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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.
Here = is the separatrix [13] separating the low latitude magnetosphere with closed geomagnetic field lines at θ ≥ θ m from the polar magnetosphere with open magnetic fieldlines (having only one footpoint on Earth), and τ the local time. θ m ~ 20° is the polar border of the auroral zone. q, Φ co, and τ co are empirical parameters ...
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.
During its second flyby of the planet on October 6, 2008, the NASA probe MESSENGER discovered that Mercury’s magnetic field shows a magnetic reconnection rate ten times higher than Earth's. Mercury's proximity to the Sun only accounts for about a third of the reconnection rate observed by MESSENGER and the cause of this discrepancy is not ...
The magnetic field of a magnetic dipole has an inverse cubic dependence in distance, so its order of magnitude at the earth surface can be approximated by multiplying the above result with (R outer core ⁄ R Earth) 3 = (2890 ⁄ 6370) 3 = 0.093 , giving 2.5×10 −5 Tesla, not far from the measured value of 3×10 −5 Tesla at the equator.
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.
Electric current passing through the conductor causes heating according to Joule's first law, resulting in the conductor expanding and the line sagging. Transmission ratings are set with a maximum allowable conductor temperature (annealing temperature) and minimum clearance rules to comply with legislation and regulation. [1]
Medium close-up view, captured with a 70 mm camera, shows tethered satellite system deployment.. Electrodynamic tethers (EDTs) are long conducting wires, such as one deployed from a tether satellite, which can operate on electromagnetic principles as generators, by converting their kinetic energy to electrical energy, or as motors, converting electrical energy to kinetic energy. [1]