SXT Status Report 29 April 1996 - 2 June 1996 (Weeks 18 - 22) ----------- Hugh Hudson SOLAR ACTIVITY There was another resurgence of activity leading to several C-class flares before the bottom dropped out again. New-cycle regions seem to be coming thick and fast now but are not yet making many flares. For the curious reader, we'll note that the coronal magnetic loops from the new-cycle regions are _not_ upside-down in spite of their reversed polarity. SXT INSTRUMENT STATUS The SXT instrument has continued to work well. There were no significant SXT errors. After extremely long exposures in support of a SoHO campaign on May 19, an artifact appeared in CCD columns near the west limb. This annealed away as have previous similar artifacts. SXT CALIBRATION ACTIVITIES Barry LaBonte (Hawaii) has analyzed the SXT gain-check data taken in April, with the conclusion that the true CCD amplifier gain is 88 electrons per DN (our nominal assumption has been 100). This is something that we will re-check, but it is encouraging (a) that the accepted value is not too far off the mark, and (b) that one can make precise measurements of the CCD parameters with current data, and (c) that the system seems to be nice and stable. We continue to refine the data base of terminator images, which allow for precise stray-light corrections of the data. CAMPAIGNS Several campaign activities were carried out during this period: filament search (2-4 May), coronal loops, with SoHO (14, 18 May), X-ray bright points (24 May - 1 June), and a micro-campaign with SoHO 6 June. 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. The results of the April 1996 eclipse can be found on "http://isasxa.solar.isas.ac.jp/~hudson/apr96.eclipse/eclipse_page.html" VISITORS Scientific visitors to ISAS during this period included Wang Jingxiu from Beijing. He is interested in many things, and his presence has been greatly appreciated - it appears that a breakthrough in our understanding of expanding active-region loops may be happening. Franta Farnik (Czech Republic) departed, with a completed draft paper on the 3 October 1993 flares and another project on pre-flare activity well started. M. Kundu is in residence at Mitaka and is of course an ISAS regular. There have been several helioseismolgy visitors at the University of Tokyo, including Jack Harvey last month, and another of them (Martin Woodard) came to ISAS for a day. Finally, B. Somov arrived from Moscow for an extensive visit at Mitaka, and we hope to see a great deal of him at ISAS. SCIENCE There was an exponential-looking increase in science output as the interval proceeded, perhaps not unconnected with the fact that four of the researchers (Hudson, Nitta, Savy, Sterling) were on their way to the SPD meeting. Some time during this interval, or near it, both H. Hara and K. Morimoto finished their PhD theses. Hara has a post at NAO, and Morimoto is going to the Cosmic Ray Research Institute from which he will get to make excursions to extremely high altitudes in Tibet to study air showers. We are thus likely to see less of Morimoto at ISAS, unfortunately. His thesis centered on the 27 Oct. 1991 flare, and he discovered quite interesting things regarding the hard X-ray (>53 keV) image morphology and the gamma-ray time variability. SEMINARS May 2: G. Slater, "Review of 'The magnetic nature of coronal holes' by Wang et al." M. Woodard, "Are there downflows beneath sunspots?" May 16: M. Kundu, "Solar radio astronomy at metric wavelengths: A revisit by Yohkoh" May 23: J. Wang, "Magnetic Flux Emergence and Cancellation" F. Farnik, "Study of the Oct 3 1993 Flares" May 30: N. Nitta, "Superhot flares: a comparison of imaging and spectral observations" All of these were quite interesting and spawned the usual vigorous discussions. In particular the Slater review of Wang et al. had a major influence on the planning for the IACG workshop that will take place in early July. The Kundu presentation points out something quite important about the SXT data: There has been a systematic re-examination of most of the meter-wave phenomenology (there are papers in the literature now on SXT views of type I, III, IV, and types II and V are coming). SXT adds high resolution and other new perspectives on these interesting physical processes. The Farnik flares, coincidentally, show clear type V signatures in jet-like ejecta from these nearly homologous events. PERSONNEL Hudson, Nitta, Slater, and Savy in residence. Weber to arrive from Montana, Nitta to return to California. Week 18 Tohbans: SSOC: K. Yaji, J.I. Khan KSC: A. Okubo, K. Yoshimura SXT Chief Observer: S Savy SXT Systems and Data Engineer: G Slater Week 19 Tohbans: SSOC: H. Hudson, G. Slater KSC: K. Yoshimura, T. Ishii SXT Chief Observer: S Savy SXT Systems and Data Engineer: G Slater Week 20 Tohbans: SSOC: M. Sawa, T. Magara KSC: H. Watanabe, T. Ishii SXT Chief Observer: S. Savy SXT Systems and Data Engineer: G Slater Week 21 Tohbans SSOC: MH. Takahashi, N. Shinohara KSC: H. Watanabe, S. Hashimzume SXT Chief Observer: N. Nitta SXT Systems and Data Engineer: G Slater Week 22 Tohbans SSOC: S. Watari, A. Sterling KSC: S. Nagai, S. Hashimzume SXT Chief Observer: N. Nitta SXT Systems and Data Engineer: G Slater