What process is responsible for generating a magnetar's phenomenal magnetic field strength?

Differential rotation of the star's interior layers

The extraordinary magnetic intensity of a magnetar is theorized to originate from the complex dynamics within the star shortly after its birth. Specifically, the differential rotation—where different layers of the star's interior spin at different rates—acts like a cosmic dynamo. This differential motion twists and stretches the existing magnetic flux lines within the star, leading to a massive amplification of the field strength. This process effectively concentrates and intensifies the magnetic field far beyond the levels seen in standard neutron stars, making the field generation intrinsically linked to the star's internal rotational mechanics during its formation phase.