Magnetic pumping in the cataclysmic variable AE Aquarii

We propose that the radio outbursts of the cata- clysmic variable AE Aqr are caused by eruptions of bubbles of fast particles from a magnetosphere surrounding the white dwarf. We investigate the acceleration process of magnetic pumpinginthemagnetospherewhichisperiodicallydrivenboth bytherelativemotionwiththecompanionandwiththeinfalling spray of gas at the spin frequency of the white dwarf. As the ac- cretion rate is relatively low, the conversion of spin energy into acceleration (rather than heating) of electrons and protons can be efficient. The accelerated particles are trapped in the white dwarf magnetosphere until their total energy content becomes comparabletothatofthetrappingmagneticfieldstructureanda MHD instability sets in. Synchrotron radiation is emitted in the expelled expanding plasmoid at radio and down to millimetric wavelengths. We find that there is sufficient energy transferred from the rotation energy of the rapidly-spinning white dwarf to fast particles by magnetic pumping to explain quiescent and flaring radio emissions.