Author name code: hochedez
ADS astronomy entries on 2022-09-14
author:"Hochedez, Jean-Francois"
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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: In-flight performance of the solar UV radiometer LYRA/PROBA-2
Authors: Stockman, Y.; BenMoussa, A.; Dammasch, I.; Defise, J. -M.;
Dominique, M.; Halain, J. -P.; Hochedez, J. -F.; Koller, S.; Schmutz,
W.; Schühle, U.
Bibcode: 2017SPIE10565E..0AS
Altcode:
LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload
(Fig. 1). The PROBA-2 [1] mission has been launched on 02 November
2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude
of 725 km. Its nominal operation duration is two years with possible
extension of 2 years. PROBA-2 is a small satellite developed under
an ESA General Support Technology Program (GSTP) contract to perform
an in-flight demonstration of new space technologies and support a
scientific mission for a set of selected instruments [2]. PROBA-2 host
17 technological demonstrators and 4 scientific instruments. The mission
is tracked by the ESA Redu Mission Operation Center. One of the four
scientific instruments is LYRA that monitors the solar irradiance at a
high cadence (> 20 Hz) in four soft X-Ray to VUV large passbands: the
"Lyman-Alpha" channel, the "Herzberg" continuum range, the "Aluminium"
and "Zirconium" filter channels. The radiometric calibration is
traceable to synchrotron source standards [3]. LYRA benefits from wide
bandgap detectors based on diamond. It is the first space assessment
of these revolutionary UV detectors for astrophysics. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
the strong solar visible light) and, therefore, visible light blocking
filters become superfluous. To correlate the data of this new detector
technology, silicon detectors with well known characteristics are also
embarked. Due to the strict allocated mass and power budget (5 kg, 5W),
and poor priority to the payload needs on such platform, an optimization
and a robustness of the instrument was necessary. The first switch-on
occured on 16 November 2009. Since then the instrument performances
have been monitored and analyzed during the commissioning period. This
paper presents the first-light and preliminary performance analysis.
Title: LYRA, solar uv radiometer on the technology demonstration
platform PROBA-2
Authors: Stockman, Y.; Hochedez, J. -F.; Schmutz, W.; BenMoussa, A.;
Defise, J. -M.; Denis, F.; D'Olieslaeger, M.; Dominique, M.; Haenen,
K.; Halain, J. -P.; Koller, S.; Koizumi, S.; Mortet, V.; Rochus, P.;
Schühle, U.; Soltani, A.; Theissen, A.
Bibcode: 2017SPIE10567E..3KS
Altcode:
LYRA is a solar radiometer part of the PROBA 2 micro satellite
payload. LYRA will monitor the solar irradiance in four soft X-Ray -
VUV passbands. They have been chosen for their relevance to Solar
Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/
Herzberg continuum range, 3/ Aluminium filter channel (including
He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric
calibration is traceable to synchrotron source standards. The
stability will be monitored by on-board calibration sources (LEDs),
which allow us to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first
space assessment of revolutionary UV detectors. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
visible light) and therefore, make dispensable visible light blocking
filters. To correlate the data of this new detector technology, well
known technology, such as Si detectors are also embarked. The SWAP
EUV imaging telescope will operate next to LYRA on PROBA-2. Together,
they will provide a high performance solar monitor for operational
space weather nowcasting and research. LYRA demonstrates technologies
important for future missions such as the ESA Solar Orbiter.
Title: Segmentation of photospheric magnetic elements corresponding to
coronal features to understand the EUV and UV irradiance variability
Authors: Zender, J. J.; Kariyappa, R.; Giono, G.; Bergmann, M.;
Delouille, V.; Damé, L.; Hochedez, J. -F.; Kumara, S. T.
Bibcode: 2017A&A...605A..41Z
Altcode:
Context. The magnetic field plays a dominant role in the solar
irradiance variability. Determining the contribution of various magnetic
features to this variability is important in the context of heliospheric
studies and Sun-Earth connection.
Aims: We studied the solar
irradiance variability and its association with the underlying magnetic
field for a period of five years (January 2011-January 2016). We used
observations from the Large Yield Radiometer (LYRA), the Sun Watcher
with Active Pixel System detector and Image Processing (SWAP) on board
PROBA2, the Atmospheric Imaging Assembly (AIA), and the Helioseismic
and Magnetic Imager (HMI) on board the Solar Dynamics Observatory
(SDO).
Methods: The Spatial Possibilistic Clustering Algorithm
(SPoCA) is applied to the extreme ultraviolet (EUV) observations
obtained from the AIA to segregate coronal features by creating
segmentation maps of active regions (ARs), coronal holes (CHs) and
the quiet sun (QS). Further, these maps are applied to the full-disk
SWAP intensity images and the full-disk (FD) HMI line-of-sight (LOS)
magnetograms to isolate the SWAP coronal features and photospheric
magnetic counterparts, respectively. We then computed full-disk
and feature-wise averages of EUV intensity and line of sight (LOS)
magnetic flux density over ARs/CHs/QS/FD. The variability in these
quantities is compared with that of LYRA irradiance values.
Results: Variations in the quantities resulting from the segmentation,
namely the integrated intensity and the total magnetic flux density
of ARs/CHs/QS/FD regions, are compared with the LYRA irradiance
variations. We find that the EUV intensity over ARs/CHs/QS/FD is well
correlated with the underlying magnetic field. In addition, variations
in the full-disk integrated intensity and magnetic flux density values
are correlated with the LYRA irradiance variations.
Conclusions:
Using the segmented coronal features observed in the EUV wavelengths as
proxies to isolate the underlying magnetic structures is demonstrated
in this study. Sophisticated feature identification and segmentation
tools are important in providing more insights into the role of various
magnetic features in both the short- and long-term changes in the solar
irradiance. The movie associated to Fig. 2 is available at http://www.aanda.org
Title: Main results of the PICARD mission
Authors: Meftah, M.; Corbard, T.; Hauchecorne, A.; Irbah, A.; Boumier,
P.; Chevalier, A.; Schmutz, W.; Ikhlef, R.; Morand, F.; Renaud, C.;
Hochedez, J. -F.; Cessateur, G.; Turck-Chièze, S.; Salabert, D.;
Rouzé, M.; van Ruymbeke, M.; Zhu, P.; Kholikov, S.; Koller, S.;
Conscience, C.; Dewitte, S.; Damé, L.; Djafer, D.
Bibcode: 2016SPIE.9904E..0ZM
Altcode:
PICARD is a mission devoted to solar variability observations through
imagery and radiometric measurements. The main goal is to provide data
for scientific investigation first in the area of solar physics, and
second in the assessment of the influence of the solar variability on
the Earth climate variability. PICARD contains a double program with
in-space and on-ground measurements. The PICARD spacecraft was launched
on June 15, 2010, commissioned in-flight in October of the same year
and was retired in April 2014. The PICARD ground-based observatory is
operational since May 2011. We shall give a short overview of the PICARD
instrumentation. New estimates of the absolute values of the total solar
irradiance, of the solar spectral irradiance at typical wavelengths,
and of the solar oblateness will be given. We will also report about
helioseismic studies. Finally, we will present our current results
about solar radius variations after six years of solar observation.
Title: Solar irradiance observations with PREMOS filter radiometers
on the PICARD mission: In-flight performance and data release
Authors: Cessateur, G.; Schmutz, W.; Wehrli, C.; Gröbner, J.;
Haberreiter, M.; Kretzschmar, M.; Rozanov, E.; Schöll, M.; Shapiro,
A.; Thuillier, G.; Egorova, T.; Finsterle, W.; Fox, N.; Hochedez,
J. -F.; Koller, S.; Meftah, M.; Meindl, P.; Nyeki, S.; Pfiffner, D.;
Roth, H.; Rouzé, M.; Spescha, M.; Tagirov, R.; Werner, L.; Wyss,
J. -U.
Bibcode: 2016A&A...588A.126C
Altcode:
Context. The PREcision Monitoring Sensor (PREMOS) is a solar radiometer
on board the French PICARD mission that was launched in June 2010
and decommissioned in April 2014.
Aims: The PREMOS radiometer
obtains solar irradiance measurements in specific spectral windows
in the UV, visible, and near-infrared. In this paper, the PREMOS
data and calibration methods are presented.
Methods: Using
back-up channels, the degradation can theoretically be assessed to
correct operational channels. However, a strong degradation within all
PREMOS channels requires the application of additional methods, namely
using back-up channels and assessing the degradation via a proxy-based
model.
Results: The corrected Level 3 PREMOS data are then used
in different contexts in order to be validated. First, the signature
of the p-mode are retrieved from the PREMOS data. The Venus transit
allows us to empirically determine the intrinsic noise level within the
PREMOS high cadence data for the visible and near-infrared channels. We
then compare the PREMOS data directly to other data sets, namely
from the SOLar-STellar Irradiance Comparison Experiment (SOLSTICE)
and the Solar Irradiance Monitor (SIM) instruments on board the SOlar
Radiation and Climate Experiment (SORCE) spacecraft. Regarding the
UV channels, we found an excellent correlation over the lifetime of
the PREMOS mission. The ratio between SORCE and PREMOS observations
is always less than 1%. Regarding the SSI measurements in the visible
and near-infrared, a comparison of short-term variations (I.e. 27-day
modulation) shows a rather good correlation by taking into consideration
the intrinsic noise within both SIM and PREMOS observations.
Title: Solar Spectral Irradiance Observations from the PICARD/PREMOS
Radiometer
Authors: Cessateur, G.; Schöll, M.; Schmutz, W. K.; Wehrli, C.;
Groebner, J.; Haberreiter, M.; Kretzschmar, M.; Shapiro, A.; Thuillier,
G. O.; Finsterle, W.; Fox, N.; Hochedez, J. F.; Koller, S.; Meftah,
M.; Nyeki, S.; Pfiffner, D.; Roth, H.; Rouze, M.; Spescha, M.; Tagirov,
R.; Werner, L.; Wyss, J.
Bibcode: 2015AGUFMSH32A..06C
Altcode:
Space weather and space climate studies require accurate Solar Spectral
Irradiance (SSI) observations. The PREcision Monitoring Sensor (PREMOS)
instrument aboard the PICARD satellite acquired solar irradiance
measurements in specific spectral windows in the UV, visible and near
infrared from October 2010 to March 2014. This contribution aims at
presenting the Level 3 data, corrected for non solar features as well
as for degradation. These level 3 data has been tested over different
scientific cases, such as observations during the Venus transit and
the presence of the p-mode signature within high-cadence data. The
PREMOS Level 3 data have also been compared to others data sets,
namely the SOLSTICE and SIM instruments aboard SORCE, for nearly 3
and half years. An excellent correlation has been found for the UV
spectral ranges. We have also found a rather good correlation for
visible and near-infrared observations for short-term variations,
for which an error of about 200 ppm has been estimated within PREMOS
visible and near-infrared observations. The PREMOS data could also
be used to address several scientific topics, i.e. for validating
semi-empirical models of the solar irradiance. We will emphasize
about our new irradiance model, COSIR for Code of Solar Irradiance
Reconstruction, which is successful at reproducing the solar modulation
as seen in the PREMOS, SoHO/Virgo and SORCE data.
Title: Degradation assessment of LYRA after 5 years on orbit -
Technology Demonstration -
Authors: BenMoussa, A.; Giordanengo, B.; Gissot, S.; Dammasch, I. E.;
Dominique, M.; Hochedez, J. -F.; Soltani, A.; Bourzgui, N.; Saito,
T.; Schühle, U.; Gottwald, A.; Kroth, U.; Jones, A. R.
Bibcode: 2015ExA....39...29B
Altcode: 2015ExA...tmp....1B
We present a long-term assessment of the radiometric calibration and
degradation of the Large Yield Radiometer (LYRA), which has been on
orbit since 2009. LYRA is an ultraviolet (UV) solar radiometer and is
the first space experiment using aboard a pioneering diamond detector
technology. We show that LYRA has degraded after the commissioning phase
but is still exploitable scientifically after almost 5 years on orbit
thanks to its redundancy design and calibration strategy correcting for
instrument degradation. We focus on the inflight detector's calibration
and show that diamond photodetectors have not degraded while silicon
reference photodiodes that are even less exposed to the Sun show an
increase of their dark current and a decrease of their photoresponse.
Title: On the Determination and Constancy of the Solar Oblateness
Authors: Meftah, M.; Irbah, A.; Hauchecorne, A.; Corbard, T.;
Turck-Chièze, S.; Hochedez, J. -F.; Boumier, P.; Chevalier, A.;
Dewitte, S.; Mekaoui, S.; Salabert, D.
Bibcode: 2015SoPh..290..673M
Altcode: 2015SoPh..tmp...22M
The equator-to-pole radius difference
(Δr=Req−Rpol) is a fundamental property of
our star, and understanding it will enrich future solar and stellar
dynamical models. The solar oblateness (Δ⊙) corresponds
to the excess ratio of the equatorial solar radius (Req)
to the polar radius (Rpol), which is of great interest for
those working in relativity and different areas of solar physics. Δr
is known to be a rather small quantity, where a positive value of
about 8 milli-arcseconds (mas) is suggested by previous measurements
and predictions. The Picard space mission aimed to measure Δr with a
precision better than 0.5 mas. The Solar Diameter Imager and Surface
Mapper (SODISM) onboard Picard was a Ritchey-Chrétien telescope that
took images of the Sun at several wavelengths. The SODISM measurements
of the solar shape were obtained during special roll maneuvers of the
spacecraft by 30° steps. They have produced precise determinations of
the solar oblateness at 782.2 nm. After correcting measurements for
optical distortion and for instrument temperature trend, we found a
solar equator-to-pole radius difference at 782.2 nm of 7.9±0.3 mas
(5.7±0.2 km) at one σ. This measurement has been repeated several
times during the first year of the space-borne observations, and we
have not observed any correlation between oblateness and total solar
irradiance variations.
Title: On solar radius measurements with PICARD
Authors: Meftah, M.; Irbah, A.; Hauchecorne, A.; Corbard, T.; Hochedez,
J. F.
Bibcode: 2014AGUFMSH13B4090M
Altcode:
Solar diameter measurements performed from the ground for several
decades seem to indicate a relation between the solar diameter and the
solar activity. If this relationship is confirmed, it would be possible
to use measurements of solar diameter as a proxy of solar activity
in the past since the 1715 solar eclipses, and to use this input for
the reconstruction of solar irradiance in climate models. However the
interpretation of ground observations is controversial, ground-based
measurements being affected by refraction, by atmospheric turbulence,
and perhaps by atmospheric aerosols scattering. The only way to be free
from atmospheric effects is to measure from space. This is the reason
why, since the beginning, the PICARD program included a space and a
ground component set up at the Calern site of the Observatoire de la
Côte dAzur. During the last 4 years, the PICARD space mission has been
used for observing the apparent solar diameter. First results of the
astrometry program include a study of the June 2012 Venus transit for
solar diameter determination. From this, the value of the solar radius
from one astronomical unit was found to be equal to 959.86 arc-seconds
at 607.1 nm. However, concerning observed variations in time of the
solar radius, instrumental effects affect the results. Space is known
to represent a harsh environment for optical instruments. Nevertheless,
we can use the PICARD data to monitor the solar radius variation. PICARD
aims to perpetuate historical series of the solar radius measurements,
in particular during the solar cycle 24. This paper presents solar
radius measurements obtained with PICARD.
Title: Solar Radius Determination from Sodism/Picard and HMI/SDO
Observations of the Decrease of the Spectral Solar Radiance during
the 2012 June Venus Transit
Authors: Hauchecorne, A.; Meftah, M.; Irbah, A.; Couvidat, S.; Bush,
R.; Hochedez, J. -F.
Bibcode: 2014ApJ...783..127H
Altcode:
On 2012 June 5-6, the transit of Venus provided a rare opportunity
to determine the radius of the Sun using solar imagers observing a
well-defined object, namely, the planet and its atmosphere, partially
occulting the Sun. A new method has been developed to estimate the solar
radius during a planetary transit. It is based on the estimation of the
spectral solar radiance decrease in a region around the contact between
the planet and the Sun at the beginning of the ingress and at the
end of the egress. The extrapolation to zero of the radiance decrease
versus the Sun-to-Venus apparent angular distance allows estimation of
the solar radius at the time of first and fourth contacts. This method
presents the advantage of being almost independent on the plate scale,
the distortion, the refraction by the planetary atmosphere, and on the
point-spread function of the imager. It has been applied to two space
solar visible imagers, SODISM/PICARD and HMI/SDO. The found results are
mutually consistent, despite their different error budgets: 959.''85
± 0.''19 (1σ) for SODISM at 607.1 nm and 959.''90 ± 0.''06 (1σ)
for HMI at 617.3 nm.
Title: Picard SODISM, a Space Telescope to Study the Sun from the
Middle Ultraviolet to the Near Infrared
Authors: Meftah, M.; Hochedez, J. -F.; Irbah, A.; Hauchecorne, A.;
Boumier, P.; Corbard, T.; Turck-Chièze, S.; Abbaki, S.; Assus,
P.; Bertran, E.; Bourget, P.; Buisson, F.; Chaigneau, M.; Damé,
L.; Djafer, D.; Dufour, C.; Etcheto, P.; Ferrero, P.; Hersé, M.;
Marcovici, J. -P.; Meissonnier, M.; Morand, F.; Poiet, G.; Prado,
J. -Y.; Renaud, C.; Rouanet, N.; Rouzé, M.; Salabert, D.; Vieau,
A. -J.
Bibcode: 2014SoPh..289.1043M
Altcode: 2013arXiv1303.0731M
The Solar Diameter Imager and Surface Mapper (SODISM) onboard the
Picard space mission provides wide-field images of the photosphere
and chromosphere of the Sun in five narrow bandpasses centered at
215.0, 393.37, 535.7, 607.1, and 782.2 nm. The Picard spacecraft
was successfully launched on 15 June 2010 into a Sun-synchronous
dawn-dusk orbit. The Picard space mission represents a European asset
in collecting solar observations useful to improve Earth climatic
models. The scientific payload consists of the SODISM imager and
of two radiometers, SOlar VAriability Picard (SOVAP) and PREcision
MOnitor Sensor (PREMOS), which measure the Total Solar Irradiance
(TSI) and part of the Solar Spectral Irradiance (SSI).
Title: The Plate Scale of the SODISM Instrument and the Determination
of the Solar Radius at 607.1 nm
Authors: Meftah, M.; Hauchecorne, A.; Crepel, M.; Irbah, A.; Corbard,
T.; Djafer, D.; Hochedez, J. -F.
Bibcode: 2014SoPh..289....1M
Altcode:
Knowledge of the Solar Diameter Imager and Surface Mapper (SODISM) plate
scale is a fundamental parameter for obtaining the solar radius. We
have determined the plate scale of the telescope on the ground and
in flight onboard the Picard spacecraft. The results show significant
differences; the main reason is that the conditions of observation are
not the same. In addition, the space environment has an impact on the
performance of a metrology instrument. Therefore, calibration in space
and under the same conditions of observation is crucial. The transit of
Venus allowed us to determine the plate scale of the SODISM telescope
and hence the absolute value of the solar radius. The transit was
observed from space by the Picard spacecraft on 5 - 6 June 2012. We
exploited the data recorded by SODISM to determine the plate scale
of the instrument, which depends on the characteristics of optical
elements (mirrors, filters, or front window). The mean plate scale at
607.1 nm is found to be 1.0643 arcseconds pixel−1 with
3×10−4 RMS. The solar radius at 607.1 nm from 1 AU is
found to be equal to 959.86 arcseconds.
Title: Segmentation of coronal features to understand the solar EUV
and UV irradiance variability
Authors: Kumara, S. T.; Kariyappa, R.; Zender, J. J.; Giono, G.;
Delouille, V.; Chitta, L. P.; Damé, L.; Hochedez, J. -F.; Verbeeck,
C.; Mampaey, B.; Doddamani, V. H.
Bibcode: 2014A&A...561A...9K
Altcode:
Context. The study of solar irradiance variability is of great
importance in heliophysics, the Earth's climate, and space weather
applications. These studies require careful identifying, tracking
and monitoring of active regions (ARs), coronal holes (CHs), and the
quiet Sun (QS).
Aims: We studied the variability of solar
irradiance for a period of two years (January 2011-December 2012)
using the Large Yield Radiometer (LYRA), the Sun Watcher using APS and
image Processing (SWAP) on board PROBA2, and the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory (SDO).
Methods: We used the spatial possibilistic clustering algorithm (SPoCA)
to identify and segment coronal features from the EUV observations of
AIA. The AIA segmentation maps were then applied on SWAP images, and
parameters such as the intensity, fractional area, and contribution
of ARs/CHs/QS features were computed and compared with the full-disk
integrated intensity and LYRA irradiance measurements.
Results:
We report the results obtained from SDO/AIA and PROBA2/SWAP images
taken from January 2011 to December 2012 and compare the resulting
integrated full-disk intensity with PROBA2/LYRA irradiance. We
determine the contributions of the segmented features to EUV and UV
irradiance variations. The variations of the parameters resulting
from the segmentation, namely the area, integrated intensity, and
relative contribution to the solar irradiance, are compared with LYRA
irradiance. We find that the active regions have a great impact on the
irradiance fluctuations. In the EUV passbands considered in this study,
the QS is the greatest contributor to the solar irradiance, with up
to 63% of total intensity values. Active regions, on the other hand,
contribute to about 10%, and off-limb structures to about 24%. We
also find that the area of the features is highly variable suggesting
that their area has to be taken into account in irradiance models,
in addition to their intensity variations.
Conclusions:
We successfully show that the feature extraction allows us to use
EUV telescopes to measure irradiance fluctuations and to quantify
the contribution of each part to the EUV spectral solar irradiance
observed with a calibrated radiometer. This study also shows that
SPoCA is viable, and that the segmentation of images can be a useful
tool. We also provide the measurement correlation between SWAP and
AIA during this analysis.
Title: Picard, a solar mission dedicated to the study of the Sun:
current results
Authors: Meftah, Mustapha; Hochedez, Jean-François; Dewitte, Steven;
Hauchecorne, Alain; Irbah, Abdanour; Boumier, Patrick; Corbard,
Thierry; Turck-Chi, Sylvaine; Zhu, Ping
Bibcode: 2014cosp...40E2063M
Altcode:
PICARD is a mission dedicated to the simultaneous measurements of the
solar total and spectral irradiances, its diameter and asphericity. It
also probes seismically the solar interior by analysing its local
intensity variation. PICARD contains a double program with in-space and
on-ground measurements. Space observations are a priori most favourable,
however, space entails also technical challenges, a harsh environment,
and a finite mission lifetime. The PICARD spacecraft, launched on June
15, 2010 will retire in April 2014. On ground, the instruments are less
affected by in-space degradation and maintenance is easily provided
so if the atmosphere is properly monitored and taken into account,
they still represent an opportunity to generate the needed long-term
time-series. That is why ground measurements have been carried out since
May 2011-and will be pursued after the space program. In this talk,
we describe both sets of instruments, and then present our current
results. In particular, we show new estimates of the absolute values
of the total solar irradiance, diameter and oblateness. We also report
about helioseismic studies and about the apparent absence of mid-term
trend in the measurement of the diameter.
Title: Dark signal correction for a lukecold frame-transfer CCD. New
method and application to the solar imager of the PICARD space mission
Authors: Hochedez, J. -F.; Timmermans, C.; Hauchecorne, A.; Meftah, M.
Bibcode: 2014A&A...561A..17H
Altcode: 2013arXiv1303.1437H
Context. Astrophysical observations must be corrected for their
imperfections of instrumental origin. When charge-coupled devices
(CCDs) are used, their dark signal is one such hindrance. In their
pristine state, most CCD pixels are cool, that is, they exhibit a
low quasi-uniform dark current, which can be estimated and corrected
for. In space, after having been hit by an energetic particle, pixels
can turn hot, viz. they start delivering excessive, less predictable,
dark current. The hot pixels therefore need to be flagged so that
a subsequent analysis may ignore them.
Aims: The image data
of the PICARD-SODISM solar telescope require dark signal correction
and hot pixel identification. Its E2V 42-80 CCD operates at -7.2 °C
and has a frame-transfer architecture. Both image and memory zones
thus accumulate dark current during integration and readout time,
respectively. These two components must be separated in order to
estimate the dark signal for any given observation. This is the main
purpose of the dark signal model presented in this paper.
Methods: The dark signal time-series of every pixel was processed
by the unbalanced Haar technique to timestamp when its dark signal
changed significantly. In-between these instants, the two components
were assumed to be constant, and a robust linear regression, with
respect to integration time, provides first estimates and a quality
coefficient. The latter serves to assign definitive estimates for
this pixel and that period.
Results: Our model is part of the
SODISM Level 1 data production scheme. To confirm its reliability,
we verified on dark frames that it leaves a negligible residual bias
(5 e-) and generates a small rms error (25 e-
rms). We also examined the distribution of the image zone dark
current. The cool pixel level is found to be 4.0 e-
pxl-1 s-1, in agreement with the predicted
value. The emergence rate of hot pixels was investigated as well. It
yields a threshold criterion at 50 e- pxl-1
s-1. The growth rate is found to be on average ~500 new hot
pixels per day, that is, 4.2% of the image zone area per year.
Conclusions: A new method for dark signal correction of a frame-transfer
CCD operating near -10 °C is described and applied. It allows making
recommendations about the implementation and scientific usage of such
CCDs. Moreover, aspects of the method (adaptation of the unbalanced Haar
technique, dedicated robust linear regression) have a generic interest.
Title: Preface
Authors: Berghmans, D.; De Groof, A.; Dominique, M.; Hochedez, J. -F.;
Leibacher, J. W.
Bibcode: 2013SoPh..286....1B
Altcode:
No abstract at ADS
Title: The Projects for Onboard Autonomy (PROBA2) Science Centre:
Sun Watcher Using APS Detectors and Image Processing (SWAP) and
Large-Yield Radiometer (LYRA) Science Operations and Data Products
Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada,
C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher,
P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.;
Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton,
D. B.; Stanger, A.; Stegen, K.; Willems, S.
Bibcode: 2013SoPh..286...93Z
Altcode: 2012SoPh..tmp..142Z
The PROBA2 Science Centre (P2SC) is a small-scale science operations
centre supporting the Sun observation instruments onboard PROBA2:
the EUV imager Sun Watcher using APS detectors and image Processing
(SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's
small, low-cost Projects for Onboard Autonomy (PROBA) and part of
ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted
at the Royal Observatory of Belgium, co-located with both Principal
Investigator teams. The P2SC tasks cover science planning, instrument
commanding, instrument monitoring, data processing, support of outreach
activities, and distribution of science data products. PROBA missions
aim for a high degree of autonomy at mission and system level, including
the science operations centre. The autonomy and flexibility of the P2SC
is reached by a set of web-based interfaces allowing the operators as
well as the instrument teams to monitor quasi-continuously the status of
the operations, allowing a quick reaction to solar events. In addition,
several new concepts are implemented at instrument, spacecraft, and
ground-segment levels allowing a high degree of flexibility in the
operations of the instruments. This article explains the key concepts
of the P2SC, emphasising the automation and the flexibility achieved
in the commanding as well as the data-processing chain.
Title: The LYRA Instrument Onboard PROBA2: Description and In-Flight
Performance
Authors: Dominique, M.; Hochedez, J. -F.; Schmutz, W.; Dammasch,
I. E.; Shapiro, A. I.; Kretzschmar, M.; Zhukov, A. N.; Gillotay, D.;
Stockman, Y.; BenMoussa, A.
Bibcode: 2013SoPh..286...21D
Altcode: 2013arXiv1302.6525D
The Large Yield Radiometer (LYRA) is an XUV-EUV-MUV (soft X-ray to
mid-ultraviolet) solar radiometer onboard the European Space Agency
Project for On-Board Autonomy 2 (PROBA2) mission, which was launched
in November 2009. LYRA acquires solar-irradiance measurements at
a high cadence (nominally 20 Hz) in four broad spectral channels,
from soft X-ray to MUV, which have been chosen for their relevance
to solar physics, space weather, and aeronomy. We briefly review
the design of the instrument, give an overview of the data products
distributed through the instrument website, and describe how the data
are calibrated. We also briefly present a summary of the main fields
of research currently under investigation by the LYRA consortium.
Title: Helioseismology with PICARD
Authors: Corbard, T.; Salabert, D.; Boumier, P.; Appourchaux, T.;
Hauchecorne, A.; Journoud, P.; Nunge, A.; Gelly, B.; Hochedez, J. F.;
Irbah, A.; Meftah, M.; Renaud, C.; Turck-Chièze, S.
Bibcode: 2013JPhCS.440a2025C
Altcode: 2013arXiv1301.6940C
PICARD is a CNES micro-satellite launched in June 2010 [17]. Its main
goal is to measure the solar shape, total and spectral irradiance during
the ascending phase of the activity cycle. The SODISM telescope onboard
PICARD also allows us to conduct a program for helioseismology in
intensity at 535.7 nm [5]. One-minute cadence low-resolution full images
are available for a so-called medium-l program, and high-resolution
images of the limb recorded every 2 minutes are used to study mode
amplification near the limb in the perspective of g-mode search. First
analyses and results from these two programs are presented here.
Title: Segmentation of Coronal Features to Understand the UV and
EUV Irradiance Variations
Authors: Kumara, S. T.; Hochedez, Jean-François; Damé, Luc;
Doddamani, Vijayakumar H.; Kariyappa, R.
Bibcode: 2012cosp...39.1641K
Altcode: 2012cosp.meet.1641K
No abstract at ADS
Title: Computer Vision for the Solar Dynamics Observatory (SDO)
Authors: Martens, P. C. H.; Attrill, G. D. R.; Davey, A. R.; Engell,
A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar, S. H.;
Savcheva, A.; Su, Y.; Testa, P.; Wills-Davey, M.; Bernasconi, P. N.;
Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F.; Cirtain, J. W.;
DeForest, C. E.; Angryk, R. A.; De Moortel, I.; Wiegelmann, T.;
Georgoulis, M. K.; McAteer, R. T. J.; Timmons, R. P.
Bibcode: 2012SoPh..275...79M
Altcode: 2011SoPh..tmp..144M; 2011SoPh..tmp..213M; 2011SoPh..tmp....8M
In Fall 2008 NASA selected a large international consortium to produce
a comprehensive automated feature-recognition system for the Solar
Dynamics Observatory (SDO). The SDO data that we consider are all of the
Atmospheric Imaging Assembly (AIA) images plus surface magnetic-field
images from the Helioseismic and Magnetic Imager (HMI). We produce
robust, very efficient, professionally coded software modules that
can keep up with the SDO data stream and detect, trace, and analyze
numerous phenomena, including flares, sigmoids, filaments, coronal
dimmings, polarity inversion lines, sunspots, X-ray bright points,
active regions, coronal holes, EIT waves, coronal mass ejections
(CMEs), coronal oscillations, and jets. We also track the emergence and
evolution of magnetic elements down to the smallest detectable features
and will provide at least four full-disk, nonlinear, force-free magnetic
field extrapolations per day. The detection of CMEs and filaments is
accomplished with Solar and Heliospheric Observatory (SOHO)/Large
Angle and Spectrometric Coronagraph (LASCO) and ground-based Hα
data, respectively. A completely new software element is a trainable
feature-detection module based on a generalized image-classification
algorithm. Such a trainable module can be used to find features that
have not yet been discovered (as, for example, sigmoids were in the
pre-Yohkoh era). Our codes will produce entries in the Heliophysics
Events Knowledgebase (HEK) as well as produce complete catalogs for
results that are too numerous for inclusion in the HEK, such as the
X-ray bright-point metadata. This will permit users to locate data on
individual events as well as carry out statistical studies on large
numbers of events, using the interface provided by the Virtual Solar
Observatory. The operations concept for our computer vision system is
that the data will be analyzed in near real time as soon as they arrive
at the SDO Joint Science Operations Center and have undergone basic
processing. This will allow the system to produce timely space-weather
alerts and to guide the selection and production of quicklook images and
movies, in addition to its prime mission of enabling solar science. We
briefly describe the complex and unique data-processing pipeline,
consisting of the hardware and control software required to handle
the SDO data stream and accommodate the computer-vision modules, which
has been set up at the Lockheed-Martin Space Astrophysics Laboratory
(LMSAL), with an identical copy at the Smithsonian Astrophysical
Observatory (SAO).
Title: Preliminary Results on Irradiance Measurements from Lyra
and Swap
Authors: Kumara, S. T.; Kariyappa, R.; Dominique, M.; Berghmans, D.;
Damé, L.; Hochedez, J. F.; Doddamani, V. H.; Chitta, Lakshmi Pradeep
Bibcode: 2012AdAst2012E...5K
Altcode: 2012AdAst2012E..10K
No abstract at ADS
Title: LYRA and SWAP, the two Solar Instruments on-board PROBA2
Authors: Dominique, M.; Berghmans, D.; Schmutz, W. K.; Dammasch, I.;
De Groof, A.; Halain, J.; Hochedez, J.; Kretzschmar, M.; Seaton, D. B.
Bibcode: 2011AGUFMSH13B1949D
Altcode:
PROBA2 (http://proba2.sidc.be) is an ESA micro-satellite that was
launched in November 2009. Two instruments on-board, SWAP and LYRA, are
devoted to solar observations. SWAP (PI: D. Berghmans) is an EUV imager
observing the corona with a bandpass centered on 174 Å at a cadence of
1-2 min. Its high contrast images, large FOV and flexible off-pointing
capabilities make SWAP particularly well suited for the study of coronal
eruptions. LYRA (PI: M. Dominique) is a UV-EUV radiometer observing
in four spectral channels, chosen for their relevance in solar physics
and aeronomy. Its very fast acquisition cadence (up to 100 Hz) allows
scientists to perform detailed analysis of solar flares. We discuss
the characteristics of both instruments, review their performance and
evolution, and highlight their complementarity to other missions. We
also present the data products that can be downloaded from the mission
website and give an overview of the various investigations for which
SWAP and LYRA data are currently used (CMEs, flares, solar variability,
and many others).
Title: The Solar Oblateness Measured On Board The PICARD Spacecraft,
and The Solar Disk Sextant Instrument
Authors: Thuillier, G. O.; Hauchecorne, A.; Sofia, S.; Girard, T.;
Hochedez, J.; Irbah, A.; Marcovici, J.; Meissonnier, M.; Meftah, M.;
Sofia, U. J.
Bibcode: 2011AGUFMSH31D..06T
Altcode:
The PICARD Spacecraft was launched on 15 June 2010. It carries four
instruments. One of them, SODISM is an imaging telescope with a 2K x 2K
CCD detector, dedicated to the measurement of the solar diameter and
the limb shape. Although the data processing is still in a validation
phase, we can already present some preliminary results concerning the
solar oblateness. These measurements are obtained during a special
operation in which the spacecraft turns around the Sun direction. The
rotation, made by 300 angular increments, allows us to determine the
instrument optical distortion and the solar oblateness. The method used
to extract this information will be described. We shall present the
preliminary results as a function of wavelength, and compare them with
measurements obtained with the SDS instrument, and with the predictions
from theoretical modeling.
Title: Monitoring the solar UV irradiance spectrum from the
observation of a few passbands
Authors: Cessateur, G.; Dudok de Wit, T.; Kretzschmar, M.; Lilensten,
J.; Hochedez, J. -F.; Snow, M.
Bibcode: 2011A&A...528A..68C
Altcode:
Context. The solar irradiance in the UV is a key ingredient in space
weather applications; however, because of the lack of continuous
and long-term observations, various indices are still used today
as surrogates for the solar spectral irradiance.
Aims: As
an alternative to current spectrometers we use a few radiometers
with properly chosen passbands and reconstruct the solar spectral
irradiance from their outputs. The feasibility of such a reconstruction
is justified by the high redundancy in the spectral variability.
Methods: Using a multivariate statistical approach, we first compared
six years of daily-averaged UV spectra and a selection of passbands
(from existing radiometers) and solar indices. This leads to a
strategy for defining those passbands that are most appropriate for
reconstructing the spectrum.
Results: With four passdbands chosen
from already existing instruments, we reconstruct the UV spectrum with
a relative error of about 20%. Better performance is achieved with a
combination of passbands than with a combination of indices.
Title: An iterative method in a probabilistic approach to the
spectral inverse problem. Differential emission measure from line
spectra and broadband data
Authors: Goryaev, F. F.; Parenti, S.; Urnov, A. M.; Oparin, S. N.;
Hochedez, J. -F.; Reale, F.
Bibcode: 2010A&A...523A..44G
Altcode: 2010arXiv1010.5170G
Context. Inverse problems are of great importance in astrophysics,
e.g., for deriving information about the physical characteristics
of hot optically thin plasma sources from their extreme ultraviolet
and X-ray spectra.
Aims: We describe and test an iterative
method developed within the framework of a probabilistic approach to
the spectral inverse problem for determining the thermal structures
of the emitting plasma. We also demonstrate applications of this
method to both high resolution line spectra and broadband imaging
data.
Methods: Our so-called Bayesian iterative method (BIM)
is an iterative procedure based on Bayes' theorem and is used to
reconstruct differential emission measure (DEM) distributions.
Results: To demonstrate the abilities of the BIM, we performed various
numerical tests and model simulations establishing its robustness and
usefulness. We then applied the BIM to observable data for several
active regions (AR) previously analyzed with other DEM diagnostic
techniques: both SUMER/SOHO (Landi & Feldman 2008, ApJ, 672, 674)
and SPIRIT/CORONAS-F (Shestov et al. 2010, Astron. Lett., 36, 44)
line spectra data, and XRT/Hinode (Reale et al. 2009, ApJ, 698, 756)
broadband imaging data. The BIM calculations confirmed the main results
for SUMER/SOHO data showing very good quantitative agreement between
both DEMs at log T ≈ 6.5 (T is the temperature in units of Kelvin)
and a slight shift for two maxima at lower temperatures with ≈30-50%
difference in the DEM values for the coolest peak. For the SPIRIT data,
we revised and validated AR DEM results including the inference of hot
plasma in ARs with an emission measure (EM) at temperatures ≈9-15 MK
comparable to the EM at ≈2-4 MK. In the case of XRT broadband data,
the BIM solutions provided evidence of hot plasma at temperatures ≈4-6
MK with EM up to ~30% as compared to that at ≈2-4 MK in a non-flaring
AR on 2006 November 12.
Conclusions: The BIM results show that
this method is an effective tool for determining the thermal structure
of emitting plasma and can be successfully used for the DEM analysis
of both line spectra and broadband imaging data. The BIM calculations
correlate with recent studies confirming the existence of hot plasma
in solar ARs. The BIM results also indicate that the coronal plasma may
have the continuous distributions predicted by the nanoflare paradigm.
Title: The effect of flares on total solar irradiance
Authors: Kretzschmar, Matthieu; de Wit, Thierry Dudok; Schmutz,
Werner; Mekaoui, Sabri; Hochedez, Jean-François; Dewitte, Steven
Bibcode: 2010NatPh...6..690K
Altcode: 2010arXiv1003.5258K
Flares are powerful bursts of energy released by relatively
poorly understood processes that take place in the atmospheres of
stars. However, although solar flares, from our own Sun, are the most
energetic events in the solar system, in comparison to the total output
of the Sun they are barely noticeable. Consequently, the total amount
of radiant energy they generate is not precisely known, and their
potential contribution to variations in the total solar irradiance
incident on the Earth has so far been overlooked. In this work, we
identify a measurable signal from relatively moderate solar flares in
total solar irradiance data. We find that the total energy radiated
by flares exceeds by two orders of magnitude the flare energy radiated
in the soft-X-ray domain only, indicating a major contribution in the
visible domain. These results have implications for our understanding
of solar-flare activity and the variability of our star.
Title: Point-like structures in solar ultraviolet images
Authors: Hochedez, Jean-François; Gissot, Samuel
Bibcode: 2010ada..confE...1H
Altcode:
No abstract at ADS
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: Computer Vision for SDO: First Results from the SDO Feature
Finding Algorithms
Authors: Martens, Petrus C.; Attrill, G.; Davey, A.; Engell, A.;
Farid, S.; Grigis, P.; Kasper, J.; Korreck, K.; Saar, S.; Su, Y.;
Testa, P.; Wills-Davey, M.; Bernasconi, P.; Raouafi, N.; Georgoulis,
M.; Deforest, C.; Peterson, J.; Berghoff, T.; Delouille, V.; Hochedez,
J.; Mampaey, B.; Verbeek, C.; Cirtain, J.; Green, S.; Timmons, R.;
Savcheva, A.; Angryk, R.; Wiegelmann, T.; McAteer, R.
Bibcode: 2010AAS...21630804M
Altcode:
The SDO Feature Finding Team produces robust and very efficient
software modules that can keep up with the relentless SDO data stream,
and detect, trace, and analyze a large number of phenomena including:
flares, sigmoids, filaments, coronal dimmings, polarity inversion
lines, sunspots, X-ray bright points, active regions, coronal holes,
EIT waves, CME's, coronal oscillations, and jets. In addition we track
the emergence and evolution of magnetic elements down to the smallest
features that are detectable, and we will also provide at least four
full disk nonlinear force-free magnetic field extrapolations per day. During SDO commissioning we will install in the near-real time data
pipeline the modules that provide alerts for flares, coronal dimmings,
and emerging flux, as well as those that trace filaments, sigmoids,
polarity inversion lines, and active regions. We will demonstrate
the performance of these modules and illustrate their use for science
investigations.
Title: Fast and Robust Segmentation of Solar EUV Images: Towards
Real Time Use in the Age of SDO
Authors: Mampaey, Benjamin; Delouille, V.; Verbeeck, C.; Hochedez,
J.; Barra, V.
Bibcode: 2010AAS...21640211M
Altcode: 2010BAAS...41..874M
Solar images from space telescopes contain a wealth of information
on solar variability, of great importance both in solar physics and
in view of Space Weather applications. Obtaining this information,
however, requires the ability to process large amounts of data
over long periods in an objective fashion. In previous work,
we have proposed a multi-channel unsupervised spatially-constrained
multichannel fuzzy clustering algorithm (SPoCA) that automatically
segments EUV solar images into Active Regions (AR), Coronal Holes (CH),
and Quiet Sun (QS). Applying SPoCA to SoHO-EIT images on almost the
full 23rd solar cycle, we obtained variations of area, mean intensity,
and relative contributions of AR, CH, and QS to the solar irradiance,
consistent with previous results. The Royal Observatory of Belgium
is a co-investigator on the SDO Science Center, a suite of software
pipeline modules for automated feature recognition and analysis of the
Solar Dynamics Observatory data. As such, we will deliver our Active
Region segmentation tool, SPoCA, to the SDO Science Center, where it
will be inserted into the SDO pipeline at Lockheed Martin Solar and
Astrophysical Laboratory to run in near real time on SDO-AIA data. In the present poster, we present the fine-tuning of the algorithm and
its implementation for optimal segmentation and performance. We show
how to combine SPoCA's detection of AR on subsequent images in order
to allow for automated tracking and naming of any region of interest,
paving the way for systematic temporal follow-up studies of AR, CH,
and QS. Finally, we indicate how to tailor the method to the
needs of the high resolution EUV images soon to be delivered by the
EUV telescope on board the Solar Dynamics Observatory.
Title: First results from the LYRA solar UV radiometer
Authors: Hochedez, Jean-François; Dammasch, I.; Schmutz, Werner
Bibcode: 2010cosp...38.1090H
Altcode: 2010cosp.meet.1090H
On November 2, 2009, the PROBA2 space mission of ESA was launched
into a sun-synchronous polar orbit allowing quasi-permanent solar
observation. Onboard PROBA2, LYRA is the first radiometer in space
that benefits from diamond ultraviolet detectors. LYRA consists of four
large pass band channels. Each channel observes the irradiance of the
Sun behind a thin metallic foil or behind an interference filter. The
detectors are either UV silicon diodes or diamond detectors, the latter
having been specifically designed for LYRA. The combination of the
spectral transmission of the filters and of the responsivity of the
detectors makes the twelve LYRA channels sensitive to different soft
X-ray and UV pass bands. Their exact choice was made in relation
to scientific questions in solar physics, aeronomy, and Space
Weather. `First Light' of the experiment occurred on January 6, 2010,
and LYRA was subsequently commissioned successfully. After few days,
it measured the first solar flares of the new solar cycle, with an
unprecedented high time resolution of 0.5 s. In the spring of 2010,
LYRA data will start feeding research investigations and space weather
forecasts. The proposed talk presents early results obtained with the
measurements of the first months in space.
Title: Solar-blind UV detectors based on wide band gap semiconductors
Authors: Schuhle, Udo; Hochedez, Jean-Francois
Bibcode: 2010ISSIR...9..429S
Altcode:
Solid-state photon detectors based on semiconductors other than
silicon are not yet considered mature technology but their current
development opens new possibilities, also for space observations. Such
devices are especially attractive for ultraviolet radiation detection,
as semiconductor materials with band gaps larger than that of silicon
can be produced and used as "visible-blind" or "solar-blind" detectors
that are not affected by daylight. Here we evaluate the advantages
of such detectors compared to silicon-based devices and report on the
semiconductor detectors that have been fabricated in recent years with
materials having large band-gap energies. We describe the most common
pixel designs and characterize their general properties.
Title: Distributing and mining SDO data in Europe
Authors: Parenti, Susanna; Delouille, Véronique; Dalla, Silvia;
Bocchialini, Karine; Ballans, Herv; Boyes, David; Chapman, Steve;
Hochedez, Jean-François; Mampaey, Benjamin; March, Mike S.; Soubrie,
Elie; Walsh, Robert
Bibcode: 2010cosp...38.2883P
Altcode: 2010cosp.meet.2883P
The properties of the highly dynamic Sun will soon be revealed by the
newly launched SDO, with data provided by its three instruments: AIA,
HMI and EVE. This suite will produce, for the first time in solar
physics, a large volume of data, equivalent to about 1.5 Tb/day,
by observing the full disk Sun continuously at high cadence. A
backbone network of data centres has been established to handle
these data and redistribute them to Europe. The Royal Observatory
of Belgium (Belgium) will receive the entire flow directly from the
Harvard-Smithsonian Center for Astrophysics. This will next be further
redistributed to University of Central Lancashire (United Kingdom),
and to Institut d'Astrophysique Spatiale (France). These institutes
will also permanently store part of the data. With such huge data rate,
it is necessary to develop automated algorithms that scan the data
and extract information related to important events or features. The
European partners have gathered within an ISSI team on 'Mining and
exploiting the NASA Solar Dynamics Observatory data in Europe', a.k.a
the Soldyneuro project. One of the outputs from the ISSI team will be
to use the feature recognition algorithms to populate the Heliophysics
Events Knowledgebase (HEK) hosted by LMSAL, and provide a service as
added value to the local database centers.
Title: Automated Feature and Event Detection with SDO AIA and HMI Data
Authors: Davey, Alisdair; Martens, P. C. H.; Attrill, G. D. R.;
Engell, A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar,
S. H.; Su, Y.; Testa, P.; Wills-Davey, M.; Savcheva, A.; Bernasconi,
P. N.; Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F. .; Cirtain,
J. W.; Deforest, C. E.; Angryk, R. A.; de Moortel, I.; Wiegelmann,
T.; Georgouli, M. K.; McAteer, R. T. J.; Hurlburt, N.; Timmons, R.
Bibcode: 2010cosp...38.2878D
Altcode: 2010cosp.meet.2878D
The Solar Dynamics Observatory (SDO) represents a new frontier in
quantity and quality of solar data. At about 1.5 TB/day, the data will
not be easily digestible by solar physicists using the same methods
that have been employed for images from previous missions. In order for
solar scientists to use the SDO data effectively they need meta-data
that will allow them to identify and retrieve data sets that address
their particular science questions. We are building a comprehensive
computer vision pipeline for SDO, abstracting complete metadata
on many of the features and events detectable on the Sun without
human intervention. Our project unites more than a dozen individual,
existing codes into a systematic tool that can be used by the entire
solar community. The feature finding codes will run as part of the SDO
Event Detection System (EDS) at the Joint Science Operations Center
(JSOC; joint between Stanford and LMSAL). The metadata produced will
be stored in the Heliophysics Event Knowledgebase (HEK), which will be
accessible on-line for the rest of the world directly or via the Virtual
Solar Observatory (VSO) . Solar scientists will be able to use the
HEK to select event and feature data to download for science studies.
Title: Space Weather data and services at SIDC / RWC Belgium
Authors: van der Linden, Ronald; Ben Moussa, Ali; Berghmans, David;
Boulvin, Olivier; Boyes, David; Cabanas Parada, Carlos; Callebaut,
Benoit; Clette, Frédéric; Dammasch, Ingolf; Delouille, Veronique;
D'Huys, Elke; Dolla, Laurent; Dominique, Marie; Dufond, Jean-Luc;
Ergen, Aydin; Giordanengo, Boris; Gissot, Samuel; Goryaev, Farid;
Hochedez, Jean-Francois; Lemaâtre, Olivier; Lisnichenko, Pavel;
Magdalenic, Jas-Mina; Mampaey, Benjamin; Marque, Christophe; Nicula,
Bogdan; Podladchikova, Elena; Pylyser, Erik; Raynal, Sophie; Rodriguez,
Luciano; Seaton, Daniël; van der Linden, Ronald; Vandersyppe, Anne;
Vanlommel, Petra; Vanraes, Stéphane; Verbeeck, Cis; Verdini, Andrea;
Wauters, Laurence; West, Matthew; Willems, Sarah; Zhukov, Andrei
Bibcode: 2010cosp...38.4202V
Altcode: 2010cosp.meet.4202V
The SIDC of the Royal Observatory of Belgium is a very active center
for solar physics research, but also provides an operational service
for data and services related to solar activity and space weather. In
this poster we present the currently available data sets and products,
with a focus on recent additions and new developments.
Title: Solar observations from PROBA2: ready for space weather
operations
Authors: Berghmans, David; Hochedez, Jean-François
Bibcode: 2010cosp...38.4184B
Altcode: 2010cosp.meet.4184B
The ESA micro satellite PROBA2 was launched on November 2, 2009. It
carries two solar instruments, the radiometer LYRA and the coronal
imager SWAP whose commissioning ended in March 2010. LYRA (PI:
J.-F. Hochedez) observes the solar irradiance in 4 wavelengths
chosen for their relevance to space weather, solar physics and Earth
aeronomy. LYRA is able to follow the time evolution of solar flares
at very high temporal resolution. SWAP (PI: D. Berghmans) takes an
image of the EUV corona of the sun every minute in an extended field of
view. SWAP is able to image all space weather significant events such
as flares, coronal holes, dimmings, etc. We will present the technical
capabilities of the two instruments and show their complementarity
with e.g. SDO. We will discuss the SWAP and LYRA data products and
how to make use of them in an operational space weather context. More
information is available at http://proba2.sidc.be.
Title: Fast and robust segmentation in the SDO-AIA era
Authors: Verbeeck, Cis; Delouille, Véronique; Mampaey, Benjamin;
Hochedez, Jean-François; Boyes, David; Barra, Vincent
Bibcode: 2010cosp...38.2868V
Altcode: 2010cosp.meet.2868V
Solar images from the Atmospheric Imaging Assembly (AIA) aboard
the Solar Dynamics Ob-servatory (SDO) will flood the solar physics
community with a wealth of information on solar variability, of
great importance both in solar physics and in view of Space Weather
applica-tions. Obtaining this information, however, requires the
ability to automatically process large amounts of data in an objective
fashion. In previous work, we have proposed a multi-channel unsupervised
spatially-constrained multi-channel fuzzy clustering algorithm (SPoCA)
that automatically segments EUV solar images into Active Regions (AR),
Coronal Holes (CH), and Quiet Sun (QS). This algorithm will run in near
real time on AIA data as part of the SDO Feature Finding Project, a
suite of software pipeline modules for automated feature recognition and
analysis for the imagery from SDO. After having corrected for the limb
brightening effect, SPoCA computes an optimal clustering with respect
to the regions of interest using fuzzy logic on a quality criterion to
manage the various noises present in the images and the imprecision
in the definition of the above regions. Next, the algorithm applies
a morphological opening operation, smoothing the cluster edges while
preserving their general shape. The process is fast and automatic. A
lower size limit is used to distinguish AR from Bright Points. As the
algorithm segments the coronal images according to their brightness,
it might happen that an AR is detected as several disjoint pieces,
if the brightness in between is somewhat lower. Morphological
dilation is employed to reconstruct the AR themselves from their
constituent pieces. Combining SPoCA's detection of AR, CH, and QS on
subsequent images allows automatic tracking and naming of any region
of interest. In the SDO software pipeline, SPoCA will auto-matically
populate the Heliophysics Events Knowledgebase(HEK) with Active Region
events. Further, the algorithm has a huge potential for correct and
automatic identification of AR, CH, and QS in any study that aims to
address properties of those specific regions in the corona. SPoCA is
now ready and waiting to tackle solar cycle 24 using SDO data. While we
presently apply SPoCA to EUV data, the method is generic enough to allow
the introduction of other channels or data, e.g., Differential Emission
Measure (DEM) maps. Because of the unprecedented challenges brought up
by the quantity of SDO data, European partners have gathered within an
ISSI team on `Mining and Exploiting the NASA Solar Dynam-ics Observatory
data in Europe' (a.k.a. Soldyneuro). Its aim is to provide automated
feature recognition algorithms for scanning the SDO archive, as well
as conducting scientific studies that combine different algorithm's
outputs. Within the Soldyneuro project, we will use data from the EUV
Variability Experiment (EVE) spectrometer in order to estimate the full
Sun DEM. This DEM will next be used to estimate the total flux from
AIA images so as to provide a validation for the calibration of AIA.
Title: DEM analysis for AIA/SDO EUV channels using a probabilistic
approach to the spectral inverse problem
Authors: Goryaev, Farid; Parenti, Susanna; Hochedez, Jean-François;
Urnov, Alexander
Bibcode: 2010cosp...38.2867G
Altcode: 2010cosp.meet.2867G
The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics
Observatory (SDO) mis-sion is designed to observe the Sun from the
photosphere to the flaring corona. These data have to improve our
understanding of processes in the solar atmosphere. The differential
emis-sion measure (DEM) analysis is one of the main methods to derive
information about coronal optically thin plasma characteristics from
EUV and SXR emission. In this work we analyze AIA/SDO EUV channels to
estimate their ability to reconstruct DEM(T) distributions. We use
an iterative method (called Bayesian iterative method, BIM) within
the framework of a probabilistic approach to the spectral inverse
problem for determining the thermal structures of the emitting plasma
sources (Goryaev et al., submitted to AA). The BIM is an iterative
procedure based on Bayes' theorem and used for the reconstruction of
DEM profiles. Using the BIM algorithm we performed various numerical
tests and model simulations demonstrating abilities of our inversion
approach for DEM analysis with AIA/SDO EUV channels.
Title: Differential emission measure for line spectra and broadband
data from the Bayesian iterative method
Authors: Goryaev, Farid; Parenti, Susanna; Urnov, Alexander; Oparin,
S. N.; Hochedez, Jean-François; Reale, Fabio
Bibcode: 2010cosp...38.2901G
Altcode: 2010cosp.meet.2901G
Inverse problems techniques allow deriving physical characteristics
of hot optically thin so-lar and stellar plasma from their extreme
ultraviolet and X-ray spectra. One of them, called Bayesian iterative
method (BIM), relies on a probabilistic Bayesian framework for the
spec-tral inverse problem, and reconstructs differential emission
measure (DEM) distributions. We present here the application of BIM
to both high resolution solar line spectra as well as to broadband
imaging data. To demonstrate its abilities, we present various
numerical tests and model simulations establishing robustness and
usefulness. We then apply BIM to several so-lar non flaring active
regions data previously analyzed with other techniques and instruments
(SOHO-SUMER, CORONAS/F-SPIRIT, and HINODE-XRT).
Title: SDO Data Access and Distribution in Europe and the WisSDOm
Data Centre in ROB, Brussels
Authors: Boyes, David; Verbeeck, Cis; Mampaey, Benjamin; Delouille,
Véronique; Hochedez, Jean-François
Bibcode: 2010cosp...38.2882B
Altcode: 2010cosp.meet.2882B
The SDO satellite, launched in February 2010, is on track to provide
images of the Sun with unprecedented detail. For example, the SDO-AIA
telescope can produce a 4k x 4k image every five seconds for each of
its four telescopes (10 spectral bands). This mission increases the
information flow available for solar observation and forecasting
by several orders of magnitude, and represents an extraordinary
new resource for both research and solar weather forecasting. This
involves a massive flow of data: over 1TB/day without pause for the
duration of the mission, which is at least 5 years, and most probably
10 years. This is not just an increase in data cadence, as the SDO
mission makes a far broader selection of data available. How can
researchers and forecasters both select and physically access the data
which is impor-tant for them? A backbone network of data centres has
been established to handle the SDO data, and the Royal Observatory of
Belgium (ROB) is the first link in a chain for European distribution
of data. This provides users with Internet access to both real-time
data and archived data in a choice of resolution and cadence. The ROB
has installed a dedicated computing system as its SDO data centre. We
present here the architecture of the system and an overview of its
capabilities and the possibilities they give for data access. The ROB
data centre is intended to provide real-time web access to the basic
images in variable resolution, plus has high speed computing resources
to generate composite and transformed images in real-time. The access
possibilities follow a generic model, and are thus applicable to access
to the data in general from any of the data centres.
Title: Pre-flight calibration of LYRA, the solar VUV radiometer on
board PROBA2
Authors: Benmoussa, A.; Dammasch, I. E.; Hochedez, J. -F.; Schühle,
U.; Koller, S.; Stockman, Y.; Scholze, F.; Richter, M.; Kroth, U.;
Laubis, C.; Dominique, M.; Kretzschmar, M.; Mekaoui, S.; Gissot, S.;
Theissen, A.; Giordanengo, B.; Bolsee, D.; Hermans, C.; Gillotay,
D.; Defise, J. -M.; Schmutz, W.
Bibcode: 2009A&A...508.1085B
Altcode:
Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet
(VUV) solar radiometer, planned to be launched in November 2009 on
the European Space Agency PROBA2, the Project for On-Board Autonomy
spacecraft.
Methods: The instrument was radiometrically
calibrated in the radiometry laboratory of the Physikalisch-Technische
Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton
radiation (BESSY II). The calibration was done using monochromatized
synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines
using reference detectors calibrated with the help of an electrical
substitution radiometer as the primary detector standard.
Results:
A total relative uncertainty of the radiometric calibration of the LYRA
instrument between 1% and 11% was achieved. LYRA will provide irradiance
data of the Sun in four UV passbands and with high temporal resolution
down to 10 ms. The present state of the LYRA pre-flight calibration
is presented as well as the expected instrument performance.
Title: Fast and robust segmentation of solar EUV images: algorithm
and results for solar cycle 23
Authors: Barra, V.; Delouille, V.; Kretzschmar, M.; Hochedez, J. -F.
Bibcode: 2009A&A...505..361B
Altcode:
Context: The study of the variability of the solar corona and the
monitoring of coronal holes, quiet sun and active regions are of great
importance in astrophysics as well as for space weather and space
climate applications.
Aims: In a previous work, we presented
the spatial possibilistic clustering algorithm (SPoCA). This is a
multi-channel unsupervised spatially-constrained fuzzy clustering method
that automatically segments solar extreme ultraviolet (EUV) images
into regions of interest. The results we reported on SoHO-EIT images
taken from February 1997 to May 2005 were consistent with previous
knowledge in terms of both areas and intensity estimations. However,
they presented some artifacts due to the method itself.
Methods:
Herein, we propose a new algorithm, based on SPoCA, that removes
these artifacts. We focus on two points: the definition of an optimal
clustering with respect to the regions of interest, and the accurate
definition of the cluster edges. We moreover propose methodological
extensions to this method, and we illustrate these extensions with the
automatic tracking of active regions.
Results: The much improved
algorithm can decompose the whole set of EIT solar images over the
23rd solar cycle into regions that can clearly be identified as quiet
sun, coronal hole and active region. The variations of the parameters
resulting from the segmentation, i.e. the area, mean intensity, and
relative contribution to the solar irradiance, are consistent with
previous results and thus validate the decomposition. Furthermore,
we find indications for a small variation of the mean intensity of
each region in correlation with the solar cycle.
Conclusions: The
method is generic enough to allow the introduction of other channels or
data. New applications are now expected, e.g. related to SDO-AIA data.
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: The DynaMICCS perspective. A mission for a complete and
continuous view of the Sun dedicated to magnetism, space weather
and space climate
Authors: Turck-Chièze, S.; Lamy, P.; Carr, C.; Carton, P. H.;
Chevalier, A.; Dandouras, I.; Defise, J. M.; Dewitte, S.; Dudok de Wit,
T.; Halain, J. P.; Hasan, S.; Hochedez, J. F.; Horbury, T.; Levacher,
P.; Meissonier, M.; Murphy, N.; Rochus, P.; Ruzmaikin, A.; Schmutz,
W.; Thuillier, G.; Vivès, S.
Bibcode: 2009ExA....23.1017T
Altcode: 2008ExA...tmp...42T
The DynaMICCS mission is designed to probe and understand the dynamics
of crucial regions of the Sun that determine solar variability,
including the previously unexplored inner core, the radiative/convective
zone interface layers, the photosphere/chromosphere layers and the
low corona. The mission delivers data and knowledge that no other
known mission provides for understanding space weather and space
climate and for advancing stellar physics (internal dynamics)
and fundamental physics (neutrino properties, atomic physics,
gravitational moments...). The science objectives are achieved
using Doppler and magnetic measurements of the solar surface,
helioseismic and coronographic measurements, solar irradiance at
different wavelengths and in-situ measurements of plasma/energetic
particles/magnetic fields. The DynaMICCS payload uses an original
concept studied by Thalès Alenia Space in the framework of the
CNES call for formation flying missions: an external occultation of
the solar light is obtained by putting an occulter spacecraft 150 m
(or more) in front of a second spacecraft. The occulter spacecraft,
a LEO platform of the mini sat class, e.g. PROTEUS, type carries
the helioseismic and irradiance instruments and the formation flying
technologies. The latter spacecraft of the same type carries a visible
and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This
mission must guarantee long (one 11-year solar cycle) and continuous
observations (duty cycle > 94%) of signals that can be very weak
(the gravity mode detection supposes the measurement of velocity
smaller than 1 mm/s). This assumes no interruption in observation
and very stable thermal conditions. The preferred orbit therefore is
the L1 orbit, which fits these requirements very well and is also an
attractive environment for the spacecraft due to its low radiation and
low perturbation (solar pressure) environment. This mission is secured
by instrumental R and D activities during the present and coming
years. Some prototypes of different instruments are already built
(GOLFNG, SDM) and the performances will be checked before launch on
the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS).
Title: Recent ROB developments on wide bandgap based UV sensors
Authors: Giordanengo, B.; Ben Moussa, A.; Hochedez, J. -F.; Soltani,
A.; de Moor, P.; Minoglou, K.; Malinowski, P.; Duboz, J. -Y.; Chong,
Y. M.; Zou, Y. S.; Zhang, W. J.; Lee, S. T.; Dahal, R.; Li, J.; Lin,
J. Y.; Jiang, H. X.
Bibcode: 2009EAS....37..199G
Altcode:
The next ESA spatial mission planned to study the Sun, Solar Orbiter
(SO), necessitates very innovative EUV detectors. The commonly used
silicon detectors suffer important limitations mainly in terms of UV
robustness and dark current level. An alternative comes from diamond
or III-nitride materials. In these materials, the radiation hardness,
solar blindness and dark current are improved due to their wide
bandgap. This paper presents the new developments on wide bandgap
materials at the Royal Observatory of Belgium (ROB). We present also
the LYRA instrument, the BOLD project, and the EUI instrument suite.
Title: 3D Reconstruction from SECCHI-EUVI Images Using an Optical-Flow
Algorithm: Method Description and Observation of an Erupting Filament
Authors: Gissot, S. F.; Hochedez, J. -F.; Chainais, P.; Antoine, J. -P.
Bibcode: 2008SoPh..252..397G
Altcode: 2008SoPh..tmp..173G
SECCHI-EUVI telescopes provide the first EUV images enabling a 3D
reconstruction of solar coronal structures. We present a stereoscopic
reconstruction method based on the Velociraptor algorithm, a multiscale
optical-flow method that estimates displacement maps in sequences of
EUV images. Following earlier calibration on sequences of SOHO-EIT
data, we apply the algorithm to retrieve depth information from the two
STEREO viewpoints using the SECCHI-EUVI telescope. We first establish
a simple reconstruction formula that gives the radial distance to
the centre of the Sun of a point identified both in EUVI-A and EUVI-B
from the separation angle and the displacement map. We select pairs
of images taken in the 30.4 nm passband of EUVI-A and EUVI-B, and
apply a rigid transform from the EUVI-B image in order to set both
images in the same frame of reference. The optical flow computation
provides displacement maps from which we reconstruct a dense map
of depths using the stereoscopic reconstruction formula. Finally,
we discuss the estimation of the height of an erupting filament.
Title: Preface: SOHO 20 - Transient events on the Sun and in the
heliosphere
Authors: Robbrecht, E.; Hochedez, J. -F.; Fleck, B.; Gurman, J.;
Forsyth, R.
Bibcode: 2008AnGeo..26.2953R
Altcode:
No abstract at ADS
Title: Quantifying and containing the curse of high resolution
coronal imaging
Authors: Delouille, V.; Chainais, P.; Hochedez, J. -F.
Bibcode: 2008AnGeo..26.3169D
Altcode: 2008arXiv0808.3068D
Future missions such as Solar Orbiter (SO), InterHelioprobe, or Solar
Probe aim at approaching the Sun closer than ever before, with on board
some high resolution imagers (HRI) having a subsecond cadence and a
pixel area of about (80 km)2 at the Sun during perihelion. In
order to guarantee their scientific success, it is necessary to evaluate
if the photon counts available at these resolution and cadence will
provide a sufficient signal-to-noise ratio (SNR). For example, if the
inhomogeneities in the Quiet Sun emission prevail at higher resolution,
one may hope to locally have more photon counts than in the case of a
uniform source. It is relevant to quantify how inhomogeneous the quiet
corona will be for a pixel pitch that is about 20 times smaller than
in the case of SoHO/EIT, and 5 times smaller than TRACE. We perform a
first step in this direction by analyzing and characterizing the spatial
intermittency of Quiet Sun images thanks to a multifractal analysis. We
identify the parameters that specify the scale-invariance behavior. This
identification allows next to select a family of multifractal processes,
namely the Compound Poisson Cascades, that can synthesize artificial
images having some of the scale-invariance properties observed on the
recorded images. The prevalence of self-similarity in Quiet Sun coronal
images makes it relevant to study the ratio between the SNR present
at SoHO/EIT images and in coarsened images. SoHO/EIT images thus play
the role of "high resolution" images, whereas the "low-resolution"
coarsened images are rebinned so as to simulate a smaller angular
resolution and/or a larger distance to the Sun. For a fixed difference
in angular resolution and in Spacecraft-Sun distance, we determine the
proportion of pixels having a SNR preserved at high resolution given a
particular increase in effective area. If scale-invariance continues
to prevail at smaller scales, the conclusion reached with SoHO/EIT
images can be transposed to the situation where the resolution is
increased from SoHO/EIT to SO/HRI resolution at perihelion.
Title: Segmentation of extreme ultraviolet solar images via
multichannel fuzzy clustering
Authors: Barra, Vincent; Delouille, Véronique; Hochedez,
Jean-François
Bibcode: 2008AdSpR..42..917B
Altcode:
The study of the variability of the solar corona and the monitoring of
its traditional regions (Coronal Holes, Quiet Sun and Active Regions)
are of great importance in astrophysics as well as in view of the Space
Weather and Space Climate applications. Here we propose a multichannel
unsupervised spatially constrained fuzzy clustering algorithm that
automatically segments EUV solar images into Coronal Holes, Quiet Sun
and Active Regions. Fuzzy logic allows to manage the various noises
present in the images and the imprecision in the definition of the
above regions. The process is fast and automatic. It is applied to
SoHO EIT images taken from February 1997 till May 2005, i.e. along
almost a full solar cycle. Results in terms of areas and intensity
estimations are consistent with previous knowledge. The method reveal
the rotational and other mid-term periodicities in the extracted time
series across solar cycle 23. Further, such an approach paves the way
to bridging observations between spatially resolved data from imaging
telescopes and time series from radiometers. Time series resulting
form the segmentation of EUV coronal images can indeed provide an
essential component in the process of reconstructing the solar spectrum.
Title: Oscillation analysis using optical flow: Application to an
EUV movie of the solar corona
Authors: Gissot, Samuel; Hochedez, J. -F.
Bibcode: 2008StMet...5..340G
Altcode:
Movies of the solar corona in Extreme UltraViolet (EUV) bandpasses
exhibit complex patterns of magnetically structured plasma features
surrounding the solar photosphere. Among the various phenomena to be
observed in the EUV movies, coronal oscillations are an essential
process for determining physical parameters of the plasma. In this
paper we demonstrate the ability of our motion estimation algorithm to
explore and analyse the oscillating motions of coronal loops present
in EUV image sequences. The motion fields of each image pair in the
sequence are estimated; selected features are tracked using the motion
estimation to form trajectories. The oscillating features are then
selected from the Morlet wavelet analysis of the trajectories that
provides parameters such as local oscillation period. The proposed
method will be particularly useful to process datasets expected from
new solar missions.
Title: Spatial and Temporal Noise in Solar EUV Observations
Authors: Delouille, V.; Chainais, P.; Hochedez, J. -F.
Bibcode: 2008SoPh..248..441D
Altcode: 2008SoPh..tmp...30D
Solar telescopes will never be able to resolve the smallest events at
their intrinsic physical scales. Pixel signals recorded by SOHO/(CDS,
EIT, SUMER), STEREO/SECCHI/ EUVI, TRACE, SDO/AIA, and even by the
future Solar Orbiter EUI/HRI contain an inherent "spatial noise" since
they represent an average of the solar signal present at subpixel
scales. In this paper, we aim at investigating this spatial noise,
and hopefully at extracting information from subpixel scales. Two
paths are explored. We first combine a regularity analysis of
a sequence of EIT images with an estimation of the relationship
between mean and standard deviation, and we formulate a scenario for
the evolution of the local signal-to-noise ratio (SNR) as the pixel
size becomes smaller. Second, we use an elementary forward modeling
to examine the relationship between nanoflare characteristics (such
as area, duration, and intensity) and the global mean and standard
deviation. We use theoretical distributions of nanoflare parameters
as input to the forward model. A fine-grid image is generated as a
random superposition of those pseudo-nanoflares. Coarser resolution
images (simulating images acquired by a telescope) are obtained by
rebinning and are used to compute the mean and standard deviation to
be analyzed. Our results show that the local SNR decays more slowly
in regions exhibiting irregularities than in smooth regions.
Title: Proper Motions of Coronal Bright Points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.; Verbanac, G.; Skokić, I.; Hanslmeier, A.
Bibcode: 2008CEAB...32..165B
Altcode:
Full-field full-resolution solar images obtained by the Extreme
Ultraviolet Imaging Telescope on board the Solar and Heliospheric
Observatory are used to analyse proper motions, velocity distributions,
lifetimes, and diffusion coefficient of coronal bright points. The
results obtained by the interactive method for three tracer subtypes
(point-like structures, small loops, and small active regions)
of coronal bright points for the period 4 June 1998 to 22 May 1999
are presented and compared. Distributions of meridional velocities,
residual azimuthal velocities and velocities of proper motions are
presented for the three tracer subtypes. Lifetimes up to 54 hours
are found for 98% of all observed coronal bright points. Small active
regions last on the average longer than point-like structures and small
loops. The correlation between the absolute velocity of proper motion
and lifetime is investigated and the mean free path (in the range from
3000 km to 15000 km) and the diffusion coefficient (approximately 200
km2/s) of coronal bright points are estimated. Finally,
characteristics of the random walk process associated to the motions
of coronal bright points are discussed in the Appendix.
Title: Coronal Bright Points as Tracers for Solar Rotation in
October-November 1999
Authors: Brajša, R.; Mulec, M.; Hanslmeier, A.; Wöhl, H.; Ruždjak,
V.; Hochedez, J. -F.
Bibcode: 2008CEAB...32..117B
Altcode:
Whole-disc full-resolution solar images taken in the extreme ultraviolet
part of the spectrum (Fe XV line at 28.4 nm) with the EIT instrument
on board the SOHO spacecraft were used to visually identify coronal
bright points appropriate for solar rotation determination. From the
time differences in successive tracer positions amounting to six hours
the solar rotation velocity was determined tracing coronal bright
points in images obtained in October and November 1999. The resulting
parameters and profiles of the solar rotation are presented.
Title: A New Model for Propagating Parts of EIT Waves: A Current
Shell in a CME
Authors: Delannée, C.; Török, T.; Aulanier, G.; Hochedez, J. -F.
Bibcode: 2008SoPh..247..123D
Altcode:
EIT waves are observed in EUV as bright fronts. Some of these bright
fronts propagate across the solar disk. EIT waves are all associated
with a flare and a CME and are commonly interpreted as fast-mode
magnetosonic waves. Propagating EIT waves could also be the direct
signature of the gradual opening of magnetic field lines during a
CME. We quantitatively addressed this alternative interpretation. Using
two independent 3D MHD codes, we performed nondimensional numerical
simulations of a slowly rotating magnetic bipole, which progressively
result in the formation of a twisted magnetic flux tube and its fast
expansion, as during a CME. We analyse the origins, the development,
and the observability in EUV of the narrow electric currents sheets that
appear in the simulations. Both codes give similar results, which we
confront with two well-known SOHO/EIT observations of propagating EIT
waves (7 April and 12 May 1997), by scaling the vertical magnetic field
components of the simulated bipole to the line of sight magnetic field
observed by SOHO/MDI and the sign of helicity to the orientation of the
soft X-ray sigmoids observed by Yohkoh/SXT. A large-scale and narrow
current shell appears around the twisted flux tube in the dynamic phase
of its expansion. This current shell is formed by the return currents
of the system, which separate the twisted flux tube from the surrounding
fields. It intensifies as the flux tube accelerates and it is co-spatial
with weak plasma compression. The current density integrated over the
altitude has the shape of an ellipse, which expands and rotates when
viewed from above, reproducing the generic properties of propagating
EIT waves. The timing, orientation, and location of bright and faint
patches observed in the two EIT waves are remarkably well reproduced. We
conjecture that propagating EIT waves are the observational signature of
Joule heating in electric current shells, which separate expanding flux
tubes from their surrounding fields during CMEs or plasma compression
inside this current shell. We also conjecture that the bright edges
of halo CMEs show the plasma compression in these current shells.
Title: On the solar rotation and activity
Authors: Brajša, R.; Wöhl, H.; Ruždjak, D.; Vršnak, B.; Verbanac,
G.; Svalgaard, L.; Hochedez, J. -F.
Bibcode: 2007AN....328.1013B
Altcode:
The interaction between differential rotation and magnetic fields in
the solar convection zone was recently modelled by Brun (2004). One
consequence of that model is that the Maxwell stresses can oppose the
Reynolds stresses, and thus contribute to the transport of the angular
momentum towards the solar poles, leading to a reduced differential
rotation. So, when magnetic fields are weaker, a more pronounced
differential rotation can be expected, yielding a higher rotation
velocity at low latitudes taken on the average. This hypothesis
is consistent with the behaviour of the solar rotation during the
Maunder minimum. In this work we search for similar signatures of
the relationship between the solar activity and rotation determined
tracing sunspot groups and coronal bright points. We use the extended
Greenwich data set (1878-1981) and a series of full-disc solar images
taken at 28.4 nm with the EIT instrument on the SOHO spacecraft
(1998-2000). We investigate the dependence of the solar rotation on
the solar activity (described by the relative sunspot number) and
the interplanetary magnetic field (calculated from the interdiurnal
variability index). Possible rotational signatures of two weak solar
activity cycles at the beginning of the 20th century (Gleissberg
minimum) are discussed.
Title: Segmentation of SoHO/EIT Images using fuzzy clustering
algorithms
Authors: Delouille, V.; Barra, V.; Hochedez, J.
Bibcode: 2007AGUFMSH13A1107D
Altcode:
The study of the variability of the solar corona and the monitoring of
its traditional regions (Coronal Holes, Quiet Sun and Active Regions)
are of great importance in astrophysics as well as in view of the
Space Weather and Space Climate applications. In this presentation,
I will propose a multi-channel unsupervised spatially- constrained
fuzzy clustering algorithm that automatically segments EUV solar
images into Coronal Holes, Quiet Sun and Active Regions. The use
of Fuzzy logic allows to manage the various noises present in the
images and the imprecision in the definition of the above mentioned
regions. The process is fast and automatic. It is applied to SoHO-EIT
images taken from January 1997 till May 2005, spanning thus almost a
full solar cycle. Results in terms of areas and intensity estimations
are consistent with previous knowledge. The method reveal the rotational
and other mid-term periodicities in the extracted time series across
solar cycle 23. Further, such an approach paves the way to bridging
observations between spatially resolved data from imaging telescopes
and time series from radiometers. Time series resulting form the
segmentation of EUV coronal images can indeed provide an essential
component in the process of reconstructing the solar spectrum.
Title: SWAP: a novel EUV telescope for space weather
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans,
David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat,
Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez,
Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank
Bibcode: 2007SPIE.6689E..0SD
Altcode: 2007SPIE.6689E..24D
The SWAP telescope (Sun Watcher using Active Pixel System detector and
Image Processing) is being developed to be part of the PROBA2 payload,
an ESA technological mission to be launched in early 2008. SWAP
is directly derived from the concept of the EIT telescope that we
developed in the '90s for the SOHO mission. Several major innovations
have been introduced in the design of the instrument in order to
be compliant with the requirements of the PROBA2 mini-satellite:
compactness with a new of-axis optical design, radiation resistance
with a new CMOS-APS detector, a very low power electronics, an athermal
opto-mechanical system, optimized onboard compression schemes combined
with prioritization of collected data, autonomy with automatic
triggering of observation and off-pointing procedures in case of
Solar event occurrence, ... All these new features result from the low
resource requirements (power, mass, telemetry) of the mini-satellite,
but also take advantage of the specificities of a modern technological
platform, such as quick pointing agility, new powerful on-board
processor, Packetwire interface and autonomous operations. These
new enhancements will greatly improve the operations of SWAP as
a space weather sentinel from a low Earth orbit while the downlink
capabilities are limited. This paper summarizes the conceptual design,
the development and the qualification of the instrument, the autonomous
operations and the expected performances for science exploitation.
Title: Modeling images of the Quiet Sun in the extreme ultraviolet
Authors: Chainais, Pierre; Delouille, Véronique; Hochedez,
Jean-François
Bibcode: 2007SPIE.6701E..11C
Altcode: 2007SPIE.6701E..31C
We address the statistical modeling of solar images provided by the
Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and
Heliospheric Observatory (SoHO, a joint ESA/NASA mission). We focus in
particular on the less structured regions, the "Quiet Sun". We first
review on a brief historical viewpoint on multifractal processes for
physical modeling. Then we present a multifractal analysis of Quiet Sun
images. Our aim is to identify a model that would permit to simulate
images that are similar to real ones, and to use the scale invariance
property to obtain artificial images at any finer resolution. We compare
various families of models including infinitely divisible cascades
and fractional stable fields that permit to synthesize images that are
statistically similar to Quiet Sun images. This modeling will assist
in promoting forthcoming high resolution observations by analysing
sub-pixel variability in today's solar corona images.
Title: Helio-informatics: Preparing For The Future Of Heliophysics
Research.
Authors: Schrijver, Carolus J.; Hurlburt, N. E.; Cheung, M. C.; Title,
A. M.; Delouille, V.; Hochedez, J.; Berghmans, D.
Bibcode: 2007AAS...210.2514S
Altcode: 2007BAAS...39..133S
The rapidly growing data volumes for space- and ground-based
observatories for Sun and heliosphere will soon make it impractical,
costly, and perhaps effectively impossible for researchers to download
and locally inspect substantial portions of the data archives. By
the end of 2008, for example, the Solar Dynamics Observatory will
downlink over 2TB/day of compressed data; such a large volume would
readily saturate internet connections to the archive site if it were
exported to a handful of researchers around the world. We envision a
revolution in research methodology towards a mode in which researchers
run autonomous event-finding algorithms at a primary data archive in
order to pre-select relatively small subsets of the data that can
subsequently be inspected and analyzed in detail at a researcher's
home institution. Teams from the SDO, Hinode, STEREO, and TRACE
missions are developing the infrastructure that is needed to make this
into a useful research tool: we are (1) defining standardized event
attributes compatible with the Virtual Observatory and EGSO concepts,
(2) developing a knowledge base supported by a web-based tool for
compound queries based on the contents of solar and heliospheric
observations, and (3) assembling a group of researchers who are
interested in helping us develop a prototype system while beta-testing
it in real scientific studies. We invite you to contact us (a) if you
have feature-finding algorithms that you would like to see applied to
existing data archives, (b) if you would like to contribute expertise
in developing the knowledge-base system, or (c) if you would like
to participate in the testing of the system for scientific use. More
information on our plans, target dates, and contact information can
be found at http://www.lmsal.com/helio-informatics/hpkb/. The
helio-informatics project is being developed with support from
the HINODE/SOT (NNM07AA01C), SDO/AIA (NNG04EA00C), STEREO/SECCHI
(N00173-02-C-2035), and TRACE (NAS5-38099) science investigations.
Title: Stationary parts of an EIT and Moreton wave: a topological
model
Authors: Delannée, C.; Hochedez, J. -F.; Aulanier, G.
Bibcode: 2007A&A...465..603D
Altcode:
Context: EIT and Moreton waves came into focus in 1997, when a
propagating disturbance on a large area of the solar disc was
discovered. The process generating the EIT and Moreton waves has
been frequently discussed.
Aims: On May 2, 1998, a halo CME
was observed related to an EIT wave, a Moreton wave, a X1 flare,
radio emission sources, and dimmings. We studied this event to find
the relation between all these structures.
Methods: We use
and co-align multi-wavelength observations and the online potential
field source surface (pfss) package.
Results: The observed EIT
and Moreton waves present some brightenings that remain at the same
location. We relate the connectivity of the coronal potential magnetic
field to the stationary brightenings. We find that the areas where the
magnetic field lines have drastic jumps of connectivity are cospatial
to the stationary brightenings of the waves.
Conclusions: .We
conclude that the EIT and Moreton waves may be due to Joule heating
resulting from the generation of electric currents in the neighboring
area of the drastic jumps of magnetic connectivity, while the magnetic
field lines are opening during a CME.
Title: Multiscale optical flow probing of dynamics in solar EUV
images. Algorithm, calibration, and first results
Authors: Gissot, S. F.; Hochedez, J. -F.
Bibcode: 2007A&A...464.1107G
Altcode:
Context: Movies of the solar atmosphere reveal motion and variations
in brightness. In particular, sequences of coronal images exhibit
the plane-of-the-sky component of the velocity combined with
other variations in the signal. The present work analyses solar
extreme-ultraviolet images, as recorded by the Extreme ultraviolet
Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory
(SoHO) and by the Transition Region and Coronal Explorer (TRACE).
Aims: Our aim is to simultaneously estimate the apparent motion
vector and the variation in brightness from two successive images.
Methods: We present a multiscale optical-flow algorithm derived
from a local gradient-based technique that estimates the deformation
parameters. Our algorithm is symmetric in the sense that it computes
the exact same estimation if the two images are swapped. This also
regularises the optical flow when two local image patterns do not match,
e.g. in case of temporal sub-sampling. Independently our algorithm
regularises the optical flow against aperture effects occurring
typically along coronal loops.
Results: We demonstrate a new
differential rotation measurement technique and the identification
of coronal events as regions exhibiting a significant brightness
variation or an outstanding velocity field. Space weather services
have motivated this study. The range of potential interests includes,
but also extends beyond, on-disc signatures of flares and coronal mass
ejection (CME). It encompasses, for example, studies of bright points
and filaments, coronal seismology, and EIT wave investigations.
Title: Solar Rotation Velocity Determined by Coronal Bright Points -
New Data and Analysis
Authors: Mulec, M.; Brajša, R.; Wöhl, H.; Hanslmeier, A.; Vršnak,
B.; Ruždjak, V.; Hochedez, J. -F.; Engler, J.
Bibcode: 2007CEAB...31....1M
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope on board the Solar and Heliospheric Observatory were used
to analyse solar differential rotation determined by tracing coronal
bright points. Rotation velocity residuals, meridional motions and
their relationship are investigated for a new data set from October
1, 1999 to March 31, 2000. Further we take care for the evolution
of the single structures, dividing them into Point-Like-Structures,
Small Loops and Small Active Regions and analysing their variation in
intensity and size.
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: LYRA - a solar UV radiometer using diamond detectors
Authors: Theissen, A.; Benmoussa, A.; Schühle, U.; Hochedez, J. -F.;
Schmutz, W.
Bibcode: 2007msfa.conf...27T
Altcode:
LYRA, the Lyman-α radiometer, is a highcadence (100 Hz) solar
VUV radiometer which will measure diskintegrated irradiances in 4
wavelength channels. Special emphasis is given on novel detectors based
on diamond which will be tested for the first time in space. Two kinds
of detectors are employed: MSM and PiNtype detectors. Their particular
advantage compared to silicon detectors lies in their solar blindness
with a UV/visible reduction ratio of at least four orders of magnitude,
which simplifies the design of UV instruments.
Title: Current and future space weather services and products from
the SIDC- Brussels
Authors: Lawrence, G.; Kretzschmar, M.; Berghmans, D.; Clete,
F.; Hochedez, J.; van der Linden, R.; Delouille, V.; Gissot, S.;
Marque, C.; Nicula, B.; Patoul, J.; Podladchikova, E.; Robbrecht,
E.; Vanlommel, P.; Dehant, V.
Bibcode: 2006AGUFMSA51A..04L
Altcode:
The SIDC-Brussels, as WDC for the sunspot index and European RWC of the
ISES, is the European hub for solar data and forecasts. Its services
and products, while long established and widely recognised and used,
are continuously being enhanced and supplemented. We present in
detail the current status and outline the imminent improvements and
additions. The Solar Weather Browser (SWB) is a free, downloadable,
multi-platform visualisation package for real-time browsing of processed
solar images from a variety of space and ground based sources, combined
with context information (events, regions IDs, etc.) via a wide choice
of overlay combinations. The Estimated International Sunspot Number
(EISN) has been produced and distributed daily since January 2006 by the
SIDC. Intended to support operational model predictions of ionospheric
radio propagation, we present some early statistical results. CACTus,
the operational Computer-Aided CME Tracking algorithm, now freely
available to the community via the SSW software framework, is being
tested for its real-time application to the STEREO/SECCHI COR-2 "space
weather beacon" coronagraph telemetry stream. Also NEMO, a software
package for the automated detection and morphological analysis of EIT
waves presently being tested, details the relation between coronal EUV
wave fronts and dimmings and characterizes their evolution; we present
sample results of both developments. The Velociraptor software processes
and interprets movies of the EUV solar corona, an algorithm identifying
outstanding motions such as loop openings that are associated to
space weather events. Sample results using EIT and TRACE data will be
shown. A new flare catalog called B2X is presented, compliled via a
method to detect automatically, and characterise according to time,
localization, size, EUV flares belonging to classes B to X anywhere
on the solar disc and at the limb. In addition we present a summary
of the full range of products available from SIDC which can be chosen
in any combination tailored to the individual, or group's needs. All
products are available via the revamped SIDC website, http://www.sidc.be
Title: SWAP: An EUV imager for solar monitoring on board of PROBA2
Authors: Katsiyannis, A. C.; Berghmans, D.; Nicula, B.; Defise,
J. -M.; Lawrence, G.; Lecat, J. -H.; Hochedez, J. -F.; Slemzin, V.
Bibcode: 2006AIPC..848..847K
Altcode:
PROBA2 is an ESA technology demonstration mission to be launched in
2007. The prime instrument on board of Proba2 is SWAP (Sun Watcher
using Active Pixel System detector and Image Processing), a full disk
solar imager with a bandpass filter centred at 17.5 nm (Fe IX-XI)
and a fast cadence of ~ 1 min. The telescope is based on an off-axis
Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced
APS CMOS will be used as a detector. As the prime goal of the SWAP is
solar monitoring and advance warning of Coronal Mass Ejections (CME),
on-board intelligence will be implemented. Image recognition software
using experimental algorithms will be used to detect CMEs during the
first phase of eruption so the event can be tracked by the spacecraft
without human intervention.
Title: Macrospicules and blinkers as seen in Shutterless EIT 304 Å
Authors: Madjarska, M. S.; Doyle, J. G.; Hochedez, J. -F.; Theissen, A.
Bibcode: 2006A&A...452L..11M
Altcode:
Aims.Small-scale transient phenomena in the solar atmosphere are
believed to play a crucial role in the coronal heating and solar
wind generation. This study aims at providing new observational
evidence on blinkers and macrospicules appearance in imager data and
in doing so, establish the long disputed relationship between these
phenomena.
Methods: .We analyse unique high-cadence images in
the transition region He ii 304 Å line obtained in a shutterless mode
of the Extreme-ultraviolet Imaging Telescope on board the Solar and
Heliospheric Observatory. The data have a cadence of approximately 68
s and a pixel size of 2.62 arcsec. The events are identified through
an automatic brightenings identification procedure. Features showing
a jet-like structure seen in projection on the disk were selected
and their light-curve further analysed.
Results: .The temporal
evolution of the intensity in three events is shown, two of them seen
on-disk as jet-like features and one above the limb. The flux increase,
size and duration derived from the light-curve of the on-disk events
show an identity with the blinker phenomenon.
Conclusions: .The
light curves of these events suggest that the off-limb and on-disk
features are in fact one and the same phenomenon and therefore that
some blinkers are the on-disk counterparts of macrospicules.
Title: Synergies between solar VUV radiometry and imaging
Authors: Hochedez, J. -F.; Dudok de Witte, T.; Delouille, V.
Bibcode: 2006cosp...36.3278H
Altcode: 2006cosp.meet.3278H
This presentation will discuss the benefits of bringing together solar
image data and VUV radiometer time series We will show in particular
that algorithmic processing allows to gain deeper insights The frame
of the investigation is the PROBA2 mission in which the LYRA VUV
radiometer operates next to the SWAP EUV imager
Title: LYRA and SWAP aboard PROBA2 - heralding future solar VUV
observations
Authors: Hochedez, J. -F.; Berghmans, D.; Defise, J. -M.
Bibcode: 2006cosp...36.3272H
Altcode: 2006cosp.meet.3272H
Two novel solar VUV instruments will be launched with the PROBA2
mission in the end of 2007 SWAP is a EUV solar imaging telescope and
LYRA is a VUV filter radiometer We will discuss the interest of the
new observations that can be expected from each of them and show in
which sense LYRA and SWAP address the technological and scientific
questions of future solar VUV observations
Title: The EUV/FUV Disc Imager of Kuafu A
Authors: Rochus, P.; Hochedez, J. -F.
Bibcode: 2006cosp...36.3256R
Altcode: 2006cosp.meet.3256R
This presentation describes the EDI remote sensing suite onboard Kuafu
A that is presently being anticipated to provide not only advanced
VUV imaging of the solar atmosphere but also coronagraphy and radiometry
Title: LYRA, a solar UV radiometer on Proba2
Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.;
Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.;
Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.;
Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar,
M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.;
Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.;
Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen,
R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P.
Bibcode: 2006AdSpR..37..303H
Altcode:
LYRA is the solar UV radiometer that will embark in 2006 onboard
Proba2, a technologically oriented ESA micro-mission. LYRA is
designed and manufactured by a Belgian Swiss German consortium (ROB,
PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international
collaborations. It will monitor the solar irradiance in four UV
passbands. They have been chosen for their relevance to Solar Physics,
Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel,
(2) the 200 220 nm Herzberg continuum range, (3) the Aluminium
filter channel (17 70 nm) including He II at 30.4 nm and (4) the
Zirconium filter channel (1 20 nm). The radiometric calibration will
be traceable to synchrotron source standards (PTB and NIST). The
stability will be monitored by onboard calibration sources (LEDs),
which allow to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first space
assessment of a pioneering UV detectors program. Diamond sensors make
the instruments radiation-hard and solar-blind: their high bandgap
energy makes them insensitive to visible light and, therefore, make
dispensable visible light blocking filters, which seriously attenuate
the desired ultraviolet signal. Their elimination augments the effective
area and hence the signal-to-noise, therefore increasing the precision
and the cadence. The SWAP EUV imaging telescope will operate next to
LYRA on Proba2. Together, they will establish a high performance solar
monitor for operational space weather nowcasting and research. LYRA
demonstrates technologies important for future missions such as the
ESA Solar Orbiter.
Title: SWAP onboard PROBA 2, a new EUV imager for solar monitoring
Authors: Berghmans, D.; Hochedez, J. F.; Defise, J. M.; Lecat, J. H.;
Nicula, B.; Slemzin, V.; Lawrence, G.; Katsyiannis, A. C.; van der
Linden, R.; Zhukov, A.; Clette, F.; Rochus, P.; Mazy, E.; Thibert,
T.; Nicolosi, P.; Pelizzo, M. -G.; Schühle, U.
Bibcode: 2006AdSpR..38.1807B
Altcode:
SWAP (Sun Watcher using Active Pixel system detector and image
processing) is a solar imager in the extreme ultraviolet (EUV)
that has been selected to fly in 2007 on the PROBA 2 technological
platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien
telescope equipped with an EUV enhanced active pixel sensor detector
(coated APS). This type of detector has advantages that promise to
be very profitable for solar EUV imaging. SWAP will provide solar
coronal images at a 1-min cadence in a bandpass centered on 17.5
nm. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or EIT-waves, associated with the
early phase of coronal mass ejections. Image processing software will
be developed that automatically detects these phenomena and sends out
space weather warnings. Together with its sister instrument LYRA, also
onboard PROBA 2, SWAP will serve as a high performance solar monitoring
tool to be used in operational space weather forecasting. The SWAP
data will complement the solar observations provided by instruments
like SOHO-EIT, and STEREO-SECCHI.
Title: Segmentation of EIT Images Using Fuzzy Clustering: a
Preliminary Study
Authors: Barra, Vincent; Delouille, V.; Hochedez, J. -F.; Chainais, P.
Bibcode: 2005ESASP.600E..77B
Altcode: 2005dysu.confE..77B; 2005ESPM...11...77B
No abstract at ADS
Title: Spicules and Blinkers as Seen in Shutterless EIT 304 Å
Authors: Madjarska, M. S.; Doyle, J. G.; Hochedez, J. F.; Theissen, A.
Bibcode: 2005ESASP.596E..73M
Altcode: 2005ccmf.confE..73M
No abstract at ADS
Title: Solar weather monitoring
Authors: Hochedez, J. -F.; Zhukov, A.; Robbrecht, E.; van der Linden,
R.; Berghmans, D.; Vanlommel, P.; Theissen, A.; Clette, F.
Bibcode: 2005AnGeo..23.3149H
Altcode:
Space Weather nowcasting and forecasting require solar observations
because geoeffective disturbances can arise from three types of solar
phenomena: coronal mass ejections (CMEs), flares and coronal holes. For
each, we discuss their definition and review their precursors in terms
of remote sensing and in-situ observations. The objectives of Space
Weather require some specific instrumental features, which we list
using the experience gained from the daily operations of the Solar
Influences Data analysis Centre (SIDC) at the Royal Observatory of
Belgium. Nowcasting requires real-time monitoring to assess quickly and
reliably the severity of any potentially geoeffective solar event. Both
research and forecasting could incorporate more observations in order
to feed case studies and data assimilation respectively. Numerical
models will result in better predictions of geomagnetic storms
and solar energetic particle (SEP) events. We review the data types
available to monitor solar activity and interplanetary conditions. They
come from space missions and ground observatories and range from
sequences of dopplergrams, magnetograms, white-light, chromospheric,
coronal, coronagraphic and radio images, to irradiance and in-situ
time-series. Their role is summarized together with indications about
current and future solar monitoring instruments.
Title: Solar activity: nowcasting and forecasting at the SIDC
Authors: Berghmans, D.; van der Linden, R. A. M.; Vanlommel, P.;
Warnant, R.; Zhukov, A.; Robbrecht, E.; Clette, F.; Podladchikova,
O.; Nicula, B.; Hochedez, J. -F.; Wauters, L.; Willems, S.
Bibcode: 2005AnGeo..23.3115B
Altcode:
The Solar Influences Data analysis Center (SIDC) is the World Data
Center for the production and the distribution of the International
Sunspot Index, coordinating a network of about 80 stations
worldwide. From this core activity, the SIDC has grown in recent years
to a European center for nowcasting and forecasting of solar activity
on all timescales. This paper reviews the services (data, forecasts,
alerts, software) that the SIDC currently offers to the scientific
community. The SIDC operates instruments both on the ground and in
space. The USET telescope in Brussels produces daily white light and
Hα images. Several members of the SIDC are co-investigators of the
EIT instrument onboard SOHO and are involved in the development of the
next generation of Europe's solar weather monitoring capabilities. While
the SIDC is staffed only during day-time (7 days/week), the monitoring
service is a 24 h activity thanks to the implementation of autonomous
software for data handling and analysis and the sending of automated
alerts. We will give an overview of recently developed techniques for
visualization and automated analysis of solar images and detection of
events significant for space weather (e.g. CMEs or EIT waves). As part
of the involvement of the SIDC in the ESA Pilot Project for Space
Weather Applications we have developed services dedicated to the
users of the Global Positioning System (GPS). As a Regional Warning
Center (RWC) of the International Space Environment Service (ISES),
the SIDC produces daily forecasts of flaring probability, geomagnetic
activity and 10.7 cm radio flux. The accuracy of these forecasts will
be investigated through an in-depth quality analysis.
Title: Swap: AN EUV Imager for Solar Monitoring on Board of PROBA2
Authors: Katsiyannis, A. C.; Berghmans, D.; Nicula, B.; Defise,
J. -M.; Lawrence, G.; Lecat, J. -H.; Hochedez, J. -F.; Slemzin, V.
Bibcode: 2005ESASP.596E..70K
Altcode: 2005ccmf.confE..70K
No abstract at ADS
Title: Space Weather with ESA's PROBA2 Mission
Authors: Lawrence, G.; Berghmans, D.; Hochedez, J. -F.; Ben-Moussa,
A.; Defise, J. -M.; Delouille, V.; Dominique, M.; Katsitannis, A.;
Lecat, J. -H.; Nicula, B.; Schmutz, W.; Slemzin, V.; Theissen, A.
Bibcode: 2005ESASP.592..685L
Altcode: 2005ESASP.592E.137L; 2005soho...16E.137L
No abstract at ADS
Title: Spatial Distribution and North-South Asymmetry of Coronal
Bright Points from Mid-1998 to Mid-1999
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Rušdjak, V.; Clette,
F.; Hochedez, J. -F.; Verbanac, G.; Temmer, M.
Bibcode: 2005SoPh..231...29B
Altcode:
Full-disc full-resolution (FDFR) solar images obtained with the Extreme
Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric
Observatory (SOHO) were used to analyse the centre-to-limb function and
latitudinal distribution of coronal bright points. The results obtained
with the interactive and the automatic method, as well as for three
subtypes of coronal bright points for the time period 4 June 1998 to 22
May 1999 are presented and compared. An indication of a two-component
latitudinal distribution of coronal bright points was found. The
central latitude of coronal bright points traced with the interactive
method lies between 10∘ and 20∘. This is
closer to the equator than the average latitude of sunspots in the
same period. Possible implications for the interpretation of the
solar differential rotation are discussed. In the appendix, possible
differences between the two solar hemispheres are analysed. More coronal
bright points were present in the southern solar hemisphere than in
the northern one. This asymmetry is statistically significant for the
interactive method and not for the automatic method. The visibility
function is symmetrical around the central meridian.
Title: SWAP: an EUV imager for solar monitoring on board of PROBA2
Authors: Katsiyannis, Athanassios C.; Berghmans, David; Hochedez,
Jean-Francois; Nicula, Bogdan; Lawrence, Gareth; Defise, Jean-Marc;
Ben-Moussa, Ali; Delouille, Veronique; Dominique, Marie; Lecat,
Jean-Herve; Schmutz, W.; Theissen, Armin; Slemzin, Vladimir
Bibcode: 2005SPIE.5901..236K
Altcode:
PROBA2 is an ESA technology demonstration mission to be launched in
early 2007. The two primary scientific instruments on board of PROBA2
are SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) and the LYRA VUV radiometer. SWAP provides a full disk
solar imaging capability with a bandpass filter centred at 17.5 nm
(FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on
an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV)
enhanced APS CMOS will be used as a detector. As the prime goal of the
SWAP is solar monitoring and advance warning of Coronal Mass Ejections
(CME), on-board intellige nce will be implemented. Image recognition
software using experimental algorithms will be used to detect CMEs
during the first phase of eruption so the event can be tracked by
the spacecraft without huma n intervention. LYRA will monitor solar
irradiance in four different VUV passbands with a cadence of up to
100 Hz. The four channels were chosen for their relevance to solar
physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220
nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that
includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter
channel. On-board calibration sources will monitor the stability of
the detectors and the filters throughout the duration of the mission.
Title: Poisson Recoding Of Solar Images For Enhanced Compression
Authors: Nicula, Bogdan; Berghmans, David; Hochedez, Jean-François
Bibcode: 2005SoPh..228..253N
Altcode:
The amount of useful scientific data that a space-borne telescope
produces is often limited by the available telemetry of the
platform. General purpose image compression schemes are usually used
to compress the image either lossy or losslessly. These schemes do not
take into account the fact that pixel values of typical solar images
are only known to within a certain uncertainty range. We present a
preprocessing method to enhance the performance (compression ratio) of
any subsequent image compression scheme. The method uses estimates of
the photon shot and thermal noises to compute a recoding look-up table
that maps the initial data into uncertainty intervals. The recoding
method is lossy in a mathematical sense but lossless in a physical
sense, since the image alterations are guaranteed to be smaller than
the Poisson noise. The performance of any further compression algorithm
is enhanced while achieving a known guaranteed maximum absolute error
for each pixel in the case of lossless compression.
Title: Wavelet Spectrum Analysis Of Eit/Soho Images
Authors: Delouille, V.; De Patoul, J.; Hochedez, J. F.; Jacques, L.;
Antoine, J. P.
Bibcode: 2005SoPh..228..301D
Altcode:
The extreme ultraviolet imaging telescope (EIT) of SOHO offers a unique
record of the solar atmosphere for its sampling in temperature, field
of view, resolution, duration, and cadence. To investigate globally and
locally its topology and evolution during the solar cycle, we consider
a multi-scale approach, and more precisely we use the wavelet spectrum.
Title: SWAP: Sun watcher with a new EUV telescope on a technology
demonstration platform
Authors: Defise, Jean-Marc; Lecat, Jean-Hervé; Mazy, Emmanuel;
Rochus, Pierre; Rossi, Laurence; Thibert, Tanguy; Gillis, Jean-Marie;
Berghmans, David; Hochedez, Jean-François; Schühle, Udo
Bibcode: 2004ESASP.554..257D
Altcode: 2004icso.conf..257D
SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) is an instrument that has been selected to fly on the
PROBA-2 technology demonstration platform, a program of the European
Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis
degraded Ritchey Chretien telescope that will image the EUV solar
corona at 19.5 nm on a specifically fabricated extreme ultraviolet
(EUV) sensitivity enhanced CMOS APS detector. The optical design and
the optical coatings are derived from the Extreme Ultraviolet Imaging
Telescope (EIT) operating on-board SOHO since 1995. It has been adapted
for a single wavelength telescope with off-axis optics. It allows to
use smaller optics and filters, with simple internal baffles avoiding
external protruding parts. The superpolished optics will receive a
multilayer coating that provides spectral selection centred on 19.5
nm and EUV reflectivity in normal incidence. This compact design is
specifically adapted for accommodation on PROBA-2, where mass and
envelope requirements are very stringent The SWAP PROBA-2 program will
be an opportunity to demonstrate this new optical concept, while it
will also validate space remote sensing with APS detectors, as well as
on-board image processing capabilities. On the science outcomes, SWAP
will provide solar corona images in the Fe XII line on a baselined 2-min
cadence. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or 'EIT-waves', associated with the
early phase of coronal mass ejections. The SWAP data will complement
the observations provided by SOHO-EIT, and STEREO-SECCHI.
Title: Development of imaging arrays for solar UV observations based
on wide band gap materials
Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis;
Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul;
Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock,
Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex,
Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos;
Omnes, Franck; John, Joachim; Van Hoof, Chris
Bibcode: 2004SPIE.5171..231S
Altcode:
Solar ultraviolet imaging instruments in space pose most demanding
requirements on their detectors in terms of dynamic range, low noise,
high speed, and high resolution. Yet UV detectors used on missions
presently in space have major drawbacks limiting their performance
and stability. In view of future solar space missions we have started
the development of new imaging array devices based on wide band gap
materials (WBGM), for which the expected benefits of the new sensors -
primarily visible blindness and radiation hardness - will be highly
valuable. Within this initiative, called "Blind to Optical Light
Detectors (BOLD)", we have investigated devices made of AlGa-nitrides
and diamond. We present results of the responsivity measurements
extending from the visible down to extreme UV wavelengths. We discuss
the possible benefits of these new devices and point out ways to build
new imaging arrays for future space missions.
Title: SWAP: Sun watcher using APS detector on-board PROBA-2, a new
EUV off-axis telescope on a technology demonstration platform
Authors: Defise, Jean-Marc; Berghmans, David; Hochedez, Jean-Francois
E.; Lecat, Jean-Herve M.; Mazy, Emmanuel; Rochus, Pierre L.; Thibert,
Tanguy; Nicolosi, Piergiorgio; Pelizzo, Maria G.; Schuehle, Udo H.;
Van der Linden, Ronald A. M.; Zhukov, Andrei N.
Bibcode: 2004SPIE.5171..143D
Altcode:
SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) is an instrument that has been selected to fly on the
PROBA-II technology demonstration platform, a program of the European
Space Agency (ESA) to be launched in 2006. This paper presents the
instrument concept and its scientific goals. SWAP uses an off-axis
Ritchey Chretien telescope that will image the EUV solar corona at 19.5
nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity
enhanced CMOS APS detector. This type of detector has advantages that
promise to be very profitable for solar EUV imaging. The SWAP design
is built on a similar concept as the MAGRITTE instrument suite for
the NASA Solar Dynamics Observatory (SDO) mission to be launched in
2007. The optics have been adapted to the detector size. The SWAP
PROBA-2 program will be an opportunity to demonstrate and validate
the optical concept of MAGRITTE, while it will also validate space
remote sensing with APS detectors. On the science outcomes, SWAP will
provide solar corona images in the Fe XII line on a baselined 1-min
cadence. Observations with this specific wavelength allow detecting
phenomena, such as solar flares or 'EIT-waves", associated with the
early phase of coronal mass ejections. Image recognition software will
be developed that automatically detects these phenomena and sends out
space weather warnings. Different modules of this software will run
both on the ground system as well as on the onboard computer of PROBA
II. The SWAP data will complement the observations provided by SOHO-EIT,
and STEREO-SECCHI.
Title: Height correction in the measurement of solar differential
rotation determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.; Roša, D.
Bibcode: 2004A&A...414..707B
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory
(SOHO) are used to analyse solar differential rotation by tracing
coronal bright points for the period June 4, 1998 to May 22, 1999. A
method for the simultaneous determination of the true solar synodic
rotation velocity and the height of the tracers is applied to data
sets analysed with interactive and automatic methods. The calculated
height of coronal bright points is on average 8000-12000 km above
the photosphere. Corrected rotation velocities are transformed
into sidereal ones and compared with results from the literature,
obtained with various methods and tracers. The differential rotation
profile determined by coronal bright points with the interactive method
corresponds roughly to the profile obtained by correlating photospheric
magnetic fields and the profile obtained from the automatic method
corresponds roughly to the rotation of sunspot groups. This result is
interpreted in terms of the differences obtained in the latitudinal
distribution of coronal bright points using the two methods.
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: LYRA: the Solar UV radiometer onboard PROBA-2
Authors: Hochedez, J. -F.; Lyra Team
Bibcode: 2004cosp...35.2934H
Altcode: 2004cosp.meet.2934H
LYRA (LYman-alpha RAdiometer) is the solar UV radiometer that
will embark in 2006 onboard PROBA-2, a technologically oriented ESA
micro-mission. A solar EUV imaging telescope, SWAP, will operate next
to it. LYRA is designed and manufactured by a Belgian-Swiss-German
consortium (ROB, PMOD/WRC, IMEC, CSL, MPS & BISA). LYRA will monitor
the solar irradiance in four carefully selected UV passbands. The
channels are being chosen for their relevance to Aeronomy, Space Weather
and Solar Physics: 1/ Lyman-alpha (121.6 nm), 2/ the 200-220 nm Herzberg
continuum range (interference filters for the two former passbands), 3/
Al filter channel (17-70 nm) covering He II-30.4 nm, 4/ XUV Zr channel
(1-20 nm), where solar variability is highest. This will make LYRA an
efficient flare monitor, and a complement to GOES-N XRS/EUV. Radiometric
calibration shall convert digital units into photon fluxes at any time
of the mission. LYRA will benefit from diamond detectors: it will be the
first space assessment of the pioneering UV detectors program, initiated
and coordinated at the ROB. Diamond, a wide bandgap material, makes
the sensors solar-blind, which allows suppressing the usual filters,
that block the unwanted visible, but attenuate seriously the desired
UV radiation. The partial removal thereof enhances the effective area,
and therefore, increases the accuracy, the cadence (up to 100Hz),
or an optimum of both. A redundancy strategy maximizes the accuracy
and the stability of the measurements. Visible and UV LEDs will allow
disentangling the various degradations (detectors or filters). The
instrument and its software are such that LYRA will be an innovative
solar monitoring tool for operational space weather nowcasting and
research. LYRA demonstrates the use of technologies crucial for future
ESA missions such as Solar Orbiter, and for other applications as well
(ozone hole, EUV lithography, etc.).
Title: Solar-Blind Diamond Detectors for Lyra, the Solar VUV
Radiometer on Board Proba II
Authors: Benmoussa, A.; Hochedez, J. -F.; Schmutz, W. K.; Schühle,
U.; Nesládek, M.; Stockman, Y.; Kroth, U.; Richter, M.; Theissen,
A.; Remes, Z.; Haenen, K.; Mortet, V.; Koller, S.; Halain, J. P.;
Petersen, R.; Dominique, M.; D'Olieslaeger, M.
Bibcode: 2003ExA....16..141B
Altcode:
Fabrication, packaging and experimental results on the calibration
of metal-semiconductor-metal (MSM) photodetectors made on diamond
are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use
diamond detectors for the first time in space for a solar physics
instrument. A set of measurement campaigns was designed to obtain the
XUV-to-VIS responsivity of the devices and other characterizations. The
measurements of responsivity in EUV and VUV spectral ranges (40 240
nm) have been carried out by the Physkalisch-Technische Bundesanstalt
(PTB) in Germany at the electron storage ring BESSY II. The longer
wavelength range from 210 to 1127 nm was measured with monochromatic
light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a
photoresponse which lie in the 35 65 mA/W range at 200 nm (corresponding
to an external quantum efficiency of 20 40%) and indicate a visible
rejection ratio (200 500 nm) higher than four orders of magnitude.
Title: Extracting the apparent motion from two successive EIT images
Authors: Gissot, Samuel F.; Hochedez, J. -F.; Dibos, F.; Brajša,
R.; Jacques, L.; Berghmans, D.; Zhukov, A.; Clette, F.; Wöhl, H.;
Antoine, J. -P.
Bibcode: 2003ESASP.535..853G
Altcode: 2003iscs.symp..853G
The EIT observations cover more than seven years of the 23rd solar
cycle. The main synoptic dataset, usually refered to as the "CME
Watch", is a nearly uninterrupted sequence of images taken in the Fe
XII bandpass at a cadence of four images per hour. In this work we
study motion tracking methods in order to estimate displacements from
frame to frame. We have implemented a novel optical flow algorithm,
and tested it on a couple of successive images. We have linked the
apparent motion occurring between two frames to the expected rotation
rate. On this short time scale (20 minutes), we are able to retrieve
the global parameters of the solar differential rotation. A strategy
for the extraction of region with reliable motion will be discussed.
Title: Solar Wind Disturbances and Their Sources in the EUV Solar
Corona
Authors: Zhukov, A. N.; Veselovsky, I. S.; Clette, F.; Hochedez,
J. -F.; Dmitriev, A. V.; Romashets, E. P.; Bothmer, V.; Cargill, P.
Bibcode: 2003AIPC..679..711Z
Altcode:
We investigate possible links between the activity manifestations in the
solar corona and conditions in the solar wind. For the reduction of this
immense task we have selected 206 events in the solar wind in 1997 -
2000 corresponding to geomagnetic events with Ap > 20 (compiled into
a database at <emph TYPE="46">http://alpha.sinp.msu.ru/apev). Up
to now, 24 events during the epoch of low solar activity (January 1997 -
January 1998) are investigated. The solar wind conditions monitored by
ACE and WIND spacecraft were traced back to the solar corona observed
by SOHO/EIT. The search for coronal signatures which are probably
associated with the disturbed solar wind conditions was performed. The
coronal sources of these 24 events are identified, namely: eruptions in
active regions, filament eruptions and coronal holes. It is shown that
halo and partial halo CMEs observed within the SOHO/LASCO sensitivity
limits are not necessary indicators of Earth-directed eruptions, and
coronal EUV dimmings can be used as a complementary indicator. We also
found that a structure now conventionally called a ``sigmoid'' cannot
be represented as a single S-shaped loop (flux tube), but exhibits an
assembly of many smaller structures. It could be formed and destroyed
via eruptions.
Title: Properties of the solar velocity field indicated by motions
of coronal bright points
Authors: Vršnak, B.; Brajša, R.; Wöhl, H.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.
Bibcode: 2003A&A...404.1117V
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
are used to analyse properties of the solar velocity field by tracing
coronal bright points from June 4, 1998 to May 22, 1999. Rotation
velocity residuals, meridional motions and their relationship are
investigated. Zones of slow and fast rotation found in motions of
coronal bright points are consistent with the pattern of torsional
oscillations, indicating that the statistical velocity pattern
of bright point motions reflects the large-scale plasma flows. A
complex pattern of meridional motion is deduced: The equatorward
flows are found to dominate at low (B<10deg) and high
(B>40deg) latitudes, whereas at mid-latitudes (B~
10deg-40deg) a poleward flow is inferred. The
complete data set shows no significant correlation between rotation
residuals and meridional motions. However, when a subsample of
coronal bright points including only the ``point-like structures''
(predominantly young bright points) is considered, a statistically
significant correlation is found. On average, faster tracers show
equatorward motion and the slower ones show poleward motion. Such
a segregation is reflected in a statistically significant
covariance of the rotation residuals and meridional velocities
in the order of -1000 m2 s-2, revealing an
equatorward transport of angular momentum. The negative value of the
covariance is provided by the high velocity tail in the velocity
distribution of point-like structures, representing less than 15%
of the population. The latitude dependence of the covariance can be
expressed as Q=-62 B + 200 m2 s-2 covering the
range B=0deg-60deg.
Title: New UV detectors for solar observations
Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.;
Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.;
Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.;
Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider,
Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.;
Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock,
Anthony J.; Van Hoof, Chris A.
Bibcode: 2003SPIE.4853..419H
Altcode:
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide bandgap
materials (in particular diamond and Al-Ga-nitrides). The investigation
is proposed in view of the Solar Orbiter (S.O.) UV instruments, for
which the expected benefits of the new sensors -primarily visible
blindness and radiation hardness- will be highly valuable. Despite
various advances in the technology of imaging detectors over the last
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations inherent to their actual material
and technology. Yet, the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will be decisive for
the forthcoming solar space missions. The advent of imagers based on
wide-bandgap materials will permit new observations and, by simplifying
their design, cheaper instruments. As for the Solar Orbiter, the
aspiration for wide-bandgap material (WBGM) based UV detectors is still
more sensible because the spacecraft will approach the Sun where the
heat and the radiation fluxes are high. We describe the motivations,
and present the program to achieve revolutionary flight cameras within
the Solar Orbiter schedule as well as relevant UV measurements.
Title: Solar rotation velocity determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. F.; Roša, D.; Hržina, D.
Bibcode: 2003HvaOB..27...13B
Altcode:
Full-disc solar images in the extreme ultraviolet part of the spectrum
from the SOHO spacecraft (instrument EIT, data in the spectral line of
Fe XV at a wavelength of 28.4 nm) are used to identify and trace coronal
bright points with the interactive and automatic method. The Solar
rotation was determined for the period June 4, 1998 to May 22, 1999
and a two-step velocity filter was applied. Histograms of latitudinal
and central meridian distance distributions of coronal bright points,
for both solar hemispheres treated together (north and south, east and
west), are presented and compared for different reduction procedures.
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: The Solar Influences Data Analysis Center: current status of
expanding activities
Authors: Clette, F.; van der Linden, R.; Cugnon, P.; Berghmans,
D.; Foullon, C.; Wouters, L.; Verwichte, E.; Hochedez, J. -F.;
Vanlommel, P.
Bibcode: 2002ESASP.506..125C
Altcode: 2002ESPM...10..125C; 2002svco.conf..125C
Over the last 24 months, the activities of the SIDC, which is the
European Regional Warning Center of the ISES, have steadily expanded. A
7-day/week service has been implemented, the SIDC Web interface has
been reworked and expanded and the number of registered users increased
further. New image data have been added, including new photospheric
and chromospheric CCD images from the Uccle Station. We summarize here
the new services provided to the community and some statistics about
the success rate of our forecasts. We also outline the orientations
of the future SIDC development.
Title: Solar differential rotation determined by tracing coronal
bright points in SOHO-EIT images. II. Results for 1998/99 obtained
with interactive and automatic methods
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.
Bibcode: 2002A&A...392..329B
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
were used to analyse solar differential rotation by tracing coronal
bright points. The results obtained with the interactive and the
automatic method for the time period June 4, 1998 to May 22, 1999 are
presented and compared. A possible north-south rotational asymmetry
and differences in the rotation velocity curves for various subtypes
of tracers are investigated.
Title: Small features in the EIT-SOHO images
Authors: Hochedez, J. -F.; Jacques, L.; Zhukov, A.; Clette, F.;
Antoine, J. -P.
Bibcode: 2002ESASP.508..295H
Altcode: 2002soho...11..295H
The Extreme ultraviolet Imaging Telescope (EIT) of SoHO incessantly
observed small coronal and transition region features: EUV bright
points, ephemeral regions, brightenings, network enhancements, loop
segments, etc. In this work, the small objects are extracted and
characterized automatically in terms of their scale, location, peak and
background intensities. We correct for the visibility bias introduced
by the expansion of bright regions that develops with the solar cycle,
and we plot the resulting instantaneous densities over the 1996-2001
period. The four time-series exhibit dissimilar trends. The 171 Å
and 195 Å channels are found to show a moderate anti-cyclic behaviour.
Title: Global asymmetry of the Sun observed in the extreme ultraviolet
radiation
Authors: Zhukov, A. N.; Veselovsky, I. S.; Hochedez, J. -F.; Clette,
F.; Panasenco, O. A.; Cugnon, P.
Bibcode: 2002ESASP.508..189Z
Altcode: 2002soho...11..189Z
We report on the observations of the solar luminosity variations in
four SOHO/EIT bandpasses over the period 1996 - 2001. Contributions
of coronal holes, intermediate brightness features, active regions
and bright points are evaluated. We find that during the epoch of low
activity a significant contribution to the longitudinal asymmetry, and
thus to the 27-day variability of the solar EUV radiation, is produced
by the numerous intermediate brightness elements that are globally
distributed over large areas (up to 2/3 of the whole surface of the Sun)
and generally correspond to the "quiet Sun". During the activity minimum
the contribution of this component is comparable to the active regions
contribution. The "quiet Sun" average brightness exhibits rotational
modulation throughout half of the solar cycle observed by SOHO.
Title: Multiscale activity observed by EIT/SoHO
Authors: Hochedez, J. -F.; Jacques, L.; Verwichte, E.; Berghmans,
D.; Wauters, L.; Clette, F.; Cugnon, P.
Bibcode: 2002ESASP.477..115H
Altcode: 2002scsw.conf..115H
The Extreme ultraviolet Imaging Telescope (EIT) of SoHO provides a
high-resolution and large sampling of the solar corona in time, space
and brightness. To extract the wealth of its physics, it is valuable to
adopt a multiscale approach. The Mexican Hat (MH) Continuous Wavelet
Transform (CWT) is used for the first time to derive statistically
the distribution of scales over 4 Mm. The global behaviour of the
small scales offers a powerful way to monitor coronal activity. This
is demonstrated with the May 1998 "CME Watch" data. This benefit
is of space weather relevance and could improve forecasting of the
solar activity.
Title: The solar influences data analysis centre
Authors: Berghmans, D.; Clette, F.; Cugnon, P.; Gabryl, J. -R.;
Hochedez, J. -F.; Van der Linden, R. A. M.; Verwichte, E.
Bibcode: 2002JASTP..64..757B
Altcode: 2002JATP...64..757B
Since 1981, the Royal Observatory of Belgium has operated the
Sunspot Index Data Centre, the World Data Centre for the Sunspot
Index. Recently, the Space Weather Forecast Centre of Paris-Meudon
was transferred and added to the activities of the SIDC. Moreover,
a complete archive of all images of the SOHO instrument EIT has
become available at the SIDC. Given all these extensions, the new
style SIDC has become a `Solar Influences Data Centre' that analyses
solar activity and provides services on three different time scales:
1. Fast warnings and real time monitoring. As the Regional Warning
Centre (RWC) for Western Europe of the International Space Environment
Service (ISES), the SIDC collects and redistributes solar, geomagnetic,
and ionospheric data in Western Europe. Short-term predictions (3 days)
and alerts are produced on a daily basis. 2. Forecasts and middle term
analysis. The SIDC takes care of the calculation of a sunspot index,
called the International Sunspot Number. We compute and broadcast the
daily, monthly, yearly international sunspot numbers, with middle range
predictions (up to 12 months). 3. Post-event analysis and long-term
solar cycle analysis. Since the launch of SOHO, EIT offers a global view
of the EUV corona over the whole rising phase of the solar activity
cycle. Such a long-duration data series is unprecedented and allows
the study of the evolution over the solar cycle of objects classes
such as active regions, coronal holes, coronal mass ejections or flares.
Title: The Solar Orbiter Mission and Design Recommendations
Authors: Schuhle, U.; Thomas, R.; Hochedez, J. -F.
Bibcode: 2002ISSIR...2..361S
Altcode: 2002ESASR...2..361S; 2002rcs..conf..361S
A short overview is given of the Solar Orbiter mission. First, the key
scientific aims of the mission are briefly described. As the mission
profile has consequences on the design of the payload instruments
and their calibration, the mission design is described. Possible
implications and problems for the cleanliness and the calibration
stability of the instruments are outlined. Some solutions are discussed.
Title: 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: New UV Detector Concepts
Authors: Hochedez, J. -F.; Schuhle, U.; Lemaire, P.
Bibcode: 2002ISSIR...2..371H
Altcode: 2002rcs..conf..371H; 2002ESASR...2..371H
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide-bandgap
semiconductor materials (in particular diamond and Al-Ganitrides). This
investigation is proposed in view of the Solar Orbiter UV instruments,
for which the expected benefits of the new sensors, visible blindness
and radiation hardness, will be highly valuable. Despite various
advances in the technology of imaging detectors over the last few
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations which are inherent to their actual material
and technology. Yet the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will all be decisive for
forthcoming solar space missions. The advent of imagers made of large
wide-bandgap semiconductors would surmount many present weaknesses. This
would open up new scientific prospects and, by simplifying their design,
would even make the instruments cheaper. As for the Solar Orbiter,
the aspiration for wide-bandgap semiconductor-based UV detectors is
still more desirable because the spacecraft will approach the Sun
where heat and radiation fluxes are high. We describe the motivations
leading to such new developments, and present a programme to achieve
revolutionary flight cameras within the Solar Orbiter schedule.
Title: Wide bandgap EUV and VUV imagers for the Solar Orbiter
Authors: Hochedez, Jean-François; Lemaire, Philippe; Pace, Emanuele;
Schühle, Udo; Verwichte, Erwin
Bibcode: 2001ESASP.493..245H
Altcode: 2001sefs.work..245H
No abstract at ADS
Title: Slow magneto-acoustic waves in coronal loops
Authors: Verwichte, E.; Nakariakov, V. M.; Berghmans, D.; Hochedez,
J. -F.
Bibcode: 2001ESASP.493..395V
Altcode: 2001sefs.work..395V
No abstract at ADS
Title: Solar differential rotation determined by tracing coronal
bright points in SOHO-EIT images. I. Interactive and automatic
methods of data reduction
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.
Bibcode: 2001A&A...374..309B
Altcode:
Full-disc solar images obtained with the Extreme Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
were used to analyse solar differential rotation determined by tracing
coronal bright points. Two different procedures were developed and
compared: an interactive and an automatic method. The interactive method
is based on the visual tracing of coronal bright points in consecutive
images using computer programs written in the Interactive Data Language
(IDL). The automatic method relies on the IDL procedure ``Regions Of
Interest (ROI) segmentation'' which is used to detect and follow bright
points in triplets of consecutive images. The test-results obtained
applying both methods by different persons who performed tracing are
presented and compared. The advantages and disadvantages of the two
methods are discussed.
Title: Global Asymmetry of the Sun Observed in the Extreme Ultraviolet
Radiation
Authors: Veselovsky, I. S.; Zhukov, A. N.; Dmitriev, A. V.; Tarsina,
M. V.; Clette, F.; Cugnon, P.; Hochedez, J. F.
Bibcode: 2001SoPh..201...27V
Altcode:
We report on observations of the solar luminosity variations in the
Fe xii line (195 Å) over the period 1996-1999, which corresponds
to the minimum and rising phase of the current 23rd solar cycle. The
relatively or rather high temporal cadence and spatial resolution of
the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar
and Heliospheric Observatory (SOHO) allowed a nearly continuous
measurement of intensity of different structures on the Sun. We
find that a significant contribution to the longitudinal asymmetry,
and thus to the 27-day variability of the solar EUV radiation,
is produced by the numerous intermediate brightness elements that
are globally distributed over large areas (up to about of the whole
surface of the Sun). When activity is low, this component even becomes
dominant over the contribution from localized active regions and bright
points. This suggests that weak magnetic field areas outside active
regions constitute an important factor through which solar activity
modulates the solar EUV luminosity.
Title: Slow magnetoacoustic waves in coronal loops: EIT and TRACE
Authors: Robbrecht, E.; Verwichte, E.; Berghmans, D.; Hochedez, J. F.;
Poedts, S.; Nakariakov, V. M.
Bibcode: 2001A&A...370..591R
Altcode:
On May 13, 1998 the EIT (Extreme ultraviolet Imaging Telescope) on board
of SoHO (Solar and Heliospheric Observatory) and TRACE (Transition
Region And Coronal Explorer) instruments produced simultaneous high
cadence image sequences of the same active region (AR 8218). TRACE
achieved a 25 s cadence in the Fe Ix (171 Å) bandpass while EIT
achieved a 15 s cadence (operating in ``shutterless mode'', SoHO JOP
80) in the Fe Xii (195 Å) bandpass. These high cadence observations
in two complementary wavelengths have revealed the existence of weak
transient disturbances in an extended coronal loop system. These
propagating disturbances (PDs) seem to be a common phenomenon in
this part of the active region. The disturbances originate from small
scale brightenings at the footpoints of the loops and propagate along
the loops. The projected propagation speeds roughly vary between 65
and 150 km s-1 for both instruments which is close to and
below the expected sound speed in the coronal loops. The measured slow
magnetoacoustic propagation speeds seem to suggest that the transients
are sound (or slow) wave disturbances. This work differs from previous
studies in the sense that it is based on a multi-wavelength observation
of an entire loop bundle at high cadence by two EUV imagers. The
observation of sound waves along the same path shows that they propagate
along the same loop, suggesting that loops contain sharp temperature
gradients and consist of either concentric shells or thin loop threads,
at different temperatures.
Title: An Analysis of the Solar Rotation Velocity by Tracing Coronal
Features
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.;
Wöhl, H.; Clette, F.; Hochedez, J. -F.
Bibcode: 2001IAUS..203..377B
Altcode:
Full-disc solar images in the extreme ultraviolet part of the spectrum
from the SOHO spacecraft (EIT) are used to identify various coronal
structures appropriate for the solar rotation determination (e.g. bright
points and coronal holes). From the time differences in tracer positions
(more than 1 image per day) solar rotation velocities are measured,
primarily by well-defined tracers, such as coronal bright points, whose
large number and broad coverage of latitudes may provide an unique
opportunity for a solar rotation analysis. The analysis started using
the SOHO data from 1997-1999 and preliminary experiences obtained
measuring solar rotation from the full-disc images in soft X-rays
from the YOHKOH (SXT) satellite were taken into account. This work is
connected to the SOHO EIT Proposal Brajsas.
Title: The European Photon Imaging Camera on XMM-Newton: The MOS
cameras
Authors: Turner, M. J. L.; Abbey, A.; Arnaud, M.; Balasini, M.;
Barbera, M.; Belsole, E.; Bennie, P. J.; Bernard, J. P.; Bignami,
G. F.; Boer, M.; Briel, U.; Butler, I.; Cara, C.; Chabaud, C.; Cole,
R.; Collura, A.; Conte, M.; Cros, A.; Denby, M.; Dhez, P.; Di Coco,
G.; Dowson, J.; Ferrando, P.; Ghizzardi, S.; Gianotti, F.; Goodall,
C. V.; Gretton, L.; Griffiths, R. G.; Hainaut, O.; Hochedez, J. F.;
Holland, A. D.; Jourdain, E.; Kendziorra, E.; Lagostina, A.; Laine,
R.; La Palombara, N.; Lortholary, M.; Lumb, D.; Marty, P.; Molendi,
S.; Pigot, C.; Poindron, E.; Pounds, K. A.; Reeves, J. N.; Reppin, C.;
Rothenflug, R.; Salvetat, P.; Sauvageot, J. L.; Schmitt, D.; Sembay,
S.; Short, A. D. T.; Spragg, J.; Stephen, J.; Strüder, L.; Tiengo,
A.; Trifoglio, M.; Trümper, J.; Vercellone, S.; Vigroux, L.; Villa,
G.; Ward, M. J.; Whitehead, S.; Zonca, E.
Bibcode: 2001A&A...365L..27T
Altcode: 2000astro.ph.11498T
The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs
to record the images and spectra of celestial X-ray sources focused
by the three X-ray mirrors. There is one camera at the focus of each
mirror; two of the cameras contain seven MOS CCDs, while the third uses
twelve PN CCDs, defining a circular field of view of 30'
diameter in each case. The CCDs were specially developed for EPIC, and
combine high quality imaging with spectral resolution close to the Fano
limit. A filter wheel carrying three kinds of X-ray transparent light
blocking filter, a fully closed, and a fully open position, is fitted
to each EPIC instrument. The CCDs are cooled passively and are under
full closed loop thermal control. A radio-active source is fitted for
internal calibration. Data are processed on-board to save telemetry by
removing cosmic ray tracks, and generating X-ray event files; a variety
of different instrument modes are available to increase the dynamic
range of the instrument and to enable fast timing. The instruments were
calibrated using laboratory X-ray beams, and synchrotron generated
monochromatic X-ray beams before launch; in-orbit calibration makes
use of a variety of celestial X-ray targets. The current calibration
is better than 10% over the entire energy range of 0.2 to 10 keV. All
three instruments survived launch and are performing nominally in
orbit. In particular full field-of-view coverage is available, all
electronic modes work, and the energy resolution is close to pre-launch
values. Radiation damage is well within pre-launch predictions and
does not yet impact on the energy resolution. The scientific results
from EPIC amply fulfil pre-launch expectations.
Title: XMM-Newton first-light observations of the Hickson galaxy
group 16
Authors: Turner, M. J. L.; Reeves, J. N.; Ponman, T. J.; Arnaud, M.;
Barbera, M.; Bennie, P. J.; Boer, M.; Briel, U.; Butler, I.; Clavel,
J.; Dhez, P.; Cordova, F.; Dos Santos, S.; Ferrando, P.; Ghizzardi,
S.; Goodall, C. V.; Griffiths, R. G.; Hochedez, J. F.; Holland, A. D.;
Jansen, F.; Kendziorra, E.; Lagostina, A.; Laine, R.; La Palombara,
N.; Lortholary, M.; Mason, K. O.; Molendi, S.; Pigot, C.; Priedhorsky,
W.; Reppin, C.; Rothenflug, R.; Salvetat, P.; Sauvageot, J.; Schmitt,
D.; Sembay, S.; Short, A.; Strüder, L.; Trifoglio, M.; Trümper,
J.; Vercellone, S.; Vigroux, L.; Villa, G.; Ward, M.
Bibcode: 2001A&A...365L.110T
Altcode: 2000astro.ph.10612T
This paper presents the XMM-Newton first-light observations of
the Hickson-16 compact group of galaxies. Groups are possibly the
oldest large-scale structures in the Universe, pre-dating clusters of
galaxies, and are highly evolved. This group of small galaxies, at a
redshift of 0.0132 (or 80 Mpc) is exceptional in the having the highest
concentration of starburst or AGN activity in the nearby Universe. So
it is a veritable laboratory for the study of the relationship between
galaxy interactions and nuclear activity. Previous optical emission
line studies indicated a strong ionising continuum in the galaxies,
but its origin, whether from starbursts, or AGN, was unclear. Combined
imaging and spectroscopy with the EPIC X-ray CCDs unequivocally reveals
a heavily obscured AGN and a separately identified thermal (starburst)
plasma, in NGC 835, NGC 833, & NGC 839. NGC 838 shows only starburst
thermal emission. Starbursts and AGN can evidently coexist in members
of this highly evolved system of merged and merging galaxies, implying
a high probability for the formation of AGN as well as starbursts in
post-merger galaxies.
Title: Long Term Variations in the Extreme UV Corona: the EIT/SoHO
perspective
Authors: Hochedez, J. -F.; Clette, F.; Verwichte, E.; Berghmans, D.;
Cugnon, P.
Bibcode: 2001IAUS..203..501H
Altcode:
Since the start of the SOHO mission, EIT offered a global view of
the extreme ultraviolet corona constinuously over the whole rising
phase of the solar activity cycle. Such a long-duration data serie
is unprecedented. We present here the current results of an ongoing
investigation of the entire EIT data set. In this process, numerous
classes of magnetic regions of all sizes (active regions, coronal
holes, bright points, plumes, transition region network, filaments)
as well as many different classes of dynamic events (CME's, flares,
jets, blinkers, macrospicules) will be identified in EIT images made
in its four bandpasses. The changes in the class properties (location,
size, area, topology, lifetime, integrated flux) or in the relationship
between different object classes can then be monitored over the fast
rise of magnetic activity towards the current maximum. We describe here
the image processing techniques developed for this search as well as
early results.
Title: Determination of the Solar Rotation Tracing EUV Bright Points
with the Automatic Method
Authors: Wöhl, H.; Brajša, R.; Vršnak, B.; Ruždjak, V.; Clette,
F.; Hochedez, J. -F.
Bibcode: 2001HvaOB..25...27W
Altcode:
Full-disc solar images in the extreme ultraviolet part of the spectrum
from the SOHO spacecraft (instrument EIT, data in the spectral
line of Fe XV at the wavelength of 28.4 nm) are used for the solar
rotation determination tracing coronal bright points. From the time
differences in tracer positions, approximately six hours, the solar
rotation velocity is determined automatically for image sequences in
several time intervals from June 4, 1998 to May 22, 1999. The resulting
rotational profiles are mutually compared.
Title: Determination of the Solar Rotation Tracing EUV Bright Points
with the Interactive Method
Authors: Brajša, R.; Wöhl, H.; Schuck, T. J.; Schawinski-Guiton,
K.; Wegner, A.; Vršnak, B.; Ruždjak, V.; Clette, F.; Hochedez, J. -F.
Bibcode: 2001HvaOB..25...13B
Altcode:
Full-disc solar images in the extreme ultraviolet part of the spectrum
from the SOHO spacecraft (instrument EIT, data in the spectral line of
Fe XV at a wavelength of 28.4 nm) are used to visually identify coronal
bright points appropriate for the solar rotation determination. From the
time differences in successive tracer positions, about six hours, the
solar rotation velocity is determined tracing coronal bright points in
several time intervals from June 4, 1998 to May 22, 1999. The resulting
rotational profiles obtained by five observers are mutually compared.
Title: Calibration and flight of the NRL EIT CalRoc
Authors: Newmark, Jeffrey S.; Moses, J. Daniel; Cook, John W.;
Delaboudiniere, Jean-Pierre; Song, Xueyan; Carabetian, Charles;
Bougnet, Marie; Brunaud, Jacqueline; Defise, Jean-Marc; Clette,
Frederic; Hochedez, Jean-Francois E.
Bibcode: 2000SPIE.4139..328N
Altcode:
The ability to derive physical parameters of the Sun from observations
by the Solar and Heliospheric Observatory (SOHO) Extreme Ultraviolet
Imaging Telescope (EIT) greatly increases the scientific return of the
mission. The absolute and time variable calibration of EIT therefore is
of extreme interest. The NRL EIT Calibration Sounding Rocket (CalRoc)
program was initiated to provide well calibrated, contemporaneous
observations in support of SOHO EIT. These observations provide
three benefits to the SOHO EIT data, absolute calibration points,
temporal and spatial information of the EIT EUV response variability
in flight via flat field information and clues to the physics of the
degradation. Details of the bandpasses of the multilayered optics and
the total telescope photometry are presented. Comparisons are shown
with the contemporaneous images from SOHO EIT. Plans for the second
CalRoc flight are discussed. Loss of reflectivity in the multilayer
mirrors has been identified as a new component to the SOHO EIT and
CalRoc degradation.
Title: Slow magnetoacoustic waves in coronal loops: EIT vs TRACE
Authors: Robbrecht, E.; Verwichte, E.; Berghmans, D.; Hochedez, J. F.;
Poedts, S.
Bibcode: 2000AIPC..537..271R
Altcode: 2000wdss.conf..271R
On May 13, 1998 the EIT (Extreme-Ultraviolet Imaging Telescope) and
TRACE (Transition Region And Coronal Explorer) instruments produced
simultaneous high cadence image sequences of the same active region
(AR 8218). TRACE achieved a 25 sec cadence in the Fe IX/X (171 Å)
bandpass while EIT achieved a 15 sec cadence (operating in `shutterless
mode,' SOHO JOP 80) in the Fe XII (195 Å) bandpass. These high
cadence observations in two complementary wavelengths have revealed
the existence of weak transient disturbances in an extended coronal
loop system. These propagating disturbances (PDs) seem to be a
common phenomenon in this part of the active region. The disturbances
originate from small scale brightenings at the footpoints of the loops
and propagate along the loops. The apparent propagation speeds roughly
vary between 65 and 150 km s-1 which is close to the expected
sound speed of the coronal loops. The measured propagation speeds seem
to suggest that the transients are sound (or slow) wave disturbances. .
Title: The Preflight Photometric Calibration of the
Extreme-Ultraviolet Imaging Telescope EIT
Authors: Dere, K. P.; Moses, J. D.; Delaboudinière, J. -P.; Brunaud,
J.; Carabetian, C.; Hochedez, J. -F.; Song, X. Y.; Catura, R. C.;
Clette, F.; Defise, J. -M.
Bibcode: 2000SoPh..195...13D
Altcode:
This paper presents the preflight photometric calibration of the
Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and
Heliospheric Observatory (SOHO). The EIT consists of a Ritchey-Chrétien
telescope with multilayer coatings applied to four quadrants of the
primary and secondary mirrors, several filters and a backside-thinned
CCD detector. The quadrants of the EIT optics were used to observe
the Sun in 4 wavelength bands that peak near 171, 195, 284, and 304
Å. Before the launch of SOHO, the EIT mirror reflectivities, the filter
transmissivities and the CCD quantum efficiency were measured and these
values are described here. The instrumental throughput in terms of an
effective area is presented for each of the various mirror quadrant
and filter wheel combinations. The response to a coronal plasma as
a function of temperature is also determined and the expected count
rates are compared to the count rates observed in a coronal hole,
the quiet Sun and an active region.
Title: Mid-Term Variations in the Extreme UV Corona: the EIT/SOHO
Perspective
Authors: Hochedez, J. F.; Clette, Frederic; Verwichte, Erwin;
Berghmans, David; Cugnon, Pierre
Bibcode: 2000ESASP.463...79H
Altcode: 2000sctc.proc...79H
No abstract at ADS
Title: Measurements of Solar Rotation Using EUV Bright Points -
Preliminary Results
Authors: Brajsa, R.; Woehl, H.; Kasabasic, M.; Rodmann, J.; Vrsnak,
B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.; Clette, F.; Hochedez, J. -F.
Bibcode: 2000HvaOB..24..153B
Altcode:
Full-disc solar images in the extreme ultraviolet part of the spectrum
from the SOHO spacecraft (instrument EIT, data in the spectral line
of Fe XV at the wavelength of 28.4 nm) are used to identify visually
various small-scale coronal structures appropriate for the determination
of the solar rotation. From the time differences in tracer positions,
approximately six hours, the solar rotation velocity is determined
tracing coronal bright points in the period June 4-14, 1998 by four
observers. The resulting rotational profiles are mutually compared
and the reduction methods are discussed.
Title: Future Diamond UV Imagers For Solar Physics
Authors: Hochedez, J. -F.; Verwichte, E.; Bergonzo, P.; Guizard, B.;
Mer, C.; Tromson, D.; Sacchi, M.; Dhez, P.; Hainaut, O.; Lemaire,
P.; Vial, J. -C.
Bibcode: 2000PSSAR.181..141H
Altcode:
No abstract at ADS
Title: An Eruptive Flare Observed by TRACE as a Test for the Magnetic
Authors: Aulaneir, G.; Deluca, E. E.; Golub, L.; Artzner, Guy; Sabine
Coquillart; Hochedez, Jean-Francois; Delaboudinier, Jean-Pierre
Bibcode: 1999ESASP.446..131A
Altcode: 1999soho....8..131A
No abstract at ADS
Title: Quantum efficiency of the XMM pn-CCD camera
Authors: Hartmann, Robert; Hartner, Gisela D.; Briel, Ulrich G.;
Dennerl, Konrad; Haberl, Frank; Strueder, Lothar; Truemper, Joachim;
Bihler, Edgar; Kendziorra, Eckhard; Hochedez, Jean-Francois E.;
Jourdain, Erick; Dhez, Pierre; Salvetat, Philippe; Auerhammer, Jutta
M.; Schmitz, D.; Scholze, Frank; Ulm, Gerhard
Bibcode: 1999SPIE.3765..703H
Altcode:
The quantum efficiency of the pn-CCD detector on the XMM satellite
mission was determined in the spectral range between 150 eV and 15
keV. The unstructured entrance window of the device, which is formed by
an ultrathin reverse biased pn-junction, results in an excellent spatial
homogeneity with a good spectroscopic performance and high detection
efficiency for low energy photons. The large sensitive thickness of
the detector guarantees a high quantum efficiency for photons up to 10
keV. We give a review of the calibration techniques applied for quantum
efficiency measurements at the Synchrotron Radiation Facility at the
Institut d'Astrophysique Spatial in Orsay and the radiometry laboratory
of the Physikalisch-Technische Bundesandstalt at the electron storage
ring BESSY in Berlin. We summarize the applied data correction such as
charge transfer loss and split event recognition and describe the data
analysis to conclude in an absolute quantum efficiency of the pn-CCD.
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: Ground-calibration GSE for the XMM-EPIC instrument at the
Orsay Synchrotron facility
Authors: Trifoglio, Massimo; Gianotti, Fulvio; Stephen, Jon B.;
Balasini, M.; Hochedez, Jean-Francois E.; Chiappetti, Lucio; Glukhov,
R. A.; Hainaut, Olivier; Jourdain, Erick; La Palombara, N.; Marty,
Philippe B.; Moreno, T.; Musso, C.
Bibcode: 1998SPIE.3445..558T
Altcode:
The European Photon Imaging Camera (EPIC) is one of the major
instruments on board the European Space Agency's X-ray Multi-Mirror
cornerstone mission planned for launch at the end of the century. Ground
calibrations have been performed in 1997 and 1998 on the electrical
and flight models of the MOS-CCD and on the flight model of the
p-n-CCD focal plane cameras at he Synchrotron facility at IAS Orsay in
France. The complexity of the imaging systems required a correspondingly
sophisticated calibration equipment, capable of automatically setting
and calibrating the synchrotron beam at a particular energy, controlling
the camera head movement in synchronism with the CCD frame readout,
initializing the instrument and acquiring both the instrument data
and the facility monitor data in realtime. Furthermore, always in
real-time, the data stream was unpacked and stored as photon lists
in FITS format and made available via NFS to the off-line analysis
software. Contemporaneously, a quick look program allowed the operator
to continuously monitor the calibration procedure from a scientific
point of view, ensuring the correct operation of the system. The
calibration system from the point of view of the instrument and the
current status of the project is described.
Title: Spicules and Macrospicules: Simultaneous Hα and He II (304
Å) Observations
Authors: Georgakilas, A. A.; Dara, H.; Zachariadis, Th.; Alissandrakis,
C. E.; Koutchmy, S.; Delannée, C.; Delaboudinière, J. -P.; Hochedez,
J. -F.
Bibcode: 1998ASPC..155..376G
Altcode: 1998sasp.conf..376G
No abstract at ADS
Title: Polar jets and plasmoids:Results from JOP 57
Authors: Delannee, C.; Koutchmy, S.; Delaboudiniere, J. -P.; Hochedez,
J. -F.; Vial, J. -C.; Dara, H.; Georgakilas, A.
Bibcode: 1998ESASP.421..129D
Altcode: 1998sjcp.conf..129D
No abstract at ADS
Title: EIT Observations of the Extreme Ultraviolet Sun
Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner,
G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.;
Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard,
R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus,
P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.;
Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark,
J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.;
Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R.
Bibcode: 1997SoPh..175..571M
Altcode:
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO
spacecraft has been operational since 2 January 1996. EIT observes
the Sun over a 45 x 45 arc min field of view in four emission line
groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination
of the instrument flatfield, the instrument scattering function, and
the instrument aging were necessary for the reduction and analysis
of the data. The observed structures and their evolution in each
of the four EUV bandpasses are characteristic of the peak emission
temperature of the line(s) chosen for that bandpass. Reports on the
initial results of a variety of analysis projects demonstrate the range
of investigations now underway: EIT provides new observations of the
corona in the temperature range of 1 to 2 MK. Temperature studies of
the large-scale coronal features extend previous coronagraph work
with low-noise temperature maps. Temperatures of radial, extended,
plume-like structures in both the polar coronal hole and in a low
latitude decaying active region were found to be cooler than the
surrounding material. Active region loops were investigated in detail
and found to be isothermal for the low loops but hottest at the loop
tops for the large loops.
Title: In-orbit diagnostics of EIT EUV CCD radiation-induced aging
Authors: Defise, Jean-Marc; Clette, Frederic; Moses, John Daniel;
Hochedez, Jean-Francois E.
Bibcode: 1997SPIE.3114..598D
Altcode:
The extreme UV imaging telescope (EIT) on-board SOHO is performing a
global survey of the extreme ultraviolet (EUV) solar corona. Operating
since January 96, EIT has been producing tens thousands of images of the
Sun in four narrow channels (171, 195, 284 and 304 angstrom). orbiting
around the L1 Lagrangian point and oriented permanently towards the
Sun, the EIT mission is a unique opportunity to study an instrument
continuously exposed to solar EUV radiations. The backside thinned
CCD detector is showing significant changes in its overall signal
and in local 'burn in' regions. Periodic bakeouts allowed to
restore a good efficiency. However, a specific observation program
has been set up to diagnose the origin of the signal decay. In this
framework, photon transfer analyses are performed on solar EUV images,
providing good indications on the local charge collection efficiency
status. Calibration lamp images are also used to eluate the signal
recovery in the visible range. The signal degradation seems to be the
result of two competing effects: periodic deposition of a contamination
layer, and charge mobility change in the CCD Si layer as a function
of the accumulated EUV dose. In this paper, the CCD quantum properties
evolution is discussed, as well as the contamination issue. Preliminary
diagnostics on the CCD aging under EUV radiations are exposed.
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.;
Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier,
F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.;
Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.;
Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.;
Llebaria, A.; Schwenn, R.; Simnett, G. M.
Bibcode: 1997SoPh..175..601D
Altcode:
We present the first observations of the initiation of a coronal mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
experiment on SOHO show that the CME began in a small volume and was
initially associated with slow motions of prominence material and a
small brightening at one end of the prominence. Shortly afterward,
the prominence was accelerated to about 100 km s-1 and
was preceded by a bright loop-like structure, which surrounded an
emission void, that traveled out into the corona at a velocity of
200-400 km s-1. These three components, the prominence,
the dark void, and the bright loops are typical of CMEs when seen at
distance in the corona and here are shown to be present at the earliest
stages of the CME. The event was later observed to traverse the LASCO
coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest
is the fact that this large-scale event, spanning as much as 70 deg in
latitude, originated in a volume with dimensions of roughly 35" (2.5
x 104 km). Further, a disturbance that propagated across
the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the
west limb.
Title: Institut d'Astrophysique Spatiale (IAS) 0.1- to 15-keV
Synchrotron Radiation Facility beam lines
Authors: Dhez, Pierre; Jourdain, Erick; Hainaut, Olivier; Hochedez,
Jean-Francois E.; Labeque, Alain; Salvetat, Philippe; Song, Xue Yan
Bibcode: 1997SPIE.3114..134D
Altcode:
Two beam lines have been built at the Institute d'Astrophysique Spatiale
(IAS) d'Orsay to perform absolute calibration of the EPIC (European
photon imaging camera). EPIC consists of three x-ray charge coupled
device (CCD) cameras having imaging and spectroscopic performances set
at the Wolter telescope focal planes on board the x-ray multi mirror
mission (XMM) planned to be launched by ESA in August 1999. To cover
the desired 0.1 - 15 keV range a dedicated beam line has been built
on each synchrotron sources of the Laboratoire pour l'Utilisation du
Rayonnement Synchrotron (LURE): SACO (0.8 GeV) and DCI (1.5 GeV). Both
beam lines are merging in a clean 23 m(superscript 3) vacuum tank
containing the camera to calibrate. (1) The SACO windowless beam line
is equipped with a grating monochromator. Four plane VLS gratings are
used to cover the low energy range (0.1 - 1.2 keV). A triple grazing
incidence mirror system set in front of the entrance slit removes
the overlapping orders. (2) The high energy beam line on DCI has a 50
micrometer beryllium window and a double flat crystals monochromator
equipped with four different crystal pairs. A double grazing incidence
mirror system set close to the source absorbs the high energy photon
spectra. CCD calibrations will be performed during 1997 second semester
and years 1998.
Title: Association of Extreme-Ultraviolet Imaging Telescope (EIT)
Polar Plumes with Mixed-Polarity Magnetic Network
Authors: Wang, Y. -M.; Sheeley, N. R.; Dere, K. P.; Duffin, R. T.;
Howard, R. A.; Michels, D. J.; Moses, J. D.; Harvey, J. W.; Branston,
D. D.; Delaboudinière, J. -P.; Artzner, G. E.; Hochedez, J. F.;
Defise, J. M.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert,
W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Clette, F.
Bibcode: 1997ApJ...484L..75W
Altcode:
SOHO EIT spectroheliograms showing the polar coronal holes during the
present sunspot minimum are compared with National Solar Observatory
(Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The
chromospheric λ8542 magnetograms, obtained on a routine, near-daily
basis since 1996 June, reveal the Sun's strong polar fields with
remarkable clarity. We find that the Fe IX λ171 polar plumes occur
where minority-polarity flux is in contact with flux of the dominant
polarity inside each polar hole. Moreover, the locations of ``plume
haze'' coincide approximately with the patterns of brightened He
II λ304 network within the coronal hole. The observations appear
to be consistent with mechanisms of plume formation involving
magnetic reconnection between unipolar flux concentrations and nearby
bipoles. The fact that minority-polarity fields constitute only a small
fraction of the total magnetic flux within the polar holes suggests
that plumes are not the main source of the high-speed polar wind.
Title: Polar Jets and Plasmoids: Preliminary Results from JOP 57
Authors: Delannée, C.; Koutchmy, S.; Delaboudiniè, J. -P.; Hochedez,
J. -F.; Vial, J. -C.; Dara, H.; Georgakilas, A.
Bibcode: 1997ESASP.404..327D
Altcode: 1997cswn.conf..327D
No abstract at ADS
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker,
D. G.; Delaboudiniere, J. P.; Hochedez, J. F.; Lamy, P. L.; Schwenn,
R.; Simnett, G. M.; Defise, J. M.; Catura, R. C.
Bibcode: 1997IAUJD..19E..18D
Altcode:
We present the first observations of the initiation of a corona mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
and LASCO experiments on SOHO show that the CME starts in a small volume
and is associated with slow motions of prominence material. At about
the same time, a shock wave is created that travels out into the corona
at a velocity of 400 km s^{-1} ahead of an eruptive prominence. This
shock wave is clearly the event that is later seen as a classical CME
when observed in the coronagraph above 1.5 solar radii. Although the
CME clearly starts in a small region, a chain of activity near the
limb may also be associated with this event.
Title: First Results from EIT
Authors: Clette, F.; Delaboudiniere, J. -P.; Artzner, G. E.; Brunaud,
J.; Gabriel, A. H.; Hochedez, J. -F.; Millier, F.; Song, X. Y.; Au, B.;
Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.;
Defise, J. -M.; Jamar, C.; Rochus, P.; Chauvineau, J. -P.; Marioge,
J. -P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman,
J. B.; Neupert, W. M.; Maucherat, A.; Cugnon, P.; van Dessel, E. L.
Bibcode: 1997ASPC..118..268C
Altcode: 1997fasp.conf..268C
The Extreme-UV Imaging telescope has already produced more than 15000
wide-field images of the corona and transition region, on the disk
and up to 1.5R_⊙ above the limb, with a pixel size of 2.6\arcsec. By
using four different emission lines, it provides the global temperature
distribution in the quiet corona, in the range 0.5 to 3*E(6) K. Its
excellent sensitivity and wide dynamic range allow unprecedented views
of low emission features, even inside coronal holes. Those so-called
``quiet'' regions actually display a wide range of dynamical phenomena,
in particular at small spatial scales and at time scales going down
to only a few seconds, as revealed by all EIT time sequences of
full- or partial-field images. The initial results presented here
demonstrate the importance of this wide-field imaging experiment for
a good coordination between SOHO and ground-based solar telescopes,
as well as for science planning.
Title: SWAN: A Study of Solar Wind Anisotropies on SOHO with Lyman
Alpha Sky Mapping
Authors: Bertaux, J. L.; Kyrölä, E.; Quémerais, E.; Pellinen, R.;
Lallement, R.; Schmidt, W.; Berthé, M.; Dimarellis, E.; Goutail,
J. P.; Taulemesse, C.; Bernard, C.; Leppelmeier, G.; Summanen,
T.; Hannula, H.; Huomo, H.; Kehlä, V.; Korpela, S.; Leppälä,
K.; Strömmer, E.; Torsti, J.; Viherkanto, K.; Hochedez, J. F.;
Chretiennot, G.; Peyroux, R.; Holzer, T.
Bibcode: 1995SoPh..162..403B
Altcode:
On board the SOHO spacecraft poised at L1 Lagrange point, the
SWAN instrument is mainly devoted to the measurement of large scale
structures of the solar wind, and in particular the distribution with
heliographic latitude of the solar wind mass flux. This is obtained from
an intensity map of the sky Lymanα emission, which reflects the shape
of the ionization cavity carved in the flow of interstellar H atoms
by the solar wind. The methodology, inversion procedure and related
complications are described. The subject of latitude variation of the
solar wind is shortly reviewed: earlier Lymanα results from Prognoz in
1976 are confirmed by Ulysses. The importance of the actual value of the
solar wind mass flux for the equation of dynamics in a polar coronal
hole is stressed. The instrument is composed of one electronic unit
commanding two identical Sensor Units, each of them allowing to map
a full hemisphere with a resolution of 1°, thanks to a two-mirrors
periscope system. The design is described in some details, and the
rationale for choice between several variants are discussed. A hydrogen
absorption cell is used to measure the shape of the interplanetary
Lymanα line and other Lyman α emissions. Other types of observations
are also discussed : the geocorona, comets (old and new), the solar
corona, and a possible signature of the heliopause. The connexion
with some other SOHO instruments, in particular LASCO, UVCS, SUMER,
is briefly discussed.
Title: EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission
Authors: Delaboudinière, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel,
A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.;
Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise,
J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.;
Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.;
Neupert, W. M.; Maucherat, A.; Clette, F.; Cugnon, P.; Van Dessel,
E. L.
Bibcode: 1995SoPh..162..291D
Altcode:
The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field
images of the corona and transition region on the solar disc and up to
1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated
optics will select spectral emission lines from Fe IX (171 å), Fe
XII (195 å), Fe XV (284 å), and He II (304 å) to provide sensitive
temperature diagnostics in the range from 6 × 104 K to 3
× 106 K. The telescope has a 45 x 45 arcmin field of view
and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial
resolution. The EIT will probe the coronal plasma on a global scale,
as well as the underlying cooler and turbulent atmosphere, providing
the basis for comparative analyses with observations from both the
ground and other SOHO instruments. This paper presents details of the
EIT instrumentation, its performance and operating modes.
Title: Calibration of the EIT instrument for the SOHO mission
Authors: Defise, Jean-Marc; Song, Xueyan Y.; Delaboudiniere,
Jean-Pierre; Artzner, Guy E.; Carabetian, Charles; Hochedez,
Jean-Francois E.; Brunaud, Jacqueline; Moses, John D.; Catura,
Richard C.; Clette, Frederic; Maucherat, Andre J.
Bibcode: 1995SPIE.2517...29D
Altcode:
Optical characteristics in the wavelength range 15 - 75 nm of the
EUV imaging telescope to be launched soon on the SOHO mission are
discussed. Bandpasses and photometric sensitivity of the multilayered
optics telescope have been measured by a dedicated synchrotron light
source at Orsay, France.
Title: Performance of back-illuminated Tektronix CCDs in the extreme
ultraviolet
Authors: Moses, John D.; Howard, Russell A.; Wang, Dennis; Catura,
Richard C.; Lemen, J. R.; Shing, Lawrence; Stern, Robert A.; Hochedez,
Jean-Francois E.; Delaboudiniere, Jean-Pierre
Bibcode: 1993SPIE.2006..252M
Altcode:
The quantum efficiency (QE) and flat field characteristics of
back-illuminated 1024 X 1024 Tektronix CCDs have been measured in the
extreme ultraviolet (EUV) between 44 and 1216 angstroms. These CCDs have
been fabricated for the focal plane detector of the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observing
spacecraft. The back-side surface of the EIT CCDs have been specially
processed to enhance and stabilize the EUV QE. All requirements for
QE are met by these devices, although a poorly understood variation
of QE with temperature will complicate data analysis.
Title: Tuning multilayered mirror light traps for rejection of
30.4-nm radiation
Authors: Delaboudiniere, Jean-Pierre; Hochedez, Jean-Francois;
Chauvineau, Jean-Pierre; Valiergue, Laurence
Bibcode: 1993SPIE.1742..296D
Altcode:
Very efficient mirrors designed for rejection of the 30.4 nm HeII line
while transmitting the 28.4 nm FeXV line are needed for observations
of the solar corona. Light traps, based on multilayered structures,
using moderately absorbing diffractor layers of SiO2 and aluminum
as spacer material, have been successfully fabricated providing
dramatically high rejection ratios. However, accurate tuning at the
desired wavelength has proven to be extremely difficult to achieve in
combination with high nominal reflectivity. Very slight deviations
of thicknesses or optical constants can easily destroy the desired
antiresonance effect. Classical Mo/Si structures, although somewhat
less selective, can also be specially designed for this application
and they prove more amenable to proper adjustment.
Title: Extreme ultraviolet response of a Tektronix 1024 x 1024 CCD
Authors: Moses, Daniel J.; Hochedez, Jean-Francois E.; Howard,
Russell A.; Au, Benjamin D.; Wang, Dennis; Blouke, Morley
Bibcode: 1992SPIE.1656..526M
Altcode:
The goal of the detector development program for the Solar and
Heliospheric Spacecraft (SOHO) EUV Imaging Telescope (EIT) is an
Extreme UltraViolet (EUV) CCD (Charge Coupled Device) camera. The
Naval Research Lab (NRL) SOHO COD Group has developed a design for
the EIT camera and is screening CCDs for flight application. Tektronix
Inc. have fabricated 1024x1024 CCDs for the EIT program. As a part of
the CCD screening effort the quantum efficiency (QE) of a prototype
CCD has been measured in the NRL EUV laboratory over the wavelength
range of 256 to 735 Angstroms. A simplified model has been applied to
these QE measurements to illustrate the relevant physical processes
that determine the performance of the detector.
Title: Diamond Based UV Detectors for Space Missions
Authors: Moses, D.; Marchywka, M.; Brueckner, G. E.; Socker, D. G.;
Hochedez, J. -F.
Bibcode: 1991BAAS...23.1318M
Altcode:
No abstract at ADS
Title: Use of thinned backside illuminated CCD from the extreme
ultraviolet to the soft ultraviolet
Authors: Hochedez, Jean-Francois E.; Lemaire, Philippe; Delaboudiniere,
Jean-Pierre; Cougrand, Bernard; Barba, Julien
Bibcode: 1989SPIE.1070...53H
Altcode:
No abstract at ADS