I must echo Charles' sentiment: I have just read the paper through, and it is a fine piece of work.  Well done, and persuasively demonstrated. 



On Jul 14, 2013, at 8:00 PM, "Anny Malanushenko" <malanushenko@physics.montana.edu> wrote:

Dear colleagues, 

  our paper about cross-sections of coronal loops has been accepted to ApJ and it is now available on arXiv:  http://arxiv.org/abs/1307.3440 , the abstract is below.

 Key points:
  - coronal loops may be very non-circular in cross-section
  - when we see bright thin overdense strands over dim underdense fuzz, we might be looking at the structures of similar size at the base and of the same scale height, which simply happened to expand in different directions with respect to our line of sight
  - we need to be aware of this effect as it may pose selection bias towards loops which expand along our line of sight more than across it 
 
It was a pleasure to meet many of you at the SPD and I was very happy to receive such a positive feedback on this work! 
Anny 

 "On Anisotropy in Expansion of Magnetic Flux Tubes in the Solar Corona"
 A. Malanushenko, C. J. Schrijver

 Abstract: Most 1d hydrodynamic models of plasma confined to magnetic flux tubes assume circular cross-section of these tubes. We use potential field models to show that flux tubes in circumstances relevant to the solar corona do not in general maintain the same cross-sectional shape through their length and therefore the assumption of a circular cross-section is rarely true. We support our hypothesis with mathematical reasoning and numeric experiments. We demonstrate that lifting this assumption in realistic non-circular loops make apparent expansion of magnetic flux tubes consistent with that of observed coronal loops. We propose that in a bundle of ribbon-like loops those that are viewed along the wide direction would stand out against those that are viewed across the wide direction, due to the difference in their column depths. That would impose a bias towards selecting loops that appear not to be expanding seen projected in the plane of sky. An implication of this selection bias is that the preferentially selected non-circular loops would appear to have increased pressure scale height even if they are resolved by current instruments.
_______________________________________________
Loops mailing list
Loops@solar.physics.montana.edu
https://mithra.physics.montana.edu/mailman/listinfo/loops