| MadSci Network: Astronomy |
Good question! Especially because nobody really knows the answer for sure - neutron stars in general, and their magnetic fields in particular, are not very well understood by anyone. So unfortunately we can't give you an absolutely definite answer.
However, scientists are pretty sure that the magnetic fields around neutron stars won't flip like those around the earth and the sun. The magnetic fields of the earth and sun are generated by a 'dynamo.' This is another very complicated bit of physics that we don?t completely understand, but the basic idea is that the rotating fluid in each body (the whole sun is fluid, while the outer layer of the earth's core is molten iron) sustains a current, which in turn sustains the magnetic field. Instabilities in the current flow cause variations in the magnetic field strength and direction. On the sun, these variations are periodic (the so-called 'solar cycle'); on earth, the variations are much more complicated and have no set period.
However, the fields around neutron stars have an even more complicated origin. Neutron stars, as you may know, are remnants left when a massive star undergoes a supernova explosion. The star expels its outer layers in the process, but the magnetic field is retained. Maxwell's laws of electrodynamics demand that a quantity called 'magnetic flux' be conserved in most processes; this quantity is simply the magnetic field strength multiplied by the area through which it passes. During the supernova, the field is compressed to the approximate size of the neutron star, so the area decreases dramatically. Therefore, the magnetic field strength increases dramatically in the process - sometimes by eight or more orders of magnitude! The neutron stars' magnetic field, then, is also a fossil of the massive star. The fossil field is not maintained by a dynamo - we think! - so there is no expectation for the field to flip polarity as the sun's does.
To my knowledge, there are also no observations that would support a magnetic polarity reversal in these objects. The properties of a pulsar depend strongly on the magnetic field of the neutron star, and the pulse period would change if the magnetic field changed. When the earth and sun flip polarity, the field strength decreases and then increases again during the switch. We could observe this easily in the pulse timing, and we have not. Of course, not all neutron stars are pulsars - and it is possible, if unlikely, that other stars are different.
To learn more about the solar dynamo, check out this NASA page.
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