Author name code: briand ADS astronomy entries on 2022-09-14 author:"Briand, Carine" ------------------------------------------------------------------------ Title: Role of hard X-ray emission in ionospheric D-layer disturbances during solar flares Authors: Briand, Carine; Clilverd, Mark; Inturi, Srivani; Cecconi, Baptiste Bibcode: 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. 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. Bibcode: 2022A&A...663A.173K Altcode:
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.
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.
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.
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.

Movie is available at https://www.aanda.org Title: Solar EUV-Enhancement and Thermospheric Disturbances Authors: Briand, C.; Doerksen, K.; Deleflie, F. Bibcode: 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+ ions of ionospheric origin, which may occur over the EUV-enhancement period. 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. Bibcode: 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⊙. 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. 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. Bibcode: 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.
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.
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).
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. 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 Bibcode: 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. Title: Hard X-ray impact on the ionosphere D-layer: new results from VLF measurements Authors: Briand, Carine; Inturi, Srivani; Cecconi, Baptiste Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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 ωp 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⪉mbdaDe 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 2ω0 in the nanosecond regime. The results of PIC simulations and of the first experiment that hold in September 2018 will be presented. 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 Bibcode: 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. Title: Groupe de Travail Soleil Heliosphere-Magnetospheres (SHM) Authors: Auchère, F.; Astafyeva, E.; Baudin, F.; Bourdarie, S.; Briand, C.; Brun, S.; Célestin, S.; Génot, V.; Kretzschmar, M.; Leblanc, F.; Rouillard, A.; Sahraoui, F. Bibcode: 2019shm..rept....1A Altcode: Les grandes questions scientifiques abordées dans le cadre de la thématique Soleil Héliosphère et Magnétosphères (SHM) couvrent l'ensemble des problématiques liées aux relations entre notre étoile et le système solaire. Cela commence par l'étude de la structure interne du Soleil à travers l'observation multi-spectrales, l'hélio-sismologie et la modélisation ; par l'étude de l'origine de la couronne solaire, son chauffage et l'accélération du vent solaire et des particules énergétiques solaires lors d'événements énergétiques solaires ; et enfin par l'étude de la propagation du vent solaire et des mécanismes de chauffage de celui-ci par dissipation turbulente. Title: Electromagnetic Simulations of Solar Radio Emissions Authors: Henri, P.; Sgattoni, A.; Briand, C.; Amiranoff, F.; Riconda, C. Bibcode: 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 T2f, 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 T2f radio wave is independent of the beam parameters, approximately 10-5 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. 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 Bibcode: 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. 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. Bibcode: 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. Title: Full PIC simulations of solar radio emission Authors: Sgattoni, A.; Henri, P.; Briand, C.; Amiranoff, F.; Riconda, C. Bibcode: 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. Title: The NOIRE Study Authors: Cecconi, B.; Laurens, A.; Briand, C.; Girard, J.; Bucher, M.; Puy, D.; Segret, B.; Bentum, M. Bibcode: 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. Bibcode: 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.

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)

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).

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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 m2, 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 Bibcode: 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. Bibcode: 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. Bibcode: 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, http://cdpp.eu/). 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 Vsw 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∥, 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. Bibcode: 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 ×106K. 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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−1 to −1.7 MHz s−1, but their positive drift rates vary in a wider range from 0.44 MHz s−1 to 6 MHz s−1. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Te/Tp. 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 ((ɛ0E2)/(nkBT)>10-4). 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Te = Tp. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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.
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.
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-1 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-1 and a short lifetime of about 1 s. The third population presents an average positive frequency drift of +0.95 MHz s-1 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2003AN....324..299D Altcode: No abstract at ADS Title: THEMIS : Status and perspectives Authors: Ceppatelli, G.; Briand, C. Bibcode: 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.

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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2002NCimC..25..709M Altcode: No abstract at ADS Title: THEMIS: Status and Perspectives Authors: Ceppatelli, G.; Briand, C. Bibcode: 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 Mgb2 Stokes Parameters Authors: Briand, C.; Martínez Pillet, V. Bibcode: 2001ASPC..236..565B Altcode: 2001aspt.conf..565B No abstract at ADS Title: Last news from THEMIS Authors: Ceppatelli, Guido; Briand, Carine Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1998IBUAA..12...39K Altcode: No abstract at ADS Title: Velocity fields around magnetic flux tubes. Authors: Briand, C.; Solanki, S. K. Bibcode: 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. Bibcode: 1996JAF....53....5A Altcode: No abstract at ADS Title: The MG i lambda 285.21 Nanometer Line: an Example of Non-LTE Line Formation Authors: Uitenbroek, Han; Briand, Carine Bibcode: 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. Title: Empirical models of solar magnetic elements: constraints imposed by MgI Stokes profiles. Authors: Briand, C.; Solanki, S. K. Bibcode: 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. Title: Center-to-limb observations of the lambda 285.2 NM MgI UV resonance line Authors: Briand, C.; Lemaire, P. Bibcode: 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. Title: Mg I UV and IR Lines of the Quiet Sun Authors: Briand, C.; Lemaire, P. Bibcode: 1994emsp.conf...53B Altcode: No abstract at ADS Title: High Resolution Measurements of the 273-293 nm Solar Spectrum from a Balloon Instrumentation Authors: Lemaire, P.; Briand, C.; Staath, E.; Samain, D. Bibcode: 1993BAAS...25.1221L Altcode: No abstract at ADS Title: Exploitation des observations de Jupiter. Authors: Briand, C. Bibcode: 1990EuAst...4..288B Altcode: No abstract at ADS