
compared to coronal green line (Fe XIV) observations obtained with the
Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained
in the same time frame. Intercomparisons of spectral line profiles
among LASCO, SUMER, and UVCS are also planned. The LASCO research is
supported by NASA Grant NDPR S92835D; the UVCS research is supported by
NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory,
by the Italian Space Agency and by Switzerland, and SUMER is financially
supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution).
---------------------------------------------------------
Title: The Ultraviolet Coronagraph Spectrometer for the Solar and
Heliospheric Observatory
Authors: Kohl, J. L.; Esser, R.; Gardner, L. D.; Habbal, S.; Daigneau,
P. S.; Dennis, E. F.; Nystrom, G. U.; Panasyuk, A.; Raymond, J. C.;
Smith, P. L.; Strachan, L.; Van Ballegooijen, A. A.; Noci, G.;
Fineschi, S.; Romoli, M.; Ciaravella, A.; Modigliani, A.; Huber,
M. C. E.; Antonucci, E.; Benna, C.; Giordano, S.; Tondello, G.;
Nicolosi, P.; Naletto, G.; Pernechele, C.; Spadaro, D.; Poletto, G.;
Livi, S.; Von Der Lühe, O.; Geiss, J.; Timothy, J. G.; Gloeckler,
G.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W.;
Fowler, W.; Fisher, R.; Jhabvala, M.
1995SoPh..162..313K Altcode:
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is composed of
three reflecting telescopes with external and internal occultation and
a spectrometer assembly consisting of two toric grating spectrometers
and a visible light polarimeter. The purpose of the UVCS instrument is
to provide a body of data that can be used to address a broad range
of scientific questions regarding the nature of the solar corona and
the generation of the solar wind. The primary scientific goals are
the following: to locate and characterize the coronal source regions
of the solar wind, to identify and understand the dominant physical
processes that accelerate the solar wind, to understand how the coronal
plasma is heated in solar wind acceleration regions, and to increase the
knowledge of coronal phenomena that control the physical properties of
the solar wind as determined byin situ measurements. To progress toward
these goals, the UVCS will perform ultraviolet spectroscopy and visible
polarimetry to be combined with plasma diagnostic analysis techniques
to provide detailed empirical descriptions of the extended solar corona
from the coronal base to a heliocentric height of 12 solar radii.
---------------------------------------------------------
Title: Ultraviolet Coronagraph Spectrometer for the Solar and
Heliospheric Observatory: instrument description and calibration
overview
Authors: Kohl, J. L.; Esser, R.; Gardner, Larry D.; Habbal, S.;
Daigneau, P. S.; Nystrom, George U.; Raymond, John C.; Strachan,
Leonard; van Ballegooijen, A. A.; Noci, G.; Fineschi, Silvano; Romoli,
Marco; Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.;
Benna, C.; Giordano, S.; von der Luehe, Oskar; Tondello, Giuseppe;
Nicolosi, Piergiorgio; Naletto, Giampiero; Pernechele, Claudio;
Geiss, J.; Gloeckler, G.; Poletto, G.; Spadaro, D.; Allegra, A.;
Basile, G.; Brusa, R.; Wood, B.; Siegmund, Oswald H.
1995SPIE.2517...40K Altcode:
The SOHO ultraviolet coronagraph spectrometer (UVCS/SOHO) is
composed of three reflecting telescopes with external and internal
occultation and a spectrometer assembly consisting of two toric grating
spectrometers and a visible light polarimeter. The UVCS will perform
ultraviolet spectroscopy and visible polarimetry to be combined with
plasma diagnostic analysis techniques to provide detailed empirical
descriptions of the extended solar corona from the coronal base to a
heliographic height of 12 R. In this paper, the salient features of
the design of the UVCS instrument are described. An overview of the
UVCS test and calibration activities is presented. The results from
the calibration activity have demonstrated that the UVCS can achieve
all its primary scientific observational goals.
---------------------------------------------------------
Title: X-Ray and EUV/FUV Spectroscopy and Polarimetry
Authors: Fineschi, Silvano
1995SPIE.2517.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Determining coronal electron temperatures from observations
with UVCS/SOHO
Authors: Fineschi, S.; Esser, R.; Habbal, S. R.; Karovska, M.; Romoli,
M.; Strachan, L.; Kohl, J. L.; Huber, M. C. E.
1995sowi.confQ..68F Altcode:
The electron temperature is a fundamental physical parameter of the
coronal plasma. Currently, there are no direct measurements of this
quantity in the extended corona. Observations with the Ultraviolet
Coronagraph Spectrometer (UVCS) aboard the upcoming Solar and
Heliospheric Observatory (SOHO) mission can provide the most direct
determination of the electron kinetic temperature (or, more precisely,
the electron velocity distribution along the line of sight). This
measurement is based on the observation of the Thomson-scattered Lyman
alpha (Ly-alpha) profile. This observation is made particularly
challenging by the fact that the integrated intensity of the
electron-scattered Ly-alpha line is about 10<SUP>3</SUP> times fainter
than that of the resonantly-scattered Ly-alpha component. In addition,
the former is distributed across 50 A (FWHM), unlike the latter that
is concentrated in 1 A. These facts impose stringent requirements on
the stray-light rejection properties of the coronagraph/spectrometer,
and in particular on the requirements for the grating. We make use of
laboratory measurements of the UVCS Ly-alpha grating stray-light, and of
simulated electron-scattered Ly-alpha profiles to estimate the expected
confidence levels of electron temperature determination. Models of
different structures typical of the corona (e.g., streamers, coronal
holes) are used for this parameter study.
---------------------------------------------------------
Title: Coronal magnetic field diagnostics via the Hanle effect of
Lyman series lines
Authors: Fineschi, S.; Habbal, S. R.
1995sowi.confR..68F Altcode:
The magnetic field plays a major role in the physics of the solar
corona. However, there are no direct measurements of this physical
parameter. We describe a method that can provide the most direct
determination of the vector magnetic field in the extended corona
(i.e., at heliocentric heights between 1.2 R(solar radius) and 2.0
R(solar radius)). The method is based on polarimetric observations of
UV lines of the Lyman series, that is, Lyman alpha (Ly-alpha), lambda
1216 A, Lyman beta (Ly-beta), lambda 1025 A, and Lyman gamma (Ly-gamma),
lambda 972 A. These lines have a collisional and a resonantly scattered
component. Linear polarization is induced in the resonant component by
the anisotropy in the chromospheric radiation field that illuminates the
corona. Magnetic fields can be suitably determined through the effects
that they induce on this resonance polarization (Hanle effect). The
Hanle effect of the Ly-alpha is sensitive to field strengths in the 10
- 100 gauss range. The resonance polarization of Ly-beta and Ly-gamma
is sensitive, through the Hanle effect, to fields with strengths
between 3 - 30 gauss, and 0.3 - 6 gauss, respectively. We describe a
new method for separating the resonant from the collisional component
of the Ly-beta and Ly-gamma; the method is based on the approximation,
valid within 10%, that the collisional component of the Ly-alpha is
negligible, in typical coronal conditions. From the intensity and
the polarization of the resonant components of these Lyman lines, the
strength and direction of coronal fields can be determined. We model
the sensitivity of Hanle-effect diagnostics for different coronal
structures (e.g., coronal holes and loops).
---------------------------------------------------------
Title: The Ultraviolet Coronagraph Spectrometer for the Solar and
Hellospheric Observatory
Authors: Raymond, J. C.; Kohl, J. L.; Esser, R.; Gardner, L. D.;
Habbal, S.; Strachan, L.; van Ballegooijen, A. A.; Noci, G.; Fineschi,
S.; Romoli, M.; Huber, M. C. E.; Antonucci, E.; Benna, C.; von der
Luhe, O.; Naletto, G.; Nicolosi, P.; Pernechele, C.; Tondello, G.;
Geiss, J.; Gloeckler, G.; Spadaro, D.; Daigneau, P. S.; Nystrom,
G. U.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W.
1995SPD....26..720R Altcode: 1995BAAS...27..970R
No abstract at ADS
---------------------------------------------------------
Title: The Ultraviolet Coronagraph Spectrometer
Authors: Noci, G.; Kohl, J. L.; Huber, M. C. E.; Antonucci, E.;
Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Raymond,
J. C.; Romoli, M.; Spadaro, D.; Strachan, L.; Tondello, G.; van
Ballegooijen, A.
1995LNP...444..261N Altcode: 1995cmer.conf..261N
The Ultraviolet Coronagraph Spectrometer (UVCS) is an instrument onboard
the Solar and Heliospheric (SOHO) spacecraft, a joint ESA/NASA mission
to be launched in 1995. The UVCS will provide ultraviolet spectroscopic
measurements to determine the primary plasma parameters of the solar
corona (temperatures, densities, velocities), from its base to as high
as 10 R<SUB>⊙</SUB>. We review briefly, here, its science objectives
and give an instrument description.
---------------------------------------------------------
Title: UVCS Science from SOHO
Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Huber, M. C. E.;
Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Pernechele,
C.; Raymond, J. C.; Romoli, M.; Spadaro, Daniele; Strachan, L.;
Tondello, G.; van Ballegooijen, A.
1995jena.conf...80A Altcode:
The ultraviolet Coronagraph Spectrometer (UVCS), to be launched on
board SOHO in 1995, has been designed to determine the primary plasma
parameters in order to obtain a far more complete description of the
coronal plasma than presently exists. This will be accomplished by
obtaining ultraviolet spectroscopic observations in some EUV lines (HI
Ly Alpha, O VI, Mg X, Si XII, Fe XII) and in the visible continuum,
form the base of the solar corona to as high as 12 solar radii. The
profiles and intensities of the measured UV lines are sensitive
to effective temperature of protons, minor ions and electrons; ion
densities; chemical abundances; and outflow velocities of protons and
ions into the solar wind. The electron density is determined by means
of white light observations. The UVCS data will be used to address a
broad range of scientific questions concerning the nature of the solar
corona and the generation of the solar wind. The primary scientific
objectives are in fact those of identifying the source regions of the
slow and fast solar wind, understanding the dominant processes that
accelerate the solar wind, and the mechanisms for heating the coronal
plasma in the extended corona.
---------------------------------------------------------
Title: UVCS/SOHO capability for determining coronal conditions before,
during and after CMEs
Authors: Strachan, L.; Raymond, J. C.; Kohl, J. L.; Noci, G.;
Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner,
L. D.; Nicolosi, P.; Romoli, M.
1994ESASP.373..421S Altcode: 1994soho....3..421S
No abstract at ADS
---------------------------------------------------------
Title: X-Ray and Ultraviolet Spectroscopy and Polarimetry
Authors: Fineschi, Silvano
1994SPIE.2283.....F Altcode: 1994QB468.X73......
No abstract at ADS
---------------------------------------------------------
Title: Polarization characterization of LY alpha holographic gratings
with a triple-reflection polarizer
Authors: Romoli, Marco; Fineschi, Silvano; Gardner, Larry D.; Kohl,
J. L.
1994SPIE.2283..288R Altcode:
The diffraction efficiency of holographic gratings depends on the
degree and orientation of the linear polarization of the incident
light. A test has been run to measure the reflectance efficiency at Kr
1236 angstrom of two holographic gratings in the orders +1, 0, $min1,
as a function of the angle of the incident beam polarization plane. To
this purpose, a triple-reflection polarizer, optimized for Ly(alpha)
(1216 angstrom) has been fabricated and characterized. The test has
been run to demonstrate that the coronal resonantly scattered Ly(alpha)
can be measured using a holographic grating in the Ly(alpha) channel
of the ultraviolet coronagraph spectrograph (UVCS) of the Solar
and Heliospheric Observatory (SOHO) without introducing relevant
polarization biases inside the instrument.
---------------------------------------------------------
Title: Ultraviolet Coronagraph Spectrometer for the Solar and
Heliospheric Observatory: optical testings
Authors: Fineschi, Silvano; Romoli, Marco; Gardner, Larry D.; Kohl,
J. L.; Noci, G.; Tondello, Giuseppe
1994SPIE.2283...30F Altcode:
The Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and
Heliospheric (SOHO) mission has been developed for spectroscopic
and polarimetric determinations of temperatures, densities and flow
velocities in the extended solar corona. The instrument consists of two
ultraviolet (UV) spectrometers and a visible light (VL) polarimeter. The
grating of the UV channel optimized for the HI Lyman (alpha) (Ly-(alpha)
) line ((lambda) 1236 angstrom) and that for the OVI doublet ((lambda)
(lambda) 1032/1037 angstrom) have been characterized.
---------------------------------------------------------
Title: Electron coronal density irregularity $\overline{n^2} /
(\overline{n})^2$ from measurements of K-coronal and Lyman lines
brightnesses
Authors: Fineschi, Silvano; Romoli, Marco
1994SSRv...70..353F Altcode:
We propose a technique to derive the coronal density irregularity
factoroverline {n^2 } /(bar n)^2 , wheren is the electron density. The
absolute photometric comparison between the intensity of UV lines and
the white-light K-coronal polarized brightness (pB) provides an unique
constraint on the inhomogeneity of the corona. The ratio of the measured
H I Lyman β (Ly-β) line intensity to the resonant-scattering dominated
H I Lyman α (Ly-α) intensity can be used to extract the collisonal
component of the Ly-β. This component yields an estimate ofoverline
{n^2 } . The quantity(bar n)^2 is then obtained from white-light
K-coronal measurements. The use of lines of the same atomic species
minimizes the effects due to outflow velocities (i.e., Doppler dimming),
and reduces the errors introduced by the uncertainties in the ionization
balance, the atomic parameters, and the solar abundances. The UVCS/SOHO
unique capability of performing cotemporal and cospatial measurements
of the Ly-α and Ly-β lines, and ofpB makes this instrument ideal
for implementing this technique.
---------------------------------------------------------
Title: Simulated observations of the electron coronal density
irregularity $\overline{n^2} / (\overline{n})^2$
Authors: Romoli, Marco; Fineschi, Silvano
1994SSRv...70..359R Altcode:
A technique to derive the coronal density irregularity factoroverline
{n^2 } /(bar n)^2 , wheren is the electron density, has been proposed
by Fineschi and Romoli (1993). This technique will exploit the unique
UVCS capability of cotemporal and cospatial measurements of both UV
line radiation and K-coronal polarized brightness,pB. The ratio of the
measured H I Lyman β (Ly-β) line intensity to the resonant-scattering
dominated H I Lyman α (Ly-α) intensity can be used to extract the
collisional component of the Ly-β. This component yields an estimate
ofoverline {n^2 } . The quantity(bar n)^2 is then obtained from the UVCS
white-light K-coronal measurements. We present simulated observations of
the UVCS for coronal atmosphere models with different filling factors
and electron density profiles, and for different coronal structures
(e.g., coronal holes, streamers). These simulations will show how
the proposed technique may be used to probe inhomogeneities of the
solar corona.
---------------------------------------------------------
Title: Ultraviolet coronagraph spectrometer (UVCS) for the solar
and heliospheric (SOHO) mission
Authors: Fineschi, Silvano; Naletto, Giampiero; Nicolosi, Piergiorgio;
Noci, G.; Pernechele, Claudio; Romoli, Marco; Spadaro, D.; Tondello,
Giuseppe
1994SPIE.2209..348F Altcode:
The optical performances of the Ultraviolet Coronagraph Spectrometer
(UVCS) of the Solar and Heliospheric Observatory (SOHO) mission have
been tested. A laboratory evaluation unit (LEU) of the spectrometer
assembly (SPA) consisting of the structure equipped with breadboard
models of the entrance slit assembly (ESA), a grating drive mechanism
(GDM) mounting a toroidal grating for the Ly(alpha) channel and a
multi-anode microchannel array (MAMA) detector has been integrated
and aligned. Both tests with visible and UV radiation have been
performed. Aberration and stray light measurements have shown
satisfactory performances of the instrument almost in compliance
with the scientific requirements. A LEU and a flight unit of the
White Light Channel (WLC) have been integrated and aligned in a
proper light-tight housing and in the flight spectrometer assembly
respectively. Measurements of the polarimeter modulation curve and
the relative error have shown performances within the specificated
requirements.
---------------------------------------------------------
Title: X-Ray and Ultraviolet Polarimetry
Authors: Fineschi, Silvano
1994SPIE.2010.....F Altcode: 1994QB468.X74......
No abstract at ADS
---------------------------------------------------------
Title: Fabrication and test of a wide-field H-Lyman alpha
coronagraph/polarimeter
Authors: Hoover, Richard B.; Walker, Arthur B.; Fineschi, Silvano;
Baker, Phillip C.; Zukic, Muamer; Kim, Jongmin
1994SPIE.2010..104H Altcode:
The Wide Field H-Lyman (alpha) Coronagraph/Polarimeter is currently
being developed for solar research. This instrument has been designed
to produce high resolution full-disk images of the Sun in a narrow
bandpass centered at the neutral hydrogen Lyman (alpha) (Ly-(alpha) )
line ((lambda) 1215.7 angstroms). It has higher sensitivity and a wider
field-of-view than the coronagraph which produced solar Ly-(alpha)
images on May 13, 1991 during the MSSTA flight. The all-reflecting
polarizers use advanced induced transmission and absorption thin film
multilayer coatings to optimize the reflectivity and polarization
properties at 1215.7 angstroms. We describe the instrument and discuss
the current status of the fabrication of the Wide Field H-Lyman (alpha)
Coronagraph/Polarimeter.
---------------------------------------------------------
Title: Stray light analysis of a reflecting UV coronagraph/polarimeter
with multilayer optics
Authors: Fineschi, Silvano; Romoli, Marco; Hoover, Richard B.; Baker,
Phillip C.; Zukic, Muamer; Kim, Jongmin; Walker, Arthur B.
1994SPIE.2010...78F Altcode:
An analysis is presented of the stray light expected in a
Coronagraph/Polarimeter operating at the H I Lyman (alpha) (Ly-(alpha)
) line ((lambda) 121.6 nm) and utilizing multilayer interference film
optics and ultrasmooth substrates (i.e., rms-smoothness <EQ 0.1
nm). This instrument is designed to measure the linear polarization of
the coronal Ly-(alpha) up to 2 solar radii (R.) from sun center. The
interpretation through the Hanle effect of these measurements would
yield information on the magnetic fields of the solar corona. Analytical
methods and laboratory measurements of substrate rms-smoothness
are used to carry out the stray light analysis. Our analysis shows
that with the use of ultrasmooth multilayer optics, it is possible
to design UV coronagraphs that, unlike visible light coronagraphs,
can observe the inner corona (i.e., up to heliocentric distances of
about 2 R.) without occulters.
---------------------------------------------------------
Title: Ultraviolet Coronal Spectrometer Observations During Spartan
Mission 201-1
Authors: Gardner, L. D.; Fineschi, S.; Hassler, D.; Romoli, M.;
Strachan, L.; Kohl, J. L.
1993BAAS...25.1200G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: LY-A-CO-PO (LY α coronograph/polarimeter): an instrument to
measure coronal magnetic fields
Authors: Fineschi, S.; Chiuderi, C.; Poletto, G.; Hoover, R. B.;
Walker, A. B. C., Jr.
1993MmSAI..64..441F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Polarimetry of HI Lyman-alpha for coronal magnetic field
diagnostics
Authors: Fineschi, Silvano; Hoover, Richard B.; Zukic, Muamer; Kim,
Jongmin; Walker, Arthur B. C., Jr.; Baker, Phillip C.
1993SPIE.1742..423F Altcode:
Measurements of the linear polarization of the hydrogen Lyman
(alpha) (Ly-(alpha) ) line from the solar corona can be used as a
means of probing coronal magnetic fields, the knowledge of which is
presently very limited. In this paper, we discuss and analyze the
possible sources of observational and instrumental uncertainty that
can be encountered in measuring magnetic fields of the solar corona
through polarimetric observations of the Hanle effect of the control
Ly-(alpha) line. The Hanle effect is the modification of the linear
polarization of a resonantly scattered line, due to the presence
of a magnetic field. Simulated observations are used to examine
how polarimetric measurements of this effect are affected by the
line-of-sight integration, the electron collisions, and the Ly-(alpha)
geocorona. We plan to implement the coronal magnetic field diagnostics
via the Ly-(alpha) Hanle effect using an all- reflecting Ly-(alpha)
coronagraph/polarimeter (Ly(alpha) CoPo) which employs reflecting
multilayer mirrors, polarizers, and filters. We discuss here the
requirements for such an instrument, and analyze the sources of
instrumental uncertainty for polarimetric observations of the coronal
Ly-(alpha) Hanle effect. We conclude that the anticipated polarization
signal from the corona and the expected performance of the Ly(alpha)
CoPo instrument are such that the Ly-(alpha) Hanle effect method for
coronal field diagnostics is feasible.
---------------------------------------------------------
Title: Design and fabrication of the all-reflecting H-Lyman alpha
coronagraph/polarimeter
Authors: Hoover, Richard B.; Johnson, R. B.; Fineschi, Silvano; Walker,
Arthur B. C., Jr.; Baker, Phillip C.; Zukic, Muamer; Kim, Jongmin
1993SPIE.1742..439H Altcode:
We have designed, analyzed, and are now fabricating an All-Reflecting
H-Lyman (alpha) Coronagraph/Polarimeter for solar research. This
new instrument operates in a narrow bandpass centered at (lambda)
1215.7 angstroms--the neutral hydrogen Lyman (alpha) (Ly- (alpha) )
line. It is shorter and faster than the telescope which produced solar
Ly-(alpha) images as a part of the MSSTA payload that was launched
on May 13, 1991. The Ly-(alpha) is produced and linearly polarized
in the solar corona by resonance scattering, and the presence of a
magnetic field modifies this polarization according to the Hanle
effect. The Lyman (alpha) Coronagraph/Polarimeter instrument has
been designed to measure coronal magnetic fields by interpreting,
via the Hanle effect, the measured linear polarization of the coronal
Ly-(alpha) line. Ultrasmooth mirrors, polarizers, and filters are
being flow-polished for this instrument from CVD silicon carbide
substrates. These optical components will be coated using advanced
induced transmission and absorption thin film multilayer coatings,
to optimize the reflectivity and polarization properties at 1215.7
angstroms. We describe some of the solar imaging results obtained
with the MSSTA Lyman (alpha) coronagraph. We also discuss the optical
design parameters and fabrication plans for the All-Reflecting H-Lyman
(alpha) Coronagraph/Polarimeter.
---------------------------------------------------------
Title: Electron Impact Polarization of Atomic Spectral Lines. I. A
General Theoretical Scheme
Authors: Fineschi, Silvano; Landi Degl'Innocenti, Egidio
1992ApJ...392..337F Altcode:
A suitable theoretical scheme able to describe, in a wide variety of
astrophysical situations, the phenomenon of atomic line polarization
by electron impact is developed. Starting from the general principles
of quantum mechanics and assuming the Born approximation, the rate
equations for the density matrix elements of a multilevel atomic
system, interacting with a nonrelativistic electron beam having any
kind of angular distribution, are derived in full generality. The
resulting theory generalizes the previous ones by accounting for the
collisional rates and the cross sections concerning both inelastic and
superelastic collisions (in any geometrical situation), and, moreover,
by taking into account the coherences among Zeeman sublevels split by
a magnetic field. As an example of particular relevance, the general
formulas derived in the first sections of the paper are subsequently
particularized to the case of the electric dipole interaction.
---------------------------------------------------------
Title: The SPARTAN Ultraviolet Coronagraph
Authors: Gardner, L. D.; Esser, R.; Habbal, S. R.; Hassler, D. M.;
Raymond, J. C.; Strachan, L.; van Ballegooijen, A. A.; Kohl, J. L.;
Fineschi, S.
1992AAS...180.5202G Altcode: 1992BAAS...24..815G
An ultraviolet coronagraph (UVC) is being prepared for a series of
orbital flights on NASA's Spartan 201 which is deployed and retrieved
by Shuttle. The Spartan 201 payload consists of the UVC and a white
light coronagraph developed by the High Altitude Observatory. Spartan
is expected to provide 26 orbits of solar observations per flight. The
first flight is scheduled for May 1993 and subsequent flights
are planned to occur at each polar passage of Ulysses (1994 and
1995). The UVC measures the intensity and spectral line profile of
resonantly scattered H I Ly-alpha and the intensities of O VI lambda
1032 and lambda 1037 at heliocentric heights between 1.3 and 3.5 solar
radii. A description of the UVC instrument, its characteristics, and the
observing program for the first flight will be presented. The initial
scientific objective is to determine the random velocity distribution
and bulk outflow velocity of coronal protons and the density and outflow
velocity of O(5+) in polar coronal holes and adjoining high latitude
streamers. This work is supported by NASA under Grant No. NAG5-613 to
the Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: Hydrogen Lyman-alpha coronagraph/polarimeter
Authors: Fineschi, Silvano; Hoover, Richard B.; Walker, Arthur
B. C., Jr.
1992SPIE.1546..402F Altcode: 1992SPIE.2011..402F
The present treatment of vector magnetic field measurement in coronas
by means of the Hanle effect of the Lyman-alpha line uses data from
all-reflecting imaging coronagraph/polarimeters. The polarization
sensitivity, bandpass, and spatial resolution of these instruments are
defined through a modeling of the Hanle-effect signature in Lyman-alpha
emission from coronal magnetic loops; the line-of-sight integration
through an inhomogeneous coronal medium is taken into account. The
use of the Hanle effect to measure solar corona vector magnetic fields
is verified.
---------------------------------------------------------
Title: Optical configurations of H I Lyman-alpha
coronagraph/polarimeters
Authors: Hoover, Richard B.; Fineschi, Silvano; Walker, Arthur B. C.,
Jr.; Johnson, R. B.; Zukic, Muamer
1992SPIE.1546..414H Altcode: 1992SPIE.2011..414H
The Multi-Spectral Solar Telescope Array (MSSTA) has obtained
numerous high-resolution soft X-ray/EUV/FUV solar images with
multilayer telescopes; these show dramatic prominences, spicules,
and threadlike limb structures. There is excellent correlation
between faint Lyman-alpha coronal structures seen in the digitized
MSSTA images and prominences seen in H-alpha images gathered by
ground-based observatories. The MSSTA has established the feasibility
of an all-reflecting, imaging Ly-alpha coronagraph/polarimeter.
---------------------------------------------------------
Title: Polarimetry of extreme ultraviolet lines in solar astronomy.
Authors: Fineschi, Silvano; Hoover, Richard B.; Fontenla, Juan M.;
Walker, Arthur B. C., Jr.
1991OptEn..30.1161F Altcode:
Several mechanisms can induce a detectable amount of linear polarization
in spectral lines emitted by the outer solar atmosphere at EUV/FUV
wavelengths: (1) Polarization in FUV lines (up to 20%) can be
originated by resonance scattering of radiation anisotropically
illuminating the emitting atoms. (2) Impact line polarization can
arise from anisotropic collisional excitation of the EUV-emitting
atoms by particles (electrons, protons) with non-Maxwellian velocity
distributions. The authors suggest how new technological developments
in the production of ultrasmooth, low-scatter flow-polished mirror
substrates and high-quality multilayer and interference film coatings
can make possible some new optical instruments for the observation of
these polarization effects. They describe several FUV/EUV polarimeter
designs based on these polarization optics.
---------------------------------------------------------
Title: Imaging polarimeters for solar extreme ultraviolet astronomy.
Authors: Hoover, Richard B.; Fineschi, Silvano; Fontenla, Juan M.;
Walker, Arthur B. C., Jr.
1991OptEn..30.1169H Altcode:
The authors describe new EUV/FUV (100Å ≤ λ ≤ 1500Å) polarimeter
instrument concepts for solar research. These instruments are
designed to observe linear polarization in EUV/FUV spectral lines
originating in the outer solar atmosphere, specifically: (1) a new
coronagraph/polarimeter operating at 1215.7Å (neutral hydrogen Lyman
α), which could observe this line in the near solar corona and lead to
the first direct measurements of both strength and direction of coronal
magnetic fields and (2) a new multilayer EUV imaging polarimeter,
operating at wavelengths of strong helium emission lines (e.g.,
304Å, 584Å), which could observe impact polarization phenomena and
provide information concerning the relative importance of thermal and
nonthermal processes in solar flares. The authors discuss several
instrument configurations and provide theoretical calculations and
performance predictions.
---------------------------------------------------------
Title: The H-Lyman α Coronagraph/Polarimeter
Authors: Fineschi, S.; Hoover, R. B.; Walker, A. B. C., Jr.
1991BAAS...23.1038F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar EUV/FUV line polarimetry. Pt. 1. Observational parameters
and theoretical considerations.
Authors: Fineschi, Silvano; Hoover, Richard B.; Fontenla, Juan M.;
Walker, Arthur B. C., Jr.
1991SPIE.1343..376F Altcode:
Several mechanisms can induce a detectable amount of linear polarization
(≥1%) in spectral lines emitted by the outer solar atmosphere at
EUV/FUV wavelengths (100 Å ≤ λ ≤ 1500 Å). The authors suggest
how new technological developments associated with the production of
ultra-smooth, low scatter, flow-polished mirror substrates and high
quality multilayer and interference film coatings can make possible
some exciting new optical instruments which should permit observations
of these polarization effects. They describe some new types of EUV/FUV
polarimeters based on these polarization optics.
---------------------------------------------------------
Title: Solar EUV/FUV line polarimetry: instruments and methods
Authors: Hoover, Richard B.; Fineschi, Silvano; Fontenla, Juan M.;
Walker, Arthur B.
1991SPIE.1343..389H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Electron Impact Polarization Expected in Solar EUV Lines from
Flaring Chromospheres/Transition Regions
Authors: Fineschi, S.; Fontenla, J. M.; MacNeice, P.; Ljepojevic, N. N.
1991max..conf...95F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Electron impact polarization expected in solar EUV lines from
flaring chromospheres/transition regions
Authors: Fineschi, S.; Fontenla, Juan M.; MacNeice, P.; Ljepojevic,
N. N.
1991deas.reptR....F Altcode:
We have evaluated lower bounds on the degree of impact Extreme
Ultraviolet/Ultraviolet (EUV/UV) line polarization expected during
solar flares. This polarization arises from collisional excitation by
energetic electrons with non-Maxwellian velocity distributions. Linear
polarization was observed in the S I 1437 A line by the Ultraviolet
Spectrometer and Polarimeter/Solar Maximum Mission (UVSP/SMM) during a
flare on 15 July 1980. An early interpretation suggested that impact
excitation by electrons propagating through the steep temperature
gradient of the flaring transition region/high chromosphere produced
this polarization. Our calculations show that the observed polarization
in this UV line cannot be due to this effect. We find instead that,
in some flare models, the energetic electrons can produce an impact
polarization of a few percent in EUV neutral helium lines (i.e.,
lambda lambda 522, 537, and 584 A).
---------------------------------------------------------
Title: Impact Line Polarization in Hot Solar Plasmas with
Non-Maxwellian Electron Distributions
Authors: Fineschi, S.; Fontenla, J. M.; MacNeice, P.; Ljepojevic, N. N.
1990BAAS...22..826F Altcode:
No abstract at ADS
