SXT Status Report 13-26 September 1999 (Weeks 38-39) N. Nitta, H. Hudson SUMMARY Activity in this two-week reporting period was generally low with only one M-class flare. A combination of uplink problems (transmitter) and a major typhoon conspired at the Kagoshima Space Center (KSC), so that we lost two days of data (23-24 September), but things have resumed normal since then. There were no official campaigns, but we started exploring our sequences to observe large-scale loops between active regions in the north and south hemispheres. Evolution of these loops can be important in understanding some of the coronal mass ejections. SOLAR ACTIVITY Apart from the lack of intense flares, the GOES background level dropped to B3-4 around 23 September, looking as if solar maximum were still in a distant future or were already over. All the regions but one (AR 8700) that were seen during this period were in either alpha or beta configuration. OBSERVING CAMPAIGNS We did not have official campaigns. But 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 outstanding issues at the moment. Stray-light corrections are generally going well, although not perfect, with the existing database of terminator (sunset) images. We are still working on a better idea as to the necessary sampling of terminators in pointing and time. SXT OBSERVING SEQUENCE TABLES ------------------------------------------------------------- UT Date & Time Pass Table ID ============================================================= 13-SEP-99 22:57 3 990913 P3 ARS1 DARK 14-SEP-99 19:45 1 990914 P1 ARS1 DIFF 15-SEP-99 00:54 4 990914 P4 ARS1 STD 15-SEP-99 18:18 1 990915 P1 ARS0 IL+VER0 15-SEP-99 21:42 3 990915 P3 ARS1 STD 16-SEP-99 18:31 1 990916 P1 ARS0 IL-VER0 16-SEP-99 21:55 3 990916 P3 ARS1 STD 19-SEP-99 17:31 1 990919 P1 ARS1 STD 20-SEP-99 19:26 3 990920 P3 ARS1 DARK 21-SEP-99 16:16 1 990921 P1 ARS0 IL VER1 21-SEP-99 19:40 3 990921 P3 ARS1 STD 25-SEP-99 18:52 3 990925 P3 ARS1 WEND ============================================================= SCIENCE We missed a "flare-less CME" (http://umbra.nascom.nasa.gov/eit/cme/#19990920), as observed by EIT/LASCO, because of poor coverage. The flare-CME relation is still a hot topic, and widely different views exist even among the SXT Chief Observers (the authors, for example). The unfortunate term "flareless" is the one being used by our SOHO counterpart, Joe Gurman. The following weekly science nuggets were produced. 24-Sep-99: Coronal Magnetic Implosions 17-Sep-99: Hot Loops and Cool Loops 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 summarizes Hudson's personal idea about solar magnetic implosions. A full paper will follow in Solar Physics. SEMINARS 16 September: Y. Hanaoka (NAOJ/Nobeyama) "Radio and X-ray Observations of the Flares Caused by Interacting Loops" A time analysis of the Nobeyama images at their full 50 ms resolution indicated that the location of the acceleration site was in the vicinity of the compact loop that appeared to interact with larger-scale loops. This is probably one of the best examples showing that microwave data can be essential. YOHKOH OPERATIONS ISSUES We had a small (C2.8) flare, which unexpectedly triggered Yohkoh flare mode, but the automatic region selection (ARS) software of SXT did not pick up the flare, which was apparently too faint. It appears that the selected region was close to an area of enhanced stray-light in the ARS patrol images. The higher flare mode threshold we have been using for the past few weeks will therefore reduce the number of flares that escape the SXT partial frame images. We found at least two examples of flare data interrupted in the middle of the impulsive phase. They coincided with downlinks at NASA stations. Further discussion may be needed as to how the spacecraft operators at ISAS (=SSOC tohbans) should choose between night-time and Wallops passes. A related topic may be implementation of a system in which the SSOC tohbans request NASA stations to add passes for the current week. This is to compensate the long data gaps that result from a significant number of KSC passes being lost to other ISAS missions. PERSONNEL N. Nitta returned to Palo Alto. B. Handy arrived from Bozeman. A. Sterling is at last (!) on his way to Huntsville, after serving as a BCS resident scientist for almost a decade. TOHBANS (spacecraft operators) Tohbans for week 38 SSOC: H. Hudson (Kubo), Y. Hanaoka KSC: W. Yoneshima, K. Fujiki SXT_CO: N. Nitta SXT_SW: - Tohbans for week 39 SSOC: M.Yamaguchi, S.Watari / K.Marubashi KSC: K.Fujiki, S.Kato SXT_CO: N. Nitta, H. Hudson SXT_SW: -