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Author name code: briand
ADS astronomy entries on 2022-09-14
author:"Briand, Carine"
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Title: Role of hard X-ray emission in ionospheric D-layer disturbances
during solar flares
Authors: Briand, Carine; Clilverd, Mark; Inturi, Srivani; Cecconi,
Baptiste
2022EP&S...74...41B Altcode:
Any disturbance of the ionosphere may affect operational activities
based on HF communication. The electron density is a critical parameter
that controls levels of HF-signal absorption. A significant part
of the HF absorption takes place in the D-layer. The increase of X
radiations during solar flares generates noticeable perturbations of
the electron density of the D-layer. However, the ionosphere reacts
with some delay to the solar forcing. Several studies have addressed
this question of ionospheric sluggishness from the time delay between
VLF narrow-band transmissions and soft X-ray emissions during solar
flares. Our study initially considers the interpretation of the VLF
amplitude time profile. In particular, we show that the maximum of
X-ray emission can be associated with a reversal in the VLF amplitude
variation with time, i.e. exhibiting a peak or a trough. Then,
building on this insight, we perform estimates of the time delay
between VLF and soft X-rays during 67 events between 2017 and 2021,
thus including the major flares of 2017. We show that the time delay
can become negative for flares above X2, proving that soft X-rays are
not the initial source of ionization in the case of major flares. From
a careful analysis of RHESSI data for some events of September 2017,
we demonstrate that radiation above 40 keV (i.e. hard X-rays) is an
important forcing source of the ionosphere. This is of crucial interest
in the frame of space weather forecasting since the hard X-rays are
produced several minutes before the peak of soft X-rays.
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Title: The relativistic solar particle event on 28 October 2021:
Evidence of particle acceleration within and escape from the solar
corona
Authors: Klein, Karl-Ludwig; Musset, Sophie; Vilmer, Nicole; Briand,
Carine; Krucker, Säm; Francesco Battaglia, Andrea; Dresing, Nina;
Palmroos, Christian; Gary, Dale E.
2022A&A...663A.173K Altcode:
<BR /> Aims: We analyse particle, radio, and X-ray observations
during the first relativistic proton event of solar cycle 25 detected
on Earth. The aim is to gain insight into the relationship between
relativistic solar particles detected in space and the processes of
acceleration and propagation in solar eruptive events. <BR /> Methods:
To this end, we used ground-based neutron monitor measurements of
relativistic nucleons and space-borne measurements of electrons with
similar speed to determine the arrival times of the first particles at 1
AU and to infer their solar release times. We compared the release times
with the time histories of non-thermal electrons in the solar atmosphere
and their escape to interplanetary space, as traced by radio spectra and
X-ray light curves and images. <BR /> Results: Non-thermal electrons
in the corona are found to be accelerated in different regions. Some
are confined in closed magnetic structures expanding during the course
of the event. Three episodes of electron escape to the interplanetary
space are revealed by groups of decametric-to-kilometric type III
bursts. The first group appears on the low-frequency side of a type
II burst produced by a coronal shock wave. The two latter groups
are accompanied at higher frequencies by bursts with rapid drifts
to both lower and higher frequencies (forward- or reverse-drifting
bursts). They are produced by electron beams that propagate both sunward
and anti-sunward. The first relativistic electrons and nucleons observed
near Earth are released with the third group of type III bursts, more
than ten minutes after the first signatures of non-thermal electrons
and of the formation of the shock wave in the corona. Although the
eruptive active region is near the central meridian, several tens of
degrees east of the footpoint of the nominal Parker spiral to the Earth,
the kilometric spectrum of the type III bursts and the in situ detection
of Langmuir waves demonstrate a direct magnetic connection between the
L1 Lagrange point and the field lines onto which the electron beams
are released at the Sun. <BR /> Conclusions: We interpret the forward-
and reverse-drifting radio bursts as evidence of reconnection between
the closed expanding magnetic structures of an erupting flux rope and
ambient open magnetic field lines. We discuss the origin of relativistic
particles near the Earth across two scenarios: (1) acceleration at the
CME-driven shock as it intercepts interplanetary magnetic field lines
rooted in the western solar hemisphere and (2) an alternative where
the relativistic particles are initially confined in the erupting
magnetic fields and get access to the open field lines to the Earth
through these reconnection events. <P />Movie is available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243903/olm">https://www.aanda.org</A>
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Title: Solar EUV-Enhancement and Thermospheric Disturbances
Authors: Briand, C.; Doerksen, K.; Deleflie, F.
2021SpWea..1902840B Altcode:
The increase of energetic electromagnetic flux during solar flares
and particle precipitation during geomagnetic activity are among
the most important sources of neutral density disturbances to the
Earth's thermosphere. However, disentangling the role of X and EUV
radiation during solar flares is difficult due to the rarity of
sufficiently isolated EUV-enhancements. Past work investigating the
role of EUV-enhancements has been based on simulations only. This
study focuses on the analysis of the response of the thermosphere to
relatively long-lasting (between 1 and 2 days) EUV-enhancements. These
events take place in isolation from coronal mass ejections, but
often occur during the recovery phase of flare events. Using the
Gravity Recovery and Climate Experiment and Challenging Minisatellite
Payload accelerometer-derived density datasets, we show that the
EUV-enhancements slow the thermosphere's recovery from a flare, and
maintain a high level density perturbation "plateau" lasting several
hours. The level of disturbance was found to be between 30% and 70%
compared to the thermosphere's density without any disturbance. The
duration of this plateau is long enough that it may be important for
estimating satellite drag. Over the duration of the EUV-enhancements,
Dst drops are also observed, indicating ring current activity. The
proposed physical mechanism driving the Dst changes is linked to the
increased production of O<SUP>+</SUP> ions of ionospheric origin,
which may occur over the EUV-enhancement period.
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Title: Observations of Shock Propagation through Turbulent Plasma
in the Solar Corona
Authors: Carley, Eoin P.; Cecconi, Baptiste; Reid, Hamish A.; Briand,
Carine; Sasikumar Raja, K.; Masson, Sophie; Dorovskyy, Vladimir;
Tiburzi, Caterina; Vilmer, Nicole; Zucca, Pietro; Zarka, Philippe;
Tagger, Michel; Grießmeier, Jean-Mathias; Corbel, Stéphane; Theureau,
Gilles; Loh, Alan; Girard, Julien N.
2021ApJ...921....3C Altcode: 2021arXiv210805587C
Eruptive activity in the solar corona can often lead to the propagation
of shock waves. In the radio domain the primary signature of such
shocks are type II radio bursts, observed in dynamic spectra as bands
of emission slowly drifting toward lower frequencies over time. These
radio bursts can sometimes have an inhomogeneous and fragmented
fine structure, but the cause of this fine structure is currently
unclear. Here we observe a type II radio burst on 2019 March 20th using
the New Extension in Nançay Upgrading LOFAR, a radio interferometer
observing between 10-85 MHz. We show that the distribution of size
scales of density perturbations associated with the type II fine
structure follows a power law with a spectral index in the range of α =
-1.7 to -2.0, which closely matches the value of -5/3 expected of fully
developed turbulence. We determine this turbulence to be upstream of
the shock, in background coronal plasma at a heliocentric distance of
~2 R<SUB>⊙</SUB>. The observed inertial size scales of the turbulent
density inhomogeneities range from ~62 Mm to ~209 km. This shows that
type II fine structure and fragmentation can be due to shock propagation
through an inhomogeneous and turbulent coronal plasma, and we discuss
the implications of this on electron acceleration in the coronal shock.
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Title: Pulsars with NenuFAR: Backend and pipelines
Authors: Bondonneau, L.; Grießmeier, J. -M.; Theureau, G.; Cognard,
I.; Brionne, M.; Kondratiev, V.; Bilous, A.; McKee, J. W.; Zarka, P.;
Viou, C.; Guillemot, L.; Chen, S.; Main, R.; Pilia, M.; Possenti,
A.; Serylak, M.; Shaifullah, G.; Tiburzi, C.; Verbiest, J. P. W.;
Wu, Z.; Wucknitz, O.; Yerin, S.; Briand, C.; Cecconi, B.; Corbel, S.;
Dallier, R.; Girard, J. N.; Loh, A.; Martin, L.; Tagger, M.; Tasse, C.
2021A&A...652A..34B Altcode: 2020arXiv200902076B
Context. NenuFAR (New extension in Nançay upgrading LOFAR) is a new
radio telescope developed and built on the site of the Nançay Radio
Observatory. It is designed to observe the largely unexplored frequency
window from 10 to 85 MHz, offering a high sensitivity across its full
bandwidth. NenuFAR has started its "early science" operation in July
2019, with 58% of its final collecting area. <BR /> Aims: Pulsars are
one of the major phenomena utilized in the scientific exploitation of
this frequency range and represent an important challenge in terms
of instrumentation. Designing instrumentation at these frequencies
is complicated by the need to compensate for the effects of both the
interstellar medium and the ionosphere on the observed signal. We have
designed a dedicated backend and developed a complete pulsar observation
and data analysis pipeline, which we describe in detail in the present
paper, together with first science results illustrating the diversity of
the pulsar observing modes. <BR /> Methods: Our real-time pipeline LUPPI
(Low frequency Ultimate Pulsar Processing Instrumentation) is able to
cope with a high data rate and provide real-time coherent de-dispersion
down to the lowest frequencies reached by NenuFAR (10 MHz). The full
backend functionality is described, as the available pulsar observing
modes (folded, single-pulse, waveform, and dynamic spectrum). <BR />
Results: We also present some of the early science results of NenuFAR
on pulsars: the detection of 12 millisecond pulsars (eight of which are
detected for the first time below 100 MHz); a high-frequency resolution
mapping of the PSR B1919+21 emission profile and a detailed observation
of single-pulse substructures from PSR B0809+74 down to 16 MHz; the high
rate of giant-pulse emission from the Crab pulsar detected at 68.7 MHz
(43 events per minute); and the illustration of the very good timing
performance of the instrumentation, which allows us to study dispersion
measure variations in great detail.
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Title: Observations of shock propagation through turbulent plasma
in the solar corona
Authors: Carley, Eoin; Cecconi, Baptiste; Reid, Hamish; Briand,
Carine; Sasikumar Raja, K.; Masson, Sophie; Dorovskyy, Vladimir;
Tiburzi, Caterina; Zucca, Pietro
2021EGUGA..2313113C Altcode:
Eruptive activity in the solar corona can often lead to the propagation
of shockwaves. In the radio domain the primary signature of such
shocks are type II radio bursts, observed in dynamic spectra as
bands of emission slowly drifting towards lower frequencies over
time. These radio bursts can sometimes have inhomogeneous and
fragmented fine structure, but the cause of this fine structure is
currently unclear. Here we observe several type II radio bursts on
2019-March-20th using the New Extension in Nancay Upgrading LOFAR
(NenuFAR), a radio interferometer observing between 10-85 MHz. We
show that the distribution of size-scales of density perturbations
associated with the fine structure of one type II follows a power law
with a spectral index of -1.71, which closely matches the value of -5/3
expected of fully developed turbulence. We determine this turbulence to
be upstream of the shock, in background coronal plasma at a heliocentric
distance of ~2 Rsun. The observed inertial size-scales of the turbulent
density inhomogeneities range from ~62 Mm to ~209 km. This shows that
type II fine structure and fragmentation can be due to shock propagation
through an inhomogeneous and turbulent coronal plasma, and we discuss
the implications of this on electron acceleration in the coronal shock.
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Title: Hard X-ray impact on the ionosphere D-layer: new results from
VLF measurements
Authors: Briand, Carine; Inturi, Srivani; Cecconi, Baptiste
2021EGUGA..23.5623B Altcode:
The ionospheric electron density reacts to a change of ionization
condition by a time delay Δt. Appleton (1953) demonstrated that this
time delay is inversely proportional to the product of the electron
density Ne and recombination rate coefficient α. Thus, the evaluation
of the time difference between the peak time of VLF emission, which
is supposed to represent the instant of maximum ionization, and the
ionization source's peak time provides an easy way to estimate α
Ne. First used to evaluate the increase of electron density at noon
from H α peak emission, this technic was also employed to estimate the
recombination rate during solar flares. The GOES Soft X-ray emissions
(i.e. in the range 1.5-12keV) are then considered to determine the
ionising source peak time.Based on VLF measurements obtained from the
SUPERSID antenna installed at the Meudon site of the Paris Observatory
(France), we computed each flare's time delay from January 2017. We
benefit from the events of September 2017, the strongest from the
last 10 years. We thus demonstrate the prominent role of Hard X-Rays
in ionizing the D-layer of the ionosphere.
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Title: Impacts of solar events on atmospheric density variations as
revealed by Satellite Laser Ranging orbits.
Authors: Deleflie, Florent; Hé, Changyong; Briand, Carine; Sammuneh,
Muhammad Ali; Visser, Pieter
2020EGUGA..2221223D Altcode:
This paper is focused on precise orbitography with SLR data, using
as well when they are available accelerometric data, as in the
GRACE mission. The main purpose of this paper is to analyse whether
low SLR satellite orbits (namely Starlette, Stella, Lares, Ajisai)
are sensitive or not to variations of the atmospheric density due to
solar events over the period 2003-2019, and including the ones that
occurred in 2017.The relationships between solar events and the way
they modify the density of the Earth's thermosphere, as revealed by
perturbations induced on artificial satellites orbits, are in fact of
crucial importance for satellite operators. A wide literature focused
on these issues already exists, but it appears to the authors that some
improvements of thermosphere models are still expected, especially at
high latitudes. This paper aims, hence, at contributing to fill a gap
in that direction. We first select over the period 1984-2019 a list
of solar events that may be representative of the conditions that may
heat the terrestrial atmosphere, in terms of geometrical configurations
and the intensity of solar activity. The goal is to identify whether
these events have impacted or not the thermospheric density at some
relevant altitudes; therefore, a post-fit residual analysis is provided,
accounting for the whole set of tracking data acquired by the stations
of the ILRS network. A comprehensive comparison between precise results
obtained with SLR and accelerometric data, using different atmospheric
drag modelling, is then provided.
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Title: Solar radio emissions: from simulations to laser experiment
Authors: Briand, Carine; Depierreux, Sylvie; Henri, Pierre; Marques,
Jean-Raphael; Lancia, Livia; Riconda, Caterina; Sgattoni, Andrea;
Amiranoff, François
2019EGUGA..21.7140B Altcode:
Solar flares generate intense electromagnetic radiation in the
radio domain (1-100 MHz), part of which corresponds to emission at
the electron plasma frequency ω<SUB>p</SUB> or its second harmonic
2ω_p. These waves are the signature of electron beams propagating
in the interplanetary medium. Detected by space and ground-based
radio telescopes, these electromagnetic waves can be used to remotely
infer the characteristics of the electron beams. If the main steps
of the process from electron beam to Electron Plasma Waves and
mode conversion to electromagnetic radiations are known, several
questions are still unresolved, in particular: (i) the efficiency
of the conversion, (ii) the directionality of the process. To tackle
these questions first PIC simulations, then laboratory laser-plasma
experiment have been performed. If the parameters of the interplanetary
plasma and laser-generated plasmas are very different in absolute
values, they happen to be very similar in relative numbers (such
as k⪉mbda<SUB>De</SUB> and T_e/T_i), which makes these laser
experiments suitable for astrophysical purposes. The experiment was
designed for the LULI 2000 facility (Ecole Polytechnique, France)
operated at 2ω<SUB>0</SUB> in the nanosecond regime. The results of
PIC simulations and of the first experiment that hold in September
2018 will be presented.
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Title: Atmospheric Density Variations and Orbit Perturbations in
Relation to Isolated Solar X-flare Events
Authors: Deleflie, Florent; Doerksen, Kelsey; Briand, Carine; Sammuneh,
Muhammad Ali; Sagnières, Luc
2019EGUGA..2115338D Altcode:
The relationships between solar flares and the way they modify the
density of the Earth's thermosphere, as revealed by perturbations
induced on artificial satellites orbits, are of crucial importance for
satellite operators. A wide literature dealing with the solar flare
events and their relationships with geomagnetic storms already exists
; but, it appears to the authors that there is a lack of research
focusing only on the effects of the solar flares, i.e. solar events
without any accompaniment of Coronal Mass Ejections (CMEs). This paper
is focused on the investigation of the thermosphere's response to
X-class solar flare events from 2002-2017. The thermosphere density
is derived from the on-board accelerometers of the Gravity Recovery
and Climate Experiment (GRACE) twin satellites, and the CHallenging
Minisatellite Payload (CHAMP) satellite. The accelerometric data are
also compared to the accelerations provided by classical and recent
atmospheric drag models, thanks to a post-fit residual analysis of
the orbits of those spacecrafts. As a result, the consequences of
the density disturbances on satellite re-entry are enlightened. It
appears in particular that the trajectory of the GRACE satellites are
sensitive to those single events, as their effects to the orbits is
higher than the current accuracy of the trajectory. As expected, the
effects of such single events are all the higher as the area-to-mass
ratio is high, and some examples based on major events (such as the
ones that occured in early december 2006) are also provided.
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Title: Groupe de Travail Soleil Heliosphere-Magnetospheres (SHM)
Authors: Auchère, F.; Astafyeva, E.; Baudin, F.; Bourdarie, S.;
Briand, C.; Brun, S.; Célestin, S.; Génot, V.; Kretzschmar, M.;
Leblanc, F.; Rouillard, A.; Sahraoui, F.
2019shm..rept....1A Altcode:
Les grandes questions scientifiques abordées dans le cadre de la
thématique Soleil Héliosphère et Magnétosphères (SHM) couvrent
l'ensemble des problématiques liées aux relations entre notre
étoile et le système solaire. Cela commence par l'étude de la
structure interne du Soleil à travers l'observation multi-spectrales,
l'hélio-sismologie et la modélisation ; par l'étude de l'origine
de la couronne solaire, son chauffage et l'accélération du vent
solaire et des particules énergétiques solaires lors d'événements
énergétiques solaires ; et enfin par l'étude de la propagation
du vent solaire et des mécanismes de chauffage de celui-ci par
dissipation turbulente.
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Title: Electromagnetic Simulations of Solar Radio Emissions
Authors: Henri, P.; Sgattoni, A.; Briand, C.; Amiranoff, F.;
Riconda, C.
2019JGRA..124.1475H Altcode:
Solar radio emissions are electromagnetic waves emitted in the
solar wind as a consequence of electron beams accelerated during
solar flares or interplanetary shocks such as interplanetary coronal
mass ejections. Different physical mechanisms have been suggested to
describe their origin. A good understanding of the emission process
would enable to infer the kinetic energy transferred from accelerated
electrons to radio waves. Even if the electrostatic case has been
extensively studied, full electromagnetic simulations were attempted
only recently. In this work, we report large-scale 2D3V electromagnetic
particle-in-cell simulations that enable to identify the generation of
both electrostatic and electromagnetic waves originated by a succession
of plasma instabilities. They confirm that an efficient mechanism to
generate solar radio emissions close to T<SUB>2f</SUB>, the harmonic
of the plasma frequency, is a multistage model based on a succession
of nonlinear three-wave interaction processes. Through a parametric
study of the electron beam parameters, we show that (i) the global
efficiency of the multistep conversion mechanism from the electron
beam kinetic energy to the T<SUB>2f</SUB> radio wave is independent
of the beam parameters, approximately 10<SUP>-5</SUP> in all tested
configurations, while (ii) the directivity of the electromagnetic
radio wave strongly depends on the origin electron beam. Those results
represent a step forward toward the use of solar wind radio emissions,
observed remotely, as a diagnostic for the properties of the electron
beam located at the source of the radio emission, and therefore to
eventually better characterize remotely electron acceleration mechanisms
in space regions not directly accessible to in situ measurements.
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Title: NOIRE Study Report: Towards a Low Frequency Radio
Interferometer in Space
Authors: Cecconi, Baptiste; Dekkali, Moustapha; Briand, Carine; Segret,
Boris; Girard, Julien; Laurens, André; Lamy, Alain; Valat, David;
Delpech, Michel; Bruno, Mickael; Gélard, Patrick; Bucher, Martin;
Nenon, Quentin; Grießmeier, Jean-Mathias; Boonstra, Albert-Jan;
Bentum, Mark
2018EGUGA..20.3648C Altcode: 2017arXiv171010245C
Ground based low frequency radio interferometers have been developed in
the last decade and are providing the scientific community with high
quality observations. Conversely, current radioastronomy instruments
in space have a poor angular resolution with single point observation
systems. Improving the observation capabilities of the low frequency
range (a few kHz to 100 MHz) requires to go to space and to set up a
space based network of antenna that can be used as an interferometer. We
present the outcome of the NOIRE (Nanosatellites pour un Observatoire
Interférométrique Radio dans l'Espace / Nanosatellites for a Radio
Interferometer Observatory in Space) study which assessed, with help
of CNES' PASO, the feasibility of a swarm of nanosatellites dedicated
to a low frequency radio observatory. With such a platform, space
system engineering and instrument development must be studied as a
whole: each node is a sensor and all sensors must be used together to
obtain a measurement. The study was conducted on the following topics:
system principle and concept (swarm, node homogeneity); Space and time
management (ranging, clock synchronization); Orbitography (Moon orbit,
Lagrange point options); Telecommunication (between nodes and with
ground) and networking; Measurements and processing; Propulsion;
Power; Electromagnetic compatibility. No strong show-stopper was
identified during the preliminary study, although the concept is not
yet ready. Several further studies and milestones are identified. The
NOIRE team will collaborate with international teams to try and build
this next generation of space systems.
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Title: French SKA White Book - The French Community towards the
Square Kilometre Array
Authors: Acero, F.; Acquaviva, J. -T.; Adam, R.; Aghanim, N.; Allen,
M.; Alves, M.; Ammanouil, R.; Ansari, R.; Araudo, A.; Armengaud, E.;
Ascaso, B.; Athanassoula, E.; Aubert, D.; Babak, S.; Bacmann, A.;
Banday, A.; Barriere, K.; Bellossi, F.; Bernard, J. -P.; Bernardini,
M. G.; Béthermin, M.; Blanc, E.; Blanchet, L.; Bobin, J.; Boissier,
S.; Boisson, C.; Boselli, A.; Bosma, A.; Bosse, S.; Bottinelli,
S.; Boulanger, F.; Boyer, R.; Bracco, A.; Briand, C.; Bucher, M.;
Buat, V.; Cambresy, L.; Caillat, M.; Casandjian, J. -M.; Caux,
E.; Célestin, S.; Cerruti, M.; Charlot, P.; Chassande-Mottin, E.;
Chaty, S.; Christensen, N.; Ciesla, L.; Clerc, N.; Cohen-Tanugi, J.;
Cognard, I.; Combes, F.; Comis, B.; Corbel, S.; Cordier, B.; Coriat,
M.; Courtin, R.; Courtois, H.; Da Silva, B.; Daddi, E.; Dallier, R.;
Dartois, E.; Demyk, K.; Denis, J. -M.; Denis, L.; Djannati-Ataï, A.;
Donati, J. -F.; Douspis, M.; van Driel, W.; El Korso, M. N.; Falgarone,
E.; Fantina, A.; Farges, T.; Ferrari, A.; Ferrari, C.; Ferrière, K.;
Flamary, R.; Gac, N.; Gauffre, S.; Genova, F.; Girard, J.; Grenier,
I.; Griessmeier, J. -M.; Guillard, P.; Guillemot, L.; Gulminelli,
F.; Gusdorf, A.; Habart, E.; Hammer, F.; Hennebelle, P.; Herpin, F.;
Hervet, O.; Hughes, A.; Ilbert, O.; Janvier, M.; Josselin, E.; Julier,
A.; Lachaud, C.; Lagache, G.; Lallement, R.; Lambert, S.; Lamy, L.;
Langer, M.; Larzabal, P.; Lavaux, G.; Le Bertre, T.; Le Fèvre, O.;
Le Tiec, A.; Lefloch, B.; Lehnert, M.; Lemoine-Goumard, M.; Levrier,
F.; Limousin, M.; Lis, D.; López-Sepulcre, A.; Macias-Perez, J.;
Magneville, C.; Marcowith, A.; Margueron, J.; Marquette, G.; Marshall,
D.; Martin, L.; Mary, D.; Masson, S.; Maurogordato, S.; Mazauric,
C.; Mellier, Y.; Miville-Deschênes, M. -A.; Montier, L.; Mottez, F.;
Mourard, D.; Nesvadba, N.; Nezan, J. -F.; Noterdaeme, P.; Novak, J.;
Ocvirk, P.; Oertel, M.; Olive, X.; Ollier, V.; Palanque-Delabrouille,
N.; Pandey-Pommier, M.; Pennec, Y.; Pérault, M.; Peroux, C.; Petit,
P.; Pétri, J.; Petiteau, A.; Pety, J.; Pratt, G. W.; Puech, M.;
Quertier, B.; Raffin, E.; Rakotozafy Harison, S.; Rawson, S.; Renaud,
M.; Revenu, B.; Richard, C.; Richard, J.; Rincon, F.; Ristorcelli,
I.; Rodriguez, J.; Schultheis, M.; Schimd, C.; Semelin, B.; Sol, H.;
Starck, J. -L.; Tagger, M.; Tasse, C.; Theureau, G.; Torchinsky, S.;
Vastel, C.; Vergani, S. D.; Verstraete, L.; Vigouroux, X.; Vilmer,
N.; Vilotte, J. -P.; Webb, N.; Ysard, N.; Zarka, P.
2017arXiv171206950A Altcode:
The "Square Kilometre Array" (SKA) is a large international radio
telescope project characterised, as suggested by its name, by a total
collecting area of approximately one square kilometre, and consisting
of several interferometric arrays to observe at metric and centimetric
wavelengths. The deployment of the SKA will take place in two sites,
in South Africa and Australia, and in two successive phases. From its
Phase 1, the SKA will be one of the most formidable scientific machines
ever deployed by mankind, and by far the most impressive in terms of
data throughput and required computing power. With the participation
of almost 200 authors from forty research institutes and six private
companies, the publication of this French SKA white paper illustrates
the strong involvement in the SKA project of the French astronomical
community and of a rapidly growing number of major scientific and
technological players in the fields of Big Data, high performance
computing, energy production and storage, as well as system integration.
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Title: Full PIC simulations of solar radio emission
Authors: Sgattoni, A.; Henri, P.; Briand, C.; Amiranoff, F.;
Riconda, C.
2017AGUFMSH33B2786S Altcode:
Solar radio emissions are electromagnetic (EM) waves emitted in the
solar wind plasma as a consequence of electron beams accelerated
during solar flares or interplanetary shocks such as ICMEs. To
describe their origin, a multi-stage model has been proposed in the
60s which considers a succession of non-linear three-wave interaction
processes. A good understanding of the process would allow to infer
the kinetic energy transfered from the electron beam to EM waves,
so that the radio waves recorded by spacecraft can be used as a
diagnostic for the electron beam.Even if the electrostatic problem
has been extensively studied, full electromagnetic simulations were
attempted only recently. Our large scale 2D-3V electromagnetic PIC
simulations allow to identify the generation of both electrostatic
and EM waves originated by the succession of plasma instabilities. We
tested several configurations varying the electron beam density and
velocity considering a background plasma of uniform density. For
all the tested configurations approximately 105 of the electron-beam
kinetic energy is transfered into EM waves emitted in all direction
nearly isotropically. With this work we aim to design experiments
of laboratory astrophysics to reproduce the electromagnetic emission
process and test its efficiency.
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Title: The NOIRE Study
Authors: Cecconi, B.; Laurens, A.; Briand, C.; Girard, J.; Bucher,
M.; Puy, D.; Segret, B.; Bentum, M.
2016sf2a.conf..339C Altcode:
NOIRE (Nanosats pour un Observatoire Interférométrique Radio dans
l'Espace; Nanosats for a space borne interferometric radio observatory)
is an ongoing feasibility study with CNES and in collaboration with
Dutch colleagues. The goal is to assess the feasibility of a low
frequency space radio interferometer using nanosatellites.
---------------------------------------------------------
Title: Solar radio emissions: 2D full PIC simulations
Authors: Pierre, H.; Sgattoni, A.; Briand, C.; Amiranoff, F.;
Riconda, C.
2016AGUFMSH21E2569P Altcode:
Solar radio emissions are electromagnetic waves observed at the local
plasma frequency and/or at twice the plasma frequency. To describe
their origin a multi-stage model has been proposed by Ginzburg
& Zhelezniakov (1958) and further developed by several authors,
which consider a succession of non-linear three-wave interaction
processes. Electron beams accelerated by solar flares travel in the
interplanetary plasma and provide the free energy for the development
of plasma instabilities. The model describes how part of the free
energy of these beams can be transformed in a succession of plasma
waves and eventually into electromagnetic waves. Following the work of
Thurgood & Tsiklauri (2015) we performed several 2D Particle In Cell
simulations. The simulations follow the entire set of processes from the
electron beam propagation in the background plasma to the generation of
the electromagnetic waves in particular the 2ωp emission, including
the excitation of the low frequency waves. As suggested by Thurgood
& Tsiklauri (2015) it is possible to identify regimes where the
radiation emission can be directly linked to the electron beams. Our
attention was devoted to estimate the conversion efficiency from
electron kinetic energy to the em energy, and the growth rate of the
several processes which can be identified. We studied the emission
angles of the 2ωpradiation and compared them with the theoretical
predictions of Willes et. al. (1995). We also show the role played by
some numerical parameters i.e. the size and shape of the simulation
box. This work is the first step to prepare laser-plasma experiments. <P
/>V. L. Ginzburg, V. V. Zhelezniakov On the Possible Mechanisms of
Sporadic Solar Radio Emission (Radiation in an Isotropic Plasma)
Soviet Astronomy, Vol. 2, p.653 (1958) <P />J. O. Thurgood and
D. Tsiklauri Self-consistent particle-in-cell simulations of funda-
mental and harmonic plasma radio emission mechanisms. Astronomy &
Astrophysics 584, A83 (2015). <P />A. Willes, P. Robinson and D. Melrose
(1995). Second harmonic electromagnetic emis- sion via Langmuir wave
coalescence. Physics of Plasmas, 3(1), 149-159 (1995).
---------------------------------------------------------
Title: Langmuir waveforms at interplanetary shocks: STEREO statistical
analysis
Authors: Briand, C.
2016AGUFMSH21A2499B Altcode:
Wave-particle interactions and particle acceleration are the two main
processes allowing energy dissipation at non collisional shocks. Ion
acceleration has been deeply studied for many years, also for their
central role in the shock front reformation. Electron dynamics is
also important in the shock dynamics through the instabilities they
can generate which may impact the ion dynamics.Particle measurements
can be efficiently completed by wave measurements to determine the
characteristics of the electron beams and study the turbulence of the
medium. Electric waveforms obtained from the S/WAVES instrument of the
STEREO mission between 2007 to 2014 are analyzed. Thus, clear signature
of Langmuir waves are observed on 41 interplanetary shocks. These data
enable a statistical analysis and to deduce some characteristics of
the electron dynamics on different shocks sources (SIR or ICME) and
types (quasi-perpendicular or quasi-parallel). The conversion process
between electrostatic to electromagnetic waves has also been tested
in several cases.
---------------------------------------------------------
Title: Mapping the radio sky from 0.1 to 100 MHz with NOIRE
Authors: Cecconi, B.; Laurens, A.; Briand, C.; Girard, J.; Bucher,
M.; Puy, D.; Segret, B.; Bentum, M.
2016sf2a.conf..343C Altcode:
The goal of the NOIRE study (Nanosats pour un Observatoire
Interférométrique Radio dans l'Espace) is to assess the scientific
interest and technical feasibility of a space borne radio interferometer
operating from a few kHz to a few 10 MHz. Such observatory would be
able to build a global sky map with an unprecedented spatial resolution
depending on the selected technical implementation. We present a review
of our understanding of the Galactic mapping, assessing the instrument
requirement for such observations.
---------------------------------------------------------
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: The modern radio astronomy network in Ukraine: UTR-2, URAN
and GURT
Authors: Konovalenko, A.; Sodin, L.; Zakharenko, V.; Zarka, P.;
Ulyanov, O.; Sidorchuk, M.; Stepkin, S.; Tokarsky, P.; Melnik, V.;
Kalinichenko, N.; Stanislavsky, A.; Koliadin, V.; Shepelev, V.;
Dorovskyy, V.; Ryabov, V.; Koval, A.; Bubnov, I.; Yerin, S.; Gridin,
A.; Kulishenko, V.; Reznichenko, A.; Bortsov, V.; Lisachenko, V.;
Reznik, A.; Kvasov, G.; Mukha, D.; Litvinenko, G.; Khristenko,
A.; Shevchenko, V. V.; Shevchenko, V. A.; Belov, A.; Rudavin, E.;
Vasylieva, I.; Miroshnichenko, A.; Vasilenko, N.; Olyak, M.; Mylostna,
K.; Skoryk, A.; Shevtsova, A.; Plakhov, M.; Kravtsov, I.; Volvach,
Y.; Lytvinenko, O.; Shevchuk, N.; Zhouk, I.; Bovkun, V.; Antonov,
A.; Vavriv, D.; Vinogradov, V.; Kozhin, R.; Kravtsov, A.; Bulakh, E.;
Kuzin, A.; Vasilyev, A.; Brazhenko, A.; Vashchishin, R.; Pylaev, O.;
Koshovyy, V.; Lozinsky, A.; Ivantyshin, O.; Rucker, H. O.; Panchenko,
M.; Fischer, G.; Lecacheux, A.; Denis, L.; Coffre, A.; Grießmeier,
J. -M.; Tagger, M.; Girard, J.; Charrier, D.; Briand, C.; Mann, G.
2016ExA....42...11K Altcode: 2016ExA...tmp....7K
The current status of the large decameter radio telescope UTR-2
(Ukrainian T-shaped Radio telescope) together with its VLBI system
called URAN is described in detail. By modernization of these
instruments through implementation of novel versatile analog and digital
devices as well as new observation techniques, the observational
capabilities of UTR-2 have been substantially enhanced. The total
effective area of UTR-2 and URAN arrays reaches 200 000 m<SUP>2</SUP>,
with 24 MHz observational bandwidth (within the 8-32 MHz frequency
range), spectral and temporal resolutions down to 4 kHz and 0.5 msec in
dynamic spectrum mode or virtually unlimited in waveform mode. Depending
on the spectral and temporal resolutions and confusion effects, the
sensitivity of UTR-2 varies from a few Jy to a few mJy, and the angular
resolution ranges from ~ 30 arcminutes (with a single antenna array)
to a few arcseconds (in VLBI mode). In the framework of national and
international research projects conducted in recent years, many new
results on Solar system objects, the Galaxy and Metagalaxy have been
obtained. In order to extend the observation frequency range to 8-80
MHz and enlarge the dimensions of the UTR-2 array, a new instrument -
GURT (Giant Ukrainian Radio Telescope) - is now under construction. The
radio telescope systems described herein can be used in synergy with
other existing low-frequency arrays such as LOFAR, LWA, NenuFAR,
as well as provide ground-based support for space-based instruments.
---------------------------------------------------------
Title: Langmuir waves: a database from the STEREO mission
Authors: Briand, Carine; Henri, Pierre; Génot, Vincent; Lormant,
Nicolas; Dufourg, Nicolas; Cecconi, Baptiste; Nguyen, Quynh-Nhu
2016EGUGA..18.6005B Altcode:
Langmuir waves are ubiquitous in the planetary environments and the
interplanetary medium. These electrostatic waves occur in the range
10-30 kHz in the solar wind. They are of interest as they are linked
to the electron dynamics. Moreover, they are at the origin of the
most intense electromagnetic radio waves related to solar flare and
interplanetary shocks. The waveform analyzers of the WAVES instrument
onboard of STEREO spacecraft have been observing the interplanetary
medium since more than seven years. A complete database of the observed
Langmuir waves is accessible to the community from the CDPP website
(http://cdpp.eu/). We present here the details of the available
information, as well as some analysis on different heliophysical
contexts (interplanetary medium, shocks in particular).
---------------------------------------------------------
Title: Division E Commission 49: Interplanetary Plasma and Heliosphere
Authors: Mann, Ingrid; Manoharan, P. K.; Gopalswamy, Natchimuthuk;
Briand, Carine; Chashei, Igor V.; Gibson, Sarah E.; Lario, David;
Hanaoka, Yoichiro; Malandraki, Olga; Kontar, Eduard; Richardson,
John D.
2016IAUTA..29..300M Altcode:
After a little more than forty years of work related to the
interplanetary plasma and the heliosphere the IAU's Commission 49 was
formally discontinued in 2015. The commission started its work when
the first spacecraft were launched to measure the solar wind in-situ
away from Earth orbit, both inward and outward from 1 AU. It now
hands over its activities to a new commission during an era of space
research when Voyager 1 measures in-situ the parameters of the local
interstellar medium at the edge of the heliosphere. The commission will
be succeeded by C.E3 with a similar area of responsibility but with more
focused specific tasks that the community intends to address during the
coming several years. This report includes a short description of the
motivation for this commission and of the historical context. It then
describes work from 2012 to 2015 during the present solar cycle 24 that
has been the weakest in the space era so far. It gave rise to a large
number of studies on solar energetic particles and cosmic rays. Other
studies addressed e.g. the variation of the solar wind structure
and energetic particle fluxes on long time scales, the detection of
dust in the solar wind and the Voyager measurements at the edge of the
heliosphere. The research is based on measurements from spacecraft that
are at present operational and motivated by the upcoming Solar Probe
+ and Solar Orbiter missions to explore the vicinity of the Sun. We
also report here the progress on new and planned radio instruments
and their importance for heliospheric studies. Contributors to this
report are Carine Briand, Yoichiro Hanaoka, Eduard Kontar, David Lario,
Ingrid Mann, John D. Richardson.
---------------------------------------------------------
Title: STEREO database of interplanetary Langmuir electric waveforms
Authors: Briand, C.; Henri, P.; Génot, V.; Lormant, N.; Dufourg,
N.; Cecconi, B.; Nguyen, Q. N.; Goetz, K.
2016JGRA..121.1062B Altcode:
This paper describes a database of electric waveforms that is
available at the Centre de Données de la Physique des Plasmas (CDPP,
<A href="http://cdpp.eu/">http://cdpp.eu/</A>). This database is
specifically dedicated to waveforms of Langmuir/Z-mode waves. These
waves occur in numerous kinetic processes involving electrons in space
plasmas. Statistical analysis from a large data set of such waves
is then of interest, e.g., to study the relaxation of high-velocity
electron beams generated at interplanetary shock fronts, in current
sheets and magnetic reconnection region, the transfer of energy between
high and low frequencies, the generation of electromagnetic waves. The
Langmuir waveforms were recorded by the Time Domain Sampler (TDS) of the
WAVES radio instrument on board the STEREO mission. In this paper, we
detail the criteria used to identify the Langmuir/Z-mode waves among the
whole set of waveforms of the STEREO spacecraft. A database covering the
November 2006 to August 2014 period is provided. It includes electric
waveforms expressed in the normalized frame (B,B × Vsw,B × (B ×
Vsw)) with B and V<SUB>sw</SUB> the local magnetic field and solar
wind velocity vectors, and the local magnetic field in the variance
frame, in an interval of ±1.5 min around the time of the Langmuir
event. Quicklooks are also provided that display the three components of
the electric waveforms together with the spectrum of E<SUB>∥</SUB>,
together with the magnitude and components of the magnetic field in
the 3 min interval, in the variance frame. Finally, the distribution
of the Langmuir/Z-mode waves peak amplitude is also analyzed.
---------------------------------------------------------
Title: The Storm of Decameter Spikes During the Event of 14 June 2012
Authors: Shevchuk, N. V.; Melnik, V. N.; Poedts, S.; Dorovskyy, V. V.;
Magdalenic, J.; Konovalenko, A. A.; Brazhenko, A. I.; Briand, C.;
Frantsuzenko, A. V.; Rucker, H. O.; Zarka, P.
2016SoPh..291..211S Altcode: 2015SoPh..tmp..171S
An event on 14 June 2012, observed with the radio telescopes UTR-2
(Kharkov, Ukraine), URAN-2 (Poltava, Ukraine), and NDA (Nançay, France)
during a joint Summer campaign, is analyzed and discussed. The high
solar activity resulted in a storm of spikes, and a storm of Type III
bursts, Type IIIb bursts, and a Type IV burst observed in the decameter
band. During the observed time interval, the average flux of radio
emission changed twice. Using spikes as a tool for diagnostics of
plasma parameters, we followed variations of the coronal temperature
and the coronal magnetic field in the observed time interval. Thus,
in frames of the model described in this article the observed decameter
spikes' durations of 0.3 - 1 seconds correspond to the coronal plasma
temperatures of ≈0.1 -0.6 ×10<SUP>6</SUP>K. At the same time the
spikes' frequency bandwidths of 25 - 80 kHz give us the magnetic-field
value of about 2 G.
---------------------------------------------------------
Title: Division II: Commission 49: Interplanetary Plasma and the
Heliosphere
Authors: Gopalswamy, Natchimuthuk; Mann, Ingrid; Bougeret, Jean-Louis;
Briand, Carine; Lallement, Rosine; Lario, David; Manoharan, P. K.;
Shibata, Kazunari; Webb, David F.
2015IAUTB..28..112G Altcode:
The President of IAU Commission 49 (C49; Interplanetary Plasma and the
Heliosphere), Nat Gopalswamy, chaired the business meeting of C10,
which took place on August 23, 2012 in the venue of the IAU General
Assembly in Beijing (2:00 - 3:30 PM, Room 405).
---------------------------------------------------------
Title: Flare-related radio emission: a kinetic point-of-view
Authors: Briand, Carine
2015IAUGA..2254941B Altcode:
During a flare, high energy electrons (1-100 keV) are expelled
from the solar corona and travel along the interplanetary magnetic
field lines. These electrons are at the origin of one of the most
prominent features of the meter-decameter ranges of frequency: the
so-called solar type III radio emissions.Several theories have been
proposed to explain the generation of these emissions. They all refer
to small scale plasma processes. During this talk, we will show how
STEREO/WAVES measurements have been able to give strong support to the
model initially proposed by Ginzburg & Zheleznyakov: the three
wave-coupling.Using new capabilities of waveform analyses provided
by the instruments onboard the two STEREO spacecraft, we present a
complete set of direct evidence for three-wave coupling occurring
during a Type III emission and involving two Langmuir waves and an
ion acoustic wave. Evidence cover not only the energy and momentum
conservation but also the phase coupling.Then, we present Vlasov
numerical simulations that support the observations. We indeed show
that the amplitude of the wave packets are within the expected values
when correctly considering the non monochromatic character of the waves
and their finite interaction time.Finally, during a specific event when
two electron beams interact, we show that the lack of Langmuir waves
coherence reduces the efficiency of the Langmuir parametric decay,
and as a consequence reduces the intensity of the Type III emission.
---------------------------------------------------------
Title: Cancellation analysis of current density in solar active
region NOAA10019
Authors: De Vita, Gaetano; Vecchio, Antonio; Sorriso-Valvo, Luca;
Briand, Carine; Primavera, Leonardo; Servidio, Sergio; Lepreti, Fabio;
Carbone, Vincenzo
2015JSWSC...5A..28D Altcode:
Solar flares are often associated with changes in the fine magnetic
structure of the emitting active region. Such topological modification
results in variations of both the scaling properties of the fields'
fluctuations, and the fractal dimension of the associated gradients. The
use of cancellation analysis of the current density has been attempted
for the identification and quantitative estimation of such changes. The
characteristics of the magnetic vector as measured by THEMIS telescope
for the active region NOAA10019 have been studied in this paper,
suggesting the presence of disrupted current filaments. The variation
of the fractal dimension of the current structures, and in particular
their smoothing, is discussed in relationship with occurrence of one
flare in the active region.
---------------------------------------------------------
Title: Langmuir waves across the heliosphere
Authors: Briand, C.
2015JPlPh..81b3204B Altcode:
All the bodies of the solar system are embedded in the supersonic flux
of energetic particles emitted by the Sun. Since the advent of the space
age, the models to describe the interaction of this plasma flow with
the planets, asteroids, comets etc. have drastically progressed. The
possibilities of in situ measurements of the particle distributions
and electromagnetic fields have enabled the plasma theories to be
tested under astrophysical conditions. Energy transfer from the Sun
to the outermost regions of the heliosphere as well as the processes
leading to the dissipation of this energy are central questions
for heliophysicists. Understanding the dynamics of the particles is
thus critical. It is a particularly complicated subject since the
medium is (almost) non-collisional. Thus, next to the description of
the particles, the development of waves must be considered. Indeed,
they participate to the exchange of energy between different species
that would not interact otherwise. In other words, waves may play the
role of collisions. This paper concentrates on Langmuir waves for
their strong links with the electron dynamics. The basic processes
of growth and saturation of the Langmuir waves are reviewed to stress
their diagnostic capabilities. Then, the characteristics of the waves
are described in the several heliophysical contexts: the planetary
environments (in particular the ionosphere, the magnetotail and the
foreshock) and in the interplanetary medium (in quiescent conditions
of the solar wind or during transient events). A particular emphasis
is given to results obtained in the last 15 years.
---------------------------------------------------------
Title: Decameter Type III Bursts with Changing Frequency Drift-Rate
Signs
Authors: Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.;
Briand, C.; Dorovskyy, V. V.; Zarka, P.; Frantsuzenko, A. V.; Rucker,
H. O.; Rutkevych, B. P.; Panchenko, M.; Denis, L.; Zaqarashvili, T.;
Shergelashvili, B.
2015SoPh..290..193M Altcode: 2018arXiv180208336M; 2014SoPh..tmp..117M
We discuss properties of type III bursts that change the sign of their
drift rate from negative to positive and vice versa. Moreover, these
bursts may change the sign of their drift rates more than once. These
particular type III bursts were observed simultaneously by the
radio telescopes UTR-2 (Ukrainian T-shaped Radio telescope, Kharkov,
Ukraine), URAN-2 (Ukrainian Radio telescope of the Academy of Sciences,
Poltava, Ukraine), and by the NDA (Nançay Decametric Array, Nancay,
France) in the frequency range 8 - 41 MHz. The negative drift rates
of these bursts are similar to those of previously reported decameter
type III bursts and vary from −0.7 MHz s<SUP>−1</SUP> to −1.7
MHz s<SUP>−1</SUP>, but their positive drift rates vary in a wider
range from 0.44 MHz s<SUP>−1</SUP> to 6 MHz s<SUP>−1</SUP>. Unlike
inverted U-bursts, the tracks of these type III bursts have C- or
inverted C-shapes.
---------------------------------------------------------
Title: The Planeterrella: A planetary auroral simulator
Authors: Lilensten, J.; Lamy, L.; Briand, C.; Barthélémy, M.;
Cecconi, B.
2014CAPJ...16...18L Altcode:
This article presents a plasma physics experiment which makes it
possible to produce polar lights. The experiment, named Planeterrella,
involves shooting electrons onto a magnetised sphere placed in a vacuum
chamber. Inspired by Kristian Birkeland's Terrella, but with several
different configurations and technical improvements, the experiment
allows the user to simulate and visualise simple geophysical and
astrophysical situations. Several Planeterrellas are now used across
Europe and the USA. The design of the original experiment and the
expertise of its first authors are shared freely with any public
institute and are outlined in this article.
---------------------------------------------------------
Title: Sapce based low frequency interferometric radioastronomy:
the path towards the imaging of the inner heliosphere.
Authors: Cecconi, B.; Zarka, P. M.; Girard, J. N.; Klein Wolt, M.;
Boonstra, A. J.; Baan, W.; Briand, C.; Maksimovic, M.; Segret, B.
2014AGUFMSM31A4155C Altcode:
Low frequency radioastronomy observatories for the heliosphere have been
using similar instrumentation for decades. The Cassini, STEREO, and
the future Solar Orbiter mission are embarking goniopolarmetric radio
receiver connected to 3 electric wire antennas. Such instrument provides
the spectral matrix (or part of it) from which the wave parameters
can be derived. They require a point source assumption (plane wave) to
derive the direction of arrival of the wave, the polarization and the
flux density. In case of a spatially extended source (disk shaped, with
a given radial profile), the source centroid direction and the apparent
source size can also be derived. This type of instrumentation cannot
provide much more parameters, as there is a maximum of to 9 independent
measurements for each time-frequency step (i.e. an instantaneous set
of measurements). Radio maps can be produced a posteriori combining
consecutive data at the cost of averaging out small scale temporal
variations. Furthermore, these inversion do not allow solving for
several sources, or for complex source geometry. We present a concept
of radioastronomy instrumentation using a swarm of small satellites
(possibly cubesats) with sensitive radio receivers measuring the wave
front and phase of the radio waves on each spacecraft. This instrument
will also provide 3-dimensional interferometric measurement from which
real imaging capabilities will arise, as it is now occurring on ground
at frequencies above 15 MHz, with the LOFAR interferometer in Europe,
or the LWA in teh USA. The proposed concept will be very complementary
to these instruments, as they will be orepating from a few kHz to a
few 10 Mhz from space, and thus not affected by the ionospheric cutoff
at 10 MHz. Such resolved imaging capabilities of the inner heliosphere
would be a real step forward to better understand the radio emissions
mechanisms and the energetic at the orgin of the radio sources,
as well as the propagation processes. We will present the various
existing projects and the roadmap to reach this goal.
---------------------------------------------------------
Title: The science case for an orbital mission to Uranus: Exploring
the origins and evolution of ice giant planets
Authors: Arridge, C. S.; Achilleos, N.; Agarwal, J.; Agnor, C. B.;
Ambrosi, R.; André, N.; Badman, S. V.; Baines, K.; Banfield, D.;
Barthélémy, M.; Bisi, M. M.; Blum, J.; Bocanegra-Bahamon, T.;
Bonfond, B.; Bracken, C.; Brandt, P.; Briand, C.; Briois, C.; Brooks,
S.; Castillo-Rogez, J.; Cavalié, T.; Christophe, B.; Coates, A. J.;
Collinson, G.; Cooper, J. F.; Costa-Sitja, M.; Courtin, R.; Daglis,
I. A.; de Pater, I.; Desai, M.; Dirkx, D.; Dougherty, M. K.; Ebert,
R. W.; Filacchione, G.; Fletcher, L. N.; Fortney, J.; Gerth, I.;
Grassi, D.; Grodent, D.; Grün, E.; Gustin, J.; Hedman, M.; Helled,
R.; Henri, P.; Hess, S.; Hillier, J. K.; Hofstadter, M. H.; Holme,
R.; Horanyi, M.; Hospodarsky, G.; Hsu, S.; Irwin, P.; Jackman, C. M.;
Karatekin, O.; Kempf, S.; Khalisi, E.; Konstantinidis, K.; Krüger,
H.; Kurth, W. S.; Labrianidis, C.; Lainey, V.; Lamy, L. L.; Laneuville,
M.; Lucchesi, D.; Luntzer, A.; MacArthur, J.; Maier, A.; Masters, A.;
McKenna-Lawlor, S.; Melin, H.; Milillo, A.; Moragas-Klostermeyer,
G.; Morschhauser, A.; Moses, J. I.; Mousis, O.; Nettelmann, N.;
Neubauer, F. M.; Nordheim, T.; Noyelles, B.; Orton, G. S.; Owens, M.;
Peron, R.; Plainaki, C.; Postberg, F.; Rambaux, N.; Retherford, K.;
Reynaud, S.; Roussos, E.; Russell, C. T.; Rymer, A. M.; Sallantin, R.;
Sánchez-Lavega, A.; Santolik, O.; Saur, J.; Sayanagi, K. M.; Schenk,
P.; Schubert, J.; Sergis, N.; Sittler, E. C.; Smith, A.; Spahn, F.;
Srama, R.; Stallard, T.; Sterken, V.; Sternovsky, Z.; Tiscareno,
M.; Tobie, G.; Tosi, F.; Trieloff, M.; Turrini, D.; Turtle, E. P.;
Vinatier, S.; Wilson, R.; Zarka, P.
2014P&SS..104..122A Altcode:
Giant planets helped to shape the conditions we see in the Solar System
today and they account for more than 99% of the mass of the Sun's
planetary system. They can be subdivided into the Ice Giants (Uranus
and Neptune) and the Gas Giants (Jupiter and Saturn), which differ
from each other in a number of fundamental ways. Uranus, in particular
is the most challenging to our understanding of planetary formation
and evolution, with its large obliquity, low self-luminosity, highly
asymmetrical internal field, and puzzling internal structure. Uranus
also has a rich planetary system consisting of a system of inner natural
satellites and complex ring system, five major natural icy satellites,
a system of irregular moons with varied dynamical histories, and a
highly asymmetrical magnetosphere. Voyager 2 is the only spacecraft to
have explored Uranus, with a flyby in 1986, and no mission is currently
planned to this enigmatic system. However, a mission to the uranian
system would open a new window on the origin and evolution of the
Solar System and would provide crucial information on a wide variety
of physicochemical processes in our Solar System. These have clear
implications for understanding exoplanetary systems. In this paper
we describe the science case for an orbital mission to Uranus with
an atmospheric entry probe to sample the composition and atmospheric
physics in Uranus' atmosphere. The characteristics of such an orbiter
and a strawman scientific payload are described and we discuss the
technical challenges for such a mission. This paper is based on a white
paper submitted to the European Space Agency's call for science themes
for its large-class mission programme in 2013.
---------------------------------------------------------
Title: Electrostatic fluctuations in the solar wind: An evidence of
the link between Alfvénic and electrostatic scales
Authors: Vecchio, A.; Valentini, F.; Donato, S.; Carbone, V.; Briand,
C.; Bougeret, J.; Veltri, P.
2014JGRA..119.7012V Altcode:
Electrostatic activity in the frequency range of few kHz represents
a very common phenomenon observed in the solar wind since first
observation from Helios spacecraft. In this paper we present a
detailed comparison between electrostatic fluctuations detected by
STEREO spacecraft and the results of kinetic numerical simulations. By
using a novel approach, made by a combination of two different
numerical models, we provide a convincing interpretation of the space
observations in terms of the electrostatic branch of the so-called
ion-bulk waves able to survive against Landau damping even at small
values of T<SUB>e</SUB>/T<SUB>p</SUB>. The comparison between data and
numerical simulations allows to characterize the chain of physical
mechanisms, able to efficiently transfer energy from the Alfvénic
scales down to scales of the order of the Debye length, through the
excitation of the observed electrostatic fluctuations.
---------------------------------------------------------
Title: The Nonlinear and Nonlocal Link between Macroscopic Alfvénic
and Microscopic Electrostatic Scales in the Solar Wind
Authors: Valentini, F.; Vecchio, A.; Donato, S.; Carbone, V.; Briand,
C.; Bougeret, J.; Veltri, P.
2014ApJ...788L..16V Altcode:
The local heating of the solar-wind gas during its expansion represents
one of the most intriguing problems in space plasma physics and
is at present the subject of a relevant scientific effort. The
possible mechanisms that could account for local heat production in
the interplanetary medium are most likely related to the turbulent
character of the solar-wind plasma. Nowadays, many observational and
numerical analyses are devoted to the identification of fluctuation
channels along which energy is carried from large to short wavelengths
during the development of the turbulent cascade; these fluctuation
channels establish the link between macroscopic and microscopic
scales. In this Letter, by means of a quantitative comparison between
in situ measurements in the solar wind from the STEREO spacecraft and
numerical results from kinetic simulations, we identify an electrostatic
channel of fluctuations that develops along the turbulent cascade in a
direction parallel to the ambient magnetic field. This channel appears
to be efficient in transferring the energy from large Alfvénic to
short electrostatic acoustic-like scales up to a range of wavelengths
where it can finally be turned into heat, even when the electron to
proton temperature ratio is of the order of unity.
---------------------------------------------------------
Title: Inhibition of type III radio emissions due to the interaction
between two electron beams: Observations and simulations
Authors: Briand, C.; Henri, P.; Hoang, S.
2014JGRA..119.2365B Altcode:
We report the peculiar interaction of two type III bursts observed in
the solar wind. As electron beams propagating on the same magnetic field
lines cross, a spectacular depletion of the type III radio emission
is observed. We combine observations from the WAVES experiment on
board the STEREO mission together with kinetic plasma simulations to
study the extinction of type III radio emission resulting from the
interaction between two electron beams. The remote observations enable
to follow the electron beams in the interplanetary medium and show
that the level of radiated radio waves is recovered after the beam
crossing. The in situ observations of beam-driven Langmuir waves give
evidence for Langmuir decay. The density fluctuations are extracted
from in situ observations. The velocity of the beams is independently
evaluated from in situ observations of decaying Langmuir waves and
remote radio observations. The kinetic simulations show that the level
of beam-driven Langmuir waves is reduced as the two beams cross. We
show that the slow beam induced a strong reduction of the quasilinear
relaxation of the fast beam, limiting the amplitude of the generated
Langmuir waves. Moreover, in the case of two electron beams, the lack
of Langmuir wave coherence reduces the efficiency of the Langmuir
parametric decay. We thus conclude that the observed depletion of the
type III radio emission is independent of the radio emission mechanism,
as long as it depends on the Langmuir amplitude and coherence.
---------------------------------------------------------
Title: Low frequency radioastronomy of the inner heliosphere: the
way forward.
Authors: Cecconi, Baptiste; Zarka, Philippe; Bergman, Jan; Falcke,
Heino; Boonstra, Albert-Jan; Briand, Carine; Girard, Julien; Klein
Wolt, Marc; Baan, Willem; Segret, Boris; Maksimovic, Milan
2014cosp...40E.468C Altcode:
Low frequency radioastronomy observatories for the heliosphere have
been using similar instrumentation for decades. The Cassini, STEREO,
and the future Solar Orbiter mission are embarking goniopolarmetric
radio receiver connected to 3 electric antennas. Such instrument
provides the spectral matrix (or part of it) from which the wave
parameters can be derived. With a point source assumption (plane wave),
we derive the direction of arrival of the wave, the polarization and
the flux density. In case of a spatially extended source (disk shaped,
with a given radial profile), the source centroid direction and the
apparent source size is provided. This type of instrumentation cannot
provide much more parameters, as there is a maximum of to 9 independent
measurements for each time-frequency step. We propose a concept of
radioastronomy instrumentation using a swarm of small satellites
(possibly cubesats) with sensitive radio receivers measuring the wave
front and phase of the radio waves on each spacecraft. This instrument
will also provide 3-dimensional interferometric measurement. Such
resolved imaging capabilities of the inner heliosphere would be a
real step forward to better understand the radio emissions mechanisms
and the propagation processes. We will present the various existing
projects and the roadmap to reach the goal.
---------------------------------------------------------
Title: Decameter type III bursts with positive and negative frequency
drift rates
Authors: Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.; Briand,
C.; Dorovskyy, V. V.; Zarka, P.; Frantzusenko, A. V.; Rucker, H. O.;
Rutkevych, B. P.; Panchenko, M.; Zaqarashvili, T.; Shergelashvili, B.
2013EPSC....8..738M Altcode:
We report about observations of decameter type III bursts
whose frequency drift rates vary their signs from negative to
positive. Moreover drift rates of some bursts vary the sign some
times. Positive drift rates for some bursts are changed from 0.44
MHz/s to 12 MHz/s. At the same time the negative drift rates of these
bursts are standard values for decameter type III bursts. A possible
interpretation of such phenomenon on the base of plasma mechanism of
type III burst generation is discussed. The sense of this interpretation
is that group velocity of type III electromagnetic waves generated
by fast electrons at some conditions can be smaller than velocity of
these electrons.
---------------------------------------------------------
Title: Synchronized observations by using the STEREO and the largest
ground-based decametre radio telescope
Authors: Konovalenko, A. A.; Stanislavsky, A. A.; Rucker, H. O.;
Lecacheux, A.; Mann, G.; Bougeret, J. -L.; Kaiser, M. L.; Briand, C.;
Zarka, P.; Abranin, E. P.; Dorovsky, V. V.; Koval, A. A.; Mel'nik,
V. N.; Mukha, D. V.; Panchenko, M.
2013ExA....36..137K Altcode: 2013ExA...tmp....5K; 2013ExA...tmp....8K
We consider the approach to simultaneous (synchronous) solar
observations of radio emission by using the STEREO-WAVES instruments
(frequency range 0.125-16 MHz) and the largest ground-based
low-frequency radio telescope. We illustrate it by the UTR-2 radio
telescope implementation (10-30 MHz). The antenna system of the
radio telescope is a T-shape-like array of broadband dipoles and is
located near the village Grakovo in the Kharkiv region (Ukraine). The
third observation point on the ground in addition to two space-based
ones improves the space-mission performance capabilities for the
determination of radio-emission source directivity. The observational
results from the high sensitivity antenna UTR-2 are particularly useful
for analysis of STEREO data in the condition of weak event appearances
during solar activity minima. In order to improve the accuracy of flux
density measurements, we also provide simultaneous observations with
a large part of the UTR-2 radio telescope array and its single dipole
close to the STEREO-WAVES antennas in sensitivity. This concept has
been studied by comparing the STEREO data with ground-based records
from 2007-2011 and shown to be effective. The capabilities will be
useful in the implementation of new instruments (LOFAR, LWA, MWA,
etc.) and during the future Solar Orbiter mission.
---------------------------------------------------------
Title: Decametric type III bursts with variable sign of frequency
drift rate
Authors: Melnik, V. M.; Brazhenko, A. I.; Konovalenko, O. O.; Briand,
C.; Rutkevych, B. P.; Zarka, P.; Zaqarashvili, T.; Dorovskyy, V. V.;
Frantsuzenko, A. V.; Stanislavsky, A. A.
2013RRPRA..18..117M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational properties of decameter type IV bursts
Authors: Melnik, Valentin; Brazhenko, Anatoly; Rucker, Helmut;
Konovalenko, Alexander; Briand, Carine; Dorovskyy, Vladimir; Zarka,
Philippe; Frantzusenko, Anatoly; Panchenko, Michael; Poedts, Stefan;
Zaqarashvili, Teimuraz; Shergelashvili, Bidzina
2013EGUGA..1510206M Altcode:
Oscillations of decameter type IV bursts were registered during
observations of solar radio emission by UTR-2, URAN-2 and NDA in
2011-2012. Large majority of these bursts were accompanied by coronal
mass ejections (CMEs), which were observed by SOHO and STEREO in the
visible light. Only in some cases decameter type IV bursts were not
associated with CMEs. The largest periods of oscillations P were some
tens of minutes. There were some modes of long periods of oscillations
simultaneously. Periods of oscillations in flux and in polarization
profiles were close. Detailed properties of oscillations at different
frequencies were analyzed on the example of two type IV bursts. One of
them was observed on April 7, 2011 when a CME happened. Another one
(August 1, 2011) was registered without any CME. The 7 April type IV
burst had two periods in the frames 75-85 and 35-85 minutes. Interesting
feature of these oscillations is decreasing periods with time. The
observed decreasing rates dP/dt equaled 0.03-0.07. Concerning type
IV burst observed on August 1, 2011 the period of its oscillations
increases from 17 min. at 30 MHz to 44 min. at 10 MHz. Connection of
type IV burst oscillations with oscillations of magnetic arches and
CMEs at corresponding altitudes are discussed. The work is fulfilled
in the frame of FP7 project "SOLSPANET".
---------------------------------------------------------
Title: Planetary and exoplanetary low frequency radio observations
from the Moon
Authors: Zarka, P.; Bougeret, J. -L.; Briand, C.; Cecconi, B.;
Falcke, H.; Girard, J.; Grießmeier, J. -M.; Hess, S.; Klein-Wolt,
M.; Konovalenko, A.; Lamy, L.; Mimoun, D.; Aminaei, A.
2012P&SS...74..156Z Altcode:
We analyze the planetary and exoplanetary science that can be carried
out with precursor as well as future low frequency radio instruments on
the Moon, assessing the limiting noise sources, comparing them to the
average and peak spectra of all planetary radio components as they will
be seen from the Lunar surface or orbit. We identify which objectives
will be accessible with each class of instrument, and discuss the
interest of these observations compared to observations by planetary
probes and to ground-based observations by large low-frequency radio
arrays. The interest of goniopolarimetry is emphasized for pathfinder
missions.
---------------------------------------------------------
Title: Simultaneous observations of solar sporadic radio emission
by the radio telescopes UTR-2, URAN-2 and NDA within the frequency
range 8-42 MHz
Authors: Melnik, V.; Konovalenko, A.; Brazhenko, A.; Briand, C.;
Dorovskyy, V.; Zarka, P.; Denis, L.; Bulatzen, V.; Frantzusenko, A.;
Rucker, H.; Stanislavskyy, A.
2012epsc.conf..540M Altcode: 2012espc.conf..540M
From 25 June till 12 August 2011 sporadic solar radio emission was
observed simultaneously by three separate radio telescopes: UTR-2
(Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay,
France). During these observations some interesting phenomena were
observed. Some of them are discussed in this paper.
---------------------------------------------------------
Title: Radio Astronomy from the Moon
Authors: Cecconi, Baptiste; Bougeret, J. -L.; Zarka, Philippe; Thide,
Bo; Bergman, Jan; Falcke, Heino; Berthelier, Jean-Jacques; Gurvits,
Leonid; Griessmeier, Jean-Mathias; Briand, Carine; Zaslavsky, Arnaud;
Roettgering, Huub; Aminaei, A.; Klein-Wolt, Marc; Konovalenko,
Alexander; Woan, Graham; Garrett, Mike; Gizani, Nectaria
2012cosp...39..282C Altcode: 2012cosp.meet..282C
No abstract at ADS
---------------------------------------------------------
Title: Commission 49: Interplanetary Plasma and Heliosphere
Authors: Gopalswamy, Natchimuthuk; Mann, Ingrid; Bougeret, Jean-Louise;
Briand, Carine; Lallement, Rosine; Lario, David; Manoharan, P. K.;
Shibata, Kazunari; Webb, David F.
2012IAUTA..28...95G Altcode:
Commission 49 (Interplanetary Plasma and Heliosphere) is part of
IAU Division II (Sun and Heliosphere). The research topics include
large-scale solar disturbances such as coronal mass ejections (CMEs),
shocks, and corotating interaction regions (CIRs) propagating into
the heliosphere. The disturbances propagate through the solar wind,
which essentially defines the heliosphere. The solar disturbances
provide large-scale laboratory to study plasma processes over various
time and spatial scales, the highest spatial scale being the size
of the heliosphere itself (~100 AU). These solar disturbances are
related to solar activity in the form of active regions and coronal
holes. Solar eruptions are accompanied by particle acceleration and
the particles can be hazardous to life on earth in various ways from
modifying the ionosphere to damaging space technology and increasing
lifetime radiation dosage to astronauts and airplane crew. Particle
acceleration in solar eruptions poses fundamental physics questions
because the underlying mechanisms are not fully understood. One of
important processes is the particle acceleration by shocks, which occurs
throughout the heliosphere. The heliosphere has both neutral and ionized
material, with interesting interaction between the two components.
---------------------------------------------------------
Title: Alfvén: magnetosphere—ionosphere connection explorers
Authors: Berthomier, M.; Fazakerley, A. N.; Forsyth, C.; Pottelette,
R.; Alexandrova, O.; Anastasiadis, A.; Aruliah, A.; Blelly, P. -L.;
Briand, C.; Bruno, R.; Canu, P.; Cecconi, B.; Chust, T.; Daglis,
I.; Davies, J.; Dunlop, M.; Fontaine, D.; Génot, V.; Gustavsson,
B.; Haerendel, G.; Hamrin, M.; Hapgood, M.; Hess, S.; Kataria, D.;
Kauristie, K.; Kemble, S.; Khotyaintsev, Y.; Koskinen, H.; Lamy, L.;
Lanchester, B.; Louarn, P.; Lucek, E.; Lundin, R.; Maksimovic, M.;
Manninen, J.; Marchaudon, A.; Marghitu, O.; Marklund, G.; Milan, S.;
Moen, J.; Mottez, F.; Nilsson, H.; Ostgaard, N.; Owen, C. J.; Parrot,
M.; Pedersen, A.; Perry, C.; Pinçon, J. -L.; Pitout, F.; Pulkkinen,
T.; Rae, I. J.; Rezeau, L.; Roux, A.; Sandahl, I.; Sandberg, I.;
Turunen, E.; Vogt, J.; Walsh, A.; Watt, C. E. J.; Wild, J. A.;
Yamauchi, M.; Zarka, P.; Zouganelis, I.
2012ExA....33..445B Altcode: 2011ExA...tmp...35V; 2011ExA...tmp..160B; 2011ExA...tmp..136B
The aurorae are dynamic, luminous displays that grace the night skies
of Earth's high latitude regions. The solar wind emanating from
the Sun is their ultimate energy source, but the chain of plasma
physical processes leading to auroral displays is complex. The
special conditions at the interface between the solar wind-driven
magnetosphere and the ionospheric environment at the top of Earth's
atmosphere play a central role. In this Auroral Acceleration Region
(AAR) persistent electric fields directed along the magnetic field
accelerate magnetospheric electrons to the high energies needed
to excite luminosity when they hit the atmosphere. The "ideal
magnetohydrodynamics" description of space plasmas which is useful in
much of the magnetosphere cannot be used to understand the AAR. The
AAR has been studied by a small number of single spacecraft missions
which revealed an environment rich in wave-particle interactions,
plasma turbulence, and nonlinear acceleration processes, acting on a
variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster
magnetospheric research mission is now fortuitously visiting the AAR,
but its particle instruments are too slow to allow resolve many of
the key plasma physics phenomena. The Alfvén concept is designed
specifically to take the next step in studying the aurora, by making
the crucial high-time resolution, multi-scale measurements in the
AAR, needed to address the key science questions of auroral plasma
physics. The new knowledge that the mission will produce will find
application in studies of the Sun, the processes that accelerate the
solar wind and that produce aurora on other planets.
---------------------------------------------------------
Title: Simultaneous observations of solar sporadic radio emission
by the radio telescopes UTR-2, URAN-2 and NDA within the frequency
range 8-41MHz
Authors: Melnik, V. N.; Konovalenko, A. A.; Rucker, H. O.; Brazhenko,
A. I.; Briand, C.; Dorovskyy, V. V.; Zarka, P.; Denis, L.; Bulatzen,
V. G.; Frantzusenko, A. V.; Stanislavskyy, A. A.
2012EGUGA..14.9905M Altcode:
From 25 June till 12 August 2011 sporadic solar radio emission
was observed simultaneously by three separate radio telescopes:
UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay,
France). During these observations several type II bursts with double
and triple harmonics were registered, as well as type II bursts with
complex herringbone structure. The events of particular interest were
type II bursts registered on 9 and 11 August 2011. These bursts had
opposite sign of circular polarization at different parts of their
dynamic spectra. In our opinion we registered the emissions, which came
from the different parts of the shock propagating through the solar
corona. We have observed also groups of type III bursts merged into
one burst, type III bursts with triple harmonics and type III bursts
with "split" polarization. In addition some unusual solar bursts were
registered: storms of strange narrow-band (up to 500kHz) bursts with
high polarization degree (about 80%), decameter spikes of extremely
short durations (200-300ms), "tadpole-like" bursts with durations of
1-2s and polarization degree up to 60%.
---------------------------------------------------------
Title: New results on interplanetary type III radio storms from
multi-spacecraft combined STEREO-A/B and WIND observations
Authors: Briand, C.; Belyaev, V.; Bougeret, J. H.; Krupar, V.; Bonnin,
X.; Cecconi, B.; Hoang, S.
2011AGUFMSH13A1928B Altcode:
Interplanetary (IP) type III radio storms were intensively studied in
the 80's (Bougeret et al. 1984a,b) using observations from a single
radio instrument on the ISEE-3 spacecraft located at the Lagrange
point L1. These studies showed that the IP storms trace long lasting
(several days) streams of energetic electrons occurring in corotating
regions of enhanced density, appearing to be the extension of active
regions through the IP space at levels 0.05 - 0.8 AU. These studies
were consistent with the hypothesis of steady conditions in the storm
region over periods of several days. We propose the hypothesis that the
overall duration of an IP storm observed from one vantage point directly
results from the beaming of the radio radiation when the steady radio
source corotates with the Sun. The goal of the present study is to
track the evolution of the IP radio storms observed from three vantage
points separated by about 90 degrees and spanning 180 degrees (STEREO-B,
WIND, STEREO-A), over a time period of the order of a solar rotation,
in order to test the limits of the above hypothesis and to track the
evolution of the IP radio storms over periods close to a solar rotation.
---------------------------------------------------------
Title: Observations of Langmuir ponderomotive effects using the
Solar TErrestrial RElations Observatory spacecraft as a density probe
Authors: Henri, P.; Meyer-Vernet, N.; Briand, C.; Donato, S.
2011PhPl...18h2308H Altcode:
Langmuir ponderomotive effects are nonlinear effects that enable
to couple the electron and ion dynamics in space plasmas. The main
difficulty to provide observational evidence of such nonlinear coupling
is to simultaneously observe both fluctuations of plasma density
and electric field. We have thus developed a new method to measure
and to calibrate in situ small scale density fluctuations. Density
fluctuations in the solar wind are measured using the observed
quasistatic fluctuations of the STEREO spacecraft floating
potential in the frequency range, where the spacecraft floating
potential is in quasistatic equilibrium between photoionization
and electron attachment, whereas the potential of the antenna,
of much longer equilibrium time scale, is blind to the density
fluctuations. Density fluctuations and Langmuir waves are thus
directly and simultaneously measured using a dataset of more than
three years of STEREO/WAVES measurements. We present here the first
observational evidence for ponderomotive effects in the solar wind that
nonlinearly couple density fluctuations to high energy Langmuir waves
((ɛ<SUB>0</SUB>E<SUP>2</SUP>)/(nk<SUB>B</SUB>T)>10<SUP>-4</SUP>).
---------------------------------------------------------
Title: Waves at the electron plasma frequency associated with solar
wind magnetic holes: STEREO/Cluster observations
Authors: Briand, C.; Soucek, J.; Henri, P.; Mangeney, A.
2010JGRA..11512113B Altcode:
Magnetic depressions are common structures of the interplanetary
medium. These magnetic holes can be just isolated dips of the amplitude
of the field or they can be associated with discontinuities in the
field orientation (tangential or rotational). Electrostatic waves
at the plasma frequency (Langmuir waves) are often observed in these
magnetic structures. The aim of the present paper is to provide the
main characteristics of these waves and to propose a mechanism to
explain their formation. The study is based on a statistical analysis
of observations performed by STEREO (between March 2007 and August
2009) and Cluster (between 2002 and 2005) when each mission was in
the free solar wind. Complementary information is provided by the
two missions through the different instrumental configurations. We
first provide new characteristics of the waves (polarization, energy,
spectrum, occurrence). We then show that the occurrence of Langmuir
waves activity inside a hole is closely linked to the presence of a
significant electron strahl outside the hole. Finally, we propose a
scenario for the generation of the Langmuir waves inside the holes.
---------------------------------------------------------
Title: Temporal Evolution of the Solar-Wind Electron Core Density
at Solar Minimum by Correlating SWEA Measurements from STEREO A and B
Authors: Opitz, A.; Sauvaud, J. -A.; Fedorov, A.; Wurz, P.; Luhmann,
J. G.; Lavraud, B.; Russell, C. T.; Kellogg, P.; Briand, C.; Henri,
P.; Malaspina, D. M.; Louarn, P.; Curtis, D. W.; Penou, E.; Karrer,
R.; Galvin, A. B.; Larson, D. E.; Dandouras, I.; Schroeder, P.
2010SoPh..266..369O Altcode: 2010SoPh..tmp..152O
The twin STEREO spacecraft provide a unique tool to study the
temporal evolution of the solar-wind properties in the ecliptic since
their longitudinal separation increases with time. We derive the
characteristic temporal variations at ∼ 1 AU between two different
plasma parcels ejected from the same solar source by excluding
the spatial variations from our datasets. As part of the onboard
IMPACT instrument suite, the SWEA electron experiment provides the
solar-wind electron core density at two different heliospheric vantage
points. We analyze these density datasets between March and August
2007 and find typical solar minimum conditions. After adjusting for
the theoretical time lag between the two spacecraft, we compare the
two density datasets. We find that their correlation decreases as
the time difference increases between two ejections. The correlation
coefficient is about 0.80 for a time lag of a half day and 0.65 for two
days. These correlation coefficients from the electron core density are
somewhat lower than the ones from the proton bulk velocity obtained in
an earlier study, though they are still high enough to consider the
solar wind as persistent after two days. These quantitative results
reflect the variability of the solar-wind properties in space and time,
and they might serve as input for solar-wind models.
---------------------------------------------------------
Title: Vlasov-Poisson simulations of electrostatic parametric
instability for localized Langmuir wave packets in the solar wind
Authors: Henri, P.; Califano, F.; Briand, C.; Mangeney, A.
2010JGRA..115.6106H Altcode: 2013arXiv1301.5155H; 2010JGRA..11506106H
Recent observation of large-amplitude Langmuir waveforms during a type
III event in the solar wind has been interpreted as the signature of
the electrostatic decay of beam-driven Langmuir waves. This mechanism
is thought to be a first step to explain the generation of type III
radio emission. The threshold for this parametric instability in
the typical solar wind condition has been investigated through 1D-1V
Vlasov-Poisson simulations. We show that the amplitude of the observed
Langmuir beatlike waveforms is of the order of the effective threshold
computed from the simulations. The expected levels of associated ion
acoustic density fluctuations have also been computed for comparison
with observations.
---------------------------------------------------------
Title: Waves at the plasma frequency inside magnetic holes: STEREO
and Cluster observations
Authors: Briand, C.; Soucek, J.; Mangeney, A.; Bale, S. D.; Goetz, K.
2010AIPC.1216..271B Altcode:
Magnetic isolated large amplitude depressions in the interplanetary
magnetic field are commonly observed in the solar wind. Some of these
magnetic structures are accompanied by bursts of electrostatic waves
close to electron plasma frequency. Combining STEREO/WAVES and IMPACT
data we are able to accurately localize the waves emission. We show
that they also appear inside kinetic holes, themselves situated inside
larger holes. We provide, for the first time, the detailed waveform
of the waves that reveal their very bursty nature. These results are
complemented by CLUSTER data, which allow to resolve the electron
distribution and obtain a better description of spatio-temporal
variations in Langmuir wave activity. Such observations are confronted
to different emission mechanisms.
---------------------------------------------------------
Title: Vlasov simulations of Langmuir Electrostatic Decay and
consequences for Type III observations
Authors: Henri, P.; Califano, F.; Briand, C.; Mangeney, A.
2010AIPC.1216..288H Altcode: 2013arXiv1301.3066H
The electrostatic decay enables energy transfer from a finite amplitude
Langmuir to a backscattered daughter Langmuir wave and ion acoustic
density fluctuations. This mechanism is thought to be a first step
for the generation of type III solar radio emissions at twice the
plasma frequency. The electrostatic decay is here investigated through
Vlasov-Poisson simulations by considering Langmuir localized wave
packets in the case T<SUB>e</SUB> = T<SUB>p</SUB>. Simulation results
are found to be in good agreement with recently reported observations
from the STEREO mission of the electrostatic decay of beam-driven
Langmuir waves during a type III burst.
---------------------------------------------------------
Title: Vlasov simulations of strong Langmuir turbulence
Authors: Henri, P.; Mangeney, A.; Califano, F.; Briand, C.
2009AGUFMSH53A1304H Altcode:
Strong Langmuir turbulence describes the evolution of intense and
coherent electric fields that couple to the ion background, in an
unmagnetized plasma. It is of common interest in ionospheric physics
and laboratory plasmas and may be of great relevance in space physics
where electric fields are high (shocks, early stage of type III). Strong
Langmuir turbulence has been intensively studied for more than three
decades by using the Zakharov equations that couple the evolution
of the enveloppe of the high frequency electric field and the plasma
density. These have successfully described self-focusing and collapse
of intense Langmuir fluctuations, as well as the formation of density
cavitons. However, the fluid like approximation underlying the Zakharov
equations breaks out when the electric field gets close to the electron
thermal energy, what commonly happens at the end of the Langmuir
collapse. In this case, a kinetic approach has to be considered for
the study of the long time evolution of strong turbulence, including in
particular the kinetic effects on heated particules and the ion fluid
nonlinearities. We perform 1D and 2D Vlasov-Poisson simulations with
periodic boundary conditions to investigate strong Langmuir turbulence
in an unmagnetized plasma. We observe self-focusing of Langmuir waves
and formation of cavitons. We also analyse the difference between
1D and 2D strong Langmuir turbulence. A special emphasis is given
to electronic kinetic effects and proton dynamics to illustrate the
discrepancies with the Zakharov model.
---------------------------------------------------------
Title: Microscale properties of Langmuir waves observed by STEREO
and CLUSTER inside solar wind magnetic holes
Authors: Soucek, J.; Briand, C.; Mangeney, A.; Bale, S.; Goetz, K.;
Pickett, J. S.
2009AGUFMSH13B1527S Altcode:
Magnetic holes, solitary large amplitude depressions in the
interplanetary magnetic field, are commonly observed in the solar
wind. Some of these magnetic structures are accompanied by bursts of
electrostatic waves close to the electron plasma frequency localized
inside the magnetic holes. In this study we used data from the S/WAVES
instrument on board of the STEREO spacecraft to demonstrate the first
waveform observations of these waves and to analyze their polarization
and modulation. The results are complemented by multi-spacecraft
Cluster observations of these phenomena, which allow to resolve the
electron distribution and obtain a better description of spatio-temporal
variations in Langmuir wave activity. Comparing to previous studies of
this phenomenon, the high resolution of the data allows to study the
structure of these waves at electron scales. We present a detailed
analysis of several observed magnetic holes and discuss possible
mechanisms responsible for excitation of these waves.
---------------------------------------------------------
Title: Direct evidence for three-wave coupling in the solar wind
during a type~III emission from STEREO/SWAVES data.
Authors: Henri, P.; Briand, C.; Califano, F.; Mangeney, A.
2009epsc.conf...50H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Preface to the Proceedings of the European General Assembly
on IHY 2007
Authors: Briand, C.; Antonucci, E.; Haubold, H. J.
2009EM&P..104....1B Altcode: 2009EM&P..tmp....3B
No abstract at ADS
---------------------------------------------------------
Title: Evidence for wave coupling in type III emissions
Authors: Henri, P.; Briand, C.; Mangeney, A.; Bale, S. D.; Califano,
F.; Goetz, K.; Kaiser, M.
2009JGRA..114.3103H Altcode: 2009JGRA..11403103H
Using new capabilities of waveform analyses provided by the S/WAVES
instruments onboard the two STEREO spacecraft, we present for the first
time a complete set of direct evidence for three-wave coupling occurring
during a type III emission and involving two Langmuir waves and an
ion acoustic wave. Information on the Doppler-shifted frequencies and
especially the phases of the waves are used in order to check first
the conservation of momentum and energy, through Fourier analyses,
and second the phase locking between the waves, through bicoherence
analyses. Wavelet analyses allow us to resolve for the first time the
coupling regions, in which spatial length is estimated to be 18 +/- 5
km. The wave packets travel at comparable speed, and the characteristic
available interaction time is about 1 s. Interpretations of the phase
coupling and evaluation of the growth rate of the waves tend to favor
the parametric decay, at least in the observational events considered
in this work.
---------------------------------------------------------
Title: Bipolar electrostatic structures observed in the solar wind :
comparative study between WIND/WAVES and STEREO/WAVES
Authors: Briand, C.; Califano, F.; Mangeney, A.; Henri, P.; Bale,
S. D.; Goetz, K.; Kaiser, M.
2008AGUFMSH43A1636B Altcode:
Bipolar electrostatic structures are commonly observed in planetary
magnetospheric environments but also in the solar wind. They may play a
crucial role in transporting energy over long distances. In an earlier
work, Mangeney et al. (1998) and Lacombe et al. (2002) have shown,
in the solar wind, the presence of a small potential drop across the
structures. This work was based on in-situ measurements obtained by the
WAVES radio instrument of the WIND mission. The STEREO/WAVES instruments
provide us with new in-situ measurements of bipolar electrostatic
structures. We will present a comparative study of the observations
from the three instruments. A model based on Vlasov-Ampere simulations
will be proposed to explain the differences between the measurements
of the two instruments.
---------------------------------------------------------
Title: Electrostatic coupling: STEREO/WAVES observations in the
solar wind and Vlasov simulations.
Authors: Henri, P.; Califano, F.; Briand, C.; Mangeney, A.; Bale,
S. D.; Goetz, K.; Kaiser, M.
2008AGUFMSH21A1566H Altcode:
The TDS (Time Domain Sampler) part of the WAVES experiment on board
STEREO enables the study of high resolution in-situ electric field
waveforms in the solar wind. From different TDS datasets, we show
evidence for three-wave coupling, involving Langmuir waves and ion
acoustic waves. The three waves show the expected resonant relations
for doppler-shifted frequencies and bicoherence studies show a good
phase locking between the three waves. Vlasov-Ampere simulations have
also been performed to study the electrostatic coupling mechanism in
1D and compared to the STEREO/WAVES observations.
---------------------------------------------------------
Title: Faint solar radio structures from decametric observations
Authors: Briand, C.; Zaslavsky, A.; Maksimovic, M.; Zarka, P.;
Lecacheux, A.; Rucker, H. O.; Konovalenko, A. A.; Abranin, E. P.;
Dorovsky, V. V.; Stanislavsky, A. A.; Melnik, V. N.
2008A&A...490..339B Altcode:
Aims: Decameter radio observations of the solar corona reveal the
presence of numerous faint frequency drifting emissions, similar to
“solar S bursts” which are reported in the literature. We present
a statistical analysis of the characteristics of these emissions and
propose a mechanism to excite the Langmuir waves thought to be at
the origin of these emissions. <BR />Methods: The observations were
performed between 1998 and 2002 with the Digital Spectro Polarimeter
(DSP) receivers operated at the UTR-2 and Nançay decameter radio
telescopes in the frequency range 15-30 MHz. Our theoretical
explanation is based on Vlasov-Ampère simulations. <BR />Results:
Based on the frequency drift rate, three populations of structures can
be identified. The largest population presents an average negative
frequency drift of -0.9 MHz s<SUP>-1</SUP> and a lifetime up to 11
s (median value of 2.72 s). A second population shows a very small
frequency drift of -0.1 MHz s<SUP>-1</SUP> and a short lifetime of
about 1 s. The third population presents an average positive frequency
drift of +0.95 MHz s<SUP>-1</SUP> and a lifetime of up to 3 s. Also,
the frequency drift as a function of frequency is consistent with the
former results, which present results in higher frequency range. No
specific relationship was found between the occurrence of these
emissions and the solar cycle or presence of flares. Assuming that these
emissions are produced by “electron clouds” propagating the solar
corona, we deduce electron velocities of about 3-5 times the electron
thermal velocity. As previously shown, a localized, time-dependent
modulation of the electron distribution function (heating) leads to
low velocity electron clouds (consistent with observations), which,
in turn, can generate Langmuir waves and electromagnetic signals by
nonlinear processes.
---------------------------------------------------------
Title: Eigenmode Structure in Solar-Wind Langmuir Waves
Authors: Ergun, R. E.; Malaspina, D. M.; Cairns, Iver H.; Goldman,
M. V.; Newman, D. L.; Robinson, P. A.; Eriksson, S.; Bougeret, J. L.;
Briand, C.; Bale, S. D.; Cattell, C. A.; Kellogg, P. J.; Kaiser, M. L.
2008PhRvL.101e1101E Altcode:
We show that observed spatial- and frequency-domain signatures of
intense solar-wind Langmuir waves can be described as eigenmodes
trapped in a parabolic density well. Measured solar-wind electric
field spectra and waveforms are compared with 1D linear solutions and,
in many cases, can be represented by 1 3 low-order eigenstates. To
our knowledge, this report is the first observational confirmation
of Langmuir eigenmodes in space. These results suggest that linear
eigenmodes may be the starting point of the nonlinear evolution,
critical for producing solar type II and type III radio bursts.
---------------------------------------------------------
Title: Coherent electric structures: Vlasov-Ampère simulations and
observational consequences
Authors: Briand, C.; Mangeney, A.; Califano, F.
2008JGRA..113.7219B Altcode:
Coherent electrostatic structures, like bipolar electric pulses
(also called electrostatic solitary waves) or Langmuir waves,
are frequently observed in many astrophysical plasma of the Earth
environment (plasma sheet boundary layer, Earth bow shock, auroral
regions etc.) or in the solar wind. They are thought to play a
crucial role in the energy transfer from small to large scale and
to reconnection processes. Numerous simulations have studied their
emergence and evolution. Most of them are based on the development
of two stream instabilities. Another mechanism is investigated here:
the plasma is excited by a localized, time dependent modulation of
the electron distribution function (heating of the electrons). The
investigation is performed through a 1D Vlasov-Ampere code, in open
boundary conditions. We explore the response of the plasma to several
heating conditions, mass ratio and density gradient. We find that the
heating leads to the development of an extended turbulent domain. We
also show that the history of the electrostatic solitary waves (ESW)
strongly depends on the presence of a density gradient and the mass
ratio between species. If the positive charged neutralizing background
is composed of heavy ions, the ESW turns back to the entrance domain
when a density gradient is included. From the observational point of
view, this means that the electric field shows a polarity reversal
with time.
---------------------------------------------------------
Title: S/WAVES: The Radio and Plasma Wave Investigation on the
STEREO Mission
Authors: Bougeret, J. L.; Goetz, K.; Kaiser, M. L.; Bale,
S. D.; Kellogg, P. J.; Maksimovic, M.; Monge, N.; Monson, S. J.;
Astier, P. L.; Davy, S.; Dekkali, M.; Hinze, J. J.; Manning, R. E.;
Aguilar-Rodriguez, E.; Bonnin, X.; Briand, C.; Cairns, I. H.; Cattell,
C. A.; Cecconi, B.; Eastwood, J.; Ergun, R. E.; Fainberg, J.; Hoang,
S.; Huttunen, K. E. J.; Krucker, S.; Lecacheux, A.; MacDowall, R. J.;
Macher, W.; Mangeney, A.; Meetre, C. A.; Moussas, X.; Nguyen, Q. N.;
Oswald, T. H.; Pulupa, M.; Reiner, M. J.; Robinson, P. A.; Rucker,
H.; Salem, C.; Santolik, O.; Silvis, J. M.; Ullrich, R.; Zarka, P.;
Zouganelis, I.
2008SSRv..136..487B Altcode: 2008SSRv..tmp....9B
This paper introduces and describes the radio and plasma wave
investigation on the STEREO Mission: STEREO/WAVES or S/WAVES. The
S/WAVES instrument includes a suite of state-of-the-art experiments
that provide comprehensive measurements of the three components of the
fluctuating electric field from a fraction of a hertz up to 16 MHz, plus
a single frequency channel near 30 MHz. The instrument has a direction
finding or goniopolarimetry capability to perform 3D localization
and tracking of radio emissions associated with streams of energetic
electrons and shock waves associated with Coronal Mass Ejections
(CMEs). The scientific objectives include: (i) remote observation and
measurement of radio waves excited by energetic particles throughout
the 3D heliosphere that are associated with the CMEs and with solar
flare phenomena, and (ii) in-situ measurement of the properties of
CMEs and interplanetary shocks, such as their electron density and
temperature and the associated plasma waves near 1 Astronomical Unit
(AU). Two companion papers provide details on specific aspects of the
S/WAVES instrument, namely the electric antenna system (Bale et al.,
Space Sci. Rev., 2007) and the direction finding technique (Cecconi
et al., Space Sci. Rev., 2007).
---------------------------------------------------------
Title: International Heliophysical Year: European Activities
Authors: Briand, C.
2007SunGe...2....5B Altcode:
The First European General Assembly of the "International Heliophysical
Year" (IHY) took place at the headquarters of the Centre Nationial
de la Recherche Scientifique (CNRS) in Paris, France, 10-13 January
2006. There were 113 participants representing 27 nations. The
science concerned with the International Heliophysical Year programme
was first illustrated. Then, the status of current instruments as
well as practical information on the campaign management policy was
given. Twenty European National Coordinators described the progress
of their IHY activities. Representatives from Egypt, Angola and the
coordinator of the Balkan, Black and Caspian Sea Region also reported
on the progress of IHY activities in their respective regions. People
from the IHY Secretariat provided a summary of the global IHY efforts
including the United Nations Basic Space Sciences Program. In the
education and public outreach front, a variety of activities have been
planned: TV and radio shows, board games on space weather, specific
programmes for schools and universities, workshops for teachers are some
of the actions that were presented by the delegates. Beyond of these
national and individual initiatives, specific activities requiring
European coordination were discussed. This paper provides an extended
summary of the main talks and discussions that held during the meeting.
---------------------------------------------------------
Title: First Results of the S/WAVES Experiment on the STEREO Mission.
Authors: Bonnin, X.; Maksimovic, M.; Bougeret, J. -L.; Goetz, K.;
Bale, S. D.; Kaiser, M. L.; Reiner, M. J.; Cecconi, B.; Briand, C.;
Krucker, S.; S/Waves Team
2007sf2a.conf..582B Altcode:
We present the first results of the STEREO/Waves (S/Waves) investigation
on the STEREO Mission. The S/Waves instrument includes a suite of
state-of-the-art sub-instruments that provide comprehensive measurements
of the three components of the electric field from a fraction of a
Hertz up to 16 MHz, plus a single frequency channel near 30 MHz. The
instrument has a direction finding or goniopolarimetry capability,
used to perform 3-D localization and tracking of streams of energetic
electrons and of shock waves associated with Coronal Mass Ejections
(CMEs). The scientific objectives include (i) remote observation and
measurement of energetic phenomena throughout the 3-D heliosphere
that are associated with the CMEs and with solar flare phenomena,
and (ii) in-situ measurement of the properties of CMEs, such as their
electron density and temperature and the associated plasma waves near
1 Astronomical Unit.
---------------------------------------------------------
Title: T he Faint Drifting Decameter Radio Bursts From The Solar
Corona
Authors: Briand, C.; Zaslavsky, A.; Lecacheux, A.; Zarka, P.;
Maksimovic, M.; Mangeney, A.
2007ESASP.641E..56B Altcode:
The radio observations of solar corona at decameter wavelengths reveal
the presence of numerous faint, frequency drifting structures. We
analyse observations performed on July 13th , 2002 with the DSP
wideband spectrometer instrument implemented at the UTR-2 radiote-
lescope. The main characteristics of these structures are statistically
studied. Three populations of bursts are iden- tifies. The largest
one presents negative frequency drifts of about -0.89 MHz.s-1 and a
lifetime extending up to 11 sec (median value 2.72 sec). A second one
shows positive frequency drifts of about +0.95 MHz.s-1 and a life- time
extending up to 3 sec. The last population consists in structures with
very small frequency drifts of about -0.1 MHz.s-1 and a shorter lifetime
(about 1 sec). Assuming that those emissions are the signature of elec-
tron beams propagating through the solar corona, we deduce that they
have a velocity of about 3-5 times the electron thermal velocity. A
new mechanism is proposed to explain the formation of plasma waves with
such low beam velocity: spatially localized, temporal fluctuations of
the electron distribution function width (heating).
---------------------------------------------------------
Title: Science Plans for the International Heliophysical Year
Authors: Davila, J. M.; Gopalswamy, N.; Harrison, R. A.; Stamper,
R.; Briand, C.; Potgieter, M. S.
2006AGUSM.U34A..04D Altcode:
On October 4, 1957, only 53 years after the beginning of flight in Kitty
Hawk, the launch of Sputnik 1 marked the beginning of the space age;
as mankind took the first steps to leaving the protected environment of
Earth's atmosphere. Discovery of the radiation belts, the solar wind,
and the structure of Earth's magnetosphere prepared the way for the
inevitable human exploration to follow. Soon, Cosmonauts and Astronauts
orbited Earth, and then in 1969, Astronauts landed on the Moon. Today
a similar story is unfolding, the spacecraft Voyager has crossed the
termination shock, and will soon leave the heliosphere. For the first
time, man will begin to explore the local interstellar medium. It is
inevitable that, during the next 50 years, exploration of the solar
system including the Moon, Mars and the outer planets will be the
focus of the space program, and like 50 years ago, unmanned probes
will lead the way, followed by human exploration. The International
Geophysical Year (IGY) of 1957, a broad-based and all-encompassing
effort to push the frontiers of geophysics, resulted in a tremendous
increase of knowledge in space physics, Sun-Earth Connection, planetary
science and the heliosphere in general. Now, 50 years later, we have
the unique opportunity to further advance our knowledge of the global
heliosphere and its interaction with the interstellar medium through
the International Heliophysical Year (IHY) in 2007, and to raise
public awareness of space physics. This presentation will focus on
global science planning efforts and campaigns for all participating
IHY nations.
---------------------------------------------------------
Title: Mercury Transit for Stray Light Evaluation: IPM-THEMIS Case
Authors: Briand, C.; Mattig, W.; Ceppatelli, G.; Mainella, G.
2006SoPh..234..187B Altcode:
Mercury's transit on the solar disk offers ideal conditions to determine
the stray light level of instruments. We present here the results on the
stray light level deduced from the observation of the Mercury transit
on 2003 May 7th at the secondary focus of the THEMIS telescope with the
broad-band and spectral channels of the IPM instrument. The scattered
light in the broad-band channel is about 17% and about 25% in the
spectral channel. The spread function was deduced for the two channels
taking into account the observations on the limb and on Mercury's disk.
---------------------------------------------------------
Title: IHY Science and Organization in Europe
Authors: Bougeret, J. -L.; Briand, C.; Bonet Navaro, J. A.; Breen,
A.; Candidi, M.; Georgevia, K.; Harrison, R.; Marsden, R.; Schmieder,
B.; von Steiger, R.
2006cosp...36.3226B Altcode: 2006cosp.meet.3226B
We present the scientific and organizational approach to the
International Heliophysical Year in Europe A summary is given of the
First European General Assembly of the IHY that was held in Paris in
January 2006 Initiatives and expected returns are described
---------------------------------------------------------
Title: Variable Coronal Heating and Beam Formation
Authors: Briand, C.; Mangeney, A.; Califano, F.
2005ESASP.600E..81B Altcode: 2005ESPM...11...81B; 2005dysu.confE..81B
No abstract at ADS
---------------------------------------------------------
Title: The Detection of Photospheric Impacts from Chromospheric
Impulsive Events
Authors: Moretti, P. F.; Berrilli, F.; Sebastianelli, A.; Briand,
C.; Pietropaolo, E.
2003ApJ...589L.109M Altcode:
Multiwavelength solar observations were carried out at the THEMIS
telescope in order to investigate the propagation of the plasma jets
during and after a flare occurrence. The data obtained in the Hα,
Na I D2, and Fe I 557.6 nm lines show that the perturbations detected
in the higher layers due to a B-class flare do penetrate down to
the photosphere. The observational evidence of such perturbations is
crucial for the identification of the source of the solar oscillations.
---------------------------------------------------------
Title: Chromospheric polarity reversal on sunspots: New insight
from spectro-polarimetric measurements
Authors: Briand, C.; Vecchio, A.
2003A&A...403L..33B Altcode:
We present here spectro-polarimetric observations of chromospheric
and photospheric lines on an active region. We show that the presence
of polarity reversal between photosphere and chromosphere cannot be
detected relying on magnetograms and broad band and even narrow band
filters only. We demonstrate that opposite signs in CaII magnetograms in
sunspots compare to photospheric magnetograms are not due to a reversal
of the magnetic field, but rather due to the presence of line core
emission as suggested from theoretical arguments by Sánchez Almeida
(\cite{Sanchez97}).
---------------------------------------------------------
Title: Phase diversity at THEMIS : first implementation
Authors: Del Moro, D.; Criscuoli, S.; Bonet, J. A.; Márquez, I.;
Lemen, C.; Briand, C.
2003MmSAI..74..811D Altcode:
Phase diversity techniques actually provide robust post-processing
methods to restore solar images degraded by seeing-optical
aberrations. We present preliminary results of the application of a
Partitioned Phase-Diverse Speckle (PPDS) technique at THEMIS. The images
have been acquired using the IPM broad-band CCD camera and reduced
using a suitable IDL code. The spectral analysis of unrestored/restored
images shows a significant improvement of image quality, achieving
diffraction limited resolution.
---------------------------------------------------------
Title: Phase diversity at THEMIS : first implementation
Authors: Del Moro, D.; Lemen, C.; Bonet, J. A.; Márquez, I.;
Criscuoli, S.; Briand, C.
2003AN....324..299D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: THEMIS : Status and perspectives
Authors: Ceppatelli, G.; Briand, C.
2003MmSAI..74..790C Altcode:
A brief presentation of the scientific results obtained with THEMIS is
given together with the improvements which are imperative to maintain
THEMIS in the group of the most relevant solar telescopes in the
world. <P />Based on observations made with THEMIS telescope operated
on the island of Tenerife by THEMIS SL in the Spanish Observatorio
del Teide of the Instituto de Astrofisica de Canarias
---------------------------------------------------------
Title: Pointing and tracking analysis of alt-azimuthal multi-focus
telescopes: the THEMIS case
Authors: Mainella, G.; Briand, C.; Maréchal, L.; Le Men, C.
2003AN....324..309M Altcode:
We discuss the pointing and tracking configuration of THEMIS which may
be considered as representative of those alt-azimuthal telescopes with
an optical configuration with multiple focal planes, not all locked to
both the alt-azimuthal coordinates. In the THEMIS case two focal planes
are present. The primary focus F1 is locked to the alt-azimuthal mount,
while the secondary focus F2 (which is used by the instruments), is
only locked to the azimuth angle. The different contributions to the
final accuracy of both absolute pointing and tracking as observed at F2
are defined, and an extimation of the contribution of each component
of the whole chain which affects the field position at F2 (software,
mechanical and optical) is given. The experimental data are the
result of a test campaign carried on at THEMIS in February and March
2002. We can say that (a) for all the used observing configurations,
the tracking accuracy is coherent at any point along the trajectory with
the correspondent absolute pointing accuracy, which is an indication
for the quality of the telescope dynamical performances (b) the main
contribution to the residual field shift which is observed at F2 arises
from the opto-mechanical alignment configuration of the optics between
F1 and F2, which therefore is the crucial point for such multi-focus
configuration. More informations can be found at the official THEMIS
website (http://www.themis.iac.es).
---------------------------------------------------------
Title: Solar activity I: aspects of magnetic activity
Authors: Briand, C.
2003AN....324..357B Altcode:
It is now accepted that the solar activity has direct impact on the
Earth climate, but is also responsible for the geomagnetic storms. It
is thus fundamental to understand the mechanisms responsible for this
activity. We present here first some aspects of the solar activity
at the different atmospheric layers of the sun: active region at
photospheric levels, filaments (prominences) and flares at chromospheric
level and CME's at coronal level. A quick sum-up of the principal
characteristics of each is given as well as the key questions still
under investigation. In the second part, two principal parameters are
presented to describe these features: helicity and topology. Finally,
we sum-up the observational challenges for new solar telescopes.
---------------------------------------------------------
Title: THEMIS and DOT joint observations on NOAA 9716
Authors: Briand, C.; Collados, M.; Sütterlin, P.
2002ESASP.505..361B Altcode: 2002IAUCo.188..361B; 2002solm.conf..361B
Ephemeral magnetic emergence has been detected in a decaying β region
observed in December 2001 simultaneously with the DOT and THEMIS. We
present here the main characteristics of this phenomenon. Also the
time evolution of a small group of pores is shown together with the
time evolution of an horizontal magnetic field overlying them.
---------------------------------------------------------
Title: THEMIS: instrumentation, results and perspectives
Authors: Briand, C.; Ceppatelli, G.
2002ESASP.505...11B Altcode: 2002IAUCo.188...11B; 2002solm.conf...11B
THEMIS was built with very specific scientific objectives which
implied severe instrumental constraints. Both are presented in this
paper. Taking into account these constraints, we detail the present
instrumental set-up and explain the mid-term projects. Some scientific
results are presented in order to illustrate the observational
capabilities of the telescope.
---------------------------------------------------------
Title: Telescope guide and pointing precision at THEMIS
Authors: Mainella, G.; Briand, C.
2002NCimC..25..709M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: THEMIS: Status and Perspectives
Authors: Ceppatelli, G.; Briand, C.
2002sf2a.conf...95C Altcode:
We will briefly present here the scientific results obtained with
THEMIS, through the publications issued in 2001. We will then describe
the mid-term improvements, stressing that they are imperative to
maintain the position of THEMIS in the group of the most relevant
solar telescopes in the world.
---------------------------------------------------------
Title: ASP Observations - First Analysis of Mgb<SUB>2</SUB> Stokes
Parameters
Authors: Briand, C.; Martínez Pillet, V.
2001ASPC..236..565B Altcode: 2001aspt.conf..565B
No abstract at ADS
---------------------------------------------------------
Title: Last news from THEMIS
Authors: Ceppatelli, Guido; Briand, Carine
2001MmSAI..72..558C Altcode:
THEMIS started a new observing campaign on May 1st 2000. In this
paper a sum up of the main aims of THEMIS will be presented. Then, the
present status of the observing modes will be described. Finally, we
will present some results obtained during the last observing campaigns.
---------------------------------------------------------
Title: Solar arch filaments observed with THEMIS
Authors: Mein, P.; Briand, C.; Heinzel, P.; Mein, N.
2000A&A...355.1146M Altcode:
Arch Filaments (AF) have been observed in the Ca Ii 8542 Å line with
the THEMIS telescope in September 1998. We present a preliminary
analysis of MSDP spectro-imaging data. A cloud-model fit provides
line-of-sight velocities and a set of plausible values for the model
parameters. The high sensitivity of the filament opacity to temperature,
coupled with the rough linearity versus electronic density, shows that
this Ca Ii line should be very efficient to complement usual Hα data
for a more rigorous diagnostics. Based on observations made with the
THEMIS telescope operated on the island of Tenerife by CNRS-CNR in
the spanish Observatorio del Teide of the Instituto de Astrofisica
de Canarias
---------------------------------------------------------
Title: Scaling behavior of the vertical velocity field in the solar
photosphere
Authors: Consolini, G.; Carbone, V.; Berrilli, F.; Bruno, R.;
Bavassano, B.; Briand, C.; Caccin, B.; Ceppatelli, G.; Egidi, A.;
Ermolli, I.; Florio, A.; Mainella, G.; Pietropaolo, E.
1999A&A...344L..33C Altcode:
We analyze, for the first time, the scaling behavior of the photospheric
vertical velocity field. Our analysis is based on data collected by the
Italian Panoramic Monocromator (IPM) mounted at the THEMIS telescope
at the Spanish “Observatorio del Teide” (Tenerife) of the Instituto
de Astrofisica de Canarias. We investigate the occurrence of scaling in
the cancellations between downflow and upflow of the vertical velocity
field, showing that the field possesses well pronunced sign-singularity
in the range of scales from more than 10 Mm down to the granulation
scale. Based on THEMIS/CNRS--INSU/CNR telescope observations
---------------------------------------------------------
Title: Dependence of the photospheric vertical flow characteristics
on the granule dimension
Authors: Berrilli, F.; Florio, A.; Consolini, G.; Bavassano, B.;
Briand, C.; Bruno, R.; Caccin, B.; Carbone, V.; Ceppatelli, G.; Egidi,
A.; Ermolli, I.; Mainella, G.; Pietropaolo, E.
1999A&A...344L..29B Altcode:
The first high spectral resolution and white-light images obtained at
the THEMIS telescope with the Italian Panoramic Monochromator (IPM), are
analyzed to study intensity and velocity fluctuations in the photosphere
of the sun. Monochromatic images, in two spectral ranges around 538.03
nm (C I line) and 557.61 nm (Fe I line), are used to characterize the
vertical structure of the photosphere. Granulation cells and granules
are obtained by segmentation of white-light images using suitable
finding algorithms. We observe the height dependence of velocity
vs. intensity fluctuations, and we found a dependence of velocity and
intensity on granule dimension. Our results show that granules increase
their intensity with dimension in the lower solar photosphere. In the
higher photosphere, on the contrary, the intensity decreases with the
dimension. Based on THEMIS/CNRS-INSU/CNR telescope observations
---------------------------------------------------------
Title: Spectral Law and Polarization Properties of the Low-Frequency
Waves at the Magnetopause
Authors: Rezeau, L.; Belmont, G.; Cornilleau-Wehrlin, N.; Reberac,
F.; Briand, C.
1999GeoRL..26..651R Altcode:
The magnetic fluctuations, at the magnetopause and in the adjacent
magnetosheath, exhibit power law spectra which are very reminiscent
of turbulent spectra. In prospect of future modelizations of such a
turbulence, new information is brought about the experimental properties
of these fluctuations. The power laws spectra previously obtained in
the ULF range are shown to hold also in VLF, up to the lower hybrid
frequency. Concerning the polarization, 1) the direction with respect
to the static magnetic field is shown to be dominantly perpendicular
at low frequencies, consistently with Shear Alfven modes in this range,
and 2) no right-hand sense of rotation can be evidenced at frequencies
higher than the proton gyrofrequency, although one could expect the
fast magnetosonic mode to be dominant in this range. The physical
implications of this last observation for the non linear effects at
work in the turbulence are briefly discussed.
---------------------------------------------------------
Title: First observational campaign at the THEMIS: image quality
and seeing
Authors: Arnaud, J.; Briand, C.; Ceppatelli, G.
1998NewAR..42..499A Altcode:
The THEMIS and its instrumentation are described. The well known diurnal
seeing pattern is confirmed by the seeing measurements taken to date.
---------------------------------------------------------
Title: Velocity fields below the magnetic canopy of solar flux tubes:
evidence for high-speed downflows?
Authors: Briand, C.; Solanki, S. K.
1998A&A...330.1160B Altcode:
It is well-established that velocities in the immediate surroundings of
solar magnetic elements produce an asymmetry in the Stokes V profiles
emerging from the magnetic feature. Conversely, the observed Stokes V
asymmetry can be used to infer the velocity field. Taking as constraints
the area asymmetries of the Stokes V profiles of two lines of neutral
magnesium (lambda 457nm and lambda 517nm) observed near the center of
the solar disk, the (vertical) component of the velocity field below
the magnetic canopy of flux tubes is investigated. We find that the
strong Mg I b_2 line at 517nm qualitatively extends the diagnostic
capabilities of Stokes V asymmetry, mainly due to the fact that it is
sensitive to velocities over a large range of heights and hence also at
relatively large distances from the flux tube axis. In order to retrieve
the observed area asymmetry of both lines, up- as well as downflows
have to be introduced in the models. If the temperature differences
between the two flows are neglected then a downflow of 1.5 - 2km s(-1)
close to the edge of the flux tube and an almost equally strong upflow
at greater distances (corresponding to the central part of a granule)
reproduces the observed area asymmetries. If we take into account
that the temperature in the downflow is lower than in the upflow,
we can only reproduce the observations if the downflow is fast (>=
5 km s(-1) ) and concentrated into narrow lanes.
---------------------------------------------------------
Title: THEMIS-IPM: performance analysis of the system and future
developments
Authors: Mainella, G.; Bavassano, B.; Berrilli, F.; Briand, C.; Bruno,
R.; Caccin, B.; Cantarano, S.; Ceppatelli, G.; Egidi, A.
1998MmSAI..69..659M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High spatial resolution observations of the solar spectral
lines.
Authors: Kostyk, R. I.; Shchukina, N. G.; Briand, C.
1998IBUAA..12...39K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Velocity fields around magnetic flux tubes.
Authors: Briand, C.; Solanki, S. K.
1997joso.proc...55B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: THEMIS: Télescope Héliographique pour l'Étude du Magnétisme
et des Instabilités Solaires.
Authors: Arnaud, J.; Briand, C.; Rayrole, J.
1996JAF....53....5A Altcode:
No abstract at ADS
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Title: The MG i lambda 285.21 Nanometer Line: an Example of Non-LTE
Line Formation
Authors: Uitenbroek, Han; Briand, Carine
1995ApJ...447..453U Altcode:
We discuss how the Mg I λ285.21 nm line is formed in the context of
standard plane-parallel modeling. The line appears to be very sensitive
to the nonlocal radiation field determining the balance between neutral
and singly ionized magnesium. We resolve between conflicting results
in earlier λ285.21 nm line modeling by showing that, in the quite
Sun, the line forms at sufficiently low density for partial frequency
redistribution to take effect and give rise to small emission reversals
in the core. We find this to be true only if we take proper account
of UV line blanketing at the relevant Mg I ionization edges. In
this case there is good agreement between theoretical line profiles
and spatially averaged spectra from the Solar Maximum Mission (SMM)
Ultraviolet Spectrometer and Polarimeter (UVSP) and from the French
RASOLBA balloon experiment. Spatially resolved spectra obtained with
the latter instrument show considerable variation in the line core,
with emission present only in some locations and absent in others.
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Title: Empirical models of solar magnetic elements: constraints
imposed by MgI Stokes profiles.
Authors: Briand, C.; Solanki, S. K.
1995A&A...299..596B Altcode:
Although the temperature structure of small-scale magnetic features
in the lower and middle photosphere has been constrained quite well,
there are still considerable uncertainties in the upper photospheric
and lower chromospheric thermal structure. As a step towards an
improvement of this situation we investigate, using a non-LTE analysis,
the diagnostic capabilities of the Stokes I and V profiles of the Mg
I b_2_ 517.3nm and the Mg I 457.1nm lines. We find that the V profile
of the former line can constrain the magnetic element thermal and
velocity structure near the temperature minimum, which goes beyond
the capabilities of the commonly used Fe I and II lines. The λ457.1nm
line, on the other hand, does not provide any additional information
on its own. A comparison of synthetic profiles with plage and network
Stokes I and V spectra confirms the findings of Bruls & Solanki
(???) that the chromospheric temperature rise starts at a substantially
lower height in magnetic elements than in the quiet Sun. Some of the
ambiguities in previous empirical models of magnetic elements are also
removed. We confirm that small-scale magnetic features are associated
with larger line broadening velocities than the quiet Sun, particularly
in the higher layers. Finally, the Mg I b_2_ line is revealed to be
a direct diagnostic of the merging height of magnetic elements.
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Title: Center-to-limb observations of the lambda 285.2 NM MgI UV
resonance line
Authors: Briand, C.; Lemaire, P.
1994A&A...282..621B Altcode:
We present here new results about the 285.212 nm Mg I resonance
line. The spectra have been obtained from the RASOLBA balloon experiment
of the LPSP launched in 1986 from France. The data have both high
spectral (1.5 pm) and spatial (1 sec) resolution. Spectra of either
the Sun center and the solar limb have been recorded in the 280 nm
range. We paid a careful attention on the spatial evolution of the Mg
I absorption line with the hope to find predicted but not confirmed
emission feature in the central core. The very faint emission detected
at Sun center becomes bright when observed off-limb. We give some
measurements of the Mg I core Doppler shifts.
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Title: Mg I UV and IR Lines of the Quiet Sun
Authors: Briand, C.; Lemaire, P.
1994emsp.conf...53B Altcode:
No abstract at ADS
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Title: High Resolution Measurements of the 273-293 nm Solar Spectrum
from a Balloon Instrumentation
Authors: Lemaire, P.; Briand, C.; Staath, E.; Samain, D.
1993BAAS...25.1221L Altcode:
No abstract at ADS
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Title: Exploitation des observations de Jupiter.
Authors: Briand, C.
1990EuAst...4..288B Altcode:
No abstract at ADS