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1. The Dominant Role of Brewer‐Dobson Circulation on 17 O‐Excess Variations in Snow Pits at Dome A, Antarctica

Author

Hongxi Pang, Peng Zhang, Shuangye Wu, Jean Jouzel, Hans Christian Steen‐Larsen, Ke Liu, Wangbin Zhang, Jinhai Yu, Chunlei An, Deliang Chen, Shugui Hou, Nanjing University (NJU), University of Gothenburg (GU), University of Dayton, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Bergen (UiB), Polar Research Institute of China (PRIC), and We thank all of the CHINARE-26 and CHINARE-32 scientists, technicians, and porters for their hard work in the field. We thank Amaelle Landais (LSCE) for the 17O-excess measurements and her constructive comments on this paper. We also thank Tongmei Wang for her advice on calculating the residual circulation. This work was jointly supported by the National Natural Science Foundation of China (41622605, 41830644, 91837102, 42021001), the Chinese Arctic and Antarctic Administration (CXPT2020012), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and the Swedish STINT (CH2019-8377).

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, Geophysics, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

Recent studies have suggested that water isotopologues in snow pits from remote East Antarctica can be influenced by the input of stratospheric water, which has anomalously high 17O-excess values. However, it remains unclear whether the 17O-excess records preserved in snow and ice from this region can be used to reconstruct stratosphere-troposphere exchange (STE). In this study, we present high-resolution 17O-excess records from two snow pits at Dome A, the highest point of the Antarctic ice sheet. The 17O-excess records show a significant positive correlation with the strength of the Brewer-Dobson circulation (BDC), the hemispheric-scale troposphere-stratosphere overturn circulation. Stronger BDC leads to more stratospheric water input over Antarctica and higher 17O-excess, and vice versa. In addition, the 17O-excess records also have a significant positive correlation with the Southern Annular Mode (SAM) index, because SAM modulates Antarctic precipitation, which has a dilution effect on the stratospheric water input. The 17O-excess records do not show significant correlations with local temperature and relative humidity in the moisture source region. These results suggest the dominant effect of BDC on 17O-excess and indicate the potential for using 17O-excess records in ice cores from remote sites in East Antarctica for reconstructing long-term variations of STE, and understanding their mechanisms and climate effects. publishedVersion

Published
2022

2. Water content trends in K2-138 and other low-mass multiplanetary systems

Author

Acuña, Lorena, Lopez, Theo, Morel, Thierry, Deleuil, Magali, Mousis, Olivier, Aguichine, Artyom, Marcq, Emmanuel, Santerne, Alexandre, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), We would like to thank Maria Bergemann and Matthew Raymond Gent for a preliminary analysis of the stellar spectrum. This research has made use of the services of the ESO Science Archive Facility. This research was made possible through the use of the AAVSO hotometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis enter/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion aboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. This research has made use of the ExoplanetFollow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/ gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in Ochsenbein et al. (2000). T.M. acknowledges financial support from Belspo for contract PRODEX PLATO mission development. We acknowledge the anonymous referee whose comments helped improve and clarify this manuscript., and Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), [SDU]Sciences of the Universe [physics], Space and Planetary Science, planets and satellites: composition, Stars: abundances, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astronomy and Astrophysics, Astrophysics::Earth and Planetary Astrophysics, planets and satellites: individual: K2-138, Stars: individual: K2-138, planets and satellites: interiors, Astrophysics - Earth and Planetary Astrophysics
Abstract

Super-Earths and sub-Neptunes have been found simultaneously in multiplanetary systems, suggesting that they are appropriate to study composition and formation within the same environment. We perform a homogeneous interior structure analysis of five multiplanetary systems to explore the compositional trends and its relation with planet formation. For K2-138, we present revised masses and stellar host chemical abundances to improve the constraints on the planetary interior. We conduct a line-by-line differential spectroscopic analysis on the stellar spectra to obtain its chemical abundances and the planetary parameters. We select multiplanetary systems with five or more low-mass planets that have both mass and radius data available. We carry out a homogeneous interior structure analysis on the systems K2-138, TOI-178, Kepler-11, Kepler-102 and Kepler-80 and estimate the volatile mass fraction of their planets assuming a volatile layer constituted of water in steam and supercritical phases. Our interior-atmosphere model takes into account the effects of irradiation on the surface conditions. K2-138 inner planets present an increasing volatile mass fraction with distance from its host star, while the outer planets present an approximately constant water content. This is similar to the trend observed in TRAPPIST-1 in a previous analysis with the same interior-atmosphere model. The Kepler-102 system could potentially present this trend. In all multiplanetary systems, the low volatile mass fraction of the inner planets could be due to atmospheric escape while the higher volatile mass fraction of the outer planets can be the result of accretion of ice-rich material in the vicinity of the ice line with later inward migration. Kepler-102 and Kepler-80 present inner planets with high core mass fractions which could be due to mantle evaporation, impacts or formation in the vicinity of rocklines., 15 pages, 4 figures. Accepted for publication in A&A

Published
2022

3. Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer

Author

M. González, Benoît Commerçon, R. Mignon-Risse, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), This work was supported by the CNRS 'Programme National de Physique Stellaire' (PNPS), The numerical simulations we have presented in this paper were produced on the CEA machine Alfvén and using HPC resources from GENCI-CINES (Grant A0080407247). The visualisation of RAMSES data has been done with the OSYRIS python package., Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Bordeaux Sciences Agro [Gradignan], and Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)

Subjects
Magnetohydrodynamics (MHD), Astrophysics::High Energy Astrophysical Phenomena, Stars: formation, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Stars: protostars, Acceleration, 0103 physical sciences, Radiative transfer, Protostar, Astrophysics::Solar and Stellar Astrophysics, Stars: massive, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Methods: numerical, 010308 nuclear & particles physics, Turbulence, Ambipolar diffusion, Velocity dispersion, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics - Astrophysics of Galaxies, Magnetic field, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Outflow, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

(Abridged) Most massive protostars exhibit bipolar outflows. Nonetheless, there is no consensus regarding the mechanism at the origin of these outflows, nor on the cause of the less-frequently observed monopolar outflows. We aim to identify the origin of early massive protostellar outflows, focusing on the combined effects of radiative transfer and magnetic fields in a turbulent medium. We use four state-of-the-art radiation-magnetohydrodynamical simulations following the collapse of massive 100 Msun pre-stellar cores with the Ramses code. Turbulence is taken into account via initial velocity dispersion. We use a hybrid radiative transfer method and include ambipolar diffusion. We find that turbulence delays the launching of outflows, which appear to be mainly driven by magnetohydrodynamical processes. Magnetic tower flow and the magneto-centrifugal acceleration contribute to the acceleration and the former operates on larger volumes than the latter. Our finest resolution, 5 AU, does not allow us to get converged results on magneto-centrifugally accelerated outflows. Radiative acceleration takes place as well, dominates in the star vicinity, enlarges the outflow extent, and has no negative impact on the launching of magnetic outflows (up to M~17 Msun, L~1e5 Lsun). The associated opening angles (20-30 deg when magnetic fields dominate) suggest additional (de-)collimating effects to meet observational constraints. Outflows are launched nearly perpendicular to the disk and are misaligned with the initial core-scale magnetic fields, in agreement with several observational studies. In the most turbulent run, the outflow is monopolar. We conclude that magnetic processes dominate the acceleration of massive protostellar outflows up to ~17 Msun, against radiative processes. Turbulence perturbs the outflow launching and is a possible explanation for monopolar outflows., Accepted for publication in A&A, 20 pages, 15 figures

Published
2021

4. A SPHERE survey of self-shadowed planet-forming disks

Author

A. Garufi, C. Dominik, C. Ginski, M. Benisty, R. G. van Holstein, Th. Henning, N. Pawellek, C. Pinte, H. Avenhaus, S. Facchini, R. Galicher, R. Gratton, F. Ménard, G. Muro-Arena, J. Milli, T. Stolker, A. Vigan, M. Villenave, T. Moulin, A. Origne, F. Rigal, J.-F. Sauvage, L. Weber, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire Franco-Chilien d'Astronomie (LFCA), Universidad de Chile = University of Chile [Santiago] (UCHILE)-Pontificia Universidad Católica de Chile (UC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Universidad de Concepción - University of Concepcion [Chile], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Leiden Observatory [Leiden], Universiteit Leiden, Lakeside Labs [Klagenfurt], University of Cambridge [UK] (CAM), Università degli Studi di Milano = University of Milan (UNIMI), European Southern Observatory (ESO), Observatoire de Paris, Université Paris sciences et lettres (PSL), INAF - Osservatorio Astronomico di Padova (OAPD), Institute for Particle Physics and Astrophysics [ETH Zürich] (IPA), Department of Physics [ETH Zürich] (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), DOTA, ONERA, Université Paris Saclay [Palaiseau], ONERA-Université Paris-Saclay, Geneva Observatory, Université de Genève = University of Geneva (UNIGE), SPHERE was funded by ESO, with additional contributions from CNRS (France), MPIA (Germany), INAF (Italy), FINES (Switzerland) and NOVA (Netherlands). SPHERE also received funding from the European Commission Sixth and Seventh Framework Programmes as part of the Optical Infrared Coordination Network for Astronomy (OPTICON) under grant number RII3-Ct-2004-001566 for FP6 (2004–2008), grant number 226604 for FP7 (2009–2012) and grant number 312430 for FP7 (2013–2016). We also acknowledge financial support from the Programme National de Planètologie (PNP) and the Programme National de Physique Stellaire (PNPS) of CNRS-INSU in France. This paper also makes use of the following ALMA data: ADS/JAO.ALMA#2015.1.01600.S and 2015.1.00847.S. ALMAis a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.This work was supported by the PRIN-INAF 2016 'The Cradle of Life – GENESIS-SKA (General Conditions in Early Planetary Systems for the rise of life with SKA)', the project PRIN-INAF-MAIN-STREAM 2017 'Protoplanetary disks seen through the eyes of new-generation instruments', the PRIN-INAF 2019 'Planetary systems at young ages (PLATEA)', the program PRIN-MIUR 2015 STARS in the CAOS – Simulation Tools for Astrochemical Reactivity and Spectroscopy in the Cyberinfrastructure for Astrochemical Organic Species (2015F59J3R, MIUR Ministero dell’Istruzione, dell’Università, della Ricerca e della Scuola Normale Superiore), the European Marie Sklodowska-Curie Actions under the European Union’s Horizon 2020 research and innovation program through the Project 'AstroChemistry Origins' (ACO), Grant No 811312, INAF/Frontiera (Fostering high ResolutiON Technology and Innovation for Exoplanets and Research in Astrophysics) through the 'Progetti Premiali' funding scheme of the Italian Ministry of Education, University, and Research, as well as NSF grants AST- 1514670 and NASA NNX16AB48G, the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA (CUP C52I13000140001).C.D. and C.G. acknowledge support from the NWO TOP grant 'Herbig Ae/Be stars, Rosetta stones for understanding the formation of planetary systems', project number 614.001.552. T.H. acknowledges support from the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28., European Project: 811312, European Project: 832428, and Low Energy Astrophysics (API, FNWI)

Subjects
Physics, Earth and Planetary Astrophysics (astro-ph.EP), Protoplanetary disks, [PHYS]Physics [physics], Polarimetric, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, [SPI]Engineering Sciences [physics], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Planet, Astrophysics of Galaxies (astro-ph.GA), Techniques: Polarimetric, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

To date, nearly two hundred planet-forming disks have been imaged with high resolution. Our propensity to study bright and extended objects is however biasing our view of the disk demography. In this work, we contribute to alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE that look faint in scattered light. Sources were selected based on a low far-IR excess from the spectral energy distribution. The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets is only detected from a small portion of the disk extent. The mild anti-correlation between the disk brightness and the near-IR excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk in penumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outer disk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks from the literature with either no shadow or with sign of azimuthally confined shadows., Accepted for publication in A\&A

Published
2021

5. A deconvolution technique to correct deep images of galaxies from instrumental scattered light

Author

Pierre-Alain Duc, Pierre Chanial, Stephen Gwyn, Harald Kuntschner, Jean-Charles Cuillandre, Emin Karabal, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), European Southern Observatory (ESO), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Observatoire de Paris, Université Paris sciences et lettres (PSL), National Research Council of Canada (NRC), The paper is based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Point spread function, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], FOS: Physical sciences, Flux, techniques: image processing, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, cD, techniques: photometric, 0103 physical sciences, Galaxy formation and evolution, Surface brightness, galaxies: elliptical and lenticular, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Sample (graphics), Galaxy, galaxies: photometry, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: elliptical and lenticular, cD, galaxies: stellar content, Halo, Deconvolution, Astrophysics - Instrumentation and Methods for Astrophysics, galaxies: evolution
Abstract

Deep imaging of the diffuse light emitted by the stellar fine structures and outer halos around galaxies is now often used to probe their past mass assembly. Because the extended halos survive longer than the relatively fragile tidal features, they trace more ancient mergers. We use images reaching surface brightness limits as low as 28.5-29 mag.arcsec-2 (g-band) to obtain light and color profiles up to 5-10 effective radii of a sample of nearby early-type galaxies. They were acquired with MegaCam as part of the CFHT MATLAS large programme. These profiles may be compared to those produced by simulations of galaxy formation and evolution, once corrected for instrumental effects. Indeed they can be heavily contaminated by the scattered light caused by internal reflections within the instrument. In particular, the nucleus of galaxies generates artificial flux in the outer halo, which has to be precisely subtracted. We present a deconvolution technique to remove the artificial halos that makes use of very large kernels. The technique based on PyOperators is more time efficient than the model-convolution methods also used for that purpose. This is especially the case for galaxies with complex structures that are hard to model. Having a good knowledge of the Point Spread Function (PSF), including its outer wings, is critical for the method. A database of MegaCam PSF models corresponding to different seeing conditions and bands was generated directly from the deep images. It is shown that the difference in the PSFs in different bands causes artificial changes in the color profiles, in particular a reddening of the outskirts of galaxies having a bright nucleus. The method is validated with a set of simulated images and applied to three representative test cases: NGC 3599, NGC 3489, and NGC 4274, and exhibiting for two of them a prominent ghost halo. The method successfully removes it., Comment: 10 pages, 11 figures, accepted for publication in A&A

Published
2017

6. Variability in fluence and spectrum of high-energy photon bursts produced by lightning leaders

Author

Wei Xu, Sebastien Celestin, Victor P. Pasko, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Communications and Space Sciences Laboratory [PennState] (CSSL), Pennsylvania State University (Penn State), Penn State System-Penn State System, and Part of the simulation results presented in this paper has been obtained using the computer cluster at the Centre de Calcul Scientifique en région Centre (CCSC).

Subjects
Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Photon, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Electron, Astrophysics, Photon energy, 01 natural sciences, 7. Clean energy, Fluence, Lightning, Spectral line, Corona (optical phenomenon), Geophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; In this paper, we model the production and acceleration of thermal runaway electrons during negative corona flash stages of stepping lightning leaders and the corresponding terrestrial gamma ray flashes (TGFs) or negative cloud-to-ground (−CG) lightning-produced X-ray bursts in a unified fashion. We show how the source photon spectrum and fluence depend on the potential drop formed in the lightning leader tip region during corona flash and how the X-ray burst spectrum progressively converges toward typical TGF spectrum as the potential drop increases. Additionally, we show that the number of streamers produced in a negative corona flash, the source electron energy distribution function, the corresponding number of photons, and the photon energy distribution and transport through the atmosphere up to low-orbit satellite altitudes exhibit a very strong dependence on this potential drop. This leads to a threshold effect causing X-rays produced by leaders with potentials lower than those producing typical TGFs extremely unlikely to be detected by low-orbit satellites. Moreover, from the number of photons in X-ray bursts produced by −CGs estimated from ground observations, we show that the proportionality between the number of thermal runaway electrons and the square of the potential drop in the leader tip region during negative corona flash proposed earlier leads to typical photon fluences on the order of 1 ph/cm2 at an altitude of 500 km and a radial distance of 200 km for intracloud lightning discharges producing 300 MV potential drops, which is consistent with observations of TGF fluences and spectra from satellites.

Published
2015

7. Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit

Author

Pierre-Yves Longaretti, S. Fromang, Geoffroy Lesur, Heloise Meheut, M. Joos, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), The simulations presented in this paper were granted access to the HPC resources of CCRT under the allocation x2012042231 made by GENCI (Grand Équipement National de Calcul Intensif), European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), European Project: 294110,EC:FP7:PEOPLE,FP7-PEOPLE-2011-CIG,HALLDISCS(2012), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Angular momentum, FOS: Physical sciences, Astrophysics, Magnetohydrodynamic turbulence, 01 natural sciences, magnetohydrodynamics (MHD), methods: numerical, accretion, Magnetorotational instability, 0103 physical sciences, Magnetic pressure, Magnetic Prandtl number, 010306 general physics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Earth and Planetary Astrophysics (astro-ph.EP), Physics, Turbulence, accretion disks, turbulence, protoplanetary disks, Fluid Dynamics (physics.flu-dyn), Astronomy and Astrophysics, Physics - Fluid Dynamics, Computational physics, Magnetic field, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

Angular momentum transport in accretion discs is often believed to be due to magnetohydrodynamic turbulence mediated by the magnetorotational instability. Despite an abundant literature on the MRI, the parameters governing the saturation amplitude of the turbulence are poorly understood and the existence of an asymptotic behavior in the Ohmic diffusion regime is not clearly established. We investigate the properties of the turbulent state in the small magnetic Prandtl number limit. Since this is extremely computationally expensive, we also study the relevance and range of applicability of the most common subgrid scale models for this problem. Unstratified shearing boxes simulations are performed both in the compressible and incompressible limits, with a resolution up to 800 cells per disc scale height. The latter constitutes the largest resolution ever attained for a simulation of MRI turbulence. In the presence of a mean magnetic field threading the domain, angular momentum transport converges to a finite value in the small Pm limit. When the mean vertical field amplitude is such that {\beta}, the ratio between the thermal and magnetic pressure, equals 1000, we find {\alpha}~0.032 when Pm approaches zero. In the case of a mean toroidal field for which {\beta}=100, we find {\alpha}~0.018 in the same limit. Both implicit LES and Chollet-Lesieur closure model reproduces these results for the {\alpha} parameter and the power spectra. A reduction in computational cost of a factor at least 16 (and up to 256) is achieved when using such methods. MRI turbulence operates efficiently in the small Pm limit provided there is a mean magnetic field. Implicit LES offers a practical and efficient mean of investigation of this regime but should be used with care, particularly in the case of a vertical field. Chollet-Lesieur closure model is perfectly suited for simulations done with a spectral code., Comment: Accepted for publication in A&A

Published
2015

8. Vortex cycles at the inner edges of dead zones in protoplanetary disks

Author

S. Fromang, Heloise Meheut, Julien Faure, Henrik N. Latter, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Applied Mathematics and Theoretical Physics (DAMTP), University of Cambridge [UK] (CAM), J.F., S.F., and H.M. acknowledge funding from the European Research Council underthe European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement No. 258729. HL acknowledges support via STFC grant ST/G/002584/1. The simulations presented in this paper were granted access to the HPC resources of Cines under the allocation x2013042231 and x2014042231 made by GENCI (Grand Equipement National de Calcul Intensif)., European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), and Department of Applied Mathematics and Theoretical Physics / Centre for Mathematical Sciences (DAMTP/CMS)

Subjects
010504 meteorology & atmospheric sciences, FOS: Physical sciences, Context (language use), Astrophysics, Protoplanetary disk, 01 natural sciences, Instability, Physics::Fluid Dynamics, 0103 physical sciences, planets and satellites: formation, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Computer simulation, Turbulence, protoplanetary disks, Rossby wave, Astronomy and Astrophysics, Laminar flow, Mechanics, Vortex, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

In protoplanetary disks, the inner boundary between the turbulent and laminar regions is a promising site for planet formation because solids may become trapped at the interface itself or in vortices generated by the Rossby wave instability. The disk thermodynamics and the turbulent dynamics at that location are entwined because of the importance of turbulent dissipation on thermal ionization and, conversely, of thermal ionisation on the turbulence. However, most previous work has neglected this dynamical coupling and have thus missed a key element of the physics in this region. In this paper, we aim to determine how the the interplay between ionization and turbulence impacts on the formation and evolution of vortices at the interface between the active and the dead zones. Using the Godunov code RAMSES, we have performed a 3D magnetohydrodynamic global numerical simulation of a cylindrical model of an MRI--turbulent protoplanetary disk, including thermodynamical effects as well as a temperature-dependant resistivity. The comparison with an analogous 2D viscous simulation has been extensively used to help identify the relevant physical processes and the disk's long-term evolution. We find that a vortex formed at the interface, due to Rossby wave instability, migrates inward and penetrates the active zone where it is destroyed by turbulent motions. Subsequently, a new vortex emerges a few tens of orbits later at the interface, and the new vortex migrates inward too. The sequence repeats itself, resulting in cycles of vortex formation, migration, and disruption. This behavior is successfully reproduced using two different codes. In this paper, we characterize this vortex life cycle and discuss its implications for planet formation at the dead/active interface. Our simulations highlight the importance of thermodynamical processes for the vortex evolution at the dead zone inner edge., Comment: 13 pages, 15 figures

Published
2015

9. Thanatology in protoplanetary discs - The combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones

Author

Geoffroy Lesur, Sebastien Fromang, Matthew W. Kunz, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Department of Astrophysical Sciences [Princeton], Princeton University, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Support for G.L. was provided by the European Community via contract PCIG09-GA-2011-294110. Support for M.W.K. was provided by NASA through Einstein Postdoctoral Fellowship Award Number PF1-120084, issued by theChandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. Support for S.F. was provided by the European Research Council under the European Union’s Seventh Framework Programme(FP7/2007-2013)/ERC Grant agreement n 258729. Most of the the computa-tions presented in this paper were performed using the Froggy platform of theCIMENT infrastructure (https://ciment.ujf-grenoble.fr), which is supported bythe Rhône-Alpes region (GRANT CPER07_13 CIRA), the OSUG@2020 labex(reference ANR10 LABX56) and the Equip@Meso project (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by theAgence Nationale pour la Recherche. This work was granted access to the HPCresources of IDRIS under allocation x2014042231 made by GENCI (GrandEquipement National de Calcul Intensif), European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112))

Subjects
010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astrophysics, 01 natural sciences, magnetohydrodynamics (MHD), accretion, Hall effect, Magnetorotational instability, 0103 physical sciences, Magnetic pressure, Diffusion (business), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), stars: formation, Accretion (meteorology), Ambipolar diffusion, accretion disks, protoplanetary disks, Astronomy and Astrophysics, Mechanics, Magnetic field, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, instabilities, Astrophysics::Earth and Planetary Astrophysics, Magnetohydrodynamics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

Protoplanetary discs are poorly ionised due to their low temperatures and high column densities, and are therefore subject to three "non-ideal" magnetohydrodynamic effects: Ohmic dissipation, ambipolar diffusion, and the Hall effect. The existence of magnetically driven turbulence in these discs has been a central question since the discovery of the magnetorotational instability. Early models considered Ohmic diffusion only and led to a scenario of layered accretion, in which a magnetically "dead" zone in the disc midplane is embedded within magnetically "active" surface layers at distances ~1-10 au from the central protostellar object. Recent work has suggested that a combination of Ohmic dissipation and ambipolar diffusion can render both the midplane and surface layers of the disc inactive and that torques due to magnetically driven outflows are required to explain the observed accretion rates. We reassess this picture by performing three-dimensional numerical simulations that include, for the first time, all three non-ideal MHD effects. We find that the Hall effect can generically "revive" dead zones by producing a dominant azimuthal magnetic field and a large-scale Maxwell stress throughout the midplane, provided the angular velocity and magnetic field satisfy Omega.B > 0. The attendant large magnetic pressure modifies the vertical density profile and substantially increases the disc scale height beyond its hydrostatic value. Outflows are produced, but are not necessary to explain accretion rates, 16 pages, 18 figures, 3 tables, accepted for publication in Astronomy & Astrophysics

Published
2014

10. Statistics of whistler mode waves in the outer radiation belt: Cluster STAFF-SA measurements

Author

Michael A. Balikhin, Hugo Breuillard, Didier Mourenas, Oleksiy Agapitov, G. Rolland, Vladimir Krasnoselskikh, Yuri V. Khotyaintsev, Anton Artemyev, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Swedish Institute of Space Physics [Kiruna] (IRF), Centre d'Études de Limeil-Valenton (CEA-DAM), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Automatic Control and Systems Engineering, University of Sheffield [Sheffield], Centre National d'Études Spatiales [Toulouse] (CNES), for their assistance in evaluating this paper. This work was supported by CNES through the grant 'Modeles d’ondes' and Cluster Co-I DWP.Swedish Research Council, grant 2007-4377, and European Project: 284520,EC:FP7:SPA,FP7-SPACE-2011-1,MAARBLE(2012)

Subjects
Physics, Hiss, 010504 meteorology & atmospheric sciences, Whistler, Wave propagation, 01 natural sciences, Physics::Geophysics, L-shell, symbols.namesake, Geophysics, Amplitude, Earth's magnetic field, Space and Planetary Science, Surface wave, [SDU]Sciences of the Universe [physics], Van Allen radiation belt, 0103 physical sciences, Statistics, Physics::Space Physics, symbols, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; [1] ELF/VLF waves play a crucial role in the dynamics of the radiation belts and are partly responsible for the main losses and the acceleration of energetic electrons. Modeling wave-particle interactions requires detailed information of wave amplitudes and wave normal distribution over L-shells and over magnetic latitudes for different geomagnetic activity conditions. We performed a statistical study of ELF/VLF emissions using wave measurements in the whistler frequency range for 10 years (2001–2010) aboard Cluster spacecraft. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8 Hz to 4 kHz. We present distributions of wave magnetic and electric field amplitudes and wave normal directions as functions of magnetic latitude, magnetic local time, L-shell, and geomagnetic activity. We show that wave normals are directed approximately along the background magnetic field (with the mean value of  — the angle between the wave normal and the background magnetic field, about 10 ı –15 ı) in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude: Plasmaspheric hiss normal angles increase with latitude to quasi-perpendicular direction at 35 ı –40 ı where hiss can be reflected; lower band chorus are observed as two wave populations: One population of wave normals tends toward the resonance cone and at latitudes of around 35 ı –45 ı wave normals become nearly perpendicular to the magnetic field; the other part remains quasi-parallel at latitudes up to 30 ı. The observed angular distribution is significantly different from Gaussian, and the width of the distribution increases with latitude. Due to the rapid increase of  , the wave mode becomes quasi-electrostatic, and the corresponding electric field increases with latitude and has a maximum near 30 ı. The magnetic field amplitude of the chorus in the day sector has a minimum at the magnetic equator but increases rapidly with latitude with a local maximum near 12 ı –15 ı. The wave magnetic field maximum is observed in the night sector at L > 7 during low geomagnetic activity (at L 5 for K p > 3). Our results confirm the strong dependence of wave amplitude on geomagnetic activity found in earlier studies. (2013), Statistics of whistler-mode waves in the outer radiation belt: Cluster STAFF-SA measurements

Published
2013