Dear colleagues
    please find at the following link the preprint of a work accepted for publication on the ApJ Letters, showing new strong evidence of finely-structured loops with impulsive nanoflare activity in active regions:

http://arxiv.org/abs/1106.1591

The abstract is below.

Best regards
Fabio Reale

Solar Dynamics Observatory discovers thin high temperature strands in coronal active regions

Authors: Fabio Reale, Massimiliano Guarrasi, Paola Testa, Edward E. DeLuca, Giovanni
                               Peres, Leon Golub

Abstract: One scenario proposed to explain the million degrees solar corona is a finely-stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently it has been shown that the observed difference in appearance of cool and warm coronal loops (~1 MK, ~2-3 MK, respectively) -- warm loops appearing "fuzzier" than cool loops -- can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ~10 MK. That work predicts that images of hot coronal loops (>~6 MK) should again show fine structure. Here we show that the predicted effect is indeed widely observed in an active region with the Solar Dynamics Observatory, thus supporting a scenario where impulsive heating of fine loop strands plays an important role in powering the active corona.