SXT Status Report 1 April 1996 - 15 April 1996 (Weeks 15 - 16) ----------- Serge Savy 15-Apr-96 The last two weeks saw the start of a coordinated X-ray bright-point campaign with ground observers and SoHO lasting for 9 days. Otherwise operations have been straightforward. SOLAR ACTIVITY The sun has been quiet with no major flares, but several small emerging flux regions appeared and much diffuse structure was visible in the corona. AR7955 produced a B-class flare on 3 April. AR7956 was observed in week 15. SXT INSTRUMENT STATUS The SXT instrument has continued to work well. There were no significant SXT errors. SXT CALIBRATION ACTIVITIES The main effort for SXT calibration continues to be the "terminator" program, whereby correction images are obtained by acquiring pictures when the X-ray sun has set but the visible sun is unaffected by atmospheric absorption. These images still show the scattered optical light, and we have found that excellent corrections for this effect can be made by proper use of the terminator data. We continue to work on ways of getting such correction images efficiently and in the right filters. In particular, to cover the use of the filters in the SoHO campaigns, we have been acquiring additional terminator images. PASS CONFLICTS Pass conflicts with ASCA: Week 14: 5 KSC pass conflicts. Week 15: 6 KSC pass conflicts. CAMPAIGNS On April 6 we started an X-ray Bright Point campaign coordinated by Karen Harvey (SPC). SoHO (all imaging instruments), and several ground observers are participating. The SXT chief observer selected the target for the campaign each day. The Kitt Peak observations feature image-resolved line profile information in 10830, so that these data are much more comprehensive than any of our bright-point campaigns before. The Sun cooperated with many bright points. Our target was a 1x3 (2.5x8 arcmin) region near disc centre. On 9 April we moved our field of view slightly north to observe a small active region that had appeared. The target for 14 and 15 April was also near disc centre, and AR7956 was conveniently within our field of view. The campaign ended on 15 April. VISITORS Scientific visitors to ISAS during this period included F. Farnik (Czech Republic), K. Harvey (USA), and J. Harvey (USA). SCIENCE Savy helped Farnik et al. with the analysis of the 3 October 1993 flare, which is characterized by very impulsive, very hard hard X-ray spectra. He also started a survey of the early rise phase of flares to assess the evidence for pre-flare heating. There was continued work on the flares of October 1995, which produced type II bursts and also puzzled the Yohkoh analysis software temporarily. Hudson submitted an abstract to the SPD on these events. Meanwhile, there was continued interest in the 13-Jan-92 "Masuda" event. J. Sato was able to get image information from HXT without the use either of pixons or MEM, by using the fan-beams. These results contribute to the development of our knowledge both of the solar physics and to the HXT image response. Because the research workers actively engaged on studying this flare are in many physical locations (Fuchinobe, Mitaka, Toyokawa, Palermo, Wroclaw, Greenbelt, Caltech, Bozeman, Berkeley, Palo Alto, and Honolulu at least - in rough order of longitude) - we are discussing the idea of launching a CDAW meeting using the World-Wide Web as a medium of discussion. SEMINARS Week 14 seminar was by Y. Yan (Beijing Astronomical Observatory) on "The Extrapolated Force-Free Magnetic Fields and their Associations with Yohkoh Soft X-ray Observations". The seminar for week 15 seminar was by F. Farnik (Ondrejov, Czech Republic / ISAS) on " Two examples of SXT data analysis - large coronal structures seen in full disk images and relation between pre-flares and flares as seen in partial frame images ". PERSONNEL Slater arrived on 5 April for a six week stay. Week 14 Tohbans: SSOC: H. Hara, H Nakajima KSC: S Yasuno, T Takano SXT Chief Observer: S Savy SXT Systems and Data Engineer: Week 15 Tohbans: SSOC: Kubo, Shinoda KSC: Masuda, Takano SXT Chief Observer: S Savy SXT Systems and Data Engineer: G Slater