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Magnetic North and Solar East

  1. Oct 31, 2014 #1
    This morning I was momentarily struck by the coincidence that magnetic North and "solar East" (the direction of the rising sun) happened to be (approximately) perpendicular, but now it doesn't really seem coincidental; as I understand it, spinning of the earth causes a current that leads to the magnetic poles, as well as the sunrise.

    So, if you woke up on an unknown planet with a compass and you faced magnetic north (assuming one existed), would the sun (or whatever astronomical object/objects) always come up over your right shoulder?
  2. jcsd
  3. Oct 31, 2014 #2


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    The sun does not rise every day at the same point of the horizon. In other words, what you call the 'solar East' lies in the same place only two days in the year.
  4. Oct 31, 2014 #3
    I intended to cover that with the weasle-word "approximate", along with e.g. the deviation of magnetic from geological "North", finite propagation speed of electromagnetic effects, general-relativistic corrections, &c.
  5. Oct 31, 2014 #4


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    In our planet, what you call 'the solar East' varies widely with the latitude of the observer and the time of the year. On the equator, where that variation is minimal, tha azimuth of the rising sun may depart +/- 22,5 degrees from due East, and that extreme azimuth grows with the latitude of the observer, reaching a maximum of 90 degrees at the arctic circle, where the sun rises due north in the summer solstice, and due south in the winter solstice.
  6. Oct 31, 2014 #5
    Even on earth, It doesn't always work. The magnetic field flips, but the direction of rotation does not.
  7. Oct 31, 2014 #6


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    Staff Emeritus
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    Jupiter's magnetic poles are opposite to Earth's yet it spins in the same direction. In fact, the "north" pole of the Earth is actually a "south" magnetic pole, with the "north" magnetic pole at the southern geographic pole. The reason we call the north pole "north" is because the north pole of a magnet (like the needle in a compass) will seek the magnetic pole located there.
  8. Oct 31, 2014 #7


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    Staff: Mentor

    The earth's magnetic field is generated by movement of the iron core, and there's a lot more to that than just the rotation of the surface of the earth. Wikipedia is not always reliable, but in this case the article looks pretty reasonable: http://en.wikipedia.org/wiki/Earth's_magnetic_field
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