Trigger Shy? Flare-less Active Region Circular Prominence Eruption

Prominence eruptions have been studied since the days of Skylab, and generally fall into two categories based on their locations: quiet Sun and active regions. Quiescent prominences are generally slow to grow and take can days to erupt, with or without any evidence of energization prior to eruption. By contrast, active region prominences generally erupt on time scales of hours or minutes, and are often accompanied by powerful flares. This study reports on an observation of an unusual circular prominence eruption located in an active region which occurs without any evidence of flaring as a trigger. The prominence is under the dome surface of a raining null point topology, which was part of the extended decay phase of the active region designated NOAA 12488/12501. One half of the prominence undergoes a partial eruption, and the cool plasma subsequently drains onto the side which did not erupt, followed by a poorly-structured CME observed by SOHO LASCO C2 shortly after the eruption. We analyze both the failed eruption and secondary CME using SDO AIA, STEREO-A, and SOHO LASCO imagery. The location of the null-point topology raises critical questions about the role of open/closed boundaries in eruptive phenomena and CME structure. The poor structure of the outflowing CME is likely the result of the destruction of the flux rope through reconnection as it passes through the null-point structure, and possibly through additional overlying closed field. The eruption does not show a trigger, but arcades and ribbons form over the erupted half of the prominence. Taken together, the failed eruption presents eruption characteristics of both a CME and a jet, with potential evidence of a low-energy reconnection mechanism driving failed eruptions in highly decayed but still topologically compact magnetic fields.