Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for May 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 We continue to update and improve the operations in Japan. The computers are continually being improved with hardware elements and software to provide additional capacity, flexibility, and speed. There was also an important augmentation of disk storage capacity provided by Prof Yoshiaki Ogawara (ISAS). There are some personnel changes with Richard Canfield moving from Hawaii to Montana State University on June 1, and Tom Metcalf coming to Lockheed-Martin at the same time. << Solar Activity >> Solar activity started out low in the beginning of the month, with only one B class flare on 5 May. The solar activity then picked up with the appearance of AR7962. A CME associated with this region was observed between 17:39-19:29 UT on 5-May by MLSO. Two C-class flares occurred, one on 6-May, the other on 7-May. The region grew to be quite large and would eventually reappear in early June. Hal Zirin reported Big Bear observations of new cycle page (with pores). The high-latitude regions that are reported as being associated with solar cycle 23 have not been very active. << Campaigns >> Four campaigns were run during the month. The first was the filament Page 2 hunt campaign that was run during the beginning of the month. In mid-May Jim Klimchuk organized a collaboration with SOHO instruments (CDS and SUMER) to try to measure filling factors in coronal loops. Three special SXT tables were loaded, on three different days (13, 14, and 18 May) to observe AR7962. The last table was used over the weekend, for coordinated observations with CDS on Sunday 19 May. This led to an effect observed in the CCD (see report under Operations and Health). During the last week (27-31 May) of the month a X-ray bright point campaign was conducted as organized by Karen Harvey. Finally, there was a VLA/SOHO campaign, the VLA portion being organized by Markus Aschwanden. << Science >> The group at ISAS during the past month (Nitta, Hudson, Savy, Slater) have been enjoying fruitful collaborations with Jingziu Wang from Beijing and Franta Farnik from Prague (Astronomical Institute, Ondrejov). Also during the month several Yohkoh team members prepared talks and poster presentations for the upcoming AAS/SPD meeting in Madison, Wisconsin. Serge Savy and others have found an example of large active region loops which appear to be shrinking. This is a new result, since most other analyses seem to indicate continuous expansion of coronal loops. Greg Slater implemented the installation of newly purchased disk drives that were provided by Prof Yoshiaki Ogawara. The drives were installed on the NASA-owned isass0/1 workstations. The additional disk storage will enable a better organization of the key databases and should provide for improved redundancy. Barry LaBonte (Hawaii) has analyzed the SXT gain-check data taken in April, with the conclusion that the true CCD amplifier gain is 88 (+-1.4) electrons per DN (our nominal assumption has been 100). This is a preliminary result that will be checked again. << 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 continue to 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 per day. The WEB access statistics in May were 34000 accesses and 682 Mbytes transferred. Gary Linford worked on a version of Poster #3 (The Changing Sun) that could be printed as an A-sized lithograph. It was thought that this could make a good handout. By reducing the amount of text on the back Page 3 in the figure captions, it was possible to reduce the poster to an attractive format. 10,000 copies were printed and they have been well received. << Yohkoh Operations and Health >> On 20 May 1996 a feature was observed in the SXT CCD images starting at the position of AR 7962, which had been observed with deep exposures over the weekend during the campaign conducted with SOHO. The feature was approximately one column wide and looked something like a column blemish, but did not share all the characteristics of a column blemish. In particular, the intensity of this feature was independent of exposure time. After its discovery, the long exposures were removed and the intensity rapidly decreased with an half-life of about 1 day. This particular phenomenon is probably not unique, as other deep over exposures have produced similar artifacts. The location on the CCD is where the bulk of the flux has been detected with SXT (near the equator at the solar limbs). After a few days the effects of the artifact had disappeared. We expect to use greater care in the future when making deep exposures of regions near the limb. 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 6-May-96 Pass 1: 960506-0308 recovered in the same pass SXT bitmap error 9-May-96 Pass 4: 960509-0517 recovered in the same pass SXT bitmap error 11-May-96 Pass 1: 960511-0204 recovered in the same pass SXT seu error* 11-May-96 Pass 4: 960511-0514 recovered first pass next day. The error on 11 May 1996 showed up as a SXT shutter error, but all evidence suggests there was no actual shutter error, and that the error was caused by an SEU. Page 4 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Feb-94 195399 90297 802603 298653 1101256 424962 27.54 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 6908 2869 25437 1460 26897 12274 31.33 Apr-96 6556 1847 42141 610 42751 16769 28.17 May-96 0 0 0 0 0 0 0.00 Jun-96 0 0 0 0 0 0 0.00 Total 371452 159502 1548049 363289 1911338 767949 28.66 Number of Full Frame Images Received: 371452 Number of Observing Region Images Received: 1911338 Total: 2282790 Approximate Number of Shutter Moves/CCD Readouts: 3991003 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 -------------------------------------------------------------------------------- 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-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 50.85 762.9 136982 8973 20.3 N/A Apr-96 51.16 774.4 142770 9523 19.9 N/A May-96 N/A N/A N/A N/A 0.0 N/A Jun-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 6 << Personnel Travel >> SXT Foreign Travel between 1-MAY-96 and 31-MAY-96 HUDSON 1-MAY-96 * 14-MAY-96 14 26-MAY-96 31-MAY-96 * 6 (total of 20 days) LEMEN 1-MAY-96 31-MAY-96 31 (total of 31 days) NITTA 5-MAY-96 31-MAY-96 * 27 (total of 27 days) SAVY 1-MAY-96 * 7-MAY-96 7 (total of 7 days) SLATER 1-MAY-96 * 31-MAY-96 * 31 (total of 31 days) ---------------------------------------------------------------- Grand Total of 116 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-MAY-96 SXT Foreign Travel between 1-JUN-96 and 30-JUN-96 ALEXANDER 22-JUN-96 30-JUN-96 * 9 (total of 9 days) HUDSON 1-JUN-96 * 30-JUN-96 * 30 (total of 30 days) NITTA 1-JUN-96 * 5-JUN-96 5 (total of 5 days) SAVY 15-JUN-96 30-JUN-96 * 16 (total of 16 days) SLATER 1-JUN-96 * 5-JUN-96 5 (total of 5 days) WEBER 1-JUN-96 30-JUN-96 * 30 (total of 30 days) ---------------------------------------------------------------- Grand Total of 95 days for 6 people NOTE: The "*" signifies travel that actually ends after 30-JUN-96 Respectfully submitted, James R. Lemen Frank M. Friedlaender Page 7 ================================================================= Montana State Univ Activity Report for April 1996-May 1996 ================================================================= Over the April-May bimester the MSU team worked on organizational details for the Chapman Conference on "Coronal Mass Ejections: Causes and Consequences" which is to take place in Bozeman in August. Approximately 140 participants are expected. The interviews of candidates for the tenure-track faculty position in solar astrophysics was completed and Dana Longcope has accepted the position. Acton was given the MSU Wiley Award for Meritorious Research. We enjoyed a visit by Jim Lemen and Keith Strong in May on the Yohkoh Public Outreach Project. Michelle Larson invented a "movie theater" theme for the YPOP page which we all agreed is an excellent vehicle for achieving internet access to the YPOP movies and other outreach/educational materials. YPOP Creative Design and Definition Team member Art Carlson and David Alexander took the first steps towards defining a documentary about Yohkoh and the Yohkoh Team that is intended to communicate the "people side" of scientific research. Two new grad students have decided to work with the MSU solar group in this period. Meredith Wills completed her BS at Harvard (where she has worked with Leon Golub) and has accepted a teaching assistantship for the fall semester. For the summer she will work as a research assistant on SXT. Steve Guimond has completed 2 years of grad studies in physics and hopes to pass his comprehensive examinations at the end of summer. In the meantime, he will work with Dick Canfield beginning in June as a research assistant. MSU has requested that Lockheed-Martin (L-M) give the university all of the L-M owned equipment that came to Montana with Acton. We are also pressing forward to acquire a 500 platter CD-ROM jukebox on Yohkoh funds through L-M. A CD-ROM writer and exabyte tape deck have been purchased with MSU funds. Four computers arrived from Hawaii in advance of Dick Canfield. Handy and Kellen have worked hard to incorporate these into the solar group network. Bargatze has made progress on creating wide-field SXT images from offpoint observations in '92-'94. It appears that the quality of the 100+ composite images will be quite good. These images will be used for high-corona studies. Several SXT images have been supplied to Dr. Dan Baker, University of Colorado, Boulder, and Dr. Joe Allen, National Geophysical Data Center, in support of a new collaborative effort investigating conditions which have lead to several, serious operational anomalies on geostationary spacecraft -- most notably, a 50% solar panel power loss suffered by the Canadian Anik E1 communication satellite. David Alexander achieved permanent residency status in the US. Thanks to all who wrote supporting letters his application. Work continues with Welsch on the effects of a superhot component on the interpretation of non-thermal line broadening and with with Dave Weston on 3-D geometry of flares with Giovanni Peres. Pixon work continues with Tom Metcalf and Jim McTiernan, testing the Page 8 various pixon parameter choices with pseudo HXT data as a testing ground. Weber submitted his paper, "Differential Rotation of the Solar Soft X-Ray Corona" for the Proceedings of the Second Napoli Thinkshop on Physics and Astrophysics: The Inconstant Sun. Alexander completed the paper for proceedings of Bath meeting with Tom Metcalf and Hugh Hudson: "Pixon reconstruction and the Masuda event of 13-JAN-92". Handy has commenced some initial work on analysis of EIT images from SoHO with Jim Lemen. He attended the LASCO/EIT Consortium meeting held in Greenbelt. Page 9 ======================================================================= Univ of Calif, Berkeley Activity Report for April 1996-May 1996 ======================================================================= J. McTiernan spent most of the last two months looking into the possible scattering of Xray photons by the ND filter, so far with inconclusive results. The presence of the ND filter, on average, causes an increase in the width of the radial profile of flare sources of the order of 0.1 FR pixels. This is the only effect that can be traced directly to the presence of the ND filter. The "sawtooth" pattern often seen in SXT time profiles is an exposure time effect, and not due to the ND filter, for sets of images with both Open and ND configurations, and similar exposure times, the images don't show this effect. One clue to the effect is that background pixels are more likely to be negative for shorter exposures. Some of the difference between background levels for long and short exposures is due to scattered X-rays from the source (there are more of these for longer exposures) but the difference does not typically show the flare time profile; there seems to be non-flare X-ray emission present, which is not accounted for by dark current subtraction. For bright pixels in Al.1 images, and the shortest exposures (0.07 msec), the emission seems to be underestimated by a few percent, when compared with longer (greater than 1 msec) exposures. This is a function of flare size--larger flares show less of an effect. This work is still continuing, and there may be a report, after McTiernan returns from the AAS/SPD meeting in Madison WI. Page 10 ============================================================= Univ of Hawaii Activity Report for April 1996-May 1996 ============================================================= MAJOR ACTIVITIES FOR APRIL AND MAY 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, presentation of results at meetings, preparation of manuscripts, and changes in personnel. Operational support for SXT was provided by Hudson at ISAS, by Nitta at Mees, by Canfield, Jiao, LaBonte, and Metcalf in Manoa. Several personnel changes occurred at the end of the reporting period. Canfield left for Montana State University, where he will have increased involvement in the SXT project. Hudson left for Solar Physics Research Corporation; he will continue to work on SXT operations and research at ISAS. Metcalf left for Lockheed Martin Palo Alto Research Labs, where he will continue to work on SXT projects involving Mees vector magnetograms. Remaining at UH, LaBonte will take over as PI of the UH Yohkoh contract and Jiao will continue to work on his thesis, under the guidance of A. McClymont. Hudson described Yohkoh observations related to the solar wind at in an invited talk at the AGU in Baltimore. He helped F. Farnik finish a paper on the remarkable flat-spectrum hard X-ray bursts of 3 October 1993, and in the meanwhile discovered that these flares homologously produced jets associated with type V radio bursts. This is the last category of meter-wave radio bursts now identified with soft X-ray structures seen at high resolution with SXT. The flares themselves turned out to be quite interesting and provided considerable support for the Neupert effect. Metcalf continued a project with 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 with J. Li on the manuscript for the paper studying the relationship between HXR flare sources and photospheric electric current systems. Metcalf worked on the IVM H-alpha linear polarization study and is revising the paper, after receiving the referee's report. Jiao report on progress on his thesis in a poster at the Workshop on Measurements and Analyses of the 3-D Solar Magnetic Field in Huntsville. For AR 6919 on 16-Nov-91 he found that the observed soft X-ray structures may not outline low level magnetic loops but may be formed by many short traverse magnetic flux arcs which sit side by side, rather than a single loop. At the workshop Jiao had many constructive discussions with magnetic field experts. Upon returning, he improved his methods and codes for 3-D coronal magnetic field Page 11 reconstruction. He worked on a paper based on the above poster and also worked with A. McClymont and Z. Mikic on another more general paper on problems and progress in computing 3-D coronal active region magnetic fields from boundary data. These two papers will be submitted for a special edition of solar physics by the end of May. Jiao also improved his code to generate solar observation target information based on any kind of full solar disk images and provided it as a tool to the upcoming SUMER campaign coordinator. Canfield worked with Pevtsov and H. Zirin to complete a paper describing the interesting 8-May-1992 flare, which developed a striking helical structure in SXT images, then erupted. He also worked with Pevtsov, McClymont, and Acton to complete a paper on the relationship of helical structures seen in SXT images to the magnetic helicity observed in the photosphere with Haleakala Stokes Polarimeter vector magnetograms. He accomplished the transfer of several workstations to MSU and Lockheed/Martin for SXT and related work, but did not succeed to establish IDL on these workstations. He developed an agreement among Mees and SXT scientists to handle and archive the Mees data to maximize scientific productivity at UH, MSU, and LMPARL. He developed an SXT subcontract budget and statement of work for UH after June 1. He traveled to Washington to attend the meeting of the Sun Earth Connections Advisory Subcommittee and to Bozeman to handle the transfer of the Mees MCCD data archive. PLANS FOR JUNE AND JULY Hudson will work on the Type II counterpart events observed in October 1995, and present preliminary results at the SPD meeting in Madison. Otherwise he intends to work as hard as possible on CME-related topics and HXT data analysis. A paper with Dave Webb on the dimming signature in limb flares will be drafted, we hope prior to the Bozeman meeting. He is helping to organize a small workshop at ISSI (International Space Science Institute) in Bern, on the general subject of coronal hole boundary development. This will take place the second week of July. Metcalf will start work on a new version of the SXT pixon code. He will continue his collaborations with J. Li on HXT images and currents, and Hudson and Alexander on MEM and pixons methods of HXT image reconstruction, and with G. Fisher. Jiao will continue his thesis work, under the guidance of A. McClymont, R. Canfield, and Z. Mikic, on three dimensional reconstruction of solar coronal magnetic field. For one month he will visit ISAS for collaborative research, scientific presentations, and SSOC toban duty. Canfield will participate in the Solar Magnetic Initiative workshop in Boulder will write up his results (with Pevtsov) on helicity and trans-equatorial reconnection of active regions, for the proceedings of the Bath meeting. He plans to complete a paper on signatures of convection in the helicity of solar photospheric magnetic fields, working with A. Pevstov and G. Glatzmaier. He plans to work with grad Page 12 student S. Guimond to transfer the Mees Stokes Polarimeter dataset to CD. He plans to work with J. Li and T. Metcalf to finish the paper on HXT images and maps of photospheric vertical electric currents. PUBLICATIONS AND PRESENTATIONS DURING APRIL AND MAY Papers submitted "Yohkoh Observations of Flares with Flat Hard X-ray Spectra", F. Farnik, H. Hudson, and T. Watanabe, Astronomy & Astrophys. "The Solar Antecedents of Magnetic Storms", H.S. Hudson, proceedings of Chapman Conference on Magnetic Storms (Pasadena) "Magnetic Storms: Current Understanding and Outstanding Questions", Y. Kamide, R.L. McPherron, W. D. Gonzalez, D.C. Hamilton, H. S. Hudson, J.A. Joselyn, S.W. Kahler, L.R. Lyons, H. Lundstedt, and E. Szuszczewicz, proceedings of Chapman Conference on Magnetic Storms (Pasadena) "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, submitted to Astrophys. J. "Reconnection and Helicity in a Solar Flare", A.A. Pevtsov, R. C. Canfield, and H. Zirin, Astrophys. J. "Helicity of Solar Magnetic Fields in Photosphere and Corona", A.A. Pevtsov, R.C. Canfield, A.N. McClymont, and L.W. Acton, Astrophys. J. Papers accepted "Pixon-Based Multiresolution Image Reconstruction for Yohkoh's Hard X-Ray Telescope", T.R. Metcalf, H.S. Hudson, T. Kosugi, R.C. Puetter, and R.K. Pina, Astrophys. J. (July 20, 1996) "3D Magnetic Reconnection at an X-ray Bright Point" C.H. Mandrini, P. Demoulin, L. van Driel-Gesztelyi, B. Schmieder, G. Cauzzi, and A. Hofmann, Solar Physics Papers published "Large-Scale Active Coronal Phenomena in Yohkoh SXT Images. I. Post-Flare Giant Arches Rising with Constant Speed", Z. Svestka, F. Farnik, H.S. Hudson, Y. Uchida, P. Hick, and J.R. Lemen, Solar Phys. 161, 363, 1996. "A Test of a New Flare Loop Scaling Law Using Yohkoh SXT and GOES Observations", T. R. Metcalf and G. H. Fisher, Astrophys. J., 462, 977, 1996. Page 13 Abstracts Submitted and Presentations "Soft X-ray Observations and the Solar Wind", H.S. Hudson and D.F. Webb, Spring AGU meeting (Baltimore). "Yohkoh Observations of Coronal Dimming", D.F. Webb, H.S. Hudson, and J.R. Lemen, poster at AGU meeting (Baltimore). "Reconstruction of the 3-D Solar Magnetic Field", L. Jiao, R. C. Canfield, A.N. McClymont, and Z. Mikic, poster at Workshop on Measurements and Analyses of the 3-D Solar Magnetic Field (Huntsville). Page 14 ============================================================ Stanford Univ Activity Report for April 1996-May 1996 ============================================================ Gary Linford recently prepared a montage of full-disk coronal images covering the period November 1991 to July 1995. It is striking that this montage provides evidence that the entire Sun takes part in the solar cycle. The solar cycle does not involve only sunspots, and it is not confined only to the sunspot zone. These data have prompted Peter Sturrock to give further thought to the mechanism of the solar cycle. Rather than adopt a model (such as the dynamo model) in which magnetic field is recycled every 11 years, mainly in the sunspot zone, he has looked for a model in which there is a new supply of magnetic flux, at alternating polarity, every 11 years. This leads him to a model in which the solar cycle originates in a rotating cell in the radiative zone that contains a poloidal flux loop and delivers flux, of alternating polarity, to the base of the convection zone every 11 years. This model seems to have some advantages over the dynamo model and its consequences are being analyzed further. Roumeliotis has derived a compact description of a force-free magnetic field, in terms of the magnitude and direction of the field at each point in space. As a specific application of this alternative description of force-free fields, an observational procedure has been formulated for resolving the troublesome 180-degree ambiguity in the transverse field measured by a vector magnetogram. The approach involves the use of simultaneous vector magnetograms from two levels in the solar atmosphere. A paper has been submitted to the Astrophysical Journal. Roumeliotis has also been evaluating an idea for reconstructing force-free magnetic fields by a global minimization approach. The method incorporates the description of a force-free field described above. He has obtained an expression which is a volume integral that involves the magnetic field and electric current, which has the property that a magnetic field which minimizes this volume integral is guaranteed to be a force-free field. This leads to the idea of attempting to minimize this volume integral with the constraint that the magnetic field has prescribed values over the photosphere, where we have magnetograph observations. Initial experiments in which the reconstruction method is applied to analytic force-free fields has yielded very promising results. Slava Glukhov has continued working on a paper detailing his analysis of SXT observations of a giant coronal helmet streamer. The results reported in this paper will form part of Slava's Ph.D. dissertation. Slava has also been examining SXT images for emission characteristics of shell-like, rather than loop-like, coronal structures. He has found unambiguous evidence of the existence of such structures, and intends also to include this finding in his dissertation. Mike Wheatland is preparing a paper describing the results of his collaboration with Peter Sturrock and Loren Acton on the analysis of Page 15 SXT observations of two regions of extended, diffuse (quiet) corona. The principal result of this study is that the observed regions may be well represented as spherically symmetric, barometric atmospheres with a conserved, radially inwards heat flux. Consequently, there is substantial non-thermal energy deposition beyond the observed range of heights. The implications for coronal heating mechanisms are being considered. Page 16 =========================================================================== Solar Physics Research Corp. Activity Report for February 1996-March 1996 =========================================================================== Karen L. Harvey Activities during this reporting period have been directed toward: (1) writing up the results on X-ray Bright Points for publication in the Proceedings for the March 1996 Bath meeting on `Observations of Magnetic Reconnection in the Solar Atmosphere'. (2) preparation of a poster paper on X-ray Bright Points to be presented at the summer AAS/SPD meeting in June 1996. (3) acquiring additional observations of XBPs though a collaboration of several ground-based observatories and the Yohkoh SXT instrument May 27-31, 1996. During this run, we recorded the HeI 10830 line profile and a nearby SiI line at every pixel in the scan area (512 x 512 arc-sec) using the NSO/KP spectromagnetograph. The cadence of these data is 5 minutes. We are in the process of analyzing these data, along with similar observations taken during the April 1996 XBP collaboration, using software developed by Matt Penn and Harry Jones to fit the He I line profile and . Quantities derived for both the HeI and SiI lines are the velocity (measured relative to a terrestrial water vapor line), equivalent width, line depth. (4) 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. (5) 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). Page 17 ------------------------------------------------------------------------------- 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 | 7 June 1996 May 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 May 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 | 18 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office