  Observations of the T Tauri spectroscopic binary DQ Tau in April 2008
captured an unusual flare at 3 mm, which peaked at an observed max flux of 0.5
Jy (about 27x the quiescent value). Here we present follow-up mm observations
that demonstrate a periodicity to the phenomenon. While monitoring 3 new
periastron encounters, we detect flares within 17.5 hrs (or 4.6%) of the
orbital phase of the first reported flare, and we constrain the main emitting
region to a stellar height of 3.7-6.8 Rstar. The recorded activity is
consistent with the proposed picture for synchrotron emission initiated by a
magnetic reconnection event when the two stellar magnetospheres of the highly
eccentric (e=0.556) binary are believed to collide near periastron as the stars
approach a minimum separation of 8 Rstar (~13 Rsolar). The similar light curve
decay profiles allow us to estimate an average flare duration of 30 hrs.
Assuming one mm flare per orbit, DQ Tau could spend approximately 8% of its
15.8-d orbital period in an elevated flux state. Our analysis of the mm
emission provides an upper limit of 5% on the linear polarization. We discuss
the extent to which a severely entangled magnetic field structure and Faraday
rotation effects are likely to reduce the observed polarization fraction. We
also predict that, for the current picture, the stellar magnetospheres must be
misaligned at a significant angle or, alternatively, that the topologies of the
outer magnetospheres are poorly described by a well-ordered dipole inside a
radius of 7 Rstar. Finally, to investigate whether reorganization of the
magnetic field during the interaction affects mass accretion, we also present
simultaneous optical (VRI) monitoring, as an established tracer of accretion
activity in this system. We find that an accretion event can occur coincident
in both time and duration with the synchrotron fallout of a magnetic
reconnection event.
