  Quasi-periodic plasmoid formation at the tip of magnetic streamer structures
is observed to occur in experiments on the Big Red Ball as well as in
simulations of these experiments performed with the extended-MHD code, NIMROD.
This plasmoid formation is found to occur on a characteristic timescale
dependent on pressure gradients and magnetic curvature in both experiment and
simulation. Single mode, or laminar, plasmoids exist when the pressure gradient
is modest, but give way to turbulent plasmoid ejection when the system drive is
higher, producing plasmoids of many sizes. However, a critical pressure
gradient is also observed, below which plasmoids are never formed. A simple
heuristic model of this plasmoid formation process is presented and suggested
to be a consequence of a dynamic loss of equilibrium in the high-$\beta$ region
of the helmet streamer. This model is capable of explaining the periodicity of
plasmoids observed in the experiment and simulations and produces plasmoid
periods of 90 minutes when applied to 2D models of solar streamers with a
height of $3R_\odot$. This is consistent with the location and frequency at
which periodic plasma blobs have been observed to form by LASCO and SECCHI
instruments.
