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The MUSCLES treasury survey. V. FUV flares on active and inactive M Dwarfs

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arXiv 2018年

作者： Loyd, R.O. Parke France, Kevin Youngblood, Allison Schneider, Christian Brown, Alexander Hu, Renyu Segura, Antígona Linsky, Jeffrey Redfield, Seth Tian, Feng Rugheimer, Sarah Miguel, Yamila Froning, Cynthia S. School of Earth and Space Exploration Arizona State University TempeAZ85287 United States Laboratory for Atmospheric and Space Physics BoulderCO80309 United States Goddard Space Flight Center GreenbeltMD20771 United States Hamburger Sternwarte Gojenbergsweg 112 Hamburg21029 Germany Keplerlaan 1 AZNoordwijk2201 Netherlands Center for Astrophysics and Space Astronomy University of Colorado 389 UCB BoulderCO80309 United States Jet Propulsion Laboratory California Institute of Technology PasadenaCA91109 United States Division of Geological and Planetary Sciences California Institute of Technology PasadenaCA91125 United States NASA Astrobiology Institute Virtual Planetary Laboratory Box 351580 U.W. SeattleWA98195 United States Instituto de Ciencias Nucleares Universidad Nacional Autónoma de México Mexico JILA University of Colorado and NIST 440 UCB BoulderCO80309 United States Astronomy Department and Van Vleck Observatory Wesleyan University MiddletownCT06459 United States Department of Earth System Science Tsinghua University Beijing100084 China Centre for Exoplanet Science University of St. Andrews School of Earth and Environmental Sciences Irvine Building North Street St. AndrewsKY16 9AL United Kingdom Harvard Smithsonian Center for Astrophysics 60 Garden Street CambridgeMA02138 United States Carl Sagan Institute Department of Astronomy Cornell University IthacaNY14853 United States Leiden Observatory LeidenNL-2333 CA Netherlands Department of Astronomy/McDonald Observatory C1400 University of Texas at Austin AustinTX78712 United States

M dwarf stars are known for their vigorous aring. This aring could impact the climate of orbiting planets, making it important to characterize M dwarf ares at the short wavelengths that drive atmospheric chemistry and escape. We conducted a far-ultraviolet are survey of 6 M dwarfs from the recent MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary systems) observations, as well as 4 highly-active M dwarfs with archival data. When comparing absolute are energies, we found the active-M-star ares to be about 10× more energetic than inactive-M-star ares. However, when are energies were normalized by the star's quiescent ux, the active and inactive samples exhibited identical are distributions, with a power-law index of -0:76+0:1-0:09(cumulative distribution). The rate and distribution of ares are such that they could dominate the FUV energy budget of M dwarfs, assuming the same distribution holds to ares as energetic as those cataloged by Kepler and ground-based surveys. We used the observed events to create an idealized model are with realistic spectral and temporal energy budgets to be used in photochemical simulations of exoplanet atmospheres. Applied to our own simulation of direct photolysis by photons alone (no particles), we find the most energetic observed ares have little effect on an Earth-like atmosphere, photolyzing ∼0.01% of the total O3column. The observations were too limited temporally (73 h cumulative exposure) to catch rare, highly energetic ares. Those that the power-law fit predicts occur monthly would photolyze ∼1% of the O3column and those it predicts occur yearly would photolyze the full O3column. Whether such energetic ares occur at the rate predicted is an open question. Copyright © 2018, The Authors. All rights reserved.

关键词： Surveys

Generalised Error Functions from the Kerr Metric

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Chinese Physics Letters 2016年第3期33卷 12-16页

作者：唐文林罗子人刘润球 Science and Technology on Aerospace Flight Dynamics Laboratory Beijing Aerospace Control Center Department of Aerospace Guidance Navigation and Control School of AstronauticsBeihang University QUEST Center of Quantum Engineering and Space-Time Research Leibniz Universitt Hannover Max Planck Institute for Gravitational Physics(Albert Einstein Institute) Institute of Applied Mathematics Morningside Center of Mathematics and LESCInstitute of Computational MathematicsAcademy of Mathematics and System ScienceChinese Academy of Sciences

Motivated by the effort to understand the mathematical structure underlying the Teukolsky equations in a Kerr metric background, a homogeneous integral equation related to the prolate spheroidal function is studied. From the consideration of the Fredholm determinant of the integral equation, a family of generalized error function is defined, with which the Fredholm determinant of the sinc kernel is also evaluated. An analytic solution of a special ease of the fifth Painlev~ transcendent is then worked out explicitly.

关键词： of is exp in Generalised Error Functions from the Kerr Metric from

GAFD Special issue on "Physics and Algorithms of the Pencil Code" f-mode strengthening from a localised bipolar subsurface magnetic field

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arXiv 2018年

作者： Singh, Nishant K. Raichur, Harsha Käpylä, Maarit J. Rheinhardt, Matthias Brandenburg, Axel Käpylä, Petri J. Max Planck Institute for Solar System Research Göttingen37077 Germany ReSoLVE Centre of Excellence Dept. of Computer Science Aalto University FI-00076 Finland NORDITA KTH Royal Inst. of Technology Stockholm University Stockholm10691 Sweden Dept. of Astronomy AlbaNova University Center Stockholm University Stockholm10691 Sweden JILA Dept. of Astrophysical and Planetary Sciences University of Colorado Boulder United States Laboratory for Atmospheric and Space Physics 3665 Discovery Drive BoulderCO80303 United States Georg-August-Universität Göttingen Institut für Astrophysik Friedrich-Hund-Platz 1 GöttingenD 37077 Germany

Recent numerical work in helioseismology has shown that a periodically varying subsurface magnetic field leads to a fanning of the f-mode, which emerges from a density jump at the surface. In an attempt to model a more realistic situation, we now modulate this periodic variation with an envelope, giving thus more emphasis on localised bipolar magnetic structures in the middle of the domain. Some notable findings are: (i) compared to the purely hydrodynamic case, the strength of the f-mode is significantly larger at high horizontal wavenumbers k, but the fanning is weaker for the localised subsurface magnetic field concentrations investigated here than the periodic ones studied earlier;(ii) when the strength of the magnetic field is enhanced at a fixed depth below the surface, the fanning of the f-mode in the kω diagram increases proportionally in such a way that the normalised f-mode strengths remain nearly the same in different such cases;(iii) the unstable Bloch modes reported previously in case of harmonically varying magnetic fields are now completely absent when more realistic localised magnetic field concentrations are imposed beneath the surface, thus suggesting that the Bloch modes are unlikely to be supported during most phases of the solar cycle;(iv) the f-mode strength appears to depend also on the depth of magnetic field concentrations such that it shows a relative decrement when the maximum of the magnetic field is moved to a deeper layer. We argue that detections of f-mode perturbations such as those being explored here could be effective tracers of solar magnetic fields below the photosphere before these are directly detectable as visible manifestations in terms of active regions or sunspots. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Bihelical spectrum of solar magnetic helicity and its evolution

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arXiv 2018年

作者： Singh, Nishant K. Käpylä, Maarit J. Brandenburg, Axel Käpylä, Petri J. Lagg, Andreas Virtanen, Ilpo Max Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 GöttingenD-37077 Germany ReSoLVE Centre of Excellence Department of Computer Science Aalto University PO Box 15400 AaltoFI-00076 Finland NORDITA KTH Royal Institute of Technology Stockholm University Roslagstullsbacken 23 StockholmSE-10691 Sweden Department of Astronomy AlbaNova University Center Stockholm University StockholmSE-10691 Sweden JILA Department of Astrophysical and Planetary Sciences University of Colorado Box 440 BoulderCO80303 United States Laboratory for Atmospheric and Space Physics 3665 Discovery Drive BoulderCO80303 United States Leibniz Institute for Astrophysics Potsdam An der Sternwarte 16 Potsdam14482 Germany ReSoLVE Centre of Excellence Space Climate research unit University of Oulu P.O.Box 3000 OuluFIN-90014 Finland

Using a recently developed two-scale formalism to determine the magnetic helicity spectrum (Brandenburg et al. 2017), we analyze synoptic vector magnetograms built with data from the Vector Spectromagnetograph (VSM) instrument on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) telescope during January 2010–July 2016. In contrast to an earlier study using only three Carrington rotations, our analysis includes 74 synoptic Carrington rotation maps. We recover here bihelical spectra at different phases of solar cycle 24, where the net magnetic helicity in the majority of the data is consistent with a large-scale dynamo with helical turbulence operating in the Sun. More than 20% of the analyzed maps, however, show violations of the expected sign rule. Copyright © 2018, The Authors. All rights reserved.

关键词： Turbulence

Cloud Atlas: Weak color modulations due to rotation in the planetary-mass companion GU Psc b and 11 other brown dwarfs

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arXiv 2019年

作者： Lew, Ben W.P. Apai, Dániel Zhou, Yifan Radigan, Jacqueline Marley, Mark Schneider, Glenn Cowan, Nicolas B. Miles-Páez, Paulo A. Manjavacas, Elena Karalidi, Theodora Bedin, L.R. Lowrance, Patrick J. Burgasser, Adam J. Lunar and Planetary Laboratory University of Arizona 1640 E. University Blvd TucsonAZ85718 United States Department of Astronomy and Steward Observatory University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States Lunar and Planetary Laboratory University of Arizona 1640 E. University Blvd TucsonAZ85718 United States Earths in Other Solar Systems Team NASA Nexus for Exoplanet System Science Department of Astronomy University of Texas AustinTX78712 United States Utah Valley University 800 West University Parkway OremUT84058 United States NASA Ames Research Center Naval Air Station Moffett Field Mountain ViewCA94035 United States Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada Department of Earth & Planetary Sciences McGill University 3450 rue University MontréalQCH3A 0E8 Canada European Southern Observatory Karl-Schwarzschild-Straße 2 Garching85748 Germany W.M. Keck Observatory Mamalahoa Hwy KamuelaHI96743 United States Department of Physics University of Central Florida 4000 Central Florida Boulevard OrlandoFL32816 United States INAF-Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 PadovaI-35122 Italy IPAC-Spitzer MC 314-6 California Institute of Technology PasadenaCA91125 United States Astrophysics and Space Science University of California San Diego La JollaCA92093 United States

Among the greatest challenges in understanding ultra-cool brown dwarf and exoplanet atmospheres is the evolution of cloud structure as a function of temperature and gravity. In this study, we present the rotational modulations of GU Psc b – a rare mid-T spectral type planetary-mass companion at the end of the L/T spectral type transition. Based on the HST/WFC3 1.1-1.67 µm time-series spectra, we observe a quasi-sinusoidal light curve with a peak-to-trough flux variation of 2.7% and a minimum period of eight hours. The rotation-modulated spectral variations are weakly wavelength-dependent, or largely gray between 1.1-1.67 µm. The gray modulations indicate that heterogeneous clouds are present in the photosphere of this low-gravity mid-T dwarf. We place the color and brightness variations of GU Psc b in the context of rotational modulations reported for mid-L to late-T dwarfs. Based on these observations, we report a tentative trend: mid-to-late T dwarfs become slightly redder in J − H color with increasing J-band brightness, while L dwarfs become slightly bluer with increasing brightness. If this trend is verified with more T-dwarf samples, it suggests that in addition to the mostly gray modulations, there is a second-order spectral-type dependence on the nature of rotational modulations. Copyright © 2019, The Authors. All rights reserved.

关键词： Extrasolar planets

Ghost imaging based on Pearson correlation coefficients

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Chinese Physics B 2015年第5期24卷 340-345页

作者：俞文凯姚旭日刘雪峰李龙珍翟光杰 Key Laboratory of Electronics and Information Technology for Space System Center for Space Science and Applied ResearchChinese Academy of Sciences University of Chinese Academy of Sciences

Correspondence imaging is a new modality of ghost imaging, which can retrieve a positive/negative image by simple conditional averaging of the reference frames that correspond to relatively large/small values of the total intensity measured at the bucket detector. Here we propose and experimentally demonstrate a more rigorous and general approach in which a ghost image is retrieved by calculating a Pearson correlation coefficient between the bucket detector intensity and the brightness at a given pixel of the reference frames, and at the next pixel, and so on. Furthermore, we theoretically provide a statistical interpretation of these two imaging phenomena, and explain how the error depends on the sample size and what kind of distribution the error obeys. According to our analysis, the image signal-to-noise ratio can be greatly improved and the sampling number reduced by means of our new method.

关键词： coherence image forming and processing probability theory

Chaos Control and Bifurcation Behavior for a Sprott E system with Distributed Delay Feedback

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International Journal of Automation and computing 2015年第2期12卷 182-191页

作者： Chang-Jin Xu Yu-Sen Wu Guizhou Key Laboratory of Economics System Simulation Guizhou University of Finance and Economics School of Mathematics and Statistics Henan University of Science and Technology

In this paper, the problem of controlling chaos in a Sprott E system with distributed delay feedback is considered. By analyzing the associated characteristic transcendental equation, we focus on the local stability and Hopf bifurcation nature of the Sprott E system with distributed delay feedback. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions are derived by using the normal form theory and center manifold theory. Numerical simulations for justifying the theoretical analysis are provided.

关键词： Sprott E system chaos control stability Hopf bifurcation distributed delay.

Generating scalable entanglement of ultracold bosons in superlattices through resonant shaking

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arXiv 2017年

作者： Cao, Lushuai Deng, Xing Zhu, Qian-Ru Xu, Xiao-Fan Fang, Xue-Ting Gao, Xiang Schmelcher, Peter Hu, Zhong-Kun MOE Key Laboratory of Fundamental Physical Quantities Measurement Hubei Key Laboratory of Gravitation and Quantum Physics School of Physics Huazhong University of Science and Technology Wuhan430074 China Institute of Space-based Information System China Academy of Electronics and Information Technology Beijing100041 China Zentrum für Optische Quantentechnologien Universität Hamburg Luruper Chaussee 149 Hamburg22761 Germany Hamburg Centre for Ultrafast Imaging Luruper Chaussee 149 Hamburg22761 Germany

Based on a one-dimensional double-well superlattice with a unit filling of ultracold atoms per site, we propose a scheme to generate scalable entangled states in the superlattice through resonant lattice shakings. Our scheme utilizes periodic lattice modulations to entangle two atoms in each unit cell with respect to their orbital degree of freedom, and the complete atomic system in the superlattice becomes a cluster of bipartite entangled atom pairs. To demonstrate this we perform ab initio quantum dynamical simulations using the Multi-Layer Multi-Configuration Time-Dependent Hartree Method for Bosons, which accounts for all correlations among the atoms. The proposed clusters of bipartite entanglements manifest as an essential resource for various quantum applications, such as measurement based quantum computation. The lattice shaking scheme to generate this cluster possesses advantages such as a high scalability, fast processing speed, rich controllability on the target entangled states, and accessibility with current experimental techniques. Copyright © 2017, The Authors. All rights reserved.

关键词： Quantum entanglement

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

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arXiv 2019年

作者： Tubiana, C. Rinaldi, G. Güttler, C. Snodgrass, C. Shi, X. Hu, X. Marschall, R. Fulle, M. Bockelée-Morvan, D. Naletto, G. Capaccioni, F. Sierks, H. Arnold, G. Barucci, M.A. Bertaux, J.-L. Bertini, I. Bodewits, D. Capria, M.T. Ciarniello, M. Cremonese, G. Crovisier, J. da Deppo, V. Debei, S. de Cecco, M. Deller, J. de Sanctis, M.C. Davidsson, B. Doose, L. Erard, S. Filacchione, G. Fink, U. Formisano, M. Fornasier, S. Gutiérrez, P.J. Ip, W.-H. Ivanovski, S. Kappel, D. Keller, H.U. Kolokolova, L. Koschny, D. Krueger, H. la Forgia, F. Lamy, P.L. Lara, L.M. Lazzarin, M. Levasseur-Regourd, A.C. Lin, Z.-Y. Longobardo, A. López-Moreno, J.J. Marzari, F. Migliorini, A. Mottola, S. Rodrigo, R. Taylor, F. Toth, I. Zakharov, V. Max Planck Institute for Solar System Research Göttingen Germany Istituto di Astrofisica e Planetologia Spaziali Istituto Nazionale di Astrofisica Rome Italy Institute for Astronomy University of Edinburgh Royal Observatory EdinburghEH9 3HJ United Kingdom Institute for Geodesy and Geoinformation Science Technical University Berlin Straße des 17. Juni 135 Berlin10623 Germany International Space Science Institute Bern Switzerland INAF – Osservatorio Astronomico Trieste Italy LESIA Observatoire de Paris PSL Research University CNRS Sorbonne Université Univ. Paris Diderot Sorbonne Paris Cité 5 place Jules Janssen MeudonF-92195 France Department of Physics Oxford University Oxford United Kingdom Institut für Planetenforschung Berlin Germany Lunar and Planetary Laboratory University of Arizona Tucson United States Physics Department Auburn University AuburnAL36849 United States Laboratoire Atmosphères Milieux et Observations Spatiales CNRS Université de Versailles Saint-Quentin-en-Yvelines 11 boulevard d’Alembert Guyancourt78280 France Centro de Astrobiologia CSIC-INTA Torrejon de ArdozMadrid Spain Science Support Office European Space Research and Technology Centre/ESA Keplerlaan 1 Postbus 299 NoordwijkZH2201 AZ Netherlands Jet Propulsion Laboratory M/S 183-401 4800 Oak Grove Drive PasadenaCA91109 United States LATMOS CNRS/UVSQ/IPSL 11 Boulevard d’Alembert Guyancourt78280 France University of Padova Department of Physics and Astronomy "Galileo Galilei" Vicolo dell’Osservatorio 3 Padova35122 Italy INAF Astronomical Observatory of Padova Vicolo dell’Osservatorio 5 Padova35122 Italy CNR-IFN UOS Padova LUXOR Via Trasea 7 Padova35131 Italy University of Padova Department of Industrial Engineering Via Venezia 1 Padova35131 Italy University of Trento Faculty of Engineering Via Mesiano 77 Trento38121 Italy c/ Glorieta de la Astronomia s/n Granada18008 Spain Institute of Physics and Astronomy University of Potsdam Potsdam

Context. On 27 April 2015, when 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving towards perihelion, the OSIRIS and VIRTIS-M instruments on board Rosetta simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the dust, H2O and CO2 gas spatial distribution in the inner coma. To do this we performed a quantitative analysis of the release of dust and gas and compared the observed H2O production rate with the one calculated using a thermo-physical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H2O emission band) and 4200 nm (CO2 emission band). We measured the average signal in a circular annulus, to study spatial variation around the comet, and in a sector of the annulus, to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet centre. Results. The spatial correlation between dust and water, both coming from the sun-lit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0◦ sub-solar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO2 production. An excess of measured water production, with respect to the value calculated using a simple thermo-physical model, is observed when the head lobe and regions of the Southern hemisphere with strong seasonal variations are illuminated (sub-solar longitude 270◦– 50◦). A drastic decrease in dust production, when the water production (both measured and from the model) displays a maximum, happens when typical Northern consolidated regions are illuminated and the Southern hemisphere regions wi

关键词： Comets