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| Paper: |
The Structural Variability of the Solar EUV Network |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
612 |
| Authors: |
Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Keenan, F. P. |
| Abstract: |
Observations of the quiet Sun with the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) are reported for the upper chromosphere, transition region, and corona. The changing structure of the EUV network is examined over a temperature range of 1.5 x 10^4 K to 1.2 x 10^6 K using a variety of properties of the characteristic intensity distributions. The distribution of intensity in small (4 x 4 arcmins^2) areas of the quiet Sun at Sun centre has been examined. These distributions were found to consist of both a low intensity core distribution combined with an extended tail associated with the transition region EUV network. Network properties such as relative area, emission, contrast, and fractal dimension have been derived by fitting two Gaussians (one representing the cell distribution, the other the network) to each frequency histogram and then using the cross-over point of the two Gaussians as a boundary point between the two components. The integrity of the network displays a well defined relationship with temperature showing a noticeable structural enhancement in the temperature range 1.1 x 10^5 K to 2.5 x 10^5 K together with a dramatic change in integrity at coronal (>= 10^6 K) temperatures. |
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