An exact solution for the magnetic diffusion problem with a step-function resistivity model Bo Xiao, Ganghua Wang, Li Zhao, Chunsheng Feng and Shi Shu Eur. Phys. J. Plus, 139 4 (2024) 305 Published online: 02 April 2024 DOI: 10.1140/epjp/s13360-024-05086-2