Author name code: auchere
ADS astronomy entries on 2022-09-14
author:"Auchere, Frederic"
------------------------------------------------------------------------
Title: What drives decayless kink oscillations in active region
coronal loops on the Sun?
Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter,
Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David;
Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle,
Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis;
Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel;
Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J.
Bibcode: 2022arXiv220904251M
Altcode:
We study here the phenomena of decayless kink oscillations in a system
of active region (AR) coronal loops. Using high resolution observations
from two different instruments, namely the Extreme Ultraviolet Imager
(EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly
(AIA) on board the Solar Dynamics Observatory, we follow these AR
loops for an hour each on three consecutive days. Our results show
significantly more resolved decayless waves in the higher-resolution
EUI data compared with the AIA data. Furthermore, the same system of
loops exhibits many of these decayless oscillations on Day-2, while on
Day-3, we detect very few oscillations and on Day-1, we find none at
all. Analysis of photospheric magnetic field data reveals that at most
times, these loops were rooted in sunspots, where supergranular flows
are generally absent. This suggests that supergranular flows, which
are often invoked as drivers of decayless waves, are not necessarily
driving such oscillations in our observations. Similarly, our findings
also cast doubt on other possible drivers of these waves, such as a
transient driver or mode conversion of longitudinal waves near the loop
footpoints. In conclusion, through our analysis we find that none of
the commonly suspected sources proposed to drive decayless oscillations
in active region loops seems to be operating in this event and hence,
the search for that elusive wave driver needs to continue.
Title: Quiet Sun Center to Limb Variation of the Linear Polarization
Observed by CLASP2 Across the Mg II h and k Lines
Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.;
Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto,
T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi,
L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu,
T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De;
Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán,
J.; Carlsson, M.; Leenaarts, J.
Bibcode: 2022ApJ...936...67R
Altcode: 2022arXiv220701788R
The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket
mission was launched on 2019 April 11. CLASP2 measured the four Stokes
parameters of the Mg II h and k spectral region around 2800 Å along a
200″ slit at three locations on the solar disk, achieving the first
spatially and spectrally resolved observations of the solar polarization
in this near-ultraviolet region. The focus of the work presented here
is the center-to-limb variation of the linear polarization across these
resonance lines, which is produced by the scattering of anisotropic
radiation in the solar atmosphere. The linear polarization signals of
the Mg II h and k lines are sensitive to the magnetic field from the
low to the upper chromosphere through the Hanle and magneto-optical
effects. We compare the observations to theoretical predictions
from radiative transfer calculations in unmagnetized semiempirical
models, arguing that magnetic fields and horizontal inhomogeneities
are needed to explain the observed polarization signals and spatial
variations. This comparison is an important step in both validating and
refining our understanding of the physical origin of these polarization
signatures, and also in paving the way toward future space telescopes
for probing the magnetic fields of the solar upper atmosphere via
ultraviolet spectropolarimetry.
Title: Automatic detection technique for solar filament oscillations
in GONG data
Authors: Luna, Manuel; Merou Mestre, Joan-René; Auchère, Frédéric
Bibcode: 2022arXiv220905087L
Altcode:
Solar filament oscillations have been known for decades. Now thanks
to the new capabilities of the new telescopes, these periodic motions
are routinely observed. Oscillations in filaments show key aspects of
their structure. A systematic study of filament oscillations over the
solar cycle can shed light on the evolution of the prominences. This
work is a proof of concept that aims to automatically detect and
parameterise such oscillations using H$\alpha$ data from the GONG
network of telescopes. The proposed technique studies the periodic
fluctuations of every pixel of the H$\alpha$ data cubes. Using the FFT
we compute the power spectral density (PSD). We define a criterion
to consider whether it is a real oscillation or whether it is a
spurious fluctuation. This consists in considering that the peak in
the PSD must be greater than several times the background noise with
a confidence level of 95\%. The background noise is well fitted to a
combination of red and white noise. We applied the method to several
observations already reported in the literature to determine its
reliability. We also applied the method to a test case, which is a
data set in which the oscillations of the filaments were not known a
priori. The method shows that there are areas in the filaments with PSD
above the threshold value. The periodicities obtained are in general
agreement with the values obtained by other methods. In the test case,
the method detects oscillations in several filaments. We conclude that
the proposed spectral technique is a powerful tool to automatically
detect oscillations in prominences using H$\alpha$ data.
Title: A highly dynamic small-scale jet in a polar coronal hole
Authors: Mandal, Sudip; Chitta, Lakshmi Pradeep; Peter, Hardi;
Solanki, Sami K.; Cuadrado, Regina Aznar; Teriaca, Luca; Schühle,
Udo; Berghmans, David; Auchère, Frédéric
Bibcode: 2022A&A...664A..28M
Altcode: 2022arXiv220602236M
We present an observational study of the plasma dynamics at the base
of a solar coronal jet, using high resolution extreme ultraviolet
imaging data taken by the Extreme Ultraviolet Imager on board Solar
Orbiter, and by the Atmospheric Imaging Assembly on board Solar
Dynamics Observatory. We observed multiple plasma ejection events
over a period of ∼1 h from a dome-like base that is ca. 4 Mm wide
and is embedded in a polar coronal hole. Within the dome below the
jet spire, multiple plasma blobs with sizes around 1−2 Mm propagate
upwards to the dome apex with speeds of the order of the sound speed
(ca. 120 km s−1). Upon reaching the apex, some of these
blobs initiate flows with similar speeds towards the other footpoint
of the dome. At the same time, high speed super-sonic outflows
(∼230 km s−1) are detected along the jet spire. These
outflows as well as the intensity near the dome apex appear to be
repetitive. Furthermore, during its evolution, the jet undergoes
many complex morphological changes, including transitions between
the standard and blowout type eruption. These new observational
results highlight the underlying complexity of the reconnection
process that powers these jets and they also provide insights into
the plasma response when subjected to rapid energy injection.
Movies associated to Figs. 1, 2, and 4 are available at https://www.aanda.org
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
Bibcode: 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 ⊙ 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: 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
Bibcode: 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: The Magnetic Origin of Solar Campfires: Observations by Solar
Orbiter and SDO
Authors: Panesar, Navdeep Kaur; Zhukov, Andrei; Berghmans, David;
Auchere, Frederic; Müller, Daniel; Tiwari, Sanjiv Kumar; Cheung, Mark
Bibcode: 2022cosp...44.2564P
Altcode:
Solar campfires are small-scale, short-lived coronal brightenings,
recently observed in 174 Å images by Extreme Ultraviolet Imager (EUI)
on board Solar Orbiter (SolO). Here we investigate the magnetic origin
of 52 campfires, in quiet-Sun, using line-of-sight magnetograms from
Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager
(HMI) together with extreme ultraviolet images from SolO /EUI and
SDO/Atmospheric Imaging Assembly (AIA). We find that the campfires
are rooted at the edges of photospheric magnetic network lanes; (ii)
most of the campfires reside above neutral lines and 77% of them appear
at sites of magnetic flux cancelation between the majority-polarity
magnetic flux patch and a merging minority-polarity flux patch, with
a flux cancelation rate of ∼1018 Mx hr‑1; some of the smallest
campfires come from the sites where magnetic flux elements were barely
discernible in HMI; (iii) some of the campfires occur repeatedly
from the same neutral line; (iv) in the large majority of instances
(79%), campfires are preceded by a cool-plasma structure, analogous to
minifilaments in coronal jets; and (v) although many campfires have
"complex" structure, most campfires resemble small-scale jets, dots,
or loops. Thus, "campfire" is a general term that includes different
types of small-scale solar dynamic features. They contain sufficient
magnetic energy (∼1026-1027 erg) to heat the solar atmosphere
locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to
over 1 hour, with most of the campfires having a lifetime of <10
minutes. The average lengths and widths of the campfires are 5400 ±
2500 km and 1600 ± 640 km, respectively. Our observations suggest that
(a) the presence of magnetic flux ropes may be ubiquitous in the solar
atmosphere and not limited to coronal jets and larger-scale eruptions
that make CMEs, and (b) magnetic flux cancelation, most likely driven
by magnetic reconnection in the lower atmosphere, is the fundamental
process for the formation and triggering of most campfires.
Title: Transient small-scale brightenings in the quiet solar corona:
a model for campfires observed with Solar Orbiter
Authors: Chen, Yajie; Peter, Hardi; Berghmans, David; Tian, Hui;
Auchère, Frédéric; Przybylski, Damien
Bibcode: 2022cosp...44.2557C
Altcode:
Recent observations by the Extreme Ultraviolet Imager (EUI) on
board Solar Orbiter have revealed prevalent small-scale transient
brightenings in the quiet solar corona termed "campfires". To
understand the generation mechanism of these coronal brightenings,
we constructed a self-consistent and time-dependent quiet-Sun
model extending from the upper convection zone to the lower corona
using a realistic three-dimensional radiation magnetohydrodynamic
simulation. From the model we have synthesized the coronal emission
in the EUI 174 passband. We identified several transient coronal
brightenings similar to those in EUI observations. The size and
lifetime of these coronal brightenings are mostly 0.5-4 Mm and ~2 min,
respectively. These brightenings are generally located at a height of
2-4 Mm above the photosphere, and the local plasma is often heated
above 1 MK. By examining the magnetic field structures before and
after the occurrence of brightenings, we concluded that these coronal
brightenings are generated by component magnetic reconnection between
interacting bundles of magnetic field lines or neighboring field lines
within highly twisted flux ropes. Occurring in the coronal part of
the atmosphere, these events generally reveal no obvious signature
of flux emergence or cancellation in photospheric magnetograms. These
transient coronal brightenings may play an important role in heating
of the local coronal plasma.
Title: Automated technique for detecting oscillations in solar
filaments
Authors: Luna, Manuel; Auchere, Frederic; Mérou-Mestre, Joan-René
Bibcode: 2022cosp...44.2425L
Altcode:
Solar prominences/filaments are cold plasma hanging in the hot
corona. There is a much larger magnetic structure that hosts this
cold plasma: the filament channel. It has proved that oscillations in
solar prominences are common and give information about their filament
channels. The systematic study of these oscillations over several
solar cycles will give us relevant information about the dynamics and
structure of the prominences as the magnetic stress evolves during
the cycle. In this study, we propose an efficient method to detect
and characterize the oscillations in solar filaments using H alpha
data. This technique uses spectral methods where the periodogram is
calculated for each pixel of the images in the time sequence. It is
necessary to calculate the background noise and we consider that we
have a positive detection when the significance is higher than 95%. In
this study, we set the basis for a future large-scale study of these
periodic motions in solar filaments.
Title: Automatic detection of small-scale EUV brightenings observed
by the Solar Orbiter/EUI
Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.;
Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin,
É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.;
Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti,
S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.;
Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N.
Bibcode: 2022A&A...663A.128A
Altcode: 2022arXiv220404027A
Context. Accurate detections of frequent small-scale extreme ultraviolet
(EUV) brightenings are essential to the investigation of the physical
processes heating the corona.
Aims: We detected small-scale
brightenings, termed campfires, using their morphological and
intensity structures as observed in coronal EUV imaging observations
for statistical analysis.
Methods: We applied a method based
on Zernike moments and a support vector machine (SVM) classifier
to automatically identify and track campfires observed by Solar
Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA).
Results: This method
detected 8678 campfires (with length scales between 400 km and 4000 km)
from a sequence of 50 High Resolution EUV telescope (HRIEUV)
174 Å images. From 21 near co-temporal AIA images covering the same
field of view as EUI, we found 1131 campfires, 58% of which were
also detected in HRIEUV images. In contrast, about 16%
of campfires recognized in HRIEUV were detected by AIA. We
obtain a campfire birthrate of 2 × 10−16 m−2
s−1. About 40% of campfires show a duration longer than 5
s, having been observed in at least two HRIEUV images. We
find that 27% of campfires were found in coronal bright points and
the remaining 73% have occurred out of coronal bright points. We
detected 23 EUI campfires with a duration greater than 245 s. We found
that about 80% of campfires are formed at supergranular boundaries,
and the features with the highest total intensities are generated at
network junctions and intense H I Lyman-α emission regions observed
by EUI/HRILya. The probability distribution functions for
the total intensity, peak intensity, and projected area of campfires
follow a power law behavior with absolute indices between 2 and 3. This
self-similar behavior is a possible signature of self-organization,
or even self-organized criticality, in the campfire formation
process. Supplementary material (S1-S3) is available at https://www.aanda.org
Title: Abundance diagnostics in active regions with Solar
Orbiter/SPICE
Authors: Giunta, Alessandra; Peter, Hardi; Parenti, Susanna; Buchlin,
Eric; Thompson, William; Auchere, Frederic; Kucera, Therese; Carlsson,
Mats; Janvier, Miho; Fludra, Andrzej; Hassler, Donald M.; Grundy,
Timothy; Sidher, Sunil; Guest, Steve; Leeks, Sarah; Fredvik, Terje;
Young, Peter
Bibcode: 2022cosp...44.2583G
Altcode:
With the launch of Solar Orbiter in February 2020, we are now able to
fully explore the link between the solar activity on the Sun and the
inner heliosphere. Elemental abundance measurements provide a key tracer
to probe the source regions of the solar wind and to track it from the
solar surface and corona to the heliosphere. Abundances of elements
with low first ionisation potential (FIP) are enhanced in the corona
relative to high-FIP elements, with respect to the photosphere. This is
known as the FIP effect, which is measured as abundance bias (FIP bias)
of low and high FIP elements. This effect is vital for understanding the
flow of mass and energy through the solar atmosphere. The comparison
between in-situ and remote sensing composition data, coupled with
modelling, will allow us to trace back the source of heliospheric
plasma. Solar Orbiter has a unique combination of in-situ and remote
sensing instruments that will help to make such a comparison. In
particular, the SPICE (Spectral Imaging of the Coronal Environment)
EUV spectrometer records spectra in two wavelength bands, 70.4-79.0
nm and 97.3-104.9 nm. SPICE is designed to provide spectroheliograms
using a core set of emission lines arising from ions of both low-FIP
and high-FIP elements such as C, N, O, Ne, Mg, S and Fe. These lines
are formed over a wide range of temperatures from 20,000 K to over 1
million K, enabling the analysis of the different layers of the solar
atmosphere. SPICE spectroheliograms can be processed to produce FIP
bias maps, which can be compared to in-situ measurements of the solar
wind composition of the same elements. During the Solar Orbiter Cruise
Phase, SPICE observed several active regions. We will present some of
these observations and discuss the SPICE diagnostic potential to derive
relative abundances (e.g., Mg/Ne) and the FIP bias in those regions.
Title: The SPICE spectrograph on Solar Orbiter: an introduction and
results from the first Orbits
Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin,
Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera,
Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta,
Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy;
Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina
Bibcode: 2022cosp...44.1338A
Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument is
the EUV imaging spectrometer on board the Solar Orbiter mission. With
its ability to derive physical properties of the coronal plasma,
SPICE is a key component of the payload to establish the connection
between the source regions and the in-situ measurements of the solar
wind. The spacecraft was successfully launched in February 2020 and
completed its cruise phase in December 2021. During this period,
the remote sensing instruments were mostly operated during limited
periods of time for 'checkout' engineering activities and synoptic
observations. Nonetheless, several of these periods provided enough
opportunities already to obtain new insights on coronal physics. During
the march 2022 perihelion - close to 0.3 AU - SPICE will provide
its highest spatial resolution data so far. Coordinated observations
between the remote sensing and in-situ instruments will provide the
first opportunity to use the full potential of the Solar Orbiter
mission. We will review the instrument characteristics and present
initial results from the cruise phase and first close encounter.
Title: Prominence eruption observed in He II 304 Å up to >6
R⊙ by EUI/FSI aboard Solar Orbiter
Authors: Mierla, M.; Zhukov, A. N.; Berghmans, D.; Parenti, S.;
Auchère, F.; Heinzel, P.; Seaton, D. B.; Palmerio, E.; Jejčič, S.;
Janssens, J.; Kraaikamp, E.; Nicula, B.; Long, D. M.; Hayes, L. A.;
Jebaraj, I. C.; Talpeanu, D. -C.; D'Huys, E.; Dolla, L.; Gissot, S.;
Magdalenić, J.; Rodriguez, L.; Shestov, S.; Stegen, K.; Verbeeck,
C.; Sasso, C.; Romoli, M.; Andretta, V.
Bibcode: 2022A&A...662L...5M
Altcode: 2022arXiv220515214M
Aims: We report observations of a unique, large prominence
eruption that was observed in the He II 304 Å passband of the Extreme
Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on
15-16 February 2022.
Methods: Observations from several vantage
points - Solar Orbiter, the Solar-Terrestrial Relations Observatory,
the Solar and Heliospheric Observatory, and Earth-orbiting satellites -
were used to measure the kinematics of the erupting prominence and the
associated coronal mass ejection. Three-dimensional reconstruction was
used to calculate the deprojected positions and speeds of different
parts of the prominence. Observations in several passbands allowed us
to analyse the radiative properties of the erupting prominence.
Results: The leading parts of the erupting prominence and the leading
edge of the corresponding coronal mass ejection propagate at speeds
of around 1700 km s−1 and 2200 km s−1,
respectively, while the trailing parts of the prominence are
significantly slower (around 500 km s−1). Parts of the
prominence are tracked up to heights of over 6 R⊙. The
He II emission is probably produced via collisional excitation rather
than scattering. Surprisingly, the brightness of a trailing feature
increases with height.
Conclusions: The reported prominence
is the first observed in He II 304 Å emission at such a great
height (above 6 R⊙). Movies are available at https://www.aanda.org
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.
Bibcode: 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: Validation of a Wave Heated 3D MHD Coronal-wind Model using
Polarized Brightness and EUV Observations
Authors: Parenti, Susanna; Réville, Victor; Brun, Allan Sacha;
Pinto, Rui F.; Auchère, Frédéric; Buchlin, Éric; Perri, Barbara;
Strugarek, Antoine
Bibcode: 2022ApJ...929...75P
Altcode: 2022arXiv220310876P
The physical properties responsible for the formation and evolution
of the corona and heliosphere are still not completely understood. 3D
MHD global modeling is a powerful tool to investigate all the possible
candidate processes. To fully understand the role of each of them,
we need a validation process where the output from the simulations
is quantitatively compared to the observational data. In this work,
we present the results from our validation process applied to the
wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At
this stage of the model development, we focus the work to the coronal
regime in quiescent condition. We analyze three simulation results,
which differ by the boundary values. We use the 3D distributions of
density and temperature, output from the simulations at the time of
around the first Parker Solar Probe perihelion (during minimum of
the solar activity), to synthesize both extreme ultraviolet (EUV)
and white-light-polarized (WL pB) images to reproduce the observed
solar corona. For these tests, we selected AIA 193 Å, 211 Å, and
171 Å EUV emissions, MLSO K-Cor, and LASCO C2 pB images obtained on
2018 November 6 and 7. We then make quantitative comparisons of the
disk and off limb corona. We show that our model is able to produce
synthetic images comparable to those of the observed corona.
Title: The magnetic drivers of campfires seen by the Polarimetric
and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
Bibcode: 2022A&A...660A.143K
Altcode: 2022arXiv220213859K
Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
(SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
termed campfires, that have been proposed to be brightenings near the
apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
magnetic processes driving these campfires are not understood.
Aims: During the cruise phase of SO and at a distance of 0.523
AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
offering the possibility to investigate the surface magnetic field
dynamics underlying campfires at a spatial resolution of about 380
km.
Methods: We used co-spatial and co-temporal data of the
quiet-Sun network at disc centre acquired with the High Resolution
Imager of SO/EUI at 17.4 nm (HRIEUV, cadence 2 s) and the
High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
min). Campfires that are within the SO/PHI−SO/EUI common field
of view were isolated and categorised according to the underlying
magnetic activity.
Results: In 71% of the 38 isolated events,
campfires are confined between bipolar magnetic features, which seem to
exhibit signatures of magnetic flux cancellation. The flux cancellation
occurs either between the two main footpoints, or between one of the
footpoints of the loop housing the campfire and a nearby opposite
polarity patch. In one particularly clear-cut case, we detected the
emergence of a small-scale magnetic loop in the internetwork followed
soon afterwards by a campfire brightening adjacent to the location
of the linear polarisation signal in the photosphere, that is to
say near where the apex of the emerging loop lays. The rest of the
events were observed over small scattered magnetic features, which
could not be identified as magnetic footpoints of the campfire hosting
loops.
Conclusions: The majority of campfires could be driven
by magnetic reconnection triggered at the footpoints, similar to the
physical processes occurring in the burst-like EUV events discussed
in the literature. About a quarter of all analysed campfires, however,
are not associated to such magnetic activity in the photosphere, which
implies that other heating mechanisms are energising these small-scale
EUV brightenings.
Title: The role of asymmetries in coronal rain formation during
thermal non-equilibrium cycles
Authors: Pelouze, Gabriel; Auchère, Frédéric; Bocchialini, Karine;
Froment, Clara; Mikić, Zoran; Soubrié, Elie; Voyeux, Alfred
Bibcode: 2022A&A...658A..71P
Altcode: 2021arXiv211009975P
Context. Thermal non-equilibrium (TNE) produces several observables
that can be used to constrain the spatial and temporal distribution
of solar coronal heating. Its manifestations include prominence
formation, coronal rain, and long-period intensity pulsations in
coronal loops. The recent observation of abundant periodic coronal rain
associated with intensity pulsations allowed for these two phenomena
to be unified as the result of TNE condensation and evaporation
cycles. On the other hand, many observed intensity pulsation events
show little to no coronal rain formation.
Aims: Our goal is
to understand why some TNE cycles produce such abundant coronal
rain, while others produce little to no rain.
Methods:
We reconstructed the geometry of the periodic coronal rain event,
using images from the Extreme Ultraviolet Imager (EUVI) onboard the
Solar Terrestrial Relations Observatory (STEREO), and magnetograms
from the Helioseismic and Magnetic Imager (HMI). We then performed 1D
hydrodynamic simulations of this event for different heating parameters
and variations of the loop geometry (9000 simulations in total). We
compared the resulting behaviour to simulations of TNE cycles that do
not produce coronal rain.
Results: Our simulations show that
both prominences and TNE cycles (with and without coronal rain) can
form within the same magnetic structure. We show that the formation
of coronal rain during TNE cycles depends on the asymmetry of the
loop and of the heating. Asymmetric loops are overall less likely
to produce coronal rain, regardless of the heating. In symmetric
loops, coronal rain forms when the heating is also symmetric. In
asymmetric loops, rain forms only when the heating compensates for
the asymmetry. Movie associated to Fig. 5 is available at https://www.aanda.org
Title: Empirical relations between the intensities of Lyman lines
of H and He+
Authors: Gordino, M.; Auchère, F.; Vial, J. -C.; Bocchialini, K.;
Hassler, D. M.; Bando, T.; Ishikawa, R.; Kano, R.; Kobayashi, K.;
Narukage, N.; Trujillo Bueno, J.; Winebarger, A.
Bibcode: 2022A&A...657A..86G
Altcode: 2022arXiv220101519G
Context. Empirical relations between major UV and extreme UV spectral
lines are one of the inputs for models of chromospheric and coronal
spectral radiances and irradiances. They are also needed for the
interpretation of some of the observations of the Solar Orbiter
mission.
Aims: We aim to determine an empirical relation between
the intensities of the H I 121.6 nm and He II 30.4 nm Ly-α lines.
Methods: Images at 121.6 nm from the Chromospheric Lyman-Alpha
Spectro Polarimeter (CLASP) and Multiple XUV Imager (MXUVI) sounding
rockets were co-registered with simultaneous images at 30.4 nm from the
EIT and AIA orbital telescopes in order to derive a spatially resolved
relationship between the intensities.
Results: We have obtained
a relationship between the H I 121.6 nm and He II 30.4 nm intensities
that is valid for a wide range of solar features, intensities, and
activity levels. Additional SUMER data have allowed the derivation of
another relation between the H I 102.5 nm (Ly-β) and He II 30.4 nm
lines for quiet-Sun regions. We combined these two relationships to
obtain a Ly-α/Ly-β intensity ratio that is comparable to the few
previously published results.
Conclusions: The relationship
between the H I 121.6 nm and He II 30.4 nm lines is consistent with the
one previously obtained using irradiance data. We have also observed
that this relation is stable in time but that its accuracy depends on
the spatial resolution of the observations. The derived Ly-α/Ly-β
intensity ratio is also compatible with previous results.
Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.;
Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.;
Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.;
Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long,
D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca,
L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.;
Jacques, L.; Berghmans, D.
Bibcode: 2021A&A...656A..35Z
Altcode: 2021arXiv210902169Z
Context. The three-dimensional fine structure of the solar atmosphere
is still not fully understood as most of the available observations
are taken from a single vantage point.
Aims: The goal of the
paper is to study the three-dimensional distribution of the small-scale
brightening events ("campfires") discovered in the extreme-UV quiet Sun
by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter.
Methods: We used a first commissioning data set acquired by the EUI's
High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and
we combined it with simultaneous data taken by the Atmospheric Imaging
Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171
Å passband. The two-pixel spatial resolution of the two telescopes
is 400 km and 880 km, respectively, which is sufficient to identify
the campfires in both data sets. The two spacecraft had an angular
separation of around 31.5° (essentially in heliographic longitude),
which allowed for the three-dimensional reconstruction of the campfire
position. These observations represent the first time that stereoscopy
was achieved for brightenings at such a small scale. Manual and
automatic triangulation methods were used to characterize the campfire
data.
Results: The height of the campfires is located between
1000 km and 5000 km above the photosphere and we find a good agreement
between the manual and automatic methods. The internal structure of
campfires is mostly unresolved by AIA; however, for a particularly
large campfire, we were able to triangulate a few pixels, which are
all in a narrow range between 2500 and 4500 km.
Conclusions: We
conclude that the low height of EUI campfires suggests that they belong
to the previously unresolved fine structure of the transition region and
low corona of the quiet Sun. They are probably apexes of small-scale
dynamic loops heated internally to coronal temperatures. This work
demonstrates that high-resolution stereoscopy of structures in the
solar atmosphere has become feasible.
Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1
Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier;
Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song,
Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil,
Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman,
Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri
Bibcode: 2021AGUFMSH52A..06M
Altcode:
Probing the magnetic nature of the Suns atmosphere requires measurement
of the Stokes I, Q, U and V profiles of relevant spectral lines (of
which Q, U and V encode the magnetic field information). Many of the
magnetically sensitive lines formed in the chromosphere and transition
region are in the ultraviolet spectrum, necessitating observations
above the absorbing terrestrial atmosphere. The Chromospheric
Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown
successfully in April 2019, as a follow-on to the successful flight in
September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP). Both projects were funded by NASAs Heliophysics Technology
and Instrument Development for Science (H-TIDeS) program to develop
and test a technique for observing the Sun in ultraviolet light,
and for quantifying the polarization of that light. By demonstrating
successful measurement and interpretation of the polarization in
hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP
and CLASP2 missions are vital first steps towards routine quantitative
characterization of the local thermal and magnetic conditions in the
solar chromosphere. In October of 2021, we re-flew the CLASP2 payload
with a modified observing program to further demonstrate the maturity
of the UV spectropolarimetry techniques, and readiness for development
into a satellite observatory. During the reflight, called CLASP2.1,
the spectrograph slit was scanned across an active region plage to
acquire a two-dimensional map of Stokes V/I, to demonstrate the ability
of UV spectropolarimetry to yield chromospheric magnetic fields over
a large area. This presentation will display preliminary results from
the flight of CLASP2.1.
Title: 3D modelling of Titov-Demoulin modified Flux Ropes propagation
in the Solar Wind
Authors: Regnault, Florian; Janvier, Miho; Strugarek, Antoine; Auchere,
F.; Al-Haddad, Nada
Bibcode: 2021AGUFMSH33A..04R
Altcode:
Interplanetary Coronal Mass Ejections (ICMEs) originate from the
eruption of complex magnetic structures occurring in our stars
atmosphere. They propagate in the interplanetary medium, where they
can be probed by spacecraft. ICMEs are known to generate geomagnetic
storms that can disturb our technologies on earth, this is why they
are a subject of interest. Studying ICMEs could, therefore, allow us to
predict and lower their impact in our technology. We present the results
of the propagation simulation of a set of Titov-Demoulin flux ropes
(Titov et al. 2014) with different magnetic fields and sizes at the
initiation. This is done with the 3D MHD module of the PLUTO code. Our
grid starts at the low corona and goes up to 2 astronomical units. This
allows us to study the effect of the magnetic field intensity or the
size of the flux rope at the initiation on its properties during the
propagation, highlighting then the physical processes happening during
their journey in the inner heliosphere. The evolution of the magnetic
field of the flux rope during the propagation agrees with evolution
laws deduced from in situ observations. We also simulate in situ
profiles that spacecraft would have measured at Mercury and at Earth,
and we compare with the results of Janvier et al. 2019 and Regnault et
al. 2020. We find a good match between simulated in situ profiles and
typical profiles obtained in these studies. The magnetic components
of the simulated flux rope match well with what we are expecting from
theory (Lundquist et al. 1950). This simulation helps us to have a
better understanding of the physical mechanisms that happen during
propagation of an ICME.
Title: Full Vector Velocity Reconstruction Using Solar Orbiter
Doppler Map Observations.
Authors: Podladchikova, Olena; Harra, Louise; Barczynski, Krzysztof;
Mandrini, Cristina; Auchere, F.; Berghmans, David; Buchlin, Eric;
Dolla, Laurent; Mierla, Marilena; Parenti, Susanna; Rodriguez, Luciano
Bibcode: 2021AGUFMNG35B0432P
Altcode:
The Solar Orbiter mission opens up opportunities forthe
combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different space spectrometerswill
be located at wide angles to each other, allowing three-dimensional
(3D) spectroscopy of the solar atmosphere.The aim of this work is to
prepare the methodology to facilitate the reconstruction of 3D vector
velocities from two stereoscopicLOS Doppler velocity measurements using
the Spectral Imaging of the Coronal Environment (SPICE) on board the
Solar Orbiter andthe near-Earth spectrometers, while widely separated in
space. We develop the methodology using the libraries designed earlier
for the STEREO mission but applied to spectroscopicdata from the Hinode
mission and the Solar Dynamics Observatory. We use well-known methods
of static and dynamic solar rotationstereoscopy and the methods of
EUV stereoscopic triangulation for optically-thin coronal EUV plasma
emissions. We develop new algorithms using analytical geometry in
space to determine the 3D velocity in coronal loops. We demonstrate
our approach with the reconstruction of 3D velocity vectors in plasma
flows along "open" and "closed"magnetic loops. This technique will be
applied first to an actual situation of two spacecraft at different
separations with spectrometers onboard (SPICE versus the Interface
Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer)
during the Solar Orbiternominal phase. We summarise how these
observations can be coordinated.
Title: Campfires observed by EUI: What have we learned so far?
Authors: Berghmans, David; Auchere, F.; Zhukov, Andrei; Mierla,
Marilena; Chen, Yajie; Peter, Hardi; Panesar, Navdeep; Chitta, Lakshmi
Pradeep; Antolin, Patrick; Aznar Cuadrado, Regina; Tian, Hui; Hou,
Zhenyong; Podladchikova, Olena
Bibcode: 2021AGUFMSH21A..02B
Altcode:
Since its very first light images of the corona, the EUI/HRIEUV
telescope onboard Solar Orbiter has observed small localised
brightenings in the Quiet Sun. These small localised brightenings,
have become known as campfires, and are observed with length scales
between 400 km and 4000 km and durations between 10 sec and 200
sec. The smallest and weakest of these HRIEUV brightenings have
not been previously observed. Simultaneous observations from the
EUI High-resolution Lyman- telescope (HRILYA) do not show localised
brightening events, but the locations of the HRIEUV events clearly
correspond to the chromospheric network. Comparisons with simultaneous
AIA images shows that most events can also be identified in the
17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although
they appear weaker and blurred. Some of the larger campfires have
the appearance of small interacting loops with the brightening
expanding from the contact point of the loops. Our differential
emission measure (DEM) analysis indicated coronal temperatures. We
determined the height for a few of these campfires to be between 1
and 5 Mm above the photosphere. We interpret these events as a new
extension to the flare-microflare-nanoflare family. Given their low
height, the EUI campfires could stand as a new element of the fine
structure of the transition region-low corona, that is, as apexes
of small-scale loops that undergo internal heating all the way up to
coronal temperatures. 3D MHD simulations with the MURaM code revealed
brightenings that are in many ways similar to the campfires by EUI. The
brightenings in the simulations suggest that campfires are triggered by
component reconnection inside flux bundles rather than flux emergence
or cancellation. Nevertheless, some of the observed campfires can
be clearly linked to flux cancellation events and, intriguingly,
are preceded by an erupting cool plasma structure. Analysis of the
dynamics of campfires revealed that some have the appearance of coronal
microjets, the smallest coronal jets observed in the quiet Sun. The
HRIEUV images also reveal transient jets on a somewhat bigger scale
with repeated outflows on the order of 100 km s1. In this paper we
will provide an overview of the campfire related phenomena that EUI
has observed and discuss the possible relevance for coronal heating.
Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot,
Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester,
Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin,
Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith,
Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David;
Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca,
Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre;
Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David
Bibcode: 2021AGUFMSH21A..03Z
Altcode:
We study the three-dimensional distribution of small-scale brightening
events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun
by the EUI telescope onboard the Solar Orbiter mission. We use one of
the first commissioning data sets acquired by the HRI_EUV telescope of
EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous
SDO/AIA dataset taken in the very similar 171 A passband. The spatial
resolution of the two telescopes is sufficient to identify the campfires
in both datasets. The angular separation between the two spacecraft of
around 31.5 degrees allowed for the three-dimensional reconstruction
of the position of campfires. This is the first time that stereoscopy
was achieved for structures at such a small scale. Manual and automatic
triangulation methods were used. The height of campfires is between 1000
km and 5000 km above the photosphere, and there is a good agreement
between the results of manual and automatic methods. The internal
structure of campfires is mostly not resolved by AIA, but for a large
campfire we could triangulate a few pixels, which are all in a narrow
height range between 2500 and 4500 km. The low height of campfires
suggests that they belong to the previously unresolved fine structure
of the transition region and low corona of the quiet Sun. They are
probably apexes of small-scale dynamic loops internally heated to
coronal temperatures. This work demonstrates that high-resolution
stereoscopy of structures in the solar atmosphere has become possible.
Title: Extreme-UV quiet Sun brightenings observed by the Solar
Orbiter/EUI
Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.;
Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.;
Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.;
Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.;
Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.;
Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.;
Inhester, B.
Bibcode: 2021A&A...656L...4B
Altcode: 2021arXiv210403382B
Context. The heating of the solar corona by small heating events
requires an increasing number of such events at progressively smaller
scales, with the bulk of the heating occurring at scales that are
currently unresolved.
Aims: The goal of this work is to study the
smallest brightening events observed in the extreme-UV quiet Sun.
Methods: We used commissioning data taken by the Extreme Ultraviolet
Imager (EUI) on board the recently launched Solar Orbiter mission. On
30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its
High Resolution EUV telescope (HRIEUV, 17.4 nm passband)
reached an exceptionally high two-pixel spatial resolution of 400
km. The size and duration of small-scale structures was determined
by the HRIEUV data, while their height was estimated
from triangulation with simultaneous images from the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory
mission. This is the first stereoscopy of small-scale brightenings
at high resolution.
Results: We observed small localised
brightenings, also known as `campfires', in a quiet Sun region with
length scales between 400 km and 4000 km and durations between 10 s and
200 s. The smallest and weakest of these HRIEUV brightenings
have not been previously observed. Simultaneous observations from the
EUI High-resolution Lyman-α telescope (HRILya) do not show
localised brightening events, but the locations of the HRIEUV
events clearly correspond to the chromospheric network. Comparisons with
simultaneous AIA images shows that most events can also be identified
in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA,
although they appear weaker and blurred. Our differential emission
measure analysis indicated coronal temperatures peaking at log T ≈
6.1 − 6.15. We determined the height for a few of these campfires to
be between 1000 and 5000 km above the photosphere.
Conclusions:
We find that `campfires' are mostly coronal in nature and rooted in the
magnetic flux concentrations of the chromospheric network. We interpret
these events as a new extension to the flare-microflare-nanoflare
family. Given their low height, the EUI `campfires' could stand as a
new element of the fine structure of the transition region-low corona,
that is, as apexes of small-scale loops that undergo internal heating
all the way up to coronal temperatures.
Title: Capturing transient plasma flows and jets in the solar corona
Authors: Chitta, L. P.; Solanki, S. K.; Peter, H.; Aznar Cuadrado,
R.; Teriaca, L.; Schühle, U.; Auchère, F.; Berghmans, D.; Kraaikamp,
E.; Gissot, S.; Verbeeck, C.
Bibcode: 2021A&A...656L..13C
Altcode: 2021arXiv210915106C
Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma
jets are typical signatures of magnetic reconnection and the associated
impulsive heating of the solar atmospheric plasma. To gain new insights
into the process, high-cadence observations are required to capture
the rapid response of plasma to magnetic reconnection as well as the
highly dynamic evolution of jets. Here, we report the first 2 s cadence
extreme-UV observations recorded by the 174 Å High Resolution Imager of
the Extreme Ultraviolet Imager on board the Solar Orbiter mission. These
observations, covering a quiet-Sun coronal region, reveal the onset
signatures of magnetic reconnection as localized heating events. These
localized sources then exhibit repeated plasma eruptions or jet
activity. Our observations show that this spatial morphological change
from localized sources to jet activity could occur rapidly on timescales
of about 20 s. The jets themselves are intermittent and are produced
from the source region on timescales of about 20 s. In the initial
phases of these events, plasma jets are observed to exhibit speeds,
as inferred from propagating intensity disturbances, in the range of
100 km s−1 to 150 km s−1. These jets then
propagate to lengths of about 5 Mm. We discuss examples of bidirectional
and unidirectional jet activity observed to have been initiated from
the initially localized bursts in the corona. The transient nature
of coronal bursts and the associated plasma flows or jets along with
their dynamics could provide a benchmark for magnetic reconnection
models of coronal bursts and jets. Movies are available at https://www.aanda.org
Title: Propagating brightenings in small loop-like structures in
the quiet-Sun corona: Observations from Solar Orbiter/EUI
Authors: Mandal, Sudip; Peter, Hardi; Chitta, Lakshmi Pradeep;
Solanki, Sami K.; Aznar Cuadrado, Regina; Teriaca, Luca; Schühle,
Udo; Berghmans, David; Auchère, Frédéric
Bibcode: 2021A&A...656L..16M
Altcode: 2021arXiv211108106M
Brightenings observed in solar extreme-ultraviolet images are generally
interpreted as signatures of micro- or nanoflares occurring in the
transition region or at coronal temperatures. Recent observations
with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have
revealed the smallest of such brightenings (called campfires) in the
quiet-Sun corona. Analyzing EUI 174 Å data obtained at a resolution
of about 400 km on the Sun with a cadence of 5 s on 30 May 2020,
we report here a number of cases in which these campfires exhibit
propagating signatures along their apparently small (3-5 Mm) loop-like
structures. The measured propagation speeds are generally between 25
km s−1 and 60 km s−1. If the loop plasma is
assumed to be at a million Kelvin, these apparent motions would be
slower than the local sound speed. Furthermore, these brightenings
exhibit nontrivial propagation characteristics such as bifurcation,
merging, reflection, and repeated plasma ejections. We suggest that
these features are manifestations of the internal dynamics of these
small-scale magnetic structures and could provide important insights
into the dynamic response (∼40 s) of the loop plasma to the heating
events and also into the locations of the heating events themselves. Movies associated to Figs 2-5, A.1, and B.1 are available at https://www.aanda.org
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.
Bibcode: 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.
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.
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.
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−1. 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.
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. Movies are available at https://www.aanda.org
Title: First observations from the SPICE EUV spectrometer on Solar
Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
Chitta, L. P.
Bibcode: 2021A&A...656A..38F
Altcode: 2021arXiv211011252F
Aims: We present first science observations taken during the
commissioning activities of the Spectral Imaging of the Coronal
Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
mission. SPICE is a high-resolution imaging spectrometer operating at
extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
the possible types of observations to give prospective users a
better understanding of the science capabilities of SPICE.
Methods: We have reviewed the data obtained by SPICE between April
and June 2020 and selected representative results obtained with
different slits and a range of exposure times between 5 s and 180
s. Standard instrumental corrections have been applied to the raw
data.
Results: The paper discusses the first observations
of the Sun on different targets and presents an example of the full
spectra from the quiet Sun, identifying over 40 spectral lines from
neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
magnesium, and iron. These lines cover the temperature range between
20 000 K and 1 million K (10 MK in flares), providing slices of the
Sun's atmosphere in narrow temperature intervals. We provide a list
of count rates for the 23 brightest spectral lines. We show examples
of raster images of the quiet Sun in several strong transition region
lines, where we have found unusually bright, compact structures in the
quiet Sun network, with extreme intensities up to 25 times greater
than the average intensity across the image. The lifetimes of these
structures can exceed 2.5 hours. We identify them as a transition
region signature of coronal bright points and compare their areas and
intensity enhancements. We also show the first above-limb measurements
with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
and O VI lines. We discuss the potential to use abundance diagnostics
methods to study the variability of the elemental composition that can
be compared with in situ measurements to help confirm the magnetic
connection between the spacecraft location and the Sun's surface,
and locate the sources of the solar wind.
Conclusions: The
SPICE instrument successfully performs measurements of EUV spectra
and raster images that will make vital contributions to the scientific
success of the Solar Orbiter mission.
Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
Bibcode: 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−1 from 4 R⊙
to 6 R⊙. 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: Transient small-scale brightenings in the quiet solar corona:
A model for campfires observed with Solar Orbiter
Authors: Chen, Yajie; Przybylski, Damien; Peter, Hardi; Tian, Hui;
Auchère, F.; Berghmans, D.
Bibcode: 2021A&A...656L...7C
Altcode: 2021arXiv210410940C
Context. Recent observations by the Extreme Ultraviolet Imager (EUI) on
board Solar Orbiter have characterized prevalent small-scale transient
brightenings in the corona above the quiet Sun termed campfires.
Aims: In this study we search for comparable brightenings in a numerical
model and then investigate their relation to the magnetic field and the
processes that drive these events.
Methods: We used the MURaM
code to solve the 3D radiation magnetohydrodynamic equations in a box
that stretches from the upper convection zone to the corona. The model
self-consistently produces a supergranular network of the magnetic
field and a hot corona above this quiet Sun. For the comparison with
the model, we synthesized the coronal emission as seen by EUI in its
174 Å channel, isolated the seven strongest transient brightenings,
and investigated the changes of the magnetic field in and around these
in detail.
Results: The transients we isolated have a lifetime of
about 2 min and are elongated loop-like features with lengths around 1
Mm to 4 Mm. They tend to occur at heights of about 2 Mm to 5 Mm above
the photosphere, a bit offset from magnetic concentrations that mark
the bright chromospheric network, and they reach temperatures of above
1 MK. As a result, they very much resemble the larger campfires found
in observations. In our model most events are energized by component
reconnection between bundles of field lines that interact at coronal
heights. In one case, we find that untwisting a highly twisted flux
rope initiates the heating.
Conclusions: Based on our study, we
propose that the majority of campfire events found by EUI are driven
by component reconnection and our model suggests that this process
significantly contributes to the heating of the corona above the quiet
Sun. Movies associated to Figs. 2, 4, 5, and A1 are available at https://www.aanda.org
Title: Stereoscopic measurements of coronal Doppler velocities
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C. H.; Auchère, F.; Berghmans, D.; Buchlin, É.; Dolla, L.; Mierla,
M.; Parenti, S.; Rodriguez, L.
Bibcode: 2021A&A...655A..57P
Altcode: 2021arXiv210802280P
Context. The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time different space spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere.
Aims: The aim of this
work is to prepare a methodology to facilitate the reconstruction
of 3D vector velocities from two stereoscopic line of sight (LOS)
Doppler velocity measurements using the Spectral Imaging of the
Coronal Environment (SPICE) on board the Solar Orbiter and the
near-Earth spectrometers, while widely separated in space.
Methods: We developed the methodology using the libraries designed
earlier for the STEREO mission, but applied to spectroscopic data
from the Hinode mission and the Solar Dynamics Observatory. We used
well-known methods of static and dynamic solar rotation stereoscopy and
the methods of extreme ultraviolet (EUV) stereoscopic triangulation
for optically thin coronal EUV plasma emissions. We developed new
algorithms using analytical geometry in space to determine the 3D
velocity in coronal loops.
Results: We demonstrate our approach
with the reconstruction of 3D velocity vectors in plasma flows along
`open' and `closed' magnetic loops. This technique will be applied
to an actual situation of two spacecraft at different separations
with spectrometers on board during the Solar Orbiter nominal phase:
SPICE versus the Interface Region Imaging Spectrograph (IRIS) and
Hinode imaging spectrometer. We summarise how these observations can
be coordinated. Movies associated to Fig. 1 are available at https://www.aanda.org
Title: The Magnetic Origin of Solar Campfires
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Berghmans, David;
Cheung, Mark C. M.; Müller, Daniel; Auchere, Frederic; Zhukov, Andrei
Bibcode: 2021ApJ...921L..20P
Altcode: 2021arXiv211006846P
Solar campfires are fine-scale heating events, recently observed by
Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI
174 Å images, together with EUV images from Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms
from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the
magnetic origin of 52 randomly selected campfires in the quiet solar
corona. We find that (i) the campfires are rooted at the edges of
photospheric magnetic network lanes; (ii) most of the campfires reside
above the neutral line between majority-polarity magnetic flux patch and
a merging minority-polarity flux patch, with a flux cancelation rate of
~1018 Mx hr-1; (iii) some of the campfires occur
repeatedly from the same neutral line; (iv) in the large majority of
instances, campfires are preceded by a cool-plasma structure, analogous
to minifilaments in coronal jets; and (v) although many campfires have
"complex" structure, most campfires resemble small-scale jets, dots,
or loops. Thus, "campfire" is a general term that includes different
types of small-scale solar dynamic features. They contain sufficient
magnetic energy (~1026-1027 erg) to heat the solar
atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1
minute to over 1 hr, with most of the campfires having a lifetime of
<10 minutes. The average lengths and widths of the campfires are 5400
± 2500 km and 1600 ± 640 km, respectively. Our observations suggest
that (a) the presence of magnetic flux ropes may be ubiquitous in the
solar atmosphere and not limited to coronal jets and larger-scale
eruptions that make CMEs, and (b) magnetic flux cancelation is the
fundamental process for the formation and triggering of most campfires.
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
Bibcode: 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: Magnetic imaging of the outer solar atmosphere (MImOSA)
Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
Bibcode: 2021ExA...tmp...95P
Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability of
planets orbiting these host stars. Although the magnetic field at the
surface of the Sun is reasonably well characterised by observations,
the information on the magnetic field in the higher atmospheric layers
is mainly indirect. This lack of information hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution
and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is
designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter
based on a 30 cm telescope that combines high throughput in the
extreme UV with polarimetry to connect the magnetic measurements
of the other two instruments. Placed in a near-Earth orbit, the data
downlink would be maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-based
observatories. This mission to measure the magnetic field will finally
unlock the driver of the dynamics in the outer solar atmosphere and
thereby will greatly advance our understanding of the Sun and the
heliosphere.
Title: Vector Velocities Measurements with the Solar Orbiter SPICE
Spectrometer
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C.; Auchère, F.; Berghmans, D.; Buchlin, E.; Dolla, L.; Mierla, M.;
Parenti, S.; Rodriguez, L.
Bibcode: 2021AAS...23831312P
Altcode:
The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere. Here we develop a methodology to
prepare for this kind of analysis, by using data from the Hinode mission
and the Solar Dynamics Observatory, respectively. We employ solar
rotation to simulate measurements of spectrometers with different views
of the solar corona. The resulting data allow us to apply stereoscopic
tie-pointing and triangulation techniques designed for the STEREO
spacecraft pair, and to perform 3D analysis of the Doppler shifts of
a quasi-stationary active region. Our approach allows the accurate
reconstruction of 3D velocity vectors in plasma flows along "open" and
"closed" magnetic loops. This technique will be applied to the actual
situation of two spacecraft at different separations with spectrometers
on board (the Solar Orbiter Spectral Imaging of the Coronal Environment
versus the Interface Region Imaging Spectrograph (IRIS) and Hinode
imaging spectrometer) and we summarise how these observations can be
coordinated to assess vector velocity measurements. This 3D spectroscopy
method will facilitate the understanding of the complex flows that
take place throughout the solar atmosphere.
Title: Mapping of Solar Magnetic Fields from the Photosphere to the
Top of the Chromosphere with CLASP2
Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.;
del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.;
Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.;
Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil,
G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.;
Asensio Ramos, A.; Carlsson, M.; Leenaarts, J.
Bibcode: 2021AAS...23810603M
Altcode:
Coronal heating, chromospheric heating, and the heating &
acceleration of the solar wind, are well-known problems in solar
physics. Additionally, knowledge of the magnetic energy that
powers solar flares and coronal mass ejections, important drivers
of space weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of photospheric
magnetic measurements into the corona is fraught with difficulties and
uncertainties, partly due to the vastly different plasma beta between
the photosphere and the corona. Better results in understanding
the coronal magnetic field should be derived from measurements of
the magnetic field in the chromosphere. To that end, we are pursuing
quantitative determination of the magnetic field in the chromosphere,
where plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown
on a sounding rocket in April 2019, succeeded in measuring all four
Stokes polarization parameters in UV spectral lines formed by singly
ionized Magnesium and neutral Manganese. Because these ions produce
spectral lines under different conditions, CLASP2 thus was able to
quantify the magnetic field properties at multiple heights in the
chromosphere simultaneously, as shown in the recent paper by Ishikawa
et al. In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the chromosphere;
and we will illustrate what is next for the CLASP missions and the
demonstration of UV spectropolarimetry in the solar chromosphere.
Title: Signatures of coronal hole substructure in the solar wind:
combined Solar Orbiter remote sensing and in situ measurements
Authors: Horbury, T. S.; Laker, R.; Rodriguez, L.; Steinvall, K.;
Maksimovic, M.; Livi, S.; Berghmans, D.; Auchere, F.; Zhukov, A. N.;
Khotyaintsev, Yu. V.; Woodham, L.; Matteini, L.; Stawarz, J.; Woolley,
T.; Bale, S. D.; Rouillard, A.; O'Brien, H.; Evans, V.; Angelini,
V.; Owen, C.; Solanki, S. K.; Nicula, B.; Muller, D.; Zouganelis, I.
Bibcode: 2021arXiv210414960H
Altcode:
Context. The Sun's complex corona is the source of the solar wind
and interplanetary magnetic field. While the large scale morphology
is well understood, the impact of variations in coronal properties
on the scale of a few degrees on properties of the interplanetary
medium is not known. Solar Orbiter, carrying both remote sensing
and in situ instruments into the inner solar system, is intended
to make these connections better than ever before. Aims. We combine
remote sensing and in situ measurements from Solar Orbiter's first
perihelion at 0.5 AU to study the fine scale structure of the solar
wind from the equatorward edge of a polar coronal hole with the aim
of identifying characteristics of the corona which can explain the in
situ variations. Methods. We use in situ measurements of the magnetic
field, density and solar wind speed to identify structures on scales
of hours at the spacecraft. Using Potential Field Source Surface
mapping we estimate the source locations of the measured solar wind
as a function of time and use EUI images to characterise these solar
sources. Results. We identify small scale stream interactions in the
solar wind with compressed magnetic field and density along with speed
variations which are associated with corrugations in the edge of the
coronal hole on scales of several degrees, demonstrating that fine
scale coronal structure can directly influence solar wind properties
and drive variations within individual streams. Conclusions. This early
analysis already demonstrates the power of Solar Orbiter's combined
remote sensing and in situ payload and shows that with future, closer
perihelia it will be possible dramatically to improve our knowledge
of the coronal sources of fine scale solar wind structure, which is
important both for understanding the phenomena driving the solar wind
and predicting its impacts at the Earth and elsewhere.
Title: Mapping solar magnetic fields from the photosphere to the
base of the corona
Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán,
Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère,
Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler,
Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage,
Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge,
Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.;
Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán,
Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit
Bibcode: 2021SciA....7.8406I
Altcode: 2021arXiv210301583I
Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind to
its main driver, the magnetic field. Here we report unprecedented
spectropolarimetric observations of an active region plage and
its surrounding enhanced network, showing circular polarization in
ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We
infer the longitudinal magnetic field from the photosphere to the
very upper chromosphere. At the top of the plage chromosphere the
field strengths reach more than 300 gauss, strongly correlated with
the Mg II $k$ line core intensity and the electron pressure. This
unique mapping shows how the magnetic field couples the different
atmospheric layers and reveals the magnetic origin of the heating in
the plage chromosphere.
Title: 20 years of ACE data: how superposed epoch analyses reveal
generic features in interplanetary CME profiles
Authors: Regnault, Florian; Dasso, Sergio; Auchere, Frederic; Demoulin,
Pascal; Janvier, Miho; Strugarek, Antoine
Bibcode: 2021cosp...43E1017R
Altcode:
Interplanetary Coronal Mass Ejections (ICMEs) result from solar flares
occurring in our star's atmosphere. These large-scale magnetized
structures propagate in the interplanetary medium where they can be
probed by spacecraft. Depending on their speed, ICMEs may accumulate
enough solar wind plasma to form a turbulent sheath ahead of them. They
therefore consist of two main substructures : a sheath and a magnetic
ejecta (ME). The magnetic ejecta is the main body of an ICME where
the magnetic field is more intense and with less variance than that
of the ambient solar wind. We present a statistical study using the
superposed epoch analysis technique on a catalog of around 400 ICMEs
where we consider the profiles of the physical parameters of the ICMEs
(the magnetic field intensity, the speed, temperature, ...) seen at
1 AU by the ACE spacecraft. In particular, we investigate different
possible classifications of ICMEs, for example based on their speeds,
the phase of the solar cycle when they are detected, and the detection
of an associated magnetic cloud (MCs, a subset of MEs with a clear
rotation of the magnetic field as well as a low plasma temperature
compared with the solar wind). We confirm that slow ICMEs have a
more symmetric profile than fast ICMEs, therefore generalizing the
work made on a sample of 44 ICMEs with clearly identified magnetic
clouds by Masias-Meza et al. (2016). We also find that fast ICMEs
show signs of compression in both their magnetic ejecta and in their
sheath. Furthermore, we do not find any impact of the solar cycle on the
generic features of ICMEs. However, more extreme events are observed
during the active parts of the cycle, widening the distributions of
all parameters. Finally, we find that ICMEs with or without a detected
magnetic cloud show similar profiles, which confirms the hypothesis
that both types of events correspond to similar ICMEs, and that the
ones with no detected magnetic clouds may be observed when crossed
sufficiently away from the flux rope core.
Title: The Extreme ultraviolet imager onboard Solar Orbiter
Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere,
Frederic; Long, David; Schuehle, Udo; Rochus, Pierre
Bibcode: 2021cosp...43E.949B
Altcode:
The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
instrument package of the ESA/NASA Solar Orbiter mission that will
explore the inner heliosphere and observe the Sun from vantage points
close to the Sun and out of the ecliptic. With EUI we aim to improve our
understanding of the structure and dynamics of the solar atmosphere,
globally as well as at high resolution, and from high solar latitude
perspectives. The EUI consists of three telescopes, the Full Sun Imager
(FSI) and two High Resolution Imagers (HRIs), which are optimised
to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a
coverage from chromosphere up to corona. The EUI instrument design
will be reviewed, and its scientific objectives and plans will be
discussed. Early results of the EUI commissioning will be presented.
Title: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA):
Unlocking the driver of the dynamics in the upper solar atmosphere
Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J.
Bibcode: 2021arXiv210101566P
Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability
of planets orbiting these host stars. The lack of information on the
magnetic field in the higher atmospheric layers hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution and high
sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to
measure the large-scale magnetic field in the corona with an aperture
of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with
polarimetry to connect the magnetic measurements of the other two
instruments. This mission to measure the magnetic field will unlock
the driver of the dynamics in the outer solar atmosphere and thereby
greatly advance our understanding of the Sun and the heliosphere.
Title: Stereoscopic Measurements of Coronal Doppler Velocities aboard
Solar Orbiter
Authors: Podladchikova, Olena; Harra, Louise K.; Mandrini, Cristina
H.; Rodriguez, Luciano; Parenti, Susanna; Dolla, Laurent; Buchlin,
Eric; Auchere, Frederic; Mierla, Marilena; Barczynski, Krzysztof
Bibcode: 2021cosp...43E.957P
Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region.We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI), the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
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
Bibcode: 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: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
L.; Thompson, W. T.; Williams, D.
Bibcode: 2020AGUFMSH038..09Z
Altcode:
Linking solar activity on the surface and in the corona to the inner
heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. Solar
Orbiter's unique combination of remote sensing and in-situ instruments
coupled with observation from other missions such as Parker Solar
Probe will allow us to compare in-situ and remote sensing composition
data. With the addition of modeling, these new results will allow us
to trace back the source of heliospheric plasma. As high telemetry
will not always be available with SPICE, we have developed a method
for measuring relative abundances that is both telemetry efficient
and reliable. Unlike methods based on Differential Emission Measure
(DEM) inversion, the Linear Combination Ratio (LCR) method does not
require a large number of spectral lines. This new method is based
on linear combinations of UV spectral lines. The coefficients of
the combinations are optimized such that the ratio of two linear
combinations of radiances would yield the relative abundance of two
elements. We present some abundance diagnostics tested on different
combinations of spectral lines observable by SPICE.
Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
D.; Young, P. R.
Bibcode: 2020AGUFMSH038..03P
Altcode:
We will present some of the early data of the Spectral Imaging of the
Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
unique features of SPICE is its capability to record a wide range of
wavelengths in the extreme UV with the possibility to record spectral
lines giving access to a continuous plasma temperature range from 10.000
K to well above 1 MK. The data taken so far were for commissioning
purposes and they can be used for a preliminary evaluation of the
science performance of the instrument. Here we will concentrate on
sample spectra covering the whole wavelength region and on the early
raster maps acquired in bright lines in the quiet Sun close to disk
center. Looking at different quiet Sun features we investigate the
thermal structure of the atmosphere and flow structures. For this
we apply fits to the spectral profiles and check the performance in
terms of Doppler shifts and line widths to retrieve the structure of
the network in terms of dynamics. While the amount of data available
so far is limited, we will have a first look on how quiet Sun plasma
responds to heating events. For this, we will compare spectral lines
forming at different temperatures recorded at strictly the same time.
Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
W. T.; Tustain, S.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH038..02F
Altcode:
SPICE (Spectral Imaging of Coronal Environment) is one of the remote
sensing instruments onboard Solar Orbiter. It is an EUV imaging
spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
bands with exposures as short as 1s. SPICE is the only Solar Orbiter
instrument that can measure EUV spectra from the disk and low corona
of the Sun and record all spectral lines simultaneously. SPICE uses
one of three narrow slits, 2"x11', 4''x11', 6''x11', or a wide slit
30''x14'. The primary mirror can be scanned in a direction perpendicular
to the slit, allowing raster images of up to 16' in size. We
present an overview of the first SPICE data taken on several days
during the instrument commissioning carried out by the RAL Space team
between 2020 April 21 and 2020 June 14. We also include results from
SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
taken between June 16-21st. We give examples of full spectra
from the quiet Sun near disk centre and provide a list of key spectral
lines emitted in a range of temperatures between 10,000 K and over 1
million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
neon, sulphur and magnesium. We show examples of first raster images
in several strong lines, obtained with different slits and a range
of exposure times between 5s and 180s. We describe the temperature
coverage and density diagnostics, determination of plasma flows, and
discuss possible applications to studies of the elemental abundances
in the corona. We also show the first off-limb measurements with SPICE,
as obtained when the spacecraft pointed at the limb.
Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
Bibcode: 2020SPIE11444E..0NS
Altcode:
Solar-C (EUVST) is the next Japanese solar physics mission to
be developed with significant contributions from US and European
countries. The mission carries an EUV imaging spectrometer with
slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
Telescope) as the mission payload, to take a fundamental step towards
answering how the plasma universe is created and evolves and how the
Sun influences the Earth and other planets in our solar system. In
April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
(Japan Aerospace Exploration Agency) has made the final down-selection
for this mission as the 4th in the series of competitively chosen
M-class mission to be launched with an Epsilon launch vehicle in mid
2020s. NASA (National Aeronautics and Space Administration) has selected
this mission concept for Phase A concept study in September 2019 and
is in the process leading to final selection. For European countries,
the team has (or is in the process of confirming) confirmed endorsement
for hardware contributions to the EUVST from the national agencies. A
recent update to the mission instrumentation is to add a UV spectral
irradiance monitor capability for EUVST calibration and scientific
purpose. This presentation provides the latest status of the mission
with an overall description of the mission concept emphasizing on key
roles of the mission in heliophysics research from mid 2020s.
Title: Observation of Smallest Ever Detected Brightening Events with
the Solar Orbiter EUI HRI-EUV Imager
Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere,
F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado,
R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
Bibcode: 2020AGUFMSH038..01P
Altcode:
The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter
acquired its first images in May 2020. The passband of the 17.4 nm
High Resolution Imager (HRI-EUV) is dominated by emission lines of
Fe IX and Fe X, that is the 1 million degree solar corona. The solar
atmosphere at this temperature is dynamic at all scales, down to the
highest spatial resolution available from instruments priori to Solar
Orbiter. During the Commissioning phase, HRI-EUV acquired several high
temporal resolution (a few seconds) sequences at quiet Sun regions at
disk center. The instrument revealed a multitude of brightenings at
the smallest-ever detectable spatial scales which, at that time, was
about 400 km (two pixels). These events appear to be present everywhere
all the time. We present the first results of the analysis of these
sequences with the aim of understanding the role of these small scale
events in the heating of the solar corona.
Title: Stereoscopic Measurements of Coronal Doppler Velocities
Authors: Podladchikova, O.; Harra, L. K.; Barczynski, K.; Mandrini,
C. H.; Auchere, F.; Buchlin, E.; Dolla, L.; Mierla, M.; Rodriguez, L.
Bibcode: 2020AGUFMSH038..07P
Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of two spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region. We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI),the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
Title: Optical design of the Chromospheric LAyer Spectro-Polarimeter
(CLASP2)
Authors: Tsuzuki, Toshihiro; Ishikawa, Ryohko; Kano, Ryouhei; Narukage,
Noriyuki; Song, Donguk; Yoshida, Masaki; Uraguchi, Fumihiro; Okamoto,
Takenori J.; McKenzie, David; Kobayashi, Ken; Rachmeler, Laurel;
Auchere, Frederic; Trujillo Bueno, Javier
Bibcode: 2020SPIE11444E..6WT
Altcode:
Chromospheric LAyer Spectro-Polarimeter (CLASP2) was a sounding
rocket experiment, which is a follow-up mission to the Chromospheric
Lyman-Alpha Spectro-Polarimeter (CLASP1) in 2015. To measure the
magnetic fields in the upper solar atmosphere in a highly quantitative
manner, CLASP2 changes the target wavelengths from the hydrogen Ly-α
line (121.567 nm) to Mg II lines near 280 nm. We reused the main
structure and most of the optical components in the CLASP1 instrument,
which reduced the turnaround time and cost. We added a magnifying
optical system to maintain the wavelength resolution, even at the
longer wavelength of CLASP2. Here, we describe the optical design and
performance of the CLASP2 instrument.
Title: Calibrating optical distortions in the Solar Orbiter SPICE
spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
D.; Sidher, S.
Bibcode: 2020AGUFMSH0360029T
Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
Solar Orbiter is a high-resolution imaging spectrometer operating
at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
image onto the entrance slit of the spectrometer section. A Toroidal
Variable Line Space (TVLS) grating images the entrance slit onto a
pair of MCP-intensified APS detectors. Ray-tracing analysis prior
to launch showed that the instrument was subject to a number of
small image distortions which need to be corrected in the final data
product. We compare the ray tracing results with measurements made in
flight. Co-alignment with other telescopes on Solar Orbiter will also
be examined.
Title: First results from the EUI and SPICE observations of Alpha
Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH0360024B
Altcode:
On June 16th 2020 Solar Orbiter made a dedicated observing campaign
where the spacecraft pointed to the solar limb to allow some of the
high resolution instruments to observe the ingress (at the east limb)
and later the egress (west limb) of the occultation of the star Alpha
Leonis by the solar disk. The star was chosen because its luminosity and
early spectral type ensure high and stable flux at wavelengths between
100 and 122 nanometers, a range observed by the High Resolution EUI
Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
of the SPICE spectrograph. Star observations, when feasible, allow
to gather a great deal of information on the instrument performances,
such as the radiometric performance and the instrument optical point
spread function (PSF). We report here the first results from the
above campaign for the two instruments.
Title: Solar Orbiter: connecting remote sensing and in situ
measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
Y.; Laker, R.
Bibcode: 2020AGUFMSH038..10H
Altcode:
A key science goal of the Solar Orbiter mission is to make connections
between phenomena on the Sun and their manifestations in interplanetary
space. To that end, the spacecraft carries a carefully tailored
payload of six remote sensing instruments and four making in situ
measurements. During June 2020, while the spacecraft was around 0.5
AU from the Sun, the remote sensing instruments operated for several
days. While this was primarily an engineering activity, the resulting
observations provided outstanding measurements and represent the ideal
first opportunity to investigate the potential for making connections
between the remote sensing and in situ payloads on Solar Orbiter. We present a preliminary analysis of the available remote sensing and
in situ observations, showing how connections can be made, and discuss
the potential for further, more precise mapping to be performed as
the mission progresses.
Title: First Images and Initial In-Flight Performance of the Extreme
Ultraviolet Imager On-Board Solar Orbiter.
Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra,
L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.;
Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C.
Bibcode: 2020AGUFMSH0360025A
Altcode:
The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is
composed of two High Resolution Imagers working at 121.6 (HRI-LYA,
H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one
dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition
region) and 17.4 nm (Fe IX/X, corona). During the commissioning period
following the launch of Solar Orbiter and two and a half months of
outgassing, EUI acquired its first solar images on May 12th, 2020 at
about 0.67 AU. Most of the capabilities of the instrument have been
tested during the following weeks, which revealed excellent overall
performance. HRI-EUV already provided images with an angular resolution
equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide
images of the Sun at Lyman alpha, which have been otherwise relatively
rare, with sub-second cadence capability. FSI will provide context for
connection science but it will also explore regions of the corona never
imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI
uses a complex on-board image processing system including advanced
image compression and event detection algorithms. In particular,
commissioning tests confirm the good performance of the compression,
which is critical given the limited total telemetry volume imposed by
the mission profile. In this paper, we present the main characteristics
of the first images taken in each channel and we provide an initial
assessment of the in-flight performance.
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
Bibcode: 2020AGUFMSH0360003T
Altcode:
The Solar Orbiter spacecraft carries a powerful set of remote
sensing instruments that allow studying the solar atmosphere with
unprecedented diagnostic capabilities. Many such diagnostics require
the simultaneous usage of more than one instrument. One example of that
is the capability, for the first time, to obtain (near) simultaneous
spatially resolved observations of the emission from the first three
lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
can observe the Lyman beta and gamma lines in its long wavelength
(SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
(FSI-304). Being hydrogen and helium the main components of our star,
these very bright transitions play an important role in the energy
budget of the outer atmosphere via radiative losses and the measurement
of their profiles and radiance ratios is a fundamental constraint to
any comprehensive modelization effort of the upper solar chromosphere
and transition region. Additionally, monitoring their average ratios
can serve as a check out for the relative radiometric performance of
the two instruments throughout the mission. Although the engineering
data acquired so far are far from ideal in terms of time simultaneity
(often only within about 1 h) and line coverage (often only Lyman beta
was acquired by SPICE and not always near simultaneous images from all
three telescopes are available) the analysis we present here still
offers a great opportunity to have a first look at the potential of
this diagnostic from the two instruments. In fact, we have identified
a series of datasets obtained at disk center and at various positions
at the solar limb that allow studying the Lyman alpha to beta radiance
ratio and their relation to He II 30.4 as a function of the position
on the Sun (disk center versus limb and quiet Sun versus coronal holes).
Title: Very high-resolution observations of the solar atmosphere
in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard
Solar Orbiter
Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot,
S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.;
Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
Bibcode: 2020AGUFMSH0360026A
Altcode:
The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of
three telescopes, the Full Sun Imager (FSI) and two High Resolution
Imagers (HRIs). The two HRI telescopes provide images of the base
of the corona, near to the chromosphere, and of the 1 million K
corona. In fact, the HRI-EUV telescope operates around 17.4 nm to
obtain images dominated by emission from lines generated from Fe-IX
and X ions, formed at about 1 MK, while the HRI-LYA telescope provides
narrow band images dominated by the H I Lyman alpha line at 121.6 nm,
formed in the upper chromosphere/lower transition region of the solar
atmosphere around 20,000 K. Thus, the two imagers provide a powerful
diagnostics of the solar structural organization, in terms of loop
hierarchies and connectivity. Here we present an analysis of the first
two near-simultaneous (within 15s) high-resolution images of the solar
quiet atmosphere obtained near disk center by the two high-resolution
telescopes on May 30th 2020, during the commissioning phase of the
mission , when Solar Orbiter was at about 0.56 AU from the Sun.
Title: A sensitivity analysis of the updated optical design for
EUVST on the Solar-C mission
Authors: Kawate, Tomoko; Tsuzuki, Toshihiro; Shimizu, Toshifumi;
Imada, Shinsuke; Katsukawa, Yukio; Hara, Hirohisa; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Hattori, Tomoya; Narasaki, Shota; Warren, Harry P.;
Teriaca, Luca; Korendyke, Clarence M.; Brown, Charles M.; Auchere,
Frederic
Bibcode: 2020SPIE11444E..3JK
Altcode:
The EUV high-throughput spectroscopic telescope (EUVST) onboard the
Solar-C mission has the high spatial (0.4'') resolution over a wide
wavelength range in the vacuum ultraviolet. To achieve high spatial
resolution under a design constraint given by the JAXA Epsilon launch
vehicle, we further update the optical design to secure margins
needed to realize 0.4'' spatial resolution over a field of view of
100''×100''. To estimate the error budgets of spatial and spectral
resolutions due to installation and fabrication errors, we perform a
sensitivity analysis for the position and orientation of each optical
element and for the grating parameters by ray tracing with the Zemax
software. We obtain point spread functions (PSF) for rays from 9
fields and at 9 wavelengths on each detector by changing each parameter
slightly. A full width at half maximum (FWHM) of the PSF is derived at
each field and wavelength position as a function of the perturbation
of each optical parameter. Assuming a mount system of each optical
element and an error of each optical parameter, we estimate spatial
and spectral resolutions by taking installation and fabrication errors
into account. The results of the sensitivity analysis suggest that
budgets of the total of optical design and the assembly errors account
for 15% and 5.8% of our budgets of the spatial resolution in the long
wavelength and short wavelength bands, respectively. On the other hand,
the grating fabrication errors give a large degradation of spatial and
spectral resolutions, and investigations of compensators are needed
to relax the fabrication tolerance of the grating surface parameters.
Title: 20 Years of ACE Data: How Superposed Epoch Analyses Reveal
Generic Features in Interplanetary CME Profiles
Authors: Regnault, F.; Janvier, M.; Démoulin, P.; Auchère, F.;
Strugarek, A.; Dasso, S.; Noûs, C.
Bibcode: 2020JGRA..12528150R
Altcode: 2020arXiv201105050R
Interplanetary coronal mass ejections (ICMEs) are magnetic structures
propagating from the Sun's corona to the interplanetary medium. With
over 20 years of observations at the L1 libration point, ACE offers
hundreds of ICMEs detected at different times during several solar
cycles and with different features such as the propagation speed. We
investigate a revisited catalog of more than 400 ICMEs using the
superposed epoch method on the mean, median, and the most probable
values of the distribution of magnetic and plasma parameters. We also
investigate the effects of the speed of ICMEs relative to the solar
wind, the solar cycle, and the existence of a magnetic cloud on the
generic ICME profile. We find that fast-propagating ICMEs (relatively
to the solar wind in front) still show signs of compression at 1 au, as
seen by the compressed sheath and the asymmetric profile of the magnetic
field. While the solar cycle evolution does not impact the generic
features of ICMEs, there are more extreme events during the active part
of the cycle, widening the distributions of all parameters. Finally, we
find that ICMEs with or without a detected magnetic cloud show similar
profiles, which confirms the hypothesis that ICMEs with no detected
magnetic clouds are crossed further away from the flux rope core. Such
a study provides a generic understanding of processes that shape the
overall features of ICMEs in the solar wind and can be extended with
future missions at different locations in the solar system.
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.
Bibcode: 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.
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.
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.
Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
Bibcode: 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: 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.
Bibcode: 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.
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.
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.
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.
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: Understanding the origins of the heliosphere: integrating
observations and measurements from Parker Solar Probe, Solar Orbiter,
and other space- and ground-based observatories
Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron,
N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.;
St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; 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.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper,
J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.;
De Groof, A.; Williams, D.
Bibcode: 2020A&A...642A...4V
Altcode:
Context. The launch of Parker Solar Probe (PSP) in 2018, followed
by Solar Orbiter (SO) in February 2020, has opened a new window in
the exploration of solar magnetic activity and the origin of the
heliosphere. These missions, together with other space observatories
dedicated to solar observations, such as the Solar Dynamics Observatory,
Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations
from WIND and ACE, and ground based multi-wavelength observations
including the DKIST observatory that has just seen first light,
promise to revolutionize our understanding of the solar atmosphere
and of solar activity, from the generation and emergence of the Sun's
magnetic field to the creation of the solar wind and the acceleration of
solar energetic particles.
Aims: Here we describe the scientific
objectives of the PSP and SO missions, and highlight the potential for
discovery arising from synergistic observations. Here we put particular
emphasis on how the combined remote sensing and in situ observations of
SO, that bracket the outer coronal and inner heliospheric observations
by PSP, may provide a reconstruction of the solar wind and magnetic
field expansion from the Sun out to beyond the orbit of Mercury in the
first phases of the mission. In the later, out-of-ecliptic portions of
the SO mission, the solar surface magnetic field measurements from SO
and the multi-point white-light observations from both PSP and SO will
shed light on the dynamic, intermittent solar wind escaping from helmet
streamers, pseudo-streamers, and the confined coronal plasma, and on
solar energetic particle transport.
Methods: Joint measurements
during PSP-SO alignments, and magnetic connections along the same
flux tube complemented by alignments with Earth, dual PSP-Earth,
and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will
allow a better understanding of the in situ evolution of solar-wind
plasma flows and the full three-dimensional distribution of the
solar wind from a purely observational point of view. Spectroscopic
observations of the corona, and optical and radio observations,
combined with direct in situ observations of the accelerating solar
wind will provide a new foundation for understanding the fundamental
physical processes leading to the energy transformations from solar
photospheric flows and magnetic fields into the hot coronal plasma
and magnetic fields and finally into the bulk kinetic energy of the
solar wind and solar energetic particles.
Results: We discuss
the initial PSP observations, which already provide a compelling
rationale for new measurement campaigns by SO, along with ground-
and space-based assets within the synergistic context described above.
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal.
Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing.
Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
Title: The Solar Orbiter Heliospheric Imager (SoloHI)
Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke,
C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch,
S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton,
M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin,
D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.;
Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl,
A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker,
J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère,
F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.;
Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J.
Bibcode: 2020A&A...642A..13H
Altcode:
Aims: We present the design and pre-launch performance of
the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument
prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently
scheduled for launch in 2020.
Methods: The goal of this paper
is to provide details of the SoloHI instrument concept, design, and
pre-flight performance to give the potential user of the data a better
understanding of how the observations are collected and the sources
that contribute to the signal.
Results: The paper discusses
the science objectives, including the SoloHI-specific aspects, before
presenting the design concepts, which include the optics, mechanical,
thermal, electrical, and ground processing. Finally, a list of planned
data products is also presented.
Conclusions: The performance
measurements of the various instrument parameters meet or exceed the
requirements derived from the mission science objectives. SoloHI is
poised to take its place as a vital contributor to the science success
of the Solar Orbiter mission.
Title: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
Bibcode: 2020A&A...642A...1M
Altcode: 2020arXiv200900861M
Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
2015-2025 programme and a mission of international collaboration between
ESA and NASA, will explore the Sun and heliosphere from close up and
out of the ecliptic plane. It was launched on 10 February 2020 04:03
UTC from Cape Canaveral and aims to address key questions of solar and
heliospheric physics pertaining to how the Sun creates and controls
the Heliosphere, and why solar activity changes with time. To answer
these, the mission carries six remote-sensing instruments to observe
the Sun and the solar corona, and four in-situ instruments to measure
the solar wind, energetic particles, and electromagnetic fields. In
this paper, we describe the science objectives of the mission, and how
these will be addressed by the joint observations of the instruments
onboard.
Methods: The paper first summarises the mission-level
science objectives, followed by an overview of the spacecraft and
payload. We report the observables and performance figures of each
instrument, as well as the trajectory design. This is followed by a
summary of the science operations concept. The paper concludes with a
more detailed description of the science objectives.
Results:
Solar Orbiter will combine in-situ measurements in the heliosphere
with high-resolution remote-sensing observations of the Sun to address
fundamental questions of solar and heliospheric physics. The performance
of the Solar Orbiter payload meets the requirements derived from the
mission's science objectives. Its science return will be augmented
further by coordinated observations with other space missions and
ground-based observatories. ARRAY(0x207ce98)
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
Bibcode: 2020A&A...642A...8R
Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere.
Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor.
Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products.
Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
Title: 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
Bibcode: 2020A&A...642A..10A
Altcode: 2019arXiv191108462A
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⊙ to about 9 R⊙, 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.
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.
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.
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. Metis website:
http://metis.oato.inaf.it
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
Bibcode: 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: Spectroscopic detection of coronal plasma flows in loops
undergoing thermal non-equilibrium cycles
Authors: Pelouze, Gabriel; Auchère, Frédéric; Bocchialini, Karine;
Froment, Clara; Parenti, Susanna; Soubrié, Elie
Bibcode: 2020A&A...634A..54P
Altcode: 2019arXiv191202538P
Context. Long-period intensity pulsations were recently detected in
the EUV emission of coronal loops and attributed to cycles of plasma
evaporation and condensation driven by thermal non-equilibrium
(TNE). Numerical simulations that reproduce this phenomenon
also predict the formation of periodic flows of plasma at coronal
temperatures along some of the pulsating loops.
Aims: We aim
to detect these predicted flows of coronal-temperature plasma in
pulsating loops.
Methods: We used time series of spatially
resolved spectra from the EUV imaging spectrometer (EIS) onboard
Hinode and tracked the evolution of the Doppler velocity in loops in
which intensity pulsations have previously been detected in images
of SDO/AIA.
Results: We measured signatures of flows that are
compatible with the simulations but only for a fraction of the observed
events. We demonstrate that this low detection rate can be explained
by line of sight ambiguities combined with instrumental limitations,
such as low signal-to-noise ratio or insufficient cadence. Movies associated to Figs. 1, 4, 7, 10 are available at https://www.aanda.org
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.
Bibcode: 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
models1 and indirect measurements through helioseismic
observations2, 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
sporadic3,4. In this Letter, we present simultaneous global
images of the helium (out to a heliocentric distance of 3R⊙
(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⊙). The morphology of the He+
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: The SPICE (Spectral Imaging of the Coronal Environment)
Ultraviolet Imaging Spectrograph Investigation
Authors: Hassler, D.; Auchere, F.; Carlsson, M.; Fludra, A.; Giunta,
A. S.; Mueller, D.; Peter, H.; Parenti, S.; Teriaca, L.; Fredvik, T.
Bibcode: 2019AGUFMSH24A..02H
Altcode:
One of the primary objectives of the Solar Orbiter mission is to link
remote sensing observations of the solar surface structures with in-situ
observations of solar wind streams. The SPICE (Spectral Imaging of the
Coronal Environment) instrument will characterize the plasma properties
of regions near the Sun to directly compare with in-situ measurements
from both Solar Orbiter & Parker Solar Probe. Specifically, SPICE
will map outflow velocities of surface features to solar wind structures
with similar composition (FIP, M/q) measured in-situ by the SWA/HIS
instrument on Solar Orbiter. These observations will help discriminate
models of solar wind origin by matching composition signatures in
solar wind streams to surface feature composition, and discriminate
physical processes that inject material from closed structures into
solar wind streams. This presentation will provide an overview of
the SPICE investigation, including science & measurement objective,
instrument design, capabilities and performance as measured during
calibration prior to delivery to the Solar Orbiter spacecraft. The
presentation will also provide a description of the operations concept
and data processing during the mission.
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz,
W. K.; Schühle, U.
Bibcode: 2019AGUFMSH21D3291R
Altcode:
The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
instrument package of the ESA/NASA Solar Orbiter mission that will
explore the inner heliosphere and observe the Sun from vantage points
close to the Sun and out-of-the-ecliptic. EUI aims at improving our
understanding of the structure and dynamics of the solar atmosphere. EUI
will take images of the solar atmosphere, globally as well as at high
resolution, and from high solar latitude perspectives. EUI consists
of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm
and 30.4 nm to provide a coverage from chromosphere up to corona. EUI
is designed to cope with the strong constraints that Solar Orbiter has
as a deep space mission. Limited telemetry availability is compensated
by state-of-the-art image compression, on board image processing and
event selection. The imposed power limitations and potentially harsh
radiation environment lead to the usage of novel CMOS sensors. As
the unobstructed field of view of the telescopes needs to protrude
through the spacecraft heat shield, the apertures were kept as small as
possible. This lead to a systematic effort to optimize the throughput
of every optical element and the reduction of noise levels in the
sensor. In this paper we review the design of the two elements of
the EUI instrument: the Optical Bench System and the Common Electronic
Box. Particular attention is also given to the on board software,
the intended operations, the ground software and the foreseen data
products. EUI will bring unique science opportunities thanks to its
specific design, its viewpoint and thanks to the planned synergies with
the other Solar Orbiter instruments. We highlight in particular science
opportunities brought by the out-of-ecliptic vantage point of the solar
poles, the high resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding
Rocket Mission: First Results
Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchere,
F.; Rachmeler, L.; Kano, R.; Song, D.; Okamoto, J.; Kobayashi, K.;
Yoshida, M.
Bibcode: 2019AGUFMSH44A..06M
Altcode:
A major challenge for heliophysics is to decipher the magnetic structure
of the chromosphere, because of its vital role in the transport of
energy into the corona and solar wind. Routine satellite measurements
of the chromospheric magnetic field will dramatically improve our
understanding of the chromosphere and its connection to the rest of
the solar atmosphere. Before such a satellite can be considered for
flight, we must refine the measurement techniques by exploring emission
lines with a range of magnetic sensitivities. In 2015, CLASP achieved
the first measurement of linear polarization produced by scattering
processes in a far UV resonance line (hydrogen Lyman-α), and the
first exploration of the magnetic field (via the Hanle effect) and
geometrical complexity in quiet regions of the chromosphere/corona
transition region. These measurements are a first step towards
routine quantitative characterization of the local thermal and magnetic
conditions in this key layer of the solar atmosphere. Nonetheless,
Lyman-α is only one of the magnetically sensitive spectral lines in
the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry
by acquiring groundbreaking measurements in the Mg II h and k spectral
lines near 280 nm, whose cores form about 100 km below the Lyman-α
core. These lines are sensitive to a larger range of field strengths
than Lyman-α, through both the Hanle and Zeeman effects. CLASP2
captures measurements of linear and circular polarization to enable
the first determination of all 4 Stokes parameters in chromospheric
UV radiation. Coupled with numerical modeling of the observed spectral
line polarization (anisotropic radiation pumping with Hanle, Zeeman and
magneto-optical effects), CLASP2 is a pathfinder for determination
of the magnetic field's strength and direction, as well as of the
geometry of the plasma in the upper solar chromosphere. CLASP2
was launched from White Sands Missile Range in April 2019. In this
presentation, we will summarize the characteristics of the CLASP2
flight, the performance of the UV telescope and spectropolarimeter,
and our preliminary findings.
Title: From PROBA2/SWAP to Solar Orbiter/EUI: exploring the outer
edge of the EUV corona.
Authors: Berghmans, D.; D'Huys, E.; Zhukov, A.; Auchere, F.
Bibcode: 2019AGUFMSH13A..01B
Altcode:
SWAP is a small coronal EUV imager onboard the ESA microsatellite
PROBA2. Thanks to its large field of view (54 arcmin), spacecraft
offpoints and applied image processing, SWAP has been able to show the
structures of the EUV corona more than 1 Rsun above the limb. This
"middle corona" is in between the classical off limb EUV corona
as seen by e.g. SDO/AIA and the much further white light corona as
seen by e.g. the LASCO coronagraphs and is thus a poorly observed
region. The Middle Corona harbours interesting physics, as it is
here where the solar wind accelerates and the topology of streamers
and pseudo-streamers fade in the solar wind. SWAP imagery has shown
how 'coronal fan' structures in the middle corona survive many solar
rotations and how the extended corona above the solar poles reverses
polarity. The Full Sun Imager (FSI, part of Extreme Ultraviolet Imager
EUI onboard Solar Orbiter) will take this further with a field of view
of 228 arcmin. Furthermore, as embarked on the Solar Orbiter mission
(launch 2020) FSI will be the first to image all this from out of the
ecliptic. In this paper we will review the Middle Corona results of
SWAP and provide an outlook on what to expect from EUI/FSI.
Title: Center-to-Limb Variation of the polarization of Mg II h &
k lines as measured by CLASP2
Authors: Rachmeler, L.; McKenzie, D. E.; Ishikawa, R.; Kano, R.;
Trujillo Bueno, J.; Kobayashi, K.; Song, D.; Yoshida, M.; Auchere,
F.; Okamoto, J.
Bibcode: 2019AGUFMSH11D3380R
Altcode:
The Chromospheric LAyer SpectroPolarimeter 2 (CLASP2) is a sounding
rocket that was launched from White Sands Missile Range in April
2019. CLASP2 is a reflight of the CLASP instrument, and has been
modified to observe the polarization of the Magnesium II h & k
lines in the solar chromosphere. The instrument contains a slit-jaw
context imager at Lyman Alpha (~121.6nm) and two spectropolarimetric
cameras that capture Mg II h & k near 280nm. A rotating polarization
modulation unit allows us to capture the full polarization state of
Mg II h & k; the measured polarization signals are sensitive
to the Hanle and the Zeeman magnetic effects, and magneto-optical
effects. The center-to-limb variations (CLV) of the intensity of
these lines has been measured, but the CLV of the polarization signals
has only been investigated theoretically. The first flight of CLASP,
which measured the linear polarization of the Lyman alpha line, found
a surprising lack of CLV in the line core (Kano et al. 2017), which
has important implications for the magnetic strength and geometrical
complexity of the chromosphere-corona transition region (Trujillo Bueno
et al. 2018). We present here initial results on the CLV of the Mg II
polarization signals.
Title: High-frequency Wave Propagation Along a Spicule Observed
by CLASP
Authors: Yoshida, Masaki; Suematsu, Yoshinori; Ishikawa, Ryohko;
Okamoto, Takenori J.; Kubo, Masahito; Kano, Ryouhei; Narukage,
Noriyuki; Bando, Takamasa; Winebarger, Amy R.; Kobayashi, Ken;
Trujillo Bueno, Javier; Auchère, Frédéric
Bibcode: 2019ApJ...887....2Y
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding
rocket experiment, launched in 2015 September, observed the hydrogen
Lyα line (121.6 nm) in an unprecedented high temporal cadence of
0.3 s. CLASP performed sit-and-stare observations of the quiet Sun
near the limb for 5 minutes with a slit perpendicular to the limb
and successfully captured an off-limb spicule evolving along the
slit. The Lyα line is well suited for investigating how spicules
affect the corona because it is sensitive to higher temperatures than
other chromospheric lines, owing to its large optical thickness. We
found high-frequency oscillations of the Doppler velocity with periods
of 20-50 s and low-frequency oscillation of periods of ∼240 s on
the spicule. From a wavelet analysis of the time sequence data of
the Doppler velocity, in the early phase of the spicule evolution,
we found that waves with a period of ∼30 s and a velocity amplitude
of 2-3 km s-1 propagated upward along the spicule with a
phase velocity of ∼470 km s-1. In contrast, in the later
phase, possible downward and standing waves with smaller velocity
amplitudes were also observed. The high-frequency waves observed in
the early phase of the spicule evolution would be related with the
dynamics and the formation of the spicules. Our analysis enabled us to
identify the upward, downward, and standing waves along the spicule
and to obtain the velocity amplitude of each wave directly from the
Doppler velocity for the first time. We evaluated the energy flux
by the upward-propagating waves along the spicule, and discussed the
impact to the coronal heating.
Title: Pointing the NTT at the Sun: Studying the Solar Corona During
the Total Eclipse
Authors: Dennefeld, M.; Koutchmy, S.; Sèvre, F.; Fathivavsari,
H.; Auchère, F.; Baudin, F.; Abdi, S.; Sinclaire, P.; Saviane, I.;
Labraña, F.; Schmidtobreick, L.
Bibcode: 2019Msngr.177...54D
Altcode:
No abstract at ADS
Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
Bibcode: 2019SPIE11118E..07S
Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
Title: Optical alignment of the Solar Orbiter EUI flight instrument
Authors: Mazzoli, A.; Halain, J. -P.; Auchère, F.; Barbay, J.;
Meining, S.; Philippon, A.; Morinaud, G.; Roose, S.; Hellin, M. -L.;
Jacques, L.; Schühle, U.; Dumesnil, C.; Mercier, R.; Renotte, E.;
Rochus, P.
Bibcode: 2019SPIE11180E..1OM
Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet
(17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It
is composed of three channels, each one containing a telescope. Two
of these channels are high resolution imagers (HRI) at respectively
17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly ), each one composed of two
off-axis aspherical mirrors. The third channel is a full sun imager
(FSI) composed of one single off-axis aspherical mirror and working
at 17.1 nm and 30.4 nm alternatively. This paper presents the optical
alignment of each telescope. The alignment process involved a set of
Optical Ground Support Equipment (OGSE) such as theodolites, laser
tracker, visible-light interferometer as well as a 3D Coordinates
Measuring Machine (CMM). The mirrors orientation have been measured
with respect to reference alignment cubes using theodolites. Their
positions with respect to reference pins on the instrument optical
bench have been measured using the 3D CMM. The mirrors orientations and
positions have been adjusted by shimming of the mirrors mount during
the alignment process. After this mechanical alignment, the quality
of the wavefront has been checked by interferometric measurements,
in an iterative process with the orientation and position adjustment
to achieve the required image quality.
Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding
Rocket Mission: First Results
Authors: McKenzie, David Eugene; Ishikawa, Ryohko; Kano, Ryouhei;
Rachmeler, Laurel; Trujillo Bueno, Javier; Kobayashi, Ken; Song,
Donguk; Yoshida, Masaki; Auchere, Frederic; Okamoto, Takenori
Bibcode: 2019AAS...23412601M
Altcode:
A major challenge for heliophysics is to decipher the magnetic structure
of the chromosphere, because of its vital role in the transport of
energy into the corona and solar wind. Routine satellite measurements
of the chromospheric magnetic field will dramatically improve our
understanding of the chromosphere and its connection to the rest of
the solar atmosphere. Before such a satellite can be considered for
flight, we must refine the measurement techniques by exploring emission
lines with a range of magnetic sensitivities. In 2015, CLASP achieved
the first measurement of linear polarization produced by scattering
processes in a far UV resonance line (hydrogen Lyman-α), and the
first exploration of the magnetic field (via the Hanle effect) and
geometrical complexity in quiet regions of the chromosphere-corona
transition region. These measurements are a first step towards
routine quantitative characterization of the local thermal and magnetic
conditions in this key layer of the solar atmosphere. Nonetheless,
Lyman-α is only one of the magnetically sensitive spectral lines in the
UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by
acquiring ground-breaking measurements in the Mg II h and k spectral
lines near 280 nm, whose cores form about 100 km below the Lyman-α
core. These lines are sensitive to a larger range of field strengths
than Lyman-α, through both the Hanle and Zeeman effects. CLASP2 will
capture measurements of linear and circular polarization to enable the
first determination of all 4 Stokes parameters in chromospheric UV
radiation. Coupled with numerical modeling of the observed spectral
line polarization (anisotropic radiation pumping with Hanle, Zeeman
and magneto-optical effects), CLASP2 is a pathfinder for determination
of the magnetic field's strength and direction, as well as of the
geometry of the plasma in the upper solar chromosphere. CLASP2
will launch from White Sands Missile Range in April 2019. In this
presentation, we will summarize the characteristics of the CLASP2
flight, the performance of the UV telescope and spectropolarimeter,
and our preliminary findings.
Title: Lyman-α imaging polarimetry with the CLASP2 sounding rocket
mission
Authors: Kano, Ryouhei; Ishikawa, Ryohko; McKenzie, David Eugene;
Trujillo Bueno, Javier; Song, Donguk; Yoshida, Masaki; Okamoto,
Takenori; Rachmeler, Laurel; Kobayashi, Ken; Auchere, Frederic
Bibcode: 2019AAS...23430216K
Altcode:
Ultraviolet polarimetry offers a unique opportunity to explore the upper
solar chromosphere and the transition region (TR) to the million-degree
corona. These outer atmospheric regions play a key role in the transfer
of mass and energy from the solar photosphere to the corona. With
a sounding rocket experiment called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP), in September 2015 we succeeded in obtaining
the first measurement of the linear polarization produced by scattering
processes in the hydrogen Lyman-α line of the solar disk radiation. The
analysis and interpretation of such spectro-polarimetric observation
allowed us to obtain information on the geometrical complexity of
the corrugated surface that delineates the TR, as well as on the
magnetic field strength via the Hanle effect. At the same time, the
CLASP slit-jaw (SJ) optics system, which is a Lyman-α filter imager
characterized by a FWHM= 7 nm, allowed us to obtain broad-band Stokes-I
and Q/I images over a large field of view. The obtained broad-band
Q/I images are dominated by the scattering polarization signals of the
Lyman-α wings, and not by the much weaker line-center signals where
the Hanle effect operates. Recently, Alsina Ballester et al. (2019,
ApJ, in press) showed that the scattering polarization signals of the
Lyman-α wings are sensitive to chromospheric magnetic fields via the
magneto-optical effects. Therefore, Lyman-α imaging polarimetry is of
scientific interest also for magnetic-field investigations. On April
11, 2019, we performed another sounding rocket experiment, called
the Chromospheric LAyer Spectro-Polarimeter (CLASP2). We used the
same instrument after significant modifications in order to obtain
spectro-polarimetric observations of a plage and a quiet region in
the ionized magnesium lines around 280 nm (i.e., the Mg II h &
k lines). At the same time, the CLASP2 SJ optics system allowed us to
obtain broad-band Q/I and U/I images at the Lyman-α wavelength, in
addition to the well-known SJ intensity images. In this presentation,
we provide a first overview of the CLASP2 SJ data.
Title: Modeling the Scattering Polarization of the Hydrogen Lyα
Line Observed by CLASP in a Filament Channel
Authors: Štěpán, J.; Trujillo Bueno, J.; Gunár, S.; Heinzel, P.;
del Pino Alemán, T.; Kano, R.; Ishikawa, R.; Narukage, N.; Bando,
T.; Winebarger, A.; Kobayashi, K.; Auchère, F.
Bibcode: 2019ASPC..526..165S
Altcode:
The 400 arcsec spectrograph slit of CLASP crossed mainly quiet
regions of the solar chromosphere, from the limb towards the solar
disk center. Interestingly, in the CLASP slit-jaw images and in the
SDO images of the He II line at 304 Å, we can identify a filament
channel (FC) extending over more than 60 arcsec crossing the slit of
the spectrograph. In order to interpret the peculiar spatial variation
of the Q/I and U/I signals observed by CLASP in the hydrogen Lyα line
(1216 Å), we perform multi-dimensional radiative transfer modeling
in given filament models. In this contribution, we show the first
results of the two-dimensional calculations we have carried out, with
the aim of determining the filament thermal and magnetic structure by
comparing the theoretical and the observed polarization signals. Our
results suggest that the temperature gradients in the filament observed
by CLASP are significantly larger than previously thought.
Title: Comprehensive Determination of the Hinode/EIS Roll Angle
Authors: Pelouze, Gabriel; Auchère, Frédéric; Bocchialini, Karine;
Harra, Louise; Baker, Deborah; Warren, Harry P.; Brooks, David H.;
Mariska, John T.
Bibcode: 2019SoPh..294...59P
Altcode: 2019arXiv190311923P
We present a new coalignment method for the EUV Imaging Spectrometer
(EIS) on board the Hinode spacecraft. In addition to the pointing
offset and spacecraft jitter, this method determines the roll angle
of the instrument, which has never been systematically measured, and
which is therefore usually not corrected. The optimal pointing for EIS
is computed by maximizing the cross-correlations of the Fe XII 195.119
Å line with images from the 193 Å band of the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory (SDO). By
coaligning 3336 rasters with high signal-to-noise ratio, we estimate
the rotation angle between EIS and AIA and explore the distribution
of its values. We report an average value of (−0.387±0.007 )
∘. We also provide a software implementation of this method
that can be used to coalign any EIS raster.
Title: Comparison of Scattering Polarization Signals Observed by
CLASP: Possible Indication of the Hanle Effect
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pomtieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
Bibcode: 2019ASPC..526..305I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP; Kano et
al. 2012; Kobayashi et al. 2012; Kubo et al. 2014) observed, for the
first time, the linear polarization produced by scattering processes
in the hydrogen Lyman-α (121.57 nm) and Si III (120.56 nm) lines of
the solar disk radiation. The complexity of the observed scattering
polarization (i.e., conspicuous spatial variations in Q/I and U/I
at spatial scales of 10″-20″ and the absence of center-to- limb
variation at the Lyman-α center; see Kano et al. 2017) motivated us
to search for possible hints of the operation of the Hanle effect by
comparing: (a) the Lyman-α line center signal, for which the critical
field strength (BH) for the onset of the Hanle effect is
53 G, (b) the Lyman-α wing, which is insensitive to the Hanle effect,
and (c) the Si III line, whose BH = 290 G. We focus on four
regions with different total unsigned photospheric magnetic fluxes
(estimated from SDO/HMI observations), and compare the corresponding
U/I spatial variations in the Lyman-α wing, Lyman-α center, and Si III
line. The U/I signal in the Lyman-α wing shows an antisymmetric spatial
distribution, which is caused by the presence of a bright structure in
all the selected regions, regardless of the total unsigned photospheric
magnetic flux. In an internetwork region, the Lyman-α center shows an
antisymmetric spatial variation across the selected bright structure,
but it does not show it in other more magnetized regions. In the Si III
line, the spatial variation of U/I deviates from the above-mentioned
antisymmetric shape as the total unsigned photospheric magnetic flux
increases. We argue that a plausible explanation of this differential
behavior is the operation of the Hanle effect. This work, presented
in an oral contribution at this Workshop, has been published on The
Astrophysical Journal (Ishikawa et al. 2017).
Title: Solar data, dataproducts, and tools at MEDOC
Authors: Buchlin, Eric; Caminade, Stéphane; Dufourg, Nicolas;
Auchère, Frédéric; Baudin, Frédéric; Bocchialini, Karine;
Boumier, Patrick; Janvier, Miho; Parenti, Susanna; Alingery, Pablo;
Ballans, Hervé; Chane-Yook, Martine; Dexet, Marc; Mercier, Claude;
Poulleau, Gilles
Bibcode: 2019EGUGA..2117362B
Altcode:
MEDOC (Multi-Experiment Data and Operation Centre), initially created
as a European data and operation centre for the SOHO mission, has
grown with data from other solar physics space missions, from STEREO
to SDO. Derived data products such as DEM maps from SDO/AIA, synoptic
EUV intensity maps from SOHO/EIT, and catalogues of solar structures
are also automatically produced and redistributed. Both the data and
the derived data products are publicly available from web interfaces
and from programmatic interfaces (with clients for IDL and Python),
allowing classical data analysis as well as automatic queries, data
download, and processing to be made on large datasets.
Title: Groupe de Travail Soleil Heliosphere-Magnetospheres (SHM)
Authors: Auchère, F.; Astafyeva, E.; Baudin, F.; Bourdarie, S.;
Briand, C.; Brun, S.; Célestin, S.; Génot, V.; Kretzschmar, M.;
Leblanc, F.; Rouillard, A.; Sahraoui, F.
Bibcode: 2019shm..rept....1A
Altcode:
Les grandes questions scientifiques abordées dans le cadre de la
thématique Soleil Héliosphère et Magnétosphères (SHM) couvrent
l'ensemble des problématiques liées aux relations entre notre
étoile et le système solaire. Cela commence par l'étude de la
structure interne du Soleil à travers l'observation multi-spectrales,
l'hélio-sismologie et la modélisation ; par l'étude de l'origine
de la couronne solaire, son chauffage et l'accélération du vent
solaire et des particules énergétiques solaires lors d'événements
énergétiques solaires ; et enfin par l'étude de la propagation
du vent solaire et des mécanismes de chauffage de celui-ci par
dissipation turbulente.
Title: The EUI instrument onboard Solar Orbiter: the EUV corona
imaged differently
Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric;
Harra, Louise; Schmutz, Werner; Schühle, Udo
Bibcode: 2018csc..confE..73B
Altcode:
The ESA Solar Orbiter mission is designed to determine how the Sun
creates and controls the heliosphere. The spacecraft will bring
a combination of in situ and remote sensing instruments out of the
ecliptic (>30°) and close to the sun (0.3 solar-radii). The launch
of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme
Ultraviolet Imager is part of the remote-sensing package of Solar
Orbiter, to be operating during 3 ten-day periods of each orbit around
the Sun, which last roughly half a year. These 3 periods will correspond
to perihelion and maximal solar latitude north and south. The Extreme
Ultraviolet Imager is itself a suite of three UV and EUV telescopes
that observe the solar atmosphere both globally as well as at very
high resolution. The two high-resolution imagers (HRIs) will image the
solar atmosphere in the chromospheric Lyman alpha line and the coronal
17nm pass band with a resolution of 0.5 arcsec. From perihelion, this
will correspond to a pixel footprint on the solar disc of (110km)^2
. The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV
passbands, will provide a global view of the solar atmosphere and is
therefore an essential building block for the "connection science"
of the Solar Orbiter mission. The FSI field of view is large enough
(228arcmin) that, even at perihelion and at maximal off-points by Solar
Orbiter, the full solar disk remains in the field of view. This large
FOV and the FSI's high sensitivity will allow to image the "transition
corona" where the topology of streamers and pseudo-streamers fades in
the solar wind. Furthermore, FSI will be the first to image all this
from out of the ecliptic. In this talk we will give an overview of the
EUI instrument. We will focus on the novel aspects of EUI that will
allow it to image beyond what previous EUV imagers could show us: EUV
imaging from the highest solar latitude, with the widest field-of-view
and at highest spatial resolution.
Title: The Coronal Monsoon: Thermal Nonequilibrium Revealed by
Periodic Coronal Rain
Authors: Auchère, Frédéric; Froment, Clara; Soubrié, Elie; Antolin,
Patrick; Oliver, Ramon; Pelouze, Gabriel; Voyeux, Alfred
Bibcode: 2018csc..confE.114A
Altcode:
We report on the discovery of periodic coronal rain in an off-limb
sequence of SDO/AIA images. The showers are co-spatial and in phase
with periodic (6.6 hr) intensity pulsations of coronal loops of the
sort described by Auchère et al. (2014) and Froment et al. (2015,
2017. These new observations make possible a unified description of
both phenomena. Coronal rain and periodic intensity pulsations of loops
are two manifestations of the same physical process: evaporation /
condensation cycles resulting from a state of thermal nonequilibrium
(TNE). The fluctuations around coronal temperatures produce the
intensity pulsations of loops, and rain falls along their legs
if thermal runaway cools the periodic condensations down and below
transition-region (TR)temperatures. This scenario is in line with the
predictions of numerical models of quasi-steadily and footpoint heated
loops. This event of periodic coronal rain is compared with a similar
event showing only pulsations at coronal temperatures but no significant
cool rain fall. For both events we have stereoscopic observations from
the SDO and STEREO spacecraft which allows reconstruction of the 3D loop
geometries. Comparison with numerical simulations suggest that these two
events correspond to two regimes of TNE: one with "full condensations"
(coronal rain) and another in which "incomplete condensations" start
to develop but are pushed down one loop leg before they can reach
chromospheric temperatures. These new observations impose severe
constrains on the spatio-temporal distribution of coronal heating.
Title: CLASP Constraints on the Magnetization and Geometrical
Complexity of the Chromosphere-Corona Transition Region
Authors: Trujillo Bueno, J.; Štěpán, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Ishikawa,
R.; Kano, R.; Winebarger, A.; Auchère, F.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
Bibcode: 2018ApJ...866L..15T
Altcode: 2018arXiv180908865T
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
suborbital rocket experiment that on 2015 September 3 measured
the linear polarization produced by scattering processes in the
hydrogen Lyα line of the solar disk radiation. The line-center
photons of this spectral line radiation mostly stem from the
chromosphere-corona transition region (TR). These unprecedented
spectropolarimetric observations revealed an interesting surprise,
namely that there is practically no center-to-limb variation (CLV) in
the Q/I line-center signals. Using an analytical model, we first show
that the geometric complexity of the corrugated surface that delineates
the TR has a crucial impact on the CLV of the Q/I and U/I line-center
signals. Second, we introduce a statistical description of the solar
atmosphere based on a 3D model derived from a state-of-the-art radiation
magnetohydrodynamic simulation. Each realization of the statistical
ensemble is a 3D model characterized by a given degree of magnetization
and corrugation of the TR, and for each such realization we solve the
full 3D radiative transfer problem taking into account the impact
of the CLASP instrument degradation on the calculated polarization
signals. Finally, we apply the statistical inference method presented
in a previous paper to show that the TR of the 3D model that produces
the best agreement with the CLASP observations has a relatively weak
magnetic field and a relatively high degree of corrugation. We emphasize
that a suitable way to validate or refute numerical models of the upper
solar chromosphere is by confronting calculations and observations
of the scattering polarization in ultraviolet lines sensitive to the
Hanle effect.
Title: A Statistical Inference Method for Interpreting the CLASP
Observations
Authors: Štěpán, J.; Trujillo Bueno, J.; Belluzzi, L.; Asensio
Ramos, A.; Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; Kano, R.;
Winebarger, A.; Auchère, F.; Ishikawa, R.; Narukage, N.; Kobayashi,
K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara,
H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.;
Cirtain, J.; Champey, P.; De Pontieu, B.; Carlsson, M.
Bibcode: 2018ApJ...865...48S
Altcode: 2018arXiv180802725S
On 2015 September 3, the Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) successfully measured the linear polarization produced by
scattering processes in the hydrogen Lyα line of the solar disk
radiation, revealing conspicuous spatial variations in the Q/I and U/I
signals. Via the Hanle effect, the line-center Q/I and U/I amplitudes
encode information on the magnetic field of the chromosphere-corona
transition region, but they are also sensitive to the three-dimensional
structure of this corrugated interface region. With the help of a simple
line-formation model, here we propose a statistical inference method
for interpreting the Lyα line-center polarization observed by CLASP.
Title: Current State of UV Spectro-Polarimetry and its Future
Direction
Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara,
Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito;
Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi,
. Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier;
Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts,
Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke;
Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel;
Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan,
Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey,
Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David;
Rachmeler, Laurel; Bethge, Christian
Bibcode: 2018cosp...42E1564I
Altcode:
To obtain quantitative information on the magnetic field in low beta
regions (i.e., upper chromosphere and above) has been increasingly
important to understand the energetic phenomena of the outer
solar atmosphere such as flare, coronal heating, and the solar wind
acceleration. In the UV range, there are abundant spectral lines that
originate in the upper chromosphere and transition region. However,
the Zeeman effect in these spectral lines does not give rise to easily
measurable polarization signals because of the weak magnetic field
strength and the larger Doppler broadening compared with the Zeeman
effect. Instead, the Hanle effect in UV lines is expected to be a
suitable diagnostic tool of the magnetic field in the upper atmospheric
layers. To investigate the validity of UV spectro-polarimetry and
the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP), which is a NASA sounding- rocket experiment, was launched at
White Sands in US on September 3, 2015. During its 5 minutes ballistic
flight, it successfully performed spectro-polarimetric observations
of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly
high polarization sensitivity of 0.1% in this wavelength range. CLASP
observed the linear polarization produced by scattering process in VUV
lines for the first time and detected the polarization signals which
indicate the operation of the Hanle effect. Following the success
of CLASP, we are confident that UV spectro-polarimetry is the way
to proceed, and we are planning the second flight of CLASP (CLASP2:
Chromospheric LAyer SpectroPolarimeter 2). For this second flight we
will carry out spectro-polarimetry in the Mg II h and k lines around
280 nm, with minimum modifications of the CLASP1 instrument. The linear
polarization in the Mg II k line is induced by scattering processes and
the Hanle effect, being sensitive to magnetic field strengths of 5 to 50
G. In addition, the circular polarizations in the Mg II h and k lines
induced by the Zeeman effect can be measurable in at least plage and
active regions. The combination of the Hanle and Zeeman effects could
help us to more reliably infer the magnetic fields of the upper solar
chromosphere. CLASP2 was selected for flight and is being developed for
launch in the spring of 2019.Based on these sounding rocket experiments
(CLASP1 and 2), we aim at establishing the strategy and refining the
instrument concept for future space missions to explore the enigmatic
atmospheric layers via UV spectro-polarimetry.
Title: Wavefront error measurements and alignment of CLASP2 telescope
with a dual-band pass cold mirror coated primary mirror
Authors: Yoshida, Masaki; Song, Donguk; Ishikawa, Ryoko; Kano, Ryouhei;
Katsukawa, Yukio; Suematsu, Yoshinori; Narukage, Noriyuki; Kubo,
Masahito; Shinoda, Kazuya; Okamoto, Takenori J.; McKenzie, David E.;
Rachmeler, Laurel A.; Auchère, Frédéric; Trujillo Bueno, Javier
Bibcode: 2018SPIE10699E..30Y
Altcode:
"Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding
rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP)" that succeeded in observing for the first time the linear
polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is
scheduled to be launched in 2019. In CLASP2, we will carry out full
Stokes-vector spectropolarimetric observations in the Mg ii h and k
lines near 280 nm with the spectro-polarimeter (SP), while imaging
observations in the Lyman-α line will be conducted with the slitjaw
optics (SJ). For the wavelength selection of CLASP2, the primary
mirror of the telescope uses a new dual-band pass cold mirror coating
targeting both at 121.6 nm and 280 nm. Therefore, we have to perform
again the alignment of the telescope after the installation of the
recoated primary mirror. Before unmounting the primary mirror from
the telescope structure, we measured the wave-front error (WFE) of the
telescope. The measured WFE map was consistent with what we had before
the CLASP flight, clearly indicating that the telescope alignment has
been maintained even after the flight. After the re-coated primary
mirror was installed the WFE was measured, and coma aberration was
found to be larger. Finally, the secondary mirror shim adjustments
were carried out based on the WFE measurements. In CLASP2 telescope,
we improved a fitting method of WFE map (applying 8th terms circular
Zernike polynomial fitting instead of 37th terms circular Zernike
fitting) and the improved method enables to achieve better performance
than CLASP telescope. Indeed, WFE map obtained after the final shim
adjustment indicated that the required specification (< 5.5 μm
RMS spot radius) that is more stringent than CLASP telescope was met.
Title: Optical alignment of the high-precision UV spectro-polarimeter
(CLASP2)
Authors: Song, Donguk; Ishikawa, Ryohko; Kano, Ryouhei; Yoshida,
Masaki; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Shinoda, Kazuya;
Hara, Hirohisa; Okamoto, Takenori J.; Auchère, Frédéric; McKenzie,
David E.; Rachmeler, Laurel A.; Trujillo Bueno, Javier
Bibcode: 2018SPIE10699E..2WS
Altcode:
Chromospheric LAyer Spectro-Polarimeter (CLASP2) is our next sounding
rocket experiment after the success of Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP1). CLASP2 is scheduled to launch in 2019,
and aims to achieve high precision measurements (< 0.1 %) of the
linear and circular polarizations in the Mg ii h and k lines near the
280 nm, whose line cores originate in the upper solar chromosphere. The
CLASP2 spectro-polarimeter follows very successful design concept of
the CLASP1 instrument with the minimal modification. A new grating was
fabricated with the same radius of curvature as the CLASP1 grating, but
with a different ruling density. This allows us to essentially reuse
the CLASP1 mechanical structures and layout of the optics. However,
because the observing wavelength of CLASP2 is twice longer than that
of CLASP1, a magnifier optical system was newly added in front of the
cameras to double the focal length of CLASP2 and to maintain the same
wavelength resolution as CLASP1 (0.01 nm). Meanwhile, a careful optical
alignment of the spectro-polarimeter is required to reach the 0.01 nm
wavelength resolution. Therefore, we established an efficient alignment
procedure for the CLASP2 spectro-polarimeter based on an experience
of CLASP1. Here, we explain in detail the methods for achieving the
optical alignment of the CLASP2 spectro-polarimeter and discuss our
results by comparing with the performance requirements.
Title: The Coronal Monsoon: Thermal Nonequilibrium Revealed by
Periodic Coronal Rain
Authors: Auchere, Frederic; Soubrie, Elie; Antolin, Patrick; Froment,
Clara; Oliver, Ramon; Pelouze, Gabriel
Bibcode: 2018cosp...42E.144A
Altcode:
We report on the discovery of periodic coronal rain in an off-limb
sequence of SDO/AIA images. The showers are co-spatial and in phase
with periodic (6.6 hr) intensity pulsations of coronal loops of the
sort described by Auchère et al. (2014) and Froment et al. (2015,
2017}. These new observations make possible a unified description of
both phenomena. Coronal rain and periodic intensity pulsations of loops
are two manifestations of the same physical process: evaporation /
condensation cycles resulting from a state of thermal nonequilibrium
(TNE). The fluctuations around coronal temperatures produce the
intensity pulsations of loops, and rain falls along their legs
if thermal runaway cools the periodic condensations down and below
transition-region (TR) temperatures. This scenario is in line with the
predictions of numerical models of quasi-steadily and footpoint heated
loops.This event of periodic coronal rain is compared with a similar
event showing only pulsations at coronal temperatures but no significant
cool rain fall. For both events we have stereoscopic observations from
the SDO and STEREO spacecraft which allows reconstruction of the 3D loop
geometries. Comparison with numerical simulations suggest that these two
events correspond to two regimes of TNE: one with "full condensations"
(coronal rain) and another in which "incomplete condensations" start
to develop but are pushed down one loop leg before they can reach
chromospheric temperatures.These new observations impose severe
constrains on the spatio-temporal distribution of coronal heating.
Title: Prospects for coronal magnetic field measurements from space
Authors: Auchere, Frederic
Bibcode: 2018cosp...42E.143A
Altcode:
Despite its fundamental importance as a driver for the physics
of the Sun and of the helio-sphere, 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 dfficult
quantity to measure. Our knowledge of its strength and orientation
is largely 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
clearly identified by the international heliophysics community as a key
element in the understanding of our star.In the past ten years, reliable
ground based coronal magnetic field measurements have emerged. However,
these measurements wil always be limited by the difficulty to observe
the corona from the ground. Much like routine coronagraphic observations
from space by SOHO/LASCO haverevolutionized our knowledge of the solar
corona, space based polarimetric observations are expected to lead
to major breakthroughs. In this perspective, we will review the past
and future projects of space missions designed to measure the coronal
magnetic field from space.
Title: Search for predicted periodic flows in loops undergoing
thermal non-equilibrium
Authors: Pelouze, Gabriel; Parenti, Susanna; Bocchialini, Karine;
Soubrie, Elie; Auchere, Frederic; Froment, Clara
Bibcode: 2018cosp...42E2623P
Altcode:
Long-period intensity pulsations have been recently detected in
coronal loopswith EUV images of both SoHO/EIT (Auchère et al.,
2014) and SDO/AIA (Froment etal., 2015). These pulsations have
been interpreted as resulting from thermalnon-equilibrium (TNE),
thus providing a signature of a highly-stratified andquasi-constant
heating at the loops footpoints (Froment et al., 2017; Auchèreet al.,
2016). Depending on the adequacy between the geometry of the loop
andthe characteristics of the heating, this can result in either
complete (atchromospheric temperatures) or incomplete (> 1 MK)
condensation and evaporationcycles, that are responsible for the
observed intensity pulsations. Using 1Dhydrodynamic simulations,
Froment et al. (2017) were able to reproduce theobserved pulsations,
with incomplete condensation for the active region studiedin their
previous paper. The simulations also predict periodic plasma flowsalong
the loops footpoints, with velocities up to 40 km/s. We try to detect
these flows by using time series of spatially resolved spectrafrom
the EUV spectrometer Hinode/EIS. We systematically search for EIS
datasetsthat correspond to the observation of pulsation events among
the 3000+ thatwere detected in AIA data, between 2010 and 2016. For the
9 datasets that arefound, we derive series of Doppler velocity maps,
which allows us to track theevolution of the plasma velocity in the
loop over several pulsation periods. Wethen compare these data to the
results of previous simulations andobservations. However the expected
pulsations in velocity cannot be identifiedin any of the datasets that
we analysed. We demonstrate that line of sightambiguities, combined
with low signal to noise ratio or lack of time cadence,can explain
this non-detection.
Title: The EUI flight instrument of Solar Orbiter: from optical
alignment to end-to-end calibration
Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.;
Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado,
R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.;
Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin,
M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli,
A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.;
Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P.
Bibcode: 2018SPIE10699E..0HH
Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral
ranges. The development of the EUI instrument has been successfully
completed with the optical alignment of its three channels' telescope,
the thermal and mechanical environmental verification, the electrical
and software validations, and an end-toend on-ground calibration of
the two-units' flight instrument at the operating wavelengths. The
instrument has been delivered and installed on the Solar Orbiter
spacecraft, which is now undergoing all preparatory activities before
launch.
Title: On the Occurrence of Thermal Nonequilibrium in Coronal Loops
Authors: Froment, C.; Auchère, F.; Mikić, Z.; Aulanier, G.;
Bocchialini, K.; Buchlin, E.; Solomon, J.; Soubrié, E.
Bibcode: 2018ApJ...855...52F
Altcode: 2018arXiv180204010F
Long-period EUV pulsations, recently discovered to be common in active
regions, are understood to be the coronal manifestation of thermal
nonequilibrium (TNE). The active regions previously studied with
EIT/Solar and Heliospheric Observatory and AIA/SDO indicated that
long-period intensity pulsations are localized in only one or two
loop bundles. The basic idea of this study is to understand why. For
this purpose, we tested the response of different loop systems, using
different magnetic configurations, to different stratifications and
strengths of the heating. We present an extensive parameter-space study
using 1D hydrodynamic simulations (1020 in total) and conclude that the
occurrence of TNE requires specific combinations of parameters. Our
study shows that the TNE cycles are confined to specific ranges in
parameter space. This naturally explains why only some loops undergo
constant periodic pulsations over several days: since the loop geometry
and the heating properties generally vary from one loop to another in
an active region, only the ones in which these parameters are compatible
exhibit TNE cycles. Furthermore, these parameters (heating and geometry)
are likely to vary significantly over the duration of a cycle, which
potentially limits the possibilities of periodic behavior. This study
also confirms that long-period intensity pulsations and coronal rain are
two aspects of the same phenomenon: both phenomena can occur for similar
heating conditions and can appear simultaneously in the simulations.
Title: The Coronal Monsoon: Thermal Nonequilibrium Revealed by
Periodic Coronal Rain
Authors: Auchère, Frédéric; Froment, Clara; Soubrié, Elie; Antolin,
Patrick; Oliver, Ramon; Pelouze, Gabriel
Bibcode: 2018ApJ...853..176A
Altcode: 2018arXiv180201852A
We report on the discovery of periodic coronal rain in an off-limb
sequence of Solar Dynamics Observatory/Atmospheric Imaging Assembly
images. The showers are co-spatial and in phase with periodic (6.6 hr)
intensity pulsations of coronal loops of the sort described by Auchère
et al. and Froment et al. These new observations make possible a unified
description of both phenomena. Coronal rain and periodic intensity
pulsations of loops are two manifestations of the same physical
process: evaporation/condensation cycles resulting from a state of
thermal nonequilibrium. The fluctuations around coronal temperatures
produce the intensity pulsations of loops, and rain falls along their
legs if thermal runaway cools the periodic condensations down and
below transition-region temperatures. This scenario is in line with
the predictions of numerical models of quasi-steadily and footpoint
heated loops. The presence of coronal rain—albeit non-periodic—in
several other structures within the studied field of view implies that
this type of heating is at play on a large scale.
Title: EUV high resolution imager on-board solar orbiter: optical
design and detector performances
Authors: Halain, J. P.; Mazzoli, A.; Rochus, P.; Renotte, E.; Stockman,
Y.; Berghmans, D.; BenMoussa, A.; Auchère, F.
Bibcode: 2017SPIE10564E..3VH
Altcode:
The EUV high resolution imager (HRI) channel of the Extreme Ultraviolet
Imager (EUI) on-board Solar Orbiter will observe the solar atmospheric
layers at 17.4 nm wavelength with a 200 km resolution. The HRI channel
is based on a compact two mirrors off-axis design. The spectral
selection is obtained by a multilayer coating deposited on the mirrors
and by redundant Aluminum filters rejecting the visible and infrared
light. The detector is a 2k x 2k array back-thinned silicon CMOS-APS
with 10 μm pixel pitch, sensitive in the EUV wavelength range. Due to
the instrument compactness and the constraints on the optical design,
the channel performance is very sensitive to the manufacturing,
alignments and settling errors. A trade-off between two optical
layouts was therefore performed to select the final optical design
and to improve the mirror mounts. The effect of diffraction by the
filter mesh support and by the mirror diffusion has been included
in the overall error budget. Manufacturing of mirror and mounts has
started and will result in thermo-mechanical validation on the EUI
instrument structural and thermal model (STM). Because of the limited
channel entrance aperture and consequently the low input flux, the
channel performance also relies on the detector EUV sensitivity,
readout noise and dynamic range. Based on the characterization of
a CMOS-APS back-side detector prototype, showing promising results,
the EUI detector has been specified and is under development. These
detectors will undergo a qualification program before being tested
and integrated on the EUI instrument.
Title: Comparison of Solar Fine Structure Observed Simultaneously
in Lyα and Mg II h
Authors: Schmit, D.; Sukhorukov, A. V.; De Pontieu, B.; Leenaarts,
J.; Bethge, C.; Winebarger, A.; Auchère, F.; Bando, T.; Ishikawa,
R.; Kano, R.; Kobayashi, K.; Narukage, N.; Trujillo Bueno, J.
Bibcode: 2017ApJ...847..141S
Altcode: 2017arXiv170900035S
The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the
Sun in H I Lyα during a suborbital rocket flight on 2015 September
3. The Interface Region Imaging Telescope (IRIS) coordinated with the
CLASP observations and recorded nearly simultaneous and co-spatial
observations in the Mg II h and k lines. The Mg II h and Lyα lines
are important transitions, energetically and diagnostically, in the
chromosphere. The canonical solar atmosphere model predicts that these
lines form in close proximity to each other and so we expect that the
line profiles will exhibit similar variability. In this analysis, we
present these coordinated observations and discuss how the two profiles
compare over a region of quiet Sun at viewing angles that approach the
limb. In addition to the observations, we synthesize both line profiles
using a 3D radiation-MHD simulation. In the observations, we find that
the peak width and the peak intensities are well correlated between the
lines. For the simulation, we do not find the same relationship. We
have attempted to mitigate the instrumental differences between IRIS
and CLASP and to reproduce the instrumental factors in the synthetic
profiles. The model indicates that formation heights of the lines
differ in a somewhat regular fashion related to magnetic geometry. This
variation explains to some degree the lack of correlation, observed
and synthesized, between Mg II and Lyα. Our analysis will aid in the
definition of future observatories that aim to link dynamics in the
chromosphere and transition region.
Title: CLASP/SJ Observations of Rapid Time Variations in the Lyα
Emission in a Solar Active Region
Authors: Ishikawa, Shin-nosuke; Kubo, Masahito; Katsukawa, Yukio;
Kano, Ryouhei; Narukage, Noriyuki; Ishikawa, Ryohko; Bando, Takamasa;
Winebarger, Amy; Kobayashi, Ken; Trujillo Bueno, Javier; Auchère,
Frédéric
Bibcode: 2017ApJ...846..127I
Altcode:
The Chromospheric Lyα SpectroPolarimeter (CLASP) is a sounding
rocket experiment launched on 2015 September 3 to investigate the
solar chromosphere and transition region. The slit-jaw (SJ) optical
system captured Lyα images with a high time cadence of 0.6 s. From
the CLASP/SJ observations, many variations in the solar chromosphere
and transition region emission with a timescale of <1 minute
were discovered. In this paper, we focus on the active region within
the SJ field of view and investigate the relationship between short
(<30 s) temporal variations in the Lyα emission and the coronal
structures observed by Solar Dynamics Observatory/Atmospheric Imaging
Assembly (AIA). We compare the Lyα temporal variations at the coronal
loop footpoints observed in the AIA 211 Å (≈2 MK) and AIA 171 Å
(≈0.6 MK) channels with those in the regions with bright Lyα features
without a clear association with the coronal loop footpoints. We find
more short (<30 s) temporal variations in the Lyα intensity in the
footpoint regions. Those variations did not depend on the temperature
of the coronal loops. Therefore, the temporal variations in the Lyα
intensity at this timescale range could be related to the heating of
the coronal structures up to temperatures around the sensitivity peak
of 171 Å. No signature was found to support the scenario that these
Lyα intensity variations were related to the nanoflares. Waves or
jets from the lower layers (lower chromosphere or photosphere) are
possible causes for this phenomenon.
Title: The VUV instrument SPICE for Solar Orbiter: performance
ground testing
Authors: Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.;
Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi,
Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy;
Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej;
Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.;
Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy;
Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred;
Munro, Grant J.; Holmes, William; Doyle, Peter
Bibcode: 2017SPIE10397E..08C
Altcode:
SPICE is an imaging spectrometer operating at vacuum ultraviolet
(VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a
facility instrument on the Solar Orbiter mission, which carries
10 science instruments in all, to make observations of the Sun's
atmosphere and heliosphere, at close proximity to the Sun, i.e to
0.28 A.U. at perihelion. SPICE's role is to make VUV measurements
of plasma in the solar atmosphere. SPICE is designed to achieve
spectral imaging at spectral resolution >1500, spatial resolution
of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many
strong constraints on the instrument design imposed by the mission
requirements prevent the imaging performance from exceeding those of
previous instruments, but by being closer to the sun there is a gain in
spatial resolution. The price which is paid is the harsher environment,
particularly thermal. This leads to some novel features in the design,
which needed to be proven by ground test programs. These include a
dichroic solar-transmitting primary mirror to dump the solar heat, a
high in-flight temperature (60deg.C) and gradients in the optics box,
and a bespoke variable-line-spacing grating to minimise the number of
reflective components used. The tests culminate in the systemlevel test
of VUV imaging performance and pointing stability. We will describe how
our dedicated facility with heritage from previous solar instruments,
is used to make these tests, and show the results, firstly on the
Engineering Model of the optics unit, and more recently on the Flight
Model. For the keywords, select up to 8 key terms for a search on your
manuscript's subject.
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel; E McKenzie, David; Ishikawa, Ryohko;
Trujillo Bueno, Javier; Auchère, Frédéric; Kobayashi, Ken;
Winebarger, Amy; Bethge, Christian; Kano, Ryouhei; Kubo, Masahito;
Song, Donguk; Narukage, Noriyuki; Ishikawa, Shin-nosuke; De Pontieu,
Bart; Carlsson, Mats; Yoshida, Masaki; Belluzzi, Luca; Stepan, Jiri;
del Pino Alemná, Tanausú; Ballester, Ernest Alsina; Asensio Ramos,
Andres
Bibcode: 2017SPD....4811010R
Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.;
Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.;
Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.;
De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.;
del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
Bibcode: 2017shin.confE..79R
Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
Title: SOLARIS: Solar Sail Investigation of the Sun
Authors: Appourchaux, Thierry; Auchère, Frédéric; Antonucci, Ester;
Gizon, Laurent; MacDonald, Malcolm; Hara, Hirohisa; Sekii, Takashi;
Moses, Daniel; Vourlidas, Angelos
Bibcode: 2017arXiv170708193A
Altcode:
In this paper, we detail the scientific objectives and outline
a strawman payload of the SOLAR sail Investigation of the Sun
(SOLARIS). The science objectives are to study the 3D structure
of the solar magnetic and velocity field, the variation of total
solar irradiance with latitude, and the structure of the corona. We
show how we can meet these science objective using solar-sail
technologies currently under development. We provide a tentative
mission profile considering several trade-off approaches. We also
provide a tentative mass budget breakdown and a perspective for a
programmatic implementation.
Title: Indication of the Hanle Effect by Comparing the Scattering
Polarization Observed by CLASP in the Lyα and Si III 120.65 nm Lines
Authors: Ishikawa, R.; Trujillo Bueno, J.; Uitenbroek, H.; Kubo, M.;
Tsuneta, S.; Goto, M.; Kano, R.; Narukage, N.; Bando, T.; Katsukawa,
Y.; Ishikawa, S.; Giono, G.; Suematsu, Y.; Hara, H.; Shimizu, T.;
Sakao, T.; Winebarger, A.; Kobayashi, K.; Cirtain, J.; Champey, P.;
Auchère, F.; Štěpán, J.; Belluzzi, L.; Asensio Ramos, A.; Manso
Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.
Bibcode: 2017ApJ...841...31I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding
rocket experiment that has provided the first successful measurement
of the linear polarization produced by scattering processes in
the hydrogen Lyα line (121.57 nm) radiation of the solar disk. In
this paper, we report that the Si III line at 120.65 nm also shows
scattering polarization and we compare the scattering polarization
signals observed in the Lyα and Si III lines in order to search for
observational signatures of the Hanle effect. We focus on four selected
bright structures and investigate how the U/I spatial variations vary
between the Lyα wing, the Lyα core, and the Si III line as a function
of the total unsigned photospheric magnetic flux estimated from Solar
Dynamics Observatory/Helioseismic and Magnetic Imager observations. In
an internetwork region, the Lyα core shows an antisymmetric spatial
variation across the selected bright structure, but it does not show
it in other more magnetized regions. In the Si III line, the spatial
variation of U/I deviates from the above-mentioned antisymmetric
shape as the total unsigned photospheric magnetic flux increases. A
plausible explanation of this difference is the operation of the Hanle
effect. We argue that diagnostic techniques based on the scattering
polarization observed simultaneously in two spectral lines with very
different sensitivities to the Hanle effect, like Lyα and Si III,
are of great potential interest for exploring the magnetism of the
upper solar chromosphere and transition region.
Title: Erratum: “On the Fourier and Wavelet Analysis of Coronal Time
Series” (2016,
ApJ, 825, 110)
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
Bibcode: 2017ApJ...838..166A
Altcode:
No abstract at ADS
Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV
Range. Part II: In-Flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.;
Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
Bibcode: 2017SoPh..292...57G
Altcode:
The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding
rocket instrument designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm). The instrument
was successfully launched on 3 September 2015 and observations were
conducted at the solar disc center and close to the limb during the
five-minutes flight. In this article, the disc center observations are
used to provide an in-flight calibration of the instrument spurious
polarization. The derived in-flight spurious polarization is consistent
with the spurious polarization levels determined during the pre-flight
calibration and a statistical analysis of the polarization fluctuations
from solar origin is conducted to ensure a 0.014% precision on the
spurious polarization. The combination of the pre-flight and the
in-flight polarization calibrations provides a complete picture of
the instrument response matrix, and a proper error transfer method
is used to confirm the achieved polarization accuracy. As a result,
the unprecedented 0.1% polarization accuracy of the instrument in the
vacuum ultraviolet is ensured by the polarization calibration.
Title: Discovery of Scattering Polarization in the Hydrogen Lyα
Line of the Solar Disk Radiation
Authors: Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchère, F.;
Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.;
Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu,
T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.;
Štěpán, J.; Asensio Ramos, A.; Manso Sainz, R.; Champey, P.;
Cirtain, J.; De Pontieu, B.; Casini, R.; Carlsson, M.
Bibcode: 2017ApJ...839L..10K
Altcode: 2017arXiv170403228K
There is a thin transition region (TR) in the solar atmosphere where
the temperature rises from 10,000 K in the chromosphere to millions
of degrees in the corona. Little is known about the mechanisms that
dominate this enigmatic region other than the magnetic field plays a
key role. The magnetism of the TR can only be detected by polarimetric
measurements of a few ultraviolet (UV) spectral lines, the Lyα line
of neutral hydrogen at 121.6 nm (the strongest line of the solar UV
spectrum) being of particular interest given its sensitivity to the
Hanle effect (the magnetic-field-induced modification of the scattering
line polarization). We report the discovery of linear polarization
produced by scattering processes in the Lyα line, obtained with
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) rocket
experiment. The Stokes profiles observed by CLASP in quiet regions of
the solar disk show that the Q/I and U/I linear polarization signals are
of the order of 0.1% in the line core and up to a few percent in the
nearby wings, and that both have conspicuous spatial variations with
scales of ∼10 arcsec. These observations help constrain theoretical
models of the chromosphere-corona TR and extrapolations of the
magnetic field from photospheric magnetograms. In fact, the observed
spatial variation from disk to limb of polarization at the line core
and wings already challenge the predictions from three-dimensional
magnetohydrodynamical models of the upper solar chromosphere.
Title: High-Reflectivity Coatings for a Vacuum Ultraviolet
Spectropolarimeter
Authors: Narukage, Noriyuki; Kubo, Masahito; Ishikawa, Ryohko;
Ishikawa, Shin-nosuke; Katsukawa, Yukio; Kobiki, Toshihiko; Giono,
Gabriel; Kano, Ryouhei; Bando, Takamasa; Tsuneta, Saku; Auchère,
Frédéric; Kobayashi, Ken; Winebarger, Amy; McCandless, Jim; Chen,
Jianrong; Choi, Joanne
Bibcode: 2017SoPh..292...40N
Altcode:
Precise polarization measurements in the vacuum ultraviolet (VUV)
region are expected to be a new tool for inferring the magnetic fields
in the upper atmosphere of the Sun. High-reflectivity coatings are key
elements to achieving high-throughput optics for precise polarization
measurements. We fabricated three types of high-reflectivity coatings
for a solar spectropolarimeter in the hydrogen Lyman-α (Lyα ; 121.567
nm) region and evaluated their performance. The first high-reflectivity
mirror coating offers a reflectivity of more than 80 % in Lyα
optics. The second is a reflective narrow-band filter coating that has
a peak reflectivity of 57 % in Lyα , whereas its reflectivity in the
visible light range is lower than 1/10 of the peak reflectivity (∼5
% on average). This coating can be used to easily realize a visible
light rejection system, which is indispensable for a solar telescope,
while maintaining high throughput in the Lyα line. The third is a
high-efficiency reflective polarizing coating that almost exclusively
reflects an s-polarized beam at its Brewster angle of 68° with a
reflectivity of 55 %. This coating achieves both high polarizing power
and high throughput. These coatings contributed to the high-throughput
solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.
Title: Long-period Intensity Pulsations in Coronal Loops Explained
by Thermal Non-equilibrium Cycles
Authors: Froment, C.; Auchère, F.; Aulanier, G.; Mikić, Z.;
Bocchialini, K.; Buchlin, E.; Solomon, J.
Bibcode: 2017ApJ...835..272F
Altcode: 2017arXiv170101309F
In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon
that can occur when the heating is both highly stratified and
quasi-constant. Unambiguous observational identification of TNE
would thus permit us to strongly constrain heating scenarios. While
TNE is currently the standard interpretation of coronal rain, the
long-term periodic evolution predicted by simulations has never been
observed. However, the detection of long-period intensity pulsations
(periods of several hours) has been recently reported with the Solar
and Heliospheric Observatory/EIT, and this phenomenon appears to be very
common in loops. Moreover, the three intensity-pulsation events that we
recently studied with the Solar Dynamics Observatory/Atmospheric Imaging
Assembly (AIA) show strong evidence for TNE in warm loops. In this
paper, a realistic loop geometry from linear force-free field (LFFF)
extrapolations is used as input to 1D hydrodynamic simulations. Our
simulations show that, for the present loop geometry, the heating has
to be asymmetrical to produce TNE. We analyze in detail one particular
simulation that reproduces the average thermal behavior of one of the
pulsating loop bundle observed with AIA. We compare the properties of
this simulation with those deduced from the observations. The magnetic
topology of the LFFF extrapolations points to the presence of sites
of preferred reconnection at one footpoint, supporting the presence
of asymmetric heating. In addition, we can reproduce the temporal
large-scale intensity properties of the pulsating loops. This simulation
further strengthens the interpretation of the observed pulsations as
signatures of TNE. This consequently provides important information
on the heating localization and timescale for these loops.
Title: Polarization Calibration of the Chromospheric Lyman-Alpha
SpectroPolarimeter for a 0.1 % Polarization Sensitivity in the VUV
Range. Part I: Pre-flight Calibration
Authors: Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa,
Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.
Bibcode: 2016SoPh..291.3831G
Altcode: 2016SoPh..tmp..177G
The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) is a sounding
rocket experiment designed to measure for the first time the linear
polarization of the hydrogen Lyman-α line (121.6 nm) and requires
a 0.1 % polarization sensitivity, which is unprecedented for a
spectropolarimeter in the vacuum UV (VUV) spectral range.
Title: Discovery of Ubiquitous Fast-Propagating Intensity Disturbances
by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP)
Authors: Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Kano, R.; Bando,
T.; Narukage, N.; Ishikawa, R.; Hara, H.; Giono, G.; Tsuneta, S.;
Ishikawa, S.; Shimizu, T.; Sakao, T.; Winebarger, A.; Kobayashi, K.;
Cirtain, J.; Champey, P.; Auchère, F.; Trujillo Bueno, J.; Asensio
Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu,
B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.
Bibcode: 2016ApJ...832..141K
Altcode:
High-cadence observations by the slit-jaw (SJ) optics system of the
sounding rocket experiment known as the Chromospheric Lyman Alpha
Spectropolarimeter (CLASP) reveal ubiquitous intensity disturbances
that recurrently propagate in either the chromosphere or the transition
region or both at a speed much higher than the speed of sound. The
CLASP/SJ instrument provides a time series of two-dimensional images
taken with broadband filters centered on the Lyα line at a 0.6 s
cadence. The multiple fast-propagating intensity disturbances appear in
the quiet Sun and in an active region, and they are clearly detected in
at least 20 areas in a field of view of 527″ × 527″ during the 5
minute observing time. The apparent speeds of the intensity disturbances
range from 150 to 350 km s-1, and they are comparable
to the local Alfvén speed in the transition region. The intensity
disturbances tend to propagate along bright elongated structures away
from areas with strong photospheric magnetic fields. This suggests
that the observed fast-propagating intensity disturbances are related
to the magnetic canopy structures. The maximum distance traveled by
the intensity disturbances is about 10″, and the widths are a few
arcseconds, which are almost determined by a pixel size of 1.″03. The
timescale of each intensity pulse is shorter than 30 s. One possible
explanation for the fast-propagating intensity disturbances observed
by CLASP is magnetohydrodynamic fast-mode waves.
Title: Thermal Non-Equilibrium Revealed by Periodic Pulses of Random
Amplitudes in Solar Coronal Loops
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
Bibcode: 2016usc..confE.131A
Altcode:
We recently detected variations in extreme ultraviolet intensity in
coronal loops repeating with periods of several hours. Models of loops
including stratified and quasi-steady heating predict the development
of a state of thermal non-equilibrium (TNE): cycles of evaporative
upflows at the footpoints followed by falling condensations at the
apex. Based on Fourier and wavelet analysis, we demonstrate that the
observed periodic signals are indeed not signatures of vibrational
modes. Instead, superimposed on the power law expected from the
stochastic background emission, the power spectra of the time series
exhibit the discrete harmonics and continua expected from periodic
trains of pulses of random amplitudes. These characteristics reinforce
our earlier interpretation of these pulsations as being aborted
TNE cycles.
Title: Fourier and Wavelet Analysis of Coronal Time Series
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
Bibcode: 2016usc..confE.130A
Altcode:
Using Fourier and wavelet analysis, we critically re-assess the
significance of our detection of periodic pulsations in coronal
loops. We show that the proper identification of the frequency
dependence and statistical properties of the different components of
the power spectra provies a strong argument against the common practice
of data detrending, which tends to produce spurious detections around
the cut-off frequency of the filter. In addition, the white and red
noise models built into the widely used wavelet code of Torrence &
Compo cannot, in most cases, adequately represent the power spectra of
coronal time series, thus also possibly causing false positives. Both
effects suggest that several reports of periodic phenomena should
be re-examined. The Torrence & Compo code nonetheless effectively
computes rigorous confidence levels if provided with pertinent models of
mean power spectra, and we describe the appropriate manner in which to
call its core routines. We recall the meaning of the default confidence
levels output from the code, and we propose new Monte-Carlo-derived
levels that take into account the total number of degrees of freedom
in the wavelet spectra. These improvements allow us to confirm that
the power peaks that we detected have a very low probability of being
caused by noise.
Title: Long-period Intensity Pulsations as the Manifestation of the
Heating Stratification and Timescale in Coronal Loops
Authors: Froment, Clara; Auchère, Frédéric; Aulanier, Guillaume;
Mikić, Zoran; Bocchialini, Karine; Buchlin, Eric; Solomon, Jacques
Bibcode: 2016usc..confE..47F
Altcode:
In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon
that can occur when the heating is both highly-stratified and
quasi-constant. Unambiguous observational identification of TNE
would thus permit to strongly constrain heating scenarios. Up to
now, while TNE is the standard interpretation of coronal rain, it
was not believed to happen commonly in warm coronal loops. Recently,
the detection of long-period intensity pulsations (periods of several
hours) has been reported with SoHO/EIT. This phenomenon appears to be
very common in loops (Auchère et al. 2014). In Froment et al. 2015,
three intensity-pulsation events studied with SDO/AIA, show strong
evidence for TNE in warm loops. We use realistic loop geometries
from LFFF extrapolations for one of these events are used as input
to a 1D hydrodynamic simulation of TNE. A highly-stratified heating
function is chosen to reproduce the observed period of pulsation and
temperature of the loops. With these conditions, the heating function
has to be asymmetric. The magnetic topology of the LFFF extrapolations
points to the presence of sites of preferred reconnection at one
footpoint, supporting the presence of asymmetric heating. We compared
the properties of the simulated loop with the properties deduced
from observations. We found that the 1D hydrodynamic simulation
can reproduce the large temporal scale intensity properties of the
pulsating loops (Froment et al. 2016, submitted). This simulation
further strengthen the interpretation of the observed pulsations as
signatures of TNE. This implies that the heating for these loops is
highly-stratified and that the frequency of the heating events must
be high compared to the typical cooling time.
Title: GAIA-DEM: a database providing AIA/SDO DEM maps
Authors: Guennou, C.; Auchère, F.; Bocchialini, F.; Soubrié, E.;
Mercier, C.; Parenti, S.; Alingery, P.
Bibcode: 2016usc..confE.108G
Altcode:
The Gaussian AIA DEm Maps (GAIA-DEM) database at MEDOC (IAS) provides
through a simple and intuitive web interface DEM inversions of the
SDO/AIA data, computed every 30min. The Gaussian approximation is used
to describe the main features of the true DEM(log T) by its first
moments. For each date, maps of the three Gaussian fit parameters
(central temperature, total emission measure and Gaussian width) and
of the chi^2 are available in FITS format. Users can preview the maps
before downloading them. In addition, users can display the initial
SDO/AIA images using Helioviewer, and query the database through
webservices accessible from IDL and Python clients. This presentation
is for the "Thermal Diagnostics with SDO/AIA" mini-workshop.
Title: A small mission concept to the Sun-Earth Lagrangian L5 point
for innovative solar, heliospheric and space weather science
Authors: Lavraud, B.; Liu, Y.; Segura, K.; He, J.; Qin, G.; Temmer,
M.; Vial, J. -C.; Xiong, M.; Davies, J. A.; Rouillard, A. P.; Pinto,
R.; Auchère, F.; Harrison, R. A.; Eyles, C.; Gan, W.; Lamy, P.;
Xia, L.; Eastwood, J. P.; Kong, L.; Wang, J.; Wimmer-Schweingruber,
R. F.; Zhang, S.; Zong, Q.; Soucek, J.; An, J.; Prech, L.; Zhang,
A.; Rochus, P.; Bothmer, V.; Janvier, M.; Maksimovic, M.; Escoubet,
C. P.; Kilpua, E. K. J.; Tappin, J.; Vainio, R.; Poedts, S.; Dunlop,
M. W.; Savani, N.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T.;
DeForest, C.; Webb, D.; Lugaz, N.; Fuselier, S. A.; Dalmasse, K.;
Tallineau, J.; Vranken, D.; Fernández, J. G.
Bibcode: 2016JASTP.146..171L
Altcode:
We present a concept for a small mission to the Sun-Earth Lagrangian L5
point for innovative solar, heliospheric and space weather science. The
proposed INvestigation of Solar-Terrestrial Activity aNd Transients
(INSTANT) mission is designed to identify how solar coronal magnetic
fields drive eruptions, mass transport and particle acceleration that
impact the Earth and the heliosphere. INSTANT is the first mission
designed to (1) obtain measurements of coronal magnetic fields from
space and (2) determine coronal mass ejection (CME) kinematics with
unparalleled accuracy. Thanks to innovative instrumentation at a vantage
point that provides the most suitable perspective view of the Sun-Earth
system, INSTANT would uniquely track the whole chain of fundamental
processes driving space weather at Earth. We present the science
requirements, payload and mission profile that fulfill ambitious science
objectives within small mission programmatic boundary conditions.
Title: Thermal Non-equilibrium Revealed by Periodic Pulses of Random
Amplitudes in Solar Coronal Loops
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
Bibcode: 2016ApJ...827..152A
Altcode: 2016arXiv160803789A
We recently detected variations in extreme ultraviolet intensity in
coronal loops repeating with periods of several hours. Models of loops
including stratified and quasi-steady heating predict the development
of a state of thermal non-equilibrium (TNE): cycles of evaporative
upflows at the footpoints followed by falling condensations at the
apex. Based on Fourier and wavelet analysis, we demonstrate that the
observed periodic signals are indeed not signatures of vibrational
modes. Instead, superimposed on the power law expected from the
stochastic background emission, the power spectra of the time series
exhibit the discrete harmonics and continua expected from periodic
trains of pulses of random amplitudes. These characteristics reinforce
our earlier interpretation of these pulsations as being aborted
TNE cycles.
Title: The qualification campaign of the EUI instrument of Solar
Orbiter
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle,
U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Verbeeck, C.; Smith, P.
Bibcode: 2016SPIE.9905E..2XH
Altcode:
The Extreme Ultraviolet Imager (EUI) instrument is one of the ten
scientific instruments on board the Solar Orbiter mission to be launched
in October 2018. It will provide full-sun and high-resolution images of
the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in
the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument
design has been completed with the Assembly, Integration and Test
(AIT) of the instrument two-units Qualification Model (QM). Optical,
electrical, electro-magnetic compatibility, thermal and mechanical
environmental verifications were conducted and are summarized here. The
integration and test procedures for the Flight Model (FM) instrument
and sub-systems were also verified. Following the Qualification Review,
the flight instrument activities were started with the assembly of
the flight units. The mechanical and thermal acceptance tests and an
end-to-end final calibration in the (E)UV will then be conducted before
delivery for integration on the Solar Orbiter Spacecraft by end of 2016.
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
Bibcode: 2016cosp...41E.607F
Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.
Title: Optical alignment of the Chromospheric Lyman-Alpha
Spectro-Polarimeter using sophisticated methods to minimize activities
under vacuum
Authors: Giono, G.; Katsukawa, Y.; Ishikawa, R.; Narukage, N.;
Kano, R.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.;
Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.
Bibcode: 2016SPIE.9905E..3DG
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
sounding-rocket instrument developed at the National Astronomical
Observatory of Japan (NAOJ) as a part of an international
collaboration. The instrument main scientific goal is to achieve
polarization measurement of the Lyman-α line at 121.56 nm emitted from
the solar upper-chromosphere and transition region with an unprecedented
0.1% accuracy. The optics are composed of a Cassegrain telescope
coated with a "cold mirror" coating optimized for UV reflection and
a dual-channel spectrograph allowing for simultaneous observation of
the two orthogonal states of polarization. Although the polarization
sensitivity is the most important aspect of the instrument, the spatial
and spectral resolutions of the instrument are also crucial to observe
the chromospheric features and resolve the Ly-α profiles. A precise
alignment of the optics is required to ensure the resolutions, but
experiments under vacuum conditions are needed since Ly-α is absorbed
by air, making the alignment experiments difficult. To bypass this
issue, we developed methods to align the telescope and the spectrograph
separately in visible light. We explain these methods and present
the results for the optical alignment of the CLASP telescope and
spectrograph. We then discuss the combined performances of both parts
to derive the expected resolutions of the instrument, and compare them
with the flight observations performed on September 3rd 2015.
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
Bibcode: 2016cosp...41E.681G
Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.
Title: On the Fourier and Wavelet Analysis of Coronal Time Series
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
Bibcode: 2016ApJ...825..110A
Altcode: 2016arXiv160605251A
Using Fourier and wavelet analysis, we critically re-assess the
significance of our detection of periodic pulsations in coronal
loops. We show that the proper identification of the frequency
dependence and statistical properties of the different components of the
power spectra provides a strong argument against the common practice
of data detrending, which tends to produce spurious detections around
the cut-off frequency of the filter. In addition, the white and red
noise models built into the widely used wavelet code of Torrence &
Compo cannot, in most cases, adequately represent the power spectra of
coronal time series, thus also possibly causing false positives. Both
effects suggest that several reports of periodic phenomena should
be re-examined. The Torrence & Compo code nonetheless effectively
computes rigorous confidence levels if provided with pertinent models of
mean power spectra, and we describe the appropriate manner in which to
call its core routines. We recall the meaning of the default confidence
levels output from the code, and we propose new Monte-Carlo-derived
levels that take into account the total number of degrees of freedom
in the wavelet spectra. These improvements allow us to confirm that
the power peaks that we detected have a very low probability of being
caused by noise.
Title: Chromospheric LAyer SpectroPolarimeter (CLASP2)
Authors: Narukage, Noriyuki; McKenzie, David E.; Ishikawa, Ryoko;
Trujillo-Bueno, Javier; De Pontieu, Bart; Kubo, Masahito; Ishikawa,
Shin-nosuke; Kano, Ryouhei; Suematsu, Yoshinori; Yoshida, Masaki;
Rachmeler, Laurel A.; Kobayashi, Ken; Cirtain, Jonathan W.; Winebarger,
Amy R.; Asensio Ramos, Andres; del Pino Aleman, Tanausu; Štępán,
Jiri; Belluzzi, Luca; Larruquert, Juan Ignacio; Auchère, Frédéric;
Leenaarts, Jorrit; Carlsson, Mattias J. L.
Bibcode: 2016SPIE.9905E..08N
Altcode:
The sounding rocket Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) was launched on September 3rd, 2015, and successfully detected
(with a polarization accuracy of 0.1 %) the linear polarization signals
(Stokes Q and U) that scattering processes were predicted to produce
in the hydrogen Lyman-alpha line (Lyα 121.567 nm). Via the Hanle
effect, this unique data set may provide novel information about the
magnetic structure and energetics in the upper solar chromosphere. The
CLASP instrument was safely recovered without any damage and we have
recently proposed to dedicate its second flight to observe the four
Stokes profiles in the spectral region of the Mg II h and k lines
around 280 nm; in these lines the polarization signals result from
scattering processes and the Hanle and Zeeman effects. Here we describe
the modifications needed to develop this new instrument called the
"Chromospheric LAyer SpectroPolarimeter" (CLASP2).
Title: Lifecycle of a large-scale polar coronal pseudostreamer/cavity
system
Authors: Guennou, Chloé; Auchere, Frederic; Seaton, Daniel; Rachmeler,
Laurel
Bibcode: 2016cosp...41E.749G
Altcode:
Coronal cavities, tunnel-like areas of rarefied density, provide
important information about the magnetic structures that support
prominences. The magnetic energy is stored through the twisted or shared
magnetic field, ultimately released through Coronal Mass Ejections
(CME). To be able to forecast these energetic releases of material
and prevent potential terrestrial consequences, the understanding
of the cavity 3D morphology, magnetic and thermal properties are
essential. The prominences embedded in the cavity only trace a small
part of the magnetic field, whereas the much larger cavity provides more
information about the magnetic field morphology. As a result, a clear
understanding of the coronal volume of the cavity significantly advances
our understanding of both the pre-eruption equilibrium and the triggers
of such eruptions. Determining both morphological and thermodynamical
coronal structures is difficult due to the optically thin nature of the
plasma. Observations are subject to integration along the line-of-sight
(LOS). This effect can strongly complicate both the derivation and the
interpretation of important physical quantities. One way to deduce
the 3D structure is with Solar Rotational Tomography (SRT). The 3D
plasma emissivity is estimated from EUV/white light images taken
from different viewpoints. Physical properties can be then derived
using Differential Emission Measure analysis from multi-wavelength 3D
reconstructions. We applied this technique to an exceptional large-scale
coronal pseudostreamer/cavity system in the southern polar region of
the solar corona that was visible for approximately a year starting
in February 2014. It is unusual to see such a large closed-field
structure embedded within the open polar coronal hole. We investigate
this structure to document its formation, evolution and eventually its
shrinking process using data from both the PROBA2/SWAP and SDO/AIA EUV
imagers. We found that the cavity temperature is extremely stable with
time and is essentially at a similar or slightly hotter temperature
than the surrounding pseudostreamer. Two regimes in cavity thermal
properties were observed: during the first 5 months of observation,
we found lower density depletion and highly multi-thermal plasma,
while after the pseudostreamer became stable and slowly shrank, the
depletion was more pronounced and the plasma was less multithermal. As
the thermodynamic properties are strongly correlated with the magnetic
structure, these results provide constraints on both the trigger of
CMEs and the processes that maintain cavities stability for such a
long lifetime.
Title: Tracking a large pseudostreamer to pinpoint the southern
polar magnetic field reversal
Authors: Rachmeler, Laurel; Guennou, Chloé; Seaton, Daniel B.;
Gibson, Sarah; Auchère, Frédéric
Bibcode: 2016SPD....4740104R
Altcode:
The reversal of the solar polar magnetic field is notoriously hard
to pin down due to the extreme viewing angle of the pole. In Cycle
24, the southern polar field reversal can be pinpointed with high
accuracy due to a large-scale pseudostreamer that formed over the
pole and persisted for approximately a year. We tracked the size
and shape of this structure with multiple observations and analysis
techniques including PROBA2/SWAP EUV images, AIA EUV images, CoMP data,
and 3D tomographic reconstructions. We find that the heliospheric field
reversed polarity in February 2014, whereas in the photosphere the last
vestiges of the previous polar field polarity remained until March 2015.
Title: Lifecycle of a large-scale polar coronal pseudostreamer/cavity
system
Authors: Guennou, Chloé; Rachmeler, Laurel; Seaton, Daniel; Auchère,
Frédéric
Bibcode: 2016FrASS...3...14G
Altcode:
We report on an exceptional large-scale coronal pseudostreamer/cavity
system in the southern polar region of the solar corona that was
visible for approximately a year starting in February 2014. It is
unusual to see such a large closed-field structure embedded within the
open polar coronal hole. We investigate this structure to document its
formation, evolution and eventually its shrinking process using data
from both the PROBA2/SWAP and SDO/AIA EUV imagers. In particular, we
used EUV tomography to find the overall shape and internal structure
of the pseudostreamer and to determine its 3D temperature and density
structure using DEM analysis. We found that the cavity temperature
is extremely stable with time and is essentially at a similar or
slightly hotter temperature than the surrounding pseudostreamer. Two
regimes in cavity thermal properties were observed: during the first
5 months of observation, we found lower density depletion and highly
multi-thermal plasma, while after the pseudostreamer became stable and
slowly shrank, the depletion was more pronounced and the plasma was less
multithermal. As the thermodynamic properties are strongly correlated
with the magnetic structure, these results provide constraints on both
the trigger of CMEs and the processes that maintain cavities stability
for such a long lifetime.
Title: Spectro-polarimetric observation in UV with CLASP to probe
the chromosphere and transition region
Authors: Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère,
Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi,
Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori;
Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi;
Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto;
Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi,
Luca; Carlsson, Mats
Bibcode: 2016SPD....4710107K
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA
sounding-rocket experiment that was performed in White Sands in
the US on September 3, 2015. During its 5-minute ballistic flight,
CLASP successfully made the first spectro-polarimetric observation in
the Lyman-alpha line (121.57 nm) originating in the chromosphere and
transition region. Since the Lyman-alpha polarization is sensitive
to magnetic field of 10-100 G by the Hanle effect, we aim to infer
the magnetic field information in such upper solar atmosphere with
this experiment.The obtained CLASP data showed that the Lyman-alpha
scattering polarization is about a few percent in the wings and
the order of 0.1% in the core near the solar limb, as it had been
theoretically predicted, and that both polarization signals have a
conspicuous spatio-temporal variability. CLASP also observed another
upper-chromospheric line, Si III (120.65 nm), whose critical field
strength for the Hanle effect is 290 G, and showed a measurable
scattering polarization of a few % in this line. The polarization
properties of the Si III line could facilitate the interpretation of
the scattering polarization observed in the Lyman-alpha line.In this
presentation, we would like to show how the upper chromosphere and
transition region are seen in the polarization of these UV lines and
discuss the possible source of these complicated polarization signals.
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
Bibcode: 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: 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.
Bibcode: 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: The extreme ultraviolet imager of solar orbiter: optical
design and alignment scheme
Authors: Halain, J. -P.; Mazzoli, A.; Meining, S.; Rochus, P.; Renotte,
E.; Auchère, F.; Schühle, U.; Delmotte, F.; Dumesnil, C.; Philippon,
A.; Mercier, R.; Hermans, A.
Bibcode: 2015SPIE.9604E..0HH
Altcode:
The Extreme Ultraviolet Imager (EUI) is one of the remote sensing
instruments on-board the Solar Orbiter mission. It will provide
dual-band full-Sun images of the solar corona in the extreme ultraviolet
(17.1 nm and 30.4 nm), and high resolution images of the solar disk in
both extreme ultraviolet (17.1 nm) and vacuum ultraviolet (Lyman-alpha
121.6 nm). The EUI optical design takes heritage of previous similar
instruments. The Full Sun Imager (FSI) channel is a single mirror
Herschel design telescope. The two High Resolution Imager (HRI)
channels are based on a two-mirror optical refractive scheme, one
Ritchey-Chretien and one Gregory optical design for the EUV and the
Lyman-alpha channels, respectively. The spectral performances of the
EUI channels are obtained thanks to dedicated mirror multilayer coatings
and specific band-pass filters. The FSI channel uses a dual-band mirror
coating combined with aluminum and zirconium band-pass filters. The HRI
channels use optimized band-pass selection mirror coatings combined
with aluminum band-pass filters and narrow band interference filters
for Lyman-alpha. The optical performances result from accurate mirror
manufacturing tolerances and from a two-step alignment procedure. The
primary mirrors are first co-aligned. The HRI secondary mirrors
and focal planes positions are then adjusted to have an optimum
interferometric cavity in each of these two channels. For that purpose
a dedicated alignment test setup has been prepared, composed of a dummy
focal plane assembly representing the detector position. Before the
alignment on the flight optical bench, the overall alignment method
has been validated on the Structural and Thermal Model, on a dummy
bench using flight spare optics, then on the Qualification Model to
be used for the system verification test and qualifications.
Title: The extreme UV imager telescope on-board the Solar Orbiter
mission: overview of phase C and D
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz,
W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo,
M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C.
Bibcode: 2015SPIE.9604E..0GH
Altcode:
The Solar Orbiter mission is composed of ten scientific instruments
dedicated to the observation of the Sun's atmosphere and its
heliosphere, taking advantage of an out-of ecliptic orbit and at
perihelion reaching a proximity close to 0.28 A.U. On board Solar
Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun
image sequences of the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm), and high-resolution image sequences of the solar disk
in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet
(121.6 nm). The EUI concept uses heritage from previous similar extreme
ultraviolet instrument. Additional constraints from the specific orbit
(thermal and radiation environment, limited telemetry download) however
required dedicated technologies to achieve the scientific objectives
of the mission. The development phase C of the instrument and its
sub-systems has been successfully completed, including thermomechanical
and electrical design validations with the Structural Thermal Model
(STM) and the Engineering Model (EM). The instrument STM and EM units
have been integrated on the respective spacecraft models and will
undergo the system level tests. In parallel, the Phase D has been
started with the sub-system qualifications and the flight parts
manufacturing. The next steps of the EUI development will be the
instrument Qualification Model (QM) integration and qualification
tests. The Flight Model (FM) instrument activities will then follow
with the acceptance tests and calibration campaigns.
Title: CLASP: A UV Spectropolarimeter on a Sounding Rocket for
Probing theChromosphere-Corona Transition Regio
Authors: Ishikawa, Ryohko; Kano, Ryouhei; Winebarger, Amy; Auchere,
Frederic; Trujillo Bueno, Javier; Bando, Takamasa; Narukage,
Noriyuki; Kobayashi, Ken; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Giono, Gabriel; Tsuneta, Saku; Hara, Hirohisa; Suematsu,
Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Ichimoto, Kiyoshi;
Cirtain, Jonathan; De Pontieu, Bart; Casini, Roberto; Manso Sainz,
Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca
Bibcode: 2015IAUGA..2254536I
Altcode:
The wish to understand the energetic phenomena of the outer solar
atmosphere makes it increasingly important to achieve quantitative
information on the magnetic field in the chromosphere-corona
transition region. To this end, we need to measure and model the
linear polarization produced by scattering processes and the Hanle
effect in strong UV resonance lines, such as the hydrogen Lyman-alpha
line. A team consisting of Japan, USA, Spain, France, and Norway has
been developing a sounding rocket experiment called the Chromospheric
Lyman-alpha Spectro-Polarimeter (CLASP). The aim is to detect the
scattering polarization produced by anisotropic radiation pumping in
the hydrogen Lyman-alpha line (121.6 nm), and via the Hanle effect to
try to constrain the magnetic field vector in the upper chromosphere
and transition region. In this talk, we will present an overview
of our CLASP mission, its scientific objectives, ground tests made,
and the latest information on the launch planned for the Summer of 2015.
Title: Probing Solar Cycle 24's southern polar field reversal with
a pseudostreamer
Authors: Rachmeler, Laurel A.; Guennou, Chloe; Seaton, Daniel;
Auchère, Frédéric
Bibcode: 2015shin.confE..65R
Altcode:
In Solar Cycle 24 the northern hemisphere reached activity maximum
around late 2011, while the south has trailed by at least two years. The
northern hemispheric polar field reversal has been fragmented and
complicated by poleward surges of both polarities. The southern polar
field, on the other hand, has progressed in a straightforward manner:
the boundary between the old cycle's positive field and the new cycle's
negative field has moved progressively southward. Determining when the
polar field flips sign is a difficult task because the photospheric
magnetic field at the poles is either poorly, or not at all, observed
depending on the solar B-angle. Here, we report on a pseudostreamer
that we observed at the southern pole for a year beginning in February
2014, and we use this feature to determine the southern polar field
reversal. We tracked the formation, evolution, and disappearance of
the pseudostreamer using limb identification and tomography with SWAP
17.4 nm EUV images. The pseudostreamer overlayed a roughly circular
polarity inversion line at the photosphere; both the pseudostreamer
and the inversion line gradually shrank as the new cycle's negative
field moved poleward. Using the morphology of the pseudostreamer, we
determined that the southern polar coronal field completely reversed in
approximately March 2015. All of the field inside the pseudostreamer is
closed field, including the former cycle's positive polar field. Thus
the heliospheric field, which is composed of open structures, reversed
polarity a year earlier, when the pseudostreamer first formed.
Title: Evidence for Evaporation-incomplete Condensation Cycles in
Warm Solar Coronal Loops
Authors: Froment, C.; Auchère, F.; Bocchialini, K.; Buchlin, E.;
Guennou, C.; Solomon, J.
Bibcode: 2015ApJ...807..158F
Altcode: 2015arXiv150408129F
Quasi-constant heating at the footpoints of loops leads to evaporation
and condensation cycles of the plasma: thermal non-equilibrium
(TNE). This phenomenon is believed to play a role in the formation
of prominences and coronal rain. However, it is often discounted
as being involved in the heating of warm loops because the
models do not reproduce observations. Recent simulations have
shown that these inconsistencies with observations may be due to
oversimplifications of the geometries of the models. In addition,
our recent observations reveal that long-period intensity pulsations
(several hours) are common in solar coronal loops. These periods are
consistent with those expected from TNE. The aim of this paper is to
derive characteristic physical properties of the plasma for some of
these events to test the potential role of TNE in loop heating. We
analyzed three events in detail using the six EUV coronal channels
of the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We
performed both a differential emission measure (DEM) and a time-lag
analysis, including a new method to isolate the relevant signal from
the foreground and background emission. For the three events, the DEM
undergoes long-period pulsations, which is a signature of periodic
heating even though the loops are captured in their cooling phase,
as is the bulk of the active regions. We link long-period intensity
pulsations to new signatures of loop heating with strong evidence for
evaporation and condensation cycles. We thus simultaneously witness
widespread cooling and TNE. Finally, we discuss the implications of
our new observations for both static and impulsive heating models.
Title: Instant: An Innovative L5 Small Mission Concept for Coordinated
Science with Solar Orbiter and Solar Probe Plus
Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.;
Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.;
Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.;
Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies,
J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard,
T. A.; DeForest, C. E.
Bibcode: 2014AGUFMSH21B4109L
Altcode:
We will present both the science objectives and related instrumentation
of a small solar and heliospheric mission concept, INSTANT:
INvestigation of Solar-Terrestrial Activity aNd Transients. It will be
submitted as an opportunity to the upcoming ESA-China S-class mission
call later this year. This concept was conceived to allow innovative
measurements and unprecedented, early determination of key properties
of Earthbound CMEs from the L5 vantage point. Innovative measurements
will include magnetic field determination in the corona thanks to
Hanle measurement in Lyman-α and polarized heliospheric imaging
for accurate determination of CME trajectories. With complementary
in situ measurements, it will uniquely permit solar storm science,
solar storm surveillance, and synergy with Solar Orbiter and Solar
Probe Plus (the ESA-China S2 mission launch is planned in 2021).
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.
Bibcode: 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: Precision VUV Spectro-Polarimetry for Solar Chromospheric
Magnetic Field Measurements
Authors: Ishikawa, R.; Bando, T.; Hara, H.; Ishikawa, S.; Kano, R.;
Kubo, M.; Katsukawa, Y.; Kobiki, T.; Narukage, N.; Suematsu, Y.;
Tsuneta, S.; Aoki, K.; Miyagawa, K.; Ichimoto, K.; Kobayashi, K.;
Auchère, F.; Clasp Team
Bibcode: 2014ASPC..489..319I
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV
spectro-polarimeter optimized for measuring the linear polarization
of the Lyman-α line (121.6 nm) to be launched in 2015 with NASA's
sounding rocket (Ishikawa et al. 2011; Narukage et al. 2011; Kano et
al. 2012; Kobayashi et al. 2012). With this experiment, we aim to (1)
observe the scattering polarization in the Lyman-α line, (2) detect
the Hanle effect, and (3) assess the magnetic fields in the upper
chromosphere and transition region for the first time. The polarization
measurement error consists of scale error δ a (error in amplitude
of linear polarization), azimuth error Δφ (error in the direction
of linear polarization), and spurious polarization ɛ (false linear
polarization signals). The error ɛ should be suppressed below 0.1%
in the Lyman-α core (121.567 nm ±0.02 nm), and 0.5% in the Lyman-α
wing (121.567 nm ±0.05 nm), based on our scientific requirements shown
in Table 2 of Kubo et al. (2014). From scientific justification, we
adopt Δ φ<2° and δ a<10% as the instrument requirements. The
spectro-polarimeter features a continuously rotating MgF2
waveplate (Ishikawa et al. 2013), a dual-beam spectrograph with a
spherical grating working also as a beam splitter, and two polarization
analyzers (Bridou et al. 2011), which are mounted at 90 degree from
each other to measure two orthogonal polarization simultaneously. For
the optical layout of the CLASP instrument, see Figure 3 in Kubo et
al. (2014). Considering the continuous rotation of the half-waveplate,
the modulation efficiency is 0.64 both for Stokes Q and U. All the raw
data are returned and demodulation (successive addition or subtraction
of images) is done on the ground. We control the CLASP polarization
performance in the following three steps. First, we evaluate the
throughput and polarization properties of each optical component in
the Lyman-α line, using the Ultraviolet Synchrotron ORbital Radiation
Facility (UVSOR) at the Institute for Molecular Science. The second
step is polarization calibration of the spectro-polarimeter after
alignment. Since the spurious polarization caused by the axisymmetric
telescope is estimated to be negligibly small because of the symmetry
(Ishikawa et al. 2014), we do not perform end-to-end polarization
calibration. As the final step, before the scientific observation near
the limb, we make a short observation at the Sun center and verify
the polarization sensitivity, because the scattering polarization
is expected to be close to zero at the Sun center due to symmetric
geometry. In order to clarify whether we will be able to achieve the
required polarization sensitivity and accuracy via these steps, we
exercise polarization error budget, by investigating all the possible
causes and their magnitudes of polarization errors, all of which are not
necessarily verified by the polarization calibration. Based on these
error budgets, we conclude that a polarization sensitivity of 0.1% in
the line core, δ a<10% and Δ φ<2° can be achieved combined
with the polarization calibration of the spectro-polarimeter and the
onboard calibration at the Sun center(refer to Ishikawa et al. 2014,
for the detail). We are currently conducting verification tests
of the flight components and development of the UV light source for
the polarization calibration. From 2014 spring, we will begin the
integration, alignment, and calibration. We will update the error
budgets throughout the course of these tests.
Title: A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP)
Authors: Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.;
Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.;
Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway,
T.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchère,
F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; Asensio Ramos,
A.; Štěpán, J.; Carlsson, M.
Bibcode: 2014ASPC..489..307K
Altcode:
A sounding-rocket experiment called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is presently under development to measure
the linear polarization profiles in the hydrogen Lyman-alpha (Lyα)
line at 121.567 nm. CLASP is a vacuum-UV (VUV) spectropolarimeter to aim
for first detection of the linear polarizations caused by scattering
processes and the Hanle effect in the Lyα line with high accuracy
(0.1%). This is a fist step for exploration of magnetic fields in
the upper chromosphere and transition region of the Sun. Accurate
measurements of the linear polarization signals caused by scattering
processes and the Hanle effect in strong UV lines like Lyα are
essential to explore with future solar telescopes the strength
and structures of the magnetic field in the upper chromosphere and
transition region of the Sun. The CLASP proposal has been accepted by
NASA in 2012, and the flight is planned in 2015.
Title: Current progress of optical alignment procedure of CLASP's
Lyman-alpha polarimetry instrument
Authors: Giono, G.; Ishikawa, R.; Katsukawa, Y.; Bando, T.; Kano, R.;
Suematsu, Y.; Narukage, N.; Sakao, Taro; Kobayashi, K.; Auchère, F.
Bibcode: 2014SPIE.9144E..3EG
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a
sounding-rocket instrument currently under development at the
National Astronomical Observatory of Japan (NAOJ) as a part of an
international collaboration. CLASP's optics are composed of a Cassegrain
telescope and a spectro-polarimeter which are designed to achieve an
unprecedentedly accurate polarization measurement of the Ly-α line
at 121.6nm emitted from the solar upper-chromosphere and transition
region. CLASP's first flight is scheduled for August 2015. Reaching
such accuracy requires a careful alignment of the optical elements
to optimize the image quality at 121.6 nm. However Ly-α is absorbed
by air and therefore the optics alignment has to be done under vacuum
condition which makes any experiment difficult. To bypass this issue,
we proposed to align the telescope and the spectrograph separately
in visible light. Hence we present our alignment procedure for both
telescope and spectro-polarimeter. We will explain details about the
telescope preliminary alignment before mirrors coating, which was done
in April 2014, present the telescope combined optical performance
and compare them to CLASP tolerance. Then we will present details
about an experiment designed to confirm our alignment procedure for
the CLASP spectro-polarimeter. We will discuss the resulting image
quality achieved during this experiment and the lessons learned.
Title: The extreme UV imager of solar orbiter: from detailed design
to flight model
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.;
Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.;
Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith,
P.; Winter, B.
Bibcode: 2014SPIE.9144E..08H
Altcode:
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. After the breadboarding and prototyping activities that
focused on key technologies, the EUI project has completed the design
phase and has started the final manufacturing of the instrument and its
validation. The EUI instrument has successfully passed its Critical
Design Review (CDR). The process validated the detailed design of
the Optical Bench unit and of its sub-units (entrance baffles, doors,
mirrors, camera, and filter wheel mechanisms), and of the Electronic
Box unit. In the same timeframe, the Structural and Thermal Model
(STM) test campaign of the two units have been achieved, and allowed
to correlate the associated mathematical models. The lessons learned
from STM and the detailed design served as input to release the
manufacturing of the Qualification Model (QM) and of the Flight Model
(FM). The QM will serve to qualify the instrument units and sub-units,
in advance of the FM acceptance tests and final on-ground calibration.
Title: Long-period intensity pulsations in the solar corona during
activity cycle 23
Authors: Auchère, F.; Bocchialini, K.; Solomon, J.; Tison, E.
Bibcode: 2014A&A...563A...8A
Altcode: 2013arXiv1312.3792A
We report on the detection (10σ) of 917 events of long-period (3 to
16 h) intensity pulsations in the 19.5 nm passband of the SOHO Extreme
ultraviolet Imaging Telescope. The data set spans from January 1997
to July 2010, i.e. the entire solar cycle 23 and the beginning of
cycle 24. The events can last for up to six days and have relative
amplitudes up to 100%. About half of the events (54%) are found
to happen in active regions, and 50% of these have been visually
associated with coronal loops. The remaining 46% are localized in
the quiet Sun. We performed a comprehensive analysis of the possible
instrumental artefacts and we conclude that the observed signal is
of solar origin. We discuss several scenarios that could explain the
main characteristics of the active region events. The long periods
and the amplitudes observed rule out any explanation in terms of
magnetohydrodynamic waves. Thermal non-equilibrium could produce the
right periods, but it fails to explain all the observed properties
of coronal loops and the spatial coherence of the events. We propose
that moderate temporal variations of the heating term in the energy
equation, so as to avoid a thermal non-equilibrium state, could be
sufficient to explain those long-period intensity pulsations. The
large number of detections suggests that these pulsations are common
in active regions. This would imply that the measurement of their
properties could provide new constraints on the heating mechanisms
of coronal loops. Movies are available in electronic form at http://www.aanda.org
Title: INSTANT: INvestigation of Solar-Terrestrial Associated
Natural Threats
Authors: Lavraud, Benoit; Vial, Jean-Claude; Harrison, Richard; Davies,
Jackie; Escoubet, C. Philippe; Zong, Qiugang; Auchere, Frederic; Liu,
Ying; Bale, Stuart; Gopalswamy, Nat; Li, Gang; Maksimovic, Milan;
Liu, William; Rouillard, Alexis
Bibcode: 2014cosp...40E1758L
Altcode:
The INSTANT mission will tackle both compelling solar and heliospheric
science objectives and novel space weather capabilities. This is
allowed by combining innovative and state-of-the-art instrumentation
at an appropriate off-Sun-Earth line location on an orbit lagging
the Earth around the Sun, near the L5 Lagrangian point. It is an
affordable mission that tackles major objectives of the European and
Chinese communities in terms of space physics and space weather. The
science objectives are: 1. What is the magnetic field magnitude and
topology in the corona? 2. How does the magnetic field reconfigure
itself during CME eruptions? 3. What are the sources and links between
the slow and fast winds? 4. How do CMEs accelerate and interact in the
interplanetary medium? The mission will further allow the following
crucial space weather capabilities: 5. Three-days advance knowledge
of CIR properties that reach Earth. 6. Twelve hours to 2 days advance
warning of Earth-directed CMEs. 7. Thanks to Lyman-α observations,
first-ever capability of determining the magnetic field magnitude and
orientation of Earth-directed CMEs. The mission will be proposed in
the context of the upcoming ESA-China S-class call for mission.
Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP)
Authors: Kano, Ryouhei; Katsukawa, Yukio; Kubo, Masahito; Auchere,
Frederic; Ishikawa, Ryohko; Kobayashi, Ken; Narukage, Noriyuki;
Trujillo Bueno, Javier; Bando, Takamasa; Ishikawa, Shin-nosuke
Bibcode: 2014cosp...40E1383K
Altcode:
In the solar chromosphere, magneto-hydrodynamic waves and super-sonic
jets ubiquitously happen as revealed by the Japanese solar satellite
Hinode. Now, we understand that the solar chromosphere is not a simple
intermediate layer smoothly connecting the photosphere and corona,
but a site where those dynamics may play an important role in the
chromospheric and coronal heating. Such discoveries imply that the
next frontier in solar physics lies in simultaneous observations
between the dynamics and magnetic structures in the chromosphere and
transition region, where the gas-dominant photosphere changes to the
magnetic-dominant corona. Therefore, we promote the Chromospheric
Lyman-Alpha SpectroPolarimeter (CLASP), which is a NASA's sounding
rocket experiment scheduled in 2015 for aiming to infer the magnetic
field information in the solar chromosphere and transition region. CLASP
makes precise measurement (0.1%) of the polarization profile of the
Lyman-alpha line, and aims to make the first ever measurement of the
Hanle effect polarization caused by magnetic fields in the upper solar
atmosphere. It is also a pathfinder to establish a new measurement
tool for chromospheric and transition-region magnetic fields, and to
make progress on chromospheric studies in future missions.
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
Bibcode: 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: The Solar EUV flux in the 3D Heliosphere
Authors: Auchere, Frederic; Von Steiger, Rudolf; McMullin, Donald;
Newmark, Jeffrey
Bibcode: 2014cosp...40E.150A
Altcode:
The absolute measurement of solar EUV flux and its time dependence
provide critical data on the solar driven photo chemistry which results
in solar system objects. For example, the Solar HeII 30.4 nm emission
is a major contributor to photo-ionization in the heliosphere, and thus
30.4 nm measurements provide the data required to determine the absolute
photoionization rate of neutral interstellar helium flowing into our
solar system. However, because of the orbit characteristics of the vast
majority of spacecraft, the solar irradiance has mostly been measured at
Earth or at least in the plane of the ecliptic. Therefore, the existing
data ignore the fact that the angular distribution of the solar flux
is largely anisotropic. Indeed, in the far and extreme ultraviolet,
the chromosphere and the corona display very contrasted structures. At
solar minimum, the polar regions are darkened by large coronal holes,
and in the most active part of the solar cycle, bright active regions
are scattered around the solar globe at low heliocentric latitudes. To
date, due to the small number of off- ecliptic measurements, very
few attempts have been made to investigate these variations. The
implications of the anisotropy of the solar irradiance are diverse. For
example, in the case of the 121.6 nm line of H I, the latitudinal
anisotropy must be taken into account when modeling the Lyman alpha
resonantly backscattered sky background. Identically, the anisotropy
must be included in the modeling of the intensity of the HI 121.6 nm
and He II 30.4 nm resonantly scattered coronal lines. We present here
a generalization of an earlier work on the anisotropy of the 30.4
nm EUV flux. Our empirical model, is now able to synthethize solar
spectra as seen from any point in the heliosphere in the 10 to 50 nm
wavelength range. The model is based on a Differential Emission Measure
resonstruction of the spectrum from reprojected EUV Carrington maps of
the Sun. We present the results obtained on the 3D distribution of the
Solar EUV flux during solar cycle 23. We discuss their consequences
on the GAS/Ulysses measurements of the Helium abundance in the Local
Interstellar Medium.
Title: Observations and possible interpretations of very long period
intensity pulsations in solar coronal loops
Authors: Froment, Clara; Solomon, Jacques; Buchlin, Eric; Bocchialini,
Karine; Auchere, Frederic; Guennou, Chloe
Bibcode: 2014cosp...40E.903F
Altcode:
We discovered that intensity pulsations with periods ranging from 3
to 16 hours are common in solar coronal loops. Initially developed
for EIT/SOHO 195 nm images, the automatic detection algorithm is now
running on AIA/SDO data and allows detection of pulsation events in
six coronal bands simultaneously. From may 2010 to december 2013, we
detected more than 2000 events in the 6 EUV bands. We focus our study
on pulsations in active regions and in particular in solar coronal
loops where most of events are detected. A multi-wavelength analysis
of some characteristic events is presented to help understand their
physical nature. We perform a Differential Emission Measure analysis
on AIA time series in order to determine the temporal variations of the
thermal structure of the pulsating loops. This analysis gives important
clues to investigate possible physical interpretations in particular in
term of small perturbations of loops in static equilibrium and to study
how this can constraint coronal heating models. We will also compare
our observations to the results of a MHD turbulence and heating model
of coronal loops.
Title: Future L5 Missions for Solar Physics and Space Weather
Authors: Auchere, Frederic; Gopalswamy, Nat
Bibcode: 2014cosp...40E.148A
Altcode:
Coronal mass ejections (CMEs) and corotating interaction regions (CIR)
are the sources of intense space weather in the heliosphere. Most of
the current knowledge on CMEs accumulated over the past few decades
has been derived from observations made from the Sun-Earth line,
which is not the ideal vantage point to observe Earth-affecting
CMEs (Gopalswamy et al., 2011a,b). In this paper, the advantages of
remote-sensing and in-situ observations from the Sun-Earth L5 point
are discussed. Locating a mission at Sun-Earth L5 has several key
benefits for solar physics and space weather: (1) off the Sun-Earth
line view is critical in observing Earth-arriving parts of CMEs,
(2) L5 coronagraphic observations can also provide near-Sun space
speed of CMEs, which is an important input to models that forecast
Earth-arrival time of CMEs, (3) backside and frontside CMEs can be
readily distinguished even without inner coronal imagers, (4) preceding
CMEs in the path of Earth-affecting CMEs can be identified for a better
estimate of the travel time, (5) CIRs reach the L5 point a few days
before they arrive at Earth, and hence provide significant lead time
before CIR arrival, (6) L5 observations can provide advance knowledge
of CME and CIR source regions (coronal holes) rotating to Earth view,
and (7) magnetograms obtained from L5 can improve the surface magnetic
field distribution used as input to MHD models that predict the
background solar wind. The paper also discusses L5 mission concepts
that can be achieved in the near future. References Gopalswamy, N.,
Davila, J. M., St. Cyr, O. C., Sittler, E. C., Auchère, F., Duvall,
T. L., Hoeksema, J. T., Maksimovic, M., MacDowall, R. J., Szabo,
A., Collier, M. R. (2011a), Earth-Affecting Solar Causes Observatory
(EASCO): A potential International Living with a Star Mission from
Sun-Earth L5 JASTP 73, 658-663, DOI: 10.1016/j.jastp.2011.01.013
Gopalswamy, N., Davila, J. M., Auchère, F., Schou, J., Korendyke,
C. M. Shih, A., Johnston, J. C., MacDowall, R. J., Maksimovic, M.,
Sittler, E., et al. (2011b), Earth-Affecting Solar Causes Observatory
(EASCO): a mission at the Sun-Earth L5, Solar Physics and Space Weather
Instrumentation IV. Ed. Fineschi, S. & Fennelly, J., Proceedings
of the SPIE, Volume 8148, article id. 81480Z, DOI: 10.1117/12.901538
Title: Innovative multilayer coated optics for Solar Physics
Authors: Meltchakov, Evgueni; Auchere, Frederic; Delmotte, Franck;
De Rossi, Sebastien; Mercier, Raymond; Zhang, Xueyan
Bibcode: 2014cosp...40E2069M
Altcode:
Development of multilayer coated optics with specific spectral
characteristics and enhanced temporal, thermal and radiation
stability requires an innovative approach to the design of reflecting
multilayers and optimization of the coating process. Here we report
on the progress in design, calculations and fabrication of reflecting
multilayer coatings for solar imaging in the extreme ultra-violet
(EUV) range. We will present recent results of characterization of
new tri-component periodic multilayer structures containing aluminum
as a low absorbing material within the spectral range from 17 to
40 nm. The EUV peak reflectance of these coatings (for instance,
the Al/Mo/SiC multilayers) reaches 56% at 17.4 nm and 42% at 30 nm,
highest reported up to now for these wavelengths. We have studied the
temporal and thermal stability of structural and optical parameters
of Al-based multilayer coatings as well as the resistivity of the
coatings to high-energy and high-dose proton irradiation. A special
attention will be drawn to specific bi-periodic systems with enhanced
selectivity, which possess two efficient reflection bands and attenuate
some unwanted emission lines in the EUV range. Experimental results
show that such multilayer coatings are good candidates for the EUV
imaging telescopes of Solar Orbiter and future solar missions.
Title: UV spectropolarimeter design for precise polarization
measurement and its application to the CLASP for exploration of
magnetic fields in solar atmosphere
Authors: Narukage, Noriyuki; Katsukawa, Yukio; Hara, Hirohisa; Kubo,
Masahito; Auchere, Frederic; Ishikawa, Ryohko; Kano, Ryouhei; Bando,
Takamasa; Ishikawa, Shin-nosuke; Suematsu, Yoshinori; Tsuneta, Saku
Bibcode: 2014cosp...40E2232N
Altcode:
In order to measure the magnetic field in the region where the
hot plasma from 10 (4) K to 10 (6) K is occupied, e.g., for solar
atmosphere, the polarimetric measurements in ultra violet (UV)
with 0.1% accuracy are required. In this paper, we propose a new
UV spectropolarimeter design with 0.1% sensitivity in polarization
measurement. This spectropolarimeter has two devices for the 0.1%
accuracy. First, all optical components except the waveplate are the
reflective type ones that can be equipped with the high reflectivity
coating for the high throughput. Secondly, it equips the optically
symmetric dual channels to measure the orthogonal linear polarization
state simultaneously, using a concave diffraction grating as both the
spectral dispersion element and the beam splitter. These two devices
make the spurious polarizations caused by the photon noise, by the
intensity variation of the observation target, and, by the instrument
itself, enough small to achieve the 0.1% accuracy in polarization
measurement. The spectropolarimeter thus designed is currently under
fabrication for the sounding rocket project of Chromospheric Lyman-Alpha
SpectroPolarimeter (CLASP) that aims at the direct measurement of the
magnetic fields in solar atmosphere with Lyman-alpha line (121.6 nm)
for the first time.
Title: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
Bibcode: 2013SoPh..288..389B
Altcode: 2013arXiv1304.5488B
We present the lessons learned about the degradation observed in
several space solar missions, based on contributions at the Workshop
about On-Orbit Degradation of Solar and Space Weather Instruments
that took place at the Solar Terrestrial Centre of Excellence (Royal
Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
workshop was to open discussions related to the degradation observed
in Sun-observing instruments exposed to the effects of the space
environment. This article summarizes the various lessons learned
and offers recommendations to reduce or correct expected degradation
with the goal of increasing the useful lifespan of future and ongoing
space missions.
Title: Can the Differential Emission Measure Constrain the Timescale
of Energy Deposition in the Corona?
Authors: Guennou, C.; Auchère, F.; Klimchuk, J. A.; Bocchialini,
K.; Parenti, S.
Bibcode: 2013ApJ...774...31G
Altcode: 2013arXiv1306.3114G
In this paper, the ability of the Hinode/EIS instrument to detect
radiative signatures of coronal heating is investigated. Recent
observational studies of active region cores suggest that both
the low and high frequency heating mechanisms are consistent with
observations. Distinguishing between these possibilities is important
for identifying the physical mechanism(s) of the heating. The
differential emission measure (DEM) tool is one diagnostic that
allows us to make this distinction, through the amplitude of the
DEM slope coolward of the coronal peak. It is therefore crucial to
understand the uncertainties associated with these measurements. Using
proper estimations of the uncertainties involved in the problem
of DEM inversion, we derive confidence levels on the observed DEM
slope. Results show that the uncertainty in the slope reconstruction
strongly depends on the number of lines constraining the slope. Typical
uncertainty is estimated to be about ±1.0 in the more favorable cases.
Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
Zender, J.
Bibcode: 2013SoPh..286...43S
Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
The Sun Watcher with Active Pixels and Image Processing (SWAP) is
an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
(PROBA2) mission launched on 2 November 2009. SWAP has a spectral
bandpass centered on 17.4 nm and provides images of the low solar
corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
an imaging cadence of about two minutes. SWAP is designed to monitor
all space-weather-relevant events and features in the low solar
corona. Given the limited resources of the PROBA2 microsatellite,
the SWAP telescope is designed with various innovative technologies,
including an off-axis optical design and a CMOS-APS detector. This
article provides reference documentation for users of the SWAP image
data.
Title: Chromospheric Lyman Alpha SpectroPolarimeter: CLASP
Authors: Kobayashi, Ken; Kano, R.; Trujillo Bueno, J.; Winebarger,
A. R.; Cirtain, J. W.; Bando, T.; De Pontieu, B.; Ishikawa, R.;
Katsukawa, Y.; Kubo, M.; Narukage, N.; Sakao, T.; Tsuneta, S.;
Auchère, F.; Asensio Ramos, A.; Belluzzi, L.; Carlsson, M.; Casini,
R.; Hara, H.; Ichimoto, K.; Manso Sainz, R.; Shimizu, T.; Stepan,
J.; Suematsu, Y.; Holloway, T.
Bibcode: 2013SPD....44..142K
Altcode:
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV
spectropolarimeter optimized for measuring the linear polarization of
the Lyman-alpha line (121.6 nm). The Lyman-alpha line is predicted to
show linear polarization caused by atomic scattering in the chromosphere
and modified by the magnetic field through the Hanle effect. The
Hanle effect is sensitive to weaker magnetic fields than Zeeman
effect, and is not canceled by opposing fields, making it sensitive
to tangled or unresolved magnetic field structures. These factors make
the Hanle effect a valuable tool for probing the magnetic field in the
chromosphere above the quiet sun. To meet this goal, CLASP is designed
to measure linear polarization with 0.1% polarization sensitivity
at 0.01 nm spectral resolution and 10" spatial resolution. CLASP is
scheduled to be launched in 2015.
Title: The LYOT+ UV/EUV instrumentation for measuring the magnetic
field in the corona
Authors: Auchère, Frederic; Vial, Jean Claude
Bibcode: 2013EGUGA..1513788A
Altcode:
The solar corona is the seat of a variability which involves basic
processes of plasma-magnetic field interaction in the universe,
while also being a source of disturbances for spacecraft, technology,
and possibly for human beings. Of special interest are coronal mass
ejections (CMEs) with their associated Eruptive Prominences (EPs). Since
they are basically driven by instabilities of the magnetic field in the
corona, the measurement of the magnetic field before, after (and during)
the event is critical in the corona. Also of interest for these studies
and the source of the solar wind, the radial velocity of the plasma is a
critical parameter to be determined. We present a new proposal to CNES
called LYOT+ which meets the above-mentioned objectives: measurement
of the coronal magnetic field up to 2 solar radii, of the electron
density and the radial velocity. These measurements are complemented
by EUV images of the underlying corona providing plasma diagnostic and
magnetic field morphology. We describe the proposed combination of EUV
imager and VUV and visible coronagraph. A main feature of the proposed
instrumentation is the extended overlap of the fields-of-view of both
instruments. In our presentation, we focus on the polarimetric concept
which leads to the determination of the magnetic field through the
Hanle effect. We also mention the extensive studies already performed
in designing the instrumentation and testing parts of it. In summary,
science, instrumentation and constraints on missions on which LYOT+
could be implemented, are presented.
Title: Tomographic reconstructions of large scale coronal structures
Authors: Guennou, C.; Auchère, F.; Seaton, D.; Canou, A.; Barbey,
N.; Bocchialini, K.
Bibcode: 2013enss.confE..83G
Altcode:
Classical plasma diagnostic techniques suffer from the line of sight
(LOS) integration problem, which can confuse structures to the point
that measurements crucial to the understanding of coronal physics are
difficult to interpret. Tomography provides one way of understanding the
LOS content, giving important insights on the morphology and physical
properties of the coronal structures. Large scale, long-lived, arch-like
structures are observed in the field of view of EUV telescopes at
mid-latitudes, most notably in the 174 nm passband. In the present work,
we use tomographic inversions of the solar corona the 3D morphology of
these structures. We focus on a 28 days period of data from July/August
2012 during which some of these features were observed up to 1.7 Rsol by
the SWAP/PROBA2 telescope. Additional multi-wavelength observations in
the 6 bands of AIA/SDO are used to derive the corresponding 3-D maps
of electron density and temperature. The results are then compared
with global magnetic field extrapolations. We conclude by proposing
an interpretation of the morphology of these structures as seen in
EUV images.
Title: TomograPy: A Fast, Instrument-Independent, Solar Tomography
Software
Authors: Barbey, N.; Guennou, C.; Auchère, F.
Bibcode: 2013SoPh..283..227B
Altcode: 2011SoPh..tmp..181B; 2011SoPh..tmp..250B; 2011arXiv1103.5904B;
2011SoPh..tmp..126B
Solar tomography has progressed rapidly in recent years thanks to the
development of robust algorithms and the availability of more powerful
computers. It can today provide crucial insights in solving issues
related to the line-of-sight integration present in the data of solar
imagers and coronagraphs. However, there remain challenges such as the
increase of the available volume of data, the handling of the temporal
evolution of the observed structures, and the heterogeneity of the data
in multi-spacecraft studies. We present a generic software package that
can perform fast tomographic inversions that scales linearly with the
number of measurements, linearly with the length of the reconstruction
cube (and not the number of voxels), and linearly with the number of
cores and can use data from different sources and with a variety of
physical models: TomograPy (http://nbarbey.github.com/TomograPy/), an
open-source software freely available on the Python Package Index. For
performance, TomograPy uses a parallelized-projection algorithm. It
relies on the World Coordinate System standard to manage various data
sources. A variety of inversion algorithms are provided to perform
the tomographic-map estimation. A test suite is provided along with
the code to ensure software quality. Since it makes use of the Siddon
algorithm it is restricted to rectangular parallelepiped voxels but
the spherical geometry of the corona can be handled through proper
use of priors. We describe the main features of the code and show
three practical examples of multi-spacecraft tomographic inversions
using STEREO/EUVI and STEREO/COR1 data. Static and smoothly varying
temporal evolution models are presented.
Title: Coronal Temperature Maps from Solar EUV Images: A Blind Source
Separation Approach
Authors: Dudok de Wit, T.; Moussaoui, S.; Guennou, C.; Auchère, F.;
Cessateur, G.; Kretzschmar, M.; Vieira, L. A.; Goryaev, F. F.
Bibcode: 2013SoPh..283...31D
Altcode: 2012SoPh..tmp..258D; 2012arXiv1203.0116D; 2012SoPh..tmp..276D
Multi-wavelength solar images in the extreme ultraviolet (EUV) are
routinely used for analysing solar features such as coronal holes,
filaments, and flares. However, images taken in different bands often
look remarkably similar, as each band receives contributions coming from
regions with a range of different temperatures. This has motivated the
search for empirical techniques that may unmix these contributions and
concentrate salient morphological features of the corona in a smaller
set of less redundant source images. Blind Source Separation (BSS)
does precisely this. Here we show how this novel concept also provides
new insight into the physics of the solar corona, using observations
made by SDO/AIA. The source images are extracted using a Bayesian
positive source-separation technique. We show how observations made
in six spectral bands, corresponding to optically thin emissions,
can be reconstructed by a linear combination of three sources. These
sources have a narrower temperature response and allow for considerable
data reduction, since the pertinent information from all six bands can
be condensed into a single composite picture. In addition, they give
access to empirical temperature maps of the corona. The limitations
of the BSS technique and some applications are briefly discussed.
Title: GAIA-DEM : The Gaussian AIA DEm Maps database
Authors: Guennou, C.; Auchère, F.; Soubrié, E.; Bocchialini, K.
Bibcode: 2013enss.confE...7G
Altcode:
Providing the amount of emitting material as a function of the
temperature along the line-of-sight, the Differential Emisssion Measure
(DEM) analysis is a widespread diagnostic tool, used for most types of
coronal structures. With six available coronal bands, the AIA instrument
on board the SDO satellite provides new possibilities to more reliably
estimate the DEM than previous UV imagers, and over a large FOV. The
purpose of this database is to provide synoptic Gaussian DEM inversions
of the AIA data. Using our recent results (Guennou et al. 2012a and
2012b), these maps can be then interpreted, taking advantage of our new
tools developed to facilitate the DEM interpretation. The GAIA database
provides the best Gaussian DEM fit matching the observations. A Gaussian
form is a good first order approximation to determine the main thermal
characteristics of the coronal plasma. With generally four inversions
per day, at a 6 hours cadence, this database enables the user to
quickly examine the global evolution of the thermal structure of the
solar corona. DEM maps are available at http://medoc-dem.ias.u-psud.fr/.
Title: FESTIVAL 5.0 - AIA and more !
Authors: Auchère, F.; Soubrié, E.
Bibcode: 2013enss.confE.141A
Altcode:
FESTIVAL is an open source IDL-based browser designed for simultaneous
and dynamic compositing of multi-instrument imaging data. FESTIVAL
is very flexible and works with FITS files, which allows advanced
processing. It is distributed as a Solar Software package. Initially
developed for SECCHI, FESTIVAL now supports most space imaging
telescopes, the latest additions being AIA /SDO and SWAP / Proba2. Its
native zoom/pan mouse navigation mode makes it well suited to the large
format of AIA images. In additio, version 5.0 brings a variety of new
features making FESTIVAL even more powerful: enhanced search options,
base and N-x running differences, solar rotation compensation, remote
access to the MEDOC data archive, etc.
Title: Can the Differential Emission Measure diagnostic be used to
constrain the timescale of energy deposition in the corona?
Authors: Guennou, C.; Auchère, F.; Klimchuk, J. A.; Bocchialini,
K.; Parenti, S.
Bibcode: 2013enss.confE..34G
Altcode:
Differential emission measure (DEM) analysis is a widespread tool used
to diagnose the thermal properties of coronal plasmas. The slope of
the DEM distribution coolward of the coronal peak (near 3-4MK in active
regions) can be used to diagnose the timescale for the energy deposition
repeating on a given magnetic strand. Recent AR studies suggest that
some active region cores are consistent with low frequency heating
mechanisms, where the plasma cools completely before being reheated,
while other show consistency with high frequency energy deposition,
where rapid reheating causes the temperature to fluctuate about
a particular value. Distinguishing between these possibilities is
important for identifying the physical mechanism of the heating. It is
therefore crucial to understand the uncertainties in measurements of
observed DEM slopes. In this work, based on a probabilistic approach
and Monte Carlo simulations, we carefully assess the errors in the
slopes determined from EIS data. We consider both the random errors due
to photon counting statistics, and the systematic errors associated
with uncertainties in atomic physics and instrument calibration. The
technique developed provides all the solutions consistent with the data
and their associated probabilities. We demonstrate how the quality
and the accuracy of the inversion are affected by the presence of
noises and systematic errors, and we characterise the quality of the
DEM inversion and its statistical properties. From these results,
estimation of the uncertainties in the reconstructed slopes can be
derived, thereby allowing a proper interpretation of the degree of
agreement between observations and heating model predictions.
Title: MEDIA : MEDoc Interface for AIA
Authors: Alingery, P.; Soubrié, E.; Auchère, F.; Bocchialini, K.;
Boignard, J. P.; Buchlin, E.; Malappert, J. C.; Parenti, S.
Bibcode: 2013enss.confE..88A
Altcode:
MEDOC, the space solar data center at Orsay
(http://www.ias.u-psud.fr/medoc) is now providing a new web access
to the AIA/SDO level 1 images. This interface has the advantage of
being simple, intuitive, very stable and fast. The full resolution
4k x 4k AIA level 1 images archived at MEDOC are downloaded from
upstream DRMS nodes with a 1 minute cadence at all wavelengths. The
dataset will be kept online on a redundant archive for the whole SDO
mission duration. The FITS files are accessible via an user friendly
web interface (http://medoc-sdo.ias.u-psud.fr) that allows users
to request data by selecting a date range, the desired wavelengths
and a sampling rate (choosing a cadence from 1 minute to 1 day). For
each file, users can preview the image (using the Helioviewer tool)
or display the header information before downloading the FITS files
(with or without Rice-compression). This web interface was built
using Sitools2, a tool developed by CNES, the French space agency, and
supports most browsers. For more advanced users, a Search/Get Python
module is also available at http://sdo.ias.u-psud.fr/python. The users
can use it to build more complex yet more powerful queries. We encourage
everyone in Europe and beyond to use these new services!
Title: On the Accuracy of the Differential Emission Measure
Diagnostics of Solar Plasmas. Application to SDO/AIA. II. Multithermal
Plasmas
Authors: Guennou, C.; Auchère, F.; Soubrié, E.; Bocchialini, K.;
Parenti, S.; Barbey, N.
Bibcode: 2012ApJS..203...26G
Altcode: 2012arXiv1210.2302G
Differential emission measure (DEM) analysis is one of the most
used diagnostic tools for solar and stellar coronae. Being an inverse
problem, it has limitations due to the presence of random and systematic
errors. We present in this series of papers an analysis of the
robustness of the inversion in the case of SDO/AIA observations. We
completely characterize the DEM inversion and its statistical
properties, providing all the solutions consistent with the data along
with their associated probabilities, and a test of the suitability of
the assumed DEM model. While Paper I focused on isothermal conditions,
we now consider multithermal plasmas and investigate both isothermal and
multithermal solutions. We demonstrate how the ambiguity between noises
and multithermality fundamentally limits the temperature resolution
of the inversion. We show that if the observed plasma is multithermal,
isothermal solutions tend to cluster on a constant temperature whatever
the number of passbands or spectral lines. The multithermal solutions
are also found to be biased toward near-isothermal solutions around 1
MK. This is true even if the residuals support the chosen DEM model,
possibly leading to erroneous conclusions on the observed plasma. We
propose tools for identifying and quantifying the possible degeneracy
of solutions, thus helping the interpretation of DEM inversion.
Title: On the Accuracy of the Differential Emission Measure
Diagnostics of Solar Plasmas. Application to SDO/AIA. I. Isothermal
Plasmas
Authors: Guennou, C.; Auchère, F.; Soubrié, E.; Bocchialini, K.;
Parenti, S.; Barbey, N.
Bibcode: 2012ApJS..203...25G
Altcode: 2012arXiv1210.2304G
Differential emission measure (DEM) analysis is a major diagnostic
tool for stellar atmospheres. However, both its derivation and its
interpretation are notably difficult because of random and systematic
errors, and the inverse nature of the problem. We use simulations with
simple thermal distributions to investigate the inversion properties
of SDO/AIA observations of the solar corona. This allows a systematic
exploration of the parameter space, and using a statistical approach
the respective probabilities of all the DEMs compatible with the
uncertainties can be computed. Following this methodology, several
important properties of the DEM inversion, including new limitations,
can be derived and presented in a very synthetic fashion. In this first
paper, we describe the formalism and we focus on isothermal plasmas
as building blocks to understand the more complex DEMs studied in the
second paper. The behavior of the inversion of AIA data being thus
quantified, and we provide new tools to properly interpret the DEM. We
quantify the improvement of the isothermal inversion with six AIA bands
compared to previous EUV imagers. The maximum temperature resolution
of AIA is found to be 0.03 log Te , and we derive a rigorous
test to quantify the compatibility of observations with the isothermal
hypothesis. However, we demonstrate limitations in the ability of AIA
alone to distinguish different physical conditions.
Title: Measurements and Modeling of Heliospheric EUV Spectral
Irradiance and Luminosity
Authors: Floyd, L. E.; McMullin, D. R.; Auchere, F.
Bibcode: 2012AGUFMSH11B2212F
Altcode:
For more than 15 years, The EIT and the later EUVI instruments aboard
SoHO and STEREO, respectively, have provided a time series of images
of the solar radiance in the HeII 30.4 nm transition region and
three coronal emission lines (FeIX/X, FeXII, and FeXV) of differing
temperatures. While the EIT measurements were gathered from a position
very near to the Earth-Sun axis, the EUVI measurements were gathered at
angles ranging up to and in excess of ±90 degrees in solar longitude
from the Earth-Sun axis. Using a Differential Emission Measure (DEM)
model, these measurements provide the basis for estimates of the
spectral irradiance for the entire solar spectrum up to about 50 nm at
any position in the heliosphere. These spectra are utilized in this
work for two purposes. First, the photoionization rate of neutral He
at each position is calculated. Neutral He is of interest because it
traverses the heliopause relatively undisturbed and therefore provides a
measure of isotopic parameters beyond the heliosphere. Second, we use
these generate a time series of estimates of the solar EUV spectral
luminosity extending from the recent post Solar Cycle 23 minimum
into the current unusually weak rise of Solar Cycle 24. Because this
EUV spectral luminosity is the sum of all solar radiation at each
wavelength in every direction, their time series should not contain
any systematic 27-day solar rotation periodicities as do typical solar
activity indices and its presence would be an indication of time series
reliability. This EUV luminosity time series is compared with other
solar indices such as SSN and the F10.7 radio flux.
Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
Bibcode: 2012ExA....34..273T
Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1'' and 0.3''), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with
0.14'' per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s - 1 or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
Title: Chromospheric Lyman-alpha spectro-polarimeter (CLASP)
Authors: Kano, Ryouhei; Bando, Takamasa; Narukage, Noriyuki; Ishikawa,
Ryoko; Tsuneta, Saku; Katsukawa, Yukio; Kubo, Masahito; Ishikawa,
Shin-nosuke; Hara, Hirohisa; Shimizu, Toshifumi; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Sakao, Taro; Goto, Motoshi; Kato, Yoshiaki; Imada,
Shinsuke; Kobayashi, Ken; Holloway, Todd; Winebarger, Amy; Cirtain,
Jonathan; De Pontieu, Bart; Casini, Roberto; Trujillo Bueno, Javier;
Štepán, Jiří; Manso Sainz, Rafael; Belluzzi, Luca; Asensio Ramos,
Andres; Auchère, Frédéric; Carlsson, Mats
Bibcode: 2012SPIE.8443E..4FK
Altcode:
One of the biggest challenges in heliophysics is to decipher the
magnetic structure of the solar chromosphere. The importance of
measuring the chromospheric magnetic field is due to both the key role
the chromosphere plays in energizing and structuring the outer solar
atmosphere and the inability of extrapolation of photospheric fields to
adequately describe this key boundary region. Over the last few years,
significant progress has been made in the spectral line formation
of UV lines as well as the MHD modeling of the solar atmosphere. It
is found that the Hanle effect in the Lyman-alpha line (121.567 nm)
is a most promising diagnostic tool for weaker magnetic fields in
the chromosphere and transition region. Based on this groundbreaking
research, we propose the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP) to NASA as a sounding rocket experiment, for making the first
measurement of the linear polarization produced by scattering processes
and the Hanle effect in the Lyman-alpha line (121.567 nm), and making
the first exploration of the magnetic field in the upper chromosphere
and transition region of the Sun. The CLASP instrument consists
of a Cassegrain telescope, a rotating 1/2-wave plate, a dual-beam
spectrograph assembly with a grating working as a beam splitter, and
an identical pair of reflective polarization analyzers each equipped
with a CCD camera. We propose to launch CLASP in December 2014.
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
Bibcode: 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: The EUI instrument on board the Solar Orbiter mission: from
breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
Bibcode: 2012SPIE.8443E..07H
Altcode:
The Solar Orbiter mission will explore the connection between the Sun
and its heliosphere, taking advantage of an orbit approaching the Sun at
0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. To achieve the required scientific performances under the
challenging constraints of the Solar Orbiter mission it was required
to further develop existing technologies. As part of this development,
and of its maturation of technology readiness, a set of breadboard and
prototypes of critical subsystems have thus been realized to improve
the overall instrument design. The EUI instrument architecture, its
major components and sub-systems are described with their driving
constraints and the expected performances based on the breadboard and
prototype results. The instrument verification and qualification plan
will also be discussed. We present the thermal and mechanical model
validation, the instrument test campaign with the structural-thermal
model (STM), followed by the other instrument models in advance of
the flight instrument manufacturing and AIT campaign.
Title: On the Thermal diagnostics of Coronal Loops with SDO/AIA
Authors: Guennou, Chloe; Parenti, Susanna; Bocchialini, Karine;
Soubrie, Elie; Auchere, Frederic; Barbey, Nicolas
Bibcode: 2012cosp...39..675G
Altcode: 2012cosp.meet..675G
With simultaneous observations in 6 coronal bands, AIA has the
capability to provide spectral diagnostics over an extended field of
view at high resolution and high cadence. Therefore, DEM diagnostics of
coronal loops can in principle be performed routinely for statistical
studies. We investigate here the pertinence of the DEM analysis with
AIA. The inevitable presence of noises and uncertainties, incompleteness
of the atomic physics databases lead to notable difficulties in the
inversion process. The complications involved in the derivation of
the DEM are one of the reasons of the controversial results regarding
the thermal structure and thus the heating scenario of the coronal
loops. The purpose of this work, based on a probabilistic approach, is
precisely to investigate the properties of the solutions, providing a
quantification of the DEM inversion problem robustness. The technique
relies on Monte Carlo simulations of observed intensities in the six
AIA coronal bands. The comparison between the known inputs and the
inversion results allows us to determine the degree of robustness. This
approach provides all the solutions consistent with the data along with
their associated probabilities, as well as a test of the validity of
the assumptions made on the DEM shape. Applications to SDO/AIA coronal
loops data are presented.
Title: Tomographic reconstruction of polar plumes
Authors: Auchère, F.; Guennou, C.; Barbey, N.
Bibcode: 2012EAS....55..207A
Altcode:
We present a tomographic reconstruction of polar plumes as observed in
the Extreme Ultraviolet in January 2010. Plumes are elusive structures
visible in polar coronal holes that may play an important role in the
acceleration of the solar wind. However, despite numerous observations,
little is irrefutably known about them. Because of line of sight
effects, even their geometry is subject to debate. Are they genuine
cylindrical features of the corona or are they only chance alignments
along the line of sight? Tomography provides a means to reconstruct
the volume of an optically thin object from a set of observations
taken from different vantage points. In the case of the Sun, these are
typically obtained by using a solar rotation worth of images, which
limits the ability to reconstruct short lived structures. We present
here a tomographic inversion of the solar corona obtained using only
6 days of data. This is achieved by using simultaneously three space
telescopes (EUVI/STEREO and SWAP/PROBA2) in a very specific orbital
configuration. The result is the shortest possible tomographic snapshot
of polar plumes. The 3D reconstruction shows both quasi-cylindrical
plumes and a network pattern that can mimic them by line of sight
superimpositions. This suggests that the controversy on plume geometry
is due to the coexistence of both types of structures.
Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic
field in the upper atmosphere of our closest star
Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad,
A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt,
W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.;
Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald,
V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.;
Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.;
Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.;
Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C.
Bibcode: 2012ExA....33..271P
Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P
The magnetic field plays a pivotal role in many fields of
Astrophysics. This is especially true for the physics of the solar
atmosphere. Measuring the magnetic field in the upper solar atmosphere
is crucial to understand the nature of the underlying physical
processes that drive the violent dynamics of the solar corona—that
can also affect life on Earth. SolmeX, a fully equipped solar space
observatory for remote-sensing observations, will provide the first
comprehensive measurements of the strength and direction of the
magnetic field in the upper solar atmosphere. The mission consists
of two spacecraft, one carrying the instruments, and another one in
formation flight at a distance of about 200 m carrying the occulter to
provide an artificial total solar eclipse. This will ensure high-quality
coronagraphic observations above the solar limb. SolmeX integrates two
spectro-polarimetric coronagraphs for off-limb observations, one in
the EUV and one in the IR, and three instruments for observations on
the disk. The latter comprises one imaging polarimeter in the EUV for
coronal studies, a spectro-polarimeter in the EUV to investigate the low
corona, and an imaging spectro-polarimeter in the UV for chromospheric
studies. SOHO and other existing missions have investigated the emission
of the upper atmosphere in detail (not considering polarization),
and as this will be the case also for missions planned for the near
future. Therefore it is timely that SolmeX provides the final piece of
the observational quest by measuring the magnetic field in the upper
atmosphere through polarimetric observations.
Title: Earth-Affecting Solar Causes Observatory (EASCO): a mission
at the Sun-Earth L5
Authors: Gopalswamy, Nat; Davila, Joseph M.; Auchère, Frédéric;
Schou, Jesper; Korendyke, Clarence M.; Shih, Albert; Johnston, Janet
C.; MacDowall, Robert J.; Maksimovic, Milan; Sittler, Edward; Szabo,
Adam; Wesenberg, Richard; Vennerstrom, Suzanne; Heber, Bernd
Bibcode: 2011SPIE.8148E..0ZG
Altcode: 2011SPIE.8148E..30G; 2011arXiv1109.2929G
Coronal mass ejections (CMEs) and corotating interaction regions
(CIRs) as well as their source regions are important because of
their space weather consequences. The current understanding of CMEs
primarily comes from the Solar and Heliospheric Observatory (SOHO)
and the Solar Terrestrial Relations Observatory (STEREO) missions,
but these missions lacked some key measurements: STEREO did not have a
magnetograph; SOHO did not have in-situ magnetometer. SOHO and other
imagers such as the Solar Mass Ejection Imager (SMEI) located on the
Sun-Earth line are also not well-suited to measure Earth-directed
CMEs. The Earth-Affecting Solar Causes Observatory (EASCO) is a
proposed mission to be located at the Sun-Earth L5 that overcomes
these deficiencies. The mission concept was recently studied at the
Mission Design Laboratory (MDL), NASA Goddard Space Flight Center,
to see how the mission can be implemented. The study found that the
scientific payload (seven remote-sensing and three in-situ instruments)
can be readily accommodated and can be launched using an intermediate
size vehicle; a hybrid propulsion system consisting of a Xenon ion
thruster and hydrazine has been found to be adequate to place the
payload at L5. Following a 2-year transfer time, a 4-year operation
is considered around the next solar maximum in 2025.
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
Bibcode: 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: Development of multilayer thin film filters for the full-sun
imager on Solar Orbiter
Authors: Auchère, Frédéric; Zhang, Xueyan; Delmotte, Franck;
Meltchakov, Evgueni; BenMoussa, Ali
Bibcode: 2011SPIE.8148E..0NA
Altcode: 2011SPIE.8148E..21A
Membranes a few hundred nanometers thick are used in EUV optics to
make, for example, beams splitters or passband filters. Despite their
necessity in numerous applications these components are, because of
their thinness, extremely fragile and their implementation in space
instruments is always difficult. The authors are developing thin film
filters for the Full Sun Imager, one of the EUV telescopes on board
the Solar Orbiter mission with objectives of high optical efficiency
and mechanical strength. These filters are specifically designed
to isolate one or the other of the two passbands (17.4 and 30.4 nm)
reflected by the telescope's dual band mirror coating. In this paper
we present the optical properties of the prototype components.
Title: Morphology, dynamics and plasma parameters of plumes and
inter-plume regions in solar coronal holes
Authors: Wilhelm, K.; Abbo, L.; Auchère, F.; Barbey, N.; Feng, L.;
Gabriel, A. H.; Giordano, S.; Imada, S.; Llebaria, A.; Matthaeus,
W. H.; Poletto, G.; Raouafi, N. -E.; Suess, S. T.; Teriaca, L.; Wang,
Y. -M.
Bibcode: 2011A&ARv..19...35W
Altcode: 2011arXiv1103.4481W
Coronal plumes, which extend from solar coronal holes (CH) into the high
corona and—possibly—into the solar wind (SW), can now continuously
be studied with modern telescopes and spectrometers on spacecraft,
in addition to investigations from the ground, in particular, during
total eclipses. Despite the large amount of data available on these
prominent features and related phenomena, many questions remained
unanswered as to their generation and relative contributions to
the high-speed streams emanating from CHs. An understanding of the
processes of plume formation and evolution requires a better knowledge
of the physical conditions at the base of CHs, in plumes and in the
surrounding inter-plume regions. More specifically, information is
needed on the magnetic field configuration, the electron densities
and temperatures, effective ion temperatures, non-thermal motions,
plume cross sections relative to the size of a CH, the plasma bulk
speeds, as well as any plume signatures in the SW. In spring 2007, the
authors proposed a study on `Structure and dynamics of coronal plumes
and inter-plume regions in solar coronal holes' to the International
Space Science Institute (ISSI) in Bern to clarify some of these aspects
by considering relevant observations and the extensive literature. This
review summarizes the results and conclusions of the study. Stereoscopic
observations allowed us to include three-dimensional reconstructions
of plumes. Multi-instrument investigations carried out during several
campaigns led to progress in some areas, such as plasma densities,
temperatures, plume structure and the relation to other solar phenomena,
but not all questions could be answered concerning the details of
plume generation process(es) and interaction with the SW.
Title: AIA Observations of Sunspot Waves
Authors: Leibacher, John W.; Soubrié, E.; Auchère, F.; Baudin, F.
Bibcode: 2011SPD....42.2115L
Altcode: 2011BAAS..43S.2115L
Waves in the low solar atmosphere above sunspots i) present an
interesting phenomenon in their own right, ii) are potentially a probe
of magnetic structures (e.g. "plumes") in the sunspot atmosphere and a
source of excitation of higher, coronal loop waves, and iii) are coupled
to umbral flashes and sub-surface, helioseismic waves in a manner that
is not fully understood. We present an analysis of AIA observations
of waves in AR 11092, showing their propagation, temporal coherence,
and angular symmetry; characterizing them in terms of frequency,
amplitude, and propagation speed.
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.
Bibcode: 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. 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. 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. 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: TomograPy: A Fast, Instrument-Independent, Solar Tomography
Software
Authors: Barbey, Nicolas; Guennou, Chloé; Auchère, Frédéric
Bibcode: 2011ascl.soft04001B
Altcode:
TomograPy is an open-source software freely available on the Python
Package Index that can perform fast tomographic inversions that scale
linearly with the number of measurements, linearly with the length of
the reconstruction cube (and not the number of voxels) and linearly
with the number of cores and can use data from different sources
and with a variety of physical models. For performance, TomograPy
uses a parallelized-projection algorithm. It relies on the World
Coordinate System standard to manage various data sources. A variety
of inversion algorithms are provided to perform the tomographic-map
estimation. A test suite is provided along with the code to ensure
software quality. Since it makes use of the Siddon algorithm it is
restricted to rectangular parallelepiped voxels but the spherical
geometry of the corona can be handled through proper use of priors.
Title: Earth-Affecting Solar Causes Observatory (EASCO): A potential
International Living with a Star Mission from Sun-Earth L5
Authors: Gopalswamy, N.; Davila, J. M.; St. Cyr, O. C.; Sittler,
E. C.; Auchère, F.; Duvall, T. L.; Hoeksema, J. T.; Maksimovic, M.;
MacDowall, R. J.; Szabo, A.; Collier, M. R.
Bibcode: 2011JASTP..73..658G
Altcode:
This paper describes the scientific rationale for an L5 mission
and a partial list of key scientific instruments the mission should
carry. The L5 vantage point provides an unprecedented view of the
solar disturbances and their solar sources that can greatly advance
the science behind space weather. A coronagraph and a heliospheric
imager at L5 will be able to view CMEs broadsided, so space speed
of the Earth-directed CMEs can be measured accurately and their
radial structure discerned. In addition, an inner coronal imager
and a magnetograph from L5 can give advance information on active
regions and coronal holes that will soon rotate on to the solar
disk. Radio remote sensing at low frequencies can provide information
on shock-driving CMEs, the most dangerous of all CMEs. Coordinated
helioseismic measurements from the Sun-Earth line and L5 provide
information on the physical conditions at the base of the convection
zone, where solar magnetism originates. Finally, in situ measurements
at L5 can provide information on the large-scale solar wind structures
(corotating interaction regions (CIRs)) heading towards Earth that
potentially result in adverse space weather.
Title: Initiation and Early Development of the 2008 April 26 Coronal
Mass Ejection
Authors: Huang, J.; Démoulin, P.; Pick, M.; Auchère, F.; Yan, Y. H.;
Bouteille, A.
Bibcode: 2011ApJ...729..107H
Altcode:
We present a detailed study of a coronal mass ejection (CME) with
high temporal cadence observations in radio and extreme-ultraviolet
(EUV). The radio observations combine imaging of the low corona with
radio spectra in the outer corona and interplanetary space. The EUV
observations combine the three points of view of the STEREO and SOHO
spacecraft. The beginning of the CME initiation phase is characterized
by emissions that are signatures of the reconnection of the outer part
of the erupting configuration with surrounding magnetic fields. Later
on, a main source of emission is located in the core of the active
region. It is an indirect signature of the magnetic reconnection
occurring behind the erupting flux rope. Energetic particles are also
injected in the flux rope and the corresponding radio sources are
detected. Other radio sources, located in front of the EUV bright
front, trace the interaction of the flux rope with the surrounding
fields. Hence, the observed radio sources enable us to detect the main
physical steps of the CME launch. We find that imaging radio emissions
in the metric range permits us to trace the extent and orientation of
the flux rope which is later detected in interplanetary space. Moreover,
combining the radio images at various frequencies with fast EUV imaging
permits us to characterize in space and time the processes involved
in the CME launch.
Title: Minimization of the shadow patterns produced by periodic mesh
grids in extreme ultraviolet telescopes
Authors: Auchère, Frédéric; Rizzi, Julien; Philippon, Anne;
Rochus, Pierre
Bibcode: 2011JOSAA..28...40A
Altcode:
Thin metallic films are used as passband filters in space telescopes
operating in the extreme ultraviolet (EUV). Because of their thinness,
typically 100 to 200nm, they are very sensitive to static pressure
differentials and to mechanic and acoustic vibrations. Therefore,
they are difficult to manage in all phases of a space program, from
manufacturing to vacuum testing to launch. A common solution to this
problem is to reinforce them with fine mesh grids with pitches ranging
from a few hundred micrometers to a few millimeters. Depending on their
location in the optical path, the main effect of these periodic grids
is either to diffract light or to cast penumbral shadows on the focal
plane. In this paper, we analyze the formation of the shadow modulation
patterns and derive design rules to minimize their amplitude. The
minimization principle is illustrated by an application to a solar
EUV telescope.
Title: Center-to-Limb Variation in the Solar HeII 30.4 nm Emission
Line from STEREO EUVI
Authors: Floyd, L. E.; McMullin, D. R.; Auchere, F.
Bibcode: 2010AGUFMSH31C1803F
Altcode:
The variation of radiant energy that emerges from the each portion of
the solar surface depends on the temperature and density structure
of the solar atmosphere in those emitting regions. For wavelengths
where the opacity is sufficiently large, some of the emissions are
blocked by overlying plasma. HeII 30.4 nm (optically thick) solar
emissions fall into this category. Accordingly, the center-to-limb
(C2L) brightness variation across the solar disk will differ from that
of optically thin emissions. Knowledge of the C2L variation provides
important constraints on solar radiative transfer models in the lower
transition region where these emissions are formed. Images from the
EUVI instruments aboard the two STEREO spacecraft for the first time
provide direct measurements of the C2L variation, especially in the
channel centered on the strong HeII 30.4 nm emission. In general,
comparisons of simultaneous images taken from different viewing angles
in the ecliptic plane where the same regions of the Sun are measured
provide the basis for C2L estimates. After 4 years of the STEREO
mission, the increasing satellite separation provides the baseline
dataset for sampling at nearly all angles. Simultaneous images are
corrected for instrumental responsivity degradation and converted to
purely HeII 30.4 nm radiation using a DEM model (ref needed). The C2L is
expressed as parameterized models whose specific values are determined
via iteration with the initial estimate based on pre-DEM images. Solar
surface region types are segregated into different parameter sets by
the implied intensity at disk center. Validation of the responsivity
model is provided by measurements along the meridian halfway between
the two satellites and through intercomparisons with simultaneous
images from similar EIT instrument aboard SOHO. Validation of the
model and approach are provided through similar calculations obtained
for optically thin coronal lines such as FeXV.
Title: The technical challenges of the Solar-Orbiter EUI instrument
Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry;
Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric;
Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence;
Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François;
Ben Moussa, Ali
Bibcode: 2010SPIE.7732E..0RH
Altcode: 2010SPIE.7732E..20H
The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of
a suite of two high-resolution imagers (HRI) and one dual-band full
Sun imager (FSI) that will provide EUV and Lyman-α images of the
solar atmospheric layers above the photosphere. The EUI instrument is
based on a set of challenging new technologies allowing to reach the
scientific objectives and to cope with the hard space environment of
the Solar Orbiter mission. The mechanical concept of the EUI instrument
is based on a common structure supporting the HRI and FSI channels,
and a separated electronic box. A heat rejection baffle system is
used to reduce the Sun heat load and provide a first protection level
against the solar disk straylight. The spectral bands are selected by
thin filters and multilayer mirror coatings. The detectors are 10μm
pitch back illuminated CMOS Active Pixel Sensors (APS), best suited
for the EUI science requirements and radiation hardness. This paper
presents the EUI instrument concept and its major sub-systems. The
current developments of the instrument technologies are also summarized.
Title: Definition of an imaging spectrometer meeting the needs of
UV solar physics
Authors: Ruiz de Galarreta Fanjul, C.; Philippon, A.; Vial, J. -C.;
Lemaire, P.; Maillard, J. -P.; Buisset, C.; Appourchaux, T.;
Auchère, F.
Bibcode: 2010SPIE.7732E..36R
Altcode: 2010SPIE.7732E..99R
The study of the outer solar atmosphere requires combining imaging
and spectroscopy in the UV lines formed in the high chromosphere,
the transition region and the corona. We start from the science
requirements and we define the instrumental specifications in terms
of field-of-view (FOV), spatial, temporal and spectral resolution and
bandpass. We propose two different all-reflection optical architectures
based on interferometric techniques: Spatial Heterodyne Spectroscopy
(SHS); and Imaging Transform Spectrometer (IFTS). We describe the
different set-ups and compare the potential performances of the two
types of solutions, and discuss their feasibility. We conclude that
IFTS appears to be the best solution, meeting the needs of UV solar
physics. However, we point out the many difficulties to be encountered,
especially as far as metrology is concerned.
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.
Bibcode: 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. NRL
was supported by the Office of Naval Research and NASA under NDPRS6598G.
Title: Hanle signatures of the coronal magnetic field in the linear
polarization of the hydrogen Lα line
Authors: Derouich, M.; Auchère, F.; Vial, J. C.; Zhang, M.
Bibcode: 2010A&A...511A...7D
Altcode: 2009arXiv0912.5068D
Aims: This paper is dedicated to the assessment of the validity
of future coronal spectro-polarimetric observations and to prepare their
interpretation in terms of the magnetic field vector.
Methods:
We assume that the polarization of the hydrogen coronal Lα line is
due to anisotropic scattering of an incident chromospheric radiation
field. The anisotropy is due to geometrical effects but also to the
inhomogeneities of the chromospheric regions which we model by using
Carrington maps of the Lα. Because the corona is optically thin, we
fully consider the effects of the integration over the line-of-sight
(LOS). As a modeling case, we include a dipolar magnetic topology
perturbed by a non-dipolar magnetic structure arising from a prominence
current sheet in the corona. The spatial variation of the hydrogen
density and the temperature is taken into account. We determine the
incident radiation field developed on the tensorial basis at each
point along the LOS. Then, we calculate the local emissivity vector
to obtain integrated Stokes parameters with and without coronal
magnetic field.
Results: We show that the Hanle effect is an
interesting technique for interpreting the scattering polarization of
the Lαλ1216 line in order to diagnose the coronal magnetic field. The
difference between the calculated polarization and the zero magnetic
field polarization gives us an estimation of the needed polarimetric
sensitivity in future polarization observations. We also obtain
useful indications about the optimal observational strategy.
Conclusions: Quantitative interpretation of the Hanle effect on the
scattering linear polarization of Lα line can be a crucial source
of information about the coronal magnetic field at a height over the
limb h < 0.7 R⊙. Therefore, one needs the development
of spatial instrumentation to observe this line. Present address:
Colorado Research Associates Division, NorthWest Research Associates,
Inc., 3380 Mitchell Ln., Boulder, CO 80301, USA.
Title: The SDO data centre at IDOC/MEDOC in France
Authors: Parenti, Susanna; Bocchialini, Karine; Soubrie, Elie;
Auchere, Frederic; Ballans, Herv; Buchlin, Eric; Gabriel, Alan;
Mercier, Claude; Poulleau, Gilles; Vial, Jean-Claude
Bibcode: 2010cosp...38.2888P
Altcode: 2010cosp.meet.2888P
The IDOC/MEDOC centre at the Institut d'Astrophysique Spatiale (IAS,
Université Paris 11/CNRS) has a long experience in solar data archiving
and distribution, including almost 15 years of data from SOHO, STEREO
and TRACE. The center is now expanding its activity and becoming a
Pˆle Thématique Solaire of the CNES and INSU/CNRS. Part of the new
activities of the centre will be linked to the arrival of the enormous
volume of the new SDO data. The center will be one of the three European
centers to receive and redistribute the data to the community. It will
also be the only European site to permanently store about 10% of the
data (mainly from AIA). In continuity with its previous activities,
SDO data will be included in the data visualization tool FESTIVAL
and it will provide new services, like tools for the solar feature
identification (filaments, EUV intensity fluctuations). We will present
an overview of the facilities and activities of the centre in relation
to the SDO data.
Title: On the observations and possible interpretations of very long
period intensity oscillations of solar coronal loops
Authors: Solomon, Jacques; Auchere, Frederic; Bocchialini, Karine;
Gabriel, Alan; Tison, Emmanuelle
Bibcode: 2010cosp...38.2853S
Altcode: 2010cosp.meet.2853S
A comprehensive analysis of intensity oscillations in the Fe XII
line (19.5 nm) observed with EIT/SoHO in solar coronal loops during
solar cycle 23 (january 1997-september 2008) was performed. About
450 occurences of oscillations were obtained with periods ranging
between 3.4 and 13.6 hours and with durations up to about a
hundred hours. Interpratations in term of slow waves or of thermal
nonequilibrium were examined. However numerous inconsistencies arise
between current theories (in fact mostly expressed in terms of various
numerical simulations) and observations. Presently the lack of a direct
link between those very long oscillation periods and the characteristic
physical parameters of the loops (density, temperature, loop geometry)
hampers making progress in this major issue. This situation requires
an effort in a specific time analysis of the classical system of
equations of the problem: the question is examined from different
angles in relation to the data.
Title: Large-scale Extreme-Ultraviolet Disturbances Associated with
a Limb Coronal Mass Ejection
Authors: Dai, Y.; Auchère, F.; Vial, J. -C.; Tang, Y. H.; Zong, W. G.
Bibcode: 2010ApJ...708..913D
Altcode:
We present composite observations of a coronal mass ejection (CME)
and the associated large-scale extreme-ultraviolet (EUV) disturbances
on 2007 December 31 by the Extreme-ultraviolet Imager (EUVI) and COR1
coronagraph on board the recent Solar Terrestrial Relations Observatory
mission. For this limb event, the EUV disturbances exhibit some typical
characteristics of EUV Imaging Telescope waves: (1) in the 195 Å
bandpass, diffuse brightenings are observed propagating oppositely
away from the flare site with a velocity of ~260 km s-1,
leaving dimmings behind; (2) when the brightenings encounter the
boundary of a polar coronal hole, they stop there to form a stationary
front. Multi-temperature analysis of the propagating EUV disturbances
favors a heating process over a density enhancement in the disturbance
region. Furthermore, the EUVI-COR1 composite display shows unambiguously
that the propagation of the diffuse brightenings coincides with a
large lateral expansion of the CME, which consequently results in a
double-loop-structured CME leading edge. Based on these observational
facts, we suggest that the wave-like EUV disturbances are a result of
magnetic reconfiguration related to the CME liftoff rather than true
waves in the corona. Reconnections between the expanding CME magnetic
field lines and surrounding quiet-Sun magnetic loops account for the
propagating diffuse brightenings; dimmings appear behind them as a
consequence of volume expansion. X-ray and radio data provide us with
complementary evidence.
Title: Modeling and forecasting the 3D solar EUV flux
Authors: Auchere, Frederic; McMullin, Donald
Bibcode: 2010cosp...38.1097A
Altcode: 2010cosp.meet.1097A
The UV/EUV solar flux drives many physical processes in the
heliosphere. One of its most important effects are the complex
photochemistry reactions produced in the Planet's atmospheres. It is
thus a key parameter in space weather, and there is today a clear
need for reliable modeling and forecasting of the UV/EUV flux. The
STEREO mission offers un unprecedented opportunity to improve and
validate irradiance models and the associated pre-dictions. Indeed,
the separation angle of the two probes allow or a better coverage of
the solar surface, and the B probe monitors the upcoming hemisphere of
the Sun a few days before it is visible from Earth. The authors have
developped an empirical model of the three-dimensional EUV solar flux
based on EIT/SOHO data. Taking into account the flux anisotropies,
it can be used to compute and predict the irradiance at any position
in the heliosphere. We present in this paper the generalization of
this model to EUVI/STEREO data, and present the improved forecasting
performances compared to those of the previous version.
Title: Automatic detection and statistical analysis of intensity
oscillations in the solar corona with SDO
Authors: Auchere, Frederic; Bocchialini, Karine; Solomon, Jacques;
Gabriel, Alan; Tison, Emmanuelle
Bibcode: 2010cosp...38.2863A
Altcode: 2010cosp.meet.2863A
We present the generalization to SDO data of our automatic oscillation
detection algorithm. This technique was successfully tested using EIT
data on board SOHO at 19.5 nm from January 1997 to September 2008,
i.e almost the entire solar cycle 23. In the EIT data set we detected
400 oscillations whose periods range between 3.4 and 13.6 h with a
maximum around 6-7 hours. Most of the oscillations are localized in
coronal structures associated with active regions and last several
tens of hours. The AIA data will allow the detection of similar events
in several coronal temperature bands simultaneously, which will help
understand their physical nature.
Title: Polarimetry of the Lα Line for Coronal Magnetic Field
Diagnostic
Authors: Derouich, M.; Auchère, F.; Vial, J. C.; Millard, A. A.
Bibcode: 2009ASPC..405..389D
Altcode:
Measurement and physical interpretation of the scattering polarization
of the Extreme-ultraviolet (EUV) and Far-UV (FUV) spectral lines
provide a largely unexplored diagnostic of coronal magnetic field. In
this context, we present the LYOT (LYman Orbiting Telescope) project
that makes it possible to observe the Lα λ1216 line polarization
in the solar corona. Because the corona is optically thin, it
is necessary to consider the effects of the integration over the
line-of-sight (LOS). The LOS effects have been usually addressed for
non polarimetric studies where the unknown is a scalar quantity (the
intensity) but not a Stokes vector. Previous studies investigating the
coronal polarization are generally concerned with a local position of
the scattering center and a deterministic magnetic field (see Raouafi
et al.~2002 for a measurement and interpretation of the O VI λ 1032
line polarization). Here, we perform computations that test whether
a LOS integrated Hanle effect can be detected in order to access to
the magnetic field topology.
Title: Coronal and Interplanetary Structures Associated with Type
III Bursts
Authors: Pick, M.; Kerdraon, A.; Auchère, F.; Stenborg, G.; Bouteille,
A.; Soubrié, E.
Bibcode: 2009SoPh..256..101P
Altcode:
This paper pursues former studies of the coronal structures that
are associated with radio type III bursts by taking advantage of
the new capabilities of STEREO/SECCHI. The data analysis has been
performed for 02 and 03 June 2007. During these two days several
type III bursts, which were detected in the corona and in the
interplanetary medium, occurred during the observing time of the
Nançay radioheliograph. Electron beams accelerated in the same active
region and producing type III emissions almost at the same time,
can propagate in different well defined coronal structures below 15
R⊙. Then, these structures become imbedded in the same
plasma sheet which can be tracked up to 0.25 AU. Inhomogeneities travel
along these structures; their velocities measured between 15 and 35
R⊙ are typical of those of a slow solar wind. Comparison
with PFSS magnetic field extrapolation shows that its connection
with the IP magnetic field is different from what is suggested by the
present observations.
Title: Design and performance of two-channel EUV multilayer mirrors
with enhanced spectral selectivity
Authors: Hecquet, Christophe; Delmotte, Franck; Ravet-Krill,
Marie-Françoise; de Rossi, Sébastien; Jérome, Arnaud; Bridou,
Françoise; Varnière, Françoise; Meltchakov, Evgueni; Auchère,
Frédéric; Giglia, Angelo; Mahne, Nicola; Nanaronne, Stefano
Bibcode: 2009ApPhA..95..401H
Altcode: 2009ApPhA.tmp...37H
In this paper, we present a study on two-channel multilayer mirrors
which can operate at two wavelengths in Extreme Ultraviolet (EUV)
spectral range. We propose a new method to design two-channel EUV
multilayer mirrors with enhanced spectral selectivity. The mirror
structure is a stack of two periodic multilayers separated by a buffer
layer. We have defined the main parameters which allow adjustment of
the distance between different order Bragg’s peak and of wavelength
positions of reflectivity minima. Two mirrors have been designed and
deposited for solar EUV telescope applications by using this method. The
first mirror reflects Fe IX-X line (17.1 nm) and Fe XVI (33.5 nm) lines
with attenuation of the He II line (30.4 nm). The second mirror reflects
Fe IX-X and He II lines with attenuation of Fe XV (28.4 nm) and Fe XVI
lines. Measurements with synchrotron radiation source confirm that,
in both cases, for these mirrors, we are able to adjust reflectivity
maxima (Bragg peak position) and minima. Such multilayers offer new
possibilities for compact design of multi-wavelength EUV telescopes
and/or for high spectral selectivity.
Title: Stellar and galactic environment survey (SAGE)
Authors: Barstow, M. A.; Burleigh, M. R.; Bannister, N. J.; Lapington,
J. S.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.; Auchere,
F.; Bode, M. F.; Bromage, G. E.; Gibson, B.; Collier Cameron, A.;
Cassatella, A.; Delmotte, F.; Ravet, M. -F.; Doyle, J. G.; Jeffery,
C. S.; Gaensicke, B.; Jordan, C.; Kappelmann, N.; Werner, K.;
Lallement, R.; de Martino, D.; Matthews, S. A.; Phillips, K. J. H.;
Del Zanna, G.; Orio, M.; Pace, E.; Pagano, I.; Schmitt, J. H. M. M.;
Welsh, B. Y.
Bibcode: 2009Ap&SS.320..231B
Altcode: 2008Ap&SS.tmp..161B
This paper describes a proposed high resolution soft X-ray and
Extreme Ultraviolet (EUV) spectroscopy mission to carry out a survey
of Stellar and Galactic Environments (SAGE). The payload is based on
novel diffraction grating technology which has already been proven in
a sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. Much of the technical detail of
the instrumentation has been reported elsewhere and we concentrate
our discussion here on the scientific goals of a SAGE base-line
mission, demonstrating the scientific importance of high resolution
spectroscopy in the Extreme Ultraviolet for the study of stars and
the local interstellar medium.
Title: Solar EUV/FUV irradiance variations: analysis and observational
strategy
Authors: Kretzschmar, Matthieu; Dudok de Wit, Thierry; Lilensten, Jean;
Hochedez, Jean-Francois; Aboudarham, Jean; Amblard, Pierre-Olivier;
Auchère, Frederic; Moussaoui, Said
Bibcode: 2009AcGeo..57...42K
Altcode: 2008AcGeo..57...42K; 2008AcGeo.tmp...50K
The knowledge of solar extreme and far ultraviolet (EUV) irradiance
variations is essential for the characterization of the Earth’s
upper atmosphere. For a long time, this knowledge has been based
on empirical models, which are themselves based on proxies of the
solar activity. However, the accurate modeling and prediction of the
Earth’s upper atmosphere necessitate to improve the precision on the
irradiance and its variations below about 200 nm. Here, we present a
review of recent works made by the authors that aim at quantifying the
irradiance variability at these wavelengths, and that lead to new way
of monitoring the solar EUV/FUV irradiance spectrum. In more details,
it is shown that the quantification of the high level of redundancy in
the solar spectrum variability allows to envisage measuring only a small
portion of the spectrum without losing essential knowledge. Finally,
we discuss what should and could be measured in order to retrieve the
solar extreme and far ultraviolet spectrum.
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.
Bibcode: 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: Stellar And Galactic Environment survey (SAGE)
Authors: Barstow, M. A.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.;
Auchere, F.; Bannister, N. J.; Bode, M. F.; Bromage, G. E.; Burleigh,
M. R.; Collier Cameron, A.; Cassatella, A.; Delmotte, F.; Doyle, J. G.;
Gaensicke, B.; Gibson, B.; Jeffery, C. S.; Jordan, C.; Kappelmann,
N.; Lallement, R.; Lapington, J. S.; de Martino, D.; Matthews, S. A.;
Orio, M.; Pace, E.; Pagano, I.; Phillips, K. J. H.; Ravet, M. -F.;
Schmitt, J. H. M. M.; Welsh, B. Y.; Werner, K.; Del Zanna, G.
Bibcode: 2009ExA....23..169B
Altcode: 2008ExA...tmp...25B
This paper describes a proposed high resolution soft X-ray and Extreme
Ultraviolet spectroscopy mission to carry out a survey of Stellar
and Galactic Environments (SAGE). The payload is based on novel
diffraction grating technology which has already been proven in a
sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. We discuss the goals of a SAGE
base-line mission and demonstrate the scientific importance of high
resolution spectroscopy in the Extreme Ultraviolet for the study of
stars and the local interstellar medium.
Title: Solar EUV Spectral Irradiance Throughout The 3-Dimensional
Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J. W.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
Bibcode: 2008AGUFMSH13B1522M
Altcode:
When Ulysses moved from 30 to 80 degrees in solar latitude (July
2001), the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. This concept has been tested through the development of a
3-Dimensional solar EUV model for the Heliosphere. The model concept
has been presented earlier, and we are now presenting results and
applications of the new model. Using daily SOHO EIT observations,
over successive Carrington rotations, we have developed a three-
dimensional model for solar EUV fluxes observed at any heliospheric
position, projected to any heliospheric position. The combined
effects of solar rotational and latitude-dependent flux variability
are explicitly treated in this model. The flux model will be compared
with other direct spectral irradiance observations in the ecliptic
plane, such as those available from the TIMED SEE instrument as well
as broadband measurements available from the SOHO/SEM irradiance time
series. These comparisons will be used in part to validate the current
results. We then use this flux to compute the photoionization rate of
the in-flowing neutral Helium, and compare the modeled change with that
observed along the spacecraft trajectory with the direct measurements
from the out-of-ecliptic Ulysses GAS observations. The unique GAS
comparisons will provide validation of the original hypothesis as to
the latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than an increase of the neutral He density.
Title: Which solar EUV indices are best for reconstructing the solar
EUV irradiance?
Authors: Dudok de Wit, T.; Kretzschmar, M.; Aboudarham, J.; Amblard,
P. -O.; Auchère, F.; Lilensten, J.
Bibcode: 2008AdSpR..42..903D
Altcode: 2007astro.ph..2053D
The solar EUV irradiance is of key importance for space weather. Most
of the time, however, surrogate quantities such as EUV indices have to
be used by lack of continuous and spectrally resolved measurements of
the irradiance. The ability of such proxies to reproduce the irradiance
from different solar atmospheric layers is usually investigated by
comparing patterns of temporal correlations. We consider instead
a statistical approach. The TIMED/SEE experiment, which has been
continuously operating since February 2002, allows for the first time
to compare in a statistical manner the EUV spectral irradiance to five
EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices,
and the He I equivalent width. Using multivariate statistical methods,
we represent in a single graph the measure of relatedness between these
indices and various strong spectral lines. The ability of each index
to reproduce the EUV irradiance is discussed; it is shown why so few
lines can be effectively reconstructed from them. All indices exhibit
comparable performance, apart from the sunspot number, which is the
least appropriate. No single index can satisfactorily describe both
the level of variability on time scales beyond 27 days, and relative
changes of irradiance on shorter time scales.
Title: The EUV Sun as the superposition of elementary Suns
Authors: Amblard, P. -O.; Moussaoui, S.; Dudok de Wit, T.; Aboudarham,
J.; Kretzschmar, M.; Lilensten, J.; Auchère, F.
Bibcode: 2008A&A...487L..13A
Altcode: 2008arXiv0809.0566A
Aims: Many studies assume that the solar irradiance in the EUV can be
decomposed into different contributions, which makes modelling the
spectral variability considerably easier. We consider a different
approach in which these contributions are not imposed a priori
but effectively and robustly inferred from spectral irradiance
measurements.
Methods: This is a source separation problem with
a positivity constraint, for which we use a Bayesian solution.
Results: Using five years of daily EUV spectra recorded by the
TIMED/SEE satellite, we show that the spectral irradiance can be
decomposed into three elementary spectra. Our results suggest that they
describe different layers of the solar atmosphere rather than specific
regions. The temporal variability of these spectra is discussed.
Title: Two channel multilayer mirrors for astrophysics
Authors: Gautier, Julien; Delmotte, Franck; Françoise Ravet, Marie;
Jérome, Arnaud; Bridou, Françoise; Varnière, Francoise; Auchère,
Frédéric
Bibcode: 2008OptCo.281.3032G
Altcode:
A two-channel mirror reflecting both Fe-IX/X (λ = 17.1 nm) and He-II
(30.4 nm) resonance lines at near normal incidence has been designed,
fabricated and characterized. These two passbands are often chosen in
space instruments designed for the observation of the solar corona. The
mirror structure used for optimization is a superposition of two
periodic multilayers with three components per period. It has been
designed by using optimization software with an appropriate merit
function. The theoretical reflectivity for both resonance lines can
reach 0.25. It is shown that, by using a set of filters, one can select
either the Fe-IX/X or the He-II channel. The spectral response of the
two-channel mirror has been measured on synchrotron radiation source on
a large wavelength range, from 12 nm to 35 nm. Experimental reflectivity
reaches 0.32 for the Fe-IX/X line and 0.19 for the He-II line.
Title: FESTIVAL: A Multiscale Visualization Tool for Solar Imaging
Data
Authors: Auchère, F.; Soubrié, E.; Bocchialini, K.; LeGall, F.
Bibcode: 2008SoPh..248..213A
Altcode: 2008SoPh..tmp...59A
Since 4 December 2006, the SECCHI instrument suites onboard the
two STEREO A and B probes have been imaging the solar corona and the
heliosphere on a wide range of angular scales. The EUVI telescopes have
a plate scale of 1.7 arcseconds pixel−1, while that of the
HI2 wide-angle cameras is 2.15 arcminutes pixel−1, i.e. 75
times larger, with the COR1 and COR2 coronagraphs having intermediate
plate scales. These very different instruments, aimed at studying
Coronal Mass Ejections and their propagation in the heliosphere,
create a data visualization challenge. This paper presents FESTIVAL,
a SolarSoftware package originally developed to be able to map the
SECCHI data into dynamic composite images of the sky as seen by the
STEREO and SOHO probes. Data from other imaging instruments can also
be displayed. Using the mouse, the user can quickly and easily zoom in
and out and pan through these composite images to explore all spatial
scales from EUVI to HI2 while keeping the native resolution of the
original data. A large variety of numerical filters can be applied,
and additional data (i.e. coordinate grids, stars catalogs, etc.) can
be overlaid on the images. The architecture of FESTIVAL is such that
it is easy to add support for other instruments and these new data
immediately benefit from the already existing capabilities. Also,
because its mapping engine is fully 3D, FESTIVAL provides a convenient
environment to display images from future out-of-the-Ecliptic solar
missions, such as Solar Orbiter or Solar Probe.
Title: A Time-Evolving 3D Method Dedicated to the Reconstruction of
Solar Plumes and Results Using Extreme Ultraviolet Data
Authors: Barbey, Nicolas; Auchère, Frédéric; Rodet, Thomas; Vial,
Jean-Claude
Bibcode: 2008SoPh..248..409B
Altcode: 2008SoPh..tmp...65B; 2008arXiv0802.0113B
An important issue in the tomographic reconstruction of the solar poles
is the relatively rapid evolution of the polar plumes. We demonstrate
that it is possible to take into account this temporal evolution in
the reconstruction. The difficulty of this problem comes from the fact
that we want a four-dimensional reconstruction (three spatial dimensions
plus time) whereas we only have three-dimensional data (two-dimensional
images plus time). To overcome this difficulty, we introduce a model
that describes polar plumes as stationary objects whose intensity varies
homogeneously with time. This assumption can be physically justified
if one accepts the stability of the magnetic structure. This model
leads to a bilinear inverse problem. We describe how to extend linear
inversion methods to these kinds of problems. Studies of simulations
show the reliability of our method. Results for SOHO/EIT data show
that we can estimate the temporal evolution of polar plumes to improve
the reconstruction of the solar poles from only one point of view. We
expect further improvements from STEREO/EUVI data when the two probes
will be separated by about 60°.
Title: Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI)
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Cook, J. W.; Hurley,
A.; Davila, J. M.; Thompson, W. T.; St Cyr, O. C.; Mentzell, E.;
Mehalick, K.; Lemen, J. R.; Wuelser, J. P.; Duncan, D. W.; Tarbell,
T. D.; Wolfson, C. J.; Moore, A.; Harrison, R. A.; Waltham, N. R.;
Lang, J.; Davis, C. J.; Eyles, C. J.; Mapson-Menard, H.; Simnett,
G. M.; Halain, J. P.; Defise, J. M.; Mazy, E.; Rochus, P.; Mercier,
R.; Ravet, M. F.; Delmotte, F.; Auchere, F.; Delaboudiniere, J. P.;
Bothmer, V.; Deutsch, W.; Wang, D.; Rich, N.; Cooper, S.; Stephens,
V.; Maahs, G.; Baugh, R.; McMullin, D.; Carter, T.
Bibcode: 2008SSRv..136...67H
Altcode: 2008SSRv..tmp...64H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is a five telescope package, which has been developed for
the Solar Terrestrial Relation Observatory (STEREO) mission by the
Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics
Laboratory (USA), the Goddard Space Flight Center (USA), the University
of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the
Max Planck Institute for Solar System Research (Germany), the Centre
Spatiale de Leige (Belgium), the Institut d’Optique (France) and the
Institut d’Astrophysique Spatiale (France). SECCHI comprises five
telescopes, which together image the solar corona from the solar disk to
beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI:
1 1.7 R⊙), two traditional Lyot coronagraphs (COR1: 1.5 4
R⊙ and COR2: 2.5 15 R⊙) and two new designs
of heliospheric imagers (HI-1: 15 84 R⊙ and HI-2: 66 318
R⊙). All the instruments use 2048×2048 pixel CCD arrays
in a backside-in mode. The EUVI backside surface has been specially
processed for EUV sensitivity, while the others have an anti-reflection
coating applied. A multi-tasking operating system, running on a PowerPC
CPU, receives commands from the spacecraft, controls the instrument
operations, acquires the images and compresses them for downlink
through the main science channel (at compression factors typically
up to 20×) and also through a low bandwidth channel to be used for
space weather forecasting (at compression factors up to 200×). An
image compression factor of about 10× enable the collection of images
at the rate of about one every 2 3 minutes. Identical instruments,
except for different sizes of occulters, are included on the STEREO-A
and STEREO-B spacecraft.
Title: Review on the solar spectral variability in the EUV for space
weather purposes
Authors: Lilensten, J.; Dudok de Wit, T.; Kretzschmar, M.; Amblard,
P. -O.; Moussaoui, S.; Aboudarham, J.; Auchère, F.
Bibcode: 2008AnGeo..26..269L
Altcode:
The solar XUV-EUV flux is the main energy source in the terrestrial
diurnal thermosphere: it produces ionization, dissociation, excitation
and heating. Accurate knowledge of this flux is of prime importance
for space weather. We first list the space weather applications that
require nowcasting and forecasting of the solar XUV-EUV flux. We
then review present models and discuss how they account for the
variability of the solar spectrum. We show why the measurement of the
full spectrum is difficult, and why it is illusory to retrieve it from
its atmospheric effects. We then address the problem of determining
a set of observations that are adapted for space weather purposes,
in the frame of ionospheric studies. Finally, we review the existing
and future space experiments that are devoted to the observation of
the solar XUV-EUV spectrum.
Title: Polarisation and magnetic depolarization of the Lyman-alpha
line in the corona : the line-of-sight effects
Authors: Vial, Jean-Claude; Derouich, Moncef; Auchere, Frederic;
Zhang, Mei
Bibcode: 2008cosp...37.3340V
Altcode: 2008cosp.meet.3340V
In view of the importance of measuring coronal magnetic field and of
the capability of measuring linear polarization in the Lyman α line
with the LYOT coronagraph on board the SMESE mission, we carried out
some calculations of the degrees of depolarization resulting from the
presence of a magnetic field. Our calculation is based on a simple
magnetic field model where a current sheet in the field represents
a solar prominence. We focus in this study on the effect of the
line-of-sight integration at various locations in the corona on the
polarizing/depolarizing properties. Other magnetic configurations are
also considered and are under the study.
Title: The EUV Sun as a superposition of 3 elementary Suns
Authors: Dudok de Wit, Thierry; Kretzschmar, Matthieu; Moussaoui,
Saïd; Amblard, Pierre-Olivier; Lilensten, Jean; Auchere, Frederic;
Aboudarham, Jean
Bibcode: 2008cosp...37..763D
Altcode: 2008cosp.meet..763D
Many studies assume that the solar irradiance in the EUV can be
decomposed into different contributions, which considerably eases
the modelling of the spectral variability for thermosphere/ionosphere
models. We consider a different approach, in which these contributions
are not imposed a priori but inferred from the spectral irradiance
measurements. This problem can be considered as a source separation
problem with positivity constraint, for which we use a recent Bayesian
method. Using five years of daily EUV spectra recorded by the SEE
instrument onboard TIMED, we show that the spectral irradiance can be
decomposed into three elementary spectra. The first one is associated
with the quiet Sun, the second one with active regions, whereas the
third one captures the cold contribution from the chromosphere.
Title: SMESE (SMall Explorer for Solar Eruptions): A microsatellite
mission with combined solar payload
Authors: Vial, J. -C.; Auchère, F.; Chang, J.; Fang, C.; Gan, W. Q.;
Klein, K. -L.; Prado, J. -Y.; Rouesnel, F.; Sémery, A.; Trottet,
G.; Wang, C.
Bibcode: 2008AdSpR..41..183V
Altcode:
The SMESE (SMall Explorer for Solar Eruptions) mission is a
microsatellite proposed by France and China. The payload of SMESE
consists of three packages: LYOT (a Lyman α imager and a Lyman α
coronagraph), DESIR (an Infra-red Telescope working at 35 80 and
100 250 μm), and HEBS (a High Energy Burst Spectrometer working
in X- and gamma-rays). The scientific objectives of the mission are
shortly presented. We describe the three instrumental packages and the
profile of the mission which accommodates them. With a launch around
2012 2013, the SMESE microsatellite mission will provide a unique
tool for detecting and understanding eruptions (flares and coronal
mass ejections). Observations should start around solar maximum, and
continue in the declining phase of activity, at a time when the Solar
Dynamics Observatory (SDO) should still be operating.
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Wang, D.; Plunkett, S. P.; Baugh, R.; McMullin, D. R.;
Davila, J. M.; Thompson, W. T.; Lemen, J. R.; Wuelser, J.; Harrison,
R. A.; Waltham, N. R.; Davis, C. J.; Eyles, C. J.; Defise, J.; Halain,
J.; Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet,
M. F.
Bibcode: 2007AGUSMSH33A..01H
Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft, launched 25 October 2006, are orbiting the Sun, one Ahead
of the Earth and the other Behind, each separating from Earth at about
22 degrees per year. The varying separation means that we will have
different observational capabilities as the spacecraft separate and
therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained. We will show some of
the initial results.
Title: Stereo Observations Of The Solar Corona Using The Secchi
Experiment
Authors: Plunkett, Simon P.; Howard, R. A.; Moses, J. D.; Vourlidas,
A.; Socker, D.; Newmark, J.; Wang, D.; Baugh, R.; Davila, J.;
Thompson, W.; St. Cyr, O. C.; Lemen, J.; Wuelser, J. P.; Harrison,
R. A.; Waltham, N.; Davis, C. J.; Eyles, C. J.; Defise, J. M.; Halain,
J. P.; Bothmer, V.; Delaboudiniere, J. P.; Auchere, F.; Mercier, R.;
Ravet, M. F.
Bibcode: 2007AAS...21011901P
Altcode: 2007BAAS...39..243P
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs,
and two telescopes that comprise the heliospheric imager. The main
objective of SECCHI is to observe coronal mass ejections (CMEs) from
their birth at the sun, through the corona and into the heliosphere. A
complete instrument suite is being carried on each of the two STEREO
spacecraft, which will provide the first sampling of a CME from two
vantage points as the spacecraft separate from each other at the rate
of about 45 degrees per year. We will show examples of some of the
data and some of the initial stereo results.
Title: Multispectral analysis of solar EUV images: linking temperature
to morphology
Authors: Dudok de Wit, T.; Auchère, F.
Bibcode: 2007A&A...466..347D
Altcode: 2007astro.ph..2052D
Context: Solar images taken simultaneously at different wavelengths in
the EUV are widely used for understanding structures such as flares,
coronal holes, loops, etc. The line-of-sight integration and the finite
spectral resolution of EUV telescopes, however, hinders interpretation
of these individual images in terms of temperature bands. Traditional
approaches involve simple visualisation or explicit modelling. We take
a more empirical approach, using statistical methods.
Aims:
The morphology of solar structures changes with the wavelength of
observation and, therefore, with temperature. We explore the possibility
of separating the different solar structures from a linear combination
of images.
Methods: Using a blind source separation approach,
we build a new set of statistically independent "source" images from
the original EUV images. Two techniques are compared: the singular
value decomposition and independent component analysis.
Results:
The source images show more contrast than the original ones, thereby
easing the characterisation of morphological structures. A comparison
with the differential emission measure shows that each source image
also isolates structures with specific emission temperatures.
Title: SMESE: A SMall Explorer for Solar Eruptions
Authors: Vial, J. -C.; Auchère, F.; Chang, J.; Fang, C.; Gan, W. Q.;
Klein, K. -L.; Prado, J. -Y.; Trottet, G.; Wang, C.; Yan, Y. H.
Bibcode: 2007AdSpR..40.1787V
Altcode:
The SMall Explorer for Solar Eruptions (SMESE) mission is a
microsatellite proposed by France and China. The payload of SMESE
consists of three packages: LYOT (a Lyman α imager and a Lyman α
coronagraph), DESIR (an Infra-Red Telescope working at 35-80 and
100-250 μm), and HEBS (a High-Energy Burst Spectrometer working in
X- and γ-rays). The status of research on flares and coronal mass
ejections is briefly reviewed in the context of on-going missions such
as SOHO, TRACE and RHESSI. The scientific objectives and the profile of
the mission are described. With a launch around 2012-2013, SMESE will
provide a unique tool for detecting and understanding eruptions (flares
and coronal mass ejections) close to the maximum phase of activity.
Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter
Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra,
L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar,
M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti,
S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.;
Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.;
Winter, B.; Zhukov, A.
Bibcode: 2007ESASP.641E..33H
Altcode:
The scientific objectives of Solar Orbiter rely ubiquitously on EUI,
its suite of solar atmosphere imaging telescopes. In the configuration
discussed here, EUI includes three co-aligned High Resolution Imagers
(HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme
ultraviolet passbands, dominated by coronal emission. Another HRI is
designed for the hydrogen Lyman α radiation in the far UV, imaging the
Chromosphere and the lower Transition Region. The current EUI design
and some of its development challenges are highlighted. EUI profits from
co-rotation phases, solar proximity and departure from the ecliptic. In
synergy with the other S.O. payload, EUI probes the dynamics of the
solar atmosphere, provides context data for all investigations and helps
to link in-situ and remote-sensing observations. In short, it serves all
four top-level goals of the mission. For these reasons, the EUI suite
is keenly anticipated in the European scientific community and beyond.
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, D.; Vourlidas, A.; Newmark, J.; Socker,
D. G.; Plunkett, S.; Wang, D.; Baugh, R.; McMullin, D.; Davila, J.;
St. Cyr, C.; Thompson, W. T.; Lemen, J.; Wuelser, J.; Harrison, R. A.;
Waltham, N. R.; Davis, C.; Eyles, C. J.; Defise, J.; Halain, J.;
Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet, M.
Bibcode: 2006AGUFMSM12A..02H
Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft will orbit the Sun, one Ahead of the Earth and the other
Behind, each separating from Earth at about 22 degrees per year. The
varying separation means that we will have different observational
capabilities as the spacecraft separate and therefore differing science
goals. The primary science objectives all are focused on understanding
the physics of the CME process their initiation, 3D morphology,
propagation, interaction with the interplanetary medium and space
weather effects. By observing the CME from multiple viewpoints with UV
and coronagraphic telescopes and by combining these observations with
radio and in-situ observations from the other instruments on STEREO as
well as from other satellites and ground based observatories operating
at the same time, answers to some of the outstanding questions will
be obtained. STEREO follows the very successful SOHO mission. SOHO's
success was primarily due to the highly complementary nature of the
instruments, but it was partly due to the very stable platform. The
L1 orbit enables an extremely stable thermal environment and thus
very stable pointing, as well as uninterrupted solar viewing. The
STEREO will have both of these characteristics, but in addition will
have multi-viewpoint viewing of CMEs, which will greatly enhance the
many discoveries that SOHO data have produced. We have been developing
techniques to interpret the observations from multiple viewpoints and
to perform 3-dimensional deconvolution of the CME observations using
forward modeling and inversion techniques. A continuous downlink of
STEREO data will provide a low-resolution, real- time view from all
of the instruments. The full data are downlinked once a day and will
be available about 24 hours later. We will present some preliminary
results from the instrument, which is expected to be launched in
October/November, 2006
Title: Rotational Tomography of the Solar Corona-Calculation of the
Electron Density and Temperature
Authors: Barbey, Nicolas; Auchère, Frédéric; Rodet, Thomas;
Bocchialini, Karine; Vial, Jean-Claude
Bibcode: 2006ESASP.617E..82B
Altcode: 2006soho...17E..82B
No abstract at ADS
Title: Helium/Hydrogen Fractionation in the Solar Wind-How Much is
Due to Inefficient Coulomb Drag?
Authors: Bochsler, P.; Auchère, F.; Skoug, R. M.
Bibcode: 2006ESASP.617E..28B
Altcode: 2006soho...17E..28B
No abstract at ADS
Title: SMESE: a combined UV-IR-X-gamma solar mission
Authors: Millard, Anne A.; Auchere, Frederic; Fang, Cheng; Gan,
Weiqun; Molodij, Guillaume; Prado, Jean-Yves; Rouesnel, Frederic;
Semery, Alain; Trottet, Gerard; Vial, Jean-Claude; Yan, Yihua; Wu, Ji
Bibcode: 2006SPIE.6266E..0JM
Altcode: 2006SPIE.6266E..15M
SMESE (SMall Explorer For the study of Solar Eruptions) is a
Franco-Chinese microsatellite mission. The scientific objectives of
SMESE are the study of coronal mass ejections and flares. Its payload
consists of three instrument packages : LYOT, DESIR and HEBS. LYOT is
composed of a Lyman α (121.6 nm) coronagraph, a Lyman α disk imager
and a far UV disk imager. DESIR is an infrared telescope working at 35
μm and 150 μm. HEBS is a high energy burst spectrometer working in
X rays and γ rays covering the 10 keV to 600 MeV range. SMESE will
be launched around 2011, providing a unique opportunity of detecting
and understanding eruptions at the maximum activity phase of the solar
cycle in a wide range of energies. The instrumentation on board SMESE
is described in this paper.
Title: From the Sun to the Earth: impact of the 27-28 May 2003 solar
events on the magnetosphere, ionosphere and thermosphere
Authors: Hanuise, C.; Cerisier, J. C.; Auchère, F.; Bocchialini,
K.; Bruinsma, S.; Cornilleau-Wehrlin, N.; Jakowski, N.; Lathuillère,
C.; Menvielle, M.; Valette, J. -J.; Vilmer, N.; Watermann, J.; Yaya, P.
Bibcode: 2006AnGeo..24..129H
Altcode:
During the last week of May 2003, the solar active region AR 10365
produced a large number of flares, several of which were accompanied
by Coronal Mass Ejections (CME). Specifically on 27 and 28 May three
halo CMEs were observed which had a significant impact on geospace. On
29 May, upon their arrival at the L1 point, in front of the Earth's
magnetosphere, two interplanetary shocks and two additional solar
wind pressure pulses were recorded by the ACE spacecraft. The
interplanetary magnetic field data showed the clear signature of a
magnetic cloud passing ACE. In the wake of the successive increases
in solar wind pressure, the magnetosphere became strongly compressed
and the sub-solar magnetopause moved inside five Earth radii. At
low altitudes the increased energy input to the magnetosphere was
responsible for a substantial enhancement of Region-1 field-aligned
currents. The ionospheric Hall currents also intensified and the entire
high-latitude current system moved equatorward by about 10°. Several
substorms occurred during this period, some of them - but not all -
apparently triggered by the solar wind pressure pulses. The storm's
most notable consequences on geospace, including space weather effects,
were (1) the expansion of the auroral oval, and aurorae seen at mid
latitudes, (2) the significant modification of the total electron
content in the sunlight high-latitude ionosphere, (3) the perturbation
of radio-wave propagation manifested by HF blackouts and increased
GPS signal scintillation, and (4) the heating of the thermosphere,
causing increased satellite drag. We discuss the reasons why the May
2003 storm is less intense than the October-November 2003 storms,
although several indicators reach similar intensities.
Title: Can the EUV spectrum and its variability be reconstructed
from a small set of spectral lines ?
Authors: Dudok de Wit, T.; Lilensten, J.; Aboudarham, J.; Amblard,
P. -O.; Auchère, F.; Kretzschmar, M.
Bibcode: 2006cosp...36..991D
Altcode: 2006cosp.meet..991D
The severe lack of continuously measured and spectrally resolved solar
EUV spectra is a major obstacle towards modelling the impact of the
solar irradiance on the ionosphere The usual solution involves the
measurement of various proxies We consider a different approach in
which the EUV spectrum and its variability are reconstructed from the
linear combination of a few spectral lines Using three years of spectra
from TIMED and a statistical classification technique we demonstrate
that 5 to 8 lines only are needed and in addition show which lines
are the best candidates These results are valuable for instrument
specification and also provide new insight into the comparison of
solar proxies against the EUV irradiance
Title: A brief introduction to SMESE mission
Authors: Wang, C.; Fang, C.; Gan, W.; Prado, J. -Y.; Trottet, G.;
Vial, J. -C.; Yan, Y.; Auchere, F.; Chang, J.; Molodi, G.
Bibcode: 2006ilws.conf..211W
Altcode:
Small Exploration for Solar Eruptions (SMESE) is a joint mission
between France and China to investigate the two main types of eruption
events on the Sun: Coronal Mass Ejections (CME) and solar flares,
and their relationship. SMESE will provide a set of unprecedented
and complementary measurements including Ly-alpha imager, Ly-alpha
coronagraph, EUV imager, Detection of Solar Infra red radiation,
Hard X-ray/gamma ray spectrometry. SMESE aims to study, among others,
the CME triggering mechanism and its acceleration in the corona, the
particle acceleration by CME and solar flare, the physical association
of the CME and solar flare etc. SMESE will be launched in the next
solar maximum between 2010-2012.
Title: SMESE, a SMall Explorer for the Study of solar Eruptions
Authors: Vial, J. -C.; Auchère, F.; Chang, J.; Fang, C.; Gan, W. Q.;
Molodij, G.; Prado, J. -Y.; Trottet, G.; Wang, C.; Yan, Y. H.
Bibcode: 2006cosp...36.3287V
Altcode: 2006cosp.meet.3287V
The SMESE Small Explorer for the Study of solar Eruptions mission is
a microsatellite proposed by France and China The payload of SMESE
consists of three packages LYOT a suite of two UV and EUV imagers and
a Lyman alpha coronagraph DESIR an Infra-Red Telescope working at 35
and 150 mu and HEBS a High Energy Burst Spectrometer working in X-
and gamma -rays The status of research on Coronal Mass Ejections and
flares will be briefly recalled in the context of on-going missions
such as SOHO TRACE and RHESSI The scientific objectives and the profile
of the mission will be described With a launch around 2011 SMESE will
provide a unique tool for detecting and understanding eruptions flares
and coronal mass ejections in the maximum phase of activity when the
Solar Dynamics Observatory SDO should still be operating
Title: SMESE: a Small Explorer for the Study of Solar Eruptions
Authors: Vial, J. -C.; Auchère, F.; Chang, J.; Fang, C.; Gan, W. Q.;
Molodij, G.; Prado, J. -Y.; Trottet, G.; Wang, C.; Yan, Y. H.
Bibcode: 2006cosp...36.3294V
Altcode: 2006cosp.meet.3294V
The SMESE Small Explorer for the Study of solar Eruptions mission is
a microsatellite proposed by France and China The payload of SMESE
consists of three packages LYOT a suite of two UV and EUV imagers and
a Lyman alpha coronagraph DESIR an Infra-Red Telescope working at 35
and 150 mu and HEBS a High Energy Burst Spectrometer working in X- and
gamma -rays The status of research on Coronal Mass Ejections will be
briefly recalled in the context of on-going missions such as SOHO TRACE
and RHESSI The scientific objectives and the profile of the mission
will be described With a launch around 2011 SMESE will provide a unique
tool for detecting and understanding eruptions flares and coronal mass
ejections in the maximum phase of activity and for the determination
of the morphology of the low corona from where the solar wind originates
Title: An atlas of solar events: 1996 2005
Authors: Artzner, G.; Auchère, F.; Delaboudinière, J. P.; Bougnet, M.
Bibcode: 2006AdSpR..38..390A
Altcode:
Coronal mass ejections (CMEs) are observed in the plane of the sky in
coronographic images. As the solar surface is masked by an occulting
disk it is not clear whether halo CMEs are directed towards or away
from the Earth. Observations of the solar corona on the solar disk
by the extreme ultraviolet imaging telescope (EIT) on board the Solar
Heliospheric Observatory SoHO can help to resolve this. Quasi-continuous
observations of the solar corona were obtained from April 1997 up to
the current date at a 12 min cadence in the coronal line of FeXII, as
part of a “CME watch program”. At a slower 6 h cadence an additional
synoptic program investigates the chromosphere and the corona at four
different wavelengths. Large coronal solar events appear when viewing
animations of the CME watch program. Fainter events do appear when
viewing running difference animations of the CME watch program. When
looking for additional spectral information from raw running differences
of the synoptic program it is difficult to disentangle intrinsic solar
events from the parasitic effect of the solar rotation. We constructed
at www.ias.u-psud.fr/medoc/EIT/movies/ an atlas of more than 40,000
difference images from the synoptic programme, corrected for an
average solar rotation, as well as more than 200,000 instantaneous and
difference images from the CME watch program. We present case studies
of specific events in order to investigate the source of darkenings or
dimmings in difference images, due to the removal of emitting material,
the presence of obscuring material or large changes in temperature. As
the beneficial effect of correcting for the solar rotation vanishes at
the solar limb, we do not investigate the case of prominence Doppler
dimming. As a by-product of the atlas of solar events we obtain a
number of quiet time sequences well suited to precisely measure the
differential solar rotation by the apparent displacement of tracers.
Title: The Beleinos cornerstone: the Sun, the star close to Earth
Authors: Appourchaux, T.; Auchère, F.; Bocchialini, K.; Bonnet,
R. M.; Gabriel, A.; Vial, J. -C.
Bibcode: 2005ESASP.588..389A
Altcode: 2005tssc.conf..389A
No abstract at ADS
Title: Observations of Solar EUV Radiation with the CORONAS-F/SPIRIT
and SOHO/EIT Instruments
Authors: Slemzin, V. A.; Kuzin, S. V.; Zhitnik, I. A.; Delaboudiniere,
J. -P.; Auchere, F.; Zhukov, A. N.; van der Linden, R.; Bugaenko,
O. I.; Ignat'ev, A. P.; Mitrofanov, A. V.; Pertsov, A. A.; Oparin,
S. N.; Stepanov, A. I.; Afanas'ev, A. N.
Bibcode: 2005SoSyR..39..489S
Altcode:
The SPIRIT complex onboard the CORONAS-F satellite has routinely
imaged the Sun in the 171, 175, 195, 284, and 304 Å spectral bands
since August 2001. The complex incorporates two telescopes. The
Ritchey-Chretien telescope operates in the 171, 195, 284, and
304 Å bands and has an objective similar to that of the SOHO/EIT
instrument. The Herschel telescope obtains solar images synchronously
in the 175 and 304 Å bands with two multilayer-coated parabolic
mirrors. The SPIRIT program includes synoptic observations, studies of
the dynamics of various structures on the solar disk and in the corona
up to 5 solar radii, and coordinated observations with other spaceborne
and ground-based telescopes. In particular, in the period 2002-2003,
synoptic observations with the SPIRIT Ritchey-Chretien telescope were
coordinated with regular 6-hour SOHO/EIT observations. Since June 2003,
when EIT data were temporarily absent ( SOHO keyholes), the SPIRIT
telescope has performed synoptic observations at a wavelength of 175
A. These data were used by the Solar Influence Data Analysis Center
(SIDC) at the Royal Observatory of Belgium for an early space weather
forecast. We analyze the photometric and spectral parameters of the
SPIRIT and EIT instruments and compare the integrated (over the solar
disk) EUV fluxes using solar images obtained with these instruments
during the CORONAS-F flight from August 2001 through December 2003.
Title: A Model for Solar EUV Flux Helium Photoionization Throughout
the 3-Dimensional Heliosphere
Authors: Auchère, F.; McMullin, D. R.; Cook, J. W.; Newmark, J. S.;
von Steiger, R.; Witte, M.
Bibcode: 2005ESASP.592..327A
Altcode: 2005soho...16E..49A; 2005ESASP.592E..49A
No abstract at ADS
Title: EMMA: The EIT MPEG Movies Archive at the Multi Experiment
Data Operation Center
Authors: Auchère, F.
Bibcode: 2005ESASP.592..671A
Altcode: 2005ESASP.592E.133A; 2005soho...16E.133A
No abstract at ADS
Title: CORONAS-F/SPIRIT EUV observations of October-November 2003
solar eruptive events in combination with SOHO/EIT data
Authors: Grechnev, V. V.; Chertok, I. M.; Slemzin, V. A.; Kuzin, S. V.;
Ignat'ev, A. P.; Pertsov, A. A.; Zhitnik, I. A.; DelaboudinièRe,
J. -P.; AuchèRe, F.
Bibcode: 2005JGRA..110.9S07G
Altcode: 2005JGRA..11009S07G
The extraordinary solar activity of October-November 2003 manifested
itself in many powerful eruptive events, including large coronal mass
ejections (CMEs) and extremely powerful flares. A number of major
events were accompanied by practically all known phenomena of the solar
activity, both local and large-scale, and caused severe space weather
disturbances. We study large-scale posteruptive activity manifestations
on the Sun associated with CMEs, i.e., dimmings and coronal waves,
observed with extreme-ultraviolet telescopes, the SPIRIT on the
CORONAS-F spacecraft and the EIT on the SOHO. During that period,
observations with a cadence of 15 to 45 min were carried out by the
SPIRIT in the 175 Å and 304 Å bands simultaneously. The EIT observed
with 12-min cadence in the 195 Å band as well as with 6-hour cadence
in the 171, 284, and 304 Å bands. These data complement each other
both in the temporal and spectral coverage. Our analysis reveals
that largest-scale dimmings covered almost the whole southern part of
the Sun's visible side and exhibited homology, with one homological
structure being changed to another configuration on 28 October. These
structures show connections between large superactive and smaller
regions that constituted a huge activity complex responsible for the
extraordinary solar activity of that period. Coronal waves were observed
at 175 Å as well as at 195 Å in some events, in areas where there were
no active regions, but in the 175 Å images they look fainter. They
were not accompanied by deep, long-living dimmings. By contrast,
such dimmings were observed in active regions, in their vicinity,
and between them. These facts rule out the direct relation of the
phenomena of long-term dimmings and coronal waves. On 18 November, a
motion of an ejecta was observed at the solar disk as a propagation of
a dark feature only in the 304 Å band, which can be interpreted as an
absorption in a "cloud" formed from material of the eruptive filament,
which probably failed to become a CME core.
Title: Formation flyers applied to solar coronal observations:
the ASPICS mission
Authors: Vives, S.; Lamy, P.; Auchere, F.; Vial, J. -C.; Koutchmy,
S.; Arnaud, J.; Prado, J. -Y.; Frassetto, F.; Naletto, G.
Bibcode: 2005SPIE.5901..305V
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 observing
the inner corona inside typically 2-2.5 solar radii. Formation flyers
open new perspectives and allow to conceive 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 approximately 100 m from the first one. ASPICS
(Association de Satellites Pour l'Imagerie Coronographique Solaire)
is a mission proposed to CNES in the framework of their demonstration
program of formation flyers which is presently under study to exploit
this technique for coronal observations. In the baseline concept,
ASPICS includes three coronagraphs operating in three spectral
domains: the visible continuum (K-corona brightness), the HI Lyman
alpha emission line at 121.6 nm, and the HeII emission line at 30.4
nm. Their unvignetted fields of view extend from 1.1 to 3.2 solar radii
with a typical spatial resolution of 3 arcsec. In order to connect
coronal activity to photospheric events, ASPICS further includes
two disk imagers. The first one is devoted to the HI Lyman alpha
emission line. The second one is a multi-channel instrument similar to
SOHO/EIT and devoted to the HeII (30.4 nm), FeIX/X (17.1 nm) and FeXII
(19.5 nm) emission lines. Two concepts of the space system are under
consideration: a symmetric configuration where the disk imagers and
the external occulter are on one spacecraft and the coronagraphs on
the other, an asymmetric configuration where the external occulter is
on one spacecraft and the scientific instruments are regrouped on the
other one.
Title: Innovative designs for the imaging suite on Solar Orbiter
Authors: Auchere, Frederic; Song, Xueyen; Rouesnel, Frederic;
Appourchaux, Thierry; Fourmon, Jean-Jacques; Le Clec'h,
Jean-Christophe; Berthe, Michel; Defise, Jean-Marc; Mazy, Emmanuel;
Rochus, Pierre L.; Mercier, Raymond; Ravet, Marie-Francoise
Bibcode: 2005SPIE.5901..298A
Altcode:
Orbiting around the Sun on an inclined orbit with a 0.2 UA perihelion,
the Solar Orbiter probe will provide high resolution views of the Sun
from various angles unattainable from Earth. Together with a set of high
resolution imagers, the Full Sun Imager is part of the EUV Imaging suite
of the Solar Orbiter mission. The mission's ambitious characteristics
draw severe constraints on the design of these instruments. We present
a photometrically efficient, compact, and lightweight design for the
Full Sun Imager. With a 5 degrees field of view, this telescope will
be able to see the global solar coronal structure from high viewing
angles. Thermal solutions reducing the maximum power trapped in the
High Resolution Imagers are also proposed.
Title: The Heliospheric He II 30.4 nm Solar Flux During Cycle 23
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
Bibcode: 2005ApJ...625.1036A
Altcode:
Because of the orbit characteristics of the vast majority of
spacecraft, the solar flux has predominantly been measured at Earth
or at least in the plane of the ecliptic. Therefore, the existing
data do not directly demonstrate the fact that the latitudinal
distribution of the extreme-ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV the nonuniform distribution of very
contrasted bright features (i.e., active regions) and dark features
(i.e., coronal holes) at the surface of the Sun produces both the
obvious rotational (or longitudinal) modulation of the flux and also
a strong latitudinal anisotropy. Although largely ignored up to now,
the latitudinal anisotropy affects the physical conditions in the
corona and heliosphere and should therefore be taken into account in
several solar and heliospheric physics applications. We describe in this
paper a technique for computing the He II 30.4 nm flux at an arbitrary
position in the heliosphere from Solar and Heliospheric Observatory
(SOHO) EUV Imaging Telescope (EIT) images. This procedure was used to
produce daily all-sky maps of the 30.4 nm flux from 1996 January to 2003
August, covering the first 8 yr of solar cycle 23. As could be expected
from the examination of the EIT images, the 30.4 nm flux was found to
be strongly anisotropic. The anisotropy Ipol/Ieq
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% difference was also discovered
between the north and south polar fluxes. The generalization of this
technique to other lines of the EUV and far-ultraviolet (FUV) spectrum
is discussed.
Title: Effect of the H I Lyα Chromospheric Flux Anisotropy on the
Total Intensity of the Resonantly Scattered Coronal Radiation
Authors: Auchère, F.
Bibcode: 2005ApJ...622..737A
Altcode:
In modeling of the resonantly scattered solar coronal Lyα line of
H I, the intensity of the chromospheric source is often assumed to
be uniform. We investigate the validity of this assumption. After
establishing a correlation between the H I 121.6 nm and He II 30.4 nm
line intensities, we build Carrington maps of the Lyα chromosphere from
SOHO EUV Imaging Telescope data. These maps are used to compute the Lyα
irradiance throughout the corona and heliosphere. A 15% latitudinal
anisotropy is found at 1 AU at solar minimum, and this value becomes
larger closer to the Sun. The effect of the flux anisotropy on the
total intensity of the Lyα resonantly scattered coronal radiation is
quantified. We find that at solar minimum, the uniform-disk assumption
leads to systematic overestimates of the total intensity of the polar
regions by 15% on average. The evolution of this effect with solar
activity and the case of other resonantly scattered coronal lines
are discussed.
Title: Model of the all-sky He II 30.4 nm solar flux
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
Bibcode: 2005AdSpR..35..388A
Altcode:
Because of the orbit characteristics of the vast majority of spacecraft,
the solar flux has been generally measured at Earth or in the plane
of the ecliptic. So far, most published studies did not consider
the fact that the extreme ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV, the distribution of very contrasted
bright and dark features at the surface of the Sun produces both the
obvious rotational (longitudinal) modulation of the flux, but also a
strong latitudinal anisotropy. Although largely ignored up to now, the
latitudinal anisotropy affects the physical conditions in the corona
and heliosphere. We describe an empirical model of the all-sky He II
30.4 nm flux based on EIT/ SOHO data. The 30.4 nm flux was found to be
strongly anisotropic. The anisotropy Ipol/ Ieq
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% asymmetry was also discovered
between the north and south polar fluxes.
Title: A Model For EUV Flux Throughout The 3-Dimensional Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
Bibcode: 2004AGUFMSH21B0423M
Altcode:
After July 2001, when Ulysses moved from 30 to 80 degrees in solar
latitude, the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. We have developed a three-dimensional model for solar EUV
fluxes observed at any heliospheric position, using daily SOHO EIT
observations, over successive Carrington rotations, projected to
any heliospheric position. The combined effects of solar rotational
and latitude-dependent flux variability are explicitly treated in
this model. The flux model has been directly compared with other
direct irradiance observations in the ecliptic plane with the SOHO/SEM
irradiance time series for validation. We then use this flux to compute
the photoionization rate of the in-flowing neutral He, and compare the
modeled change with time along the spacecraft trajectory with the direct
measurements from the out -of -ecliptic Ulysses GAS observations. The
3-D model developed will be directly applicable to STEREO EUV images
from the SECCHI instrument suite. As the two spacecraft separate, the
amount of the solar surface observed will increase through the mission,
providing more accurate solar inputs.
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.
Bibcode: 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: On the nature of EIT waves, EUV dimmings and their link to CMEs
Authors: Zhukov, A. N.; Auchère, F.
Bibcode: 2004A&A...427..705Z
Altcode:
EIT waves and extreme-ultraviolet (EUV) dimmings attract particular
attention as they frequently accompany Coronal Mass Ejections
(CMEs). We present several examples of EIT waves and EUV dimmings with
particular morphologies previously unreported in the literature. We
report for the first time an EIT wave in the Fe XV (284 Å) bandpass
of the SOHO/EIT instrument. The observations of this event confirm
previous results that an EIT wave is a purely coronal phenomenon
that does not propagate in the transition region plasma. Two EIT
wave events initiated close to the solar limb are investigated,
thus permitting us to see simultaneously the wave and the magnetic
configuration of the CME. These observations suggest that EIT wave
can be regarded as a bimodal phenomenon. The wave mode represents a
wave-like propagating disturbance. Its characteristic features are
propagation of a bright front to large distances from dimming sites
and quasi-circular appearance. The eruptive mode is the propagation
of a dimming and of an EIT wave as a result of successive opening of
magnetic field lines during the CME lift-off. It can be identified by
noting the expansion of a dimming and the appearance of another dimming
ahead of a bright front. We reveal the temperature structure of the EUV
dimmings that appeared after the classical EIT wave event on May 12,
1997, using differential emission measure (DEM) maps obtained through
the analysis of images in four EIT bandpasses. The part of the CME
mass contained in the low corona observed by the EIT is estimated to
be about 1015 g. It appears that around 50% of this total
CME mass in the low corona is contained outside of transient coronal
holes. It is shown that at present it is difficult to reconcile all
the observational facts into a coherent physical model. In particular,
the physical nature of the wave mode of EIT waves remains elusive. Movies are available in electronic form at http://www.edpsciences.org
Title: EIT Observations of the 15 November 1999 Mercury Transit
Authors: Auchère, F.; Artzner, G. E.
Bibcode: 2004SoPh..219..217A
Altcode:
The Mercury transit of 15 November 1999 has been observed from space
by the SOHO and TRACE spacecraft. We exploited the data recorded by
EIT/SOHO to determine the stray-light level and the plate-scale of
the instrument. The asymmetric distribution of stray light across the
images is confirmed, but the absolute amount was found to be higher
than previously estimated. The plate scale averaged over wavelengths
was found to be 2.627±0.001 arc sec pixel−1, in excellent
agreement with two previous and independent determinations.
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.
Bibcode: 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: EUVI: the STEREO-SECCHI extreme ultraviolet imager
Authors: Wuelser, Jean-Pierre; Lemen, James R.; Tarbell, Theodore
D.; Wolfson, C. J.; Cannon, Joseph C.; Carpenter, Brock A.; Duncan,
Dexter W.; Gradwohl, Glenn S.; Meyer, Syndie B.; Moore, Augustus S.;
Navarro, Rosemarie L.; Pearson, J. D.; Rossi, George R.; Springer,
Larry A.; Howard, Russell A.; Moses, John D.; Newmark, Jeffrey S.;
Delaboudiniere, Jean-Pierre; Artzner, Guy E.; Auchere, Frederic;
Bougnet, Marie; Bouyries, Philippe; Bridou, Francoise; Clotaire,
Jean-Yves; Colas, Gerard; Delmotte, Franck; Jerome, Arnaud; Lamare,
Michel; Mercier, Raymond; Mullot, Michel; Ravet, Marie-Francoise;
Song, Xueyan; Bothmer, Volker; Deutsch, Werner
Bibcode: 2004SPIE.5171..111W
Altcode:
The Extreme Ultraviolet Imager (EUVI) is part of the SECCHI instrument
suite currently being developed for the NASA STEREO mission. Identical
EUVI telescopes on the two STEREO spacecraft will study the structure
and evolution of the solar corona in three dimensions, and specifically
focus on the initiation and early evolution of coronal mass ejections
(CMEs). The EUVI telescope is being developed at the Lockheed Martin
Solar and Astrophysics Lab. The SECCHI investigation is led by the
Naval Research Lab. The EUVI"s 2048 x 2048 pixel detectors have a
field of view out to 1.7 solar radii, and observe in four spectral
channels that span the 0.1 to 20 MK temperature range. In addition to
its view from two vantage points, the EUVI will provide a substantial
improvement in image resolution and image cadence over its predecessor
SOHO-EIT, while complying with the more restricted mass, power, and
volume allocations on the STEREO mission.
Title: H/He+ intensity variations of the cool corona
Authors: Noens, J. -C.; Balestat, M. -F.; Jimenez, R.; Rochain, S.;
Romeuf, D.; Auchere, F.; Delaboudiniere, P.; Koutchmy, S.
Bibcode: 2004IAUS..223..291N
Altcode: 2005IAUS..223..291N
No abstract at ADS
Title: An atlas of solar events: 1997-2004
Authors: Artzner, G.; Auchère, F.; Delaboudinière, J. P.; Bougnet, M.
Bibcode: 2004cosp...35.2494A
Altcode: 2004cosp.meet.2494A
Coronal mass ejections (CMEs) are observed in the plane of the sky
from coronographic images. As the solar surface is then masked by an
occulting disk, it is not clear wether halo CMEs are directed towards
the Earth or in the opposite direction. Observations of the solar corona
on the solar disk from the Extreme Ultraviolet Imaging Telescope EIT on
board the Solar Heliospheric Observatory SoHO do help in order to make
a choice. Quasi-continuous observations of the corona of the Sun have
been therefore obtained from april 1997 up to now at a twelve minute
cadence in the coronal line of FeXII, as a CME watch program. At a
slower six hours cadence an additional synoptic program investigates
the chromosphere and the corona at four different wavelengths. Large
coronal solar events appear when viewing animations of the CME watch
program. Fainter events do appear when viewing running difference
animations of the CME watch program. When looking for additional
spectral information from raw running differences of the synoptic
program it is difficult to disentangle intrinsic solar events from
the parasitic effect of the solar rotation. We constructed from the
synoptic program observations an atlas of more than 20 000 difference
images corrected for an average solar rotation. We present case studies
of specific events in order to investigate the source of darkenings in
difference images, either removal of emitting material, interposition
of obscuring material or large changes of temperature. Statistics
of brigtenings and darkenings along solar cycle 23 are presented. We
speculate about future observations from the STEREO mission in order
to obtain better diagnostics about darkenings. As a by product of the
atlas of solar events we obtain a number of quiet time sequences well
suited in order to precisely measure the differnetial solar rotation
by the apparent displacement of tracers.
Title: Model for 3-D Heliospheric EUV Irradiance and Photoionization
Authors: Auchère, F.; McMullin, D.; Cook, J.; Newmark, J.; Vonsteiger,
R.; Witte, M.; Quémerais, E.
Bibcode: 2004cosp...35.2558A
Altcode: 2004cosp.meet.2558A
For 8 years now, the EIT instrument on board SOHO continuously monitored
the solar activity in four passbands of the EUV spectrum. With the
SOHO mission extended, it is likely that the final EIT data set will
cover one complete solar cycle. This exceptional data set offers an
unprecedented opportunity to investigate the long-term variations of
the solar EUV irradiance. Furthermore, with the spatial resolution of
the EIT/SOHO instrument, the data can also be used to study variations
of the solar irradiance with heliocentric latitude. It is indeed
clear that the wide intensity range of the various emitting regions
(polar coronal holes, equatorial active regions, etc.) produces
a latitude-dependant irradiance. To date, due to the small number
of off-ecliptic measurements, very few attempts have been made to
investigate these variations. We present here an empirical model of the
EUV solar flux at any point in the heliosphere derived from EIT/SOHO
data. At 30.4 nm, the anisotropy I_⊥ / I_∥ between the irradiance
above (⊥) and within (∥) the ecliptic plane is found to range
from about 0.8 at solar minimum to about 0.6 at solar maximum. Our
anisotropic EUV fluxes are used to improve the present estimates of
the photoionization rate of in-flowing neutral helium. These new rates
are compared to the relative changes of neutral helium density measured
by the GAS/Ulysses instrument.
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.
Bibcode: 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: The solar high-resolution imager - coronagraph LYOT mission
Authors: Vial, Jean-Claude; Song, Xueyan; Lemaire, Philippe; Gabriel,
Alan H.; Delaboudiniere, Jean-Pierre; Bocchialini, Karine; Koutchmy,
Serge L.; Lamy, Philippe L.; Mercier, Raymond; Ravet, Marie Francoise;
Auchere, Frederic
Bibcode: 2003SPIE.4853..479V
Altcode:
The LYOT (LYman Orbiting Telescope) solar mission is proposed to
be implemented on a micro-satellite of CNES (France) under phase A
study. It includes two main instruments, which image the solar disk
and the low corona up to 2.5 Ro in the H I Lyman-α line
at 121.6 nm. The spatial resolution is about 1” for the disk and
2.5” for corona. It also carries an EIT-type telescope in the He II
(30.4 nm) line. The coronagraph needs a super polished mirror at the
entrance pupil to minimize the light scattering. Gratings and optical
filters are used to select the Lyman-α wavelength. VUV cameras with
2048×2048 pixels record solar images up to every 10 seconds. The
satellite operates at a high telemetry rate (more then 100 kb/s,
after onboard data compression). The envisaged orbits are either
geostationary or heliosynchronous. Possible launch dates could be end
of 2006 - beginning of 2007.
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.
Bibcode: 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: 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.
Bibcode: 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 Radiometric Calibration of the Extreme Ultraviolet
Imaging Telescope
Authors: Clette, F.; Hochedez, J. -F.; Newmark, J. S.; Moses, J. D.;
Auchère, F.; Defise, J. -M.; Delaboudinière, J. -P.
Bibcode: 2002ISSIR...2..121C
Altcode: 2002ESASR...2..121C; 2002rcs..conf..121C
After a five-year effort, the analysis of the pre-flight and in-flight
calibrations of EIT is finally yielding firm results. In this
introductory overview, we will summarize what we learned "internally"
from EIT itself. This includes the interpretation of the pre-flight
calibrations, the original flat-field components (CCD, grid), the
in-flight determination of the point-spread function and straylight and
the compensation of the in-orbit response degradation. Based on this
experience, we conclude with some suggestions of possible improvements
to future calibrations, on SOHO and other planned missions.
Title: SWRI/LASP Sounding Rocket Inter-Calibration With The Eit
Instrument On Board SOHO
Authors: Auchère, Frédéric; Hassler, Donald M.; Slater, David C.;
Woods, Thomas N.
Bibcode: 2001SoPh..202..269A
Altcode:
Two successful sounding rocket flights were launched on 15 May 1997 and
2 November 1998 with an objective of providing inter-calibration with
several of the instruments on board SOHO and TRACE. We will discuss
here the results of the inter-calibration between the SwRI/LASP rocket
imaging instruments and the Extreme-ultraviolet Imaging Telescope (EIT)
on SOHO. The Multiple XUV Imager (MXUVI) sounding rocket instrument
is a multi-layer mirror telescope equipped with an internal occulter
and light trap to provide full-disk images of Fe ix/x 17.1 nm and
off-limb observations of He ii 30.4 nm. The SOHO/EIT instrument is
also a full-disk multi-layer imager with four channels, Fe ix/x 17.1
nm, Fe xii 19.5 nm, Fe xv 28.4 nm and He ii 30.4 nm. By comparison
with the EIT observations taken at the same time, we provide new
flat-field determinations for EIT which help quantify the sensitivity
degradation of the EIT detector, as well as provide a measure of the
off-limb stray-light characteristics of the two instruments. We find
that the EIT stray-light function is strongly asymmetric, with greater
stray light in the 17.1 and 19.5 nm quadrants than the 30.4 and 28.4
nm quadrants. Two possible causes of this asymmetry are the polishing
processes of the EIT mirrors and the asymmetric support grid pattern
in the foil mesh at the EIT pupil.
Title: The Height Variations of the Solar Chromosphere
Authors: Auchère, F.
Bibcode: 2001AGUSM..SH21B03A
Altcode:
We present a five year survey of the height of the solar chromosphere,
as observed by the Extreme Ultraviolet Imaging Telescope (EIT) in
its four bandpasses : 17.1 nm (FeIX/FeX), 19.5 nm (FeXII), 28.4 nm
(FeXV), and 30.4 nm (HeII). Spatial pole-equator variations, as well
as long-term temporal variations were investigated. The chromosphere
was found to be prolate in all four wavelengths, with typical values
of Δ D/D = 5x 10-3 in HeII and 1x 10-3 in the
three iron lines. We found a very good correlation of the prolateness
effect with the presence of polar coronal holes, and could follow
its vanishing as the solar cycle peaked. The similitude between our
results and previous observations made in various other lines suggest
that the prolateness is a fundamental aspect of the solar atmosphere.
Title: In-flight Calibration of SOHO EIT
Authors: Newmark, J. S.; Cook, J. W.; Auchere, F.; Moses, J. D.;
Clette, F.
Bibcode: 2001AGUSM..SP21B06N
Altcode:
The SOHO EIT response has varied both temporally and spatially
throughout the mission. A large effort has been put forth into
understanding instrument responsivity changes, the spectral response
and absolute calibration. The latter two have been completed (Dere et
al. 2000, Newmark 2000). The response degradation process consists of
several components which are difficult to separate in detail. The two
basic processes contributing to the degradation are 1) the absorption
of EUV before it interacts with the CCD by a surface contaminant plus
possible blackening of the entrance filter and 2) the reduction of
charge collection efficiency (CCE) in the CCD due to EUV induced device
damage. A method utilizing the in-flight calibration lamps has been
developed which accurately characterizes the sensitivity changes. We
present absolutely calibrated SOHO EIT data from 1996 - 2000.
Title: An Observational Study of Helium in the Solar Corona with
the EIT Instrument on Board the SOHO Spacecraft
Authors: Auchere, F.
Bibcode: 2000PhDT........69A
Altcode:
Helium is the second most abundant element in the Universe. The
understanding of the physicals processes associated with helium as well
as the determination of the helium abundance both have implications
in various research fields such as cosmology, stellar evolution
or the physics of the solar wind. Helioseismology techniques give
accurate measurements of the helium abundance in the solar interior,
spectroscopic techniques provide diagnostics in the photosphere and
in the chromosphere, and in situ measurements in the solar wind at 1
A.U. are carried out with particle detectors. But very few observations
of helium exist in the corona and therefore, our knowledge of helium
at intermediate distances between the photosphere and the solar wind
is essentially based on theoretical studies. The present work is a
tentative contribution to help constraint the observational knowledge
of helium in the solar corona. The EIT telescope on board the SOHO
spacecraft can observe the solar corona up to 2 Rs in an interval
of wavelengths in the extreme ultraviolet spectrum including the
resonance line of the He+ ion at 30.378 nm. This line being formed in
the solar corona by resonant scattering of the chromospheric flux by
coronal He+ ions, its intensity is proportional to the number density
of He+ ions. Therefore, the observation of this line in the corona can
potentially provide interesting diagnostics of the coronal helium. In
spite of the contamination by other spectral lines, it seems that a
non negligible fraction of the signal recorded by EIT in its 30.4 nm
bandpass can be attribuated to the resonance line of He+. Furthermore,
a preliminary study seems to show that the observed intensity gradients
are anomalously low in the polar regions. The aim of the present work
was to investigate further these preliminary results. We first carried
out a detailed critical analysis of the characteristics of the EIT
instrument in order to confirm that the 30.378 nm line of He+ in the
corona can be detected in the 30.4 nm bandpass of EIT. This analysis
implies a precise evaluation of several calibration parameters such
as the flat-field of the detector, the contamination of the 30.4 nm
bandpass and the instrumental stray light level. In order to interpret
the intensities measured with EIT, we developed a model of the intensity
of the resonance line of He+ in the corona, with the existing models
for the Lyman alpha line of neutral hydrogen as a starting point. This
model requires as an input some physical parameters such as the
electron temperature and electron density, which were independently
determined either from previous results or from new observations. The
comparisons between the observed intensity and the prediction of the
model seem to confirm the results of the preliminary analysis. In
the equatorial regions, the intensity gradient of the resonance line
of He+ is compatible with the electron density scale height. But at
high latitudes in the polar coronal holes, the intensity gradient seems
significatively smaller than what is expected from the computations. One
can interpret this observation by an accumulation of helium in the polar
coronal holes, where the fast solar wind originate. If the coronal
ionisation balance computed in the model is valid, this accumulation
of He+ could be the signature of an enhanced helium abundance in the
corona. Some theoretical models of the corona/solar wind system show
that the helium abundance could indeed be 20% or more in the corona,
even though it is 10% in the solar interior and 4% in the solar
wind. Because helium is four times more massive than hydrogen, it is
clear the an enhanced helium abundance in the corona would greatly
impact the energy and momentum uxes in the solar wind. However, further
observations, especially with a better spectral resolution and a lower
stray light level, are needed to confirm those of EIT.
Title: Results from the 2 November 1998 SwRI/LASP Sounding Rocket
Campaign
Authors: Hassler, D. M.; Auchere, F.; Handy, B.; Strachan, L.; Slater,
D.; Woods, T. N.
Bibcode: 2000SPD....31.0216H
Altcode: 2000BAAS...32..813H
We present results from the November 2, 1998 SwRI/LASP sounding rocket
campaign with the dual purpose of providing inter-calibration for the
SOHO/EIT and TRACE instruments and providing a measure of the coronal
helium abundance by direct comparison of the coronal Ly-alpha lines
of He II (304 angstroms) and H I (1216 angstroms). The sounding rocket
payload provided full-disk solar images of Fe IX/X 171 and H I Ly-alpha
1216 for inter-calibration with the SOHO/EIT and TRACE instruments,
respectively, as well as off-limb observations of the He II 304 line to
be compared with off-limb SOHO/UVCS observations of the H I 1216 line
to provide a constraint on the coronal helium abundance. This work
has been funded in part by NASA under grant NAG5-5140 to Southwest
Research Institute.
Title: In-Flight Determination of the Plate Scale of the
Extreme-Ultraviolet Imaging Telescope
Authors: Auchère, F.; DeForest, C. E.; Artzner, G.
Bibcode: 2000ApJ...529L.115A
Altcode:
Using simultaneous observations of the Michelson Doppler Imager
and Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar
and Heliospheric Observatory spacecraft, we determined in flight
the plate scale of the EIT. We found a value of 2.629"+/-0.001"
pixel-1, in fair agreement with the 2.627"+/-0.001"
pixel-1 value deduced from recent laboratory measurements
of the focal length and much higher by 7 σ than the 2.622"
pixel-1 value of the preflight calibrations. The plate
scale is found to be constant across the field of view, confirming
the negligible distortion level predicted by the theoretical models
of the EIT. Furthermore, the 2 σ difference between our results and
the latest laboratory measurements, although statistically small, may
confirm a recent work suggesting that the solar photospheric radius
may be 0.5 Mm lower than the classically adopted value of 695.99 Mm.
Title: In Flight Determination of the Plate Scale of the EIT
Authors: Auchere, F.; DeForest, C. E.; Artzner, G.
Bibcode: 1999astro.ph.12213A
Altcode:
Using simultaneous observations of the MDI and EIT instruments on
board the SoHO spacecraft, we determined in flight the plate scale
of the EIT. We found a value of 2.629+-0.001 arc seconds per pixel,
in fair agreement with the 2.627+-0.001 arc seconds per pixel value
deduced from recent laboratory measurements of the focal length, and
much higher by 7 sigma than the 2.622 arc seconds per pixel value of
the pre-flight calibrations. The plate scale is found to be constant
across the field of view, confirming the negligible distortion level
predicted by the theoretical models of the EIT. Furthermore, the 2 sigma
difference between our results and the latest laboratory measurements,
although statistically small, may confirm a recent work suggesting that
the solar photospheric radius may be 0.5 Mm lower than the classically
adopted value of 695.99 Mm.
Title: SwRI/LASP sounding rocket intercalibration with the EIT
instrument on board SoHO
Authors: Auchere, Frederic; Hassler, Donald M.; Slater, David C.;
Woods, Thomas N.
Bibcode: 1999SPIE.3765..351A
Altcode:
Two successful sounding rocket flights were launched on May 15, 1997
and November 2, 1998 with an objective of providing inter-calibration
with several of the instruments on board SoHO and TRACE. We will
discuss here the results of the inter-calibration between the SwRI/LASP
rocket imaging instruments and the Extreme-UV Imaging Telescope (EIT)
on SoHO. The MXUVI sounding rocket instrument is a multi-layer mirror
telescope equipped with a special internal occulter and light trap to
provide full disk imags of Fe IX/X 17.1 nm and off-limb observations of
He II 30.4 nm. The SoHO/EIT instrument is also a full disk multi-layer
imager with four channels, Fe IX/X 17.1 nm, FE XII 19.5 nm, Fe XV 28.4
nm and He II 30.4 nm. By comparison with the EIT observations taken at
the same time we can quantify the sensitivity degradation of the EIT
detector, as well as measure the off-limb stray- light characteristics
of the two instruments.
Title: The Prolate Solar Chromosphere
Authors: Koutchmy, S.; di Folco, E.; Auchere, F.; Baudin, F.;
Delaboudinière, J. -P.; Koutchmy, O.; Noëns, J. -C.; Rondi, S.;
Jimemez, R.; Smartt, R. N.
Bibcode: 1999ESASP.446..385K
Altcode: 1999soho....8..385K
The solar prolateness above h=2Mm is now well established from
measurements performed during the years of solar minimum in HeII, Hα
and K3CaII lines. Low level coronal emissions usually penetrate deep
enough to completely mask this effect and show CH, quite similarly to
the behaviour of the HeI lines (D3; 1083nm) which does not show the
prolateness. We discuss the most recent observations for 1999 given
by a new facility developped at Pic du Midi Observatory (HACO II)
and we compare the results with EIT results in HeII. We also brielfly
discuss the possible interpretations of the prolateness effect. We
favor topological effects implying a large number of nano-flares
and ejecta during the interactions of small-scale low level network
magnetic fields with the more static large-scale magnetic field.
Title: In-flight characterization and compensation of the optical
properties of the EIT instrument
Authors: Defise, Jean-Marc; Clette, Frederic; Auchere, Frederic
Bibcode: 1999SPIE.3765..341D
Altcode:
Onboard the SOHO spacecraft, the Extreme UV Imaging Telescope
(EIT) is imagin successfully the EUV solar corona since January
96. EIT is a normal incidence telescope, segmented in 4 separate
quadrants. Each of those quadrants reflects extreme UV (EUV) light
in a narrow bandpass defined by multilayer coatings deposited on
the mirrors and by aluminum filters used to reject the visible and
IR part of the solar irradiance. The specific configuration of the
optical system is generating artifacts that must be compensated in the
raw solar images. However, the only information available to improve
image quality comes from the continuous survey of the solar corona
accomplished in flight by EIT. In-flight image characteristics and
instrumental aspects are discussed in this paper, showing how methods
can be derived to clean up the EIT data. The current investigations
are addressing the internal vignetting, the shadow pattern of grids
supporting the focal filters, the determination of the instrumental
point spread function and the assessment of the telescope focusing,
as well as the relation between those factors.
Title: SwRI/LASP sounding rocket inter-calibration with SOHO/EIT.
Authors: Hassler, D. M.; Auchere, F.; Slater, D.; Woods, T. N.
Bibcode: 1999BAAS...31.1241H
Altcode:
No abstract at ADS
Title: SwRI/LASP Sounding Rocket Inter-calibration with SOHO/EIT
Authors: Hassler, D. M.; Auchere, F.; Slater, D.; Woods, T. N.
Bibcode: 1999AAS...19410803H
Altcode:
Two successful sounding rocket flights were launched on May 15, 1997
and Nov. 2, 1998 with an objective of providing inter-calibration with
several of the instruments on SOHO and TRACE. We will discuss here
the results of this inter-calibration between the SwRI/LASP rocket
imaging instruments and the Extreme Ultraviolet Imaging Telescope (EIT)
on SOHO. The Multiple XUV Imager (MXUVI) sounding rocket instrument is
a multi-layer mirror telescope equiped with a special internal occulter
and light trap to provide full disk images of Fe IX/X 171 A and off-limb
observations of He II 304 A. The SOHO/EIT instrument is also a full disk
multi-layer imager with four channels, Fe IX/X 171 A, Fe XII 195 A,
Fe XV 284 A and He II 304 A. By comparison with the EIT observations
taken at the same time we can quantify the sensitivity degradation or
"limb-burning" of the EIT detector and construct a "flat field", as
well as measure the off-limb stray light characteristics of the EIT
He II 304 A channel. We will also discuss the radiometric calibration
transfer between the rocket instrument and EIT.
Title: Equivalent focal length measurements
Authors: Artzner, Guy E.; Auchere, Frederic; Delaboudiniere,
Jean-Pierre; Hochedez, Jean-Francois E.
Bibcode: 1999SPIE.3737...32A
Altcode:
Converting linear coordinates in the plane of the detector of
an astronomical instrument to celestial coordinates involves in
principle the equivalent focal length of the instrument. However,
most methods in astrometry manage to reduce observations in a global
manner without actually measuring a focal length. We point out a case
for solar space observations where the long term stability of angular
distance measurements is better than the ground calibration of the
angular value of a pixel. We report and discuss this ground calibration.
Title: The prolate solar chromosphere
Authors: Auchere, F.; Boulade, S.; Koutchmy, S.; Smartt, R. N.;
Delaboudiniere, J. P.; Georgakilas, A.; Gurman, J. B.; Artzner, G. E.
Bibcode: 1998A&A...336L..57A
Altcode:
We present a comparative analysis of the chromospheric solar
limb prolateness, using strictly simultaneous H_alpha ground-based
observations and Heriptsize{II} space-based observations. The typical
prolateness is found to be Delta D/D=5.5*E(-3) in Heriptsize{II}
and 1.2*E(-3) in H_alpha . The first measurements in the 30.4 nm
Heriptsize{II} line over a period of two years, as well as coronal
data, are discussed to explore further the origin of the prolateness
and its possible consequences.
Title: The polar extension of the solar chromosphere
Authors: Auchère, F.; Delaboudinière, J. P.; Koutchmy, S.;
Boulade, S.
Bibcode: 1998ESASP.421..245A
Altcode: 1998sjcp.conf..245A
No abstract at ADS