[Loops] A paper on Fan Loops

[Durgesh Tripathi]

Dear Friends,

Please find in the link a paper on Fan loops that is just published in ApJ.

*http://iopscience.iop.org/article/10.3847/1538-4357/835/2/244/pdf*

Please let us know of any comments/suggestions you have on the paper.

For your information, I copied the abstract below:

Abstract: A comprehensive study of the physical parameters of active 
region fan loops is
presented using the observations recorded with the Interface Region 
Imaging Spectrometer
(IRIS), the EUV Imaging Spectrometer (EIS) on board Hinode, and the 
Atmospheric Imaging
Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board 
the Solar Dynamics
Observatory (SDO). The fan loops emerging from non-flaring AR 11899 
(near the disk center)
on 2013 November 19 are clearly discernible in AIA 171 Å images and in 
those obtained in
Fe VIII and Si VII images using EIS. Our measurements of electron 
densities reveal that the
footpoints of these loops are at an approximately constant pressure with 
electron densities
of log Ne = 10.11 cm−3 at log [T/K ] T K = 5.15 (O IV), and log Ne = 8.9 
cm−3 at
log  [T/K] = 6.15 (Si X).  The electron temperature diagnosed across the 
fan loops by means
of EM-Loci suggest that two temperature components exist at log [T/K ] = 
4.95 at the footpoints.
These components are picked up by IRIS lines and EIS lines, 
respectively. At higher heights, the loops
are nearly isothermal at log [T/K ] = 5.95, which remained constant 
along the loop. The measurement
of the Doppler shift using IRIS lines suggests that the plasma at the 
footpoints of these loops is
predominantly redshifted by 2–3 km s−1 in C II, 10–15 km s−1 in Si IV, 
and 15–20 km s−1 in O IV,
reflecting the increase in the speed of downflows with increasing 
temperature from log [T/K ] = 4.40 to 5.15.
These observations can be explained by low-frequency nanoflares or 
impulsive heating, and provide
further important constraints on the modeling of the dynamics of fan loops.

Best,
-Durgesh




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