  Multi-wavelength solar images in the EUV are routinely used for analysing
solar features such as coronal holes, filaments, and flares. However, images
taken in different bands often look remarkably similar as each band receives
contributions coming from regions with a range of different temperatures. This
has motivated the search for empirical techniques that may unmix these
contributions and concentrate salient morphological features of the corona in a
smaller set of less redundant source images. Blind Source Separation (BSS)
precisely does this. Here we show how this novel concept also provides new
insight into the physics of the solar corona, using observations made by
SDO/AIA. The source images are extracted using a Bayesian positive source
separation technique. We show how observations made in six spectral bands,
corresponding to optically thin emissions, can be reconstructed by linear
combination of three sources. These sources have a narrower temperature
response and allow for considerable data reduction since the pertinent
information from all six bands can be condensed in only one single composite
picture. In addition, they give access to empirical temperature maps of the
corona. The limitations of the BSS technique and some applications are briefly
discussed.
