The NSF ’ s Karl G. Jansky Very Large Array ( VLA ) is used to observe 122 magnetic cataclysmic variables ( MCVs ) during three observing semesters ( 13B , 15A , and 18A ) .
We report radio detections of 33 stars with fluxes in the range 6–8031 \mu Jy .
Twenty-eight stars are new radio sources , increasing the number of radio detected MCVs to more that 40 .
A surprising result is that about three-quarters ( 24 of 33 stars ) of the detections show highly circularly polarized radio emission of short duration , which is characteristic of electron cyclotron maser emission .
We argue that this emission originates from the lower corona of the donor star , and not from a region between the two stars .
Maser emission enables a more direct estimate of the mean coronal magnetic field of the donor star , which we estimate to be 1–4 kG assuming a magnetic filling factor of 50 % .
A two-sample Kolmogorov-Smirnov test supports the conclusion that the distribution function of radio detected MCVs with orbital periods between 1.5–5 hours is similar to that of all MCVs .
This result implies that rapidly-rotating ( P _ { spin } < 10 days ) , fully convective stars can sustain strong magnetic dynamos .
These results support the model of Taam & Spruit ( 37 ) that the change in angular momentum loss across the fully convective boundary at P _ { orb } \approx 3 hours is due to a change in the magnetic field structure of the donor star from a low-order to high-order multipolar field .