Back Reaction to the Spectrum of Magnetic Field in the Kinetic Dynamo Theory --- Modified Kulsrud and Anderson Equation ---

We take account of the lowest order back reaction on the fluid and modify the Kulsrud and Anderson equation $\partial_t{\cal E}_M= 2 \gamma {\cal E}_M$ obtained in the kinetic dynamo theory, where ${\cal E}_M$ is the energy density of the magnetic field. Furthermore, we apply our present result to some astrophysical stages where the magnetic field is expected to be amplified by the dynamo mechanism.