[Loops] [1106.1591] Solar Dynamics Observatory discovers thin high temperature strands in coronal active regions

[Fabio Reale]

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

<http://arxiv.org/find/astro-ph/1/au:+Golub_L/0/1/0/all/0/1>

    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. 


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