Blunting the spike: the cataclysmic variable minimum period

The standard picture of cataclysmic variable (CV) secular evolution predicts a spike in the CV distribution near the observed short-period cut-off P0≃ 78 min, which is not observed. We show that an intrinsic spread in minimum (‘bounce’) periods Pb resulting from a genuine difference in some parameter controlling the evolution can remove the spike without smearing the sharpness of the cut-off. The most probable second parameter is different admixtures of magnetic stellar wind braking (at up to 5 times the GR rate) in a small tail of systems, perhaps implying that the donor magnetic field strength at formation is a second parameter specifying CV evolution. We suggest that magnetic braking resumes below the gap with a wide range, being well below the GR rate in most CVs, but significantly above it in a small tail.