The polars VV Pup and V393 Pav were observed with XMM-Newton during states of low accretion rate with peak X-ray luminosities of \sim 1 \times 10 ^ { 30 } and \sim 1 \times 10 ^ { 31 } erg s ^ { -1 } , respectively .
In both polars , accretion onto the white dwarf was extremely irregular , and the accretion rate varied by more than 1 order of magnitude on timescales of \sim 1 hr .
Our observations suggest that this type of irregular accretion is a common phenomenon in polars during the low state .
The likely cause of the accretion rate fluctuations are coronal mass ejections or solar flares on the companion star that intermittently increase the mass transfer into the accretion stream .
Our findings demonstrate that the companion stars in cataclysmic variables possess highly active atmospheres .