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It seems that the model of an "aligned" rotator is a common model to describe most features of isolated pulsars:

Since the first works on pulsar magnetospheres, a stationary force- free magnetosphere of an aligned rotator has been considered as an underlying model for the real pulsar magnetosphere for more than 30 years.

(Quote and figure below are randomly somewhat randomly picked from Timokhin, 2006.)

My very basic question is now: Why a rotating dipole field in vacuum should produce any radiation (or current)?

The whole geometry seems to have cylindrical symmetry, as rotation and dipole axis are supposed to be aligned:

enter image description here

So spinning it around its symmetry axis should not change the B-field anywhere in space. And without a varying B-field, no current or radiation.

Obviously I am missing something here.

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  • $\begingroup$ Although not an exact duplicate, the excellent answer in this question: astronomy.stackexchange.com/questions/98/… might answer yours; briefly, the dipole axis is normally not perfectly aligned with the spin axis. $\endgroup$
    – antlersoft
    Commented May 28 at 13:22

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What you describe would not appear as a pulsar. The usual model of a pulsar has non-aligned magnetic and rotation axes, in order to get a Doppler boosted and beamed cone of radiation to sweep across the direction of an observer at regular intervals.

The main radiation mechanisms are caused by particle acceleration from the neutron star surface along the magnetic field lines. Such particles can cause synchrotron or curvature radiation and this would occur even if the rotation and magnetic axes were aligned.

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