In non-magnetic cataclysmic variables, the white dwarf is not strongly magnetized and the accretion disk is able to extend all the way to the surface of the white dwarf. In polars, the white dwarf is strongly magnetized and the accretion disk is truncated at the magnetosphere of the white dwarf. This truncation of the accretion disk leads to the formation of a bright spot where the accretion stream impacts the surface of the white dwarf.
IPs are thought to be in a transitional state between non-magnetic cataclysmic variables and polars. The white dwarfs in IPs are only weakly magnetized and the accretion disks are only partially truncated. This leads to the formation of a weak bright spot on the surface of the white dwarf, as well as a jet of material that is ejected from the accretion disk along the magnetic field lines of the white dwarf.
IPs are rare objects, with only about 50 known examples. However, they are an important part of the evolutionary picture of cataclysmic variables. They provide a glimpse into the process by which non-magnetic cataclysmic variables evolve into polars.
