Due to their low temperature and high density, coronal rain blobs have been observed in Hâ┐ and Ca ii H and K. Optically thick blobs can also be observed in absorption in EUV lines such as those of the ions Mg vi, Mg vii, Si vii or Fe ix. Observing time at the SST has been acquired for observations in the red beam with the CRISP spectropolarimeter and in the blue beam. We request co-observations in the same time period with Hinode/SOT, Hinode/EIS and IRIS. Hinode/XRT is also requested for context active region coronal loop observations.
Time period: Ideally, the acquired observations should elapse at least a 1 hour non-interrupted observation sequence in the period August 4, 2013 -August 13, 2013, provided excellent seeing conditions at the SST. It is not necessary for observations to be on consecutive days. Observations should be conducted between 10 -15 UT (SAA-free period), in order to overlap with the best seeing at La Palma (8 12 UT). Short interruptions should be avoided within this time interval.
Target of interest: The target should be an active region towards the solar limb (preferably east limb) within 30â┐â┐.from the limb (in order to secure both good AO locking at the SST and off-limb coronal rain observations). Particularly, effort will be made to co-observe with IRIS. The target of observation at the SST will be chosen according to the following guidelines, which will be executed depending on the IRIS observing programs at the time. We would like the SOT and EIS instruments to follow the same guidelines:
Main requisite: Active Region. If IRIS is observing a QS region then no co-observation with IRIS and look for an AR on limb.
1. The main goal is to co-observe with IRIS on off-limb coronal loops with coronal rain (active regions)
2. If IRIS is running on-disk wave programs, we will follow IRIS with the observing program specified in section 2.1 (although with lower probability of detection, coronal rain can also be observed on-disk, Antolin et al. 2012)
3. Only if IRIS is not running a wave program or the main requisite is not satisfied, and there is a suitable target close to the limb, we will run our own program (see section 2.1) without IRIS co-pointing.