SXT Status Report May 25 through June 6, 1999 (Weeks 22-23) H. Hudson, D. McKenzie SUMMARY Solar activity remained at a high background level, but with ony four M-class flares. SXT conducted many joint observations with SOHO, TRACE, and ground-based observatories (notably Tenerife). There were no technical problems with SXT. SOLAR ACTIVITY There were many active regions, including several rather fine sigmoid structures. The science nugget for Week 23 deals with the sigmoid consequences, which nicely erupted (according to expectations) but waited for a long time before doing so (no handle on that yet). Most of the M-class flares occurred during orbit day, but there was good coverage for the one on May 29. It was interesting and was observed well (as a clear loop) at Nobeyama. Rumor has it that the June 2 event provided confirmation (via data from another satellite) of the accretion flow found by McKenzie in the Jan. 20 event - one of SXT's big discoveries (according to HSH). AR 8558 - not at all sigmoidal - developed a sunspot area of 600 millionths but few flares. OBSERVING CAMPAIGNS This has been another busy season for observing campaigns, owing partly to the activity at the Swedish Vacuum Solar Telescope (La Palma). This has included a long series of observations (SOHO JOP 103) aiming at "moss", for which it appears that the SXT data (high temperature, high pressure) may play a key role in the interpretation of the newly discovered transition-region structure. The correspondents here have been Tom Berger and Bart Depontieu from LMSAL. In Week 23 we will carry out a collaboration with UVCS and others (correspondents Jing Li from Hawaii, John Raymond from CfA), for which we are doing an offpoint. This is the first systematic offpoint observation we have attempted in a long time, and in the meanwhile we have learned a great deal about the key factor of stray-light corrections. So we have hopes to be able to make effective comparisons between SXT temperatures and parameters measured by UVCS and the others. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES One cycle of offpoint terminators is complete (3 filters), and the normal-pointing terminators (10 filters) is almost complete for the epoch commencing April 18, 1999 (spacecraft points to E9.89 S2.77 in arc min roughly, relative to the normal pointing position). Unfortunately we still lack Be for the normal pointing but are striving mightily. The "streak artifact" noted in the last status report has disappeared, and we have not carried out the threatened redefinition of the "normal point" coordinates. We should return to this after the offpoint campaign and after the April 18 epoch is completely covered. SXT OBSERVING SEQUENCE TABLES -------------------------------------------------------- JST Day/UT Day Pass Table ID ======================================================== Mon 24-May-99 2 990524 P2 ARS1 STD Tue 25-May-99 2 990525 P2 ARS1 DARKCAL Wed 26-May-99 2 990526 P2 ARS2 ST+J103 Thu 27-May-99 2 990527 P2 ARS2 DF+J103 Fri 28-May-99 2 990528 P2 ARS2 ST+J103 Sat 29-May-99 2 990529 P2 ARS1 STD Mon 31-MAY-99 2 990530 P2 ARS2 STJ103* Mon 31-MAY-99 5 990530 P5 ARS2 STJ103* Tue 1-JUN-99 3 990531 P3 ARS2 DIJ103* Wed 2-JUN-99 3 990601 P3 ARS2 DAJ103* Thu 3-JUN-99 4 990602 P4 ARS2 STJ103* Fri 4-JUN-99 4 990604 P4 ARS2 STJ103* Sat 5-JUN-99 3 990604 P3 ARS1 STD* ======================================================= SCIENCE Weekly science nuggets were: 4-Jun-99: "Two 'loaded guns.' Two clean misses" 28-May-99: "An anemone. A flasher" 21-May-99: "Plasma ejection and flow" The full list of nuggets is kept on http://www.solar.isas.ac.jp/sxt_co/index.html , and the current week's nugget also normally resides on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html . For those of you who are curious, the "loaded gun" is a reference to a comment by A. C. Sterling in the NASA press conference on sigmoids - an active region described this way (typically American, eh?) may well unload its stress into an eruption and a CME. SEMINARS May 23: "Soft X-ray Counterparts of Magnetic Flux Ropes" S. Watari (CRL) Clearly an important subject, since SXT sees so many nice signatures of large-scale coronal organization, and yet there are such strong links to the physics of compact structures. It's also a very practical subject (cf the June 4 science nugget, whose too-cute title refers of course to coronal mass ejections. YOHKOH OPERATIONS ISSUES No particular issues during this period. VISITORS AND PERSONNEL Greg Slater arrived to a tumultuous welcome, just missing a very nice birthday party. Dave McKenzie left, on his way directly to Chicago to see how many SPD meeting participants would stay until the very end of the conference just to appreciate magnetic reconection. TOHBANS (spacecraft operators) Tohbans for week 22 SSOC: K.Yaji, S.Watari KSC: R.Haga, R.Kano SXT_CO: D. McKenzie SXT_SW: - Tohbans for week 23 SSOC: M.Sawa, S.Nagata KSC: R.Kano, Y.Nakagawa SXT_CO: H. Hudson SXT_SW: G. Slater