[en] The stability of an axisymmetric tandem mirror with an inverted (or hollow) pressure profile is treated within the framework of scalar-pressure, ideal magnetohydrodynamics. A two-surface sharp-boundary model is formulated to describe the low-m ballooning stability of the annular plasma in the paraxial limit. Included in the analysis are the stabilizing effects of an externally-applied force, such as the rf-induced ponderomotive force, and of a perfectly-conducting lateral wall. It is shown that there is a stability boundary associated with each of these effects. In critical ranges of the plasma's annular thickness, the rf intensity and the wall position, the stability regions merge giving complete stability at all values of the plasma pressure