explanation blue bibcodes open ADS page with paths to full text
Author name code: buchlin
ADS astronomy entries on 2022-09-14
author:"Buchlin, Eric"
---------------------------------------------------------
Title: What drives decayless kink oscillations in active region
coronal loops on the Sun?
Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter,
Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David;
Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle,
Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis;
Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel;
Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J.
2022arXiv220904251M Altcode:
We study here the phenomena of decayless kink oscillations in a system
of active region (AR) coronal loops. Using high resolution observations
from two different instruments, namely the Extreme Ultraviolet Imager
(EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly
(AIA) on board the Solar Dynamics Observatory, we follow these AR
loops for an hour each on three consecutive days. Our results show
significantly more resolved decayless waves in the higher-resolution
EUI data compared with the AIA data. Furthermore, the same system of
loops exhibits many of these decayless oscillations on Day-2, while on
Day-3, we detect very few oscillations and on Day-1, we find none at
all. Analysis of photospheric magnetic field data reveals that at most
times, these loops were rooted in sunspots, where supergranular flows
are generally absent. This suggests that supergranular flows, which
are often invoked as drivers of decayless waves, are not necessarily
driving such oscillations in our observations. Similarly, our findings
also cast doubt on other possible drivers of these waves, such as a
transient driver or mode conversion of longitudinal waves near the loop
footpoints. In conclusion, through our analysis we find that none of
the commonly suspected sources proposed to drive decayless oscillations
in active region loops seems to be operating in this event and hence,
the search for that elusive wave driver needs to continue.
---------------------------------------------------------
Title: FIP fractionation in the turbulent solar chromosphere and
corona: incompressible and compressible models
Authors: Reville, Victor; Buchlin, Eric; Verdini, Andrea; Rouillard,
Alexis; Velli, Marco; Lavarra, Michael; Poirier, Nicolas
2022cosp...44.2576R Altcode:
Low first ionisation potential (FIP) elements show enriched abundances
in the slow solar wind and coronal loops compared to photospheric
values. Turbulence is likely to be a key physical mechanism to explain
these abundances. Turbulent mixing is indeed essential to prevent
gravitational settling of heavy elements. Moreover, the average
turbulent Lorentz force, the ponderomotive force, could explain
the preferential lifting of low FIP ions in the upper chromosphere
and transition region. In this talk, we use unidimensional models
of the solar atmosphere, to compute the turbulent properties around
the transition regions in several regimes. We use the incompressible
(or reduced) MHD formalism with the SHELL-ATM code, and show that the
turbulent field is consistent with both coronal heating and significant
FIP fractionation. Then, we use the compressible MHD code PLUTO, and
compare the turbulent properties of the two models. In particular,
we look at the effect of chromospheric shocks on the propagation of
Alfvén waves near the top of the chromosphere that may act to modify
wave properties in the ionisation region of heavy elements. This work
has been funded by the ERC project SLOW SOURCE - DLV-819189
---------------------------------------------------------
Title: Elemental composition diagnostics for Hinode/EIS
Authors: Zambrana Prado, Natalia; Buchlin, Eric; Pelouze, Gabriel;
Young, Peter
2022cosp...44.2581Z Altcode:
In order to explore the connection between the solar atmosphere and
the solar wind, it is helpful to look at the elemental abundances for
they carry evidence of the origin region of the escaping plasma. This
is due to the first ionization potential (FIP) effect which results
in an enhancement of the abundances of low FIP elements. To provide
composition maps, we developed the Linear Combination Ratio (or LCR)
method which allows for relative abundance measurements forgoing the
need of differential emission measure inversion. This method has been
thoroughly tested on synthetic spectra and on spectroscopic data. The
proof of concept for the LCR method was published in Zambrana Prado
and Buchlin [2019], in that paper we focused on measuring the FIP
bias between sulfur and a mixture of iron and silicon. In this paper
we consider the most commonly-used EIS studies and identify element
pairs that can be used as diagnostics of the FIP effect. We apply the
LCR method and obtain FIP bias measurements in sample datasets. This
demonstrates that a large portion of the EIS archive can be used
for abundance diagnostics, and the LCR method opens the possibility
of deriving abundance ratio maps semi-automatically leading to new
data products for the community. We developed the LCR method further
by designing a numerical procedure based on a statistical approach
and the Bayes theorem to compute uncertainties of these FIP bias
diagnostics. It can take into account uncertainties in the atomic
physics and in the instrument calibration. It provides the probability
distribution of the real FIP bias of the plasma given the measurement
provided by the LCR method. Hinode has been coordinating with other
resources such as ALMA, PSP, Solar Orbiter, and DKIST, just to name a
few. These new diagnostics come as an add-on to our tool-belt, opening
the possibility to see through an additional perspective over a decade
and a half of coronal spectra.
---------------------------------------------------------
Title: Forecasting the Kp index a few days ahead using solar imaging
and neural networks alone: is it achievable?
Authors: Bernoux, Guillerme; Sicard, Angelica; Buchlin, Eric; Janvier,
Miho; Brunet, Antoine
2022cosp...44.3330B Altcode:
Over the past decade, data-driven methods using near-Earth solar
wind parameters to forecast geomagnetic indices have shown very good
performance, mostly outperforming many empirical and physics-based
models in terms of accuracy. In addition, these forecasting models have
recently shown their relevance to drive various magnetospheric models
in space weather pipelines. However, these methods still suffer from
many limitations, among which their restriction to a short effective
forecasting horizon (often up to approximately 6 hours at best). This is
not surprising, as these lead-times are of the same order of magnitude
as the solar wind-magnetosphere coupling time-lags. Therefore, in order
to increase the forecasting horizon, one solution would be to use more
spatially remote data, such as solar imaging. In order to address this
issue, we introduce SERENADE, a deep learning-based model driven only
by Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA)
data that can provide probabilistic forecasts of geomagnetic indices
such as Kp up to a few days ahead. We evaluate the model and discuss its
advantages and drawbacks based on these first results. In particular,
we compare it with baseline models and assess the performance of our
model according to the solar cycle phase. We show that our method
is promising, especially since it is only a first model that can be
improved in many aspects.
---------------------------------------------------------
Title: Automatic detection of small-scale EUV brightenings observed
by the Solar Orbiter/EUI
Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.;
Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin,
É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.;
Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti,
S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.;
Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N.
2022A&A...663A.128A Altcode: 2022arXiv220404027A
Context. Accurate detections of frequent small-scale extreme ultraviolet
(EUV) brightenings are essential to the investigation of the physical
processes heating the corona. <BR /> Aims: We detected small-scale
brightenings, termed campfires, using their morphological and
intensity structures as observed in coronal EUV imaging observations
for statistical analysis. <BR /> Methods: We applied a method based
on Zernike moments and a support vector machine (SVM) classifier
to automatically identify and track campfires observed by Solar
Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA). <BR /> Results: This method
detected 8678 campfires (with length scales between 400 km and 4000 km)
from a sequence of 50 High Resolution EUV telescope (HRI<SUB>EUV</SUB>)
174 Å images. From 21 near co-temporal AIA images covering the same
field of view as EUI, we found 1131 campfires, 58% of which were
also detected in HRI<SUB>EUV</SUB> images. In contrast, about 16%
of campfires recognized in HRI<SUB>EUV</SUB> were detected by AIA. We
obtain a campfire birthrate of 2 × 10<SUP>−16</SUP> m<SUP>−2</SUP>
s<SUP>−1</SUP>. About 40% of campfires show a duration longer than 5
s, having been observed in at least two HRI<SUB>EUV</SUB> images. We
find that 27% of campfires were found in coronal bright points and
the remaining 73% have occurred out of coronal bright points. We
detected 23 EUI campfires with a duration greater than 245 s. We found
that about 80% of campfires are formed at supergranular boundaries,
and the features with the highest total intensities are generated at
network junctions and intense H I Lyman-α emission regions observed
by EUI/HRI<SUB>Lya</SUB>. The probability distribution functions for
the total intensity, peak intensity, and projected area of campfires
follow a power law behavior with absolute indices between 2 and 3. This
self-similar behavior is a possible signature of self-organization,
or even self-organized criticality, in the campfire formation
process. <P />Supplementary material (S1-S3) is available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243257/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Simulating the FIP effect in coronal loops using a
multi-species kinetic-fluid model.
Authors: Poirier, Nicolas; Buchlin, Eric; Verdini, Andrea; Rouillard,
Alexis; Velli, Marco; Reville, Victor; Lavarra, Michael; Blelly,
Pierre-Louis; Indurain, Mikel
2022cosp...44.2577P Altcode:
We investigate abundance variations of heavy ions in coronal loops. We
develop and exploit a multi-species model of the solar atmosphere
(called IRAP's Solar Atmospheric Model: ISAM) that solves for the
transport of neutral and charged particles from the chromosphere to
the corona. We investigate the effect of different mechanisms that
could produce the First Ionization Potential (FIP) effect. We compare
the effects of the thermal, friction and ponderomotive force. The
propagation, reflection and dissipation of Alfvén waves is solved
using two distinct models, the first one from Chandran et al. (2011)
and the second one that is a more sophisticated turbulence model called
Shell-ATM. ISAM solves a set of 16-moment transport equations for
both neutrals and charged particles with a comprehensive treatment of
particle interactions and ionization/recombination processes. Protons
and electrons are heated by Alfvén waves, which then heat up the heavy
ions via collision processes. We show comparisons of our results with
other models and observations, with an emphasis on FIP biases. This
work was funded by the European Research Council through the project
SLOW SOURCE - DLV-819189.
---------------------------------------------------------
Title: Abundance diagnostics in active regions with Solar
Orbiter/SPICE
Authors: Giunta, Alessandra; Peter, Hardi; Parenti, Susanna; Buchlin,
Eric; Thompson, William; Auchere, Frederic; Kucera, Therese; Carlsson,
Mats; Janvier, Miho; Fludra, Andrzej; Hassler, Donald M.; Grundy,
Timothy; Sidher, Sunil; Guest, Steve; Leeks, Sarah; Fredvik, Terje;
Young, Peter
2022cosp...44.2583G Altcode:
With the launch of Solar Orbiter in February 2020, we are now able to
fully explore the link between the solar activity on the Sun and the
inner heliosphere. Elemental abundance measurements provide a key tracer
to probe the source regions of the solar wind and to track it from the
solar surface and corona to the heliosphere. Abundances of elements
with low first ionisation potential (FIP) are enhanced in the corona
relative to high-FIP elements, with respect to the photosphere. This is
known as the FIP effect, which is measured as abundance bias (FIP bias)
of low and high FIP elements. This effect is vital for understanding the
flow of mass and energy through the solar atmosphere. The comparison
between in-situ and remote sensing composition data, coupled with
modelling, will allow us to trace back the source of heliospheric
plasma. Solar Orbiter has a unique combination of in-situ and remote
sensing instruments that will help to make such a comparison. In
particular, the SPICE (Spectral Imaging of the Coronal Environment)
EUV spectrometer records spectra in two wavelength bands, 70.4-79.0
nm and 97.3-104.9 nm. SPICE is designed to provide spectroheliograms
using a core set of emission lines arising from ions of both low-FIP
and high-FIP elements such as C, N, O, Ne, Mg, S and Fe. These lines
are formed over a wide range of temperatures from 20,000 K to over 1
million K, enabling the analysis of the different layers of the solar
atmosphere. SPICE spectroheliograms can be processed to produce FIP
bias maps, which can be compared to in-situ measurements of the solar
wind composition of the same elements. During the Solar Orbiter Cruise
Phase, SPICE observed several active regions. We will present some of
these observations and discuss the SPICE diagnostic potential to derive
relative abundances (e.g., Mg/Ne) and the FIP bias in those regions.
---------------------------------------------------------
Title: The SPICE spectrograph on Solar Orbiter: an introduction and
results from the first Orbits
Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin,
Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera,
Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta,
Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy;
Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina
2022cosp...44.1338A Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument is
the EUV imaging spectrometer on board the Solar Orbiter mission. With
its ability to derive physical properties of the coronal plasma,
SPICE is a key component of the payload to establish the connection
between the source regions and the in-situ measurements of the solar
wind. The spacecraft was successfully launched in February 2020 and
completed its cruise phase in December 2021. During this period,
the remote sensing instruments were mostly operated during limited
periods of time for 'checkout' engineering activities and synoptic
observations. Nonetheless, several of these periods provided enough
opportunities already to obtain new insights on coronal physics. During
the march 2022 perihelion - close to 0.3 AU - SPICE will provide
its highest spatial resolution data so far. Coordinated observations
between the remote sensing and in-situ instruments will provide the
first opportunity to use the full potential of the Solar Orbiter
mission. We will review the instrument characteristics and present
initial results from the cruise phase and first close encounter.
---------------------------------------------------------
Title: Validation of a Wave Heated 3D MHD Coronal-wind Model using
Polarized Brightness and EUV Observations
Authors: Parenti, Susanna; Réville, Victor; Brun, Allan Sacha;
Pinto, Rui F.; Auchère, Frédéric; Buchlin, Éric; Perri, Barbara;
Strugarek, Antoine
2022ApJ...929...75P Altcode: 2022arXiv220310876P
The physical properties responsible for the formation and evolution
of the corona and heliosphere are still not completely understood. 3D
MHD global modeling is a powerful tool to investigate all the possible
candidate processes. To fully understand the role of each of them,
we need a validation process where the output from the simulations
is quantitatively compared to the observational data. In this work,
we present the results from our validation process applied to the
wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At
this stage of the model development, we focus the work to the coronal
regime in quiescent condition. We analyze three simulation results,
which differ by the boundary values. We use the 3D distributions of
density and temperature, output from the simulations at the time of
around the first Parker Solar Probe perihelion (during minimum of
the solar activity), to synthesize both extreme ultraviolet (EUV)
and white-light-polarized (WL pB) images to reproduce the observed
solar corona. For these tests, we selected AIA 193 Å, 211 Å, and
171 Å EUV emissions, MLSO K-Cor, and LASCO C2 pB images obtained on
2018 November 6 and 7. We then make quantitative comparisons of the
disk and off limb corona. We show that our model is able to produce
synthetic images comparable to those of the observed corona.
---------------------------------------------------------
Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.;
Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.;
Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.;
Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long,
D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca,
L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.;
Jacques, L.; Berghmans, D.
2021A&A...656A..35Z Altcode: 2021arXiv210902169Z
Context. The three-dimensional fine structure of the solar atmosphere
is still not fully understood as most of the available observations
are taken from a single vantage point. <BR /> Aims: The goal of the
paper is to study the three-dimensional distribution of the small-scale
brightening events ("campfires") discovered in the extreme-UV quiet Sun
by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter. <BR />
Methods: We used a first commissioning data set acquired by the EUI's
High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and
we combined it with simultaneous data taken by the Atmospheric Imaging
Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171
Å passband. The two-pixel spatial resolution of the two telescopes
is 400 km and 880 km, respectively, which is sufficient to identify
the campfires in both data sets. The two spacecraft had an angular
separation of around 31.5° (essentially in heliographic longitude),
which allowed for the three-dimensional reconstruction of the campfire
position. These observations represent the first time that stereoscopy
was achieved for brightenings at such a small scale. Manual and
automatic triangulation methods were used to characterize the campfire
data. <BR /> Results: The height of the campfires is located between
1000 km and 5000 km above the photosphere and we find a good agreement
between the manual and automatic methods. The internal structure of
campfires is mostly unresolved by AIA; however, for a particularly
large campfire, we were able to triangulate a few pixels, which are
all in a narrow range between 2500 and 4500 km. <BR /> Conclusions: We
conclude that the low height of EUI campfires suggests that they belong
to the previously unresolved fine structure of the transition region and
low corona of the quiet Sun. They are probably apexes of small-scale
dynamic loops heated internally to coronal temperatures. This work
demonstrates that high-resolution stereoscopy of structures in the
solar atmosphere has become feasible.
---------------------------------------------------------
Title: Full Vector Velocity Reconstruction Using Solar Orbiter
Doppler Map Observations.
Authors: Podladchikova, Olena; Harra, Louise; Barczynski, Krzysztof;
Mandrini, Cristina; Auchere, F.; Berghmans, David; Buchlin, Eric;
Dolla, Laurent; Mierla, Marilena; Parenti, Susanna; Rodriguez, Luciano
2021AGUFMNG35B0432P Altcode:
The Solar Orbiter mission opens up opportunities forthe
combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different space spectrometerswill
be located at wide angles to each other, allowing three-dimensional
(3D) spectroscopy of the solar atmosphere.The aim of this work is to
prepare the methodology to facilitate the reconstruction of 3D vector
velocities from two stereoscopicLOS Doppler velocity measurements using
the Spectral Imaging of the Coronal Environment (SPICE) on board the
Solar Orbiter andthe near-Earth spectrometers, while widely separated in
space. We develop the methodology using the libraries designed earlier
for the STEREO mission but applied to spectroscopicdata from the Hinode
mission and the Solar Dynamics Observatory. We use well-known methods
of static and dynamic solar rotationstereoscopy and the methods of
EUV stereoscopic triangulation for optically-thin coronal EUV plasma
emissions. We develop new algorithms using analytical geometry in
space to determine the 3D velocity in coronal loops. We demonstrate
our approach with the reconstruction of 3D velocity vectors in plasma
flows along "open" and "closed"magnetic loops. This technique will be
applied first to an actual situation of two spacecraft at different
separations with spectrometers onboard (SPICE versus the Interface
Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer)
during the Solar Orbiternominal phase. We summarise how these
observations can be coordinated.
---------------------------------------------------------
Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot,
Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester,
Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin,
Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith,
Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David;
Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca,
Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre;
Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David
2021AGUFMSH21A..03Z Altcode:
We study the three-dimensional distribution of small-scale brightening
events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun
by the EUI telescope onboard the Solar Orbiter mission. We use one of
the first commissioning data sets acquired by the HRI_EUV telescope of
EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous
SDO/AIA dataset taken in the very similar 171 A passband. The spatial
resolution of the two telescopes is sufficient to identify the campfires
in both datasets. The angular separation between the two spacecraft of
around 31.5 degrees allowed for the three-dimensional reconstruction
of the position of campfires. This is the first time that stereoscopy
was achieved for structures at such a small scale. Manual and automatic
triangulation methods were used. The height of campfires is between 1000
km and 5000 km above the photosphere, and there is a good agreement
between the results of manual and automatic methods. The internal
structure of campfires is mostly not resolved by AIA, but for a large
campfire we could triangulate a few pixels, which are all in a narrow
height range between 2500 and 4500 km. The low height of campfires
suggests that they belong to the previously unresolved fine structure
of the transition region and low corona of the quiet Sun. They are
probably apexes of small-scale dynamic loops internally heated to
coronal temperatures. This work demonstrates that high-resolution
stereoscopy of structures in the solar atmosphere has become possible.
---------------------------------------------------------
Title: Extreme-UV quiet Sun brightenings observed by the Solar
Orbiter/EUI
Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.;
Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.;
Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.;
Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.;
Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.;
Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.;
Inhester, B.
2021A&A...656L...4B Altcode: 2021arXiv210403382B
Context. The heating of the solar corona by small heating events
requires an increasing number of such events at progressively smaller
scales, with the bulk of the heating occurring at scales that are
currently unresolved. <BR /> Aims: The goal of this work is to study the
smallest brightening events observed in the extreme-UV quiet Sun. <BR />
Methods: We used commissioning data taken by the Extreme Ultraviolet
Imager (EUI) on board the recently launched Solar Orbiter mission. On
30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its
High Resolution EUV telescope (HRI<SUB>EUV</SUB>, 17.4 nm passband)
reached an exceptionally high two-pixel spatial resolution of 400
km. The size and duration of small-scale structures was determined
by the HRI<SUB>EUV</SUB> data, while their height was estimated
from triangulation with simultaneous images from the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory
mission. This is the first stereoscopy of small-scale brightenings
at high resolution. <BR /> Results: We observed small localised
brightenings, also known as `campfires', in a quiet Sun region with
length scales between 400 km and 4000 km and durations between 10 s and
200 s. The smallest and weakest of these HRI<SUB>EUV</SUB> brightenings
have not been previously observed. Simultaneous observations from the
EUI High-resolution Lyman-α telescope (HRI<SUB>Lya</SUB>) do not show
localised brightening events, but the locations of the HRI<SUB>EUV</SUB>
events clearly correspond to the chromospheric network. Comparisons with
simultaneous AIA images shows that most events can also be identified
in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA,
although they appear weaker and blurred. Our differential emission
measure analysis indicated coronal temperatures peaking at log T ≈
6.1 − 6.15. We determined the height for a few of these campfires to
be between 1000 and 5000 km above the photosphere. <BR /> Conclusions:
We find that `campfires' are mostly coronal in nature and rooted in the
magnetic flux concentrations of the chromospheric network. We interpret
these events as a new extension to the flare-microflare-nanoflare
family. Given their low height, the EUI `campfires' could stand as a
new element of the fine structure of the transition region-low corona,
that is, as apexes of small-scale loops that undergo internal heating
all the way up to coronal temperatures.
---------------------------------------------------------
Title: First observations from the SPICE EUV spectrometer on Solar
Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
Chitta, L. P.
2021A&A...656A..38F Altcode: 2021arXiv211011252F
<BR /> Aims: We present first science observations taken during the
commissioning activities of the Spectral Imaging of the Coronal
Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
mission. SPICE is a high-resolution imaging spectrometer operating at
extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
the possible types of observations to give prospective users a
better understanding of the science capabilities of SPICE. <BR />
Methods: We have reviewed the data obtained by SPICE between April
and June 2020 and selected representative results obtained with
different slits and a range of exposure times between 5 s and 180
s. Standard instrumental corrections have been applied to the raw
data. <BR /> Results: The paper discusses the first observations
of the Sun on different targets and presents an example of the full
spectra from the quiet Sun, identifying over 40 spectral lines from
neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
magnesium, and iron. These lines cover the temperature range between
20 000 K and 1 million K (10 MK in flares), providing slices of the
Sun's atmosphere in narrow temperature intervals. We provide a list
of count rates for the 23 brightest spectral lines. We show examples
of raster images of the quiet Sun in several strong transition region
lines, where we have found unusually bright, compact structures in the
quiet Sun network, with extreme intensities up to 25 times greater
than the average intensity across the image. The lifetimes of these
structures can exceed 2.5 hours. We identify them as a transition
region signature of coronal bright points and compare their areas and
intensity enhancements. We also show the first above-limb measurements
with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
and O VI lines. We discuss the potential to use abundance diagnostics
methods to study the variability of the elemental composition that can
be compared with in situ measurements to help confirm the magnetic
connection between the spacecraft location and the Sun's surface,
and locate the sources of the solar wind. <BR /> Conclusions: The
SPICE instrument successfully performs measurements of EUV spectra
and raster images that will make vital contributions to the scientific
success of the Solar Orbiter mission.
---------------------------------------------------------
Title: An operational approach to forecast the Earth's radiation
belts dynamics
Authors: Bernoux, Guillerme; Brunet, Antoine; Buchlin, Éric; Janvier,
Miho; Sicard, Angélica
2021JSWSC..11...60B Altcode:
The Ca index is a time-integrated geomagnetic index that correlates
well with the dynamics of high-energy electron fluxes in the outer
radiation belts. Therefore, Ca can be used as an indicator for the state
of filling of the radiation belts for those electrons. Ca also has the
advantage of being a ground-based measurement with extensive historical
records. In this work, we propose a data-driven model to forecast Ca
up to 24 h in advance from near-Earth solar wind parameters. Our model
relies mainly on a recurrent neural network architecture called Long
Short Term Memory that has shown good performances in forecasting other
geomagnetic indices in previous papers. Most implementation choices
in this study were arbitrated from the point of view of a space system
operator, including the data selection and split, the definition of a
binary classification threshold, and the evaluation methodology. We
evaluate our model (against a linear baseline) using both classical
and novel (in the space weather field) measures. In particular, we use
the Temporal Distortion Mix (TDM) to assess the propensity of two time
series to exhibit time lags. We also evaluate the ability of our model
to detect storm onsets during quiet periods. It is shown that our model
has high overall accuracy, with evaluation measures deteriorating in
a smooth and slow trend over time. However, using the TDM and binary
classification forecast evaluation metrics, we show that the forecasts
lose some of their usefulness in an operational context even for time
horizons shorter than 6 h. This behaviour was not observable when
evaluating the model only with metrics such as the root-mean-square
error or the Pearson linear correlation. Considering the physics of
the problem, this result is not surprising and suggests that the use
of more spatially remote data (such as solar imaging) could improve
space weather forecasts.
---------------------------------------------------------
Title: Stereoscopic measurements of coronal Doppler velocities
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C. H.; Auchère, F.; Berghmans, D.; Buchlin, É.; Dolla, L.; Mierla,
M.; Parenti, S.; Rodriguez, L.
2021A&A...655A..57P Altcode: 2021arXiv210802280P
Context. The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time different space spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere. <BR /> Aims: The aim of this
work is to prepare a methodology to facilitate the reconstruction
of 3D vector velocities from two stereoscopic line of sight (LOS)
Doppler velocity measurements using the Spectral Imaging of the
Coronal Environment (SPICE) on board the Solar Orbiter and the
near-Earth spectrometers, while widely separated in space. <BR />
Methods: We developed the methodology using the libraries designed
earlier for the STEREO mission, but applied to spectroscopic data
from the Hinode mission and the Solar Dynamics Observatory. We used
well-known methods of static and dynamic solar rotation stereoscopy and
the methods of extreme ultraviolet (EUV) stereoscopic triangulation
for optically thin coronal EUV plasma emissions. We developed new
algorithms using analytical geometry in space to determine the 3D
velocity in coronal loops. <BR /> Results: We demonstrate our approach
with the reconstruction of 3D velocity vectors in plasma flows along
`open' and `closed' magnetic loops. This technique will be applied
to an actual situation of two spacecraft at different separations
with spectrometers on board during the Solar Orbiter nominal phase:
SPICE versus the Interface Region Imaging Spectrograph (IRIS) and
Hinode imaging spectrometer. We summarise how these observations can
be coordinated. <P />Movies associated to Fig. 1 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140457/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Magnetic imaging of the outer solar atmosphere (MImOSA)
Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
2021ExA...tmp...95P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability of
planets orbiting these host stars. Although the magnetic field at the
surface of the Sun is reasonably well characterised by observations,
the information on the magnetic field in the higher atmospheric layers
is mainly indirect. This lack of information hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution
and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is
designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter
based on a 30 cm telescope that combines high throughput in the
extreme UV with polarimetry to connect the magnetic measurements
of the other two instruments. Placed in a near-Earth orbit, the data
downlink would be maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-based
observatories. This mission to measure the magnetic field will finally
unlock the driver of the dynamics in the outer solar atmosphere and
thereby will greatly advance our understanding of the Sun and the
heliosphere.
---------------------------------------------------------
Title: Vector Velocities Measurements with the Solar Orbiter SPICE
Spectrometer
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C.; Auchère, F.; Berghmans, D.; Buchlin, E.; Dolla, L.; Mierla, M.;
Parenti, S.; Rodriguez, L.
2021AAS...23831312P Altcode:
The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere. Here we develop a methodology to
prepare for this kind of analysis, by using data from the Hinode mission
and the Solar Dynamics Observatory, respectively. We employ solar
rotation to simulate measurements of spectrometers with different views
of the solar corona. The resulting data allow us to apply stereoscopic
tie-pointing and triangulation techniques designed for the STEREO
spacecraft pair, and to perform 3D analysis of the Doppler shifts of
a quasi-stationary active region. Our approach allows the accurate
reconstruction of 3D velocity vectors in plasma flows along "open" and
"closed" magnetic loops. This technique will be applied to the actual
situation of two spacecraft at different separations with spectrometers
on board (the Solar Orbiter Spectral Imaging of the Coronal Environment
versus the Interface Region Imaging Spectrograph (IRIS) and Hinode
imaging spectrometer) and we summarise how these observations can be
coordinated to assess vector velocity measurements. This 3D spectroscopy
method will facilitate the understanding of the complex flows that
take place throughout the solar atmosphere.
---------------------------------------------------------
Title: The flare likelihood and region eruption forecasting
(FLARECAST) project: flare forecasting in the big data & machine
learning era
Authors: Georgoulis, Manolis K.; Bloomfield, D. Shaun; Piana,
Michele; Massone, Anna Maria; Soldati, Marco; Gallagher, Peter T.;
Pariat, Etienne; Vilmer, Nicole; Buchlin, Eric; Baudin, Frederic;
Csillaghy, Andre; Sathiapal, Hanna; Jackson, David R.; Alingery,
Pablo; Benvenuto, Federico; Campi, Cristina; Florios, Konstantinos;
Gontikakis, Constantinos; Guennou, Chloe; Guerra, Jordan A.;
Kontogiannis, Ioannis; Latorre, Vittorio; Murray, Sophie A.; Park,
Sung-Hong; von Stachelski, Samuelvon; Torbica, Aleksandar; Vischi,
Dario; Worsfold, Mark
2021JSWSC..11...39G Altcode: 2021arXiv210505993G
The European Union funded the FLARECAST project, that ran from January
2015 until February 2018. FLARECAST had a research-to-operations
(R2O) focus, and accordingly introduced several innovations into the
discipline of solar flare forecasting. FLARECAST innovations were:
first, the treatment of hundreds of physical properties viewed as
promising flare predictors on equal footing, extending multiple
previous works; second, the use of fourteen (14) different machine
learning techniques, also on equal footing, to optimize the immense
Big Data parameter space created by these many predictors; third,
the establishment of a robust, three-pronged communication effort
oriented toward policy makers, space-weather stakeholders and the wider
public. FLARECAST pledged to make all its data, codes and infrastructure
openly available worldwide. The combined use of 170+ properties (a
total of 209 predictors are now available) in multiple machine-learning
algorithms, some of which were designed exclusively for the project,
gave rise to changing sets of best-performing predictors for the
forecasting of different flaring levels, at least for major flares. At
the same time, FLARECAST reaffirmed the importance of rigorous training
and testing practices to avoid overly optimistic pre-operational
prediction performance. In addition, the project has (a) tested new
and revisited physically intuitive flare predictors and (b) provided
meaningful clues toward the transition from flares to eruptive flares,
namely, events associated with coronal mass ejections (CMEs). These
leads, along with the FLARECAST data, algorithms and infrastructure,
could help facilitate integrated space-weather forecasting efforts
that take steps to avoid effort duplication. In spite of being
one of the most intensive and systematic flare forecasting efforts
to-date, FLARECAST has not managed to convincingly lift the barrier of
stochasticity in solar flare occurrence and forecasting: solar flare
prediction thus remains inherently probabilistic.
---------------------------------------------------------
Title: First data for abundance diagnostics with SPICE, the EUV
spectrometer on-board Solar Orbiter
Authors: Zambrana Prado, Natalia; Buchlin, Éric; Peter, Hardi
2021EGUGA..2315555Z Altcode:
Linking solar activity on the surface and in the corona to the
heliosphere is one of Solar Orbiter"s main goals. Its EUV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest,
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. From
the 16th to the 22nd of November 2020, the Solar Orbiter remote
sensing checkout window STP-122 was carried out. During this period
of observations, SPICE was lucky to catch a small AR in its field
of view. We carried out abundance specific observations in order
to provide relative FIP bias measurements with SPICE. Furthermore,
data from other types of observations carried out during that same
week allow us to identify the spectral lines that could be used for
abundance diagnostics. We take the SPICE instrument characteristics
into account to give recommendations regarding the types of studies
to carry out to obtain such abundance measurements.
---------------------------------------------------------
Title: Modeling Solar Wind Variations over an 11 Year Cycle with
Alfvén Wave Dissipation: A Parameter Study
Authors: Hazra, Soumitra; Réville, Victor; Perri, Barbara; Strugarek,
Antoine; Brun, Allan Sacha; Buchlin, Eric
2021ApJ...910...90H Altcode: 2021arXiv210111511H
We study the behavior and properties of the solar wind using a
2.5D Alfvén wave (AW)-driven wind model. We first systematically
compare the results of an AW-driven wind model with a polytropic
approach. Polytropic magnetohydrodynamic wind models are thermally
driven, while AWs act as additional acceleration and heating mechanisms
in the AW-driven model. We confirm that an AW-driven model is required
to reproduce the observed bimodality of slow and fast solar winds. We
are also able to reproduce the observed anticorrelation between the
terminal wind velocity and the coronal source temperature with the
AW-driven wind model. We also show that the wind properties along an 11
yr cycle differ significantly from one model to the other. The AW-driven
model again shows the best agreement with observational data. Indeed,
solar surface magnetic field topology plays an important role in the
AW-driven wind model, as it enters directly into the input energy
sources via the Poynting flux. On the other hand, the polytropic wind
model is driven by an assumed pressure gradient; thus, it is relatively
less sensitive to the surface magnetic field topology. Finally, we note
that the net torque spinning down the Sun exhibits the same trends in
the two models, showing that the polytropic approach still correctly
captures the essence of stellar winds.
---------------------------------------------------------
Title: Investigating the origin of the FIP effect with a shell
turbulence model
Authors: Réville, Victor; Rouillard, Alexis P.; Velli, Marco; Verdini,
Andrea; Buchlin, Éric; Lavarra, Michael; Poirier, Nicolas
2021FrASS...8....2R Altcode: 2021arXiv210101440R
The enrichment of coronal loops and the slow solar wind with elements
that have low First Ionization Potential, known as the FIP effect,
has often been interpreted as the tracer of a common origin. A current
explanation for this FIP fractionation rests on the influence of
ponderomotive forces and turbulent mixing acting at the top of the
chromosphere. The implied wave transport and turbulence mechanisms are
also key to wave-driven coronal heating and solar wind acceleration
models. This work makes use of a shell turbulence model run on open
and closed magnetic field lines of the solar corona to investigate
with a unified approach the influence of magnetic topology, turbulence
amplitude and dissipation on the FIP fractionation. We try in particular
to assess whether there is a clear distinction between the FIP effect
on closed and open field regions.
---------------------------------------------------------
Title: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA):
Unlocking the driver of the dynamics in the upper solar atmosphere
Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J.
2021arXiv210101566P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability
of planets orbiting these host stars. The lack of information on the
magnetic field in the higher atmospheric layers hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution and high
sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to
measure the large-scale magnetic field in the corona with an aperture
of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with
polarimetry to connect the magnetic measurements of the other two
instruments. This mission to measure the magnetic field will unlock
the driver of the dynamics in the outer solar atmosphere and thereby
greatly advance our understanding of the Sun and the heliosphere.
---------------------------------------------------------
Title: Stereoscopic Measurements of Coronal Doppler Velocities aboard
Solar Orbiter
Authors: Podladchikova, Olena; Harra, Louise K.; Mandrini, Cristina
H.; Rodriguez, Luciano; Parenti, Susanna; Dolla, Laurent; Buchlin,
Eric; Auchere, Frederic; Mierla, Marilena; Barczynski, Krzysztof
2021cosp...43E.957P Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region.We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI), the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
---------------------------------------------------------
Title: The MDOR/PDOR on-line module for MISO, the planning software
of Solar Orbiter instruments
Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio;
Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso,
Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola;
Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche,
Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère,
Frédéric; Romoli, Marco
2020SPIE11452E..0SV Altcode:
Solar Orbiter is a solar mission that will approach the Sun down to a
minimum perihelion of 0.28 AU and will increase its orbit inclination
with respect to the ecliptic up to a maximum angle of 34 deg. For
imagers aboard Solar Orbiter there will be three 10-days remote sensing
windows per orbit. Observations shall be carefully planned at least 6
months in advance. The Multi Instrument Sequence Organizer (MISO) is
a web based platform developed by the SPICE group and made available
to support Solar Orbiter instruments teams in planning observations
by assembling Mission Database sequences. Metis is the UV and visible
light coronagraph aboard Solar Orbiter. Metis is a complex instrument
characterized by a rich variety of observing modes, which required a
careful commissioning activity and will need support for potential
maintenance operations throughout the mission. In order to support
commissioning and maintenance activities, the Metis team developed
a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct
Operation Request) module integrated in MISO and made available to all
Solar Orbiter instruments. An effort was made in order to interpret
the coding philosophy of the main project and to make the additional
module as homogeneous as possible both to the web interface and to the
algorithm logic, while integrating characteristics which are peculiar
to PDORs and MDORs. An user friendly web based interface allows the
operator to build the operation request and to successively modify or
integrate it with further or alternative information. In the present
work we describe the PDOR/MDOR module for MISO by addressing its logic
and main characteristics.
---------------------------------------------------------
Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
L.; Thompson, W. T.; Williams, D.
2020AGUFMSH038..09Z Altcode:
Linking solar activity on the surface and in the corona to the inner
heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. Solar
Orbiter's unique combination of remote sensing and in-situ instruments
coupled with observation from other missions such as Parker Solar
Probe will allow us to compare in-situ and remote sensing composition
data. With the addition of modeling, these new results will allow us
to trace back the source of heliospheric plasma. As high telemetry
will not always be available with SPICE, we have developed a method
for measuring relative abundances that is both telemetry efficient
and reliable. Unlike methods based on Differential Emission Measure
(DEM) inversion, the Linear Combination Ratio (LCR) method does not
require a large number of spectral lines. This new method is based
on linear combinations of UV spectral lines. The coefficients of
the combinations are optimized such that the ratio of two linear
combinations of radiances would yield the relative abundance of two
elements. We present some abundance diagnostics tested on different
combinations of spectral lines observable by SPICE.
---------------------------------------------------------
Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
D.; Young, P. R.
2020AGUFMSH038..03P Altcode:
We will present some of the early data of the Spectral Imaging of the
Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
unique features of SPICE is its capability to record a wide range of
wavelengths in the extreme UV with the possibility to record spectral
lines giving access to a continuous plasma temperature range from 10.000
K to well above 1 MK. The data taken so far were for commissioning
purposes and they can be used for a preliminary evaluation of the
science performance of the instrument. Here we will concentrate on
sample spectra covering the whole wavelength region and on the early
raster maps acquired in bright lines in the quiet Sun close to disk
center. Looking at different quiet Sun features we investigate the
thermal structure of the atmosphere and flow structures. For this
we apply fits to the spectral profiles and check the performance in
terms of Doppler shifts and line widths to retrieve the structure of
the network in terms of dynamics. While the amount of data available
so far is limited, we will have a first look on how quiet Sun plasma
responds to heating events. For this, we will compare spectral lines
forming at different temperatures recorded at strictly the same time.
---------------------------------------------------------
Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
W. T.; Tustain, S.; Williams, D.; Young, P. R.
2020AGUFMSH038..02F Altcode:
SPICE (Spectral Imaging of Coronal Environment) is one of the remote
sensing instruments onboard Solar Orbiter. It is an EUV imaging
spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
bands with exposures as short as 1s. SPICE is the only Solar Orbiter
instrument that can measure EUV spectra from the disk and low corona
of the Sun and record all spectral lines simultaneously. SPICE uses
one of three narrow slits, 2"x11', 4”x11', 6”x11', or a wide slit
30”x14'. The primary mirror can be scanned in a direction perpendicular
to the slit, allowing raster images of up to 16' in size. <P />We
present an overview of the first SPICE data taken on several days
during the instrument commissioning carried out by the RAL Space team
between 2020 April 21 and 2020 June 14. We also include results from
SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
taken between June 16-21<SUP>st</SUP>. We give examples of full spectra
from the quiet Sun near disk centre and provide a list of key spectral
lines emitted in a range of temperatures between 10,000 K and over 1
million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
neon, sulphur and magnesium. We show examples of first raster images
in several strong lines, obtained with different slits and a range
of exposure times between 5s and 180s. We describe the temperature
coverage and density diagnostics, determination of plasma flows, and
discuss possible applications to studies of the elemental abundances
in the corona. We also show the first off-limb measurements with SPICE,
as obtained when the spacecraft pointed at the limb.
---------------------------------------------------------
Title: Observation of Smallest Ever Detected Brightening Events with
the Solar Orbiter EUI HRI-EUV Imager
Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere,
F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado,
R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
2020AGUFMSH038..01P Altcode:
The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter
acquired its first images in May 2020. The passband of the 17.4 nm
High Resolution Imager (HRI-EUV) is dominated by emission lines of
Fe IX and Fe X, that is the 1 million degree solar corona. The solar
atmosphere at this temperature is dynamic at all scales, down to the
highest spatial resolution available from instruments priori to Solar
Orbiter. During the Commissioning phase, HRI-EUV acquired several high
temporal resolution (a few seconds) sequences at quiet Sun regions at
disk center. The instrument revealed a multitude of brightenings at
the smallest-ever detectable spatial scales which, at that time, was
about 400 km (two pixels). These events appear to be present everywhere
all the time. We present the first results of the analysis of these
sequences with the aim of understanding the role of these small scale
events in the heating of the solar corona.
---------------------------------------------------------
Title: Stereoscopic Measurements of Coronal Doppler Velocities
Authors: Podladchikova, O.; Harra, L. K.; Barczynski, K.; Mandrini,
C. H.; Auchere, F.; Buchlin, E.; Dolla, L.; Mierla, M.; Rodriguez, L.
2020AGUFMSH038..07P Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of two spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region. We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI),the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
---------------------------------------------------------
Title: Calibrating optical distortions in the Solar Orbiter SPICE
spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
D.; Sidher, S.
2020AGUFMSH0360029T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
Solar Orbiter is a high-resolution imaging spectrometer operating
at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
image onto the entrance slit of the spectrometer section. A Toroidal
Variable Line Space (TVLS) grating images the entrance slit onto a
pair of MCP-intensified APS detectors. Ray-tracing analysis prior
to launch showed that the instrument was subject to a number of
small image distortions which need to be corrected in the final data
product. We compare the ray tracing results with measurements made in
flight. Co-alignment with other telescopes on Solar Orbiter will also
be examined.
---------------------------------------------------------
Title: First results from the EUI and SPICE observations of Alpha
Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360024B Altcode:
On June 16th 2020 Solar Orbiter made a dedicated observing campaign
where the spacecraft pointed to the solar limb to allow some of the
high resolution instruments to observe the ingress (at the east limb)
and later the egress (west limb) of the occultation of the star Alpha
Leonis by the solar disk. The star was chosen because its luminosity and
early spectral type ensure high and stable flux at wavelengths between
100 and 122 nanometers, a range observed by the High Resolution EUI
Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
of the SPICE spectrograph. Star observations, when feasible, allow
to gather a great deal of information on the instrument performances,
such as the radiometric performance and the instrument optical point
spread function (PSF). <P />We report here the first results from the
above campaign for the two instruments.
---------------------------------------------------------
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360003T Altcode:
The Solar Orbiter spacecraft carries a powerful set of remote
sensing instruments that allow studying the solar atmosphere with
unprecedented diagnostic capabilities. Many such diagnostics require
the simultaneous usage of more than one instrument. One example of that
is the capability, for the first time, to obtain (near) simultaneous
spatially resolved observations of the emission from the first three
lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
can observe the Lyman beta and gamma lines in its long wavelength
(SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
(FSI-304). Being hydrogen and helium the main components of our star,
these very bright transitions play an important role in the energy
budget of the outer atmosphere via radiative losses and the measurement
of their profiles and radiance ratios is a fundamental constraint to
any comprehensive modelization effort of the upper solar chromosphere
and transition region. Additionally, monitoring their average ratios
can serve as a check out for the relative radiometric performance of
the two instruments throughout the mission. Although the engineering
data acquired so far are far from ideal in terms of time simultaneity
(often only within about 1 h) and line coverage (often only Lyman beta
was acquired by SPICE and not always near simultaneous images from all
three telescopes are available) the analysis we present here still
offers a great opportunity to have a first look at the potential of
this diagnostic from the two instruments. In fact, we have identified
a series of datasets obtained at disk center and at various positions
at the solar limb that allow studying the Lyman alpha to beta radiance
ratio and their relation to He II 30.4 as a function of the position
on the Sun (disk center versus limb and quiet Sun versus coronal holes).
---------------------------------------------------------
Title: Differential Emission Measure Evolution as a Precursor of
Solar Flares
Authors: Gontikakis, C.; Kontogiannis, I.; Georgoulis, M. K.; Guennou,
C.; Syntelis, P.; Park, S. H.; Buchlin, E.
2020arXiv201106433G Altcode:
We analyse the temporal evolution of the Differential Emission Measure
(DEM) of solar active regions and explore its usage in solar flare
prediction. The DEM maps are provided by the Gaussian Atmospheric
Imaging Assembly (GAIA-DEM) archive, calculated assuming a Gaussian
dependence of the DEM on the logarithmic temperature. We analyse
time-series of sixteen solar active regions and a statistically
significant sample of 9454 point-in-time observations corresponding to
hundreds of regions observed during solar cycle 24. The time-series
analysis shows that the temporal derivatives of the Emission Measure
dEM/dt and the maximum DEM temperature dTmax/dt frequently exhibit
high positive values a few hours before M- and X-class flares,
indicating that flaring regions become brighter and hotter as the flare
onset approaches. From the point-in-time observations we compute the
conditional probabilities of flare occurrences using the distributions
of positive values of the dEM/dt, and dTmax/dt and compare them with
corresponding flaring probabilities of the total unsigned magnetic flux,
a conventionally used, standard flare predictor. For C-class flares,
conditional probabilities have lower or similar values with the ones
derived for the unsigned magnetic flux, for 24 and 12 hours forecast
windows. For M- and X-class flares, these probabilities are higher
than those of the unsigned flux for higher parameter values. Shorter
forecast windows improve the conditional probabilities of dEM/dt,
and dTmax/dt in comparison to those of the unsigned magnetic flux. We
conclude that flare forerunner events such as preflare heating or small
flare activity prior to major flares reflect on the temporal evolution
of EM and Tmax. Of these two, the temporal derivative of the EM could
conceivably be used as a credible precursor, or short-term predictor,
of an imminent flare.
---------------------------------------------------------
Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
2020A&A...642A...6A Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements. <BR /> Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together. <BR /> Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis. <BR /> Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
---------------------------------------------------------
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.
---------------------------------------------------------
Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
2020A&A...642A...2R Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk. <BR /> Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies. <BR /> Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter. <BR /> Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission. <BR /> Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.
---------------------------------------------------------
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
<BR /> Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission. <BR /> Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal. <BR /> Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing. <BR /> Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
2020A&A...642A...8R Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere. <BR /> Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives. <BR />
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor. <BR /> Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products. <BR /> Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
---------------------------------------------------------
Title: Relative abundance diagnostics with SPICE, the EUV spectrometer
on-board Solar Orbiter
Authors: Zambrana Prado, Natalia; Buchlin, Eric; Peter, Hardi
2020EGUGA..2220154Z Altcode:
With the launches of Parker Solar Probe and Solar Orbiter, we are
closer than ever to linking solar activity on the surface and in the
corona to the inner heliosphere. In this quest, relative abundance
measurements will be key as different structures on the Sun have
different abundances as a consequence of the FIP (First Ionization
Potential) effect.Comparing in-situ and remote sensing composition
data, coupled with modeling, will allow us to trace back the source of
heliospheric plasma. Solar Orbiter has a unique combination of in-situ
and remote sensing instruments that will hopefully allow us to make
such comparisons.High telemetry will not always be available with SPICE
(SPectral Imaging of the Coronal Environment), the EUV spectrometer
on board Solar Orbiter. We have therefore developed a method for
measuring relative abundances that is both telemetry efficient and
reliable. Unlike methods based on Differential Emission Measure (DEM)
inversion, the Linear Combination Ratio (LCR) method does not require a
large number of spectral lines. This new method is based on optimized
linear combinations of only a few UV spectral lines. We present some
abundance diagnostics applied to synthesized radiances of spectral
lines observable by SPICE.
---------------------------------------------------------
Title: Measuring relative abundances in the solar corona with
optimized linear combinations of spectral lines
Authors: Zambrana Prado, N.; Buchlin, E.
2019sf2a.conf..383Z Altcode:
Elemental abundances in some coronal structures differ significantly
from photospheric abundances, with a dependence on the First Ionization
Potential (FIP) of the element. Measuring these FIP-dependent abundance
biases is important for coronal and heliospheric physics. We aim
at building a method for optimal determination of FIP biases in the
corona from spectroscopic observations, in a way that is in practice
independent from Differential Emission Measure (DEM) inversions. We
optimize linear combinations of spectroscopic lines of low-FIP and
high-FIP elements so that the ratio of the corresponding radiances
yields the relative FIP bias with a good accuracy, for any DEM in a
small set of typical DEMs. These optimized linear combinations of
lines allow to retrieve a test FIP bias map with a good accuracy,
for all DEMs in the map. The method provides a convenient, fast, and
accurate way of computing relative FIP bias maps. It could be used
to optimize the use of existing observations and the design of new
observations and instruments.
---------------------------------------------------------
Title: Measuring relative abundances in the solar corona with
optimised linear combinations of spectral lines
Authors: Zambrana Prado, Natalia; Buchlin, Éric
2019A&A...632A..20Z Altcode: 2019arXiv191002886Z
Context. Elemental abundances in some coronal structures differ
significantly from photospheric abundances, with a dependence on
the first ionization potential (FIP) of the element. Measuring these
FIP-dependent abundance biases is important for coronal and heliospheric
physics. <BR /> Aims: We aim to build a method for optimal determination
of FIP biases in the corona from spectroscopic observations in a way
that is in practice independent from differential emission measure
(DEM) inversions. <BR /> Methods: We optimised linear combinations of
spectroscopic lines of low-FIP and high-FIP elements so that the ratio
of the corresponding radiances yields the relative FIP bias with good
accuracy for any DEM in a small set of typical DEMs. <BR /> Results:
These optimised linear combinations of lines allow retrieval of a test
FIP bias map with good accuracy for all DEMs in the map. The results
also compare well with a FIP bias map obtained from observations
using a DEM-dependent method. <BR /> Conclusions: The method provides
a convenient, fast, and accurate way of computing relative FIP bias
maps. It can be used to optimise the use of existing observations and
the design of new observations and instruments.
---------------------------------------------------------
Title: Some relationships between radiative and atmospheric quantities
through 1D NLTE modeling of prominences in the Mg II lines
Authors: Vial, J. -C.; Zhang, P.; Buchlin, É.
2019A&A...624A..56V Altcode:
Context. With more than four years of IRIS observations, and in order
to avoid building customized diagnostics for each observation, it is
useful to derive some simple relations between spectra and physical
quantities. This is even more useful for the k and h lines of Mg
II, which require complex non-local-thermodynamic-equilibrium NLTE
treatments. <BR /> Aims: The aim of this work concerning prominences
is to correlate observable spectral features in h and k lines of Mg II
to physical quantities such as the density and the emission measure
(EM) in the same way as similar correlations have been obtained in
the hydrogen lines. In this way, and within approximations done on
some parameters such as temperature, it is possible to build pixel by
pixel an IRIS map of the above-mentioned quantities. <BR /> Methods:
In order to simplify and shorten the modeling, we chose to compute
one-dimensional (1D) isothermal and isobaric models that are treated
with the PROM7 NLTE code available at MEDOC (IAS). We built a set of
models with large ranges of temperature, pressure, and thickness. At
all altitudes considered, we paid attention to the exact computation
of the incident radiation. Then we compared the emergent Mg II h and k
intensities with the corresponding hydrogen and electron densities and
EMs. <BR /> Results: From the NLTE computation, we derive correlations
between the k and h emergent intensities on one hand and the densities
and EM on the other hand. With some assumptions on the temperature,
we obtain a unique relation between the k (and h) intensities and the
EM that should be useful for deriving either the hydrogen and electron
densities or the effective thickness of an observed prominence. <BR
/> Conclusions: From NLTE modeling, we have provided a relationship
between observable integrated intensities of the Mg II resonance
lines and prominence plasma EM, which will contribute to a first-order
analysis of long time series of spectroscopic observations, for example,
with IRIS. We anticipate building more complex relations between the
profiles and other plasma quantities.
---------------------------------------------------------
Title: Launch of a CME-associated eruptive prominence as observed
with IRIS and ancillary instruments
Authors: Zhang, P.; Buchlin, É.; Vial, J. -C.
2019A&A...624A..72Z Altcode:
<BR /> Aims: In this paper we focus on the possible observational
signatures of the processes which have been put forward for explaining
eruptive prominences. We also try to understand the variations in the
physical conditions of eruptive prominences and estimate the masses
leaving the Sun versus the masses returning to the Sun during eruptive
prominences. <BR /> Methods: As far as velocities are concerned, we
combined an optical flow method on the Atmospheric Imaging Assembly
(AIA) 304 Å and Interface Region Imaging Spectrograph (IRIS). Mg II
h&k observations in order to derive the plane-of-sky velocities
in the prominence, and a Doppler technique on the IRIS Mg II h&k
profiles to compute the line-of-sight velocities. As far as densities
are concerned, we compared the absolute observed intensities with values
derived from non-local thermodynamic equilibrium radiative transfer
computations to derive the total (hydrogen) density and consequently
compute the mass flows. <BR /> Results: The derived electron
densities range from 1.3 × 10<SUP>9</SUP> to 6.0 × 10<SUP>10</SUP>
cm<SUP>-3</SUP> and the derived total hydrogen densities range from
1.5 × 10<SUP>9</SUP> to 2.4 × 10<SUP>11</SUP> cm<SUP>-3</SUP>
in different regions of the prominence. The mean temperature is
around 1.1 × 10<SUP>4</SUP> K, which is higher than in quiescent
prominences. The ionization degree is in the range of 0.1-10. The
total (hydrogen) mass is in the range of 1.3 × 10<SUP>14</SUP>-3.2
× 10<SUP>14</SUP> g. The total mass drainage from the prominence
to the solar surface during the whole observation time of IRIS is
about one order of magnitude smaller than the total mass of the
prominence. <P />The movie associated to Fig. 2 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201834259/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Solar data, dataproducts, and tools at MEDOC
Authors: Buchlin, Eric; Caminade, Stéphane; Dufourg, Nicolas;
Auchère, Frédéric; Baudin, Frédéric; Bocchialini, Karine;
Boumier, Patrick; Janvier, Miho; Parenti, Susanna; Alingery, Pablo;
Ballans, Hervé; Chane-Yook, Martine; Dexet, Marc; Mercier, Claude;
Poulleau, Gilles
2019EGUGA..2117362B Altcode:
MEDOC (Multi-Experiment Data and Operation Centre), initially created
as a European data and operation centre for the SOHO mission, has
grown with data from other solar physics space missions, from STEREO
to SDO. Derived data products such as DEM maps from SDO/AIA, synoptic
EUV intensity maps from SOHO/EIT, and catalogues of solar structures
are also automatically produced and redistributed. Both the data and
the derived data products are publicly available from web interfaces
and from programmatic interfaces (with clients for IDL and Python),
allowing classical data analysis as well as automatic queries, data
download, and processing to be made on large datasets.
---------------------------------------------------------
Title: Nonlinear diffusion models for gravitational wave turbulence
Authors: Galtier, Sébastien; Nazarenko, Sergey V.; Buchlin, Éric;
Thalabard, Simon
2019PhyD..390...84G Altcode: 2018arXiv180907623G
A fourth-order and a second-order nonlinear diffusion model in spectral
space are proposed to describe gravitational wave turbulence in the
approximation of strongly local interactions. We show analytically
that the model equations satisfy the conservation of energy and wave
action, and reproduce the power law solutions previously derived
from the kinetic equations with a direct cascade of energy and
an explosive inverse cascade of wave action. In the latter case,
we show numerically by computing the second-order diffusion model
that the non-stationary regime exhibits an anomalous scaling which is
understood as a self-similar solution of the second kind with a front
propagation following the law k<SUB>f</SUB> ∼<SUP>(t<SUB>∗</SUB> -
t) 3 . 296</SUP>, with t <t<SUB>∗</SUB>. These results are relevant
to better understand the dynamics of the primordial universe where
potent sources of gravitational waves may produce space-time turbulence.
---------------------------------------------------------
Title: A New Method for Measuring Relative Abundances in the Solar
Corona
Authors: Zambrana Prado, Natalia; Buchlin, Eric
2018csc..confE..79Z Altcode: 2018csc..confE..79P
Linking the Solar Wind to its origin in the solar atmosphere is a
difficult task. One way forward is to use composition data measured
in situ and remotely. Indeed, different structures on the Sun have
different abundances, that become frozen at a certain height, and
therefore we can determine where certain wind plasma detected in
situ comes from. However, systematically determining these abundances
from remote-sensing observations is difficult because it usually first
requires an accurate determination of the Differential Emission Measure
(DEM). We present a new method to measure relative abundances using UV
spectroscopy, which aims at being independent from the DEM. This method
relies on optimizing linear combinations of spectral lines. We test
this method using DEMs obtained from AIA observations and creating
synthetic intensities with them. This allows us to test the method
accurately and to find the best linear combinations. This method could
be used semi-automatically for optimal abundance determinations from
existing observations as well as for designing new observations such as
those from the SPICE spectrometer from the future Solar Orbiter mission.
---------------------------------------------------------
Title: The SDO AIA and HMI archive at MEDOC
Authors: Alingery, Pablo; Buchlin, Éric; Caminade, Stéphane; Ballans,
Hervé; Baudin, Frédéric; Parenti, Susanna; Bocchialini, Karine
2018csc..confE.113A Altcode:
MEDOC, created as the European data and operations center for SoHO,
hosts also data from STEREO, SDO, and various other solar physics
missions. The SDO archive at MEDOC represents more than 415TB of data,
and covers the full length of the mission. It includes aia.lev1 data at
a minimum cadence of 60s in the EUV channels (12s at specific periods of
interest), and most of the 720s-cadence HMI series. It is complemented
by a database of DEM maps derived from AIA. MEDOC provides a reliable,
convenient, and fast (especially for European users) access to these
SDO data, by a web interface and webservices. We also provide IDL
and Python clients to these webservices, allowing complex queries and
automated analyses on large datasets to be made.
---------------------------------------------------------
Title: SPICE Operations and Scientific Exploitation
Authors: Buchlin, Eric
2018cosp...42E.454B Altcode:
The SPICE spectrometer will address key science goals of the Solar
Orbiter mission, including science questions on the origin of CMEs,
the acceleration of energetic particles, and the connectivity to the
heliosphere.The SPICE Operations and Scientific Exploitation Team
Consortium was selected by ESA in 2016. Support for the operations
and scientific exploitation of SPICE is shared between 4 main agencies
in Europe (CNES, UKSA, the Norwegian Space Center, and DLR) and NASA
in the United States. The lead funding agency is CNES, responsible
for providing leadership and coordinating the collective efforts to
ensure that the SPICE operations activities are conducted smoothly.The
Consortium will operate SPICE and provide operations support to the
Solar Orbiter project to fulfill the mission's science objectives,
including: <P />Planning of SPICE operations, in coordination with
other Solar Orbiter instruments. <P />Providing ESA with a data
processing pipeline for low-latency data, and operating a processing
pipeline up to calibrated data products. <P />Maintaining the SPICE
instrument, including monitoring and troubleshooting instrument health
and safety. <P />Providing software and support to the scientific
community to work with SPICE data. <P />We will present the tasks
to be performed by the consortium, the consortium team structure and
responsibilities, as well as an overview of the capabilities of the
instrument and its contributions to the Solar Orbiter science goals.
---------------------------------------------------------
Title: An analysis of simultaneous observations of a CME-associated
eruptive prominence with IRIS, AIA/SDO, EUVI/STEREO and K-COR
Authors: Zhang, Ping; Vial, Jean-Claude; Buchlin, Eric
2018cosp...42E3836Z Altcode:
We present the simultaneous observations of a CME-associated eruptive
prominence which have been made by the Interface Region Imaging
Spectrograph (IRIS), Atmospheric Imaging Assembly (AIA) of SDO, EUVI
of STEREO and the ground-based K-COR coronagraph. IRIS observations
started on 2014 May 28 at 11:25 UT, lasted for about 4.5 hours. With
the aim of deriving the velocity vector, we first combined an optical
flow method on the AIA 304 observations to compute the POS velocities
in the prominence and a Doppler technique with the IRIS observations
to compute the LOS velocities. Then we characterized the Mg h and k
profiles (time and space-dependent) and compared with the signatures
of various (1000) prominence models through NLTE radiative transfer
computations (I.A.S. PROM7 code). We paid much attention to the exact
incident radiation in various lines and continua. The model parameters
include pressure, temperature, height, thickness, radial and turbulence
velocities. Having selected the best (fitting) models, we were able
to derive the total (hydrogen) density and compute the mass flows. We
also used the STEREO observations to derive the 3D geometry of the
prominence and K-COR to derive the density later on in the process of
eruption. Applying this method to more prominences observed by IRIS
could help to reduce the large range of thermodynamic parameters in
eruptive prominences and to improve their MHD modeling.
---------------------------------------------------------
Title: Physical conditions in a prominence eruption during its
pre-eruption and acceleration
Authors: Zhang, Ping; Vial, Jean-Claude; Buchlin, Eric
2018cosp...42E3837Z Altcode:
We rely upon the simultaneous observations of a CME-associated
eruptive prominence which have been made by the Interface Region
Imaging Spectrograph (IRIS), Atmospheric Imaging Assembly (AIA) of
SDO, EUVI of STEREO and the ground-based K-COR coronagraph. We focus
on the determination of mass flows in order to detect a possible mass
loading. In order to derive the full velocity vector, we combine an
optical flow method on the AIA 304 and IRIS SJI observations to compute
the POS velocities in the prominence and a Doppler technique with the
IRIS observations to compute the LOS velocities. Then we focus on the
determination of densities through the combination of spectroscopic
observations and NLTE modelling. We first characterize the Mg II h and
k profiles (time and space-dependent!) through a grid of 6 typical
profiles (reversed and unreversed). Then we compare them with the
signatures of hundreds of prominence models through NLTE radiative
transfer computations (I.A.S. PROM7 code). Much attention is paid to
the exact incident radiation in various lines and continua. Having
selected the best (fitting) models, we are able to derive the total
(hydrogen) density and compute the mass flows. The derivation of
physical parameters (e.g. velocity) also takes into account the STEREO
observations to derive the 3D geometry of the prominence and K-COR to
derive the density later on in the process of eruption.
---------------------------------------------------------
Title: Understanding the usage of the Helioviewer Project clients
and services
Authors: Ireland, Jack; Zahniy, Serge; Mueller, Daniel; Nicula, Bogdan;
Verstringe, Freek; Bourgoignie, Bram; Buchlin, Eric; Alingery, Pablo
2018tess.conf30286I Altcode:
The Helioviewer Project enables visual exploration of the Sun
and the inner heliosphere for everyone, everywhere via intuitive
interfaces and novel technology. The project mainly develops two
clients, helioviewer.org and JHelioviewer, and the server-side
capabilities accessed via those clients. Images from many different
ground and space-based sources are currently available from multiple
servers. Solar and heliospheric feature and event information,
magnetic field extrapolations and important time-series can also be
browsed and visualized using Helioviewer Project clients. Users of the
Helioviewer Project have made over two million movies and many millions
of screenshots since detailed (and anonymous) logging of Helioviewer
Project usage was implemented in February 2011. These usage logs are
analyzed to give a detailed breakdown on user interaction with solar
and heliospheric data via Helioviewer Project clients and services. We
present summary statistics on how our users are using our clients
and services, which data they are interested in, and how they choose
to interact with different data sources. At the poster presentation
we will also be soliciting ideas from the community to improve our
clients and services.
---------------------------------------------------------
Title: On the Occurrence of Thermal Nonequilibrium in Coronal Loops
Authors: Froment, C.; Auchère, F.; Mikić, Z.; Aulanier, G.;
Bocchialini, K.; Buchlin, E.; Solomon, J.; Soubrié, E.
2018ApJ...855...52F Altcode: 2018arXiv180204010F
Long-period EUV pulsations, recently discovered to be common in active
regions, are understood to be the coronal manifestation of thermal
nonequilibrium (TNE). The active regions previously studied with
EIT/Solar and Heliospheric Observatory and AIA/SDO indicated that
long-period intensity pulsations are localized in only one or two
loop bundles. The basic idea of this study is to understand why. For
this purpose, we tested the response of different loop systems, using
different magnetic configurations, to different stratifications and
strengths of the heating. We present an extensive parameter-space study
using 1D hydrodynamic simulations (1020 in total) and conclude that the
occurrence of TNE requires specific combinations of parameters. Our
study shows that the TNE cycles are confined to specific ranges in
parameter space. This naturally explains why only some loops undergo
constant periodic pulsations over several days: since the loop geometry
and the heating properties generally vary from one loop to another in
an active region, only the ones in which these parameters are compatible
exhibit TNE cycles. Furthermore, these parameters (heating and geometry)
are likely to vary significantly over the duration of a cycle, which
potentially limits the possibilities of periodic behavior. This study
also confirms that long-period intensity pulsations and coronal rain are
two aspects of the same phenomenon: both phenomena can occur for similar
heating conditions and can appear simultaneously in the simulations.
---------------------------------------------------------
Title: IRIS Observations of Spicules and Structures Near the
Solar Limb
Authors: Alissandrakis, C. E.; Vial, J. -C.; Koukras, A.; Buchlin,
E.; Chane-Yook, M.
2018SoPh..293...20A Altcode: 2018arXiv180102082A
We have analyzed Interface Region Imaging Spectrograph (IRIS)
spectral and slit-jaw observations of a quiet region near the South
Pole. In this article we present an overview of the observations, the
corrections, and the absolute calibration of the intensity. We focus
on the average profiles of strong (Mg II h and k, C II and Si IV),
as well as of weak spectral lines in the near ultraviolet (NUV) and
the far ultraviolet (FUV), including the Mg II triplet, thus probing
the solar atmosphere from the low chromosphere to the transition
region. We give the radial variation of bulk spectral parameters as
well as line ratios and turbulent velocities. We present measurements
of the formation height in lines and in the NUV continuum from which
we find a linear relationship between the position of the limb and
the intensity scale height. We also find that low forming lines,
such as the Mg II triplet, show no temporal variations above the limb
associated with spicules, suggesting that such lines are formed in a
homogeneous atmospheric layer and, possibly, that spicules are formed
above the height of 2<SUP>″</SUP>. We discuss the spatio-temporal
structure of the atmosphere near the limb from images of intensity as
a function of position and time. In these images, we identify p-mode
oscillations in the cores of lines formed at low heights above the
photosphere, slow-moving bright features in O I and fast-moving bright
features in C II. Finally, we compare the Mg II k and h line profiles,
together with intensity values of the Balmer lines from the literature,
with computations from the PROM57Mg non-LTE model, developed at the
Institut d' Astrophysique Spatiale, and estimated values of the physical
parameters. We obtain electron temperatures in the range of ∼8000 K
at small heights to ∼20 000 K at large heights, electron densities
from 1.1 ×10<SUP>11</SUP> to 4 ×10<SUP>10</SUP>cm−<SUP>3</SUP>
and a turbulent velocity of ∼24 kms−<SUP>1</SUP>.
---------------------------------------------------------
Title: CDPP supporting tools to Solar Orbiter and Parker Solar Probe
data exploitation
Authors: Genot, V. N.; Cecconi, B.; Dufourg, N.; Gangloff, M.; André,
N.; Bouchemit, M.; Jacquey, C.; Pitout, F.; Rouillard, A.; Nathanaël,
J.; Lavraud, B.; Durand, J.; Tao, C.; Buchlin, E.; Witasse, O. G.
2017AGUFMSH23D2677G Altcode:
In recent years the French Centre de Données de la Physique des
Plasmas (CDPP) has extended its data analysis capability by designing
a number of new tools. In the solar and heliospheric contexts, and
in direct support to the forthcoming solar ESA and NASA missions in
these fields, these tools comprise of the Propagation Tool which helps
linking solar perturbations observed both in remote and in-situ data;
this is achieved through direct connection to the companion solar
database MEDOC and the CDPP AMDA database. More recently, in the
frame of Europlanet 2020 RI, a 1D MHD solar wind propagation code
(Tao et al., 2005) has been interfaced to provide real time solar
wind monitors at cruising probes and planetary environments using ACE
real time data as inputs (Heliopropa service). Finally, simulations,
models and data may be combined and visualized in a 3D context with
3DView. This presentation will overview the various functionalities
of these tools and provide examples, in particular a 'CME tracking'
case recently published (Witasse et al., 2017). Europlanet 2020 RI
has received funding from the European Union's Horizon 2020 research
and innovation programme under grant agreement No 654208.
---------------------------------------------------------
Title: The Next Level in Automated Solar Flare Forecasting: the EU
FLARECAST Project
Authors: Georgoulis, M. K.; Bloomfield, D.; Piana, M.; Massone,
A. M.; Gallagher, P.; Vilmer, N.; Pariat, E.; Buchlin, E.; Baudin,
F.; Csillaghy, A.; Soldati, M.; Sathiapal, H.; Jackson, D.; Alingery,
P.; Argoudelis, V.; Benvenuto, F.; Campi, C.; Florios, K.; Gontikakis,
C.; Guennou, C.; Guerra, J. A.; Kontogiannis, I.; Latorre, V.; Murray,
S.; Park, S. H.; Perasso, A.; Sciacchitano, F.; von Stachelski, S.;
Torbica, A.; Vischi, D.
2017AGUFMSA21C..07G Altcode:
We attempt an informative description of the Flare Likelihood And
Region Eruption Forecasting (FLARECAST) project, European Commission's
first large-scale investment to explore the limits of reliability
and accuracy achieved for the forecasting of major solar flares. We
outline the consortium, top-level objectives and first results of
the project, highlighting the diversity and fusion of expertise
needed to deliver what was promised. The project's final product,
featuring an openly accessible, fully modular and free to download
flare forecasting facility will be delivered in early 2018. The
project's three objectives, namely, science, research-to-operations and
dissemination / communication, are also discussed: in terms of science,
we encapsulate our close-to-final assessment on how close (or far)
are we from a practically exploitable solar flare forecasting. In
terms of R2O, we briefly describe the architecture of the FLARECAST
infrastructure that includes rigorous validation for each forecasting
step. From the three different communication levers of the project we
finally focus on lessons learned from the two-way interaction with the
community of stakeholders and governmental organizations. The FLARECAST
project has received funding from the European Union's Horizon 2020
research and innovation programme under grant agreement No. 640216.
---------------------------------------------------------
Title: Understanding the usage of the Helioviewer Project clients
and services
Authors: Ireland, J.; Zahniy, S.; Mueller, D.; Nicula, B.; Verstringe,
F.; Bourgoignie, B.; Buchlin, E.; Alingery, P.
2017AGUFMSH51C2507I Altcode:
The Helioviewer Project enables visual exploration of the Sun
and the inner heliosphere for everyone, everywhere via intuitive
interfaces and novel technology. The project mainly develops two
clients, helioviewer.org and JHelioviewer, and the server-side
capabilities accessed via those clients. Images from many different
ground and space-based sources are currently available from multiple
servers. Solar and heliospheric feature and event information,
magnetic field extrapolations and important time-series can also be
browsed and visualized using Helioviewer Project clients. Users of the
Helioviewer Project have made over two million movies and many millions
of screenshots since detailed (and anonymous) logging of Helioviewer
Project usage was implemented in February 2011. These usage logs are
analyzed to give a detailed breakdown on user interaction with solar
and heliospheric data via Helioviewer Project clients and services. We
present summary statistics on how our users are using our clients
and services, which data they are interested in, and how they choose
to interact with different data sources. At the poster presentation
we will also be soliciting ideas from the community to improve our
clients and services.
---------------------------------------------------------
Title: A propagation tool to connect remote-sensing observations
with in-situ measurements of heliospheric structures
Authors: Rouillard, A. P.; Lavraud, B.; Génot, V.; Bouchemit, M.;
Dufourg, N.; Plotnikov, I.; Pinto, R. F.; Sanchez-Diaz, E.; Lavarra,
M.; Penou, M.; Jacquey, C.; André, N.; Caussarieu, S.; Toniutti,
J. -P.; Popescu, D.; Buchlin, E.; Caminade, S.; Alingery, P.; Davies,
J. A.; Odstrcil, D.; Mays, L.
2017P&SS..147...61R Altcode: 2017arXiv170200399R
The remoteness of the Sun and the harsh conditions prevailing in the
solar corona have so far limited the observational data used in the
study of solar physics to remote-sensing observations taken either from
the ground or from space. In contrast, the 'solar wind laboratory'
is directly measured in situ by a fleet of spacecraft measuring the
properties of the plasma and magnetic fields at specific points in
space. Since 2007, the solar-terrestrial relations observatory (STEREO)
has been providing images of the solar wind that flows between the
solar corona and spacecraft making in-situ measurements. This has
allowed scientists to directly connect processes imaged near the
Sun with the subsequent effects measured in the solar wind. This new
capability prompted the development of a series of tools and techniques
to track heliospheric structures through space. This article presents
one of these tools, a web-based interface called the 'Propagation Tool'
that offers an integrated research environment to study the evolution
of coronal and solar wind structures, such as Coronal Mass Ejections
(CMEs), Corotating Interaction Regions (CIRs) and Solar Energetic
Particles (SEPs). These structures can be propagated from the Sun
outwards to or alternatively inwards from planets and spacecraft
situated in the inner and outer heliosphere. In this paper, we present
the global architecture of the tool, discuss some of the assumptions
made to simulate the evolution of the structures and show how the tool
connects to different databases.
---------------------------------------------------------
Title: Validating coronal magnetic field reconstruction methods
using solar wind simulations and synthetic imagery
Authors: Pinto, Rui; Rouillard, Alexis; Génot, Vincent; Amari, Tahar;
Buchlin, Eric; Arge, Nick; Sasso, Clementina; Andretta, Vincenzo;
Bemporad, Alessandro
2017EGUGA..1913650P Altcode:
We present an ongoing effort within the ESA Modeling and Data Analysis
Working Group (MADAWG) to determine automatically the magnetic
connectivity between the solar surface and any point in interplanetary
space. The goal is to produce predictions of the paths and propagation
delays of plasma and energetic particle propagation. This is a key
point for the data exploitation of the Solar Orbiter and Solar Probe
Plus missions, and for establishing connections between remote and
in-situ data. The background coronal magnetic field is currently
determined via existing surface magnetograms and PFSS extrapolations,
but the interface is ready to include different combinations of coronal
field reconstruction methods (NLFFF, Solar Models), wind models (WSA,
MULTI-VP), heliospheric models (Parker spiral, ENLIL, EUHFORIA). Some
model realisations are also based on advanced magnetograms based on
data assimilation techniques (ADAPT) and the HELCATS catalogue of
simulations. The results from the different models will be combined in
order to better assess the modelling uncertainties. The wind models
provide synthetic white-light and EUV images which are compared to
coronographic imagery, and the heliospheric models provide estimations
of synthetic in-situ data wich are compared to spacecraft data. A part
of this is work (wind modelling) is supported by the FP7 project #606692
(HELCATS).
---------------------------------------------------------
Title: Erratum: “On the Fourier and Wavelet Analysis of Coronal Time
Series” (<A href="https://doi.org/10.3847/0004-637x/825/2/110">2016,
ApJ, 825, 110</A>)
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
2017ApJ...838..166A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Long-period Intensity Pulsations in Coronal Loops Explained
by Thermal Non-equilibrium Cycles
Authors: Froment, C.; Auchère, F.; Aulanier, G.; Mikić, Z.;
Bocchialini, K.; Buchlin, E.; Solomon, J.
2017ApJ...835..272F Altcode: 2017arXiv170101309F
In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon
that can occur when the heating is both highly stratified and
quasi-constant. Unambiguous observational identification of TNE
would thus permit us to strongly constrain heating scenarios. While
TNE is currently the standard interpretation of coronal rain, the
long-term periodic evolution predicted by simulations has never been
observed. However, the detection of long-period intensity pulsations
(periods of several hours) has been recently reported with the Solar
and Heliospheric Observatory/EIT, and this phenomenon appears to be very
common in loops. Moreover, the three intensity-pulsation events that we
recently studied with the Solar Dynamics Observatory/Atmospheric Imaging
Assembly (AIA) show strong evidence for TNE in warm loops. In this
paper, a realistic loop geometry from linear force-free field (LFFF)
extrapolations is used as input to 1D hydrodynamic simulations. Our
simulations show that, for the present loop geometry, the heating has
to be asymmetrical to produce TNE. We analyze in detail one particular
simulation that reproduces the average thermal behavior of one of the
pulsating loop bundle observed with AIA. We compare the properties of
this simulation with those deduced from the observations. The magnetic
topology of the LFFF extrapolations points to the presence of sites
of preferred reconnection at one footpoint, supporting the presence
of asymmetric heating. In addition, we can reproduce the temporal
large-scale intensity properties of the pulsating loops. This simulation
further strengthens the interpretation of the observed pulsations as
signatures of TNE. This consequently provides important information
on the heating localization and timescale for these loops.
---------------------------------------------------------
Title: Space-weather assets developed by the French space-physics
community
Authors: Rouillard, A. P.; Pinto, R. F.; Brun, A. S.; Briand, C.;
Bourdarie, S.; Dudok De Wit, T.; Amari, T.; Blelly, P. -L.; Buchlin,
E.; Chambodut, A.; Claret, A.; Corbard, T.; Génot, V.; Guennou, C.;
Klein, K. L.; Koechlin, L.; Lavarra, M.; Lavraud, B.; Leblanc, F.;
Lemorton, J.; Lilensten, J.; Lopez-Ariste, A.; Marchaudon, A.; Masson,
S.; Pariat, E.; Reville, V.; Turc, L.; Vilmer, N.; Zucarello, F. P.
2016sf2a.conf..297R Altcode:
We present a short review of space-weather tools and services developed
and maintained by the French space-physics community. They include
unique data from ground-based observatories, advanced numerical
models, automated identification and tracking tools, a range of space
instrumentation and interconnected virtual observatories. The aim of
the article is to highlight some advances achieved in this field of
research at the national level over the last decade and how certain
assets could be combined to produce better space-weather tools
exploitable by space-weather centres and customers worldwide. This
review illustrates the wide range of expertise developed nationally
but is not a systematic review of all assets developed in France.
---------------------------------------------------------
Title: Thermal Non-Equilibrium Revealed by Periodic Pulses of Random
Amplitudes in Solar Coronal Loops
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
2016usc..confE.131A Altcode:
We recently detected variations in extreme ultraviolet intensity in
coronal loops repeating with periods of several hours. Models of loops
including stratified and quasi-steady heating predict the development
of a state of thermal non-equilibrium (TNE): cycles of evaporative
upflows at the footpoints followed by falling condensations at the
apex. Based on Fourier and wavelet analysis, we demonstrate that the
observed periodic signals are indeed not signatures of vibrational
modes. Instead, superimposed on the power law expected from the
stochastic background emission, the power spectra of the time series
exhibit the discrete harmonics and continua expected from periodic
trains of pulses of random amplitudes. These characteristics reinforce
our earlier interpretation of these pulsations as being aborted
TNE cycles.
---------------------------------------------------------
Title: The SDO AIA and HMI archive at MEDOC
Authors: Alingery, P.; Wang, G.; Buchlin, E.; Caminade, S.; Ballans,
H.; Baudin, F.; Parenti, S.
2016usc..confE..97A Altcode:
MEDOC, created as the European data and operations center for SoHO,
hosts also data from STEREO, SDO, and various other solar physics
missions. The SDO archive at MEDOC represents more than 250TB of data,
and covers the full length of the mission. It includes aia.lev1 data at
a minimum cadence of 60s in the EUV channels (12s at specific periods of
interest), and most of the 720s-cadence HMI series. It is complemented
by a database of DEM maps derived from AIA, that will be presented at
the mini-workshop on thermal diagnostics. MEDOC provides a reliable,
convenient, and fast (especially for European users) access to these
SDO data, by a web interface and webservices. We also provide IDL
and Python clients to these webservices, allowing complex queries and
automated analyses on large datasets to be made.
---------------------------------------------------------
Title: The SDO AIA and HMI archive at MEDOC
Authors: Buchlin, Eric
2016usc..confE..97B Altcode:
MEDOC, created as the European data and operations center for SoHO,
hosts also data from STEREO, SDO, and various other solar physics
missions. The SDO archive at MEDOC represents more than 250TB of data,
and covers the full length of the mission. It includes aia.lev1 data at
a minimum cadence of 60s in the EUV channels (12s at specific periods of
interest), and most of the 720s-cadence HMI series. It is complemented
by a database of DEM maps derived from AIA, that will be presented at
the mini-workshop on thermal diagnostics. MEDOC provides a reliable,
convenient, and fast (especially for European users) access to these
SDO data, by a web interface and webservices. We also provide IDL
and Python clients to these webservices, allowing complex queries and
automated analyses on large datasets to be made.
---------------------------------------------------------
Title: Energetic characterisation and statistics of solar coronal
brightenings
Authors: Buchlin, Eric
2016usc..confE.102B Altcode:
To explain the high temperature of the corona, much attention has been
paid to the distribution of energy in dissipation events. Indeed, if the
event energy distribution is steep enough, the smallest, unobservable
events could be the largest contributors to the total energy dissipation
in the corona. Previous observations have shown a wide distribution of
energies but remain inconclusive about the precise slope. Furthermore,
these results rely on a very crude estimate of the energy. On the other
hand, more detailed spectroscopic studies of structures such as coronal
bright points do not provide enough statistical information to derive
their total contribution to heating. We aim at getting a better estimate
of the distributions of the energy dissipated in coronal heating events
using high-resolution, multi-channel EUV data. To estimate the energies
corresponding to heating events and deduce their distribution, we
detected brightenings in five EUV channels of SDO/AIA. We combined the
results of these detections and used maps of temperature and emission
measure derived from the same observations to compute the energies. We
obtain distributions of areas, durations, intensities, and energies
(thermal, radiative, and conductive) of events. These distributions
are power laws and we also find power-law correlations between event
parameters. The energy distributions indicate that the energy from
a population of events like the ones we detect represents a small
contribution to the total coronal heating, even when extrapolating to
smaller scales. The main explanations for this are how heating events
can be extracted from observational data, and the incomplete knowledge
of the thermal structure and processes in the coronal plasma attainable
from available observations.
---------------------------------------------------------
Title: Fourier and Wavelet Analysis of Coronal Time Series
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
2016usc..confE.130A Altcode:
Using Fourier and wavelet analysis, we critically re-assess the
significance of our detection of periodic pulsations in coronal
loops. We show that the proper identification of the frequency
dependence and statistical properties of the different components of
the power spectra provies a strong argument against the common practice
of data detrending, which tends to produce spurious detections around
the cut-off frequency of the filter. In addition, the white and red
noise models built into the widely used wavelet code of Torrence &
Compo cannot, in most cases, adequately represent the power spectra of
coronal time series, thus also possibly causing false positives. Both
effects suggest that several reports of periodic phenomena should
be re-examined. The Torrence & Compo code nonetheless effectively
computes rigorous confidence levels if provided with pertinent models of
mean power spectra, and we describe the appropriate manner in which to
call its core routines. We recall the meaning of the default confidence
levels output from the code, and we propose new Monte-Carlo-derived
levels that take into account the total number of degrees of freedom
in the wavelet spectra. These improvements allow us to confirm that
the power peaks that we detected have a very low probability of being
caused by noise.
---------------------------------------------------------
Title: Energetic characterisation and statistics of solar coronal
brightenings
Authors: Joulin, V.; Buchlin, E.; Solomon, J.; Guennou, C.
2016usc..confE.102J Altcode:
To explain the high temperature of the corona, much attention has been
paid to the distribution of energy in dissipation events. Indeed, if the
event energy distribution is steep enough, the smallest, unobservable
events could be the largest contributors to the total energy dissipation
in the corona. Previous observations have shown a wide distribution of
energies but remain inconclusive about the precise slope. Furthermore,
these results rely on a very crude estimate of the energy. On the other
hand, more detailed spectroscopic studies of structures such as coronal
bright points do not provide enough statistical information to derive
their total contribution to heating. We aim at getting a better estimate
of the distributions of the energy dissipated in coronal heating events
using high-resolution, multi-channel EUV data. To estimate the energies
corresponding to heating events and deduce their distribution, we
detected brightenings in five EUV channels of SDO/AIA. We combined the
results of these detections and used maps of temperature and emission
measure derived from the same observations to compute the energies. We
obtain distributions of areas, durations, intensities, and energies
(thermal, radiative, and conductive) of events. These distributions
are power laws and we also find power-law correlations between event
parameters. The energy distributions indicate that the energy from
a population of events like the ones we detect represents a small
contribution to the total coronal heating, even when extrapolating to
smaller scales. The main explanations for this are how heating events
can be extracted from observational data, and the incomplete knowledge
of the thermal structure and processes in the coronal plasma attainable
from available observations.
---------------------------------------------------------
Title: Long-period Intensity Pulsations as the Manifestation of the
Heating Stratification and Timescale in Coronal Loops
Authors: Froment, Clara; Auchère, Frédéric; Aulanier, Guillaume;
Mikić, Zoran; Bocchialini, Karine; Buchlin, Eric; Solomon, Jacques
2016usc..confE..47F Altcode:
In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon
that can occur when the heating is both highly-stratified and
quasi-constant. Unambiguous observational identification of TNE
would thus permit to strongly constrain heating scenarios. Up to
now, while TNE is the standard interpretation of coronal rain, it
was not believed to happen commonly in warm coronal loops. Recently,
the detection of long-period intensity pulsations (periods of several
hours) has been reported with SoHO/EIT. This phenomenon appears to be
very common in loops (Auchère et al. 2014). In Froment et al. 2015,
three intensity-pulsation events studied with SDO/AIA, show strong
evidence for TNE in warm loops. We use realistic loop geometries
from LFFF extrapolations for one of these events are used as input
to a 1D hydrodynamic simulation of TNE. A highly-stratified heating
function is chosen to reproduce the observed period of pulsation and
temperature of the loops. With these conditions, the heating function
has to be asymmetric. The magnetic topology of the LFFF extrapolations
points to the presence of sites of preferred reconnection at one
footpoint, supporting the presence of asymmetric heating. We compared
the properties of the simulated loop with the properties deduced
from observations. We found that the 1D hydrodynamic simulation
can reproduce the large temporal scale intensity properties of the
pulsating loops (Froment et al. 2016, submitted). This simulation
further strengthen the interpretation of the observed pulsations as
signatures of TNE. This implies that the heating for these loops is
highly-stratified and that the frequency of the heating events must
be high compared to the typical cooling time.
---------------------------------------------------------
Title: GAIA-DEM: a database providing AIA/SDO DEM maps
Authors: Buchlin, Eric
2016usc..confE.108B Altcode:
The Gaussian AIA DEm Maps (GAIA-DEM) database at MEDOC (IAS) provides
through a simple and intuitive web interface DEM inversions of the
SDO/AIA data, computed every 30min. The Gaussian approximation is used
to describe the main features of the true DEM(log T) by its first
moments. For each date, maps of the three Gaussian fit parameters
(central temperature, total emission measure and Gaussian width) and
of the chi^2 are available in FITS format. Users can preview the maps
before downloading them. In addition, users can display the initial
SDO/AIA images using Helioviewer, and query the database through
webservices accessible from IDL and Python clients. This presentation
is for the "Thermal Diagnostics with SDO/AIA" mini-workshop.
---------------------------------------------------------
Title: Automated detection, characterization, and tracking of
filaments from SDO data
Authors: Buchlin, E.; Mercier, C.; Vial, J. -C.
2016usc..confE.100B Altcode:
Thanks to the cadence and continuity of AIA and HMI observations, SDO
offers unique data for detecting, characterizing, and tracking solar
filaments, until their eruptions, which are often associated with
coronal mass ejections. Because of the requirement of short latency
when aiming at space weather applications, and because of the important
data volume, only an automated detection can be worked out. We present
the code "FILaments, Eruptions, and Activations detected from Space"
(FILEAS) that we have developed for the automated detection and
tracking of filaments. Detections are based on the analysis of AIA
30.4 nm He II images and on the magnetic polarity inversion lines
derived from HMI. Following the tracking of filaments as they rotate
with the Sun, filament characteristics are computed and a database of
filaments parameters is built. We are currently building a database
of filament detections by this code, covering the full SDO mission,
and that will be made available to the community.
---------------------------------------------------------
Title: Thermal Non-equilibrium Revealed by Periodic Pulses of Random
Amplitudes in Solar Coronal Loops
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
2016ApJ...827..152A Altcode: 2016arXiv160803789A
We recently detected variations in extreme ultraviolet intensity in
coronal loops repeating with periods of several hours. Models of loops
including stratified and quasi-steady heating predict the development
of a state of thermal non-equilibrium (TNE): cycles of evaporative
upflows at the footpoints followed by falling condensations at the
apex. Based on Fourier and wavelet analysis, we demonstrate that the
observed periodic signals are indeed not signatures of vibrational
modes. Instead, superimposed on the power law expected from the
stochastic background emission, the power spectra of the time series
exhibit the discrete harmonics and continua expected from periodic
trains of pulses of random amplitudes. These characteristics reinforce
our earlier interpretation of these pulsations as being aborted
TNE cycles.
---------------------------------------------------------
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
2016cosp...41E.607F Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.
---------------------------------------------------------
Title: Energetic characterisation and statistics of solar coronal
brightenings
Authors: Buchlin, Eric; Solomon, Jacques; Joulin, Vincent; Guennou,
Chloé
2016cosp...41E.257B Altcode:
To explain the high temperature of the corona, much attention
has been paid to the distribution of energy in dissipation events,
which might be caused by turbulent reconnection. Indeed, if the event
energy distribution is steep enough, the smallest, unobservable events
could be the largest contributors to the total energy dissipation in
the corona. Previous observations have shown a wide distribution of
energies but remain inconclusive about the precise slope. Furthermore,
these results rely on a very crude estimate of the energy. On the
other hand, more detailed spectroscopic studies of structures such as
coronal bright points do not provide enough statistical information
to derive their total contribution to heating. We aim at getting a
better estimate of the distributions of the energy dissipated in coronal
heating events using high-resolution, multi-channel Extreme Ultra-Violet
(EUV) data. To estimate the energies corresponding to heating events
and deduce their distribution, we detect brightenings in five EUV
channels of the Atmospheric Imaging Assembly (AIA) on-board the Solar
Dynamics Observatory (SDO). We combine the results of these detections
and we use maps of temperature and emission measure derived from the
same observations to compute the energies. We obtain distributions
of areas, durations, intensities, and energies (thermal, radiative,
and conductive) of events. These distributions are power-laws, and
we find also power-law correlations between event parameters. The
energy distributions indicate that the energy from a population of
events like the ones we detect represents a small contribution to the
total coronal heating, even when extrapolating to smaller scales. The
main explanations for this are how heating events can be extracted
from observational data, and the incomplete knowledge of the thermal
structure and processes in the coronal plasma attainable from available
observations.
---------------------------------------------------------
Title: Enabling Solar Flare Forecasting at an Unprecedented Level:
the FLARECAST Project
Authors: Georgoulis, Manolis K.; Pariat, Etienne; Massone, Anna
Maria; Vilmer, Nicole; Jackson, David; Buchlin, Eric; Csillaghy,
Andre; Bommier, Veronique; Kontogiannis, Ioannis; Gallagher, Peter;
Gontikakis, Costis; Guennou, Chloé; Murray, Sophie; Bloomfield,
D. Shaun; Alingery, Pablo; Baudin, Frederic; Benvenuto, Federico;
Bruggisser, Florian; Florios, Konstantinos; Guerra, Jordan; Park,
Sung-Hong; Perasso, Annalisa; Piana, Michele; Sathiapal, Hanna;
Soldati, Marco; Von Stachelski, Samuel; Argoudelis, Vangelis;
Caminade, Stephane
2016cosp...41E.657G Altcode:
We attempt a brief but informative description of the Flare
Likelihood And Region Eruption Forecasting (FLARECAST) project,
European Commission's first large-scale investment to explore the
limits of reliability and accuracy for the forecasting of major solar
flares. The consortium, objectives, and first results of the project
- featuring an openly accessible, interactive flare forecasting
facility by the end of 2017 - will be outlined. In addition, we will
refer to the so-called "explorative research" element of project,
aiming to connect solar flares with coronal mass ejections (CMEs)
and possibly pave the way for CME, or eruptive flare, prediction. We
will also emphasize the FLARECAST modus operandi, namely the diversity
of expertise within the consortium that independently aims to science,
infrastructure development and dissemination, both to stakeholders and
to the general public. Concluding, we will underline that the FLARECAST
project responds squarely to the joint COSPAR - ILWS Global Roadmap
to shield society from the adversities of space weather, addressing
its primary goal and, in particular, its Research Recommendations
1, 2 and 4, Teaming Recommendations II and III, and Collaboration
Recommendations A, B, and D. The FLARECAST project has received funding
from the European Union's Horizon 2020 research and innovation programme
under grant agreement No. 640216.
---------------------------------------------------------
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
2016cosp...41E.681G Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.
---------------------------------------------------------
Title: Automated detection, characterization, and tracking of
filaments from SDO data
Authors: Buchlin, Eric; Vial, Jean-Claude; Mercier, Claude
2016cosp...41E.258B Altcode:
Thanks to the cadence and continuity of AIA and HMI observations, SDO
offers unique data for detecting, characterizing, and tracking solar
filaments, until their eruptions, which are often associated with
coronal mass ejections. Because of the requirement of short latency
when aiming at space weather applications, and because of the important
data volume, only an automated detection can be worked out. We present
the code "FILaments, Eruptions, and Activations detected from Space"
(FILEAS) that we have developed for the automated detection and tracking
of filaments. Detections are based on the analysis of AIA 30.4 nm He
II images and on the magnetic polarity inversion lines derived from
HMI. Following the tracking of filaments as they rotate with the Sun,
filament characteristics are computed and a database of filaments
parameters is built. We present the algorithms and performances of the
code, and we compare its results with the filaments detected in Hα and
already present in the Heliophysics Events Knowledgebase. We finally
discuss the possibility of using such a code to detect eruptions in
real time.
---------------------------------------------------------
Title: On the Fourier and Wavelet Analysis of Coronal Time Series
Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.;
Solomon, J.
2016ApJ...825..110A Altcode: 2016arXiv160605251A
Using Fourier and wavelet analysis, we critically re-assess the
significance of our detection of periodic pulsations in coronal
loops. We show that the proper identification of the frequency
dependence and statistical properties of the different components of the
power spectra provides a strong argument against the common practice
of data detrending, which tends to produce spurious detections around
the cut-off frequency of the filter. In addition, the white and red
noise models built into the widely used wavelet code of Torrence &
Compo cannot, in most cases, adequately represent the power spectra of
coronal time series, thus also possibly causing false positives. Both
effects suggest that several reports of periodic phenomena should
be re-examined. The Torrence & Compo code nonetheless effectively
computes rigorous confidence levels if provided with pertinent models of
mean power spectra, and we describe the appropriate manner in which to
call its core routines. We recall the meaning of the default confidence
levels output from the code, and we propose new Monte-Carlo-derived
levels that take into account the total number of degrees of freedom
in the wavelet spectra. These improvements allow us to confirm that
the power peaks that we detected have a very low probability of being
caused by noise.
---------------------------------------------------------
Title: Energetic characterisation and statistics of solar coronal
brightenings
Authors: Joulin, V.; Buchlin, E.; Solomon, J.; Guennou, C.
2016A&A...591A.148J Altcode: 2016arXiv160502780J
Context. To explain the high temperature of the corona, much
attention has been paid to the distribution of energy in dissipation
events. Indeed, if the event energy distribution is steep enough,
the smallest, unobservable events could be the largest contributors to
the total energy dissipation in the corona. Previous observations have
shown a wide distribution of energies but remain inconclusive about
the precise slope. Furthermore, these results rely on a very crude
estimate of the energy. On the other hand, more detailed spectroscopic
studies of structures such as coronal bright points do not provide
enough statistical information to derive their total contribution
to heating. <BR /> Aims: We aim at getting a better estimate of the
distributions of the energy dissipated in coronal heating events using
high-resolution, multi-channel extreme ultraviolet (EUV) data. <BR />
Methods: To estimate the energies corresponding to heating events
and deduce their distribution, we detected brightenings in five
EUV channels of the Atmospheric Imaging Assembly (AIA) on board
the Solar Dynamics Observatory (SDO). We combined the results of
these detections and used maps of temperature and emission measure
derived from the same observations to compute the energies. <BR />
Results: We obtain distributions of areas, durations, intensities,
and energies (thermal, radiative, and conductive) of events. These
distributions are power laws and we also find power-law correlations
between event parameters. <BR /> Conclusions: The energy distributions
indicate that the energy from a population of events like the ones we
detect represents a small contribution to the total coronal heating,
even when extrapolating to smaller scales. The main explanations for
this are how heating events can be extracted from observational data,
and the incomplete knowledge of the thermal structure and processes in
the coronal plasma attainable from available observations. <P />Two
movies attached to Fig. 3 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201526254/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Evidence for Evaporation-incomplete Condensation Cycles in
Warm Solar Coronal Loops
Authors: Froment, C.; Auchère, F.; Bocchialini, K.; Buchlin, E.;
Guennou, C.; Solomon, J.
2015ApJ...807..158F Altcode: 2015arXiv150408129F
Quasi-constant heating at the footpoints of loops leads to evaporation
and condensation cycles of the plasma: thermal non-equilibrium
(TNE). This phenomenon is believed to play a role in the formation
of prominences and coronal rain. However, it is often discounted
as being involved in the heating of warm loops because the
models do not reproduce observations. Recent simulations have
shown that these inconsistencies with observations may be due to
oversimplifications of the geometries of the models. In addition,
our recent observations reveal that long-period intensity pulsations
(several hours) are common in solar coronal loops. These periods are
consistent with those expected from TNE. The aim of this paper is to
derive characteristic physical properties of the plasma for some of
these events to test the potential role of TNE in loop heating. We
analyzed three events in detail using the six EUV coronal channels
of the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We
performed both a differential emission measure (DEM) and a time-lag
analysis, including a new method to isolate the relevant signal from
the foreground and background emission. For the three events, the DEM
undergoes long-period pulsations, which is a signature of periodic
heating even though the loops are captured in their cooling phase,
as is the bulk of the active regions. We link long-period intensity
pulsations to new signatures of loop heating with strong evidence for
evaporation and condensation cycles. We thus simultaneously witness
widespread cooling and TNE. Finally, we discuss the implications of
our new observations for both static and impulsive heating models.
---------------------------------------------------------
Title: Automated detection, characterization, and tracking of
filaments from SDO data
Authors: Buchlin, Eric; Vial, Jean-Claude; Mercier, Claude; Goujon,
Jean-Baptiste
2014cosp...40E.425B Altcode:
Thanks to the cadence and continuity of AIA and HMI observations, SDO
offers unique data for detecting, characterizing, and tracking solar
filaments, until their eruptions, which are often associated with
coronal mass ejections. Because of the requirement of short latency
when aiming at space weather applications, and because of the important
data volume, only an automated detection can be worked out. We present
the code "FILaments, Eruptions, and Activations detected from Space"
(FILEAS) that we have developed for the automated detection and tracking
of filaments. Detections are based on the analysis of AIA 30.4 nm He
II images and on the magnetic polarity inversion lines derived from
HMI. Following the tracking of filaments as they rotate with the Sun,
filament characteristics are computed and a database of filaments
parameters is built. We present the algorithms and performances of
the code, and we compare its results with the filaments detected in
Halpha and already present in the Heliophysics Events Knowledgebase. We
finally discuss the possibility of using such a code to detect eruptions
in real time.
---------------------------------------------------------
Title: Energetic characterisation and statistics of solar coronal
brightenings
Authors: Joulin, Vincent; Solomon, Jacques; Buchlin, Eric
2014cosp...40E1352J Altcode:
The high temperature of the corona could be due to a large contribution
of the smallest, unobservable events if the energy distribution of
heating events is steep enough. Previous observations have shown a
wide distribution of energies but remain inconclusive about the precise
slope. Furthermore, these results rely on a very crude estimate of the
energy. We aim at getting a better estimate of the distributions of
the energy dissipated in coronal heating events using high-resolution,
multi-channel Extreme Ultra-Violet (EUV) data. To estimate the energies
corresponding to heating events and deduce their distribution, we detect
brightenings in five EUV channels of the Atmospheric Imaging Assembly
(AIA) onboard the Solar Dynamics Observatory (SDO). We regroup the
results of these detections and we use maps of temperature and emission
measure derived from the same observations to compute the thermal,
conducted, and radiated energies. The distributions of these energies
are wide power-laws, but small events seem not to be sufficient to
account for the total heating needed to sustain coronal temperatures.
---------------------------------------------------------
Title: Observations and possible interpretations of very long period
intensity pulsations in solar coronal loops
Authors: Froment, Clara; Solomon, Jacques; Buchlin, Eric; Bocchialini,
Karine; Auchere, Frederic; Guennou, Chloe
2014cosp...40E.903F Altcode:
We discovered that intensity pulsations with periods ranging from 3
to 16 hours are common in solar coronal loops. Initially developed
for EIT/SOHO 195 nm images, the automatic detection algorithm is now
running on AIA/SDO data and allows detection of pulsation events in
six coronal bands simultaneously. From may 2010 to december 2013, we
detected more than 2000 events in the 6 EUV bands. We focus our study
on pulsations in active regions and in particular in solar coronal
loops where most of events are detected. A multi-wavelength analysis
of some characteristic events is presented to help understand their
physical nature. We perform a Differential Emission Measure analysis
on AIA time series in order to determine the temporal variations of the
thermal structure of the pulsating loops. This analysis gives important
clues to investigate possible physical interpretations in particular in
term of small perturbations of loops in static equilibrium and to study
how this can constraint coronal heating models. We will also compare
our observations to the results of a MHD turbulence and heating model
of coronal loops.
---------------------------------------------------------
Title: Automated detection, characterization, and tracking of
filaments from SDO data
Authors: Buchlin, E.; Mercier, C.; Vial, -C., J.
2013enss.confE..78B Altcode:
Thanks to the cadence and continuity of AIA and HMI observations, SDO
offers unique data for detecting, characterizing, and tracking solar
filaments, until their eruptions, which can be associated to coronal
mass ejections. Because of the requirement of short latency when
aiming at space weather applications, and because of the important
data volume, only an automated detection can be worked out. We
present the code "FILaments, Eruptions, and Activations detected
from Space" (FILEAS) that we are developing at IAS for the automated
detection and tracking of filaments. Using data either from local
files or from DRMS, detections are based on analysis of AIA 30.4 nm
He II images and on magnetic polarity inversion lines derived from
HMI. Following the tracking of filaments as their rotate with the Sun,
filament characteristics are computed. We discuss the algorithms and
performances of the code, and we compare its results with the filaments
detected in Halpha and already present in the HEK. We finally discuss
the possibility of using this code for detecting eruptions in real time.
---------------------------------------------------------
Title: MEDIA : MEDoc Interface for AIA
Authors: Alingery, P.; Soubrié, E.; Auchère, F.; Bocchialini, K.;
Boignard, J. P.; Buchlin, E.; Malappert, J. C.; Parenti, S.
2013enss.confE..88A Altcode:
MEDOC, the space solar data center at Orsay
(http://www.ias.u-psud.fr/medoc) is now providing a new web access
to the AIA/SDO level 1 images. This interface has the advantage of
being simple, intuitive, very stable and fast. The full resolution
4k x 4k AIA level 1 images archived at MEDOC are downloaded from
upstream DRMS nodes with a 1 minute cadence at all wavelengths. The
dataset will be kept online on a redundant archive for the whole SDO
mission duration. The FITS files are accessible via an user friendly
web interface (http://medoc-sdo.ias.u-psud.fr) that allows users
to request data by selecting a date range, the desired wavelengths
and a sampling rate (choosing a cadence from 1 minute to 1 day). For
each file, users can preview the image (using the Helioviewer tool)
or display the header information before downloading the FITS files
(with or without Rice-compression). This web interface was built
using Sitools2, a tool developed by CNES, the French space agency, and
supports most browsers. For more advanced users, a Search/Get Python
module is also available at http://sdo.ias.u-psud.fr/python. The users
can use it to build more complex yet more powerful queries. We encourage
everyone in Europe and beyond to use these new services!
---------------------------------------------------------
Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1” and 0.3”), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280” on the Sun with
0.14” per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s<SUP> - 1</SUP> or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
---------------------------------------------------------
Title: Flows in a Small Active Region as Seen by Hinode and SoHO
Authors: Boutry, C.; Buchlin, É.; Vial, J.
2012ASPC..454..233B Altcode:
We report on a multi-instrument study performed on Active Region 10943
located at Sun center on 20 Feb. 2007. We use XRT images, magnetic
field maps from SoHO/MDI and we focus on EIS spectra from which we
build maps of the Doppler shift and intensity of Fe XII 195.12 Å. We
paid a special attention to the absolute wavelength calibration taking
into account the orbital temperature effect. We observe coronal loops
between opposite polarities of the region and straight downflows seen
in faint regions.
---------------------------------------------------------
Title: Flows at the Edge of an Active Region: Observation and
Interpretation
Authors: Boutry, C.; Buchlin, E.; Vial, J. -C.; Régnier, S.
2012ApJ...752...13B Altcode: 2012arXiv1204.1377B
Upflows observed at the edges of active regions have been proposed as
the source of the slow solar wind. In the particular case of Active
Region (AR) 10942, where such an upflow has been already observed,
we want to evaluate the part of this upflow that actually remains
confined in the magnetic loops that connect AR 10942 to AR 10943. Both
active regions were visible simultaneously on the solar disk and were
observed by STEREO/SECCHI EUVI. Using Hinode/EIS spectra, we determine
the Doppler shifts and densities in AR 10943 and AR 10942 in order to
evaluate the mass flows. We also perform magnetic field extrapolations
to assess the connectivity between AR 10942 and AR 10943. AR 10943
displays a persistent downflow in Fe XII. Magnetic extrapolations
including both ARs show that this downflow can be connected to the
upflow in AR 10942. We estimate that the mass flow received by AR 10943
areas connected to AR 10942 represents about 18% of the mass flow from
AR 10942. We conclude that the upflows observed on the edge of active
regions represent either large-scale loops with mass flowing along them
(accounting for about one-fifth of the total mass flow in this example)
or open magnetic field structures where the slow solar wind originates.
---------------------------------------------------------
Title: Automated detection of filaments from He II images
Authors: Buchlin, E.; Mercier, C.; Vial, J. -C.
2012EAS....55..175B Altcode:
For space weather applications, it is important to understand filaments
evolution and especially their eruptions associated with coronal mass
ejections. In view of the cadence and continuity of SDO observations,
AIA and HMI offer a unique tool for such a program. Because of the
data volume and the requirement of short latency, only an automated
detection can be worked out. We present a new method for the automated
detection and tracking of filaments, based on the analysis of AIA 30.4
nm He ii images, with the capability to use also the magnetic field
measured by HMI.
---------------------------------------------------------
Title: Flows in the Vicinity of Two Active Regions as Seen by Hinode,
STEREO, and SoHO
Authors: Boutry, C.; Buchlin, E'.; Vial, J.; Régnier, S.
2012ASPC..455...83B Altcode:
We observed active region 10943 located at Sun center on February 20,
2007 and we characterized its interactions with active region 10942 by
using a multi-instrument comparison between Hinode/XRT and STEREO/SECCHI
images, magnetic field maps from SoHO/MDI, and Hinode/EIS spectra
from which we built maps of the Doppler shift and the intensity of the
Fe XII 195.12 Å line. The results are consistent with some material
exchange between the two regions separated by 400″.
---------------------------------------------------------
Title: Kinematics and helicity evolution of a loop-like eruptive
prominence
Authors: Koleva, K.; Madjarska, M. S.; Duchlev, P.; Schrijver, C. J.;
Vial, J. -C.; Buchlin, E.; Dechev, M.
2012A&A...540A.127K Altcode: 2012arXiv1202.4541K
<BR /> Aims: We aim at investigating the morphology as well as
kinematic and helicity evolution of a loop-like prominence during its
eruption. <BR /> Methods: We used multi-instrument observations from
AIA/SDO, EUVI/STEREO and LASCO/SoHO. The kinematic, morphological,
geometrical, and helicity evolution of a loop-like eruptive
prominence were studied in the context of the magnetic flux rope
model of solar prominences. <BR /> Results: The prominence eruption
evolved as a height-expanding twisted loop with both legs anchored
in the chromosphere of a plage area. The eruption process consisted
of a prominence activation, acceleration, and a phase of constant
velocity. The prominence body was composed of counter-clockwise twisted
threads around the main prominence axis. The twist during the eruption
was estimated at 6π (3 turns). The prominence reached a maximum height
of 526 Mm before contracting to its primary location and was partially
reformed in the same place two days after the eruption. This ejection,
however, triggered a coronal mass ejection (CME) observed in LASCO
C2. The prominence was located in the northern periphery of the CME
magnetic field configuration and, therefore, the background magnetic
field was asymmetric with respect to the filament position. The physical
conditions of the falling plasma blobs were analysed with respect to
the prominence kinematics. <BR /> Conclusions: The same sign of the
prominence body twist and writhe, as well as the amount of twisting
above the critical value of 2π after the activation phase indicate that
possibly conditions for kink instability were present. No signature
of magnetic reconnection was observed anywhere in the prominence body
and its surroundings. The filament/prominence descent following the
eruption and its partial reformation at the same place two days later
suggest a confined type of eruption. The asymmetric background magnetic
field possibly played an important role in the failed eruption. <P
/>Movies showing the temporal evolution are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Intermittent turbulent dynamo at very low and high magnetic
Prandtl numbers
Authors: Buchlin, E.
2011A&A...534L...9B Altcode: 2011arXiv1109.4442B
Context. Direct numerical simulations of plasmas have shown that the
dynamo effect is efficient even at low Prandtl numbers, i.e., the
critical magnetic Reynolds number Rm<SUB>c</SUB> that is necessary
for a dynamo to be efficient becomes smaller than the hydrodynamic
Reynolds number Re when Re → ∞. <BR /> Aims: We test the conjecture
that Rm<SUB>c</SUB> tends to a finite value when Re → ∞, and we
study the behavior of the dynamo growth factor γ at very low and high
magnetic Prandtl numbers. <BR /> Methods: We use local and nonlocal
shell models of magnetohydrodynamic (MHD) turbulence with parameters
covering a much wider range of Reynolds numbers than direct numerical
simulations, that is of astrophysical relevance. <BR /> Results:
We confirm that Rm<SUB>c</SUB> tends to a finite value when Re →
∞. As Rm → ∞, the limit to the dynamo growth factor γ in the
kinematic regime follows Re<SUP>β</SUP>, and, similarly, the limit
for Re → ∞ of γ behaves like Rm<SUP>β'</SUP>, with β ≈ β'
≈ 0.4. <BR /> Conclusions: Our comparison with a phenomenology
based on an intermittent small-scale turbulent dynamo, together with
the differences between the growth rates in the different local and
nonlocal models, indicate that nonlocal terms contribute weakly to
the dynamo effect. <P />Figures 5 and 6 are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Automated detection of filaments in SDO data
Authors: Buchlin, É.; Mercier, C.; Engin, S.; Parenti, S.; Vial,
J. -C.
2010sf2a.conf..297B Altcode:
Solar eruption can eject billions of tons of plasma to the
interplanetary space, with geophysical effects and impacts on human
activities. The time constraints for space weather application as well
as the huge volume of data that needs to be analyzed, especially since
the launch of SDO, imply that the detection of solar filaments and their
eruptions must be automated. Most current detection codes use Hα data,
which are not available frequently enough for these applications. We
present a new detection code that we have developed at IAS and that uses
the high spatial and temporal-resolution SDO/AIA He II 30.4 nm data.
---------------------------------------------------------
Title: Nonlinear diffusion equation for Alfvén wave turbulence
Authors: Galtier, S.; Buchlin, É.
2010sf2a.conf..299G Altcode:
We discuss about the possibility to derive rigorously a nonlinear
diffusion equation for incompressible MHD turbulence. The background
of the analysis is the asymptotic Alfvén wave turbulence equations
from which a differential limit is taken. The result is a universal
diffusion-type equation in k-space which describes in a simple way
and without free parameter the energy transport perpendicular to
the external magnetic field B_0 for transverse fluctuations. It is
compatible with both the thermodynamic equilibrium and the finite flux
spectra derived by Galtier et al. (2000). This new system offers a
powerful description of a wide class of astrophysical plasmas.
---------------------------------------------------------
Title: Nonlinear Diffusion Equations for Anisotropic
Magnetohydrodynamic Turbulence with Cross-helicity
Authors: Galtier, Sébastien; Buchlin, Éric
2010ApJ...722.1977G Altcode: 2010arXiv1008.3515G
Nonlinear diffusion equations of spectral transfer are systematically
derived for anisotropic magnetohydrodynamics in the regime of
wave turbulence. The background of the analysis is the asymptotic
Alfvén wave turbulence equations from which a differential limit is
taken. The result is a universal diffusion-type equation in k-space
which describes in a simple way and without free parameter the energy
transport perpendicular to the external magnetic field B<SUB>0</SUB>
for transverse and parallel fluctuations. These equations are compatible
with both the thermodynamic equilibrium and the finite flux spectra
derived by Galtier et al. it improves therefore the model built
heuristically by Lithwick & Goldreich for which only the second
solution was recovered. This new system offers a powerful description
of a wide class of astrophysical plasmas with non-zero cross-helicity.
---------------------------------------------------------
Title: Automated detection of filaments and their eruptions from
AIA and HMI/SDO data
Authors: Buchlin, Eric; Mercier, Claude; Vial, Jean-Claude
2010cosp...38.2862B Altcode: 2010cosp.meet.2862B
The superior temporal, spatial and spectral range of AIA on SDO provides
a completely new view of the dynamic nature of coronal loops. In this
paper, we will examine preliminary results of a number of loop examples
as their evolution is followed closely in time and space across the
AIA filters. The implications of these observational results on the
heating and cooling mechanisms operating will be discussed.
---------------------------------------------------------
Title: The SDO data centre at IDOC/MEDOC in France
Authors: Parenti, Susanna; Bocchialini, Karine; Soubrie, Elie;
Auchere, Frederic; Ballans, Herv; Buchlin, Eric; Gabriel, Alan;
Mercier, Claude; Poulleau, Gilles; Vial, Jean-Claude
2010cosp...38.2888P Altcode: 2010cosp.meet.2888P
The IDOC/MEDOC centre at the Institut d'Astrophysique Spatiale (IAS,
Université Paris 11/CNRS) has a long experience in solar data archiving
and distribution, including almost 15 years of data from SOHO, STEREO
and TRACE. The center is now expanding its activity and becoming a
Pˆle Thématique Solaire of the CNES and INSU/CNRS. Part of the new
activities of the centre will be linked to the arrival of the enormous
volume of the new SDO data. The center will be one of the three European
centers to receive and redistribute the data to the community. It will
also be the only European site to permanently store about 10% of the
data (mainly from AIA). In continuity with its previous activities,
SDO data will be included in the data visualization tool FESTIVAL
and it will provide new services, like tools for the solar feature
identification (filaments, EUV intensity fluctuations). We will present
an overview of the facilities and activities of the centre in relation
to the SDO data.
---------------------------------------------------------
Title: Turbulent heating and cooling of coronal loops
Authors: Buchlin, Eric; Bradshaw, Stephen J.; Cargill, Peter J.;
Velli, Marco
2010cosp...38.2834B Altcode: 2010cosp.meet.2834B
In the solar corona, MHD turbulence is likely to be the process
producing small scales, at which heating processes become efficient and
are able to sustain the high coronal temperatures. However, as these
small scales are too small to be observable, comparison between models
and observations rely on indirect consequences of the heating. For this
reason we build a model of a coronal loop including at the same time
the heating processes (anisotropic turbulence driven by Alfvén waves),
the cooling processes (convection, conduction, and radiation based on
atomic physics), and the forward-modeling of spectroscopic observable
variables (such as the evolution of UV spectral line profiles). We show
that including the feedback of the cooling on the heating processes is
important in such models. The heating is intermittent and sufficient
to heat the loop at temperatures of more than a million degrees, with
realistic values of the amplitude of the forcing (corresponding to
motions of the photospheric footpoints of the loop). We discuss the
importance of small scale heating in the corona and the relevance of
its description by our model.
---------------------------------------------------------
Title: Turbulence in the Sub-Alfvénic Solar Wind Driven by Reflection
of Low-Frequency Alfvén Waves (Invited)
Authors: Verdini, A.; Velli, M. M.; Buchlin, E.
2009AGUFMSH51C..07V Altcode:
We study the formation and evolution of a turbulent spectrum
of Alfvén waves driven by reflection off the solar wind density
gradients, starting from the coronal base up to 17 solar radii, well
beyond the Alfvénic critical point, and using a 2D shell model to
describe nonlinear interactions. We find that the turbulent spectra
are influenced by the nature of reflected waves. Close to the base,
these give rise to a flatter and steeper spectrum for the outgoing
and reflected waves respectively. At higher heliocentric distance both
spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent
dissipation is found to account for at least half of the heating
required to sustain the background imposed solar wind and its shape is
found to be determined by the reflection-determined turbulent heating
below 1.5 solar radii. Therefore reflection and reflection-driven
turbulence are shown to play a key role in the acceleration of the
fast solar wind and origin of the turbulent spectrum found at 0.3 AU
in the heliosphere.
---------------------------------------------------------
Title: Electron density in the quiet solar coronal transition region
from SoHO/SUMER measurements of S VI line radiance and opacity
Authors: Buchlin, E.; Vial, J. -C.
2009A&A...503..559B Altcode: 2009arXiv0906.1367B
Context: The steep temperature and density gradients that are measured
in the coronal transition region challenge the model interpretation
of observations. <BR />Aims: We derive the average electron density
< n<SUB>e</SUB> > in the region emitting the S vi lines. We use
two different techniques, which allow us to derive linearly-weighted
(opacity method) and quadratically-weighted (emission measure method)
electron density along the line-of-sight, to estimate a filling factor
or derive the layer thickness at the formation temperature of the
lines. <BR />Methods: We analyze SoHO/SUMER spectroscopic observations
of the S vi lines, using the center-to-limb variations in radiance,
the center-to-limb ratios of radiance and line width, and the radiance
ratio of the 93.3-94.4 nm doublet to derive the opacity. We also
use the emission measure derived from radiance at disk center. <BR
/>Results: We derive an opacity τ<SUB>0</SUB> at S vi 93.3 nm line
center of the order of 0.05. The resulting average electron density
< {n<SUB>e</SUB>}>, under simple assumptions concerning the
emitting layer, is 2.4 × 10<SUP>16</SUP> m<SUP>-3</SUP> at T = 2 ×
10<SUP>5</SUP> K. This value is higher than (and inconsistent with)
the values obtained from radiance measurements (2 × 10<SUP>15</SUP>
m<SUP>-3</SUP>). The last value corresponds to an electron pressure
of 10<SUP>-2</SUP> Pa. Conversely, taking a classical value for the
density leads to a too high value of the thickness of the emitting
layer. <BR />Conclusions: The pressure derived from the emission
measure method compares well with previous determinations. It implies
a low opacity of between 5 × 10<SUP>-3</SUP> and 10<SUP>-2</SUP>. It
remains unexplained why a direct derivation leads to a much higher
opacity, despite tentative modeling of observational biases. Further
measurements in S vi and other lines emitted at a similar temperature
should be completed, and more realistic models of the transition region
need to be used.
---------------------------------------------------------
Title: Turbulence in the Sub-Alfvénic Solar Wind Driven by Reflection
of Low-Frequency Alfvén Waves
Authors: Verdini, A.; Velli, M.; Buchlin, E.
2009ApJ...700L..39V Altcode: 2009arXiv0905.2618V
We study the formation and evolution of a turbulent spectrum of Alfvén
waves driven by reflection off the solar wind density gradients,
starting from the coronal base up to 17 solar radii, well beyond
the Alfvénic critical point. The background solar wind is assigned
and two-dimensional shell models are used to describe nonlinear
interactions. We find that the turbulent spectra are influenced by the
nature of the reflected waves. Close to the base, these give rise to
a flatter and steeper spectrum for the outgoing and reflected waves,
respectively. At higher heliocentric distance both spectra evolve
toward an asymptotic Kolmogorov spectrum. The turbulent dissipation
is found to account for at least half of the heating required to
sustain the background imposed solar wind and its shape is found to be
determined by the reflection-determined turbulent heating below 1.5
solar radii. Therefore, reflection and reflection-driven turbulence
are shown to play a key role in the acceleration of the fast solar wind
and origin of the turbulent spectrum found at 0.3 AU in the heliosphere.
---------------------------------------------------------
Title: Reflection Driven MHD Turbulence in the Solar Atmosphere
and Wind
Authors: Verdini, A.; Velli, M.; Buchlin, E.
2009EM&P..104..121V Altcode: 2008EM&P..tmp...33V
Alfvénic turbulence is usually invoked and used in many solar wind
models (Isenberg and Hollweg, 1982, J. Geophys. Res. 87:5023;
Tu et al. 1984, J. Geophys. Res. 89:9695; Hu et al. 2000,
J. Geophys. Res. 105:5093; Li 2003, Astron. Astrphys. 406:345; Isenberg
2004, J. Geophys. Res. 109:3101) as a process responsible for the
transfer of energy, released at large scale in the photosphere, towards
small scale in the corona, where it is dissipated. Usually an initial
spectrum is prescribed since the closest constraint to the spectrum is
given by Helios measurements at 0.3 AU. With this work we intend to
study the efficiency of the reflection as a driver for the nonlinear
interactions of Alfvén waves, the development of a turbulent spectrum
and its evolution in the highly stratified solar atmosphere inside
coronal holes. Our main finding is that the perpendicular spectral slope
changes substantially at the transition region because of the steep
density gradient. As a result a strong turbulent heating occurs, just
above the transition region, as requested by current solar wind models.
---------------------------------------------------------
Title: Turbulence in anisotropic heliospheric plasmas
Authors: Buchlin, E.; Verdini, A.; Cargill, P. J.; Velli, M.
2008sf2a.conf..547B Altcode:
An alternative approach to Direct Numerical Simulations (DNS)
of Magnetohydrodynamics (MHD) is presented, providing insight
into the statistical properties of highly-turbulent, intermittent,
anisotropic MHD turbulence: a set of shell-models coupled by Alfvén
waves travelling along the axial magnetic field and which interact
non-linearly, producing perpendicular fluctuations of the fields
at small scales. This model can be applied to different physical
situations; we present the cases of heating in solar coronal loops,
and of turbulence in open coronal regions at the base of the solar wind.
---------------------------------------------------------
Title: Spectroscopic Hinode Observables from Turbulent Heating and
Cooling of Coronal Loops
Authors: Buchlin, É.; Cargill, P. J.; Bradshaw, S. J.; Velli, M.
2008ASPC..397...83B Altcode:
We present a model of coronal loop turbulence allowing the fast
computation of heating in a loop at high Reynolds numbers. We
also consider the coupling of both heating and cooling processes
in loops, including for the first time a feedback of the cooling
on the heating: the heating computed by the shell-models used as an
input of a hydrodynamic model of a loop with thermal conduction and a
self-consistent treatment of radiation. We forward-model spectroscopic
variables that can be compared to Hinode observations.
---------------------------------------------------------
Title: Properties of the quiet solar coronal transition region from
full-Sun SoHO/SUMER S VI
Authors: Buchlin, E.; Vial, J.
2008ESPM...122.117B Altcode:
A series of full-Sun SoHO/SUMER observations of the quiet Sun in the
transition region lines S VI 933 and 944 (as well as Ly epsilon) has
been performed during year 1996. We use this unique data set to derive
the opacity of the S VI lines by different methods (following Dumont et
al. 1983), taking advantage from the availability of full-Sun data and
<P />of the S VI doublet: 1. using the center-to-limb variations of S
VI 933 radiance and peak spectral radiance, 2. using the center-to-limb
variations of S VI 933 line width and radiance, and 3. using the S VI
944 - 933 radiance or spectral radiance ratio at disk center. We then
deduce an average value for the density in the S VI emitting region
(in the coronal transition region). By comparing this value to the
average square density obtained by an Emission Measure analysis,
we get a tentative estimate of the filling factor in this region.
---------------------------------------------------------
Title: Alfvénic Turbulence and the Acceleration of the Fast
Solar Wind
Authors: Verdini, A.; Velli, M.; Buchlin, E.
2008ESPM...12.3.69V Altcode:
Alfvenic turbulence is usually invoked and used in many solar wind
models (Isenberg & Hollweg 1982, Tu et al. 1984, Hu et al. 2000,
Li 2003, Isenberg 2004) as a process responsible for the transfer of
energy released at large scales in the photosphere towards small scales
in the corona, where it is dissipated. Usually an initial spectrum is
prescribed since its closest constraint is given by Helios measurements
at 0.3 AU. <P />With this work we intend to study the efficiency of the
reflection as a driver for the nonlinear interactions of Alfven waves,
the eventual development of a turbulent spectrum and its evolution in
the highly stratified solar atmosphere inside coronal holes. <P />We
start imposing an upcoming flux of Alfven waves in a limited range
of perpendicular wave numbers, at the base of the corona. <P />Open
boundary conditions allow the reflected waves to leave the domain form
below and to be advected by the solar wind outside the top boundary. The
nonlinear interaction in planes perpendicular to that of propagation
(assumed to be radial) are treated with a 2D shell model, so that large
Reynolds numbers are reached. <P />Continuous interactions of counter
propagating waves form a turbulent spectrum in the low corona, before
the sonic point, in very short timescales (compared to the propagation
timescales). <P />Both the location and the value of the maximum of
the dissipation (per unit mass) scale with the rms amplitude of the
velocity fluctuations at the coronal base (delta u), while they are
less sensitive to the frequency of the input flux of Alfven waves,
provided it is small enough to power the turbulent cascade by means of
reflection. <P />For values of delta u in agreement with observational
constraints, the turbulent dissipation achieves levels capable of
sustaining a fast solar wind, with the maximum dissipation located at 2
solar radii, just below the sonic point. <P />Despite the back reaction
of the solar wind is not taken into account, this model shows that,
under reasonable assumptions, a turbulent spectrum forms in the corona
and it is able to sustain the heating and acceleration of the fast
solar wind. Finally, the scaling laws obtained with this simplified 2D
turbulence can be further constrained in order to include this mechanism
of reflection driven turbulence in more complex solar wind models.
---------------------------------------------------------
Title: Profiles of heating in turbulent coronal magnetic loops
Authors: Buchlin, E.; Cargill, P. J.; Bradshaw, S. J.; Velli, M.
2007A&A...469..347B Altcode: 2007astro.ph..2748B
Context: The location of coronal heating in magnetic loops has been
the subject of a long-lasting controversy: does it occur mostly at the
loop footpoints, at the top, is it random, or is the average profile
uniform? <BR />Aims: We try to address this question in model loops
with MHD turbulence and a profile of density and/or magnetic field
along the loop. <BR />Methods: We use the Shell-Atm MHD turbulent
heating model described in Buchlin & Velli (2007, ApJ, 662, 701),
with a static mass density stratification obtained by the HydRad model
(Bradshaw & Mason 2003, A&A, 401, 699). This assumes the absence
of any flow or heat conduction subsequent to the dynamic heating. <BR
/>Results: The average profile of heating is quasi-uniform, unless there
is an expansion of the flux tube (non-uniform axial magnetic field)
or the variation of the kinetic and magnetic diffusion coefficients
with temperature is taken into account: in the first case the heating
is enhanced at footpoints, whereas in the second case it is enhanced
where the dominant diffusion coefficient is enhanced. <BR />Conclusions:
These simulations shed light on the consequences on heating profiles
of the complex interactions between physical effects involved in a
non-uniform turbulent coronal loop.
---------------------------------------------------------
Title: Shell Models of RMHD Turbulence and the Heating of Solar
Coronal Loops
Authors: Buchlin, E.; Velli, M.
2007ApJ...662..701B Altcode: 2006astro.ph..6610B
A simplified nonlinear numerical model for the development
of incompressible magnetohydrodynamics in the presence of a
strong magnetic field B<SUB>∥</SUB> and stratification, nicknamed
“Shell-Atm,” is presented. In planes orthogonal to the mean field,
the nonlinear incompressible dynamics is replaced by two-dimensional
shell models for the complex variables u and b, allowing one to reach
large Reynolds numbers while at the same time carrying out sufficiently
long integrations to obtain good statistics at moderate computational
cost. The shell models of different planes are coupled by Alfvén waves
propagating along B<SUB>∥</SUB>. The model may be applied to open or
closed magnetic field configurations where the axial field dominates and
the plasma pressure is low; here we apply it to the specific case of a
magnetic loop of the solar corona heated by means of turbulence driven
by photospheric motions, and we use statistics for its analysis. The
Alfvén waves interact nonlinearly and form turbulent spectra in the
directions perpendicular and, through propagation, also parallel
to the mean field. A heating function is obtained and shown to be
intermittent; the average heating is consistent with values required
for sustaining a hot corona and is proportional to the aspect ratio of
the loop to the -1.5 power, and characteristic properties of heating
events are distributed as power laws. Cross-correlations show a delay
of dissipation compared with energy content.
---------------------------------------------------------
Title: Multiscale Hall-Magnetohydrodynamic Turbulence in the
Solar Wind
Authors: Galtier, Sébastien; Buchlin, Eric
2007ApJ...656..560G Altcode: 2006astro.ph.10759G
The spectra of solar wind magnetic fluctuations exhibit a
significant power-law steepening at frequencies f>1 Hz. The
origin of this multiple scaling is investigated through dispersive
Hall magnetohydrodynamics. We perform three-dimensional numerical
simulations in the framework of a highly turbulent shell model and
show that the large-scale magnetic fluctuations are characterized by a
k<SUP>-5/3</SUP>-type spectrum that steepens at scales smaller than the
ion inertial length d<SUB>i</SUB>, to k<SUP>-7/3</SUP> if the magnetic
energy overtakes the kinetic energy, or to k<SUP>-11/3</SUP> in the
opposite case. These results are in agreement both with a heuristic
description à la Kolmogorov and with the range of power-law indices
found in the solar wind.
---------------------------------------------------------
Title: Coronal Turbulence And Intermittency From Solar Orbiter
Observations
Authors: Buchlin, É.; Vial, J. -C.
2007ESASP.641E..23B Altcode:
Turbulent motions and magnetic fields are a key component of coronal
heating mechanisms. They are indeed likely to produce the small scales
at which the mechanisms such as reconnection are efficient enough. The
properties of turbulence (and the associated intermit- tency) may thus
have an influence on the energy dissipation in the corona, and need to
be characterized from observations. Although turbulence is omnipresent
from the Sun to the heliosphere, good observations of MHD turbulence
have not yet been performed in the corona, in lines emitted at high
temperature, where the heating actually occurs. We propose a study
of coordinated EUS- EUI-VIM observations, with better resolution and
counting statistics than ever before, whose main goal is to get and
interpret the spatial statistics (spectra and structure functions)
of the velocity field in lines emitted at high temperatures (log10
T ≥ 6.4), together with the plasma and magnetic environment of the
observed region. These statistics will help us understand the precise
role of coronal turbulence in the coronal heating processes.
---------------------------------------------------------
Title: Modeling the Radiative Signatures of Turbulent Heating in
Coronal Loops
Authors: Parenti, S.; Buchlin, E.; Cargill, P. J.; Galtier, S.; Vial,
J. -C.
2006ApJ...651.1219P Altcode:
The statistical properties of the radiative signature of a coronal loop
subject to turbulent heating obtained from a three-dimensional (3D)
magnetohydrodynamics (MHD) model are studied. The heating and cooling of
a multistrand loop is modeled and synthetic spectra for Fe XII 195.12,
Fe XV 284.163, and Fe XIX 1118.06 Å are calculated, covering a wide
temperature range. The results show that the statistical properties
of the thermal and radiative energies partially reflect those of the
heating function in that power-law distributions are transmitted,
but with very significant changes in the power-law indices. There is
a strong dependence on the subloop geometry. Only high-temperature
radiation (~10<SUP>7</SUP> K) preserves reasonably precise information
on the heating function.
---------------------------------------------------------
Title: Alfvén Waves and Turbulence in the Inner Corona
Authors: Verdini, A.; Buchlin, E.; Velli, M.
2006ESASP.617E.115V Altcode: 2006soho...17E.115V
No abstract at ADS
---------------------------------------------------------
Title: Looking for Signature of Coronal Heating in the Radiative
Emission of a Coronal Loop
Authors: Parenti, S.; Buchlin, E.; Cargill, P. J.; Caltier, S.; Vial,
J. -C.
2006ESASP.617E.104P Altcode: 2006soho...17E.104P
No abstract at ADS
---------------------------------------------------------
Title: A statistical study of SUMER spectral images: events,
turbulence, and intermittency
Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P.
2006A&A...451.1091B Altcode: 2005astro.ph.11042B
We analyze a series of full-Sun observations performed with the
SoHO/SUMER instrument between March and October 1996. Some parameters
(radiance, shift and width) of the S vi 93.3 nm , S vi 94.4 nm ,
and Ly \varepsilon line profiles were computed on board. Radiances
and line-of-sight velocities in a large central region of the Sun
are studied statistically: distributions of solar structures, field
Fourier spectra and structure functions are obtained. The structures
have distributions with power-law tails, the Fourier spectra of the
radiance fields also display power laws, and the normalized structure
functions of the radiance and velocity fields increase at small
scales. These results support the idea of the existence of small
scales, created by turbulence, and of intermittency of the observed
fields. These properties may provide insight into the processes needed
for heating the transition region, or, if confirmed in the corona,
the corona itself. The difficulties encountered in this analysis,
especially for the velocity data, underline the need for sensitive
ultraviolet imaging spectrometers.
---------------------------------------------------------
Title: Heating of the solar corona
Authors: Buchlin, E.
2006sf2a.conf..529B Altcode:
The mechanisms of transport and dissipation of energy in the corona
are the subject of a long-lasting controversy in solar physics, with
implications on Solar-Terrestrial physics. I review some classical
models of wave or current dissipation, and I discuss the role of
turbulence, how it can help providing the small scales at which
dissipation is more efficient, what observational and computational
difficulties arise, what is being done to overcome them, and what new
challenges we meet.
---------------------------------------------------------
Title: Reduced MHD and Shell-Model Simulations of Coronal Heating
in Magnetized Loops: Scaling Laws.
Authors: Velli, M.; Rappazzo, F.; Buchlin, E.; Einaudi, G.
2005AGUFMSH13B..03V Altcode:
We present direct magnetohydrodynamic (MHD) simulations modeling the
heating of coronal loops in the solar atmosphere via the tangling
of coronal field lines by photospheric footpoint motions within the
framework of reduced MHD. We carry out long-time 3D simulations with
the highest resolutions to date and compare them to simpler shell-model
simulations, in which the non-linear couplings in wave-number space
are drastically simplified. The latter reach much larger Reynolds
numbers but can not describe the dynamics in physical space, which
is driven by the reconnection of induced coronal magnetic fields. In
the direct numerical simulations, we reach resolutions sufficient to
derive scaling properties with Reynolds numbers, loop length, and ratio
of photospheric velocity to coronal Alfven speeds. Line-tying of the
axial field lines plays a significant role by inhibiting coalescence and
inverse cascades in the loop cross-sections, which dominate dynamics
in 2D models. To examine the role of line-tying simulations including
gradients in the density from the photosphere to the corona are also
included. Shell-model calculations are carried out for much longer
time-scales, sufficient to calculate the statistical properties of
heating. The scaling properties derived from the shell models and from
reduced MHD are compared and contrasted and on this basis we discuss
the required role of emerging flux, neglected here, in coronal heating.
---------------------------------------------------------
Title: Radiative Signatures of Coronal Loops Submitted to Turbulent
Heating
Authors: Parenti, S.; Buchlin, E.; Galtier, S.; Vial, J. -C.
2005ESASP.592..523P Altcode: 2005soho...16E..97P; 2005ESASP.592E..97P
No abstract at ADS
---------------------------------------------------------
Title: Shell-Model Simulations of MHD in a Solar Coronal Loop
Authors: Buchlin, É.; Velli, M.
2005ESASP.592..153B Altcode: 2005soho...16E..23B; 2005ESASP.592E..23B
No abstract at ADS
---------------------------------------------------------
Title: Influence of the definition of dissipative events on their
statistics
Authors: Buchlin, E.; Galtier, S.; Velli, M.
2005A&A...436..355B Altcode: 2004astro.ph.11592B
A convenient and widely used method to study the turbulent plasma in
the solar corona is to examine statistics of properties of events
(or structures) associated to flares either in observations or
in numerical simulations. Numerous papers have followed such
a methodology, using different definitions of an event, but the
reasons behind the choice of a particular definition is very rarely
discussed. We give here a comprehensive set of possible event
definitions starting from a one-dimensional data set such as a
time-series of energy dissipation. Each definition is then applied
to a time-series of energy dissipation obtained from simulations
of a shell-model of magnetohydrodynamic turbulence, or from a new
model of coupled shell-models designed to represent a magnetic loop
in the solar corona. We obtain distributions of the peak dissipation
power, total energy, duration and waiting-time associated with each
definition. These distributions are then investigated and compared,
and the influence of the definition of an event on the statistics is
discussed. In particular, power-law distributions are more likely to
appear when using a threshold. The sensitivity of the distributions to
the definition of an event seems also to be weaker for events found in
a highly intermittent time series. Some implications for statistical
results obtained from observations are discussed.
---------------------------------------------------------
Title: Shell-Model Simulations of MHD in a Solar Coronal Loop
Authors: Buchlin, E.; Velli, M.
2005AGUSMSP14A..05B Altcode:
Statistics may be necessary to keep a global view of the complexity of
astrophysical turbulence, in particular the effects of non-linear
interactions over a wide range of scales. However, from the
numerical point of view, a statistical approach to turbulence has the
contradictory needs for computing speed and for a good description
of the solutions of the MHD equations. This problem can be addressed
by simplified models like cellular automata or shell-models. In the
shell-models, the low number of well-chosen modes allows to keep
the most possible of the complex and non-linear physics of the MHD
equations while running sufficiently fast to produce statistics of
fields, of structures, and of "events". The model we present here is
designed to represent a magnetic loop in the solar corona. It consists
of a pile of shell-models, which allows to reach a wide range of
wavenumbers in cross-sections of the loop and model the non-linear
couplings between these modes. The shell-models are also coupled by
Alfvén waves propagating along the loop. We study the statistical
properties of intermittent energy dissipation and of the velocity and
magnetic fields produced by this model. These statistical properties
can be compared to statistics issued from observations, like structure
functions or events distributions.
---------------------------------------------------------
Title: Simplified Simulations of MHD in a Coronal Loop by Coupled
Shell-Models
Authors: Buchlin, É.; Velli, M.; Galtier, S.
2004ESASP.575..120B Altcode: 2004soho...15..120B
No abstract at ADS
---------------------------------------------------------
Title: Modelling the Radiative Signatures of Turbulent Heating in
Coronal Loops
Authors: Parenti, S.; Buchlin, E.; Galtier, S.; Vial, J. -C.
2004ESASP.575..497P Altcode: 2004soho...15..497P
No abstract at ADS
---------------------------------------------------------
Title: Simplified simulations of MHD
Authors: Buchlin, É.; Velli, Marco; Galtier, Sébastien; Vial,
Jean-Claude
2004sf2a.conf...91B Altcode: 2004sf2a.confE.334B
Because of the wide range of scales involved in MHD turbulence, a
statistical approach may become necessary to keep a global view of this
complex phenomenon. In particular, in the framework of the heating of
the solar corona, the smallest events are not directly detectable by the
current instruments but may be integrated to a statistical study. From
the numerical point of view, the contradictory needs for computing speed
and good description of MHD solutions may be addressed by simplified
models, which keep the most possible of the complex and non-linear
physics of the MHD equations but run sufficiently fast to produce
statistics of fields, of structures, and of "events". We propose
two such models which have been originally developed to represent
coronal loops (with forcing and Alfvén wave reflection at the loop's
foot-points), but which may be adapted to represent any region with
a dominant large-scale magnetic field. The first model consists of a
set of cellular automata, in which the non-linear terms of the MHD
equations are modelled by a threshold dynamics on current density
(Buchlin et al. A&A, 2003). In the second model, the cellular
automata are replaced by shell-models of MHD, so as to reach a greater
range of wavenumbers and to model more realistically the non-linear
couplings between modes at different scales. The results obtained
with these models will be presented and consequences of this study
for observational statistics and for theory of MHD turbulence will
be discussed.
---------------------------------------------------------
Title: Signatures and models of small-scale turbulent coronal heating
Authors: Buchlin, E.
2004PhDT........41B Altcode:
In solar physics, the complexity and small scales generated by
magnetohydrodynamic (MHD) turbulence suggest to tackle the problem of
the heating of the corona using statistics. We use therefore spectra of
the fields, distributions of probability of structures or events, and
structure functions, to analyze observations and numerical simulations,
and to detect common signatures of turbulence, intermittency, and
small-scale heating. <P />Our numerical simulations model a coronal
magnetic loop, which is excited by the motions of the photosphere,
and in which non-linearly interacting Alfvén waves propagate. As
we need statistics, we need to simplify these interactions: we have
chosen to model these interactions by cellular automata on one hand,
and then by shell-models on the other hand. The results of these loop
models are consistent with observations, and allow to understand some
observational effects. Furthermore, signatures of intermittency can
be found in the shell-model-based model, which includes a better
representation of the non-linear terms of MHD than the cellular
automata model. The analysis of these models and of their parametric
behavior gives some information on the heating mechanisms in the corona
and some clues about the interpretation of observations. <P />We also
analyze the intensity and velocity fields observed in 1996 on the quiet
Sun with the SoHO/SUMER spectrograph. The statistics of these fields
(mainly the intensity field, as the velocity field is regrettably too
noisy) acquaint us with the turbulent nature of the corona and with
its intermittency. <P />The discrepancy between the distributions of
events observed by different authors in the corona leads us finally
to interest ourselves to the different possible definitions of an
event. We give a comprehensive set of such definitions and we compare
them, using lowly and highly intermittent signals.
---------------------------------------------------------
Title: Simplified simulations of non-linear interactions in an
anisotropic plasma
Authors: Buchlin, E.; Velli, M.; Galtier, S.
2004cosp...35.3555B Altcode: 2004cosp.meet.3555B
Statistics may be necessary to keep a global view of the complexity of
astrophysical turbulence, in particular the effects of non-linear
interactions over a wide range of scales. However, from the
numerical point of view, a statistical approach to turbulence has the
contradictory needs for computing speed and for a good description
of the solutions of the MHD equations. This problem can be addressed
by simplified models, for example models with a reduced number of
well-chosen modes, which keep the most possible of the complex and
non-linear physics of the MHD equations but run sufficiently fast to
produce statistics of fields, of structures, and of "events". The model
we present here was orginally designed to represent a magnetic loop
in the solar corona, but may in fact help to understand turbulence in
any region with a dominant magnetic field ěc{B}_0. It consists of a
pile of shell-models, which allow to reach a wide range of wavenumbers
in the directions orthogonal to ěc{B}_0 and model the non-linear
couplings between these modes. The shell-models are also coupled by
Alfvén waves propagating along ěc{B}_0. We study the statistical
properties of energy dissipation and of the velocity and magnetic
fields produced by this model.
---------------------------------------------------------
Title: Signatures et modélisations du chauffage coronal turbulent
à micro-échelles
---------------------------------------------------------
Title: Signatures et modélisations du chauffage
coronal turbulent à micro-échelles
---------------------------------------------------------
Title: Signatures and modeling
of turbulent coronal heating at micro-scales;
Authors: Buchlin, Éric
2004PhDT.......315B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Statistical Study of SOHO/SUMER Full-Sun Images
Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P.; Galtier, S.
2004ESASP.547..337B Altcode: 2004soho...13..337B
A series of full-Sun observations was performed with the SoHO/SUMER
instrument between March and October 1996. Some moments of the
S VI 93.3nm, S VI 94.4nm, and Ly line profiles were computed
on-board. Intensities and line-of-sight velocities in a large central
region of the Sun are studied statistically: histograms of intensities
are computed, as well as histograms of total intensities of "events",
and structure functions of the intensity field. Some statistics of
velocities are the first to be obtained from observational data. The
aim is to compare these statistics to results previously obtained with
SoHO/EIT and by numerical simulations of MHD. Signatures of turbulent
intermittency are also researched.
---------------------------------------------------------
Title: Statistical properties of turbulence and intermittency in
the solar corona observed in EUV
Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P.
2004cosp...35.3556B Altcode: 2004cosp.meet.3556B
Statistical properties of the fields observed on the Sun in EUV may
help to understand turbulence in the solar corona and give clues to
the processes involved in the heating of the corona to millions of
degrees. In this study, we use a series of full-Sun images obtained
in 1996 by the SUMER spectroheliograph on SoHO. Each observation
consists of eight limb-to-limb raster scans in the lines Ly ɛ, S VI
193.3 nm, and S VI 194.4 nm. Intensities, Doppler velocity shifts and
line widths were computed on-board. A context spectrum was measured
for each observation. Intensities and line-of-sight velocities data
in a large central region of the Sun are then studied statistically:
histograms of data values and of events, structure functions, and
other statistics are computed. They are compared to results obtained
by imaging instruments like SoHO/EIT and to numerical simulations of
MHD. Structure functions of the velocity field reveal that turbulence
in the corona may be intermittent.
---------------------------------------------------------
Title: A solar cellular automata model issued from reduced MHD
Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Vial, J. -C.
2003AIPC..679..335B Altcode:
A three-dimensional cellular automata (CA) model inspired by the reduced
magnetohydrodynamic equations is presented to describe impulsive events
generated along a coronal magnetic loop. It consists of a set of planes,
distributed along the loop, between which the information propagates
through Alfvén waves. Statistical properties in terms of power laws are
obtained in agreement with SoHO observations of X-ray bright points of
the quiet Sun. Physical meaning and limits of the model are discussed.
---------------------------------------------------------
Title: A simplified numerical model of coronal energy dissipation
based on reduced MHD
Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Einaudi,
G.; Vial, J. -C.
2003A&A...406.1061B Altcode: 2002astro.ph.12444B
A 3D model intermediate between cellular automata (CA) models and
the reduced magnetohydrodynamic (RMHD) equations is presented to
simulate solar impulsive events generated along a coronal magnetic
loop. The model consists of a set of planes distributed along a
magnetic loop between which the information propagates through Alfvén
waves. Statistical properties in terms of power-laws for energies and
durations of dissipative events are obtained, {and their} agreement
with X-ray and UV flares observations {is discussed}. The existence
of observational biases is {also} discussed.
---------------------------------------------------------
Title: Distributions of Coronal Events: Simulations and Event
Definitions
Authors: Buchlin, Éric; Galtier, Sébastien; Velli, Marco; Vial,
Jean-Claude
2003ANS...324..109B Altcode: 2003ANS...324..P15B
No abstract at ADS
---------------------------------------------------------
Title: A Solar Cellular Automata Model Issued From Reduced MHD
Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Vial, J. -C.
2002sf2a.conf..129B Altcode:
A three-dimensional cellular automata model inspired by the reduced
magnetohydrodynamic equations is presented to describe impulsive events
generated along a coronal magnetic loop. It consists of a set of planes,
distributed along the loop, between which the information propagates
through Alfven waves. Statistical properties in terms of power laws are
obtained in agreement with SoHO observations of X-ray bright points of
the quiet Sun. Physical meaning and limits of the model are discussed.
---------------------------------------------------------
Title: Recent SOHO/SUMER Observations of a Polar and Equatorial
Coronal Hole
Authors: Buchlin, E.; Hassler, D. M.
2000SPD....31.0201B Altcode: 2000BAAS...32..810B
SUMER observations have provided new insight into the structure of
the source region of the solar wind, and its relationship to the
chromospheric magnetic network. Specifically, velocity maps in Ne
VIII, formed at the base of the corona, show a relationship between
outflow velocity and the underlying network structure (Hassler et al.,
Science, 1999). However, the time cadence of these observations had to
be increased to tell whether these velocity signatures correspond to
steady state or transient flows. We present two new observing campaigns
that we have organized and performed in 1999 (March 8 and November 3-8)
to address this outstanding question while preserving sufficient FOV,
involving observations from SOHO (SUMER, EIT, MDI, CDS), TRACE and
Kitt Peak. Preliminary analysis of the observations from March 8,
1999 suggest that the majority of the observed flows in both the
south polar coronal hole and the equatorial quiet Sun region are
relatively quiescent (or slowly evolving) on the time scale of the SUMER
observations of 2 hours. However, one significant high speed transient
flow (20-30 km/s) was identified in a SUMER scan at the south polar
coronal hole, and corresponds to an explosive event or jet observed by
TRACE in Fe IX/X 171 which lasted less than an hour. During the November
campaign, extensive, coordinated observations were made of an equatorial
coronal hole which began on the East limb and rotated across the MDI
high resolution FOV at central meridian. Complete coronal hole scans
(5 to 9 hours long), several series of three 2-hour long scans and
time series with 1 min cadence were made. Intensity, line-of-sight
velocity, and line width maps will be presented for emission lines
formed at three different heights in the solar atmosphere (Si II 1533,
C IV 1548, and Ne VIII 770). This work has been funded in part by NASA
under grant NAG5-7815 to Southwest Research Institute.
