  We report on interaction of the legs of the erupting filament of 2012 August
31 and associated prominent supra-arcade downflows (P-SADs) as observed by the
Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. We employ
a number of image processing techniques to enhance weak interacting features.
As the filament erupts, both legs stretch outwards. The positive-polarity leg
also untwists and splits into two parts. The first part runs into the conjugate
(negative-polarity) leg, tearing it apart. The second part then converges into
the remnant of the conjugate leg, after which both weaken and finally
disappear. All these episodes of interaction of oppositely-oriented filament
legs are followed by appearance of P-SADs, seen in the on-disk projection to be
shaped as loop-tops, along with many weaker SADs. All SADs are preceded by hot
supra-arcade downflowing loops. This observed evolution is consistent with the
three-dimensional rr-rf (leg-leg) reconnection, where the erupting flux rope
reconnects with itself. In our observations, as well as in some models, the
reconnection in this geometry is found to be long-lasting. It plays a
substantial role in the evolution of the flux rope of the erupting filament and
leads to prominent supra-arcade downflows.
