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The presence of a magnetic toroidic dipole moment T in condensed matter is due to the presence of a magnetoelectric effect: Application of a magnetic field H in the plane of a toroidal solenoid leads via the Lorentz force to an accumulation of current loops and thus to an electric polarization perpendicular to both T and H.
In physics, the magnetomotive force (abbreviated mmf or MMF, symbol ) is a quantity appearing in the equation for the magnetic flux in a magnetic circuit, Hopkinson's law. [1] It is the property of certain substances or phenomena that give rise to magnetic fields : F = Φ R , {\displaystyle {\mathcal {F}}=\Phi {\mathcal {R}},} where Φ is the ...
As a simple example from the physics of magnetically confined plasmas, consider an axisymmetric system with circular, concentric magnetic flux surfaces of radius (a crude approximation to the magnetic field geometry in an early tokamak but topologically equivalent to any toroidal magnetic confinement system with nested flux surfaces) and denote the toroidal angle by and the poloidal angle by .
This behavior is described by the Landau–Lifshitz–Gilbert equation: [21] [22] = where γ is the gyromagnetic ratio, m is the magnetic moment, λ is the damping coefficient and H eff is the effective magnetic field (the external field plus any self-induced field). The first term describes precession of the moment about the effective field ...
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
In the following, it is assumed that the system is 2-dimensional with as the invariant axis, i.e. produces 0 for any quantity. Then the magnetic field can be written in cartesian coordinates as = (,, (,)), or more compactly, = ^ + ^, where (,) ^ is the vector potential for the in-plane (x and y components) magnetic field.
The magnetic field of permanent magnets can be quite complicated, especially near the magnet. The magnetic field of a small [note 6] straight magnet is proportional to the magnet's strength (called its magnetic dipole moment m). The equations are non-trivial and depend on the distance from the magnet and the orientation of the magnet.
Applications to the boussinesq-equations, Schmitt, B. J. and von Wahl, W; in The Navier–Stokes Equations II — Theory and Numerical Methods, pp. 291–305; Lecture Notes in Mathematics, Springer Berlin/ Heidelberg, Vol. 1530/ 1992. Anelastic Magnetohydrodynamic Equations for Modeling Solar and Stellar Convection Zones, Lantz, S. R. and Fan ...