Chapter 60: τ-MHD: Magnetohydrodynamics

When a conducting fluid moves through a magnetic field, the fluid and the field evolve together: currents generate fields, fields exert forces, and at large scales the two become inseparable. This is magnetohydrodynamics (MHD). In τ³, the MHD equations emerge by coupling the τ-Navier–Stokes dynamics of defect transport

to the B-sector holonomy of the electromagnetic field. This chapter derives the τ-MHD system, introduces the magnetic Reynolds number, and shows how Alfv'en waves arise as coupled T² modes.