SXT OPERATIONS STATUS REPORT FOR WEEK ENDING 14 March 1992 ---------------------------------------------------------- OPERATIONS ---------- The Sun remained quiet this week with no major flares and only a couple of bright active regions. Operationally it was a busy week. We suffered two SEU events on Monday (9 Mar) at the first pass and the other on Friday (13 March, of course). There was some concern expressed at the weekly ops meeting that SXT may not have been properly safed when the error was noted as the manuals were not clear and too voluminous to follow. Shibata-san has offered to make a summary of the required procedures. No damage was done as SXT turned out to be in a standard safe configuration. We followed the usual recovery procedure in the subsequent orbits and little data was lost. A patch was made sucessfully on Monday to the SXT-J software to help monitor such events. The operations meeting was again held on Tuesday. There was a problem with the failure of the STT to track Canopus. The origins of the problem and possible ways to avoid it were discussed. During this period (25 Feb to 9 March) the roll angle may have been in error by as much as 3 degrees. There was some discussion of DSN problems in advance of the visit to JPL by Professor Ogawara. Keith Strong was asked to write a report on this but Bob Bentley volunteered to do it instead as there was an unexpected shortage of SXT tobans (due to a meeting in Nagoya and illness) which he (KTS) had to help fill. We were surprised to hear that there was little knowledge of the upcoming campaign with the VLA (CoMStOC) and so Professor Ogawara requested a report on the aims of the several upcoming campaigns and how communications will operate especially with region selection being of importance. Naraiki Nitta, as campaign coordinator, was asked to supply this. On Wednesday we attempted a small repoint of Yohkoh to test the X-ray response of the SXT CCD in the areas where damage has been seen in the diffuser images. The plan was to offset by 3 arcmin east and then return to sun center. Owing to a misunderstanding in the manuals the coodinates input to the commands were assumed to be relative not absolute. This was incorrect and so we offpointed by about 3 arcmin east and about 5 arcmin south. Consequently the return was also in error as we ended up pointed too far south and west. This was sorted out between passes and we were correctly pointed by the end of the 5th pass. A quick check of the CCD response by Akita-san and Keith Strong shows no obvious sign of a degradation in the X-ray sensivity in the "damaged" areas but a more rigerous analysis of these data needs to be made of these data. Mons Morrison created the first data archive tape and sent it to Lockheed on Tuesday (10 March). There has been a great deal of progress on tape compatibility with the BCS team and improvements to our primary data access routines that should speed joint analysis of Yohkoh data. More details of the progress are given in Mons Morrisons daily software reports. SCIENCE PROGRESS ---------------- We held the first in a series of SXT science meetings on Saturday (14 March). We discussed tracking tests for the upcoming week and decided to try to track the 7099/7100 active region complex by two methods: ARS2 and ART. This will enable us to test out which is more effective for CoMStOC and Hida campaigns. Hara-san will set up the tables. Keith Strong presented the scientific highlights of the SXT data for the week and there followed much spectulation on the physical processes and magnetic configurations that might be responsible. Although the Sun had been very quiet there were a number of interesting and exciting observations: 1) The large region that produced the big flares of the last two weeks set behind the west limb but showed an intriguing variety of large scale structures, including a double jet or "searchlight" event. There was also a helmet structure that was strickingly similar to that seen on the east limb two weeks before. Whether this was the same configurartion (implying it is very stable) or a reactivation of the same structure will have to wait for a more detailed analysis. There were several long duration events seen by GOES that we expect come from this region. 2) There was a C1 flare associated with a filament eruption betwen 0200 UT and 0900 UT on 12 March. Fortunately we did not go into flare mode and made a patrol image at the right time so we have full frame and partial frame images simultaneously. Hence we have excellent time resolution on the flare site while being able to see the large-scale reconnection associated with it. A bright feature that can only be described as a 'y' shaped loop (maybe the origin of the brgiht ridges we have seen in privious similar events) formed slowly infront of the usual helmet structure. This does not seem to fit into any of the standard models. Late in the eruption two helmets form that are clearly joined at the cusps. 3) Possibily even more interesting was the preflare configuration of the large-scale field and its evolution prior to the filament eruption. There are radical changes on 10 and 11 March which we can only partially follow because of the lack of reformatted DSN data. A typical polar region configuration seems to produce a high rope-like structure on 11 March that slowly unravels from both ends simultaneously forming what could be interpreted as a coil. Before the filament eruption the "coil" has become faint and seems to have dispersed. We have seen examples of such "coils" or spiral structures before but they have been dismissed as geometrical effects (as this one might be). 4) With the Sun being so quiet there are new opportunities that are not generally available. A small bright point near disk center produced a typical bright-point flare (sub C-level) involving a large-scale loop which fills with a velocity of over 500 km/s. As there was no other activity at that time the BCS is able too get S XV spectra and determine the temperature and timing of the event which should enable us to derive more accurate emission measures and velocities from the SXT data. 5) There has been considerable discussion over the last week about dark features. Several clear examples were visible in the data collected recently, where absorbing loops seem to form in and over existing bright structures. Several people have noted the lack of bright intersection points despite the forest of loops we see in active regions. Could this mean that the corona maybe more optically thick than we have believed to date? PERSONNEL --------- Human resources have been very thinly stretched this week with only two U-side people here as part of the SXT team. We should not let our numbers present at ISAS drop to this level again. Jaques Dubau is visiting ISAS for a week otherwise there have been no changes. We expect Loren Acton, Len Culhane, and Frank Friedlaender to come to ISAS as well as the return of Hugh Hudson. John Mariska and Keith Strong leave on Friday (20 March). Keith Strong 15 March 1992