A strong uniform magnetic field is suddenly imposed on a mass of conducting incompressible fluid initially in isotropic turbulent motion. Initial time derivatives of the spectrum are calculated through third order. After identification of terms, the simplifying assumptions of large mechanical and small magnetic Reynolds numbers are made, and the initial three‐dimensional spectrum assumed to be a Dirac shell; these permit the calculation and plotting of the one‐dimensional spectra. Interpretation of these spectra leads to the conclusion that the immediate effect of the field is to attenuate modes having cross‐field velocities and those having cross‐field node lines.