Transition region and coronal structuring
E. O'Shea 1,
P.T. Gallagher 1,2,
M. Mathioudakis 1,
K.J.H. Phillips 2,
F.P. Keenan 1 and
A.C. Katsiyannis 1
Received 27 August 1999 / Accepted 17 February 2000
In this paper we examine regions of internetwork, network and bright network emission, observed in the quiet Sun with the Coronal Diagnostic Spectrometer (CDS ) onboard SoHO. The slopes of the emission measure distributions, between 5.4 log Te 6.0, are found to differ in each region, suggesting the presence of different atmospheric structures. From an analysis of emission area the network is shown to have two populations of structures, a low transition region group and a coronal group. Using MDI magnetograms the bright network emission is shown to originate from regions of strong magnetic field composed of bipolar loops and unipolar funnels, that extend from the low transition region up to the corona. Up to 30% of all radiative losses between 5.7 log Te 6.3 are found to come from these continuous bright network structures. Cross-sectional areas calculated from redshift values suggest that the area expansion seen in the bright network emission is the result of flux tube expansion into the corona, accompanied by either a downflow or upflow of material.
Key words: techniques: image processing methods: observational Sun: corona Sun: transition region Sun: UV radiation Sun: atmosphere
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© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000