  The prevailing theory for the origin of cosmic magnetic fields is that they
have been amplified to their present values by the turbulent dynamo inductive
action in the protogalactic and galactic medium. Up to now, in calculation of
the turbulent dynamo, it has been customary to assume that there is no the back
reaction of the magnetic field on the turbulence, as long as the magnetic
energy is less than the turbulent kinetic energy. This assumption leads to the
kinematic dynamo theory. However, the applicability of the kinematic dynamo
theory to protogalaxies is rather limited. The reason is that in protogalaxies
the temperature is very high, and the viscosity is dominated by ions. As the
magnetic field strength grows in time, the ion cyclotron time becomes shorter
than the ion collision time, and the plasma becomes strongly magnetized. As a
result, the ion viscosity becomes the Braginskii viscosity. Thus, in
protogalaxies the back reaction sets in much earlier, at field strengths much
lower than the energy equipartition field strengths, and the turbulent dynamo
becomes what we call the magnetized turbulent dynamo. The purpose of this
thesis is to lay the theoretical groundwork for the magnetized turbulent
dynamo. In particular, we predict that the magnetic energy growth rate in the
magnetized dynamo theory is up to ten time larger than that in the kinematic
dynamo theory. We also briefly discuss how the Braginskii viscosity can aid the
development of the inverse cascade of magnetic energy after the energy
equipartition time.
