Previous observations performed with the CDS and SUMER instruments have revealed that the upper chromosphere and the transition region as well are not static, but display significant changes and variability even in case of the quiet solar atmosphere (see e.g. review Judge, 1997, contributions of Betta et al., 1997, Steffens et al., 1997, or Wikstol et al., 1997). These findings support few older results obtained from different instruments, e.g. HRTS time series (Cheng, 1991). Our previous observations of the chromosphere and the transition region made only with the SUMER spectrometer (UDP 188.8.131.52, Curdt et al., 1997a) have confirmed those results. They have shown additionally, that the temporal variability of the spectral lines originated in those layers is significantly different in the supergranular boundaries and internetwork (Curdt et al., 1997b, Kucera et al., 1998). MDI magnetograms taken simultaneously with the 2D CDS rasters of the coronal line intensities have shown that the occasional merging of the opposite magnetic polarities in the supergranular boundaries correlate with the coronal emission brightening above these quiet solar atmosphere regions. The concept of 'magnetic carpet' was proposed as the explanation of this phenomenon (e.g. Tarbell, 1997, Judge, 1997, Schrijver, 1997). The behaviour of these phenomena in the chromosphere and the transition region has not be revealed by observations till now.
Therefore the present JOP is proposed to trace such behaviour. Our aim is to study the supergranular network and internetwork, addressing the detailed temporal and spatial evolution of different events through the solar atmosphere. Significant volume of data obtained from the equatorial coronal holes as well as outside of them would be advantageous for the sufficiently reliable investigation.
The careful planing of the necessary data acquisition for the post-facto alignment has been performed in order to reach the highest possible adjustment of SUMER slit position within the field of view (FOV) of other instruments.
The proposed JOP is similar to some other ones which are focused mainly on the internetwork research (e.g. JOPs 013, 022) or on active regions (e.g. JOPs 017, 018, 034, 075).