  The Sun's internal structure and dynamics can be studied with
helioseismology, which uses the Sun's natural acoustic oscillations to build up
a profile of the solar interior. We discuss how solar acoustic oscillations are
affected by the Sun's magnetic field. Careful observations of these effects can
be inverted to determine the variations in the structure and dynamics of the
Sun's interior as the solar cycle progresses. Observed variations in the
structure and dynamics can then be used to inform models of the solar dynamo,
which are crucial to our understanding of how the Sun's magnetic field is
generated and maintained.
