April 11, 2005
Bldg 21, Rm 183A, 3:30 pm

Coronal Loop Heating by Nanoflares: 
Current Status and the Promise of New Missions

Spiros Patsourakos
Naval Research Lab

Regions of enhanced magnetic flux on the Sun, active regions, are threaded by
numerous coronal loops emitting in the EUV and SXR. Coronal loops are ensembles of
closed magnetic field lines loaded with hot and tenuous plasma. They are the main
building blocks of active regions. Since EUV and SXR emissions affect the chemistry
and dynamics of the terrestrial atmosphere, understanding how loops are heated to
million degree temperatures is a cornerstone problem for both solar physics and the
discipline of Sun-Earth connections.

The new stream of satellite data (YOHKOH, SOHO, TRACE)
led to a completely novel picture for coronal loops.
Coronal loops are not consistent with 
static equilibrium theory and can be characterized
by broad Differential Emission Measure distributions
within their cross-sections. Nanoflares occurring
at sub-resolution strands, collectively making up
the observed 'macroscopic' loops, with repetition times longer 
than the coronal cooling time provide a natural explanation
for the bulk of the observations.


With this talk we address the following questions: 
(1) Can steady-flow models explain the TRACE and EIT loop observations ?
(2) Can SXT and TRACE observations help determining
the spatial distribution of nanoflare heating along coronal loops ?
(3) What is the non-thermal spectral line broadening
expected by the nanoflare model ?
(4) How are observations from the new array of space missions (SOLAR-B, STEREO, SDO) 
suited for studying nanoflares ?
We conclude with the first steps towards global coronal models based on nanoflares.


Research supported by NASA and ONR.