Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for March 1996) 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 The SXT Extended Mission contract has finally been executed for another year of operations. The contract goes through January 26, 1997. All of the Co-I sub-contracts are being implemented in order to maintain a continuity of effort. John Owens of NASA MSFC will be at the Solar and Astrophysics Laboratory on April 16 for other business, and we will have an opportunity to brief him on a variety of SXT related activities. The Lockheed group is looking forward to expanding slightly with the addition of Tom Metcalf, who will be joining us in June. He came to Palo Alto and visited the laboratory for one day in preparation for his move in the summer. << Solar Activity >> During the month the Sun has been at a low level of activity. Many brightpoints can be regularly observed over most of the disk. Three active regions were observed: 7952, 7953 and 7954. AR7952 produced many microflares but only one exceeded C level and this flare did not trigger the Yohkoh flare-mode. AR7953 produced several B class events on 22 March 1996 and a C-class flare on 23 March, at 19:30 UT. << Campaigns >> SoHO conducted its first observing campaign, JOP-039 on polar plumes, 7-8 Mar. To support this, SXT PFI's were placed at the S pole to study the high-temperature components of any bright points. Indeed, bright Page 2 points occurred, but at the time of writing the SXT data reduction has not been completed. Please see the SoHO Web material for further details. At the end of the month Yohkoh was preparing to collaborate with Karen Harvey and SOHO on a Bright Point Campaign which is taking place in early April. << Science >> A major highlight of the month was the Yohkoh Conference on Observations of Magnetic Reconnection in the Solar Atmosphere, which was held in Bath, England on 20-22 March. The meeting was well attended by about 85 scientists from Japan, the US and Europe. Bob Bentley (MSSL) was the chairman of the local organizing committee. Nariaki Nitta spent a month in Japan and assisted Serge Savy and Hugh Hudson in Chief Observer tasks, as well as working on several flares using SXT, BCS, and HXT data. He visited Meudon and worked with Pierre Lantos on a transient associated filament eruption and with Brigitte Schmieder and Lidia van Driel-Gesztelyi on the AR 7260 paper. After presenting results at the Bath meeting he worked with Louise Harra- Murnion on BCS Fe XXVI observations. Jean-Pierre Wuelser continues to take his regular turn as Mees chief observer. He is working on the Mees data obtained during the first SOHO mini campaign of the south pole. Mees obtained a time series of 40 vector magnetograms during a seven-hour interval. An abstract has been prepared for the SPD meeting this summer. James Lemen continues to work on the 21-Feb-92 coronal dimining event with Hugh Hudson and David Webb. Related to this topic, he helped Science magazine editor Kim Peterson, who wrote an article entitled "Dim Corona Foreshadows Storms" that appeared in the 1 March 1996 (Vol 271) edition of Science. Lemen also spent a week working with Dick Fisher and Lika Guhathakurta (GSFC) on the Spartan white light coronagraph data taken during the 3rd Spartan campaign in September 1995. Sam Freeland wrote software to reprocess the Spartan data to make it available for easier scientific analysis and Gary Linford wrote the most important data sets onto a CD-ROM that Fisher and Guhathakurta took back to Goddard. Several science projects involving the Yohkoh and Spartan data sets have been identified. This month we include the University Co-I reports which include a wide range of scientific and outreach activities. << Publications>> Karen Harvey maintains a list of Yohkoh publications. Her list was last updated on Feb 6, 1996. We intend to publish this list next month. A summary of Yohkoh publications from the list folloows: Page 3 Number of papers by Year: 1987 1 1988 1 1989 4 1990 3 1991 19 1992 37 1993 14 1994 57 1995 74 1996 17* *=Total through 6-Feb-1996 -------- Total: 227 << 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). Links to the SXT home page have been made from various places around the world. The typical statistics for the SXT homepage access are running at about 16,000 file accesses per month. The new Web form page continues to receive a couple of dozen requests per month for the posters. Last month the Yohkoh Public Outreach Project (YPOP) homepage went "online" (see http://www.space.lockheed.com/YPOP ). This page is being developed jointly with MSU to ultimately make Yohkoh/SXT movies available over the Internet and to provide public and educational outreach. We expect much more progress to be made on this page in the coming months. Finally, we are making preparations to provide Yohkoh movies to Paul Dusenbery, Space Science Institute, Boulder, who is is collaborating with meteorologist Bob Ryan at KNBC in Washington, DC to prepare a space weather forecast. The facilities of channel 4 will be made available for this purpose. << Yohkoh Operations and Health >> During March there was a planned 3-day shutdown of the ISAS operations mainframe computer. During this time the spacecraft and SXT operations were reduced to a minimum. In February, three of the mainframe computers that are used to support Yohkoh operations were replaced with two new machines. It appears that all the software issues involving the switch to the new machines have been successfully resolved. Because of the configuration of the new machines, the access of these machines is somewhat more limited, since only a few designated workstations can make telnet and ftp connections. Fortunately, the Yohkoh software environment is fairly flexible so that various tasks can be moved from workstation to workstation quite easily. Page 4 Yohkoh and the SXT continue to function very well. There has been no further increase in the SXT stray light since 16-Aug-1995. 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 bitmap error 11-Mar-96 Pass 3: 960311-0413 recovered in the same pass SXT bitmap error 16-Mar-96 Pass 1; 960316-0309 recovered in the same pass Page 5 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Dec-93 181465 84653 751015 281874 1032889 399959 27.58 Jan-94 6934 2804 28567 10960 39527 13746 25.80 Feb-94 7000 2840 23021 5819 28840 11257 28.07 Mar-94 7736 2627 69273 3733 73006 31464 30.12 Apr-94 6142 2741 22707 3390 26097 12338 32.10 May-94 7070 2679 25260 3040 28300 10862 27.74 Jun-94 7417 2738 36795 1996 38791 15760 28.89 Jul-94 7488 2941 50540 3275 53815 24153 30.98 Aug-94 7370 2337 35067 3993 39060 13485 25.66 Sep-94 7079 2552 25131 2855 27986 10677 27.62 Oct-94 7244 2497 25868 5884 31752 10319 24.53 Nov-94 6569 1941 26243 1956 28199 9293 24.79 Dec-94 6429 2456 26763 2583 29346 11904 28.86 Jan-95 6870 2349 26103 1699 27802 10211 26.86 Feb-95 6556 2545 23635 3825 27460 10111 26.91 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 3528 1293 13341 1084 14425 5940 29.17 Apr-96 0 0 0 0 0 0 0.00 Total 361516 156079 1493812 362303 1856115 744846 28.64 Number of Full Frame Images Received: 361516 Number of Observing Region Images Received: 1856115 Total: 2217631 Approximate Number of Shutter Moves/CCD Readouts: 3895167 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 6 << 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 (%) Jan-94 46.00 580.9 39074 3088 22.5 / 2 20.3 N/A Feb-94 46.03 582.1 40449 3246 19.3 N/A Mar-94 45.92 578.0 39715 3420 18.2 N/A Apr-94 45.97 579.9 41302 3721 25.2 / 3 17.8 N/A May-94 46.25 590.3 45476 3557 18.3 N/A Jun-94 45.83 574.6 39340 3547 17.8 N/A Jul-94 46.76 609.5 53417 3990 18.2 N/A Aug-94 46.98 617.6 57624 4050 25.2 / 3 18.2 N/A Sep-94 47.07 620.9 58580 4028 18.3 N/A Oct-94 47.34 631.3 64974 4346 19.0 N/A Nov-94 47.64 642.4 70877 4703 20.4 N/A Dec-94 47.82 649.1 74246 4917 21.5 N/A Jan-95 48.55 676.7 89758 5457 20.0 N/A Feb-95 48.70 682.1 92457 5781 25.2 / 3 20.5 N/A 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 50.54 751.0 130683 8499 20.3 N/A Apr-96 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 7 << Personnel Travel >> SXT Foreign Travel between 1-MAR-96 and 31-MAR-96 HUDSON 4-MAR-96 16-MAR-96 13 30-MAR-96 31-MAR-96 * 2 (total of 15 days) NITTA 1-MAR-96 * 14-MAR-96 14 (total of 14 days) SAVY 1-MAR-96 * 17-MAR-96 17 25-MAR-96 31-MAR-96 * 7 (total of 24 days) ---------------------------------------------------------------- Grand Total of 53 days for 3 people NOTE: The "*" signifies travel that actually ends after 31-MAR-96 SXT Foreign Travel between 1-APR-96 and 30-APR-96 HUDSON 1-APR-96 * 30-APR-96 * 30 (total of 30 days) SAVY 1-APR-96 * 30-APR-96 * 30 (total of 30 days) SLATER 1-APR-96 30-APR-96 * 30 (total of 30 days) HARVEY 13-APR-96 27-APR-96 15 (total of 15 days) ---------------------------------------------------------------- Grand Total of 105 days for 4 people NOTE: The "*" signifies travel that actually ends after 30-APR-96 Respectfully submitted, James R. Lemen Frank M. Friedlaender Page 8 ================================================================= Montana State Univ Activity Report for February 1996-March 1996 ================================================================= The Montana State Solar Group has been busy with research and outreach during the past two months. Five papers were accepted for publication and a sixth was submitted. Travel to scientific meetings and for public outreach purposes kept many of us out of town more than we'd like. Plans are in place for increasing the size of the Solar Group over the summer and fall. Richard Canfield, currently at the University of Hawaii, has accepted a position of Research Professor at Montana State University (MSU) which will commence in the summer of 1996. Alexi Pevtsov, presently a post-doc at Hawaii working with Canfield on studies of magnetic helicity will also make the move to MSU with Canfield. Screening of applicants for the new tenure track faculty position in solar astrophysics has been completed. Five outstanding individuals have accepted the invitation to visit the MSU campus in April and May for interviews. This position will be filled in time for the fall semester. Finally, Charles Kankelborg, who is finishing his Ph.D. at Stanford under Prof. A. B. C. Walker, Jr., has accepted a post-doc position on the TRACE program at MSU. We expect Kankelborg to move to Bozeman in July. The Yohkoh Public Outreach Project (YPOP) at MSU is continuing to make headway in its first few months under the leadership of David Alexander, Dave Thomas of the Math Department and with the efforts of graduate student Michelle Larson. In February, Alexander and Larson attended the 2nd Annual Pre-college Education Workshop hosted by the Space Science Institute in Boulder, Colorado. At that meeting they presented a joint poster paper entitled "Yohkoh Public Outreach Project". Further YPOP progress can be noted on the new YPOP homepage (http://solar.physics.montana.edu/YPOP/), and development of the "Structure of the Sun" theme. Local exposure of this worthy project have been achieved through an article in the newsletter of MSU office of Research and Creative Activities, by two local television news stations, and by a series of pieces on a local radio station. Activities of individual members: Loren Acton: After submitting his paper for the 9th Coolstar Workshop, Acton plunged into further study of use of SXT fluxes for solar irradiance inputs to aeronomy investigations. With the help of Dave Weston he has been modeling the ratio of SXT derived fluxes to "actual" fluxes for various differential emission measure models. He has also done multi-thermal Mewe spectrum fits to the "standard" solar spectrum used in aeronomy, the Donnelly and Pope semi-empirical spectrum published over 20 years ago. A 4-temperature fit of 0.5, 1.0, 2.5, and 5.5 MK is a good fit but probably bears little resemblance to the actual solar x-ray spectrum at any given time. Correspondence with essentially all of the US groups in this field has led to the conclusion that we sure need a solar irradiance mission that reaches soft x-ray wavelengths! Page 9 The Hudson, Acton and Freeland paper to ApJ on the 13 Nov 94 event was finally accepted. The Sturrock, Wheatland and Acton letter to ApJ on interpretation of the positive temperature gradient in the quiet diffuse corona was also accepted in February. On yet another "outreach note", Acton reports that he had the privilege of giving assemblies on space and science to over 1500 middle schoolers in the Missoula, MT, area as part of the "MSU for a Day" outreach program. He spoke to the IEEE Engineer's week banquet in Butte, and the Montana Opthamological Association banquet at Big Sky, MT. In the month of March he gave public lectures in Dillon and Helena, MT, Bath, England, and twice in Dublin, Ireland. Travel included a trip east to visit Mariska and Judith Lean at NRL on the irradiance business (they are going to collaborate), a trip even _further_ east to attend the magnetic reconnection meeting in Bath, and attendance at two NASA committee meetings. David Alexander: Alexander has been busy working with several of the graduate students, working on YPOP, handling the transition of the MSU Solar Group budget from the old SXT grant to the new one, and doing his own research. He is also involved with installing CDS software on one of the MSU workstations. In particular, Alexander has been looking at the use of "pixons" as an image reconstruction method for the HXT instrument onboard Yohkoh. He gave a Relativity/Astrophysics seminar on this topic to the MSU Dept. of Physics ("A pixon reconstruction method for hard X-ray imaging"), and also presented a paper at the Yohkoh meeting in Bath, England on his study of the "13-Jan-92 event" using pixons. This poster can be viewed at http://solar.physics.montana.edu/alexander/pixons/pixons_Bath1.html. Some time was spent on revising his paper "Geometrical Considerations in Imaging the Solar Corona" (co-author S. Katsev), which has been accepted for publication in Solar Physics. Lee Bargatze: Dr. Bargatze continues to work on the creation and study of SXT "wide field" images, prepared from the YOHKOH/SXT offpoint observations of 1993 and 1994. Nearly all of the offpoint images have been restored to disk by reading ~70 exabyte tapes. Several composite image mosaics have been assembled and within a week nearly all image mosaics (~60 images usually taken once per week) will be completed. Data quality (straylight) issues and cleaning up the mosaicing IDL programs still require attention. Bargatze has won an NSF/JSPS one-year fellowship for work at Nagoya University and plans to depart for Japan this summer. Brian Handy (thesis student): Handy has completed specification and ordering of optical components for the TRACE UV channel. He is now concerned with the application of flight coatings. Currently he is actively involved with defining his thesis topic involving analysis of SoHO/EIT and SXT observations. Handy continues to provide remote (from Palo Alto!) computer systems assistance to the MSU Solar Group. Page 10 Mark Weber (thesis student): His largest project in this period was to prepare the poster paper "Differential Rotation in the Corona" (co-authors Alexander and Acton) for the Second Napoli Thinkshop On Physics and Astrophysics: The Inconstant Sun. The paper will be finished and written up for publication in the Thinkshop Proceedings next month. Weber's paper with Taeil Bai et al ("The Origin of the '26-day' Periodicity Observed by Ulysses") was wrapped up for submission to the Journal of Geophysical Research. Finally, Weber has been involved with preparations for the Chapman Conference on CMEs to be held at MSU in August 1996. Among other duties he has helped to design the conference logo. David Weston: Weston and Acton's paper "Spectral Averaging of the Point Spread Function of Yohkoh's SXT" has been accepted for publication in Solar Physics. He has also been working on a second paper with Acton on the SXT response to model solar differential emission measures. This work is intended to permit estimation of improved formal uncertainties on SXT X-ray irradiance. He is also beginning work on the "geometry problem", which Alexander has already achieved some progress on with Katsev. Brian Welsch: With Alexander, Welsch now has some results showing the disparity between soft X-ray line profiles determined from a specific DEM distribution and those determined from the equivalent line ratio temperatures. They are analyzing the effects of a variable amount of superhot material on the determination of the non-thermal velocity obtained from these lines. Michelle Larson: Larson is heavily involved with YPOP at MSU, and devotes much of her time to this subject. In addition to the various YPOP projects mentioned above, she has also: completed writing text and collected electronic images about the different structure regions of the sun; put all of this on the web in a format that will eventually be usable by the public; and attended the PNACP (Pacific Northwest Association of College Physics) meeting in Auburn, WA. She reports that this was a very informative meeting about innovative teaching techniques and that the theme of the meeting was active learning. Larson is a physics graduate student studying science education, and brings this background to bear in her YPOP association. Michael Kellen: Kellen has concentrated his efforts on SXT dark frame correction statistics with Acton, and on providing high level assistance with computer systems matters. Page 11 ======================================================================= Univ of Calif, Berkeley Activity Report for February 1996-March 1996 ======================================================================= J McTiernan presented a paper at the Yohkoh Reconnection Conference, in Bath, England titled "The Variation of Emission Measure versus Temperature During Solar Flares Observed by the Yohkoh SXT and GOES". This paper detailed the differences between the flare decay phase density versus temperature relations obtained by the two different instruments, and introduced the use of a differential emission measure, or DEM, obtained using the SXT and GOES. A paper on this subject is being prepared for the conference proceedings and submission to Ap.~J. The next step is the addition of BCS data to the calculation, which will give us a better idea of the behavior of the high temperature plasma. Once this is done, we will use the DEM's to infer the low energy cutoff of hard X-rays: This number is needed for estimates of the energy released in nonthermal electrons, and is in fact not known due to the presence of thermal emission, which in extreme cases can extend to energies $>$30~keV. In order to estimate the amount of nonthermal emission present in a flare, we need to estimate the amount of high temperature (20 to $>$30~MK) thermal emission. Previous work using the Yohkoh BCS and HXT assumed isothermal plasma emission, and gave unsatisfactory results. We expect the DEM method to do better. Preliminary results show that the thermal emission only accounts for a few percent of emission in the HXT-LO channel during the flare rise phase, with the fraction increasing as the HXR emission reaches a maximum and then decays. This means that non-thermal emission is indeed present in the HXT-LO energy range during the impulsive phase. This does NOT mean that the cutoff energy of the accelerated electron spectrum extends down to 10 keV; the cutoff in the electron spectrum is always higher than any cutoff in the observed photon spectrum. We can use thick-target models to estimate the difference, and get the electron cutoff energy from the photon spectrum obtained by HXT. Results from this calculation will be presented at the AAS/SPD meeting in Madison, WI, in June. Page 12 ============================================================= Univ of Hawaii Activity Report for February 1996-March 1996 ============================================================= MAJOR ACTIVITIES FOR FEBRUARY AND MARCH 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 enabled by travel to Japan, presentation of results at meetings, and preparation of manuscripts. Operational support for SXT was provided by Hudson at ISAS, by Nitta and Douglass at Mees and by Mickey, Canfield, Jiao, LaBonte, and Metcalf in Manoa. Reduction of NASA support for Mees Solar observatory forced the reduction of Mees observations to a very low level. Observer Jeff Douglass left for another position, due to lack of funds. Henceforth, the telescopes will be operated only five days a week, primarily in morning hours, and engineering and technical support will be limited to less than one week per month. Working with Canfield and McClymont, Jiao began the 3-D reconstruction of coronal magnetic fields at the San Diego Supercomputer Center (SDSC). He further improved his data preparation methods based on his new experience and understanding. He also improved the codes ability to compare observations and computations in 3-D. The data are processed on a 3-D non-uniform staggered mesh with non-linear MHD evolution with constant Alfven speed profile to enhance convergence of the weak field regions and non-uniform viscosity and resistivity to curb large vertical flow. For AR6919 on November 16, 1991, he found soft X-ray emitting loop do not outline low level magnetic loops but is formed by many short traverse magnetic flux arcs which either sit side by side or intersect with each other (if they obey the 'law' of brightening-at-loop-apex, their bright tops will be chained together like a loop.) This demonstrates the value of 3-D reconstruction of the magnetic field for interpreting soft X-ray data. Metcalf worked with G. Fisher on a project comparing SXT non-flare images and photospheric vector magnetograms. The study will look for correlations between SXR intensity and various measures of non-potentiality in the magnetograms in an effort to understand the mechanisms of coronal heating. Metcalf began a project with H. Hudson and D. Alexander comparing MEM and pixon HXT light curves for the 1992 January 13 limb flare. They are looking at differences in the light curve for the loop top source computed with the two reconstruction algorithms. Metcalf worked on the IVM H-alpha linear polarization study and the paper has been submitted. Metcalf analyzed AR7734 (1995 June 15) magnetograms for Yoshimura at Kyoto University. Hudson described Yohkoh observations of coronal mass ejections at the Chapman conference on magnetic storms (JPL, February). The conference Page 13 organizers were much taken with the dimming signature of the 28 Aug. 1992 flare in particular (D. Webb is responsible for spotting this), so it was featured in the JPL press release for the conference. This resulted in many interviews with media people and a chance to meet John Kappenman (Minnesota Power) who is an authority on damage to the commercial power grid on the Earth as a result of great storms. Hudson also presented (with trepidation) an "anti-reconnection" point of view on flare development at the Yohkoh magnetic reconnection meeting in Bath, England, along with a poster paper on coronal dimming. Canfield worked with Pevtsov and Zirin on the May 8, 1992 flare. This is an eruptive flare which shows a dramatic twisted loop just before the eruption; they interpret the eruption in terms of the kink instability in force-free fields. Canfield worked with Pevtsov and McClymont on trans-equatorial active region interconnections. Their study shows that active regions whose magnetic fields are twisted in the same sense (right or left-handed) tend to connect with one another, while those with the opposite sense do not. They explain the phenomenon in terms of the closure of coronal current systems. PLANS FOR APRIL AND MAY Jiao will undertake a 3-D coronal magnetic field study for AR7321 and other ARs in the next two months. He will carry out a convergence study (resolution comparison) on a good candidate like AR7220/AR7222. He will participate in the Huntsville meeting on 3-D magnetic fields. Metcalf will start work on a new version of the SXT pixon code. He will continue to work on the new Mees Observatory WWW home page. He will continue collaborations with J. Li on hard X-ray footpoints and currents, H. Hudson on methods of image reconstruction for HXT, and G. Fisher on the relationship between free magnetic energy and soft X-ray brightness. Hudson intends to work with ISAS/NAO visitors F. Farnik and M. Kundu as much as possible. Farnik's efforts include work on flares that bend the envelope of the Neupert Effect, namely events with extremely rapid and flat-spectrum hard X-ray spikes. He also intends to return to the question of flare precursors, working now on disk events. In terms of more personal research efforts, Hudson would like to continue with the Type II bursts of November 1995 and with CMEs. He also intends to do some work on coronal global patterns in preparation for the AGU meeting in May, in the context of solar-wind origins. Canfield plans to finish the paper with A. Pevtsov and H. Zirin on the role of magnetic reconnection and helicity in the Yohkoh flare of 08 May, 1992. He also plans to finish the paper with Pevtsov and Glatzmaier on coherent flows in the convection zone and their signatures in the average helicity of active regions. Finally, he will organize the relocation of UH/SXT personnel to Montana State University, Solar Physics Research Corporation, and Lockheed/Martin. Page 14 PUBLICATIONS AND PRESENTATIONS DURING NOVEMBER, DECEMBER, AND JANUARY Papers submitted "Impact Polarization in Solar Flares: A Search for Low Energy Proton Beams", Thomas R. Metcalf, Donald L. Mickey, Jean-Pierre Wuelser, Richard C. Canfield, K. Shibasaki, T. Kosugi, and S. Tsuneta, Astrophys. J., submitted. "Yohkoh Observations of Coronal Mass Ejections", H.S. Hudson, Proc. IAU Colloq. 153 (Makuhari, Japan). "Electron Time-of-Flight Distances and Flare Loop Geometries compared from CGRO and Yohkoh Observations", M.J. Aschwanden, M.J. Wills, H.S. Hudson, T. Kosugi, and R.A. Schwartz, Ap. J. Papers accepted "A solar flare event with global consequences", H.S. Hudson, L.W. Acton and S.L. Freeland, Ap. J. Papers published "Statistical study of solar X-ray jets observed with the Yohkoh soft X-ray telescope," M. Shimojo, S. Hashimoto, K. Shibata, T. Hirayama, H.S. Hudson, and L.W. Acton, P.A.S.J. 48, 123-136. "First images of a solar flare at millimeter wavelengths, A. V. R. Silva, S. M. White, R. P. Lin, I. de Pater, K. Shibasaki, H.S. Hudson, and M. R. Kundu, Ap. J. (Lett.) L49, 1996. "Energetic particles and coronal mass ejections in the high latitude heliosphere: Ulysses-LET observations", V. Bothmer, R.G. Marsden, T.R. Sanderson, K.J. Trattner, K.-P. Wenzel, A. Balogh, R.J. Forsyth, B.E. Goldstein, Y. Uchida, and H.S. Hudson, G.R.L., Dec. 1995 Presentations given "Magnetic Chirality and Coronal Reconnection", R.C. Canfield, A.A. Pevtsov, and A.N. McClymont, Yohkoh Conference on Observations of Magnetic Reconnection in the Solar Atmosphere, Bath. "The Solar Antecedents of Coronal Mass Ejections", H.S. Hudson, at the Chapman Conference on Magnetic Storms (JPL, Feb. 1996). "Observational Problems for Standard Flare Models based on Magnetic Reconnection", H.S. Hudson, at the Yohkoh conference on reconnection (Bath, Mar. 1996). "Coronal Dimming in Soft X-rays", H.S. Hudson, J.R. Lemen, and D.F. Webb, poster at the Yohkoh conference on reconnection (Bath, Mar. 1996). Page 15 Abstracts submitted "Soft X-ray Observations and the Solar Wind", H.S. Hudson and D.F. Webb, AGU Spring Meeting Page 16 ============================================================ Stanford Univ Activity Report for February 1996-March 1996 ============================================================ The collaboration between Wheatland and Sturrock and Acton has been extended to include the analysis of a second region of diffuse (quiet) corona, observed by the SXT on August 26, 1992. Both this region and the earlier one (May 9, 1992) exhibit a steady radial increase of temperature, out to 0.7 and 0.9 solar radii above the limb respectively. The observed filter ratio data is well fitted in each case by integration over the line of sight of a model atmosphere in hydrostatic equilibrium and with a temperature profile due to a conserved (radially inward) heat flux. An Abel inversion procedure has also been applied to the data, and this gives results consistent with the radially symmetric, conserved heat flux model. These results imply that the non-thermal energy responsible for heating these pieces of the quiet corona is being deposited beyond the observed range of heights. An earlier analysis of the May 9 region has appeared in the Astrophysical Journal (1996, ApJ 461: L115). Comparison of SXT images and white-light images from the MLSO MK3 Coronameter demonstrate that both of the observed regions underly extended coronal streamers. The observed regions are believed to be heated by non-thermal energy deposited near the tops of very extended loops. The implications for coronal heating are being pursued. During the reporting period, Wheatland concluded his investigation (in collaboration with Sturrock) of the avalanche model of solar flares. The influence of the size distribution of active regions on the model flare frequency versus energy distribution was considered. A paper was submitted to the Astrophysical Journal. Roumeliotis continues to work on the problem of merging multiple SXT images to produce a single image of significantly better resolution than the individual frames. His approach will incorporate a novel adaptive smoothing algorithm, designed to accurately recover sharp gradients in images. He has also devised a new approach to reconstructing force-free coronal magnetic fields from boundary data, using a minimization principle. The new technique is being tested on progressively more realistic force-free field models. During this period, Taeil Bai concluded his work (performed in collaboration with Acton and others) on the quasi-periodic variations observed by the Ulysses spacecraft. The data confirmed the existence of a long-lived (greater than two years) coronal hole in the southern hemisphere. A paper was submitted to the Journal of Geophysical Research. Page 17 =========================================================================== Solar Physics Research Corp. Activity Report for February 1996-March 1996 =========================================================================== Karen L. Harvey (1) Activities during this reporting period have primarily been directed to a thorough analysis of data obtained during several XBP collaborative campaigns. The preliminary results of this analysis were presented at a meeting on `Observations of Magnetic Reconnection in the Solar Atmosphere' in March 1996 as an invited talk on "Observations of X-ray Bright Points" and also will be presented as a poster paper at the summer AAS/SPD meeting in June 1996. In the analysis so far, 23 days of data have been reviewed for which both SXT PFIs and NSO/KP magnetograms or HeI 10830 observations exist. The total number of XBPs in these data is 239. The general character- istics of the XBPs are as follows: 133 (53%) show gradual intensity changes, 91 (37%) flared, 9 (4%) showed some suggestion of ejecta or jets. The size range of the XBPs is 10-46 arc-seconds with a lifetime range of 5 min to >5 hours, where 26 (10%) were observer for a period of less than 15 minutes. Intensity changes during XBP flares occur in seconds. For 52 XBPs observed on 7 days, we find that 85% of the XBPs are associated with one of the following magnetic field changes: Canceling Bipole = Observed mutual decrease of magnetic flux during encounters of network elements of opposite polarity. Emerging Bipole = Magnetic elements of opposite polarity that form and separate with time. Emerging/Canceling Bipole = An emerging bipole where one or both poles encounter and cancel with opposite polarity network. Eight (15%) of 52 XBPs were associated with no bipole (i.e. unipolar magnetic network), no measurable field, or little change in the field. _____________________________________________________________ Association of XBPs to Magnetic Field (analysis of 7 days) _____________________________________________________________ Magnetic Field Changes % of XBPs Number _____________________________________________________________ Canceling Magnetic Bipoles 64% 33 Emerging Bipoles 8 4 Emerging then Canceling Bipoles 13 7 No Bipole, No measurable B , or || Little change in B 15 8 || Page 18 _____________________________________________________________ _____________________________________________________________ Association of Magnetic Bipoles to XBPs _____________________________________________________________ Most Canceling Bipoles (network elements) have an XBP (> 80%) Only a Few Emerging Bipoles have an XBP (< 25%) _____________________________________________________________ All XBPs and have associated HeI 10830 dark points, even the short-lived XBPs. However, not all HeI 10830 dark points have XBP counterparts. We conclude that: The emergence or cancelation of photospheric magnetic flux is not in itself a necessary and sufficient condition for the occurrence of an XBP, and the occurrence and variability of XBPs result from the interaction and reconnection (at times sporadic) of the emerging and canceling magnetic fields with existing, local magnetic fields. This analysis will continue during the next few months and incorporate the data from BBSO and MSO. (2) Preparation of NSO/KP full-disk magnetograms and He I 10830 spectro- magnetograms for SXT investigators for studies of the magnetic field and He I 10830 structures associated with X-ray structures. (3) Continued collection and updating of the bibliography of Yohkoh papers. --------------------------------- Papers in preparation: --------------------------------- K. L. Harvey, "Observations of X-Ray Bright Points", in The Proceedings of `Observations of Magnetic Reconnection in the Solar Atmosphere', R.D.B. Bentley and J.T. Mariska (eds.), held March 20-22, 1996, Bath, UK (1996). --------------------------------- Abstracts submitted: --------------------------------- K. L. Harvey, "Observations of X-Ray Bright Points", AAS/SPD meeting, Madison, WI, June 1996 (poster paper). Page 19 ------------------------------------------------------------------------------- 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 April 1996 March 1996 |------------------------------- | 6. PERFORMING ORG | CODE: O/91-30 -----------------------------------------------|------------------------------- 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/91-30 |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 March 1996 |------------------------------- |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 | 19 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office