Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for May 1997) OVERVIEW The YOHKOH Mission is a program of the Japanese Institute of Space and Astronautical Science (ISAS) with collaboration by the U. S. National Aeronautics and Space Administration and the U. K. Science and Engineering Research Council. The YOHKOH satellite was launched on 30 August 1991 from Kagoshima Space Center (KSC) in Japan. The purpose of this mission is to study high energy phenomena in solar flares and the Sun's corona. Under an international cooperative agreement, Lockheed, under NASA contract, is providing a scientific investigation using the Soft X-ray Telescope (SXT), one of the primary experiments of the mission. The SXT was developed at the Lockheed Palo Alto Research Laboratory in cooperation with the National Astronomical Observatory of Japan, and the Institute for Astronomy of the University of Tokyo. MAJOR PROGRAMMATIC ACTIVITIES IN THE MONTH Efforts to prepare for the senior review presentation continued. Data access for all interested users remains an important item on our programmatic priority list. The instrument continues to provide good data and we are looking forward to operations through solar maximum. << Solar Activity >> Solar activity continued its gradual rise this month with a number of new cycle regions crossing the disk. On the disk this month were AR's 8037 through 8051. The GOES background was at the A level at the beginning of May but increased to B level as several moderately active AR's crossed the disk at the end of the month. There were several periods of flare activity. The most dramatic was around 22 May with several C class flares and one M class flare. Unfortunately, the M flare occurred during Yohkoh night. << Campaigns >> A major series of joint observations took place at the end of May. These were coordinated from the SOHO center in Paris (MEDOC) by Brigitte Schmieder. SXT also observed, but with no special setup, during the EUV rocket flight of Woods and Hassler. We continue trying to follow SOHO planning, especially CDS targets. For Yohkoh operations, there is a text file accessible on the Web at Page 2 http://www.space.lockheed.com/SXT/html2/First_Light.html which also lists the current SXT Chief Observer, or the Unix command: # finger campaign@isass0.solar.isas.ac.jp | more The SOHO target planning is available from: http://sohowww.nascom.nasa.gov/operations/targets/today << Science >> Acton completed a paper on the accuracy of temperature and spectral irradiance values derived from SXT thin-filter ratios. He did this by modeling the SXT response to 25 different DEM models from the literature for all kinds of solar features. The SXT results are excellent for EM-weighted mean temperature and spectral irradiance within the SXT bandpass when the SXT-derived temperatures are used to derive the irradiance. Acton also analyzed the results from the first open/open UV flood of the SXT CCD. The effects were minor but seemed to be beneficial. Alexander and Metcalf submitted the final version of their paper on the Masuda event emphasizing the spectral properties of the flare in hard X-rays. The paper has now been accepted to ApJ. The conclusions are that a) a compact loop-top hard X-ray source exists with an impulsive temporal profile spanning the peak of the flare, b) the loop-top source is non-thermal in nature at the peak of the flare, c) there is a distinct dearth of HXT LO channel emission, relative to the higher energy channels, from the loop-top region indicating either a very hard spectrum or the presence of a low energy cut-off in the energetic electron spectrum, d) the footpoint and loop-top emission during the impulsive phase of the flare are produced by two distinct particle populations, e) following the main phase of this flare, the loop-top is clearly thermal in nature with a peak temperature of about 40 MK which decreases with time as the event proceeds, f) the disparity between the present Pixon results and previous MEM results is primarily due to the intrinsically better photometry achieved by the Pixon method and the avoidance of suppression effects in the present analysis. Nitta identified about 50 events from Pike's list of Fe XXVI flares that have good SXT coverage. Various morphologies found in SXT images suggests that there are two types of superhot emission. In the majority of flares, the superhot plasma is probably the high-temperature end of evaporation, but there are some events in which it is from a diffuse structure that is separate from the main flare loop. Nitta also studied about two dozen flares which are sometimes classified as 'simple loop' flares. They are often accompanied by obvious blueshifts in BCS Ca XIX line profiles. Interestingly, these events generally show clear secondary (and diffuse) structure, i.e., they should not be 'simple loop' flares. It is possible that the dynamic behavior as revealed by BCS observations actually results from such a diffuse area. Pevtsov and Sandborgh used Yohkoh data to identify coronal structures and their relationship to areas of large-scale helicity. Sandborgh will present preliminary results of this study at the SPD meeting in Bozeman. Page 3 << Public Use of SXT Images >> We are continuing to make Yohkoh/SXT images available for a variety of uses. Efforts continue to make selected images available on the Lockheed SXT WWW homepage (http://www.space.lockheed.com/SXT/). We receive requests for the Yohkoh posters (#2 and #3) by way of the form on the SXT homepage. Currently we receive requests via our homepage at the rate of 2 or 3 per day. The WEB access statistics in May were 42021 accesses and 1216 Mbytes transferred. << Yohkoh Operations and Health >> Yohkoh and the SXT continue to function very well. There has been no further increase in stray light since 25 August 1996. The quiet patrol image has been changed to Al/Mg (DPE=17) to try to improve the performance of the active region selection algorithm for times when the Sun is very quiet. SXT experienced a normal level of Single Event Upset (SEU) events during the month: SXT bit map error 1-May-97 Pass ?: 970501-0308 recovered in the same pass SXT bit map error 24-May-97 Pass 2: 970524-1030 recovered in the same pass Page 4 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Feb-95 279369 120700 1195988 336882 1532870 595539 27.65 Mar-95 5915 2082 21485 3448 24933 8485 25.39 Apr-95 6244 2266 22946 4493 27439 9688 26.09 May-95 7084 2884 29617 2647 32264 15331 32.21 Jun-95 7210 3087 25251 307 25558 12045 32.03 Jul-95 6418 4145 21180 1639 22819 15109 39.84 Aug-95 7683 2597 26115 2181 28296 10537 27.13 Sep-95 6546 2853 22006 1753 23759 10433 30.51 Oct-95 6937 3502 22177 3853 26030 13044 33.38 Nov-95 5745 2944 21252 517 21769 12119 35.76 Dec-95 6163 2615 24059 901 24960 11652 31.83 Jan-96 6474 2530 27015 1708 28723 14151 33.01 Feb-96 6200 2581 21380 890 22270 10773 32.60 Mar-96 6908 2869 25437 1460 26897 12274 31.33 Apr-96 7172 2124 45445 671 46116 18848 29.01 May-96 6925 2426 30272 1089 31361 12367 28.28 Jun-96 7522 2716 31984 1536 33520 14489 30.18 Jul-96 5954 1995 29886 4769 34655 12427 26.39 Aug-96 7214 3010 21187 1607 22794 9887 30.25 Sep-96 6904 2618 29906 303 30209 12663 29.54 Oct-96 7405 2853 16463 1842 18305 8034 30.50 Nov-96 7001 2296 24292 5395 29687 9340 23.93 Dec-96 7144 2643 25331 2087 27418 10412 27.52 Jan-97 7186 2747 21126 1257 22383 9915 30.70 Feb-97 6016 2034 22097 1072 23169 8961 27.89 Mar-97 7152 1300 26991 1209 28200 6394 18.48 Apr-97 6018 1055 23639 3890 27529 5349 16.27 May-97 5942 1085 22733 1798 24531 5314 17.81 Jun-97 0 0 0 0 0 0 0.00 Total 460451 188557 1877260 391204 2268464 895580 28.30 Number of Full Frame Images Received: 460451 Number of Observing Region Images Received: 2268464 Total: 2728915 Approximate Number of Shutter Moves/CCD Readouts: 4783149 NOTES: * The loss of images is mainly due to BDR overwrites, but there are also occasional DSN dumps which are lost. * It is common to have observing regions which contain more than 64 lines, which requires multiple exposures to make a single observing region image. This is why the number of shutter moves is larger than the number of images received plus those lost. Page 5 << Engineering Summary Table >> Month Avg Dark Level # of Dark Spikes CCD Warmings Front Optical (DN) (e/sec) Over 48 Over 64 High / # Support Trans Temp /Days Temp (%) Mar-95 48.35 668.9 85527 5271 19.4 N/A Apr-95 48.72 682.8 93904 5627 19.1 N/A May-95 48.73 683.4 94000 5820 18.8 N/A Jun-95 49.08 696.3 100780 6281 19.6 N/A Jul-95 49.34 706.2 106408 6628 18.1 N/A Aug-95 49.72 720.4 114414 7101 19.5 N/A Sep-95 49.79 723.1 115165 7222 19.6 N/A Oct-95 50.29 741.9 126452 7911 20.2 N/A Nov-95 50.11 735.1 122163 7814 25.2 / 2 20.3 N/A Dec-95 50.19 737.9 123705 7927 22.6 N/A Jan-96 50.81 761.3 136197 8888 21.5 N/A Feb-96 50.67 755.8 133263 8705 22.5 / 2 21.5 N/A Mar-96 50.85 762.9 136982 8973 20.3 N/A Apr-96 51.14 773.6 142250 9500 19.9 N/A May-96 51.16 774.4 140697 10018 19.1 N/A Jun-96 51.56 789.2 147705 10634 20.7 N/A Jul-96 57.45 1010.2 146293 12228 19.8 N/A Aug-96 52.58 827.5 165676 12393 19.6 N/A Sep-96 52.47 823.3 162784 12350 20.0 N/A Oct-96 52.21 813.8 157689 12047 22.5 / 2 21.3 N/A Nov-96 52.45 822.9 161683 12534 21.9 N/A Dec-96 53.08 846.2 171224 13860 22.9 N/A Jan-97 52.35 818.9 164785 11354 23.8 / 7 23.3 N/A Feb-97 51.95 803.9 159426 10346 21.1 N/A Mar-97 55.99 955.6 158428 12190 21.2 N/A Apr-97 53.14 848.4 176207 13265 20.8 N/A May-97 52.97 842.1 172100 13147 20.0 N/A Jun-97 N/A N/A N/A N/A 0.0 N/A NOTES: * The dark current calculations are using full half resolution 2.668 sec images not taken in during the SAA. The dark current rate assumes a "fat zero" of 30.5 DN and a gain of 100 e/DN. * The entrance filter failure of 13-Nov-92 eliminated the capability of taking optical images, so the optical transmission is not available after Nov-92. It also caused an increase in the dark current signal, however some of the increase shown here is an increase in the readout noise and is not a function of exposure duration. Page 6 << Personnel Travel >> SXT Foreign Travel between 1-MAY-97 and 31-MAY-97 ALEXANDER 1-MAY-97 * 1-MAY-97 1 (total of 1 days) HUDSON 1-MAY-97 * 18-MAY-97 18 (total of 18 days) SAVY 7-MAY-97 31-MAY-97 * 25 (total of 25 days) SLATER 27-MAY-97 31-MAY-97 * 5 (total of 5 days) WEBER 22-MAY-97 31-MAY-97 * 10 (total of 10 days) ---------------------------------------------------------------- Grand Total of 59 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-MAY-97 SXT Foreign Travel between 1-JUN-97 and 30-JUN-97 HUDSON 2-JUN-97 23-JUN-97 22 (total of 22 days) SAVY 1-JUN-97 * 25-JUN-97 25 (total of 25 days) SLATER 1-JUN-97 * 27-JUN-97 27 (total of 27 days) WEBER 1-JUN-97 * 24-JUN-97 24 (total of 24 days) ---------------------------------------------------------------- Grand Total of 98 days for 4 people NOTE: The "*" signifies travel that actually ends after 30-JUN-97 Respectfully submitted, James R. Lemen Frank M. Friedlaender Page 7 ================================================================= Montana State Univ Activity Report for April 1997-May 1997 ================================================================= (R. C. Canfield) INTRODUCTION The MSU group carried out operations, data analysis, graduate and undergraduate research, and public outreach, and organized and participated in meetings. Congratulations are in order for David Weston, who received a job offer that was too good to refuse. At the end of May he wound up his work on SXT with Loren Acton and set off for the Boeing Company in Seattle, where he will work in their Physics Technology Group. YOHKOH AND SXT OPERATIONS Mark Weber served as SXT Chief observer at ISAS for one week in May. Dick Canfield served as Yohkoh Duty Scientist for Mees Solar Observatory for one week in April and one week in May. Loren Acton served as SXT Chief observer at ISAS for one week in April. Loren Acton analyzed the results from the first open/open UV flood of the SXT CCD. The effects were minor but seemed to be beneficial. His results are on show_pix/calibration. A longer flood of this type has been completed, but the results have not yet been fully analyzed. RESEARCH AND EDUCATION Brian Handy and Michael Foley successfully installed a Phillips CD-ROM writer, replacing the HP 4020i that failed more often than it worked. Under Alex Pevtsov's supervision, Jen Greenfield got all the Mees Stokes Polarimeter data written from tape to CD, and distributed to Lockheed-Martin and Hawaii. Michael Foley got the CD jukebox working. Mark Weber, with lots of help from Brian Handy and Greg Slater, was able to get the high-density Exabyte tape drive in operation, to confirm the ability to read the new high-density SXT tapes. Mark Weber contributed a revised version of . This version displays all data through the most recent filter degeneration. Mark Weber, using the new CD jukebox, made substantial progress with data processing on his thesis work on differential rotation in coronal holes. Sean Sandborgh finished his interactive IDL program, and is now using it on SXT data to identify large-scale coronal flux systems, which he will subsequently relate to large-scale helicity areas. Page 8 Papers Accepted: "X-ray network flares of the quiet sun", Krucker, S., Benz, A.O., Bastian, T.S. and Acton, L.W., accepted by Astrophysical Journal (1997). "Nitric Oxide Abundance in the Mesosphere/Lower Thermosphere Region: Roles of Solar Soft X Rays, Suprathermal N(4S) Atoms, and Vertical Transport", P. K. Swaminathan, D. F. Strobel, D. G. Kupperman, C. Krishna Kumar, L. Acton, R. DeMajistre, J. -H. Yee, L. Paxton, D. E. Anderson and D. J. Strickland, accepted by JGR(Space Physics), (1997). "Periodic Modulation ox X-Ray Intensity from Coronal Loops: Heating by Coronal Absorption?" D. McKenzie (MSU), D. Mullan (Bartol Research Institute), accepted by Solar Physics. "Search for Periodicity in Image Sequences from Yohkoh Soft X-Ray Telescope," D. McKenzie, accepted by PASP, to appear as one-page dissertation summary, June 1997. Papers Published: "On the Subphotospheric Origin of Coronal Electric Currents" A.A. Pevtsov, R.C. Canfield, and A.N. McClymont, ApJ, 481, 973, (1997). "Fine structure of the X-ray and radio emissions of the quiet solar corona", Benz, A.O., Krucker, S., Acton, L.W. and Bastian, T.S., Astron. Astrophys., 320, 993-1000, (1997). Abstracts Submitted "Conversion of YOHKOH X-ray Observations to Spectral Radiance", L. Acton, D. Weston), M. Bruner, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. "Using the WWW to Make Yohkoh SXT Images Available to the Public: The Yohkoh Public Outreach Project" M. Larson, D. McKenzie, T. Slater, L. Acton, D. Alexander, S. Freeland, J. Lemen, T. Metcalf, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. "Co-Temporal Evolution of Magnetic Sources of Coronal and Chromospheric/Photospheric Irradiance Variability" J.L. Lean, J.T. Mariska (Naval Research Laboratory), L.W. Acton, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. "On the Origin of Helicity in Active Region Magnetic Fields" R.C. Canfield, A.A. Pevtsov, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. Page 9 "NOAA 7926: A Kinked, Submerging Omega-loop?" A.A. Pevtsov, R.C. Canfield, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. "Coronal Structure as a Diagnostic of the Solar Dynamo" S. Sandborgh, R.C. Canfield, A.A. Pevtsov, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. Search for Periodicity in Image Sequences from Yohkoh Soft X-Ray Telescope", D.E. McKenzie, Annual Meeting of the Solar Physics Division of the American Astronomical Society, Bozeman, June 27 - July 1. "Implications of Magnetic Helicity Observations", R.C. Canfield, Solar-B Science and Technical Meeting, ISAS, May 6-8 (invited). OUTREACH and SERVICE: The group set up displays and conducted briefings on solar physics research at the formal dedication of the new Engineering and Physical Sciences building we now occupy. Hundreds of posters and other outreach materials were distributed to the general public in attendance. Acton, Canfield, and Weston worked on SPD meeting preparations. Canfield organized the scientific sessions and sorted the abstracts. Acton and Weston worked on local arrangements. Loren Acton and Dick Canfield participated in the Solar-B meeting in Japan, contributing discussions of the implications of various Yohkoh SXT results for the Solar-B mission. Canfield and Pevtsov submitted a proposal for an AGU Chapman Conference on magnetic helicity in laboratory and space plasmas. McKenzie worked on the Solar Tour and YPOP Program Room page, distributed SXT videos (tens) to teachers and posters (hundreds) to the general public. Page 10 ======================================================================= Univ of Calif, Berkeley Activity Report for April 1997-May 1997 ======================================================================= (J. McTiernan) The Yohkoh work here at UCB in the past two months has concentrated on the calculation of Differential Emission Measures (DEM) for soft X-ray flares, using the SXT and BCS detectors. Results from this work will be presented at the SPD meeting in Montana this month. A total of 93 flares have been analyzed; the DEM models are obtained by varying the amount of Emission Measure in preset temperature bins (in the range of 3 to 31 MK), and minimizing chi-squared. From our preliminary results, we see that the flare plasma is not isothermal, and it is difficult to describe the DEM using a smoothly decreasing function. Early in most flares, up to the peak times for the BCS Fe XXV and Ca XIX, channels, it appears that there are two components, which merge during the flare decay phase. The low-temperature emission measure is always larger than the high-temperature emission measure. (Two-component temperature models have also been tried with similar results.) This is not what we expect from flare-loop models, in which the DEM increases from low temperatures up to a cusp at the loop-top temperature, and this is true even for cases for which only one flare loop seems to be visible. Page 11 ============================================================= Univ of Hawaii Activity Report for April 1997-May 1997 ============================================================= (B. LaBonte) Our activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition (including designated Yohkoh campaigns) at Mees, collaborative analysis of Yohkoh/Mees data, and preparation of manuscripts. Operational support for SXT was provided by Nitta at Mees and LaBonte in Manoa. Our colleagues Jiao and Mickey at Manoa, Canfield at Montana State University, Wuelser and Metcalf at Lockheed, and Hudson at Solar Physics Research Corporation aided in advice and oversight of Mees operations. Observations of the new cycle active regions have dominated this interval. Mickey traveled to Mees for maintenance of the IVM and alignment and testing of the Stokes Polarimeter. LaBonte continued work on the isolated active region AR 7978 / 7981. He completed the work on the reduction procedures for the IVM magnetic data to remove the effects of differential seeing and image motion to permit accurate comparison with the SXT images of the flaring structures. LaBonte has completed a paper, with H.-K. Chang and D.-Y. Chou of Tsing Hua University, Taiwan, demonstrating a new method for observation of magnetic and other structures below the solar surface. Analogous to our viewing of objects via ambient light, structures inside the Sun can be observed with ambient sound. The ability to follow magnetic structure below the surface is an important counterpart of the observation of structure above the surface and can help decide issues of flux emergence and connectivity. The Solar section of the new IfA graduate student recruiting brochure features an SXT image and discussion of the coordinated spacecraft/ground observatory/theory science that is the SXT investigation. PUBLICATIONS AND PRESENTATIONS DURING APRIL AND MAY Papers submitted: "Ambient Acoustic Imaging in Helioseismology". by H.-K. Chang, D.-Y. Chou, B. J. LaBonte, and the TON Team, Nature. Page 12 ============================================================ Stanford Univ Activity Report for April 1997-May 1997 ============================================================ (M. Wheatland) It is well known that magnetic flux is lost from the Sun due to the cancelation of flux fragments of opposite polarity. Coronal X-ray bright points are associated with flux cancelation and may be the result of local coronal heating produced by cancelation events. Clare Parnell is currently working on combining a theoretical model for energy release due to flux cancelation with solar flux observations. Using records of the numbers and sizes of cancelling magnetic features observed on the Sun each day and extrapolating to smaller scales than those observed, an estimate of the total energy released in the corona (due to cancelations) is produced. This investigation will determine whether cancelation events play a significant role in the energetics of coronal quiet regions. Mike Wheatland and George Roumeliotis have continued to work on a new method for reconstructing force-free fields from boundary data. The goal is to develop a code that reliably reconstructs fields from active region vector magnetogram data, and hence allows investigation of the role of magnetic field in the physics of solar flares and coronal heating. Our method is based on the procedure of evolving a trial field in such a way as to minimize the divergence and the self force of the field everywhere in the region of interest. Recent work has focused on the boundary conditions needed for the method to succeed - to this end we have applied the method to a number of simple, analytic fields. In the near future the code will be applied to vector magnetogram data generously provided by Tom Metcalf at Lockheed. The standard view of the solar cycle is that the observed field is cyclically regenerated via a dynamo mechanism. Shortcomings of the dynamo model have lead Peter Sturrock to re-examine the possibility that the observed field is produced instead from a fossil field in the radiative zone. A rotating cell of fossil field is assumed to interact with the base of the convection zone to produce the seed field for the a solar cycle. The dynamics of a rotating cell in the radiative zone are being investigated by a new summer student, Sang Hyun Kim. Guenther Walther (of the Statistics department at Stanford) has been working with Peter Sturrock and Mike Wheatland on an analysis of the Homestake solar neutrino data. In a follow-up to that project, Guenther has investigated the much publicized apparent anti-correlation between the neutrino flux and the sunspot cycle. Guenther has demonstrated that the significance of the correlation arises as a result of misuse of popular tests for correlation. Non-parametric measures of association are built on quite strong assumptions that are generally violated in a time series context. Guenther has applied a valid statistical test and finds no significant correlation between solar neutrinos and the sunspot cycle. He has prepared a paper on these important findings. Page 13 =========================================================================== Solar Physics Research Corp. Activity Report for April 1997-May 1997 =========================================================================== (Karen L. Harvey and Hugh S. Hudson) KAREN L. HARVEY: Activities for Harvey in the last two months include: (1) Continuation of analysis of XBPs observations obtained though a collaboration of several ground-based observatories and the Yohkoh SXT instrument, and SOHO in early April 1996, concentrating on 12 April, which had the most complete coverage of a wide range of observations. Completed with Matt Penn the derivation of line depth, equivalent width, velocity from fitting of the observed He I 10830 line profile. Comparisons with a series of EIT images made in He II 304, Fe IX/X 195, Fe XII 171 lines. Based on a question from Dan Moses, re-examined the earlier result that all EIT Fe XII XBPs could be detected in the SXT images. This correspondence was verified is this second analysis. It might be that the higher contrast between the background and the Fe IX/X and Fe XII XBPs is contributing to the misinterpretation that more XBPs can be seen in the EIT data. The results from the comparison of the many data sets acquired on 12 April 1996 -- the He I 10830 line profiles, MDI magnetograms, EIT images, CDS and Sumer data -- will be presented as a poster paper and the 1997 SPD meeting in Bozeman. (2) Continued development and refinement IDL program to draw the irregular coronal hole boundaries on the NSO/KP He I 10830 spectroheliograms and its adaptation for the NSO/KP Carrington rotation He I 10830 maps. A version of the program for the full-disk NSO data is now being used to prepare the preliminary coronal hole maps on a daily basis; these maps as gif images are located on the NSO archive (argo.tuc.noao.edu: directory kpvt/daily/lowres). (3) Preparation of NSO/KP full-disk magnetograms and He I 10830 spectromagnetograms for SXT investigators for studies of the magnetic field and He I 10830 structures associated with X-ray structures. Planned Activities in Next Two Months Activities for June and July are continue the analysis of the data acquired during the April 1996 observing campaign in preparation for the SPD meeting. Analysis will also continue on the data from other XBPs campaigns and the writing of the first in a series of planned papers on X-Ray Bright Points. Plans are to continue the analysis of the history of the activity complex 7958/7978, the evolution of the fields and connections, and the producing drafts of the next two papers planned on this work. The coronal hole boundary routines and their implementation will be finalized. Page 14 HUGH S. HUDSON: Activities in April and May H. Hudson visited Sydney to work with D. Melrose for about a week. The effort was concentrated on understanding the Masuda event, but it is not clear that much progress was made except to find that there are already 21 papers on this subject! He also participated in the AGU meeting at the end of May and at that time spent a few days at GSFC admiring Moreton waves in the EIT data. He also served as SSOC tohban for one week and as SXT chief observer on other occasions. The first of a projected series of seminar "tutorials" on CMEs was on May 14. The sequence of remarkable CME events continues. Sterling and Hudson submitted a paper on the Apr. 7 "halo" CME event, which appeared in the SXT data as a neat pair of transient coronal holes. This was also a Moreton wave event (see below), although not observed as such by SXT unfortunately. Plans for June and July Moreton waves are the most exciting thing in the SOHO/Yohkoh data analysis domain right now, and Hudson is trying to catch up with the EIT lead in this area. It appears that SXT coverage is USUALLY quite poor for Moreton waves, because of the occurrence of flare mode and because of the tendency for flares to happen during orbit night. However now that EIT has shown the way (thanks to improved cadence) it will be extremely desirable to go back and search in the Yohkoh archives for favorably observed events. Other work is concentrated on CMEs, especially the October 5 "spine" event. S. Watari is presenting some material on this at Oslo, and Hudson is presenting more information at the SPD meeting in Bozeman. We hope to complete a paper analyzing the spine and flux rope behavior after these meetings. Papers published Harra-Murnion, L. K., Culhane, J. L., Hudson, H. S., Fujiwara, T., Kato, T., and Sterling, A. C., ``Isolating the Footpoint Characteristics of a Solar Flare Loop'', Solar Phys., 171, 103-122, 1997. Farnik, F., Hudson, H., and Watanabe, T., ``Yohkoh observations of flares with flat hard X-ray spectra'', Astron. Astrophys., 320, 620-630, 1997. Sterling, A. C., Hudson, H. S., and Watanabe, T., ``Electron temperatures of the corona above a solar active region determined from S xv spectra'', Ap. J., 479, 149, 1997. Sterling, A. C., Hudson, H. S., Lemen, J. R., and Zarro, D. M., ``Temporal Variations of Solar Flare Spectral Properties: Page 15 Hard X-Ray Fluxes and Fe xxv, Ca xix, and Wide-Band Soft X-Ray Fluxes, Temperatures, and Emission Measures'', Ap. J., 110, 115., 1997. Papers submitted Sterling, A. C., and Hudson, H. S., ``Soft X-ray Observations of a 'Halo' CME'', submitted to Ap. J. (May, 1997). Page 16 ------------------------------------------------------------------------------- NASA REPORT DOCUMENTATION PAGE (IN LIEU OF NASA FORM 1626) --------------------|--------------------------|------------------------------- 1. REPORT NO. | 2. GOVERNMENT | 3. RECIPIENT'S DR-01 | ACCESSION NO. | CATALOG NO. --------------------|--------------------------|------------------------------- 4. TITLE AND SUBTITLE | 5. REPORT DATE Monthly progress report - for the month of | 10 June 1997 May 1997 |------------------------------- | 6. PERFORMING ORG | CODE: O/H1-12 -----------------------------------------------|------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- J. R. Lemen | TION REPORT NO: F. M. Friedlaender | |------------------------------- -----------------------------------------------|10. WORK UNIT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS | Lockheed Palo Alto Research Labs B/252 |------------------------------- Solar & Astrophysics Laboratory O/H1-12 |11. CONTRACT OR GRANT NO. 3251 Hanover Street, Palo Alto Ca. 94304 | NAS8 - 40801 -----------------------------------------------|------------------------------- 12. SPONSORING AGENCY NAME AND ADDRESS |13. TYPE OF REPORT AND Marshall Space Flight Center (Explorer Program)| PERIOD COVERED Huntsville Alabama 35812 | Progress report for the month | of May 1997 |------------------------------- |14. SPONSORING AGENCY | CODE MSFC / AP32 -----------------------------------------------|------------------------------- 15. SUPPLEMENTARY NOTES ------------------------------------------------------------------------------- 16. ABSTRACT The SOLAR-A Mission is a program of the Institute of Space and Astronautical Science (ISAS), the Japanese agency for scientific space activity. The SOLAR-A satellite was launched on August 30, 1991, to study high energy phenomena in solar flares. As an international cooperative agreement, Lockheed, under NASA contract, is providing a scientific investigation and has prepared the Soft X-ray Telescope (SXT), one of the two primary experiments of the mission. --------------------------------------|---------------------------------------- 17. KEY WORDS (SUGGESTED BY | 18. DISTRIBUTION STATEMENT AUTHOR(S)) Solar-A, X-ray, CCD, | Space Science, Solar Physics ------------------------|-------------|----------|-----------------|----------- 19. SECURITY CLASSIF. | 20. SECURITY CLASSIF. | 21. NO OF PAGES |22. PRICE (OF THIS REPORT) | (OF THIS PAGE) | | None | None | 16 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office