SXT Status Report 9 October - 5 November 1995 (Weeks 41, 42, 43 and 44) --------- Serge Savy 13-Nov-95 This past four weeks have been rather busy. There were the eclipse observations, the Chromospheric Activity and Coronal Loops campaign with Brigitte Schmieder (Meudon), and some special observations for George Roumeliotis (Stanford). The eclipse observations on 24-Oct were a great success but the special operations associated with them led to problems with Yohkoh operational control for several days afterward. Normal operation was restored by Saturday 28-Oct. The recovery process required careful checks, but after hard work by senior Tohbans, (especially Te. Watanabe), helped by NEC specialists, the Yohkoh setup was restored in several stages over a few days. Yohkoh and SXT have been operating normally since 28-Oct-95 05:00:47 UT. There is no problem now with either the spacecraft or the instruments. SOLAR ACTIVITY Activity was high in week 41 with 4 regions on the disk towards the end of week. AR7912 showed a complex field geometry and this resulted in a series of C flares and one M-class flare that was well-observed by Yohkoh. The interesting activity continued in week 42, with a spectacular eruption from an unusual M2 class flare on 20 October. Several X-ray Jets from small flares in active region AR7912 were also well observed with SXT. One of these X-ray Jets coincided with significantly blueshifted Yohkoh BCS X-ray spectra. During the following weeks activity decreased until the appearance of bright AR7921 on the East limb, which produced an beautiful CME at 21:00 (UT) on 3 Nov that was observed in the SXT PFIs. SXT INSTRUMENT STATUS SXT has been operating normally since the recovery of Yohkoh fixed pointing on 28 October. There have been no significant SXT errors in the last four weeks. CALIBRATION STATUS Special effort is being made to build up a suitable database of terminator images for stray light corrections. This will involve taking terminator images at special pointings offset to correct somewhat for pointing drift during an orbit. PASS CONFLICTS Week 41: 9 KSC passes lost to Asuka, none to SFU. Week 42: 9 KSC passes lost to Asuka, none to SFU. Week 43: ASUKA team kindly moved their holiday from Sunday 22 October to Tuesday 24 October so that Yohkoh could have all the KSC passes on the day of the eclipse, and later in the week they donated one KSC pass (no. 5 on 25-Oct) for the recovery of Yohkoh operation. Week 44: 10 KSC passes lost to Asuka, none to SFU. CAMPAIGNS On 12 October we made special observations for George Roumeliotis (Stanford). The objective was to obtain high time cadence PFIs of an active region on which to test a special image processing technique with a view to removing the SXT PSF to obtain high resolution images. AR7912 was observed in 1x1 PFIs with the AlMg filter. In week 42 we started a campaign entitled "Chromospheric Activity and Coronal Loops" which involved observers from Pic du Midi. It was coordinated with B. Schmieder, P. Mein, L. Roudier, L. Van Driel- Gesztelyi. The campaign was officially scheduled for 19-25 Oct, but in fact coordinated observations started two days early on 17 Oct, and ran until the eclipse on 24 Oct. A PFI active region target was selected each day by the SXT Chief Observer for coordinated observations between the hours 06:00-16:00 UT. The main focus of our attention was AR7912 from 17 Oct until 22 Oct when it disappeared over the west limb; the rest of the campaign concentrated on AR7918. These active regions were observed in ARS2 mode with the AlMg and Al12 filters. The eclipse on 24-Oct-95 consisted of four episodes (all between KSC contact times): an eclipse of the corona; partial eclipse of the disc; another partial eclipse; and finally another eclipse of the corona. (See Kevin Reardon's ephemeris plot at http://galileo.ifa.hawaii.edu/reardon/eclipse.html). The eclipse committee (Te.Watanabe, H.Hudson, R.Kano, T.Yoshida, K.Marubashi, J.Lemen, S.Savy) did a great job planning operations for the eclipse. R.Kano and T.Yoshida worked particularly hard to prepare the command files. The plan was to offpoint Yohkoh to take FFIs of the two coronal eclipses and observe the partial eclipses with normal pointing. The PFIs were 4x1 segments centered alternately on each pole in an attempt to observe solar plumes. The time cadence was 64 seconds for the PFIs at each pole and 32 seconds for the FFIs. The eclipse observations were a great success with spectacular images recorded. Unfortunately a mistake was made predicating the direction of one of the coronal eclipses such that Yohkoh was offpointed in the wrong direction during that coronal eclipse. The Asuka team kindly moved their holiday from Sunday 22 October to Tuesday 24 October so that Yohkoh could have all the KSC passes for the eclipse. Thanks to Jim Lemen's hard work and cooperation from Joe Gurman (GSFC), the SXT movies of the eclipse were made available on the World-Wide-Web within a few hours of the observations. For these, and more information about the eclipse see http://www.space.lockheed.com/SXT/eclipse.html . SCIENCE Eclipse PFI observations were carried out with optimization to study the X-ray counterparts of polar rays or plumes. We aim at exploiting the eclipse images taken from the ground, and this is scientifically related to the Koutchmy-Hara campaign activity. The success of this effort will not be known until coordinated data comparisons are carried out. Prior to the eclipse, two rather spectacular flare events happened (13 and 20 October). Both of these had meter-wave Type II bursts, and for each the SXT data showed spectacular ejections. It is probable that analysis of these events will identify the low-altitude structure of the disturbance exciting the Type II bursts. The striking morphological result is that the flare ejecta have no hint of spherical symmetry, as suggested by the shock propagation models of Type II burst formation - these may therefore be more applicable at higher altitudes (lower frequencies) than near the impulsive core of the flare. SEMINARS Week 41: J. Sato (NAO) on "HXR and SXR Images of the 15-Mar-93 Flare" and M. Shimojo (Tokai University) who spoke of recent work on identifying common features of flares and jets. Week 42: Bernie Jackson (UCSD/STElab) on "Active Region Imprints on IPS Measurements". H. Watanabe (STELAB) gave some related comments. Week 43: No seminar. Week 44: No seminar. PERSONNEL Dr. Gan from the Purple Mountain Observatory in China arrived during week 41 for a three month stay at ISAS. He is currently investigating chromospheric evaporation. At the end of week 43 Jim Lemen returned to the U.S. after a productive 5 week stint as Chief Observer. Loren Acton arrived at the end of week 43 for a one month stay. Laurence Shing left ISAS at the end of week 44 after writing and installing software for the mounting of MOs and CD-ROMs on all the machines at ISAS, among many other useful things. Week 41 Tohban: SSOC: A. Sterling, H. Hudson KSC: H. Watanabe, M. Takahashi SXT Chief Observer: J. Lemen, Serge Savy SXT Systems and Data Engineer: L. Shing Week 42 Tohban: SSOC: K. Marubashi, J. Lemen KSC: M. Takahashi, K. Yoshimura SXT Chief Observer: J. Lemen, Serge Savy SXT Systems and Data Engineer: L. Shing Week 43 Tohban: SSOC: S. Morita, Te. Watanabe KSC: K. Yoshimura, M. Akioka SXT Chief Observer: J. Lemen, Serge Savy SXT Systems and Data Engineer: L. Shing Week 44 Tohban: SSOC: R. Kano, M. Mizutani KSC: M. Akioka, M. Yamamoto SXT Chief Observer: Serge Savy SXT Systems and Data Engineer: L. Shing