Simulating Starfish: Numerical Investigation of the Starfish HANE EMP and Diamagnetic Cavity Evolution with Comparison to Observational Data

Starfish Prime was a high altitude nuclear explosion (HANE) that produced a significant geomagnetic disturbance within the Earth's ionosphere. The E3 electromagnetic pulse (EMP) was recorded on Johnston Island, and sounding rockets measured the magnetic field evolution within the diamagnetic bubble (Dyal 2006).

We present kinetic simulations of Starfish Prime, using our spherical hybrid PIC code Topanga. Key features of Topanga include: prompt X-ray ionization; atmospheric and debris ions modeled as individual species; a chemistry reaction network; a hydrodynamic solver; neutral-ion coupling; and an FDTD Maxwell solver that propagates electromagnetic fields in the presence of a tensor conductivity.

Our global simulations cover a 60x60 degree patch in latitude and longitude that spans an altitude range of 0-2000 km above the surface of the Earth. The simulation domain encloses the HANE blast bubble and X-ray ionization patch. We find that the E3a signal is due to ionospheric waves that propagate around the ionization patch, which is a novel result. We also find good agreement for both the E3 signal and diamagnetic cavity evolution compared with observations (Dyal 2006).