A fixed magnetic field will induce an electrical current in a conductive object moving through the field. The strength of the eddy currents will depend on the shape and composition of the conductor and also how fast it is moving. The electrical current produces ohmic heating in the conductor, and some of the kinetic energy of the moving conductor will be turned to heat. This is how induction brakes work.

I wonder if this principle applies to fast moving conductors like asteroids or satellites that encounter planetary magnetic fields. Are planetary magnetic fields strong enough to act as induction brakes on moving conductors? A satellite experiencing induction braking would fall to a lower and lower orbit and eventually out of orbit. Passing asteroids might have their course deviated more than would be expected just from gravity.

My search turned up only this abstract, which attempted to explain why meteorites are hot via this principle.


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  • $\begingroup$ Low Earth orbit speed is 7.8 km/sec. I have not heard of this type of heating or effects on orbits in the Space Age. $\endgroup$ – Keith McClary Feb 6 at 3:22
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    $\begingroup$ Sort of related: en.wikipedia.org/wiki/Electrodynamic_tether $\endgroup$ – PM 2Ring Feb 6 at 5:12
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    $\begingroup$ @PM2Ring You could totally make an answer out of that, it's very much related. $\endgroup$ – Florin Andrei Feb 6 at 6:32
  • $\begingroup$ @Florin Maybe someone else could make a good answer to this question from the info in that Wikipedia article, but not me. ;) Ideally, an answer to this question will have some hard numbers and equations relating to the braking and heating effects. $\endgroup$ – PM 2Ring Feb 6 at 9:30
  • $\begingroup$ @KeithMcClary we need to amplify the Earth's magnetic field! :-) $\endgroup$ – Carl Witthoft Feb 6 at 15:39

If an object is moving at constant velocity through a uniform B field then, in its rest frame, it will experience a combination of uniform E and B fields which would not produce the effects you suggest. Any such effects would have to be due to the spacial rate of change of the field, which I think would be very small.


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