SXT Status Report December 15, 1998 through January 4, 1999 (Weeks 51-01) H. Hudson, M. Weber SUMMARY This report covers the New Year's holiday period as Yohkoh enters its 9th calendar year. Solar activity was high, but there were no X-class flares. Neither Yohkoh nor SXT had any technical problems, even with the holiday stress. There were no formal coordinated observations, but SXT tracked the TRACE active region. SOLAR ACTIVITY The GOES background flux hovered not far from the C level during almost the whole interval. (see the weekly plots on our "science nugget" Web pages at http://www.solar.isas.ac.jp/sxt_co/index.html). Oddly there were no X-class flares, confounding the wisdom of those who assert that the "luminosity function" of flare occurrence - the flat power law - is a universal property. Among the 13 M-class flares we obtained some rather interesting observation, not all of which are noted in the science nuggets. AR 8421 - the TRACE choice - had reached a sunspot area of 670 millionths by Jan. 1 (longitude W27). At "first light" on Jan. 4, it was at the limb poised to be occulted, very large and very bright - hence the rather high GOES background level (near C). OBSERVING CAMPAIGNS There were no formal coordinate campaign observations during the interval, but we were glad that we could follow AR 8421 as TRACE did. SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES All functions have been normal. SXT OBSERVING SEQUENCE TABLES ----------------------------------------------------------------- JST Day UT Time Pass Table ID ================================================================= 14-DEC-98 10:03 3 981214 P3 ARS1 DARKCAL 15-DEC-98 10:20 3 981215 P3 ARS1 STD 16-DEC-98 08:53 3 981216 P3 ARS1 STD+DIFF 16-DEC-98 12:20 5 981216 P5 ARS1 STD 19-DEC-98 07:59 3 981219 P3 ARS1 STD 20-DEC-98 08:16 3 981220 P3 ARS1 STD 21-DEC-98 06:49 3 981221 P3 ARS1 DARKCAL 22-DEC-98 07:06 4 981222 P4 ARS1 STD 23-DEC-98 05:39 3 981223 P3 ARS1 STD 24-DEC-98 04:12 2 981224 P2 ARS1 STD+DIFF 24-DEC-98 09:22 5 981224 P5 ARS1 STD 25-DEC-98 02:46 2 981225 P2 ARS1 STD 27-DEC-98 03:02 2 981226 P2 ARS1 STD 28-DEC-98 03:34 4 981228 P4 ARS1 DARKCAL 29-DEC-98 02:08 2 981229 P2 ARS1 STD+DIFF 29-DEC-98 05:34 4 981229 P4 ARS1 STD 30-DEC-98 00:42 2 981230 P2 ARS1 NEWYEAR ===================================================== NEW YEAR BREAK As is customary at ISAS and everywhere in Japan, formal activities cease for a few days over New Year's. During this time we don't track Yohkoh from KSC but there are limited data dumps to DSN - limited because the on-board command recorder can't handle normal operations for long periods of no uplink. This year the last Kagoshima pass of 1998 was 30-DEC-98 11:24:44 (30-DEC-98 02:24:44) 11:38:29 13.8 0.0 13.8 and the first of 1999 was 5-JAN-99 06:12:44 ( 4-JAN-99 21:12:44) 06:23:44 11.0 0.0 11.0 during which interval we had 12 DSN data dumps. For 5.8 days or about 90 orbits, this DSN coverage can deal with about half - not bad, and thank you NASA! Also thanks to the skillful Yohkoh tohbans (Sakao_san?) who were able to cram 12 recorder playbacks, plus everything else, into a 128-entry command buffer. SCIENCE Things slowed down scientifically at ISAS as the holidays arrived, but this may have been unfortunate in view of the nice things being observed. Some of these are summarized in the science nuggets (see below). Probably the most important of these is the Christmas Day report of a probable Moreton wave, which had been actually observed in May 1998. Its scientific importance is great, since the SXT view of these things differs a lot from the meter-wave radio, H-alpha, or EIT views. We understand why we don't see many global waves (see Jim Lemen's analysis), but our current observing sequence table does actually allow us to see them, as shown by this example. Thus we hope we'll get many more as the cycle nears maximum. It would really be wonderful to have a global coronal wave observed in the same flare producing a photospheric wave of the type detected by MDI! Please check out all or any of the recent weekly science nuggets embedded in the SXT operations reports: 11-Dec-98 A confused arcade 18-Dec-98 Homologous compact flares 25-Dec-98 A Moreton wave at last? 1-Jan-98 A coronal microflare The URL's for these and for the full list of science nuggets can be found on http://www.solar.isas.ac.jp/sxt_co/index.html, and the current week's nugget is also always kept on http://www.solar.isas.ac.jp/sxt_co/SXTweekly.html. SEMINARS Dec. 17, 1998: G. Hanoun (Independent/RAL) "Advances in Computer Simulation and Visualization in Solar Flare Research" H. Hudson (SPRC/ISAS): "Ejecta from the X-class Flares of the New Cycle" OPERATIONS ISSUES No particular issues. VISITORS AND PERSONNEL Mark Weber ended his tour, we hope not the last but his thesis is being finished rapidly, so it may have been. In any case, "thanks" from fellow SXT_CO's. George Hanoun visited from RAL and showed us some interesting software. TOHBANS (spacecraft operators) Tohbans for week 51 SSOC : N. Kobayashi, S. Tsuneta KSC : Y. Nakagawa, M. Nishino SXT_CO: M. Weber SXT_SW: - Tohbans for week 52-53 SSOC : T. Sakao, H. Nakajima KSC : M. Nishino, Te. Watanabe SXT_CO: H. Hudson SXT_SW: - Tohbans for week 01 SSOC : - KSC : - SXT_CO: H. Hudson SXT_SW: -