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This work examines the relation between the fractal properties of the photospheric magnetic patterns and those of the coronal magnetic fields in solar active regions.Our results show no correlation between the fractal dimensions of the…

Solar and Stellar Astrophysics · Physics 2015-05-14 M. Dimitropoulou , M. Georgoulis , H. Isliker , L. Vlahos , A. Anastasiadis , D. Strintzi , X. Moussas

We apply the combined technique of postselected amplification and photon-recycling to an optical setup of magnetic field precision measurement. We propose two recycling schemes and carry out analytic expressions for the amplified signal and…

Quantum Physics · Physics 2025-10-09 Yazhi Niu , Jialin Li , Lupei Qin , Xin-Qi Li

Solar magnetic fields play a key role in understanding the nature of the coronal phenomena. Global coronal magnetic fields are usually extrapolated from photospheric fields, for which farside data is taken when it was at the frontside,…

Solar and Stellar Astrophysics · Physics 2022-04-28 Hyun-Jin Jeong , Yong-Jae Moon , Eunsu Park , Harim Lee

We present a quasi-linearly scaling, first order polynomial finite element method for the solution of the magnetostatic open boundary problem by splitting the magnetic scalar potential. The potential is determined by solving a Dirichlet…

Computational Physics · Physics 2014-04-25 Lukas Exl , Thomas Schrefl

Estimates of velocities from time series of photospheric and/or chromospheric vector magnetograms can be used to determine fluxes of magnetic energy (the Poynting flux) and helicity across the magnetogram layer, and to provide…

Astrophysics · Physics 2007-10-03 B. T. Welsch , G. H. Fisher

The 3D magnetic topology of a solar active region (NOAA 10956) was reconstructed using a linear force-free field extrapolation constrained using the twin perspectives of \emph{STEREO}. A set of coronal field configurations was initially…

Solar and Stellar Astrophysics · Physics 2015-05-18 Paul A. Conlon , Peter T. Gallagher

In this study, photospheric vector magnetograms obtained with the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS), are used as boundary conditions to model the three-dimensional nonlinear force-free (NLFF) coronal…

Solar and Stellar Astrophysics · Physics 2015-05-30 Tilaye Tadesse , T. Wiegelmann , B. Inhester , A. Pevtsov

Recently, a family of tractable NMF algorithms have been proposed under the assumption that the data matrix satisfies a separability condition Donoho & Stodden (2003); Arora et al. (2012). Geometrically, this condition reformulates the NMF…

Machine Learning · Statistics 2013-12-30 Abhishek Kumar , Vikas Sindhwani

Directly observing exoplanets with coronagraphs is impeded by the presence of speckles from aberrations in the optical path, which can be mitigated in hardware with wavefront control as well as in post-processing. This work explores using…

Instrumentation and Methods for Astrophysics · Physics 2025-04-03 Yinzi Xin , Laurent Pueyo , Romain Laugier , Leonid Pogorelyuk , Ewan S. Douglas , Benjamin J. S. Pope , Kerri L. Cahoy

This paper presents a novel approach to sound source separation that leverages spatial information obtained during the recording setup. Our method trains a spatial mixing filter using solo passages to capture information about the room…

Non-negative matrix factorization (NMF) is one of the most popular decomposition techniques for multivariate data. NMF is a core method for many machine-learning related computational problems, such as data compression, feature extraction,…

Numerical Analysis · Computer Science 2017-12-07 Gabriele Torre , Michael Graber

External biasing forces are often applied to enhance sampling in regions of phase space which would otherwise be rarely observed. While the typical goal of these experiments is to calculate the potential of mean force (PMF) along the…

Statistical Mechanics · Physics 2010-10-27 David D. L. Minh

AIMS: We develop an optimization principle for computing stationary MHD equilibria. METHODS: Our code for the self-consistent computation of the coronal magnetic fields and the coronal plasma uses non-force-free MHD equilibria. Previous…

Astrophysics · Physics 2008-11-26 Thomas Wiegelmann , Thomas Neukirch

Factorization of the Gaussian RBF kernel is developed for free-mesh interpolation in the flat, polynomial limit corresponding to Taylor expansion and the Vandermonde basis of geometric moments. With this spectral approximation, a top-down…

Numerical Analysis · Mathematics 2015-11-05 Matt Challacombe

In this study, we introduce a novel approach for deriving the solution of the ideal force-free steady-state pulsar magnetosphere in three dimensions. Our method involves partitioning the magnetosphere into the regions of closed and open…

High Energy Astrophysical Phenomena · Physics 2024-01-17 Ioannis Dimitropoulos , Ioannis Contopoulos , Vassilis Mpisketzis , Evangelos Chaniadakis

When modeling global satellite data to recover a planetary magnetic or gravitational potential field and evaluate it elsewhere, the method of choice remains their analysis in terms of spherical harmonics. When only regional data are…

Geophysics · Physics 2017-10-11 Alain Plattner , Frederik J. Simons

Nuclear medicine (NM) images inherently suffer from large amounts of noise and blur. The purpose of this research is to reduce the noise and blur while maintaining image integrity for improved diagnosis. The proposed solution is to increase…

Computer Vision and Pattern Recognition · Computer Science 2007-05-23 D. L. Falk , D. M. Rubin , T. Marwala

Using solar wind observation near PSP perihelions as constraints, we have investigated the parameters in various PFSS model methods. It's found that the interplanetary magnetic field extrapolation with source surface height $R_\mathrm{SS} =…

Solar and Stellar Astrophysics · Physics 2023-05-23 Yuechun Song

Accurate extraction of multicomponent linear frequency modulation (LFM) signal parameters, such as onset frequency, linear modulation frequency, amplitude, and initial phase, is of great importance in the fields of ISAR, cognitive radio,…

Information Theory · Computer Science 2024-12-06 Huigaung Zhang

General relativistic force-free electrodynamics is one possible plasma-limit employed to analyze energetic outflows in which strong magnetic fields are dominant over all inertial phenomena. The amazing images of black hole shadows from the…

Computational Physics · Physics 2021-03-09 J. F. Mahlmann , M. A. Aloy , V. Mewes , P. Cerdá-Durán