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Bergerat Françoise, Homberg Catherine, Angelier Jacques, Bellou Magalie, . (2011). Surface traces of the Minnivellir, Réttarnes and Tjörvafit seismic faults in the South Iceland Seismic Zone: Segmentation, lengths and magnitude of related earthquakes
. Tectonophysics, 498(14), 11–26.
Keywords: South Iceland Seismic Zone, Transform zone, Paleoseismic fault, Fault segmentation, Offset fault vs. earthquake magnitude, Riedel-type fault pattern,
Programme: 316
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Lynner Colton, Long Maureen D, . (2014). Sub-slab anisotropy beneath the Sumatra and circum-Pacific subduction zones from source-side shear wave splitting observations
. Geochemistry, Geophysics, Geosystems, 15(6), 2262–2281.
Abstract: Understanding the dynamics of subduction is critical to our overall understanding of plate tectonics and the solid Earth system. Observations of seismic anisotropy can yield constraints on deformation patterns in the mantle surrounding subducting slabs, providing a tool for studying subduction dynamics. While many observations of seismic anisotropy have been made in subduction systems, our understanding of the mantle beneath subducting slabs remains tenuous due to the difficulty of constraining anisotropy in the sub-slab region. Recently, the source-side shear wave splitting technique has been refined and applied to several subduction systems worldwide, making accurate and direct measurements of sub-slab anisotropy feasible and offering unprecedented spatial and depth coverage in the sub-slab mantle. Here we present source-side shear wave splitting measurements for the Central America, Alaska-Aleutians, Sumatra, Ryukyu, and Izu-Bonin-Japan-Kurile subduction systems. We find that measured fast splitting directions in these regions generally fall into two broad categories, aligning either with the strike of the trench or with the motion of the subducting slab relative to the overriding plate. Trench parallel fast splitting directions dominate beneath the Izu-Bonin, Japan, and southern Kurile slabs and part of the Sumatra system, while fast directions that parallel the motion of the downgoing plate dominate in the Ryukyu, Central America, northern Kurile, western Sumatra, and Alaska-Aleutian regions. We find that plate motion parallel fast splitting directions in the sub-slab mantle are more common than previously thought. We observe a correlation between fast direction and age of the subducting lithosphere; older lithosphere (>95 Ma) is associated with trench parallel splitting while younger lithosphere (<95 Ma) is associated with plate motion parallel fast splitting directions. Finally, we observe source-side splitting for deep earthquakes (transition zone depths) beneath Japan and Sumatra, suggesting the presence of anisotropy at midmantle depths beneath these regions.
Keywords: source-side splitting, sub-slab anisotropy, shear wave splitting, 7240 Subduction zones, 7208 Mantle,
Programme: 133
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Lentas K, Ferreira AMG, Clévédé E, Roch J, . (2014). Source models of great earthquakes from ultra low-frequency normal mode data
. Physics of the Earth and Planetary Interiors, 233, 41–67.
Keywords: Source inversions, Normal modes, Rupture kinematics, Large magnitude earthquakes,
Programme: 133
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Masson S, Démoulin P, Dasso S, Klein K-L, . (2012). The interplanetary magnetic structure that guides solar
. A&A, 538, A32.
Abstract: Context. Relating in-situ measurements of relativistic solar particles to their parent activity in the corona requires understanding the magnetic structures that guide them from their acceleration site to the Earth. Relativistic particle events are observed at times of high solar activity, when transient magnetic structures such as interplanetary coronal mass ejections (ICMEs) often shape the interplanetary magnetic field (IMF). They may introduce interplanetary paths that are longer than nominal, and magnetic connections rooted far from the nominal Parker spiral.
Aims: We present a detailed study of the IMF configurations during ten relativistic solar particle events of the 23rd activity cycle to elucidate the actual IMF configuration that guides the particles to the Earth, where they are measured by neutron monitors.
Methods: We used magnetic field (MAG) and plasma parameter measurements (SWEPAM) from the ACE spacecraft and determined the interplanetary path lengths of energetic particles through a modified version of the velocity dispersion analysis based on energetic particle measurements with SoHO/ERNE.
Results: We find that the majority (7/10) of the events is detected in the vicinity of an ICME. Their interplanetary path lengths are found to be longer (1.5-2.6 AU) than those of the two events propagating in the slow solar wind (1.3 AU). The longest apparent path length is found in an event within the fast solar wind, probably caused by enhanced pitch angle scattering. The derived path lengths imply that the first energetic and relativistic protons are released at the Sun at the same time as electron beam emitting type III radio bursts.
Conclusions: The timing of the first high-energy particle arrival on Earth is mainly determined by the type of IMF in which the particles propagate. Initial arrival times are as expected from Parker's model in the slow solar wind, and significantly longer in or near transient structures such as ICMEs.
Keywords: solar-terrestrial relations / Sun: heliosphere / methods: data analysis
Programme: 227
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Andre R. (1997). Etude des Structures Fines de la Convection Ionosphérique Observées par SuperDARN : Structures à Forte Divergence de Vitesse = Study of Fine Structures in the Ionospheric Convection Recorded by SuperDARN : Structure with High Velocity Divergence. Bachelor's thesis, , .
Abstract: Thèse de Dotorat, Université d'Orléans. Discipline: Physique des Gaz et des plasmas
La chaîne de radars à diffusion cohérente SuperDARN observe dans les régions polaires, les mouvements de convection du plasma ionosphérique qui sont induits par les interactions Soleil-Terre. Le premier objectif de ce travail est de mettre en place des outils permettant l'étude des structures fines se développant dans la convection ionosphérique. Deux thèmes complémentaires sont développés : – L'application d'une théorie de la diffusion collective permet d'extraire des paramètres (temps de cohérence, coefficient de diffusion) caractérisant la turbulence micro-échelle (L?15 m) donnant naissance au signal enregistré par les radars. On utilise ces paramètres pour séparer différents régimes de turbulence, pour mettre en valeur des zones de transfert d'énergie entre l'ionosphère et la magnétosphère. – La deuxième direction consiste à mettre en place une méthode d'analyse permettant de construire des cartes vectorielles de vitesses qui optimisent la résolution de base du radar (L?45 km). Une telle méthode doit faire face à des difficultés propres aux radars utilisés, à savoir une localisation incertaine de la mesure, introduite par l'utilisation d'une onde haute fréquence (HF), et une dépendance des vecteurs entre eux due à la forme des volumes analysés. Ces problèmes sont résolus par une étude détaillée sur la propagation des ondes HF et sur la localisation des mesures, puis par la mise en place d'une méthode d'analyse spectrale haute résolution performante qui augmente la quantité d'information déduite d'une seule donnée radar. Cette méthode de cartographie à haute résolution a permis de mettre en évidence dans les données SuperDARN, des structures caractérisées par une très forte divergence des vitesses, qui sont en contradiction avec l'hypothèse largement admise d'un mouvement sans divergence. L'ensemble des caractéristiques macro-échelles (45 km) et micro-échelles (15 m) de ces structures, conduit à une interprétation en termes de démagnétisation locale et temporaire des ions du plasma dans l'ionosphère aurorale. Cette étude se termine par la proposition de mécanismes capables de reproduire ces observations.
Keywords: Solar terrestrial relation ; Polar ionosphere ; Convection ; Radar observation ; Fine structure ; Scattering theory ; Analysis method ; Velocity distribution
Programme: 312
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Ghelfi A, Maurin D, Cheminet A, Derome L, Hubert G, Melot F, . (2013). Neutron monitors and muon detectors for solar modulation studies: 2. time series . Adv Space Res, .
Abstract: The level of solar modulation at different times (related to the solar activity) is a central question of solar and galactic cosmic-ray physics. In the first paper of this series, we have established a correspondence between the uncertainties on ground-based detectors countrates and the parameter / (modulation level in the force-field approximation) reconstructed from these count rates. In this second paper, we detail a procedure to obtain a reference / time series from neutron monitor data. We show that we can have an unbiased and accurate. We also discuss the potential of Bonner spheres spectrometers and muon detectors to provide / time series. Two by-products of this calculation are updated / values for the cosmic-ray database and a web interface to retrieve and plot from the 50&amp;rsquo;s to today (http://lpsc.in2p3.fr/crdb).
Keywords: Solar modulation, Cosmic rays, Neutron monitor, Muon detector,
Programme: 1112
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Gaya-Piqué, L.R.; Curto, J.J.; Torta, J.M.; Chulliat, A. (2008). Equivalent ionospheric currents for the 5 December 2006 solar flare effect determined from spherical cap harmonic analysis. J. Geophys. Res., 113.
Abstract: In this paper we analyze the prompt solar flare effect (SFE) associated to a strong X-ray flare that occurred on 5 December 2006 by using spherical cap harmonic analysis applied to the variations recorded in the European magnetic observatories network. The regional model allows the simultaneous modeling in space and time of the ionospheric equivalent current system responsible for the SFE, as well as for the regular diurnal variation S R on that day. It is found that the SFE equivalent current system does not form as an enhancement of the S R system. Its focus is distinct from that of the SR, and it is located between 3 and 10° higher in latitude and circa 40 min later in local time.
Keywords: solar flare effects; SCHA; magnetic observatories; 1530 Geomagnetism and Paleomagnetism: Rapid time variations; 2409 Ionosphere: Current systems; 2447 Ionosphere: Modeling and forecasting; 7974 Space Weather: Solar effects; 0545 Computational Geophysics: Modeling
Programme: 139
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Rinaldi Matteo, Decesari Stefano, Carbone Claudio, Finessi Emanuela, Fuzzi Sandro, Ceburnis Darius, O'Dowd Colin D, Sciare Jean, Burrows John P, Vrekoussis Mihalis, Ervens Barbara, Tsigaridis Kostas, Facchini Maria Cristina, . (2011). Evidence of a natural marine source of oxalic acid and a possible link to glyoxal
. J. Geophys. Res., 116(D16), D16204–.
Abstract: This paper presents results supporting the existence of a natural source of oxalic acid over the oceans. Oxalate was detected in “clean-sector” marine aerosol samples at Mace Head (Ireland) (5320′N, 954′W) during 2006, and at Amsterdam Island (3748′S, 7734′E) from 2003 to 2007, in concentrations ranging from 2.7 to 39 ng m-3 and from 0.31 to 17 ng m-3, respectively. The oxalate concentration showed a clear seasonal trend at both sites, with maxima in spring-summer and minima in fall-winter, being consistent with other marine biogenic aerosol components (e.g., methanesulfonic acid, non-sea-salt sulfate, and aliphatic amines). The observed oxalate was distributed along the whole aerosol size spectrum, with both a submicrometer and a supermicrometer mode, unlike the dominant submicrometer mode encountered in many polluted environments. Given its mass size distribution, the results suggest that over remote oceanic regions oxalate is produced through a combination of different formation processes. It is proposed that the cloud-mediated oxidation of gaseous glyoxal, recently detected over remote oceanic regions, may be an important source of submicrometer oxalate in the marine boundary layer. Supporting this hypothesis, satellite-retrieved glyoxal column concentrations over the two sampling sites exhibited the same seasonal concentration trend of oxalate. Furthermore, chemical box model simulations showed that the observed submicrometer oxalate concentrations were consistent with the in-cloud oxidation of typical marine air glyoxal mixing ratios, as retrieved by satellite measurements, at both sites.
Keywords: SOA, cloud processes, glyoxal, marine aerosol, oxalic acid, 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), 0320 Atmospheric Composition and Structure: Cloud physics and chemistry, 0322 Atmospheric Composition and Structure: Constituent sources and sinks, 3311 Atmospheric Processes: Clouds and aerosols,
Programme: 415
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Masson-Delmotte, V.; Hou, S.; Ekaykin, A.; Jouzel, J.; Aristarain, A.; Bernardo, R.T.; Bromwich, D.; Cattani, O.; Delmotte, M.; Falourd, S.; Frezzotti, M.; Gallée, H.; Genoni, L.; Isaksson, E.; Landais, A.; Helsen, M.M.; Hoffmann, G.; Lopez, J.; Morgan, V.; Motoyama, H.; Noone, D.; Oerter, H.; Petit, J.R.; Royer, A.; Uemura, R.; Schmidt, G.A.; Schlosser, E.; Simões, J.C.; Steig, E.J.; Stenni, B.; Stievenard, M.; van den Broeke, M.R.; van de Wal, R.S.W.; van de Berg, W.J.; Vimeux, F.; White, J.W.C. (2008). A Review of Antarctic Surface Snow Isotopic Composition: Observations, Atmospheric Circulation, and Isotopic Modeling*. Journal of climate, 21(13), 3359–3387.
Abstract: A database of surface Antarctic snow isotopic composition is constructed using available measurements, with an estimate of data quality and local variability. Although more than 1000 locations are documented, the spatial coverage remains uneven with a majority of sites located in specific areas of East Antarctica. The database is used to analyze the spatial variations in snow isotopic composition with respect to geographical characteristics (elevation, distance to the coast) and climatic features (temperature, accumulation) and with a focus on deuterium excess. The capacity of theoretical isotopic, regional, and general circulation atmospheric models (including “isotopic” models) to reproduce the observed features and assess the role of moisture advection in spatial deuterium excess fluctuations is analyzed.
Keywords: Snow; Antarctica; Atmospheric circulation; Isotopic analysis; In situ observations
Programme: 355;454
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Libois Quentin, Picard Ghislain, Dumont Marie, Arnaud Laurent, Sergent Claude, Pougatch Evelyne, Sudul Marcel, Vial David, . (2014). Experimental determination of the absorption enhancement parameter of snow
. Journal of Glaciology, 60(222), 714–724.
Abstract: In optical models snow is commonly treated as a disperse collection of particles. In this representation, the penetration depth of solar radiation is sensitive to the shape of the particles, in particular to the absorption enhancement parameter, B, that quantifies the lengthening
Keywords: SNOW, SNOW CHEMISTRY, SNOW PHYSICS, SNOW/ICE SURFACE PROCESSES,
Programme: 1110
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