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We conducted radio-interferometric observations of the well known binarycataclysmic system AM Herculis. This particular system is formed by themagnetic white dwarf (primary) and the red dwarf (secondary), and is theprototype of so-called polars. Our observations were conducted with theEuropean VLBI Network (EVN) in the e-EVN mode at 5 GHz. We obtained sixastrometric measurements spanning one year, which make it possible to updatethe annual parallax for this system with the best precision to date($\pi=11.29\pm0.08$ mas), equivalent to the distance of $88.6\pm0.6$ pc. Thesystem was observed mostly in the quiescent phase (visual magnitude$m_v\sim15.3$), when the radio emission was at the level of about $300~\mu$Jy.Our analysis suggests that the radio flux of AM Herculis is modulated with theorbital motion. Such specific properties of the radiation can be explainedusing the emission mechanism similar to the scenario proposed for V471 Tauriand, in general, for RS CVn type stars. In this scenario the radio emissionarises near the surface of the red dwarf, where the global magnetic fieldstrength may reach a few kG. We argue that the quiescent radio emissiondistinguishes AM Herculis together with AR Ursae Majoris (the second knownpersistent radio polar) from other polars, as the systems with a magnetizedsecondary star.

Another look at AM Herculis $-$ radio-astrometric campaign with the e-EVN at 6 cm