We present a statistical analysis of 43 coronal dimming events , associated with Earth-directed CMEs that occurred during the period of quasi-quadrature of the SDO and STEREO satellites .
We studied coronal dimmings that were observed above the limb by STEREO/EUVI and compared their properties with the mass and speed of the associated CMEs .
The unique position of satellites allowed us to compare our findings with the results from ( ) , who studied the same events observed against the solar disk by SDO/AIA .
Such statistics is done for the first time and confirms the relation of coronal dimmings and CME parameters for the off-limb viewpoint .
The observations of dimming regions from different lines-of-sight reveal a similar decrease in the total EUV intensity ( c = 0.60 \pm 0.14 ) .
We find that the ( projected ) dimming areas are typically larger for off-limb observations ( mean value of 1.24 \pm 1.23 \times 10 ^ { 11 } km ^ { 2 } against 3.51 \pm 0.71 \times 10 ^ { 10 } km ^ { 2 } for on-disk ) , with a correlation of c = 0.63 \pm 0.10 .
This systematic difference can be explained by the ( weaker ) contributions to the dimming regions higher up in the corona , that can not be detected in the on-disk observations .
The off-limb dimming areas and brightnesses show very strong correlations with the CME mass ( c = 0.82 \pm 0.06 and c = 0.75 \pm 0.08 ) , whereas the dimming area and brightness change rate correlate with the CME speed ( c \sim 0.6 ) .
Our findings suggest that coronal dimmings have the potential to provide early estimates of mass and speed of Earth-directed CMEs , relevant for space weather forecasts , for satellite locations both at L1 and L5 .