[Loops] [1205.4553] The role of radiative losses in the late evolution of pulse-heated coronal loops/strands

[Fabio Reale]

Dear colleagues
      please find at the following link the preprint of a work accepted 
for publication in Astronomy & Astrophysics, showing the importance of 
updating the radiative losses on loop modeling, in particular on the 
very late phases of pulse-heated loop evolution:

http://arxiv.org/abs/1205.4553

This work may help to understand, for instance, why we see much fewer 
warm loops in active regions, than expected from a model of loop cooling 
from a hotter status. Special thanks to Peter Cargill for useful 
suggestions on the analytic part. Please contact me if you wish to have 
a 2-column version of the preprint.
The abstract is below.

Best regards
Fabio Reale

The role of radiative losses in the late evolution of pulse-heated 
coronal loops/strands
F. Reale, E. Landi

Abstract: Radiative losses from optically thin plasma are an important 
ingredient for modeling plasma confined in the solar corona. Spectral 
models are continuously updated to include the emission from more 
spectral lines, with significant effects on radiative losses, especially 
around 1 MK. We investigate the effect of changing the radiative losses 
temperature dependence due to upgrading of spectral codes on predictions 
obtained from modeling plasma confined in the solar corona. The 
hydrodynamic simulation of a pulse-heated loop strand is revisited 
comparing results using an old and a recent radiative losses function. 
We find significant changes in the plasma evolution during the late 
phases of plasma cooling: when the recent radiative loss curve is used, 
the plasma cooling rate increases significantly when temperatures reach 
1-2 MK. Such more rapid cooling occurs when the plasma density is larger 
than a threshold value, and therefore in impulsive heating models that 
cause the loop plasma to become overdense. The fast cooling has the 
effect of steepening the slope of the emission measure distribution of 
coronal plasmas with temperature at temperatures lower than ~2 MK. The 
effects of changes in the radiative losses curves can be important for 
modeling the late phases of the evolution of pulse-heated coronal loops, 
and, more in general, of thermally unstable optically thin plasmas.

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Dr. Fabio Reale, Ph.D.
Professore Associato
Dipartimento di Fisica, Universita` di Palermo
P.za Parlamento 1, 90134 Palermo - ITALY
Tel: +39 091 233 237
Fax: +39 091 233 444
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