SXT Status Report 18 November 1996 - 09 December 1996 (Weeks 47-49) M. Weber, H. Hudson, N. Nitta, S. Savy QUOTE OF THE WEEK: "We could say we were studying filling factors!" -- M Weber, at the Yohkoh Thanksgiving dinner/science conference. SUMMARY Solar activity staged a small comeback as the GOES-observed X-ray background climbed nearly two decades-- due mostly to the passage of the highly active AR 7999 across the disk. Ironically, there were almost no campaigns or coordinated observations with other instruments during this exciting period, with the exception of a few days each for the SoHO programs JOP003 and JOP057. The SXT and Yohkoh have been operating smoothly. SOLAR ACTIVITY Entering Week 47, solar activity was extremely low. This changed when AR 7999 came onto the disk about Nov. 21. This region continued to grow and become more active as it crossed to the west; it raised the general X-ray background flux by nearly two decades at one point and provided a flurry of C-class events, and even an M-class event. The passage of AR 7999 beyond the west limb allowed the solar X-ray flux to drop to its previous depressed levels. At the W limb passage Yohkoh adjusted its pointing to watch the W limb corona in hopes of another nice CME like the Oct. 5 event. SXT INSTRUMENT STATUS SXT continues to perform well and to return excellent observations. The terminator image program proceeds successfully. A new S/C W 3' terminator in thin Al was gotten during the offpoint period. The renewed activity provided us with many flare-mode triggers. These showed that the new flare observation sequence table written to emphasize ejecta had problems, which have now been fixed. SXT CALIBRATION ACTIVITIES The program to collect terminator images is up to date, and proceeds apace with observations now. The normal pointing of the S/C was adjusted 30 arcsec N because (1) the Sun is pursuing its annual drift to the north of our field of view, and (2) next week we will be focussing PFIs on the solar north pole to coordinate with JOP 057. PASS CONFLICTS There is presently little overlap between Yohkoh and ASCA KSC-Pass times. Akebono continues to take infrequent KSC passes. Previous Status Reports have noted a rumor/possibility that NASA may close the DSN 26-meter antenna network. If this happens, spacecraft in low Earth orbit such as Yohkoh will be restricted to Wallops and partial coverage at Santiago, apparently. In such a case we speculate that a large fraction of the non-KSC telemetry would be lost, and that our coverage would decrease significantly. CAMPAIGNS A campaign with SoHO JOP 003 to observe CME onsets ended on November 20. We watched large-scale loops associated with a many-rotation-old active region, but nothing happened (unfortunately) to extend the success stories of 25 September and 5 October. The two events from September and October are the first for which we know that we have simultaneous Yohkoh and SoHO observations of CMEs. We note again that the current low level of solar activity seems to be a help since the X-ray signatures of CMEs may be quite faint. On November 21, we were able to accomodate a late request from the SoHO/MDI team to observe AR 7997 for one day. We continued to track the active region for a day or so after that on our own initiative. Finally, on December 5 we performed a successful test-run of an SXT table for the upcoming SoHO JOP 057 (polar jets) campaign. The campaign will actually begin in the next reporting interval. For Yohkoh operations, the SXT weekly observing plan is available on the Web at http://www.space.lockheed.com/SXT/html2/First_Light.html or with "finger campaign@isass0.solar.isas.ac.jp | more" . See http://sohowww.nascom.nasa.gov/operations/targets/today" for SoHO target planning. VISITORS Dr Brigitte Schmieder of Meudon spent roughly half of her two-week visit to Japan at ISAS, where she was able to spend some time looking at the Yohkoh data from observing campaigns she organized in June and September of this year. These observations focussed on the formation of prominences and filaments. She also found time to visit Kyoto and Mitaka to discuss her work. SEMINARS Nov 27 H Hudson (SPRC): "Being Skeptical about the Classical Reconnection Model for Solar Flares". (Delivered to the ISAS Space Plasma Physics Group.) Nov 28 B Schmieder (Meudon): "Filaments and Prominences as seen in SoHO/CDS and SUMER". N Nitta (LMPARL): "Hard X-rays from Microflares". Dec 5 B Schmieder (Meudon): "Signatures of Emerging Flux in the Corona". All of these talks were well received, and we were particularly delighted to hear Dr Schmieder speak twice on her (and her colleagues') promising research. SCIENCE Khan continued studying homologous flares, a topic that resonated with flares during week 49 and microflares reported in the Dec. 5 seminar by Brigitte Schmieder. Perhaps there is a middle ground that would permit reconnection models to coexist with the apparent lack of topology changes in such events: only a small flux transfer occurs, in which the domains simply adjust on undetectably small scales. Sterling continued to study limb passages of these nice quiet-Sun active regions and to push back the frontiers of BCS signal-to-noise ratio. Hudson and Joe Gurman (SOHO) exchanged movie files showing the fine eruptive event of Nov. 30. SXT caught the expansion phase, showing a massive slowly-moving ejection; The EIT movie in FeXII shows a wonderful display of post-flare loops and catches a hint of the actual CME that must have accompanied this event. PERSONNEL L Acton returned to Montana, and was replaced with M Weber. G Slater and N Nitta departed. Week 47 Tohbans SSOC: A Okubo and J I Khan KSC: H Watanabe and Y Suematsu SXT CO: N Nitta Software: G Slater Week 48 Tohbans SSOC: S Masuda and N Nitta KSC: Y Suematsu and T Takano SXT CO: M Weber Software: --- Week 49 Tohbans SSOC: H Nakajima and H Hudson KSC: T Takano and S Kubo SXT CO: M Weber Software: ---