SXT Status Report 25 June 1996 - 15 July 1996 (Weeks 26 - 28) D. Alexander, H. Hudson, J. Lemen INTRODUCTION Yohkoh and SXT operations were busy during this period, thanks to the tremendous surge of solar activity and several collaborative observations with SOHO. The SXT experienced no problems or errors of significance and is currently functioning well. The rainy season in Japan ended bang on schedule with the return of summer. The hot muggy weather is welcomed by the bugs if not the chief observers (see JOKE). SOLAR ACTIVITY Solar activity was low except for the the wonderful activity of 8-14 July, during which the flux in the soft band of the GOES detectors varied by four decades. This activity culminated in the first X-class flare in a long time. Yohkoh missed this one but got good observations of M-class and lesser flares. Zirin pointed out that this region was an old-cycle region and that we are seeing surprisingly few new-cycle regions. For those truly curious, though, SXT got a good view of coronal loops in one new-cycle region and - the loops ARE NOT UPSIDE-DOWN in spite of the reversed polarity. SXT INSTRUMENT STATUS The SXT instrument has continued to work well. There were no significant SXT errors. No recurrence of the faint exposure-related artifact of 18 May occurred, even through the strong July activity. SXT CALIBRATION ACTIVITIES A SOHO-related campaign to study the outer corona required a new offpoint (nominally 5' E) and associated terminator image acquisition. This all worked fine and the new offpoint position turned out not to have severe stray-light problems. In the meantime, we continue to refine the data base of terminator images. During the past reporting interval, SXT began a series of long-exposure images through the Be filter as a possible aid in calibrating the orbital phase dependence of the BCS rest wavelength in the SXV channel. Any variations of the rest wavelength position would reflect spacecraft flexure, which we know quite well for SXT (and HXT) but not so well at present for BCS. This is most directly done when a single active region is present, in order not to have confused spectra. These data are now available and ready for analysis. CAMPAIGNS In general there are now many opportunities for Yohkoh and SoHO to work together, and we would like to stay as closely in touch as possible. For Yohkoh operations, there is a text file accessible with "finger campaign@isass0.solar.isas.ac.jp | more" or the Web at "http://www.space.lockheed.com/SXT/homepage.html". See "http://sohowww.nascom.nasa.gov/operations/targets/today" for SoHO target planning. VISITORS Scientific visitors to ISAS during this period included Wang Jingxiu from Beijing, B. Somov from Moscow, and M. Kundu from the University of Maryland. SCIENCE Wang Jingxiu and various colleagues (four S's: Savy, Shibata, Slater, and Somov among others) have been working diligently on the apparent expansions and contractions of magnetic loops in a well-observed active region. This has been a model exercise in SXT data analysis and close participation by theorists. H. Hudson participated in a small workshop "Open and Closed Field Lines and Coronal Holes", co-sponsored by the IACG and ISSI (Bern). This focused on several aspects of the relationship between interplanetary observations of solar-wind streams and the solar structures at their origin. In particular, the Skylab data pretty well established the origin of the fast streams to be in the coronal holes. But our generation has been left with the task of identifying the slow wind more explicitly than the general association with streamers noted by Gosling and others. The results from this workshop will not be in proceedings form, but will be strictly on the World-Wide Web (URL to be provided next report). D. Alexander continued his work on HXT image interpretation, exploiting the new pixon-based reconstructions as well as MEM for the Masuda flare. This work and research by S. Tsuneta on the same event show that there are many things still to be learned here. Alexander is helping to organize a narrowly-focused workshop on HXT to learn as much as possible about new software developments. HXT will provide the only hard X-ray imaging observations of flares in the next maximum, and fortunately it is functioning almost perfectly. SEMINARS June 27: K. Ichimoto (NAO) "Measurement of the coronal electron temperature at the total solar eclipse on 1994 November 3" July 4: S. Savy (ARC/ISAS) "Soft X-ray preflare brightening" A. Sterling (CPI/ISAS) "BCS results from Madison" B. Somov (MSU/NAO) "On the thermal instability of shrinking loops" July 18: S. Yashiro and K. Shibata D. Alexander (U Montana/LMPARL) "Soft X-ray Loop-top Sources: Physics or Fiction?" H. Hudson (SPRC/ISAS) "Litvinenko's theory of log-N/log-S" PERSONNEL Alexander, Hudson, Savy, Lemen, and Weber were in residence at different times. Savy is attending COSPAR; Hudson participated in the IACG/ISSI workshop mentioned above, and Lemen and Alexander are preparing for the AGU meeting in Brisbane. Week 26 Tohbans SSOC: S. Yashiro and K. Shibata KSC: S. Tanuma and S. Nagata SXT Chief Observer: M Weber Week 27 Tohbans SSOC: T. Yokoyama and M. Miyashita KSC: S. Nagata and H. Tonooka SXT Chief Observer: S. Savy Week 28 Tohbans SSOC: Te. Watanabe S. Kubo KSC: H. Tonooka and Masanori Nishio SXT Chief Observer: D. Alexander, J. Lemen JOKE Two astronauts are on a flight when something goes horribly wrong. The spacecraft starts plummeting towards the Sun. After the expletives of resignation have subsided the astronauts start to converse calmly. 1st astronaut: Do you know that it's 5000 degrees Kelvin on the surface of the Sun? 2nd astronaut: Yeah, but it's that DRY heat.