SXT Status Report 1 Dec. 1997 - 14 Dec. 1997 (Weeks 49-50) M. Weber, S. Savy, H. Hudson SUMMARY Solar activity relaxed somewhat during this period, with no further X-class flares but some major eruptive events. SXT has operated well. There were no formal campaigns. SOLAR ACTIVITY There was only one M flare, but many smaller flares as the GOES background level hovered between B2 and B4 for the whole interval. NOAA AR 8113 dominated the scene, punctuating its departure with the huge arcade/CME event reported below; it continued to show off even after the W limb passage. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES SXT continues to operate well. There was a surprisingly smooth pattern of ground-station contacts, including one miraculous bonus (see discussion below) from a "lost weekend". Special tables were prepared to help Acton study the variation of dark signal with phase of orbital motion. Data archiving is complete through Week 46 (ending Nov. 17, 1997). The handover to Wallops for ground-station scheduling is on track. There is now a Wallops ftp "mailbox" and agreement on procedures and file configurations. We expect to begin running in parallel this month and complete the switchover fairly shortly afterwards. The Wallops staff (Rick Jones) are going to great pains to be sure that the transition does not change our interface any more than necessary, and we are glad for some of the changes - no more RASM, for example. WEB-BASED SCIENCE REPORTS The scheme of weekly reporting by the SXT Chief Observer on Web pages has continued. The current report is now at ftp://isass0.solar.isas.ac.jp/pub/sxt_co/SXTweekly.html and deals with the amazing arcade that developed on Dec. 6, 1997. In the near term, at least, this URL will be a fixed point of reference for these "science nuggets". Previous reports in this series are at the following URLs: ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971024.html dimming ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971031.html EIT Calroc ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971107.html Nov 6 flare ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971114.html Nov 14 LDE ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971121.html Movies of ejecta! ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971128.html X2.9 ejective flare ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971205.html Solar cycle ftp://isass0.solar.isas.ac.jp/pub/sxt_co/971128.html Amazing arcade A few brief comments about the "amazing arcade". This C-class flare produced the brightest and largest arcade we have seen for years, and also was the source (apparently) of an equally amazing CME. We are getting so that we know what corresponds to what rather well, except for occasional "problem" CMEs such as Jan. 6, 1997, for which a very geoeffective ejection resulted from an almost undetectable perturbation of the lower atmosphere. This event was extremely well covered by SXT, except of course it was too large for the PFIs to see completely. It involved complex motions of a set of fine filamentary structures, unfortunately recorded mostly in Q resolution, somewhat reminiscent of the structures seen in the event of October 5, 1996, except that one was from two days beyond the limb. The good coverage was the result of a miracle. Normally on Sunday the Kagoshima Space Center does not operate for telemetry. However the precession of the Yohkoh orbit sometimes makes it necessary to shift the holiday date or to skip the holiday completely. That happened this time - the event coincided exactly with the "extra" telemetry dumps. Amazing! Finally, the Dec. 6 arcade appeared in a quiet interval, preceded and followed by swarms of flares and microflares. Is this a general pattern or just the SXT chief observers' feverish imaginations at work? PASS CONFLICTS AT KSC (Akebono, HALCA, ASCA) Week 49, none! Week 50, none! CAMPAIGNS There were no formal campaigns during these two weeks. Some further attempts, not very successful, were made to look out for jets in response to Shimojo's standing request. For Yohkoh target planning, 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 AND PERSONNEL No personnel changes this interval. Hudson made a day trip to Nobeyama (Dec. 11) to work on the X9 flare from Nov. 6. SEMINARS There were no Yohkoh seminars during these weeks. People are getting ready for the workshop at Nobeyama during Week 51. TOHBANS Tohbans for Week 49: SSOC : T.Ishii and K.Hori KSC : Y.Suematsu and H.Tonooka SXT_CO: M. Weber SXT_SW: - Tohbans for Week 50: SSOC : M.Sawa and S.Tanuma KSC : H.Tonooka and M.Torii SXT_CO: M. Weber SXT_SW: -