Report from ISAS 3 October - 9 October, 1994 James R. Lemen David Alexander SUMMARY During the 3-9 October week SXT continued to participate in the "Chromospheric Ejections and Coronal Loops" campaign organized by Brigitte Schmieder. This campaign has now ended. SXT operations went well. Planning and testing of sequences was conducted for the Coronal Synoptic Campaign. Even though the solar activity is low, many interesting features can be easily seen in the SXT images. Some additional excitement in the form of a couple of major earthquakes complemented the usual activity here at ISAS. The first earthquake measured 8.2 on the Richter scale with an aftershock the following day of strength 7.3. These 'quakes occurred quite far out in the Pacific and most of the damage was confined to the island of Hokkaido and the northern part of Honshu. We were shaken but not stirred. OPERATIONS This week's operation went very well. We participated in a campaign which typically meant many SXT table loads and additional effort by the SXT Chief Observer. Hirohisa Hara was one of the KSC Tohbans, and this was a big help for the Chief Observer. Hara san transfered some SXT tables from ISAS to KSC to eliminate the need for the Chief Observer to come to ISAS in the middle of some nights. Some terminator offpoints were planned, but the terminator program has taken a lower priority to the recent spate of campaigns. Some off-point terminators are still needed to complete the set required to analyze the SPARTAN datasets. We tested a series of spacecraft off-pointings for the Coronal Synoptic Campaign. op_first_guess was modified to allow a series of commands to be easily inserted in the OP. This enables us to plan off-pointings fairly easily. For the Campaign we are taking long exposures at 4 arcmin east, west, and south pointings relative to the nominal pointing. All the exposures are taken during one orbit, so as to minimize the impact on the long-term movie. A lot of work was done by Freeland and Alexander on improving the First_light display. Many suggestions were made for its improvement. It now provides a very useful and informative tool for planning SXT observations and for monitoring the status of the Sun. SOLAR ACTIVITY Solar activity was low this week despite there being seven separate active regions on the disk during the time covered by this report. There were 8 C-class events registered by the GOES satellites, with C7.3 being the most intense. PERSONNEL Marilyn Bruner has returned to California. Jean-Pierre Wuelser returned to Hawaii on 3 Oct 94. Hugh Hudson and James Lemen arrived at ISAS at the end of September. They will both spend a week in Hawaii at the CDAW beginning 17 October. David Alexander arrived on 3 October and has taken over as the Chief Observer. Sam Freeland made good progress in getting the archive reformatting caught up (there is only a two-week backlog now). He has now returned to California. Joe Khan (MSSL) has left after making a five-week visit. SCIENCE There was a flurry of activity this week as Alphonse Sterling busily prepared his paper for the Astronomical Society of Japan meeting, Joe Khan, Louise Harra, Jim Lemen, Hugh Hudson and Alphonse tried to come to grips with some interesting over-the-limb flares, and David Alexander tried to complete his manuscripts for the SoHO Workshop held in Colorado last week. Khan et al. are working on the study of homologous flares as they cross the limb using HXT, SXT and BCS data. Alexander, together with Greg Slater, Hugh Hudson, Alan McAllister and Karen Harvey have been studying the eruptive event of April 14 1994. Mark Weber, Loren Acton and Alexander (all MSU) are working on measuring the rotation of the solar corona using a Fourier analysis technique on the mission long SXT data. Hori-san (a student at Sendai) has developed a 1-D numerical simulation of conduction and evaporation in a flaring loop. She has calculated the temperature, pressure, density, emission measure, and velocity and used these to calculated the expected intensities in the different SXT filters. The ISAS Yohkoh seminar was held on Thursday with two talks: one by Dr. M. Ding of Nanking University in China and the other by Prof. Y. Uchida. Dr. Ding talked about the numerical modelling of white light flares at Nanking. Their results are quite surprising and interesting. From the results of their simulation they conclude that most of the heat source is low and suggest that reconnection in the photosphere is one possibility for this. Prof. Uchida discussed simple loop flares, concentrating on 17-Feb-1992. There was quite an animated discussion which effectively prevented Uchida-san from discussing arcade type flares. Uchida-san (along with Joe Khan) has studied the BATSE, HXT and SXT data for this event and argues that the observed behaviour of the hard X-ray emission, together with the detailed timing of the observed footpoint/coronal emission suggest a more complicated geometry than a simple bipole in these events. He also raised some difficulties with both the electron-beam driven and conduction-driven evaporation models of solar flares commonly discussed.