Two-component structure of the solar Transition Region

We studied the morphology of the quiet Sun in the Transition Region, using observations of the SUMER spectrograph in three emission lines (Si II, 1533 Angstrom, C IV, 1548 Angstrom and Ne VIII, 770 Angstrom), emitted respectively in the chromosphere, the low transition region and the low corona, as well as EIT images in the four passbands of the instrument. We computed the mean autocorrelation function for the intensity images in order to estimate the characteristic size of the features present in the Transition Region. Moreover, we deduced autocorrelation functions for the Dopplergrams and line width images. Specifically, using images of the C IV emission line tail component, as this is estimated by a double Gaussian fit, we studied the morphology of the coronal funnels, as they appear at 10(5) K (formation temperature of the C IV line). We found that the size of the intensity bright features is always larger than the size of the structures of the dopplergrams and dopplerwidths, at all altitudes. The mean size of the structures of the tail component intensity is smaller than the one of the core intensity component.