We present Roche tomograms of the K4V secondary star in the cataclysmic variable AE Aqr , reconstructed from two datasets taken 9 days apart , and measure the differential rotation of the stellar surface .
The tomograms show many large , cool starspots , including a large high-latitude spot and a prominent appendage down the trailing hemisphere .
We find two distinct bands of spots around 22 ^ { \circ } and 43 ^ { \circ } latitude , and estimate a spot coverage of 15.4-17 per cent on the northern hemisphere .

Assuming a solar-like differential rotation law , the differential rotation of AE Aqr was measured using two different techniques .
The first method yields an equator-pole lap time of 269 d and the second yields a lap time of 262 d. This shows the star is not fully tidally locked , as was previously assumed for CVs , but has a co-rotation latitude of \sim 40 ^ { \circ } .
We discuss the implications that these observations have on stellar dynamo theory , as well as the impact that spot traversal across the L 1 point may have on accretion rates in CVs as well as some of their other observed properties .

The entropy landscape technique was applied to determine the system parameters of AE Aqr .
For the two independent datasets we find M _ { 1 } = 1.20 and 1.17 ~ { } \mathrm { M } _ { \odot } , M _ { 2 } = 0.81 and 0.78 ~ { } \mathrm { M } _ { \odot } , and orbital inclinations of 50 ^ { \circ } to 51 ^ { \circ } at optimal systemic velocities of \gamma = -64.7 and -62.9 kms -1 .