Dynamics of the transition region

In this review, we consider the problem of the apparent redshifts of the UV lines in the transition region and review the basic observations made over the last decades, especially the observations of the last few years from s atellite observatories. Moreover, we revise the most popular theoretical ex planations for the motions in the transition region. This review is a contr ibution to the understanding of the physical processes in this important la yer of the solar atmosphere and it points out the pending problems. (C) 200 0 Elsevier Science B.V. All rights reserved.