SXT OPERATIONS STATUS REPORT FOR WEEK ENDING 7 March 1992 -------------------------------------------------------- OPERATIONS ---------- Another quiet week as far as instrument and spacecraft problems are concerned. There was one SEU-related problem early in the week when a warm reset error was discovered during a KSC contact as SXT was not taking images. A standard recovery was made and SXT performed flawlessly for the rest of the week. The Yohkoh orbit apogee is moving back to correspond to the SAA times so if the past has been anything to go by we might expect an increase in such events for the next couple of weeks. The Sun has continued to be relatively quiet but has nevertheless produced some interesting data: 1) On 29 Feb 1992 a small flare in the SE quaderant produced "filled" a large loop (2 arc min) with hot plasma. At the time of maximum brightness of this loop (09:23 UT) a twisted pair of very fine loops were seen to light up from the far end foot point of the flare loop to a point at high latitude nearly half a solar radius away in about 8 minutes - a propagation speed of over 500 km/s. 2) The region that produced the M4 and X3 flares has now set over the west limb. While it remains large and complex it does seem to have simplified considerably since its east limb passage and following the X flare. There is less height structure but still many interconnections between it and surrounding activity centers. The disk passage of this region will be a good subject to study for active region evolution and its relation to flares. 3) There are still relatively few bright points and those that are visible tend to be intense and long-lived often ending their existance in a small flare. The monday operations meeting was delayed until Tuesday, this made for a fairly difficult handover of SSOC duties on Monday, compounded by the orbital phasing of the KCS passes moving earlier in the day. So we adopted a policy that in future the SSOC tobans will make Monday's plan if the first KSC pass falls on the Monday (JST). Mons Morrison led a discussion on and answered questions about the reformatter and archiving plan. Kosugi-san and Keith Strong were SSOC tobans this week. Shibata-san and Akita-san were SXT tobans. There will be a Yohkoh-wide workshop at ISAS on 30/1 March to discuss science plans, calibration and software issues. There will be a number of splinter meetings. One on alignment was suggested and there will be various team sessions (SXT at 1:30 pm on 31 March). An SXT team meeting was chaired by Shibata-san on Saturday 7 March from 11 am - 5 pm which covered many interesting and important topics. While it was mostly in Japanese two very able translators (Shimizu-san and Alan McAlister) made it possible for Keith Strong to participate fully in the meeting. The highlights of the meeting were: 1) A discussion of the upcoming Osaka ASJ meeting. A list of possible papers was discussed and potential authors form Japan and foreign institutes. A list of titles is being translated into English by Alan McAllister and will be circulated to potential coauthors this week by the DUC's. The list comprised 28 entries ranging from quiet-sun evolution to Gamma-ray flares showing the power and flexibility of this mission. It is hoped that several members of the US and UK teams will be able to attend the meeting. It is to be held from 13-15 May 1992. 2) The PASJ papers were also discussed. Tsuneta-san volunteered to make up a final list by early next week and Keith Strong will put it on the Team Bullatin Board after discussions with Uchida-san. It has been decided to allow multiple entries and review in April the most mature for inclusion in the PASJ special issue for publication in October. We have not yet had a reply about additional space being available in PASJ so it is not known how many papers will be included. 3) There was a long discussion about up-coming campaigns, in particular the CoMStOC campaign to use Yohkoh and the VLA to improve our measurements of coronal magnetic fields, and a campaign by Hida Observatory to look at emerging flux regions with SXT and their H-aplha telescope. The CoMStOC campaign will occur from the begining of April and continue through May but will not be continuous, only requiring observations on the VLA days. It is hoped that several rocket flights will happen in this time frame especially Marilyn Bruner's. The Hida campaign overlaps CoMStOC being from 20 April to 9 May. While this initially looked like a conflict in schedule after some discussion of goals it looks as though the two programsd could complement one another by providing data at times when the other groups have none. The largest potential problem is the target selection during the common days, if the VLA is willing to let Hida choose the active region to observe then there would be no problem. If they can not follow the Hida region there should be plenty of full disk data to support both groups. It was suggested that the campaign coordinators (Joan Schmelz/Gordon Holman and Akioka-san, respectively) make contact through Nariaki Nitta and arrange a mutually benificial programme. 4) We decided to hold a weekly or fortnightly SXT science meeting to help spread knowledge of the SXT data obtained during the week and foster collaboration between the team members. The first of these will be at 1:30 pm on 14 March 1992 at ISAS. I will not give details of the progress Mons Morrison has been making on the TEST_RD software as he has covered that well in his extensive software reports. He did have an extremely encouraging and useful discussion with Sakao-san but the reformatted data base and its potential use by the HXT and WBS teams. Sakao-san, Mons Morrison, Andrew Phillips, and Keith Strong managed to get the VMS workstation on the network. It's node number is 40.937. SCIENCE PROGRESS ---------------- Interesting discoveries were made with regard to the structure of flare events. Alan McAlister and Uchida-san have found examples of filament eruptions that show that during the onset there is a bright ribbon running along the length of the arcade either inside the arcade or along the apex of the loops. We have also found an intriguing example of a helmet structure seen in soft X-rays that is not open at the top but actually reconnects back to another similar structure raising doubts about the orginal simple models of these structures. Most of the science work at present is the gathering of data and quantifying results in preparation for the PASJ articles. PERSONNEL --------- John Mariska from NRL has come for a 3-week visit to ISAS and Jaques Dubau has visited for a few days. We had another group of school teachers come but unfortunately the SONY optical disk had been returned to the manufacturer and was not available but the SXT movie was on tape. Keith Strong will generate a new data set on the replacement disk. Keith Strong 8 Mar 1992