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I find sources saying that Earth's magnetic field rotates with Earth, but there are few sources saying that the electromagnetic field rotates with Earth. I realize the question may have a complicated answer due to the way electric and magnetic fields are related and due to relativity, but is there a straight answer?

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  • Your compass needle points to one place during the day. That direction does change slowly (years), but clearly your local magnetic field is constant over a day. – Jon Custer Apr 09 '22 at 15:37
  • @JonCuster: Yes, but you and your compass are rotating with the Earth as well. I suspect the OP wants to know if the field changes with respect to the "fixed stars" due to the Earth's rotation. – Michael Seifert Apr 09 '22 at 15:40
  • are you contrasting magnetic with "electromagnetic"? the rotation of the earth will rotate the magnetic field with repect to the planetary system, and some electromagnetic radiation will be induced see the second answer here https://physics.stackexchange.com/questions/158557/would-a-rotating-magnet-emit-photons-if-so-what-causes-the-torque-that-gradual – anna v Apr 09 '22 at 15:54
  • Thank you, all. Yes, Jon, I know that the magnetic field rotates with Earth, but as Michael points out, I'm asking about the electromagnetic field which, as he puts it, would move relative to the "fixed stars" if it rotated with Earth. Yes, Anna, I'm distinguishing them. I've followed your link, but I'm not sure I've found an answer. Another way of putting it: If I'm sitting on the equator, am I in motion relative to Earth's electromagnetic field? – Anasker Apr 09 '22 at 17:18
  • AFAIK the dipole field of the earth's magnet will be radiating photons due to the rotation of the earth . There is no general electromagnetic field of the earth. The photons will be moving with respect to you motionless at the equator. – anna v Apr 09 '22 at 17:40
  • Thank you, Anna. Photons moving, yes, but since light propagates through the electromagnetic field at c, and since photons move relative to me at c, doesn't this mean the EM field is at rest relative to me and thus Earth? – Anasker Apr 09 '22 at 21:55

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