[aerohead]

My reading of magnetic polar drift doesn't emphasize any diminishment in field strength, only 'orientation.'
The magnetic 'poles' in an 'excursion' may 'tilt' up to 45-degrees, but they're just as strong.
In a full reversal, the poles are 'flipped' but just as strong.
It makes no difference if the aurora take place over the tropics.
The Earth's 'innards' are sufficiently solid, or super-high-viscosity plastic, so as to preclude any 'fast' dynamical movements.Thousands of years are necessary.