SXT Status Report 6 November - 22 November 1999 (Weeks 46-47) N.V. Nitta, H.S. Hudson, D.E. McKenzie SUMMARY Activity was high, apparently the greatest 10-cm flux level since 1992, but there were no X flares. Yohkoh survived the Leonids and observed a Mercury transit. There were no major problems. SOLAR ACTIVITY No less than 26 M-class flares, but no X-class events. Often during these two weeks there were as many as a dozen numbered active regions on the disk. AR 8765 (S13, CMP @ Nov. 16) reached 1280 millionths - a big spot group. On the X-ray side, the images again showed us remarkable variations in the trans-equatorial loop structures. OBSERVING CAMPAIGNS There were no formal joint observing campaigns, but there were special activities associated with the Leonids and with Mercury. For the Leonids, the Yohkoh team decided to shut down high voltages (reduce them in the case of BCS) as was done last year. This status ran from approximately 00:00 UT Nov. 17 until mid-day Nov. 18. No trouble resulted either from the meteors or from the power commanding. However we did miss an M7.9 event because flare mode cannot be triggered with the high voltages out. Yohkoh's second Mercury transit was a dud scientifically, because it coincided with one of the regular outages of Canopus lock, so that the roll angle could not be re-calibrated. Nevertheless we made images in FFIs and the planet can clearly be seen swimming through the corona. The equivalent TRACE movie - their first - is spectactular and appeared immediately on APOD (http:////antwrp.gsfc.nasa.gov/apod). If we can make it until 2004, we will get a larger planet to work with (Venus). Please see our webpages for more details about campaigns past and future: 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 A normal pointing update was made on 19-Nov-99. New software is available so that this is not so hard to do - it reads the current set point from the OPOG archive via the name of the OG, and computes a new OG based on the offset of the current data from the nominal CCD sun-center position. The flare trigger was back at its high level through this interval, but we had an ARS miss on the M8 flare of 14-Nov. The flare patrol picked a bright portion of the same active region in this case, so that the low-resolution frames observed the event, but not high-resolution data (see http://isass1.solar.isas.ac.jp/sxt_co/991119/ars_991114.html). We are now obtaining images at the patrol image setting to see how they look - probably this miss resulted from the very hard-spectrum, compact, impulsive nature of the flare. D. McKenzie is experimenting with AEC parameters in an attempt to get a fixed offset exposure level. This would help in flare mode, since we currently run the low-resolution images at fixed exposures. When X events finally do happen, we don't want these images to be too saturated, since we are seeing so many interesting effects at these resolutions now. Final data reformatting is complete through 6 November 1999. SXT OBSERVING SEQUENCE TABLES ------------------------------------------------------------- UT Date & Time Pass Table ID ============================================================= 9-NOV-99 20:39 3 991108 P3 ARS1 DIFF* 10-NOV-99 17:28 1 991110 P1 MERCURY* 10-NOV-99 20:53 3 991110 P3 ARS1 DARK* 11-NOV-99 15:59 1 991111 P1 ARS1 STD* 12-NOV-99 17:54 2 991112 P2 ARS1 STD* 13-NOV-99 18:07 3 991113 P3 ARS1 STD* 15-NOV-99 15:08 2 991115 P1 ARS2 MERC* 16-NOV-99 15:21 2 991116 P2 ARS1 DARK* 17-NOV-99 13:51 1 991117 P1 ARS1 DIFF 17-NOV-99 18:59 4 991117 P4 ARS1 STD* 19-NOV-99 14:17 2 991119 P2 ARS1 STD 20-NOV-99 11:07 1 991120 P1 ARS1 AEC-EXP 20-NOV-99 14:30 3 991120 P3 ARS1 WKEND ============================================================= SCIENCE The weekly science nuggets: 12-Nov-99: Preparing for a (second) transit of Mercury This deals with the trans-equatorial loop observations, and provides links to the several earlier nuggets on related topics. 19-Nov-99: Another eruptive flare This nugget shows the Mercury transit and also comments on a well-observed flare in which complex motions (expansion and collapse) can be seen in the low-resolution images. 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 . SEMINARS November 11, 1999, 10:30-12:00: K. Shibasaki (Nobeyama) "High-beta disruption in the solar corona" PERSONNEL Nariaki Nitta arrived to continue the general clean-up activities initiated by the royal visitors. Dick Canfield successfully completed a tohban tour and a draft tutorial, and returned to Bozeman. Hugh Hudson visited Okinawa for two days and was amazed by the chrysanthemum plantations. TOHBANS (spacecraft operators) Tohbans for week 46 SSOC: K. Shibasaki, H. Kozu KSC: M. Yamaguchi, T. Morimoto SXT_CO: H. Hudson SXT_SW: - Tohbans for week 47 SSOC: M. Sawa, K. Matsuzaki KSC: M. Yamaguchi (-11/16), T. Morimoto, R. Haga (11/16-) SXT_CO: N. Nitta SXT_SW: -