Rapid Oscillations in Cataclysmic Variables

I give an overview of the rich phenomenology of dwarf nova oscillations(DNOs) and Quasi-periodic Oscillations (QPOs) observed in cataclysmic variablestars (CVs). The favoured interpretation of these rapid brightness modulations(3 - >1000 s time scales) is that they are magnetic in nature - magneticallychannelled accretion from the inner accretion disc for DNOs and possiblemagnetically excited travelling waves in the disc for QPOs. There is increasingevidence for the magnetic aspects, which extend to lower field the well knownproperties of strong field (polars) and intermediate strength field(intermediate polars) CVs. The result is that almost all CVs show the presenceof magnetic fields on their white dwarf primaries - though for many theintrinsic field may be locally enhanced by the accretion process itself. Thereare many parallel behaviours with the QPOs seen in X-Ray binaries, with highand low frequency X-Ray QPOs resembling respectively the DNOs and QPOs in CVs.Comment: Invited Review for PASP, accepted for publication in the February 2004 issue of PAS