We use coronal imaging observations with SDO/AIA , and Hinode/EIS spectral data , to explore the potential of narrow band EUV imaging data for diagnosing the presence of hot ( T \gtrsim 5 MK ) coronal plasma in active regions .
We analyze observations of two active regions ( AR 11281 , AR 11289 ) with simultaneous AIA imaging , and EIS spectral data , including the Ca xvii line ( at 192.8 Å ) which is one of the few lines in the EIS spectral bands sensitive to hot coronal plasma even outside flares .
After careful coalignment of the imaging and spectral data , we compare the morphology in a 3 color image combining the 171 , 335 , and 94Å AIA spectral bands , with the image obtained for Ca xvii emission from the analysis of EIS spectra .
We find that in the selected active regions the Ca xvii emission is strong only in very limited areas , showing striking similarities with the features bright in the 94Å ( and 335Å ) AIA channels and weak in the 171Å band .
We conclude that AIA imaging observations of the solar corona can be used to track hot plasma ( 6-8 MK ) , and so to study its spatial variability and temporal evolution at high spatial and temporal resolution .