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Evolution of Magnetic Helicity Under Kinetic Magnetic Reconnection...

By: J. Büchner; T. Wiegelmann

Description: School of Mathematics and Statistics, University of St. Andrews, St. Andrews, KY16 9SS, United Kingdom. We investigate the evolution of magnetic helicity under kinetic magnetic reconnection in thin current sheets. We use Harris sheet equilibria and superimpose an external magnetic guide field. Consequently, the classical 2D magnetic neutral line becomes a field line here, causing a B ≠ 0 reconnection. While without a guide field, the ...

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Bayesian Modeling and Significant Features Exploration in Wavelet ...

By: F. Godtliebsen; D. V. Divine

Description: Department of Mathematics and Statistics, Faculty of Science, University of Troms\o, 9037, Norway. This study proposes and justifies a Bayesian approach to modeling wavelet coefficients and finding statistically significant features in wavelet power spectra. The approach utilizes ideas elaborated in scale-space smoothing methods and wavelet data analysis. We treat each scale of the discrete wavelet decomposition as a sequence of independent random variab...

Berger, J. (Ed.): Statistical decision theory and Bayesian analysis, Springer Verlag, 1985.; Box, E., Jenkins, G., and Reinsel, G.: Time series analysis: Forecasting and control, Prentice-Hall, Englewood Cliffs, 1994.; Chaudhuri, P. and Marron, J.: SiZer for exploration of structures in curves, J. Am. Statist. Assoc., 94, 807–823, 1999.; Dansgaard, W., Johnsen, S., Clausen, H., Dahl-Jensen, D., Gundestrup, N., Hammer, C., Hvidberg, C., Steffensen, J., Sveinbjornsdottir, ...

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Localized Alfvénic Solutions of Nondissipative and Compressible Mh...

By: G. Chanteur

Description: Centre d'étude des Environnments Terrestre et Planetéaires, Vélizy, France. Alfvénic solutions of nondissipative MHD are entirely determined by their magnetic configuration. With the supplementary assumption of incompressibility any solenoidal field can be used to construct an Alfvénic solution. It is demonstrated that for nondissipative and compressible MHD the energy equation constrains the magnetic field of Alfvénic solutions to have a constant stren...

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Continuous Partial Trends and Low-frequency Oscillations of Time S...

By: P. M. A. Miranda; A. R. Tomé

Description: Universidade da Beira Interior, Department of Physics, and Centro de Geofísica da Universidade de Lisboa, Portugal. This paper presents a recent methodology developed for the analysis of the slow evolution of geophysical time series. The method is based on least-squares fitting of continuous line segments to the data, subject to flexible conditions, and is able to objectively locate the times of significant change in the series tendencies. The time distr...

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A Kalman Filter Application to a Spectral Wave Model : Volume 12, ...

By: A. Pires Silva; M. C. Bernadino; J. P. Pinto

Description: Marinha, Instituto Hidrográfico, Portugal. A sequential time dependent data assimilation scheme based on the Kalman filter is applied to a spectral wave model. Usually, the first guess covariance matrices used in optimal interpolation schemes are exponential spreading functions, which remain constant. In the present work the first guess correlation errors evolve in time according to the dynamic constraints of the wave model. A system error noise is dedu...

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Mixed Layer in a Stably Stratified Fluid : Volume 1, Issue 4 (30/1...

By: A. Mangeney; F. Califano

Description: Observatoire de Paris-Meudon (DESPA), 5 Place Jansen, 92195 Meudon, France. We present a numerical study of the generation and evolution of a mixed layer in a stably stratified layer of Boussinesq fluid. We use an external forcing in the equation of motion to model the experimental situation where the mechanical energy input is due to an oscillating grid.
The results of 2D and 3D numerical simulations indicate that the basic mechanism for the entr...

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Cellular Automaton for Realistic Modelling of Landslides : Volume ...

By: E. Segre; C. Deangeli

Description: Istituto di Cosmo-Geofisica del C.N.R., Torino, Italy. A numerical model is developed for the simulation of debris flow in landslides over a complex three dimensional topography. The model is then validated by comparing a simulation with reported field data. Our model is in fact a realistic elaboration of simpler "sandpile automata", which have in recent years been studied as supposedly paradigmatic of "self-organized criticality". Statistics and scalin...

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Shoaling of Internal Solitary Waves at the Asiaex Site in the Sout...

By: A. Warn-varnas; K. G. Lamb

Description: Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada. The interaction of barotropic tides with Luzon Strait topography generates westward propagating internal bores and solitary waves trains which eventually shoal and dissipate on the western side of the South China Sea. Two-dimensional numerical simulations of this shoaling process at the site of the Asian Seas International Acoustic Experiment (ASIAEX) hav...

Grimshaw, R., Pelinovsky, E., and Poloukhina, O.: Higher-order Korteweg-de Vries models for internal solitary waves in a stratified shear flow with a free surface, Nonlin. Processes Geophys., 9, 221–235, doi:10.5194/npg-9-221-2002, 2002.; Osborne, A. R. and Burch, T. L.: Internal solitons in the Andaman Sea, Science, 208, 451–460, 1980.; Apel, J. R., Holbrook, J. R., Liu, A. K., and Tsai, J. J.: The Sulu Sea internal s...

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Identification of Magnetic Anomalies Based on Ground Magnetic Data...

By: A. A. Karbalaei Ramezanali; F. Feizi; E. Mansouri

Description: Young Researchers and Elite Club, South Tehran Branch, Islamic Azad University, Tehran, Iran. Ground magnetic anomaly separation using reduction-to-the-pole (RTP) technique and the fractal concentration-area (C-A) method has been applied to the Qoja-Kandi prosepecting area in NW Iran. The geophysical survey that resulted in the ground magnetic data was conducted for magnetic elements exploration. Firstly, RTP technique was applied for recognizing u...

Abedi, M., Torabi, S. A., and Norouzi, G. H.: Application of fuzzy AHP method to integrate geophysical data in a prospect scale, a case study: seridune copper deposit, B. Geofis. Teor. Appl., 54, 145–164, 2013.; Agterberg, F. P., Cheng, Q., Brown, A., and Good, D.: Multifractal modeling of fractures in the Lac du Bonnet batholith, Manitoba, Comput. Geosci., 22, 497–507, 1996.; Arian, M.: Physiographic-tectonic zoning of Iran's sedimentary basins, Open Journal of Geology,...

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A Variational Formulation for Translation and Assimilation of Cohe...

By: M. Plu

Description: Laboratoire de l'Atmosphère et des Cyclones, UMR8105, Unité mixte CNRS/Météo-France/Université de La Réunion, and CNRM-GAME, Météo-France/CNRS, Toulouse, France. The assimilation of observations from teledetected images in geophysical models requires one to develop algorithms that would account for the existence of coherent structures. In the context of variational data assimilation, a method is proposed to allow the background to be translated so as to ...

Michel, Y.: Displacing potential vorticity structures by the assimilation of pseudo-observations, Mon. Weather Rev., 139, 549–565, 2011.; Beezley, J. D. and Mandel, J.: Morphing ensemble Kalman filters, Tellus, 60A, 131–140, 2008.; Chen, Y. and Snyder, C.: Assimilating vortex position with an ensemble Kalman filter, Mon. Weather Rev., 135, 1828–1845, 2007.; Deckmyn, A. and Berre, L.: A wavelet approach to representing background error covariances in a limited-area model,...

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Empirical Correction Techniques: Analysis and Applications to Chao...

By: L. Kocarev; D. Smilkov; L. Basnarkov; I. Trpevski

Description: Macedonian Academy of Sciences and Arts, Skopje, Macedonia. Contemporary tools for reducing model error in weather and climate forecasting models include empirical correction techniques. In this paper we explore the use of such techniques on low-order atmospheric models. We first present an iterative linear regression method for model correction that works efficiently when the reference truth is sampled at large time intervals, which is typical for real...

Allgaier, N., Harris, K., and Danforth, C.: Empirical correction of a toy climate model, Phys. Rev. E, 85, 026201, doi:10.1103/PhysRevE.85.026201, 2012.; Anderson, J. L.: An ensemble adjustment Kalman filter for data assimilation, Mon. Weather Rev., 129, 2884–2903, 2001.; Bishop, C.: Pattern recognition and machine learning, Springer New York, 2006.; Basnarkov, L. and Kocarev, L.: Forecast improvement in Lorenz 96 ...

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Anisotropic Scaling Features and Complexity in Magnetospheric-cusp...

By: M. Kretzschmar; G. Consolini; B. Popielawska; A. W. Wernik; M. Materassi; M. Roca-sogorb; J. Bergman; E. Yordanova; K. Stasiewicz

Description: Space Research Center, Polish Academy of Sciences, Warsaw, Poland. Magnetospheric cusps are high-latitude regions characterized by a highly turbulent plasma, playing a special role in the solar wind-magnetosphere interaction. Here, using POLAR satellite magnetic field vector measurements we investigate the anisotropic scaling features of the magnetic field fluctuations in the northern cusp region. Our results seem to support the hypothesis of a 2D-MHD tu...

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Bifurcations and Instabilities in Rotating, Two-layer Fluids: II. ...

By: P. L. Read; I. M. Moroz; A. F. Lovegrove

Description: Atmospheric, Oceanic and Planetary Physics, University of Oxford, United Kingdom. In this paper, we show that the behavior of weakly nonlinear waves in a 2-layer model of baroclinic instability on a b-plane with varying viscosity is determined by a single, degenerate codimension three bifurcation. In the process, we show how previous studies, using the method of multiple scales to derive evolution equations for th...

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Preface Large Amplitude Internal Waves in the Coastal Ocean : Volu...

By: A. Scotti; K. Helfrich; R. Grimshaw

Description: Department of Mathematical Sciences, Loughborough University, Leicestershire, UK. No abstract available.

Grimshaw, R.: Internal solitary waves. In: Environmental Stratified Flows, edited by: Grimshaw, R., Kluwer, Boston, Chapter~1, 1–28, 2001.; Helfrich, K. R. and Melville, W. K.: Long nonlinear internal waves, Annu. Rev. Fluid Mech., 38, 395–425, 2006.; Grimshaw, R., Pelinovsky, E., Talipova, T., and Kurkina, O.: Internal solitary waves: propagation, deformation and disintegration, Nonlin. Processes Geophys., 17, 633–649, http://dx.doi.org/10.5194/npg-17-633-2010doi:10.519...

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An Artificial Neural Network Technique for Downscaling Gcm Outputs...

By: E. Coppola; F. Giorgi; R. Chadwick

Description: Department of Meteorology, University of Reading, UK. An Artificial Neural Network (ANN) approach is used to downscale ECHAM5 GCM temperature (T) and rainfall (R) fields to RegCM3 regional model scale over Europe. The main inputs to the neural network were the ECHAM5 fields and topography, and RegCM3 topography. An ANN trained for the period 1960–1980 was able to recreate the RegCM3 1981–2000 mean T and R fields with reasonab...

Bastos, L. and O'Hagan, A.: Diagnostics for Gaussian process emulators, Technometrics, 51, 425–438, 2008.; Bishop, C.: Neural Networks for Pattern Recognition, Clarendon Press, UK, 2000.; Busch, U. and Heimann, D.: Statistical-dynamical extrapolation of a nested regional climate simulation, Clim. Res., 19, 1–13, 2001.; Chadwick, R. and Grimes, D.: An artificial neural network approach to multi-spectral rainfall estimation over Africa., J. Hydrometeor., submitted, 2011.; ...

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Brief Communication: Breeding Vectors in the Phase Space Reconstru...

By: D. Kaufman; A. S. Sharma; K. Ide; E. Lynch; E. Kalnay

Description: Department of Atmospheric and Oceanic Science, University of Maryland, College Park, College Park, MD 20742, USA. Bred vectors characterize the nonlinear instability of dynamical systems and so far have been computed only for systems with known evolution equations. In this article, bred vectors are computed from a single time series data using time-delay embedding, with a new technique, nearest-neighbor breeding. Since the dynamical propertie...

Abarbanel, H. D. I., Brown, R., Sidorowich, J. J., and Tsimring, L. S.: The analysis of observed chaotic data in physical systems, Rev. Mod. Phys., 65, 1331–1392, 1993.; Chen, J. and Sharma, A. S.: Modeling and prediction of the magnetospheric dynamics during intense geospace storms, J. Geophys. Res., 111, A04209, doi:10.1029/2005JA011359, 2006.; Evans, E., Bhatti, N., Kinney, J., Pann, L., Pena, M., Yang, S. C., Kalnay,...

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Earthquake Sequencing: Chimera States with Kuramoto Model Dynamics...

By: M. Cavers; A. Ware; K. Vasudevan

Description: Department of Mathematics and Statistics, University of Calgary, Calgary, Alberta T2N 1N4, Canada. Earthquake sequencing studies allow us to investigate empirical relationships among spatio-temporal parameters describing the complexity of earthquake properties. We have recently studied the relevance of Markov chain models to draw information from global earthquake catalogues. In these studies, we considered directed graphs as graph theoretic repres...

Abrams, D. M. and Strogatz, S. H.: Chimera states for coupled oscillators, Phys. Rev. Lett., 93, 174102, doi:10.1103/PhysRevLett.93.174102, 2004.; Abrams, D. M., Mirollo, R., Strogatz, S. H., and Wiley, D. A.: Solvable model for chimera states of coupled oscillators, Phys. Rev. Lett., 101, 084103, doi:10.1103/PhysRevLett.101.084103, 2008.; Arenas, A., ...

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Horton Laws for Hydraulic-geometric Variables and Their Scaling Ex...

By: O. J. Mesa; V. K. Gupta

Description: Department of Civil, Environmental and Architectural Engineering and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA. An analytical theory is presented to predict Horton laws for five Hydraulic-Geometric (H-G) variables (stream discharge Q, width W, depth D, velocity U, slope S, and friction n'). The theory builds on the concept of dimensional analysis, ...

Jarvis, R. S. and Woldenberg, M. J.: River networks, vol. 80, Hutchinson Ross, New York, USA, 1984.; Barenblatt, G. I.: Scaling, self-similarity, and intermediate asymptotics, Cambridge Univ Pr, 1996.; Berry, M. and Bradley, P.: The application of network analysis to the study of branching patterns of large dendritic fields, Brain Res., 109, 111–132, 1976.; Borchert, R. and Slade, N. A.: Bifurcation ratios and the adaptive geometry of trees, Botanical Gazette, 142, 394–4...

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Cosmic Ray Momentum Diffusion in the Presence of Nonlinear Alfvén ...

By: G. Michałek; M. Ostrowsky

Description: Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland. The relation between the spatial diffusion coefficient along the magnetic field, kII, and the momentum diffusion coefficient, Dp, for relativistic cosmic ray particles is modelled using Monte Carlo simulations. Wave fields with vanishing wave helicity and cross-helicity, constructed by superpos...

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Electrostatic Shock Properties Inferred from Akr Fine Structure : ...

By: J. Jasperse; R. A. Treumann; M. Berthomier; R. Pottelette

Description: CETP-CNRS, 4 Rue de Neptune, F-94107 Saint-Maur des Fossés, France. The auroral kilometric radiation (AKR) consists of a large number of fast drifting elementary radiation events that have been interpreted as travelling electron holes resulting from the nonlinear evolution of electron-acoustic waves. The elementary radiation structures sometimes become reflected or trapped in slowly drifting larger structures where the parallel electric ...

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