Spatially averaged flux in the northern (green) and southern (black) active region measured by SDO/HMI over time, starting on August 13, 2010 at 00:00 UT, which is more than a day before the eruption. The dashed line indicates the approximate start time of the eruption. This figure shows a clear decrease in flux for the southern region for the entire time range. The flux in the northern region increases at first, but then levels off in the hours before the eruption.