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Markus J. Aschwanden Submitted: 2007-12-19 15:59
Using the stereoscopically derived 3D geometry of 30 loops observed with
STEREO/EUVI (described in Paper I), we determine here the electron density
profiles n_e(s) and electron temperature profiles Te(s) from a
triple-filter analysis of the stereoscopic images taken in the wavelengths
of lambda= 171, 195, and 284 ang .
The statistical results of our analysis of 7 complete loops are:
observed loop widths wobs=2.6pm 0.1 Mm, corresponding to effective
loop widths of w=1.1pm0.3 Mm if corrected for the instrumental
point-spread function, loop flux ratios floop/ftotal = 0.11 pm 0.04,
mean loop (DEM peak) temperatures T_p=1.1 pm 0.2 MK,
DEM temperature gaussian widths sigmaDEM=0.35pm 0.04 MK,
temperature variations along loops sigma_T/T_p=0.24 pm 0.05,
(resolution-corrected) loop base densities
n_e=(2.2 pm 0.5) imes 109 cm-3, loop lengths of
L=130 pm 67 Mm, and all quantities are found to agree between
STEREO/A and B within a few percent.
The temperature profiles T(s) along loops are found to be nearly constant,
within the uncertainties of the background subtraction.
The density profiles n_e(s) are consistent with the gravitational stratification
of hydrostatic loops, n_e(h)=nbase exp(-h/lambda_T), defined by
the temperature scale heights lambda_T and stereoscopically measured
from the height profiles h(s). The stereoscopic 3D reconstruction allows us
for the first time to accurately measure the loop length L and to test
loop scaling laws. We find that the observations are not consistent with
equilibrium solutions, but rather display the typical overpressures of
loops that have been previously heated to higher temperatures and cool down
in a non-equilibrium state, similarly to earlier EIT and TRACE measurements.
Authors: Markus J. Aschwanden, Nariaki Nitta, Jean-Pierre Wuelser, and James Lemen
Publication Status: ApJ (in press, accepted March 4, 2008)
Last Modified: 2008-03-04 14:52