why do neutron stars have strong magnetic fields
Neutron star The origins of the strong magnetic field are as yet unclear.[21] One hypothesis is that of "flux freezing", or conservation of the original magnetic flux during the formation of the neutron star.[21] If an object has a certain magnetic flux over its surface area, and that area shrinks to a smaller area, but the magnetic flux is conserved, then the magnetic field would correspondingly increase. Likewise, a collapsing star begins with a much larger surface area than the resulting neutron star, and conservation of magnetic flux would result in a far stronger magnetic field. However, this simple explanation does not fully explain magnetic field strengths of neutron stars.[21]