Abstract:
The chromospheric network extended to the transition region as the solar EUV network disperses at the coronal level. The EUV emission lines from the transition region give information about different atmospheric heights. The network properties have been obtained from the daily spectroscopic data from the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) in two lines He i 584.5 Å and O v 630 Å. The synoptic changes in the line intensity, skewness of intensity distribution, mean
contrast and network index with respect to the sunspot cycle were studied for a period of 11 years from 1996
to 2006. We have obtained the cross correlation of the monthly average of these quantities with the monthly
sunspot number. The mean intensity and skewness of the two lines generally show a positive correlation with
the sunspot cycle. The network contrast and network index of the He i shows a definite negative correlation
with the sunspot cycle. The negative correlations shown by the He i line are unexpected which could be due to
its anomalous behaviour. There are differences in the behaviour of the two lines regarding the time lag with the
sunspot cycle and the magnitude of the correlation which is always higher for the He i line. The results have
implications to the studies of solar irradiance, magnetic flux transfer and solar atmospheric dynamics.
