High-resolution imaging of the solar chromosphere corona transition region

The properties of a previously unresolved extreme-ultraviolet (EUV) emissio n in solar active regions are examined using coordinated data sets from the Transition Region and Coronal Explorer (TRACE) satellite, the Michelson Do ppler Imager on the Solar and Heliospheric Observatory satellite, the Soft X-Ray Telescope (SXT) on the Yohkoh satellite, and the ground-based Swedish Vacuum Solar Telescope (SVST) on La Palma. The emission appears most promi nently in TRACE Fe IX/Fe x 171 Angstrom images as a bright dynamic network surrounding dark inclusions on scales of 2-3 Mm, confined to layers approxi mately 1-3 Mm thick with base heights approximately 2-4 Mm above the photos phere. It is seen only above plage regions that underlie (3-5) x 10(6) K co ronal loops visible in SXT images. The bright EUV elements emit at temperat ures of about 10(6) K. Fine-scale motions and brightness variations of the emission occur on timescales of 1 minute or less. The dark inclusions corre spond to jets of chromospheric plasma seen in simultaneous SVST filtergrams in the wings of H alpha. The combined characteristics imply that we are at least partially resolving the structure and dynamics of the conductively h eated upper transition region between the solar chromosphere and corona.