SOHO Joint Operations Programme 103 TRANSITION REGION MOSS Authors: B. De Pontieu, L. Fletcher, T. E. Berger, C. Kankelborg Version: May 12, 1999 Objective: Recent observations of solar active regions with the Transition Region And Coronal Explorer (TRACE) have revealed finely textured, low-lying extreme ultraviolet (EUV) emission, called the ``moss'', appearing as a bright dynamic pattern with dark inclusions over plage regions. Using previous datasets from CDS, TRACE, SXT, and SVST, we determined the basic properties of the moss: the bright pattern is structured on spatial scales of 2-3 arcsec with dynamic behavior on time scales of less than 1 minute. The moss interacts with chromospheric jets (spicules) which correspond to the dark inclusions seen in the EUV. Te ~ 0.6-1.5 MK and ne ~ 2-5x10^9 cm-3 at a temperature of 1.3 MK. It is apparently the conductively heated EUV emission at the footpoints of 2-5 MK coronal loops. However, the detailed dynamics of moss emission, and particularly their relation to magnetic field structures, remain unclear. The main scientific goals of this JOP are fivefold: one, to investigate temporal variability of the bright moss elements to determine the relative importance of intrinsic changes in brightness and obscuration by chromospheric jets; two, to establish the relationship of moss dynamics to that of underlying magnetic flux elements; three, to investigate how moss relates to cooler transition region structures, e.g. C~IV; four, to study the relationship of changes in emission in hot coronal loops to moss emission; five, to further refine DEM and density measurements, and their temporal variability, for constraint of model parameters. In this JOP, we will examine the dynamics of the moss plasma and changes in the physical parameters on fast time scales (~30 sec), using CDS rasters, MDI high-res magnetograms, TRACE 171A and CIV movies, SXT partial frames, and SVST (La Palma) Ca II K-line, H-alpha, and G-band movies. Local Correlation Tracking (LCT) flowmapping techniques will be used to establish the photospheric flowfield in plage regions with and without associated moss. The relation of moss emission to chromospheric spicules or fibrils is examined in detail using H-alpha movies and dopplergrams. Pointing: Active region with substantial plage, preferably near disk center and in the MDI high-res FOV. Instruments: CDS --- We want to have AR_MON run once, then MOSS_1M for about 100 minutes, then AR_MON again. If CDS support is available, we can run MOSS_1M again after that for 100 minutes. The MOSS_1M study is the new basic 2-shot, 1 minute duration study. It should be planned with N repeats of last raster and M pointings. Regarding pointing of MOSS_1M, here's an excerpt from Dave Pike's message to me: > Rotation compensation (pseudo feature tracking) is > possible using the single study if the planner loads > the study with as many 'pointings' as > necessary and spends a little time entering the required > locations for each. The pointing changes can utilise the > mirror rather than the OPS with > a switch in the command preparation tool (CPT). We will want rotation compensation for MOSS_1M as described above. We expect to supply the CDS-planner with all information about re-pointings. Dave Pike has offered to double-check. Also, include at some point, two runs of NISAT_S, one on an active region with moss close to disk center and one on an active region (preferably the same one) closer to the limb. This will be done only a few times and is not part of the 'day-to-day' operations. We have high-priority CDS support from May 31 to June 4. During the MEDOC campaign from May 18 to May 30 we would like occasional support if possible. Contact: B. De Pontieu (bdp@lmsal.com) or L. Fletcher (fletcher@lmsal.com) MDI --- Magnetic field measurements of MDI in the high resolution mode (if applicable) during (some of) the La Palma observing times. Would very much like MDI support when CDS observes. Contact: T. Berger (berger@lmsal.com). TRACE ----- Wavelengths: 171, 195, CIV series (1550,1600,1700), WL. Frame: 512x512 pixels centered subfield read, 1x1 binning. Compression: Lossless. Exposure: AEC. 3 specialized sequences: a. EUV high rate: 171 cadence = 20 sec, context 1600 every 2 minutes and WL context images every 10 minutes. b. EUV high rate: 171 cadence = 20 sec, CIV (1550/1600/1700) every 2 minutes and WL context images every 10 minutes. c. EUV very high rate: 171 images at a cadence of 10 seconds, WL every 10 minutes. This requires a lossless 512x512 171 frame: cck.stdaeccenterhalf171Q0.ufrm Contact: C. Kankelborg (kankel@icarus.physics.montana.edu). Yohkoh/SXT ----------- Pointing: continuous coverage of single TRACE-selected active region presumably near disk center. Duration: several hours during 8h to 18h UT. Filters: thin Al and Dagwood ONLY. Frame: 128x128 pixel subframe, 1x1 binning. Exposure: short. Mode: standard. Cadence: as high as possible. Contact: L. Fletcher. SVST ------- Observing time available at the SVST/La Palma on the following dates (1999): May 16 to June 4, 8h to 18h UT every day. Wavelengths: G-band 4305: 160x160 arcsec FOV 20 sec cadence. Ca II~K 3933: 160x160 arcsec FOV 20 sec cadence. H-alpha 6563: 150x100 arcsec FOV Line scans: 5 positions 50 sec cadence/position. Fe I 6302: 150x100 arcsec FOV Magnetogram scans 50 sec cadence Contact: T. Berger (berger@lmsal.com) & B. De Pontieu SUMER ------- Slit 8 (0.2"x120") Transmit five image frames of 50x120 px^2 (~ 2 Angstroems windows, Image Format 10) at the wavelengths of N V (1238.821, 1242.8), Si II (1251.16, Mg X (624.95)+ C I (1249.0), O V (629.73). We will use the following command in the SUMER sequence: lambda18 750 1242.4 1238.821 1249.5 1251.16 1259.46 0.0 0.0 0.0 Exposure time will be 30 seconds. This will transmit 5 images at a cadence of 30 sec in a sit-and-stare mode. We can do this for 100 Minutes (200 repetitions) to be in phase with the CDS sequence. We can have a small raster of about 30"x120" before the sequence to find co-registration with CDS in the O V (629.73) line. We will have support from SUMER during May 31 to June 4. Contact: Udo Schuehle (schuehle@linmpi.mpg.de). References ---------- http://blackadder.lmsal.com/~bdp/moss_apjl_pp.ps http://blackadder.lmsal.com/~bdp/mosslett_sub.ps --------------