Compared to the large numbers of coronal sources and white dwarf stars found in the EUV all-sky survey catalogues, the number of cataclysmic variable detections is small, numbering only ≈25 objects. Nevertheless, many of these systems were bright enough to have been suitable targets for spectroscopic observations with EUVE, but these studies were complicated by the fact that the sources are highly variable and the exposure times needed to produce good signal-to-noise were at least 50 ks for the brightest sources, much longer than the binary and rotation periods. Hence, with EUVE it was only possible to obtain observations of the time averaged spectrum, except in periods of outburst, which lasted for several days.

Cataclysmic variables can be conveniently divided into two groups: (i) those where the white dwarf does not have a significant magnetic field (<0.1–1 MG) and accretion onto its surface occurs via an accretion disc (e.g. figure 9.1); (ii) the polars–systems in which the white dwarf does have a strong magnetic field (≈10–100 MG) which prevents the formation of an accretion disc and channels accrete material onto the magnetic poles of the white dwarf along the field lines (figure 9.2). A small number of magnetic systems, the intermediate polars, have weaker fields (B ≈ 1–10 MG) allowing a partial disc to accumulate which is disrupted by the field in its inner regions. As in the polars, accretion onto the white dwarf follows the field lines onto the magnetic poles (figure 9.2).