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- ItemMineral dust in Central Asia: Combining lidar and other measurements during the Central Asian dust experiment (CADEX)(Les Ulis : EDP Sciences, 2018) Althausen, Dietrich; Hofer, Julian; Abdullaev, Sabur; Makhmudov, Abduvosit; Baars, Holger; Engelmann, Ronny; Wadinga Fomba, Khanneh; Müller, Konrad; Schettler, Georg; Klüser, Lars; Kandler, Konrad; Nicolae, D.; Makoto, A.; Vassilis, A.; Balis, D.; Behrendt, A.; Comeron, A.; Gibert, F.; Landulfo, E.; McCormick, M.P.; Senff, C.; Veselovskii, I.; Wandinger, U.Mineral dust needs to be characterized comprehensively since it contributes to the climate change in Tajikistan / Central Asia. Lidar results from the measurements of mineral dust during CADEX are compared with results of sun photometer measurements, satellite-based measurements, and chemical analysis of ground samples. Although the dust is often advected from far-range sources, it impacts on the local conditions considerably.
- ItemPromoting access to and use of seismic data in a large scientific community(Les Ulis : EDP Sciences, 2017) Michel, Eric; Belkacem, Kevin; Samadi, Reza; de Assis Peralta, Raphael; Renié, Christian; Abed, Mahfoudh; Lin, Guangyuan; Christensen-Dalsgaard, Jørgen; Houdek, Günter; Handberg, Rasmus; Gizon, Laurent; Burston, Raymond; Nagashima, Kaori; Pallé, Pere; Poretti, Ennio; Rainer, Monica; Mistò, Angelo; Panzera, Maria Rosa; Roth, Markus; Monteiro, Mário J. P. F. G.; Cunha, Margarida S.; Ferreira, João Miguel T. S.The growing amount of seismic data available from space missions (SOHO, CoRoT, Kepler, SDO,…) but also from ground-based facilities (GONG, BiSON, ground-based large programmes…), stellar modelling and numerical simulations, creates new scientific perspectives such as characterizing stellar populations in our Galaxy or planetary systems by providing model-independent global properties of stars such as mass, radius, and surface gravity within several percent accuracy, as well as constraints on the age. These applications address a broad scientific community beyond the solar and stellar one and require combining indices elaborated with data from different databases (e.g. seismic archives and ground-based spectroscopic surveys). It is thus a basic requirement to develop a simple and effcient access to these various data resources and dedicated tools. In the framework of the European project SpaceInn (FP7), several data sources have been developed or upgraded. The Seismic Plus Portal has been developed, where synthetic descriptions of the most relevant existing data sources can be found, as well as tools allowing to localize existing data for given objects or period and helping the data query. This project has been developed within the Virtual Observatory (VO) framework. In this paper, we give a review of the various facilities and tools developed within this programme. The SpaceInn project (Exploitation of Space Data for Innovative Helio- and Asteroseismology) has been initiated by the European Helio- and Asteroseismology Network (HELAS).
- ItemMineral dust in central Asia: 18-month lidar measurements in Tajikistan during the central Asian dust experiment (CADEX)(Les Ulis : EDP Sciences, 2018) Hofer, Julian; Althausen, Dietrich; Abdullaev, Sabur F.; Makhmudov, Abduvosit; Nazarov, Bakhron I.; Schettler, Georg; Fomba, K.Wadinga; Müller, Konrad; Heinold, Bernd; Baars, Holger; Engelmann, Ronny; Ansmann, Albert; Nicolae, D.; Makoto, A.; Vassilis, A.; Balis, D.; Behrendt, A.; Comeron, A.; Gibert, F.; Landulfo, E.; McCormick, M.P.; Senff, C.; Veselovskii, I.; Wandinger, U.Tajikistan is often affected by atmospheric mineral dust. The direct and indirect radiative effects of dust play a sensitive role in the climate system in Central Asia. The Central Asian Dust Experiment (CADEX) provides first lidar measurements in Tajikistan. The autonomous multiwavelength polarization Raman lidar PollyXT was operated for 1.5 years (2015/16) in Dushanbe. In spring, lofted layers of long-range transported dust and in summer/ autumn, lower laying dust from local or regional sources with large optical thicknesses occurred.
- ItemDynamical studies on the generation of periodic surface structures by femtosecond laser pulses(Les Ulis : EDP Sciences, 2013) Rosenfeld, A.; Höhm, S.; Bonse, J.; Krüger, J.The dynamics of the formation of laser-induced periodic surface structures (LIPSS) on fused silica upon irradiation with linearly polarized fs-laser pulses (50 fs pulse duration, 800 nm center wavelength) is studied experimentally using a double pulse experiment with cross polarized pulse sequences and a trans illumination femtosecond time-resolved (0.1 ps - 1 ns) pump-probe diffraction approach. The results in both experiments confirm the importance of the ultrafast energy deposition and the laser-induced free-electron plasma in the conduction band of the solids for the formation of LIPSS.
- ItemThe first SEPServer event catalogue ~68-MeV solar proton events observed at 1 AU in 1996-2010(Les Ulis : EDP Sciences, 2013) Vainio, R.; Valtonen, E.; Heber, B.; Malandraki, O.E.; Papaioannou, A.; Klein, K.-L.; Afanasiev, A.; Agueda, N.; Aurass, H.; Battarbee, M.; Braune, S.; Dröge, W.; Ganse, U.; Hamadache, C.; Heynderickx, D.; Huttunen-Heikinmaa, K.; Kiener, J.; Kilian, P.; Kopp, A.; Kouloumvakos, A.; Maisala, S.; Mishev, A.; Miteva, R.; Nindos, A.; Oittinen, T.; Raukunen, O.; Riihonen, E.; Rodríguez-Gasén, R.; Saloniemi, O.; Sanahuja, B.; Scherer, R.; Spanier, F.; Tatischeff, V.; Tziotziou, K.; Usoskin, I.G.; Vilmer, N.SEPServer is a three-year collaborative project funded by the seventh framework programme (FP7-SPACE) of the European Union. The objective of the project is to provide access to state-of-the-art observations and analysis tools for the scientific community on solar energetic particle (SEP) events and related electromagnetic (EM) emissions. The project will eventually lead to better understanding of the particle acceleration and transport processes at the Sun and in the inner heliosphere. These processes lead to SEP events that form one of the key elements of space weather. In this paper we present the first results from the systematic analysis work performed on the following datasets: SOHO/ERNE, SOHO/EPHIN, ACE/EPAM, Wind/WAVES and GOES X-rays. A catalogue of SEP events at 1 AU, with complete coverage over solar cycle 23, based on high-energy (~68-MeV) protons from SOHO/ERNE and electron recordings of the events by SOHO/EPHIN and ACE/EPAM are presented. A total of 115 energetic particle events have been identified and analysed using velocity dispersion analysis (VDA) for protons and time-shifting analysis (TSA) for electrons and protons in order to infer the SEP release times at the Sun. EM observations during the times of the SEP event onset have been gathered and compared to the release time estimates of particles. Data from those events that occurred during the European day-time, i.e., those that also have observations from ground-based observatories included in SEPServer, are listed and a preliminary analysis of their associations is presented. We find that VDA results for protons can be a useful tool for the analysis of proton release times, but if the derived proton path length is out of a range of 1 AU < s a 2 3 AU, the result of the analysis may be compromised, as indicated by the anti-correlation of the derived path length and release time delay from the associated X-ray flare. The average path length derived from VDA is about 1.9 times the nominal length of the spiral magnetic field line. This implies that the path length of first-arriving MeV to deka-MeV protons is affected by interplanetary scattering. TSA of near-relativistic electrons results in a release time that shows significant scatter with respect to the EM emissions but with a trend of being delayed more with increasing distance between the flare and the nominal footpoint of the Earth-connected field line.
- ItemNonlinear optical mechanism of forming periodical nanostructures in large bandgap dielectrics(Les Ulis : EDP Sciences, 2013) Grunwald, R.; Das, S.K.; Debroy, A.; McGlynn, E.; Messaoudi, H.Nonlinear excitation mechanisms of plasmons and their influence on femtosecond-laser induced sub-wavelength ripple generation on dielectric and semiconducting transparent materials are discussed. The agreement of theoretical and experimental data indicates the relevance of the model.
- ItemA multi-model approach to X-ray pulsars: Connecting spectral and timing models to pin down the intrinsic emission characteristics of magnetized, accreting neutron stars(Les Ulis : EDP Sciences, 2014) Schönherr, G.; Schwarm, F.; Falkner, S.; Becker, P.; Wilms, J.; Dauser, T.; Wolff, M.T.; Wolfram, K.; West, B.; Pottschmidt, K.; Kretschmar, P.; Ferrigno, C.; Klochkov, D.; Nishimura, O.; Kreykenbohm, I.; Caballero, I.; Staubert, R.The emission characteristics of X-ray pulsars are governed by magnetospheric accretion within the Alfvén radius, leading to a direct coupling of accretion column properties and interactions at the magnetosphere. The complexity of the physical processes governing the formation of radiation within the accreted, strongly magnetized plasma has led to several sophisticated theoretical modelling efforts over the last decade, dedicated to either the formation of the broad band continuum, the formation of cyclotron resonance scattering features (CRSFs) or the formation of pulse profiles. While these individual approaches are powerful in themselves, they quickly reach their limits when aiming at a quantitative comparison to observational data. Too many fundamental parameters, describing the formation of the accretion columns and the systems' overall geometry are unconstrained and different models are often based on different fundamental assumptions, while everything is intertwined in the observed, highly phase-dependent spectra and energy-dependent pulse profiles. To name just one example: the (phase variable) line width of the CRSFs is highly dependent on the plasma temperature, the existence of B-field gradients (geometry) and observation angle, parameters which, in turn, drive the continuum radiation and are driven by the overall two-pole geometry for the light bending model respectively. This renders a parallel assessment of all available spectral and timing information by a compatible across-models-approach indispensable. In a collaboration of theoreticians and observers, we have been working on a model unification project over the last years, bringing together theoretical calculations of the Comptonized continuum, Monte Carlo simulations and Radiation Transfer calculations of CRSFs as well as a General Relativity (GR) light bending model for ray tracing of the incident emission pattern from both magnetic poles. The ultimate goal is to implement a unified fitting model for phase-resolved spectral and timing data analysis. We present the current status of this project.
- ItemStudy of mixed phase clouds over west Africa: Ice-crystal corner reflection effects observed with a two-wavelength polarization lidar(Les Ulis : EDP Sciences, 2018) Veselovskii, Igor; Goloub, Philippe; Podvin, Thierry; Tanre, Didier; Ansmann, Albert; Korenskiy, Michail; Borovoi, Anatoli; Hu, Qiaoyun; Bovchaliuk, Valentin; Whiteman, David N.; Nicolae, D.; Makoto, A.; Vassilis, A.; Balis, D.; Behrendt, A.; Comeron, A.; Gibert, F.; Landulfo, E.; McCormick, M.P.; Senff, C.; Veselovskii, I.; Wandinger, U.Lidar sounding is used for the analysis of possible contribution of the corner reflection (CR) effect to the total backscattering in case of ice crystals. Our study is based on observations of mixed phase clouds performed during the SHADOW campaign in Senegal. Mie-Raman lidar allows measurements at 355 nm and 532 nm at 43 dg. off-zenith angle, so the extinction and backscattering Ångström exponents can be evaluated. In some measurements we observed the positive values of backscattering Ångström exponent, which can be attributed to the corner reflection by horizontally oriented ice plates.
- ItemHot moons and cool stars(Les Ulis : EDP Sciences, 2013) Heller, R.; Barnes, R.The exquisite photometric precision of the Kepler space telescope now puts the detection of extrasolar moons at the horizon. Here, we firstly review observational and analytical techniques that have recently been proposed to find exomoons. Secondly, we discuss the prospects of characterizing potentially habitable extrasolar satellites. With moons being much more numerous than planets in the solar system and with most exoplanets found in the stellar habitable zone being gas giants, habitable moons could be as abundant as habitable planets. However, satellites orbiting planets in the habitable zones of cool stars will encounter strong tidal heating and likely appear as hot moons.
- ItemUltrafast structural and vibrational dynamics of the hydration shell around DNA(Les Ulis : EDP Sciences, 2013) Elsaesser, T.; Szyc, LŁ.; Yang, M.Two-dimensional infrared spectroscopy in the frequency range of OH- and NH stretch excitations serves for a direct mapping of hydration dynamics around DNA. A moderate slowing down of structural dynamics and resonant OH stretch energy transfer is observed in the DNA water shell compared to bulk water.