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Schematic view of the different current systems which shape the Earth's magnetosphere. In many MHD systems most of the electric current is compressed into thin nearly-two-dimensional ribbons termed current sheets. [10] These can divide the fluid into magnetic domains, inside of which the currents are relatively weak.
The equation for this limit, = [], has the solution [4] (,) = ^ + ^ As can be seen in the figure to the right, the fluid drags the magnetic field lines so that they obtain the sinusoidal character of the flow field. For the limit , the magnetic diffusion equation = is just a vector-valued form of the heat equation.
A current sheet is an electric current that is confined to a surface, rather than being spread through a volume of space. Current sheets feature in magnetohydrodynamics (MHD), a model of electrically conductive fluids : if there is an electric current through part of the volume of such a fluid, magnetic forces tend to expel it from the fluid ...
Schematic of the Birkeland or Field-Aligned Currents and the ionospheric current systems they connect to, Pedersen and Hall currents. [1]A Birkeland current (also known as field-aligned current, FAC) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere.
Magnetic reconnection is a breakdown of "ideal-magnetohydrodynamics" and so of "Alfvén's theorem" (also called the "frozen-in flux theorem") which applies to large-scale regions of a highly-conducting magnetoplasma, for which the Magnetic Reynolds Number is very large: this makes the convective term in the induction equation dominate in such regions.
In order to incorporate magnetic systems into the first law of thermodynamics, it is necessary to formulate the concept of magnetic work.The magnetic contribution to the quasi-static work done by an arbitrary magnetic system is [1]
Both of these alloys have <100> easy axes for magnetostriction and demonstrate sufficient ductility for sensor and actuator applications. [6] Schematic of a whisker flow sensor developed using thin-sheet magnetostrictive alloys. Another very common magnetostrictive composite is the amorphous alloy Fe 81 Si 3.5 B 13.5 C 2 with its trade name ...
The heliospheric current sheet rotates along with the Sun with a period of about 25 days, during which time the peaks and troughs of the skirt pass through the Earth's magnetosphere, interacting with it. Near the surface of the Sun, the magnetic field produced by the radial electric current in the sheet is of the order of 5 × 10 −6 T. [2]