SXT Status Report August 16 through September 13, 1999 (Weeks 34-37) **** YOHKOH's EIGHTH BIRTHDAY! ***** H. Hudson, N. Nitta SUMMARY This status report covers a four-week period. Activity was both high and low during this month, including the second X-class flare of the year. Coordinated observing activity included Whole Sun Month - 3 and a Max Millenium campaign oriented around sigmoids. SXT experienced no technical difficulties. Happy Birthday, dear observatory! BIRTHDAY The 8th anniversary of Yohkoh's launch (August 31, 1991) came and went uneventfully. The spacecraft and all of its instruments are functioning usefully, although one or two signs of age have appeared over the years. The new solar maximum appears to be showing us things that the old one didn't, and anyway we are getting better at understanding the data so that progress continues apace. We look forward to the next ~3 years of data (2002 is the bitter end of orbit decay, depending upon the degree of solar activity in the meanwhile). SOLAR ACTIVITY The X-class flare happened on August 28, on which day there were no fewer than 7 "delta" spot groups were present (but none the preceding day). By the 31st there were 10 delta-configuration groups. Who knows what this sudden spate of complex regions signifies! In any case, the last week of this reporting period saw a return to low activity levels (on September 7, there were five groups, no deltas, maximum area 60 millionths - a feeble level indeed). OBSERVING CAMPAIGNS The major coordination has been through the Whole Sun Month - 3 joint observations, plus a special sigmoid study embedded in it. Please see our Web pages for full information regarding past and future campaign plans: http://isass1.solar.isas.ac.jp/sxt_co/sxt_catalog.html http://isass1.solar.isas.ac.jp/sxt_co/sxt_future.html SXT INSTRUMENT STATUS AND CALIBRATION ACTIVITIES There are no issues at present. As always, we are tinkering with the terminator program and trying to get the best possible stray-light corrections for the Al.1 filter. It was something of a surprise to obtain some rather well-corrected images recently, for which the sun-center coordinates of the data and correction images differed by at least three full pixels. We hope by the next reporting period to have some better idea about the necessary sampling in pointing and time. SXT OBSERVING SEQUENCE TABLES ------------------------------------------------------------- JST Day Pass Table ID ============================================================= 16-AUG-99 12:42 3 990816 P3 ARS1 STD 17-AUG-99 09:31 1 990817 P1 ARS1 DARK 17-AUG-99 12:56 3 990817 P3 ARS1 DIFF 18-AUG-99 14:54 4 990818 P1 ARS1 QRES (Postponed from pass 1) 19-AUG-99 08:18 1 990819 P1 ARS2 SIG 19-AUG-99 15:08 5 990819 P5 ARS1 QRES* 20-AUG-99 17:32 1 990820 P1 ARS0 SIG 20-AUG-99 13:40 4 990820 P4 ARS1 QRES 21-AUG-99 08:47 2 990821 P2 ARS1 STD 23-AUG-99 07:32 1 990823 P3 ARS1 STD 24-AUG-99 09:29 3 990824 P3 ARS1 DARK 25-AUG-99 09:43 3 990825 P3 ARS1 DIFF 26-AUG-99 04:51 1 990826 P1 ARS1 STD 27-AUG-99 06:46 2 990827 P2 ARS1 STD 28-AUG-99 08:43 3 990828 P3 ARS1 STD 31-AUG-99 06:00 3 990831 P3 ARS1 DARK 01-SEP-99 02:49 1 990901 P1 ARS1 DIFF 01-SEP-99 07:57 4 990901 P4 ARS1 STD 02-SEP-99 04:46 3 990902 P3 ARS1 STD 03-SEP-99 01:36 1 990903 P1 ARS1 STD 04-SEP-99 03:31 3 990904 P3 ARS1 STD 06-SEP-99 02:16 2 990906 P2 ARS1 STD 07-SEP-99 02:29 3 990906 P3 ARS1 DARK 07-SEP-99 23:17 1 990907 P1 ARS1 DIFF 08-SEP-99 04:27 4 990907 P4 ARS1 STD 08-SEP-99 21:50 1 990908 P1 ARS1 1FFI 09-SEP-99 01:14 3 990908 P3 ARS1 STD 10-SEP-99 01:28 3 990909 P3 ARS1 STD 10-SEP-99 20:41 1 990910 P1 ARS0 ILHRQD 11-SEP-99 01:42 4 990910 P4 ARS1 STD ============================================================= SCIENCE 10-Sep-99: CME/Flare on 1999 July 25 3-Sep-99: Large-Scale Disturbances 27-Aug-99: A New SXT Observing Program 20-Aug-99: Seeing-Impaired Folk and an Elephant 13-Aug-99: Eclipse observations - a QRT success The full list of nuggets is kept on http://isass1.solar.isas.ac.jp/sxt_co/index.html , and the current week's nugget also normally resides on http://isass1.solar.isas.ac.jp/sxt_co/SXTweekly.html . The most recent nugget is the second on the July 25 flare, which was caught both by Yohkoh and by TRACE - there are not many good examples of this yet, and we are planning a deliberate flare-hunting campaign that will (we hope) also involve SUMER coordination. SEMINARS 9-Sep: P. Sturrock (Stanford U.) "Chromospheric Magnetic Reconnection and its possible relationship to Coronal Heating" This interesting talk called to mind the Axford-McKenzie model for fast-wind formation, and also brought to mind the interesting talk by Yuri Litvinenko at the Monterey meeting - why should reconnection not preferentially happen near the temperature minimum region? YOHKOH OPERATIONS ISSUES The Yohkoh flare mode threshold has been doubled in level as a test, following extensive discusssions. This seems to work fine but we do not intend to make this permanent, pending analysis of the current behavior. VISITORS AND PERSONNEL H. Hudson left ISAS to attend the TRACE Monterey workshop, during which interval H. Hara helped with CO duties. N. Nitta arrived after the workshop and has been carrying out CO duties. P. A. Sturrock (Stanford U.) visited on two days and discussed CMEs, coronal heating, dynamo theory, and various other subjects. TOHBANS (spacecraft operators) Tohbans for week 34 SSOC: T. Yokoyama, A. Sterling KSC: S. Fujimaki, K. Hori SXT_CO: H. Hudson SXT_SW: - Tohbans for week 35 SSOC: M. Irie, H. Hara KSC: M. Hata, S. Fujimaki SXT_CO: H. Hudson SXT_SW: - Tohbans for week 36 SSOC: Te.Watanabe, M. Miyashita KSC: M. Hata, Y. Suematsu SXT_CO: N. Nitta SXT_SW: - Tohbans for week 37 SSOC: K.Akita, M.Sawa KSC: Y. Suematsu, W. Yoneshima SXT_CO: N. Nitta SXT_SW: -