explanation blue bibcodes open ADS page with paths to full text
Author name code: degroof
ADS astronomy entries on 2022-09-14
author:"De Groof, Anik"
---------------------------------------------------------
Title: Solar Orbiter's first close encounter with the Sun: preparation
of the coordinated science campaigns
Authors: de Groof, Anik; Müller, Daniel; Zouganelis, Yannis; Walsh,
Andrew; Williams, David
2022cosp...44.1537D Altcode:
After a Cruise Phase of 21 months, Solar Orbiter entered its first
scientific orbit on 27 November 2021 after a Gravity Assist Manoeuvre
(GAM) by the Earth. The spacecraft entered a highly elliptical orbit
that will bring it up to its first close perihelion on 17 March 2022,
at 0.32AU from the Sun. In the following years, further GAMs by Venus
will lead it even closer to the Sun and also out of the ecliptic
plane. Solar Orbiter's main goal is to study the connection between
the solar activity close to the star's surface and its effects as seen
in the heliosphere, the bubble-like region of space under the Sun's
influence including all solar planets. Therefore, its main scientific
goals can only be achieved by coordinated observations of both the
6 remote-sensing telescopes onboard, observing the dynamic Sun, and
the 4 in-situ instruments measuring the effects in the solar wind
surrounding the spacecraft. This coordination takes careful planning
and optimisation of the mission resources, in order to fully exploit
the capabilities of this exciting mission. In this contribution,
we present the science operations as planned for the first year of
Nominal mission phase, i.e. the first two orbits. By the time of the
COSPAR meeting, Solar Orbiter will have made its first close encounter
and most of the data from the perihelion will have arrived!
---------------------------------------------------------
Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
2020A&A...642A...6A Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements. <BR /> Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together. <BR /> Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis. <BR /> Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
---------------------------------------------------------
Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
2020A&A...642A...2R Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk. <BR /> Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies. <BR /> Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter. <BR /> Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission. <BR /> Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.
---------------------------------------------------------
Title: Coordination of the in situ payload of Solar Orbiter
Authors: Walsh, A. P.; Horbury, T. S.; Maksimovic, M.; Owen, C. J.;
Rodríguez-Pacheco, J.; Wimmer-Schweingruber, R. F.; Zouganelis,
I.; Anekallu, C.; Bonnin, X.; Bruno, R.; Carrasco Blázquez, I.;
Cernuda, I.; Chust, T.; De Groof, A.; Espinosa Lara, F.; Fazakerley,
A. N.; Gilbert, H. R.; Gómez-Herrero, R.; Ho, G. C.; Krucker,
S.; Lepri, S. T.; Lewis, G. R.; Livi, S.; Louarn, P.; Müller, D.;
Nieves-Chinchilla, T.; O'Brien, H.; Osuna, P.; Plasson, P.; Raines,
J. M.; Rouillard, A. P.; St Cyr, O. C.; Sánchez, L.; Soucek, J.;
Varsani, A.; Verscharen, D.; Watson, C. J.; Watson, G.; Williams, D. R.
2020A&A...642A...5W Altcode:
Solar Orbiter's in situ coordination working group met frequently
during the development of the mission with the goal of ensuring
that its in situ payload has the necessary level of coordination to
maximise science return. Here we present the results of that work,
namely how the design of each of the in situ instruments (EPD, MAG,
RPW, SWA) was guided by the need for coordination, the importance of
time synchronisation, and how science operations will be conducted
in a coordinated way. We discuss the mechanisms by which instrument
sampling schemes are aligned such that complementary measurements
will be made simultaneously by different instruments, and how burst
modes are scheduled to allow a maximum overlap of burst intervals
between the four instruments (telemetry constraints mean different
instruments can spend different amounts of time in burst mode). We
also explain how onboard autonomy, inter-instrument communication,
and selective data downlink will be used to maximise the number of
transient events that will be studied using high-resolution modes of
all the instruments. Finally, we briefly address coordination between
Solar Orbiter's in situ payload and other missions.
---------------------------------------------------------
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.
---------------------------------------------------------
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
<BR /> Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission. <BR /> Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal. <BR /> Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing. <BR /> Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
---------------------------------------------------------
Title: Understanding the origins of the heliosphere: integrating
observations and measurements from Parker Solar Probe, Solar Orbiter,
and other space- and ground-based observatories
Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron,
N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.;
St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; Auchère, F.;
Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker,
S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli,
M.; Solanki, S. K.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper,
J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.;
De Groof, A.; Williams, D.
2020A&A...642A...4V Altcode:
Context. The launch of Parker Solar Probe (PSP) in 2018, followed
by Solar Orbiter (SO) in February 2020, has opened a new window in
the exploration of solar magnetic activity and the origin of the
heliosphere. These missions, together with other space observatories
dedicated to solar observations, such as the Solar Dynamics Observatory,
Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations
from WIND and ACE, and ground based multi-wavelength observations
including the DKIST observatory that has just seen first light,
promise to revolutionize our understanding of the solar atmosphere
and of solar activity, from the generation and emergence of the Sun's
magnetic field to the creation of the solar wind and the acceleration of
solar energetic particles. <BR /> Aims: Here we describe the scientific
objectives of the PSP and SO missions, and highlight the potential for
discovery arising from synergistic observations. Here we put particular
emphasis on how the combined remote sensing and in situ observations of
SO, that bracket the outer coronal and inner heliospheric observations
by PSP, may provide a reconstruction of the solar wind and magnetic
field expansion from the Sun out to beyond the orbit of Mercury in the
first phases of the mission. In the later, out-of-ecliptic portions of
the SO mission, the solar surface magnetic field measurements from SO
and the multi-point white-light observations from both PSP and SO will
shed light on the dynamic, intermittent solar wind escaping from helmet
streamers, pseudo-streamers, and the confined coronal plasma, and on
solar energetic particle transport. <BR /> Methods: Joint measurements
during PSP-SO alignments, and magnetic connections along the same
flux tube complemented by alignments with Earth, dual PSP-Earth,
and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will
allow a better understanding of the in situ evolution of solar-wind
plasma flows and the full three-dimensional distribution of the
solar wind from a purely observational point of view. Spectroscopic
observations of the corona, and optical and radio observations,
combined with direct in situ observations of the accelerating solar
wind will provide a new foundation for understanding the fundamental
physical processes leading to the energy transformations from solar
photospheric flows and magnetic fields into the hot coronal plasma
and magnetic fields and finally into the bulk kinetic energy of the
solar wind and solar energetic particles. <BR /> Results: We discuss
the initial PSP observations, which already provide a compelling
rationale for new measurement campaigns by SO, along with ground-
and space-based assets within the synergistic context described above.
---------------------------------------------------------
Title: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
2020A&A...642A...1M Altcode: 2020arXiv200900861M
<BR /> Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
2015-2025 programme and a mission of international collaboration between
ESA and NASA, will explore the Sun and heliosphere from close up and
out of the ecliptic plane. It was launched on 10 February 2020 04:03
UTC from Cape Canaveral and aims to address key questions of solar and
heliospheric physics pertaining to how the Sun creates and controls
the Heliosphere, and why solar activity changes with time. To answer
these, the mission carries six remote-sensing instruments to observe
the Sun and the solar corona, and four in-situ instruments to measure
the solar wind, energetic particles, and electromagnetic fields. In
this paper, we describe the science objectives of the mission, and how
these will be addressed by the joint observations of the instruments
onboard. <BR /> Methods: The paper first summarises the mission-level
science objectives, followed by an overview of the spacecraft and
payload. We report the observables and performance figures of each
instrument, as well as the trajectory design. This is followed by a
summary of the science operations concept. The paper concludes with a
more detailed description of the science objectives. <BR /> Results:
Solar Orbiter will combine in-situ measurements in the heliosphere
with high-resolution remote-sensing observations of the Sun to address
fundamental questions of solar and heliospheric physics. The performance
of the Solar Orbiter payload meets the requirements derived from the
mission's science objectives. Its science return will be augmented
further by coordinated observations with other space missions and
ground-based observatories. <P />ARRAY(0x207ce98)
---------------------------------------------------------
Title: Solar Orbiter's Science Activity Plan: Translating Questions
into Action
Authors: Zouganelis, Y.; Mueller, D.; De Groof, A.; Walsh, A. P.;
Williams, D.
2019AGUFMSH21D3315Z Altcode:
Solar Orbiter is a mission, scheduled for launch in February 2020,
with as main goal to observe solar activity from close by, both in and
out of the ecliptic, and to link it to the solar wind as sensed by its
in-situ sensors. The payload consists of 6 remote-sensing and 4 in-situ
instrument suites, which will have to coordinate their operations in
order to address the four mission objectives: (1) What drives the solar
wind and where does the heliospheric 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? We have to consider, however, that
each orbit around the Sun has different characteristics, including the
relative positions of the Earth and spacecraft (affecting downlink
rates and communications blackouts), trajectory events (such as
gravitational assist manoeuvres), and the phase of the solar activity
cycle. Furthermore, each orbit's science telemetry will be downloaded
during the next, so orbits cannot be planned individually. So how
will those science questions be translated into an actual plan of
observations that will fit into the mission? First, the component
questions are broken down into answerable questions along with the
observations they need from the payload. Then, in order to address this,
the so-called Science Activity Plan (SAP) has been developed. The
SAP groups together objectives that require similar observations
into Solar Orbiter Observing Plans (SOOPs), resulting in a strategic,
top-level view of the optimal opportunities for science observations
across the mission lifetime, allowing all four mission objectives to
be addressed. In this presentation, we introduce Solar Orbiter's SAP
through a series of examples and the strategy being followed.
---------------------------------------------------------
Title: An Unusual Widespread Solar Energetic Particle Event
Authors: Rodriguez-Garcia, L.; Gomez-Herrero, R.; Zouganelis, Y.;
Rodriguez-Pacheco, J.; Dresing, N.; Williams, D.; De Groof, A.
2019AGUFMSH23C3355R Altcode:
Over the course of several hours, a Solar Energetic Particle (SEP) event
was observed by the twin spacecraft of the Solar TErrestrial RElations
Observatory (STEREO A and B), by several near-Earth spacecraft like the
SOlar and Heliospheric Observatory (SOHO), and by the MErcury Surface,
Space ENvironment, GEochemistry and Ranging (MESSENGER) in orbit around
Mercury. These multiple observation points covered a considerable
angular span of 222 degrees in the ecliptic plane. The widespread SEP
event was associated with a halo Coronal Mass Ejection (CME) passing
through the SOHO/ Large Angle and Spectrometric Coronagraph ( LASCO)
field of view, with a plane-of-sky speed of 877 km/s. The CME was
accompanied by type III and type II radio bursts but, surprisingly ,
in spite of the 360 degree remote-sensing coverage of the solar disk
at different wavelengths, no major solar flare was observed. The SEP
event showed a very gradual rise of particle intensities at STEREO-A,
STEREO-B and the Earth, and the particle onset at STEREO-B and the
Earth were delayed by several hours with respect to the estimated
lift-off time of the CME. Unexpectedly, this was also the case for
STEREO-A, relatively well connected to the source. However, MESSENGER,
located closer to the Sun and slightly better connected to the source
than STEREO-A, observed a clear electron increase with much shorter
temporal delay. It is remarkable that all the spacecraft-observed
electron increases approach relativistic energies and proton increases
reach energies beyond 50 MeV. To disentangle the possible scenarios for
particle acceleration and propagation during this unusual widespread
SEP event, particles anisotropies, onset-timing dispersion and act ive
r egion m agnetic foot-point separation are discussed. To understand
their possible effect on the SEP interplanetary propagation conditions,
the identification and 3D geometric characterisation of the CME, as
well as of previously ejected Interplanetary Coronal Mass Ejections
(ICME) and shocks, are analysed. Different physical scenarios explaining
the wide spread of the SEP such as, a wide coronal shock, cross-field
diffusion and particle confinement in the interplanetary medium are
discussed and compared with the observational signatures.
---------------------------------------------------------
Title: Solar Orbiter Science Operations: Not A Typical Heliophysics
Mission
Authors: Walsh, A. P.; De Groof, A.; Williams, D.; Sánchez, L.;
Zouganelis, Y.
2019AGUFMSH21D3314W Altcode:
ESA's Solar Orbiter is scheduled for launch in February 2020, and will
approach the Sun to a distance of 0.28 AU, in an orbit progressively
more inclined to the Ecliptic plane. Solar Orbiter will provide
landmark new views of a star, up-close, often observing its poles,
while measuring the coupling of the solar phenomena and features to
the relatively pristine solar wind that it will measure in situ. The
unique orbit of the spacecraft and the arrangement and composition of
its scientific payload impose unique constraints on how scientific
operations can be conducted. These operations involve long- to very
short-term planning in carefully arranged steps, which have much more
in common with planetary encounter missions than preceding heliophysics
missions. In this presentation, we explain the details of how science
observations will be arranged and conducted, often very far from Earth,
and how data from the mission will be returned and distributed.
---------------------------------------------------------
Title: The Energy Spectrum of the Solar Wind Core
Authors: Walsh, A. P.; Toledo Redondo, S.; Osuna, P.; Zouganelis,
Y.; Masson, A.; De Groof, A.; Perrone, D.; Roberts, O. W.; Taylor, M.
2017AGUFMSH23D2685W Altcode:
The solar wind electron distribution is typically characterised
as having three components, a broadly isotropic core at the lowest
energies, an isotropic halo at higher energies and a field-aligned
strahl at energies similar to those of the halo. Historically,
the core has been described by a Maxwellian distribution function
while the halo and strahl are known to be suprathermal and have been
described using kappa functions. We use high energy resolution Cluster
PEACE measurements to re-examine the spectral shape of the observed
distributions at core energies and find that, at least some of the time,
a kappa function better describes them than a Maxwellian. During these
times, no spectral break is found at typical halo energies. We discuss
the causes and implications of this in the context of Solar Orbiter
and Parker Solar Probe.
---------------------------------------------------------
Title: Performances of swap on-board PROBA-2
Authors: Halain, J. -P.; Berghmans, D.; Defise, J. -F.; Rochus, P.;
Nicula, B.; de Groof, A.; Seaton, D.
2017SPIE10565E..0SH Altcode:
The PROBA2 mission has been launched on 2nd November2009 with a Rockot
launcher to a Sunsynchronous orbit at an altitude of 725 km. Its
nominal operation duration is two years with possible extension of
2 years. PROBA2 is a small satellite developed under an ESA General
Support Technology Program (GSTP) contract to perform an in-flight
demonstration of new space technologies and support a scientific
mission for a set of selected instruments. The mission is tracked by
the ESA Redu Mission Operation Center.
---------------------------------------------------------
Title: Solar Orbiter Science Operations: Not A Typical Heliophysics
Mission
Authors: Williams, David R.; De Groof, Anik; Walsh, Andrew
2017SPD....4811408W Altcode:
ESA’s Solar Orbiter is scheduled for launch in February 2019, and will
approach the Sun to a distance of 0.28 AU, in an orbit progressively
more inclined to the Ecliptic plane. Solar Orbiter will provide
landmark new views of a star, up-close, often observing its poles,
while measuring the coupling of the solar phenomena and features
to the relatively pristine solar wind that it measure in situ. The
unique orbit of the spacecraft and the arrangement and composition of
its scientific payload impose unique constraints on how scientific
operations can be conducted. These operations involve long- to very
short-term planning in carefully arranged steps, which have much in
common with planetary-encounter missions than preceding heliophysics
missions. In this presentation, we explain the details of how science
observations will be arranged and conducted, often very far from Earth,
and how data from the mission will be returned and distributed.
---------------------------------------------------------
Title: Solar signatures and eruption mechanism of the August 14,
2010 coronal mass ejection (CME)
Authors: D'Huys, Elke; Seaton, Daniel B.; De Groof, Anik; Berghmans,
David; Poedts, Stefaan
2017JSWSC...7A...7D Altcode: 2017arXiv170108814D
On August 14, 2010 a wide-angled coronal mass ejection (CME) was
observed. This solar eruption originated from a destabilized filament
that connected two active regions and the unwinding of this filament
gave the eruption an untwisting motion that drew the attention
of many observers. In addition to the erupting filament and the
associated CME, several other low-coronal signatures that typically
indicate the occurrence of a solar eruption were associated with this
event. However, contrary to what was expected, the fast CME (v >
900 km s<SUP>-1</SUP>) was accompanied by only a weak C4.4 flare. We
investigate the various eruption signatures that were observed for this
event and focus on the kinematic evolution of the filament in order to
determine its eruption mechanism. Had this solar eruption occurred just
a few days earlier, it could have been a significant event for space
weather. The risk of underestimating the strength of this eruption based
solely on the C4.4 flare illustrates the need to include all eruption
signatures in event analyses in order to obtain a complete picture of
a solar eruption and assess its possible space weather impact.
---------------------------------------------------------
Title: Solar Wind Core Electrons: Kappa or Maxwellian?
Authors: Walsh, A. P.; Osuna, P.; Toledo Redondo, S.; Zouganelis, Y.;
Masson, A.; De Groof, A.; Mueller, D.; Perrone, D.; Roberts, O. W.;
Taylor, M. G.; Turc, L.
2016AGUFMSH51D2608W Altcode:
Solar wind core electrons are typically considered to have a Maxwellian
velocity distribution function. However, most measurements made of
them to date don't have sufficient energy resolution to distinguish
between a Maxwellian and a kappa distribution at low energies. Here
we present a survey of solar wind electron velocity distribution
functions observed by Cluster PEACE in its highest energy resolution
mode, which is sufficient to distinguish between Maxwellian and kappa
distributions for energies below 15eV. Initial results suggest that a
kappa distribution better fits the data than a Maxwellian in all cases;
in the majority of cases the difference in goodness of fit between a
kappa and Maxwellian is small but in some cases, a kappa distribution
fits the data significantly better.
---------------------------------------------------------
Title: A virtual appliance as proxy pipeline for the Solar
Orbiter/Metis coronagraph
Authors: Pancrazzi, M.; Straus, T.; Andretta, V.; Spadaro, D.; Haugan,
S. V.; de Groof, A.; Carr, R.; Focardi, M.; Nicolini, G.; Landini,
F.; Baccani, C.; Romoli, M.; Antonucci, E.
2016SPIE.9913E..4LP Altcode:
Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted
to the study of the Sun that will be launched in October 2018. Metis is
designed to perform imaging of the solar corona in the UV at 121.6 nm
and in the visible range where it will accomplish polarimetry studies
thanks to a variable retarder plate. Due to mission constraints, the
telemetry downlink on the spacecraft will be limited and data will be
downloaded with delays that could reach, in the worst case, several
months. In order to have a quick overview on the ongoing operations
and to check the safety of the 10 instruments on board, a high-priority
downlink channel has been foreseen to download a restricted amount of
data. These so-called Low Latency Data will be downloaded daily and,
since they could trigger possible actions, they have to be quickly
processed on ground as soon as they are delivered. To do so, a proper
processing pipeline has to be developed by each instrument. This
tool will then be integrated in a single system at the ESA Science
Operation Center that will receive the downloaded data by the Mission
Operation Center. This paper will provide a brief overview of the on
board processing and data produced by Metis and it will describe the
proxy-pipeline currently under development to deal with the Metis
low-latency data.
---------------------------------------------------------
Title: PROBA2/SWAP EUV images of the large-scale EUV corona up to 3
solar radii: Can we close the gap in coronal magnetic field structure
between 1.3 and 2.5 solar radii?
Authors: De Groof, Anik; Seaton, Daniel B.; Rachmeler, Laurel;
Berghmans, David
2015TESS....140901D Altcode:
The EUV telescope PROBA2/SWAP has been observing the solar corona in
a bandpass near 17.4 nm since February 2010. SWAP's wide field-of-view
provides a unique and continuous view of the extended EUV corona up to
2-3 solar radii. By carefully processing and combining multiple SWAP
images, low-noise composites were produced that reveal large-scale,
EUV-emitting, coronal structures. These extended structures appear
mainly above or at the edges of active regions and typically curve
towards the poles. As they persist for multiple Carrington rotations
and cannot easily be related to white-light features, they give an
interesting view on how the coronal magnetic field is structured
between 1.3 and 2-3 solar radii, in the gap between SDO/AIA’s FOV
and typical lower boundaries of coronagraph FOVs. With the help of
magnetic field models, we analyse the geometry of the extended EUV
structures in more detail and compare with sporadic EUV coronagraph
measurements up to as close as 1.5Rs. The opportunities that Solar
Orbiter’s future observations will bring are explored.
---------------------------------------------------------
Title: SWAP Observations of the Long-term, Large-scale Evolution of
the Extreme-ultraviolet Solar Corona
Authors: Seaton, Daniel B.; De Groof, Anik; Shearer, Paul; Berghmans,
David; Nicula, Bogdan
2013ApJ...777...72S Altcode: 2013arXiv1309.1345S
The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar
telescope on board the Project for On-Board Autonomy 2 spacecraft has
been regularly observing the solar corona in a bandpass near 17.4 nm
since 2010 February. With a field of view of 54 × 54 arcmin, SWAP
provides the widest-field images of the EUV corona available from
the perspective of the Earth. By carefully processing and combining
multiple SWAP images, it is possible to produce low-noise composites
that reveal the structure of the EUV corona to relatively large
heights. A particularly important step in this processing was to remove
instrumental stray light from the images by determining and deconvolving
SWAP's point-spread function from the observations. In this paper,
we use the resulting images to conduct the first-ever study of the
evolution of the large-scale structure of the corona observed in the
EUV over a three year period that includes the complete rise phase of
solar cycle 24. Of particular note is the persistence over many solar
rotations of bright, diffuse features composed of open magnetic fields
that overlie polar crown filaments and extend to large heights above
the solar surface. These features appear to be related to coronal fans,
which have previously been observed in white-light coronagraph images
and, at low heights, in the EUV. We also discuss the evolution of the
corona at different heights above the solar surface and the evolution
of the corona over the course of the solar cycle by hemisphere.
---------------------------------------------------------
Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
Zender, J.
2013SoPh..286...43S Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
The Sun Watcher with Active Pixels and Image Processing (SWAP) is
an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
(PROBA2) mission launched on 2 November 2009. SWAP has a spectral
bandpass centered on 17.4 nm and provides images of the low solar
corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
an imaging cadence of about two minutes. SWAP is designed to monitor
all space-weather-relevant events and features in the low solar
corona. Given the limited resources of the PROBA2 microsatellite,
the SWAP telescope is designed with various innovative technologies,
including an off-axis optical design and a CMOS-APS detector. This
article provides reference documentation for users of the SWAP image
data.
---------------------------------------------------------
Title: Preface
Authors: Berghmans, D.; De Groof, A.; Dominique, M.; Hochedez, J. -F.;
Leibacher, J. W.
2013SoPh..286....1B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SoFAST: Automated Flare Detection with the PROBA2/SWAP
EUV Imager
Authors: Bonte, K.; Berghmans, D.; De Groof, A.; Steed, K.; Poedts, S.
2013SoPh..286..185B Altcode: 2012SoPh..tmp..288B
The Sun Watcher with Active Pixels and Image Processing (SWAP)
EUV imager onboard PROBA2 provides a non-stop stream of coronal
extreme-ultraviolet (EUV) images at a cadence of typically 130
seconds. These images show the solar drivers of space-weather, such
as flares and erupting filaments. We have developed a software tool
that automatically processes the images and localises and identifies
flares. On one hand, the output of this software tool is intended
as a service to the Space Weather Segment of ESA's Space Situational
Awareness (SSA) program. On the other hand, we consider the PROBA2/SWAP
images as a model for the data from the Extreme Ultraviolet Imager (EUI)
instrument prepared for the future Solar Orbiter mission, where onboard
intelligence is required for prioritising data within the challenging
telemetry quota. In this article we present the concept of the software,
the first statistics on its effectiveness and the online display in
real time of its results. Our results indicate that it is not only
possible to detect EUV flares automatically in an acquired dataset,
but that quantifying a range of EUV dynamics is also possible. The
method is based on thresholding of macropixelled image sequences. The
robustness and simplicity of the algorithm is a clear advantage for
future onboard use.
---------------------------------------------------------
Title: The Projects for Onboard Autonomy (PROBA2) Science Centre:
Sun Watcher Using APS Detectors and Image Processing (SWAP) and
Large-Yield Radiometer (LYRA) Science Operations and Data Products
Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada,
C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher,
P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.;
Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton,
D. B.; Stanger, A.; Stegen, K.; Willems, S.
2013SoPh..286...93Z Altcode: 2012SoPh..tmp..142Z
The PROBA2 Science Centre (P2SC) is a small-scale science operations
centre supporting the Sun observation instruments onboard PROBA2:
the EUV imager Sun Watcher using APS detectors and image Processing
(SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's
small, low-cost Projects for Onboard Autonomy (PROBA) and part of
ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted
at the Royal Observatory of Belgium, co-located with both Principal
Investigator teams. The P2SC tasks cover science planning, instrument
commanding, instrument monitoring, data processing, support of outreach
activities, and distribution of science data products. PROBA missions
aim for a high degree of autonomy at mission and system level, including
the science operations centre. The autonomy and flexibility of the P2SC
is reached by a set of web-based interfaces allowing the operators as
well as the instrument teams to monitor quasi-continuously the status of
the operations, allowing a quick reaction to solar events. In addition,
several new concepts are implemented at instrument, spacecraft, and
ground-segment levels allowing a high degree of flexibility in the
operations of the instruments. This article explains the key concepts
of the P2SC, emphasising the automation and the flexibility achieved
in the commanding as well as the data-processing chain.
---------------------------------------------------------
Title: Temperature Response of the 171 Å Passband of the SWAP Imager
on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO
Authors: Raftery, Claire L.; Bloomfield, D. Shaun; Gallagher, Peter
T.; Seaton, Daniel B.; Berghmans, David; De Groof, Anik
2013SoPh..286..111R Altcode:
We calculated the temperature response of the 171 Å passbands of
the Sun Watcher using APS detectors and image Processing (SWAP)
instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2)
satellite. These results were compared to the temperature responses
of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar
and Heliospheric Observatory (SOHO), the Transition Region and Coronal
Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard
the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft,
and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO). Multiplying the wavelength-response functions
for each instrument by a series of isothermal synthetic spectra and
integrating over the range 165 - 195 Å produced temperature-response
functions for the six instruments. Each temperature response was
then multiplied by sample differential emission-measure functions
for four different solar conditions. For any given plasma condition
(e.g. quiet Sun, active region), it was found that the overall variation
with temperature agreed remarkably well across the six instruments,
although the wavelength responses for each instrument have some
distinctly different features. Deviations were observed, however,
when we compared the response of any one instrument to different solar
conditions, particularly for the case of solar flares.
---------------------------------------------------------
Title: The SWAP EUV Imaging Telescope. Part II: In-flight Performance
and Calibration
Authors: Halain, J. -P.; Berghmans, D.; Seaton, D. B.; Nicula, B.;
De Groof, A.; Mierla, M.; Mazzoli, A.; Defise, J. -M.; Rochus, P.
2013SoPh..286...67H Altcode: 2012SoPh..tmp..317H; 2012arXiv1210.3551H
The Sun Watcher with Active Pixel System detector and Image
Processing (SWAP) telescope was launched on 2 November 2009
onboard the ESA PROBA2 technological mission and has acquired
images of the solar corona every one to two minutes for more than
two years. The most important technological developments included in
SWAP are a radiation-resistant CMOS-APS detector and a novel onboard
data-prioritization scheme. Although such detectors have been used
previously in space, they have never been used for long-term scientific
observations on orbit. Thus SWAP requires a careful calibration to
guarantee the science return of the instrument. Since launch we have
regularly monitored the evolution of SWAP's detector response in-flight
to characterize both its performance and degradation over the course
of the mission. These measurements are also used to reduce detector
noise in calibrated images (by subtracting dark-current). Because
accurate measurements of detector dark-current require large telescope
off-points, we also monitored straylight levels in the instrument to
ensure that these calibration measurements are not contaminated by
residual signal from the Sun. Here we present the results of these
tests and examine the variation of instrumental response and noise as
a function of both time and temperature throughout the mission.
---------------------------------------------------------
Title: PROBA2: Mission and Spacecraft Overview
Authors: Santandrea, S.; Gantois, K.; Strauch, K.; Teston, F.; Proba2
Project Team; Tilmans, E.; Baijot, C.; Gerrits, D.; Proba2 Industry
Team; de Groof, A.; Schwehm, G.; Zender, J.
2013SoPh..286....5S Altcode:
Within the European Space Agency's (ESA) General Support and Technology
Programme (GSTP), the Project for On-Board Autonomy (PROBA) missions
provide a platform for in-orbit technology demonstration. Besides
the technology demonstration goal, the satellites allow to provide
services to, e.g., scientific communities. PROBA1 has been providing
multi-spectral imaging data to the Earth observation community for a
decade, and PROBA2 provides imaging and irradiance data from our Sun
to the solar community. This article gives an overview of the PROBA2
mission history and provides an introduction to the flight segment,
the ground segment, and the payload operated onboard. Important aspects
of the satellite's design, including onboard software autonomy and the
functionality of the navigation and guidance, are discussed. PROBA2
successfully proved again within the GSTP concept that it is possible
to provide a fast and cost-efficient satellite design and to combine
advanced technology objectives from industry with focussed objectives
from the science community.
---------------------------------------------------------
Title: Study of a Prominence Eruption using PROBA2/SWAP and
STEREO/EUVI Data
Authors: Mierla, M.; Seaton, D. B.; Berghmans, D.; Chifu, I.; De Groof,
A.; Inhester, B.; Rodriguez, L.; Stenborg, G.; Zhukov, A. N.
2013SoPh..286..241M Altcode: 2012SoPh..tmp...66M; 2012arXiv1203.6732M
Observations of the early rise and propagation phases of solar eruptive
prominences can provide clues about the forces acting on them through
the behavior of their acceleration with height. We have analyzed such an
event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A
feature at the top of the erupting prominence was identified and tracked
in images from the three spacecraft. The triangulation technique was
used to derive the true direction of propagation of this feature. The
reconstructed points were fitted with two mathematical models: i) a
power-law polynomial function and ii) a cubic smoothing spline, in order
to derive the accelerations. The first model is characterized by five
degrees of freedom while the second one is characterized by ten degrees
of freedom. The results show that the acceleration increases smoothly,
and it is continuously increasing with height. We conclude that the
prominence is not accelerated immediately by local reconnection,
but rather is swept away as part of a large-scale relaxation of the
coronal magnetic field.
---------------------------------------------------------
Title: Solar TErrestrial Relations Observatory-A (STEREO-A) and
PRoject for On-Board Autonomy 2 (PROBA2) Quadrature Observations of
Reflections of Three EUV Waves from a Coronal Hole
Authors: Kienreich, I. W.; Muhr, N.; Veronig, A. M.; Berghmans, D.;
De Groof, A.; Temmer, M.; Vršnak, B.; Seaton, D. B.
2013SoPh..286..201K Altcode: 2012SoPh..tmp..138K
We investigate the interaction of three consecutive large-scale coronal
waves with a polar coronal hole, simultaneously observed on-disk by the
Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
27 January 2011. All three extreme ultraviolet (EUV) waves originate
from the same active region, NOAA 11149, positioned at N30E15 in the
STEREO-A field of view and on the limb in PROBA2. For the three primary
EUV waves, we derive starting velocities in the range of ≈ 310 km
s<SUP>−1</SUP> for the weakest up to ≈ 500 km s<SUP>−1</SUP>
for the strongest event. Each large-scale wave is reflected at the
border of the extended coronal hole at the southern polar region. The
average velocities of the reflected waves are found to be smaller than
the mean velocities of their associated direct waves. However, the
kinematical study also reveals that in each case the ending velocity
of the primary wave matches the initial velocity of the reflected
wave. In all three events, the primary and reflected waves obey the
Huygens-Fresnel principle, as the incident angle with ≈ 10° to
the normal is of the same magnitude as the angle of reflection. The
correlation between the speed and the strength of the primary EUV waves,
the homologous appearance of both the primary and the reflected waves,
and in particular the EUV wave reflections themselves suggest that the
observed EUV transients are indeed nonlinear large-amplitude MHD waves.
---------------------------------------------------------
Title: Quasi-Periodic Pulsations during the onset of solar flares:
multi-instrumental comparison
Authors: West, M. J.; Dolla, L.; Marque, C.; Seaton, D. B.; Van
Doorsselaere, T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof,
A.; Schmutz, W.; Verdini, A.; Zender, J.; Zhukov, A. N.
2013enss.confE..82W Altcode:
Quasi-periodic pulsations have been observed in the rising phase of
solar flares for many years. Observations have been made over a wide
spectral range, extending from X-rays to radio wavelengths. The
current generation of spacebourne instruments, especially SDO,
EVE and ESP, have exceptionally high sampling rates and allow us
to make more detailed observations of this phenomena. In this work,
we compare short-period oscillations (around 10 s) observed in flare
events by multiple instruments: the radiometer channels of SDO/EVE-ESP
(soft X-ray, coronal and chromospheric passbands), the EUV channels of
the radiometer PROBA2/LYRA, the RHESSI passbands and short-wavelength
radio observations.
---------------------------------------------------------
Title: Plasmoid Ejection at a Solar Total Eclipse
Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.;
Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.;
Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton,
D.; Slemzin, V.
2012EAS....55..223K Altcode:
The existence of coronal plasmoids has been postulated for many years
in order to supply material to streamers and possibly to the solar
wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made
under the 2.2 solar radii (R0) occulting disk to look at the ultimate
sources of the SW; EUV imagers are preferably devoted to the analysis
of the corona on and very near the solar disk. Here, in addition to
eclipse white-light (W-L) snapshots, we used the new SWAP space-borne
imager designed for the systematic survey of coronal activity in the
EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using
summed and co-aligned images, the corona can then be evaluated for the
1st time up to the limit of this FOV. At the time of the July 11, 2010,
solar total eclipse a 20h continuous run of observations was collected,
including images taken during eclipse totality from several ground
observing locations where W-L data were collected. A plasmoid-like
off-limb event was followed using the SWAP summed
---------------------------------------------------------
Title: STEREO-A and PROBA2 Quadrature Observations of Reflections
of three EUV Waves from a Coronal Hole
Authors: Kienreich, Ines Waltraud; Muhr, Nicole; Veronig, Astrid;
Berghmans, David; de Groof, Anik; Temmer, Manuela; Vršnak, Bojan;
Seaton, Dan
2012arXiv1204.6472K Altcode: 2012arXiv1204.6472W
We investigate the interaction of three consecutive large-scale coronal
waves with a polar coronal hole, simultaneously observed on-disk by the
Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
January 27, 2011. All three extreme-ultraviolet(EUV) waves originate
from the same active region NOAA 11149 positioned at N30E15 in the
STEREO-A field-of-view and on the limb in PROBA2. We derive for the
three primary EUV waves start velocities in the range of ~310 km/s for
the weakest up to ~500 km/s for the strongest event. Each large-scale
wave is reflected at the border of the extended coronal hole at the
southern polar region. The average velocities of the reflected waves
are found to be smaller than the mean velocities of their associated
direct waves. However, the kinematical study also reveals that in each
case the end velocity of the primary wave matches the initial velocity
of the reflected wave. In all three events the primary and reflected
waves obey the Huygens-Fresnel principle, as the incident angle with
~10° to the normal is of the same size as the angle of reflection. The
correlation between the speed and the strength of the primary EUV waves,
the homologous appearance of both the primary and the reflected waves,
and in particular the EUV wave reflections themselves implicate that the
observed EUV transients are indeed nonlinear large-amplitude MHD waves.
---------------------------------------------------------
Title: Time Delays in Quasi-periodic Pulsations Observed during the
X2.2 Solar Flare on 2011 February 15
Authors: Dolla, L.; Marqué, C.; Seaton, D. B.; Van Doorsselaere,
T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof, A.; Schmutz,
W.; Verdini, A.; West, M. J.; Zender, J.; Zhukov, A. N.
2012ApJ...749L..16D Altcode: 2012arXiv1203.6223D
We report observations of quasi-periodic pulsations (QPPs) during the
X2.2 flare of 2011 February 15, observed simultaneously in several
wavebands. We focus on fluctuations on timescale 1-30 s and find
different time lags between different wavebands. During the impulsive
phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager
channels in the range 25-100 keV lead all the other channels. They
are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the
extreme-ultraviolet (EUV) channels of the Euv SpectroPhotometer (ESP)
on board the Solar Dynamic Observatory. The zirconium and aluminum
filter channels of the Large Yield Radiometer on board the Project for
On-Board Autonomy satellite and the soft X-ray (SXR) channel of ESP
follow. The largest lags occur in observations from the Geostationary
Operational Environmental Satellite, where the channel at 1-8 Å leads
the 0.5-4 Å channel by several seconds. The time lags between the
first and last channels is up to ≈9 s. We identified at least two
distinct time intervals during the flare impulsive phase, during which
the QPPs were associated with two different sources in the Nobeyama
RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels
showed different lags during these two intervals. To our knowledge,
this is the first time that time lags are reported between EUV and
SXR fluctuations on these timescales. We discuss possible emission
mechanisms and interpretations, including flare electron trapping.
---------------------------------------------------------
Title: LYRA and SWAP, the two Solar Instruments on-board PROBA2
Authors: Dominique, M.; Berghmans, D.; Schmutz, W. K.; Dammasch, I.;
De Groof, A.; Halain, J.; Hochedez, J.; Kretzschmar, M.; Seaton, D. B.
2011AGUFMSH13B1949D Altcode:
PROBA2 (http://proba2.sidc.be) is an ESA micro-satellite that was
launched in November 2009. Two instruments on-board, SWAP and LYRA, are
devoted to solar observations. SWAP (PI: D. Berghmans) is an EUV imager
observing the corona with a bandpass centered on 174 Å at a cadence of
1-2 min. Its high contrast images, large FOV and flexible off-pointing
capabilities make SWAP particularly well suited for the study of coronal
eruptions. LYRA (PI: M. Dominique) is a UV-EUV radiometer observing
in four spectral channels, chosen for their relevance in solar physics
and aeronomy. Its very fast acquisition cadence (up to 100 Hz) allows
scientists to perform detailed analysis of solar flares. We discuss
the characteristics of both instruments, review their performance and
evolution, and highlight their complementarity to other missions. We
also present the data products that can be downloaded from the mission
website and give an overview of the various investigations for which
SWAP and LYRA data are currently used (CMEs, flares, solar variability,
and many others).
---------------------------------------------------------
Title: LYRA Observations of Two Oscillation Modes in a Single Flare
Authors: Van Doorsselaere, T.; De Groof, A.; Zender, J.; Berghmans,
D.; Goossens, M.
2011ApJ...740...90V Altcode:
We analyze light curves from the LYRA irradiance experiment on
board PROBA2 during the flare of 2010 February 8. We see both long-
and short-period oscillations during the flare. The long-period
oscillation is interpreted in terms of standing slow sausage modes;
the short-period oscillation is thought to be a standing fast sausage
mode. The simultaneous presence of two oscillation modes in the same
flaring structure allows for new coronal seismological applications. The
periods are used to find seismological estimates of the plasma-β and
the density contrast of the flaring loop. Also the wave mode number
is estimated from the observed periods.
---------------------------------------------------------
Title: Validation of CME Detection Software (CACTus) by Means of
Simulated Data, and Analysis of Projection Effects on CME Velocity
Measurements
Authors: Bonte, K.; Jacobs, C.; Robbrecht, E.; De Groof, A.; Berghmans,
D.; Poedts, S.
2011SoPh..270..253B Altcode: 2011SoPh..tmp...52B; 2011SoPh..tmp...72B
In the context of space weather forecasting, an automated detection
of coronal mass ejections (CMEs) becomes more and more important
for efficiently handling a large data flow which is expected from
recently-launched and future solar missions. In this paper we validate
the detection software package "CACTus" by applying the program to
synthetic data from our 3D time-dependent CME simulations instead of
observational data. The main strength of this study is that we know
in advance what should be detected. We describe the sensitivities
and strengths of automated detection, more specific for the CACTus
program, resulting in a better understanding of CME detection on one
hand and the calibration of the CACTus software on the other hand,
suggesting possible improvements of the package. In addition, the
simulation is an ideal tool to investigate projection effects on CME
velocity measurements.
---------------------------------------------------------
Title: First light of SWAP on-board PROBA2
Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc;
Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre;
Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo
2010SPIE.7732E..0PH Altcode: 2010SPIE.7732E..18H
The SWAP telescope (Sun Watcher using Active Pixel System detector
and Image Processing) is an instrument launched on 2nd November 2009
on-board the ESA PROBA2 technological mission. SWAP is a space weather
sentinel from a low Earth orbit, providing images at 174 nm of the
solar corona. The instrument concept has been adapted to the PROBA2
mini-satellite requirements (compactness, low power electronics and
a-thermal opto-mechanical system). It also takes advantage of the
platform pointing agility, on-board processor, Packetwire interface
and autonomous operations. The key component of SWAP is a radiation
resistant CMOS-APS detector combined with onboard compression and
data prioritization. SWAP has been developed and qualified at the
Centre Spatial de Liège (CSL) and calibrated at the PTBBessy
facility. After launch, SWAP has provided its first images on 14th
November 2009 and started its nominal, scientific phase in February
2010, after 3 months of platform and payload commissioning. This
paper summarizes the latest SWAP developments and qualifications,
and presents the first light results.
---------------------------------------------------------
Title: SWAP onboard PROBA2: An Innovative EUV Imager Designed for
Space Weather
Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.;
Schuehle, U.
2008ESPM...122.116D Altcode:
PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite
that is being prepared for launch in 2009. Its primary goal is the
demonstration of new technologies in the space environment. Furthermore,
the satellite carries an ambitious suite of both in-situ and
remote sensing instruments for monitoring space weather, despite
the modest onboard resources. Both the spacecraft and the remote
sensing instruments are mainly developed within Belgium. <P />One of
the main instruments, SWAP (Sun Watcher with APS detectors and image
Processing), is a compact EUV imager. It carries the first APS detector
with an EUV sensitive scintillator coating to be flown in orbit. In
addition to the new detector, the PROBA2/SWAP design is innovative
in the sense that the instrument will make heavy use of on-board data
processing and autonomous operations. These will range from automatic
off-pointing and tracking of appropriate solar events, to pre-downlink
data prioritisation, and feature and event recognition procedures. <P
/>We discuss the first results of the SWAP pre-flight calibration and
the strengths and weaknesses of the instrument [2]. With a narrow
spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an
image cadence of 1 min, its design is ideal for monitoring most CME
associated phenomena on the solar disk and close to the limb. <P />[1]
Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689,
66890S <P />[2] De Groof A., Berghmans D., Nicula B., et al. 2008,
Solar Phys. 249, 147-163
---------------------------------------------------------
Title: CMOS-APS Detectors for Solar Physics: Lessons Learned during
the SWAP Preflight Calibration
Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.;
Defise, J. -M.; Thibert, T.; Schühle, U.
2008SoPh..249..147D Altcode: 2008SoPh..tmp...62D
CMOS-APS imaging detectors open new opportunities for remote sensing
in solar physics beyond what classical CCDs can provide, offering
far less power consumption, simpler electronics, better radiation
hardness, and the possibility of avoiding a mechanical shutter. The
SWAP telescope onboard the PROBA2 technology demonstration satellite
of the European Space Agency will be the first actual implementation
of a CMOS-APS detector for solar physics in orbit. One of the goals
of the SWAP project is precisely to acquire experience with the
CMOS-APS technology in a real-live space science context. Such a
precursor mission is essential in the preparation of missions such as
Solar Orbiter where the extra CMOS-APS functionalities will be hard
requirements. The current paper concentrates on specific CMOS-APS
issues that were identified during the SWAP preflight calibration
measurements. We will discuss the different readout possibilities that
the CMOS-APS detector of SWAP provides and their associated pros and
cons. In particular we describe the "image lag" effect, which results in
a contamination of each image with a remnant of the previous image. We
have characterised this effect for the specific SWAP implementation
and we conclude with a strategy on how to successfully circumvent the
problem and actually take benefit of it for solar monitoring.
---------------------------------------------------------
Title: SWAP: a novel EUV telescope for space weather
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans,
David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat,
Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez,
Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank
2007SPIE.6689E..0SD Altcode: 2007SPIE.6689E..24D
The SWAP telescope (Sun Watcher using Active Pixel System detector and
Image Processing) is being developed to be part of the PROBA2 payload,
an ESA technological mission to be launched in early 2008. SWAP
is directly derived from the concept of the EIT telescope that we
developed in the '90s for the SOHO mission. Several major innovations
have been introduced in the design of the instrument in order to
be compliant with the requirements of the PROBA2 mini-satellite:
compactness with a new of-axis optical design, radiation resistance
with a new CMOS-APS detector, a very low power electronics, an athermal
opto-mechanical system, optimized onboard compression schemes combined
with prioritization of collected data, autonomy with automatic
triggering of observation and off-pointing procedures in case of
Solar event occurrence, ... All these new features result from the low
resource requirements (power, mass, telemetry) of the mini-satellite,
but also take advantage of the specificities of a modern technological
platform, such as quick pointing agility, new powerful on-board
processor, Packetwire interface and autonomous operations. These
new enhancements will greatly improve the operations of SWAP as
a space weather sentinel from a low Earth orbit while the downlink
capabilities are limited. This paper summarizes the conceptual design,
the development and the qualification of the instrument, the autonomous
operations and the expected performances for science exploitation.
---------------------------------------------------------
Title: a Multi-Wavelength View on Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; de Pontieu, B.; Hansteen,
V. H.
2005ESASP.600E..30M Altcode: 2005dysu.confE..30M; 2005ESPM...11...30M
No abstract at ADS
---------------------------------------------------------
Title: The Dynamic Sun: Challenges for Theory and Observations
Authors: Danesy, D.; Poedts, S.; de Groof, A.; Andries, J.
2005ESASP.600E....D Altcode: 2005dysu.confE....D; 2005ESPM...11.....D
No abstract at ADS
---------------------------------------------------------
Title: Multiwavelength Analysis of Downflows Along AN Off-Limb Loop
Authors: de Groof, A.; Müller, D. A. N.; Poedts, S.
2005ESASP.600E..29D Altcode: 2005ESPM...11...29D; 2005dysu.confE..29D
No abstract at ADS
---------------------------------------------------------
Title: Downflows Along AN Off-Limb Loop Seen both in 30.4NM and Hα
Authors: de Groof, A.; Müller, D. A. N.; Poedts, S.
2005ESASP.596E..36D Altcode: 2005ccmf.confE..36D
No abstract at ADS
---------------------------------------------------------
Title: a Multi-Wavelength View on Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; de Pontieu, B.; Hansteen,
V. H.
2005ESASP.596E..37M Altcode: 2005ccmf.confE..37M
No abstract at ADS
---------------------------------------------------------
Title: Detailed comparison of downflows seen both in EIT 30.4 nm
and Big Bear Hα movies
Authors: de Groof, A.; Bastiaensen, C.; Müller, D. A. N.; Berghmans,
D.; Poedts, S.
2005A&A...443..319D Altcode:
An EIT shutterless campaign was conducted on 11 July 2001 and provided
120 high-cadence (68 s) 30.4 nm images of the north-eastern quarter
of the Sun. Systematic intensity variations are seen which appear
to propagate along an off-disk loop-like structure. In this paper we
study the nature of these intensity variations by confronting the EIT
observations studied in De Groof et al. (2004, A&A, 415, 1141)
with simultaneous Hα images from Big Bear Solar Observatory. With
the goal to carefully co-register the two image sets, we introduce a
technique designed to compare data of two different instruments. The
image series are first co-aligned and later overplotted in order to
visualize and compare the behaviour of the propagating disturbances
in both data sets. Since the same intensity variations are seen in
the EIT 30.4 nm and in the Hα images, we confirm the interpretation
of De Groof et al. (2004, A&A, 415, 1141) that we are observing
downflows of relatively cool plasma. The origin of the downflows is
explained by numerical simulations of "catastrophic cooling" in a
coronal loop which is heated predominantly at its footpoints.
---------------------------------------------------------
Title: High-speed coronal rain
Authors: Müller, D. A. N.; De Groof, A.; Hansteen, V. H.; Peter, H.
2005A&A...436.1067M Altcode:
At high spatial and temporal resolution, coronal loops are observed to
have a highly dynamic nature. Recent observations with SOHO and TRACE
frequently show localized brightenings "raining" down towards the solar
surface. What is the origin of these features? Here we present for
the first time a comparison of observed intensity enhancements from an
EIT shutterless campaign with non-equilibrium ionization simulations
of coronal loops in order to reveal the physical processes governing
fast flows and localized brightenings. We show that catastrophic cooling
around the loop apex as a consequence of footpoint-concentrated heating
offers a simple explanation for these observations. An advantage of
this model is that no external driving mechanism is necessary as the
dynamics result entirely from the non-linear character of the problem.
---------------------------------------------------------
Title: Coronal MHD Waves and Theoretical Constraints of Wave Heating
Authors: Poedts, S.; de Groof, A.
2004ESASP.575...62P Altcode: 2004soho...15...62P
No abstract at ADS
---------------------------------------------------------
Title: Thermal Instability as the Origin of High Speed Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; Hansteen, V. H.; Peter, H.
2004ESASP.575..291M Altcode: 2004soho...15..291M
No abstract at ADS
---------------------------------------------------------
Title: Intensity variations in EIT shutterless mode: Waves or flows?
Authors: De Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
Poedts, S.
2004A&A...415.1141D Altcode:
On 11 July 2001 an EIT shutterless campaign was conducted which provided
120 high-cadence (68 s) 304 Å images of the north eastern quarter of
the Sun. The most interesting feature seen in the data is an off-limb
half loop structure along which systematic intensity variations are
seen which appear to propagate from the top of the loop towards its
footpoint. We investigate the underlying cause of these propagating
disturbances, i.e. whether they are caused by waves or by plasma
flows. First we identify 7 blobs with the highest intensities and
follow them along the loop. By means of a location-time plot, bulk
velocities can be measured at several locations along the loop. The
velocity curve found this way is then compared with characteristic
wave speeds and with the free-fall speed in order to deduce the nature
of the intensity variations. Additional information on density and
temperature is derived by measuring the relative intensity enhancements
and comparing the EIT 304 Å sequence with Big Bear data and 171 Å
data (TRACE/EIT). The combination of all these constraints gives us an
insight on the nature and origin of these intensity variations. The
idea of slow magneto-acoustic waves is rejected, and we find several
arguments supporting that these intensity variations are due to
flowing/falling plasma blobs.
---------------------------------------------------------
Title: Active Region Oscillations as Observed by CDS, EIT and TRACE
Authors: Banerjee, D.; O'Shea, E.; de Groof, A.; Poedts, S.
2004ESASP.547...39B Altcode: 2004soho...13...39B
No abstract at ADS
---------------------------------------------------------
Title: Thermal non-equilibrium in coronal loops: A road to complex
evolution
Authors: Müller, Daniel; de Groof, A.; Hansteen, V. H.; Peter, H.
2004IAUS..223..289M Altcode: 2005IAUS..223..289M
At high spatial and temporal resolution, coronal loops are observed to
have a highly dynamic nature. Recent observations with SOHO and TRACE
frequently show localized brightening "raining" down towards the solar
surface. What is the origin of these features? Here we present for
the first time a comparison of observed intensity enhancements from an
EIT shutterless campaign with non-equilibrium ionization simulations
of coronal loops in order to reveal the physical processes governing
fast flows and localized brightening. We show that catastrophic cooling
around the loop apex as a consequence of footpoint-concentrated heating
offers a simple explanation for these observations. An advantage of
this model is that no external driving mechanism is necessary as the
dynamics result entirely from the non-linear character of the system.
---------------------------------------------------------
Title: Intensity Variations in EIT Shutterless Mode: Waves or Flows?
Authors: de Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
Poedts, S.
2004ESASP.547..245D Altcode: 2004soho...13..245D
On 11 July 2001 an EIT shutterless campaign was conducted which provided
120 high-cadence (68s) 304 Å images of the north eastern quarter of the
Sun. The most interesting feature seen in the data is an off-limb half
loop structure along which systematic intensity variations appear to
propagate from the top of the loop towards its footpoint. We investigate
the underlying cause of these propagating disturbances, i.e. whether
they are caused by waves or by plasma flows. First we identify 7 blobs
with the highest intensities and follow them along the loop. By means
of a location-time plot, bulk velocities can be measured at several
locations along the loop. The velocity curve found this way is then
compared with characteristic wave speeds and with the free-fall speed
in order to deduce the nature of the intensity variations. Additional
information is derived by measuring the relative intensity enhancements
and comparing the EIT 304 Å sequence with Big Bear and 171 Å data. The
idea of slow magneto-acoustic waves is rejected, and we find several
arguments supporting that these intensity variations are due to
flowing/falling plasma blobs.
---------------------------------------------------------
Title: Waves and oscillations in magnetic fields
Authors: Goossens, Marcel; de Groof, Anik; Andries, Jesse
2002ESASP.505..137G Altcode: 2002solm.conf..137G; 2002IAUCo.188..137G
This paper gives an overview of the theory of MHD waves in magnetic
plasma configurations in the solar atmosphere. The emphasis is on basic
properties that are independent of specific equilibrium models but
are rather related to the intrinsic structuring and non-uniformity
of the plasma. The discussion is confined to MHD waves in uniform
and 1-d cylindrical equilibrium models of magnetic flux tubes with
a straight magnetic field. These models contain sufficient physics
for understanding basic properties of MHD waves and still allow for
a relatively straightforward and transparent mathematical analysis.
---------------------------------------------------------
Title: Fast and Alfvén waves driven by azimuthal footpoint motions
Authors: de Groof, Anik; Goossens, Marcel
2002ESASP.505..389D Altcode: 2002solm.conf..389D; 2002IAUCo.188..389D
The excitation of Alfvén and fast magnetosonic waves in footpoint
driven coronal loops is studied in the framework of resonant
absorption. Previous studies revealed that in case of radial footpoint
motions, quasi-modes are essential for effective wave dissipation
in the loops. We now investigate the role they play in azimuthally
driven loops. For a periodic driver, the efficiency of resonant
absorption strongly depends on the driving frequency ω<SUB>d</SUB>:
only for quasi-mode frequencies coupling has a positive effect on the
growth of the (single) Alfvén resonance. The problem of single-shell
heating can be solved by considering a more realistic, random driver:
a variety of resonant Alfvén waves are excited and multiple resonant
peaks appear, with length scales which are short enough for effective
dissipation. When more realistic loop lengths are considered, the
resonant surfaces are even more numerous resulting in globally heated
loops.
---------------------------------------------------------
Title: Fast and Alfvén waves driven by azimuthal footpoint
motions. I. Periodic driver
Authors: De Groof, A.; Paes, K.; Goossens, M.
2002A&A...386..681D Altcode:
The excitation of Alfvén and fast magneto-acoustic waves in coronal
loops driven by footpoint motions is studied in linear, ideal MHD. The
analysis is restricted to azimuthally polarized footpoint motions
so that only Alfvén waves are directly excited which couple to
fast magneto-acoustic waves at later times. In the present study a
periodic driver is applied at one end of the loop. The effects of a
more realistic random driver are studied in the companion paper De
Groof & Goossens (2002) (hereafter referred to as Paper II). The
first part of the paper is devoted to the study of resonant absorption
and phase-mixing in the absence of coupling (azimuthal wavenumber
k<SUB>y</SUB>=0). Since the density varies across the loop, resonances
occur at the magnetic surfaces where the driving frequency equals the
local Alfvén frequency. In a second part where Alfvén waves with
k<SUB>y</SUB> !=q 0 coupling to fast waves are taken into account, we
find that the behaviour of the MHD waves is strongly dependent on the
driving frequency omega<SUB>d</SUB> . Especially driving frequencies
equal to a quasi-mode frequency seem to make the difference. The fast
waves excited in these cases are global oscillations of the system
and form quasi-modes as they are damped through the resonant coupling
with Alfvén modes. Since these resonances occur at the same location
where the original Alfvén wave peaks, the resonant peak is further
amplified. While in most cases coupling has a negative effect on the
growth of the directly excited Alfvén waves, driving with a quasi-mode
frequency leads to a faster growth of the resonant peaks and a more
efficient decrease in length scales than in the uncoupled case.
---------------------------------------------------------
Title: Fast and Alfvén waves driven by azimuthal footpoint
motions. II. Random driver
Authors: De Groof, A.; Goossens, M.
2002A&A...386..691D Altcode:
The excitation of Alfvén and fast magneto-acoustic waves in coronal
loops driven by footpoint motions is studied in linear, ideal MHD. The
analysis is restricted to azimuthally polarized footpoint motions
so that only Alfvén waves are directly excited to couple to fast
magneto-acoustic waves at later times. In the companion paper De
Groof et al. (\cite{Groof02a}) (hereafter referred to as Paper I),
the behaviour of the MHD waves is studied in case of a monochromatic
driver. In the present study, the effects of a more realistic random
driver are investigated.\ First, we consider loops of equal length and
width in order to limit the number of quasi-modes in the frequency
range of the driver so that the influence of quasi-modes in the
system can easily be detected. In contrast to the single resonant
surface which was found in case of a periodic driver (see Paper I),
a random pulse train excites a variety of resonant Alfvén waves and
consequently the small length scales built up are spread over the
whole width of the loop. The specific effects of the quasi-modes are
not so easily recognized as for radial footpoint motions (De Groof
& Goossens \cite{Groof00a}) since the resonances corresponding to
directly and indirectly excited Alfvén waves are mixed together. In
the second part of the paper, longer loops are considered. Since more
quasi-modes are involved, the resonant surfaces are more numerous and
widely spread throughout the whole loop volume. On the other hand,
it takes more time for the MHD waves to cross the loop and to form
standing waves. Nevertheless this negative effect does not have too much
impact since the simulations show that after a small time interval,
resonant surfaces are created all over the loop, with length scales
which are short enough for effective dissipation.
---------------------------------------------------------
Title: Resonant absorption in randomly driven coronal loops
Authors: de Groof, Anik; Goossens, Marcel
2000AIPC..537..208D Altcode: 2000wdss.conf..208D
De Groof et al. '98 [1] and '00 [2] studied the time evolution of fast
magnetosonic and Alfvén waves in a coronal loop driven by radially
polarized footpoint motions in linear ideal MHD. Footpoint driving
seems to be an efficient way of generating resonant absorption since the
input energy is mainly stored in body modes which keep the energy in the
loop. The most important feature in this study is the stochastic driving
of the loop. While in earlier models with a periodic driver or a single
pulse, the loop is only heated at one single layer, we now find multiple
resonance layers which results in a more globally heated loop. Moreover,
these resonances (created on a realistic time scale) have length scales
which are small enough to explain energy dissipation. An important
aspect to take into account is the mass transfer between corona and
chromosphere since the density becomes time dependent and consequently,
the resonant surfaces shift throughout the loop [3]. Combined with
the multiple resonances we found in the previous study, this result
can lead to the globally heated coronal loops we observe. .
---------------------------------------------------------
Title: Randomly driven fast waves in coronal loops. II. with coupling
to Alfvén waves
Authors: De Groof, A.; Goossens, M.
2000A&A...356..724D Altcode:
We study the time evolution of fast magnetosonic and Alfvén waves in a
coronal loop driven by random footpoint motions. The footpoint motions
are assumed to be polarized normal to the magnetic flux surfaces in
linear ideal MHD. De Groof et al. (1998) (Paper I) showed that the
input energy is mainly stored in the body modes when the fast waves
are decoupled from the Alfvén waves. Hence driving at the loop's feet
forms a good basis for resonant absorption as heating mechanism. In
order to determine the efficiency of resonant absorption, we therefore
study the energy transfer from the body modes to the resonant Alfvén
waves in the case of coupling. We find that the growth of Alfvén mode
energy depends on several parameters. Subsequently we check whether
the necessary small lengthscales are created on a realistic time scale
for the coronal loop. We find that Alfvén resonances are built up
at the magnetic surfaces, where local Alfvén frequencies equal the
quasi-modes frequencies, on time scales comparable to the lifetime
of the loop. Finally we conclude that a random footpoint driving can
produce enough resonances to give rise to a globally heated coronal
loop.
---------------------------------------------------------
Title: Randomly Driven Fast Waves in Coronal Loops
Authors: de Groof, A.; Goossens, M.
1999ESASP.448..251D Altcode: 1999ESPM....9..251D; 1999mfsp.conf..251D
No abstract at ADS
---------------------------------------------------------
Title: Random driven fast waves in coronal loops. I. Without coupling
to Alfven waves
Authors: de Groof, A.; Tirry, W. J.; Goossens, M.
1998A&A...335..329D Altcode:
In this paper we study the time evolution of fast MHD waves in a coronal
loop driven by footpoint motions in linear ideal MHD. We restrict the
analysis to footpoint motions polarized normal to the magnetic flux
surfaces such that the fast waves are driven directly. By supposing
the azimuthal wave number k_y to be zero, the fast waves are decoupled
from the Alfven waves. As a first step to real stochastic driving,
we consider the loop to be driven by a train of identical pulses
with random time intervals in between. The solution is written as a
superposition of eigenmodes whose excitation is determined by the
time dependence of the footpoint motion through a convolution and
by the spatial dependence of the footpoint motion through a scalar
product. An important result from the simulations is that the amount
of kinetic energy associated with the body modes is much larger than
the amount corresponding to the leaky modes. This means that most of
the input energy is stored within the loop. For k_y!=q 0, body modes
can resonantly couple to Alfven waves at certain magnetic surfaces
and hence the energy of the body modes can then be dissipated around
the resonant magnetic surfaces. Using a gamma distribution for the
time intervals between the successive pulses, we analytically derive
a relation between the mean value of the kinetic energy contribution
of each eigenmode, the eigenfrequency, the number of pulses and the
width of the pulses. The larger the variance of the distribution, the
less the power spectrum reveals fine structure, peaks around certain
preferred frequencies. The analytical results confirm the output from
the numerical simulations.
