THE RELATIONSHIP BETWEEN UV AND X-RAY ACTIVE-REGION STRUCTURES

Yohkoh and the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) jointly observed two brightenings in a ctive region NOAA 7981 on 6 August 1996. Combining the UV data from CD S with information from the high time resolution coronal images obtain ed with the Soft X-ray Telescope (SXT) on Yohkoh, provides us with imp ortant information on the relationship between the transition region a nd corona. Our observations show that cool plasma (T-e = 2.2 x 10(5) K ) can lie at the same altitude as the hot coronal plasma (T-e = 1 - 4 x 10(6) K). The lower temperature structure is not formed from the coo ling of the hotter coronal loop. We are also able to observe a low tem perature cut-off of T-e 1 - 4 x 10(6) K for a loop which repeatedly br ightened over the period of approximately one day.