Dear collegues, let me point out a new paper "Coronal fuzziness modelled with pulse-heated multistranded loop systems" by Guarrasi, Reale & Peres, accepted on ApJ : we model the well-known evidence of coronal fuzziness increasing with temperature (e.g. Tripathi et al. 2009) as due to multi-stranded nanoflare-heated loop structure, and in particular to the higher filling factor of "warm" (2-3 MK) strands. You can find a preprint on:
http://arxiv.org/abs/1006.3495
Best regards
Fabio Reale