We study the coronal dimming caused by the fast halo CME ( deprojected speed v = 1250 km s ^ { -1 } ) associated with the C3.7 two-ribbon flare on 2012 September 27 , using Hinode/EIS spectroscopy and SDO/AIA Differential Emission Measure ( DEM ) analysis .
The event reveals bipolar core dimmings encompassed by hook-shaped flare ribbons located at the ends of the flare-related polarity inversion line , and marking the footpoints of the erupting filament .
In coronal emission lines of \log T [ { K } ] = 5.8 - 6.3 , distinct double component spectra indicative of the superposition of a stationary and a fast up-flowing plasma component with velocities up to 130 km s ^ { -1 } are observed at regions , which were mapped by the scanning EIS slit close in time of their impulsive dimming onset .
The outflowing plasma component is found to be of the same order and even dominant over the stationary one , with electron densities in the upflowing component of 2 \times 10 ^ { 9 } cm ^ { -3 } at \log T [ { K } ] = 6.2 .
The density evolution in core dimming regions derived from SDO/AIA DEM analysis reveals impulsive reductions by 40–50 % within \lesssim 10 min , and remains at these reduced levels for hours .
The mass loss rate derived from the EIS spectroscopy in the dimming regions is of the same order than the mass increase rate observed in the associated white light CME ( 1 \times 10 ^ { 12 } { g s } ^ { -1 } ) , indicative that the CME mass increase in the coronagraphic field-of-view results from plasma flows from below and not from material piled-up ahead of the outward moving and expanding CME front .