SOHO Joint Operations Programme 86 ================================== CDS/TRACE - 18th May 1998 ------------------------- Transient Features in Active Regions ------------------------------------ H.E. Mason, P.R. Young & C.J. Schrijver Active regions have been found to exhibit transient enhancements in emission from the transition region and corona. These could be due to energy released by emerging flux or reconnection higher in the solar atmosphere. Active regions brightenings have been studied using CDS observations by Mason et al (1997), Fludra et al (1997), Young and Mason (1997). Our particular interest is in the determination of the physical parameters - electron density, temperature and element abundance. This information relates to the nature of the energy release and heating in active regions. The CDS observations complement the high cadence images from TRACE (and EIT), by providing simultaneous data in a number of spectral diagnostic lines formed at different temperatures through from 10^5 to 3 x 10^6 K. In this JOP, TRACE scans the active region in a number of different filters over an area of 5x5 arcmin^2. For CDS the principal requirement is to scan a smaller portion of this region (around 2x2 arcmins) in a number of specific diagnostic lines, with the aim of determining the physical parameters and the behaviour of the transition region emission with respect to the coronal emission. TRACE will give information on the large-scale active region structures and transient features. CDS 1) An overview raster (LARGEBP2/v30, 4' x 4', 1hr 46 mins) 2) Several repeats of (TREG22/v12, 2' x 2', 34 mins each) 3) Another large raster (LARGE_T/v9, 4' x 4', 42 mins) DURATION: 6-8 hours SUGGESTED OBSERVING PERIOD: repeated a few times as AR transits disk TRACE Contact: Karel Schrijver Suggested sequence(s): cjs.tracking.1x1.all1 - takes all wavebands at 4 1/2 min cadence, duration 6 hours, full fov cjs.fastdynamics.1x1.civcontext - C IV at 1 min cadence, 171 & 195 at 15 min cadence, half fov