  This work examines the effect of the embedded magnetic field strength on the
non-linear development of the magnetic Rayleigh-Taylor Instability (RTI) (with
a field-aligned interface) in an ideal gas close to the incompressible limit in
three dimensions. Numerical experiments are conducted in a domain sufficiently
large so as to allow the predicted critical modes to develop in a physically
realistic manner. The ratio between gravity, which drives the instability in
this case (as well as in several of the corresponding observations), and
magnetic field strength is taken up to a ratio which accurately reflects that
of observed astrophysical plasma, in order to allow comparison between the
results of the simulations and the observational data which served as
inspiration for this work. This study finds reduced non-linear growth of the
rising bubbles of the RTI for stronger magnetic fields, and that this is
directly due to the change in magnetic field strength, rather than the indirect
effect of altering characteristic length scales with respect to domain size. By
examining the growth of the falling spikes, the growth rate appears to be
enhanced for the strongest magnetic field strengths, suggesting that rather
than affecting the development of the system as a whole, increased magnetic
field strengths in fact introduce an asymmetry to the system. Further
investigation of this effect also revealed that the greater this asymmetry, the
less efficiently the gravitational energy is released. By better understanding
the under-studied regime of such a major phenomenon in astrophysics, deeper
explanations for observations may be sought, and this work illustrates that the
strength of magnetic fields in astrophysical plasmas influences observed RTI in
subtle and complex ways.
