...What they found was that within milliseconds after the two stars make contact, the neutron fluid within the region enters a Kelvin–Helmholtz instability. This is a physics way of saying the fluid becomes turbulent. You've likely seen such an instability before. If you gently blow out a candle, there is a smooth stream of smoke that rises off the wick. But as it rises, the stream becomes swirly and random. That transition is where it reaches the instability.

The thing about Kelvin–Helmholtz instability is that it can mix things up tremendously. In the simulations, this mixes the neutron material so fully and quickly that the magnetic field is amplified significantly. This mixing trickles through the rest of the material, dragging the magnetic field with it. As a result, the magnetic field of the merged neutron star can be more than 300 times stronger than the initial magnetic fields...