Transition-region network boundaries in the quiet sun: Width variation with temperature as observed with CDS on SOHO

We report here the results of a study of the temperature variation of the n etwork boundary thicknesses in the quiet-Sun transition region. A Fourier-b ased two-dimensional autocorrelation method has been applied to 240 " x 240 " rasters obtained in several transition-region lines by the CDS spectrome ter on SOHO. The quantitative variation of the network boundary width with temperature has been obtained for the first time in a full two-dimensional field. It appears that network boundaries have an almost constant width up to a temperature of about 10(5.4) K and then fan out rapidly at coronal tem peratures. This expansion of the transition-region network boundaries with temperature is found to be quantitatively in agreement with earlier theoret ical models of the transition region.