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The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The…

Astrophysics · Physics 2009-11-10 Mingtian Xu , Frank Stefani , Gunter Gerbeth

The conventional magnetic induction equation that governs hydromagnetic dynamo action is transformed into an equivalent integral equation system. An advantage of this approach is that the computational domain is restricted to the region…

Astrophysics · Physics 2009-06-23 Mingtian Xu , Frank Stefani , Gunter Gerbeth

The paper deals with the integral equation approach to steady kinematic dynamo models in finite domains based on Biot-Savart's law. The role of the electric potential at the boundary is worked out explicitly. As an example, a modified…

Astrophysics · Physics 2009-05-20 Frank Stefani , Gunter Gerbeth , Karl-Heinz Rädler

We present an elegant method of determining the eigensolutions of the induction and the dynamo equation in a fluid embedded in a vacuum. The magnetic field is expanded in a complete set of functions. The new method is based on the…

Instrumentation and Methods for Astrophysics · Physics 2015-05-14 M. Schrinner , D. Schmitt , J. Jiang , P. Hoyng

We present a collection of well-conditioned integral equation methods for the solution of electrostatic, acoustic or electromagnetic scattering problems involving anisotropic, inhomogeneous media. In the electromagnetic case, our approach…

Numerical Analysis · Mathematics 2018-05-15 Lise-Marie Imbert-Gerard , Felipe Vico , Leslie Greengard , Miguel Ferrando

The integral equation approach to partial differential equations (PDEs) provides significant advantages in the numerical solution of the incompressible Navier-Stokes equations. In particular, the divergence-free condition and boundary…

Numerical Analysis · Mathematics 2020-02-26 Ludvig af Klinteberg , Travis Askham , Mary Catherine Kropinski

The problem of the harmonic oscillator with a centrally located delta function potential can be exactly solved in one dimension where the eigenfunctions are expressed as superpositions of the Hermite polynomials or as confluent…

Quantum Physics · Physics 2021-08-18 Indrajit Ghose , Parongama Sen

The induction equation of kinematic magnetohydrodynamics is mathematically equivalent to a system of integral equations for the magnetic field in the bulk of the fluid and for the electric potential at its boundary. We summarize the recent…

Fluid Dynamics · Physics 2017-07-26 Frank Stefani , Mingtian Xu , Gunter Gerbeth , Thomas Wondrak

When scale separation in space and time is poor, the alpha effect and turbulent diffusivity have to be replaced by integral kernels. Earlier work in computing these kernels using the test-field method is now generalized to the case in which…

Solar and Stellar Astrophysics · Physics 2012-01-11 M. Rheinhardt , A. Brandenburg

We present a new algorithm which is named the Dynamical Functional Particle Method, DFPM. It is based on the idea of formulating a finite dimensional damped dynamical system whose stationary points are the solution to the original…

Numerical Analysis · Mathematics 2013-03-25 Mårten Gulliksson , Sverker Edvardsson , Andreas Lind

The existence of magnetohydrodynamic mean-field alpha^2-dynamos with spherically symmetric, isotropic helical turbulence function alpha is related to a non-self-adjoint spectral problem for a coupled system of two singular second order…

Mathematical Physics · Physics 2014-11-20 Uwe Guenther , Heinz Langer , Christiane Tretter

Plasmonics has attracted much attention not only because it has useful properties such as strong field enhancement, but also because it reveals the quantum nature of matter. To handle quantum plasmonics effects, ab initio packages or…

Mesoscale and Nanoscale Physics · Physics 2018-02-08 Kun Ding , C. T. Chan

We develop an efficient numerical scheme for the 3D mean-field spherical dynamo equation. The scheme is based on a semi-implicit discretization in time and a spectral method in space based on the divergence-free spherical harmonic…

Numerical Analysis · Mathematics 2019-10-04 Ting cheng , Lina Ma , Jie Shen

We give an algebraic derivation of the eigenvalues of energy of a quantum harmonic oscillator on the surface of constant curvature, i.e. on the sphere or on the hyperbolic plane. We use the method proposed by Daskaloyannis for fixing the…

Quantum Physics · Physics 2024-10-24 Atulit Srivastava , Sanjeev Kant Soni

The eigenvalues and eigenfunctions of a linear {\alpha}^{2}-dynamo have been computed for different spatial distributions of an isotropic \alpha-effect. Oscillatory solutions are obtained when \alpha exhibits a sign change in the radial…

Earth and Planetary Astrophysics · Physics 2012-08-08 A. Giesecke , F. Stefani , G. Gerbeth

We show that the isotropic 3-wave kinetic equation is equivalent to the mean field rate equations for an aggregation-fragmentation problem with an unusual fragmentation mechanism. This analogy is used to write the theory of 3-wave…

Statistical Mechanics · Physics 2015-05-13 C. Connaughton

The numerical analysis for the small amplitude motion of an elastic beam with internal damping is investigated in domain with moving ends. An efficient numerical method is constructed to solve this moving boundary problem. The stability and…

Numerical Analysis · Mathematics 2019-07-05 Natanael Quintino , Mauro Rincon

There are two usual computational methods for linear (waves and instabilities) problem: eigenvalue (dispersion relation) solver and initial value solver. In fact, we can introduce an idea of the combination of them, i.e., we keep time…

Plasma Physics · Physics 2012-11-27 Hua-sheng Xie

It is shown, that the saturated $\alpha$-effect taken from the nonlinear dynamo equations for the thin disk can still produce exponentially growing magnetic field in the case, when this field does not feed back on the $\alpha$. For negative…

Fluid Dynamics · Physics 2015-05-18 M. Reshetnyak

We propose an iterative finite element method for solving non-linear hydromagnetic and steady Euler's equations. Some three-dimensional computational tests are given to confirm the convergence and the high efficiency of the method.

Numerical Analysis · Mathematics 2009-12-01 Cédric Boulbe , Tahar Zamène Boulmezaoud , T. Amari
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